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Path planning is an important primitive in robotics. In this paper, a new Informed Sampling Space (ISS) driven Informative Path Planning (IPP) approach is developed to facilitate autonomous robots to navigate and explore unknown and hazardous environments for in-situ resource utilization efficiently. The developed ISS-driven IPP approach is targeted on multi-objective optimization enabling the robot to plan its path from start to target locations in the environment and simultaneously explore multiple high-interest areas efficiently. The high-interest areas could be locations advised by a human supervisor or from the robot's prior knowledge of the environment. Typically, a cost function (time, distance, etc.) is used in sampling-based path planners. A new cost function is also developed to incorporate the high-interest spots in this paper, which is based on Multivariate normal (MVN) probability density function (PDF) and a normalization function. Two different IPP models are developed using the new cost function to assist robot navigation. IPP with RRT* is used in the first model with no heuristics, while IPP with RRT* and heuristic ISS is used in the second model. Simulation and comparative analysis substantiate the efficacy and robustness of our approach. The simulation results corroborate that our proposed ISS-driven IPP with RRT* converges rapidly towards the near-optimal solution with respect to both navigation time and environment exploration. • Adaptive cost function incorporates the influence of prior information states. • Multivariate normal probability density function is used to disseminate information. • IPP framework is developed using information map and a sampling-based path planner. • ISS-driven IPP addresses the global sampling problem by ignoring trivial states. • Tree pruning after each subsequent optimization minimizes computational complexity. [ABSTRACT FROM AUTHOR]

• A constrained path planning algorithm for Ackerman mobile robot is proposed. • An improved ant colony algorithm with angle constraint is introduced. • An improved B-spline curve smoothing method with curvature constraint is proposed to ensure that the smooth path follows the maximum curvature limit of the mobile robot. In this paper, a new approach is proposed for the smooth path planning of Ackermann mobile robots based on an improved ant colony algorithm and B-spline curves. Firstly, by incorporating path length constraints and path smoothing constraints into the objective function, the smooth path planning problem for Ackermann mobile robots is transformed into a multi-objective optimization problem. Secondly, to address the limitations of the traditional ant colony algorithm, an improved ant colony algorithm based on the turning angle constraint (IACO-TAC) is proposed. IACO-TAC incorporates the distance factor and steering angle penalty factor in the heuristic function to reduce the path search's blindness. Moreover, the pheromone update method is improved, consisting of local pheromone update and global pheromone update, which uses a reward penalty mechanism to improve the convergence speed of the algorithm and increases the pheromone concentration of the global optimal path, respectively. Thirdly, an improved B-spline curve smoothing algorithm that considers the minimum turning radius constraint is proposed to generate a path that satisfies the kinematic constraints of the Ackermann mobile robot. Finally, the proposed method is evaluated by conducting gradient comparison experiments and ant colony algorithm comparison experiments on maps of different sizes. The experimental results demonstrate that our method exhibits a fast convergence rate and plans a path that balances path length and turn frequency while satisfying the kinematic constraints of the mobile robot. Thus, the proposed method offers an efficient and smooth path planning solution for Ackermann mobile robots in complex environments. [ABSTRACT FROM AUTHOR]

An underactuated nonholonomic Dubins-vehicle-like robot with a lower-limited turning radius travels with a constant speed in a plane, which hosts unknown complex objects. In its local frame, the robot has sensorial access only to the part of the scene that is within a finite zone of visibility and in direct line of sight. It is required to approach and then circumnavigate the objects, with maintaining a given distance to the currently nearest of them, so that the ideal targeted path is the equidistant curve of the set of the objects. The focus is on the case where this curve cannot be perfectly traced due to excessive contortions and singularities. So the objective is restated as that of automatically finding, approaching and repeatedly tracing an approximation of the equidistant curve that is the best among those trackable by the robot with respecting safety concerns. Though pre-computation of this approximation is a hard problem of computational geometry, we show that autonomously seeking and tracking this approximation can be performed on-the-fly at a miserable computational cost via implementation of the proposed navigation law. This law is hybrid and operates in only a few discrete modes; within any mode, it is reactive, i.e., it directly converts the current observation into the current control. Nonlocal convergence of this law is justified by mathematically rigorous results and is confirmed by computer simulations and real-world experiments. • Underactuated nonholonomic Dubins-vehicle-like robot with a lower-limited turning radius. • Circumnavigation of unknown objects, with desirably maintaining a given distance to them. • Equidistant curve that is untrackable due to excessive contortion and singularities. • On-the-fly generation of the optimal trackable approximation at a miserable computational cost. • Computationally cheap (reactive) controller that simultaneously generates the path and ensures its tracking. [ABSTRACT FROM AUTHOR]

We develop an algorithm for the motion and task planning of a system composed of multiple robots and unactuated objects under tasks expressed as Linear Temporal Logic (LTL) constraints. The robots and objects evolve subject to uncertain dynamics in an obstacle-cluttered environment. The key part of the proposed solution is the intelligent construction of a coupled transition system that encodes the motion and tasks of the robots and the objects. We achieve such a construction by designing appropriate adaptive control protocols in the lower level, which guarantee the safe robot navigation/object transportation in the environment while compensating for the dynamic uncertainties. The transition system is efficiently interfaced with the temporal logic specification via a sampling-based algorithm to output a discrete path as a sequence of synchronized actions of the robots; such actions satisfy the robots' as well as the objects' specifications. The robots execute this discrete path by using the derived low level control protocol. Numerical experiments verify the proposed framework. • Robot tasks expressed by temporal logics offer great versatility and efficiency. • Simple items/objects often have to undergo processes and tasks. • New algorithm provides robot actions that satisfy theirs and objects' tasks. • Robot actions consist of robot navigation and cooperative object transportation. • Adaptive control is used to tackle uncertainty in robots' and objects' dynamics. [ABSTRACT FROM AUTHOR]

To effectively mitigate the spread of epidemics, disinfection robots are increasingly utilized for automatic disinfection. However, tradition robots and disinfection methods cannot ensure controllable disinfection coverage, potentially causing damage to sensitive surfaces and humans. In this paper, we introduce a novel Ultraviolet-C disinfection robot system built on the mobile manipulator structure. We propose a new multi-side disinfection end-effector to broaden the disinfection scope and improve adaptability to complex surfaces. In order to coordinate the movements of the base and manipulator, we propose a joint base placement and multi-configuration disinfected path planning(JPMDP) method. The algorithm generates the minimal number of mobile base placements and forms the disinfection path with the shortest working time. We have conducted extensive experiments in both simulated and real environments. Experimental results demonstrate that our system offers more comprehensive coverage in less time compared to traditional strategies, making it more efficient and adaptable to complex environments. • Proposing a novel UV-C disinfection robot for epidemic control. • Introducing a multi-side disinfection end-effector for complex surface adaptability. • Presenting a JPMDP method for optimal coordination of base and manipulator movements. • Validating the system's efficiency through extensive simulations and real tests. [ABSTRACT FROM AUTHOR]

• Smart agriculture system: Precision agriculture, often known as smart agriculture, is a cutting-edge agricultural method that makes use of technology to maximize resource management and crop yield. To improve decision-making and overall agricultural practices, it entails the integration of many technologies, including sensors, automation, data analytics, and remote monitoring. • Optimization: Enhancement The term "agriculture system" describes the application of data analysis and technology to enhance and optimize agricultural processes. To maximize agricultural productivity, resource management, and decision-making, it entails the integration of multiple technologies, including automation, remote sensing, data analytics, and precision agriculture. • Regulation skidding: In agriculture, regulation skidding is a technique used to manage the movement of mobile robots over dirt and water on sloping terrain. It entails building short-term, makeshift barriers or dams across the slope out of boulders, dirt, or other materials. By slowing down water flow and allowing it to seep into the ground, these barriers improve soil moisture and lessen erosion. • Four wheeled mobile robots: Certain four-wheeled mobile robots are autonomous in the context of agriculture, which means they can move and function without assistance from an operator. Some, however, are only partially autonomous, requiring human intervention in the form of direction or oversight. • Linear-quadratic regulator (LQR): To minimize a quadratic cost function of the state and control variables of a linear time-invariant system, an optimum control strategy characterized as a linear-quadratic regulator (LQR) is applied. It is a commonly utilized control theory technique with applications in the field of agriculture. Use of wheeled mobile robot systems could be crucial in addressing some of the future issues facing agriculture. However, robot systems on wheels are currently unstable and require a control mechanism to increase stability, resulting in much research requirement to develop an appropriate controller algorithm for wheeled mobile robot systems. Proportional, integral, derivative (PID) controllers are currently widely used for this purpose, but the PID approach is frequently inappropriate due to disruptions or fluctuations in parameters. Other control approaches, such as linear-quadratic regulator (LQR) control, can be used to address some of the issues associated with PID controllers. In this study, a kinematic model of a four-wheel skid-steering mobile robot was developed to test the functionality of LQR control. Three scenarios (control cheap, non-zero state expensive; control expensive, non-zero state cheap; only non-zero state expensive) were examined using the characteristics of the wheeled mobile robot. Peak time, settling time, and rising time for cheap control based on these scenarios was found to be 0.1 s, 7.82 s, and 4.39 s, respectively. [ABSTRACT FROM AUTHOR]

Robot sequential decision-making in the real world is a challenge because it requires the robots to simultaneously reason about the current world state and dynamics, while planning actions to accomplish complex tasks. On the one hand, declarative languages and reasoning algorithms support representing and reasoning with commonsense knowledge. But these algorithms are not good at planning actions toward maximizing cumulative reward over a long, unspecified horizon. On the other hand, probabilistic planning frameworks, such as Markov decision processes (MDPs) and partially observable MDPs (POMDPs), support planning to achieve long-term goals under uncertainty. But they are ill-equipped to represent or reason about knowledge that is not directly related to actions. In this article, we present an algorithm, called iCORPP, to simultaneously estimate the current world state, reason about world dynamics, and construct task-oriented controllers. In this process, robot decision-making problems are decomposed into two interdependent (smaller) subproblems that focus on reasoning to "understand the world" and planning to "achieve the goal" respectively. The developed algorithm has been implemented and evaluated both in simulation and on real robots using everyday service tasks, such as indoor navigation, and dialog management. Results show significant improvements in scalability, efficiency, and adaptiveness, compared to competitive baselines including handcrafted action policies. • This article formally introduces the Integrated Reasoning and Planning (IRP) problem for robots. An IRP problem has a factored state space that is specified by a set of endogenous and exogenous variables. • This article introduces a sequential decision-making algorithm, called Interleaved Commonsense Reasoning and Probabilistic Planning (iCORPP), for addressing IRP problems. • This article presents systematic evaluations of iCORPP using two tasks of mobile robot navigation, and spoken dialog systems, as demonstrated on a real robot. • This article builds on our previous research that appeared in two conference papers (Zhang and Stone, 2015; Zhang et al., 2017). This article unifies their terminology, problem statements, and algorithms. • Compared to our prior work, this article introduces a new problem statement in Section 4.1, which covers the problems addressed in both conference papers. • To address the IRP problem, we have reformulated the iCORPP algorithm (Section 4.2) into a novel form that includes the three key steps of "logical reasoning," "probabilistic reasoning over world states," and "probabilistic reasoning about world dynamics." [ABSTRACT FROM AUTHOR]

The goal of this research is to devise guaranteed defense policies that allow to protect a given region from the entrance of smart mobile invaders by detecting them using a team of defending agents equipped with identical line sensors. By designing cooperative defense strategies that ensure all invaders are detected, conditions on the defenders' speed are derived. Successful accomplishment of the defense task implies invaders with a known limit on their speed cannot slip past the defenders and enter the guarded region undetected. The desired outcome of the defense protocols is to defend the area and additionally to expand it as much as possible. Expansion becomes possible if the defenders' speed exceeds a critical speed that is necessary to only defend the initial region. We present results on the total search time, critical speeds and maximal expansion possible for two types of novel pincer-movement defense processes, circular and spiral, for any even number of defenders. The proposed spiral process allows to detect invaders at nearly the lowest theoretically optimal speed, and if this speed is exceeded, it also allows to expand the protected region almost to the maximal area. • Development of guaranteed defense policies of a given region against smart invaders. • Theoretical and simulative analysis of trajectories, speeds and search times. • Introduction of two novel pincer guarding and expansion strategies. • Comparison between developed defense pincer sweep guarding and expansion strategies. • Performance of spiral defense pincer protocol provides state-of-the-art results. [ABSTRACT FROM AUTHOR]

Non-prehensile cooperative object transportation is a challenging model problem for distributed control and organization methods but also has practical applications. Therefore, it is widely studied in distributed robotics research. This paper describes and evaluates a novel transportation scheme for differential-drive mobile robots that is, to the authors' best knowledge, the most versatile scheme of its kind successfully evaluated with real-world hardware. The proposed scheme can conceptually deal with any number of robots and arbitrary polygonal objects, including non-convex ones, without having to retune, retrain, or reconfigure any of the control parameters between different scenarios. This is achieved by splitting the task into a formation control and a formation finding task, both of which are tackled with model-based approaches using distributed optimization. Formation control and formation finding are complicated by the robots' non-holonomic kinematic constraints. Therefore, a tailored distributed model predictive controller is used for formation control. Finding formations relies on a multibody-dynamics representation of the robots-object system to properly account for contact and non-holonomic constraints. Due to these measures, the transportation scheme achieves a very satisfactory performance and dexterity in real-world hardware experiments utilizing network communication and distributed computation. • First time such a versatile scheme is shown to work with non-holonomic robot hardware. • Convex and non-convex object shapes can be considered. • Fully distributed decision-making, no scenario-specific parameter tuning. • Non-holonomic constraints are naturally considered using multibody dynamics. • Distributed predictive control and distributed optimization serve as key methods. [ABSTRACT FROM AUTHOR]

• The issue featured with concurrent job operations - mobile robots scheduling problems in complex FMS environment. • A logical and practical approach for the selection of GA parameters based on fuzzy rules to improve the solution to the complex combinatorial NP-hard scheduling problem. • Adaptively adjustment of genetic operator, i.e., crossover and mutation for better exploration and exploitation activities in searching process. Flexible Manufacturing Systems (FMS) is known as one of the recurring themes that possess these promising characteristics with a synergistic combination of productivity-efficiency transport and flexibility through a number of machine tools alongside other material handling devices. In FMS, mobile robots are commonly deployed in material handling system for the purpose of increasing the efficiency and productivity of the manufacturing process. A reliable, efficient, and optimal scheduling is the most important in manufacturing system. The scheduling problems can become highly complex, especially in large-scale systems with numerous tasks and constraints. Thus, schedule optimization becomes crucial to enhance target performance by determining the best allocations and sequences of resources under specified constraints. Recently, Genetic Algorithm (GA) is a remarkably applicable search algorithm to solve scheduling problems to the way that near optimal could be found. While the performance of GA much depends on the selection of the main parameters, a standard GA may suffer from the issue of premature convergence due to the lack of control on its parameters especially crossover and mutation operators. As there is no specific method or way to tune these parameters, the algorithm is prone to converge on the local optimum, thereby leading to performance degradation. To overcome such flaw, this paper proposed an improved Genetic Algorithm using an adaptive Fuzzy Logic to control crossover and mutation operators (FGAOC) for the solution to the NP-hard problem of scheduling mobile robot within Job-Shop FMS environment. The proposed algorithm has been evaluated in several case studies such as small and large-scale problem, various numbers of mobile robots and the 40-test benchmark problem. The results have demonstrated that the proposed FGAOC has delivered a good performance in exploration-exploitation activities with better solution quality. [ABSTRACT FROM AUTHOR]

We address a motion planning and control problem for mobile robots to satisfy rich, time-varying tasks expressed as Signal Temporal Logic (STL) specifications. The specifications may include tasks with nested temporal operators or time-conflicting requirements (e.g., achieving periodic tasks or tasks defined within the same time interval). Moreover, the tasks can be defined in locations changing with time (i.e., dynamic targets), and their future motions are not known a priori. This unpredictability requires an online control approach which motivates us to investigate the use of control barrier functions (CBFs). The proposed CBFs take into account the actuation limits of the robots and a feasible sequence of STL tasks. They define time-varying feasible sets of states the system must always stay inside. We show the feasible sequence generation process that even includes the decomposition of periodic tasks and alternative scenarios due to disjunction operators. The sequence is used to define CBFs, ensuring STL satisfaction. We also show some theoretical results on the correctness of the proposed method. We illustrate the benefits of the proposed method and analyze its performance via simulations and experiments with aerial robots. • A robot must satisfy a signal temporal logic (STL) specification by visiting time-varying regions. • The future trajectories of time-varying regions are unknown. • The STL specification may include nested temporal operators or time-conflicting requirements. • We propose Sequential CBFs to drive a robot to its dynamic targets based on its STL specification. • The proposed algorithm is supported by theoretical results and tested via experiments. [ABSTRACT FROM AUTHOR]

Hedge algebra is gaining increasing attention due to its high efficiency and fast calculation speed compared to fuzzy logic. This paper proposes the first algebra-based formation controller with a leader–follower approach to maintain the desired formation of multiple robots. In each time step, the controller computes the desired positions of the followers and strives to minimize the distance between them and their desired positions. We evaluate the performance of this controller on our robots using ROS in a virtual environment with Gazebo. Our work proves hedge algebra's significant potential in the mobile robots' domain, specifically in formation control. HAFC allows not only the precise formation of a robot swarm into any desired formation, with minimal deviation but also adaptive transition to the different formations. Our results show that HAFC can effectively maintain the desired formation of multiple robots, even in certain extraordinary situations. Furthermore, HAFC exhibits higher efficiency than the fuzzy logic-based controller, as evidenced by its faster adaptation rate and shorter computation time. The proposed approach has the potential to be applied in various real-world scenarios, such as surveillance, transportation, and exploration, where the robot has to move in formation and change formation accordingly with the terrain. • This work is the first study in formation control of mobile robots and adaptive formation translation based on the Hedge-algebras theory. • HAFC exhibits higher efficiency compared to the fuzzy logic-based controller, as evidenced by its faster adaptation rate and shorter computation time. • The simulation is implemented on ROS and obtain a high accuracy and miniature errors. A structure is proposed so as to conduct real formation experiments. • The proposed approach has the potential to be applied in various real-world scenarios, such as surveillance, transportation, and exploration, where the robots have to move in formation and change formation accordingly with the terrain. [ABSTRACT FROM AUTHOR]

One of the main issues in robotics systems is planning and tracking a safe path in diverse environments. This paper addresses an optimal methodology for generating the desired path and thereafter forces the mobile robot to follow the designed reference path. The proposed technique has the potential to tackle the inherent challenges and intricacies of the environment, enabling the robot to navigate both static and dynamic workspaces. Several simulations are exploited to verify the captured theoretical results. Three cases were examined in a static environment, achieving average performance metrics for reference signals in the X- and Y-directions, and heading tracking of 99.62%, 99.64%, and 95.08%, respectively. For the dynamic environment, two cases were studied, with average performance in following the Y-direction and heading angle recorded as 97.58% and 86.79%, respectively. Simulation results show that the controller calculated the optimal signal with an average computational time of 7 ms per iteration for static environments and 21.3 ms per iteration for dynamic environments. • Low computational time : the computational time of path planner and path following is studied, and for the later, CasADi toolkit is used to minimize the computational time. • Path planner algorithm is complete : guarantees to find an existing path. • Systematic approach : the whole algorithm is explained in the paper facilitates further studies and enables a better understanding of the approach. • Applicable to a wide range of robot types : the proposed algorithm is suitable for any spatial search, and easily extentable to higher dimensions. [ABSTRACT FROM AUTHOR]

Mobile robots have increasingly been used in warehouses, factories, open spaces, on roads, and urban areas to transport goods and people. Path planning in complex and large environments using classical graph-based search is computationally too intensive. One of the main challenges of mobile robotics is describing the large robot's workspaces with a reduction of graph complexity and improvement of path planning efficiency. A representation by a hierarchical graph (H-graph) facilitates graph creation and reduces the complexity of path planning. In this paper, we present an algorithm for autonomously generating a hierarchical graph of the environment from floor plans. The hierarchical abstraction depicts the environment in levels, from the most detailed to the most abstract representation of the environment, where pre-computed partial paths at the most detailed level are graph edges at a higher level. We use the E* algorithm to find partial paths in the most detailed abstraction level, and we propose the extraction of higher levels automatically from lower levels. We verified the proposed H-graph creation on three cases: our University premises as an example of a multi-building environment, a large warehouse with a lot of shelves, and an outdoor urban environment which is represented by a city map. All cases result in five abstract levels. The result shows that the path planning algorithm searches about 50 to 800 times fewer nodes when using the H-graph as the environment representation than when using a plain graph representing the entire environment as an occupancy grid map. • Autonomous creation of an H-graph with five or more levels. • Generation of nodes in H-graph that represent the elevators and the passages between the buildings. • Autonomous creation of an H-Graph with natural close-to-optimal paths and autonomous identification of bridge nodes. • Analysis of partial paths and nodes of the H-graph on three cases of environment. • Analysis of the created hierarchy on the path planning examples in three cases of environment using three different resolutions. [ABSTRACT FROM AUTHOR]

We present a novel method for navigation of mobile robots in challenging dynamic environments. The method, which is based on Nonlinear Model Predictive Control (NMPC), hinges upon a specially devised constraint for dynamics-aware collision avoidance. In particular, the constraint builds on the notion of avoidable collision state , taking into account the robot actuation capabilities in addition to the robot–obstacle relative distance and velocity. The proposed approach is applied to both ground and flying robots and tested in a variety of static and dynamic environments. Comparative simulations with an NMPC using a purely distance-based collision avoidance constraint confirm the superiority of the dynamics-aware version, especially for high-speed navigation among moving obstacles. Moreover, the results indicate that the method can work with relatively short prediction horizons and is therefore amenable to real-time implementation. • Robot navigation among obstacles at high-speed using Model Predictive Control. • Dynamics-aware collision avoidance enhances robot safety. • Dynamics-aware collision avoidance outperforms its distance-based counterpart. • Integration of velocity fields aids the robot in circumventing obstacles. [ABSTRACT FROM AUTHOR]

This paper proposes an optimization-based adaptive local planner to address the aggressive motion planning problem of an autonomous mobile robot in realistic semi-structured scenarios. The goal is to enable the robot to perform autonomous navigation tasks at the limit of its speed capability to maximize the efficiency, while ensuring safety and feasibility. The proposed approach constitutes an integrated scheme that leverages real-time hierarchical collision avoidance constraints reformulation and handles the heterogeneous constraints using a unified nonlinear optimization. An aggressiveness adaption method is employed to cope with disturbances instead of relying on excessive obstacle inflation, resulting in reduced conservatism while enhancing safety. The efficacy of the proposed method is demonstrated through simulation and experimental results. Compared with previous work, the proposed approach provides significant improvements in navigation success rate without sacrificing the task efficiency. • A real-time less-conservative method to avoid static structured obstacles. • A collision-aware velocity governor to balance cautious and aggressive behaviour. • An unified optimization-based navigation framework with practical validation. [ABSTRACT FROM AUTHOR]

Autonomous inspection and maintenance tasks with robots in oil and gas refineries require moving along pipelines and manipulation dexterity in cluttered environments. This paper investigates the problem of controlling a wheeled mobile manipulator endowed with a snake-like arm to inspect the structures while stabilizing the supporting pipe. A model predictive control approach stabilizes the wheeled robot on the pipe. When the wheel torques saturate, the stabilization task leverages the resulting propagating force on the wheeled robot given by the snake-like arm's dynamics. The significant number of degrees of freedom given by the snake-like arm allows a prioritized redundancy resolution scheme with hybrid motion/force tracking to inspect the same and adjacent pipes while avoiding self-collisions and environmental impacts. Simulations in the realistic Gazebo environment validate the achieved preliminary results. • Pipe inspection requires moving along pipelines and dexterity in cluttered environments. • Novel over-actuated hybrid platform to inspect the structures while stabilizing on the pipe. • Exploiting the arm dynamic in an optimization algorithm for the stabilization task. • Development of a parallel motion-interaction control with redundancy resolution. [ABSTRACT FROM AUTHOR]

We present an autonomous approaching scheme for mobile robot traversing obstacle stairwells, which overcomes the restricted field of vision caused by obstacles. The scheme consists of three parts: stair localization, structural parameter estimation, and nearing the stair. We use LIDAR with full-angle and long-distance measurement capabilities to initially determine the location of the stairs, and estimate staircase parameters using a depth camera with intensive data. Then, we propose an algorithm to optimize the location of stairs for real-time correction of target point locations during approaching. Finally, we conducted tests to verify the accuracy of the estimated stair positions and structural parameters and performed a comprehensive experiment to demonstrate the effectiveness of the scheme, in which the robot approaches autonomously to the front of the stairs around multiple obstacles. • We develop the double scales normal and selection (DSNS) algorithm to identify stair from sparse point clouds. • We develop the multi-plane joint recognition (MPJR) algorithm to estimate the structural parameter. • We propose the sliding window multi-round voting mechanism (SWMRVM) algorithm to optimize the stair position from recognition. [ABSTRACT FROM AUTHOR]

Localization is a self-position estimation problem and is one of the most critical research areas in autonomous mobile robots. This study presents novel solutions to two significant practical challenges in localization. The initial challenge pertains to the lack of distinct features within the environment, while the second involves the imperfectness of the map. Many studies are based on Extended Kalman Filter (EKF) and they need specific features from the environment for localization. The edges and corners are the popular natural feature types to be used in grid maps. The proposed study promises accurate and fast position tracking in the grid maps which have very few corners and edges. To achieve high performance in such a challenging map, we propose the virtual dynamic point landmark (VDPL) approach in this paper. VDPL does not need specific features such as edges and corners, and any part of the map can be used as a landmark. Since the real-world applications are based on imperfect maps, mostly generated by SLAM (Simultaneous Localization and Mapping) algorithm, the probabilistic distribution of the measurement model and measurement predictions are incorrect. In this study, the position errors that occur as a result of this incorrectness are alleviated by modifying the EKF algorithm. The modified equations of EKF for taking into account the map errors are clearly shown in the paper. The efficiency of the proposed solution is demonstrated in multiple simulations which are performed in randomly generated maps. Moreover, the benefits and real-time performance of the proposed approach are provided by real-world tests using an autonomous wheelchair platform. We believe that the methods developed in this study will improve the localization performance of autonomous robots that operate in challenging environments in terms of feature structure. [ABSTRACT FROM AUTHOR]

This paper focuses on the multiple radiation source search problems, where the mobile robot identifies the number and parameters of sources online while exploring an unknown environment. The radiation superposition and the limited observations improve the difficulty of estimation, and the exploration trajectory is also associated with estimation. A novel search strategy based on receding horizon planning is proposed, which includes the observation, estimation, and exploration modules. The observation module filters and records the radiation intensity for estimation. In the estimation module, an adaptive differential evolution algorithm is integrated into the peak suppression particle filter to avoid the local optimum. The multi-source radiation gain model is conceived to determine the observation position in the exploration module. The strategy trades off exploration of unknown areas and exploitation of known radiation fields. The results of simulations and experiments demonstrate that the proposed strategy can identify the parameters and quantities of all sources in multi-modal radiation fields. Furthermore, our strategy exhibits superior performance in searching for multi-radiation sources in unknown environments compared with the boustrophedon path and the Next-Best-View planner. • A robot search strategy is proposed and evaluated for unknown radiation environments. • Combine ADE optimization with the PSPF algorithm to improve estimation efficiency. • An exploration scheme is proposed to balance exploration and exploitation. [ABSTRACT FROM AUTHOR]

Collaboration of multiple mobile robots becomes important in situations where collaborative tasks are required. For this purpose, a method including obstacle detection based on collaborative path planning of multiple Autonomous Mobile Robots (AMRs) has been developed. This study ensures the usability of collaborative omnidirectional AMRs technologies in various fields. In the study, novel path planning and obstacle avoidance algorithms are developed for collaborative mobile robots with omnidirectional mobility. Essentially, these algorithms include motion planning performed by obstacle avoidance with two identical 3-wheel omnidirectional mobile robots (TWOMR). Numerical calculations of the collaborative algorithm have been performed after the kinematic calculations, and tested algorithms developed for the proposed model. As a result, it has been observed that the path planning and obstacle avoidance algorithms developed for collaborative omnidirectional AMRs successfully follow the Master robot in the most efficient trajectory without collision and it has been observed that the developed method works with high accuracy. [Display omitted] • The most efficient collision-free trajectory planning for collaborative mobile robots. • Path planning and obstacle avoidance algorithm at the safe following distance. • Path planning of collaborative autonomous omnidirectional mobile robots. • A novel method is used to realize avoidance motion for robots successfully. [ABSTRACT FROM AUTHOR]

This paper surveys the supportive technologies currently available for ground mobile robots used for autonomous mapping in agriculture. Unlike previous reviews, we describe state-of-the-art approaches and technologies aimed at extracting information from agricultural environments, not only for navigation purposes but especially for mapping and monitoring. The state-of-the-art platforms and sensors, the modern localization techniques, the navigation and path planning approaches, as well as the potentialities of artificial intelligence towards autonomous mapping in agriculture are analyzed. According to the findings of this review, many examples of recent mobile robots provide full navigation and autonomous mapping capability. Significant resources are currently devoted to this research area, in order to further improve mobile robot capabilities in this complex and challenging field. • We review hardware technologies for autonomous robotic mapping in agriculture. • Modern localization and mapping approaches for mobile robotics are discussed. • Path planning strategies for autonomous navigation in agriculture are analyzed. • The role of artificial intelligence for robotic mapping and monitoring is explored. • Future trends and challenges for robotic mapping in agriculture are highlighted. [ABSTRACT FROM AUTHOR]

Swarm robotics involves the study of the behavior of a set of robots in carrying out collective tasks, such as alignment, navigation and formation. During cooperative tasks execution, the communication among robots can contribute to successfully performing tasks through an efficient messages exchange. This paper proposes a communication strategy for swarm robots, the so-called Double-Wave Swarm, aiming at alignment and navigation tasks. The Double-Wave Swarm is an improvement of a prior Wave Swarm communication approach that uses the concept of wave propagation for message exchange between neighbors. Double-Wave Swarm provides better communication network connectivity when compared to the former approach. Experiments with the robot simulator CoppeliaSim (V-REP) validate the proposed communication and highlight its efficiency and robustness while running alignment and navigation tasks. Also, the Double-Wave Swarm proved to be superior during swarm formation navigation into environments with obstacles in different scenarios if compared with Wave Swarm. • DWS is an improvement on an earlier WS communication approach. • DWS increases the connectivity between robots when compared to WS. • Sharing information through DWS helps in locating and orienting swarm robots. • DWS is a robust and effective approach to in formation navigation of multi-robots. [ABSTRACT FROM AUTHOR]

Mobile robots with multi locomotion modes have excellent terrain adaptability. However, traditional multi-locomotion mobile robots are usually actuated by a large number of motors, making their structures heavy and bulky. As a result, the controls become complex, the load-to-mass ratio is low, and the energy consumption is high. Inspired by the bio-mechanism of worms, a novel tensegrity-based multi-locomotion mobile robot, named TJUBot, has been designed. It is actuated by only two motors, yet it has the potential to realize three locomotion modes: earthworm-like, inchworm-like, and tumbling locomotion. The design of these three locomotion modes has been implemented based on kinematic and dynamic models, and the driving law of the two motors under each locomotion mode has been established. Notably, the robot's locomotion has been analyzed under five different terrains. A laboratory prototype of TJUBot has been developed, and experiments demonstrate that the robot can adjust to five types of terrains using the three locomotion modes. For instance, on flat ground, it achieves a maximum velocity of 2.34 BL/min, and it can pass through confined spaces with a minimum height of 1.26 BH. Moreover, the robot can climb slopes with a maximum angle of 7°, overcome obstacles with a maximum height of 0.52 BH, and traverse gaps with a maximum width as 0.35 BL. Herein, BL and BH represent the body length and body height of the robot, respectively. In addition, TJUBot exhibits outstanding performance in terms of its load-to-mass ratio, which is measured at 5.56, and its low energy consumption of 0.69J/m, as observed in experiments. The promising results obtained from these experiments indicate that TJUBot holds significant potential for applications in multi-terrain environments. [Display omitted] • A novel tensegrity robot with three locomotion modes and two actuators is designed. • Multi-locomotion modes design based on kinematic and dynamic models is conducted. • Gait analysis of the multi-locomotion modes under typical terrains is carried out. • Experiments show that the robot has high load-to-mass ratio and low energy consumption. [ABSTRACT FROM AUTHOR]

Trajectory planning tasks for non-holonomic or collaborative systems are naturally modeled by state spaces with non-Euclidean metrics. However, existing proofs of convergence for sample-based motion planners only consider the setting of Euclidean state spaces. We resolve this issue by formulating a flexible framework and set of assumptions for which the widely-used PRM*, RRT, and RRT* algorithms remain asymptotically optimal in the non-Euclidean setting. The framework is compatible with collaborative trajectory planning: given a fleet of robotic systems that individually satisfy our assumptions, we show that the corresponding collaborative system again satisfies the assumptions and therefore has guaranteed convergence for the trajectory-finding methods. Our joint state space construction builds in a coupling parameter 1 ≤ p ≤ ∞ , which interpolates between a preference for minimizing total energy at one extreme and a preference for minimizing the travel time at the opposite extreme. We illustrate our theory with trajectory planning for simple coupled systems, fleets of Reeds–Shepp vehicles, and a highly non-Euclidean fractal space. [ABSTRACT FROM AUTHOR]

In recent years, the navigation capabilities of mobile robots in off-road environments have increased significantly, opening up new potential applications in a variety of settings. By accurately identifying different types of terrain in unstructured environments, safe automated navigation can be supported. However, to enable safe path planning and execution, the traversability costs of the terrain types need to be accurately estimated. Such estimations are often performed manually by experts who possess information about the environment and are familiar with the capabilities of the robotic system or using simplified experiments. In this paper, we present an automated pipeline for generating traversability costs that use recorded locomotion data from a realistic experiment and descriptive information on the terrain obtained from earth observation data. The main contribution is that the cost estimation for different terrain types is based on locomotion data obtained in realistic standardized experiments. Moreover, by repeating the experiments with different robot systems we are easily able to reflect the actual capabilities of the systems. Experiments were conducted in an alpine off-road environment to record locomotion data of four different robot systems and to investigate the performance and validity of the proposed pipeline. The recorded locomotion data for the different robots are publicly available at https://robonav.ist.tugraz.at/data/ • Pipeline to estimate traversability costs for robots using recorded locomotion data. • Interpolation of costs for uncovered terrain classes using order relations. • Realistic off-road locomotion datasets for four heterogeneous robots. • Provision of guidelines for robot-specific recording of locomotion data. [ABSTRACT FROM AUTHOR]

The Robot Operating System 2 (ROS 2) is rapidly impacting the intelligent machines sector — on space missions, large agriculture equipment, multi-robot fleets, and more. Its success derives from its focused design and improved capabilities targeting product-grade and modern robotic systems. Following ROS 2's example, the mobile robotics ecosystem has been fully redesigned based on the transformed needs of modern robots and is experiencing active development not seen since its inception. This paper comes from the desks of the key ROS Navigation maintainers to review and analyze the state of the art of robotics navigation in ROS 2. This includes new systems without parallel in ROS 1 or other similar mobile robotics frameworks. We discuss current research products and historically robust methods that provide differing behaviors and support for most every robot type. This survey consists of overviews, comparisons, and expert insights organized by the fundamental problems in the field. Some of these implementations have yet to be described in literature and many have not been benchmarked relative to others. We end by providing a glimpse into the future of the ROS 2 mobile robotics ecosystem. • ROS 2's Nav2 has a number of new algorithms and capabilities suitable for a large number of applications. • This survey analyzes ROS 2 algorithm's capabilities and benchmarks performance. • Explains systems provided to build robust autonomous navigation systems in dynamic environments. [ABSTRACT FROM AUTHOR]

In the last years, Multi-Robot Systems (MRS) have experienced considerable recognition due to various possible real-world applications. Multi-Robot Task Allocation (MRTA) is among the most interesting MRS problems. This problem concerns the situation when a set of given tasks must be performed by a team of mobile robots with the intention of optimizing an objective function (e.g., minimizing the mission time). This paper aims to present MRTA applications and categorizes methods into market-based, behavior-based, and optimization-based approaches. The paper focus on the latter and review several works in order to point out their advantages and limitations and to identify possible future research opportunities. Furthermore, a statistical analysis is provided to identify the most used methods and the evolution of the topic over the years. [ABSTRACT FROM AUTHOR]

"Smart cities" is a popular concept in modern urban development that demands innovative solutions to enhance various aspects of our lives. This paper introduces a novel application that aims to improve public road maintenance by utilizing a flying robot to repaint partially erased sections of the sidewalks' edges that are typically marked with black and white colors. The first contribution of this paper is the development of a fuzzy-logic-based stabilization system for an octocopter, which can serve as a liquids transporter and be equipped with a robot arm. The second contribution is the design of an embedded energy harvester for the flying robot, which optimizes the management of available power sources. Additionally, this project includes a complementary heuristic study that clarifies fundamental concepts related to a computer vision-based decision-making system. [ABSTRACT FROM AUTHOR]

Autonomous systems for monitoring and surveying are increasingly used in retail stores, since they improve the overall performance of the store and reduce the manpower cost. Moreover, an automated system improves the accuracy of collected data by avoiding human-related factors. This paper presents ROCKy, a mobile robot for data collection and surveying in a retail store that autonomously navigates and monitors store shelves based on real-time store heat maps; ROCKy is designed to automatically detect Shelf Out of Stock (SOOS) and Promotional Activities (PA) based on Deep Convolutional Neural Networks (DCNNs). The deep learning approach evaluates visual and textual content of an image simultaneously to classify and map SOOS and PA events during working hours. The proposed approach was applied and tested on several real scenarios, presenting a new public dataset with more than 14.000 annotated shelves images. Experimental results confirmed the effectiveness of the approach, showing high accuracy (up to 87%) in comparison with the existing state of the art SOOS and PA monitoring solutions, and a signification reduction of retail surveying time (45%). • ROCKy is a mobile robot for data collection and surveying in a retail store. • ROCKy detects Shelf Out of Stock and Promotional Activities based on Deep Learning. • The deep learning approach evaluates visual and textual content of an image. • The approach was applied on a new public dataset with annotated shelves images. • Experimental results confirmed the effectiveness of the approach. [ABSTRACT FROM AUTHOR]

This paper considers the motion planning problem for multiple tethered planar mobile robots. Each robot is attached to a fixed base by a flexible cable. Since the robots share a common workspace, the interactions amongst the robots, cables, and obstacles pose significant difficulties for planning. Previous works have studied the problem of detecting whether a target cable configuration is intersecting (or entangled). Here, we are interested in the motion planning problem: how to plan and coordinate the robot motions to realize a given non-intersecting target cable configuration. We identify four possible modes of motion, depending on whether (i) the robots move in straight lines or following their cable lines; (ii) the robots move sequentially or concurrently. We present an in-depth analysis of Straight/Concurrent, which is the most practically-interesting mode of motion. In particular, we propose algorithms that (a) detect whether a given target cable configuration is realizable by a Straight/Concurrent motion, and (b) return a valid coordinated motion plan. The algorithms are analyzed in detail and validated in simulations and in a hardware experiment. • Plan coordinated motions for tethered mobile robots, avoiding cable entanglement. • Detect realizability of a target cable configuration by Straight/Concurrent motion. • Guarantee to return a valid coordinated motion plan if there exists one. • Improve efficiency, reduce localization errors and enhance working area safety. • Demonstrate the capability of the proposed algorithms on hardware robotic system. [ABSTRACT FROM AUTHOR]

Emerging industrial applications involving mobile manipulation in the presence of humans is driving attention towards steerable wheeled mobile robots (SWMR), since these can perform arbitrary 2 D planar trajectories, providing a reasonable compromise between maneuverability (necessary for human avoiding algorithms) and effectiveness. Instantaneous center of rotation (ICR) based kinematic models and controllers are the most suited for such robots, as they assure the existence of a unique ICR point at all times. However, unsatisfactory behavior do exist in numerous applications requiring frequent changes in the sign of the angular velocity command. This is typically the case for robot heading control: moving the ICR point from one border of the 2 D ICR space to the other makes it pass by the robot geometric center, where only pure rotations are feasible. This behavior is not desirable and should be avoided. In this paper, we propose a novel complementary route ICR controller, where the ICR can go from one extreme to the other by means of border switching in one sample period. Thanks to this approach, fast response to the velocity commands is achieved with little steering motion. The new algorithm has been tested successfully in simulations and experiments, and is more time efficient with far more satisfactory behavior than the state-of-art direct route based controllers. These results have been also confirmed quantitatively, using a newly developed metric, the command fulfillment index (CFI). [ABSTRACT FROM AUTHOR]

In order to synthesize controllers for wheeled mobile robots (WMRs), some design techniques are usually based on the assumption that the set of kinematic constraints are fully satisfied. Nevertheless, when a WMR moves on a trajectory, phenomena such as slipping, skidding and deformability (also related to flexibility) can cause violation of kinematic constraints as well as system instability. Previous research has shown that to make the tracking error converge toward a small neighborhood containing the origin, in WMRs that moving at different speeds, it can be used an outer closed-loop scheme based on an auxiliary control law with aid of estimations of the slipping and skidding variations. But, although these previous works use slipping/skidding variations, the flexibility parameter is not taken into account to compute the auxiliary control law, making the outer closed-loop less robust for different flexibility values in the dynamic. The work reported here proposes a control scheme fully influenced by the flexibility parameter and whose robustness will be based on an auxiliary control law that uses a nonlinear function in terms of flexibility and slipping/skidding variations. The results obtained from experimental and simulations tests will show that the flexible auxiliary control law not only ensures that the error converges to a small neighborhood close to origin but also it is more insensitive to the speed increasing of the WMR. • Wheeled mobile robots become unstable with slipping, skidding, and flexibility. • Tracking error converges toward a neighborhood of the origin when an auxiliary control law is used. • Better robustness is guaranteed when the flexibility is included in the auxiliary control law. • Dynamic confined space of velocities can be used to synthesize a flexible version of the auxiliary control law. • The flexible auxiliary control law is more insensitive to the speed increasing. [ABSTRACT FROM AUTHOR]

When working in dynamic environment, traditional SLAM framework performs poorly due to interference from dynamic objects. By taking advantages of deep learning in object detection, a semantic simultaneous localization and mapping framework named Dynamic-SLAM is proposed, in order to solve the problem of SLAM in dynamic environment. First, based on the convolutional neural network, an SSD object detector which combines prior knowledge is constructed to detect dynamic objects in the newly detection thread at semantic level. Then, in view of low recall rate of the existing SSD object detection network, a missed detection compensation algorithm based on the speed invariance in adjacent frames is proposed, which greatly improves the recall rate of detection. Finally, a feature-based visual SLAM system is constructed, which processes the feature points of dynamic objects through a selective tracking algorithm in the tracking thread, to significantly reduce the error of pose estimation caused by incorrect matching. The recall rate of the system is increased from 82.3% to 99.8% compared with the original SSD network. Several experiments show that the localization accuracy of Dynamic-SLAM is higher than the state-of-the-art systems. The system successfully localizes and constructs an accurate environmental map in real-world dynamic environment by using a mobile robot. In sum, our experimental demonstrations verify that Dynamic-SLAM shows improved accuracy and robustness in robot localization and mapping comparing to the state-of-the-art SLAM system in dynamic environment. • An SSD object detector is constructed to detect dynamic objects with prior knowledge in the newly detection thread. • Missed detection compensation algorithm based on the speed invariance in adjacent frames is proposed. • Selection tracking algorithm is proposed to eliminate the dynamic objects and improve the robustness and accuracy of the system. • A feature-based Dynamic-SLAM system combined semantic information is constructed to realize the detection of dynamic environment in robot localization and mapping. [ABSTRACT FROM AUTHOR]

Novelty detection is a very useful function for detecting abnormal data in any application. An expectation-based novelty-detection approach has been introduced that learns the dynamic relationship model among normal data in order to predict the next expected data. Most novelty-detection systems use an offline approach with a fixed structure, a system type that has limitations when the data count in the environment is unknown. A new expectation-based novelty-detection system features an online recurrent neural network approach that learns the data by inserting new nodes or deleting unused nodes from its structure. Generally, to detect novelties, a global novelty threshold is defined to filter out all input data as novel whenever the prediction error of the network exceeds the threshold. However, because a neural network cannot learn to predict all classes of input data perfectly, using a global novelty threshold leads to the misclassification of the insufficiently learned normal data as novel. To overcome this problem, the novelty-detection system has been improved to learn local novelty thresholds alongside its learning to predict expectations. The proposed algorithm is applied to an online novelty detection using colour and depth data obtained from a Kinect sensor on a mobile robot. The performance of the expected novelty detector and its limitations during experiments are analysed and shown. Furthermore, colour and depth data as inputs into the novelty filter are separately analysed and their contributions on the overall novelty detection highlighted. In conclusion, the performance of the novelty filter could further be improved by applying a better feature-selection technique to extract more interesting features from high-dimensional input data. [ABSTRACT FROM AUTHOR]

Desert ants use the polarization of skylight and a combination of stride and ventral optic flow integration processes to track the nest and food positions when traveling, achieving outstanding performances. Navigation sensors such as global positioning systems and inertial measurement units still have disadvantages such as their low resolution and drift. Taking our inspiration from ants, we developed a 2-pixel celestial compass which computes the heading angle of a mobile robot in the ultraviolet range. The output signals obtained with this optical compass were investigated under various weather and ultraviolet conditions and compared with those obtained on a magnetometer in the vicinity of our laboratory. After being embedded on-board the robot, the sensor was first used to compensate for random yaw disturbances. We then used the compass to keep the Hexabot robot's heading angle constant in a straight forward walking task over a flat terrain while its walking movements were imposing yaw disturbances. Experiments performed under various meteorological conditions showed the occurrence of steady state heading angle errors ranging from 0. 3 ∘ (with a clear sky) to 2. 9 ∘ (under changeable sky conditions). The compass was also tested under canopies and showed a strong ability to determine the robot's heading while most of the sky was hidden by the foliage. Lastly, a waterproof, mono-pixel version of the sensor was designed and successfully tested in a preliminary underwater benchmark test. These results suggest this new optical compass shows great precision and reliability in a wide range of outdoor conditions, which makes it highly suitable for autonomous robotic outdoor navigation tasks. A celestial compass and a minimalistic optic flow sensor called M 2 APix (based on Michaelis–Menten Auto-adaptive Pixels) were therefore embedded on-board our latest insectoid robot called AntBot, to complete the previously mentioned ant-like homing navigation processes. First the robot was displaced manually and made to return to its starting-point on the basis of its absolute knowledge of the coordinates of this point. Lastly, AntBot was tested in fully autonomous navigation experiments, in which it explored its environment and then returned to base using the same sensory modes as those on which desert ants rely. AntBot produced robust, precise localization performances with a homing error as small as 0.7% of the entire trajectory. [ABSTRACT FROM AUTHOR]

Abstract As autonomous service robots become more affordable and thus available for the general public, there is a growing need for user-friendly interfaces to control these systems. Control interfaces typically get more complicated with increasing complexity of robotic tasks and environments. Traditional control modalities such as touch, speech or gesture are not necessarily suited for all users. While some users can make the effort to familiarize themselves with a robotic system, users with motor disabilities may not be capable of controlling such systems even though they need robotic assistance most. In this paper, we present a novel framework that allows these users to interact with a robotic service assistant in a closed-loop fashion, using only thoughts. The system is composed of several interacting components: a brain–computer interface (BCI) that uses non-invasive neuronal signal recording and co-adaptive deep learning, high-level task planning based on referring expressions, navigation and manipulation planning as well as environmental perception. We extensively evaluate the BCI in various tasks, determine the performance of the goal formulation user interface and investigate its intuitiveness in a user study. Furthermore, we demonstrate the applicability and robustness of the system in real-world scenarios, considering fetch-and-carry tasks, close human–robot interactions and in presence of unexpected changes. As our results show, the system is capable of adapting to frequent changes in the environment and reliably accomplishes given tasks within a reasonable amount of time. Combined with high-level task planning based on referring expressions and an autonomous robotic system, interesting new perspectives open up for non-invasive BCI-based human–robot interactions. Highlights • BCI-controlled autonomous robotic service assistant. • First online brain–computer-interface using deep learning. • Menu-driven language generation based on referring expressions. • Modular ROS-based mobile robot interaction. • Experimental evaluation with a real robot. [ABSTRACT FROM AUTHOR]

Mobile robots are essential tools for gathering knowledge of the environment and monitoring areas of interest as well as industrial assets. Informative Path Planning methodologies have been successfully applied making robots able to autonomously acquire information and explore unknown surroundings. Rapidly-exploring Information Gathering approaches have been validated in real-world applications, proving they are the way to go when aiming for Information Gathering tasks. In fact, RIG can plan paths for robots with several degrees of freedom and rapidly explore complex workspaces by using the state-of-the-art Voronoi-biased expansion. Nevertheless, it is an efficient solution when most of the area is unknown but its effectiveness decreases as the exploration/gathering evolves. This paper introduces an innovative informed expansion for IG tasks that combines the Kernel Density Estimation technique and a rejection sampling algorithm. By learning online the distribution of the acquired information (i.e., the discovered map), the proposed methodology generates samples in the unexplored regions of the workspace, and thus steers the tree toward the most promising areas. Realistic simulations and an experimental campaign, conducted in the underwater robotics domain, provide a proof-of-concept validation for the developed informed expansion methodology and demonstrate that it enhances the performance of the RIG algorithm. • Informed sampling methodology for enhancing sampling-based IG algorithm performance. • Informed expansion for biasing RIG expansion toward unexplored areas. • KDE technique for learning online the distribution of the acquired data. • Single-stage planning paradigm for exploration tasks that can run on compact robots. • Real-world experiments conducted in the context of underwater robotics. [ABSTRACT FROM AUTHOR]

This paper focuses on the mobile robot path planning problem of optimizing the performance metrics of bidirectional A* algorithm in randomized two-dimensional map environments. An algorithm called direction constraints adaptive extended bidirectional A* (DCAE-BA*), which is an improvement of the traditional target dynamic bidirectional A* algorithm (TTD-BA*), is proposed to improve the performance metrics of the algorithm. Regarding the improvement, we propose the adaptive extension method and the direction-constrained optimal node extension method (DCONE). Simulation experiments were conducted for DCAE-BA*, TTD-BA* and traditional A* algorithm (A*) in a large number of random two-dimensional map environments. The simulation experimental scenarios consider four types of start and end point relative directions and three obstacle proportions to objectively and comprehensively evaluate the performance of the proposed algorithms. The results show that different scenarios have a significant impact on the algorithm performance metrics. Finally, the overall performance of the proposed algorithm is evaluated with a large number of experiments in "random" scenarios, and the results show that DCAE-BA* obtains significantly better search time for all three obstacle proportions, and better path length and number of expanded nodes for 10% and 25% obstacle proportions. The effectiveness of the proposed DCAE-BA* algorithm is demonstrated, which provides an essential reference for the path planning of mobile robots in a random 2D map environment. • DCAE-BA* is improved by adaptive extension and direction-constrained optimal node extension (DCONE). • The Start-End Dir and obstacle proportions have a significant impact on the algorithm metrics. • Overall, the DCAE-BA* has the highest computational efficiency for all three types of obstacle proportion. • DCAE-BA* optimizes the path length in the "diagonal" scenario most significantly. • As the proportion of obstacles increases, the metric optimization effect decreases. [ABSTRACT FROM AUTHOR]

This work addresses collision avoidance in the formation control of a group of mobile robots with first-order dynamics perturbed by lateral and longitudinal slipping parameters. A Generalized Proportional–Integral Observer (GPIO) is designed to estimate these perturbations. Then, an Active Disturbance Rejection Control (ADRC) is proposed to solve the well-known formation control avoiding collisions among the agents. The control strategy only depends on the agents' position measurements. On the other hand, Continuous Repulsive Vector Fields (C-RVFs) are developed to avoid collisions among the agents. For this purpose, a parameter depending on the inter-robot distance is developed to scale the RVFs properly. By proposing C-RVFs, the chattering is eliminated when using Discontinuous RVFs (D-RVFs). Numerical simulations and real-time experiments illustrate the agents' performance when they are at risk of collision. • Solve the problem of collision avoidance and formation in a multi-agent system. • The control design only depends on the agents' position measurements. • By proposing a smooth function, the RVFs are continuous functions. • It is proven that a surface is repulsive when the agents are at risk of collision. [ABSTRACT FROM AUTHOR]

Learning from demonstration (LfD) is an intuitive strategy for transferring human motion skills to robots in an agile and adaptable manner. The major goal of LfD is to identify significant movement primitives (MPs) from human demonstrations and then recompose those intrinsic primitives to adapt to a variety of new situations. However, maintaining the simplicity of MPs representation while guaranteeing their adaptability is not an easy undertaking. To achieve these two goals, two approaches are possible: (1) learning models that can capture and utilize the inherent patterns and main characteristics of the human demonstrations, and (2) dynamical systems that can respond to perturbations online without requiring to re-plan the entire trajectory. In this paper, we present a novel and efficient model that combines these two benefits to formulate MPs using a fuzzy dynamical system (Fuzzy-DS), which enables robots to adaptively alter the learned motion skills to meet various additional constraints in the process of performing tasks. Due to the joint use of a fuzzy inference system and a dynamic system, Fuzzy-DS is well-suited to human inputs and intuitive fuzzy rules, resulting in a computationally efficient model. To verify the effectiveness of the proposed method, experiments have been designed where the robot learned a plant pruning task and a pick-and-place task, subsequently, it can replicate and generalize these tasks to novel situations. [ABSTRACT FROM AUTHOR]

Quadruped robots can mimic animal locomotion mode and have great potential usage in unstructured environments. However, as mobile platforms, quadruped robots often lack manipulation capabilities. In this project, we equipped the quadruped robot SDU-ADog with a torque-controlled 6-DOF arm. A novel control framework which combines virtual model control (VMC) and prioritized whole-body control (WBC) for the whole system is proposed in this paper. VMC finds optimal target ground reaction forces while compensating the arm's inertia, and then makes the robot compliant to external disturbance. Prioritized WBC deals with multiple tasks in an optimal fashion and achieves efficiency and robustness of robot's locomotion and manipulation. The effectiveness of our framework has been evaluated through a set of robot dynamic simulations conducted in Webots. The robot can finish balance maintaining with moving arm, fixed point tracking while trotting, and locomotion over different obstacles with an end-point task. • We devise a control framework for legged mobile manipulators which considers the full kinematics and dynamics model of the robot. • We stabilize the robot's CoM position and orientation by combining VMC and WBC. • We validate the method's robustness by simulations of fixed-point tracking while trotting over obstacles. • The robustness is further validated by experiments on our robot. The results show that our control frame work is valid and easy to transfer from simulation to reality. [ABSTRACT FROM AUTHOR]

This study investigates operability and acceptability issues in the teleoperation of robots. Prior studies have proposed efficient approaches to increase human perceptual ability and robot autonomy but with reduced operability and acceptance. We propose a novel teleoperation method that overcomes the weaknesses of existing approaches while inheriting their strengths. The key feature of our method is switching the teleoperated robot world from real to virtual. The user study results showed that the proposed method offered an improved user experience compared to the conventional methods, while task efficiency was equivalent in all methods. The contributions of this paper include the proposal of the teleoperation method by seamless switching between real and virtual space, the proposal of an image transformation method and visual effect to achieve seamless switching, and verification of the practicality of the proposed system through experiments on actual mobile robots. • Illusory control improved the operability and acceptability of the robot system. • An image transformation using neural networks for seamless transitions. • A visual effect that amplifies the sense of speed for seamless transitions. [ABSTRACT FROM AUTHOR]

Abstract Q-learning, a type of reinforcement learning, has gained increasing popularity in autonomous mobile robot path planning recently, due to its self-learning ability without requiring a priori model of the environment. Yet, despite such advantage, Q-learning exhibits slow convergence to the optimal solution. In order to address this limitation, the concept of partially guided Q-learning is introduced wherein, the flower pollination algorithm (FPA) is utilized to improve the initialization of Q-learning. Experimental evaluation of the proposed improved Q-learning under the challenging environment with a different layout of obstacles shows that the convergence of Q-learning can be accelerated when Q-values are initialized appropriately using the FPA. Additionally, the effectiveness of the proposed algorithm is validated in a real-world experiment using a three-wheeled mobile robot. Highlights • We propose an improved Q-learning to solve path planning of a mobile robot. • The flower pollination algorithm is used to initialize the Q-table prior to the implementation of Q-learning. • Its effectiveness is tested in solving the optimal path in different test cases. • Performance comparison with classical Q-learning and other modified Q-learning is made. • The proposed model shows improvement in terms of computational time than others. [ABSTRACT FROM AUTHOR]

Abstract Robots operating in populated environments, such as hospitals, office environments or airports, encounter a large variety of people with some of them having an advanced need for cautious interaction because of their advanced age or motion impairments. To provide appropriate assistance and support robot helpers require the ability to recognize people and their potential requirements. In this article, we present a people detection framework that distinguishes people according to the mobility aids they use. Our framework uses a deep convolutional neural network for detecting people in image data. For human-aware robots it is necessary to know where people are in a 3D world reference frame instead of only locating them in a 2D image, therefore we add a 3D centroid regression output to the network to predict the Cartesian position of people. We further use a probabilistic class, position and velocity tracker to account for false detections and occlusions. Our framework comes in two variants: The depth only variant targets high privacy demands, while the RGB only framework provides improved detection performance for non-critical applications. Both variants do not require additional geometric information about the environment. We demonstrate our approach using a dedicated dataset acquired with the support of a mobile robotic platform. The dataset contains five classes: pedestrian, person in wheelchair, pedestrian pushing a person in a wheelchair, person using crutches and person using a walking frame. Our framework achieves an mAP of 0.87 for RGB and 0.79 for depth images at a detection distance threshold of 0.5 m on our dataset, with a runtime of 53 ms per image. The annotated dataset is publicly available and our framework is made open source as a ROS people detector. Highlights • Deep learning-based framework for 3D people detection. • Perception of people according to their mobility aids. • Flexible with respect to the employed sensor modality: RGB or depth. • Probabilistic position, velocity and class estimation module enhances detector. • Enables service robots to assist people according to their impairments. [ABSTRACT FROM AUTHOR]

Abstract Autonomous navigation of mobile robots is often based on information from a variety of heterogeneous sensors; hence, extrinsic sensor calibration is a fundamental step in the fusion of such information. In this paper, we address the problem of extrinsic calibration of a radar–LiDAR–camera sensor system. This problem is primarily challenging due to sparse informativeness of radar measurements. Namely, radars cannot extract rich structural information about the environment, while their lack of elevation resolution, that is nevertheless accompanied by substantial elevation field of view, introduces uncertainty in the origin of the measurements. We propose a novel calibration method which involves a special target design and two-step optimization procedure to solve the aforementioned challenges. First step of the optimization is minimization of a reprojection error based on an introduced point–circle geometric constraint. Since the first step is not able to provide reliable estimates of all the six extrinsic parameters, we introduce a second step to refine the subset of parameters with high uncertainty. We exploit a pattern discovered in the radar cross section estimation that is correlated to the missing elevation angle. Additionally, we carry out identifiability analysis based on the Fisher Information Matrix to show minimal requirements on the dataset and to verify the method through simulations. We test the calibration method on a variety of sensor configurations and address the problem of radar vertical misalignment. In the end, we show via extensive experiment analysis that the proposed method is able to reliably estimate all the six parameters of the extrinsic calibration. Highlights • Extrinsic radar–camera–LiDAR calibration estimated accurately in all 6DoF. • Radar's missing elevation angle compensated with radar cross section measurements. • Method is suitable for radar vertical misalignment detection. • Identifiability analysis confirms chosen transform parametrization. • Identifiability analysis provides minimal requirements on the dataset. [ABSTRACT FROM AUTHOR]

Abstract Accurate localization is an essential technology for flexible automation. Industrial applications require mobile platforms to be precisely localized in complex environments, often subject to continuous changes and reconfiguration. Most of the approaches use precomputed maps both for localization and for interfacing robots with workers and operators. This results in increased deployment time and costs as mapping experts are required to setup the robotic systems in factory facilities. Moreover, such maps need to be updated whenever significant changes in the environment occur in order to be usable within commanding tools. To overcome those limitations, in this work we present a robust and highly accurate method for long-term LiDAR-based indoor localization that uses CAD-based architectural floor plans. The system leverages a combination of graph-based mapping techniques and Bayes filtering to maintain a sparse and up-to-date globally consistent map that represents the latest configuration of the environment. This map is aligned to the CAD drawing using prior constraints and is exploited for relative localization, thus allowing the robot to estimate its current pose with respect to the global reference frame of the floor plan. Furthermore, the map helps in limiting the disturbances caused by structures and clutter not represented in the drawing. Several long-term experiments in changing real-world environments show that our system outperforms common state-of-the-art localization methods in terms of accuracy and robustness while remaining memory and computationally efficient. Highlights • Build a pose graph online using trajectory priors to align it to the floor plan. • Switch to pure localization whenever the environment is sufficiently mapped. • Estimate the robot pose using relative localization with respect to the pose graph. • Maintain an up-to-date pose graph in changing environments using Bayes filtering. • Bound memory consumption and runtime to enable long-term operation. [ABSTRACT FROM AUTHOR]

Abstract The problem of object localization and recognition on autonomous mobile robots is still an active topic. In this context, we tackle the problem of learning a model of visual saliency directly on a robot. This model, learned and improved on-the-fly during the robot's exploration provides an efficient tool for localizing relevant objects within their environment. The proposed approach includes two intertwined components. On the one hand, we describe a method for learning and incrementally updating a model of visual saliency from a depth-based object detector. This model of saliency can also be exploited to produce bounding box proposals around objects of interest. On the other hand, we investigate an autonomous exploration technique to efficiently learn such a saliency model. The proposed exploration, called Reinforcement Learning-Intelligent Adaptive Curiosity (RL-IAC) is able to drive the robot's exploration so that samples selected by the robot are likely to improve the current model of saliency. We then demonstrate that such a saliency model learned directly on a robot outperforms several state-of-the-art saliency techniques, and that RL-IAC can drastically decrease the required time for learning a reliable saliency model. [ABSTRACT FROM AUTHOR]

Abstract When applied in some harsh environments (e.g. in poisonous atmosphere or underwater), odor source localization robots are able to perform better than animals without being hurt. During the past three decades, robotic odor source localization has become a popular research field with various algorithms being proposed. These algorithms can be roughly divided into four categories: gradient-based algorithms, bio-inspired algorithms, multi-robot algorithms and probabilistic and map-based algorithms. In this paper, we present a literature review of these four categories and discuss their pros and cons. We also discuss the current trends and some future challenges according to some research papers published in recent years. [ABSTRACT FROM AUTHOR]

Abstract This article proposes a method for sensor fusion between odometers, gyroscope, accelerometer, magnetometer and visual landmark localization system. The method is designed for estimation of all 6 degrees of freedom (both translation and attitude) of a wheeled robot moving in uneven terrain. The fusion method is based on continuous estimation of the mean square error of each estimated value and allows different sampling rates of each sensor. Due to the simple implementation, it is suitable for real-time processing in the low-cost hardware. In order to evaluate the precision of the estimated position, stochastical models of sensors (with parameters matching real hardware sensors) were used and random trajectories were simulated. The virtual experiments showed that the method is resistant to the failure of any sensor except the odometers; however, each sensor provides improvement in the resultant precision. Highlights • Article proposes new sensor fusion method combining variety of sensors' readings. • Method utilizes inertial sensors, landmarks, odometers and magnetometer. • The method is suitable for estimating the position of a wheeled vehicle. • The simplicity of the method allows its implementation into low-cost hardware. [ABSTRACT FROM AUTHOR]