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Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Safety is the very necessary issue that must be considered during human-robot collaboration in the same workspace or area. Methods: In this manuscript, a nonlinear autoregressive model with an exog-enous inputs neural network (NARXNN) is developed for the detection of collisions between a manipulator and human. The design of the NARXNN depends on the dynamics of the manipulator's joints and considers only the signals of the position sensors that are intrinsic to the manipulator's joints. Therefore, this network could be applied and used with any conventional robot. The data used for training the designed NARXNN are generated by two experiments considering the sinusoidal joint motion of the manipulator. The first experiment is executed using a free-of-contact motion, whereas in the second experiment, random collisions by human hands are performed with the robot. The training process of the NARXNN is carried out using the Levenberg–Marquardt algorithm in MATLAB. The evaluation and the effectiveness (%) of the developed method are investigated taking into account different data and conditions from the used data for training. The experiments are executed using the KUKA LWR IV manipulator. Results: The results prove that the trained method is efficient in estimating the external joint torque and in correctly detecting the collisions. Conclusions: Eventually, a comparison is presented between the proposed NARXNN and the other NN architectures presented in our previous work. [ABSTRACT FROM AUTHOR]

One application of counter-cryptanalysis is detecting whether a message block is involved in a collision attack, such as the detection of MD5 and SHA-1. Stevens and Shumow speeded up the detection of SHA-1 by introducing unavoidable conditions in message blocks. They left a challenge: how to determine unavoidable conditions for MD5. Later, Shen et al. found that the unavoidable conditions of MD5 were the sufficient conditions located in the last round of differential paths. In this paper, we made further work. We discover sufficient conditions in the second round that can also be used as unavoidable conditions. With additional sufficient conditions, we subdivide three sets and distinguish seven more classes. As a result, compared with Shen's collision detection algorithm, our improved algorithm reduces the collision detection cost by 8.18%. Finally, we find that they do exist in the differential paths constructed by the automatic tool "HashClash". [ABSTRACT FROM AUTHOR]

Copyright of Transactions of Nanjing University of Aeronautics & Astronautics is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel tool orientation optimisation algorithm is proposed for 5-axis NC machining with a short ball-end cutter. It can generate collision-free and smooth tool orientations along with a safe and shortest tool length (SSTL). The use of shorter cutters without collision is a key advantage of 5-axis machining because the magnitude of tool deflection and the stability of cutting process are greatly affected by the slenderness ratio of the cutter. Existing methods can calculate the SSTL in the NC simulation process. However, the SSTL is essentially determined by the tool orientations and should be considered in the process of tool path generation. To overcome this limitation, a new tool orientation optimisation algorithm is proposed. The SSTL is determined by optimising the tool orientations under the constraints of global collision avoidance and tool orientation smoothness. The algorithm first computes the global accessibility cone and the SSTL along each accessible tool orientation. Then the tool orientations are optimised based on the discrete dynamic programming with the SSTL along the whole tool path being the optimisation objective. Finally, the tool path is generated by globally smoothing the tool orientations. Computational examples and cutting experiment are given to illustrate the validity and efficiency of the proposed algorithm. [ABSTRACT FROM AUTHOR]

A graphics process unit (GPU) based approach that generates collision-free and orientation-smooth tool paths for five-axis NC finishing machining of complicated shapes is presented. A new GPU-based method is proposed to compute accessibility cones of cutter location (CL) points for a ball-end cutter and tool orientations are then optimised in the accessibility cones. Three steps in the approach are GPU-based accessibility computation, feasibility map and orientation optimisation. Unlike the existing visibility concept, the diameters of both tools and tool-holders are taken into consideration and the actual accessibility cone is computed directly and efficiently based on occlusion query functionality of the graphics hardware. Next, a feasibility map is used to select feasible orientations due to the limits of collision avoidance and the machine tool. Finally, tool orientations are globally optimised to generate an orientation-smooth tool path. The proposed algorithms allow an acceptable computing time and hardware requirement to generate collision-free and orientation-smooth tool paths for complicated shapes. Examples show the efficiency of computing accessibility cones. The finishing tool paths for machining an impeller are generated as examples and cutting experiments confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

Diffusion-based molecular communication (DMC) with interacting carrier molecules allows exploring a variety of new communication paradigms. Simulating these interactions on a network scale is however hard from an analytic point of view, and continuous detection of which couples of particles may interact is a computationally expensive task. This work proposes different algorithms that allow detecting which particles are interacting. Hierarchical grid based approaches are explored and designed to maximally exploit the parallelism offered by multiple-graphics processing units (multi-GPU) systems. An implementation of the proposed algorithm is compared to some of our previous work in this domain and to a state-of-the-art collision detection library and nanosimulator. Performance tests indicate a speedup of up to a factor 100 compared to the collision detection algorithm implemented in the nanosimulator, and a factor 77 relative to the collision detection library. [ABSTRACT FROM AUTHOR]

Nowadays there are many real-time applications such as robotic motion, driver-less vehicle, intelligent target shooter(bullets and missiles), traffic routing in which human intervention is avoided. This paper proposes an exciting and generalized approach for intelligent target hitting in an obstructed path using physical body animation and genetic algorithm. This approach uses the concepts of the genetic algorithm to train the object for finding the right path to target and concepts of physical body animation to provide the motion and to react as per the collision with obstacles. Physical body animation provides a very natural feel of a real-time environment as we deal with all the external natural forces such as gravity, wind resistance the object and so on. Proposed approach deals not only with the static target but also deals with the dynamic target during the simulation. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a novel, high-performance, graphical processing unit-based algorithm for efficiently solving two-dimensional linear programs in batches. The domain of two-dimensional linear programs is particularly useful due to the prevalence of relevant geometric problems. Batch linear programming refers to solving numerous different linear programs within one operation. By solving many linear programs simultaneously and distributing workload evenly across threads, graphical processing unit utilization can be maximized. Speedups of over 22 times and 63 times are obtained against state-of-the-art graphics processing unit and CPU linear program solvers, respectively. Highlights • Novel algorithm based on incremental linear programming, optimized for GPU. • Distributes computational workload evenly between threads in blocks. • Up to 22 times faster against a state-of-the-art GPU linear program solver. • Up to 63 times faster against a state-of-the-art CPU linear program solver. [ABSTRACT FROM AUTHOR]

The signed distance function (or oriented distance function) of a set in a metric space determines the distance of a given point from the boundary of the set, with the sign determined by whether the point is in the set or in its complement. The knowledge of signed distance functions is a very valuable information in various fields of applied mathematics such as collision detection, binary classification, shape analysis, fuzzy numbers ranking and level set methods. One distinguished feature of the signed distance function is that it reflects the geometric structure of the set much better than the distance function does. We explore many interesting analytical properties of signed distance functions and use them to construct convex functions with not convex subdifferential domains. Several examples are presented to illustrate most of these fine properties. [ABSTRACT FROM AUTHOR]

Abstract An EAST Articulated Maintenance Arm (EAMA), upgraded based on an articulated inspection arm (AIA), which was successfully operated in Tore Supra in 2008, was developed for the purpose of the inspection and maintenance of damaged internal components during plasma discharges without breaking the East Advanced Superconducting Tokamak (EAST) ultra-high vacuum condition. However, the coupling structure and high redundancy of the EAMA, due to the requirement of coverage ratio and the limitation of the EAST environment, produces a limited accuracy in positioning control. Therefore, the optimal design of the geometric parameters plays a vital role in the EAMA's performance. In this paper, the main characteristics of the EAMA system are investigated to formulate the optimization into a multi-objective problem. Furthermore, an approach based on the Monte Carlo method, integrated with a dedicated collision detection algorithm in the EAST environment, is elaborated on, which is utilized to calculate the collision-free workspace of the EAMA. With the knowledge of the workspace, the coverage ratio is obtained by a progressive meshing technique. Finally, several groups of geometric parameters are sampled to calculate the corresponding value of the objective functions, and the optimized combination of the geometric parameters is obtained by comparing the results. [ABSTRACT FROM AUTHOR]

Massive multiple-input multiple-output (MIMO) systems, where base stations (BSs) are equipped with hundreds of antennas, are an attractive way to handle the rapid growth of data traffic. As the number of user equipments (UEs) increases, the initial access and handover in contemporary networks will be flooded by user collisions. In this paper, a random access protocol is proposed that resolves collisions and performs timing estimation by simply utilizing the large number of antennas envisioned in massive MIMO networks. UEs entering the network perform spreading in both time and frequency domains, and their timing offsets are estimated at the BS in closed form using a subspace decomposition approach. This information is used to compute channel estimates that are subsequently employed by the BS to communicate with the detected UEs. The favorable propagation conditions of massive MIMO suppress interference among UEs, whereas the inherent timing misalignments improve the detection capabilities of the protocol. Numerical results are used to validate the performance of the proposed procedure in massive MIMO networks, under uncorrelated and correlated fading channels. With $2.5 \times 10^{3}$ UEs that may simultaneously become active with probability 1%, a total of 16 frequency–time codes, and 100 antennas, a given UE is detected with probability 75%, and the accuracy of its timing estimate is on the order of few samples. [ABSTRACT FROM AUTHOR]

The 21st century is defined as the era of technological development. With drastic increase in population, automation is becoming the need of the hour in order to make life more comfortable and easy. Due to the advancement and development in the field of automation and embedded system, the notion of smart car has become very popular. Smart cars are modernizing trends in the traditional automobile industry. Companies across the globe have been investing a huge amount of resources on the production and design of smart cars. Every technological development needs to overcome certain obstacles, and hence, in this paper, a design of a collision detection system for smart car using light fidelity (Li-Fi) and ultrasonic sensor on the Arduino platform is proposed. This design consists of an ultrasonic sensor, an Arduino processor, and a Li-Fi circuit. The ultrasonic is used for measurement of distance between vehicles, and Arduino processes the data and makes decisions accordingly. Data transmission between vehicles is ensued using a Li-Fi transmitter circuit and a Li-Fi receiver circuit. The transmitter circuit is mounted on the tail lights of the leading car and the receiver circuit is mounted on the front side of the car that follows. Using visible light communication, the transmitter circuit transmits the calculated speed and the information is received by the receiver circuit of the second car. On the basis of the information received, the speed of the second car is changed in order to avoid collision. In this paper, a system that can detect and thus avoid collision between vehicles and prevent accidents is proposed and studied. [ABSTRACT FROM AUTHOR]

We present a novel approach to using Bounding Volume Hierarchies (BVHs) for collision detection of volumetric meshes for digital prototyping based on accurate simulation. In general, volumetric meshes contain more primitives than surface meshes, which in turn means larger BVHs. To manage these larger BVHs, we propose an algorithm for splitting meshes into smaller chunks with a limited-size BVH each. Limited-height BVHs make guided, all-pairs testing of two chunked meshes well-suited for GPU implementation. This is because the dynamically generated work during BVH traversal becomes bounded. Chunking is simple to implement compared to dynamic load balancing methods and can result in an overall two orders of magnitude speedup on GPUs. This indicates that dynamic load balancing may not be a well suited scheme for the GPU. The overall application timings showed that data transfers were not the bottleneck. Instead, the conversion to and from OpenCL friendly data structures was causing serious performance impediments. Still, a simple OpenMP acceleration of the conversion allowed the GPU solution to beat the CPU solution by 20 percent. We demonstrate our results using rigid and deformable body scenes of varying complexities on a variety of GPUs. [ABSTRACT FROM AUTHOR]

Distracted driving is a growing problem that leads to many deaths in the world. Causes of distraction are speeding, eating, texting, drinking, answering phone calls, reading billboards, adjusting vehicle equipment, and attending to passengers. These deaths could be prevented by a cognitive agent-based collision detection and auto collision avoidance (CABCD-CA) system. In order to reduce accidents caused by distraction, this paper presents a (CABCD-CA) system. The research is two-fold, first designed as a fuzzy inference system, which takes distraction, speed, and distance as input and produces the chances of an accident using fuzzy logic. Then, different probabilities of accidents are provided to the cognitive agent, which, in turn, performs appropriate collision avoidance manoeuvrers. The agent-based simulation of the CABCD-CA system is validated using VOMAS agent approach. Extensive testing has proved the success of the proposed system for avoiding collisions due to the distraction of the human driver. [ABSTRACT FROM AUTHOR]

Abstract Physical human–robots cooperation is desirable for future robotic applications while poses the fundamental problem of how to ensure personnel safety. Dynamic impact and quasi-static clamping are two common scenarios that could potentially lead to human injuries and should be detected as sensitive as possible. Combining insights from of the extended state observer (ESO) and robot dynamics, an efficient collision detection method based on only proprioceptive sensors (encoders and torque sensors) is introduced. In addition to detection, the proposed method provides magnitude and direction information of force signals covering a general class of actuator faults. Simulations give a quantitative comparison between the proposed scheme and the widely used method based on general momenta. Experimental results with a 7-DOF collaborative robot further illustrate the effectiveness of the proposed method. The collisions occurring in the form of dynamic impact as well as quasi-static clamping are verified. Highlights • A new collision detection strategy based on the extended state observer is presented for flexible joint robots. • Both the dynamic and quasi-static impacts in human–robot interaction can be detected and identified with this method. • The proposed observer can give accurate estimation of contact force with limited error. • This method has been extensively tested with a 7-DOF collaborative robot. It proves to be effective in limiting the impact forces far below the level set by human–robot interaction standards. [ABSTRACT FROM AUTHOR]

The integrated transmission system of military armored vehicle is a kind of complex transmission system, which includes power transfer, power shifting, steering and manipulation. The transmission system is the key component for realizing the overall system functions of military armored vehicle. The rationality of structure design and feasibility of assembly are the precondition for implementation of function of transmission system, which are inseparable with the step of assembly design. In order to provide a prediction for the two designs in design stage of integrated transmission system, a pragmatic system to support virtual assembly for military armored vehicle integrated transmission system is established in this paper. In the virtual assembly system, the reconstruction method of assembly features of transmission system is investigated to implement the models transform from CAD system to virtual assembly. The planning method of virtual assembly sequence is proposed, which is based on the combination of cut set method of graph theory with interactive planning in virtual environment. The sequence planning method applied the pre-identified strategy for the subassembly to improve combination explosion problem of cut set method and reduce the blindness and uncertainty caused by the direct using of interactive planning. The mixed collision checking method based on the geometrical features is presented, which can meet the real-time performance and accuracy of virtual assembly. The parts accurate positioning method based on the reconstruction of assembly features elements is proposed, which can be used for the accurate positioning in virtual environment. With these technologies and methods, the system has been successfully applied to the virtual assembly for a certain type of integrated transmission system of military armored vehicle. [ABSTRACT FROM AUTHOR]

The paper proposes a novel method for detecting indicators of image forgery by locating grid alignment abnormalities in JPEG compressed image bitmaps. The method evaluates multiple grid positions with respect to a fitting function, and areas of lower contribution are identified as grid discontinuities and possibly tampered areas. An image segmentation step is introduced to differentiate between discontinuities produced by tampering and those that are attributed to image content, making the output maps easier to interpret by suppressing non-relevant activations. Our evaluations, on both synthetically produced datasets and real world tampering cases against seven methods from the literature, highlight the effectiveness of the proposed method in its ability to produce output maps that are clear and readable, and which can achieve successful detections on cases where other algorithms fail. [ABSTRACT FROM AUTHOR]

In order to solve the problem of lack of immersion in the MOOC curriculum, through research on key technologies, a MOOC teaching interactive system based on virtual reality was constructed to improve it. Through the decomposition of complex objects or the addition of blank sub-objects, the system built corresponding collision detectors to achieve more realistic collision detection effects. The immersive and interactive nature of the virtual user in the virtual scene was enhanced. The results showed that the system used the immersive, interactive and constructive sense of virtual reality to build people's interest in learning. Therefore, the MOOC teaching interactive system based on virtual reality has a good sense of immersion, interaction and conceivability. [ABSTRACT FROM AUTHOR]

Voxelization is a crucial process for many computer graphics applications such as collision detection, rendering of translucent objects, and global illumination. However, in some situations, although the mesh looks good, the voxelization resultmay be undesirable. In this paper,we describe a novel voxelizationmethod that uses the graphics processing unit for surface voxelization. Our improvements on the voxelization algorithm can address a problem of state-of-the-art voxelization, which cannot deal with thin parts of the mesh object.We improve the quality of voxelization on both normal mediation and surface correction. Furthermore, we investigate our voxelizationmethods on indirect illumination, showing the improvement on the quality of real-time rendering. [ABSTRACT FROM AUTHOR]

Abstract: Bounding volume hierarchy (BVH) has been widely adopted as the acceleration structure in broad‐phase collision detection. Previous state‐of‐the‐art BVH‐based collision detection approaches exploited the spatio‐temporal coherence of simulations by maintaining a bounding volume test tree (BVTT) front. A major drawback of these algorithms is that large deformations in the scenes decrease culling efficiency and slow down collision queries. Moreover, for front‐based methods, the inefficient caching on GPU caused by the arbitrary layout of BVH and BVTT front nodes becomes a critical performance issue. We present a fast and robust BVH‐based collision detection scheme on GPU that addresses the above problems by ordering and restructuring BVHs and BVTT fronts. Our techniques are based on the use of histogram sort and an auxiliary structure BVTT front log, through which we analyze the dynamic status of BVTT front and BVH quality. Our approach efficiently handles inter‐ and intra‐object collisions and performs especially well in simulations where there is considerable spatio‐temporal coherence. The benchmark results demonstrate that our approach is significantly faster than the previous BVH‐based method, and also outperforms other state‐of‐the‐art spatial subdivision schemes in terms of speed. [ABSTRACT FROM AUTHOR]

In order to solve the collision in the detection process of robotic ultrasonic automatic detection system, the ultrasonic detection system is divided into collision and stationary bodies, and the collision detection algorithm based on the distance field is introduced. Based on the kinematics equation of robot, the collision detection is carried out in the virtual environment of the ultrasonic automatic detection system, and the anti-collision detection of the system during the detection process of magnesium alloy shell is realized. The variation law of the shortest distance between the stationary body and the collision body is analyzed by comparing the detected results of different scanning parameters, and the ultrasonic detection process optimization of magnesium alloy shell is realized. The experimental results show that the improved algorithm can improve the efficiency of collision detection by 80. 62%, which can meet the requirements of collision efficiency during ultrasonic testing of magnesium alloy shell and guarantee the same precision as the traditional distance field detection algorithm at the critical position [ABSTRACT FROM AUTHOR]

Computer simulation, which has been proved to be an effective approach to problem solving, is nowadays widely used in modern science. However, it requires a lot of computing resources, which are difficult for general users to acquire. In this paper, we design a Web based system to implement on-line simulation system for ordinary users. As a useful example, the simulation of one type of collision detection model is presented in this paper. Moreover, the software application of simulation is offered as a service on Web. Meanwhile, the incorporation of general vector machine (GVM, a type of neural network) to intelligently predict the relationship between simulation parameters and computation resources is presented, which could further provide more information for system monitoring and scheduling. The system has demonstrated efficiency and intuitiveness for users of this type of applications. [ABSTRACT FROM AUTHOR]

The new 802.11ac standard aims at achieving Gbps data throughput for individual users by exploiting enhanced physical-layer features, such as higher modulation levels, Multiple Input Multiple Output (MIMO), and wider bandwidths. However, the heterogeneity of bandwidth in a network can cause asymmetric interferences in which certain transmissions cannot be sensed by some other nodes. As a result, the conventional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may not work well in 802.11ac networks. We call this the Hidden Channel (HC) problem, which is shown to be real via experiments with USRP and WARP boards. To solve this problem, we propose bandwidth adaptation based on post-CCA, which is a clear channel assessment (CCA) procedure performed after completing a transmission. Post-CCA in wireless networks helps mimic the CSMA with Collision Detection (CSMA/CD) mechanism in the wired Ethernet, thus enhancing channel assessment capability. Using post-CCA, we propose Post-CCA based Bandwidth Adaptation (PoBA) that alters bandwidth and channel configuration dynamically by applying a reinforcement learning mechanism. Post-CCA and PoBA do not require any hardware modification and are also compliant with the 802.11 standards. PoBA is shown via simulation to increase network-wide throughput, channel utilization and fairness, and also lower packet error probability. [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this study was to develop a procedure for medical tool path planning in minimally-invasive knee surgery. The collision-free paths for the tool were obtained using the control locations method with a hybrid optimization strategy. The tool and knee elements were described with surface meshes. The knee model allowed for bones displacement and variable incision size and location. The proposed procedure was proven to be effective in path planning for minimally-invasive surgery. It can serve as a valuable aid in surgery planning and may also be used in systems for autonomous or semi-autonomous knee surgery. [ABSTRACT FROM PUBLISHER]

The article discusses the orthopedic intervention where a robot control system (RCS) Handheld robotic devices (HHRDs) with multiple degrees of freedom (doF) that has improved the accuracy and adapted in orthopedic surgical workflows. Topics include different control modes of HHRDs; algorithm for collision detection, position and speed control; simulation environment and prototype; and ways in which t RCS protects defined regions from being penetrated by the HHRD.

This paper proposes an interference detection method for multiuser-multiple input multiple output (MU-MIMO) transmission, which utilizes periodical preamble signals in the frequency domain and the concept of full-duplex transmission when assuming idle antennas at the access point (AP) in MU-MIMO. In the propose method, collision detection (CD) of MU-MIMO is achieved by utilizing asynchronous MU-MIMO called random access MU-MIMO. In random access MU-MIMO, several antennas that are not used for the transmission exist, due to asynchronous MU-MIMO. Hence, idle antennas at the AP can receive preamble signals while the transmit antennas at the AP transmit the preamble signals: this procedure is regarded as full-duplex transmission, which cancels the self-interference between AP antennas. The interference can be detected by subtracting the short preamble signal, which is multiplied by the estimated channel response using the received signal after the FFT processing. Moreover, we utilize dual polarization to reduce the mutual coupling between transmit and receive antennas at the AP. Through a computer simulation, it is shown that the proposed method can successfully detect collision from other user terminals (UTs) with OFDM signals when the interfering power from the interfering user terminal (IT) is greater than the noise power. In addition, the interfering power from IT at the AP and the desired user terminal (DT) is measured in an actual indoor environment, and the possibility of using the proposed method at the AP is discussed by using the measurement results. [ABSTRACT FROM AUTHOR]

Flying in unknown environments may lead to unforeseen collisions, which may cause serious damage to the robot and/or its environment. In this context, fast and robust collision detection combined with safe reaction is, therefore, essential and may be achieved using external wrench information. Also, deliberate physical interaction requires a control loop designed for such a purpose and may require knowledge of the contact wrench. In principle, the external wrench may be measured or estimated. Whereas measurement poses large demands on sensor equipment, additional weight, and overall system robustness, in this paper we present a novel model-based method for external wrench estimation in flying robots. The algorithm is based on the onboard inertial measurement unit and the robot's dynamics model only. We design admittance and impedance controllers that use this estimate for sensitive and robust physical interaction. Furthermore, the performance of several collision detection and reaction schemes is investigated in order to ensure collision safety. The identified collision location and associated normal vector located on the robot's convex hull may then be used for sensorless tactile sensing. Finally, a low-level collision reflex layer is provided for flying robots when obstacle avoidance fails, also under wind influence. Our experimental and simulation results show evidence that the methodologies are easily implemented and effective in practice. [ABSTRACT FROM PUBLISHER]

Robot assistants and professional coworkers are becoming a commodity in domestic and industrial settings. In order to enable robots to share their workspace with humans and physically interact with them, fast and reliable handling of possible collisions on the entire robot structure is needed, along with control strategies for safe robot reaction. The primary motivation is the prevention or limitation of possible human injury due to physical contacts. In this survey paper, based on our early work on the subject, we review, extend, compare, and evaluate experimentally model-based algorithms for real-time collision detection, isolation, and identification that use only proprioceptive sensors. This covers the context-independent phases of the collision event pipeline for robots interacting with the environment, as in physical human–robot interaction or manipulation tasks. The problem is addressed for rigid robots first and then extended to the presence of joint/transmission flexibility. The basic physically motivated solution has already been applied to numerous robotic systems worldwide, ranging from manipulators and humanoids to flying robots, and even to commercial products. [ABSTRACT FROM PUBLISHER]

We present an efficient and accurate algorithm for self-collision detection in deformable models. Our approach can perform discrete and continuous collision queries on triangulated meshes. We present a simple and linear time algorithm to perform the normal cone test using the unprojected 3D vertices, which reduces to a sequence point-plane classification tests. Moreover, we present a hierarchical traversal scheme that can significantly reduce the number of normal cone tests and the memory overhead using front-based normal cone culling. The overall algorithm can reliably detect all (self) collisions in models composed of hundreds of thousands of triangles. We observe considerable performance improvement over prior continuous collision detection algorithms. [ABSTRACT FROM AUTHOR]

To assist the visually impaired (VI), a variety of collision detection methods using monocular vision have been developed. Most conventional collision detection methods for the VI utilize feature points and their corresponding motion vectors. However, when the VI subject approaches a non-textured object/obstacle, such as a door or wall, the conventional methods often fail to detect the collision on account of insufficient feature points and inaccurate motion vectors. To address this problem, this paper presents a collision detection method using image segmentation. In the proposed method, the input frame is over-segmented into superpixels by using the superpixel lattices algorithm. The segmentation result is then obtained by applying a graph-based region merging algorithm to the superpixels. Finally, the collision is detected using the geometric relationship between the size variation of the image segment and the distance variation from the camera to that segment in a real-world environment. Experimental results demonstrate that the proposed method handles a variety of scenarios, including a non-textured object, while outperforming conventional methods in terms of accuracy. [ABSTRACT FROM PUBLISHER]

We study deterministic distributed broadcasting in synchronous multiple-access channels. Packets are injected into n nodes by a window-type adversary that is constrained by a window w and injection rates individually assigned to all nodes. We investigate what queue size and packet latency can be achieved with the maximum aggregate injection rate of one packet per round, depending on properties of channels and algorithms. We give a non-adaptive algorithm for channels with collision detection and an adaptive algorithm for channels without collision detection that achieve ${\mathcal {O}}(\min (n+w,w\log n))$ packet latency. We show that packet latency has to be either Ω( wmax(1,log w n)), when w ≤ n, or Ω( w + n), when w > n, as a matching lower bound to these algorithms. We develop a non-adaptive algorithm for channels without collision detection that achieves ${\mathcal {O}}(n+w)$ queue size and ${\mathcal {O}}(nw)$ packet latency. This is in contrast with the adversarial model of global injection rates, in which non-adaptive algorithms with bounded packet latency do not exist (Chlebus et al. Distrib. Comput. 22(2), 93-116 2009). Our algorithm avoids collisions produced by simultaneous transmissions; we show that any algorithm with this property must have Ω( n w) packet latency. [ABSTRACT FROM AUTHOR]

In this paper we present an $hp$-adaptive algorithm to generate discrete higher-order polynomial Signed Distance Fields (SDFs) on axis-aligned hexahedral grids from manifold polygonal input meshes. Using an orthonormal polynomial basis, we efficiently fit the polynomials to the underlying signed distance function on each cell. The proposed error-driven construction algorithm is globally adaptive and iteratively refines the SDFs using either spatial subdivision ($h$-refinement) following an octree scheme or by cell-wise adaption of the polynomial approximation's degree ($p$-refinement). We further introduce a novel decision criterion based on an error-estimator in order to decide whether to apply $p$- or $h$-refinement. We demonstrate that our method is able to construct more accurate SDFs at significantly lower memory consumption compared to previous approaches. While the cell-wise polynomial approximation will result in highly accurate SDFs, it can not be guaranteed that the piecewise approximation is continuous over cell interfaces. Therefore, we propose an optimization-based post-processing step in order to weakly enforce continuity. Finally, we apply our generated SDFs as collision detector to the physically-based simulation of geometrically highly complex solid objects in order to demonstrate the practical relevance and applicability of our method. [ABSTRACT FROM AUTHOR]

Implicitizing rational surfaces is a fundamental computational task in Computer Graphics and Computer Aided Design. Ray tracing, collision detection, and solid modeling all benefit from implicitization procedures for rational surfaces. The univariate resultant of two moving lines generated by a μ-basis for a rational curve represents the implicit equation of the rational curve. But although the multivariate resultant of three moving planes corresponding to a μ-basis for a rational surface is guaranteed to contain the implicit equation of the surface as a factor, μ-bases for rational surfaces are difficult to compute. Moreover, μ-bases for a rational surface often have high degrees, so these resultants generally contain many extraneous factors. Here we develop fast algorithms to implicitize rational tensor product surfaces by computing the resultant of three moving planes corresponding to three syzygies with low degrees. These syzygies are easy to compute, and the resultants of the corresponding moving planes generally contain fewer extraneous factors than the resultants of the moving planes corresponding to μ-bases. We predict and compute all the possible extraneous factors that may appear in these resultants. Examples are provided to clarify and illuminate the theory. [ABSTRACT FROM AUTHOR]

Haptics applications such as surgery simulations require collision detections that are more precise than others. An efficient collision detection method based on the clustering of bounding spheres was proposed in our prior study. This paper analyzes and compares the applied effects of the five most common subdivision surface methods on some 3D models for haptic collision detection. The five methods are Butterfly, Catmull-Clark, Mid-point, Loop, and LS3 (Least Squares Subdivision Surface). After performing a number of experiments, we have concluded that LS3 method is the most appropriate for haptic simulations. The more we applied surface subdivision, the more the collision detection results became precise. However, it is observed that the performance becomes better until a certain threshold and degrades afterward. In order to reduce the performance degradation, we adopted our prior work, which was the fast and precise collision detection method based on adaptive clustering. As a result, we obtained a notable improvement of the speed of collision detection. [ABSTRACT FROM AUTHOR]

The precise operation of mobile cranes contributes to the safety and efficiency of lift works, among which accurate location is one of the most critical aspects. Considering the complexities and dynamics of construction sites, this paper presents an approach for crane location determination based on the simulation of mobile crane operations. First a data processing method is developed to enable the automated conversion from BIM (Building Information Modeling) and schedule plan to the simulation system. Then the reachability and work radius of mobile cranes are examined for selecting the initial feasible location points. The bounding box method is used for the collision detection to ensure the safety of crane operations. Also, the minimum number of relocation and the lift time are taken into account to determine the final feasible location points of mobile cranes. [ABSTRACT FROM AUTHOR]

This paper presents a real-time lightweight fluid simulation based on a particle fluid technique developed for mobile environment . The Bullet physics engine and smoothed particle hydrodynamic (SPH) fluid algorithm will be used for our lightweight fluid simulation. First, we describe an advanced collision detection mechanism that will be used. By using this method, less computational resources are required. Secondly, we present a simplified SPH algorithm where nearby particles are grouped together to minimize the number of calculations. By decreasing the number of particles, an improved computational performance is expected. Finally, the ARM NEON based parallel computing technique was enabled to reduce execution time by lowering the number of arithmetic instructions. Several experiments are carried out where the experimental results indicate the first technique led to a 50% improvement in performance. The second technique provided a 17% overall improvement. The third technique delivered a performance improvement within the range of 26%–40%. Overall, the experimental results show that the proposed techniques provided an accumulative performance improvement of approximately 120% for all applied methodologies. [ABSTRACT FROM AUTHOR]

In this research, we implement a deformable object simulation system using OpenGL's shader language, GLSL4.3. Deformable object simulation is implemented by using volumetric mass-spring system suitable for real-time simulation among the methods of deformable object simulation. The compute shader in GLSL 4.3 which helps to access the GPU resources, is used to parallelize the operations of existing deformable object simulation systems. The proposed system is implemented using a compute shader for parallel processing and it includes a bounding box-based collision detection solution. In general, the collision detection is one of severe computing bottlenecks in simulation of multiple deformable objects. In order to validate an efficiency of the system, we performed the experiments using the 3D volumetric objects. We compared the performance of multiple deformable object simulations between CPU and GPU to analyze the effectiveness of parallel processing using GLSL. Moreover, we measured the computation time of bounding box-based collision detection to show that collision detection can be processed in real-time. The experiments using 3D volumetric models with 10K faces showed the GPU-based parallel simulation improves performance by 98% over the CPU-based simulation, and the overall steps including collision detection and rendering could be processed in real-time frame rate of 218.11 FPS. [ABSTRACT FROM AUTHOR]

This paper investigates collision detection between cylindrical or cylinder-enveloped components when mutual blocking occurs in the view of microscopes and detach control to separate objects if contact occurs. We use a projection method to convert two microscopic views to contours on a projection plane and to detect high-dimensional collision by studying the projection's relationships in low dimension. Eleven cases are totally categorized and 12 parameters are constructed for detection on the basis of relative postures and positions. Furthermore, we present a detach controller to handle with object contact according to collision status, objects’ main axis, and the computed contact position. Simulations and experiments are carried out to demonstrate the validity of the proposed method. [ABSTRACT FROM PUBLISHER]

In this paper, we propose an early preamble collision detection (e-PACD) scheme at the first step of random access (RA) procedure based on tagged preambles (PAs), which consist of both PA and tag Zadoff–Chu sequences using different root numbers, respectively. The proposed e-PACD scheme enables faster PA collision detection and notification, compared with the conventional RA scheme. Accordingly, it can reduce the RA delay and remove resource wastes which occur at the third step of the conventional RA procedure. The reduced RA delay achieved by the proposed e-PACD scheme can contribute to an ultralow latency requirement in fifth-generation (5G) cellular networks. In addition, the proposed e-PACD scheme enables the eNodeB to monitor the number of RA-attempting nodes (RA load) on each physical RA channel slot. The PACD probability and the RA load monitoring accuracy are mathematically analyzed, and the RA performance enhancement of the proposed scheme is evaluated in terms of RA success probability, average RA delay, and RA resource efficiency, compared with the conventional RA scheme. [ABSTRACT FROM PUBLISHER]

Purpose In this study, we demonstrate and evaluate a low cost, fast, and accurate avoidance framework for radiotherapy treatments. Furthermore, we provide an implementation which is patient specific and can be implemented during the normal simulation process. Methods Four patients and a treatment unit were scanned with a set of consumer depth cameras to create a polygon mesh of each object. Using a fast polygon interference algorithm, the models were virtually collided to map out feasible treatment positions of the couch and gantry. The actual physical collision space was then mapped in the treatment room by moving the gantry and couch until a collision occurred with either the patient or hardware. The physical and virtual collision spaces were then compared to determine the accuracy of the system. To improve the collision predictions, a buffer geometry was added to the scanned gantry mesh and performance was assessed as a function of buffer thickness. Results Each patient was optically scanned during simulation in less than 1 min. The average time to virtually map the collision space for 64, 800 gantry/couch states was 5.40 ± 2.88 s. The system had an average raw accuracy and negative prediction rate ( NPR) across all patients of 97.3% ± 2.4% and 96.9% ± 2.2% respectively. Using a polygon buffer of 6 cm over the gantry geometry, the NPR was raised to unity for all patients, signifying the detection of all collision events. However, the average accuracy fell from 95.3% ± 3.1% to 91.5% ± 3.6% between the 3 and 6 cm buffer as more false positives were detected. Conclusions We successfully demonstrated a fast and low cost framework which can map an entire collision space a priori for a given patient during the time of simulation. All collisions can be avoided using polygon interference, but a polygon buffer may be required to account for geometric uncertainties of scanned objects. [ABSTRACT FROM AUTHOR]

Rapid and accurate detection of collision between virtual objects is crucial for many virtual reality based applications. In order to ensure a high-level of accuracy and to meet the real-time requirement, a fast collision detection algorithm between soft bodies is proposed. The developed algorithm is a combination of stochastic methods and particle swarm optimization with adaptive Cauchy mutation. The hierarchical bounding box method is used for a rough detection in order to filter out obvious disjoint space, and the problem is converted to a nonlinear optimization problem based on the distance of points. Then particle swarm optimization with adaptive Cauchy mutation is used to find the optimal solution. When it is updated iteratively, keeping some particles experience value and variation of other particles avoids particles trapped in local optimum, which further accelerates the speed of collision detection. The algorithm is implemented and evaluated through experiments and the results confirm the advantages of the developed algorithm. [ABSTRACT FROM AUTHOR]

Mobile agents start at different nodes of an n -node network. The agents synchronously move along the network edges in a collision-free way, i.e., in no round two agents may occupy the same node. An agent has no knowledge of the number and initial positions of other agents. We are looking for the shortest time required to reach a configuration in which each agent has visited all nodes and returned to its starting location. In the scenario when each mobile agent knows the map of the network, we provide tight (up to a constant factor) lower and upper bounds on the collision-free exploration time in arbitrary graphs, and the exact bound for the trees. In the second scenario, where the network is unknown to the agents, we propose collision-free exploration strategies running in O ( n 2 ) rounds in tree networks and in O ( n 5 log ⁡ n ) rounds in networks with an arbitrary topology. [ABSTRACT FROM AUTHOR]

A new type of the spatio-temporal queries is the Intelligent Probabilistic Collision Detection Query ( IPCDQ for short). In this paper, we focus on efficiently processing the IPCDQ on moving objects with uncertainty. Given two sets O and Q of objects, each of which moves with uncertain speed and direction, a time instant t, and a probability threshold P, the IPCDQ returns each pair of objects ( o, q) (where $$o \in O$$ and $$q \in Q$$ ), whose probability of colliding with each other is greater than or equal to P at time t. The pairs of objects satisfying the IPCDQ are termed the collision-possible pairs (or CPPs for short). We utilize a $$R^{lsd}$$ -tree, in which the spatially proximate objects with similar uncertain speeds and directions are grouped together, to effectively manage the moving objects in O. Similarly, a $$R^{lsd}$$ -tree is used to index the moving objects in Q. Then, with the two $$R^{lsd}$$ -trees for O and Q, respectively, we develop the specialized index traversals combined with three pruning criteria, the location-pruning criterion, the angle-pruning criterion, and the speed-pruning criterion to efficiently determine the objects that may collide with each other. Besides, to provide the more useful information to the user, we propose a probability model to quantify the possibility of each object pair being the query result. Comprehensive experiments demonstrate the efficiency and the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]