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Cleaning tasks for vertical structures, such as building façades and walls on construction sites, are dangerous; there is a high risk of fall accidents among workers engaged in such tasks. Hence, research on the automation of wall-cleaning tasks based on robotics technology has been actively conducted in recent years. However, existing wall-cleaning robots have limitations, such as poor mobility performance or the need for additional infrastructure for operation. In this article, we designed a novel rope-driven wall-cleaning robot Edelstro-M2 with two innovative characteristics. First, both vertical and horizontal movements on the wall are possible by implementing a dual rope climbing mechanism and parallel kinematics. Second, except for a rope fixing arrangement, additional infrastructure, such as winch and building management unit systems, is not required for operation. A prototype model was developed, and real-world experiments were conducted to verify the mobility and cleaning performance of the robot. In the experiment, the robot was controlled by manual remote control. We plan to study automatic control of the robot in the future works. [ABSTRACT FROM AUTHOR]

Cable-driven parallel robots (CDPRs) are more convenient to use in large-scale applications than rigid-link robots due to the advantages such as simple structure, high load capacity, and low inertia of cables. However, using cables to drive an end-effector comes with the low equivalent stiffness issue in out-of-plane direction for the CDPRs’ planar configuration, which causes long-lasting and high amplitude out-of-plane vibrations under an external disturbance. This article presents a novel method to suppress the out-of-plane vibrations without distorting in-plane positioning control simultaneously for planar CDPRs. The proposed method provides the ease of using only the cable tensioning forces instead of an additional actuator to control the out-of-plane vibrations by decoupling the in-plane and out-of-plane dynamics. The switching stiffness control method is used for out-of-plane vibration control, while a classical control method is used for in-plane dynamics control. These two control inputs are then coupled by a bias torque variation in a torque distribution algorithm. The effectiveness of the proposed method is presented both in simulations and experimental results. The experiments are performed for the specified in-plane positions and an in-plane trajectory tracking study when the planar CDPR is excited to out-of-plane vibration in the normal direction. The out-of-plane vibration suppression time is considerably reduced compared to the free-vibration case, and any distortion on the in-plane positioning control is not observed. [ABSTRACT FROM AUTHOR]

This article presents the design and position-tracking control of a novel two-degree-of-freedom dual-rope winch robot. It is designed to be facilely installed at both corners of a building using two synthetic ropes and to move freely on the wall plane using the ropes to perform building maintenance work. This robot consists of a dual-rope winch system responsible for its movement on a plane and a thrust module that allows the robot to remain close to the wall through the force of the propeller. In the dual-rope winch system, ascending modules driven by two pulleys and connected by differential gears are arranged symmetrically; the position and posture on the plane can be determined by controlling the ropes. The robot winds a synthetic rope around the pulley to support the load with frictional force. Precise position control is difficult to implement because of the elasticity of the rope and the slip around the pulley. Therefore, in this article, a feedforward control to predict and compensate for the slip length of the rope and a proportional–integral controller to regulate the position error owing to the dynamic characteristics of the rope are proposed. Experiments to verify the performance of the controller for various trajectories were performed on the test bench. It was confirmed that the actual trajectory deviation is within 0.5% of the target trajectory. [ABSTRACT FROM AUTHOR]

This article focuses on the static workspace (SW) of aerial cable towed robots (ACTRs) with land-fixed winches and provides an optimization approach to maximize the size of such a workspace. In the structure of the studied robots, land-fixed winches beside the ACTRs, actuated by unmanned aerial vehicles (UAVs), are used to manipulate a platform to reach high-altitude poses and balance platform's interaction force/moment in such poses. Capability of UAVs in choosing and holding different positions and orientations enables the studied robots to adapt their available net wrench set (AW) to various required net wrench sets. In order to find the SW of ACTRs with land-fixed winches, at first, AW of a generic robot for a given arrangement of UAVs is developed analytically. Then, a geometrical approach is provided to find all collision-free arrangements of the UAVs. Based on that, a performance index is derived and optimized to find an optimal collision-free arrangement of the UAVs, which maximizes the magnitude of the force that can be balanced by the platform in any arbitrary direction. Finally, the application of the proposed optimization approach in size maximization of the SW is shown in an example. [ABSTRACT FROM AUTHOR]

This study proposes a novel mechanical design of a cable-driven parallel robot (CDPR), called a dual ascender robot (DAR), which consists of two ascenders and two structures for rope-measuring sensors. Unlike other CDPRs that require external structures for winches, the DAR requires only two ropes because the traction pulleys of the ascenders allow the robot to climb on the ropes. Thus, this robot can be operated in any building. Because the ascender moves on the ropes using the friction between the rope and the traction pulley, length errors owing to rope slip are inevitable. Therefore, it is difficult to estimate the position of the robot by using the length data of the ascender. To minimize this error, a sensor-fusion method that combines the rope-length and angle-sensor data with weight factors was used. However, an optimal method of selecting the sensor resolution has not been developed yet. Therefore, this study proposes a method of selecting the sensor-reflection ratio according to sensor resolution and angle- and length-sensitivity data. The sensor-fusion method was verified to achieve excellence and resistance to rope slip through simulations and experiments. Moreover, it demonstrated improved stability of approximately 4-mm error in a 20 $\text{m}\times 20$ m space under the slip condition, compared to the position-estimation method that only used the rope-length data. [ABSTRACT FROM AUTHOR]

Active heave compensation systems are typically single-degree-of-freedom systems that operate vertically to attenuate the vertical effects of wave motion. To apply compensation to towed bodies, which experience significant multiple-degree-of-freedom disturbances, a generalized motion compensation system using a “reference-point algorithm” is required that determines the length of a tow cable that should be reeled in or reeled out by an on-board winch system in response to external wave motion. This paper proposes, implements, and assesses four different reference-point algorithm approaches in both simulation and experimental environments. Of the proposed reference-point algorithms, the method that directly accounts for the tow cable angle proved to be most effective in both simulation and experimentation. It was found that there was little improvement between real-time measurements of the tow cable angle and a constant nominal tow cable angle—indicating a potential cost saving opportunity through the avoidance of real-time sheave-angle measurement. [ABSTRACT FROM AUTHOR]

Cable-driven parallel robots (CDPRs) have low moving inertia and provide high-speed motion over a large workspace. The main challenges of CDPRs stem from the fact that cables should be in tension during motion control. Cable tension is closely related to the synchronization motion relation between cables which is often omitted in the existing controllers for CDPRs. To solve it, this paper proposes two synchronization controllers in the cable space to realize the synchronization motion between cables, and finally increase the tracking accuracy of the moving platform. The two synchronization controllers are proven to guarantee asymptotic convergence to zero of both tracking error and synchronization error. The trajectory tracking experiments are implemented on a self-built three-DOF CDPR, and the experiments are compared with the traditional augmented proportional-derivative controllers neglecting synchronization. The experimental results indicate that the tracking error and the synchronization error of the moving platform decrease greatly by using the synchronization controllers. [ABSTRACT FROM AUTHOR]

In borehole radar (BHR) surveys, if the radar is either suspended by a conductive communication cable or run in a conductive water, guided waves may be induced. When they encounter impedance changes, for example, at geological interfaces, the guided waves will be reflected. These reflected guided waves (RGWs) often are relatively strong. They present themselves as obliquely striped patterns in the B-scan image, and, severely contaminate the reflections of interest. In this letter, we compare three signal processing methods to suppress RGWs: 1) running a moving average error filter along a specified dip—as in $\tau $ -p filtering; 2) pie-slice frequency–wavenumber (F-K) filtering; and 3) F-K migration-based filtering method. The third migration-based method is novel. All three methods are based on the characteristics and generating mechanism of RGWs. Real BHR data collected with a monostatic radar system illustrate their relative effectiveness. [ABSTRACT FROM AUTHOR]

In-water tests of automated launch and recovery (L&R) of a Hydroid REMUS 100 autonomous underwater vehicle (AUV) from a station-keeping 16-ft wave adaptive modular vehicle unmanned surface vehicle (USV) have been conducted to determine the feasibility of developed concepts of operation. The USV is a catamaran with a custom-configured propulsion system that enables it to maintain position and heading on the surface. AUV launch is accomplished through lowering the AUV from the USV top tray to the water surface and releasing it. Recovery is initiated through requiring the AUV to navigate toward an acoustic homing beacon on a taut line suspended from the USV. The taut line serves as docking target and as a connecting link between the two vehicles during L&R. During these operations, the USV approximately keeps station on the water surface. Once the docking is complete, the USV moves forward, towing the AUV as it is extracted onboard the USV via a customized winch mechanism. It was found that for appropriate environmental conditions, L&R of the AUV from a station-keeping USV is an effective alternative to the mobile L&R method using the same vehicles, with the same launch and recovery system. [ABSTRACT FROM AUTHOR]

Cable guiding mechanisms (CGMs) directly influence the reconfigurability of cable-driven parallel robots (CDPRs). But due to the complicated kinematic model of pulley-based CGMs, the velocity and acceleration mappings from the moving platform (MP) to the cables were unknown, the continuity of cable velocity, acceleration, and tension was unguaranteed, and the calibration pose-search method was based on inaccurate CGM models. In this paper, we establish an analytic and compact model for CGM. Based on this model, the velocity and acceleration mappings from the MP to the cables are derived. The continuities of cable trajectory and tension are proved. The exact identification Jacobian and its derivative are also formulated, leading to the increased fidelity of pose-search methods. The proposed method and formulations are verified by simulations and experiments on a redundant CDPR. [ABSTRACT FROM AUTHOR]

An alternative approach to standard computed torque with feedback linearization is proposed in this paper to control cable-driven parallel robots (CDPRs) with highly flexible cables. Exteroceptive feedback is used to measure the end-effector Cartesian position at a high sampling rate. Stability is demonstrated using singular perturbation theory. The proposed control scheme is experimentally validated on a planar 3-degree-of-freedom CDPR and its efficiency is assessed by comparison with a simple kinematic control law. [ABSTRACT FROM AUTHOR]

In this brief, a planar cable-driven parallel manipulator is controlled using a strictly positive real compensator, cable pretension is explicitly accounted for, and cable slack is avoided. A strictly positive real controller is implemented using actuator saturation prevention techniques and the solution to a linear programming problem to ensure that the cable tensions remain strictly positive. Pretension torque is directly accounted for when determining the input–output stability of the closed-loop system. Numerical simulations demonstrate that the controller can track high-acceleration trajectories with the same precision as a state-of-the-art controller from the literature, while maintaining positive cable tensions. [ABSTRACT FROM AUTHOR]

A control design approach to achieve fully autonomous takeoff and flight maneuvers with a tethered aircraft is presented and demonstrated in real-world flight tests with a small-scale prototype. A ground station equipped with a controlled winch and a linear motion system accelerates the aircraft to takeoff speed and controls the tether reeling in order to limit the pulling force. This setup corresponds to airborne wind energy (AWE) systems with ground-based energy generation and rigid aircrafts. A simple model of the aircraft’s dynamics is introduced and its parameters are identified from experimental data. A model-based, hierarchical feedback controller is then designed, whose aim is to manipulate the elevator, aileron, and propeller inputs in order to stabilize the aircraft during the takeoff and to achieve figure-of-eight flight patterns parallel to the ground. The controller operates in a fully decoupled mode with respect to the ground station. Parameter tuning and stability/robustness aspect are discussed, too. The experimental results indicate that the controller is able to achieve satisfactory performance and robustness, notwithstanding its simplicity, and confirm that the considered takeoff approach is technically viable and solves the issue of launching this kind of AWE systems in a compact space and at low additional cost. [ABSTRACT FROM AUTHOR]

The design of a prototype to carry out takeoff and flight tests with tethered aircrafts is presented. The system features a ground station equipped with a winch and a linear motion system. The motion of these two components is regulated by an automatic control system, whose goal is to accelerate a tethered aircraft to takeoff speed using the linear motion system, while reeling out the tether from the winch with low pulling force and avoiding entanglement. The mechanical, electrical, measurement, and control aspects of the prototype are described in detail. Experimental results with a manually piloted aircraft are presented, showing a good match with previous theoretical findings. [ABSTRACT FROM PUBLISHER]

The reduced gravity experienced in lunar or Martian surfaces can be simulated on the earth using a cable-driven system, where the cable lifts a person to reduce his or her weight. This paper presents a novel cable-driven system designed for the purpose. It is integrated with a head-mounted display and a motion capture system. Focusing on jump motion within the system, this paper proposes to scale the jump and reports the experiments made for quantifying the extent to which a jump can be scaled without the discrepancy between physical and virtual jumps being noticed by the user. With the tolerable range of scaling computed from these experiments, an application named retargeted jump is developed, where a user can jump up onto virtual objects while physically jumping in the real-world flat floor. The core techniques presented in this paper can be extended to develop extreme-sport simulators such as parasailing and skydiving. [ABSTRACT FROM PUBLISHER]

In this paper, a concept design for automated launch and recovery (L&R) of a small autonomous underwater vehicle (AUV) from an unmanned surface vehicle (USV) is described and its feasibility is assessed through modeling and simulation. The design is being implemented on a selected catamaran USV for deployment of a REMUS 100 AUV. The concept for launch involves lowering the AUV into the water from the center of the USV while the latter is in motion. Recovery and retrieval involves aligning the two vehicles together through acoustic positioning, lowering of a thin line with an outrigger-type depressor wing from a winch on the USV, latching of the line by the AUV using a custom pincer-type onboard mechanism, and subsequent reeling of the line for vehicle retrieval. The USV being considered can operate effectively in low to moderate sea states. The length of the recovery line can be adjusted to facilitate AUV recovery from deeper locations beneath the USV in higher sea state. The L&R process is modeled in OrcaFlex to assess its feasibility and to conduct a parametric study in support of developing optimal operations of the launch and recovery system (LARS). The resulting system is being implemented on a USV. [ABSTRACT FROM AUTHOR]

In recent years, sensorized autonomous vehicles (either AUVs or ASVs) have been increasingly used for in situ water measurements. However, collection of water samplings at depth by small-sized ASVs and their subsequent physical/chemical analysis onboard remains difficult due to size and weight constraints. This paper addresses this issue and describes the design and testing of an autonomous water monitoring and sampling system intended for operations onboard small-sized man-portable ASVs. The system is designed to collect water samples up to 50 m in depth and to measure physical water parameters along the water column. The system is composed of a probe lowered by a winch measuring physical water parameters and able to collect water samples at different selectable depths. Once the probe is returned onboard, a water distribution system transfers the collected water samples to sensors lodged in the ASV for the monitoring of chemical parameters, or into containers to transport the samples to laboratories on the mainland. The system combines small dimensions, self-cleaning capabilities, low weight, and limited power consumption allowing it to be easily installable and used on an autonomous small-sized ASVs. The sampling system was installed and tested in a robotic small-sized catamaran belonging to the HydroNet ASV class. [ABSTRACT FROM AUTHOR]

This paper presents the electrothermal modeling and simulation done on a subsea standard 7000-m-long, Kevlar-armored, electro–optic umbilical (EOU) of the deep-water remotely operated vehicle (ROV) ROSUB 6000, to determine the ampacity derating factors (ADF) when used in winch-wound configurations. The ampacity derating analysis is done, using the finite element analysis (FEA) up to 23 layers, and the identified ADF could be applied to any standard subsea umbilical operated in multilayered configurations. It is identified that the 23-layered umbilical needs to be derated to 92% for continuous operation with direct current power supply, while increased loading reduces the operation window and needs a cooldown period of 182 h. In the case of operation with 6600 V and 400 Hz, the 23-layered umbilical operation window is 7.2 h, independent of the connected active load. The results serve as a guideline for determining the tradeoff among operating voltage, frequency, cable design, ADF, and the operational window for multilayered cable configurations. [ABSTRACT FROM PUBLISHER]

This paper presents a mechatronic implementation for experimentally validating an approach toward optimal force generation for a planar underconstrained cable robot that is designed to operate on the vertical face of overhead roadway signs. The cables that actuate the robot extend over a set of rotatable pulley arms mounted at the top corners of the sign. The redundant degrees of freedom due to the pulley arms allow for improved force generation ability of the robot at all desired locations on the sign. Redundancy is resolved by optimizing the anisotropic force generated in a desired direction. The mechatronic implementation is performed using a novel smartphone-based architecture for imaging, kinematics, I/O, optimization, and control. The implementation hardware and software are detailed, and experimental results are presented, which validate the theory. [ABSTRACT FROM PUBLISHER]

This paper presents the experimental results about position mooring (PM) system applied to the barge ship. The aim of the PM is to maintain the position and motion of the ship's surge and sway directions as desired. In this paper, a system consisting of a barge vessel and mooring lines is mathematically modeled. The position and orientation of the vessel is controlled by changing the tensions of the mooring lines with the subwinch. A comparison of the newly designed mathematical model with the existing PID control method and the results of experiments indicated that the proposed designing method is more efficient than the traditional method. [ABSTRACT FROM PUBLISHER]

A guided wave is induced along a conductive logging cable or a conductive water-filled borehole during borehole radar (BHR) surveying. Such a guided wave is normally considered as unwanted interference to normal BHR waves and needs to be suppressed, either through BHR designs or data processing. In this letter, we advocate that the guided wave can be coupled onto a drill string, which can act as a forward-looking antenna for imaging ahead of the drill bit while drilling. Using data collected by a monostatic BHR with different configurations at an abandoned mine site in Brukunga, South Australia, we demonstrate that the forward-looking capability of the BHR is about 2–6 m in the tested borehole section. [ABSTRACT FROM PUBLISHER]

We present the methodology, algorithms, system design, and experiments addressing the self-assembly of large teams of autonomous robotic boats into floating platforms. Identical self-propelled robotic boats autonomously dock together and form connected structures with controllable variable stiffness. These structures can self-reconfigure into arbitrary shapes limited only by the number of rectangular elements assembled in brick-like patterns. An O(m^2) complexity algorithm automatically generates assembly plans which maximize opportunities for parallelism while constructing operator-specified target configurations with m components. The system further features an O(n^3) complexity algorithm for the concurrent assignment and planning of trajectories from n free robots to the growing structure. Such peer-to-peer assembly among modular robots compares favorably to a single active element assembling passive components in terms of both construction rate and potential robustness through redundancy. We describe hardware and software techniques to facilitate reliable docking of elements in the presence of estimation and actuation errors, and we consider how these local variable stiffness connections may be used to control the structural properties of the larger assembly. Assembly experiments validate these ideas in a fleet of 0.5 m long modular robotic boats with onboard thrusters, active connectors, and embedded computers. [ABSTRACT FROM PUBLISHER]

In this paper, a lumped-mass dynamic model of a single degree of freedom cable-actuated system is derived, and passivity-based control is considered. The dynamic model developed takes into consideration the changing cable stiffness and mass as the cable is wrapped around a winch. In addition, the change in the winch inertia as the cable is wrapped around the winch is modeled. It is assumed that the mass of the payload is much greater than the mass of the cables and the equivalent mass of the winches, which allows for an approximation where the rigid dynamics can be decoupled from the elastic dynamics of the system. This approximation enables the definition of a modified input torque and modified output rate, allowing the establishment of passive input–output mappings. Passivity-based controllers are investigated, shown to render the closed-loop system input–output stable, and tested in simulation. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic modeling and passivity-based control of a planar cable-actuated system. This system is modeled using a lumped-mass method that explicitly considers the change in cable stiffness and winch inertia that occurs when the cables are wound around their respective winches. In order to simplify the modeling process, each cable is modeled individually and then constrained to the other cables. Exploiting the fact that the payload is much more massive than the cables allows the definition of a modified output called the $\mu$ -tip rate. Coupling the $\mu$-tip rate with a modified input realizes the definition of a passive input–output map. The two degrees of freedom of the system are controlled by four winches. This overactuation is simplified by employing a set of load-sharing parameters that effectively reduce four inputs to two. The performance and robustness of the controllers are evaluated in the simulation. [ABSTRACT FROM PUBLISHER]

To fully understand the ocean environment requires sensing the full water column. Utilizing a depth adjustment system on an underwater sensor network provides this while also improving global sensing and communications. This paper presents a depth adjustment system for waters up to 50 m deep that connects to the AquaNode sensor network nodes. We performed experiments characterizing and demonstrating the functionality of the depth adjustment system. We discuss the application of this device in improving acoustic communication and also verify the functionality of a decentralized depth adjustment algorithm that optimizes the placement of the nodes for collecting sensing data. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to analyze theoretically and experimentally the stator current and load torque of a three-phase induction machine in a hoisting winch system. This is performed in order to show how these variables are influenced by the wire rope faulty conditions. When the wire rope is subject to axial and torsional loads, the outer strands can be separated from the core in a permanent way and make the rope less reliable. The term “birdcaging” is used to describe this type of phenomenon by giving a permanent appearance of a wire rope forced into compression. In a hoisting winch system, the rope is bent over a drum and a pulley, and it is torsionally stressed by the fleet angle between them. In this paper, the effect of the fleet angle is observed in the stator current and the load torque in order to detect the “birdcaging” effect. This study is performed on a 22-kW three-phase squirrel-cage induction machine driving a reduced scale winch system, and it presents an original noninvasive way to detect a wire rope fault condition. [ABSTRACT FROM AUTHOR]