Bilateral Teleoperation Control Research Articles

Performance comparison of bilateral teleoperation control of direct control, PID control, and fuzzy logic control for water tank system

Bilateral teleoperation has attracted significant research and application interests in a wide range of areas. The first and main use for bilateral teleoperation was to handle the dangerous and remote distance tasks such as space exploration and nuclear materials manipulation. In the past few years, bilateral teleoperation has found its way into other applications as a result of the development of control technologies and the latest breakthrough in artificial intelligence and machine learning. In this paper, the goal is to model bilateral teleoperation for direct control, PID control, and Fuzzy Logic control for the water tank system. The goal is to create a simulation for master-slave communication where the time delay is minimized to the optimal and accepted values. The experimental results obtained from the simulation show a fairly high accuracy in terms of all three ways of control modes, which highlights the effectiveness of the proposed system in the paper.

Adaptive FNN Backstepping Control for Nonlinear Bilateral Teleoperation With Asymmetric Time Delays and Uncertainties

Adaptive FNN Backstepping Control for Nonlinear Bilateral Teleoperation With Asymmetric Time Delays and Uncertainties

Stable Bilateral Teleoperation Control Method for Biped Robots with Time-Varying Delays

This document proposes a control scheme applied to delayed bilateral teleoperation of the forward and turn speed of a biped robot against asymmetric and time-varying delays. This biped robot is modeled as a hybrid dynamic system because it behaves as a continuous system when the leg moves forward and discrete when the foot touches the ground generating an impulsive response. It is proposed to vary online the damping according to the time delay present in the communication channel, and the walking cycle time using an optimization criterion, to decrease the teleoperation system errors. To accomplish this, a three-phase cascade calibration process is used, and their benefits are evidenced in a comparative simulation study. The first phase is an offline calibration of the inverse dynamic compensation and also the parameters of the bilateral controller. The second phase guarantees the bilateral coordination of the delayed teleoperation system, using the Lyapunov–Krasovskii stability theory, by changing the leader damping and the equivalent follower damping together. The third phase assures a stable walk of the hybrid dynamics by controlling the walking cycle time and the real damping to move the eigenvalues of the Poincaré map, numerically computed, to stable limit cycles and link this result with an equivalent continuous system to join both phases. Additionally, a fictitious force was implemented to detect and avoid possible collisions with obstacles. Finally, an intercontinental teleoperation experiment of an NAO robot via the Internet including force and visual feedback is shown.

6-DOF Bilateral Teleoperation Hybrid Control System for Power Distribution Live-Line Operation Robot

In the master-slave heterogeneous teleoperation, the workspace of the slave manipulator is usually much larger than that of the master manipulator. This paper proposes a 6-DOF bilateral hybrid teleoperation control strategy to map the workspace of the manipulators without changing the operation accuracy. The hybrid control includes the admittance and force control based on the feedback of the force sensor at the end of the manipulator. The two control strategies switched autonomously through the positioning of the Sigma.7 handle in the workspace. Compared with the classic bilateral teleoperation control, it overcomes the limitation of pre-matching the workspace of the master and slave. When the tool contacts a rigid environment, the robot can make adaptive compensation through the admittance controller even if the operator has not responded. We conduct extensive experiments to evaluate the changes in displacement and velocity before and after the switching process and under different admittance controller parameters. Finally, teleoperation is applied to live-line operation in distribution networks. The experiment proved that the control strategy is more consistent with human operation habits and can improve assembly success rate and efficiency.

An adaptive bilateral impedance control based on nonlinear disturbance observer for different flexible targets grasping

The uncertainty of environmental parameters and time-varied characteristics usually generate contact force errors resulting the inaccuracy or even task failed in many tele-operation systems. In order to solve the problem, a novel composite bilateral tele-operation controller is proposed in this paper combining adaptive impedance control with nonlinear disturbance observer-based sliding mode controller. An adaptive impedance controller is constructed to achieve high-precision tracking of desired contact forces and ensure the safety of grasping various flexible targets. A sliding mode controller on the basis of a nonlinear disturbance observer is designed, so as to accurately estimate the composite disturbance signals as well as to ensure the stability and the high accuracy of the trajectory tracking. The stability of the system is proved by the Lyapunov function. Numerical simulations and real robot experiments are performed. Results shows that our method can greatly enhance the safety of the flexible target in the process, minimize the influence of disturbance signals on the system, and improve the robustness of the system.

Leader-follower and leaderless pose consensus of robot networks with variable time-delays and without velocity measurements

This paper proposes a novel distributed controller that solves the leader-follower and the leaderless consensus problems in the task space for networks composed of robots that can be kinematically and dynamically different (heterogeneous). In the leader-follower scenario, the controller ensures that all the robots in the network asymptotically reach a given leader pose (position and orientation), provided that at least one follower robot has access to the leader pose. In the leaderless problem, the robots asymptotically reach an agreement pose. The proposed controller is robust to variable time-delays in the communication channel and does not rely on velocity measurements. The controller is dynamic, it cancels-out the gravity effects and it incorporates a proportional to the error term between the robot and the controller virtual position. The controller dynamics consists of a simple proportional scheme plus damping injection through a second-order (virtual) system. The proposed approach employs the singularity free unit-quaternions to represent the orientation of the end-effectors, and the network is represented by an undirected and connected interconnection graph. The application to the control of bilateral teleoperators is described as a special case of the leaderless consensus solution. The paper presents numerical simulations with a network composed of four 6-Degrees-of-Freedom (DoF) and one 7-DoF robot manipulators. Moreover, we also report some experiments with a 6-DoF industrial robot and two 3-DoF haptic devices.

Force-Sensor-Less Bilateral Teleoperation Control of Dissimilar Master–Slave System With Arbitrary Scaling

This study designs a high-precision bilateral teleoperation control for a dissimilar master–slave system. The proposed nonlinear control design takes advantage of a novel subsystem-dynamics-based control method that allows designing of individual (decentralized) model-based controllers for the manipulators locally at the subsystem level. Very importantly, a dynamic model of the human operator is incorporated into the control of the master manipulator. The individual controllers for the dissimilar master and slave manipulators are connected in a specific communication channel for the bilateral teleoperation to function. Stability of the overall control design is rigorously guaranteed with arbitrary time delays. Novel features of this study include the completely force-sensor-less design for the teleoperation system with a solution for a uniquely introduced computational algebraic loop, a method of estimating the exogenous operating force of an operator and the use of a commercial haptic manipulator. Most importantly, we conduct experiments on a dissimilar system in two degrees of freedom (DOFs). As an illustration of the performance of the proposed system, a force scaling factor of up to 800 and position scaling factor of up to 4 was used in the experiments. The experimental results show an exceptional tracking performance, verifying the real-world performance of the proposed concept.

Funnel-bounded synchronization control for bilateral teleoperation with asymmetric communication delays

Funnel-bounded synchronization control for bilateral teleoperation with asymmetric communication delays

Secure Teleoperation Control Using Somewhat Homomorphic Encryption

The goal of this research is to establish control theoretic methods to enhance cyber security of networked motion control systems by utilizing somewhat homomorphic encryption. The proposed approach will encrypt the entire motion control schemes including: sensor signals, model parameters, feedback gains, and performs computation in the ciphertext space to generate motion commands to servo systems without a security hole. The paper will discuss implementation of encrypted bilateral teleoperation control schemes with nonlinear friction compensation. The paper will present (1) encrypted teleoperation control realization with somewhat homomorphic encryption and (2) simulation results.

A Compliant Partitioned Shared Control Strategy for an Orbital Robot

In this letter, a novel partitioned shared controller is proposed, which exploits a fully-actuated orbital robot to perform a primary end-effector task involving environmental interactions. This task is remotely performed using a bilateral teleoperation controller, while a secondary task is automatically controlled in situ for operational safety in a partitioned manner. In particular, the proposed method is derived as a modified 4-Channel teleoperation architecture. The orbital robot's momentum and shape (joints) dynamics are exploited to benefit the controller design. Asymptotic stability and finite-gain L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -stability are proved in the absence and presence of external interactions, respectively. Furthermore, the proposed method is validated experimentally on a hardware-in-the-loop facility.

Bilateral control of teleoperator systems with time-varying delay

This paper investigates bilateral control of teleoperators with nonlinearity and uncertainty and with arbitrary bounded unknown time-varying delay. We propose two new approaches for teleoperators: a composite approach and a direct approach, and both the approaches are shown to be capable of guaranteeing the stability and infinite manipulability of teleoperators with degree one independent of the time-varying delay. The distinctive point lies in the introduction of a direct channel between the external input sources (from either the human operator or environment) and consensus equilibrium increment of the teleoperator, guided by the design paradigm for ensuring the infinite manipulability. It is demonstrated that the composite approach improves the performance of the teleoperator, and that the direct approach yields separation between the controlled dynamics of the teleoperator and the objective of achieving synchronization and infinite manipulability of the teleoperator. We also propose a hybrid bilateral controller for a typical application context. The application scenarios of the proposed approaches are further demonstrated by extensive simulation results.

Mode‐dependent switching control of bilateral teleoperation against random denial‐of‐service attacks

Mode‐dependent switching control of bilateral teleoperation against random denial‐of‐service attacks

Robust Controller for Pursuing Trajectory and Force Estimations of a Bilateral Tele-Operated Hydraulic Manipulator

In hazardous/emergency situations, public safety is of the utmost concern. In areas where human access is not possible or is restricted due to hazardous situations, a system or robot that can be distantly controlled is mandatory. There are many applications in which force cannot be applied directly while using physical sensors. Therefore, in this research, a robust controller for pursuing trajectory and force estimations while deprived of any signals or sensors for bilateral tele-operation of a hydraulic manipulator is suggested to handle these hazardous, emergency circumstances. A terminal sliding control with a sliding perturbation observer (TSMCSPO) is considered as the robust controller for a coupled leader and hydraulic follower system. The ultimate use of this controller is as a sliding perturbation observer (SPO) that can estimate the reaction force without any physical force sensors. Robust and perfect position tracking is attained with terminal sliding mode control (TSMC) in addition to control of the hydraulic follower manipulator. The force estimation and pursuing trajectory for the leader–follower system is built upon a bilateral tele-operation control approach. The difference between the reaction forces (caused by the remote environment) and the operating forces (applied by the human operator) required the involvement of an impedance model. The impedance model is implemented in the leader manipulator to provide human operators with an actual sense of the reaction force while the manipulator connects with the remote environment. A camera is used to ensure the safety of the workplace through visual feedback. The experimental results showed that the controller was robust at pursuing trajectory and force estimations for the bilateral tele-operation control of a hydraulic manipulator.

Admittance parameterization in linear networked bilateral teleoperation control

In this paper we study linear control of delayed and/or sampled bilateral teleoperation with LTI master and slave devices. A complete parameterization of admittance operators achievable with nominally stabilizing control laws is derived. The potential of this parameterization for controller synthesis is illustrated with a numerical example. In addition, a generic structure of nominally stabilizing controllers is revealed and its properties are discussed. It is shown that delay-independent nominal stabilization in linear networked bilateral teleoperation control does not imply limitations on performance and coupled stability.

Observer-based adaptive force–position control for nonlinear bilateral teleoperation with time delay

In this paper, a novel observer-based force control scheme is proposed to guarantee the position and force tracking in nonlinear teleoperation systems, subject to constant communication time delay. Stability of the teleoperation system is analytically proved using the Lyapunov stability theorem. Enough condition for asymptotic convergence of the force and position are derived. The transparency is also improved by force tracking capability of the system. The teleoperation controller is then applied to a pair of planar 2-DOF robots, connected via a communication channel with constant time delay. The experimental and simulation results demonstrate the effectiveness of the proposed control algorithm, in force estimation and dealing with time delay.

Chattering‐free fixed‐time sliding mode control for bilateral teleoperation under unknown time‐varying delay via disturbance and state observers

AbstractThis paper proposes a new chattering‐free Fixed‐time Observer‐Based Sliding Mode Control (FOBSMC) scheme for synchronization of two bilateral teleoperations under unknown time‐varying delay. The system is subjected to unknown disturbances which are estimated in a fixed time by utilizing the Disturbance Observer‐based SMC scheme. The fixed‐time State Observer‐based SMC is designed to estimate the unmeasured velocity state, while the position state is assumed to be available. Fixed‐time stability method is used to provide the system convergence time independently of initial states. A FOBSMC scheme is first designed for master system of bilateral teleoperation under unknown time‐varying delay to track the environmental torque by the human operating torque in the presence of time delay in the communication channel, as well as estimating the unknown disturbances and unmeasured states. A FOBSMC scheme is designed to synchronize slave system to master system in the presence of time delay in the communication channel, as well as estimating disturbances and states. The stability analysis is performed for closed‐loop system of combined controller‐observer by using Lyapunov theory. The efficacy of the proposed method to fulfill a good transparency and stability under time‐varying communication delays is tested by performing numerical simulation in Simulink/MATLAB.

Review of Control Methods for Upper Limb Telerehabilitation With Robotic Exoskeletons

Given the escalating unmet demand for physical rehabilitation due to the growing global aging population and the effects of the coronavirus COVID-19 including increased incidents of stroke, hospital bed shortages, and clinics closures, robotic telerehabilitation is an emerging, timely, and crucial technology. Rehabilitating the upper limbs of affected patients is of upmost importance for restoring physical function and lighten the societal burden due to disabilities. So far, the majority of the research in robotic telerehabilitation for upper limbs has been performed with end-effector-type assistive robots; however, the use of robotic exoskeletons has significant and distinctive benefits. Although there are surveys written about control methods for upper limb robotic exoskeletons and other surveys written about bilateral teleoperation control methods, there are no surveys written specifically about telerehabilitation control methods for upper limbs using robotic exoskeletons. As a result, this article reviews the state-of-the-art control strategies including various advanced linear and nonlinear control approaches for upper limb rehabilitation robotic exoskeletons, bilateral teleoperation, and several state-of-the-art telerehabilitation applications with upper limb robotic exoskeletons. The benefits, drawbacks, challenges, and future directions of existing methodologies are extensively discussed. This article offers a comprehensive overview and insight for new researchers in the area of telerehabilitation robotic exoskeletons.

Neural-network-based adaptive control for bilateral teleoperation with multiple slaves under Round-Robin scheduling protocol

A neural-network-based adaptive control scheme is developed for bilateral teleoperation systems with single-master-multiple-slaves in the presence of dynamic uncertainties and communication constraint. Discrete-time data transmitting communication network with bandwidth limitation and time-varying communication delays is considered and the Round-Robin scheduling protocol is used to orchestrate the data transmission from multiple slaves to the master. Stability criteria of the closed-loop system are established by constructing appropriate Lyapunov-Krasovskii functionals. Simulation studies are performed to illustrate the effectiveness of the proposed control algorithm.

Observer-based sliding mode control for bilateral teleoperation with time-varying delays

In this paper, a tracking control scheme is investigated for a bilateral teleoperation system with time-varying delays and dynamic uncertainties. The tracking control scheme is based on an extended state observer (ESO), a time-delay part observer and a continuous terminal sliding mode control (CTSMC) strategy. The dynamic uncertainties are dealt with by the ESO for the bilateral teleoperation system. The time-varying delays with unmeasurable derivatives are estimated by the two time-delay part observers. The CTSMC strategy is used to ensure finite-time convergence for the bilateral teleoperation system without knowing the second derivatives of tracking errors. Finally, experiment results are shown for the bilateral teleoperation system to demonstrate effectiveness of the developed tracking control scheme.

A Lyapunov Stable Controller for Bilateral Haptic Teleoperation of Single-Rod Hydraulic Actuators Subjected to Base Disturbance

In this paper, a control scheme is developed and evaluated for stable bilateral haptic teleoperation of a single-rod hydraulic actuator subjected to base disturbance. The proposed controller, based on Lyapunov stability technique, is capable of reducing position errors at master and slave sides, and provides a feel of the contact force between the actuator and the task environment to the operator without a need for direct measurement. The controller requires only the measurements of the actuator line pressures and displacements of the master and slave. The system stability is insensitive to the uncertainties of the physical parameters and of the measurement of the base point motion. Stability of the proposed controller incorporating hydraulic nonlinearities and operator dynamics with an estimated upper value for the base disturbance is analytically proven. Simulation studies validate that the proposed control system is stable while interacting with a task environment. Experimental results demonstrate the effectiveness of control scheme in maintaining stability, while having good position tracking by the hydraulic actuator as well as providing a haptic feel to the operator without direct measurement of interaction force, while the hydraulic actuator is subjected to base disturbance.