A novel control framework for nonlinear time-delayed dual-master/single-slave teleoperation

Finite-time control of dual-user haptic system with online authority transfer

A finite-time control method with online authority transfer is proposed for a class of dual-user haptic system (DUHS) with training tasks. An authority transfer strategy based on the error system reflecting task performance is designed to adjust the dominance factor so that the system can realize smooth online switching between different modes. Next, the desired position is defined according to the dominance factor, and then the sliding mode surface is constructed by the position tracking error to design a nonsingular terminal sliding-mode control. The stability and position tracking performance of DUHS are analyzed by Lyapunov theory, and the effectiveness of the proposed method is verified. The proposed method not only enables smooth online switching of task authority between the trainer and the trainee but also ensures that the position tracking error of the system converges in a finite time.

Review of Advanced Medical Telerobots

The advent of telerobotic systems has revolutionized various aspects of the industry and human life. This technology is designed to augment human sensorimotor capabilities to extend them beyond natural competence. Classic examples are space and underwater applications when distance and access are the two major physical barriers to be combated with this technology. In modern examples, telerobotic systems have been used in several clinical applications, including teleoperated surgery and telerehabilitation. In this regard, there has been a significant amount of research and development due to the major benefits in terms of medical outcomes. Recently telerobotic systems are combined with advanced artificial intelligence modules to better share the agency with the operator and open new doors of medical automation. In this review paper, we have provided a comprehensive analysis of the literature considering various topologies of telerobotic systems in the medical domain while shedding light on different levels of autonomy for this technology, starting from direct control, going up to command-tracking autonomous telerobots. Existing challenges, including instrumentation, transparency, autonomy, stochastic communication delays, and stability, in addition to the current direction of research related to benefit in telemedicine and medical automation, and future vision of this technology, are discussed in this review paper.

Exponential stability of bilateral sampled-data teleoperation systems using multirate approach

This paper develops the stability analysis for linear bilateral teleoperation systems exposed to communication constraints and multirate samplers. Dynamics of the master and slave robots are assumed to be continuous-time with discrete-time controllers. The proposed multirate design guarantees the exponential stability of the teleoperation system over a communication networks. Different sampling rates are imposed on position/velocity signals in both master and slave sides and by exerting input-delay approach, the multirate dynamics is transformed into a continuous-time system. Sufficient Krasovskii-based stability criteria are provided to preserve the exponential stability of the linear discrete-time system for asynchronously sampling intervals and update rates. This analysis is formulated as a convex optimization problem in terms of linear matrix inequalities (LMI) to calculate the longest interval between two successive sampling periods. The proposed multirate approach demonstrates that selecting adequate intervals for samplers and proper update rates for actuators has a considerable effect on the stability of the system. In order to validate the stability criteria and present the efficacy of the proposed multirate scheme, pair of two degree of freedom manipulators will be investigated and maximum allowable sampling periods and update rates are computed to preserve the exponential stability for different multirate cases.

Adaptive neural network based position tracking control for Dual-master/Single-slave teleoperation system under communication constant time delays

The novel trajectory tracking control strategies for trilateral teleoperation systems with Dual-master/Single-slave robot manipulators under communication constant time delays are proposed in this article. By incorporating this design technique into the neural network (NN) based adaptive control framework, two controllers are designed for the trilateral teleoperation systems in free motion. First, with acceleration measurements, an adaptive controller under the synchronization variables containing the position and velocity error is constructed to guarantee the position and velocity tracking errors between the trilateral teleoperation systems asymptotically converge to zero. Second, without acceleration measurements, an adaptive controller under the new synchronization variables is presented such that the trilateral teleoperation systems can obtain the same trajectory tracking performance as the first controller. Third, in term of establishing suitable Lyapunov-Krasovskii functionals, the asymptotic tracking performances of the trilateral teleoperation systems can be derived independent of the communication constant time delays. Moreover, these two controllers are obtained without the knowledge of upper bounds of the NN approximation errors, respectively. Finally, simulation results are presented to demonstrate the validity of the proposed methods.

An Energy-Based Approach for n-d.o.f. Passive Dual-User Haptic Training Systems

This paper introduces a dual-user training system whose design is based on an energetic approach. This kind of system is useful for supervised hands-on training where a trainer interacts with a trainee through two haptic devices, in order to practice on a manual task performed on a virtual or teleoperated robot (e.g., for an Minimally Invasive Surgery (MIS) task in a surgical context). This paper details the proof of stability of an Energy Shared Control (ESC) architecture we previously introduced for one degree of freedom (d.o.f.) devices. An extension to multiple degrees of freedom is proposed, along with an enhanced version of the Adaptive Authority Adjustment function. Experiments are carried out with 3 d.o.f. haptic devices in free motion as well as in contact contexts in order to show the relevance of this architecture.

Haptic Augmentation for Teleoperation through Virtual Grasping Points

Future challenges in teleoperation arise from a new complexity of tasks and from constraints in unstructured environments. In industrial applications as nuclear research facilities, the operator has to manipulate large objects whereas medical robotics requires extremely high precision. In the last decades, research optimized the transparency in teleoperation setups through accurate hardware, higher sampling rates, and improved sensor technologies. To further enhance the performance in telemanipulation, the idea of haptic augmentation has been briefly introduced in [Panzirsch et al., IEEE ICRA, 2015, pp. 312-317]. Haptic augmentation provides supportive haptic cues to the operator that promise to ease the task execution and increase the control accuracy. Therefore, an additional haptic interface can be added into the control loop. The present paper introduces the stability analysis of the resulting multilateral framework and equations for multi-DoF coupling and time delay control. Furthermore, a detailed analysis via experiments and a user study is presented. The control structure is designed in the network representation and based on passive modules. Through this passivity-based modular design, a high adaptability to new tasks and setups is achieved. The results of the user study indicate that the bimanual control brings large benefits especially in improving rotational precision.

A Systematic Review of Multilateral Teleoperation Systems

While conventional bilateral Single-Master/Single-Slave (SM/SS) teleoperation systems have received considerable attention during the past several decades, multilateral teleoperation is only recently being studied. Unlike an SM/SS system, which consists of one master-slave set, multilateral teleoperation frameworks involve a minimum of three agents in order to remotely perform a task. This paper presents an overview of multilateral teleoperation systems and classifies the existing state-of-the-art architecture based on topologies, applications, and closed-loop stability analysis. For each category, the review discusses control strategies used for various architectures as well as control challenges (e.g., closed-loop instability as a result of a delay in the communication network) for each methodology.

Passivity-based control framework for task-space bilateral teleoperation with parametric uncertainty over unreliable networks

Bilateral teleoperation systems developed in joint-space or in task-space without taking into account parameter uncertainties and unreliable communication have limited practical applications. In order to ensure stability, improve tracking performance, and enhance applicability, a novel task-space control framework for bilateral teleoperation with kinematic/dynamic uncertainties and time delays/packet losses is studied. In this paper, we have demonstrated that with the proposed control algorithms, the teleoperation system is stable and position tracking is guaranteed when the system is subjected to parametric uncertainties and communication delays. With the transformation of scattering variables, a packet modulation, called Passivity-Based Packet Modulation (PBPM), is proposed to cope with data losses, incurred in transmission of data over unreliable network. Moreover, numerical simulations and experiments are also presented to validate the efficiency of the developed control framework for task-space bilateral teleoperation.

Dual-user nonlinear teleoperation subjected to varying time delay and bounded inputs

A novel trilateral control architecture for Dual-master/Single-slave teleoperation system with taking account of saturation in actuators, nonlinear dynamics for telemanipulators and bounded varying time delay which affects the transmitted signals in the communication channels, is proposed in this paper. In this research, we will address the stability and desired position coordination problem of trilateral teleoperation system by extension of (nP+D) controller that is used for Single-master/Single-slave teleoperation system. Our proposed controller is weighted summation of nonlinear Proportional plus Damping (nP+D) controller that incorporate gravity compensation and the weights are specified by the dominance factor, which determines the supremacy of each user over the slave robot and over the other user. The asymptotic stability of closed loop dynamics is studied using Lyapunov-Krasovskii functional under conditions on the controller parameters, the actuator saturation characteristics and the maximum values of varying time delays. It is shown that these controllers satisfy the desired position coordination problem in free motion condition. To show the effectiveness of the proposed method, a number of simulations have been conducted on a varying time delay Dual-master/Single-slave teleoperation system using 3-DOF planar robots for each telemanipulator subjected to actuator saturation.

Sensor-less force-reflecting macro-micro telemanipulation systems by piezoelectric actuators

This paper establishes a novel control strategy for a nonlinear bilateral macro-micro teleoperation system with time delay. Besides position and velocity signals, force signals are additionally utilized in the control scheme. This modification significantly improves the poor transparency during contact with the environment. To eliminate external force measurement, a force estimation algorithm is proposed for the master and slave robots. The closed loop stability of the nonlinear micro-micro teleoperation system with the proposed control scheme is investigated employing the Lyapunov theory. Consequently, the experimental results verify the efficiency of the new control scheme in free motion and during collision between the slave robot and the environment of slave robot with environment, and the efficiency of the force estimation algorithm.

A dual-user teleoperation system with Online Authority Adjustment for haptic training

This paper introduces a dual-user teleoperation system for hands-on medical training. A shared control based architecture is presented for authority management. In this structure, the combination of control signals is obtained using a dominance factor. Its main improvement is Online Authority Adjustment (OAA): the authority can be adjusted manually/automatically during the training progress. Experimental results are provided to validate the performances of the system.

Design and evaluation of a trilateral shared-control architecture for teleoperated training robots

Multilateral teleoperated robots can be used to train humans to perform complex tasks that require collaborative interaction and expert supervision, such as laparoscopic surgical procedures. In this paper, we explain the design and performance evaluation of a shared-control architecture that can be used in trilateral teleoperated training robots. The architecture includes dominance and observation factors inspired by the determinants of motor learning in humans, including observational practice, focus of attention, feedback and augmented feedback, and self-controlled practice. Toward the validation of such an architecture, we (1) verify the stability of a trilateral system by applying Llewellyn's criterion on a two-port equivalent architecture, and (2) demonstrate that system transparency remains generally invariant across relevant observation factors and movement frequencies. In a preliminary experimental study, a dyad of two human users (one novice, one expert) collaborated on the control of a robot to follow a trajectory. The experiment showed that the framework can be used to modulate the efforts of the users and adjust the source and level of haptic feedback to the novice user.

Adaptive fuzzy predictive sliding control of uncertain nonlinear systems with bound-known input delay

In this paper, a new Adaptive Fuzzy Predictive Sliding Mode Control (AFP-SMC) is presented for nonlinear systems with uncertain dynamics and unknown input delay. The control unit consists of a fuzzy inference system to approximate the ideal linearization control, together with a switching strategy to compensate for the estimation errors. Also, an adaptive fuzzy predictor is used to estimate the future values of the system states to compensate for the time delay. The adaptation laws are used to tune the controller and predictor parameters, which guarantee the stability based on a Lyapunov-Krasovskii functional. To evaluate the method effectiveness, the simulation and experiment on an overhead crane system are presented. According to the obtained results, AFP-SMC can effectively control the uncertain nonlinear systems, subject to input delays of known bound.

Bilateral shared autonomous systems with passive and nonpassive input forces under time varying delay

In this paper, we address stability and tracking control problem of bilateral shared autonomous systems in the presence of passive and nonpassive input interaction forces. The design comprises delayed position and position-velocity signals with the known and unknown structures of the master and slave manipulator dynamics. Using novel Lyapunov-Krasovskii functional, stability and tracking conditions of the coupled master-slave shared autonomous systems are developed under symmetrical and unsymmetrical time varying data transmission delays. This condition allows the designer to estimate the control design parameters to ensure position, velocity and synchronizing errors of the master and slave manipulators. Finally, evaluation results are presented to demonstrate the validity of the proposed design for real-time teleoperation applications.

Adaptive synchronization and parameter identification of chaotic system with unknown parameters and mixed delays based on a special matrix structure

In this paper, we investigate the synchronization and parameter identification of chaotic system with unknown parameters and mixed delays. A new approach is proposed for designing a controller and a update rule of unknown parameters based on a special matrix structure, and the synchronization and the parameter identification are realized under the controller and the update rule. Numerical simulations are carried out to confirm the effectiveness of the approach. A significant advantage is that the process of designing a controller and a update rule become very clear and easy by the proposed approach.