High-fidelity bilateral teleoperation systems and the effect of multimodal haptics.

In master-slave teleoperation applications that deal with a delicate and sensitive environment, it is important to provide haptic feedback of slave/environment interactions to the user's hand as it improves task performance and teleoperation transparency (fidelity), which is the extent of telepresence of the remote environment available to the user through the master-slave system. For haptic teleoperation, in addition to a haptics-capable master interface, often one or more force sensors are also used, which warrant new bilateral control architectures while increasing the cost and the complexity of the teleoperation system. In this paper, we investigate the added benefits of using force sensors that measure hand/master and slave/environment interactions and of utilizing local feedback loops on the teleoperation transparency. We compare the two-channel and the four-channel bilateral control systems in terms of stability and transparency, and study the stability and performance robustness of the four-channel method against nonidealities that arise during bilateral control implementation, which include master-slave communication latency and changes in the environment dynamics. The next issue addressed in the paper deals with the case where the master interface is not haptics capable, but the slave is equipped with a force sensor. In the context of robotics-assisted soft-tissue surgical applications, we explore through human factors experiments whether slave/environment force measurements can be of any help with regard to improving task performance. The last problem we study is whether slave/environment force information, with and without haptic capability in the master interface, can help improve outcomes under degraded visual conditions.     

外骨骼式遥操作主手设计及主从异构映射算法研究

为了更好地促进机器人适应复杂的遥操作任务,开发了能够精确获取人体上肢运动信息的外骨骼式遥操作主手,并通过异构映射算法,实现对6自由度协作机械臂的遥操作．首先,基于人体仿生结构,设计了可穿戴式8自由度外骨骼主手（臂部7自由度和手部1自由度）;其次,通过改进的D-H（Denavit-Hartenberg）方法建立遥操作系统的运动学模型,基于Matlab的机器人工具箱进行了工作空间仿真,并设计主从异构映射算法;最后,实验验证外骨骼主手在遥操作系统中的可操作性,以及工作空间异构映射算法的可行性．实验表明,外骨骼主手能够控制从端机械手臂,且保证末端位置和姿态一致,可在大范围工作空间内复现人体上肢精细运动,主从跟随误差达2 mm,工作空间类似于直径1.08 m的半球形．因此,可穿戴式的外骨骼主手使操作者能更加直观地参与到遥操作系统当中,辅助操作者更加高效地完成精细复杂任务．     

手控器的性能和评价方法

手控器是主从遥操作系统的关键设备,它不仅是从机械手进行实时运动控制的输入设 备,而且是将从机械手与未知环境之间的相互作用力提供给操作者的力觉遥现装置,是人与 机器人之间建立紧密动态耦合的重要接口．因此,其性能的好坏,直接影响遥操作系统的操 作性能．近年来,在手控器研制方面的文章已发表不少,但很少涉及对手控器进行评价的方 法和量化指标．这种目标的模糊性必然造成某些设计上的盲目性．本文作者在总结多年来对 手控器研制和试验工作经验的基础上,试图对这个问题进行比较深入的探讨,初步提出了一 套评价方法和量化指标．     

A novel adaptive bilateral control scheme using similar closed‐loop dynamic characteristics of master/slave manipulators

This article presents a novel adaptive bilateral control scheme for obtaining ideal responses for teleoperation systems with uncertainties. A condition that is equivalent to getting an ideal response in teleoperation has been found to be making the closed‐loop dynamics of master and slave manipulators a similar form. An adaptive approach is applied to achieve similarity for the uncertain master and slave manipulators. Using the similar closed‐loop dynamic characteristics of master/slave teleoperation systems, excellent position and force tracking performance has been obtained without estimating the impedance of human and environment. The validity of the theoretical results is verified by experiments. © 2001 John Wiley & Sons, Inc.     

Design of a force reflection controller for telerobot systems using neural network and fuzzy logic

This paper presents a new method for selecting the force-reflection gain in a position-force type bilateral teleoperation system. The force-reflection gain greatly affects the task performance of a teleoperation system; too small gain results in poor task performance while too large gain results in system instability. The maximum boundary of the gain guaranteeing the stability greatly depends upon characteristics of the elements in the system such as: a master arm which is combined with the human operator's hand and the environments with which the slave arm contacts. In normal practice, it is, therefore, very difficult to determine such maximum boundary of the gain. To overcome this difficulty, this paper proposes a force-reflection gain selecting algorithm based on artificial neural network and fuzzy logic. The method estimates characteristics of the master arm and the environments by using neural networks and, then, determines the force-reflection gain from the estimated characteristics by using fuzzy logic. In order to show the effectiveness of the proposed algorithm, a series of experiments are conducted under various conditions of teleoperation using a laboratory-made telerobot system.     

不确定遥操作系统带干扰观测器的自适应控制

遥操作系统受到不同类型的不确定性因素影响, 这些不确定性会降低系统的透明性, 甚至会使得系统不稳定. 本文提出了一种带干扰观测器的自适应控制器(adaptive controller with disturbance observer, ACWDO) 用来处理遥操作系统中同时受到的外部干扰和内部动力学参数不确定性. 首先建立了受外部干扰的遥操作系统的非线性动力学模型; 然后分别对主机器人和从机器人设计非线性干扰观测器用来对外部干扰进行估计和补偿; 之后在干扰观测器基础之上分别对主机器人和从机器人设计自适应控制器用来处理内部不确定的动力学参数; 最后再将所设计的ACWDO融入到四通道遥操作系统结构中. 理论分析和仿真结果表明, 所设计的控制器可以取得良好的位置跟踪和力跟踪效果, 确保了遥操作系统的透明性.     

Integrated adaptive robust control for multilateral teleoperation systems under arbitrary time delays

With the increasing industrial requirements such as bigger size object, stable operation, and complex task, multilateral teleoperation systems extended from traditional bilateral teleoperation are widely developed. In this paper, the integrated control design is developed for multilateral teleoperation systems, where n master manipulators are operated by human to remotely control n slave manipulators cooperatively handling a target object. For the first time, the control objectives of multilateral teleoperation including stability, synchronization, transparency, and internal force distribution are clarified systematically. A novel communication architecture is proposed to cope with communication delays, where the estimated environmental parameters are transmitted from the slave side to the master, to replace the traditional environmental force measurement in the communication channel. A kind of nonlinear adaptive robust control technique is used to deal with nonlinearities, unknown parameters, and modeling uncertainties existing in the master, slave, and environmental dynamics, so that the excellent tracking performance is achieved in both master and slave sides. The coordinated motion/force control is designed in the slave side by the optimal internal force distribution among n slave manipulators, and the impedance control is designed in the master side to realize the target transparency behavior. In summary, the proposed control algorithm can achieve the guaranteed robust stability, the excellent synchronization and transparency performance, and the optimal internal force distribution simultaneously for multilateral teleoperation systems under arbitrary time delays and various modeling uncertainties. The simulation is carried out on a 2‐master/2‐slave teleoperation system, and the results show the effectiveness of the proposed control design. Copyright © 2015 John Wiley & Sons, Ltd.     

On tracking performance in bilateral teleoperation

This paper addresses the problem of steady-state position and force tracking in bilateral teleoperation. Passivity-based control schemes for bilateral teleoperation provide robust stability against network delays in the feedback loop and velocity tracking, but do not guarantee steady-state position and force tracking in general. Position drift due to data loss and offset of initial conditions is a well-known problem in such systems. In this paper, we introduce a new architecture, which builds upon the traditional passivity-based configuration by using additional position control on both the master and slave robots, to solve the steady-state position and force-tracking problem. Lyapunov stability methods are used to establish the range of the position control gains on the master and slave sides. Experimental results using a single-degree-of-freedom master/slave system are presented, showing the performance of the resulting system.     

Adaptive wavenet controller design for teleoperation systems with variable time delays using singular perturbation method

The main goal of controller design in teleoperation systems is to achieve stability and optimal operation in presence of factors such as time delays, system disturbances and modeling errors. This paper proposes a new method of controller design based on wavenet with singular perturbation method for the bilateral teleoperation of robots through the internet. The wavenet controller could overcome the variable time delay in teleoperation system. This new method introduces a reduced-order structure for control and stability of teleoperation systems. By using singular perturbation method, teleoperation system is decomposed into two fast and slow subsystems. This method is a step towards reduced-order modeling. In this method, we use a feedback linearization method in master subsystem and a wavenet controller for slave subsystem. In wavenet controller, we used a learning method so that the system was Lyapunov stable. As the stability of the model is highly dependent on the learning of the system, we use Lyapunov stability in this method. It has been tried to reduce the tracking error between the master and the slave subsystems. In this structure the position of master-slave are compared together and controlling signal is applied to the slave so that they can track each other in the least possible time. In all schemes the effectiveness of the system is shown through the simulations and they have been compared with each other.     

Generalized control method by state convergence for teleoperation systems with time delay

In this paper a generalized design and control method for teleoperation systems with communication time delay is presented. The design method is based on the state space formulation and it allows to obtain the control parameters for any teleoperation system where the master and the slave manipulators would be represented by nth-order linear differential equations. Through state convergence between the master and the slave, the control system allows the slave to follow the master inspite of the time delay. The method is also able to establish the desired dynamics of this convergence and the dynamics of the slave manipulator. Experimental results are presented showing the validity of the proposed design and control method.     

A Composite State Convergence Scheme for Bilateral Teleoperation Systems

State convergence is a novel control algorithm for bilateral teleoperation of robotic systems. First, it models the teleoperation system on state space and considers all the possible interactions between the master and slave systems. Second, it presents an elegant design procedure which requires a set of equations to be solved in order to compute the control gains of the bilateral loop. These design conditions are obtained by turning the master-slave error into an autonomous system and imposing the desired dynamic behavior of the teleoperation system. Resultantly, the convergence of master and slave states is achieved in a well-defined manner. The present study aims at achieving a similar convergence behavior offered by state convergence controller while reducing the number of variables sent across the communication channel. The proposal suggests transmitting composite master and slave variables instead of full master and slave states while keeping the operator’s force channel intact. We show that, with these composite and force variables; it is indeed possible to achieve the convergence of states in a desired way by strictly following the method of state convergence. The proposal leads to a reduced complexity state convergence algorithm which is termed as composite state convergence controller. In order to validate the proposed scheme in the absence and presence of communication time delays, MATLAB simulations and semi-real time experiments are performed on a single degree-of-freedom teleoperation system.      

遥操作旋转运动梁系统多目标优化控制研究

本文以旋转运动柔性梁为对象,采用基于胞映射的多目标优化方法进行遥操作系统双边控制研究.首先建立遥操作旋转运动柔性梁系统动力学方程,其次考虑信号传输时滞和系统主从端跟踪误差信号设计主端控制器和从端控制器,并利用Lyapunov稳定性理论获得保证闭环控制系统稳定的控制增益所需要满足的条件.由于满足稳定性条件并不意味着好的控制性能,最后利用基于胞映射的多目标优化方法进行优化控制设计,得到同时满足多个不同目标的控制增益的Pareto最优解集.仿真结果表明所获得的控制增益能够有效实现遥操作系统主从端的信号跟踪,并且操作者能够及时感受到从端环境的变化.     

Control of Teleoperators with Communication Time Delay through State Convergence

This paper describes a new control method of teleoperation systems with communication time delay. This method models the teleoperation system in the state space, considering all the possible interactions that could appear in the operator‐master‐slave‐environment set, and it uses the Taylor expansion to model the time delay. The control system allows that the slave manipulator follows the master in spite of the time delay in the communication channel. The tracking is achieved by state convergence between the master and the slave. The method is also able to establish the desired dynamics of this convergence and the dynamics of the slave manipulator. Furthermore, a simple design procedure is provided to obtain the control system gains. These control gains are calculated solving a set of seven equations. The control method is robust to the uncertainty of the design parameters, so it is not necessary to obtain good estimations of these parameters. Simulations and experiments with a one DOF teleoperation system are presented to verify the control method. © 2004 Wiley Periodicals, Inc.     

Adaptive Inverse Dynamics Four-Channel Control of Uncertain Nonlinear Teleoperation Systems

Most of the methods to date on bilateral control of nonlinear teleoperation systems lead to nonlinear and coupled closed-loop dynamics, even in the ideal case of perfect knowledge of the master, the slave, the human operator and the environment. Consequently, the transparency of these closed-loop systems is difficult to study. In comparison, inverse dynamics controllers can deal with the nonlinear terms in the dynamics in a way that, in the ideal case, the closed-loop systems become linear and decoupled. In this paper, for multi-d.o.f. nonlinear teleoperation systems with uncertainties, adaptive inverse dynamics controllers are incorporated into the four-channel bilateral teleoperation control framework. The resulting controllers do not need exact knowledge of the dynamics of the master, the slave, the human operator or the environment. A Lyapunov analysis is presented to prove the transparency of the teleoperation system. Simulations are also presented to show the effectiveness of the proposed approach.     

Absolute stability analysis of sampled-data scaled bilateral teleoperation systems

Stability of a bilateral teleoperation system may be jeopardized by controller discretization, which has been shown to involve energy leaks. This paper proposes a novel approach to analyzing the absolute stability of sampled-data bilateral teleoperation systems consisting of discrete-time controllers and continuous-time master, slave, operator, and environment. The proposed stability analysis permits scaling and delay in the master and the slave positions and forces. The absolute stability conditions reported here impose bounds on the gains of the discrete-time controller, the damping terms of the master and the slave, and the sampling time. A design-related application of these results is in proper selection of various control parameters and the sampling rate for stable teleoperation under discrete-time control. To explore the trade-off between the control gains and the sampling time, it is studied that how large sampling times, which require low control gains for maintaining stability, can lead to unacceptable teleoperation transparency and human task performance in a teleoperated switching task. This shows that the effect of sampling time must be taken into account because neglecting it (as in the absolute stability literature) undermines both stability and transparency of teleoperation. The resulting absolute stability condition has been verified via experiments with two Phantom Omni robots.     

A design of bilateral teleoperation systems using composite adaptive controller

This paper presents a synchronization scheme of bilateral teleoperation systems using composite adaptive controller. To design a controller for bilateral teleoperation systems, all the parameters of the master and the slave robots need to be known. However, there exist parameter uncertainties in the robot manipulators. A composite adaptive controller is designed for convergence of states and parameters of the master and the slave robots in the presence of parameter uncertainties. Consequently, position and force tracking problems in free and contact motion are solved in a synchronized manner. Through a number of simulations, the superiority of the proposed method over existing works is illustrated. Furthermore, for the validation of utility of the proposed method in an actual embedded system, the algorithms are implemented and tested in FPGA-based hardware controller.     

Stability guaranteed teleoperation: an adaptive motion/force control approach

An adaptive motion/force controller is developed for unilateral or bilateral teleoperation systems. The method can be applied in both position and rate control modes, with arbitrary motion or force scaling. No acceleration measurements are required. Nonlinear rigid-body dynamics of the master and the slave robots are considered. A model of the flexible or rigid environment is incorporated into the dynamics of the slave, while a model of the human operator is incorporated into the dynamics of the master. The master and the slave are subject to independent adaptive motion/force controllers that assume parameter uncertainty bounds. Each parameter is independently updated within its known lower and upper bounds. The states of the master (slave) are sent to the slave (master) as motion/force tracking commands instead of control actions (efforts and/or flows). Under the modeling assumptions for the human operator and the environment, the proposed teleoperation control scheme is L/sub 2/ and L/sub /spl infin// stable in both free motion and flexible or rigid contact motion and is robust against time delays. The controlled master-slave system behaves essentially as a linearly damped free-floating mass. If the parameter estimates converge, the environment impedance and the impedance transmitted to the master differ only by a control-parameter dependent mass/damper term. Asymptotic motion (velocity/position) tracking and force tracking with zero steady-state error are achieved. Experimental results are presented in support of the analysis.     

Adaptive/Robust Control for Time-Delay Teleoperation

The control of time-delay bilateral teleoperation systems involves a delicate tradeoff between the conflicting requirements of transparency and robust stability. The control design is complicated by latency in data communication between the master and slave sites, as well as uncertainties in the dynamics of operator, master, slave, and environment. This paper proposes a systematic design procedure for improving teleoperation fidelity while maintaining its stability in the presence of dynamic uncertainty and a constant time delay. In a two-step control approach, first local Lyapunov-based adaptive/nonlinear controllers are applied to linearize the system dynamics and eliminate dependency on the master and slave parameters. Teleoperation coordination, subject to parametric uncertainty in the user and environment dynamics, is then achieved by formulating an I/O time-delay $H_{infty }$ robust control synthesis that is solved via its decomposition to the so-called adobe problems. The transparency and robust stability properties of the proposed method is examined via numerical analysis. Furthermore, the results are successfully validated in experiments.      

工业机器人遥操作系统的空间映射与控制策略

针对工业机器人遥操作系统中存在的主从机器人工作空间差异以及运动控制精度与安全问题,提出了一种工作空间映射算法与位置—速度混合控制策略。首先,将遥操作划分为自由运动和交互两个阶段,在自由运动阶段采用映射算法使主从机器人的工作空间高度覆盖,使主机器人可操控的从机器人运动范围最大化。进一步,在交互阶段设计了一种位置—速度混合控制策略对工业机器人的运动进行准确的控制,使主从机器人的实际位置轨迹准确的跟随,并进一步引入反馈引导力以实现安全的控制。最后在Touch-ABB IRB120主从机器人遥操作实验平台上对所提控制方法进行验证,实验结果表明该方法使得主从机器人运动范围在高度覆盖的同时可以保证遥操作控制的精度。     

Nonlinear and Filtered Force/Position Mappings in Bilateral Teleoperation With Application to Enhanced Stiffness Discrimination

Motivated by applications involving soft-tissue manipulation such as robotic surgery, the transparency objectives in bilateral teleoperation are redefined to include monotonic nonlinear and linear-time-invariant filter mappings between the master/slave position and force signals. To demonstrate the utility of the new performance measures, a stiffness discrimination telemanipulation task of soft environments is considered. A nonlinear force mapping can enhance stiffness discrimination thresholds as shown through a set of psychophysics experiments. Lyapunov-based adaptive motion/force controllers are presented that can achieve the new transparency objectives in the presence of dynamic uncertainty in the master, slave, user, and environment and in the absence of time delay. Given a priori known bounds on unknown dynamic parameters, a framework for robust stability analysis is proposed that uses an off-axis circle criterion and the Nyquist envelope of interval plant systems. Nonlinear- and linear-filtered mappings are achieved in experiments with a two-axis teleoperation system.