This paper develops data-driven Type-2 Takagi–Sugeno (T–S) fuzzy modeling and control for bilateral teleoperation with dynamic uncertainties and time-varying delays. The Type-2 T–S fuzzy model identified based on input–output data samples describes the nonlinear teleoperation system by a weighted sum of a group of linear local models, which offers a platform to design robust control algorithms by means of mature linear theories. The fuzzy-model-based four-channel control laws are proposed to guarantee the motion synchronization and enhance the operator's force perception for the environment when the time-varying delays and large dynamic uncertainties, especially the gravity of a heavy end effector of the slave, exist. Markov processes are applied to model the time delays. The stability of the closed-loop system is proved by using the Lyapunov–Krasovskii functions. All the conditions are expressed as linear-matrix inequalities (LMI). By using the MATLAB LMI toolbox, the optimized control gains for each of the fuzzy rules are derived to achieve the optimal performance. Finally, experiments based on an experimental platform consisting of two haptic devices prove the superiority of the proposed strategy through comparison with previous work.

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Type-2 Fuzzy Modeling and Control for Bilateral Teleoperation System With Dynamic Uncertainties and Time-Varying Delays

Adaptive finite‐time control for bilateral teleoperation systems with jittering time delays

Electro-hydrostatic actuators (EHAs) possess excellent power/weight ratio and space-saving properties. However, uncertainty exists with respect to the presence of non-linear behaviors and dynamic c...

Modeling and resonance suppression control for electro-hydrostatic actuator as a two-mass resonant system

In this study, we investigated bilateral control in the vertical direction using functional electrical stimulation (FES). Bilateral control is a remote operation technique that incorporates force feedback. This technology has potential applications in everyday life, including allowing medical doctors to make diagnoses or friends to communicate using tactile sensations when far apart. However, current iterations of this technology require robot arms to be worn. This is undesirable as such arms are heavy, and arms with multi degree-of-freedom are difficult to produce. To address these problems, we investigated bilateral control using FES. However, in previous studies, which applied FES to bilateral control, control in the vertical direction and the effect of reaction forces were not investigated. In this study, we verified that vertical control is achievable. First, the movements of a human operator were shown to follow those of another operator in the vertical direction, demonstrating that vertical bilateral control using FES is effective. We next investigated whether an operator could recognize when the partner was holding a weight. This experiment demonstrated that the operator was able to recognize the presence or absence of the weight in the hand of the partner. However, shaking was observed in the arms of the master and slave. We believe that this problem can be eliminated by estimating the reaction forces of arms.

Bilateral Control in the Vertical Direction Using Functional Electrical Stimulation

This paper proposes a novel bilateral control design based on an estimated reaction force without a force sensor for a three-degree of freedom hydraulic servo system with master–slave manipulators. The proposed method is based upon sliding mode control with sliding perturbation observer (SMCSPO) using a bilateral control environment. The sliding perturbation observer (SPO) estimates the reaction force at the end effector and second link without using any sensors. The sliding mode control (SMC) is used as a bilateral controller for the robust position tracking and control of the slave device. A bilateral control strategy in a hydraulic servo system provides robust position and force tracking between master and slave. The difference between the reaction force of the slave produced by the effect of the remote environment and the operating force applied to the master by the operator is expressed in the target impedance model. The impedance model is applied to the master and allows the operator to feel the reaction force from the environment. This research experimentally verifies that the slave device can follow the trajectory of the master device using the proposed bilateral control strategy based on the estimated reaction force. This technique will be convenient for three or more degree of freedom (DOF) hydraulic servo systems used in dismantling nuclear power plants. It is worthy to mention that a camera is used for visual feedback on the safety of the environment and workspace.

https://www.mdpi.com/2079-9292/7/10/256/pdf

Estimated Reaction Force-Based Bilateral Control between 3DOF Master and Hydraulic Slave Manipulators for Dismantlement

In this study, bilateral control between electric and hydraulic actuators is investigated. Bilateral control realizes telemanipulation of remote robots with the sense of touch. We focus on the system of local (master) robots, manipulated by operators that are driven by electric actuators, and slave robots, which work in remote places that are driven by hydraulic actuators. To obtain bilateral control in this situation, we find that combination of three key techniques is necessary. The first key is oblique coordinate control, which can decouple position and force controllers of bilateral control. The second key is linearization of hydraulic actuators as third-order systems including oil compression by using disturbance observers. In the absence of linearization, the design becomes practically impossible because of the need to apply complicated models. Since the master robots are second-order systems, and the slave robots are linearized as third-order systems, oblique coordinate control cannot be implemented. Then, the last key is the agreement of system order of electric and hydraulic actuators by using a pseudodifferentiator. Two conventional controllers and the proposed method are experimentally and analytically compared. The proposed method shows the best tracking performance and is the most stable in contact control among the three controllers.

Bilateral Control Between Electric and Hydraulic Actuators Using Linearization of Hydraulic Actuators

Working in ultimate environments (e.g. working at the disaster sites) is dangerous for humans. Hence it is important to introduce teleoperated robots at the extreme environments. Since there are many heavy works, hydraulic actuators of high output power are used more than electric actuators. Therefore, it is necessary to operate remote control robots driven by hydraulic actuators. Bilateral control is remote control with the sense of force. Because most of bilateral control systems have been studied mainly using electric actuators, bilateral control using hydraulic actuators is still a challenging issue. In this research, we show the interference of position and force controllers and degradation of control performance by scaling gain in the conventional method. The control performance of the conventional research is analyzed and is experimentally verified. In addition, in this research, we show the effect of modeling error of the previously proposed bilateral controller.

Takayuki Furuya

Papers

Bilateral Control Between Electric and Hydraulic Actuators Using Linearization of Hydraulic Actuators

Experimental evaluation of bilateral control of velocity control system using electric and hydraulic actuators