448 research outputs found

    Disturbance-Estimated Adaptive Backstepping Sliding Mode Control of a Pneumatic Muscles-Driven Ankle Rehabilitation Robot.

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    A rehabilitation robot plays an important role in relieving the therapists' burden and helping patients with ankle injuries to perform more accurate and effective rehabilitation training. However, a majority of current ankle rehabilitation robots are rigid and have drawbacks in terms of complex structure, poor flexibility and lack of safety. Taking advantages of pneumatic muscles' good flexibility and light weight, we developed a novel two degrees of freedom (2-DOF) parallel compliant ankle rehabilitation robot actuated by pneumatic muscles (PMs). To solve the PM's nonlinear characteristics during operation and to tackle the human-robot uncertainties in rehabilitation, an adaptive backstepping sliding mode control (ABS-SMC) method is proposed in this paper. The human-robot external disturbance can be estimated by an observer, who is then used to adjust the robot output to accommodate external changes. The system stability is guaranteed by the Lyapunov stability theorem. Experimental results on the compliant ankle rehabilitation robot show that the proposed ABS-SMC is able to estimate the external disturbance online and adjust the control output in real time during operation, resulting in a higher trajectory tracking accuracy and better response performance especially in dynamic conditions

    Coupling Disturbance Compensated MIMO Control of Parallel Ankle Rehabilitation Robot Actuated by Pneumatic Muscles

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    To solve the poor compliance and safety problems in current rehabilitation robots, a novel two-degrees-offreedom (2-DOF) soft ankle rehabilitation robot driven by pneumatic muscles (PMs) is presented, taking advantages of the PM’s inherent compliance and the parallel structure’s high stiffness and payload capacity. However, the PM’s nonlinear, time-varying and hysteresis characteristics, and the coupling interference from parallel structure, as well as the unpredicted disturbance caused by arbitrary human behavior all raise difficulties in achieving high-precision control of the robot. In this paper, a multi-input-multi-output disturbance compensated sliding mode controller (MIMO-DCSMC) is proposed to tackle these problems. The proposed control method can tackle the un-modeled uncertainties and the coupling interference existed in multiple PMs’ synchronous movement, even with the subject’s participation. Experiment results on a healthy subject confirmed that the PMs-actuated ankle rehabilitation robot controlled by the proposed MIMO-DCSMC is able to assist patients to perform high-accuracy rehabilitation tasks by tracking the desired trajectory in a compliant manner

    Review and Analysis on Main Technology of Exoskeletal Robot System for Upper Limbs Rehabilitation

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    Major function of exoskeletal robot system for upper limbs rehabilitation is to assist patient to carry out upper limbs’ rehabilitation training. Main technology of exoskeletal robot system for upper limbs rehabilitation includes design of mechanical structure of exoskeletal robot, design of control system of exoskeletal robot and implemention of data and information transmission between exoskeletal robot and upper limbs of human body. Currently implemention of data and information transmission rely mainly on methods of acquiring sEMG signal and force feedback. Reviewing and analyzing the specific technical development and deficiency in field of exoskeletal robot system for upper limbs rehabilitation will be important way in improving and upgrading the technology in future

    Sliding Mode Control

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    The main objective of this monograph is to present a broad range of well worked out, recent application studies as well as theoretical contributions in the field of sliding mode control system analysis and design. The contributions presented here include new theoretical developments as well as successful applications of variable structure controllers primarily in the field of power electronics, electric drives and motion steering systems. They enrich the current state of the art, and motivate and encourage new ideas and solutions in the sliding mode control area

    Enhanced-PID Control Based Antagonistic Control For Pneumatic Artificial Muscle Actuators

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    Pneumatic artificial muscle (PAM) is a rubber tube clothed with a sleeve made of twisted fiber-code, and is fixed at both ends by fixture. It has a property like a spring, which enables it to change its own compliance by the inner air pressure. The advantages of pneumatic system such as high power-to-weight ratio, compactness, ease of maintenance, inherent safety and cleanliness led to the development of McKibben muscle and PAM actuators. However, the drawbacks of PAM, for example, the air compressibility and the lack of damping ability of PAM bring dynamic delay to the pressure response and cause oscillatory motion to occur. It is not easy to realize the PAM motion with high accuracy and high speed due to all the non-linear characteristics of pneumatic mechanism. In this thesis, an antagonistic-based PAM system is designed and presented. Two identical PAM actuators are connected in parallel and vertical direction which imitate the human biceps-triceps system and emphasize the analogy between the artificial muscle and human skeletal muscle behavior. Some past control algorithms on the positioning control of PAM mechanisms are discussed. In this thesis, a practical control method, namely enhanced-PID controller is proposed to control the trajectory motion of the PAM actuators. The development and modeling of the experiment setup are explained, followed by the driving characteristics of the PAM system. Two simple and straight forward steps are demonstrated as the design procedures of the enhanced-PID controller. The control structure of the proposed controller consists of a PID element, Compensator A and Compensator B. The effectiveness of the proposed control algorithm is validated in sinusoidal continuous motion. The tracking performance of the enhanced-PID controller is compared with a classic PID controller, showing that the control performance of the enhanced-PID controller is satisfactory and better in dealing with highly non-linear PAM system

    Terminal Sliding Mode Control of Mobile Wheeled Inverted Pendulum System with Nonlinear Disturbance Observer

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    A terminal sliding mode controller with nonlinear disturbance observer is investigated to control mobile wheeled inverted pendulum system. In order to eliminate the main drawback of the sliding mode control, “chattering” phenomenon, and for compensation of the model uncertainties and external disturbance, we designed a nonlinear disturbance observer of the mobile wheeled inverted pendulum system. Based on the nonlinear disturbance observer, a terminal sliding mode controller is also proposed. The stability of the closed-loop mobile wheeled inverted pendulum system is proved by Lyapunov theorem. Simulation results show that the terminal sliding mode controller with nonlinear disturbance observer can eliminate the “chattering” phenomenon, improve the control precision, and suppress the effects of external disturbance and model uncertainties effectively
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