Position control of a series elastic actuator based on global sliding mode controller design

A systematic and simple discrete sliding mode controller design scheme based on the suboptimal approach is presented. The behaviors of the control system can be determined through a preferred performance index. The AC servomotor position control is obtained using only the q-axis voltage control loop. The proposed method is simulated and experimented to verify the capability of this new sliding mode control algorithm. Properties such as easy implementation, fast resonse, and robust to external loads are demonstrated.

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Force control of an uncertain series elastic actuator system via a fuzzy sliding mode controller and a nonlinear state estimator

Proceedings of the Institution of Mechanical Engineers Part I Journal of Systems and Control Engineering ◽

10.1177/0959651819866373 ◽

2019 ◽

Vol 234 (4) ◽

pp. 462-471

Author(s):

Seyed Ali Moafi ◽

Farid Najafi

Keyword(s):

Sliding Mode ◽

Sliding Mode Controller ◽

State Estimator ◽

Series Elastic Actuator ◽

Control Scheme ◽

Chattering Free ◽

Fuzzy Sliding Mode ◽

Theory Of Lyapunov Stability ◽

Nonlinear State ◽

Series Elastic

Nowadays, series elastic actuators play an important role in actuation technology, especially for mechatronics and robotic applications. In this article, the accurate tracking of output force for a series elastic actuator is investigated. In order to achieve this aim, a novel robust control scheme is developed to overcome friction effects, backlash in the drivetrain, measurement noises (sensor inaccuracy) and uncertainties in the dynamic model. The control scheme consists of a fuzzy sliding mode controller and a nonlinear state estimator. The theory of Lyapunov stability is used for the formulation of the proposed controller and also the fuzzy logic strategy is used for tuning the sliding surface parameter in order to achieve accurate and chattering-free performance. Furthermore, a powerful estimator algorithm, unscented H-infinity filter, is added to the control scheme to improve the robustness of the system. Simulation results, as well as experimental analysis, approved the efficiency of the proposed approach in the presence of uncertainties and disturbances.

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A Fixed Structure Gain Selection Strategy for High Impedance Series Elastic Actuator Behavior

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4041449 ◽

2018 ◽

Vol 141 (2) ◽

Author(s):

Kenan Isik ◽

Gray Cortright Thomas ◽

Luis Sentis

Keyword(s):

Position Control ◽

Controller Design ◽

Selection Strategy ◽

Impedance Bandwidth ◽

Phase Margin ◽

Ideal Model ◽

Series Elastic Actuator ◽

High Impedance ◽

Position Controller ◽

Series Elastic

Series elastic actuators (SEA) are widely used for impact protection and compliant behavior, but they typically fall short in tasks calling for accurate position control. In this paper, we propose a simple and effective heuristic for tuning series elastic actuator controllers to a high impedance position control behavior, which compares favorably with previous publications. Our approach considers two models, an ideal model and a nonideal model with time delays and filtering lag. The ideal model is used to design cascaded proportional-derivative (PD)-type outer impedance and inner force loops as a function of critically damped closed-loop poles for the force and impedance loops. The nonideal model provides an estimate of the phase margin of the position controller for each candidate controller design. A simple optimization algorithm finds the best high-impedance behavior for which the nonideal model meets a desired phase margin requirement. In this way, the approach automates the trade-off between force and impedance bandwidth. The effect of important system parameters on the impedance bandwidth is also analyzed and the proposed method verified with a physical actuator.

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