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Position and stiffness control of an antagonistic variable stiffness actuator with input delay using super-twisting sliding mode control

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Abstract

Motor dynamics in antagonistic variable stiffness actuator (AVSA) is generally disregarded in control system design. This ignorance can lead to an inaccurate system model, affecting the performance of the closed-loop system. The motor dynamics can be modeled as an input-delay in actuator model. In this paper, the motor dynamics is modeled as the input time-delay for an AVSA for the first time. The stiffness of AVSA is a nonlinear function of system states; thus, stiffness tracking for an AVSA is a challenging task. Specifically, many of the existing delay compensation controllers cannot be used for stiffness tracking when the model contains input delay. To handle this issue, a nonlinear transformation is introduced and a super-twisting sliding mode control is then utilized to reach position and stiffness tracking simultaneously. Prediction-based feedback is involved together with some disturbance observers for estimating the external disturbance to compensate for the input time-delay. Simulation results show that the proposed design approach is successful in position and stiffness tracking and simultaneously in attenuating the external disturbance effect.

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Acknowledgements

This research project is supported by the Second Century Fund (C2F), Chulalongkorn University, and funded by Thailand Science Research and Innovation Fund, Chulalongkorn University (CU_FRB65_ind (14)_162_21_28). The authors would also like to thank Dr. Guohui Tian for his help and support in the simulation and comparison phase of the research.

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  1. Faculty of Engineering, International School of Engineering, Chulalongkorn University, Phayathai Road, Pathumwan District, Bangkok, 10330, Thailand

    Ali Javadi & Ronnapee Chaichaowarat

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  1. Ali Javadi
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Correspondence to Ronnapee Chaichaowarat.

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Javadi, A., Chaichaowarat, R. Position and stiffness control of an antagonistic variable stiffness actuator with input delay using super-twisting sliding mode control. Nonlinear Dyn 111, 5359–5381 (2023). https://doi.org/10.1007/s11071-022-08123-w

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