Robust Control of Dielectric Elastomer Smart Actuator for Tracking High-Frequency Trajectory

Abstract

Dielectric elastomer smart actuator (DESA) has shown great potentials in soft robot applications. The control of the DESA is one of key issues for soft robots. However, the precise control of the DESA is a challenge work, especially when tracking high-frequency trajectories and guaranteeing a certain robustness. To this end, this paper presents a robust tracking control method for a DESA to track various high-frequency trajectories. Firstly, to characterize the complex nonlinear properties (including the quadratic input, asymmetric and rate-dependent hysteresis, as well as creep) of the DESA, its dynamic model is built by combining a square function module, a modified Prandtl-Ishlinskii (P-I) hysteresis model and a linear system. Subsequently, by combining the inverse of the modified P-I hysteresis model with a square root function module, the quadratic input and asymmetric hysteresis properties of the DESA are compensated to reduce tracking the control error. Since model uncertainties and external disturbances are unavoidable in practical applications, a robust controller is designed to achieve the tracking control of the DESA, the controller also guarantees the robustness of the control system. In the end, the effectiveness of the proposed control method is demonstrated through a series of tracking control experiments with different high-frequency trajectories, whose maximal frequency is 8 (Hz). The root- mean-square errors of all experimental results are lower than 1.5%, which proves that the presented method is remarkable from the respective of the practical application.