Hybrid Adaptive Robust Control Based on CPG and ZMP for a Lower Limb Exoskeleton

In this paper, hybrid control of central pattern generators (CPGs), along with an adaptive supper-twisting sliding mode (ASTSM) control based on supper-twisting state observer, is proposed to guard against disturbances and uncertainties. Rhythmic and coordinated signals are generated using CPGs. In addition, to overcome the chattering of conventional sliding mode, supper-twisting sliding mode has been applied. The ASTSM method triggers sliding variables, and its derivatives tend to zero continuously in the presence of the uncertainties. Moreover, to acquire maximum stability, the desired trajectory of the upper limb based on zero moment point criterion is designed.

Automated summary

The paper introduces a hybrid control approach combining adaptive supper-twisting sliding mode control and central pattern generators to generate rhythmic and coordinated signals while tackling disturbances and uncertainties. The supper-twisting sliding mode is applied to reduce chattering, ensuring sliding variables and their derivatives approach zero in the presence of uncertainties. Additionally, a desired trajectory based on the zero moment point criterion is designed for maximum stability.