Active Disturbance Rejection Controller for a Flexible Walking Bioinspired Inchworm Mobile Robot Actuated With Shape Memory Alloy Devices

This study presents the development of a hybrid active disturbance rejection control (H-ADRC) implementing a homogeneous extended state observer (ESO) to solve the trajectory tracking problem of an inchworm bioinspired flexible robotic device (IBFRD) with partially unknown dynamics. The proposed controller is implemented on a self-designed IBFRD instrumented with shape memory alloys (SMAs) operating as actuators in each joint of the robotic mobile device. The set of SMAs constitutes an agonist-antagonist mechanism together with regular springs that counteract the SMA displacement. The characteristic two-anchor crawling of an inchworm is modeled as a hybrid system and exerted by a bistable pneumatic circuit that switches suction cups at the terminal links of the IBFRD to exert the inchworm walking. The corresponding reference trajectories emulate an inchworm in a regular gait cycle. Experimental results compare the H-ADRC with a proportional derivative and a proportional-integral-derivative (PID) controller. The obtained results show that the proposed H-ADRC enforces a reduced tracking error than the other controllers used for validation.