Design and Control of a Multimodal Compliant Actuator Based on a Scissor-Epicyclic Mechanism for Wearable Robotics

Abstract

Developing wearable robotic actuators by imitating the fiber activation patterns is an encouraging way to improve the performance of wearable robotics. Existing wearable robotic actuation systems cannot provide efficient assistance and accurate force delivery for human users. In this article, we develop a bionic multimodal compliant actuation system based on a scissor-epicyclic clutch mechanism that can provide fast twitch fibers (FTFs) contraction assistance, slow twitch fibers (STFs) contraction assistance or almost transform into a transparent device efficiently. In addition, a novel disturbance-observer-based virtual sliding mode torque controller (DVSMC) is designed to accurately control the output torque by eliminating unexpected external disturbance during the clutch engagement process. Comparative experimental results reveal that, under conditions without load disturbance, with load disturbance, and with time-varying load disturbance, the torque tracking error of the proposed controller is decreased by more than 60% compared with that of contrastive controllers, and the energy consumption is reduced by more than 50% compared with that of the conventional one. Finally, the experimental tests conducted on the human subject demonstrate the effectiveness of fast multimodal switching assistance and precise assistive torque delivery of the proposed wearable robotic system when interacting with human. This study highlights the significance of functional bionic design in wearable devices for human motion assistance and provides a brand-new actuation solution that could be introduced to the emerging biomimetic robot field.