Design and Control of a Novel Soft-Rigid Lower Limb Exoskeleton Robot

This paper presents a study on the design and control of a novel soft-rigid lower limb exoskeleton robot. First, based on anatomy, a novel exoskeleton structure design is proposed that applies Curl Pneumatic Artificial Muscles (CPAMs) to lower limb joints to actuate lower limb movement, and transmit force and motion through rigid parts. A phenomenological characteristic model of the CPAM based on experimental tests and fitting methods is constructed for exoskeleton control. Then, a feedforward-feedback hybrid control method based on four CPAM characteristic models is proposed to improve the control accuracy and stability of the exoskeleton. A human-in-the-loop control method based on human-robot hybrid dynamics modeling and human intentions and states is proposed to improve the human-robot interaction performance of exoskeletons. Experimental results show that feedforward-feedback hybrid control can reduce the maximum tracking error of the exoskeleton to 3.4% for hip, 2.9% for knee, and 4.7% for ankle joint. The exoskeleton can achieve intentional control based on EMG signals. With the assistance of the exoskeleton, the muscle activity of the human lower limbs is reduced by an average of 32.2%. The proposed soft-rigid lower limb exoskeleton robot has the advantages of being lightweight, having good flexibility, being comfortable wearing and having good human-computer interaction, which can improve efficiency. In the future, it will provide more effective intelligent rehabilitation equipment for patients with lower limb movement disorders.