Assist-as-Needed Control of a Robotic Orthosis Actuated by Pneumatic Artificial Muscle for Gait Rehabilitation

Abstract

Rehabilitation robots are designed to help patients improve their recovery from injury by supporting them to perform repetitive and systematic training sessions. These robots are not only able to guide the subjects' lower-limb to a designate trajectory, but also estimate their disability and adapt the compliance accordingly. In this research, a new control strategy for a high compliant lower-limb rehabilitation orthosis system named AIRGAIT is developed. The AIRGAIT orthosis is powered by pneumatic artificial muscle actuators. The trajectory tracking controller based on a modified computed torque control which employs a fractional derivative is proposed for the tracking purpose. In addition, a new method is proposed for compliance control of the robotic orthosis which results in the successful implementation of the assist-as-needed training strategy. Finally, various subject-based experiments are carried out to verify the effectiveness of the developed control system.

Modeling of Motorized Orthosis Control

“…However, this work did not explain how the control parameters can be obtained. Recently, Dao et al [35] developed a modified computed torque controller to enhance the tracking performance of a robotic orthosis of the lower limb. Their control laws proposed have similar concepts, but with different objectives and approaches.…”

“…Their control laws proposed have similar concepts, but with different objectives and approaches. In the current study, we follow the movements of the human being, whereas, in [35], they try to teach or show the correct forces and torques that must be applied to follow the desired trajectory.…”

Synchronous Position and Compliance Regulation on a Bi-Joint Gait Exoskeleton Driven by Pneumatic Muscles

“…BiGREX's MIMO SM control system considers PM pressures as state variables and allows more direct manipulation of the average PM pressure compared to [13][14][15]. A novel experimental approach was adopted to validate the system capability on adjusting the compliance from participant's perception, which guarantees a safe and compliant human-robot interaction so as to enhance the patients' trust in robots.…”

An Extended Proxy-Based Sliding Mode Control of Pneumatic Muscle Actuators

“…This control demand relies heavily on the accurate control of the actuators, including PMAs, discussed in this study. Dao et al [17] presented an assist-as-needed control of a PMA-based robotic orthosis for gait rehabilitation.…”