Discrete‐Time Sliding Mode Control With Adaptive Reaching Law for Rehabilitation Exoskeleton

ABSTRACT Wearable exoskeletons hold promise in aiding patients with lower‐limb dysfunction to regain mobility. However, due to movement disorders and nerve function impairments in patients, ensuring the accuracy and stability of exoskeleton robot motion control is crucial. This paper proposes a discrete‐time sliding mode control (DSMC) framework with an adaptive reaching law for high‐precision gait tracking in rehabilitation exoskeletons. Initially, a discrete‐time dynamics model is established based on the Lagrangian discretization criterion for the lower limb exoskeleton rehabilitation robot. Subsequently, a novel controller incorporating a discrete‐time fast terminal sliding mode surface and an adaptive reaching law is designed to address system uncertainties and disturbances. The adaptive adjustment of gain parameters enhances error convergence speed while mitigating chattering. Additionally, the stability of the control system is proven using the Lyapunov theory. Finally, the effectiveness of the proposed algorithm is verified through simulation and experimental tests.