Adaptive SMC for Lower Limb Rehabilitation Robots Using a Sliding Mode Hyperbolic ESO

In response to the requirements for precision and robustness in trajectory tracking and human-robot interaction of lower limb rehabilitation exoskeleton robots, this paper proposes a sensorless solution that integrates a Sliding Mode Hyperbolic Extended State Observer (SHESO) with Adaptive Sliding Mode Control (ASMC). In this scheme, SHESO is employed to achieve sensorless estimation of external torque disturbances. Compared with the traditional Extended State Observer (ESO), it features a faster convergence speed and a higher estimation accuracy, thereby providing reliable disturbance information for subsequent control. Based on dynamic correction of the desired trajectory by admittance control, the ASMC method further realizes accurate tracking of the corrected gait trajectory and ensures the system stability during human-robot interaction. The stability of both the observer and the controller is rigorously validated via Lyapunov stability theory, while simulation results confirm that the proposed method achieves superior performance in both external disturbance estimation and trajectory tracking.