Conceptual design of walker-exoskeleton (WAL-EX) mechanism for gait rehabilitation and assistance

Hemiplegia is a neurological condition characterized by complete motor loss on one side of the body. This condition severely limits walking ability and daily functional independence. To restore walking function, gait rehabilitation becomes an essential part of the recovery process. Traditional gait rehabilitation usually requires close supervision by a therapist. This makes the process both labor-intensive and limited in accessibility. In response to these challenges, robotic and assistive technologies have been developed to support mobility and rehabilitation in a more autonomous and efficient manner. This study presents the conceptual design of a walker–exoskeleton hybrid system, called WAL-EX, developed to assist individuals with unilateral lower-limb impairment. The WAL-EX system integrates a wearable lower-limb exoskeleton with a conventional medical walker to provide both postural support and active joint assistance. To evaluate and control the motion of the system, a seven-degree-of-freedom dynamic model representing human gait with an exoskeleton is constructed. This model serves as the basis for simulating gait mechanics and designing the control strategy. Within this framework, the healthy leg is used as a real-time reference to control the impaired side. The angular trajectories of the reference hip and knee joints are measured and mimicked in the impaired joints using two PID control systems. The control systems are simulated and evaluated on the dynamic model developed in the MATLAB/Simulink/Simmechanics environment. The joint trajectories generated by the control system for the impaired (follower) side are compared with those of the healthy (reference) side. The maximum tracking deviations are approximately 2° for the hip and 3° for the knee joints. Simulation results demonstrate that the follower joints accurately mimic the reference joint trajectories with acceptable error margins. The WAL-EX mechanism represents a conceptual, simulation-based approach that may provide a simple, potentially cost-effective solution to support both short-distance mobility and home-based gait rehabilitation, particularly for individuals with unilateral lower-limb impairments who lack access to continuous clinical therapy. However, its clinical applicability remains to be established through prototype development and experimental validation.