Most stroke patients suffer from hemiplegia and lose control on half of their body. This article proposes an assistive control strategy to induce a symmetric pattern for hemiplegic patients, using a hip exoskeleton assistance robot (HEXA-I). Combination of an impedance control, as a high-level controller, and a sliding mode control (SMC) with disturbance observer (DOB), as a low-level control, forms the proposed assistive strategy. The proposed algorithm records the trajectory of healthy leg in zero impedance mode and implements it on the affected side. A simple phase detection algorithm is used to implement the gait trajectory on the affected leg, during the swing phase. The assistive strategy is experimentally implemented on three healthy subjects by HEXA-I. The subjects were asked to simulate a hemiplegia walking. The results show that the assistive strategy would help patients to achieve a symmetric walking pattern and modify the gait of the affected side, based on their own trajectory.

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