The Realization of Virtual Environments in the Lower Limb Exoskeletal Robot

This study proposes the realization of various virtual environments using a lower limb exoskeletal robot for futuristic gait rehabilitation. The proposed method allows the user to feel virtual gravity, buoyancy, and drag while actively walking. The virtual environments include four fluidic conditions: Water, Olive oil, Honey, and Peanut Butter, and four gravitational conditions consisting of the Earth's, Moon's, Mars', and Jupiter's gravity. The control method of the lower limb exoskeletal robot is as follows. First, torque feedback is applied to control the interaction force between the exoskeletal robot and its user. Second, the reference torque is computed in real time with the dynamic equations of the human body and the kinematic data. The eight environments were implemented via the EXOWheel, a wheelchair-integrated lower limb exoskeletal robot. While attaching electromyography sensors and wearing the EXOWheel, eight healthy subjects walked actively under the virtual conditions. Experimental results show that muscular force signals adequately change depending on gravitational, buoyant, and drag effects. Blind tests confirmed that subjects could reliably distinguish all eight virtual environments.