Active synchronized motion control for comfortable walking support

The safety and comfort of user are the two important requirements that a service robot must fulfill to qualify as assistive device for elderly persons. Unlike scenarios of manipulation assistance, human user is physically attached with the robot in those of walking/mobility assistance. Any force/torque generated at the robot (end-effector) is transferred to human body that causes the discomfort and safety problem for the user. If the motion of robot system is made synchronized with human user´s movement during walking, it can be more comfortable for elderly user. This paper proposes a new control strategy for synchronized movement of walking support system with the human user´s walking. For this strategy, the average step size of a particular user is obtained through initial short test and the direction of motion is guided online by human user. Proposed scheme is implemented on SpiderBot-II, a wire-driven parallel mechanism, conceptualized for assisting elderly persons. User´s comfort is assessed through measurement of link reaction forces during walking assistance. The rationale behind such scheme is the common assistance scenario during walking. The human assistant synchronizes his walking pattern and speed with that of elderly user to make it more comfortable for the latter. Preliminary experimental results show that this control scheme is capable of realizing a comfortable walking assistance for elderly persons.