Dynamic Analysis of a Parallel Manipulator-Based Multi-function Mobility Assistive Device for Elderly

Dynamic simulation of manipulators interacting directly with human is crucial for predicating their performance before the actual use. This paper describes the dynamic analysis and simulation of a novel multi-function mobility assistive device for elderly. The device is designed to help patients who suffer from degradation of the lower limbs muscular strength. Rather than one function device, the proposed device is intended to assist in different lower limb activities, namely, sit to stand and walking activities as well as transfer paralyzed patients from bed to wheelchair and help them stand in upright position to improve blood circulation. The device is based on a non-conventional structure of a 3-RPR planer parallel manipulator which has high rigidity due to the parallel structure. It has some interesting kinematic advantages that facilitate structure and control design. Dynamic model for the assistive manipulator is derived using the first type of Lagrange's equations. A PD-computed torque controller is tuned using genetic algorithm. Simulation results prove high performance of the proposed device in terms of the low tracking error and the proper actuator force.