Kinematic analysis of a parallel manipulator-based multi-function mobility assistive device for elderly

Recently, more attention has been directed for developing robotic systems that help elderly live independently or rely less on others. This paper describes a novel multi-function mobility assistive device for elderly. The proposed device aims to help patients who don´t have enough physical strength on their lower limbs due to aging or diseases. Rather than one function device, the proposed device is designed to interactively 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 3-RPR planer parallel manipulator which offers besides the high rigidity of the parallel structure some interesting kinematic advantages. This structure provides kinematic decoupling between the position and orientation that required to position shoulder and orient trunk of the user. Also, it provides a suitable free of singularity workspace that required to perform the abovementioned activities. It also has only one dimensionless design parameter that simplifies the design. Additionally, it has high local kinematic and dynamic dexterity indices which achieve high accuracy and dynamic characteristics. Finally, the device is equipped with an active walker for walking activity. Experimental motion data of three healthy subjects that extracted using VICON human motion capturing system is used in a computer simulation to examine the performance of the device.