A Performance Evaluating Platform for Variable Stiffness Exoskeleton Joint

Zhuo Ma, Baojun Chen, Jianbin Liu, Siyang Zuo

Abstract: This paper presents a torque testing platform for variable stiffness evaluation of knee joint exoskeleton, a testing platform was designed based on the body size of a normal adult. It includes mechanical structure, control system and data acquisition. The mechanical structure is mainly composed of a stepper motor, a guide screw, a displacement sensor, a force sensor as well as thigh and calf models. A controller and Data Acquisition Board (firmware NI USB-6009) were used to control stepper motor and collect data. According to the equation of static equilibrium, a mechanical model of the platform was built to calculate disturbance torque and angle of exoskeleton joints. The joint angle measurement range of the platform is from 42° to 180° and the maximum tested torque value is 40 Nm. Finally, a test about tension spring was conducted illustrating that variable stiffness performance of joints can be evaluated by this device.