Three-Dimensional Interfacial Stress Decoupling Method for Rehabilitation Therapy Robot

Robot-assisted therapy can provide effective rehabilitation training for stroke patients. The interfacial stress between the manipulator and the grasped patient's body is very important for a rehabilitation therapy robot. This paper presents a measurement method, which is able to decouple the measurement of the three-dimensional (3-D) interfacial stress components. To implement the method, interfacial stress sensors were fabricated based on plate capacitance and a superelastic material, while a high-resolution microcapacitance measurement circuit was developed based on a minimal system microprocessor and a programmable controller, and experiments are carried out by using a 3-D stress simulation equipment. The results show that the measurement circuit is capable of measuring a range of 1 fF-30 pF capacitance with a resolution better than 1 fF, and the sensor is capable of measuring Z-direction normal compressive stress at a range of 0-3.0 kgf/cm² with a sensitivity of 101 fF/kgf/cm² and X- A nd Y-direction shear stress at a range of 0-1.0 kgf/cm² with a sensitivity of 118 fF/kgf/cm². This method can be applied to rehabilitation therapy robots to decouple the measurement of the 3-D interfacial stress components.