Development of a human upper limb-like robot for master-slave rehabilitation

Master-slave rehabilitation systems are superior to traditional robotic rehabilitation systems on the respect of enhancing therapists' abundant experience. In this paper, a human upper limb-like robot which can mimic the spasticity of stroke patient is proposed as the master device. Therapists can operate this device to perform rehabilitation. In order to mimic the severe spasticity of patients, the device is required to exert high torque. Therefore, high reduction gear was mounted on a stepping motor. As a result, the device becomes non-backdrivable, which decreases its operability. Many researches have ever proposed the admittance control, Series Elastic Actuator (SEA) to solve this problem. Considering about the conditions of our device, admittance control can be realized with a high-accuracy load cell. However, a load cell induces instabilities and high cost. Similar with the SEA, a new structure is proposed in this paper. Two elastic bars are applied to connect the robot's forearm and upper arm. By detecting the bending of these bars, the interaction force exerted on this robot can be calculated. The tiny bending is enlarged with a long bar so that the deformation of elastic bars can be more accurately detected with an optical mouse. To evaluate the efficacy of proposed structure, experiments were conducted to exert three levels resistance using the device. Experimental results show that the proposed structure is effective, and the exerted resistance can be adjusted with it.