Development of an upper limb rehabilitation robot providing symmetric bilateral movements based on inertial measurement units

Abstract

Stroke is most of the causes of disability and loss of motor function with growing population of old people. Mirror image motion enabler reflects unimpaired side motion into impaired side movements and it is effective because rehabilitation with voluntary drive makes reorganizational changes in the motor cortex. We present an upper limb rehabilitation robot providing symmetric bilateral movement for the hemiplegic stroke to rehabilitate with bilateral movements. For the unimpaired arm, a sensing unit utilizing IMUs measured the rotation joint angles of forearm. For the impaired arm, an actuating unit equipped with BLDC motors helped movements of elbow flexion/extension, wrist flexion/extension, and forearm pronation/supination. Because there are 3 axis of forearm motions, the patients can use the forearm motions of daily living. The device is portable to carry around, the patients can make daily and longer lasting treatment by transporting the device to home, hospital, and so on. Because the actuating unit and sensing unit are in different system, we need to consider the measurement of unimpaired arm motion, and the desired trajectory for the asymmetric impaired arm. We suggest the solution to make the sensing unit based on IMU sensors, and the actuating unit to drive with cable driven mechanism. The actuation of the forearm pronation/supination and wrist flexion/extension used one motor using cable driven mechanism, and two kind of motions were designed to be selectable. Through the experiments with the device, we validate the device and we expect this device to use in upper limb rehabilitation.