Development of a Simple-structured Pneumatic Robot Arm and its Control Using Low-cost Embedded Controller

The purpose of our study is to develop the flexible and lightweight actuator and apply it into a flexible robot arm. In this paper, the master-slave attitude control and the trajectory control of the flexible robot arm are proposed. This robot arm has three degree-of-freedom that is bending, expanding and contracting and will be applied into a rehabilitation device for human wrist. The master-slave control system which is proposed in this paper is necessary when a physical therapist wants to give a rehabilitation motion to a patient. While the trajectory control system is necessary when a sequential rehabilitation motion is applied to a patient. In this paper, an analytical model of a flexible robot arm is proposed for master-slave attitude control and trajectory control. Then, a compact and inexpensive control system is developed and tested. The system consists of a flexible robot arm, a low-cost embedded controller, accelerometers and small-sized quasi-servo valves which are developed by using the on/off control valve in our laboratory. The results from these experiments demonstrate that the master-slave attitude control can be realized by using an accelerometer and a simple analytical model of the robot arm. The trajectory control also was realized for a square trajectory by using an analytical model and a compact control system. The error between the desired trajectory and measured one is relatively large compared with typical robot arm. This is because by a friction that is existing in a rod-less type flexible pneumatic cylinder. The control performance can be improved by reducing the friction or by improving the control scheme.