Development of Flexible Spherical Actuator Controlled by Low-Cost Servo Valve and Embedded Controller

A wearable actuator needs to be flexible so as not to injure the human body. The purpose of our study is to develop a flexible and lightweight actuator which can be safe enough to be attached to the human body, and to apply it to a flexible mechanism and rehabilitation device. New types of flexible pneumatic actuator that can be used even if the actuator is deformed by external force have been developed in our previous studies. In this paper, we propose and test a flexible spherical actuator using the novel flexible pneumatic cylinders. The simple spherical actuator consists of two ring-shaped flexible pneumatic cylinders. They are intersected at right angle and are fixed on the base. The low-cost control system using the tested quasi-servo valves and an embedded controller (micro-computer) was also developed. The spherical actuator was also improved so as to suppress the vibration in control and to increase the stiffness of the actuator by changing the structure of the actuator. In addition, by using the quasi-servo valve controlled by the superior embedded controller, the flow rate of supply and exhaust could be controlled independently. As a result, the control performance could be improved using the improved spherical actuator and the quasi-servo valves controlled by the embedded controller with compensational method for exhaust.