Contents I. Introduction
Today, the care and welfare pneumatic devices to support a nursing care and a self-reliance of the senior and the disabled are actively researched and developed by many researchers [1] [2]. These wearable devices require many servo valves for multi degrees of freedom and precise control performance of the wearable actuator. Though, by increasing the degree of freedom, the total weight load of the wearable devices increases too. Therefore, we aim to develop a small-sized, light-weight and low-cost quasi-servo valve using on/off valves to decrease the burden of the user instead of expensive and bulky conventional electro-pneumatic servo valves((Koganei Co. Ltd. mass: 0.9kg). In our previous study [3], an inexpensive pressure control type quasi-servo valve using a low-cost embedded controller and a pressure transducer was tested. So, the compensation for decrease of output flow rate by the increase of load pressure was proposed to improve the pressure control performance of the valve. An analytical model of the pressure control type quasi-servo valve including the embedded controller was also proposed. The control performance of the valve using simple P controller was investigated theoretically [4]. In the next step, it is necessary to investigate the performance of the valve using various control schemes and sampling periods. In this paper, we estimate the pressure control performance of the valve by using PD controller with the proposed compensation method theoretically and experimentally. We also investigate the optimal control parameter of the PD controller by means of simulation.