抄録
An electro-rheological fluid of dispersion system (ERF) is a type of variable plasticity fluid which behaves like a Bingham fluid in that its yield stress varies according to the magnitude of an applied electric field. Therefore, an actuator by means of the ERF can minutely control the force with a high response. However, from another viewpoint, the ERF is regarded as a nonlinear control device with viscosity varying according to the shear rate. In practice, many researchers has pointed out that the nonlinearity of the ERF gives them great difficulty in applying it to a servo system.
In this paper, a new servo method, Electro-Rheological Motion Control (ERMC), which makes an active use of the nonlinearity of ERF, is proposed and its basic theory is approached. An antagonistic rotary actuator (ERAA) utilizing the ERF is controlled by using the ERMC. The ERAA is so constructed that a freely rotatable secondary cylinder is set concentrically between two primary drums driven by motors at the same speed in the opposite directions each other and the ERF is filled in the gap between the secondary cylinder and the primary drums. Under the ERMC, such an on-off control operation is repeated in the stopping process of the primary drums, that the output direction of an actuating torque is switched positive or negative when the control error is negative or positive, respectively. The reason why this method is adopted is due to fact that the control error occurring in on-off operation decreases as the rotational speed of the primary drum decreases because of the non-linearity of the ERF. As a result of experiments, it is confirmed that a high-precision positioning of the ERAA can be realized stably by the ERMC.
