Basic Performance of an Antagonized Pneumatic Bellows Actuator.

In the case of pneumatic bellows actuators, the external forces are easily and exactly mesured from the pressure in the chamber of the bellows because there is no sliding part which generates friction. Therefore, the bellows can be utilized as a force-sensing actuator which works as a sensor and an actuator simultaneously. In this paper, we design a new drive unit which is antagonistically moved by two bellows actuators. First, the structures of a bellows actuator and antagonized bellows actuators are explained. Next, we derive basic equations to describe dynamics of the bellows actuator system. From some experimental results the following facts are made clear. (1) Since balanced pressures in chambers can decrease the dead zone in the relation between pressure and displacement, positioning accuracy is improved. (2) The proposed drive unit can effectively change compliance on an arbitrary position. (3) The natural frequency of the bellows force sensor increases as the balanced pressure becomes large.