Abstract
In assembly, deburring, griding, not only the position and speed control but also the force control is important. A pneumatic servo seems to be effectively applied to this kind of constrained work, because its high compliance due to the air compressibility is useful to the force control.
In the force control system, the characteristics of the object intervenes in the closed loop, so its influence has to be considered in the design of controller. However, it is generally unknown and often changes during the operation. To cope with these problems, more intelligent control schemes are required.
In this study, to construct the force control system capable of accommodating to unknown objects and any other changes of operating conditions, the adaptive control strategy is applied. The controller is designed with the adaptive pole-placement method to avoid the non-minimum phase problem.
Firstly, the influence of the object stiffness on the force control performance of the pneumatic servo system is analyzed. Secondly, the structure of the adaptive control system compensating for a disturbance is described. Thirdly, the adaptability to the unknown controlled plant, the effect of the compensation for disturbance, the robustness to changes of the object stiffness and the operating pressure and the force control accuracy are experimentally examined. As a result, it can be verified that the adaptive control scheme is very effective to improve the force control performance of a pneumatic servo. Lastly, matters to be attended to decide some control system parameters necessary to install the adaptive control system are considered.
