空気圧平面パラレルマニピュレータの圧力・力センサレス位置・剛性制御(機械力学,計測,自動制御)

Abstract

This paper presents a method for controlling the position and stiffness of a pneumatic planar parallel manipulator in which the pressure and force sensors are eliminated by replacing them by observers for the purpose of cost reduction. Generally, since pneumatic manipulators are characterized by high nonlinearities such as air compressibility and friction arising in their joints and sliding parts, conventional PID controllers are insufficient for precise control. Using advanced controllers aiming at higher performance requires various sensors, but their dependence on a lot of costly sensors makes pneumatic manipulators less competitive with other power source manipulators in terms of cost. Based on our previous papers, a position controller for the pneumatic manipulator is first discussed in this paper, which introduces observer-based friction compensation for enhancing motion accuracy and pressure observers as substitutes for pressure sensors. The designed controller is further extended in order to control simultaneously the position and stiffness of the manipulator. In this controller, friction observers estimated the contact force between the manipulator's end-effector and a target object, and from these results a force sensor was removed to save costs. Several experiments were carried out to verify the performance of the proposed low-cost controller.