Position Control of a Flexible Gantry Robot Arm

초록

This paper presents new feedback actuators to achieve an accurate position control of a flexible gantry robot arm. The translational motion in the plane is generated by two d.c. motors and controlled by employing electro-rheological(ER) clutch actuators. The generated motion can be continuously controlled by controlling the intensity of electric fields imposed to the ER fluid domains of bi-directional rotating ER clutches. On the other hand, during control action of the translational motion, a flexible arm attached to the moving part produces undesirable oscillations due to its inherent flexibility. The oscillations are actively suppressed by employing feedback voltage to the piezoceramic actuator bonded on the surface of the flexible arm. Consequently, an accurate position control at the end-point of the flexible arm can be achieved. In order to accomplish this control target, the governing equations of the proposed system are derived and rewritten as transfer functions to design a robust controller. The control electric fields to be applied to the ER clutch and the control voltage for the piezoceramic actuator are determined via the loop shaping design procedures(LSDP) in the control technique. Control results are provided to evaluate the effectiveness of the proposed methodology.