Modeling and Analysis of the Dynamic Performance of a High Speed Selective Compliant Assembly Robotic Arm (SCARA) on a Compliant Support

摘要

A Selective Compliant Assembly Robotic Arm (SCARA) manipulator has been developed with rotary hydraulic actuators for industrial automation. The robotic arm is mounted on a vertical column which has an T-shaped cross section. A bond graph model has been generated for the servo valve, rotary actuator, and links. A lumped-segment torsional vibration model has been generated for the support column. During high speed movement of the manipulator this column vibrates torsionally. This deflects the actual position of the end effector (EE) from the desired position. The rotary joints of the manipulator are driven by double vane rotary hydraulic actuators fitted with rotary encoders to give relative angular positions. Currently, this arm is controlled using simple joint controllers. Since this controller uses the angular displacement of the joints with respect to (w.r.t.) the manipulator links it does not address the issue of external disturbances such as the effects of base vibration. A novel method has been proposed to compensate for EE vibration. This method uses the angle of twist of the vertical column to estimate the deflection and to modify the set point of the joint controller. The results of the analysis show that the proposed method produces a much accurate tracking performance compared to the existing conventional joint control strategy even at high manipulator speeds such as 5.5 m/s.