Modeling and control of a new robotic deburring system

A machining manipulator is subject to mechanical interaction with the object being processed. The robot performs the task in constrained work space. In constrained tasks, one is concerned with not only the position of the robot end-point, but also the contact forces, which are desired to be accommodated rather than resisted. Therefore, interaction force needs to be considered in designing and controlling deburring tools. Many researchers have proposed automated systems for grinding dies, deburring casting, removing weld beans, etc [Bopp, 1983; Gustaffson, 1983]. Usually, a deburring tool is mounted on a NC machining center or a robot manipulator. Several control laws have been developed for simultaneous control of both motion and force [Whitney, 1987; Hogan, 1984] of robotic manipulators. Despite the diversity of approaches, it is possible to classify most of the control methods into two major approaches: impedance control [Wang & Cheah, 1996; Carelli & Kelly, 1991] and hybrid position/force control [Raibert & Craig, 1981; Yoshikawa et al., 1988]. However, these methods require an accurate model of force interaction between the manipulator and the environment and are difficult to implement on typical industrial manipulators that are designed for position control. An active feedback control scheme was developed in order to supply compliance for robotic deburring as a means to accommodate the interaction force due to contact motion. Kuntze [Kuntze, 1984] suggested an active control scheme, in which the actuators are commanded to increase torques in the opposite direction of the deflections. Paul [Paul et al., 1982] applied an active isolator to a chipping robot, where the isolator attached to the arm tip reduces the vibration seen by the robot. Sharon and Hardt [Sharon and Hardt, 1984] developed a multi-axis local actuator, which compensates for positioning errors at the end point, in a limited range. Asada [Asada & Sawada, 1984] developed passive tool support mechanisms, which couple the arm tip to the workpiece surface and bear large vibratory loads. These mechanisms allow the robot to compensate for the excessive deflection when the robot contacts the workpiece. These methods reduce dynamic deflection in a certain frequency range. However, it is difficult for these control schemes, which are employed for a robot with a 1