Acoustic Range Sensing Servo Control: Improved Robot Positioning and Trajectory

摘要

Absrracr-A technique is described for improving the accuracy of the path followed by a robot arm in precision tracking of an object’s surface contour. Acoustic pulse-echo range data from a sensor mounted on a robot end effector was used to enable real time path modification, correcting for errors in the robot’s internal sensors, calibration, and servo-control. An eddy current proximity sensor positioned approximately 30 mil from the surface monitored the acoustic sensor and robot performance. In open-loop mode, both sensors produced identical results in tracking variations in distance from the surface. Variation from a linear path was as large as 10 mil. The acoustic range sensor enabled a servo control algorithm to reduce path deviation lo +3 mil using single measurements in real time. This variation is attributable to the inherent noise level of the sensor system and ambient fluctuations in sound velocity. Averaging ten measurements reduced the standard deviation in position measurement and control to +_l2 mil. The acoustic ranging system has also proved capable of correcting position error induced by a dynamic change in mass loading at the end effector.