Correcting the End Deflection of an Industrial Robot Arm and Employing a Weighing Mechanism on the Robot Arm

Abstract

The objective of this paper is to measure the static end deflection of the Puma 560 robot, under permitted load, and hence correct for it by feeding the information back to the robot controller. This measurement can also be used to sense the weight of the tool, to inform the robot of any absence of end load, or even to detect a given load to within 5% of its actual value.

When the arm of the robot is loaded, it will bend elastically provided the loading is below the yield paint. The deflection is maximum when the arm is at its full extension and positioned horizontally above ground level. This deflection is not sensed by the position feed back sensor and hence as far as the positioning system is concerned the robot arm is positioned accurately. In reality the end deflection of the arm causes the arm to be at a slightly different position from that required. This error can be reduced by calculating the deflection and correcting for it.