Positioning Accuracy of a Planer Multi-Joint Positioning System and Improvement Thereof

Abstract

In order to discuss the positioning accuracy in a horizontal plane of a planer multi-joint positioning mechanism, we propose a method that uses a reference board on which reference marks are disposed at large intervals in combination with a precision XY stage, and we construct a measurement system that realizes the measurement of positioning accuracy with a resolution of 1.2 µm over the range of 200 × 400 mm. Next, in order to improve the positioning accuracy over a wide range of the planer multi-joint positioning system, we propose a method for calibrating the link length independently of coordinates from the measurements of positioning errors taken on three arbitrarily selected points, and we experimentally verify its validity. Moreover, we show that the positioning error in a local range of 50 × 50mm is mainly a transmission error of the joint drive reducer and experimentally verify the compensation effect for the transmission error. As a result, the positioning bias error is reduced to the same level as that of the positioning resolution over the range of 350 × 150mm.