Measurement of Pose Repeatability of Stewart Platform

摘要

Manufacturing tolerances, installation errors, link offsets, and controller errors effect the positioning repeatability of serial and parallel manipulators. A variety of measurement methods have been proposed and used to measure the repeatability of serial manipulators. However, these methods might not be suitable for parallel manipulators due to limited instrumentation accessibility and the large structure involved. This article describes two measurement procedures by which the position of a target point in three-dimensional space can be determined using a single theodolite that is used to collect two sets of measurements taken from two arbitrary locations. The required hardware needed for the implementation of this method is two standard measuring tapes installed vertically at two arbitrary locations, or one horizontal bar. If the target points are located on the end effector of a manipulator, its repeatability can be measured. The procedure that uses two vertical tapes was used to measure the repeatability of a Stewart Platform and experimental results are provided.