Measurement of pose repeatabilty of stewart platform

Abstract

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. 0 1995 Iohn W i l y b Sons, lnc.

Kinematic calibration of a 3-DOF spindle head using a double ball bar

“…The coordinate-based approach deals with the identification problem by minimizing the discrepancies between the measured and computed values of the full/partial position and orientation of the end-effector directly, or the absolute coordinates of three or more reference points fixed on the end-effector. For example, Masory [8] and Zhuang [9] used a theodolite to measure the positions of three points on the platform of a Stewart platform and extracted the position and orientation information from these coordinate measurements. Vischer [10] measured the position errors of a Delta robot by attaching the end-effector to the probe of a 3D coordinate measuring machine, and the orientation errors by using three perpendicularly placed linear digital probes.…”

Vision‐based kinematic calibration of an H4 parallel mechanism: practical accuracies

“…both its position and its orientation). Among the proposed measuring devices [CSP99,VPG94,MJ95,SZ99], only a few have been used to conduct kinematic identification of a parallel structure [ZYM98,GH94b,FDAF96,VC98]. Indeed, the systems are either very expensive, tedious to use or with low working volume.…”

“…both its position and its orientation). Among the proposed measuring devices (Curtino et al , 1999; Masory and Jiahua, 1995; Schmitz and Zlegert, 1999; Vincze et al , 1994), only a few have been used to conduct kinematic identification of a parallel structure (Fried et al , 1996; Geng and Haynes, 1994a; Vischer and Clavel, 1998; Zhuang et al , 1998). Indeed, the systems are either very expensive, tedious to use or with low working volume.…”

Vision-based kinematic calibration of a H4 parallel mechanism

“…both its position and its orientation). Among the proposed measuring devices [13,14,15,16], only a few have been used to conduct kinematic identification of a parallel structure [12,17,18,19]. Indeed, the systems are either very expensive, tedious to use or with low working volume.…”