Calibration of a small size hexapod machine tool using coordinate measuring machine

Abstract

Hexapod machine tool (HMT) is a device designed for micro milling; however, the deviations of the HMT's kinematic parameters due to manufacture and assembly errors can definitely affect its running accuracy. To identify the real kinematic parameters so as to improve the running accuracy of the HMT, a novel calibration test was performed on a bridge-type coordinate measuring machine. In the present research, a mathematical model was derived to present the relationship between pose errors and the errors of kinematic parameters of the HMT, the measurement method based on coordinate measuring machine was designed and a calibration experiment was carried out subsequently. The experimental results reveal that after calibration, both the position errors and orientation errors of the HMT decreased significantly, the symmetrical errors were improved as well. In addition, it is found that the running accuracy of the HMT is running direction dependent, which depends on the HTM's structures. The present research provides researchers with a new and effective calibration method to improve the running accuracy of HMTs.

A New Efficient Stiffness Evaluation Method to Improve Accuracy of Hexapods

“…The identification of reference frame fixed to the mobile platform is done in the manner similar to the one described in [38]. The reference holes on the hexapod are used for this purpose.…”

Semi-isotropic design of a Stewart platform through constrained optimization

“…15–17 Six linear actuators are shown in the figure as b i t i with i = 1 to 6, where b i are the bottom joints located at a radius r b and t i are the top joints located at a radius r t . While the bottom joints are meant for connecting each limb with the stationary base platform BP about the semi-regular hexagon b 1 b 2 b 3 b 4 b 5 b 6 , the top joints connect the other ends of the respective limbs with the semi-regular hexagonal moving platform MP with the vertices t 1 , t 2 , t 3 , t 4 , t 5 , and t 6 . Centers O and o respectively of the bottom and top circles form the origins of the stationary global Cartesian coordinate system Oxyz and the moving Cartesian coordinate system opqr .…”

“…The early uses of Stewart platforms as motion simulator 1 and in a universal testing machine 2 have expanded to include telescope pointing and stabilization, 3 vibration isolation, 4 machining, 5 and measurement systems for force, 6 displacement, 7 and torque. 8 The aim of achieving higher working precision by utilizing the advancements in the hardware technology and the controller design together with ever expanding and more sophisticated prospective applications have kept the research interest in Stewart platform design very live.…”

An Alignment Method of Human-Robot Collaboration Based on the Six-Dimensional Force/Torque Dynamic Measurement for Large-Scale Components

“…An SPR is composed of a moving platform and a base platform, which are connected by six extensible links with spherical/universal joints. In its operational range, 6-Degrees-of-Freedom (DOF) motion of the moving platform can be achieved by the motions of the six limbs as a group [14,15]. The SPR's limbs' position and their force measurements are also very important [16].…”