Evaluation of open-loop linear drive accuracy achieved by calibration and linear thermal expansion compensation

Abstract

The study is a part of the current work on the design and creation of a precision mechanism with parallel kinematics such as a space hexapod. The positioning accuracy and repeatability of the movable platform of the machine relative to its fixed base in the structure under consideration depends on the accuracy of the actuating elements of the hexapod – linear drives. The aim of the work is to assess the achievable accuracy of the linear drive, taking into account the main factors affecting the accuracy of its rod movement. The article describes the studies of the accuracy of the open-loop linear drive, which has no common feedback on the output coordinate. The main factors affecting the accuracy of movement are highlighted. The experimentally obtained estimates of the linear drive rod displacement errors are given. A technique is proposed for improving the linear drive accuracy by programmatically calibrating its ball screw drive and compensating for linear thermal expansion (LTE) when the drive is operating in a wide temperature range. An estimate of the calibrated linear drive rod movement accuracy with LTE compensation has been obtained.