A compact 6 D.O.F geometric error measurement system with PSDs for long travel range in mMT

Miniaturized machine tools (mMTs) have been developed as a solution to accurately machine components of micro/meso-scale. Geometric errors of mMTs result in inaccurate parts. Therefore, the geometric errors of mMTs should be identified and compensated effectively which will also improve the accuracy of mMTs. The six geometric errors in a conventional machine tool system are characterized using laser interferometers, electronic devices and other measurement devices. However, these devices can measure only one or two errors in a single setup and require long and costly measurement procedures. The PSD(Position Sensitive Detecter) measurement system which is considered as an alternate has problems as well. Though PSD has high resolution, it is usually small to cover the entire travel range of the linear stages, so the PSD measurement system can't measure 6-DOF errors more than its size. And mounting errors between PSDs and beam splitters affect on characterizing errors. To overcome these disadvantages, a new configuration of PSD system is proposed in this paper. In this work the measurable range of PSD system is expanded by changing the configuration of PSD system instead of moving PSDs. The configuration consists of two modules namely laser and PSD module. And manufacturing all components of PSD measurement system as two parts not only makes the system compact and easy to set up but also reduce the mounting errors because manufacturing errors are much smaller than mounting errors. To demonstrate the effectiveness and accuracy of the proposed measurement system, the mathematical and sensitivity analysis of this PSD measurement are presented in this paper.