The design and the control of a linear motor drive for micropositioning

Abstract

This thesis is a part of SOLOMANDA (Finnish acronym for Manipulation, Detection and Analysis of Single Biological Cells) project. The project partners are Tampere University of Technology (TUT), Medical School of the University of Tampere, Technical Research Centre of Finland (VTT) and Helsinki University of Technology (HUT). The background of the project is the effort to replace use of laboratory animals and human cells of cancer origin by heterogeneous cell cultures. While Medical school focuses on cell cultures, VTT develops a machine vision system and incubation system. TUT builds a novel micromanipulator (MANiPEN) and injection methods. This thesis focuses on a development pf a linear motor drive, which is an important component of MANiPEN. The linear motor drive gives the MANiPEN ability to move along an axis. The goal is to achieve very accurate, straight and fast movement. This high precision is accomplished by those compomemets: a linear optical incremental encoder, a stepping motor, a piezoelectric sack and a crossed rolled bearing. This starts with an introduction, followed by an overview of optical encoders. Since a stepping motor with threaded rotor and a leadscrew is used as an actuation unit, the next chapter profoundly studies stepping motors; classification and excitation models are introduced. Next chapter discusses the modelling and control of the stepping motors, which is implemented in order to achieve very accurate device. Next, modelling and general methods mostly used for rotary stepping motors coupled with rotary optical encoder is given in following chapter. The experimental part of the thesis describes the design and the control of the linear motor drive. The major equipment - the shape of the linear drive, its size and performance are discussed. he specification of used actuators, sensors and other important components is given. Two different control approaches are presented - an open-loop and a close-loop control scheme. The open loop control gives a cheap and a simple solution but accuracy of the system decreases. On the other hand, the closed-loop control scheme gives system with very good accuracy but it requires more sophisticated controller. Finally, the closed-loop controller was used in the linear motor drive. The linear motor drive, which has been developed as a part of this thesis, has been successfully implemented within the MANiPEN micromanipulator. /Kir10