Analysis and Control of a Magnetic Lead Screw for Servo Application
Authors
Christensen, Simon ; Mark, Søren Elton
Term
4. term
Education
Publication year
2014
Submitted on
2014-06-03
Pages
69
Abstract
This thesis analyzes and controls a linear position servo composed of a magnetic lead screw (MLS) driven by a surface-mounted permanent magnet synchronous machine (SPMSM). The central question is how to control the MLS as a linear position servo while accounting for the MLS’s compliant force transfer and magnetic saturation in the SPMSM. An experimental platform was built to collect measurements and validate models. For the motor, flux-linkage saturation was measured and embedded in an SPMSM model, which supported a closed-loop current controller with feedforward compensation; the target was precise torque regulation and the capability to deliver up to four times the rated torque. The measured current–torque relation enabled accurate torque control with deviations within 4% and minimized current for a given torque. For the MLS, a simulation model was developed and parameters were identified experimentally; the dynamic behavior was characterized, including natural frequency and frequency response, and parameter variations were studied to reflect different applications. Comparison with experiments revealed that the test rig’s structural stiffness and damping dominated the response, prompting an extended model that included ambient stiffness and damping and was validated against measurements. A proportional position controller was designed (Ziegler–Nichols), but its performance was limited, indicating the need for more advanced control strategies; the model was linearized to support future controller design.
Denne kandidatafhandling undersøger analyse og kontrol af en lineær positionsservo opbygget af en magnetisk ledeskrue (MLS) drevet af en overflademonteret permanentmagnet-synkronmotor (SPMSM). Udgangspunktet er problemstillingen: Hvordan kontrolleres MLS’en som lineær positionsservo, når både den fjedrede kraftoverførsel i MLS’en og mætning i SPMSM’en skal håndteres? En eksperimentel platform blev udviklet til at måle og validere modeller. For motoren blev mætningen af fluxsammenkædningen målt og indarbejdet i en SPMSM-model, som dannede grundlag for en lukket strømsløjfe med feedforward-kompensering; målet var præcis momentstyring og mulighed for op til fire gange nominelt moment. Målingerne gav en strøm–moment-relation, som muliggjorde nøjagtig momentkontrol med afvigelser inden for 4 % og minimeret strømforbrug for et givent moment. For MLS’en blev en simuleringsmodel opstillet og parametre identificeret via forsøg; systemets dynamik blev karakteriseret, herunder naturlig frekvens og frekvensrespons, og parameterfølsomhed blev analyseret for forskellige anvendelser. Sammenligning med forsøg viste, at testopstillingens strukturstivhed og dæmpning prægede responsen, hvorfor en udvidet model med omgivende stivhed og dæmpning blev etableret og valideret. En proportional positionsregulator blev derefter designet (Ziegler–Nichols), men ydelsen var begrænset, hvilket peger på behov for mere avancerede kontrolstrukturer; modellen blev desuden lineariseret som grundlag for fremtidig reguleringsudvikling.
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