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Sensorlos reglering av en PMSM
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2016 (Swedish)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Sensorless Control of a PMSM: Evaluation of Different Speed and Position Estimation Methods Suitable for Control of a PMSM (English)
Abstract [en]

This thesis is done together with KTH and Husqvarna AB. Husqvarna is one of the leading producers of outdoor power equipment in the world. A chainsaw developed by Husqvarna, that is driven by a permanent magnet synchronous motor (PMSM), is currently controller by a sensorless brushless DC-based controlling strategy. But to increase eciency of the motor and to get a more exible current control, Husqvarna wants to explore the feasibility to use a sensorless PMSM-based controlling strategy instead, called eld-oriented control (FOC). Sensorless control is achieved when the speed and position information used in the control is given by an estimator instead of a sensor. The aim of this thesis is thus to evaluate di erent rotor speed and position estimators that are applicable to the FOC scheme.

The thesis will include a case study which is a PMSM that is suitable to actuate a battery operated chainsaw. The thesis is then conducted in two steps. First, a literature study was performed to get an overview of di erent speed and position estimation methods and to get enough knowledge to determine which methods that are applicable to the case study. The different methods are compared based on a few predened performance aspects that represents desired characteristics in an estimator. The second step is to model and simulate the one or two methods that according to the literature study seems best suited. In the simulations, each method will be controlling the motor while running through a set of test cases. The test cases are designed to imitate real potential scenarios for the motor that could occur when using the end-product. The different methods are also modelled both in continuous mode, to see if it works, and discrete mode to get closer to reality. The combined results from the simulations and literature study should indicate which method that is most appropriate to use in a sensorless control strategy for the motor of this case study.

From the literature study, the model reference adaptive system (MRAS) and the sliding mode observer (SMO) were chosen to be modelled and simulated. Both methods show good results in continuous mode simulations. When designed for discrete mode however, the SMO struggles and causes the whole control system to go unstable. The MRAS on the other hand, shows almost as good results as in continuous mode. The MRAS also shows an overall better estimation performance, both for di erent load cases and for motor parameter variations. Considering the MRAS is also better suited to include a resistance estimation, which is a useful feature, it will be proposed as the better option in the sensorless control of this case study.

Abstract [sv]

Det har examensarbetet ar gjort tillsammans med KTH och Husqvarna AB. Husqvarna ar en av varldens framsta tillverkare av utomhusprodukter. En motorsag som ar utvecklad av Husqvarna, som drivs av en permanent magnet synchronous motor (PMSM), regleras for tillfallet med en sensorlos brushless DC-baserad regleringsstrategi. For att oka motorns e ektivitet, och for att fa en mer exibel stromreglering, sa vill Husqvarna utforska mojligheten att anvanda en sensorlos PMSM-baserad regleringsstrategi istallet som kallas eld-oriented control (FOC). En reglering klassas som sensorlos nar informationen om motoraxelns position och hastighet som anvands i regleringen ges av en estimator istallet for en sensor. Malet med det har examensarbetet ar alltsa att utvardera olika hastighets- och positionsestimatorer som gar att tillampa i en FOC.

Arbetet kommer att innefatta en fallstudie som bestar av en PMSM som ar lamplig for att driva en batteridriven motorsag. Arbetet ar sedan uppdelat i tva steg. Forsta steget ar att gora en litteraturstudie for att fa en overblick over olika hastighets- och positionsestimatorer och for att fa tillrackligt med kunskap for att kunna avgora vilka metoder som kommer fungera i den har fallstudien. De olika metoderna jamfors i forhallande till nagra forbestamda aspekter som ska representera onskade egenskaper hos en estimator. Nasta steg ar att modellera och simulera de en eller tva metoderna som verkade mest lampliga enligt litteraturstudien. I simuleringarna sa reglerar varje metod motorn nar den kor igenom ett antal testfall. Testfallen ar konstruerade att avbilda riktiga anvandningsscenarion for motorn som skulle kunna intra a vid anvandande av slutprodukten. De olika metoderna modelleras i bade kontinuerlig form, for att se att de fungerar, och diskret form for att komma narmare verkligheten. De kombinerade resultaten fran simulationerna och litteraturstudien ar tankta att indikera vilken metod som skulle passa bast i en sensorlos regleringsstrategi for motorn i den har fallstudien.

Baserat pa litteraturstudien sa valdes model reference adaptive system (MRAS) och sliding mode observer (SMO) till att bli modellerade och simulerade. Simuleringarna for bada metoderna visar bra resultat i kontinuerlig form. Men nar SMO simuleras i diskret form sa blir den valdigt brusig och gor sa att hela reglersystem blir instabilt. MRAS visar a andra sidan lika bra resultat i diskret form som i kontinuerlig. MRAS visar ocksa en overlag battre estimeringsprestanda, bade for olika lastfall och for parametervariationer i motorn. Eftersom MRAS aven lampar sig for resistansuppskattning, vilket ar en anvandbar funktion, sa kommer den att bli foreslagen som det battre valet i det sensorlosa reglersystemet for fallstudien.

Place, publisher, year, edition, pages
2016. , 84 p.
, MMK 2016:168 MDA569
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-193592OAI: diva2:1032918
External cooperation
Husqvarna AB
Available from: 2016-10-05 Created: 2016-10-05 Last updated: 2016-10-05Bibliographically approved

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