Regulacija vrtilne hitrosti enosmernega stroja s trajnimi magneti

Krajnik, Blaž (author), Drobnič, Klemen (mentor)

V okviru diplomske naloge sem se podrobneje seznanil z enosmernim strojem s trajnimi magneti (ESTM). V 2. poglavju sem opisal njegovo zgradbo in fizikalno ozadje delovanja, s poudarkom na komutatorju, ki je ključni sestavni del vsakega enosmernega stroja in obenem razlog za krajšo življenjsko dobo in potrebo po stalnem vzdrževanju. Z matematičnim modelom sem dinamične obratovalne lastnosti ESTM zajel v obliki bločnega diagrama. Obratovalne lastnosti električnega stroja je lažje razumeti v stacionarnih razmerah, zato sem podrobneje opisal pripadajoče karakteristike, ki odsevajo razmerja med ključnimi veličinami ESTM. V 3. poglavju sem predstavil zgradbo in delovanje polnega mostiča (PM) ter opisal dve možnosti krmiljenja: unipolarno in bipolarno pulzno-širinsko modulacijo (PŠM). PM in ESTM skupaj sestavljata funkcionalno celoto – električni pogon. Ta omogoča štirikvadrantno delovanje, torej obratovanje v motorskem ali generatorskem režimu za obe smeri vrtilne hitrosti. Regulacijo vrtilne hitrosti sem predstavil v 4. poglavju. Najprej sem opozoril na nezmožnost prilagajanja magnetenja ESTM zaradi odsotnosti statorskega navitja. Ker je za regulacijo nujno natančno poznavanje vrtilne hitrosti, sem podal podrobnejšo razlago merjenja vrtilne hitrosti s pomočjo inkrementalnega dajalnika (ID). Regulacijsko zanko sklene PI regulator, katerega delovanje sem opisal na koncu tega poglavja. V sklopu naloge sem realiziral zgolj regulacijsko zanko vrtilne hitrosti. Regulacijske zanke toka zaradi majhne časovne konstante stroja nisem implementiral. Preden sem začel s praktičnim delom, sem naredil simulacije delovanja in krmiljenja ESTM v programu Simulink, kar sem predstavil v poglavju 5. Najprej sem preveril ujemanje simulacijskih rezultatov v stacionarnem stanju s karakteristikami podanimi v podatkovnem listu. Sledilo je testiranje delovanja v odprtozančnem načinu brez PI-regulatorja, kjer sem preizkušal krmiljenje stroja z unipolarno in bipolarno PŠM. Na ta način sem dobil prvo oceno obratovalnih lastnosti ESTM. Nato sem v blokovno shemo vključil PI-regulator in ponovno simuliral delovanje. Rezultati so pokazali, da ESTM z regulacijo vrtilne hitrosti dobro sledi želeni vrednosti. Regulacijski algoritem v praktičnem eksperimentu sem realiziral s pomočjo mikrokrmilnika myRIO, njegove značilnosti sem opisal v 6. poglavju. Krmilim ga preko grafičnega programskega okolja LabVIEW, kjer ima uporabnik s pomočjo virtualnega instrumenta dostop do vseh ključnih informacij pogona. Nekaj več pozornosti sem namenil zasnovi blokovnega diagrama, ki je v bistvu regulacijski program, katerega mikrokrmilnik izvaja v realnem času. V 7. poglavju sem najprej opisal eksperimentalni pogonski sistem, na katerem sem v okviru diplomske naloge opravil meritve. Sledila je praktična izvedba, kjer je bil pristop enak kot pri simulacijah. Ključno pri regulaciji je prilagajanje širine DP, ki posledično spreminja povprečno vrednost napetosti in omogoča reguliranje vrtilne hitrosti. Nenazadnje sem predstavil rezultate meritev in na koncu opozoril na dejstvo, da je na področju regulacije na splošno in konkretnega ESTM še veliko možnosti za izboljšave.

• Language: Slovenian
• Keywords: enosmerni stroj s trajnimi magneti, polni mostič, pulzno širinska modulacija, regulacija hitrosti, Simulink, myRIO, LabVIEW
• Work type: Bachelor thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2023
• PID: 20.500.12556/RUL-149965
• COBISS.SI-ID: 165075715
• Publication date in RUL: 12.09.2023

Secondary language

• Language: English
• Title: Speed control of permanent magnet DC machine

Abstract

In the course of my work, I gained a deeper understanding of the permanent magnet DC (PMDC) machine. The second chapter dealt with its structure and operating principles, especially the commutator. Although the commutator is essential for the functioning of the machine, it also leads to a shorter lifetime and the need for frequent maintenance. Using a mathematical model, I have presented the dynamic properties of the PMDC machine in a block diagram. I focused on the steady-state properties to make the machine's characteristics easier to understand. In the third chapter, the structure and operating principles of the full bridge converter are explained. It also explains how the full bridge converter can be controlled with unipolar or bipolar pulse width modulation (PWM). Finally, there is a summary of the four-quadrant operation of the full bridge converter. In fourth chapter, I discuss the speed control loop and its limitations due to the lack of a field winding. I discuss various control methods and their potential effectiveness. For any type of speed control, we need to know the speed of the motor shaft, hence the use of a quadrature encoder, the operation of which is explained. The control loop is complete with the inclusion of a PI controller. A word of warning is in order, I have only implemented the speed control loop. Due to the small value of the time constant of the machine, the implementation of the current control loop is not practical. Before starting the practical part, I simulated the operation of the PMDC machine using Simulink. The results are shown in the fifth chapter. First, I compared the results of the simulation in steady state with the properties of the machine given in the data sheet. Next, I ran simulations without the PI controller to determine the limits within which the machine can operate. In these simulations, I controlled the machine with unipolar and bipolar PWM. Then it was time to install the PI controller and run a simulation where I varied the desired shaft speed and set the controller to reach that value as quickly and with as little overshoot as possible. In this work, I used the myRIO microcontroller introduced in the sixth chapter. For control, I used the LabVIEW graphical programming environment, in which I created a project. The content of the project and the method to control the microcontroller are described in detail at the beginning of the chapter. Also, the block diagram should be noted because it serves as a program that runs in real time on the microcontroller. In the seventh chapter, I described the setup and use of the drive train to acquire measurements. The next step was to display the machine power measurements. The key element to implement speed control is the ability to set the duty cycle, which in turn determines the average value of the rotor voltage. Finally, I presented the measurement results and reminded that there is still much to learn and improve regarding speed control, both in general and for the PMDC machine studied in this work.

• Keywords: PMDC machine, full-bridge converter, pulse width modulation, speed control, Simulink, myRIO, LabVIEW