1、PDF外文：http:/ A Common-grounded BLDCM Drive System Based on FPGA Pinghua Tang, Tiecai Li Department of Electrical Engneering Harbin Industry of Technology harbin, CHINA Email: ； Abstract This paper proposed a kind of common-grounded brushless DC motor(BLDCM)drive system based on fie
2、ld programmed gate array(FPGA)control. The proposed system has two characteristics: one is that the former 60 of every drive lag applies pulse width modulation (PWM) and the latter 60 conducts constantly (PWM_ON modulation)； the other is that there are no isolating optical couplers between control c
3、ircuit and drive circuit. So the proposed system has some advantages such as reducing ripple of electromagnetic torque, simplifying drive circuit to reduce the delay of signals, and reducing the cost and bulk of drive system. A prototype is designed based on FPGA chip, and experimental results demon
4、strated the validity of relative theory. Index Terms - common-grounded drive； BLDCM； FPGA； PWM_ON modulation I. INTRODUCTION Brushless DC motor is widely applied in modern control system because of many advantages such as high efficiency, high power density, good speed characteristic an
5、d simplified control etc.1-2. In order to control BLDCM system effectively, conventional drive scheme for BLDCM system is that 120 control signals which is output by control circuit are isolated by optical couplers, then deliver to drive circuit and control the power main circuit. So conventional BL
6、DCM system presents some disadvantages such as big electromagnetic torque ripples, big volume, high cost, and signals delay by optical coupler etc. These disadvantages make conventional BLDCM system not been used in some conditions which need high precision and high stability 3-4. To overcome these
7、disadvantages of conventional BLDCM system to some extent, this paper presents a novel BLDCM system which is applied with PWM_ON modulation and common-grounded drive scheme. The proposed system has two characteristics: one is PWM_ON modulation control mode that the former 60 of every drive lag appli
8、es pulse width modulation (PWM) and the latter 60 conducted constantly in 120 period； the other is that there are no isolating optical couplers between control circuit and drive circuit. This paper deduced mathematics model of BLDCM, then analyzed operational principle of the PWM_ON modulation commo
9、n-grounded drive scheme which is used to BLDCM system, and simulation analysis about the proposed scheme is presented, finally, a 120W BLDCM system prototype isdeveloped based on FPGA chip, and experimental results were analyzed. II. BLDCM MATHEMATICAL MODEL Most BLDCM drives are based on the
10、active control to three-phase inverter to obtain square-wave current of BLDCM needed in modern times. The BLDCM mathematical model which infers below in this article includes three-phase inverter. The mathematical model of BLDCM is composed of two parts, namely mechanical equation and voltage equati
11、on. This paper makes the following three suppositions before introducing the mathematical model, as follows: (1) Three-phase stator winding A, B, C is symmetrical in spatial distribution, the higher harmonic component of magnetic field is neglected. (2) The magnetic saturation and the co
12、re loss (magnetic hysteresis loss, eddy current loss) are neglected. (3)The influence factors including temperature, frequency etc. on parameters of motor are not considered. Mechanical movement equation of electric machine is fixed and wont change with the coordinate transformation. BLD
13、CM mechanical movement equation is as follows: Te Tl=Jdtd + B (1) where Teis electromagnetic torque, TLis load torque, J is rotor and load inertia, B is friction coefficient, is rotating speed of BLDCM. Take the three-
14、phase stator voltage as the state variable. Its voltage balance equation can be expressed as (2): Ua Ra iaLa Lab Lac ia ea Ub =Rb
15、 ib + dtd Lba Lb Lbc ib +eb (2) Uc Rc ic Lca Lcb Lc ic
16、;ec Because the rotor is permanent-magnet ,La ,Lb ,Lc ,Lab ,Lba ,Lac ,Lca ,Lbc ,Lcb ,can be considered as constants, then, Ra=Rb=Rc=Rs La=Lb=Lc=L Lab=Lba=Lac=Lca=Lbc=Lcb=M &n
17、bsp; (3) ia+ib+ic=0 Therefore, we obtain the PM BLDCM voltage equation which is shown in (4): Ua Rs ia L M ia ea Ub = &nb
18、sp; Rs ib + L M dtd ib + eb (4) Uc Rs ic &n
19、bsp; L M ic ec The topology of BLDCM model is obtained from (4) and shown in Fig.1. Fig.1 Topology of BLDCM model So, mathematical model of BLDCM can be described as (1) and (4). III. PWM_ON MODULATIONCOMMON-GROUNDED DRIVE SCHEME As three-phase inverter is concerned, PWM control scheme is widely applied to control the speed and current of BLDCM control system. There are following
