直流電機(jī)轉(zhuǎn)速控制的閉環(huán)電路設(shè)計(jì)

1、直流電機(jī)轉(zhuǎn)速控制的閉環(huán)電路設(shè)計(jì)摘要 本文介紹了直流電動(dòng)機(jī)的調(diào)速原理，闡述了把PIC16F877單片機(jī)作為 主控制組件的速度控制系統(tǒng)，即利用PIC16F877單片機(jī)中的捕捉模塊、比擬模塊、 模數(shù)轉(zhuǎn)換模塊來(lái)作為觸發(fā)系統(tǒng)，并給出了程序流程圖。該系統(tǒng)具有很多優(yōu)點(diǎn)，包 括結(jié)構(gòu)簡(jiǎn)單，與主電路的同步，穩(wěn)定換檔相，足夠的轉(zhuǎn)換相位范圍，10000步控 制的角度，電機(jī)的無(wú)級(jí)平滑控制，陡脈沖前沿，足夠的振幅值，設(shè)置脈沖寬度， 穩(wěn)定性好，抗干擾能力強(qiáng)，本錢低廉，并且系統(tǒng)具有良好的實(shí)用性可以容易地實(shí) 現(xiàn)。Design of the Closed Loop Speed ControlSystem for DC Motor

2、The research is financed by the Guangzhou Municipal Science and Technology Key ProjectsAbstract This article introduces the speed control principle of DC motor, expatiates on the speed control system taking PIC16F877 SCM as the main control component, utilizes the characters of catching module, comp

3、aring module and analog-to-digital conversion module in PIC16F877 SCM to be the trigger circuit, and gives the program flow chart. The system has many advantages including simple structure, synchronization with the main circuit, stable shifting phase and enough shifting phase range, the control angl

4、e of 10000 steps, stepless smooth control of motor, steep pulse front edge,enough amplitude value, setting pulse width, good stability and anti-jamming, and cheap cost, and this speed control system with good practical values can be realized easily.Keywords PIC16F877 DC motor speed control Control c

5、ircuit PI control algorithmIntroductionThe quick development of electric technology makes the speed control of DC motor gradually translate from analog to digital, and at present, the KZ-D towage system which extensively adopts the thyristor equipment (i.e. silicon controlled hyristor, SCR) in the e

6、lectrical towage control systems to supply power to electromotor has replaced cumbersome F-D system of generator-electromotor, and especially the application of SCM technology makes the speed control technology of DC motor enter into a new phase. In the DC governor system, there are many sorts of co

7、ntrol circuit.SCM has many advantages such as high performance, quick speed, small volume, cheap price and reliable stability,extensive application and strong currency, and it can increase the ability of control and fulfill the requirement of real-time control (quick reaction). The control circuit a

8、dopting analogy or digital circuit can be implemented by SCM.In this article, we will introduce a sort of DC motor speed control system based on SCM PIC16F877.Speed regulation principle of DC motorIn Figure 1, the armature voltage is Ua, the armature current is Ia, the total resistance of armature l

9、oop is Ra, the motor constant is Ca, and the excitation flux is 中. According to KVL equation, the rotate speed of the motor is(2.1)(2.2)(2.3)(2.1)(2.2)(2.3)(3)C _兇Ca - 6QaUIaRakUa TOC o 1-5 h z 7；(攵) = 7；(左一l) + 0e(Z) qe(左一1)二心(左一l) + 0.84e(攵)一0.63e(k 1)(2.4)(Tfy“0 = Kp 1 + II L)(2.5)(2.6)Tf=T + Td(

10、2.7)Where, p s the pole-pairs, N is the number of turns. For the motor that the armature spur track number is a, the motor constant Ca=PN/60a, that means when the motor is confirmed, the value is fixed. But in Ua-hRa,Because only the winding resistance, s I aRa is very small, and Ua-IaRaUa. So it is

11、 obvious that when we change the armature voltage, the rotate speed n changes with thatoSystem composition and work principleModule frame of system hardware structureThe module block diagram of system hardware is seen in Figure 2.Work principle of the systemThe system is mainly composed by master sw

12、itch, motor exciting circuit, thyristor speed control circuit (including tachometer circuit), rectifying filter circuit, flat wave reactor and discharge circuit, energy consumption braking circuit, and the system adopts the closed loop PI regulator to implement control. When the master switch closes

13、, the single-phase AC obtains continual current with small pulse through the control of thyristor speed control circuit, and bridge rectifier, filtering and flat wave reactor for the motor, and at the same time, through the rectifying of exciting circuit, AC makes the motor obtain excitation to begi

14、n to work. The speed in the regulation trigger circuit sets the potentiometer RP1 to make the control angle output by PIC16F877 decrease when AN1 input voltage decreases, and the flow angle of thyristor increases with that, and the output voltage of main circuit increase, and the motor speed increas

15、es, and the output voltage of tachometer circuit increases, and the motor stably runs in the setting speed range through the function of PI regulator.Circuit designs of various parts in the systemDesign of main circuitThe parameters of various components in the circuit are seen in Figure 3.Press the

16、 start-up button SW, electrify the contactor KM loop, and KM normally open contact closes, and the normally closed contact opens, and start the button self-lock, the main circuit connects, and the thyristor speed control circuit controls the AC output through changing the control angle of bidirectio

17、nal thyristor, and obtains the DC through bridge rectifying and filtering, and at the same time, the motor obtains the excitation through rectifying of exciting circuit to begin to work. To limit thepulsation of DC, connect the flat wave reactor in the circuit, and the resistance R3 offers discharge

18、 loop for the flat wave reactor when the master circuit suddenly breaks off. To quicken braking and stopping, the energy consumption braking is adopted in the equipment, and the braking part is composed by the resistance R4 and master circuit contactor normally closed contact. The motor excitation i

19、s powered by the single rectifying circuit, and to prevent the uncontrollable high speed accident induced by the excitation loss of motor, in the exciting circuit, serially connect the undercurrent relay KA, and the action current can be regulated through the potentiometer RP.Design of thyristor tri

20、gger circuitThe voltages at the point A and the point B in the main circuit change to 20V through the transformer, and after bridge rectifying, the half signals about 100H occur at these two points, and the signals meet with NPN audion through voltage-division R6 and R7 to amplify, produce zero pass

21、age pulse at the collector of the audion, and catch the zero passage pulse ascending edge by CCP1 module and note the time of occurrence first, and catch the zero passage pulse descending edge, and the time difference between both is the zero passage pulse width, and the half of the value is the mid

22、point of pulse, and by this catching mode, we can exactly obtain the actual zero passage point of AC, and at thesame time, we can utilize ADC analog/digital conversion module to translate the simulation voltage of PIC16F877 pin RA1/AN1 as the setting value of thyristor control angle (setting value o

23、f motor speed), change the setting value of potentiometer RP1 and correspondingly change the setting value of thyristor control angle, and the output value of tachometer circuit is input by the pin RA1/AN1 of PIC16F877, and the value is taken as the speed feedback value through A/D conversion. The o

24、scillation frequency of SCM in the system adopts 4MHz, and according to the character of PIC16F877 order period, the resolution of thyristor control angle is the reciprocal of one fourth of SCM oscillation frequency, i.e. 1 u s, for the half wave time of 10ms of the power, the control angle can achi

25、eve 10000 steps, which can completely realize the stepless smooth control of motor.Design of tachometer circuitThe tachometer circuit is composed by the optical coded disc accreting with motor rotor and the electric pulse amplifying and shaping circuit. The frequency of electric pulse has fixed prop

26、ortion with the rotate speed of motor, and through amplifying and shaping, the electric pulse output by the optical coded disc is input from the pins RCO/T1CK1 of PIC16F877 as the standard TTL level, count by the TMR1 counter to compute the rotate speed, and compare this rotate speed with the preset

27、ting rotate speed and obtain the difference value, and PIC16F877 implements PI operation to this difference value to obtain the control increase, and send the thyristor control angle in CCP2 to change the effective voltage of two ports of the motor, and finally control the rotate speed.Software desi

28、gnTo obtain small super modulation of thyristor control angle, we design the speed closed control as the typical I system, i.e. PI regulator, which is used to regulate the thyristor control angle time Td and its control algorithm isZ/(Z) = 7；(Z l) + q)e(Z) qe(Z 1) = 7；(Z l) + 0.84e(Z) 0.63e(Z 1) (5.

29、1) (Tfy ao = Kp 1 + 卜(5.2)Where ai=kp,kp is the proportion coefficient of controller,Tt is the integral time constant, Rand is the sampling cycle.Considering that the motor time constant of electromotor in the system is 0.12s, the warps couldn t be eliminated in several sampling cycles, so we select

30、 2ms as the tachometer sampling cycle in the system.The software design module in the system mainly includes CCP1 ascending catching module, CCP1 descending catching module, control angle setting value A/D conversion module, tachometer circuit pulse timing counting module, PI regulator module and CC

31、P2 comparison output module. Suppose we obtain the zero-pass time T , and the thyristor control angle time is Td, so the comparison value which is sent into CCP2 register CCPR2H:L is Tf=T+Td. and when the comparison is consistent, output high level in the pin of CCP2 to make the thyristor connect, a

32、nd modify the value of CCPR2H:L again according to the required trigger pulse width value to sustain the output high level trigger pulse for certain time and return to low level again, so a bidirectional thyristor trigger pulse output is completed.ConclusionsThe speed control system taking PIC16F877

33、 SCM as the bidirectional thyristor trigger circuit designed in the article possesses many characters such as simple structure, reliable running, wide regulation range, good current continuity and quick response in the middle and small sized DC motor speed control system, and the rotate speed loop a

34、dopts PI control algorithm, which can effectively restrain the super modulation of rotate speed, so it is a feasible design to adopt the speed control system of SCM, and the running curve is seen in Figure 5.ReferencesKang, Huaguang & Zou, Shoubin. (2000). Base of Electric Technology: Number Part (4

35、th Edition). Beijing: Higher Education Press.Li, Xuehai. (2002). Practical Tutorial of PIC SCM. Beijing: Beijing University of Aeronautics and Astronautics Press.Su, Jianhui. (2002). Study on the Photovoltaic Water Pump System and Its Control. Thesis of Doctors Degree of Hefei University of Technolo

36、gy.Zhang, Shen. (1996). Principle and Application of DC Brushless Motor. Beijing: Machine Industry Press.appendixlaFigure 1 .Principle Diagram of DC MotorFigure 2.Block Diagram of Hardware Structure ModuleD2Figure 3.Diagram of Main Circuitprotection of magnetism lossFigure 4. Thyristor Trigger Circu

37、itFigure 5.Running Curve(2,1)(2.2)(2.3)(2.4)(2.5)(2.6)(2.7)1簡(jiǎn)介電子技術(shù)的快速開(kāi)展使得直流電機(jī)的速度控制從模擬逐步轉(zhuǎn)化為數(shù)字，目前 廣泛采用可控硅設(shè)備在電氣拖船控制系統(tǒng)中，以將電力提供給電動(dòng)機(jī)的KZ-D拖 帶系統(tǒng)，已經(jīng)取代笨重的FD發(fā)電機(jī)電動(dòng)機(jī)系統(tǒng)，特別是單片機(jī)技術(shù)的應(yīng)用使得 電機(jī)速度控制進(jìn)入了一個(gè)新的層次。在直流調(diào)速系統(tǒng)，由很多局部控制電路。SCM 具有許多優(yōu)點(diǎn)，如高性能，速度快，體積小，價(jià)格廉價(jià)，可靠穩(wěn)定，應(yīng)用廣泛， 提高控制能力并且滿足實(shí)時(shí)控制得需要。采用模擬或數(shù)字的控制電路可以用單片 機(jī)來(lái)實(shí)現(xiàn)。在這篇文章中，我們將介紹基于單片

38、機(jī)PIC16F877的一種直流電機(jī)調(diào) 速系統(tǒng)。2直流電機(jī)調(diào)速原理表一中，電壓時(shí)電流是Ia,閉環(huán)總電阻是Ra,電機(jī)電容是C，磁通是。 根據(jù)KVL方程，電機(jī)的轉(zhuǎn)速是n =3)c _兇Ca - 60aU TV 5(左)二(左一1)+qe(Z)(左一1) = 7；(左一1)+0.84e(Z)_0.63e(kl)(Tf)a = Kp + = KpTf=T + Td其中，P是極對(duì)數(shù)，N是匝數(shù)。電機(jī)的電樞支路數(shù)是a,電機(jī)電容Ca二PN|60a, 這意味著，電機(jī)一定時(shí)，電容是一定的。但是在Ua-IaR,因?yàn)镽a是繞線電阻， 所以非常小，Ua-IaRa=Ua.所以很清楚當(dāng)我們改變了電壓，轉(zhuǎn)速也隨之改變。3系統(tǒng)組

39、成和工作原理3.1系統(tǒng)的硬件結(jié)構(gòu)的模塊框系統(tǒng)硬件的模塊框圖。如圖2所示2系統(tǒng)的工作原理該系統(tǒng)主要由主開(kāi)關(guān)，電動(dòng)機(jī)的勵(lì)磁回路，二極管調(diào)速電路（包括轉(zhuǎn)速表電 路），整流濾波電路，平波電抗器，放電電路，能耗制動(dòng)電路。該系統(tǒng)采用閉環(huán) PI調(diào)節(jié)器來(lái)實(shí)現(xiàn)控制。當(dāng)主開(kāi)關(guān)關(guān)閉時(shí)，通過(guò)二極管速度控制電路的控制，和 橋式整流，濾波和平面波反響堆的處理產(chǎn)生脈沖小的連續(xù)的單相交流電，同時(shí)通 過(guò)激勵(lì)整流電路。交流電使電動(dòng)機(jī)獲得動(dòng)力開(kāi)始工作。當(dāng)輸入電壓降低時(shí)，觸發(fā) 電路的速度使得PIC16F877產(chǎn)生的輸出控制角度降低。同時(shí)，晶閘管隨流角度， 主電路輸出電壓，電機(jī)轉(zhuǎn)速，測(cè)速電路的輸出電壓提高，通過(guò)PI調(diào)節(jié)器的作用, 電機(jī)

40、穩(wěn)定運(yùn)行在設(shè)定的轉(zhuǎn)速范圍。4系統(tǒng)的各局部電路的設(shè)計(jì)主電路設(shè)計(jì)電路中各元件的參數(shù)是在圖3所示按下開(kāi)始按鈕SW,使KM電容器充電，然后KM常開(kāi)觸點(diǎn)關(guān)閉，常閉觸點(diǎn)打 開(kāi)，按下自鎖按鈕，主電路接通。然后，二極管調(diào)速電路通過(guò)改變雙向?qū)ǘO 管的控制角來(lái)控制交流電輸出，通過(guò)整橋電路獲得直流，與此同時(shí)，電機(jī)通過(guò)整 流電路獲得動(dòng)力開(kāi)始工作。為限制直流電波動(dòng)，在電路中連上電容，當(dāng)主電路斷電時(shí)，R3與電容組成 放電回路。為立即制動(dòng)，設(shè)備中采用了能耗制動(dòng)，制動(dòng)局部由R4和主電路中的常閉觸 點(diǎn)組成。電機(jī)激勵(lì)局部由單一的整流電路供電，為了防止電磁損耗使得點(diǎn)擊高的速度 不能控制引起事故，在電路中串聯(lián)了繼電器KA,和滑動(dòng)變阻器RP.。2二極管觸發(fā)電路的設(shè)計(jì)AB間的電壓通過(guò)變壓器成為20V,經(jīng)過(guò)整橋電路后，大約一半100H的信號(hào) 發(fā)生在這兩點(diǎn)，再經(jīng)過(guò)R6和R7分壓電路進(jìn)行放大，輸入三極管的兩端，在三極 管集電極產(chǎn)生過(guò)零脈沖，同時(shí)通過(guò)CCPI模塊捕獲脈沖的上升沿并記錄時(shí)間，然 后獲得下降沿并記錄時(shí)間，兩個(gè)時(shí)間的差是脈沖的寬度，該值的一半是中點(diǎn)脈沖, 通過(guò)這