外文翻譯-直流電機轉(zhuǎn)速控制的閉環(huán)電路設(shè)計

畢業(yè)設(shè)計翻譯文獻與原文題 目： 直流電機轉(zhuǎn)速控制的閉環(huán)電路設(shè)計學 院： 測控與光電工程學院 專 業(yè)： 測控技術(shù)與儀器 姓 名： 學 號： 指導教師： 直流電機轉(zhuǎn)速控制的閉環(huán)電路設(shè)計這項研究是由廣州市科技攻關(guān)項目資助摘要 本文介紹了直流電動機的調(diào)速原理，闡述了把 PIC16F877 單片機作為主控制組件的速度控制系統(tǒng)，即利用 PIC16F877 單片機中的捕捉模塊、比較模塊、模數(shù)轉(zhuǎn)換模塊來作為觸發(fā)系統(tǒng)，并給出了程序流程圖。該系統(tǒng)具有很多優(yōu)點，包括結(jié)構(gòu)簡單，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，電機的無級平滑控制，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，成本低廉，并且系統(tǒng)具有良好的實用性可以容易地實現(xiàn)。關(guān)鍵詞PIC16F877 電機控制控制電路PI 控制算法1 簡介電子技術(shù)的快速發(fā)展使得直流電機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機的 KZ-D 拖帶系統(tǒng)，已經(jīng)取代笨重的 FD 發(fā)電機電動機系統(tǒng)，特別是單片機技術(shù)的應用使得電機速度控制進入了一個新的層次。在直流調(diào)速系統(tǒng)，由很多部分控制電路。SCM 具有許多優(yōu)點，如高性能，速度快，體積小，價格便宜，可靠穩(wěn)定,應用廣泛， 提高控制能力并且滿足實時控制得需要。采用模擬或數(shù)字的控制電路可以用單片機來實現(xiàn)。在這篇文章中，我們將介紹基于單片機 PIC16F877 的一種直流電機調(diào)速系統(tǒng)。2 直流電機調(diào)速原理表一中，電壓時 Ua，電流是 Ia，閉環(huán)總電阻是 Ra，電機電容是 Ca，磁通是 。根據(jù) KVL 方程，電機的轉(zhuǎn)速是n = (Ua - Ia Ra )(CF)(2,1)Ca =pN60a(2.2)Ua - Ia Ra UaTd (k) = Td (k -1)+ a0e(k)- a1e(k -1) = Td (k -1)+ 0.84e(k)-0.63e(k -1)(2.3)(2.4)a =Tf 0Kp 1+ T a1 = Kp Tf = T + Tdt (2.5)(2.6)(2.7)其中，P 是極對數(shù)，N 是匝數(shù)。電機的電樞支路數(shù)是 a，電機電容 Ca=PN|60a, 這意味著，電機一定時，電容是一定的。但是在 Ua-IaRa,因為 Ra 是繞線電阻， 所以非常小，Ua-IaRa=Ua.所以很清楚當我們改變了電壓，轉(zhuǎn)速也隨之改變。3 系統(tǒng)組成和工作原理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3.2 系統(tǒng)的工作原理該系統(tǒng)主要由主開關(guān)，電動機的勵磁回路，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，能耗制動電路。該系統(tǒng)采用閉環(huán)PI 調(diào)節(jié)器來實現(xiàn)控制。當主開關(guān)關(guān)閉時，通過二極管速度控制電路的控制，和橋式整流，濾波和平面波反應堆的處理產(chǎn)生脈沖小的連續(xù)的單相交流電，同時通過激勵整流電路。交流電使電動機獲得動力開始工作。當輸入電壓降低時，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，晶閘管隨流角度， 主電路輸出電壓，電機轉(zhuǎn)速，測速電路的輸出電壓提高，通過 PI 調(diào)節(jié)器的作用， 電機穩(wěn)定運行在設(shè)定的轉(zhuǎn)速范圍。4 系統(tǒng)的各部分電路的設(shè)計4.1 主電路設(shè)計電路中各元件的參數(shù)是在圖 3 所示按下開始按鈕 SW，使 KM 電容器充電，然后 KM 常開觸點關(guān)閉，常閉觸點打開，按下自鎖按鈕，主電路接通。然后，二極管調(diào)速電路通過改變雙向?qū)ǘO管的控制角來控制交流電輸出，通過整橋電路獲得直流，與此同時，電機通過整流電路獲得動力開始工作。為限制直流電波動，在電路中連上電容，當主電路斷電時 ，R3 與電容組成放電回路。為立即制動，設(shè)備中采用了能耗制動，制動部分由 R4 和主電路中的常閉觸點組成。電機激勵部分由單一的整流電路供電，為了防止電磁損耗使得點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，和滑動變阻器 RP.。4.2 二極管觸發(fā)電路的設(shè)計AB 間的電壓通過變壓器成為 20V，經(jīng)過整橋電路后，大約一半 100H 的信號發(fā)生在這兩點，再經(jīng)過 R6 和 R7 分壓電路進行放大，輸入三極管的兩端，在三極管集電極產(chǎn)生過零脈沖，同時通過 CCPI 模塊捕獲脈沖的上升沿并記錄時間，然后獲得下降沿并記錄時間，兩個時間的差是脈沖的寬度，該值的一半是中點脈沖， 通過這種捕捉模式，我們可以準確的獲得交流電的零值點。同時，我們可以通過數(shù)模轉(zhuǎn)換器來改變PIC16F877 的RA1/RN1 接口的模擬電壓值作為二極管控制電路的實際值，改變變阻器 RP1 的設(shè)定值，并極大改變二極管控制電路的設(shè)定值，轉(zhuǎn)速表電路的輸出值輸入 PIC16F877 的 RA1/RN1 接口，得出的值作為速度反饋值通過模數(shù)轉(zhuǎn)換器。在單片機系統(tǒng)的振蕩頻率為 4MHz，并根據(jù) PIC16F877 的命令特點，二極管控制角的分辨率是四分之一單片機振蕩的倒數(shù)，即 1對于電力 10ms 的半波時間，控制角可以實現(xiàn) 10000 個步驟，完全實現(xiàn)電動機的無級平滑控制。4.3 轉(zhuǎn)速表電路設(shè)計轉(zhuǎn)速表電路由連接著電機轉(zhuǎn)子和放大整形電路的光電碼盤組成。電脈沖頻率與電動機的轉(zhuǎn)速成一定的比例，通過放大整形，由光電碼碼盤輸出的電脈沖從PIC16F877 的引腳 RC0/T1CK1 輸入作為標準的 TTL 電平，由計數(shù) TMR1 計數(shù)器來計算轉(zhuǎn)速，與設(shè)定的轉(zhuǎn)速比較，得到差值轉(zhuǎn)速，PIC16F877 進行 PI 運算獲得這種差異的價值來獲得控制增加，并控制二極管的控制角來有效改變 CCP2 電機的兩個端口的電壓，從而控制轉(zhuǎn)速。5 軟件設(shè)計為了在二級管控制角調(diào)制中得到微小的值，我們設(shè)計了速度控制的典型一封閉系統(tǒng)。PI 運算器用來運算二極管控制角的值 Td ，算法是Td (k ) = Td (k -1) + a0e (k ) - a1e (k -1) = Td (k -1) + 0.84e (k ) - 0.63e (k -1)(5.1)a =Tf 0Kp 1+ T t (5.2)其中，a1=KP，KP 是控制器的比例系數(shù)，Tl 是積分時間常數(shù)，Ti 是采樣周期?？紤]到系統(tǒng)中的電動機的電動機常數(shù)時間 0.12s，幾個采樣周期內(nèi)可以忽略誤差， 所以我們選擇采樣周期 2ms 的測速系統(tǒng)。在系統(tǒng)的軟件設(shè)計模塊主要包括 CCP1 上升沿捕捉模塊，CCP1 下降沿捕捉模塊，控制角度設(shè)定值的 A/D 轉(zhuǎn)換模塊，測速電路脈沖定時計數(shù)模塊，PI 調(diào)節(jié)器模塊和 CCP2 比較輸出模塊。假設(shè)我們得到過零時間 T，二極管控制角時間 Td，那么被輸入寄存器 CCP2 引腳 CCPR2H 的值 Tf=T+Td，當比較一定時，引腳輸出的高電平使得二極管導通， 修改引腳的值根據(jù)要求的脈沖寬度值維持輸出的高電平值，然后返回低電平值。雙向二極管的觸發(fā)脈沖輸出完畢。6 總結(jié)該速度控制系統(tǒng)以PIC16F877 單片機為雙向?qū)ǘO管觸發(fā)電路的設(shè)計具有許多特點，諸如結(jié)構(gòu)簡單，運行可靠，調(diào)節(jié)范圍寬，良好的電流連續(xù)性，在中小型快大小的直流電機速度控制系統(tǒng)中的快速反應等特點。和轉(zhuǎn)速環(huán)采用 PI 控制算法，能有效地抑制超調(diào)轉(zhuǎn)速，所以它是采用一種可行單片機速度控制系統(tǒng)，并運行曲線如圖 5 所示。參考書目康華光.鄒收臏. 電子技術(shù)基礎(chǔ)：數(shù)字部分（第四版）. 北京高等教育出版社,2000. 李血海. PIC 單片機實用教程. 北京航空航天大學出版社,2002.蘇建輝. 對光伏水泵系統(tǒng)及其控制的研究. 合肥科技大學的博士學位論文,2002. 張申. 無刷直流電動機的應用原理. 北京機械工業(yè)出版社,1996.附錄表一 電機原理圖表二 硬件結(jié)構(gòu)圖注；從左到右依次是主開關(guān)電路，電機激勵電路，二極管觸發(fā)電路，整流電路，平波 濾波電路，能耗制動電路。表三 主電路圖表四 觸發(fā)電路圖表五 運行圖Design of the Closed Loop Speed Control System for DC MotorThe research is financed by the Guangzhou Municipal Science and Technology KeyProjectsAbstract This article introduces the speed control principle of DC motor, expatiates on the speed control system taking PIC16F877 SCM as the main controlcomponent, utilizes the characters of catching module, comparing 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 angle 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 circuit PI control algorithm1. IntroductionThe 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 electrical 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 control 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 adopting 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 PIC16F877.2. Speed regulation principle of DC motorIn Figure 1, the armature voltage is Ua, the armature current is Ia, the total resistance of armature loop is Ra , the motor constant is Ca , and the excitation flux is .According to KVL equation, the rotate speed of the motor isn = (Ua - Ia Ra )(CF)（2.1）Ca =pN60a（2.2）Ua - Ia Ra UaTd (k ) = Td (k -1) + a0e (k ) - a1e (k -1) = Td (k -1) + 0.84e (k ) - 0.63e (k -1)（2.3）（2.4）a =Tf 0Kp 1+ T a1 = Kpt （2.5）（2.6）Tf = T + Td（2.7）Where, p s the pole-pairs,N is the number of turns. For the motor that the armaturespur track number is a, the motor constant Ca=PN/60a， that means when the motor is confirmed, the value is fixed. But in Ua-IaRa,Because only the winding resistance, s I aRa is very small, and Ua-IaRaUa . So it is obvious that when we change the armature voltage, the rotate speed n changes with that 。3. System composition and work principle3.1 Module frame of system hardware structureThe module block diagram of system hardware is seen in Figure 2.3.2 Work principle of the systemThe system is mainly composed by master switch, 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, 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 excitingcircuit, AC makes the motor obtain excitation to begin 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 increases, and the output voltage of tachometer circuit increases, and the motor stably runs in the setting speed range through the function of PI regulator.4. Circuit designs of various parts in the system4.1 Design of main circuitThe parameters of various components in the circuit are seen in Figure 3.Press the 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 bidirectional thyristor, and obtains the DC through bridge rectifying and filtering, and at the same time, the motor obtainsthe 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 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 is 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 under-current relay KA, and the action current can be regulated through the potentiometer RP.4.2 Design of thyristor trigger 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 passage 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 midpoint 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 of 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 oscillation 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. 1s,for the half wave time of 10ms of the power, the control angle can achieve 10000steps, which can completely realize the stepless smooth control of motor.4.3 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 proportion 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 RC0/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 presetting rotate speed and obtain the difference value, and PIC16F877 implements PI operation tothis 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.5. Software designTo 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 isTd (k ) = Td (k -1) + a0e (k ) - a1e (k -1) = Td (k -1) + 0.84e (k ) - 0.63e (k -1) （5.1）a =Tf 0Kp 1+ T t （5.2）Where a1=kp,kp is the proportion coefficient of controller,Tt is the integral time constant, Tiand 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 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 CCP2 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, and modify the value of CCPR2H:L again according to the required trigger pulse width value tosustain the out