外文翻译-直流电机转速控制的闭环电路设计

毕业设计翻译文献与原文题 目： 直流电机转速控制的闭环电路设计学 院： 测控与光电工程学院 专 业： 测控技术与仪器 姓 名： 学 号： 指导教师： 直流电机转速控制的闭环电路设计这项研究是由广州市科技攻关项目资助摘要 本文介绍了直流电动机的调速原理，阐述了把 PIC16F877 单片机作为主控制组件的速度控制系统，即利用 PIC16F877 单片机中的捕捉模块、比较模块、模数转换模块来作为触发系统，并给出了程序流程图。该系统具有很多优点，包括结构简单，与主电路的同步，稳定换档相，足够的转换相位范围，10000 步控制的角度，电机的无级平滑控制，陡脉冲前沿，足够的振幅值，设置脉冲宽度， 稳定性好，抗干扰能力强，成本低廉，并且系统具有良好的实用性可以容易地实现。关键词PIC16F877 电机控制控制电路PI 控制算法1 简介电子技术的快速发展使得直流电机的速度控制从模拟逐步转化为数字，目前广泛采用可控硅设备在电气拖船控制系统中，以将电力提供给电动机的 KZ-D 拖带系统，已经取代笨重的 FD 发电机电动机系统，特别是单片机技术的应用使得电机速度控制进入了一个新的层次。在直流调速系统，由很多部分控制电路。SCM 具有许多优点，如高性能，速度快，体积小，价格便宜，可靠稳定,应用广泛， 提高控制能力并且满足实时控制得需要。采用模拟或数字的控制电路可以用单片机来实现。在这篇文章中，我们将介绍基于单片机 PIC16F877 的一种直流电机调速系统。2 直流电机调速原理表一中，电压时 Ua，电流是 Ia，闭环总电阻是 Ra，电机电容是 Ca，磁通是 。根据 KVL 方程，电机的转速是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 是极对数，N 是匝数。电机的电枢支路数是 a，电机电容 Ca=PN|60a, 这意味着，电机一定时，电容是一定的。但是在 Ua-IaRa,因为 Ra 是绕线电阻， 所以非常小，Ua-IaRa=Ua.所以很清楚当我们改变了电压，转速也随之改变。3 系统组成和工作原理3.1 系统的硬件结构的模块框系统硬件的模块框图。如图 2 所示3.2 系统的工作原理该系统主要由主开关，电动机的励磁回路，二极管调速电路（包括转速表电路），整流滤波电路，平波电抗器，放电电路，能耗制动电路。该系统采用闭环PI 调节器来实现控制。当主开关关闭时，通过二极管速度控制电路的控制，和桥式整流，滤波和平面波反应堆的处理产生脉冲小的连续的单相交流电，同时通过激励整流电路。交流电使电动机获得动力开始工作。当输入电压降低时，触发电路的速度使得 PIC16F877 产生的输出控制角度降低。同时，晶闸管随流角度， 主电路输出电压，电机转速，测速电路的输出电压提高，通过 PI 调节器的作用， 电机稳定运行在设定的转速范围。4 系统的各部分电路的设计4.1 主电路设计电路中各元件的参数是在图 3 所示按下开始按钮 SW，使 KM 电容器充电，然后 KM 常开触点关闭，常闭触点打开，按下自锁按钮，主电路接通。然后，二极管调速电路通过改变双向导通二极管的控制角来控制交流电输出，通过整桥电路获得直流，与此同时，电机通过整流电路获得动力开始工作。为限制直流电波动，在电路中连上电容，当主电路断电时 ，R3 与电容组成放电回路。为立即制动，设备中采用了能耗制动，制动部分由 R4 和主电路中的常闭触点组成。电机激励部分由单一的整流电路供电，为了防止电磁损耗使得点击高的速度不能控制引起事故，在电路中串联了继电器 KA，和滑动变阻器 RP.。4.2 二极管触发电路的设计AB 间的电压通过变压器成为 20V，经过整桥电路后，大约一半 100H 的信号发生在这两点，再经过 R6 和 R7 分压电路进行放大，输入三极管的两端，在三极管集电极产生过零脉冲，同时通过 CCPI 模块捕获脉冲的上升沿并记录时间，然后获得下降沿并记录时间，两个时间的差是脉冲的宽度，该值的一半是中点脉冲， 通过这种捕捉模式，我们可以准确的获得交流电的零值点。同时，我们可以通过数模转换器来改变PIC16F877 的RA1/RN1 接口的模拟电压值作为二极管控制电路的实际值，改变变阻器 RP1 的设定值，并极大改变二极管控制电路的设定值，转速表电路的输出值输入 PIC16F877 的 RA1/RN1 接口，得出的值作为速度反馈值通过模数转换器。在单片机系统的振荡频率为 4MHz，并根据 PIC16F877 的命令特点，二极管控制角的分辨率是四分之一单片机振荡的倒数，即 1对于电力 10ms 的半波时间，控制角可以实现 10000 个步骤，完全实现电动机的无级平滑控制。4.3 转速表电路设计转速表电路由连接着电机转子和放大整形电路的光电码盘组成。电脉冲频率与电动机的转速成一定的比例，通过放大整形，由光电码码盘输出的电脉冲从PIC16F877 的引脚 RC0/T1CK1 输入作为标准的 TTL 电平，由计数 TMR1 计数器来计算转速，与设定的转速比较，得到差值转速，PIC16F877 进行 PI 运算获得这种差异的价值来获得控制增加，并控制二极管的控制角来有效改变 CCP2 电机的两个端口的电压，从而控制转速。5 软件设计为了在二级管控制角调制中得到微小的值，我们设计了速度控制的典型一封闭系统。PI 运算器用来运算二极管控制角的值 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 是控制器的比例系数，Tl 是积分时间常数，Ti 是采样周期。考虑到系统中的电动机的电动机常数时间 0.12s，几个采样周期内可以忽略误差， 所以我们选择采样周期 2ms 的测速系统。在系统的软件设计模块主要包括 CCP1 上升沿捕捉模块，CCP1 下降沿捕捉模块，控制角度设定值的 A/D 转换模块，测速电路脉冲定时计数模块，PI 调节器模块和 CCP2 比较输出模块。假设我们得到过零时间 T，二极管控制角时间 Td，那么被输入寄存器 CCP2 引脚 CCPR2H 的值 Tf=T+Td，当比较一定时，引脚输出的高电平使得二极管导通， 修改引脚的值根据要求的脉冲宽度值维持输出的高电平值，然后返回低电平值。双向二极管的触发脉冲输出完毕。6 总结该速度控制系统以PIC16F877 单片机为双向导通二极管触发电路的设计具有许多特点，诸如结构简单，运行可靠，调节范围宽，良好的电流连续性，在中小型快大小的直流电机速度控制系统中的快速反应等特点。和转速环采用 PI 控制算法，能有效地抑制超调转速，所以它是采用一种可行单片机速度控制系统，并运行曲线如图 5 所示。参考书目康华光.邹收膑. 电子技术基础：数字部分（第四版）. 北京高等教育出版社,2000. 李血海. PIC 单片机实用教程. 北京航空航天大学出版社,2002.苏建辉. 对光伏水泵系统及其控制的研究. 合肥科技大学的博士学位论文,2002. 张申. 无刷直流电动机的应用原理. 北京机械工业出版社,1996.附录表一 电机原理图表二 硬件结构图注；从左到右依次是主开关电路，电机激励电路，二极管触发电路，整流电路，平波 滤波电路，能耗制动电路。表三 主电路图表四 触发电路图表五 运行图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