基于PWM直流电机的自动闭环速度控制系统英译汉.doc

2016届毕业设计 专业英文翻译 院 、 部：电气与信息工程学院 学生姓名： 刘泰波 指导教师： 邓宝燕 职称 工程师 专 业： 电气工程及其自动化 班 级： 电气本1205班 学 号： 1230140521 完成时间： 2016年5月 基于PWM直流电机的自动闭环速度控制系统摘要抽象电力驱动系统由于其自身的易于可控性被应用于许多需要更高的可靠性、变速性的工业领域。在精度和保护应用程序当中直流电机的速度控制是非常至关重要的。电动机转速控制器的设计目的是将发送过来的数据信号转化为驱动电机的转动速度。微型控制器可以提供简单的直流电机控制系统。基于单片机的速度控制系统由电子元件、微型控制器和液晶显示器。在本文，在经过考察调查后的直流电机速度控制的直流斩波器是由ATmega8L单片机实现的。控制PWM工作周期的原理相似于控制电机端的电压，由此从而可以直接调整电机速度。这是一个根据经济的视角和准确性而具有很高的实用性和可行性的工作。在这个工作中，闭环直流电机速度控制系统的硬件软件开发进行解释和说明。期望目标是在任何负载条件下实现系统的恒速。这就意味着电机将在不同的负载下运行一个稳定的速度。介绍通过使用机械和电机技术可以控制直流电机的速度。在过去，大多数通过机械和需要大尺寸的硬件来实现直流驱动器的速度控制。这些驱动器的强大相关性是迄今为止将给ac驱动器开发推出的。一些重要的应用：轧钢厂、造纸产络筒机、起重机、机床、牵引、印刷机、纺织厂、挖掘机和起重机。部分马力功率单位的直流驱动器被广泛使用-伺服定位和跟踪方法1。可控整流器提供由一个固定的直流电压可变为一个可变的直流电压。由于他们的能力提供了一个连续可变的直流电压，可控整流器，直流截波器在现代工业设备和变速驱动器领域起到了革命性作用2。调速驱动器可能是通过控制电枢或激励的方式被广泛的操作。晶体管和半导体闸流管以及各种模拟数字芯片用于发射或控制电路使直流驱动器在无数领域的应用当中更容易控制3。最近在半导体技术发展领域不仅已经取得了更小、更快的处理器，而且微型控制器创新开发的成本大大降低4。微型处理器的潜在使用功能来控制一些或者是所有的电子功能用来证明其它们的使用性。这项工作的主要目的是熟悉硬件的设计和实现一个基于单片机的直流电机闭环速度控制与操作员在过载条件下给与的发生过载情况。电动机转速控制器的目标是将一个信号转化为所需的速度和驱动电机的速度。相关工作关于就业的固态设备控制的直流驱动器在一个合理数量的作品文献当中能够被发现。在Kurnera的论文Dayananda and Jayawikrama，阐明斩波器与PC控制直流电机速度的协作使用性。软件被开发，输送至PC电脑，因此通过计算机调速的渠道把指令输送给斩波器3。使用独立的微型控制器可以在直流电机的速度控制取得很大的进展。Nicolai和Castgnct在他们的论文中阐述了一个单片机是如何被用于速度控制的。操作系统可以概括为：整流电压驱动形式，它是由斩波器的微型控制单元（MCU）产生的PWM信号。电机的电压控制是通过测量整流电源电压模拟到数字转换器而其它的微型控制器并相应的调整PWM信号占空比5。另一个系统，它是在Khoel和Hadidi的工作报告下使用一个微型处理器，其系统的简要描述如下：通过传感终端电压和电流微型处理器从而计算电机的实际速度，然后比较电机的实际速度与参考速度并进而生成一个输入触发单元的合适控制信号。本单元驱动器是一个依次轮流提供了一种脉宽调制电压的直流电机H桥式电力场效应晶体管放大器6。本文是以具有精度高、可靠性高和适应不同电动机等级具有良好响应速度的固定直流电机速度控制系统。方法在这里计划建立这样一个地址如上所述的系统方案。随着系统是基于一个直流电机的速度控制，所以期望的目的是实现一个在任何负载条件下保持恒定的转速。这就意味着电动机将以固定的速度运行在任何负载条件。它不会伴随负载的数量。软件是由以这样一种即使是一个不熟练的操作员就可以操作它的方式。本系统描述的是设计和实现基于单片机的闭环直流电机速度控制器，通过PWM和直流斩波器控制直流电机的速度。在实施这项工作频率当中，独立的PWM工作周期可以生成0%到100%不等范围输出变量。此外，一个液晶显示器被制造成一个可以提供完整的用户界面单元的显示输出装置。因此，系统是完全独立的友好用户。突然地负荷下降，电机的速度将会非常的高。因此，输出电压也将非常的高。所以控制器单元将输出与所需电压一致的电压水平。在过度符合的情况下，电机不能按照它所需的速度要求正常运行，然后OCR将开始增加直到它达到最大值。达到最大值后，若仍没有改进的速度，也就是输出电压不匹配所需的水平，单片机就会使用液晶显示器发出一条“超负荷”消息，以便使用者可以理解条件，因此减少电动机负载。A. 系统概述通过斩波器的直流源控制电机。测速发电机的感官速度作为电压输出。这个电压是作为基于单片机的驱动电机速度输出。控制器和单片机决定了所需直流电机速度的输出电压。B.电路描述电路是基于PWM技术。ATmega-8定时器部分有特殊的功能。通过调整寄存器值（ocr，ccr等）占空比方式可以进行控制。当电动机运行在70%的工作周期，测速发电机的电压对应于这个速度值。如果发生在任何负载的情况下。期望的速度值将会下降。因此，电压将会下降得更少。这个电压值是输入单片机的ADC。通过比较微型控制器可以预知前一个值的下降速度。感应负载条件之后，它将开始增加其工作周期，直到达到所需的速度。在过载条件下，单片机将通过增加工作周期努力达到所需的速度。但是如果在最大工作周期下还不能运行，它将通过液晶显示面板向用户显示一条信息。这个消息表明了超载。现在，用户可以通过减少负载的方式再次运行机器所需要的速度。C.脉冲宽度调制脉宽调制是一种提供电能之间充分中间量和完全关闭的有效方式。当开启时是一个典型电源提供的简单电源开关全功率。脉宽调制是一种相对于最近的技术，制造出使用的现代电子功率开关。单片机，ATmega8有3定时器/计数器。其中，定时器/计数器1和2是PWM的特色。对于不同的直流电机速度我们使用定时器/counter2（8位）生成PWM。在这里我们使用阶段正确的模式。再次，它有两种operation-inverted和non-inverted不同的模式。这里本文决定使用non-inverted模式。图1 电动机控制器部分图2 系统设计D.传感器设计另一个用于速度传感为目的性的电机被称为测速发电机。测速发电机是配有连接到终端的马达和电位计的装置。测速发电机根据电机的转速通过电位计使之电压降落。如果电机在低速运行时，它将提供一个较低的数值。当它运行到最大速度时，它会给出一个更大数值的电压。E.ADC设备ADC有n位分辨率，n可以表示为8、10、12、16甚至24位。高分辨率ADC提供了一个更小的步长，可以通过ADC看出步长是最小的变化。AT-Mega-8有10位连续近似寄存器型ADC其具有6条多路复用通道。结果与讨论可以讨论如下获得的预期结果。A.斩波电路输出这是一个以晶体管我基础的一个固定频率脉冲产生的微型控制器。晶体管作为开关。电动机的输出电压取决于晶体管的时间数量。晶体管在更多的电压基础上会保持更多的时间。一个随心所欲的二极管被用于e.m.f保护其他部分。表1 在不同占空比下的电动机端电压D (Duty cycle)Voltage UsingVoltageEquation(V)Measured byMultimeter(V)100.910.811.60.11211.6B.传感器输出通过改变控制器寄存器OCR（输出比较寄存器）工作周期发现在不同占空比下的输出电压如图3所示。当占空比达到100%时，系统显示立即反应的最大电压输出。图3 占空比和输出电压通过单片机ADC的电位计压降。根据ADC的数值，单片机以决定是否将脉冲宽度增加或者是减少。图4 线路图结论介绍了基于单片机的直流电机闭环速度控制。通过测速发电机将会使用一个ATmega8L单片机实现控制永磁直流电机速度反馈。系统将友好的让用户可以任何的操作这个系统没有任何麻烦。具备液晶显示器是显示系统显示的条件。了解情况，用户可以在必要的时候改变负载的数量。PWM Based Automatic Closed Loop Speed Controlof DC Motor Atul Kumar Dewangan1, Nibbedita Chakraborty2, Sashi Shukla3, Vinod Yadu4 1Department of Electrical Engg, BIT (Durg) 2 Department of Computer Science Engineering Engg, KGP (Raigarh) 3Department of Electronics and Telecommunication Engineering KGP (Raigarh) 4Department of Electrical Engineering KGP (Raigarh) Chhattisgarh Swami Vivekanand Technical University Bhilai ,Chhatisgarh, IndiaAbstractAbstract- The electric drive systems used in many industrial applications require higher performance, reliability, variable speed due to its ease of controllability. The speed control of DC motor is very crucial in applications where precision and protection are of essence. Purpose of a motor speed controller is to take a signal representing the required speed and to drive a motor at that speed. Microcontrollers can provide easy control of DC motor. Microcontroller based speed control system consist of electronic component, microcontroller and the LCD. In this paper, implementation of the ATmega8L microcontroller for speed control of DC motor fed by a DC chopper has been investigated. The chopper is driven by a high frequency PWM signal. Controlling the PWM duty cycle is equivalent to controlling the motor terminal voltage, which in turn adjusts directly the motor speed. This work is a practical one and high feasibility according to economic point of view and accuracy. In this work, development of hardware and software of the close loop dc motor speed control system have been explained and illustrated. The desired objective is to achieve a system with the constant speed at any load condition. That means motor will run at a fixed speed instead of varying with amount of load.INTRODUCTIONSpeed control of dc motor could be achieved using mechanical or electrical techniques. In the past, speed controls of dc drives are mostly mechanical and requiring large size hardware to implement. The development has launched these drives back to a position of formidable relevance, which were hitherto predicted to give way to ac drives. Some important applications are: rolling mills, paper mills mine winders, hoists, machine tools, traction, printing presses, textile mills, excavators and cranes. Fractional horsepower dc drives are widely employed -as servo means for positioning and tracking 1. Controlled rectifiers provide a variable dc voltage from a fixed dc voltage. Due to their ability to supply a continuously variable dc voltage, controlled rectifier and dc choppers made a revolution in modern industrial equipment and variable-speed drives 2. Adjustable speed drives may be operated over a wide range by controlling armature or field excitation.Transistor and thyristor along with various analog digital chips used in firing or controlling circuits have made dc drives more accessible for control in innumerable areas of applications 3. Recent developments in the area of semiconductor technology have made smaller, faster microprocessors and microcontrollers available at reduced cost. 4 .The potential use of microprocessors to control some or all electronic functions justifies their use. The main objective of this work is to become familiar with the design and implementation of both software and hardware of a microcontroller based closed loop speed control of DC motor and to give senses of occurring overload condition to the operator at overload condition. The purpose of a motor speed controller is to take a signal representing the required speed, and to drive a motor at that speed.RELATED WORKSA reasonable number of works have found in the literature, regarding the employment of solid-state devices for the control of dc drives. The paper of Kurnera, Dayananda and Jayawikrama, elucidated the use of chopper in collaboration to PC for the control of dc motor speed. Software was developed, fed into a PC and consequently, commands were given to the chopper via the computer for control of motor speed 3.The use of standalone micro controller for the speed control of DC motor is past gaining ground. Nicolai and Castgnct have shown in their paper how a microcontroller can be used for speed control. The operation of the system can be summarized as: the drive form rectified voltage; it consists of chopper driven by a PWM signal generated from a microcontroller unit (MCU). The motor voltage control is achieved by measuring the rectified mains voltage with the analog to-digital converter present other micro controller and adjusting the PWM signal duty cycle accordingly 5. Another system that uses a microprocessor is reported in the work of khoel and Hadidi a brief description of the system is as follows: The microprocessors computes the actual speed of the motor by sensing the terminal voltage and the current, it then compares the actual speed of the motor with the reference speed and generates a suitable signal control signal which is fed into the triggering unit. This unit drives an Hbridge Power MOSFET amplifier, which in turn supplies a PWM voltage to the DC motor 6.In this paper, a dc motor with fixed speed control system is presented, which has high precision, reliability and adaptability for different motor ratings with good speed response.METHODOLOGYA scheme that address on building up such a system as described above is presented in here. As the system is based on the speed controlling of a DC motor, so the desired goal is to achieve a system with constant speed at any load condition. That means motor will run at fixed speed at any load condition. It will not vary with the amount of load. The software is made in such a way that even an unskilled operator can operate it. This system describes the design and implementation of the microcontroller based closed loop DC motor speed controller that controls the speed of a DC motor by using PWM and DC chopper.In implementing this work frequency, independent PWM output with variable duty cycle that can vary from 0% to 100% is generated. Furthermore, an LCD display was fabricated to display the output; this kind of setup provides a complete user interface unit. Hence the system is complete stand-alone and user friendly. In case of sudden load drops, the speed of the motor will be very high. As a result, output voltage will be also very high. Therefore, controller unit will sense output voltage and will compare with the desired level of voltage.In case of excessive load, motor cannot run at its desired speed, and then OCR will start increasing until reaches its maximum value. After reaching the maximum value, there remains no improvement of the speed, i.e. output voltage does not matches the desired level then microcontroller will send a message OVERLOAD using the LCD, so that the user can understand the condition and hence reduce the load of the motor.A. System OverviewThe motor to be controlled is fed by a DC source through a chopper. The tachogenerator senses the speed, which gives voltage as output. And this voltage is fed to the microcontroller to drive the speed of the motor. The output voltage of tachogenerator is provided to the microcontroller and microcontroller determines the output voltage of the chopper fed to the DC motor for desired speed.B. Circuit DescriptionThe circuit is based on PWM technique. ATmega-8s timer portion has this special feature. By adjusting register values (ocr, tccr etc) duty cycles can be controlled. When motor run at 70% of duty cycle, the tachogenerator gives a Voltage corresponds to that speed. Now if any load occurs, desired speed will be decreased. Hence, the voltage drop will be less. This voltage is fed into the ADC of microcontroller. By comparing the previous value microcontroller can sense the decrease in the speed. After sensing the load condition, it will start increasing its duty cycle until it reaches the desired speed. During overload condition, Microcontroller will try to reach the desired speed by increasing duty cycle. But if at the maximum duty cycle it fails to run it will show a message to the user through A LCD panel. The message indicates OVERLOAD. Now user can run the machine again at desired speed by decreasing the load.C. Pulse Width ModulationPWM is a very efficient way of providing intermediate amounts of electrical power between fully on and fully off. A simple power switch with a typical power source provides full power only, when switched on. PWM is a comparatively recent technique, made practical by modern electronic power switches. The microcontroller, ATmega8 has 3 timers/counter. Among them, timer/counter 1 and 2 are featured with PWM. We have used timer/counter2 (8-bit) to generate PWM for varying the speed of DC motor. We used Phase correct mode here. Again, it has 2 different mode of operation-inverted and non-inverted mode. Non-inverted mode is used here.Fig. 1 Motor Controller Sections Fig. 2 System ProgrammerD. Sensor DesignAnother motor is used for speed sensing purpose is called the tachogenerator. For a DC motor voltage is directly proportional to the speed. The tachogenerator is coupled with the motor and a potentiometer is connected to the terminal of the tachogenerator. Tachogenerator gives voltage drop across the potentiometer according to the speed of the motor. If the motor runs at a low speed, it gives a lower value. When it runs at its maximum speed, it gives a larger amount of voltage.E. ADC DeviceADC has n-bit resolution where n can be 8,10,12,16 or even 24 bits. The higher resolution ADC provides a smaller step size, where step size is the smallest change that can be discerned by an ADC. AT -Mega-8 has one 10 bit Successive Approximation Register type ADC with 6 multiplexed channels.RESULTS & DISCUSSIONThe results obtained are as expected which can be discussed as follows.A. Chopper circuit outputA pulse with fixed frequency is generated by the m