1、毕业设计翻译文献与原文题 目： 基于 PWM 的自动闭环直流电机的控制学 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： PWM Based Automatic Closed Loop Speed Controlof DC MotorAbstract The electric drive systems used in many industrial applications require higher performance, reliability, variable speed due to its ease of controllability.
2、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 ofDC motor. Microcontroll
3、er based speed control system consist ofelectronic component, microcontroller and the LCD.In this aper, implementation of the ATmega8L microcontroller for speed control of DC motor fedby a DC chopper has been investigated. The chopper is driven by a high frequency PWM signal. Controlling the PWM dut
4、y 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 con
5、trol 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.Keywords:DC motor Speed control Microcontroller ATmega8 PWM.1. TRODUCTIONSpee
6、d 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
7、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 servomeans for positioning and tracking1. Con
8、trolled rectifiers provide a variable dcvoltage 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
9、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 t
10、echnology have madesmaller, faster microprocessors and microcontrollers available at reduced cost4 .Thepotential 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 so
11、ftware 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 spee
12、d.2. R ELATED 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
13、 was developed, fed into a PC and consequently, commands were given to the chopper via the computer for control of motorspeed 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 amicrocontroller can be
14、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-dig
15、ital 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 se
16、nsing 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 isfed 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,
