DC Motor Control - A case study (FOUR QUADRANT DC MOTOR SPEED CONTROL WITH MICROCONTROLLER)
ABSTRACT .
In this book the four quadrant speed control system for DC has been studied and constructed. To achieve speed control, an electronic technique called pulse width modulation is used which generates high and low pulses. These pulses vary in the speed of the engine. For the generation of these pulses, a microcontroller is used. It is a periodic change in the program. Different speed grades and the direction are depended on different buttons. Experiment have proved that this system is of higher performance. Speed control of a machine is the most vital and important part in any industrial organization. This paper is designed to develop a four quadrant speed control system for a DC motor using microcontroller. The motor is operated in four quadrants i.e. clockwise, counter clock-wise, forward brake and reverse brake. It also has a feature of speed control. The four quadrant operation of the dc motor is best suited for industries where motors are used and as per requirement they can rotate in clockwise, counter-clockwise and also apply brakes immediately in both the directions. In case of a specific operation in industrial environment, the motor needs to be stopped immediately. In such scenario, this proposed system is very apt as forward brake and reverse brake are its integral features. Instantaneous brake in both the directions happens as a result of applying a reverse voltage across the running motor for a brief period and the speed control of the motor can be achieved with the PWM pulses generated by the microcontroller. The microcontroller used in this project is from 8051 family. Push buttons are provided for the operation of the motor which are interfaced to the microcontroller that provides an input signal to it and controls the speed of the motor through a motor driver IC. The speed and direction of DC motor has been observed on digital CRO.
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| LIST OF SYMBOL |
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| L1 | :Primary inductance |
| L2 | : Secondary inductance |
| RL | : Load resistance |
| Vp | : Primary Voltage |
| IP | : Primary current |
| Np | :Primary winding |
| NS | : Secondary winding |
| IS | : Secondary current |
| VS | : Secondary voltage |
| D | : Diode |
| R | : Resistance |
| V | : Voltage |
| µ | : micron |
| n | : Nano |
| p | : Pico |
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| LIST OF ABBREVIATIONS |
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| AC | Alternating Current |
| DC | Direct Current |
| LED | Light emitting diode |
| LCD | Liquid-crystal display |
| RF | Radio frequency |
| VR | Voltage Regulator |
| EMF | Electromotive force |
| VA | Volt-ampere |
| RAM | Random-access memory |
| ROM . | Read only memory |
| CPU | Central processing unit |
| EPROM | Erasable programmable read-only memory |
| EEPROM | Electrically erasable programmable read-only memory |
| PFCS | Program flow control section |
| ALU | Arithmetic and logic unit |
| MCU | Microcontroller unit |
| CISC | Complicated instruction set computer |
| RISC | Reduced instruction set computer |
| AVR | Advanced virtual RISC |
| PIC | Peripheral interface controller |
| PCB | Printed circuit board |
| TTL | Transistor-transistor logic |
| CMOS | Complementary metal-oxide semiconductor |
| PMOS | p-type metal-oxide semiconductor |
| NMOS | n-type metal-oxide semiconductor |
| ULN | Unique learner number |
| SSR
| Solid-state relay
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Chapter 1
CHAPTER - 1
- INTRODUCTION
Now a days DC motor plays a vital role in most of the industrial areas, it can be seen in most of the electronic devices. They are mainly used for the mechanical movements of physical applications such as rolling the bundle of sheets or CD drives, lifts etc. Many methods evolved to control the revolution of a motor. DC motors can be controlled either by software or directly by hardware. Software controlling needs computers which are bulky and common man cannot afford for it, so hardware controls are in use. Even in hardware if it is programmable device then it is preferred because it can be modelled according to the requirements of the user. It also has a feature of speed control. The four quadrant operation of the dc motor is best suited for industries where motors are used and as per requirement as they can rotate in clockwise, counter-clockwise and also apply brakes immediately in both the directions. In case of a specific operation in industrial environment, the motor needs to be stopped immediately. In such scenario, this proposed system is very apt as forward brake and reverse brake are its integral features. Instantaneous brake in both the directions happens as a result of applying a reverse voltage across the running motor for a brief period and the speed control of the motor can be achieved with the PWM pulses generated by the microcontroller.
1.1 Basic Idea
There are two types of DC motors, unidirectional and bidirectional. Unidirectional rotates in only one direction and it is specially meant for some specific applications while the bidirectional can be rotated in the clock-wise or the anti-clockwise direction. This the most widely used for industrial applications. There are two parameters to be considered in controlling the movements of a DC motor.
- Direction
- Speed
The first thing that can be controlled in a motor is its direction of rotation. Direction of the motor can be controlled by controlling the polarity of the current flowing through it. Usually a DC motors are driven by famous H-Bridge circuits made up of either transistors or the buffers or any other suitable methods. Controlling the speed of the motor is another important area to be considered. The speed of motor is directly proportional to the DC voltage applied across its terminals. Hence, if we control the voltage applied across its terminal we actually control its speed.
A PWM (Pulse Width Modulation) wave can be used to control the speed of the motor. Here the average voltage given or the average current flowing through the motor will change depending on the ON and OFF time of the pulses controlling the speed of the motor i.e. the duty cycle of the wave controls its speed.
Chapter 2
CHAPTER 2
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FOUR QUADRANT OPERATION
2.1 Principle of Operation
We will look at the four quadrant operations of a motor driving a hoist load as shown in figure below. This hoards a cage with or without any load. A rope, generally made of a steel wire is wounded on a drum to raise the cage and a balance weight. This balance is not more than that of empty cage, but less than the loaded cage. For each quadrant of operation, direction of rotation, w, load torque, TL, and motor torque Tm are shown in figure. Consider that the torque is constant and independent of engine speed. The four operating modes of a hoist are described below.
(a) Loaded Cage Moving Up
This is the first quadrant operation of the hoist in which the loaded cage is moving upwards. Due to the upward movement, the direction of rotation of motor, we want to be in anticlockwise direction, ie, positive speed. Here the load torque acts in the opposite direction to the direction of motor rotation. Therefore, to raise the hoist to upwards, the motor torque, Tm must act in the same direction of motor speed, w. So both engine speed and engine torque will be positive. To make these as positive, the power taken from the supply should be positive. This is called forward motoring.
(b) Empty Cage Moving Up
This is the quadrant-2 operation of the hoist in which unloaded cage is moving upwards. As mentioned above, the counterweight is heavier than the unloaded cage and thus can move upwards at a dangerous speed. To prevent this, engine in a torque direction, in order to produce a brake to the engine. Therefore, the motor torque, Tm wants to be negative and motor speed, we want to be positive. Since the speed of the hoist is positive, it receives the power from the supply and hence the power is positive. This quadrant operation is called forward braking.
(c) Empty Cage Moving Down
This is the quadrant-3 operation where empty cage is hoisting down as shown in figure. The downward journey of empty cage is prevented by the torque exerted by the counterweight. So the direction of motor torque, Tm should be in the same direction of motor rotation w. Due to the downward movement of the cage, the direction of rotation is reversed,
Impressum
Verlag: BookRix GmbH & Co. KG
Tag der Veröffentlichung: 07.11.2018
ISBN: 978-3-7438-8580-6
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