Design of the closed loop Speed control system for DC Motor
Overview of Project:
•This project introduces the speed control principle of DC motor, expatiates on the speed control system takingPIC16F877 as the main control component, utilizes the characters of catching module, comparing module and analog-to-digital conversion module in PIC16F877 .
Introducing DC motor
•DC Motor is a machine which converts electrical energy into mechanical energy.
Principle of DC Motor
•Principle of operation of dc motor is that when a current carrying conductor is placed in a magnetic field force is produced.
•When field magnets are excited and armature conductors produce a force which tends to rotate the armature in anticlockwise direction.
•These forces collectively produce a driving torque which sets the armature rotating, the conductors rotate.
•When the armature rotates the conductors also rotate and cut the lines of magnetic force.
•According to law of electromagnetic induction ‘emf is induced in armature conductors and this voltage is opposite to applied voltage. This emf is known as counter emf or back emf.
Open loop system
•Open loop system is a such a system which do not monitor or correct the output for disturbances.
Closed loop system
•Close loop system is a system which monitors the output and compare it to the input.
Open loop vs closed loop
•they are simpler
•They are less expensive
•If error is detected, the system corrects the output and hence corrects the effects of disturbances.
•Pulse width modulation is used when a digital system needs to control a system that expects an analog signal of varying amplitude.
•The advantage of controlling a motor with PWM instead of a real analog signal is that the full torque of the motor can be used. In DC motors, there is a linear relationship between the voltage supplied and the torque obtained from the motor the higher the voltage, the higher the torque.