CLOSED LOOP BIDIRECTIONAL TORQUE CONTROL OF

MOTOR FOR VARYING LOAD TORQUE CHARACTERISTICS

IEEE reference: New Direct Torque Control of Brushless DC Motor Electrical and Control Engineering (ICECE), 2010 International Conference. Digital Object Identifier:  10.1109/iCECE.2010.952

Abstract:

Motor control applications are abundant in the industrial space, as almost

any industry has some kind of control using motors. There are places where loads are

moved from one position to another with the help of strings and motors. At all times

loads are not constant and there is always a need to change the torque of the motor

rotation also. Further the torque of the motor varies with the speed and the voltage

applied and this has to maintained high at higher loads.

As the load varies the motor torque also varies thereby making the

bidirectional movement very difficult. This project aims at controlling the torque of the

motor movement. The motor may have different loads at different directions but the

torque can be maintained irrespective of the direction and the torque can also be different

for both directions

The torque of the motor is controlled by the industry recognized and well

known vary pulse technique. But there are two different frequencies and the width may

be different for two directions. Hence the generation of these frequencies is done

depending upon the torque and the direction

Further as the direction of the motor has to be altered at ease the power

circuitry consists of the H-bridge configuration wherein by applying varying pulses

signals to the required high power power-electronics circuitry the torque can be varied

and the direction can be set.

The speed of the motor is continuously taken from the sensor and the

speed is maintained irrespective of the change in the load by continuously comparing the

set speed and the actual speed. This gives a perfect closed loop control of the motor and

the speed and the speed is maintained at all loads.

A PC interface to the system gives a suitable means to monitor the speeds

at both directions and also it provides an easy interface for speed setting through

keyboard. The hardware monitors the speed of the motor and communicates the same to

the user interface program which displays these parameters for the user.

Thus the project combines a good power electronics circuitry and

microcontroller programming for bidirectional variable torque motor control.

Motor Power supply

Bidirectional H- Bridge

Drive

OPTO ISOLATOR

High Speed Controller

PC Interface

DC MOTOR

Power supply5V (to all

components)

PC OPTO

ISOLATOR

Feed Back SENSOR

Rectifier and power Circuit

User Indications

H Bridge Driver

H Bridge Driver

BLOCK DIAGRAM