automatic speed control of dc motor

AUTOMATIC SPEED CONTROL DRIVE

By – Munesh Kumar singh Aditya Vikram singh Anitya kumar shukla Devendra kumar

UNDER THE PROJECT GUIDANCE OF:-

Mr. Anurag Aggrawal

INTRODUCTION

• Adjustable speed drive (ASD) describes equipment used to control the speed of machinery. Many industrial processes such as assembly lines must operate at different speeds for different products. Where process conditions demand adjustment of flow from a pump or fan, varying the speed of the drive may save energy compared with other techniques for flow control.

• Where speeds may be selected from several different pre-set ranges, usually the drive is said to be adjustable speed. If the output speed can be changed without steps over a range, the drive is usually referred to as variable speed.

BLOCK DIAGRAM OF DRIVE SYSTEM

D.C. MOTOR SPEED CONTROL

• There are mainly two way to control the speed of D.C. motors

(1) Direct-current motors allow for changes of speed by adjusting the shunt field current.

(2) Another way of changing speed of a direct current motor is to change the voltage applied to the armature.

METHOD USED TO CONTROL THE SPEED

• In our project we used to control the armature Voltage to control the speed of the motor at the Various given loading conditions .

BASIC CONTROLLING OF MOTOR SPEED

• The controlling of motor armature voltage is done with the help of PWM .

• The direction of motor is controlled by H-bridge.

• There are rotational sensors are placed to measure the speed(RPM) and angular displacement of the motor.

• The Simulink modal is shown next.

FUNCTION OF H- BRIDGE

• An H bridge is an electronic circuit that enables a voltage to be applied across a load in either direction. These circuits are often used in robotics and other applications to allow DC motors to run forwards and backwards.

OPERATION

• The H-bridge arrangement is generally used to reverse the polarity of the motor, but can also be used to 'brake' the motor, where the motor comes to a sudden stop, as the motor's terminals are shorted, or to let the motor 'free run' to a stop, as the motor is effectively disconnected from the circuit. The following table summarizes operation, with S1-S4 corresponding to the diagram above.

IMPROVEMENT IN THE MODEL

• In the previous presentation we shown a Simulink modal of D.C. drive.

• Which has the variation in the speed with respect to the load as per the Simulink results.

• For improvement in this section we maintain the constant speed of the motor (D.C.) at the various loading conditions.

PROBLEMS IN THIS MODEL

• In the above shown model there are problem with the feedback network which we are used .

• We compare the output speed(RPM) and the set speed(which) required to generate the error signal.

• But this error signal does not provided proper feedback to the supply .

THE RPM VARIATION WITH LOAD TORQUE IS SHOWN BELOW

• Rpm vs time

IMPROVEMENT IN MODEL

• The feedback is applied through Hall sensor .

• The output of the Hall effect sensor is compare with the rated speed and speed controller gives the equivalent voltage to the current controller which produce the equivalent voltage as per the requirement of the load.

• The improved Simulink model is given below.

THE CONTROLLED OUTPUT

NOW WE CHECK THIS MODEL AT THE LOADING CONDITION

Applied load torque to the motor

MOTOR RATED CAPACITY IS GIVEN AS BELOW

SIMULINK BLOCKS AT THIS MODEL

SPEED VARIATION

• As we seen that the applied load torque is different at the various time intervals.

• The speed should be kept constant in these time intervals.

• The variation of the speed and armature voltage given by the simulation result shown next.

VARIATION IN ARMATURE VOLTAGE

GRAPH EXPLANATION

• As shown in the above graph the speed on the motor kept constant to the set value of the speed(2500 RPM).

• Which is equal to the rated speed of the motor.

APPLICATION OF DRIVE IN DOMESTIC AND INDUSTRIAL LOADS

• We connect the drive circuit in fan load and the automobile load .

• On connecting the load on these load we the behavior of the drive circuit.

• The both of the models and there output results are given as below.

DERIVE CIRCUIT WITH THE FAN LOAD

FAN LOAD SPECIFICATION

RPM OUTPUT ON THE FAN LOAD

DRIVE ON THE AUTOMOBILE LOAD

AUTOMOBILE LOAD SPECIFICATION

SPEED OUTPUT AT THIS LOAD

SPEED PICK-UP BY THIS DRIVE

DISTANCE COVERED

GRAPH RESULT CONCLUSION

• The drive works on the fan load as per the requirement .

• But on the automobile load the drive try to limit the rpm as per the demand but after some time it does not control the motion.

FURTHER IMPROVEMENT

• We given the speed as per the requirement of the load and this set speed compare the speed with the output and generate the error signal to control the motion of the motor as per the need.

• But it can also be automatically controlled for example by using a rotational detector such as a Gray code optical encoder.

THANKS

YOU