Project - Speed Control of a Direct Current (DC) motor

Aim:

• To design a Simulink model for the DC motor shown in Figure 1. amd aslo by Using the Proportional, Integral, and Derivative (PID) control design knowledge gained in the training to design, develop and test a controller to maintain a desired speed for the motor.

OBJECTIVE

• To Use the Proportional, Integral, and Derivative (PID) control design knowledge gained in the training to design,
• To develop and test a controller to maintain a desired speed for the motor.

INTRODUCTION

DC motor

A DC motor is any of a class of rotary electrical motors that converts direct current (DC) electrical energy into mechanical energy. The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current in part of the motor.

DC motors were the first form of motor widely used, as they could be powered from existing direct-current lighting power distribution systems. A DC motor's speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field windings. Small DC motors are used in tools, toys, and appliances. The universal motor can operate on direct current but is a lightweight brushed motor used for portable power tools and appliances. Larger DC motors are currently used in propulsion of electric vehicles, elevator and hoists, and in drives for steel rolling mills. The advent of power electronics has made replacement of DC motors with AC motors possible in many applications.

• Here the Speed control of a DC motor is either done manually by the operator or by means of an automatic control device.
• This is different to speed regulation where the speed is trying to be maintained or regulated against the natural change in speed due to a change in the load on the shaft

• so the speed can be varied by changing:

  1. The terminal voltage of the armature V
  2. The external resistance in armature circuit R_a
  3. The flux per pole

• So Terminal voltage and external resistance involve a change that affects the armature circuit while flux involves a change in the maginetic field

• so Therefore speed control of DC motor can be classified into:

  1. Armature Control Methods
  2. Field Control Methods

Simulink model :

• Here first we need to creat simulink model of the DC motor and make it as subsytem called the DC motor
• So next the subsytem of DC motor is connected to the discrete PID controller which helps in maintaining the desired speed
• So after the PID controller we need to start with the kp ki kd such as 1.0 1.0 0 after tunin accordingly so by this we can adjust the kp ki kd values as 31.5 82.3 2.3
• Which is used to obtaine the control design objectives

Simulink model of DC motor:

Matlab script:

Here we consider the following paramters:

% This file contains the design paramters to model a Dc motor
J = 0.01;  % momemt of inertia
B = 0.1;    % motor friction
Km = 0.01;  % back emf
Kt = 0.01;   % Motor torque constant
Ra = 1.0;    % aramture resistance
La = 0.5;    % aramture inductance

Output results for the subsystem DC_motor:

Now for the Design of the DC motor with Discrete PID ccontroller:

Here we consider the PID control paramters as :

Kp =1 ki = 1 kd 0

But after tuning we set kp ki kd to 31.5 82.3 2.3 which is used to obtaine the control objectives of the settling time overshoot time and steady state error

Plot for when tuning settling time as 1.5sec:

Plot for tuning as overshoot is less than 5%:

Plot for tuning as steadt state error less than 1 %

Final plot:

Now For maintaing the stabilty of a dynamic system :

Out put results:

Case : 1 When maintaining a desired speed of the motor at 100 :

Case : 2 When maintaining a desired speed of the motor at 230v :

• Here by observing the above two graphs we change the desired speed as 100 in the case1 and 230 in the case 2
• But here both the plots reamains same
• So by this we can say that we maintained desired speed of a DC motor

Conclusion:

we have desined In this project a Simulink model for the DC motor as shown in Figure 1.and also we Use the Proportional Integral and Derivative PID control design knowledge gained in the training to design develop and test a controller to maintain a desired speed for the motor