pid control of step motor by plc

ALİ RIZA GÜMÜŞ 14371962058EVREN KÖYBAŞI 28853171050VOJTECH HEMALA 90000004215

Eskişehir, 2013

PID CONTROL OF STEP MOTOR BY PLC

PID Controller

So, what is a Controller?Structure of a ControllerModes of Controllers (P, PI, PD, PID)

PI Controller

PI controller will eliminate forced oscillations and steady state error resulting in operation of on-off controller and P controller respectively.

However, introducing integral mode has a negative effect on speed of the response and overall stability of the system. Thus, PI controller will not increase the speed of response.

This problem can be solved by introducing derivative mode which has ability to predict what will happen with the error in near future and thus to decrease a reaction time of the controller.

DISCRETIZING A PID CONTROLLER

Development of discrete-time PID controller

Transforming method

Stepper motors A stepper motor is a brushless DC electric motor that divides a full rotation into a number of equal steps

Motors definitions

Step motors are seperated two main part unipolar and bipolar steppers motor.

Unipolar & BİpolarA unipolar stepper motor has one winding

with center tap(common wire) per phaseIn bipolar motors have a single winding per

phase

Operation of stepper motorsTo operate step motors , you must apply

pulse to each coil in different phase.Driving this type of motor is a bit different

from the others

Stepper motor positioningAll dc servo motors we can take position info

by connecting the potentiometer to its shaftIn step motor rotates step by step , because

of this we can divide the pot partially to determine the each step .It means each step has a voltage value.

Analog & Digital OperationsIn PLC s7 200 cpu 224 xp all operations can

be made.First of all we are looking some useful code

for this PLC. Then we will see the example of its application

Useful CodesBCDI OUT : Convert BCD to IntegerIBCD OUT: Convert Integer to BCD BTI IN, OUT Convert Byte to IntegerITB IN, OUT Convert Integer to ByteITD IN, OUT Convert Integer to Double

IntegerDTI IN, OUT Convert Double Integer to

IntegerDTR IN, OUT Convert DWord to Real

Online Subtract OperationIn this example lots of operatıons are used.The main idea is :To observe the analog output voltage of PLC

when we apply desired input voltageWe can follow these steps to solce

Examplee.g. : Choose a reference voltage as 2,4 V .Then

apply a arbitrary voltage.When you measure the analog output of PLC , you will see the voltage “applied voltage – reference (2,4 V)”. When you change the input , the output will change as proportional.

SM 0.0MOVR 2.4 , VD0 // VD0=2,4 V REFERENCEITD AIW0,VD4DTR VD4,VD4 //INPUT 32 BIT REAL NUMBER

Last page/R 3276,8,VD4MOVR VD0,AC0 //AC0=2,4 -R VD0,AC0 //AC0=AC0-

VD0*R 3276,8 , AC0TRUNC AC0,VD8DTI VD8,AQW0 //

ANALOG OUTPUT