Experiment No….

Object: - To perform an experiment on analog and digital motor control teaching using virtual control laboratory.

Apparatus Required: -

Sr. No. Name1 MS 15 DC motor control module2 The CILO interface module3 AS 3 command potentiometer4 System power5 Computer (Monitor, Mouse, UPC, etc.)6 Connecting leads

Theory:-

Wiring: - All the experiments in the analog section of this course are physically wired in the same way. Different configurations are achieved using data signal path in the computer. Fig. shows the wiring between the MS 12 DC motor module, the CLIO interface module and the AS 3 command potentiometer.The connections should be used unless instructed differently. If possible, the circuit should be left connected between experiments. Weather left connected or not, the connections should be checked at the beginning of each practical exercise.

Virtual control Laboratory Software:- Much of the instructions in this course involve observing and understanding the response of the plant under different operating conditions. Most of the observations and the change will be made using the PC based VCL software and the mouse.

Loading The Software:- start the virtual control laboratory by double clicking on the VCL icon. Some time will be spent in introducing the elements of the package.

Loading The Setup For Current Experiment:- Load the initial setup by selecting the file from tool bar. Then load setup from drop down menu. From the load dialog box select file “CA06PE02” and click ok open button.In subsequent instruction, such as command sequence will be written as

File – Load setup – CA06PE02 – OPEN

The control system elements across the top of PC screen are:1. Signal Generator2. Controller 3. The plant

The table below is the summary of the setup required for this experiment. The values shown have been set up by loading setup file CA06PE02. Any of the value may be changed by accessing the appropriate menu from the tool laboratory or by last test settings.

File Controller PlantCA06PE02 Close/Open MS 15 ANALOGSignal GeneratorSignal DC LevelLevel 1. Input ON

2. Position ON3. Velocity ON

Offset RateReference ExternalDC Motor Output potentiometer

engagedBrake Command potentiometer

180

Set the command potentiometer to 180 degree and switch power ON. Enable the motor by clicking disable box. To run the motor at half speed the input was to be set to approximately 50% of its range with open loop. There is no guarantee that the actual speed will equal the set speed. Many system work on open loop but it does not lead to good control.The first objective of control system is that the controlled output reaches the value desired of it.

Reacting to Load Change:- Enable the Motor and set the offset to 50%. The brake ‘OFF’ so this is the NO LOAD condition. Make a note of tacho voltage in table 2. Now move the eddy current brake position 1. You will see on the screen and on the Motor that the speed drops as the motor is loaded. This is half loaded condition. Again note the tacho speed in table 2 and disable the motor.

Reaching the Desired Output:- we should make the motor run at half speed for this. The tacho generator output should be 2.5V. now what input is required.The solution for above question is found out by constructing an input/output scale table. Measure the input voltage (channel 4) over the range of offset values in observation table.Disable the motor and then plot the result in graph. It can be seen that there is not a linear relationship between input voltage and speed.To run the motor at half speed, the input has to set at approximately 50% of the range with open loop there is no guarantee that output speed will equal to the set speed. Many

systems do work on open loop but it does not lead to good control. The first objective of a control system is that the controlled output reaches the desired value.

Procedure:-

1. Wire up the system as shown in wiring diagram in VCL.2. With the motor off or disable disengage the MS 15 output potentiometer from the

output shaft to reduce wear and tear.3. Start VCL software and Load CA06PE02. This setup the system as shown in fig.4. The reference input set to interval, which uses the internal signal generator to

drive the system.5. Switch on and enable motor, nothing should happen now.6. The controller is set to open loop. This means there is no feedback control.

Observation table: -

Table 1

Offset Input Voltage Tacho output voltage

Speed

0102030405060708090100

Table 2

Offset is constantLoading Tacho Voltage RPMNo Load

Half LoadFull Load

For Closed Loop (Gain 50 and Offset Constant)

Loading Tacho voltage RPMNo Load

Half LoadFull Load

Result:-