The Heating, Ventillation, and Air Conditioning Trainer Qnet

Directory

Experiment 6.1 QNET-HVACT On-Off Control        

-        Relay control        

Procedure:        

Result:        

-        Modeling        

Procedure:        

Result:        

Experiment 6.2 QNET-HVACT PI Control        

-        PI Control with Anti-Windup        

Procedure:        

Result:        

-        Effect of Saturation and Windup        

Procedure:        

Result:        

-        Effect of Set-Point Weight        

Procedure:        

Result:        

-        PI Control according to Specifications        

Procedure:        

Result:        

Discussion        

Table of Figures

Figure 6.1- 1        

Figure 6.1- 2 ( Offset=2°C )        

Figure 6.1- 3 ( Vh=3.00V )        

Figure 6.1- 4 ( Dth=0.5°C )        

Figure 6.1- 5 ( Kv=0.0112 C/V.s )        

Figure 6.2- 1 ( Kv=0.0112 C/V.s )        

Figure 6.2- 2 ( ki=0 V/C.s, kp=5 V/C )        

Figure 6.2- 3 ( Kp=0.5 V/C , ki=0.75 V/ C.s )        

Figure 6.2- 4        

Figure 6.2- 5( Tr=1.0 s )        

Figure 6.2- 6        

Figure 6.2- 7 (  bsp=1 )        

Figure 6.2- 8        

Figure 6.2- 9 ( zeta=0.9 )        

Figure 6.2- 10 ( W0=0.09 rad/s ,  p0=0.67% )        

Abstract

This experiment introduces QNET-HVACT. It is a versatile and powerful training tool which is based on NI-Elvis workstation and Labview program.

The Heating, Ventillation, and Air Conditioning Trainer QNET module is designed to operate on the NI-ELVIS platform. The basic processes are chamber temperature and ambient temperature and control the output voltage to the heating halogen light and the cooling fan.

Goal

The goal of this experiment is to design a temperature closed-loop controller that meets required specifications. The system should track and/or regulate the desired chamber temperature with minimum peak time and overshoot.

QNET-HVACT: On-Off control simple transfer function:

[pic 1]

QNET-HVACT: PI control transfer function:

[pic 2]

[pic 3]

Experiment 6.1 QNET-HVACT On-Off Control

• Relay control

Procedure:

1. The cooling fan is automatically activated when the Prototyping Board Power switch on the ELVIS unit is on. Let the actual temperature, Tc , in the Temperature (C) scope settle until it stops decreasing. Adjust the Temperature (C) scope scales to see both the reference and actual temperatures.
2. Calibrate the temperature sensors by clicking on the Calibrate button. This will align the chamber temperature Tc to the measured ambient temperature Ta.
3. Activate the control by clicking on the Start Control button.
4. In the Signal Generator section set:

• Amplitude = 0
• Frequency = 0.008 Hz
• Offset = 0.5

1. Examine the actual temperature (red) and reference temperature (blue) responses in the Temperature (C) scope.
2. Gradually vary the Offset in the Signal Generator between 0.5°C and 2°C and observe how the reference temperature, Tr, in the Temperature (C) scope is set.
3. Examine the heater voltage and the temperature variation when the relay amplitude, Vh_amp, is changed in the Control Parameters section. In particular, observe the frequency and amplitude of the chamber temperature.
4. Examine the effects when the relay mean, Vh_off, is changed.
5. Examine the effects of changing the relay width (or hysteresis), DTh, between 0.01 and 1.00.

Result:

[pic 4]

Figure 6.1- 1

[pic 5]

Figure 6.1- 2 ( Offset=2°C )

[pic 6]

Figure 6.1- 3 ( Vh=3.00V )

[pic 7]

Figure 6.1- 4 ( Dth=0.5°C )

• Modeling

Procedure:

1. In the Signal Generator section set:

• Amplitude = 0
• Frequency = 0.008 Hz
• Offset = 1.50.

1. In the Control Parameters section set:

• Vh_amp = 4.0 V
• Vh_off = 4.0 V
• DTh = 0.500.

1. Adjust the Temperature (C) scope scales to see both the reference and actual temperatures.
2. Ensure the heater control is enabled by clicking on the Start Control button.
3. Adjust the Offset in the Signal Generator to obtain a relatively symmetrical oscillation.
4. Observe the heater voltage and the chamber temperature. Consider a simple transfer
5. The VI implements an automated modeling procedure. Click on the Modeling OFF button to activate this feature. Once completed the system will display the parameter Kv in the transfer function P(s) =Kv/s.

Result:

[pic 8]

Figure 6.1- 5 ( Kv=0.0112 C/V.s )

Experiment 6.2 QNET-HVACT PI Control

• PI Control with Anti-Windup

Procedure:

1. The cooling fan is automatically activated when the Prototyping Board Power switch on the ELVIS unit is on. Let the actual temperature in the Temperature (C) scope settle until it stops decreasing.
2. Adjust the Temperature (C) scope scales to see both the reference and actual temperatures.
3. Calibrate the temperature sensors by clicking on the Calibrate button. This will align the chamber temperature Tc to the measured ambient temperature Ta.
4. Activate the control by clicking on the Start Control button.
5. In the Signal Generator section set:

• Amplitude = 0.50  
• Frequency = 0.0200 Hz
• Offset = 1.50

1. In Control Parameters set:

• kp = 4.00 V/C  
• ki = 0.5 V/(C.s) bsp = 1.00
• Tr = 1.00 s
• Tf = 0.500 s

1. Click on Update Control to implement this control.
2. Examine the temperature response to the square wave input.
3. Set ki to 0 V/(C.s) and click on Update Control. Change the proportional gain kp between 2 V/C and 6V/C and observe its effect on the temperature control performance.
4. Set kp to 0.5 V/(C.s) and click on Update Control. Change the integral gain ki between 0.25 V/(C.s) and1.0 V/(C.s) and observe its effect on the temperature control performance.

Result:

[pic 9]

Figure 6.2- 1 ( Kv=0.0112 C/V.s )

[pic 10]

Figure 6.2- 2 ( ki=0 V/C.s, kp=5 V/C )

[pic 11]

Figure 6.2- 3 ( Kp=0.5 V/C , ki=0.75 V/ C.s )

• Effect of Saturation and Windup

Procedure:

1. Perform steps 1-4 in the PI Control with Anti-Windup method.
2. In the Signal Generator section set:

• Amplitude = 0.75
• Offset = 1.50
• Frequency = 0.0200 Hz

1. In Control Parameters set:

• kp = 4.00 V/C
• ki = 2.00 V/(C.s)
• bsp = 1.00
• Tr = 100.0 s
• Tf = 0.500 s

1. Click on Update Control to implement this control.
2. Examine the control signal in the Voltage (V) scope. Does it saturate to 8 V?
3. Examine the temperature response in the Temperature (C) scope. Does the system overshoot?
4. In the Control Parameters section, set Tr= 1.0 s and click on Update Control.
5. What is effect does decreasing the anti-windup reset parameter have on the control signal and on the temperature response?

Result:

[pic 12]

Figure 6.2- 4

[pic 13]

Figure 6.2- 5( Tr=1.0 s )

• Effect of Set-Point Weight

Procedure:

1. Perform steps 1-4 in the PI Control with Anti-Windup method.
2. In Signal Generator set:

• Amplitude = 0.50
• Offset = 1.50
•  Frequency = 0.0200 Hz.

1. In Control Parameters set:

• kp = 8.00 V/C
• ki =1.00 V/(C.s)
• bsp = 0.00
• Tr = 1.00 s
• Tf = 0.500 s

1. Click on Update Control to implement this control.
2. Examine the response of the measured temperature in the Temperature (C) scope as well as the input heater voltage in the Voltage (V) scope.
3. Try the controller with a set-point weight of 1.00. Make sure you click on Update Control .
4. Study the effects that raising bsp has on the measured temperature signal in the Temperature (C) scope and the control signal shown in the Voltage (V) scope.

Result:

[pic 14]

Figure 6.2- 6

[pic 15]

Figure 6.2- 7 (  bsp=1 )

• PI Control according to Specifications

Procedure:

1. Perform steps 1-4 in the PI Control with Anti-Windup method.
2. In Signal Generator set:

• Signal Type = square wave
• Amplitude = 0.50
• Offset = 1.50
• Frequency = 0.0150 Hz

1. In the Design Specifications section, set the model gain, Kv, the damping ratio, zeta, and the natural frequency, w0 to the following:

• Kv = 0.0100 C/(V.s)
• zeta = 0.60
• w0 = 0.125 rad/s

1. Optional: Perform step 3 above for the model gain, Kv, obtained in the Modeling procedure of the QNET-HVACT: On-Off Control experiment.
2. Click on Update Design to calculate gains kp, ki, and set-point weight bsp desired to meet thespecifications w0 and zeta based on Kv.
3. Set the desired gains in the Design Specifications section to the control gains in the Control Parameters section by clicking on Set Desired.
4. Click on Update Design again to generate a simulation of the system based on the gains set in the Control Parameters section and view the settling time, Ts, and percentage overshoot, PO, in Time-Domain Specifications.
5. Implement this controller by clicking on Update Control.
6. Examine the measured temperature response. How is the performance of the controller compared to the previous controller?
7. Change the parameter zeta and click on Update Design, Set Desired, and Update Control to implement the new controller. Click on Update Design again to view the changes in the simulated Ts and PO.
8. What effect does changing the specification zeta have on the measured temperature response? How about on the control gains?
9. Vary the parameter w0 between 0.075 rad/s and 0.175 rad/s and click on the Update Design, Set Desired, and Update Control to implement the new controller. Click on Update Design again to view the changes in the simulated Ts and PO.
10. What effect does changing the specification w0 have on the measured temperature? How about on the control gains?

Result:

[pic 16]

Figure 6.2- 8

[pic 17]

Figure 6.2- 9 ( zeta=0.9 )

[pic 18]

Figure 6.2- 10 ( W0=0.09 rad/s ,  p0=0.67% )

Discussion

Experiment 6.1  

• Relay Control

(5) Actual temperature is 22.9C and reference temperature is 22.5 C

(6)After we changed the offset=2C, the reference temperature increased to 22.7C