Design of Performance Testing System for

Train Air Conditioning

Zhang Liang, Liu jianhua, Wu ruofei,Gong xiaobing

College of Power Engineering, University of Shanghai for Science and Technology; Shanghai 200093, China ;

E-mail: l_zhanghk@163.com

Abstract —The design of performance testing system for train

air conditioning was done according to the NATIONAL STANDARD TB/T 1804-2003. The cooling capacity was measured by means of air enthalpy difference method. The hardware part of the test system consists of data collection unit and test instrument, while the software is programmed with Visual Basic 6.0, accompanied with the Microsoft Access database. The PLC unit and the touch screen are employed for local control of the system to achieve precise adjustment to the temperature and humidity of environmental chamber, the speed and flow of air. In view of the system characteristics of complex nonlinearity and being difficult to control exactly, test system adopts a fuzzy PID control based on plc to control experimental parameters such as temperature and humidity.

Keywords-train air conditioning; performance test system; fuzzy

control; data acquisition

I. GENERAL DESIGN SCHEME OF THE TEST SYSTEM

Design tasks of the test system: (1) The design purpose of the test system is to test the

performance of train air conditioning according to TB/T 1804-2003 and ensure test results accurate and reliable.

(2) The operation parameters of the train air conditioning should be precisely tested and controlled. The test system should have the function of acquiring, saving and querying

experimental datum. The testing requirements for train air conditioning are show in Table 1.

(3)The testing conditions can be achieved rapidly and stably, also the operation should meet the requirements of high efficiency, high automation and high reliability.

II. DESIGN SCHEME OF THE TEST SYSTEM

At present the solution for cooling capacity testing of train air conditioning mainly includes: air enthalpy-difference method, wind pipe thermal balance method, room thermal balance method and typical ambient calorimeter etc. Among all of the methods, air enthalpy-difference method has the advantages of high testing precision and low requirement for operation environment, which is usually used in large capacity cooling testing of air conditioning. The principle is a method which is used to test the cooling capacity by calculating inlet and outlet air flow and air enthalpy difference of indoor air conditioning unit. [1] Fig 1.shows testing schematic diagram of train air conditioning.

TABLE I. TESTING REQUIREMENTS FOR TRAIN AIR CONDITIONING

Allowable error of experimental Operating Conditions

Allowable error of experimental testing conditions

Indoor Air Temperature Dry Bulb Temperature Inlet

℃

士 1 士 0.5 Outlet / /

Wet Bulb Temperature Inlet 士 0.5 士 0.25 Outlet / /

Outdoor Air Temperature Dry Bulb Temperature Inlet 士 1 士 0.5 Pressure Drop of Spray Nozzle % 2 /

External Static Pressure Pa 12.5 5 Voltage % 2 /

2009 International Conference on Energy and Environment Technology

978-0-7695-3819-8/09 $26.00 © 2009 IEEE

DOI 10.1109/ICEET.2009.27

85

2009 International Conference on Energy and Environment Technology

978-0-7695-3819-8/09 $26.00 © 2009 IEEE

DOI 10.1109/ICEET.2009.27

85

pp XC 18591005 +=

210 QQQ +=

EQq 0

0 =

Figure 1. Testing schematic diagram of train air conditioning

The cooling capacity calculating formulas are as follow:

(1)

(2) (3)

(4) (5) (6)

(7)

0Q— — Cooling capacity,(W)

0L— — Indoor air flow,(m3/s)

nh— — Return air enthalpy value,(J/kg)

ch— — Blast air enthalpy value,(J/kg)

pV— — Specific volume of air around the nozzle,(m3/kg)

pX— — Wet air volume of air around the nozzle,(kg/kg)

E — — Input total power ,(kW)

1Q— — Sensible heat cooling capacity,(W)

2Q— — Latent heat cooling capacity,(W)

0W— — Quantity of dehydration,(kg/h)

According to the requirement of control function, operation mode and management mode, the test system adopts Omron PLC and HP 34970A data acquisition instrument to composite a distributed control system. The general schematic of the control and test system is illustrated in Fig 2.

)1()(0

1pp

ncp

XVttCL

Q+

−⋅=

)1()(1047.2 0

6

2pp

nc

XVXXLQ

+−×

=

)1()(3600 0

0pp

nc

XVXXLW

+−

=

)1()(0

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cn

XVhhL

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−=

Indoor air-conditioning test room

Outdoor air-conditioning test room

Tested unit

Air flow test device

Temperature test instrument

Liquid column manometer

8686

Temperature

Pressure

OthersElectricity M

eters Electrical Parameters

P L C

Touch screen

Multiple Serial Port

Humidity

PID SSR Heater

Tested unit

Fans

Heaters

Humidifiers

Other Equipments

Com

puter

RS232/R

S485

transfer

Data A

cquisition Unit

Temperature Module

Alarm Information

Figure 2. General schematic of the control and test system

III. TEMPERATURE AND HUMIDITY CONTROL OF THE TEST

ROOM

The accuracy and stability of the operation condition directly affect the performance test result of the train air conditioning. As two vital parameters of the control parameters, temperature and humidity have characters of strong coupling, strong disturbances and long-time delay etc. The conventional PID control can’t meet the need in the experiment.

Based on the above reason, the fuzzy PID control is used to instead conventional temperature (humidity) PID controller.

The fuzzy PID control is made up of two parts: parameters-adjustable PID and fuzzy control system. The parameters-adjustable PID is used to control temperature (humidity) of the test room, while the fuzzy PID control is used to adjust three

parameters（ pK、 iK

、 dK）of PID automatically. The

controlled object is electrical heater in the control system. And the temperature (humidity) of test room is controlled by adjusting the output voltage of the controlled silicon to control the quantity of heat given up by electrical heater. Fig.3 shows the schematic diagram of fuzzy PID control of temperature (humidity). R is expected temperature (humidity) of test room (set value). Y is actual temperature (humidity) of test room (feedback value). The two-dimensional fuzzy controller of the system is carried out by PLC. The input of controller is

temperature (humidity) difference )( yre −= and change

rate of temperature (humidity) difference

)( 1−−=Δ nn eee .The output of the controller is control

value (u ). The value of expected temperature (humidity) (R)

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and actual temperature (humidity) (Y) are transferred to data acquisition module through A/D module. The A/D module sends current to the controlled silicon which adjusts output voltage of the electric heater according the current signal to adjust the temperature (humidity) of test room. It has been proved this kind of control method has a good control effect in the large inertial and pure time-delay system.

According to the requirement of standard, the frequency converter is applied in the system to control the air speed of the test room and ensure the uniformity of temperature and humidity around the test point.

Figure 3. Schematic diagram of fuzzy PID control of temperature (humidity)

IV. PARAMETERS MEASUREMENT

The measure precision of the measured data is closely related to precision of the apparatus, such as sensors data acquisition unit. For this reason it is required that all the testing instruments should have a high precision.Table.2 shows the sensors and instruments in the system.

V. SOFTWARE DESIGN OF TEST SYSTEM

To insure the safety and reliability of the test system, the correct design of hard ware and control method is essential for the system, but also a strong functional software plays a critical role. The software of the system mainly includes E-View touch screen operation system, PLC control program and data acquisition software. Depending on the advantage and strong function of the software, most of the operation can be automatically accomplish in the control room.

A. E-View touch screen software

E-View touch screen operating interface is programmed with the Easybuilder 500. All of the operation can carry out though the people-computer interface . [2] B. PLC control program

The main PLC programming task is to carry out fuzzy PID control algorithm. It uses PID control method of PLC to

realize PID control. The target-value PID control with two degrees of freedom is used, on the other hand, there is no overshooting, and response toward the target value and stabilization of disturbances can both be speeded up.

When the execution condition is ON, PID carries out target value filtered PID control with two degrees of freedom according to the parameters designated by C (set value, PID constant, etc.). It takes the specified input range of binary data from the contents of input word S and carries out the PID action according to the parameters that are set. The result is then stored as the manipulated variable in output word D.

The parameters are obtained when the execution condition turns from OFF to ON, and the Error Flag will turn ON if the settings are outside of the permissible range. [3]

If the settings are within the permissible range, PID processing will be executed using the initial values. Bumpless operation is not performed at this time. It will be used for manipulated variables in subsequent PID processing execution.

When the execution condition turns ON, the PV for the specified sampling period is entered and processing is performed. [4]

A fuzzy controlling table with the fuzzy controlling rule and fuzzy reasoning is stored in memory data. This table can adjust the PID parameters online in real time controlling. By inquiring the fuzzy controlling table, the PID constant P, Tik, Tdk can be obtained. C. Data acquisition software

In order to analyze, save the experimental data and draw curve at real time, data collector is used to communicate with PC. Data is acquired and processed at real time through software, in which different curves and data can be displayed, printed and saved. Software program consists of main interface, temperature and humidity parameters acquisition interface, second parameters interface and history enquiry interface.[5] [6]

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TABLE II. SENSORS AND INSTRUMENTS

VI. CONCLUSION

This train air conditioning performance test system is implemented with high accuracy temperature, relative humidity, pressure, flow rate and electric parameters test equipment as well as I/O modules and AD modules. The system also has experimental operation instruction, configuration operation interface, simulation and real time display of the experimental process, failure alarm and diagnosis of the system. Friendly mutual operation could be carried out through people-computer interface. Manufacture of the control system meets the demand of research on train air conditioning performance. All parameters could retain stability at certain range, and also be adjusted according to requirement of the experiment. Thus it will be much more convenient to do research on performance of train air conditioning system.

ACKNOWLEDGMENT

This paper has had the benefit of constructive criticism by Dr. Liu jianhua & Dr. Wu zhimin.

REFERENCES

[1] Hong dandan,etc. The Application Of Touch Screen And PLC In A Control System Of Heat Water Heater. New Technical Development of Refrigeration And Air-Condictioning, 2005.

[2] Easybuilder500 Chinese Operation Manual [3] OMRON CP1H CPU Unit Programming Manual, August 2005 [4] OMRON CP1H CPU Unit Operation Manual, August 2005 [5] Gong Peiceng,etc. Visual Basic 6.0 Program Design Tutorial, 2000 [6] Liu Peng,etc. “Design Of Testing And Control System Of Cold Store

For Experiment”, Cryogenics and Superconductivity, China, vol.34, Feb. 2006.

Equipment Specification Amount Range Accuracy Application temperature sensor PT100 20 -100-630℃ A级 Temperature test temperature sensor T-type thermocouple 20 -50-150℃ ±0.5℃ Temperature test

Humidity sensor VISALA 6 0%-100% 0.2Grade Air humidity test three-phase electric

quantity meter Yokogawa 6 / 0.5Grade Electric Parameter

Measurement precise transformers / 6 / 0.1Grade / data acquisition unit HP 34970A 1 / ±0.2% Data Acquisition temperature collect

module OMRONTS101 1 -200-650℃ 0.5Grade Analog- digital signal

transfer

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