Studies on torque characteristics test system of torsional vibration damper*

Tao WENG，Gong-chang REN，Rui-jiao WANG

School of Mechatronic Engineering，Shaanxi University of Science and Technology，Xi’an 710021，China

1.Introduction

During the running process of the vehicle，the condition of the engine keeps changing;the engine shaft will produce torsional vibration，at the moment of lockup clutch locking，turbine and the shell into a rigid connection，and also will produce vibration．Various vibrations existing in engine-torqueconvertergear box transmission system will influence the acceleration performance，theoverall performance and the comfort of a car［1］．The torsion damper can control the torsional vibration and noise aroused by transmission system effectively．Itis the key component to reduce the impact of various vibrations and to ensure the overa-ll performance of a car［2］．

It has a large number of tests during the design and production process of torsional vibration damper．However，the performance of the test system directly affects the accuracy of the test results．Therefore，to develop a high reliability，high precision，high speed torsional vibration damper test system has great practical significance．The paper introduces a high precision and high reliability test system，which is computer controlled，using closed loop servo control principle．The test system can undertake a variety of plate parts torsional characteristic tests．

2.System structure and working principle

Torsional damper torque characteristics tester includes the workbench，environmental system，servo control unit，electrical control unit，computer acquisition system．The system structure is shown in Figure 1．

The bench provides the support frame and the mounting platform for other mechanic-al systems，a torque is applied to the sample by the servo motor and reducer through connecting pieces and the servo motor supplies the power．When the sample needs testing in the condition that the oil temperature is high，the environmental system will provide the required temperature．Measurement and control of the whole system is achieved by the servo control unit，the temperature control unit and the computer system．

2.1.The host

The host is composed of table plate，AC servo motor，gear reducer，torque sensor，angle measuring device，connection panel，fixed end and moving table etc．

During the trial，the sample is installed through the hollow screw of the fixed end to the connection plate．The fixed end can move along the guide rails，so it is convenient for adjustment and installation．The speed of servo motor is transmitted to torsional shaft through the gear reducer，the fixed end is fixed and the torsional axis drives the connecting plate and the sample to rotate，torque sensors and angle measuring device for data acquisition［3］．

2.2.Oil source

The oil source is composed of the motor，hydraulic pump，tank，filter，control valve and other components;the hydraulic schematic diagram is shown in Figure 2．It is an important part of the hydraulic drive and servo control system，it can effectively supply the flow and pressure required by actuators，and be able to control pressure，temperature and pollution etc．．

Figure 2．Hydraulic schematic diagram

3.The data acquisition and control system

3.1.The control system

The computer，servo motor，servo motor control card，torsional torque servo motor controller，data acquisition card，sensors，regulated power supply，and various kinds of switches，schematic diagram of whole control system are shown in Figure 3．

Figure 3．Electric schematic diagram of the measurement and control system

The codes in the diagram:8940，servo motion control card;AC6616:data acquisition card;JSJ:computer;KB1:switch;KGDY:switching power supply;NG:torque sensor;SB1/2:start/reset button;SFKZQ1:torsional servo motor controller;The SM1:torsional servo motor;SQ1/2/3:torsional positive limit/negative limit/proximity switch;WYDY:regulated power supply．

We can see from the diagram that the computer is in the center of the whole system．On one hand，it links with the data acquisition card，which is used for the reception of the collected data;on the other hand，it is connected to the servo motion control card，which is responsible for sending control signals;at the same time the computer is responsible for all kinds of switch quantities controlling［4］．

3.2.Data acquisition

Data acquisition is mainly accomplished by the multi-function data acquisition card，the torque sensors and the angle measuring system．AC6616P data acquisition card，used in this system is a multifunctional and high precision A/D card，with 16 channels of single-ended or eight channels of doubleended analog inputs，input programmable-amplifier，2 DA outputs，32 digital outputs，the last two of the 16 channels of DI inputs support counting function．AC6616P uses CH PCI interface chip and gate array as the main control chip．Gate array controls analog inputs，sampling and the switch quantities．The wiring principle diagram is shown in Figure 4:

Figure 4．The wiring principle diagram of AC6616P

3.3.Servo motion control

Data collected by sensors，then transmitted to the computer in the way of digital signals after A/D conversion through the data acquisition card，the computer will compare the received values with the set values，and then send control signals to the servo motion control card to control the servo motor by torsional servo motor controller［5］．

The ADT-8940A1 motion control card adopted by the system is a high performance four-axis servo/step control card based on PCI bus，supports plugand-play．Its counter numbers up to 32 bits，I/O latency around 500 μs，largest pulse frequency about 2 MHz．The use of advanced technologies ensures that the frequency error is less than 0．1%，when the output frequency is very high．The location management uses two plus/minus counters，one of them is the logic location counter used to manage the internal drive pulse outputs，the other one is used as the actual location counter to receive the external inputs．The wiring principle diagram as shown in Figure 5:

Figure 5．The wiring principle diagram of ADT-8940A1

An ADT-8940A1 card has two input/output interfaces，including J1 which has 62 needles socket，J2 for 37 needles socket．J1 is for signal wiring of the pulse output，switch input and switch output of X，Y，Z，A axis;J2 is for signal wiring of encoder input and switch input of X，Y，Z，A axis．

The following is the initialization function of the ADT8940A1 card in the VC programming language:int CCtrlCard::Init_Board()

Result=adt8940a1_initial();

If(Result＜=0)return Result;

for(int i=1;i＜=MAXAXIS;i++)

{

set_limit_mode(0，i，0，0，0);

set_command_pos(0，i，0);

set_actual_pos(0，i，0);

set_startv(0，i，1000);

set_speed(0，i，1000);

set_acc(0，i，625);

}

return 1;

If the return value＜=0，it means that the initialization is failed，otherwise the initialization is successful．

4.The system software

The test system adopts the Window operating system as the running platform;its main task is to control the test process，according to the requirement of the torsional vibration damper characteristics tests．The main functions include user information inputting，parameters setting，real-time displaying of the test conditions and curve drawing，as well as the curve analysis and data processing，etc．．

Before the test，the user information inputting and parameter setting must be done firstly．The user information will be the attached information of curve saving and printing．Testing parameters mainly include torque，positive/negative angle，mining value point，and torque control mode．Starting test after parameters setting is completed，manual and automatic mode can be chosen．During the trial，curve drawing and the results showing will be conducted in real-time that as shown in Figure 6．

After the completion of the test，we can carry on the analysis and preservation of the curve，as well as the printing of results．

Figure 6．Curve drawing area

5.Conclusion

The performance of torsional vibration damper directly affects the efficiency of the motor drive system，and then affects the overall performance of the car，so the torsional characteristics test technology of torsional vibration damper is particularly important［6-7］．The torsional vibration damper test system in this paper is a high-precision test system based on computer servo control technology，the control precision of the torque is within 0．2%，the angle measurement accuracy is within 0．5%．The system with simple frame and plentiful functions can satisfy the requirements of a variety of plate parts torsional characteristics tests．The system software adopts modular structure，feature-rich，simple to use，can satisfy all kinds of test requirements．The system can ensure the tests’accuracy and reliability on the base of fully considering the practicability and maneuverability．The system has been put into use in related enterprises，the practical application shows that the system is reliable in performance，can meet the testing requirements of the enterprises，and has a good application prospect．

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