Design and implementation of virtual instrument te

Design and implementation of virtual instrument testing system for motor performance

Abstract: modern virtual instrument technology is applied to the field of motor performance testing, which gives full play to the characteristics of high efficiency, flexibility, compatibility and high reusability of virtual instrument technology development, designs and implements the testing of multi-channel parallel motors, and uses PID control algorithm to control calibration parameters, Finally, the remote sharing of test data and the remote control of the test system by users are realized through tcp/ip protocol

key words: Virtual Instrument Motor Testing PID tcp/ip

in recent years, with the rapid development of computer technology, motor computer-aided testing (CAT) system has been popularized in the motor industry [1]. Computer based motor performance testing has gradually replaced the traditional manual motor testing, and is developing towards automation and intelligence. However, the motor automatic test system based on the traditional development platform often faces the shortcomings of long development cycle, high cost, weak compatibility and scalability, which also hinders the wide application of the motor automatic test system

with the introduction of modern virtual instrument technology, computer and standardized virtual instrument hardware are combined through virtual instrument application software, so as to realize the software and modularization of traditional instrument functions, so as to achieve the purpose of automatic testing and analysis [2]. Using virtual instrument technology, users can easily complete the functions of signal conditioning, process control, data acquisition, analysis, display and storage, fault diagnosis and network communication of the object to be tested through the graphical programming environment and operation interface, which greatly shortens the system development cycle; At the same time, due to the use of standardized virtual instrument software and hardware, the compatibility and scalability of the test system have also been greatly enhanced; In addition, virtual instrument technology has strong flexibility and high reusability, which can minimize the scale of users' test system, and it is easy to upgrade and maintain. Users can even use existing hardware to form another test system, so as to reduce unnecessary repeated investment and reduce the development cost of the system

the virtual instrument testing system for motor performance adopts LabVIEW and LabVIEW RT virtual instrument software platforms of national instruments (Ni), as well as supporting Ni PCI data acquisition board, Ni scxi signal conditioning equipment and Ni compact FieldPoint (CFP) distributed i/o real-time system hardware. The parallel test of multi-channel electric tool performance is realized; It can automatically complete the real-time monitoring of load, torque, speed, power and body temperature according to user settings; Finally, the remote sharing of test data and the remote control of the test system by users are realized through tcp/ip protocol. The system has the characteristics of short development cycle, high efficiency and low cost. At the same time, it has strong system scalability and reusability, and has strong application value

1. System composition and working principle

1.1 System composition

the virtual instrument test system for motor performance is mainly composed of four parts: the main controller module, the CFP real-time monitoring module, the dynamometer module and the motor module to be tested, as shown in Figure 1

the main control computer module is a Dell workstation, which is used to provide a graphical user interface, complete the configuration of system hardware and the setting of user interface and control parameters, and update the waveform display of each index parameter against time in real time. After curve fitting, the motor characteristic curve is obtained, and finally the recording of test data is completed. At the same time, the main control computer also completes the measurement of non control parameters, such as input voltage and working current, through the embedded Ni PCI data acquisition card

cfp real-time monitoring module is composed of two Ni CFP distributed i/o systems. It communicates with the master computer through tcp/ip protocol, obtains control parameter commands from the master computer to control the dynamometer, and returns the data signals collected from the dynamometer module to the master computer for processing. Module a is used to complete the real-time automatic loading and the measurement of control index parameters, and provide emergency measures such as overload protection, emergency shutdown and system reconstruction after illegal shutdown; Module B is used to complete the real-time monitoring of the surface temperature of the motor to be measured

the dynamometer module is composed of hysteresis dynamometer and magnetic particle dynamometer, which are respectively applicable to different types of motors to be tested. It is used to provide a certain load for the motor to be tested, and its internal sensing equipment converts the torque, speed and output power of the motor to be tested under this load into the voltage signal acceptable to CFP real-time monitoring module a

1.1. Working principle

the virtual instrument test system for motor performance can operate in two working modes: automatic working mode and manual working mode, The main test items are:

1) motor input voltage curve

2) motor input current curve

3) motor input power curve

4) motor torque curve

5) motor speed curve

6) motor output power curve

7) surface temperature of motor body

8) internal temperature of motor body

under automatic working mode, The master computer first waits for the user to complete the setting and configuration of software and hardware. Then ask the user to choose load test or parameter test. Under load test, the user needs to set load curve, load time, cycle time, test time and other test parameters; Under the parameter setting test, the user can select the specified torque, speed or power, and set the corresponding calibration parameters, control parameters and test time. After completing the above steps, the test program can be started, and the test system will automatically load according to the load set by the user and complete the performance test of the motor to be tested at the same time; Or through a certain control algorithm to maintain the stability of calibration parameters and automatically test the motor to be tested in this state. While the system is running, the user can observe the waveform display of each index parameter to time in the real-time monitoring chart, get the motor characteristic curve after curve fitting, and export and save the chart of interest. When the test time is completed, the system will automatically terminate the test

in the manual working mode, the working principle of the system is basically similar to that in the automatic working mode, except that the system does not carry out cyclic testing, but provides an interactive testing environment, and waits for the further operation of the user after completing the specified test items

2. Hardware structure

the hardware composition block diagram of the virtual instrument test system for motor performance is shown in Figure 2

1.1. The main control computer

the main control computer selects a Dell workstation, which is embedded with an Intel Pentium 42.6g CPU, a Ni pci-6052 multi-function data acquisition card and a Ni pci-4070 high-precision flexible digital multimeter card. The pci-6052 multi-function data acquisition card is pre equipped with two Ni scxi-1120 signal conditioning cards and the supporting Ni scxi-1327 attenuation terminal, which are used to collect the input signals of the working voltage and current of the multi-channel motor to be tested; The Ni pci-4070 high-precision flexible digital multimeter card is preceded by a Ni scxi-1127 multi-channel switch card and the supporting Ni scxi-1331 multi-channel wiring terminal, which is used to scan the rotor winding resistance of the multi-channel motor to be tested, and then measure the internal rotor temperature of the motor according to the corresponding algorithm

1.2. Real time monitoring module

Ni CFP distributed i/o real-time system is selected as the real-time monitoring module. As an industrial control system, CFP has FIFO data queue, power-off data cache, watchdog status monitoring, high impact resistance and immunity, which is used to complete the core part of the system for real-time acquisition and control [3]

cfp-2020 module is selected as the real-time system controller. The controller is embedded with microprocessor, 32m DRAM and 256M flash memory chip, and supports LabVIEW real-time module. This module can be separated from the LabVIEW programming environment, run the application downloaded to the controller memory in real time, and realize the network sharing of test data through the 10/100base TX Ethernet interface embedded in the controller

a CFP di-330 is used to respond to the emergency stop switch and shut down the system in an emergency to prevent accidents; A piece of CFP do-403 is used to control the solid-state relay SSR connected to each motor to be tested, so as to realize the closure or disconnection of the working circuit by the system; A CFP ao-210 is used to provide a load signal for the dynamometer to increase or reduce the load borne by the motor to be tested, so as to control the motor under a certain load; A CFP ai-210 is used to collect the voltage signal corresponding to the torque of the motor to be tested output by the dynamometer sensing device, and measure the actual torque of the motor to be tested; A piece of cfp-ctr-502 is used to collect the TTL level signal corresponding to the speed of the motor to be measured output by the dynamometer sensing device, and measure the actual speed of the motor to be measured

1.3. The real-time temperature measurement module

the real-time temperature measurement module also adopts the Ni CFP distributed i/o real-time system. The cfp-2020 controller and four CFP tc-120 8-channel thermocouple modules are adopted, which can be directly used to measure standard J, K, t, N, R, s, e and B hot spot couples, and provide corresponding signal conditioning, double insulation isolation, input noise filtering, cold end compensation and temperature calculation of various hot spot couples. Most express plastic bags are made of waste plastic, which is used to implement front-end data sampling at the working end of the motor, The network sharing function based on tcp/ip protocol of distributed i/o is used to realize the remote sharing of data, which is conducive to the implementation of remote real-time monitoring of industrial sites

1.4. Dynamometer

dynamometer is designed according to the balance principle of force and reaction [4]. When the torque received by the stator of the motor dynamometer is equal to the torque of the measured motor, the torque value of the measured motor is directly and accurately read out by the single chip microcomputer data acquisition system. When the tested motor rotates and the rotor of the dynamometer rotates, if DC excitation voltage is added to the dynamometer, there is a magnetic field in the dynamometer. At this time, the dynamometer rotor rotates and cuts the magnetic line of force to generate armature current, and the armature current and magnetic flux interact to generate braking torque. At the same time, the dynamometer stator receives a torque in the opposite direction, which will generate compressive stress on the dynamometer sensor shaft, which is within the normal working range, The compressive stress is proportional to the torque borne by the sensor shaft. If the resistance strain gauge is pasted in the direction of the maximum compressive stress generated by the sensor axis, the resistance value at the strain will change with the magnitude of the compressive stress. Then connecting the strain gauge to a certain bridge circuit can convert the change of the compressive stress into a voltage signal, so that the magnitude of the torque can be measured

the photoelectric speed sensor is used to measure the motor speed, which has high speed resolution, small inertia and wide application. The combination of single chip microcomputer and photoelectric sensor makes the measurement of motor speed simple and has strong anti-interference ability. The photoelectric sensor is equipped with a disc with n pairs of emerging countries on the edge on the motor shaft, and the export proportion will also be greatly increased. A disc with evenly distributed serrations will be projected onto the photosensitive tube through the light. When the motor rotates for one cycle, n pulse signals will be obtained. The speed of the motor can be obtained by measuring the frequency or cycle of the pulse signal

two types of dynamometers are used here: hysteresis dynamometer and magnetic particle dynamometer. The torque measurement range of the hysteresis dynamometer is relatively small, and the maximum torque is 10n m. However, the speed is large, and the maximum speed is 12000rpm; The torque measurement range of magnetic particle dynamometer is large, and the maximum torque is 20N m. However, the speed measurement range is small, and the maximum speed is 4000rpm. The two types of dynamometers complement each other and can be applied to many types