LabVIEW is the United States National Instruments (National Instruments, NI) developed based on the graphics compiler language (G language) of the Laboratory Virtual Instrument Engineering Workbench (Laboratory Virtual Instrument Engineering Workbench), LabVIEW has a large number of data acquisition functions, easy for developers to develop [1].

LabVIEW has a large number of data acquisition functions to facilitate the development of developers [1].NI company in the software at the same time also sells its own data acquisition boards and cards, but the NI company produces a high price of data acquisition cards for small and medium-sized projects, obviously can not afford. And ordinary data acquisition card in the use of although not as convenient as the NI data card, but most of the data acquisition card comes with LabVIEW library functions, due to the existence of these library functions, for program developers, without the need to develop the underlying function, and easy to use. This test system uses the USB_DAQV1.2 data acquisition card produced by Hengkai Technology Company. The data acquisition card not only provides VC++, VB and other library functions, but also provides LabVIEW library functions [2-3].

The test system consists of servo motors, servo drives, industrial computer, data acquisition card and other related components, the test system structure is shown in Figure 1.

As can be seen from the structure diagram, the test system mainly consists of an industrial computer installed with the host computer software, the controller responsible for motor movement, the USB_DAQ V1.2 data acquisition card responsible for data acquisition, and the research object servo drive and servo motor. The entire control system implementation sequence: the controller sends the appropriate instructions to the servo drive, servo drive drive servo motor movement, servo drive on the corresponding I / O output port, these I / O output port can output the corresponding speed, current and other analog outputs, these analog access to the USB_DAQ V1.2 the corresponding data acquisition card analog input interface, in the upper computer to write the corresponding LabVIEW program. The corresponding LabVIEW program is written in the host computer, and the speed and current of the motor can be displayed in real time through the waveform display window. Through this kind of real-time display, the working characteristics of the motor can be understood, and it can provide corresponding basis for the improvement of the control system.

1 Hardware access

Due to the special characteristics of the servo drive, the signals tested in this test system are output from the corresponding I/O port of the servo drive. The test system uses Panasonic servo drive, the corresponding settings please refer to the servo drive manual, through the corresponding I / O settings, the corresponding I / O servo drive I / O connection using a twisted shielded cable and differential input method, PC output port settings for speed, current output. For differential inputs, AI0 and AI8, AI1 and AI9 constitute a group, and so on for the rest. The shielded wire is connected to AGND.

2 Software preparation

After installing the USB_DAQ V1.2 data acquisition card, it is also necessary to install the USB_DAQ V1.2 data acquisition card driver, according to the different systems installed in the computer, choose a different version of the driver to install. On the premise that the hardware is connected and the driver is installed successfully, the host computer software can be written. In the process of writing the upper computer software, the data collection is based on the non-empty query method, and the flow chart of data collection in the non-empty query method is shown in Figure 3.

3 Application of the test system in a rotary table

With the development of industry, rotary table in industrial applications more and more common, but the rotary table in the working process, the precision of the motor and the motor of the relevant performance requirements are more stringent, once a workstation problems, will affect the work of the entire production line, therefore, the user often need to know the rotary table motor of the corresponding operating parameters, so as to better understand the rotary table's operating characteristics.

3.1 Data processing

In the received data, taking into account in the process of the card may be subject to external interference and ambiguous values, in addition to hardware with shielded cables, connection method of strong interference-resistant differential inputs, in the use of software using the median filter.

yi = med(Ji), i = 0,1,2,K , n -1. i y : denotes the output sequence filtered x; n : denotes the number of elements in the input sequence x; i J : denotes the subset centered on the ith element in the input sequence x, and x

n : denotes the number of elements in the input sequence x; i J : denotes the subset centered on the ith element in the input sequence x, and the index elements outside the range of x that are equal to zero.

and the index elements outside the range of x equal to zero. Where: i { i rl i rl J x x = - - + , , 1 i i i i k x x x x - + , , , , , , 1 1 k, xi+rr-1, xi+rr}, rl : denotes the left rank of the filter; rr : denotes the right rank of the filter; Considering the data conversion and the anti-jamming, the LabVIEW data is written in the following way.

The LabVIEW data processing program is shown in Figure 4.

3.2 User Program Writing The total test program is written by synthesizing the way of data acquisition and the data processing in the process of data acquisition.

4 Conclusion

This test system applies LabVIEW to the common data acquisition card combined with the way to set the relevant parameters of the motor, because LabVIEW is a typical graphical programming language, shorten the development cycle of the host computer, and the common data acquisition card provides LabVIEW library functions to achieve a seamless connection with LabVIEW, reducing the cost of the project research and development. At the same time the application of LabVIEW data processing functions provided by the acquisition of data directly call the corresponding function, providing convenience for developers, eliminating the need for developers to write classical algorithms. Practice shows that the test system is simple, easy to operate and reliable.