Abstract: A test system for a certain type of missile servo motor was established using a computer with a built-in data acquisition card and the LabVIEW programming language. This system can generate control signals, acquire multi-channel continuous data, display waveforms in real time, and play back the data. The paper details the hardware composition, software design, and specific implementation of the functional modules. Practical results show that the system works well, has stable performance, and meets the design requirements. Keywords: Actuator; LabVIEW; Data Acquisition; Measurement System Abstract: Based on the missile actuator, a measurement system has been built using the LabVIEW programming language and a computer with a DAQ card. This system generates signals controlling the actuator and performs other functions such as long-term, high-accuracy data acquisition and storage on input channels, real-time display or review of signal waveforms, etc. This paper discusses the hardware compositions, software development, and the realization of function modules in detail. Practice proves that this system works well with stable performance and meets the design requirements. Key words: Actuator, LabVIEW, Data Acquisition, Measurement System 1 Introduction The servo motor is the actuator for attitude control of an aircraft, directly affecting the final strike effect of a missile. Rigorous testing of its performance indicators is of great significance. Traditional testing methods require numerous and complex instruments. A test system built using virtual instrument technology, equipped with necessary sensors, data acquisition cards, and other hardware, can meet the needs of actual testing and analysis. Virtual instruments are a revolutionary technology born from the rapid development of modern computer software technology, communication technology and measurement technology. Its core is to use software to realize the functions of hardware. LabVIEW, a graphical programming environment based on G language, is an innovative software product of NI in the United States. It is a powerful virtual instrument development platform and is also the most widely used, fastest developing and most powerful graphical software integrated development environment. The servo motor test system designed in this paper is a virtual instrument based on LabVIEW. The test system has the advantages of user-friendly interface, complete functions, high reliability and strong maintainability. 2 Test System Hardware Design The servo motor test system consists of two main parts: system hardware and test software. The system hardware mainly includes a computer, data acquisition card, signal control console and sensor; the software is written in LabVIEW. The composition of the servo motor test system is shown in Figure 1. (1) Computer The computer is the center for analyzing and processing data. The selection of the computer is mainly based on the configuration requirements of the application software for the computer system. LabVIEW is suitable for various versions of operating systems including Windows 2000/9X/NT and Macintosh. Hardware requirements: Intel Pentium III or higher processor, at least 16MB RAM, and at least 220MB of available hard disk space for full installation. (2) Data acquisition card According to the test requirements and considering the cooperation with the software, the PCI-6024E E series product of NI's multi-function DAQ card was selected. It is used to complete the acquisition, amplification and A/D conversion of signal data. (3) Signal control console a. Power supply section: Provides 5~15V adjustable DC voltage, as well as ±12V voltage required by the solenoid valve coil and +24V voltage required by the servo ignition. b. Signal generation and conditioning section: Mainly generates and amplifies the control signal of the solenoid valve and the servo ignition signal, and is used in conjunction with the test software. c. Wiring port board: Used to connect the signal conditioning circuit and the 68-pin pin of the data acquisition card. [align=center] Figure 1 Block diagram of the test system[/align] 3 Test system software design 3.1 Program flow design According to the requirements of the test system function design, the overall structure flowchart of the software is shown in Figure 2. The program flow is as follows: From the main interface, select to enter either ignition or external gas supply mode for testing, or enter the file reading interface to retrieve historical data for waveform and data analysis again. In ignition mode, first input the product number and other relevant test information, then adjust the amplitude of the control signal. To verify the system's normal operation, a waveform should be sent for verification. After confirming the system is normal, start the ignition test. After the test, save the data file and select to enter waveform or data analysis. The external gas supply mode is basically the same, so it is not shown again. [align=center] Figure 2 Test System Software Composition[/align] 3.2 Design of the Data Acquisition Module Data acquisition provides the data source for the entire test system and is a fundamental component of the virtual instrument. The data acquisition module mainly realizes the acquisition of the measured signal and the control of various parameters, such as the settings of data acquisition channel, input signal range, signal input method, sampling rate, sampling mode, and readout rate. After acquiring the data, the waveform is first conditioned, and then the signal is sent to the Waveform Chart control for real-time display, and simultaneously saved to disk along a temporary path. Figure 3 is a flowchart of the ignition signal acquisition module, which calls the sub-functions such as AI Config.vi and AI Start..vi in ​​Analog Input under the Data Acquisition function module in LabVIEW. [align=center] Figure 3 Flowchart of Ignition Signal Acquisition Module[/align] 3.3 Design of Control Signal Generation Module According to the system requirements, the control signals of the four solenoid valves of the servo motor and the ignition signal required to ignite the electric detonator are generated by the test system. Based on the principle of making reasonable use of PCI-6024E hardware and using software as much as possible, the high-precision pulse sequence generated by the 6024E timer/counter is used to generate the control signal. The corresponding signal generation program flowchart is shown in Figure 4. The timer/counter port and DIO port are set in the program. [align=center] Figure 4 Flowchart of Control Signal Generation Program[/align] 3.4 Design of Acquisition Signal Storage Module (1) Data Storage Format: This test system uses waveform data file format to save the acquired data. This format contains some information unique to waveform data, such as sampling start time and sampling interval. The high-level file operation function Write Waveform to File.vi can be used to easily save the collected waveform data, and Get Waveform Components can be used to decompose the information such as start time, sampling interval and amplitude. According to the sampling settings, the file size generated by collecting data for 120 seconds under ignition is about 110MB. (2) Saving path of collected data: First, a default saving path is given. After the test is completed, the operator can decide where to save the file. At this time, the saved waveform file can be transferred to the specified path. This allows the user to decide whether to save according to the acquisition situation, which is more flexible. 3.5 Design of signal waveform processing and printing module (1) Waveform processing: During the test, Waveform Chart is used to display the waveform of each channel in real time. After the test is completed, it is also necessary to replay the waveform of any channel at any time period, and select several channels for comparison. The waveform is magnified and reduced to facilitate analysis and comparison. (2) Waveform printing: Although LabVIEW is powerful in data acquisition and instrument control, its ability to generate test reports is not satisfactory. To address this issue, NI provides the Report Generation Tools package to compensate for LabVIEW's shortcomings in report generation. This toolkit adds new controls to the existing Report Generation template, enabling easy integration of LabVIEW with Word and Excel for quick and convenient report generation. The final printed waveform is shown in Figure 5. [align=center] Figure 5 Printed Test Waveform[/align] 4 Interference Signal Filtering Methods In actual testing, analysis of the acquired signals revealed that the control signal waveform generated by the system was good, while the sensor signal contained some interference. To prevent interference from affecting data analysis, the waveform needed to be processed. Hardware-wise, a small capacitor can be connected between the sensor input and ground to filter high-frequency noise, which proved effective. Software-wise, LabVIEW's filters can be used for digital filtering of the sensor signal. Since filtering square wave signals inevitably alters the waveform, the purpose of filtering is to attenuate the amplitude of interference signals while minimizing the impact on normal square wave signals. A first-order Butterworth low-pass filter was chosen here. The reason for choosing first order is that higher orders result in steeper transition bands, and the required square wave signal also contains high-frequency components. Therefore, higher orders lead to greater distortion of the square wave and phase shift, which is detrimental to obtaining the delay time. Experiments show that using higher-order filters will distort the normal square wave waveform, causing spikes at the rising and falling edges. 5. Conclusion The servo motor testing system built using the LabVIEW virtual instrument graphical programming language utilizes the "software is the instrument" approach, reducing the amount of hardware required for testing and changing the traditional operation of testing instruments. The instrument panel is simple and clear, with strong human-computer interaction. Operation is performed on the front panel, avoiding physical damage caused by misoperation. This demonstrates that virtual instruments developed using LabVIEW greatly improve testing efficiency and economic benefits. The testing system has passed acceptance testing, and its performance meets the requirements. The innovation of this paper lies in its use of LabVIEW, the most representative graphical language in the field of virtual instrumentation, as the development platform. LabVIEW boasts a user-friendly interface, powerful functionality, high development efficiency, strong maintainability, and guaranteed testing accuracy, stability, and reliability. It offers a high performance-to-price ratio, saving investment and making it suitable for computer programming in the measurement and control field. The test software developed for this system realizes functions such as signal generation, acquisition, waveform display, playback, data storage, printing, analysis, and a user-friendly interface. In summary, this test system has the following characteristics: easy operation, complete functions, high reliability, strong versatility, and low cost. References: [1] Zhou Weilin. Driver for AC1077 data acquisition card based on LabVIEW [J]. Microcomputer Information, 2006, 22-1: 121-122. [2] Meng Xiuyun. Principles of missile guidance and control system [M]. Beijing Institute of Technology Press, 2002. [3] Fan Qiang, Xu Yuntao. Introduction to virtual instrument testing system [J]. Military Communication Technology, 2001, 9-1: 16-19. [4] Wang Shulan. Modeling and simulation of missile aerodynamic servo system [J]. Computer Simulation, 1994, 1: 23-24. [5] Robert H. Bishop (translated by Qiao Ruiping). Practical tutorial of LabVIEW 6i [M]. Beijing: Electronic Industry Press, 2003. [6] National Instruments Corporation. LabVIEW NI 6023E/6024E/6025E Family Specifications, March 2004 Edition. [7] Chen Min, Tang Xiaoan. Virtual Instrument Software LabVIEW and Data Acquisition [J]. Mini Microcomputer Systems, 2001, 4: 501-503.