Abstract Specialized analytical tools are required in the research and monitoring of electric motors, most of which are traditional measuring instruments. These instruments suffer from low measurement accuracy, slow calculation speed, and inability to effectively and intuitively display relevant information. This paper introduces a new motor speed control test system developed using LabVIEW 8.20, incorporating the concept of virtual instruments. This system integrates multiple functions such as principle display, system parameter characteristic measurement, PID adjustment, result analysis, data saving, and report printing, with unique advantages, particularly in data acquisition and analysis. Its intuitive and user-friendly interface and diverse and rapid analysis processing capabilities are its greatest strengths. It can serve as a fundamental tool for electric motor research and will also have specific applications in power and automatic control systems. Keywords LabVIEW Virtual Instrument Motor Speed ​​Control China National Graphics Classification Number TU113.2+2 Document Identification Code A National Standard Subject Classification and Code 510.804 Abstract Special analysis tools are all needed in the research about electromotor and its monitor, and normally they are traditional instrument with low precision and calculation speed, also can't show intuitionistic information. Absorbing the concept of Virtual Instrument, the DC motor timing system developed in LabVIEW8.20 has variety of functions such as principle show, the system parameters measurement, PID adjustor, result analysis, data saving and record print etc, particularly the original function in data collection and analysis. The ultimate superiority of this system is its friendly user interface and diverse analysis in high speed. Thus, it can not only become the basic tool in electromotor researches, but also has special using in system such as electric power and auto control and so on. Key words LabVIEW Virtual instrument DC motor timing 1. Introduction Because electric power production is economical, transmission and distribution are easy, and use and control are convenient, electric drives are widely used in various types of production machinery. DC motors have a wide range of smooth speed regulation performance and good starting and braking performance, so DC speed control systems are the main form of speed-regulating drives. Currently offered courses such as semiconductor converter technology, automatic control systems, and computer control all involve DC motor speed control systems. Our DC motor speed control test system, developed using LabVIEW, uses computer hardware as a platform and combines it with a high-precision data acquisition card, resulting in fast calculation speed, high data storage capacity, and more intuitive and rapid result processing and analysis. It can be used as supporting experimental equipment for the aforementioned courses. 2. Introduction to Virtual Instruments and LabVIEW A virtual instrument is a modular instrument used in conjunction with a PC. It does not have a physical front panel; instead, it utilizes the PC's powerful graphical environment and online help functions to create a graphical "virtual" instrument panel, enabling control, data analysis, and display of the instrument. Users can operate the PC through a user-friendly graphical interface (virtual front panel), just like operating a traditional instrument they have defined and designed themselves. Essentially, LabVIEW organically integrates computer hardware resources with instrument hardware through software, combining the powerful computing capabilities of a computer with the measurement and control capabilities of the instrument hardware. This significantly reduces the cost and size of the instrument hardware, and enables data display, storage, and analysis through software. LabVIEW, developed by National Instruments (NI), is an excellent graphical programming development platform, short for Laboratory Virtual Instrument Engineering Workbench. It generates stand-alone executable files and is a true 32-bit compiler. Like many important software programs, LabVIEW offers versions for Windows, UNIX, Linux, and Macintosh. Compared to traditional programming languages, LabVIEW's graphical programming method can save over 85% of program development time with almost no impact on running speed, demonstrating extremely high efficiency. The version has evolved from LabVIEW 1.0 to the current LabVIEW 8.2, bringing a series of powerful new features, including compatibility with The MathWorks, Inc. MATLAB® software, and is now a very comprehensive virtual instrument development platform. LabVIEW integrates signal acquisition, measurement analysis, and data display functions, combining development, debugging, and operation. It provides almost all classic signal processing functions and a large number of modern advanced signal analysis tools, and can be easily and seamlessly integrated with various data acquisition hardware, Ethernet systems, and various mainstream fieldbuses, as well as linking to most general-purpose databases. "Software is the instrument" reflects its essential characteristic of virtual instrument technology. As one of the most widely used data acquisition and control development environments internationally, it uses icons instead of text code to create applications and has been widely applied in testing and measurement, data acquisition, instrument control, digital signal analysis, and communication simulation. 3. Instrument Composition This test system consists of two main parts: hardware and software. The hardware system includes a commonly used PC and data acquisition equipment; the software system is the instrument program package developed in the G language environment of LabVIEW 8.20. Its functions and structure are shown in Figure 1. 3.1 Data Acquisition Equipment Selection and Performance Analysis The acquisition equipment includes a PCI-1712/1712L data acquisition card, a PCL-10168 shielded cable, and an ADAM-3968 terminal block. The Advantech PCI-1712/1712L is a powerful, high-speed, multi-functional PCI bus data acquisition card. It features a 12-bit A/D converter with a 1M conversion speed and an on-board FIFO buffer (capable of storing 1K A/D sample values ​​and 32K D/A conversion data). The PCI-1712 provides 16 single-ended or 8 differential analog inputs (or mixed single-ended and differential inputs), 2 12-bit D/A analog output channels, 16 digital output channels, and 3 16-bit multi-function counter channels with 10MHz clock speeds. The PCL-10168 shielded cable is a 68-pin SCSI-II cable, 1M, specifically designed for the PCI-1712/1732 card to improve noise immunity. For better signal quality, single-strand wires are twisted into a pair to reduce crosstalk and noise from other signal sources. Furthermore, its analog and digital lines are separately shielded to eliminate electromagnetic interference/EMC issues. The ADAM-3968 terminal block is a DIN rail-mounted 68-pin SCSI-II terminal block. This low-cost, universal screw terminal block module for DIN rail mounting allows for simple and reliable connections to PC-LabCards boards with 50-pin interfaces. [align=center] Figure 1 Functional Structure Diagram of the DC Motor Speed ​​Control Test System[/align] 3.2 Software Functions and Implementation [align=center] Figure 2 Main Front Panel of the DC Motor Speed ​​Control Test System[/align] The LabVIEW-developed program consists of two main components: the front panel and the block diagram. Operators can control the instrument's startup, operation, and shutdown through a user-friendly graphical interface and graphical programming language. It performs functions such as data acquisition, analysis, display, fault diagnosis, data storage, and control output of the measured signals. The user interface of the DC motor speed control test system is shown in Figure 2. The entire test system is divided into three parts: speed control system schematic diagram, parameter characteristic testing, and main unit PID debugging. The functions of each module of the test system are described in detail below. 3.2.1 Parameter Characteristic Component Testing To study motor speed regulation, it is necessary to first understand the total resistance and total inductance of the armature circuit, as well as the electromagnetic and electromechanical time constants of the system. These parameters all need to be measured experimentally. Therefore, this part is the core of the testing system, including seven test items: measurement of the total armature circuit resistance R, measurement of the armature circuit inductance L, measurement of the flywheel inertia of the DC motor-generator-tachogenerator combination, measurement of the main circuit electromagnetic time constant, measurement of the motor electromotive force constant and torque constant, measurement of the system electromechanical time constant, and measurement of the rectifier and tachogenerator characteristics. See Figure 3. [align=center] Figure 3: Front-end and flowchart of parameter characteristic component testing[/align] 3.2.2 Main Unit PID Debugging The schematic diagram of a conventional PID control system is shown in Figure 4. [align=center] Figure 4: Schematic diagram of an analog PID control system[/align] The entire system consists of an analog PID controller and the controlled object. Since the setpoint and output value of the actual controlled object are always different, there is a certain deviation between them. The analog PID controller is based on the given value r(t) and the actual output value y(t) of the system to form the control deviation e(t) = r(t) - y(t) (1). The proportional (P), integral (I) and derivative (D) of the deviation e(t) are linearly combined to form the control quantity u(t) to control the controlled object. Its control law expression is or written in the form of transfer function (3) where Kp is the proportional coefficient of the controller; TI is the integral time constant of the controller; TD is the derivative time constant of the controller; This part is the control output part of the PID regulation of DC motor current regulation, as shown in Figure 5. As the mainstream development language of virtual instruments, LabVIEW's excellent graphical language development environment not only includes various objects for developing virtual instrument panels and rich functions for signal analysis, but also provides an external PID control toolkit, which allows us to extend the virtual instrument system to the field of automatic control and form a measurement and control system based on virtual instruments. [align=center]Figure 5 Front panel of PID control output[/align] Using NI's LabVIEW-based PID Toolkit, controller design can be performed intuitively and conveniently through a user-friendly interface within the LabVIEW environment. Furthermore, the powerful functions of LabVIEW, especially its excellent integration with data acquisition boards and other hardware, allow for the rapid construction of the required automatic control system for simulation and practical application. The program is shown in Figure 6. [align=center]Figure 6 PID control program flowchart[/align] 3.2.6 Printing and Help The analyzed parameters and results are printed (Figure 7). [align=center]Figure 7 Partial program diagram of the printing module[/align] The print subroutine is used for printing test reports. 4. Conclusion The LabVIEW-based DC motor speed control test system features flexible operation, comprehensive functions, and high analysis accuracy, effectively meeting the requirements of speed control testing. It also possesses PID control output functionality, truly embodying the idea that "software is the instrument, and the instrument is the software." In terms of hardware selection, a low-cost, high-performance data acquisition and analysis instrument was developed using a PC and a PCI data acquisition card. During software implementation, the rich application analysis toolkit provided by LabVIEW, such as the PID Toolkit, was fully utilized, avoiding extensive hardware and software development work. This testing system is simpler to use than typical plain text programming software, and its interface is aesthetically pleasing; processing results can be directly described on the front panel. References [1] Tao Yonghua. New PID Control and Its Application 2nd Edition Beijing Machinery Industry Press 2002: 8-10 [2] He Hong, Ma Shaohan, Algorithm Analysis and Design Technology, Science Press, 2004.9 [3] PID Control Toolkit for G Reference Manual. January 1998 Edition Part Number 320563B-01 [4] Lin Zhisheng, Huang Yuanfu, Lin Ning et al. Translated. Signals and Systems 2nd Edition Beijing Electronic Industry Press 2004 [5] Wu Daoti, Chief Editor. Non-electrical Quantity Measurement Technology. Xi'an: Xi'an Jiaotong University Press, September 2001 • P205. [6] Zhu Shouyun, Wang Chunhao. Virtual Technology and Its Application in Electrical Engineering. Electric World, 1997 (8) 1-3 [7] Pan Yingyu. Virtual Instruments and Their Application in Power Automation Equipment, 1999, 19 (1) 44-46 [8] Pan Yingyu, Mo Fujiang, Gao Zemin. Virtual instruments and their application in the power industry. Power System Communication, 1999(2): 11-14 [9] Huang Yixiong, Qi Lili. Power parameter testing under virtual instruments. Automation and Instrumentation, 1998, 13(1): 12-13 Author Introduction Zhao Junjuan, born in December 1983, is a master's student at Taiyuan University of Science and Technology. Her main research directions are electromagnetic measurement and intelligent instrument virtual instrument technology, etc. Han Rucheng (1959-), male, professor, master's supervisor at Taiyuan University of Science and Technology, whose main research directions are electric drive and intelligent control. Song Weiping (1961-), male, associate professor, master's supervisor at Taiyuan University of Science and Technology, whose main research directions are virtual instruments and LabVIEW programming. Contact information: Address: P.O. Box 468, Taiyuan University of Science and Technology, Shanxi Province, 030024 Tel: 13753100830; 0351-2824680 E-mail: [email protected]