The company's existing oil level sensor performance testing equipment on the production line uses a static testing method, which cannot perform full-range dynamic performance testing of oil level sensors. To conduct more accurate oil level sensor performance testing, improve quality, and shorten testing time, it is necessary to efficiently, quickly, and independently develop a completely new dynamic performance testing device for oil level sensors within a short period. This device is required to perform full-range dynamic performance testing, low oil level alarm performance testing, and breakpoint testing of various models (including over 40 vehicle models from companies such as Hafei, Chery, Xiali, GM, Great Wall, Geely, and JAC) of oil level sensors (hereinafter referred to as TSG), as well as starting current performance testing and plug polarity testing of electronic fuel pumps (hereinafter referred to as EKP). Since virtual instruments provide users with innovative technology that can significantly reduce production costs and improve productivity, measurement accuracy, and equipment performance, users can flexibly and quickly build their own measurement and control equipment according to their needs, no longer limited by traditional instruments provided by manufacturers. Therefore, considering the characteristics of this project, it was decided to apply virtual instrument technology to the development of the measurement and control equipment to complete the functions of data acquisition and automatic measurement and control. Data acquisition (DAQ) is inseparable from driver software. The NI-DAQmx driver software has many advantages, playing a significant role in shortening development time, reducing development costs, and improving measurement accuracy in this project. Hardware Design of the Measurement and Control Equipment 1. Equipment Structure The hardware of the TSG dynamic performance test equipment consists of a data acquisition system, a resistance and low oil level alarm measurement system, a motion control measurement system, a starting current measurement system, a polarity measurement system, a pneumatic system, and an alarm system, etc., and their interrelationships are shown in Figure 1. [IMG=Test System Composition]/uploadpic/THESIS/2007/12/2007121112485561930R.jpg[/IMG] Figure 1 Test System Composition 2. Data Acquisition System The data acquisition system mainly consists of PCI-6527 and PCI-6052E acquisition cards based on PCI. The PCI-6527 card is a 24-channel input, 24-channel output digital acquisition card used at 24Vdc to meet the control requirements of the TSG dynamic testing equipment, which has 20 digital input signals and 21 digital output signals. The PCI 6052E card is an analog acquisition card providing 8 differential signal inputs, a maximum sampling rate of 333kS/s, an input resolution of 16 bits, and an input range of ±10V, fully meeting the equipment's requirements of 5 analog differential inputs, a sampling rate of 4000Hz, and an input resolution of 16 bits. This system serves as the hardware core of the equipment. 3. Resistance and Low Fuel Level Alarm Measurement System As shown in Figure 2, the TSG is a nonlinear, jumping-type variable resistor with a central sliding tap. The movement of the central sliding tap is driven by the movement of the float rod, as shown in Figure 3, and the resulting change in resistance accurately reflects the amount of fuel in the tank. To accurately test the dynamic performance of the TSG, i.e., the performance of resistance changing with the height of the float rod, the PCI-6052E is needed for real-time acquisition of resistance and height values. [IMG=Oil Level Sensor TSG]/uploadpic/THESIS/2007/12/2007121112490819165Z.jpg[/IMG] Figure 2 Oil Level Sensor TSG [IMG=TSG with Float]/uploadpic/THESIS/2007/12/2007121112492434903D.jpg[/IMG] Figure 3 TSG with Float The TSG resistance value is acquired by converting the resistance signal into a voltage signal of 0~10Vdc through a sampling circuit. After signal conditioning, it is input to PCI-6052E as a differential signal. The principle is shown in Figure 4. [IMG=Sampling Circuit]/uploadpic/THESIS/2007/12/2007121112494043495W.jpg[/IMG] Figure 4. The sampling circuit is based on (where R is the resistance of TSG, VR is the voltage across R, r is the external fixed resistor, and Vr is the voltage across r). Vr is input to channel CH0 of the PCI-6052E, and VR is input to channel CH1 of the PCI-6052E. The resistance of TSG can be calculated using the formula. The method for measuring the resistance of the low oil level alarm is the same. 4. Motion Control and Measurement System The TSG float rod up-and-down movement and height measurement system consists of an SMC actuator LJ1H2022NF-400K-R2, a controller LC1-1B1VH2-L5, and a Balluff micropulse displacement sensor (including a positioning magnet BTL5-N-2814-1S, a sensor body BTL5-A11-M400-P-S32, and an L-type connector BKS-S33M-05), as shown in Figure 5. [IMG= Motion Control Measurement System]/uploadpic/THESIS/2007/12/20071211125015886712B.jpg[/IMG] Figure 5. After the developed motion control program is input into the SMC controller, the measurement and control software controls the SMC controller through the PCI-6527 to select different product motion programs. The SMC controller drives the ball screw to move the float rod up and down at a speed of 100mm/s by controlling the AC servo motor. At the same time, the actuator feeds back the position information of the ball screw to the SMC controller, realizing closed-loop control of the float rod movement. The actual motion height value is measured by the micro-pulse displacement sensor and processed into a voltage signal of 0~10Vdc, which is then input to the CH3 channel of the PCI-6052E. Application Software Development Using LabVIEW 1. Software Functional Modules LabVIEW software is a graphical development environment with a large number of built-in functions. It can complete tasks such as system simulation, data acquisition, instrument control, measurement analysis, and data display, avoiding the complex programming work of traditional development environments. The software developed this time is a set of measurement and control software for TSG dynamic performance testing based on virtual instruments, seamlessly developed using LabVIEW on the WIN2000 platform. Its software functional modules are shown in Figure 6. [IMG=Software Functional Modules]/uploadpic/THESIS/2007/12/2007121112503694411K.jpg[/IMG] Figure 6 Software Functional Module 2 TSG Dynamic Performance Test Analysis The requirements for key measurement points of four types of TSGs (more than 40 in total) during the process of the ball screw raising the float rod at a speed of 100mm/s for approximately 6 seconds are listed. Additionally, the resistance value at the low oil level alarm point needs to be measured for some products. From this, it can be seen that the TSG height range is -30～330mm, and the resistance range is 2～320Ω. Thus, in a coordinate system with height as the horizontal axis and resistance as the vertical axis, there are at least 7 judgment windows composed of height and resistance, and sampling data must be available within ±1mm of the control height point. To ensure reliable data acquisition, analysis of the measurement system revealed that for every 0.15mm interval in the float's movement height, both height and resistance values ​​must be simultaneously input to the PCI-6052E. Considering the application program is a complex measurement and control program performing numerous functions, the data sampling rate of the PCI-6052E was set to ≥4000Hz. 3. Overall Software Structure Design The TSG dynamic performance testing equipment's measurement and control software adopts a sequential structure, including two independent, parallel-running tasks: EKP performance test St8.1 and TSG dynamic performance test St8.2. After powering on and executing the initialization program written by Case, the equipment automatically selects product 009, and the program enters the operating state. Device settings and adjustments are completed by selecting functions such as device calibration, calibration adjustment, model setting, model selection, and manual operation through drop-down menus. Pressing the automatic button on the human-machine interface puts the equipment into automatic mode. 4. Data Acquisition and Curve Processing When the measurement and control software executes data acquisition, the PCI-6052E performs continuous differential data acquisition across 5 channels (2 TSG, 2 low level, and 1 height), while simultaneously calculating resistance values ​​until the float rod movement ends. On one hand, the measurement and control software packages the ordinate formed by the real-time acquired TSG resistance values ​​and the abscissa formed by the height values ​​into a cluster and inputs it into the XY Chart Buffer sub-VI. This sub-VI, along with the control limit frame sub-VI composed of key TSG measurement points, undergoes Build Cluster Array processing and is output to the Multiplot XY Graph sub-VI, ultimately plotting the real-time TSG measurement curve. Figure 7 shows the real-time measurement curve of the TSG dynamic performance. The real-time curve is used to observe the curve trend during the TSG dynamic performance test and is relatively coarse. The processing of the low level alarm real-time curve is similar. [IMG=TSG Dynamic Performance Test Real-time Measurement Curve]/uploadpic/THESIS/2007/12/2007121112510275602B.jpg[/IMG] Figure 7 TSG Dynamic Performance Test Real-time Measurement Curve. On the other hand, the measurement and control software stores the TSG resistance data, height data, and low liquid level alarm data throughout the acquisition process using one-dimensional arrays. After the float rod movement ends, the data is combined, sorted, filtered, and the results are judged in the background, simultaneously plotting the final detailed TSG dynamic performance measurement curve. Conclusion After this equipment was put into operation, the production cycle time increased from the original 90 seconds to the current 30 seconds, and the output increased by nearly 3 times. The TSG dynamic performance test process completely simulates the real state of the TSG in the tank. The equipment meets the performance requirements of relevant BOSCH plants, and its stable performance, user-friendly interface, ease of operation, and reliability have won praise.