Currently, the inspection of vehicle wheelsets before and after turning mainly relies on traditional manual measuring. The data is then manually input into the CNC lathe system for turning, and tool setting on the CNC lathe still requires manual operation, making automatic tool setting impossible. This traditional method is outdated, has low measurement accuracy, is inconvenient to operate, and is unsuitable for modern vehicle wheelset machining and information management and maintenance. Therefore, we have developed a non-contact inspection device配套 with CNC wheelsets. This device is a high-tech precision inspection device integrating optics, precision mechanics, electrical control technology, data processing, and computer technology. It adopts a completely non-contact measurement method to achieve online inspection of vehicle wheelsets before and after turning on the CNC lathe. The inspection data is processed by an industrial control computer and transmitted to the CNC lathe to guide automatic tool setting and automatic turning of the vehicle wheelsets, ensuring the geometric dimensions and machining accuracy of the vehicle wheelsets. 1. Distribution of Measured Parameters The geometric parameters of the vehicle wheelsets to be inspected and their distribution are shown in Figure 1. The wheel flange height Sh, wheel disc diameter D, wheel flange thickness Sd, wheel rim width W, and distance Ri from the inner side of the wheel rim to the reference zero point of the CNC lathe are specified. The average error of repeated measurements is less than ±0.1 mm. Since the wheel disc diameter varies among different vehicle wheelsets, determining the appropriate measurement method is crucial. Based on the analysis of the wheelsets and the characteristics of CNC lathe turning, the positioning reference for the wheelset is selected when the high-precision center of the CNC lathe is tightened against the center hole of the wheelset shaft. This reference determines the theoretical center axis as shown in Figure 1, thus obtaining the calibration value based on this theoretical center axis and the CNC lathe reference zero point. The calibration value is then fused with the measured values ​​to obtain the required geometric parameters of the vehicle wheelset. After obtaining the geometric parameters of the vehicle wheelset, serial communication is established between the industrial control computer and the PLC of the CNC lathe to transmit all parameters required for turning the wheelset to the CNC system. The CNC system can then automatically turn the wheelset based on the received parameters. 2. Basic System Composition and Measurement Control Method This detection device mainly includes a measurement and control system, a data acquisition system, and a computer processing system. The basic structure is shown in Figure 2. 2.1 Measurement and Control System The measurement and control system is the core part of the detection device, mainly including position sensors and a measurement operation control panel. Position sensors include laser sensors, eddy current sensors, and encoders. The laser sensor uses a PSD-type displacement sensor with a detection range of 60–140 mm and a resolution of 0.01 mm; the eddy current sensor uses a voltage-type displacement sensor with good reliability, high sensitivity, strong anti-interference ability, non-contact measurement, and fast response speed; the encoder uses an 11-bit absolute encoder to improve the anti-interference ability of the field environment. In addition, to avoid the adverse effects of the complex outer surface of the wheel on the measurement when installing the laser sensor, the laser sensor is tilted at a certain angle to reduce the reflection angle of the wheel-to-reflecting surface, allowing diffuse reflected light to enter the receiver as much as possible, basically meeting the light flux requirements of the receiving sensor. This greatly improves the measurement accuracy and reliability. The control system mainly consists of a measurement operation control panel and a PLC control system. A combination of these two components controls the movement of the CNC lathe's two-dimensional slide, driving various sensors to scan data and transmitting the scanned data to the data acquisition system. The measurement operation control panel uses an AT89C51 microcontroller as its processor, transmitting various operational information to the industrial computer via a PCI I/O data acquisition card. The industrial computer uses an Advantech IPC-610 chassis and a PCA-600LV motherboard. The industrial computer's measurement software processes the input data and control signals and transmits the results to the CNC lathe's PLC. The PLC then controls the movement of the CNC lathe's two-dimensional slide to achieve the detection and automatic turning of vehicle wheelsets. 2.2 Data Acquisition System The data acquisition system is the core of the detection device, mainly including analog signal acquisition, digital signal acquisition, and the input and output of digital control signals. Analog signal acquisition uses a PCI 250KS/s 16-bit A/D converter data acquisition card to acquire the output signals of the laser sensor and eddy current sensor. The analog signals output by the laser sensor and eddy current sensor are amplified by their respective amplifiers and directly input to the analog input port of the A/D data acquisition card. After A/D conversion by the data acquisition card, they are input to the industrial control computer via the PCI bus. Digital signal acquisition uses a PCI-type 96-channel TTL digital I/O data acquisition card for acquiring encoder output signals and also for outputting control signals. To reduce the workload of the industrial control computer, the output signals of each encoder are preprocessed by an AT89C51 microcontroller data processing board to output the real-time absolute position of the CNC lathe, which is then read by the industrial control computer from the PCI bus via the I/O data acquisition card. 2.3 Computer Processing System The computer processing system includes measurement control, data processing, and data transmission. Measurement control mainly involves the industrial control computer receiving control information from the measurement operation control panel and outputting corresponding control information to the measurement operation control panel. Data processing mainly involves converting the analog signals output from each sensor into digital signals using a high-precision A/D converter, then inputting them into a computer for data storage, digital filtering, and further data fusion processing. The processed data results are then displayed on the corresponding location on the control and measurement software interface for operator viewing. The measurement results are also stored and printed. Data transmission primarily involves the industrial computer transmitting the measurement results data to the PLC control system of the CNC lathe to guide the CNC lathe in the wheel turning of the vehicle. 3. Control and Measurement Software Design The control and measurement software design mainly includes two parts: 1) Microcontroller control program design; 2) Industrial computer measurement software design. 3.1 Microcontroller Control Program In this system, microcontroller control is used in two places, both using the AT89C51 microcontroller as the processor. One is the measurement control operation panel, which has five buttons: "Start Eddy Current Measurement," "Start Laser Measurement," "Measurement Result Confirmation," "Transfer Left Wheel Data," and "Transfer Right Wheel Data." Each button press illuminates its corresponding LED indicator, while the remaining buttons are locked. This button information is transmitted to the industrial computer via a data acquisition card. Upon receiving the information, the industrial computer executes its corresponding task. After completion, the industrial computer clears the button information and turns off the corresponding LED indicator via the data acquisition card. Another component is the encoder data processing board. It reads the values ​​from the absolute encoder, determines its forward and reverse rotation, and provides the encoder's revolution count and single-revolution reading in real time. It outputs the real-time absolute position of the CNC lathe and then transmits it to the digital I/O card. The industrial computer can directly read the CNC lathe's real-time position from the digital I/O card. During revolution count calculation, a level interrupt method is used. When the encoder reaches zero (i.e., all eleven output bits are low), the microcontroller's INT0 pin generates an interrupt. It then checks the previous encoder value: if it's "1", the encoder reverses, and the revolution count is decreased by 1; if it's "2047", the encoder rotates forward, and the revolution count is increased by 1. The INT1 pin of the microcontroller is connected to the data acquisition card in the industrial control computer. When the industrial control computer sends a zeroing pulse signal, the encoder data is cleared and counting restarts. 3.2 Measurement Software Design of the Industrial Control Computer The measurement software design of the industrial control computer is the focus of this system. It implements five functions: first, providing a user interface and accepting user input commands; second, providing data storage, display, query, and printing functions; third, drawing the contour graphics of the vehicle wheelset in real time based on the scanned data and comparing it with the contour graphics of a standard wheelset; fourth, communicating with the PCI data acquisition card and digital I/O card driver to realize real-time data reading; and fifth, communicating with the CNC lathe PLC system to realize automatic measurement and automatic wheelset turning. Therefore, VC++ was chosen as the development platform for visual graphic design. The program flowchart of the measurement software is shown in Figure 3. Considering the extreme differences in the surface condition of the wheelset and the interference of the field environment, the measurement software performs real-time compensation for different conditions of the wheelset and performs data fusion processing on various interferences to eliminate their impact on the measurement data. The software also includes automatic diagnosis and protection against misoperation and power failure. Conclusion This equipment was successfully developed in May 2005 and is currently operating well. Actual testing has shown that the device's stability, reliability, and measurement accuracy all exceed design requirements. Currently, this is the first testing device in China applied to wheelset CNC lathes, and it has broad development prospects.