Mule car's hard-point trial production and chassis hard-point verification is a particularly important part of the vehicle development process, especially in the current automotive industry where the vehicle development cycle is greatly shortened.
The FARO portable measuring arm is widely used in the manufacturing industry due to its flexible hardware characteristics and the powerful functions of the software CAM2. It fills the gap of the platform-type three-coordinate to the difficulty of restructuring the body and measuring the hard point of the chassis. After a long period of application research, the fitting of the measurement coordinate system and the vehicle coordinate system is unified, which provides the basis for the trial production of the Mule car and the hard point and the hard point verification of the chassis. At the same time, the measurement data under the measurement coordinate system can also be realized. Deviation analysis was performed on the bit to 3D data.
The accuracy of the Mule car trial production is of great significance for the development of the dynamic performance of the vehicle. This paper illustrates the FARO in the development process of the vehicle through the hard point verification and hard disk verification of a Mulecar prototype process. application.
At the beginning of the trial production of Mule car, the first thing to do is to develop a hard-coded prototype of the body and a hard-point verification flow chart of the chassis. This work is very important. Whether the flow chart preparation determines the hard-point prototype and the hard-point verification of the bottom and the disk. Whether it can be successfully carried out, implemented and completed without errors.
Mule car body hard trial
After completing a series of preliminary work in the Mule car trial plan, the hard-point trial work of one of the key steps was carried out. The hard-point trial production of the body is carried out on selected mature bodies. The mounting points of the chassis are changed on the body to meet the technical requirements of Mulecar. The welding requirements of the site mounting position on the vehicle body are up to the designed vehicle coordinate system. Coordinated values, and thus a high-precision Mule car trial car, how to achieve this goal? After many research experiments, this technical problem can be solved by means of FARO portable three coordinates.
First, the measurement coordinate system is fitted to the vehicle coordinate system. After placing the body on the lift, find the four reference features with the smallest manufacturing tolerances on the car, import the 3D data or coordinate values ​​of these features or input them into the CAM2 software, construct the nominal value, and then measure the actual The feature data on the vehicle body, using the function of the fitted coordinate system in the software, the measurement coordinate system is fitted to the vehicle coordinate system. When choosing a baseline feature, follow these guidelines:
(1) The principle of maximizing the distance of the reference feature space.
(2) The principle of the reference features on the same body parts as much as possible.
(3) The principle of manufacturing tolerances such as stamping and welding.
Secondly, the body mounting points are welded according to the Mule car body hard point coordinates. The following is a modification process of the Mule car rear shock absorber mounting bracket as an example to illustrate the process of the hard point trial production of the vehicle body, as shown in Figure 1. The welding process of the body mounting point is a relatively complicated process. Firstly, the mounting point that is inconsistent with the Mule car design is removed, and then the modified body part is accurately positioned by the FARO measuring arm and welded to the vehicle body. The welding process mainly includes The following aspects:
(1) Hard point mounting bracket: Create a new body mounting bracket or follow the original body mounting bracket.
(2) Body bracket welding steps: 1 Soldering, fixed in a rough position. 2 Use the FARO measuring arm to check the hard point coordinates, the mounting plane (the vehicle coordinate system) and the corresponding axis. 3 Adjust the welded bracket with a small amount (check with the FARO measuring arm while adjusting) to ensure that the hard point error is within 1mm and the mounting plane angle error is less than 0.5°. 4 Partially fix the welded bracket, and then confirm the hard point and the mounting plane. If there is any deviation, adjust it (the welding will cause deformation). 5 Fix the welded bracket completely, and finally confirm the hard point and the mounting plane.
(3) The hard-point trial of the body must ensure local strength, mounting point stiffness, and overall stiffness.
The whole body hard point trial production process is a rigorous and cumbersome process. The process of hard body trial production is the process of hard body verification. The two are a synchronous and complementary process; the hard points on the body are in accordance with the pre-plan. After the precise trial production, the whole body hard point trial work was successfully completed; then the new development parts of the chassis were assembled to the prototype Mule car prototype body to be verified by the Mulecar chassis hard point.
Mule car chassis hard point verification
The Mule car chassis hard point verification is to verify the consistency of the chassis hard point of the Mule car and the hard point of the design chassis under the load of the whole vehicle. According to the verification scheme, the Mule car is loaded under a specified load so that the load of each wheel reaches the specified design value, and the load deviation does not exceed 3% of the design load, as shown in the attached table.
After the loading is completed, the verification of the hard point of the Mule car chassis can be started. The Mule car chassis hard point verification is based on the FARO portable measuring arm with its own hardware flexible features and the powerful functions of the software, which will measure the coordinate system and the whole vehicle. The coordinate system is uniformly fitted and the measured values ​​are compared with the designed values. The fitting of the vehicle coordinate system is divided into two methods. One is to measure the hard point of the chassis and then fit the measurement coordinate system to the vehicle coordinate system during the data post-processing; the other method is The measurement coordinate system is fitted to the vehicle coordinate system when measuring the hard point of the chassis. The latter is the most widely used because of its real-time detection capabilities. It is worth noting that the selection of the fitted reference features follows the selection principle of the hard-point trial feature of the vehicle body. At the same time, it is best to ensure that the selection principle of the hard-point trial feature is selected, which helps to analyze the coordinate system and the vehicle coordinate system. Fit the uniform deviation.
After the measurement work is completed, the Mule car chassis hard point verification, verification analysis is the last work. In the measurement, since it is impossible to directly measure the actual hard spot of the chassis, but to measure some characteristic elements around the hard point of the chassis, among which there are most basic features such as plane, circle, cylinder, line and axis, so it is necessary to The data is processed further. According to the external dimensions of the components, the measurement results are offset accordingly, and the deviation of the key hard points of all Mule cars is analyzed. The analysis result is the final result of the hard point verification of the Mule car chassis. Below are the analysis results of the sub-frame, the rear torsion beam, the wheel center position and the hem arm, as shown in Figures 2 and 3.
Conclusion
In summary, the Mule car body hard point trial and chassis hard point verification is the use of FARO measuring arm hardware flexibility, reliability and software's powerful post-processing functions, targeted guidance to produce accurate, meet the design and The Mule car required by the test, its value is not only to try out the Mule car itself, but to shorten the development cycle of the whole vehicle, to complete the performance test of the chassis ahead of time, and to obtain valuable research and development time. Products can be put into the increasingly fierce market competition faster.
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