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A theoretical analysis of means and methods
The design of automobile wheel alignment and the motion analysis of suspension system are inseparable. Through long-term theory and practice, each automobile company has formed a relatively mature suspension structure, which, McPherson suspension structure is currently used in many models more mature type. The following from the practical application point of view, focuses on how to use the idea of reverse engineering, digestion and absorption of the existing mature structure, and thus the formation of optimization and matching capabilities and experimental means. This process has a wider application value for the wheel alignment design independent design optimization.
1.1 coordinate analysis of the key points of the suspension space
Chassis part design coordinate origin is usually different from the vehicle coordinate system, therefore, in order to analyze the suspension motion characteristics, first of all, the suspension assembly parts to the vehicle coordinate system. According to the kinematics analysis of the McPherson suspension structure, it can be simplified as the lower arm, the steering column, the steering tie rod and the subframe part.
For each part, through the existing drawings or measurement methods, and the model-related parts of the size, the use of CAD means to simplify the relevant parts assembly, the use of catia / mechanic module to adjust the state of the entire assembly model to the desired Design the position (eg) to obtain the three-dimensional coordinates of the suspension's key points in the design position (eg) to achieve the next kinematics analysis of the suspension.
1.2 Analysis of suspension kinematics
The above key data input, the use of Adams dynamic software for wheel positioning of the kinematic characteristics analysis (), in the software for the toe, camber, kingpin angle and kingpin pitch angle is defined as follows:
Key Points Coordinate Key Points XYZ1,210.54521.54562.493,4-146.89572.45297.85, 7144.78337.5-52.356, 8-175.02337.5-41.44916.5149.4295.841016.514.4295.8411, 12-25.4653.75-47.25 Toe: arctan [( (Z0-Z0) / (Y0-Y0)] Codeposition angle: arctan [(Y11-Y1) / (Z1-Z11)] kingpin (X11-X1) / (Z1-Z11)] Wheel alignment definition diagram This model is used to analyze the kinematic characteristics of the wheel alignment parameters with the wheel runout.
2 bench test and road test verification
The spatial coordinates of the relevant key points can be measured using a portable coordinate measuring machine (Romer 6). The device can accurately measure the spatial location of key points. According to the result of the measurement, the CAD data can be analyzed by the CAD data assembly and the actual measurement. The data can also be analyzed to analyze the kinematics characteristic of the existing assembly state of the vehicle.
The kinematics of the axle can be measured by the MTS KC suspension test. The kinematic characteristics of existing platform axles are determined by comparing the measurement results of the test benches with the calculated characteristic curves, and provide a scientific basis for the next step optimization and matching.
3 Suspension Kinematic Characteristic Analysis of Practical Application
Based on the above analysis, the basic kinematic characteristics of the existing mature suspension structures are obtained, including the kinematic characteristics of the front beam, the wheel camber, the kingpin pitch angle and the kingpin inclination angle with the wheel runout. In the actual production process of car manufacturers, usually wheel camber, kingpin and the kingpin inclination angle can not be adjusted. However, for the same platform on the different models, to optimize the wheel toe matching. This matching usually includes two aspects, one is to optimize the coordinates of the relevant key points to optimize its kinematic characteristics and improve its wheel grinding conditions; the other is by adjusting the assembly line on the front beam calibration value, so that the wheel in the whole The kinematic curve in the process of beating falls in a reasonable curve interval, and obtains the balance between maneuverability and wheel grinding condition.
3.1 improve the quality of vehicle assembly
In the actual production process of the vehicle, there is a production error between the production position and the theoretical value which affect the key points of the kinematic characteristics of the chassis.
Each key point of the chassis movement will have an impact on the kinematics of the toe beam, and the influence of different key points on the toe design position is different. Chassis assembly is a system assembly, the accumulation of a variety of errors tend to affect the final toe assembly accuracy. Therefore, it is of great practical significance to analyze the sensitivity of the toe and the changes of each key point. For the McPherson front suspension, the correlation between the critical points of the chassis and the toe in the car design state is analyzed. The change of the wheel alignment value in the direction of the three-dimensional coordinates of the spatial key points is sequentially sorted and the sensitivity sensitivity correlation analysis is carried out.
According to these related characteristics, the machining accuracy of the key points in different coordinate directions can be adjusted appropriately so as to ensure the toe accuracy of the whole vehicle assembly and improve the production quality of the whole vehicle.
3.2 Optimization of the toe-changing curve
At present, vehicle development is usually based on the existing platform to change changes, often involving changes in wheel load, for each new model, the wheels are abnormal wear and tear each design development must be considered. How to optimize the toe-changing curve, to ensure that the user can accept the wheel wear life and vehicle handling stability, but also the main application of front kinematics analysis. For the McPherson suspension structure, changing the vertical coordinate of S (corresponding to point 3 or 4) greatly affects the curvature of the toe curve, as shown in Figure 4. By changing the coordinate position of the relevant part, The wheel alignment is optimized and the wheel alignment is optimized.
Using the existing drawings, combined with CAD and CAE for sensitivity analysis, through experimental verification axle kinematic characteristics. According to the kinematics characteristic, the optimization target is determined, and finally the specific part design is realized, so as to realize the wheel alignment matching and optimization. Through the combination of experiment, analysis and calculation, it is possible to complete the match optimization of vehicle type change based on platform strategy efficiently and accurately.