Exclusive test! The result of 3 series plus anti-roll bar is surprising.
In order to maintain consistency, we set the speed of elk test at 72km/h, and locked it with speed limit function to maintain accuracy. From the subjective driving experience, there is not much difference in the overall driving experience of the chassis with and without the installation of the rear anti-roll bar.
In the original factory state, the front reaction of the vehicle when it enters the B area from the A area is still rapid. However, when the anti-roll bar was tested after installation, the response speed of the rear was obviously improved, but there was no obvious sliding or oversteer, and the overall trend was still biased towards understeer, but the response speed of the rear was faster.
●Beijing Institute of Technology-Researcher’s Conclusion (Elk)
The main purpose of this test is to compare the influence of rear anti-roll bar on vehicle handling performance. Through the test vehicles before and after installing the anti-roll bar, the elk test was carried out respectively. Collect data such as vehicle roll angle and yaw angle, and then analyze the influence of anti-roll bar installation or not on vehicle emergency lane change.
Because of the uncertainties such as the stability of driver’s input, the condition of vehicle tires, and the ground conditions of the site, each group conducted three experiments and finally took the average value. Each experiment is based on the fact that no bucket is touched and the sensor signal is valid.
●CarSim simulation analysis
Because there are many variables in this test, it is impossible to ensure the consistency of each experiment strictly, so it is necessary to analyze the control variables with the help of simulation. Through CarSim software, it can be achieved that the control variables are only the anti-roll bar, driver input, vehicle state, ground and other influencing factors, and they are strictly consistent.
In CarSim model, the vehicle with the anti-roll bar removed and the vehicle with the anti-roll bar installed were respectively set up to carry out the elk test and predict the test results. According to the test vehicle parameters, the CarSim simulation model is set up.The simulation results are shown in the following two pictures. The first picture shows the change trend of vehicle roll angle before and after installing anti-roll bar, and the second picture shows the change trend of yaw angle before and after installing anti-roll bar. The red line is the vehicle without anti-roll bar, and the blue line is the vehicle with anti-roll bar.
Above (simulation and prediction of roll angle)It can be seen that the roll angle curves are different in amplitude and change rate.
The yaw rate in the above picture (yaw angle simulation prediction) remains completely consistent. To some extent, it can be considered that the change of roll angle can reflect the influence on vehicle handling performance before and after installing anti-roll bar, and the difference of yaw angle may be caused by many factors, such as driver input.Therefore, in the analysis of the measured data, we should focus on the roll angle.
●Analysis of vehicle roll angle related data (the following two figures)
Vehicle roll angle data is collected by GPS inertial guidance gyroscope. The positive value of the collected data means that the left side of the vehicle is lifted, and the negative value means that the right side of the vehicle is lifted. In the elk test, the roll angle curves of all six experiments before and after installing the rear anti-roll bar.
It can be seen from the figure that in a single elk test, the roll angle changed three times. For the first time, after the vehicle entered Zone A, the steering wheel turned left and input, causing the vehicle to lean to the right. After the second vehicle enters the B area, the steering wheel changes from left to right, which causes the vehicle to shift its center of gravity and lean to the left with a fluctuation. The third time the vehicle entered Area C, it tilted to the right again due to inertia.
● Elk test-peak of roll angle (below)
By comparing the maximum change of the third roll angle before and after installing the anti-roll bar, we can reflect the change of the roll degree of the vehicle with or without the anti-roll bar. Define the vehicle roll angle as peak 1 when it reaches the peak for the first time, peak 2 when it reaches the peak for the second time, and peak 3 when it reaches the peak for the third time, and take all peaks as absolute values. The average value of the peak values of vehicle roll angle before and after installing the anti-roll bar is shown in the following figure.
Low center of gravity transfer rate (below)
There is a shift of center of gravity in the process of vehicle emergency lane change. During the center of gravity shift, the vehicle will roll from one side to the other. When the suspension stroke is compressed or the center of gravity is transferred, the vehicle roll angle will not change. Therefore, the time between two peak values of vehicle roll angle and the time of roll angle fluctuation after the vehicle enters Zone B can reflect the vehicle center of gravity transfer rate. It is defined that the interval between the first and second peak values of vehicles is T1, the fluctuation time of rear inclination angle in area B is T2, and the interval between the last two peak values is T3. Before and after the installation of the anti-roll bar, the center of gravity transfer time is shown in the following figure.
● Elk test conclusion
The data of milu deer roll angle has widened the gap in the limit state, which is also the most obvious project at present. The center of gravity transfer rate is understood according to the basic principle (which side is harder, it will be smoother).There is basically not much difference in the speed of the first handlebar direction (T1), but with the increase of the inertia of the vehicle changing lanes, the two center of gravity transfer rates of (T2, T3) are both faster with the rear anti-roll bar, but the gap between them is not obvious.Generally speaking, the follow-up and overall feeling of the rear are better, but the overall limit and driving characteristics of the vehicle have not changed much.
Through the four-column road simulation test-bed, the road surface conditions of daily vehicles can be restored on the test-bed.The test-bed can realize stable road excitation, avoid the influence of traffic conditions, route selection and weather environment in the actual road test, and minimize the instability in the test.
In this experiment, the light cross-country road spectrum is selected as the bench excitation input, which can restore the situation of poor road surface in daily urban use environment. Record the change of the roll angle of the test vehicle during the experiment. (as shown in the figure below)
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● Bench test conclusion
It can be seen from the figure that the inclination curves of the anti-roll bars are different, but considering that the absolute values of the inclination angles are all below 0.5 degrees. In daily use, the feeling is almost not great, so to some extent, it can be considered that whether to install the rear anti-roll bar has no significant influence on daily use.
●Test summary of BMW 325Li (Beijing institute of technology-researcher)
●Objective data evaluation
In elk test, pile-winding test and track test, the installation of rear anti-roll bar has a positive impact on reducing the degree of vehicle roll, especially in elk test. At the same time, the installation of rear anti-roll bar has certain influence on the transfer rate of vehicle center of gravity, but the effect is not significant. The test data show that the installation of rear anti-roll bar has positive significance in vehicle attitude adjustment, but has no obvious effect on improving handling performance.
In the bench test, there are some differences in the change of roll angle, but they are all in a very low range. The bench test data show that the installation of rear anti-roll bar has no significant effect on daily driving.
●Subjective evaluation of testers
Testers on the vehicle can feel the somatosensory changes in the vehicle whether the rear anti-roll bar is installed or not during the test. Before the anti-roll bar is installed, the body shakes greatly, and the body feels lifted and thrown down in the steering process, which makes the vehicle feel more stable in driving. After the anti-roll bar is installed, the car body shaking is restrained to some extent, and there is no obvious difference in the lateral shaking of people in the car, which makes the tires slip more easily in the driving of the car.
In the process of testing, the tester outside the vehicle can observe the attitude change of the vehicle with naked eyes to a certain extent. Before installing the anti-roll bar, the vehicle shakes greatly, and the compression and rebound stroke of the suspension is longer when steering. After installing the anti-roll bar, there is a significant trend to reduce the body posture sway, which visually feels that the vehicle is more stable.
● Summary
For long-wheelbase vehicles, after installing the rear anti-roll bar, the movement of the rear of the car has indeed changed, especially in the extreme driving state, which can directly perceive the change of the rear following. However, we can also see from the data that there is little improvement in performance, and daily use has no effect on comfort.
If you want to operate more directly and restore the function of the rear anti-roll bar, you can choose to install the original spare parts, but the overall improvement is not obvious. It is believed that the change of suspension performance will be more intuitive if it is replaced with the vibration isolator and adjusted in a targeted way. (Photo/Text/Photo car home Liang Qi Test Assistance and Conclusion Lin Shufeng Jia Mingxi Wang Yitong Data Conclusion Review Dong Mingming)