4569846498
Share Embed Flag
Download ePaper

4569846498

lollypop413
01.05.2017 Views

Modelling and assembly of the full vehicle 387 Vertical force (N) 10000.0 9000.0 8000.0 7000.0 6000.0 5000.0 4000.0 3000.0 2000.0 1000.0 0.0 Fig. 6.57 0.0 FRONT RIGHT TYRE – 100 km/LANE CHANGE Roll stiffness model Linkage model 1.0 _ _ _ _ _ _ _ __________ 3.0 2.0 Time (s) Vertical tyre force comparison – linkage and roll stiffness models 4.0 5.0 example, at the error measured between the experimental and simulated results for the peaks in the response or to sum the overall error from start to finish. On that basis it may seem desirable to somehow ‘score’ the models giving, say, the linkage model 8/10 and the roll stiffness model 7/10. In light of the above questions the validity of such an objective measure is debatable and it is probably more appropriate to simply state: For this vehicle, this manoeuvre, the model data, and the available benchmark test data the equivalent roll stiffness model provides reliable predictions when compared with the linkage model for considerably less investment in model elaboration. Clearly it is also possible to use an understanding of the physics of the problem to aid the interpretation of model performance. An important aspect of the predictive models is whether the simplified suspension models correctly distribute load to each tyre and model the tyre position and orientation in a way that will allow a good tyre model to determine forces in the tyre contact patch that impart motion to the vehicle and produce the desired response. Taking this a step further we can see that if we use the equivalent roll stiffness and linkage models as the basis for further comparison it is possible in Figures 6.57 and 6.58 to compare the vertical force in, for example, the front right and left tyres. The plots indicate the performance of the simple equivalent roll stiffness model in distributing the load during the manoeuvre. The weight transfer across the vehicle is also evident as is the fact that tyre contact with the ground is maintained throughout. It should also be noticed that in determining the load transfer to each wheel the equivalent roll stiffness model does not include the degrees of freedom that would allow the body to heave or pitch relative to the suspension systems. In Figures 6.59 and 6.60 a similar comparison between the two models is made, this time considering, for example, the slip and camber angles predicted in the front right tyre.

388 Multibody Systems Approach to Vehicle Dynamics 10000.0 FRONT LEFT TYRE – 100 km/h LANE CHANGE 9000.0 8000.0 Roll stiffness model Linkage model _ _ _ _ _ _ _ __________ Vertical force (N) 7000.0 6000.0 5000.0 4000.0 3000.0 2000.0 1000.0 0.0 0.0 1.0 2.0 3.0 4.0 5.0 Time (s) Fig. 6.58 Vertical tyre force comparison – linkage and roll stiffness models Slip angle (deg) 6.0 5.0 4.0 3.0 2.0 1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 0.0 FRONT RIGHT TYRE – 100 km/h LANE CHANGE Roll stiffness model Linkage model 1.0 2.0 _ _ _ _ _ _ _ __________ Time (s) 3.0 4.0 5.0 Fig. 6.59 Slip angle comparison – linkage and roll stiffness models Although the prediction of slip angle agrees well it can be seen in Figure 6.60 that the equivalent roll stiffness model with a maximum value of about 1.5 degrees underestimates the amount of camber angle produced during the simulation when compared with the linkage model where the camber angle approaches 5 degrees. Clearly the wheels in the effective roll stiffness model do not have a camber degree of freedom relative to the rigid axle parts and the camber angle produced here is purely due to tyre deflection.

388 Multibody Systems Approach to Vehicle Dynamics<br />

10000.0<br />

FRONT LEFT TYRE – 100 km/h LANE CHANGE<br />

9000.0<br />

8000.0<br />

Roll stiffness model<br />

Linkage model<br />

_ _ _ _ _ _ _<br />

__________<br />

Vertical force (N)<br />

7000.0<br />

6000.0<br />

5000.0<br />

4000.0<br />

3000.0<br />

2000.0<br />

1000.0<br />

0.0<br />

0.0<br />

1.0<br />

2.0<br />

3.0<br />

4.0<br />

5.0<br />

Time (s)<br />

Fig. 6.58<br />

Vertical tyre force comparison – linkage and roll stiffness models<br />

Slip angle (deg)<br />

6.0<br />

5.0<br />

4.0<br />

3.0<br />

2.0<br />

1.0<br />

0.0<br />

1.0<br />

2.0<br />

3.0<br />

4.0<br />

5.0<br />

6.0<br />

0.0<br />

FRONT RIGHT TYRE – 100 km/h LANE CHANGE<br />

Roll stiffness model<br />

Linkage model<br />

1.0<br />

2.0<br />

_ _ _ _ _ _ _<br />

__________<br />

Time (s)<br />

3.0<br />

4.0<br />

5.0<br />

Fig. 6.59<br />

Slip angle comparison – linkage and roll stiffness models<br />

Although the prediction of slip angle agrees well it can be seen in Figure<br />

6.60 that the equivalent roll stiffness model with a maximum value of about<br />

1.5 degrees underestimates the amount of camber angle produced during the<br />

simulation when compared with the linkage model where the camber angle<br />

approaches 5 degrees. Clearly the wheels in the effective roll stiffness model<br />

do not have a camber degree of freedom relative to the rigid axle parts and<br />

the camber angle produced here is purely due to tyre deflection.

logo

products

Resources

Company

Terms of service
Privacy policy
Cookie policy
Cookie settings
Imprint
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!