Car drives backwards after maneuver and is not slowing down

Hello,

I was trying to understand and create a simple vehicle model. So I took an implemented model from Double lane change maneuver (Passenger Vehicle/Body, Suspension, Wheels/PassVeh14DOF). I did not change any parametres, only the initial velocity to 11 m/s. The car has no torque given and so it's speed is slowly decreasing. In 10 sec time, driver starts to steer both front wheels in right or left direction (implemented as ramp signal) to 0.5 rad. Then, the vehicle loses some of it's longidutional velocity in favor of lateral velocity (which is fine). Hovewer, the car should then slowly stop moving but it does not!! After the car reaches the zero longidutional velocity, it overshoots to negative value (reverse motion) and continue to move indefinitely. It is like there is no rolling resistence implied.

This is done in 6 DOF body, Combined Slip Wheel 2DOF with Independent Mapped Front Suspension Mapped Solid Axle Rear Suspension. But moreover, when I tried to reduce the DOF by using the 3 DOF body the car was behaving differently for same maneuver in both directions (to the right it did not stop moving but to the left it did). Can someone explain this weird behavior? Am I doing something wrong? Or is there a bug in a model?

I have attached my project in .zip file below.

Any help is appreciated. Thank you.

[Andy]

I do not have access to the correct modules to run this but from just reading your description it looks like there might be a problem with rolling resistance. As the car moves forward RR would slow the car down, negative acceleration. When the cars forward speed reaches zero RR should also be zero. Is this the case with the model or does RR still want to create a negative acceleration and hence start reversing?

[Jiri Minarik]

Hi @Andy,

you are thinking exactly as I am. However, that would not explain why, when you set 0 m/s initial longidutional velocity, car has steady state velocity -0.02 m/s but, when you set 11 m/s initial longidutional velocity, car has -0.1 m/s. Even when you have 0 m/s initial longidutional velocity, there are around +10 N of front longidutional force Fxf acting on wheels (after transformation to body CS)... Another interesting fact is that after the manuever with 11 m/s initial longidutional velocity, the car has left front longidutional force positive but the right front longidutional force negative... I am not even bringing the fact that even if it would be all from rolling resistence, it would be bug.

Answer 1

[Ryan Chladny]

Hi Jiri,

Sorry to hear that you're having difficulties. I tried to reproduce this in 19b but was unsuccesful.

Can you please ensure that you have all the latest updates installed? If you are still encountering difficulties, please get in touch with Technical Support as they'll be able to help you much more quickly and escalate with Development as needed.

Best regards,

Ryan

[Jiri Minarik]

Hi Ryan,

you mean that the car stopped? And did you use the model in attached .zip file or you made your own? Well, for the R2018b release, there are no more new updates and I had the latest BugFix file downloaded anyway.

I contated the support. They answered that they were unable to reproduce the issue so I guess that I did something wrong somehow or the 0.1 m/s is insignificant and they do not think as a problem.

Best regards,

Jiří Minarik

[Jiri Minarik]

Hi Ryan,

also, I found just now that a BugFix in R2019a Update has a resolved issue named 1794026: Unexpected vehicle motion at stopped conditions and it seems that it is very similiar to what I have encountered so that is probably why you were unable to reproduce my issue in 19b.

Best regards,

Jiří Minarik