Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

Setting the initial steering angle in a Straight Line Brake event.

I am working a Straight Line Brake event,
The setting of Steering angle is 0 and the control is open loop.

The product is MotionView and the version is 2022.2.

As the vehicle moves, it will tend to move to one side.
I want the steering angle to be set to a non-zero value to balance the direction of the vehicle.
But directly setting the initial value is invalid.
I would like to ask how to set it up.

Thank you,
Ted

Find more posts tagged with

MotionView/MotionSolve

v2022.2.1

Accepted answers

Orestis_YB

Hello @TedTsai,

I believe the vehicle tends to steer from a certain side due to slight difference in the weight distribution between left and right side. Below you see the FZ contact patch force for front tires of the assembly wizard vehicle.

In open loop steer events where driver "locks" the steering wheel in a certain vales you should expect some steering. As for the results you are sharing, these are the measured results on the steering column and not the driver's output. If you plot the steer angle from driver output results you'll see that it's zero.

I believe you are using the build in straight line braking event. In there the adf is written with open loop steer value of zero no matter what the initial value is.

If you want to change this you can manually edit the export adf and then load the xml to MotionSolve. Or better manually edit the adf and create an AltairDriverFile event where you'll use the modified adf. You could also create an adf where the driver follows a straight path and a follow path steering controller. With that driver will perform the appropriate amount of steering to keep the vehicle in straight line.

I have attached an adf where I modified maneuver 2 to include a straight line path following.
You can see from the results that driver acts on steering wheel to keep it in straight line while braking. On the left is the driver output on steer angle and on the right vehicle's CG XY plot.

Here (Sequence of Straights and Arcs) is one of the ways to define path in adf file.

Hope this helps!

Best regards,
Orestes

P.S. It wasn't possible to attach an adf file. I added it as a txt. Just change the file format to .adf manually before using it to AltairDriverFile event.

event_new.txt

Christopher_Fadanelli

Hi @TedTsai ,

Yes it is possible that the steer input was too much which causes the simulation to crash.

My suggestion is to have an expression to ramp up the steering input.

To start off I would suggest to have the initial value of the steering input at 0.

Then in the Steer controller, use a STEP function to ramp the steer angle from 0 to -0.0349 radians in 0.3 seconds (time value can change).

Then in the second maneuver, have a different steering controller to keep the steer angle constant.

I'm attaching the altered adf.

Hope this helps!

Best,

Christopher Fadanelli

250417-adf_edit.txt

All comments

Orestis_YB

I believe you are using the build in straight line braking event. In there the adf is written with open loop steer value of zero no matter what the initial value is.

event_new.txt

TedTsai

Hi @Orestis_YB,

Thanks for your reply.

I can now adjust the steering wheel angle by adding an AltairDriverFile.

When I increased the angle, I ran into problems.
The program runs successfully when the steering angle is -0.0174 rad.

However, when I increase the steering angle to -0.0349 rad,
the program would generate errors and would not run.

Is this because the steering angle changes too much?
I'm not quite sure what happened.

What I want to do is, in open loop, reduce the drift by increasing the steering angle.

Attached is the adf and log converted to txt.

Could you please give me some advice?

Best regards,
Ted

250417-adf.txt

250417-log.txt