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How to set the braking torque from the front and rear axles to the four wheels separately?

Hi ~

I use Vehicle Tools of MotionView 2022.2.1, and the Model Type is Car/Small truck.

In Objects Disk Brakes, the brake torque is divided into front brakes and rear brakes. Since the default is left-right symmetry, the brake torque of the left and right front wheels will be the same, and the brake torque of the left and right rear wheels will also be the same.

How can I modify Objects Disk Brakes to change the brake force to the front-right, front-left, rear-right, rear-left wheels, and set them separately?

Thanks.

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MotionView/MotionSolve

v2022.2.1

Accepted answers

Orestis_YB

Hello @TedTsai,

as the torques applied are asymmetric you have access to each force expression. You can access this from entity editor (or panels in previous versions) as shown below.

If you see the expression it will probably use the front pressure in both sides. Instead of that you can create two new solver variables one for the pressure on each side and then use this in the brake torque expression. This is exactly what we are doing in the Assembly Wizard vehicle when ABS or ESP system is present. Here you can find more information about Disk Brake Sytem and the model set up. Also here is ABS and ESP documentation that you might find useful.

Hope this helps!

Best regards,
Orestes

GTT Adam

Hi @TedTsai,

You can modify any entity in this assembly as required. Therefore, you only need to create 4 new torques and copy the exact definition as you see in the original torques:

Front Brake (Original):

Using this definition from the front brake torque pair, below is an example on how to add new torques:

Repeat the process for the rear brakes, and then simply copy the expressions used for the left and the right sides to your new torques:

Hope this helps!

Adam Reid

Orestis_YB

Hello @TedTsai,

in the current expression of brake torque the line pressure (right and left) is referenced via attachments. That's why you are seeing the arg_ prefix. If you click on the front (or rear) brake systems you should be able to see that it has 2 attachments.

Here the value represent the solver variable ID. If you check the Disk Brakes Data Set you'll see how this ID is calculated.

If you open the expression you will see that it's an elegant way of picking the line pressure if ABS/ESP system is present or not. Depending on the if statement it will actually use either the Front Brake Line Pressure or the ABS/ESP pressures.

So this arg value is simple a Solver Variable ID selector. In your case if you have a specific solver variable ID that you want to refer to, you should replace this in the VARVAL() expression.

You can use MotionSolve Functions Help button to check the syntax of all the needed functions. Here is the VARVAL() syntax. Hope this helps!

Best regards,
Orestes

Orestis_YB

Hello @TedTsai,

the prefix arg_ usually refers to attachments of systems. If you expand Front Brake System in the expression builder you'll see that it has two attachments.

In this specific case it's just the value of an ID which links the pressure either to front line pressure or to ABS pressure if the system is present (it's what I described in my previous comment).

In the vehicle model where we have a lot of different Systems in the model, many times we need to connect an entity of one system to an entity in another system. To retain modularity of this system we are using Attachments.

Hope this helps!

Best regards,
Orestes

All comments

Orestis_YB

Hello @TedTsai,

as the torques applied are asymmetric you have access to each force expression. You can access this from entity editor (or panels in previous versions) as shown below.

GTT Adam

Hi @TedTsai,

You can modify any entity in this assembly as required. Therefore, you only need to create 4 new torques and copy the exact definition as you see in the original torques:

Front Brake (Original):

Using this definition from the front brake torque pair, below is an example on how to add new torques:

Repeat the process for the rear brakes, and then simply copy the expressions used for the left and the right sides to your new torques:

Hope this helps!

Adam Reid

TedTsai

Thanks for the explanation, I will try it out soon.

TedTsai

Hi @Orestis_YB，

I created two Solver Variables named Front Left/Right Brake Line Pressure and tried to replace the original Expression of Brake Torque.

But I can't find the same code.
The original code is 'arg_sv_brake_line_pressure_l_id.value'.
What I created is 'Model.sys_brake.sv_front_left_brake_pressure.value'.

I'm not sure what I did wrong.
Could you help me take a look?

Thank you,

Ted

Orestis_YB

Here the value represent the solver variable ID. If you check the Disk Brakes Data Set you'll see how this ID is calculated.

You can use MotionSolve Functions Help button to check the syntax of all the needed functions. Here is the VARVAL() syntax. Hope this helps!

Best regards,
Orestes

TedTsai

https://community.altair.com/discussion/comment/191583#Comment_191583

Hi @Orestis_YB,

I copied the original Front Brake Line Pressure to Front Left Brake Line Pressure.

In the Brake Torque Expression, I replaced the original code with {MODEL.sys_brakes.sv_front_left_brake_pressure.value}.

Thanks for your reply, the program can run successfully.

Best regards,

Ted

TedTsai

Hi @Orestis_YB

Thanks for your previous reply.

The original code is 'arg_sv_brake_line_pressure_l_id.value'.
I can't find the meaning and use of "arg".
Where can I learn relevant knowledge?

Best regards,
Ted

Orestis_YB

Hello @TedTsai,

the prefix arg_ usually refers to attachments of systems. If you expand Front Brake System in the expression builder you'll see that it has two attachments.