Altair RISE

A program to recognize and reward our most engaged community members

Nominate Yourself Now!

Exporting MotionView Simulation Results

Hello everyone, I've completed the kinematic simulation of the vehicle using MotionView. Now I want to export the overall slip rate of the vehicle during motion, rather than the slip of a single wheel. However, when exporting data in HyperGraph, I couldn't find the corresponding result data. Perhaps I don't know which result represents the vehicle speed or the overall slip rate. So how should I obtain this data? Thank you very much!

Best!

Find more posts tagged with

MotionView/MotionSolve

Accepted answers

GTT Adam

Hi @xiejiyin,

In the corresponding PLT file, vehicle speed can easily be found as "Long. Vel", typically listed under the request named "REQ/70000272 Driver Inputs 2: Long vel, Lat, vel, Yaw rate, Roll rate, Pitch rate, Engine speed".

CG Side slip can also easily be found as the "f2" component of "REQ/10000001 Side Slip Angle"

See below for an example from a Constant Radius standard event:

Both of these channels are displayed automatically after creating an event-specific Standard Report for any automotive event, typically on pages 5 and 6 (shown here from a Constant Radius event's Standard Report):

Hope this helps!

Adam Reid

GTT Adam

Hi @xiejiyin,

Wheel slip rate and the overall slip rate will be influenced by the vehicle performance as well as the event parameters.

Are you trying to reach some target overall slip rate and you current vehicle model is not achieving it?

Hope this helps!

Adam Reid

GTT Adam

Hi @xiejiyin,

The drive torque in the Constant Radius event will steadily increase as more torque is demanded by the Driver Model. The Driver Model will not request 100% of the available torque unless it is trying to achieve a vehicle speed well beyond it's physical limits.

Therefore, slip rates can be increased/decreased by modifying the target speed profile or by modifying the event's size. A small radius, high target speed, and short acceleration window will dramatically effect the overall vehicle slip rate.

Hope this helps!

Adam Reid

GTT Adam

Hi @xiejiyin,

If you're travelling in a straight line instead of cornering, then we would need to calculate longitudinal slip instead of lateral slip like we have been so far.

Longitudinal slip can be found in the output PLT file and is presented per wheel, as shown below:

To induce longitudinal wheel slip instead of lateral wheel slip, then some sort of a simple "drawbar test" would be ideal. You've also mentioned "sinkage" a few times in this discussion, are you completing this analysis on soft soil? If so, see below for a "drawbar" type example in which the vehicle is unable to overcome the resistance force and starts to sink into the soil:

Have the vehicle complete a Road Course event where a target speed is provided. Add a Force that acts on the vehicle body at its COG that slowly increases with respect to time. At some point, the applied Force will first make the Driver Model request maximum torque and then it will start to induce longitudinal slip as the maximum torque is surpassed by the applied resistance Force.

Hope this helps!

Adam Reid

All comments

GTT Adam

Hi @xiejiyin,

CG Side slip can also easily be found as the "f2" component of "REQ/10000001 Side Slip Angle"

See below for an example from a Constant Radius standard event:

Hope this helps!

Adam Reid

xiejiyin

Thank you very much for your response! Additionally, I would like to ask whether it is possible to directly control the slip rate of a vehicle in a vehicle simulation, or whether it can be indirectly achieved by controlling parameters such as drive torque or throttle opening? If so, how should this be implemented? Thank you again for your assistance!

Best!

GTT Adam

Hi @xiejiyin,

Wheel slip rate and the overall slip rate will be influenced by the vehicle performance as well as the event parameters.

Are you trying to reach some target overall slip rate and you current vehicle model is not achieving it?

Hope this helps!

Adam Reid

xiejiyin

Thank you very much for your response!

Yes, I want to treat the vehicle's overall slip rate as a controllable factor to observe how the vehicle performs under different slip rates. This will enable me to thoroughly and clearly investigate the relationship between slip rate, traction, and sinkage.

Best!

GTT Adam

Posted in error

xiejiyin

Thank you for your reply!

Can I achieve this solely by modifying the vehicle's drive torque, adding a drag object behind the vehicle, or other methods? Specifically, I aim to produce different slip rates while keeping all other conditions identical, thereby observing how vehicle sinkage and traction change under varying slip rates. If possible, how should this be implemented? I attempted to modify the Throttle's Maximum value in the Signal settings within RoadCourse, but neither the sink rate nor the slip rate changed.

Best!

GTT Adam

Hi @xiejiyin,

Hope this helps!

Adam Reid

xiejiyin

Thank you for your explanation! However, I still have some questions. Under straight-line driving conditions, can I achieve stable driving with different slip rates? Or is there a method to set different driving speeds for the vehicle at a fixed wheel speed, thereby achieving different slip rates? Also, I reviewed the previous simulations and noticed that the vehicle's slip rate is nearly zero during straight-line stable driving.

Best!

GTT Adam

Hi @xiejiyin,

If you're travelling in a straight line instead of cornering, then we would need to calculate longitudinal slip instead of lateral slip like we have been so far.

Longitudinal slip can be found in the output PLT file and is presented per wheel, as shown below:

Hope this helps!

Adam Reid

xiejiyin

Thank you so much! This is exactly the effect I was looking for! Does the “drawbar test” require modeling setup? I added a force at the vehicle's center of gravity and applied a backward force, but it didn't achieve the effect shown in your example.

Best!

GTT Adam

Hi @xiejiyin,

The drawbar load needs to increase as the simulation progresses, either with respect to distance or with respect to time. You have created a Linear force which will remain constant throughout the simulation. Change the type to Expression and then include an expression such as:

`STEP(TIME,0,0,30,3000)`

This will use a STEP function to slowly increase the drawbar load from 0N to 3000N over 30 seconds.

In the example I showcased, I applied the load with respect to distance travelled so it would not eventually pull the vehicle backwards. The expression would change to something along the lines of:

`STEP(DX({mkr_on_veh.idstring},{Global_Frame.idstring},{Global_Frame.idstring}), 0, 0, -10000, 3000 )`

In this example, the independent variable is the longitudinal distance travelled by the vehicle (using the DX function) in the global reference frame, and after 10m the full 3000N would be applied. Please note that the marker referenced, mkr_on_veh, is a made up name for a marker on your vehicle body and thus if you copy and paste this expression into your model it will not evaluate properly.

This behaviour can also be accomplished with a SpringDamper entity instead of a Force, as the spring force will increase the further the vehicle travels until it immobilizes the vehicle. I would recommend this approach if you are newer to MotionView.

Hope this helps!

Adam Reid