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Controlling speed through curves in vehicle simulation

Hello everyone, I am trying to use curves to control the speed of the vehicle, but I encountered some problems when setting the curves. I used expressions to set the x and y coordinates of the curves, but I kept getting error messages. However, the expressions I used worked fine when setting the sensors. What could be the reason for this? I want the speed of the vehicle to change with the displacement of the vehicle. How should I set it up? Thank you very much.

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MotionView/MotionSolve

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GTT Adam

Hi @xiejiyin,

Most standard events from the Vehicle Tools Extension require a linear input for the speed, like the double lane change below:

It should be noted that these inputs can be defined via an Expression, however they must resolve to a Linear value and not one that will update throughout the simulation.

Other events, like the Road Course event, have options for choosing a curve to define a velocity profile:

You can also choose to use Distance as the input to your curve, so that the vehicle speed will be dependent on how far the vehicle has travelled.

If you must define a speed profile with respect to distance travelled, the Road Course event is going to be the simplest way of achieving that.

Hope this helps!

Adam Reid

xiejiyin

Thank you for your previous response. If you don't mind, I have another question I'd like to ask.

When using hypergraph to plot data curves, I am not very familiar with the meaning of these parameters. How can I obtain the meaning represented by these parameters?

Best wishes!

Christopher_Fadanelli

Hi @xiejiyin ,

The Body Components represent the corresponding bodies XYZ Position and E0, E1, E2, E3 are the Orientation in Euler parameters.

For common requests (defined in outputs) MotionSolve provides the following types:

MARKER_DISPLACEMENT
MARKER_VELOCITY
MARKER_ACCELERATION
MARKER_FORCE

Marker IDs must be provided. Another type, called ELEMENTAL_FORCE, is useful for requesting forces in specific elements, such as joints and bushings.

You can also define a Post_Request element as a mathematical expression in terms of system variables using MotionSolve functions. Each request may define up to eight expressions stored in vectors labeled F1 through F8.

Finally, you may also use the REQSUB user-written subroutine REQSUB to define the request in C/C++ or Fortran.

Please look over Request Plots to learn more on how the plot files are organized.

Best,

Christopher Fadanelli

GTT Adam

Hi @xiejiyin,

In addition, it should be noted that post processing standard events can be done automatically by using the Reports Tool. The tool allows you to choose a recently completed event and create an animation and contextual plots for your review by just 1 click.

Hope this helps!

Adam Reid

xiejiyin

Thank you very much for your help！

xiejiyin

Thank you very much for your help! But I have encountered another issue. My road model is 100 metres long, and my simulation stop condition sensor is set to stop when the displacement reaches 100 metres. However, after running the simulation, the displacement curve drawn in Hypergraph only shows a displacement of 50 metres. What could be the reason for this? Below is my model. Once again, I sincerely thank you for your assistance.

Uphill_20m_10_Archive.zip

xiejiyin

Thank you very much for your reply! I want to build a 100-metre-long ramp terrain, which includes a straight section at the bottom of the slope, the ramp itself, and a straight section at the top of the slope. I tried modifying the length of the road in rdf, but it only extended the distance between the two ends of the road and did not achieve the effect I expected. Is there an error in my crg file or is there a problem with the model?

Best！

xiejiyin

Thank you for your help! I tried modifying the crg file because I noticed that the length of my road model seemed to have been compressed by half. So, I doubled the REFERENCE_LINE_INCREMENT in the crg file and then doubled the road length in the rdf file. After making these changes, the import seemed to work properly, but I'm not sure what caused the issue in the first place.