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Chris Coker

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Everything posted by Chris Coker

  1. If you are trying to simulate the loading effects of a tire going through a pot-hole, a simple spring-damper approximation will not give you the correct loading into the suspension. You should be utilizing a proper tire model, or using physical test data collecting using wheel forces transducers, and applying those to the spindles. We have an extensive library of vehicle models built into MotionView. These can be a guide on how to properly set up a model like this. For your question about K&C coefficients for your trailer model....What values do you want to compare with? The purpose of measuring K&C is to evaluate a design vs. some target data, or evalute two different vehicles, etc. Our vehicle libraries are already setup to run K&C analysis. You can likely adapt your model to work with those. Note that starting from CAD data for building a vehicle model is not the most efficient approach. Typically, we encourage users to start with an existing suspension template. Then you can take advantage of the existing events (full vehicle, half-car, K&C, etc) that have already been created. Your existing model will not work with the existing event library without significant modification.
  2. Hi, You can modify your model under Tools -> Options -> Path Management. If you convert the model to use "Relative Path Names", and then keep your graphics, and .csv data in the same folder as the .mdl, then you will not have these issues. Also, you can convert the .csv data from type of "file" to "values", and the .csv will be converted to values that are stored internally. However this doesn't address the graphics, where are always externally referenced, unless you define them using graphic primitives inside MotionView.
  3. 1. You would want to use the Altair Driver for this. If you are using the 2019.1 release, there is a "Road Course Drive" event that should work for your application. I believe the setup/usage is well defined in our help 2. A. A road file developed in ADAMS/Car may not work with MV (actually this is a really a dependency on the tire model you are using, since MotionView (and MotionSolve) only reference the path names to the road files. 2. B. The road files are referenced in the AutoTire statements. These can all be managed in the gui in MotionView. Essentially the same area you define the tire data, you define the road data. By default, they point to a "flat road" file. Note, if you are using a 3D road profile, the tire models usually require additional software licencing. Note: Altair's modified Fiala tire can support the OpenCRG (.crg) format, as well as Polyline road surfaces. One clarification, HTIRE is depreciated and not installed by default with current versions of MotionView (2017 and forward). It does not require a license, but the cosin tools required to run it are not installed by default. We have migrated to MF-Tyre as the default "free" tire. Also, the fiala tire that is available is also free. Chris
  4. If you are using CAD data, and importing it into MotionView, the CG and MOI will be correctly read into MotionView. You can define it several ways, about the part CG, the vehicle CG, or the global CG, or any other location for that matter. Usually, people will define each part's mass, inertia, and CG location relative to the part, because that's how the data/CAD is defined. You don't have to calculate anything, assuming the CAD is correct. Just define your mass, CG, and inertia the way it is defined in your CAD. The tire forces should be described in our help. In general: f2 = Fx f3 = Fy f4 = Fz f6 = Tx .... It's also pretty easy to sort out the directions by plotting them, and observing the behavior of the forces using simple events.
  5. 1. I have changed the end time to 15, yet the simulation goes on only for 6 sec. You changed the end time, not the value in the template. There is likely a templex template (assuming you are not using the Altair Driver). You can change the end time in the template, or the end time inside the Driver event. 2. I have entered the values obtained from Tools>CG\Inertia Summary>Moment of inertia into Model>Data Summary>Bodies and getting this error. Also does adding these values lead to more accurate results? The values in the CG inertia summary are used to provide you a Total values of the overall CG and inertia of the vehicle. It's getting those values from your mass properties, which you are editing in the DataSummary. You are working in a loop, editing the same numbers. The normal process works like this: 1. Mass and CG location exists for each body in the model. Update the mass and CG location for each body to match this data. 2. The CG/inertia summary provides a method to allow to sum up all of the masses and CG locations entered in step 1, and check that the overall vehicle CG and inertias are correct. Usually you will need to only update the vehicle body mass, cg, and inertia, assuming step 1 is correct.
  6. 1. To change the end time of the simulation, you will need to edit the template. To increase the lateral acceleration, you can increase the speed of the vehicle. 2. The lane change is intended to be used with a flat road. If you need to run a non-flat road, you will need to change the road definition file. Note, some tire models are not compatible with non-flat roads, or require additional licensing depending on which tire model you are using. The Altair Driver has a path follower event that will work better for this kind of event, if you need to run something other than a lane change. 3. To change the reference frame to something other than global, when using the CG/Inertia summary, you need to be using HyperWorks version 2019 or later.
  7. The error indicates there is a problem of some sort (maybe incorrectly defined properties for the graphics) As a workaround, you can try deactivating that graphic (id # 90001) that's throwing the error. The removal of the graphic will not affect the physics of the solution.
  8. If the steering wheel is steering in the correct direction (it is unclear in the screen shot), but the road wheels are steering in the wrong direction, then the coupler that defines the steering gear needs to have it's sign changed. This sign convention is usually sorted out when you review the animation from your front suspension K&C analysis. Edit: Upon reviewing the screen shot more closely, it's clear that your steering rack is in front of the wheel centerline. In the default model, the steering rack is positioned behind the rear wheels. This explains why your vehicle is steering in the opposite direction (assuming you did not update the steering coupler sign when you updated hardpoints).
  9. "Collision Detection" is a feature that's only available in post-processing. It allows you to visualize penetrations between different bodies in the mode, AFTER your simulation is completed. When you need to stop (or change) the model as a result of some condition in the model during run time, we use an entity called Sensors. I would encourage you to read up on Sensors in our help, as they are quite powerful, but there are a few things to learn. A simple way to implement a sensor in your case would be for the sensor to monitor the displacement between two bodies (which you would define via an expression). When the displacement reaches some threshold value, you tell the sensor to halt the simulation. Another possible way (I haven't personally tried this), would be to monitor the contact forces between two bodies, assuming you are using 3D contacts in the model. When the contact force is generated, use that to trigger the sensor.
  10. Under Tools -> CG/Inertia summary, MotionView can calculate the overall CG and moment of inertia of your model. It is typically calculated about the origin, but you can calculate it with respect to another reference frame if you need to.
  11. In the screenshot your model, the Altair driver has been included in the model, but no events have been added. You can right click on "Model" in the project browser, and "Add events", then add a Altair Driver File event. The allows you to point to a file that contains the details for the maneuver. The specific details for maneuvers in the Altair Driver are defined via an .adf file. This event allows you to point to your own .adf file which you can customize. You can also search our documentation on the features of the .adf file. Chris
  12. Hi- There are no existing tutorials for this workflow, since it's not a workflow that is common with most users. Usually, CAD is exported with all parts correctly positioned relative to each other. It is possible to relocate CAD once you've imported into MotionView, but it is a manual process, and must be repeated for each part. It will be rather tedious. One way is to define a reference Marker for each part (this also means you need to define a point to define the position of the reference Marker). Then you can change the reference marker for each CAD part from Global, to the new reference marker. Then, each reference marker can be individually positioned manually to re-position the CAD. Others may have better ideas, but this is a method I have used in the past, when I had no other options. Chris
  13. The CAD needs to be meshed to create a .fem file. Then you can use the Flexprep tool once you have created the .fem
  14. The static ride analysis contains user subroutines that rely on running a static analysis. You should run the static ride analysis as a static solution, not transient. If you can switch off all of the outputs that rely on user subroutines, you and probably get the analysis to run, but this really isn't the purpose of the static ride analysis event.
  15. Another quick observation on your model. The mass and inertia values of your model are all "zero". You will not get a valid solution to the basic equation F=m*a if all your "m" are zero. Kind regards, Chris
  16. Your frame graphic h3d is a graphic, not a flexbody. I would recommended initially running the model without a flexbody, to get things fully debugged. Then, create the flexbody and add it to the model. So, in short, uncheck the FlexBody (CMS) feature until you get a proper flexbody created to use with the model. Regards, Chris
  17. If you only changed hardpoints, without updating mass information, spring rates, and spring preload, etc, it's possible that your vehicle is not built in a way to expect reasonable initial conditions. Since the simulation is failing right at time t=0, this is the most logical explanation based on the info you have provided. A common practice is to build half-car models before building a full vehicle model. Then we run the half-car models through basic analysis like static ride, or Kinematics and compliance, to ensure the model is robust, and has the correct corner weights on the wheels, etc. Then, when we assemble the full vehicle model, there is a highly likelihood that the model will run successfully. Also, it is better to run more basic, open loop analysis before constant radius. I will usually run straight line acceleration as my first full vehicle event. Starting with simpler events also assists with debugging the initial model. Chris
  18. The .log file from the MotionSolve run will give you some indication if an .h3d file was created, and potentially why it wasn't written. Note, the MotionView model needs graphics created in the model in order for an h3d file to be written. Graphics can be CAD based, or can be based off of the standard, cylinder, sphere, box, beam sprindamper, etc., graphics. Note that the implicit graphics that are displayed in MotionView do not get used by MotionSolve at runtime. You may also try to debug your model first by running it without co-simulation. Chris
  19. Track width is determined by the location of the wheel centers. Change the location of the wheel center (in Y direction) and the track width will also change
  20. depending on how the coupler is defined, it's either: Rotation of steering input (in radians)/travel of steering rack (in mm) or travel of steering rack (in mm)/Rotation of steering input (in radians)
  21. In general, it's a better practice to apply your initial conditions to the Bodies, rather than the Joints. In the real (non virtual) world, F=m * a. The forces and accelerations act on the mass. The joints add constraints to the degrees of freedom to the bodies. Applying an initial displacement to a joint implies that you want an initial translation to occur immediately at time =0, because the joint is not initially in the desired location for the start of the simulation. Numerically, this can lead to problems achieving a robust solution. You can also apply a Motion to a Joint as a function of time if you need to move that joint to a particular position. This is a more reliable way to position the joint, as you are applying an enforced displacement. Chris
  22. Are you saying the model doesn't run when you change the joint from non-compliance to compliant? OR are you saying the BISTOP is active, but not creating any reaction forces. It's possible that the references you are using to define the BISTOP are removed when changing the JOINT type from non-compliant to compliant. It's also possible that the torsional rate of the bushing it too high to allow the BISTOP to function as expected, i.e. it's not rotation enough, due to the stiffness of the bushing. Investigating the .log file for any warnings when model behavior has changed, is always a good first step. Chris
  23. If you will look in our documentation, the is a very detailed explanation on the difference in normal force calculation. You can search for "MotionView Contact Best Practices", and that should give you the right location. To answer your question about which one to use....The answer is "use the one that works best for your specific problem" Sometimes I find that Impact works well for some kinds of problems. If I have trouble, say with either model robustness, or too large penetrations, then I will sometime look at the Volume method. Ultimately, the Volume method seems to be my personal favorite for more complex problems, but I have successfully used all three choices (Impact, Poisson, Volume).
  24. An advanced joint should work to define the mechanism, but I don't think you will get the correct stress (on the surface of the cam contact)
  25. You have to be very careful about how you set up an enforced motion on a problem like this. Using Marker Motion should work, but you have to take care to attach the marker at the correct location, so that you do not force the car off of the path at the motion progresses through the simulation.
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