A Look Inside VeSyMA’s Quarter Car Models

Our VeSyMA suite of libraries includes amongst half and full car models, also quarter car models for simulating vehicle suspensions. Depending on the purpose and detail required, these may be from the VeSyMA, VeSyMA-Suspensions or VeSyMA- Motorsports libraries. In this blog post I’m going to take a look around the quarter car models in these Claytex libraries.

Quarter Car Construction

A cornerstone of the entire VeSyMA suite of libraries is compatibility and reusability of models, ensuring all our libraries work together and minimising associated effort. We do this by utilising the model inheritance concept; if you’re new to this idea take a look at this post first. But in short this means:

  1. We have quarter car interfaces defining fundamental parameters and connections which are common to all models.
  2. We extend the interfaces to create templates defining a fundamental structure of the various linkage arrangements.
  3. We then populate the template with the chosen subcomponents, connections and data to produce a complete example.

The video below takes you on a tour of the quarter car models within the VeSyMA, VeSyMA-Suspensions and VeSyMA-Motorsports libraries.

Video 1 – Tour of quarter car modelling in the VeSyMA suite of libraries

Quarter Car Model Fidelity

While all the linkage examples in our libraries derive from the same base interface, the fidelity of the models varies depending on the purpose and the amount of data available.

VeSyMA’s rigid quarter car example with its minimal components and data required, supports longitudinal tests where the vehicle dynamics are unimportant, such as drive cycle tests.

VeSyMA rigid front quarter car example
Figure 1 – VeSyMA rigid front quarter car example

But when the vehicle dynamics are important, the quarter car model should contain components representative of the physical linkage, like the VeSyMA-Suspensions multibody double wishbone example below.

VeSyMA-Suspensions front double wishbone example
Figure 2 – VeSyMA-Suspensions front double wishbone example

The replaceable components in the templates in VeSyMA-Suspensions and VeSyMA-Motorsports allow the fidelity of the model to be easily increased in a plug-and-play style as more detail and data is available during development. A few examples include:

  • Dampers changed from a simple coefficient based component to a detailed hydraulic example.
  • Wishbones and links can be changed to include setup adjustments for motorsport.
  • Ideal joints can be exchanged for bushed joints.
  • Rigid mountings can be replaced for compliant mountings.

A basic multibody model like the double wishbone example above requires the following data for accurate representation of the physical system:

  • Geometry of the hardpoints
  • Spring, damper and bumpstop characteristics
  • Mass and inertia properties of the components

These values may come from CAD or measurements, depending where you are in the development process. As the complexity of the model increases, so does the data required to make it truly representative.

However if you lack the details of the quarter car components, but do know the kinematic relationship between the vehicle and hub, you could use the table based model available in VeSyMA-Suspensions.

Testing and Validation

The beauty of component orientated modelling is the fact you can test and validate individual components of your system before putting them all together. So you can identify issues early, and have confidence the bigger system models will behave as expected. With this in mind our libraries contain experiments to test your models at every level and point of the vehicle model development.

VeSyMA-Suspensions features quarter car experiments for:

  • Kinematic tests with and without the wheel fitted, as shown beneath
  • Spring-Damper strut tests
  • Bush tuning tests
Video 2 – Kinematic test of the VeSyMA-Suspension double wishbone example (front right vehicle corner)

That’s All Folks

I hope this quick tour of the quarter car modelling in the VeSyMA suite of libraries has given you a feel for the options available. Please contact us if you need support to develop special linkage arrangements not in the libraries. We also provide training to advance simulation capability with Dymola and also our libraries.

Written by: Hannah Hammond-Scott – Modelica Project Leader

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