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New customer-driven features in Vehicle Dynamics Library

John Griffin January 8, 2016

If vehicle dynamics or motorsports is the name of your game, then you may want to have a look at the some of the new features added in Vehicle Dynamics Library.

New features in Vehicle Dynamics Library continue to be added based on customer-driven requirements.  As the main developer for Vehicle Dynamics Library , I am pleased to introduce some of the newest features to you.

Cornering ground model

A new cornering ground model has been added which allows modification of the ground surface position, orientation and curvature based on input signals.


Figure 1. An example of an open-wheel racecar on a highly banked track. The banking and normal curvature and lateral curvature can either be determined by laser scanning or survey data.


This ground model can be used in quasi-steady state simulations to evaluate chassis states at a particular straight line or cornering condition. The chassis velocity and curvature result in lateral, longitudinal and vertical accelerations being applied to the vehicle.

The approach of using the chassis velocity and the ground curvatures to apply accelerations to the chassis is a novel concept.  Typically, in this type of simulation, the accelerations are applied either as a global force or by modifying the gravity vector.  The major benefit of using track geometry data is that this data can be measured directly using either laser scanning or survey data.

This ground model is particularly useful in motorsports applications to evaluate chassis states at different points on the race track.

Check out the new examples using the Cornering ground in

Examples.QuasiSteadyState and Examples.QuasiSteadyState.BankedCornering


OpenCRG® ground

OpenCRG® provides open file formats and open source tools for the detailed description and evaluation of 3D road surfaces.  OpenCRG® data sets are designed to describe very detailed patches of road surfaces which are suitable for a broad range of applications including e.g. tire and driving simulations.


Figure 2. OpenCRG is designed to efficiently handle very detailed descriptions of road patches such as the Belgian Block Road pictured above.


Because OpenCRG® is designed to efficiently handle extremely detailed road patches, it can handle such large datasets as a Belgian Block roads (Fig. 2).  These road surfaces, when used in combination with frequency and amplitude dependent bushing and tires models, allow you to evaluate the noise, vibration and harshness (NVH) characteristics of your chassis.

With OpenCRG® ground model you can use both binary and textual OpenCRG® data files.

For additional information about OpenCRG® please visit opencrg.org.

New Mounted Ride Strut

While working on projects with our automotive OEM customers, it became clear that many of their suspension designs require the ride strut to be mounted with bushings to the chassis and suspension.

The most common configurations of these mounted ride struts have now been added to the Vehicle Dynamics Library, as a standard component.

The bushing components are replaceable, and one model has two sets of translational flanges, where one can be parameterized to attach either inside or outside the mount bushings.

This is useful when springs and dampers are co-located in the suspension but attached on different sides of the mount bushings.  The highly configurable design of these two strut models fulfill the requirements of most typical passenger car applications.


Figure 3. The new mounted strut model is configurable to allow the spring/damper to be attached either inside or outside the bushings.


Bushing Visualization

The bushing visualizer has been changed to make it easier to see the relative displacement that are occurring in the bushing (see Fig. 4).


Figure 4. The bushing visualizer makes it easier to see the relative displacement between frame_b (red cylinder) and frame_a (dark grey cylinder).


The visualizer also makes it easier to understand the axes related to the force {fx, fy, fz} and torque {tx,ty,tz} components.

This can be seen in the annotated image.

A planar contact calculation filtering method has been added as an additional option to the wheel contact calculation block.

The planar filtering method calculates a center frame and contact frame based on a plane on the ground surface. The plane is defined by four contact points/frames (see Fig. 5). The coordinates of the four contact points is configurable.


Figure 5 The four planar ground contacts (blue spheres) lay on the ground surface below the hub (green spheres)


By default a rectangular shape is used, whose length and width can be parameterized to be consistent with the contact patch of the tire. Alternatively, other shapes, such as a diamond, can be used with two points of the diamond which lay on the wheel center plane.

This method is best suited for grounds with significant variation in height and road normal, such as with the Belgian Block or any high-definition road surface.

New Pitman-Idler Steering Model

A new pitman-idler steering model (Fig. 6) has been introduced in Vehicle Dynamics Library.


Figure 6 New pitman-idler steering model, often called a parallelogram steering linkage.


The pitman-idler steering linkage is often called the parallelogram steering linkage because the two sides of the linkage run parallel to each other and are typically equal length.  This type of steering linkage uses a center link, an idler arm on the passenger side, and a pitman arm on the driver side. The pitman arm attaches to the output shaft of the steering gear and is moved by turning the steering wheel.  The pitman arm attaches to the center link, which transfers the movement from the pitman arm to the idler arm on the passenger side. The tie rods are attached to the center link and transfer steering motion to the steering arms on the upright.

This model has been used extensively in NASCAR and military applications and is now included as another steering model option.

I hope that the newly added models will be useful for your applications and I would be glad to get your feedback.  Please do not hesitate to contact me to discuss new applications, desired features, or problems you encounter in your vehicle dynamics work!

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