Four wheels good: Vehicle model integration for dynamics and more

Four wheels good: Vehicle model integration for dynamics and more

Whether the goal is a faster lap time or a user-friendly ADAS function, Cruden has dynamics tool integration down to a fine art. CTO, Edwin de Vries explains in the second of our Tool Integration Series of articles.

Vehicle dynamics is where it all started for integrating engineering tools into Cruden’s driving simulators. Twenty years ago, our first simulators were used only for vehicle dynamics development, often with a motorsport focus. Cruden employed a proprietary vehicle model or a MATLAB Simulink one that interfaced with the Panthera simulator control software.

Nowadays, customers expect seamless integration with the vehicle models they use for chassis design and vehicle dynamics in other development environments. That might include software like Mechanical Simulation CarSim, IPG CarMaker or dSPACE ASM for automotive OEM projects, or tools like Simpack or Canopy in the racing world. Cruden is proud of its know-how in integrating these packages with its simulators. We’ll get to the ‘how’ a little later, but first, it’s worth noting that our original, in-house vehicle models live on in many applications.

For areas where detailed vehicle dynamic development is less important, such as human factors research or even motorsport driver training, the basic, proprietary model, which comes as standard with a Cruden simulator, is also sufficiently detailed, realistic and accurate. That model was originally built in C++ with 14 DOFs across the chassis and wheels. Some years ago, we separated it from our original simulator control software and wove it into the more modern Panthera Software Suite, in the same way that we would any other, third-party vehicle model. That in turn enables it to also function as a consistent and robust debugging tool, no matter which vehicle model a customer chooses to run.

One step up from that basic model is our Cruden Simulink Vehicle Model (CVSM), which also has a long history but remains a valuable tool for motorsport customers in series such as Formula 2, Formula 3 and endurance or sportscar racing. Its greater fidelity and tunability make it appropriate for race preparation and setup optimization work.

Simulink continues to play a role if a customer chooses to link the simulator to a third-party vehicle model. In vehicle models, as in all other areas of engineering tool integration, Cruden takes an agnostic position on third-party software via an open-interface approach. One way in which we make it easy to integrate external tools is by using Simulink as middleware. Simulink is a very common and accepted prototyping and development area for controls engineering and we’ve proven the concept over the last 10 years.

Third-party vehicle model suppliers always provide a Simulink interface, which removes the need for lengthy discussions and developments with them to resolve I/O issues. Instead, on the Cruden side, it’s a matter of compiling extensions – black box, coded blocks that establish UDP communication from the Simulink environment – and we’re good to go! Cruden engineers have become very skilled in this integration work, mapping the states and signals that we need for the most immersive, accurate and realistic driving simulator.

Another, more recently offered, route to integration is the Panthera SDK (software development kit). This consists of an API that a third party can work with in its own software to create a port to the Panthera driving simulator environment. As an example, Siemens recently used the SDK API to enable its Simcenter Amesim vehicle dynamics software to talk to the Cruden simulator software.

SDKs aren’t for everyone. A race team that uses a third-party vehicle model for its Cruden simulators likes the flexibility of the Simulink middleware, which enables it to make fast, transparent changes in an accessible environment. Manipulating the model in Simulink does not require coding skills or software compilation, so it’s relatively easy to – for example – insert a gain block to crank up the steering torque by a factor of two.

Other race teams, notably our Formula E customers, are choosing to implement the Canopy vehicle model. In recent years, Canopy’s setup optimization tool has become a popular choice in high-end motorsport. Now the vehicle model has been made available separately so that teams can use the same model on the simulator as they do for their optimization software. This provides value to the teams by removing any uncertainties in the transfer from the setup optimization tool into the driving simulator.

When it comes to integrating a vehicle model into a Cruden driving simulator for an automotive OEM, the same robust methods of Simulink middleware or the SDK are employed, but use of the Cruden Simulink Vehicle Model is less common. OEMs typically have large teams of specialists with years of experience in the likes of CarSim, CarMaker or ASM, so Cruden’s role is to ensure a familiar tool translates perfectly in the driver-in-the-loop (DIL) environment.

OEMs have long used our simulators to evaluate design decisions in an early stage of development, whether it’s a design engineer checking the latest changes or management feeling the difference as part of an approval process. But where once the focus might have been solely on the impact of a revised suspension component or tire design, nowadays the use of the simulator for HMI-related research and ADAS function development has increased.

Cruden’s current project for BMW is nearing completion. At the Munich simulator facility, BMW is taking the next step in OEM simulator use by bringing drivers from the general driving public into the simulator to evaluate early prototype designs or design decisions. These simulators must provide a non-technical ambience that feels as close as possible to stepping into a regular car.

Involving non-specialist drivers places high demands not just on the reliability and robustness of the vehicle model’s behaviour, but also on its versatility. The simulator should always drive like a real car, so it’s more important than ever to take care of even the smallest details when integrating the model into the simulator. Sometimes this might require changes to the vehicle or tire model, for example ensuring that the tires remain perfectly still when at rest, or that the effects of aligning torque don’t corrupt the steering feel when stationary. A driving simulator mimics the real world in all its dimensions, and Cruden’s engineers are experienced in revealing gaps in the model that may need filling.

Where the Cruden Simulink Vehicle Model is used, it supports tire models including Delft-Tyre and several versions of the Magic Formula. When a third-party vehicle model is being integrated into the simulator, the customer’s preferred tire model is often already inside the vehicle model, having been required for desktop simulations. Cruden plays an important role in recreating the outside world inside the simulator – the scenery, the route and the road surface, too, which makes it responsible for tire-road interaction. We use specific software to evaluate tire-road interaction, called SISTER (Server for Interactions with Surfaces and Ter-rains), which runs on triangulated road-surface meshes or a LIDAR scan. The local shape of the road is represented by the height of the road including a road normal that SISTER provides, information about surface friction and sometimes even the surface type. Nothing breaks the immersion like tire squeal on grass!

Cruden has an ongoing research project to further widen SISTER’s applicability but in the meantime, in the cases where an even finer level of surface detail is required than SISTER can provide, for example in a Formula 1 application, then it’s also possible to run the vehicle model directly on the LIDAR point cloud.

A final area of vehicle model integration is the emergence of a real-time version of the commonly used Adams multibody dynamics simulation software. In 2021, we highlighted the possibilities offered by this new tool by adding Adams Real Time to the demonstration simulator at our base in Amsterdam. This unified model approach enables an OEM to design its chassis in Adams as before, but then make a simple transition into an Adams Real Time model that can be run in the driving simulator without fear of translation errors or of fidelity being lost.

No matter which software package or supplier is involved, Cruden believes firmly in the benefits of third-party tool integration, which is a crucial step to maximizing the benefits of a DIL simulator. Our customers have proven that linking existing tools together delivers new capabilities and saves time and money in an engineering program.

Seamlessly integrated tools also deliver easy, operator-centric simulator operation. Cruden prides itself on a level of system integration that goes entirely unseen by the operator, who just needs to pick the environment, vehicle and time of day before starting the session – regardless of the fact that the vehicle model may be running on a separate PC. We think it’s a robust and elegant approach.

 

For more information, please contact Dennis Marcus via d.marcus@cruden.com or on +31 20 707 4646.

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Links to subsequent articles will be added below as they are published.

View all articles in our Tool Integration series of articles: here.

Article 1: Driving simulator and third-party engineering tool integration

Article 3: Hard decisions made easier: Hardware-in-the-Loop testing with DIL simulation

 

 

 

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