PreonLab 6.2 introduced the Full Car Suspension Model (FCSM), significantly enhancing the capabilities of the previous Car Suspension Model (CSM). FCSM accounts for more precise suspension behavior and enables more accurate and realistic simulations across a broader range of vehicle wading scenarios.
In this article, we explore how FCSM works, the new simulation possibilities it has already unlocked, and offer an outlook on what future updates may bring.
Suspension systems are among the most carefully engineered components in a car. They connect the vehicle’s body to its wheels, are essential for stability and steering, and absorb shocks and vibrations. The entire driving characteristic and handling of a car, whether it is comfort-oriented or sportive, is to a large degree determined by the suspension system and the vehicles mass distribution. By absorbing shocks and vibrations from road irregularities, suspension systems provide a smoother ride for passengers by isolating the vehicle body from harsh impacts.
Realistic suspension behavior is crucial in virtual prototyping and simulation-driven design, as it directly impacts the accuracy and reliability of simulation results. Unrealistic modeling can lead to incorrect predictions of the vehicle’s behavior under real-world conditions.
Video 1: Water Wading Video Simulation in PreonLab 6.2 using the Full Car Suspension Model (FCSM).
In the context of water wading simulations, accurate suspension is indispensable to consider the impact of hydrodynamic forces acting on the submerged vehicle, to determine exactly which vehicle components and surfaces come into contact with water, and how high water climbs into critical areas. This helps engineers undertake measures to improve design to reduce unwanted wetting in the early development stages, without costly physical prototypes. Video 1 showcases a classic water wading simulation performed using the Full Car Suspension Model (FCSM). The simulation is rendered in PreonLab and features both a volumetric material rendering of the fluid and a particle-based representation. The fluid particles are color-mapped by velocity, with red indicating minimum velocity and blue indicating maximum velocity.
When it comes to water wading simulations, there is an ever-increasing demand for solutions that enable the simulation of scenarios involving higher velocities, complex channel geometries, and intricate vehicle dynamics. With this in mind, we decided to upgrade our previous Car Suspension Model (CSM) to the comprehensive new Full Car Suspension Model (FCSM) with PreonLab 6.2.
FCSM in PreonLab is based on the work of Jazar et al. [1]. Unlike CSM, FCSM simulates the suspension unit at each of the four corners separately and considers inertial forces of the car, allowing for a more accurate representation of a shift of the center of gravity and predicting pitch and roll angles, due to hydrodynamic forces, as well as bumps and slope changes in the road. Additionally, the deformation of tires is modeled with springs, enhancing the simulation of their interaction with the road by allowing small detachments, introducing the possibility of performing simulations with aquaplaning.
In the background, the model forms a 7-DOF system of 7 differential equations to obtain the vertical displacements of all 4 wheels and the sprung mass, as well as the pitch and roll angles of the sprung mass.
This allows the movements shown in Video 2:
Video 2: 7 degrees of freedom supported in FCSM - Deflection per wheel, deflection of the sprung mass, rotation about the pitch axis, and rotation about the roll axis.
FCSM is a built-in feature in PreonLab, and this integration streamlines the setup and reduces manual overhead by eliminating the need for external scripting.
All relevant parameters for vehicle motion can be defined directly within the FCSM object in PreonLab. These include masses for the sprung mass and wheels, moments of inertia for the sprung mass, spring and damper characteristics, and the vehicle’s trajectory profile.
Currently, with PreonLab 6.2, two types of inputs are supported to define the vehicle’s trajectory:
In this mode, the vehicle follows a specified velocity profile exactly.
This is ideal when the trajectory is derived from physical measurements at a test bench or from real-world data.
This mode considers external forces such as road gradient forces and fluid resistance in addition to user-defined acceleration. It is useful when users want to consider the impact of these external forces on the vehicle trajectory during simulation. The input acceleration can be interpreted as the acceleration by the drivetrain on a flat, dry road. A starting speed can also be specified.
Videos 3, 4, and 5, and Figures 1 and 2 illustrate how different input modes affect vehicle behavior. A summary of the three simulated cases is provided in Table 1. The videos show the simulation results, while Figure 1 shows the resulting velocity profile for each case. The curve for case 3 strictly follows the input velocity, while the curves for case 1 and case 2 show the impact of the fluid forces and the road gradient on the resulting velocity profile. Figure 2 depicts the wheel deflection for the front left wheel of the vehicle, for each of the three cases.
Table 1: Three cases with varying input profiles for the vehicle trajectory that have been simulated and shown in Videos 3, 4, and 5.
Video 3: Results of the simulation performed for Case 1 i.e. using acceleration-based input for the vehicle’s trajectory.
Video 4: Results of the simulation performed for Case 2 i.e. using acceleration-based input with a starting speed of 1 m/s for the vehicle’s trajectory.
Video 5: Results of the simulation performed for Case 3 i.e. using speed-based input for the vehicle’s trajectory.
In addition to conventional water wading scenarios, FCSM enables the simulation of scenes that include deflections due to acceleration and deceleration, slope changes, road banking, snow interaction, interaction with potholes and speed bumps, as well as high vehicle velocities. Videos 6 to 8 visualize these different aspects:
Video 6: FCSM in action: Video showing deflections and rotations due to acceleration, slope change, and road banking.
Video 7: FCSM in action: Video showing deflections and rotations as a result of the vehicle’s interaction with a pile of snow, and as the vehicle interacts with potholes and speed bumps.
Video 8: FCSM in action: Video showing a fast water wading simulation where the vehicle travels at 80 km/h along, with a plot of the resulting wheel deflections.
The new Full Car Suspension Model (FCSM) in PreonLab takes the existing Car Suspension Model (CSM) to the next level! FCSM computes deflection forces for each individual wheel, taking into account not only fluid forces but also acceleration, deceleration, and weight transfer. This advanced upgrade enables more realistic and precise simulations for automotive scenarios such as fast water wading and driving on uneven terrain, including slope transitions and road banking, situations where independent wheel movement is essential.
While FCSM already improves the accuracy and performance of vehicle wading simulations, we’re not stopping here!
Our team is actively working on further enhancements. Currently, FCSM supports vehicle rotation around the roll and pitch axes. Yaw effects, which are crucial for simulating cornering or cross-stream driving, are not yet included, but are planned for future updates.
Another exciting feature already possible with FCSM is the detection of wheel lift-off, which paves the way toward realistic aquaplaning simulations. Additionally, there’s growing interest in simulating floating behavior, especially for amphibious vehicles, and there might be some updates in this direction, too.
As you can tell, there’s a lot in the pipeline!
Get in touch with us here to learn more or request a demo from our team.
Alexander Mayer, Maximillian Ferdinand Flamm – Application Engineering, FIFTY2 Technology GmbH
Gayatri Čaklović, Oussama Taoufik – PreonLab Development, FIFTY2 Technology GmbH