From Theoretical Analysis to Application

From a vehicle dynamics point of view, the powerslide is a very interesting motion of the vehicle. The powerslide may be used to evaluate driver skills, the functionality of control systems, and the nature of the tyre with respect to its limit behaviour.

The steady-state powerslide motion is unstable and dominated by the nonlinear region of the tyre characteristics at the limits of vehicle handling. Initiation and stabilisation of the manoeuvre is usually a challenge for a human driver as tyre forces at the rear axle are typically saturated. The wheel spin of the rear wheels is used to control the lateral force of the rear tyres, and in this way, the yaw motion of the vehicle is controlled. Using actuators to stabilise the drift autonomously is a popular research topic, but it becomes even more complex if a human driver is involved.

The research unit has studied the powerslide equilibrium theoretically in detail, in particular its nonlinear stability behaviour based on bifurcation analysis, the dynamic behaviour after loss of stability, aspects of controllability and observability, and different ways to stabilise the motion.  This includes different actuators, such as steering or the drive torque at the rear axle for RWD vehicles, or shifting the torque between the front and the rear axle for AWD vehicles. The basic findings have been approved by testing on dry and wet asphalt, and on surfaces with ice or snow.

Figure 1: Regular cornering (small steering and side slip angles); powerslide motion (large side slip angle of the vehicle and front towards the outside of the corner)

A classical controller was implemented in the control unit of the battery-electric sports car and tested thoroughly with the driver in the loop. The driver does not have to stabilise the powerslide. In another project, an approach based on reinforcement learning was studied and tested experimentally to find out its robustness against different driver skills and driver influences and changing friction conditions.

Based on the achieved findings a drift-assist is developed and has been evaluated by different drivers.

Figure 2: Testing at different friction conditions

References

Edelmann, Johannes, Manfred Plöchl, Peter Lugner, Werner Mack, and Anton Falkner. "Investigations on the powerslide of automobiles., opens an external URL in a new window" In Proceedings of AVEC'08. 2008.

Edelmann, Johannes, and Manfred Plöchl. "Handling characteristics and stability of the steady-state powerslide motion of an automobile., opens an external URL in a new window" Regular and Chaotic Dynamics 14 (2009): 682-692.

Edelmann, Johannes, Manfred Plöchl, and Peter Pfeffer. Analysis of steady-state vehicle handling and driver behaviour at extreme driving conditions., opens an external URL in a new window na, 2011.

Edelmann, Johannes, and Manfred Plöchl. "Controllability of the powerslide motion of an automobile with different actuation inputs., opens an external URL in a new window" PAMM 16, no. 1 (2016): 803-804.

Edelmann, Johannes, and Manfred Plöchl. "Controllability of the powerslide motion of vehicles with different drive concepts., opens an external URL in a new window" Procedia engineering 199 (2017): 3266-3271.

Edelmann, Johannes, and Manfred Plöchl. "Analysis of controllability of automobiles at steady-state cornering considering different drive concepts., opens an external URL in a new window" In Dynamics of Vehicles on Roads and Tracks Vol 1, pp. 3-8. CRC Press, 2017.

Steindl, Alois, Johannes Edelmann, and Manfred Plöchl. "Limit cycles at oversteer vehicle., opens an external URL in a new window" Nonlinear Dynamics 99 (2020): 313-321.

Steindl, Alois, Johannes Edelmann, and Manfred Plöchl. "Hopf bifurcations for an oversteer vehicle–the influence of wheel load changes., opens an external URL in a new window" PAMM 21, no. 1 (2021): e202100179.

Steindl, Alois, Johannes Edelmann, and Manfred Plöchl. "Influence of Tyre Characteristics on Periodic Motions for an Understeering Vehicle., opens an external URL in a new window" PAMM 22, no. 1 (2023): e202200289.

Edelmann, J., Eberhart, M., Steindl, A., Plöchl, M. Post-critical behaviour of the powerslide motion. (to be submitted)

Eberhart, M., Edelmann, J., Unterreiner, M., Plöchl, M.  Investigation of the powerslide with variable torque distribution and stabilization shown in a driver assistance system. (to be submitted)

Researchers

• Manuel Eberhart
• Tobias Schuster
• Florian Jaumann

Project Partners

• Cariad
• Porsche AG