Validation of a Single Contact Point Tire Model Based on the Transient Pacejka Model in the Open-Source Dynamics Software ProjectChrono

A single contact point model was implemented in the open-source dynamics engine Chrono to provide a more accurate calculation of input slip quantities to the Magic Formula equations for non steady-state, or transient, slip cases. The model is formulated using a consistent ISO z-up x-forward coordinate frame, where the slip angle was shown to be invariant with the choice of coordinate system, but the lateral force was curve not. Similar to a previous tech report by the author, the results of the model are validated against a commercially available Pac2002 model in Adams/Car. Pure lateral slip and combined lateral/longitudinal slip cases were tested, with slip ranges of κ = ±1.0, and α = ±15 degrees, with no camber or spin slip. Simulation were performed in 8 seconds, using a fixed integration step size of 0.01 seconds. It was shown that the single contact point model with the Magic Formula equations implemented in ChronoT gives accurate output for a single tire under pure and combined slip operating conditions when compared to a model in the commercial package ADAMS/Car. Reaction longitudinal and lateral forces, as well as aligning moment curves as a function of input slip rate matched nearly exactly in all cases. Even an extremely transient maneuver, a powered lane change that transitions from 100% skid to 100% longitudinal slip, showed excellent agreement between the plots of the highly non-linear aligning moment as a function of lateral slip angle.