Modelling of Articulated Heavy Vehicles for Computation of Accurate Safe Operating Envelope for Yaw Stability

Other conference contribution, 2023

As articulated heavy vehicles switch to electric power, new ways of allocating wheel forces have emerged. To improve energy efficiency, it is increasingly common to use propulsion or regenerative braking on only one unit of the vehicle combination. This leads to yaw stability problems, mainly jackknifing if the towing unit has excessive wheel forces, or trailer swing if the trailing unit has excessive wheel forces. Hence, it becomes important to allocate the total force request into different units and actuators in a safe way.

This paper formulates a nonlinear two-track model with a nonlinear tire model, combined slip, and roll degree of freedom. Thus, the presented model can accurately simulate brake-in-turn and propel-in-turn maneuvers at high lateral accelerations. And it can be used to study when the yaw instability occurs and understand if the maneuver is safe or not.

One way to ensure safe control allocation is by implementing a safe operating envelope that restricts the allocation within predefined limits. This helps maintain control of the system and prevent any potential safety hazards. In this paper, a nonlinear two-track model is utilized to simulate a range of lateral accelerations and various combinations of braking forces between the tractor and semitrailer. Through this process, an envelope is obtained which is then compared to an envelope generated from a single-track model and validated against high-fidelity model-based envelopes. This rigorous process helps to ensure the accuracy and reliability of the two-track model.