Modelling and control for high-sideslip vehicles on nonplanar roads

To extend vehicle handling limits under aggressive manoeuvres, this study investigates high-sideslip control on nonplanar roads, where terrain-induced load variations substantially affect stability but are often neglected in planar-road formulations. To address this issue, a nonplanar vehicle dynamics model is developed using a curved-ribbon road description and a first-order approximation of suspension-mediated vertical load dynamics, improving vertical-load accuracy by up to 35% compared with rigid-contact modelling in bump-road tests. Based on this model, a time-optimal planner and an optimisation-based tracking controller are designed to exploit near-limit capability while maintaining robustness to load changes. A hardware-in-the-loop (HIL) platform is constructed to evaluate the framework. Results show that, on undulating roads, the proposed approach increases achievable cornering speed by 1.3–2.5 m/s, reduces peak lateral tracking error by 0.4–0.7 m, and prevents wheel lift-off observed with planar-model controllers. The added computational burden remains moderate, with average solver time increasing by only 2.8 ms. These findings confirm that incorporating nonplanar effects is crucial for reliable high-sideslip control and demonstrate the practical feasibility of the proposed framework for near-limit autonomous manoeuvring.