On Optimal Tire Usage in the Path-Tracking Control of Four-Wheel Independent Steering Four-Wheel Independent Drive Electric Vehicles

Four-wheel independent steering four-wheel independent drive electric vehicles have an independent steering motor and an independent driving motor for each wheel, for a total of eight motors. About 28 works in this emerging field have shown path-tracking control algorithms for these vehicles, 18 of them explicitly or implicitly aspire for a condition known as optimal tire usage. This article first defines this optimality condition and explains its significance. Second, this article identifies three indicators of tire usage that aid in assessing the existing algorithms. Third, this article performs block diagram examination of four of the 18 works, revealing significant commonalities across the 28 works and identifying areas for improvement in three of the four algorithms. Lastly, this article suggests motor control systems to fill these gaps. Furthermore, it employs these motor control systems in one of the four algorithms, and illustrates path-tracking and achievement of the optimality condition in simulation. This shows that the motor control systems are sufficient (in simulation) to meet the optimality condition in one work. They are likely sufficient for all path-tracking algorithms employing appropriate control allocation to achieve the optimality condition.