Optimal tire force allocation for trajectory tracking with an over-actuated vehicle

As more actuators are implemented, vehicles are becoming over-actuated and obtaining more authority to control individual tire forces. This paper presents a method that utilizes this abundant actuating capability to allocate tire forces optimally with a convex optimization formulation. The basic objective of this optimal allocation is to keep the usage of total tire friction capability equal over the four wheels. Achieving this goal has the advantage of preventing some tires from reaching saturation before other tires do. This algorithm for optimal tire force allocation can be combined with trajectory tracking near the limits of handling to follow the desired speed, heading, and lateral position of a vehicle. Experimental results demonstrate the performance of the method for successful tracking of all three desired trajectory states simultaneously while achieving equal friction usage among the tires.