Path-Tracking Control of an Autonomous 4WS4WD Electric Vehicle Using Its Natural Feedback Loops

Abstract

A four-wheel steering four-wheel drive electric vehicle has a steering motor and a driving motor for each wheel, for a total of eight motors. Almost all of the existing path-tracking controllers for this vehicle are designed by viewing the mathematical model of the vehicle as the system of equations ẋ = f(x,u), y = h(x,u), and are mathematically sophisticated. In contrast, this brief presents a block diagrammatic representation of the model, and exploits the natural feedback loops revealed through this representation to develop two novel and useful results: 1) a mathematically simpler path-tracking controller that promises to be easier to tune and 2) a constraint on the wheel accelerations that helps constrain the wheel slips to a desired value. Simulations illustrate this solution.