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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 pathtracking controllers for this vehicle are designed by viewing the mathematical model of the vehicle as the system of equationṡ x = 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.Index Terms-Active wheel, autonomous corner module, disturbance observer (DOB), electric corner module, four-wheel steering four-wheel drive (4WS4WD), input-to-state stability (ISS), path-tracking control (PTC). 1063-6536

Permanent magnet dc motors are popular for the simplicity of their control. Exist a few methods of sensorless speed control (SSC) of these motors. Each of these methods has its limitations that restrict its wider applicability. One of these methods uses the sensing of applied armature voltage and armature current to obtain an estimate of the motor speed, and then uses this estimate for the feedback control of the motor speed. In the microcontroller-based control of a PMDC motor, or a dc motor with separate fixed excitation, driven by a switchmode dc-dc converter, the converter may have a nonlinear inputoutput characteristic that reduces the tracking accuracy of this method. This paper presents a way to obtain a compensator of this characteristic automatically, and to thus improve the performance of the method.

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