"Single Wheel" longitudinal traction control for electric vehicles

The traction control is a tool to increase stability and safety and it has a greater performance potential in electrical vehicles (EVs) than in internal combustions vehicles. Moreover, the traction control allows the EV to operate more efficiently preventing slippage in acceleration and permitting the use of use high-efficiency low-drag tires. The presented approach can compete with the well-recognized techniques, but it offers a lighter tuning procedure. This paper presents an approach to the longitudinal control of a single wheel adopting a configuration based on an adherence estimator and a controller of the adherence gradient. Two adherence gradient controllers are examined in the paper: a fuzzy controller and a sliding mode controller. In both cases, the presented approach allows for tracking a value of the adherence derivative in a wide operating range without any knowledge of the road conditions. The work is based on numerical simulations as well as experimental tests. The test bench computes in real-time the vehicle dynamic and loads accordingly, the drive under test. Both controllers were experimentally verified showing good behavior and good response to a sudden change in the road characteristics, whereas the best overall performance was recorded with the sliding mode control