Design of a model reference adaptive controller for vehicle road following

The design of a model reference adaptive controller (MRAC) for vehicle road following is discussed. There are many factors which make automatic lateral control of vehicles difficult. These include changing vehicle parameters, changing road conditions, as well as disturbances caused by wind and other factors. Traditional controllers have difficulty guaranteeing performance and stability over a wide range of parameter changes. Model reference adaptive controllers on the other hand, can guarantee both stability and performance over a wide range of slowly varying parameter changes as long as several conditions are met. Difficulties with model reference adaptive controllers (as well as other controllers) arise when saturation appears on the input or states. For vehicle applications, the steering angle is limited. Therefore, the adaptation gains for the MRAC designed in this paper were chosen so that the steering command remained reasonable, even during adaptation. We finally show that there is a tradeoff regarding input amplitude and input frequency during adaptation.