Modern automotive speed control systems are designed to provide smooth throttle movement, zero steady state speed error, good speed tracking over varying road slopes, and robustness to system varia-tions and operating conditions. Additionally, there is a need to minimize the number of controller calibrations for different vehicle applications. All of the above objectives cannot be simultaneously met by conven-tional fixed gain controllers which need different calibrations for differ-ent vehicle lines. With such requirements, an adaptive controller offers benefits over a conventional controller provided its complexity does not significantly exceed that of a conventional controller. To limit the controller complexity, the adaptive design in this study is based on sensitivity analysis and slow adaptation using gradient meth-ods. This design method allows the use of our a priori knowledge about the plant model in order to determine a stability region for a reduced or-der adaptive controller, in this case a simple PI controller. The adaptive algorithm, driven by the vehicle response to road load torque distur-bances, tunes a PI controller to continuously minimize a single perfor-mance based cost functional for each different vehicle over varying road terrain. This results in performance not possible with a fixed gain con-troller. The adaptive controller has been tested on a number of vehicles with excellent results, some of which are presented here.
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