The work described is motivated by a desire to construct a perfect virtual racing driver, which will be capable of exploiting the full capacity of a racing car. The strategy used depends on the adaptive employment of linear-optimal-preview controls. Prior research has shown how such controls can be found and applied, when only small perturbations from a trim state are involved and the linear control design is based on the relevant trim state. Here, the previous work is extended by the generation of optimal control sets for a full range of cornering effort, as a way of accommodating the saturating nonlinearity of the tyre lateral forces. Optimal control sets vary in a systematic and interesting manner as the tyres work harder. The variations and their interpretation have been discussed. The path-tracking frequency response properties of selected driver-controlled cars have been calculated and also discussed. Tracking of three challenging paths at a fixed, high speed by a car and driver with controls based on straight-running only and with an adaptive, gain-scheduling driver have been simulated, with parametrisation of the running condition of the car by front-axle-lateral-slip level. Controls for trim states which are very close together have been utilised. To maintain system stability, rate limiting on the steering wheel motion has been found necessary. With rate limiting sufficient for stability but not interfering with required control inputs, gain-switching noise observable in the results is very small. An obvious alternative to discrete gain changing is to use interpolation, which would allow a coarser grid of stored gains to be employed. Excellent path tracking of the adaptive system has been demonstrated, under circumstances for which the fixed-gain controls are inadequate. Remaining tasks include application of the adaptive controls to variable speed conditions, including limit braking and accelerating, application of the methods to more elaborate vehicles and the inclusion of learning control, so that the driver's speed ambition can be properly related to the tyre-force utilisation observed.


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    Title :

    Car driving at the limit by adaptive linear optimal preview control


    Additional title:

    Fahren am Limit mit Hilfe adaptiver linear-optimaler Preview-Regelung


    Contributors:

    Published in:

    Vehicle System Dynamics ; 47 , 12 ; 1535-1550


    Publication date :

    2009


    Size :

    16 Seiten, 14 Bilder, 2 Tabellen, 42 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English





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