The sensitivity of nominally time-optimal control systems to parameter variation

The effect of plant parameter variations on systems with nominally time-optimal feedback controllers is investigated. It is assumed that the plant parameter remains constant and that the time-optimal controller calculated for the nominal plant parameter is used. For higher-order systems remarkably small deviations of the plant parameter from its nominal value are found to yield instability. A sub-optimal controller design which results in sliding motion ensures stability and yields acceptable settling time for moderato parameter variations