Robust critical control of uncertain systems using disturbance observers

This paper considers robust critical control of uncertain systems which require that tracking errors and control inputs are strictly maintained within pre-specified constant bounds. To achieve such critical control in the presence of unknown external disturbances, measurement noises and parameter variations of plants, the disturbance observer-based control is applied. A controller is designed as a 2-degree-of-freedom controller which consists of a servo compensator and a disturbance observer. Through a numerical example of servo control system design of the actively-controlled bed for ambulances, it is shown that, even if a measurement noise is fairly small relative to an output, it gives much influence on achievement of the critical control and so it is important to consider an effect of the noise in design explicitly.