STABILITY BOUNDARIES FOR SYSTEMS WITH CONTROL CONSTRAINTS.

Although unstable systems can be stablized using feedback control, constraints on the rates and magnitudes of control variables limit the region of stability. Stability boundaries must be evaluated during control system design to assure satisfactory system performance. This analysis becomes more relevant where compromises between the degree of plant instability and upper limits on the rates and magnitudes of control variables have to be made. A recent literature survey indicates that the problem of saturation nonlinearities in the control loops of unstable system remains to be solved. Frequency-domain and singular-value methods developed to date either are not applicable or are unduly conservative, and application of variable-structure control addresses different issues. Using a linear-quadratic (LQ) controller with dominant control weighting in the cost function, the saturation and stability boundaries have been shown to be parallel. This paper presents the stability boundaries without restriction to the LQ control law. Only abstract is given.