We define feedforward control as a control policy in which the exoge-nous disturbances are known for all time at the moment when the control is applied. It is shown that disturbance decoupling by feedforward control is possible iff it is possible by PID control or iff approximate disturbance de-coupling by state feedback is possible.
The following problem was presented during the open problem session. Its title is taken from a well-known seminal paper  by R.E. Kalman. The questions posed in  and here are similar in spirit, but the setting is quite different.
Computational complexity results are obtained for decentralized discrete-event system problems. These results generalize the earlier work of Tsitsiklis, who showed that for centralized supervisory control problems (under partial observation), solution existence is decidable in polynomial time for a special type of problem but becomes computationally… (More)
—The problem discussed is that of designing a controller for a linear system that renders a quadratic functional nonnegative. Our formulation and solution of this problem is completely representation-free. The system dynamics are specified by a differential behavior, and the performance is specified through a quadratic differential form. We view control as… (More)
It is shown that foi linear dynamical systems with quadratic supply rates, a storage function can always be written as a quadratic function of the state of an associated linear dynamical system. This dynamical system is obtained by combining the dynamics of the original system with the dynamics of the supply rate. @ 1997 Elsevier Science B.V.