This paper proposes a redesign procedure for linear systems. We suppos
e that an initial satisfactory controller which yields the desired per
formance is given. Then both the plant and the controller are redesign
ed to minimize the required active control effort. Either the closed-l
oop system matrix or the closed-loop covariance matrix of the initial
design can be preserved under she redesign. Convex quadratic programmi
ng solves this problem. In addition, an iterative approach for integra
ted plant and controller design is proposed which uses the above optim
al plant/controller redesign in each iterative step. The algorithm has
guaranteed convergence and provides a sequence of designs with monoto
nically decreasing active control effort. Examples are included to ill
ustrate the procedure.