Design of feedback controllers by two-stage methods

When the eigenvalues of linear, time-invariant discrete systems are widely separated in absolute value, it is shown that the design of state or output feedback controllers can be best approached by two-stage methods. In these methods, the feedback gain matrices are computed by separately placing slow and fast eigenvalues at desired locations. Applications to the problem of independently controlling the speed and torque of petrol engine/dynamometer test rig have demonstrated the potential of the two-stage feedback design methods.