Abstract-We consider the use of dynamic output feedback control to improve the transient response to a step input, for invertible multivariable systems. A method is given for designing a linear time-invariant output feedback controller to asymptotically track a constant step reference with zero overshoot and arbitrarily small rise time, under some mild assumptions.
I. INTRODUCTIONThe problem of designing control laws to ensure a linear time invariant (LTI) plant has desirable transient response to a step input has been studied for the past few decades. The primary performance objectives include achieving a small rise time while also minimising overshoot.Some recent papers have considered the problem of designing a suitable closed-loop feedback controller to achieve a non-overshooting response. For continuous time singleinput single-output (SISO) systems, in [1] an eigenstructure assignment method is given to obtain a non-overshooting LTI state feedback controller for plants with one non-minimum phase zero. Stable non-minimum phase SISO systems are considered in [2], where the existence of an output feedback controller is proved to give a non-overshooting step response, provided the plant has no zeros on the imaginary axis. In [3] it is shown how to give two parameter feedback controller for an LTI plant that renders the step response nonovershooting. A common feature of these recent papers [1]- [3] was that they considered only SISO systems, which were assumed to be initially at rest. In some cases the transient response was deliberately slowed to avoid overshoot, which necessarily yielded a lengthy settling time. In [4], the authors used a composite nonlinear (CNF) state-feedback controller consisting of a linear term chosen to yield a rapid response, and a nonlinear component designed to reduce overshoot. A smooth nonlinear error function is employed to tune the closed-loop dynamics. The authors showed their state feedback controller could also be implemented in conjunction with an observer scheme. However, their CNF scheme did not guarantee the step response will be non-overshooting.In our recent paper [6], the present authors considered invertible stabilisable MIMO systems, and used linear statefeedback control to design a non-overshooting controller for a step reference. The design methods proposed there make use of the combined eigenvalue and eigenvector placement