Research Papers

Loss of Optimal Performance of the Finite-Horizon Continuous-Time Linear-Quadratic Controller Driven by a Reduced-Order Observer

[+] Author and Article Information
Verica Radisavljevic-Gajic

Department of Mechanical Engineering,
Villanova University,
800 E. Lancaster Avenue,
Villanova, PA 19085
e-mail: verica.gajic@villanova.edu

Milos Milanovic

Department of Mechanical Engineering,
Villanova University,
800 E. Lancaster Avenue,
Villanova, PA 19085
e-mail: mmilano5@villanova.edu

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received August 20, 2017; final manuscript received November 16, 2017; published online December 22, 2017. Assoc. Editor: Yunjun Xu.

J. Dyn. Sys., Meas., Control 140(6), 061014 (Dec 22, 2017) (8 pages) Paper No: DS-17-1418; doi: 10.1115/1.4038654 History: Received August 20, 2017; Revised November 16, 2017

In this paper, we derive an expression for the loss of optimal performance (compared to the corresponding linear-quadratic optimal performance with the instantaneous full-state feedback) when the continuous-time finite-horizon linear-quadratic optimal controller uses the estimates of the state variables obtained via a reduced-order observer. It was shown that the loss of optimal performance value can be found by solving the differential Lyapunov equation whose dimensions are equal to dimensions of the reduced-order observer. A proton exchange membrane fuel cell example is included to demonstrate the loss of optimal performance as a function of the final time. It can be seen from the simulation results that the loss of optimal performance value can be very large. The loss of optimal performance value can be drastically reduced by using the proposed least-square formulas for the choice of the reduced-order observer initial conditions.

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