2018 |
Gyunghoon Park / Hyungbo Shim / Youngjun Joo Recovering Nominal Tracking Performance in an Asymptotic Sense for Uncertain Linear Systems Journal Article In: SIAM Journal on Control and Optimization, vol. 56, no. 2, pp. 700-722, 2018. Abstract | Links | BibTeX | Tags: Disturbance observer, Internal model principle, Nominal performance recovery, Robustness @article{ParkShimJoo18, In this paper, we consider the problem of recovering a (predefined) nominal output trajectory in the presence of model uncertainty and external disturbance. In particular, whereas the nominal performance recovery (NPR) has been studied in an approximate fashion in the literature, we extend the notion of the NPR in an asymptotic sense from the perspective of the internal model principle: that is, as long as the disturbance and reference signals are generated by an exogenous system, the actual output not only is kept close to the nominal trajectory as much as desired but also asymptotically converges to the nominal one as time elapses. It is shown via the singular perturbation theory that the asymptotic NPR can be achieved for uncertain minimum-phase systems under arbitrarily large (but bounded) model uncertainty. A disturbance observer (DOB) approach is employed in the controller design, with the internal model embedded into the so-called Q-filter, which is a key component of the DOB. Simulation results for mechanical positioning systems illustrate that the asymptotic NPR can enhance robust performance of control systems. |
Gyunghoon Park / Hyungjong Kim Adaptive Regulation to Nominal Response for Uncertain Mechanical Systems and Its Application to Optical Disk Drive Journal Article In: IEEE Transactions on Industrial Electronics, vol. 65, no. 2, pp. 1450-1458, 2018. Abstract | Links | BibTeX | Tags: Frequency estimation, Mechanical system, Nominal performance recovery, Robustness @article{ParkKim18, In this paper, we present an add-on type robust controller for uncertain mechanical systems with a sinusoidal disturbance of an unknown frequency. The main purpose is to recover (predefined) nominal tracking performance in an “asymptotic” sense, that is, the actual output asymptotically converges to the nominal trajectory, as well as the maximum difference between them is maintained small enough during the operation. As a key component of the proposed controller, a disturbance observer that contains an internal model is proposed. Especially, the parameters of the internal model are updated in an “adaptive” fashion in order to cope with the unknown frequency of the disturbance, for which a frequency identifier is employed in the controller design. The nominal performance recovery of the proposed controller is analyzed in the sense of Lyapunov and singular perturbation theory. Both simulation and experimental results point out that the proposed control scheme can serve as a robust track following controller for uncertain optical disk drive systems where eccentricity of disk causes a sinusoidal disturbance. |
List of English Publication
2018 |
Recovering Nominal Tracking Performance in an Asymptotic Sense for Uncertain Linear Systems Journal Article In: SIAM Journal on Control and Optimization, vol. 56, no. 2, pp. 700-722, 2018. |
Adaptive Regulation to Nominal Response for Uncertain Mechanical Systems and Its Application to Optical Disk Drive Journal Article In: IEEE Transactions on Industrial Electronics, vol. 65, no. 2, pp. 1450-1458, 2018. |