2016 |
Junsoo Kim / Chanhwa Lee / Hyungbo Shim / Yongsoon Eun / Jin Heon Seo Detection of Sensor Attack and Resilient State Estimation for Uniformly Observable Nonlinear Systems Proceedings Article In: Proc. of 2016 IEEE 55th Conference on Decision and Control, pp. 1297-1302, IEEE, Las Vegas, NV, USA, 2016. Abstract | Links | BibTeX | Tags: Control system synthesis @inproceedings{KimLeeShimEunSeo16, This paper presents an attack-resilient estimation scheme for uniformly observable nonlinear systems having redundant sensors when a subset of sensors is corrupted by adversaries. We first design an individual high-gain observer from each measurement output so that partial information of system state is obtained. Then, a nonlinear error correcting problem is formulated by collecting all the information from each partial observers and it can be solved by exploiting redundancy. For most of the time, a computationally efficient monitoring system is running and it detects every influential attacks. A simple switching logic explores another combination of output measurement to find a correct candidate only when a residual signal exceeds its threshold. |
Hyuntae Kim / Gyunghoon Park / Hyungbo Shim / Nam Hoon Jo Arbitrarily Large Gain/phase Margin can be Achieved by DOB-based Controller Proceedings Article In: Proc. of 2016 16th International Conference on Control, Automation and Systems, pp. 447-450, IEEE, Gyeongju, South Korea, 2016. Abstract | Links | BibTeX | Tags: Control system synthesis, Uncertain systems @inproceedings{KimParkShimJo16, In this paper, we prove that the DOB-based feedback controller can guarantee arbitrarily large but bounded gain margin and phase margin. This fact reminds that the DOB-based controller plays the role of robust controller even in the classical sense. We present a design procedure that ensures desired gain/phase margin even for the plants that have parametric uncertainty. |
Youngjun Joo / Gyunghoon Park / Juhoon Back / Hyungbo Shim Embedding Internal Model in Disturbance Observer with Robust Stability Journal Article In: IEEE Transactions on Automatic Control, vol. 61, no. 10, pp. 3128-3133, 2016. Abstract | Links | BibTeX | Tags: Control system synthesis, Observer, Robustness @article{JooParkBackShim16, Abstract: The disturbance observer has been widely employed in applications due to its powerful ability for disturbance rejection and robustness under plant uncertainties. However, it rejects the disturbance approximately rather than exactly since it is usually designed without considering structural properties of disturbance. In order to improve the disturbance rejection performance, we propose a design method to embed the internal model of disturbance into the disturbance observer structure. Furthermore, a systematic design procedure is proposed so that one can always design the disturbance observer to guarantee robust stability of the closed-loop system even though uncertain parameters of the plant belong to an arbitrarily large (but bounded) set. |
Hyungbo Shim / Daniel Liberzon Nonlinear Observers Robust to Measurement Disturbances in an ISS Sense Journal Article In: IEEE Transactions on Automatic Control, vol. 61, no. 1, pp. 48-91, 2016. Abstract | Links | BibTeX | Tags: Control system synthesis, Lyapunov method @article{ShimLiberzon16, This paper formulates and studies the concept of quasi-Disturbance-to-Error Stability (qDES) which characterizes robustness of a nonlinear observer to an output measurement disturbance. In essence, an observer is qDES if its error dynamics are input-to-state stable (ISS) with respect to the disturbance as long as the plant's input and state remain bounded. We develop Lyapunov-based sufficient conditions for checking the qDES property for both full-order and reduced-order observers. We use these conditions to show that several well-known observer designs yield qDES observers, while some others do not. Our results also enable the design of novel qDES observers, as we demonstrate with examples. When combined with a state feedback law robust to state estimation errors in the ISS sense, a qDES observer can be used to achieve output feedback control design with robustness to measurement disturbances. As an application of this idea, we treat a problem of stabilization by quantized output feedback. |
2014 |
Hyungjong Kim / Hyungbo Shim / Nam Hoon Jo Adaptive Add-on Output Regulator for Rejection of Sinusoidal Disturbances and Application to Optical Disc Drives Journal Article In: IEEE Transactions on Industrial Electronics, vol. 61, no. 10, pp. 5490-5499, 2014. Abstract | Links | BibTeX | Tags: Adaptive control, Control system synthesis @article{KimShimJo14, In this paper, we revisit an add-on output feedback controller that achieves output regulation and disturbance rejection. By add-on controller, we mean an additional controller, which runs harmonically with a preinstalled controller that has been in operation for the plant. When the disturbance attenuation performance of the preinstalled controller is not satisfactory, the add-on controller can be used to eliminate the disturbance. Some advantages of the proposed add-on controller include that it can be designed without much information about the preinstalled controller and it can be plugged in the feedback loop any time in operation without causing unnecessary transient response. In particular, we propose an adaptive add-on controller, which can eliminate sinusoidal disturbances of unknown frequencies. Both simulation and experimental results of the track-following control for optical disc drive systems confirm the effectiveness of the proposed method. |
2013 |
Nam Hoon Jo / Hyungbo Shim Robust Stabilization via Disturbance Observer with Noise Reduction Proceedings Article In: Proc. of 2013 European Control Conference (ECC), pp. 2861-2866, IEEE, Zürich, Switzerland, 2013. Abstract | Links | BibTeX | Tags: Control system synthesis @inproceedings{JoShim13, In this paper, we propose a robust controller using a modified disturbance observer (DOB). This modification is asked because the conventional DOB structure does not provide with any means to tune the high-frequency response. Since the measurement noise is significant in the high-frequency range, the performance against the noise in the conventional DOB control system cannot be better than that of the closed-loop system without DOB. Inspired by the new structure given in (Xie, 2010), we propose a modified disturbance observer structure, and present a necessary and sufficient condition for robust stability of the actual closed-loop system. Illustrative examples show the effectiveness of the proposed design. |
List of English Publication
2016 |
Detection of Sensor Attack and Resilient State Estimation for Uniformly Observable Nonlinear Systems Proceedings Article In: Proc. of 2016 IEEE 55th Conference on Decision and Control, pp. 1297-1302, IEEE, Las Vegas, NV, USA, 2016. |
Arbitrarily Large Gain/phase Margin can be Achieved by DOB-based Controller Proceedings Article In: Proc. of 2016 16th International Conference on Control, Automation and Systems, pp. 447-450, IEEE, Gyeongju, South Korea, 2016. |
Embedding Internal Model in Disturbance Observer with Robust Stability Journal Article In: IEEE Transactions on Automatic Control, vol. 61, no. 10, pp. 3128-3133, 2016. |
Nonlinear Observers Robust to Measurement Disturbances in an ISS Sense Journal Article In: IEEE Transactions on Automatic Control, vol. 61, no. 1, pp. 48-91, 2016. |
2014 |
Adaptive Add-on Output Regulator for Rejection of Sinusoidal Disturbances and Application to Optical Disc Drives Journal Article In: IEEE Transactions on Industrial Electronics, vol. 61, no. 10, pp. 5490-5499, 2014. |
2013 |
Robust Stabilization via Disturbance Observer with Noise Reduction Proceedings Article In: Proc. of 2013 European Control Conference (ECC), pp. 2861-2866, IEEE, Zürich, Switzerland, 2013. |