Topics: | ||

Disturbance Observer | Synchronization and Consensus | Switched Systems and Estimation Problems |

Nonlinear Observer | Output Feedback Stabilization | Stability Analysis |

Biological Dynamics and Control | Parallel Feedforward Compensator | Control Methodologies |

Security of Control System | Control of Hybrid System | Other publication – Thesis, Book Chapters, and other topics |

mark tells my own view, which may not even be shared with my co-authors. Google Scholar Link: http://scholar.google.co.kr/citations?user=QYs4ITcAAAAJ&hl=en |

### A. Disturbance Observer

**Noise reduction disturbance observer for disturbance attenuation and noise suppression **

Nam Hoon Jo, Chanyoung Jeon, and Hyungbo Shim,

*IEEE Trans. on Industrial Electronics*, to appear, 2016

http://dx.doi.org/10.1109/TIE.2016.2618858

**Yet another tutorial of disturbance observer: Robust stabilization and recovery of nominal performance**

H. Shim, G. Park, Y. Joo, J. Back, and N.H. Jo

*Control Theory and Technology*, Special Issue on Disturbance Rejection: A Snapshot, A Necessity, and A Beginning, vol. 14, issue 3, pp. 237-249, Aug 2016

http://dx.doi.org/10.1007/s11768-016-6006-9

or, download from http://arxiv.org/abs/1601.02075

**Embedding internal model in disturbance observer with robust stability**

Y. Joo, G. Park, J. Back, and H. Shim

*IEEE Trans. on Automatic Control*, vol. 61, no. 10, pp. 3128-3133, Oct 2016

http://dx.doi.org/10.1109/TAC.2015.2503559

**Reduced-order implementation of disturbance observers for robust tracking of nonlinear systems**

J. Back and H. Shim

*IET Control Theory & Applications*, vol. 8, Iss. 17, pp. 1940-1948, 2014

http://dx.doi.org/10.1049/iet-cta.2013.1036

In order to make the disturbance observer theory be an off-the-shelf technique for robust control, we’ve rendered it as simple as possible.

**A study of disturbance observers with unknown relative degree of the plant**

N.H. Jo, Y. Joo, and H. Shim

*Automatica, *vol. 50, pp. 1730-1734, 2014

http://dx.doi.org/10.1016/j.automatica.2014.04.015

Previous results require the knowledge of relative degree of the uncertain plant, which motivated the study of unknown relative degree case. Analysis newly introduces the Newton diagram (which is a foundation of higher-order root locus), which however yields a (negative) result that underscores the importance of relative degree estimation. A constructive design is also presented when the uncertainty of the relative degree is small, though.

**Robust tracking and vibration suppression for a two-inertia system by combining backstepping approach with disturbance observer**

J.S. Bang, H. Shim, S.K. Park, and J.H. Seo

*IEEE Trans. on Industrial Electronics*, vol. 57, no. 9, pp. 3197-3206, 2010

http://dx.doi.org/10.1109/TIE.2009.2038398

Flexible robot arms (or, two-inertia systems) unfortunately do not satisfy the standing assumption for disturbance observers. This paper shows how to overcome this problem by combining the backstepping design, with experiment results.

**Disturbance observer for non-minimum phase linear systems**

N.H. Jo, H. Shim, and Y.I. Son

*Int. J. of Control, Automation, and Systems*, vol. 8, no. 5, pp. 994-1002, Oct., 2010

http://dx.doi.org/10.1007/s12555-010-0508-x

When the plant is a non-minimum phase system, application of disturbance observer technique is limited. We try to overcome this by introducing a new structure and by using the H_inf design, but this problem still remains open to our satisfaction.

**An inner-loop controller guaranteeing robust transient performance for uncertain MIMO nonlinear systems**

J. Back and H. Shim

*IEEE Trans. on Automatic Control*, vol. 54, no. 7, pp. 1601-1607, 2009

http://dx.doi.org/10.1109/TAC.2009.2017962

MIMO extension to SISO case was not straightforward because of the uncertain input gain matrix, which was our motivation of study.

**An almost necessary and sufficient condition for robust stability of closed-loop systems with disturbance observer
**H. Shim and N.H. Jo

*Automatica*, vol. 45, no. 1, pp. 296-299, 2009

http://dx.doi.org/10.1016/j.automatica.2008.10.009

New finding: The same robust stability condition as [Back and Shim 2008, AUT] can be obtained just in Laplace domain, not relying on singular perturbation in the state-space.

**Adding robustness to nominal output feedback controllers for uncertain nonlinear systems: A nonlinear version of disturbance observer**

J. Back and H. Shim

*Automatica*, vol. 44, no. 10, pp. 2528-2537, 2008

http://dx.doi.org/10.1016/j.automatica.2008.02.024

(i) Robust transient response in time domain (of course, as well as robust stability) can be obtained with disturbance observer, (ii) a new robust condition is derived which is almost necessary and sufficient when the bandwidth of the Q-filter is sufficiently large, and a design method for the Q-filter is proposed, and (iii) the disturbance observer technique is extended to nonlinear systems. Overall, the message is “disturbance observer is not just an estimator, but is a robust control method”. It is a simple addition to any nominal feedback controller, which is another benefit.

#### Conference papers:

**State-space analysis of discrete-time disturbance observer for sampled-data control systems**

Hyeonjun Yun, Gyunghoon Park, Hyungbo Shim, and H. J. Chang

In Proc. of *American Control Conf.,* Boston, July, 2016, pp. 4233-4238

http://dx.doi.org/10.1109/ACC.2016.7525587

**On robust stability of disturbance observer for sampled-data systems under fast sampling: An almost necessary and sufficient condition**

Gyunghoon Park, Youngjun Joo, Chanhwa Lee, and Hyungbo Shim

In Proc. of *IEEE 54th Conf. Decision and Control,* Osaka, December, 2015, pp. 7536-7541

http://dx.doi.org/10.1109/CDC.2015.7403409

**A generalized framework for robust stability analysis of discrete-time disturbance observer for sampled-data systems: A fast sampling approach**

Gyunghoon Park and Hyungbo Shim

In Proc. of 15th International Conference on Control, Automation and Systems (ICCAS 2015), Busan, Korea

**Asymptotic rejection of sinusoidal disturbances with recovered nominal transient performance for uncertain linear systems**

G. Park, Y. Joo, and H. Shim

In Proc. of *IEEE 53rd Conf. on Dec. and Control,* Los Angeles, USA, 2014, pp. 4404-4409

http://dx.doi.org/10.1109/CDC.2014.7040076

**Disturbance observer with noise reduction capability**

N.H. Jo and H. Shim

In Proc. of 12th European Control Conf., Zurich, Switzerland, 2013, pp. 2861-2866

**A note on disturbance observer with unknown relative degree of the plant**

N.H. Jo, Y. Joo, H. Shim, and Y.I. Son

In Proc. of IEEE 51st Conf. on Dec. and Contr., Maui, USA, 2012, pp. 943-948

http://dx.doi.org/10.1109/CDC.2012.6426142

**Rejection of polynomial-in-time disturbances via disturbance observer with guaranteed robust stability**

G. Park, Y. Joo, H. Shim, and J. Back

In Proc. of IEEE 51st Conf. on Dec. and Contr., Maui, USA, 2012, pp. 949-954

http://dx.doi.org/10.1109/CDC.2012.6425973

Disturbance observer approximately cancels the disturbances. Then, how to cancel them exactly when the model generating them is known? Answer: Use internal model principle. Then, where to put the internal model within the disturbance observer configuration? The paper answers this question, and also presents how to guarantee robust stability with the internal model.

**Analysis of discrete-time disturbance observer and a new Q-filter design using delay function**

C. Lee, Y. Joo, and H. Shim

In Proc. of 12th Int. Conf. on Control, Automation and Systems (ICCAS), Jeju Island, Korea, 2012, pp. 556-561

**Robust tracking by reduced-order disturbance observer: Linear case**

J. Back and H. Shim

In Proc. of IEEE 50th Conf. on Dec. and Control and European Control Conf. (CDC-ECC), Orlando, USA, 2011, pp. 3514-3519

http://dx.doi.org/10.1109/CDC.2011.6161399

**Can a fast disturbance observer work under unmodeled actuators?**

N.H. Jo, Y. Joo, and H. Shim

In Proc. of 11th Int. Conf. on Control, Automation and Systems (ICCAS), Seoul, Korea, 2011, pp. 561-566

Download: 11.ICCAS.Jo.DOBwUD

**An inner-loop controller guaranteeing robust transient performance for uncertain MIMO linear systems
**J. Back, H. Shim, and Y. Joo

In Proc. of 17th IFAC World Congress, Seoul, Korea, 2008, pp. 3793-3798

http://dx.doi.org/10.3182/20080706-5-KR-1001.00639

**A new disturbance observer for non-minimum phase linear systems
**H. Shim, N.H. Jo, and Y.I. Son

In Proc. of American Control Conf., Seattle, USA, 2008, pp. 3385-3389

http://dx.doi.org/10.1109/ACC.2008.4587015

**Design of a disturbance observer-based controller for DC/DC boost converter
**S.-J. Kim, Y.I. Son, H. Shim, and Y.-S. Jeong

In Proc. of IASTED Int. Conf. on Intelligent Systems and Control, Cambridge, USA, 2007, pp. 401-407

**Design of disturbance observer for non-minimum phase systems using PID controllers
**Y.I. Son, H. Shim, N.H. Jo, and S.-J. Kim

In Proc. of SICE Annual Conf., Kagawa, Japan, 2007, pp. 196-201

http://dx.doi.org/10.1109/SICE.2007.4420976

**Analysis and synthesis of disturbance observer as a tool for nonlinear robust control
**J. Back and H. Shim

In Proc. of IFAC Symp. on Nonlinear Control Systems (NOLCOS), Pretoria, South Africa, 2007, pp. 79-86

Presented as a semi-plenary talk

http://dx.doi.org/10.3182/20070822-3-ZA-2920.00064

**State space analysis of disturbance observer and a robust stability condition**

H. Shim and Y. Joo

In Proc. of 46th IEEE Conf. on Dec. and Control, New Orleans, USA, 2007, pp. 2193-2198

http://dx.doi.org/10.1109/CDC.2007.4434130

When the well-known disturbance observer technique was analyzed in the state-space domain, it naturally asked us to use the singular perturbation theory, which in turn enables the study of robust stability, recovery of nominal feedback loop, peakings in the loop, robust transient response, and so on.

### B. Synchronization and Consensus

**Robustness of synchronization of heterogeneous agents by strong coupling and a large number of agents
**Jaeyong Kim, Jongwook Yang, Hyungbo Shim, Jung-Su Kim, and Jin Heon Seo

*IEEE. Trans. on Automatic Control*, vo. 61, no. 10, pp. 3096-3102, Oct. 2016

http://dx.doi.org/10.1109/TAC.2015.2498138

**Consensus of output-coupled linear multi-agent systems under deterministic and Markov switching networks**

D. Vengertsev, H. Kim, J.H. Seo, and H. Shim

*Int. J. of Systems Science*, vol. 46, no. 10, pp. 1799-1799, 2015

http://dx.doi.org/10.1080/00207721.2013.835884

**Consensus of output-coupled linear multi-agent systems under fast switching network: Averaging approach**

H. Kim, H. Shim, J. Back, and J.H. Seo

*Automatica, *vol. 49, no. 1, pp. 267-272, 2013

http://dx.doi.org/10.1016/j.automatica.2012.09.025

What if the switching network is never connected? Even in this case, if the switching is fast, and its average (in some sense) is connected, then its net effect may be the same as a connected graph. It does not just yield approximate consensus, but leads to exact consensus.

**Output feedback consensus for high order linear systems having uniform ranks under switching topology**

J.H. Seo, J. Back, H. Kim, and H. Shim

*IET Control Theory & Applications*, vol. 6, no. 8, pp. 1118-1124, 2012

http://dx.doi.org/10.1049/iet-cta.2011.0197

Unlike [Seo et al. 2009, AUT] where the low gain approach is employed so that the convergence rate might be slow, we can apply high gain when the agents do not have zero dynamics.

**Disc margins of the discrete-time LQR and its application to consensus problem**

J. Lee, J.S. Kim, and H. Shim

*Int. J. of Systems Science*, vol. 43, no. 10, pp. 1891-1900, 2012

http://dx.doi.org/10.1080/00207721.2011.555012

Although there are a few studies on the gain/phase margin of the discrete-time LQR controllers, the disc margin (a combination of gain and phase margins expressed as complex numbers) is studied which leads to less conservative bounds. This margin helps to design a consensus controller for discrete-time case.

**A constrained consensus problem using MPC**

J. Lee, J.S. Kim, H. Song, and H. Shim

*Int. J. of Control, Automation, and Systems,* vol. 9, no. 5, pp. 952-957, 2011

http://dx.doi.org/10.1007/s12555-011-0516-5

**Output consensus of heterogeneous uncertain linear multi-agent systems**

H. Kim, H. Shim, and J.H. Seo

*IEEE Trans. on Automatic Control*, vol. 56, no. 1, pp. 200-206, 2011

http://dx.doi.org/10.1109/TAC.2010.2088710

Consensus among heterogeneous agents is of great interest because it is often the case in real world. But, at the same time, it is easily seen that the (state) consensus is not possible simply because the dynamic properties might be all different among the agents. Instead, we may ask “output” consensus with a certain internal model that is the same across the agents. For this, we embed the internal model in the (output feedback) consensus controller.

**Reduced-order consensus controllers for output-coupled SISO linear systems**

J.H. Seo, H. Shim, J. Back

*Int. J. of Control, Automation, and Systems*, vol. 8, no. 6, pp. 1356-1363, Dec. 2010

http://dx.doi.org/10.1007/s12555-010-0623-8

While [Seo et al. 2009, AUT] gives an answer to general consensus problem, it requires the same order of consensus controller as the agent. But, when a particular case where the agreed trajectory is of order one or two, it is shown that the order of consensus controller can be of order one or two, respectively. It also presents a correction of Corollary 2 of [Seo et al. 2009, AUT].

**Consensus of high-order linear systems using dynamic output feedback compensator: Low gain approach**

J.H. Seo, H. Shim, and J. Back

*Automatica*, vol. 45, no. 11, pp. 2656-2664, 2009

http://dx.doi.org/10.1016/j.automatica.2009.07.022

This may be one of the earliest results dealing with the consensus problem for general order of LTI agents. Since the consensus problem is converted into a robust control problem of single agent, the low gain feedback turns out to be helpful. The error in Corollary 2 has been fixed in Theorem 1 of [Seo et al. 2010, IJCAS].

#### Conference papers:

**On distributed optimal Kalman-Bucy filtering by averaging dynamics of heterogeneous agents**

Jaeyong Kim, Hyungbo Shim, and Jingbo Wu

to be presented at *IEEE Conf. Decision and Control,* Las Vegas, December, 2016

**Distributed Luenberger observer design**

Taekyoo Kim, Hyungbo Shim, and Dongil Dan Cho

to be presented at *IEEE Conf. Decision and Control,* Las Vegas, December, 2016

**A preliminary result on synchronization of heterogeneous agents via funnel control**

S. Trenn and H. Shim

In Proc. of IEEE 54th Conf. on Dec. and Control, Osaka, Japan, 2015, pp. 2229-2234

http://dx.doi.org/10.1109/CDC.2015.7402538

**Robust synchronization for high-order heterogeneous multi-agent systems**

Jaeyong Kim and H. Shim

In Proc. of SWARM 2015: The First Int. Symp. on Swarm Behavior and Bio-Inspired Robotics, Kyoto, Japan, 2015, pp. 293-294

**Consensus under time-delayed information on states and network**

J.G. Lee and H. Shim

In Proc. of IEEE 53rd Conf. on Dec. and Control, Los Angeles, USA, 2014, pp. 1446-1451

http://dx.doi.org/10.1109/CDC.2014.7039604

**On robustness of synchronization in heterogeneous multi-agent systems**

J. Kim, J. Yang, H. Shim, and J.S. Kim

In Proc. of 12th European Control Conf., Zurich, Switzerland, 2013, pp. 3821-3826

Download: 13.ECC.Kim.draft

Unlike [Kim et al. 2011, TAC] where the internal model is introduced for exact consensus, we do not embed the internal model assuming that we are satisfied with *approximate* consensus. A framework for this is pursued, leading to the notion of *averaged system* and *strong couplings*. Moreover, this paper answers the question: “How to make the consensus robust?” Answer: it becomes more robust as the coupling becomes stronger and as the number of agents gets larger. (The former is expected but the latter is somehow new.)

**Practical consensus for heterogeneous linear time-varying multi-agent systems**

J. Kim, J. Yang, J.S. Kim, and H. Shim

In Proc. of 12th Int. Conf. on Control, Automation and Systems (ICCAS), Jeju Island, Korea, 2012, pp. 23-28

Download: 12.ICCAS.Kim.PracCons

**Stabilizability of a group of single integrators and its application to decentralized formation problem**

H. Kim, H. Shim, J. Back, and J.H. Seo

In Proc. of IEEE 50th Conf. on Dec. and Control and 11th European Control Conf. (CDC-ECC), Orlando, USA, 2011, pp. 3514-3519

http://dx.doi.org/10.1109/CDC.2011.6161139

Making a multi-agent system (MAS) put in a desired formation by external inputs requires a certain property, and for this the previous results ask ‘controllability’ of MAS. However, controllability of MAS often ends up with counter-intuitive conclusions. Motivated by this, we claim that ‘stabilizability’ is more suitable for MAS.

**Consensus of output-coupled linear multi-agent systems under frequently connected network**

D. Vengertsev, H. Kim, H. Shim, and J.H. Seo

In Proc. of IEEE 49th Conf. on Dec. and Control, Atlanta, USA, 2010, pp. 4559-4564

http://dx.doi.org/10.1109/CDC.2010.5717998

Under a switching network, consensus can still be achieved even if the network is not always connected. Simply by utilizing the average dwell time notion, consensus is achieved if the time of being connected is larger than the time of disconnection in some sense.

**Consensus of multi-agent systems under periodic time-varying network: Averaging approach**

H. Kim, H. Shim, J. Back, and J.H. Seo

In Proc. of IFAC Symp. on Nonlinear Control Systems (NOLCOS), Bologna, Italy, 2010, pp. 155-160

http://dx.doi.org/10.3182/20100901-3-IT-2016.00157

**Consensus and synchronization of linear high-order systems via output coupling
**J.H. Seo, H. Shim, and J. Back

In Proc. of 10th European Control Conf., Budapest, Hungary, 2009, pp. 767-772

**High-order consensus of MIMO linear dynamic systems via stable compensator
**J.H. Seo, H. Shim, and J. Back

In Proc. of 10th European Control Conf., Budapest, Hungary, 2009, pp. 773-778

### C. Switched Systems and Estimation Problems

**Robust estimation algorithm for both switching signal and state of switched linear systems
**Z. Ping, C. Lee, and H. Shim

*Int. J. of Control, Automation, and Systems,*vol. 15, no. 1, pp. 95-103, 2017

http://dx.doi.org/10.1007/s12555-015-0178-9

**Comments on “Observability of switched linear systems: Characterization and observer design”**

A. Tanwani, H. Shim, and D. Liberzon

*IEEE Trans. on Automatic Control*, vol. 60, no. 12, pp. 3396-3400, 2015

http://dx.doi.org/10.1109/TAC.2015.2422483

**Hybrid-type observer design based on a sufficient condition for observability in switched nonlinear systems**

H. Shim and A. Tanwani

*Int. J. of Robust and Nonlinear Control*, vol. 24, no. 6, pp. 1064-1089, 2014

Special Issue on High-Gain Observers in Nonlinear Feedback Control

http://dx.doi.org/10.1002/rnc.2901

Simulation file: download

The observer construction of [Tanwani et al. 2013, TAC] relies on the linearity of the system; that is, the partial information gained at each mode can be easily transported to another time simply by multiplying the state transition matrix. For nonlinear systems, this is not possible and we have to devise another idea.

**Observability for switched linear systems: Characterization and observer design**

A. Tanwani, H. Shim, and D. Liberzon

*IEEE Trans. on Automatic Control*, vol. 58, no. 4, pp. 891-904, 2013*
*http://dx.doi.org/10.1109/TAC.2012.2224257

Erratum: See the comments in this file.

If a switched system is not observable at any mode, can we estimate the states (assuming that the switching signal is known)? Answer is positive if the observability is gained by switching, while it takes some time until the system becomes observable. If so, can we design an asymptotic observer? This paper illustrates a construction of such an observer, which differs from the conventional approaches where the switching effect is treated as a perturbation.

#### Conference papers:

**Real time switching signal estimation of switched linear systems with measurement noise**

C. Lee, Z. Ping, and H. Shim

In Proc. of 12th European Control Conf., Zurich, Switzerland, 2013, pp. 2180-2185

**On a sufficient condition for observability of nonlinear switched systems and observer design strategy**

H. Shim and A. Tanwani

In Proc. of American Control Conf.,* *San Francisco, USA, 2011, pp. 1206-1211

Best presentation of the session. Presentation slide: ACC11_NonSW.pdf

Simulation file (MATLAB/Simulink 2009b): ACC11m.zip

**Observability implies observer design for switched linear systems**

A. Tanwani, H. Shim, and D. Liberzon

In Proc. of 14th ACM Conf. on Hybrid Systems: Computation and Control (HSCC), Chicago, USA, 2011, pp. 3-12

http://dx.doi.org/10.1145/1967701.1967705

Erratum: download

**Switching adaptive output feedback MPC for input-constrained neutrally stable linear plants
**J.S. Kim, T.W. Yoon, and H. Shim

In Proc. of Joint Conf. of IEEE Conf. on Dec. and Control and European Control Conf., Seville, Spain, 2005,

*pp. 777-782*

http://dx.doi.org/10.1109/CDC.2005.1582251

**Common Lyapunov function for exponentially stable nonlinear systems
**H. Shim, D.J. Noh, and J.H. Seo

Presented at 4th SIAM Conf. on Control and Its Applications, Jaxsonville, USA, 1998

Best paper award of the poster session

Download: commonlf

Also has been published in Journal of Korean Institute of Electrical Engineers (English journal of KIEE), vol. 11, no. 2, pp. 108-111, 2001

For linear systems, a sufficient condition for the existence of common Lyapunov function is that the system matrices are commuting. Then, what about the nonlinear systems? A trivial extension is to ask the Lie brackets of all pairs to be zero (commuting), and that’s it.

### D. Nonlinear Observer

**Nonlinear observers robust to measurement disturbances in an ISS sense
**H. Shim and D. Liberzon

*IEEE Trans. on Automatic Control*, vol. 61, no. 1, pp. 48-61, 2016

http://dx.doi.org/10.1109/TAC.2015.2423911

**Nonlinear observer design via approximate normal form: Ball and beam system on a vibrating frame
**J. Back, N.H. Jo, Y.I. Son, H. Shim, and J.H. Seo

*IEICE Trans. on Fundamentals of Electronics, Communications and Computer Sciences*, vol. E87-A, no. 3, pp. 716-724, 2004

**Recursive observer design beyond the uniform observability
**H. Shim and J.H. Seo

*IEEE Trans. on Automatic Control*, vol. 48, no. 2, pp. 294-298, 2003

http://dx.doi.org/10.1109/TAC.2002.808485

A recursive design method for a nonlinear observer is proposed, which may be thought as an ‘observer backstepping’ (not ‘backstepping with observer’). Compared to another observer backstepping in the literature, the design begins with the farthest integrator from the output and proceeds to the output, and the error convergence is not local.

**Nonlinear observer design via passivation of error dynamics**

H. Shim, J.H. Seo and A.R. Teel

*Automatica*, vol. 39, no. 5, pp. 885-892, 2003

http://dx.doi.org/10.1016/S0005-1098(03)00023-2

Feedback gain K of the LQR controller is given by K = B^T P format (so-called L_gV-type), which yields the benefit of large gain and phase margins because passivity holds from the input to a suitably chosen output. Keeping this in mind and looking at many nonlinear observers in the literature, one finds that the observer injection gain is often given by L = P^{-1} C^T format (Kalman filter is one of them). This observation suggests that one may find the (nonlinear) error dynamics passive from a suitably chosen input to the error output. Once established, this view allows a generalized framework for analyzing nonlinear observers and some design extension to a larger class of systems. Finally, it enables a re-design of the injection gain so that the error dynamics becomes input-to-state stable from the measurement noise to the estimation error.

**An adaptive algorithm applied to a design of robust observer
**H. Shim, Y.I. Son, J. Back, and N.H. Jo

*KSME International Journal*, vol. 17, no. 10, pp. 1443-1449, 2003

**Design of an adaptive observer for a class of nonlinear systems
**Y.U. Choi, H. Shim, Y.I. Son, and J.H. Seo

*Int. J. of Control, Automation, and Systems,*vol. 1, no. 1, pp. 28-34, 2003

**Semi-global observer for multi-output nonlinear systems
**H. Shim, Y.I. Son, and J.H. Seo

*Systems & Control Letters,*vol. 42, no. 3, pp. 233-244, 2001

http://dx.doi.org/10.1016/S0167-6911(00)00098-0

Nonlinear observer design for multi-output systems has some freedom because a system can be converted into one of several possible canonical forms. Here the proposed canonical form is a block-triangular form rooted at each output, and each block is again composed of another triangular form (so that, it is a nested-triangular form). The difficulty is that each block may interfere with the other blocks, and this problem is solved simply by introducing saturation functions (sacrificing global error convergence).

**Comments on Observers for nonlinear systems in steady state
**H. Shim, J. Byun, and J.H. Seo

*IEEE Trans. on Automatic Control,*vol. 44, no. 3, p. 587, 1999

http://dx.doi.org/10.1109/9.751356

#### Conference papers:

**Back-and-forth operation of state observers and norm estimation of estimation error**

H. Shim, A. Tanwani, and Z. Ping

In Proc. of IEEE 51st Conf. on Dec. and Contr., Maui, USA, 2012, pp. 3221-3226

http://dx.doi.org/10.1109/CDC.2012.6426816

Strong computing power nowadays enables that numerical integration is performed faster than the real time (for not-too-complicated dynamics, of course). Are there any ways to utilize this surplus of computing power? We propose an observer whose numerical integration goes back-and-forth (using the stored input and output data of the plant), so that it could be interpreted as a batch-process realized on-line. Benefits: it can provide with faster convergence without using high observer gain, and the state estimate without initial transients (which is however delayed, but even the delayed information sometimes becomes useful; see [Shim and Tanwani 2013, IJRNC]), and finally it enables the (finite-time) estimation of the upper bound of the size of the estimate error.

**Reduced-order dynamic observer error linearization**

J. Yang, J. Back, J.H. Seo, and H. Shim

In Proc. of IFAC Symp. on Nonlinear Control Systems (NOLCOS), Bologna, Italy, 2010, pp. 915-920

http://dx.doi.org/10.3182/20100901-3-IT-2016.00285

**Quasi-ISS reduced-order observers and quantized output feedback
**H. Shim, D. Liberzon, and J.S. Kim

In Proc. of Joint Conf. of 48th IEEE Decision and Control (CDC) and Chinese Control Conference (CCC), Shanghai, China, 2009, pp.6680-6685

http://dx.doi.org/10.1109/CDC.2009.5400400

Nonlinear observer design with additional property of ISS from the measurement noise to the estimation error is an important problem in itself, but not as much studied as expected. We first claim that requiring ISS for the observer problem is a way too much because very few cases satisfy the property. Instead, we propose a new concept of quasi-ISS and claim that it is better suited for the observer problem. A design method is also presented, which leads to the quasi-ISS property, and its application to quantized output feedback is discussed.

**An algorithm for system immersion into nonlinear observer form: Forced system
**J. Back, H. Shim, and J.H. Seo

In Proc. of 16th IFAC World Congress, Prague, Czech Republic, 2005

http://dx.doi.org/10.3182/20050703-6-CZ-1902.00674

**An approach to robust observer construction without output derivative measurements**

Y.I. Son, H. Shim, J. Back, and N.H. Jo

In Proc. of Int. Conf. on Mechatronics and Information Technology (ICMIT), Jecheon, Korea, 2003, pp. 642-647.

**Remarks on equivalence between full order and reduced order nonlinear observers
**H. Shim and L. Praly

In Proc. of 42th IEEE Conf. on Dec. and Control, Maui, USA, 2003, pp. 5837-5840

http://dx.doi.org/10.1109/CDC.2003.1271936

For linear systems, existence conditions for a full order observer and for a reduced order observer are the same. Then what about the nonlinear case? This simple question is not easy to answer, and we can only say yes under a restriction. The construction process of full order observer from a reduced one, however, might be somehow interesting.

**Enlarging the class of linear systems admitting adaptive observers without persistent excitation
**H. Shim, Y.I. Son, J. Back and N.H. Jo

In Proc. of 7th European Control Conf., Cambridge, United Kingdom, 2003

**A systematic nonlinear observer design for a class of Euler-Lagrange systems
**R. Skjetne and H. Shim

In Proc. of 9th Mediterranean Conf. on Control and Automation (MED), Croatia, 2001

**Passivity framework for nonlinear state observer**

H. Shim and J.H. Seo

In Proc. of American Control Conf., Chicago, USA, 2000, pp. 699-705

Listed as the Five Finalist of the Student Best Paper Award

http://dx.doi.org/10.1109/ACC.2000.878991

Supplementary material: 00.ACC.Shim.supplement

**A Simple Observer for Nonlinear Systems in x-coordinate using Lipschitz Extension Technique
**H. Shim, Y.I. Son, J. Back, and J.H. Seo

In Proc. of Joint Conf. on Control, Instrumentation, Automation, and Robotics, Korea, pp. 352-356, 2000

Download: 00.conf.Shim.x-domainObs

**Saturation technique for constructing observer of multi-output nonlinear systems
**H. Shim, Y.I. Son, and J.H. Seo

In Proc. of American Control Conf., San Diego, USA, 1999, pp. 3077-3081

http://dx.doi.org/10.1109/ACC.1999.782327

### E. Output Feedback Stabilization

**Asymptotic controllability and observability imply semiglobal practical asymptotic stabilizability by sampled-data output feedback
**H. Shim and A.R. Teel

*Automatica*, vol. 39, no. 3, pp. 441-454, 2003

http://dx.doi.org/10.1016/S0005-1098(02)00278-9

In the line of research for semi-global separation principle, the existence of smooth stabilizing state feedback controller and the uniform observability of the plant are often required. It is claimed that asymptotic controllability of the plant (relaxed from the former) and just observability (relaxed from the latter) are enough if we’re satisfied with practical stability, and this is achieved by sampled-data output feedback.

**Nonlinear output feedback stabilization on a bounded region of attraction
**H. Shim and J.H. Seo

*Int. J. of Control*, vol. 73, no. 5, pp. 416-426, 2000

http://dx.doi.org/10.1080/002071700219597

A separation principle for nonlinear systems is established in terms of stabilization of the origin. Since Gauthier’s high-gain observer is employed, the overall output feedback controller has the same order as the plant.

#### Conference papers:

**On performance improvement of an output feedback control scheme for non-uniformly observable nonlinear systems
**H. Shim and A.R. Teel

In Proc. of 40th IEEE Conf. on Dec. and Control, Orlando, USA, 2001,

*pp. 1354-1359*

http://dx.doi.org/10.1109/.2001.981078

If the system is not uniformly observable but just observable, then there may exist singular inputs which destroy observability of the system. This singular input in general depends on the state of the system, which is unknown for output feedback problem. But, by utilizing the information of the outputs, we may determine whether the currently applied input is singular or not. Using this information, the performance of the controller in [Shim and Teel 2003, AUT] can be improved.

**Further results on the nonlinear separation principle: the general ‘asymptotically controllable’ case**

H. Shim and A.R. Teel

In Proc. of 5th IFAC Nonlinear Control Systems Design Symposium (NOLCOS), St. Petersburg, Russia, 2001

Download: 01.nolcos.cameraready

**Output feedback passification of nonlinear systems**

J. Byun, H. Shim, and J.H. Seo

In Proc. of American Control Conf., Chicago, USA, 2000, pp. 157-158

http://dx.doi.org/10.1109/ACC.2000.878802

While output feedback passification is often performed in the normal form, a simple and general condition is presented which doesn’t require this special structure of the system.

**Output feedback stabilization for completely uniformly observable nonlinear systems**

H. Shim, J. Jin, J.S. Lee, and J.H. Seo

In Proc. of IFAC Conf. on System Structure and Control, Nantes, France, 1998, pp.335-360

Download: 98.ifac.stab.cameraready

### F. Stability Analysis

**An asymptotic ratio characterization of input-to-state stability**

D. Liberzon and H. Shim

*IEEE Trans. on Automatic Control*, vol. 60, no. 12, pp. 3401-3404, 2015

http://dx.doi.org/10.1109/TAC.2015.2422482

**On the stability of critical point for positive systems and its applications to biological systems**

J-W Lee, N.H. Jo, H. Shim, and Y.I. Son

*J. Electr Eng Technol*, vol. 8, no. 6, pp. 1530-1541, 2013

http://dx.doi.org/10.5370/JEET.2013.8.6.1530

**Further extensions on a stability property with slowly varying inputs**

H. Shim and N.H. Jo

*Dynamics of Continuous, Discrete and Impulsive Systems*, Series B, vol. 17, no. 6, pp. 979-1000, Dec. 2010

Special issue in honor of Prof. Hassan K. Khalil’s 60th birthday

Download: 10.DCDIS.Shim.JumpAndWait.pdf

Well-known: When an equilibrium varies continuously with respect to a (constant) input and each of them is (locally) asymptotically stable, we can drive the system state along the trajectory of the equilibria by slowly varying the input (once the initial state is sufficiently close to the starting equilibrium). Underlying property for this is that the basin of attraction of each equilibrium does not vanish along the trajectory of equilbria family. New finding: If some (transcritical) bifurcation occurs (and this is the situation of HIV infection treatment of [Shim et al. 2009, AUT]), the preservation of basin of attraction is not possible. Even in this case, if the bifurcation occurs *at the boundary of positive orthant* and the system is a *positive system*, we may still have the nice stability property under slowly-varying-jump-and-wait inputs. In addition, instead of slowly-varying-jump-and-wait inputs, the slowly-varying-jump-and-wait *average* inputs do the same job.

**Note on differential regulator equation for non-minimum phase linear systems with time-varying exosystems**

H. Shim, J.S. Kim, H. Kim, and J. Back

*Automatica*, vol. 46, no. 3, pp. 605-609, 2010

http://dx.doi.org/10.1016/j.automatica.2009.12.007

Supplementary examples: http://hdl.handle.net/10371/11011

Being non-minimum phase does not cause any difficulty for linear output regulation problem with LTI exosystem, because the (static) regulator equation has a constant solution, with which the remaining task is just a stabilization. If the exosystem is an LTV system, the so-called *differential* regulator equation should be employed which has a bounded (time-varying) solution if the plant is of minimum phase. Well… in fact, even if the plant is of non-minimum phase, the differential regulator equation can still have a bounded solution, but it is non-causal. Non-causality may not cause much trouble if the (future) knowledge of S(t) (system matrix of exosystem) is available a priori, because by the non-causal solution we mean the solution of the differential regulator equation existing in computer, but not the solution of the plant.

**Determination of stability with respect to positive orthant for a class of positive nonlinear systems**

H. Shim and N.H. Jo

*IEEE Trans. on Automatic Control*, vol. 53, no. 5, pp. 1329-1334, 2008

http://dx.doi.org/10.1109/TAC.2008.921018

Supplementary material: http://hdl.handle.net/10371/5107

When an equilibrium varies continuously with respect to a (constant) input and each of them is (locally) asymptotically stable, our concern is the variation of the size of basin of attraction for each equilibrium along the trajectory of equilibria. Based on the center manifold theory, a simple algebraic condition is derived with which non-vanishing basin of attraction (with respect to positive orthant) is ensured for a class of positive systems. This particular problem arises in [Shim et al. 2009, AUT] when the stability of a biological system is analyzed.

**Further results on robustness of (possibly discontinuous) sample and hold feedback
**C.M. Kellett, H. Shim and A.R. Teel

*IEEE Trans. on Automatic Control,*vol. 49, no. 7, pp. 1081-1089, 2004

*http://dx.doi.org/10.1109/TAC.2004.831184*

It is clear that the closed-loop with a discontinuous state feedback is not robust with respect to small measurement noise in general. But, if it is implemented in a sample and hold fashion (and if a certain decrease of the Lyapunov function is ensured), then we may still get some robustness. Some intuition is from the fact that the persistent noise affects only at sampling times.

#### Conference papers:

**Improving LaSalle’s invariance principle using geometric clues
**H. Shim and J.H. Seo

In Proc. of SICE-ICASE Int. Joint Conf. (SICE-ICCAS), Busan, Korea, 2006, pp. 5253-5255

http://dx.doi.org/10.1109/SICE.2006.315832

Motivated by biological systems which are nonnegative systems in nature, we note that the equilibrium of interest often has a zero component (so that it is at the boundary of the open, forward invariant, positive orthant). Since the equilibrium is at the boundary, a non-isolated equilibrium can be asymptotically stable with respect to the positive orthant. Then, due to the non-uniform convergence rate around the boundary of invariant set, a Lyapunov function of the asymptotically stable equilibrium with respect to the positive orthant may not exist. Then, how to guarantee the asymptotic stability in such a case? LaSalle’s theorem may become of some help, but not in its standard form.

**Output regulation problem and solution for LTV minimum phase systems with time-varying exosystem
**H. Shim, J.H. Lee, J.S. Kim, and J. Back

In Proc. of SICE-ICASE Int. Joint Conf. (SICE-ICCAS), Busan, Korea, 2006, pp. 1823-1827

Received Best Paper Award

http://dx.doi.org/10.1109/SICE.2006.315719

For linear systems, when the exosystem is time-varying, one can still use most of linear output regulation techniques once the (static) regulator equation is replaced with ‘differential regulator equation’. For minimum phase systems, a detailed recipe is presented.

**A simple condition for checking non-vanishing basin of attraction stability for a class of positive nonlinear systems
**H. Shim and N.H. Jo

In Proc. of Joint Conf. of IEEE Conf. on Dec. and Control and European Control Conf., Seville, Spain, 2005, pp. 5456-5461

http://dx.doi.org/10.1109/CDC.2005.1583030

**On a stability property of nonlinear systems with periodic inputs having slowly varying average
**Y.U. Choi, H. Shim, and J.H. Seo

In Proc. of 16th IFAC World Congress, Prague, Czech Republic, 2005

http://dx.doi.org/10.3182/20050703-6-CZ-1902.00855

**A stability property of nonlinear systems with inputs having slowly varying average and its application to HIV problem
**Y.U. Choi, H. Shim, and J.H. Seo

In Proc. of American Control Conf., Portland, USA, 2005, pp. 3025-3029

http://dx.doi.org/10.1109/ACC.2005.1470435

Although [Shim et al. 2009, AUT] analyzed the slow reduction of dose (in a few hundred days) for a treatment of AIDS, one may complain that the actual effect of drug is fastly fluctuating hour-by-hour in human body (we usually take pills three times a day). If so, here’s a modified version: Drug effect can fluctuate hour-by-hour, as long as its

*average*is slowly varying.

**Non-vanishing basin of attraction with respect to a parametric variation and center manifold
**H. Shim, H.J. Chang, and J.H. Seo

In Proc. of 43rd IEEE Conf. on Dec. and Control, Paradise Island, The Bahamas, 2004, pp. 2984-2989

http://dx.doi.org/10.1109/CDC.2004.1428921

**Robustness of discontinuous feedback via sample and hold control
**C.M. Kellett, H. Shim and A.R. Teel

In Proc. of American Control Conf., Anchorage, USA, 2002, pp. 3512-3517

http://dx.doi.org/10.1109/ACC.2002.1024472

**Passivity under unmodeled dynamics
**H. Shim, J. Byun, J.S. Lee, and J.H. Seo

In Proc. of IFAC Conf. on System Structure and Control, Nantes, France, 1998, pp.221-226

Download: 98.ifac.pas_ud.cameraready

Stabilization of the (slow reduced order) model is robust under a sufficiently fast stable unmodelled dynamics. Then, what about passivity? It is clear that, even though the (slow reduced order) model is passive and the unmodelled dynamics (fast system) is stable and sufficiently fast, the full order model is not passive in general. However, under some structural conditions, passivity holds for the full order system.

### G. Biological Dynamics and Control

**A control theoretic approach to Malaria immunotherapy with state jumps**

H. Chang, A. Astolfi, and H. Shim

*Automatica*, vol. 47, no. 6, pp. 1271-1277, 2011

Special Issue on Systems Biology

http://dx.doi.org/10.1016/j.automatica.2011.03.009

**A system theoretic study on a treatment of AIDS patient by achieving long-term non-progressor
**H. Shim, N.H. Jo, H. Chang, and J.H. Seo

*Automatica*, vol. 45, no. 3, pp. 611-622, 2009

http://dx.doi.org/10.1016/j.automatica.2008.09.021

Effectiveness of the idea of gradual dose reduction [Chang et al. 2004, CDC] is mathematically proven. In particular, (i) the analysis is based on the interval (not a particular value) of parameters, and (ii) the control does not heavily rely on ‘feedback’ (although it is actually feedback). Considering the difficulty of obtaining exact parameter values for biological models, and the difficulty of frequent measurement of viral density, the proposed treatment algorithm may be quite suitable in practice.

**Optimal scheduling of drug treatment for HIV infection: Continuous dose control and receding horizon control
**H. Shim, S.J. Han, C.C. Chung, S.W. Nam, and J.H. Seo

*Int. J. of Control, Automation and Systems,*vol. 1, no. 3, pp. 401-407, 2003

Download: FinalDraft.03.IJCAS.HIV

#### Conference papers:

**Immunisation against HIV and Malaria: Control theoretic approach with state jump**

H. Chang, A. Astolfi, and H. Shim

In Proc. of American Control Conf., Baltimore, USA, 2010, pp. 474-479

**A control theoretic approach to venom immunotherapy with state jumps**

H. Chang, A. Astolfi, and H. Shim

In Proc. of Annual Int. Conf. of IEEE Engineering in Medicine and Biology Society (EMBC), 2010, pp. 742-745

http://dx.doi.org/10.1109/IEMBS.2010.5626304

**Control of infection dynamics with application to HIV/AIDS model
**H. Chang, A. Astolfi, and H. Shim

In Proc. of Joint Conf. of IEEE Decision and Control (CDC) and Chinese Control Conference (CCC), Shanghai, China, 2009, pp. 3533-3538

http://dx.doi.org/10.1109/CDC.2009.5400207

**HIV treatment: with or without consideration of the immune system
**H. Chang, A. Astolfi, and H. Shim

In Proc. of 10th European Control Conf., Budapest, Hungary, 2009, pp. 2470-2475

**An application of gradual reduction of drug dose to HIV infection model in consideration of drug resistance and drug dose
**H. Chang, N.H. Jo, and H. Shim

In Proc. of SICE-ICASE Int. Joint Conf. (SICE-ICCAS), Busan, Korea, 2006, pp. 5236-5241

http://dx.doi.org/10.1109/SICE.2006.315829

**Control of immune response of HIV infection model by gradual reduction of drug dose
**H. Chang, H. Shim, and J.H. Seo

In Proc. of 43rd IEEE Conf. on Dec. and Control, Paradise Island, The Bahamas, 2004, pp. 1048-1054

http://dx.doi.org/10.1109/CDC.2004.1428827

Dr. Chang has come up with a new idea of gradual reduction of dose, which initiated a series of research.

**Optimal scheduling of drug treatment for HIV infection: Continuous dose control and receding horizon control
**H. Shim, S.J. Han, I.S. Jeong, Y.H. Huh, C.C. Chung, S.W. Nam and J.H. Seo

In Proc. of 3rd Int. Conf. on Control, Automation and Systems (ICCAS), Gyeongju, Korea, 2003,

*pp. 1951-1956*

### H. Parallel Feedforward Compensator

**Design of Stable Parallel Feedforward Compensator and Its Application to Synchronization Problem
**Hongkeun Kim, Seongjun Kim, J. Back, H. Shim, and J.H. Seo

*Automatica,*vol. 64, no. 2, pp. 208-216, 2016

http://dx.doi.org/10.1016/j.automatica.2015.11.020

**Low-pass filter property of an input-dimensional output feedback passification controller for rotary inverted pendulum
**Y.I. Son, N.H. Jo, H. Shim, and G.J. Jeong

*IEICE Trans. on Fundamentals of Electronics, Communications and Computer Sciences*, vol. E92-A, no. 8, pp. 2133-2136, 2009

http://dx.doi.org/10.1587/transfun.E92.A.2133

**A new approach to design of a dynamic output feedback stabilizing control law for LTI systems**

Y.I. Son, H. Shim, N.H. Jo, and K.-I. Kim

*J. of Mechanical Science and Technology*, vol. 19, no. 2, pp. 618-624, 2005

**A dynamic output feedback control law for elastic joint robots via feedback-passivity approach
**Y.I. Son, H. Shim, and J.H. Seo

*J. of The Franklin Insititute*, vol. 341, no. 6, pp. 477-490, 2004

http://dx.doi.org/10.1016/j.jfranklin.2004.05.001

**A design method of an SPR system for stabilization of a crane without velocity measurement
**Y.I. Son, H. Shim, and K.I. Kim

*IEICE Trans. on Fundamentals of ECCS,*vol. E86-A, no. 11, pp. 2894-2896, 2003

**Further results on passification of non-square linear systems using an input-dimensional compensator
**Y.I. Son, H. Shim, N.H. Jo, and J.H. Seo

*IEICE Trans. on Fundamentals of ECCS,*vol. E86-A, no. 8, pp. 2139-2143, 2003

**Output feedback passification of nonlinear systems not in normal form
**Y.I. Son, H. Shim, N.H. Jo, and J.H. Seo

*IEICE Trans. on Fundamentals of ECCS,*vol.E86-A, no. 5, pp. 1312-1315, 2003

**Set-point control of elastic joint robots using only position measurements
**Y.I. Son, H. Shim, and J.H. Seo

*KSME International Journal,*vol. 16, no. 8, pp. 1079-1088, 2002

**Passification of non-square linear systems using an input-dimensional dynamic feedforward compensator
**Y.I. Son, H. Shim, K. Park, and J.H. Seo

*IEICE Trans. on Fundamentals of ECCS*, vol. E85-A, no. 2, pp. 422-431, 2002

#### Conference papers:

**Passification of SISO LTI systems through a stable feedforward compensator**

S. Kim, H. Kim, J. Back, H. Shim, and J.H. Seo

In Proc. of 11th Int. Conf. on Control, Automation and Systems (ICCAS), Seoul, Korea, 2011, pp. 107-111

Download: 11.ICCAS.Kim.StablePFC

By imposing additional condition of stability of the parallel component, a necessary and sufficient condition for the existence, as well as a design procedure, of the component is found for linear systems.

**Low-pass filter property of dynamic output feedback passivation controller
**Y.I. Son, N.H. Jo, H. Shim, and K.I. Kim

In Proc. of SICE-ICASE Int. Joint Conf. (SICE-ICCAS), Busan, Korea, 2006, pp. 821-826

http://dx.doi.org/10.1109/SICE.2006.315341

**A new approach to the design of dynamic output feedback stabilizer for LTI systems**

Y.I. Son, H. Shim, N.H. Jo, and K.I. Kim

In Proc. of American Control Conf., Boston, USA, 2004, pp. 1452-1456

**Design of a dynamic output feedback law for replacing the output derivatives
**Y.I. Son, H. Shim, N.H. Jo and K.I. Kim

In Proc. of 3rd Int. Conf. on Control, Automation and Systems (ICCAS), Gyeongju, Korea, 2003, pp. 337-341

**A passivity-based control for a crane system without velocity measurements
**Y.I. Son, Y.D. Lim, B.G. Choi, H. Shim, and N.H. Jo

In Proc. of 2nd Int. Conf. on Control, Automation and Systems (ICCAS), Jeonbuk, Korea, 2002

**Dynamic output feedback regulation of robots with flexible joints**

Y.I. Son, H. Shim, N.H. Jo and J.H. Seo

In Proc. of 2nd Int. Conf. on Control, Automation and Systems (ICCAS), Jeonbuk, Korea, 2002

**Dynamic output feedback passification with application to an elastic joint robot**

Y.I. Son, H. Shim and J.H. Seo

In Proc. of 40th IEEE Conf. on Dec. and Control, Orlando, USA, 2001, pp. 2410-2415

http://dx.doi.org/10.1109/.2001.980623

**Point-to-point control of elastic joint robots—dynamic output feedback passification approach**

Y.I. Son, H. Shim, and J.H. Seo

In Proc. of IEEE Int. Symp. on Industrial Electronics (ISIE), Busan, Korea, 2001

**Passification of nonlinear systems via dynamic output feedback**

Y.I. Son, H. Shim, and J.H. Seo

In Proc. of 38th IEEE Conf. on Dec. and Control, Phoenix, USA, 1999, pp. 4877-4878

http://dx.doi.org/10.1109/CDC.1999.833316

Passive systems are quite easy to control, but the necessary condition for passification includes minimum phase property and (relative degree = one), both of which are invariant under feedback. Then, by placing a dynamic system in parallel with the plant, both can be changed (and the parallel component will then be put in the feedback loop after the design). This is basically an ‘output re-definition’ technique with *dynamic* component.

### I. Control Methodologies

**Linear Systems with Hyperbolic Zero Dynamics Admit Output Regulator Rejecting Unknown Number of Unknown Sinusoids
**H.J. Kim and H. Shim

*IET Control Theory & Applications*, vol. 9, no. 9, pp. 1472-1480, 2015

http://dx.doi.org/10.1049/iet-cta.2014.0692

**Robust cascade control of electric motor drives using dual reduced-order PI observer**

Y.I. Son, I.H. Kim, D.S. Choi, and H. Shim

*IEEE Trans. on Industrial Electronics,* vol. 62, no. 6, pp. 3672-3682, 2015

http://dx.doi.org/10.1109/TIE.2014.2374571

**Adaptive add-on output regulator for rejection of sinusoidal disturbances and application to optical disc drives**

H.J. Kim, H. Shim, and N.H. Jo

*IEEE Trans. on Industrial Electronics,* vol. 61, no. 10, pp. 5490-5499, 2014

http://dx.doi.org/10.1109/TIE.2014.2304920

**Finite-time stabilizing dynamic control of uncertain multi-input linear systems**

S. Seo, H. Shim, and J.H. Seo

*IMA J. of Mathematical Control and Information,* vol. 28, no. 4, pp. 525-537, Dec., 2011

http://dx.doi.org/10.1093/imamci/dnr017

**Switching adaptive output feedback MPC for a class of input-constrained linear plants
**J.S. Kim, T.W. Yoon, H. Shim, and J.H. Seo

*IET Control Theory & Applications*, vol. 2, no. 7, pp. 573-582, 2008

http://dx.doi.org/10.1049/iet-cta:20070120

**Locally optimal and robust backstepping design for systems in strict feedback form with C^1 vector fields**

J. Back, S. Kang, H. Shim, and J.H. Seo

*Int. J. of Control, Automation, and Systems*, vol. 6, no. 3, pp. 364-377, 2008

**Nonsmooth feedback stabilizer for strict-feedback nonlinear systems that may not be linearizable at the origin
**J. Back, S.G. Cheong, H. Shim, and J.H. Seo

*Systems & Control Letters*, vol. 56, no. 11-12, pp. 742-752, 2007

http://dx.doi.org/10.1016/j.sysconle.2007.04.009

**Perfect tracking control for linear systems with state constraint
**D. Bang, J. Choi, and H. Shim

*Int. J. of Control, Automation, and Systems*, vol. 5, no. 2, pp. 218-222, 2007

**Discussion on: An adaptive gradient law with projection for non-smooth convex boundaries**

J. Back and H. Shim

*European Journal of Control*, vol. 12, no. 6, pp. 620-621, 2006

http://dx.doi.org/10.3166/ejc.12.620-621

**Feedback passivity approach to output feedback disturbance attenuation for uncertain nonlinear systems
**Y.I. Son, J.W. Yang, N.H. Jo, H. Shim, and J.H. Seo

*Int. J. of Systems Science*, vol. 35, no. 8, pp. 467-477, 2004

http://dx.doi.org/10.1080/00207720410001734246

#### Conference papers:

**A preliminary result on frequency-shaped model predictive control**

Hyeonjun Yun, H. J, Chang, Hyungbo Shim, and Jin Heon Seo

In Proc. of IEEE 54th Conf. Decision and Control, Osaka, December, 2015, pp. 2395-2399

http://dx.doi.org/10.1109/CDC.2015.7402566

**Global finite-time stabilization of a nonlinear system using dynamic exponent scaling
**S. Seo, H. Shim, and J.H. Seo

In Proc. of 47th IEEE Conf. on Dec. and Control, 2008, pp. 3805-3810

http://dx.doi.org/10.1109/CDC.2008.4739026

Finite-time convergence to the origin requires that the vector field is not locally Lipschitz at the origin. If a controller for this task is designed based on the backstepping procedure, then the closed-loop vector field loses local Lipschitzness not just at the origin, but also on measure-zero manifolds in the state-space. This unnecessarily annoys the analysis because the forward uniqueness needs to be established separately. We propose a different idea for finite-time convergence (with dynamic feedback); that is, we consider an extended state-space and show that the vector field is smooth on the half of the state-space. Then, we show that any solution from this half-set escapes it within a finite time through the origin. In this way, we avoid the headache of forward uniqueness of solutions. This design however is not practical because finite-time convergence does not hold with measurement noises.

**Locally optimal and globally inverse optimal controller for multi-input nonlinear systems
**H. Kim, J. Back, H. Shim, and J.H. Seo

In Proc. of American Control Conf., Seattle, USA, 2008, pp. 4486-4491

http://dx.doi.org/10.1109/ACC.2008.4587202

**Locally optimal and robust backstepping design for C^1 vector fields
**S. Kang, J. Back, H. Shim, and J.H. Seo

In Proc. of 7th Int. Conf. on Control, Automation, and Systems (ICCAS), Seoul, Korea, 2007, pp. 2212-2217

http://dx.doi.org/10.1109/ICCAS.2007.4406700

**Adaptive regulation for nonlinear systems with unknown virtual control coefficient and nonlinear parameterization
**S. Seo, H. Shim, and J.H. Seo

In Proc. of SICE-ICASE Int. Joint Conf. (SICE-ICCAS), Busan, Korea, 2006, pp. 3234-3239

http://dx.doi.org/10.1109/SICE.2006.314885

**Track following controller for optical disk drives based on adaptive output regulation
**H.J. Kim, W.H. Kim, C.C. Chung, and H. Shim

In Proc. of 16th IFAC World Congress, Prague, Czech Republic, 2005

http://dx.doi.org/10.3182/20050703-6-CZ-1902.01216

**Non-smooth feedback stabilizer for strict-feedback nonlinear systems not even linearizable at the origin
**S.G. Cheong, J. Back, H. Shim, and J.H. Seo

In Proc. of American Control Conf., Portland, USA, 2005,

*pp. 1907-1912*

http://dx.doi.org/10.1109/ACC.2005.1470247

**Design and experiment of add-on track following controller for optical disc drives based on robust output regulation
**H. Shim, H.J. Kim, and C.C. Chung

In Proc. of American Control Conf., Boston, USA, 2004, pp. 1829-1835

Engineers from industry are sometimes reluctant to replace their existing controller that has been already in their production line, even if a new control design method is discovered. As an alternative, we propose an ‘add-on’ controller whose role is just to append some performance that is lacking in the pre-installed controller. This add-on controller may not use any detailed information of the pre-installed controller simply because the information is not available (suppose that the controller is already packed in a chip, and no more document remains). In particular, output regulator is well suited for this purpose, just by appending the ability of rejecting sinusoidal disturbances exactly without perturbing the stability of the existing closed-loop.

**Design of output regulator for rejecting periodic eccentricity disturbance in optical disc drive
**H. Shim, H.J. Kim and C.C. Chung

In Proc. of 3rd Int. Conf. on Control, Automation and Systems (ICCAS), Gyeongju, Korea, 2003, pp. 452-457

**A new vision-sensorless anti-sway control system for container cranes
**Y.S. Kim, H. Shim, H. Yoshihara, N. Fujioka, H. Kasahara, S.K. Sul

In Proc. of IEEE Industry Applications Society 38th Annual Meeting, Salt Lake City, USA, 2003, pp. 262-269

**Multirate output feedback control and its application to Galvanometer servo systems**

C.C. Chung, S.H. Lee, D.S. Jeong and H. Shim

In Proc. of American Control Conf., Denver, USA, 2003

**Adaptive output feedback controllers for feedback passive nonlinear systems
**Y.I. Son, H. Shim, N.H. Jo and J.H. Seo

In Proc. of 2nd Int. Conf. on Control, Automation and Systems (ICCAS), Jeonbuk, Korea, 2002

**Output feedback stabilization of non-minimum phase nonlinear systems
**N.H. Jo, Y.I. Son and H. Shim

In Proc. of 2nd Int. Conf. on Control, Automation and Systems (ICCAS), Jeonbuk, Korea, 2002

**Semiglobal robust stabilization of nonlinear systems without vanishing condition**

N. Bok, H. Shim, Y. I. Son and J.H. Seo

In Proc. of 5th IFAC Nonlinear Control Systems Design Symposium (NOLCOS), St. Petersburg, Russia, 2001

**Robust control of nonlinear systems with nonvanishing nonlinear parametrization
**H. Shim, K.T. Yu, Y.I. Son, and J.H. Seo

In Proc. of 4th IFAC Symp. on Nonlinear Control Systems Design (NOLCOS), Enschede, The Netherlands, 1998, pp. 25-30

**Robust tracking control of nonlinear systems with pure feedback uncertainties
**J. Byun, N.H. Jo, H. Shim, and J.H. Seo

In Proc. of IFAC Conf. on System Structure and Control, Nantes, France, 1998, pp.361-366

**Backstepping design for disturbed virtual controls**

H. Shim, J. Byun, N.H. Jo, and J.H. Seo

In Proc. of American Control Conf., Philadelphia, USA, 1998, pp. 2071-2075

http://dx.doi.org/10.1109/ACC.1998.702991

**Robust stabilization of nonminimum phase nonlinear systems**

N.H. Jo, J. Byun, H. Shim, and J.H. Seo

In Proc. of American Control Conf., Philadelphia, USA, 1998, pp. 3359-3363

http://dx.doi.org/10.1109/ACC.1998.703198

**Robust stabilization of a class of MIMO nonlinear systems: Sliding mode control & passification approach**

J.S. Lee, H. Shim, J. Byun, and J.H. Seo

In Proc. of American Control Conf., Philadelphia, USA, 1998, pp. 776-780

http://dx.doi.org/10.1109/ACC.1998.703513

**Design and analysis of the nonlinear feedback linearizing controller for an electro-magnetic suspension system**

S.J. Joo, J. Byun, H. Shim, and J.H. Seo

In Proc. of 3rd IEEE Conf. on Control Applications, Glasgow, United Kingdom, 1994, pp.593-598

http://dx.doi.org/10.1109/CCA.1994.381400

### J. Security of Control System

#### Conference papers:

**Encrypting controller using fully homomorphic encryption for security of cyber-physical systems**

Junsoo Kim, Chanhwa Lee, Hyungbo Shim, Jung Hee Cheon, Andrey Kim, Miran Kim, and Yongsoo Song

6th IFAC Workshop on Distributed Estimation and Control in Networked Systems (NECSYS), Tokyo, September 2016

http://dx.doi.org/10.1016/j.ifacol.2016.10.392

**Zero-stealthy attack for sampled-data control systems: the case of faster actuation than sensing**

Jihan Kim, Gyunghoon Park, Hyungbo Shim, and Yongsoon Eun

to be presented at *IEEE Conf. Decision and Control,* Las Vegas, December, 2016

**When adversary encounters uncertain cyber-physical systems: Robust zero-dynamics attack with disclosure resources**

Gyunghoon Park, Hyungbo Shim, Chanhwa Lee, Yongsoon Eun, and Karl H. Johansson

to be presented at *IEEE Conf. Decision and Control,* Las Vegas, December, 2016

**Detection of sensor attack and resilient state estimation for uniformly observable nonlinear systems**

Junsoo Kim, Chanhwa Lee, Hyungbo Shim, Yongsoon Eun, and Jin H. Seo

to be presented at *IEEE Conf. Decision and Control,* Las Vegas, December, 2016

**A secure and robust state estimation under sensor attacks, measurement noise, and process disturbances: observer-based combinatorial approach**

Chanhwa. Lee, Hyungbo Shim, Yongsoon Eun

In Proc. of 14th *European Control Conf.,* pp. 1866-1871, Austria, Linz, 2015

http://dx.doi.org/10.1109/ECC.2015.7330811

### K. Control of Hybrid System

#### Conference papers:

**Tracking control for hybrid systems with state jumps using gluing function**

Jisu Kim, Hyungbo Shim, and Jin Heon Seo

to be presented at *IEEE Conf. Decision and Control,* Las Vegas, December, 2016

**State estimation strategy without jump detection for hybrid systems using gluing function
**J. Kim, H. Cho, A. Shamsuarov, H. Shim, and J.H. Seo

In Proc. of IEEE 53rd Conf. on Dec. And Contr., Los Angeles, USA, 2014, pp. 139-144

http://dx.doi.org/10.1109/CDC.2014.7039372

### O. Other publication

#### Intelligent Transportation: Non-stop Intersections

**Three-dimensional time-space grid allocation algorithm for traffic control of autonomous vehicles at an intersection**

Jaeyong Kim, Jin Gyu Lee, Seungjoon Lee, Hyuntae Kim, Hyungbo Shim, Yongsoon Eun, and Kangwon Lee

In Proc. of 15th International Conference on Control, Automation and Systems (ICCAS 2015), Busan, Korea

#### Book Chapter

**Observer design for switched linear systems with state jumps**

A. Tanwani, H. Shim, and D. Liberzon

Hybrid Dynamical Systems: Observation and Control, Lecture Notes in Control and Information Sciences, vol. 457, ISBN 978-3-319-10795-0, Springer, 2015

http://dx.doi.org/10.1007/978-3-319-10795-0_7

#### Thesis

**Design of robust controller for feedback linearizable nonlinear systems**

H. Shim, *M.S. Thesis*, Electrical Engineering Department, Seoul National University, 1995

**A passivity-based nonlinear observer and a semi-global separation principle**

H. Shim, *Ph.D. Dissertation*, Electrical Engineering Department, Seoul National University, 2000

Distinguished Dissertation Award

Download: 00.thesis.Shim.pdf