Control Theory Research, Kumamoto University - Hiroshi Okajima

Research Topics

Model Error Compensator (MEC) The Model Error Compensator is a compensation structure that adds robustness to existing control systems without redesigning the base controller. By minimizing the effect of model errors and disturbances in the input-output relation, MEC can be readily applied to a wide range of systems including nonlinear systems, time-delay systems, non-minimum phase systems, and MIMO systems. → Details

Dynamic Quantizer A dynamic quantizer converts high-resolution signals into lower-resolution signals while minimizing quantization error. Our research focuses on the design of feedback-type dynamic quantizers under communication rate constraints, with applications to networked control systems and AD/DA conversion. → Details

Multi-rate Control Systems In practical control systems, sensors and actuators often operate at different sampling rates. Our research addresses the analysis and design of state observers and feedback controllers for multi-rate systems, formulated using cyclic reformulation and linear matrix inequality (LMI) optimization. → Details

Vehicle Control Our research applies control theory to vehicle dynamics, including direct yaw-moment control for electric vehicles, adaptive cruise control, and platoon driving of welfare vehicles. Model-based approaches including MEC are used to achieve robust and precise vehicle motion control. → Details

MCV Observer for Overcoming Outliers The Median of Candidate Vectors (MCV) Observer is a state estimation method robust to outliers in observation signals. By generating multiple state candidates and selecting via median operation, the observer maintains estimation accuracy even when sensor outputs are contaminated by outliers. → Details

Education Topics

Linear Matrix Inequality (LMI) Linear Matrix Inequality is a powerful mathematical tool widely used in control system analysis and design. This page provides an introductory explanation of LMI and its applications in control engineering, including stability analysis and optimal controller synthesis. → Details

Academic Profiles

IFAC TC 2.2. Linear Control Systems ifac-control.org

IFAC 2023 Publicity Member (twitter)

SICE JCMSI AE SICE Journal of Control, Measurement, and System Integration Editorial Board

Outreach

Researchmap / ORCID / Google scholar / Researchgate

YouTube (Control main channel, 10700 subscribers) 

YouTube (English sub channel, 340 subscribers)

Blog

MATLAB File Exchange [Control Animation]

Github (MATLAB, Python codes)

Awards

SICE Education Contribution Award (2023)

SICE 2019 Poster Presentation Award Finalist

ICCAS 2017 Outstanding Paper Award

SICE CPD Point Award (2017)

ICCAS 2016 Outstanding Paper Award

SICE CPD Point Award (2011)

SICE 2010 Young Author Award Finalist

Selected Publications 

H. Okajima and T. Asai：Performance Limitation of Tracking Control Problem for a Class of References, IEEE Transactions on Automatic Control, Vol.56, No.11, pp.2723-2727 (2011) 

H. Okajima, H. Umei, N. Matsunaga and T. Asai：A Design Method of Compensator to Minimize Model Error, SICE Journal of Control, Measurement, and System Integration, Vol.6, No.4, pp.267-275 (2013) (T&F, Open Access) 

H. Okajima, K. Sawada and N. Matsunaga：Dynamic Quantizer Design Under Communication Rate Constraints, IEEE Transactions on Automatic Control, Vol.61, No.10, pp.3190-3196 (2016) 

H. Okajima, Model Error Compensator for adding Robustness toward Existing Control, Preprints of the IFAC World Congress, pp. 3998 - 4005 (2023)

H. Okajima, Y. Hosoe and T. Hagiwara, State Observer under Multi-rate Sensing Environment and Its Design using l2 -Induced Norm, IEEE ACCESS (2023) (Open Access)

Hiroshi Okajima, Yusuke Fujimoto, Hiroshi Oku and Haruto Kondo, Cyclic Reformulation-Based System Identification for Periodically Time-Varying Systems | IEEE Journals & Magazine | IEEE Xplore , IEEE ACCESS (2025) (Open Access) 

→ Full list with abstracts and MATLAB codes: Publications