Research Themes

• Energy saving control using discontinuous or non-positive definite input cost
  Grants-in-Aid for Scientific Research
  01 Apr. 2019 - 31 Mar. 2022
  Yamashita Yuh
  Considering an energy-saving optimal control problem when the target value of the state does not coincide with the stationary point of minimum energy consumption, we formulated the problem by slightly modifying the input cost function from the natural energy consumption and constructed a nonlinear optimal regulator that guarantees asymptotic stability. In addition, when actuators require standby power, the operation of deactivating inefficient actuators according to the value of the state values contributes to energy conservation in redundant input systems. We proposed an optimal controller design method that performs such an operation. We also proposed a control method that includes suspending the communication of sensor values according to output values.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 19H02157
• 制御リアプノフ関数を用いた入力分配制御
  科学研究費補助金(基盤研究(B))
  Apr. 2016 - Mar. 2019
  山下 裕
  日本学術振興会, Principal investigator, Competitive research funding
• Development of topological control theory for decision making
  Grants-in-Aid for Scientific Research
  01 Apr. 2015 - 31 Mar. 2018
  Nakamura Hisakazu
  This research aims to design a framework of combining decision and control from the view point of topology. The major achievements are as follows. Development of a control strategy that dynamically identifies the desired state by the minimum projection method, development of the local minimum connection method for static control Lyapunov function design, and development of a human safety assist control strategy by using control barrier functions. By the preceding achievements, this research elucidates that a control Lyapunov function and a control barrier function are effective for the combination of decision and control.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo University of Science, 15H04022
• Radon測度上の動的システムの研究と都市構造遷移モデルへの応用
  科学研究費補助金(挑戦的萌芽研究)
  Apr. 2014 - Mar. 2017
  山下 裕
  日本学術振興会, Principal investigator, Competitive research funding
• Nonlinear control theory based on generalized semiconcave functions
  Grants-in-Aid for Scientific Research
  01 Apr. 2011 - 31 Mar. 2014
  NAKAMURA Hisakazu, YAMASHITA Yuh, ITO Hiroshi, ENOMOTO Ryuji, FUKUI Yoshiro
  We proposed feed back controller design method by using disassembled differential. Moreover, we confirmed that our proposed method is available for input constrained control systems.
  We proved that Jurdjevic-Quinn type controllers permit local Caratheodory solutions of closed-loop systems.
  We analyzed desingularization phenomena on our proposed minimum projection method, and proposed a singular point assignment method for nonsmooth control Lyapunov function design. Moreover, we proposed static control Lyapunov function and static controller design methods based on dynamic extention and the minimum projection method.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Tokyo University of Science, 23360185
• Stability Analysis of Dynamical Systems on Topological Spaces
  Grants-in-Aid for Scientific Research
  2011 - 2013
  NAKAMURA Nami, YAMASHITA Yuh, NAKAMURA Hisakazu
  We have defined Lagrange stability and input-to-state stability for nonlinear systems on manifolds. Furthermore, we have presented necessary and sufficient conditions for stability by using continuous positive definite proper functions. We have designed an ISS-control Lyapunov function and an input-to-state stabilizing controller for an obstacle avoidance problem of a mobile robot. Then, we have confirmed the effectiveness of the proposed controller by computer simulation. We have proposed a sample input-to-state stabilizing controller for general nonlinear systems on manifolds.
  Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Tokyo University of Science, 23760391
• Study on the nonlinear control using transformation to state-jump system
  Grants-in-Aid for Scientific Research
  2010 - 2012
  YAMASHITA Yuh, NAKAMURA Hisakazu, NISHIDA Gou, NISHIMURA Yuki, TSUZUKI Takayuki
  his study proposes a framework of control system design methodologies bywhich the state space of a dynamical controlled object is extended by adding new continuous or discretecoordinates and a desired closed-loop is designed on the augmented space allowing state-jumps on thenew coordinates. Furthermore, methods of the degeneracy of the extended space for obtaining adiscontinuous static feedback law or a control law with discrete states are given. By introducingstate-jumps, we can construct a controller mathematically even for decision-making problems of thedynamical systems.
  Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, Principal investigator, Competitive research funding, 22360167
• Establishment of nonlinear control theory taking into account global structure of manifold
  Grants-in-Aid for Scientific Research(基盤研究(C))
  2007 - 2009
  Yuh YAMASHITA, Hisakazu NAKAMURA, Gou NISHIDA, Yuki NISHIMURA
  This study presents a general framework for controlling nonlinear systems on general manifolds including non-Euclidean spaces which precedent control theories cannot handle. Global attitude control of satellites, obstacle avoidance of vehicles, and control of acrobots are examples of our problem. This framework provides design procedures generating control laws automatically with discontinuity, logic, or randomness, of which properties are necessary to stabilize such systems on non-Euclidean spaces.
  Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 北海道大学, Principal investigator, Competitive research funding, 19560435
• Development of Plant Operator Model Incorporating Mental and Physical States
  Grants-in-Aid for Scientific Research(基盤研究(B))
  2002 - 2005
  Hirokazu NISHITANI, 今福 啓, 黒岡 武俊, 山下 裕, 小坂 洋明, 中村 文一
  This project aimed at understanding plant operator's behavior under abnormal situations through dynamic simulation by using some cognitive information processing model incorporating the mental and physical states and proposing some method to create appropriate countermeasures. We obtained the following three main results.1.We installed a new plant operator model that is a cognitive information processing model incorporating the mental and physical states on a PC and connected to an industrial boiler plant simulator for operator training. This operator model was used in analyzing the various...
  Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 奈良先端科学技術大学院大学, Coinvestigator not use grants, Competitive research funding, 14380179
• Control system design using non-smooth feedback
  Grants-in-Aid for Scientific Research(基盤研究(C))
  2003 - 2004
  Yuh YAMASHITA, 中村 文一
  1.We obtained a simple expression of the converse Lyapunov theorem for discontinuous systems. Also, the converse Lyapunov theorem for discontinuous homogeneous systems with dilations was developed, which shows that each discontinuous homogeneous strongly stable system with dilation has a homogeneous Lyapunov function. It was shown that the degree of homogeneity indicates the speed of the convergence, i.e. a homogeneous strongly stable system with a negative degree of homogeneity has a finite-time convergence property. The proof of the finite time convergence of high-order sliding mode contr...
  Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 奈良先端科学技術大学院大学->北海道大学, Principal investigator, Competitive research funding, 15560378
• Study on the construction of control theory by the notion of invariance and the development of its introductory course
  Grants-in-Aid for Scientific Research(基盤研究(C))
  2001 - 2003
  Masasuke SHIMA, 横道 政裕, 川村 武, 石動 善久, 山下 裕, 榎本 隆二
  Firstly, the role of invariance in the control theory is studied [1]Invariance with respect to the variation of parameters : Using Frazer-Duncan theorem and monotonicity conditions, we derived a necessary and sufficient condition for the stability of linear systems without regard to the variation of interval parameters, and presented a monotonization method for the system which is not monotone. [2]Feedback design considering structures of Lie algebra : Feedback stabilization and improvement of tracking properties ties are studied for the under actuated mechanical systems such as axi-symmetr...
  Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 北海道大学, Coinvestigator not use grants, Competitive research funding, 13650479
• Control Design for Nonlinear System Described by Differential-Algebraic Equations
  Grants-in-Aid for Scientific Research(基盤研究(C))
  2000 - 2002
  Yuh YAMASHITA, 黒岡 武俊
  In this research, we study controller design of nonlinear systems described by differential-algebraic equations (DAE). In nonlinear cases, it is hard to convert the system to ordinary differential equations (ODE) without redundancy, because nonlinear algebraic equations cannot be solved analytically in general.First, for nonlinear DAE systems with index one, a design method of exact I/O-linearizing control and observer is proposed, where the global-stability condition of the observer is also obtained. The estimated state variables in the observer converge to an invariant manifold determined...
  Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 奈良先端科学技術大学院大学, Principal investigator, Competitive research funding, 12650446
• Estimation of a Plant Operator's Mental State and its Application to Operator Support
  Grants-in-Aid for Scientific Research(基盤研究(B))
  2000 - 2001
  Hirokazu NISHITANI, 黒岡 武俊, 山下 裕
  We have been studying the use of multiple channel elecroencephalogram (EEG) data to infer a human's thinking state. As a result, we have confirmed off-line thinking state estimation to be effective, in experimental studies on simulator training during malfunctions and mathematical problem solving. In this research, we reconsidered the mathematical model for thinking state estimation and concluded that an artificial neural network (ANN) model is more appropriate for real-time use than the linear regression model.We developed a prototype real-time thinking state monitoring system with the ANN...
  Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 奈良先端科学技術大学院大学, Coinvestigator not use grants, Competitive research funding, 12480098
• Modeling and Simulation of Plant-Wide Control Systems
  Grants-in-Aid for Scientific Research(基盤研究(C))
  1997 - 1998
  Hirokazu NISHITANI, 北島 禎二, 黒岡 武俊, 山下 裕
  In this study, plant-wide control is regarded as the total activities generated by feedback control for continuous processes, sequential control for discrete events and supervisory control for process malfunction and equipment failure. The integration of these control elements enables safe and efficient plant control or operation. However, there is no theory for design of the plant-wide control system. Dynamic simulation is the only way to handle such a large and complicated system. In the first year, we investigated modeling and simulation techniques to evaluate system performances of a pl...
  Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 奈良先端科学技術大学院大学, Coinvestigator not use grants, Competitive research funding, 09650830
• Robust Design of Nonlinear Control Systems
  Grants-in-Aid for Scientific Research(一般研究(B))
  1994 - 1995
  Masasuke SHIMA, 川村 武, 山下 裕, 石動 善久
  In this year, we have obtained the following results.1.The nonlinear non-standard H^* control problem is studied. In this research, two cases are concerned with : (a) the case in which the direct-through term from the input to the output does not have full-rank, and (b) the case in which the direct-through term from the disturbance to the measurement output does not have full-rank. In these cases, the square compliment cannot be carried out with the usual method, and thus the Hamilton-Jacobi-Issacs partial differential inequality is not well-defined. To resolve this difficulty, the term inc...
  Ministry of Education, Culture, Sports, Science and Technology, 一般研究(B), 北海道大学, Coinvestigator not use grants, Competitive research funding, 06452248
• ハミルトン・ヤコビ偏微分方程式の数値解法
  科学研究費補助金(奨励研究(A))
  1994 - 1994
  山下 裕
  本研究では、以下の成果を得た。・正準方程式の安定多様体がハミルトン・ヤコビ偏微分方程式の解であることを利用し、時間軸を逆にとることによって、常微分方程式の数値解法に帰着させた。・上記の常微分方程式を数値的に解くにあたって、その初期点を与えるアルゴリズムを開発した。具体的には、初期サンプル点を一様に分布させ、安定多様体上の線形近似式を用いて原点近傍までシミュレートし、さらに安定多様体の1次近似を用いて2n次元の初期点を得る方法を開発した。原点近傍までの所要時間をもとに・得られた解曲線をBezier補間式で最小2乗近似し、状態量χの関数として表現した。その関数を用いて制御器を作ることが可能となった。・上記の手法を基に、購入したワークステーション上に、目的の解を高精度に得る解法パッケージを開発した。・本方法の特長の1つは、得られた解曲線の存在範囲によって、得られた解の有効な定義域が推定できることである。これは、原点でのTaylor展開による従来の方法ではできなかったことである。
  文部科学省, 奨励研究(A), 北海道大学, Principal investigator, Competitive research funding, 06750426
• 遺伝的アルゴリズムによる制御
  科学研究費補助金(奨励研究(A))
  1993 - 1993
  山下 裕
  本研究に関する研究実績は以下の通りである。1.遺伝的アルゴリズムを最適制御問題、特に最適特異制御問題の数値解法に応用した。最適制御問題の数値解法として幾つかの方法が知られているが、最適特異制御問題を解くことのできる方法は非常に少ない。本研究では、遺伝子上に幾つかの時間の点における入力の大きさをコーディングし、3次スプライン曲線でそれらをつないで、制御入力とした。最適制御においては、入力の関数が不連続となることが多いので、遺伝子上には不連続となる場所に関する情報も加えた。本研究では、槽式流通反応系の最適コスト問題に対し、これらの方法を適用したが、bang-bang制御の区間と最適特異軌道の区間が明確に現れ、良好な結果を得た。これらの成果に関して、現在、投稿準備中である。2.遺伝的アルゴリズムをファジイ制御に応用し、シミュレーションを繰り返すことによりファジイルールを自動生成する研究をおこなった。ファジィ制御の前件部の取りうるすべての組み合わせに対して、その後件部を遺伝子上にコーディングし、オフラインでシミュレーションを繰り返し遺伝的アルゴリズムを用いることで、ファジイルールを自動生成した。本研究では、この方法を車両の障害物回避問題に適用した。試行結果の評価値のみの情報で、ランダムなファジイルールが次第に、障害物を回避し目標に到達するように進化した。これらの成果に関しては、さらに...
  文部科学省, 奨励研究(A), 北海道大学, Principal investigator, Competitive research funding, 05855056
• A Study of the System Theory via Controlled Path Integral
  Grants-in-Aid for Scientific Research(一般研究(C))
  1991 - 1992
  Masasuke SHIMA, 山下 裕, 石動 善久
  In this research project, we studied the possibility of system theory based on the controlled path integrals. The dynamical behavior of the system is described by a vector field X=X_0+X_1u^1+...+X_mu^m defined on a manifold M as a state space. u=(u^1,...,u^m) are control inputs to the system. The control u(t) given on [t_0,t_1] deter mines the state trajectory p(t). Assuming that a differential form omega is given and integrating omega(X) along the trajectory, we obtain the controlled path integral associated with omega and X. Outputs of a system, Lyapunov function and the performance index...
  Ministry of Education, Culture, Sports, Science and Technology, 一般研究(C), 北海道大学, Coinvestigator not use grants, Competitive research funding, 03805020
• 非線形制御理論　　　　　　　　　　　　　　　
  Competitive research funding
• Nonlinear control theory　　　　　　　　　　　　　　　
  Competitive research funding