Kenji Fujimoto

This paper investigates the differential eigenstructure of Hankel operators for nonlinear systems. First, it is proven that the variational system and the Hamiltonian extension with extended input and output spaces can be interpreted as the Ga/spl circ/teaux differential and its adjoint of a dynamical input-output system, respectively. Second, the Ga/spl circ/teaux differential is utilized to clarify the main result the differential eigenstructure of the nonlinear Hankel operator which is closel

This paper discusses balanced realization and model order reduction for both continuous-time and discrete-time general nonlinear systems based on singular value analysis of the corresponding Hankel operators. Singular value analysis clarifies the gain structure of a given nonlinear operator. Here it is proved that singular value analysis of smooth Hankel operators defined on Hilbert spaces can be characterized by simple equations in terms of their states. A balanced realization and model order r

It has been established that the long-term infection of chronic hepatitis C leads to the increased risk of hepatic fibrosis and hepatocellular carcinoma. Currently, histological diagnosis by invasive and painful liver biopsy is the gold standard for evaluating the hepatic fibrosis stage. Because of a side effect or patient inability to cope with the pain, it is difficult to assess the fibrosis stage frequently using liver biopsy. Recently, instead of liver biopsy, many articles have been publish

In this note, a novel iterative learning control scheme for a class of Hamiltonian control systems is proposed, which is applicable to electromechanical systems. The proposed method has the following distinguished features. This method does not require either the precise knowledge of the model of the target system or the time derivatives of the output signals. Despite the lack of information, the tracking error monotonously decreases in L/sub 2/ sense and, further, perfect tracking is achieved w

In this paper a new balanced realization method for nonlinear systems is proposed which is based on singular value analysis of Hankel operators. The proposed method balances the relationship between the input-to-state behavior and the state-to-output behavior of nonlinear dynamical systems, whereas the existing results only balance the relationship among the coordinate axes of the state-space. This result is expected to be a basis for new model reduction and system identification of nonlinear sy

This letter proposes a novel framework to design a passivity based sliding mode controller for mechanical systems described by simple port-Hamiltonian systems. For this class of systems, passivity based control is often used to design a stabilizing controller which employs a physical energy of the plant system as a Lyapunov function candidate. This letter proves that there exist a special class of passivity based controllers which coincide with sliding mode ones. This approach enables us to obta