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This paper studies robust stability analysis problems of sampled-data systems against uncertainties existing in continuous-time plants. We propose to introduce periodically time-varyingscaling to robust stability analysisagainst parametric uncertainties.First, we explain what motivates usto introduce periodically time-varyingscaling to robust stability analysis against parametric uncertainties.Next, we consider periodically time-varying scaling defined througha staircase functionand show a way to determine an optimal staircase functionin the $H_\infty$ norm sense using an LMI optimization technique.We demonstrate by a numerical examplethe effectiveness of applying periodically time-varyingscaling to sampled-data systems.

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In this paper, we discuss robust D-stability analysis of uncertain polynomial matrices. By introducing polynomial-type multipliers, we show that it is possible to obtain varieties of LMI conditions for D-stability analysis in a constructive way according to the order/structure of the multipliers to be employed. Then, we show the effectiveness of the proposed LMI conditions when dealing with robust D-stability analysis problems of polytopic-type uncertain polynomial matrices.

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This paper shows an L2 stability analysis method of sampled-data systemswith time-delay using multipliers based on the passivity theorem.It is demonstrated with a numerical example that L2 stability about a sampled-data system with a given time-delay can be analyzed by introducing multipliers and applying a loop transformation.

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It is important to design such controllers that feedback systems are robust to parameter perturbations. In this report, we propose an improving method of controller parameters for SISO feedback systems in such a way that enlarge stability radius while keeping poles assigned. It is shown that the proposed procedure is carried out using gradient-based approach.

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Robust stability of linear time-delay systems has been studied by many reseachers in recent years. However, because of difficulty in dealing with uncertainties, existent robust stability conditions are often conservative and algorithms are too complex to check. In this report, robust stability of linear time-delay systems is studied by Lambert W function. Using the function, a delay-dependent robust stability condition for a class of linear time-delay systems is dirived in the form of a necessary and sufficient one. Moreover, by ubiquitously available software such as Mathematica and Maple which include the function, robust stability can be checked easily.

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In this paper, we will present an asynchronous data replication equipped with workflow controller for load balance in the distributed system. The data replication system is characterized by transaction log and synchronizedly periodical reflection from respective replica server to the primary copy server. We will propose protocol about the replica and primary copy. We will also report implementation about our protocol of the asynchronous data replication.

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In this paper, we aim at achieving accurate positioningcontrol of a pneumatic artificial antagonist-type actuation mechanism. This system has favorable characteristics such as safe interaction with humans and high flexibility. However, due to the nonlinearity of the system behavior as well as the weak rigidity of the compressed air, it is quite difficult to achieve accurate positioning control. To overcome these difficulties, in our preceding studies, we adopted the design method of two-degree-of-freedom (2DOF) LQI servo systems, by which satisfactory tracking performance for step references was achieved under various load conditions.In this paper, we consider ramp references and apply the design method of plant-variable (PV) optimal control, which could be regarded as a natural extension of the design method of 2DOF-LQI servo systems. It is demonstrated that accurate and quick tracking can be achieved for step and ramp references by this method.

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This paper investigates the problem of designing a linear state feedback control to stabilize a class of single-input uncertain linear dynamical systems. The systems under consideration contain time-varying uncertain parameters whose values are unknown but bounded in given compact sets. In view of controllability for a class of systems containing uncertain parameter, we investigate the conditions under which system can be stabilized by a linear control for all admissible variations of uncertainties.

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This paper presents a new design method of stable decoupling. The feature is that the inverse system for stable decoupling can be easily obtained from inner of the traditional feedback for decoupling.

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This paper studies a discretization method of continuous-time controllers taking account of the intersample behavior of the resulting sampled-data systems. First, we state how to evaluate the discretization error based on the Hilbert-Schmidt norm of the sampled-data frequency response. Second, we determine what we call the desirable frequency response of the discretized controller, and show that it can be obtained in a closed form in terms of the state-space representations of the controller and the plant. Furthermore, we propose some discretization methods of controllers based on the state-space formula about the desirable frequency response. We also demonstrate the effectiveness of these methods by numerical examples.

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Most practical systems include time delays due to measurement, computation, transmission and transport phenomena. For the systems including such delays in output paths, we have been developing a state predictor that predicts the current state of the system. The predictor consists of full-order observers and finite interval integrators, which estimate past state and compensate the effect of delays, respectively. In this paper, we introduce another finite interval integrators into the predictor in order to take the latest information included in the output into account.

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This paper is concerned with exponential stabilization of nonholonomicport-controlled Hamiltonian systems with respect to homogeneous norm viaoutput feedback.First, a technique is introduced which asymptotically stabilizes nonholonomic Hamiltonian systems using time-varying outputfeedback.In order to obtain a dynamic feedback, an integrator is added to thesystem firstly.Then a special class of generalized canonical transformation is utilized to let theintegrator play the role of an estimator of the unmeasurable statebased on passivity and to preserve the structure of nonholonomicHamiltonian systems.Thus, this technique achieves the time-varying output feedback stabilization of nonholonomicHamiltonian systems.Next, it is proved that this technique can be extended to render thefeedback system exponentiallystable. The technique above guarantees exponential stability of the feeback system if the design parameters arechosen in a certain way based on homogeneity of the system.Furthermore, the effectiveness of the proposed technique isdemonstrated using a four-wheeled vehicle example.

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Recent mainstream walking robots need active control at all times. On the other hand, a passive dynamic walking robot is more efficient, because it can walk without any active control. However, one shortcoming is that it cannot walk on level ground. There is a need to study new theory for efficient walking on level ground. We have constructed a new type of walking machine based on a compass type walking model. This paper describes gait control based on online simulation for the compass type walking machine.

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For more than a decade, the non-contact atomic force microscopy has been extensively studied because of its perspective to high resolution innanometer-scale. A microcantilever probe driven near its resonance frequency is utilized as a sensor to detect the interaction force between the tip of the probe and the surface of the confronted sample. By scanning the surface with keeping the interaction force constant, the topography of the surface can be imaged with resolution on molecular or atomic scale without damaging samples. However, it has been recently shown that the microcantilever probe possibly exhibits the dynamic instability including a chaotic motion due to the nonlinear tip-sample interaction force. In this paper, the time delayed feedback control method (Pyragas method) is employed to eliminate the instable motion from the microcantilever probe. The parameter region of stable operation is extended by stabilizing unstable periodic orbits embedded in the chaotic attractor.

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This study considers the problem of suppressing oscillation of a pendulum with a slider crank mechanism by which the rotary motion of the actuated crank is converted to the horizontal motion of the pivot on the slider. A stability condition for the pendulum is obtained using a Lyapunov-type function, and based on this condition two nonlinear control laws for the crank angle are constructed that effectively suppress the oscillation of the pendulum with a constant amplitude of the pivot. These controls are taken over by a linear one in some neighorhood of the equilibrium point to stabilize the whole state of the system. Numerical and experimental results are given to demonstrate the effectiveness of the proposed methods.

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The adaptive control to which the online do tuning of the controller exists as a method of preventing the reckless driving of the control system and the control deterioration in the changing environment.In this adjustment tuning, the real-time system identification of the parameter is needed.In this research, the identification method that uses consecutive least squares method and frequency response is researched as a parameter real-time identification method.

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