Nobuya Takahashi

Controllability and stabilizability of a networked control system with periodic communication constraints

Abstract This paper proposes a new model for a networked control system and considers its controllability and stabilizability. To control a linear time-invariant discrete-time plant via a bus with limited capacity, we introduce a hold device and a communication sequence which follows a given ω -periodic pattern. Incorporating the communication sequences and hold device into the original plant amounts to extending the original time-invariant state equation to a ω -periodic one which has the higher order. We assume that the communication sequence is admissible. It is shown that controllability and stabilizability of the plant are preserved in the periodic extended system under the assumption that the zeros of the communication sequence characteristic polynomial do not coincide with the eigenvalues of the plant.

Trajectory for saving energy of a direct-drive manipulator in throwing motion

In this article, equations of motion of a closed-type manipulator, whose mechanism can easily be made lighter, are derived in consideration of the characteristics of the driving source. Considering the final condition of angular displacement and angular velocity in throwing motion, trajectories of velocity for saving energy are calculated by iterative dynamic programming, and the dynamic characteristics of manipulator control based on the trajectory for saving energy are analyzed theoretically and investigated experimentally.

An LMI approach to observer-based guaranteed cost control

This article presents a design method for an observer-based guaranteed cost controller for a class of uncertain linear systems, in which full state variables cannot be measured. The perturbations are assumed to be described by structural uncertainties. The linear matrix inequality (LMI) approach is applied to design the observer-based controller. The controller and observer gains are obtained by solving the LMI optimization and feasibility problems, respectively. A numerical example shows the potential of the proposed method.

Robust control method for the inverted pendulum system with structured uncertainty caused by measurement error

In this article, we propose a design method for an inverted pendulum system with a structured uncertainty. We consider that such an uncertainty is caused by a measurement error in the rotation angle of the pendulum and effects on the system structure that cannot be included in the nominal elements. For the uncertain system obtained, we apply an integral tracking control and the guaranteed cost control to design a robust, stable, tracking control system. Finally, we show the effectiveness of our method through a numerical example.

A study of manipulator with passive revolute joint

In this article, equations of motion of a manipulator, whose mechanism has a passive revolute joint, are derived in consideration of the characteristics of driving source. Considering the fi nal condition of displacement and velocity of the passive joint, trajectories of velocity for energy saving are calculated by iterative dynamic programming. And the dynamic characteristics of manipulator control based on the trajectory for energy saving are analyzed theoretically and investigated experimentally.

Experimental analysis of the two-link manipulator in consideration of the relative motion between link and object

In this article, equations of motion of two-link manipulator are derived in consideration of characteristics of driving source. By considering for different heights of falling object, trajectories for saving energy are calculated by iterative dynamic programming method. And the dynamic characteristics of two-link system controlled based on the trajectory for saving energy are also analyzed theoretically and investigated experimentally.

Analysis of manipulator in consideration of impact absorption between link and object

In this article, equations of motion of a manipulator are derived in consideration of characteristics of driving source. By considering impact force absorption between a link and an object, trajectories for saving energy are calculated by the iterative dynamic programming method. And, the dynamic characteristics of manipulator controlled based on the trajectory for saving energy are also analyzed theoretically and investigated experimentally.

Stabilization of linear time-invariant systems with periodic communication constraints by output sample hold control

This article considers feedback control systems wherein the control loops are closed through a real-time network, and expresses the linear time-invariant system with the constraint in an input or output as a periodic discrete time system. It is shown that this system is stabilized by using output sample hold contol. This method has the merit that the capacity of a sensor-controller communication bus is small.

Analysis of a manipulator in relation to collision between a link and an object

In this article, equations of motion of a manipulator are derived after consideration of the characteristics of the driving source. By considering a collision between a link and an object, and considering the active motion to absorb the kinetic energy of the object, the trajectories for saving energy are calculated by the iterative dynamic programming (IDP) method. The dynamic characteristics of manipulator control based on the trajectory for saving energy are also analyzed theoretically and investigated experimentally.

A study of guaranteed cost control of a manipulator with a passive revolute joint

In this article, we consider the robust control problem of a two-link RR manipulator with uncertainty in the joint angle which is caused by several factors. The first purpose is to derive an uncertain linear time-invariant (LTI) system for a two-link RR manipulator which includes uncertainty in the rotational angle of each joint. The uncertainty is expressed in a system structure matrix in an explicit form. For this uncertain system, we apply guaranteed cost control. Finally, we show the effectiveness of our method by a numerical example.