Hiroo Yamaura

Improved moving properties of an omnidirectional vehicle using stepping motor

Many kinds of omnidirectional vehicles driven by DC motors have been proposed and developed for application in robotics systems, but they have various problems like stability or operability in practical use, and have to be controlled by feedback system. This paper describes the improved moving properties of an omnidirectional vehicle driven by a stepping motor. An omnidirectional vehicle, which can move in all directions without changing the body direction of the vehicle, has been developed. This omnidirectional vehicle is used as the base of a calligraphy robot which is able to write Chinese characters using a brush. The movement and the control of this vehicle are evaluated, and the fields where this vehicle can be used are examined. Experimental results show that the proposed device is useful in achieving the desired performance.

A Globally Convergent Robust Controller for Robot Manipulator

Abstract In this paper, a robust nonlinear control scheme for a trajectory tracking problem of rigid robot manipulator is proposed. In the design of this control scheme, Lyapunov stability theory and some important properties of rigid manipulator are used. the closed-loop system with the presented control scheme, is globally exponentially stable, and the output tracking error that is shaped by a formula asymptotically converges to zero. Based on this formula, a desired transient error performance may be achieved by choosing appropriate control parameters. Some simulation results are provided for illustrating the performance of this control scheme.

Optimizing fuzzy logic with genetic algorithm

We consider the existence of an optimal solution and the convergency of a genetic algorithm when it is used for optimizing fuzzy logic. The existence of an optimal solution is assured by the compactness of the the set of membership functions that defines the rules of the fuzzy logic. The convergency of the algorithm is assured by the compactness and the modification of the algorithm.

Compactness of a set of fuzzy membership functions and existence of optimal solution in fuzzy-output feedback

This paper presents a framework for studying the existence of optimal control based on fuzzy rules. The framework consists of two propositions: 1) a set of fuzzy membership functions with bounded gradients is a uniformly bounded, equi-continuous closed set, and so the set of fuzzy membership functions is sequentially compact by the Ascoli-Arzela theorem; and 2) the defuzzification function is continuous on the set of fuzzy membership functions with bounded gradients. The existence of fuzzy optimal control is proved.

Bitonic sort on a network computer with a node failure

Massively parallel computers are being realized for aiming at high performance. Bitonic sort is an efficient algorithm for network computers. But generally, it is impossible to use a bitonic sort algorithm on a network computer with a node failure. This paper presents a fault-tolerant scheme of bitonic sort algorithm for a network computer that makes it possible to tolerate a node failure without an additional hardware cost. The method does not have hardware redundancy but has software redundancy. The method does not depend on the network topology. However, the method takes about two times as many steps as that of original bitonic sort. This paper also shows that the method is applicable to a chordal ring connected computer as an example.

Existence of a Low-Order Integral Manifold and Non-linear Regulator Problems

Abstract A set of sufficient conditions which confine the solution of weak non-linear differential equations to some low order stable integral manifold are derived by applying the fixed point theorem. These conditions can be weakened substantially if the initial values of the differential equations are confined to some bounded region. These results are then applied to weak non-linear optimal regulator problems. Sufficient conditions are derived for the existence of a non-linear feedback control law which meets the neccesary conditions for optimality. An algorithm for calculating the feedback control law is proposed. Simulations using the algorithm exhibited favorable results.