Showing papers by "Keigo Watanabe published in 1997"

Impedance control for articulated robot of 6 degree-of-freedom in consideration of critically damped condition with an object dynamics

Abstract: This paper presents a new position-based impedance control that can take into account of a desired position in the force control, and gives a transformation technique from the position command to the torque command in order to apply the control to an industrial robot whose servo system is opened or to implement it in computer simulations. In order to determine a suitable compliance without trial and error, this paper introduces a new method that produces the desired time-varying compliance, giving the critical damping in contact with an object, by using information on inertia matrices. Simulation results have shown that the proposed methods are very effective for realizing it in industrial robots and for deciding the desired compliance without any complicated tuning.

A Nonlinear Robust Control Using a Fuzzy Reasoning and Its Application to a Robot Manipulator

Abstract: A simplified adaptive nonlinear robust controller (SANROC) has been studied in the literature. However, this is based on using the so-called matching condition. The present controller is not based on using such a condition. The estimate of an upper bound for uncertainties is usually increased by using the adaptive mechanism, e.g., by consisting of a monotonically increased function. In this paper, instead of using such an analytically adaptive mechanism, a fuzzy reasoning technique is also incorporated with the adaptive mechanism of SANROC. The proposed method is applied to a pantagraph type robot manipulator. The effectiveness of the present method is illustrated by some experiments.

Stochastic Fuzzy Control : Theoretical Derivation

Abstract: Stochastic fuzzy control using stochastic control theory, instead of using conventional fuzzy reasoning, is proposed. We first solve a control problem of one-step predictive output tracking for linear stochastic systems. Next, we consider dynamic multiple model adaptive control(MMAC)for the initial data distribution, under the uncertainties of the initial states. We further consider static MMAC that can be applied for cases of completely unknown plants. It is then shown that a stochastic fuzzy control has some Gaussian potential functions as membership functions and can be used to assign some a priori probabilities to the fuzzy sets or to the control rules, if the probability density function with respect to the output error is replaced by a simple characteristic function. It is also shown that the stochastic fuzzy contol becomes fuzzy control, if all of the a priori probabilities are set to be equal at any control instant.

Rotational control of an omnidirectional mobile robot using a fuzzy servo controller

Abstract: It is known that the equation of motions for an omnidirectional mobile robot is nonlinear with respect to the rotational angle between the moving and absolute coordinate systems In this paper, a fuzzy model approach is applied to the control of a time-varying rotational angle, in which multiple linear models are obtained by utilizing the original nonlinear model in some representative angles and they are used to derive the optimal type 2 servo gain matrices The effectiveness of the proposed method is illustrated by giving some simulations for the trajectory tracking control problem

An evolution strategy with competing subpopulations

Abstract: Evolution strategies, based on the natural evolution, are the algorithms to solve the parameter optimization problems numerically. In this paper, a new evolution strategy (ES) is proposed to solve optimal control problems. With a view to making a balance between exploration and exploitation, a competing subpopulation based arithmetical crossover technique is proposed. The effectiveness of the proposed ES is illustrated by some simulations for the push-cart (a discrete-time optimal control model) control problem.

A Design Method of VSS Observer for Continuous-Time Systems with Output Uncertainties

Abstract: VSS observers are considered for continuous-time systems, in which the nominal plant model is linear, but there exist bounded plant and output uncertainties. We first present a design method of a VSS observer based on use of some extensions of a conventional approach that uses an algebraic Lyapunov equation. It is then shown that such a method cannot be successfully applied to the system with any linear part, if we desire to use a unique solution to the algebraic Lyapunov equation. Namely, this method is only applicable to a restricted class of systems. In order to develop a VSS observer applicable to a wider class of systems, we next propose a design method based on use of an algebraic Riccati equation, associated with a linear filtering problem. A relationship between the two\design methods is also discussed. Simulation results show that the proposed method is effective for designing a VSS observer for a second-order nonlinear system with band limited output noise, as the output uncertainty.