Akio Nagamatsu

Approach for Simultaneous Optimization of a Structure and Control System

The design variables of both the structural and the control parameters are optimized simultaneously by the sensitivity analyse to minimize the response due to disturbances of both white noise and colored noise subjected to a constraint so that the system is stable corresponding to high-order natural modes. Three kinds of models are adopted in the approach, namely, the original spatial model by finite element method, the reduced modal model for designing the control system, and the original modal model for assuring stability of the system. The validity and the usefulness of the present approach are verified by a vibration control experiment of a steel plate

Optimum design method for hydraulic engine mounts

This paper shows the optimum design method of the hydraulic engine mount. This engine mount has been developed recently to significantly reduce the vibration in car bodies emitted by engines. The resonance peak of conventional engine-mount system can not be suppressed sufficiently. Hydrauric engine mounts are able to suppress the resonance peak by using the fluid reaction effect of the fluid enclosed in the mount. The design was recently modified by trial and error experimentation. Du to the lack of information on a suitable design, its ability had not been effectively demonstrated. In this paper, after analyzing the mount, its optimum design formula is obtained in a very simple and useful manner similar to the design equation of dynamic absorbers, The effectiveness of the formula is confirmed theoretically and experimentally.

Integrated optimum design of structure and H∞ control system

An approach for an integrated optimum design of a structure and an H∞ control system is presented. The complex method and the genetic algorithm are adopted in the optimization process in the integrated design. The structural shape and the control system, including the locations of both sensors and actuators, are optimized simultaneously by the proposed approach. The improvement of frequency response shaping under the constraint of the structural mass can be realized by the integrated optimum design presented in this paper. The desired properties with respect to the control performance and the robustness are realized by the frequency shaping ability of H∞ control. Effectiveness of the presented approach is verified by both simulation and experiment by the integrated design of a panel structure and H∞ control system.

Integrated design of structure and control system considering performance and stability

Integrated optimum design of structure and control system is expected to achieve the higher performance of various mechanical systems. Recently, much efforts have been given to develop the integrated optimization methods in order to improve the dynamic characteristics of the combined structure/control systems. The objective of this paper is to present some concepts of the integrated optimum design in vibration control problems. Some integrated optimization problems are introduced with applications.

Adaptive Control of 4WS System by Using Neural Network

SUMMARY An adaptive control system of the model following type is proposed for drive motion control of a four wheel steering (4WS) car with using neural network (NN) which has mastered nonlinear friction force between tire and road surface. A model of one rigid body is adopted which represents appropriately two kinds of car motion caused by steering action, namely the lateral displacement and the yawing rotation, and an equation of motion is described in a simplified form to make a system equation for motion control possible. Nonlinear relation between the cornering force of tire and the slip angle is obtained by numerical analysis with the tire model proposed by E. Fiala, taking friction coefficient and car speed as the parameters. The result is used as the teaching signal for NN. Three NN are used in the control system composed of both the feed-forward and the feedback circuits in order to realize adaptive control. Validity and usefulness of the proposed adaptive control system with NN are verified by t...

Optimum design of structures by sensitivity analysis

Abstract A series of researches by the authors on structural optimum design by sensitivity analysis is introduced. First, the sensitivity of the anti-resonance frequency is defined, and an approach to eliminate the resonance peak from the frequency response function is proposed using this sensitivity. Next, an experimental approach for structural optimization based on a vibration test is introduced. An approach for optimum design combined with a substructure synthesis method is proposed, in which the objective function is an impulse response function. The proposed methods are illustrated by some examples.

Optimum design method for hydraulic engine mount.

This paper shows the optimum design method of the hydraulic engine mount. This engine mount has been developed recently to significantly reduce the vibration in car bodies emitted by engines. The resonance peak of conventional engine-mount system can not be suppressed sufficiently. Hydrauric engine mounts are able to suppress the resonance peak by using the fluid reaction effect of the fluid enclosed in the mount. The design was recently modified by trial and error experimentation. Du to the lack of information on a suitable design, its ability had not been effectively demonstrated. In this paper, after analyzing the mount, its optimum design formula is obtained in a very simple and useful manner similar to the design equation of dynamic absorbers, The effectiveness of the formula is confirmed theoretically and experimentally.

Robust identification and control design for engine mount

The increasing attention on the applications of advanced robust control to automotive motivates the investigation of engine mount. The state-space frequency domain identification method is used to construct a model for robust control design. Then an H/sub /spl infin// controller is calculated by the linear inequality matrix algorithm for the vibration suppression of engine mount.

Vibration analysis and structural optimization of a press machine

Abstract The natural modes and corresponding frequencies of a C-type press machine are analysed by the component mode synthesis method. The total structure is divided into 32 components. The natural modes of each component are calculated individually by the finite element method. The degrees of freedom of the components are reduced with the local model coordinates. The equations of motion of all components are combined to make up the total equation of motion. The impact force and the dynamic response of this press machine at the moment of actual punching of a steel plate are measured. The same dynamic response is calculated by the time-domain simulation analysis. The calculated result of the relative displacement between the punch and the die agrees well with the measured result in actual punching. The optimum design is performed by a sensitivity analysis. As a result, the maximum value of the relative displacement between the punch and the die decreases to 40 percent of the usual machine value.

Integrated optimum design of structure and servosystem with dynamic compensator

Approaches for optimum design of structure and servosystem to achieve high speed positioning and stability are developed in this paper. Both the structural optimization considering controllability and the integrated optimum design of structure and servosystem are discussed to realize the desired properties of the closed-loop system. This paper considers two types of the servosystem, namely one is composed of dynamic compensator for single input and single output system, and the other is composed of LQI control system. The desired frequency characteristics of the servosystem are achieved by the integrated optimization of structure and dynamic compensator. The integrated optimization of structure and LQI control system can improve the time history response of the closed-loop system. Furthermore, assuring the stability against the high order modes of the structure is satisfied by the integrated optimizations. Simulation and experimental results with a simplified positioning device show the effectiveness and the practicability of the proposed approaches.