Tomoyoshi Takeuchi

An autonomous fuzzy mobile robot

Autonomous mobile robots should have the capability of recognizing their environments and manoeuvring through those environments on the basis of their own judgement. Fuzzy control is suitable for autonomous mobile robot control where the amount of information to be handled is limited as much as possible and the processing is simple. Autonomous mobile control of a robot is derived from two kinds of controls: for obstacle avoidance and for guidance following an appropriate path to a destination point. Fuzzy control of a robot for obstacle avoidance based on finding permissible passageways using the edges between the floor and the wall or obstacles obtained by processing the image from a CCD camera in front of the robot is developed. Furthermore, guidance control of the robot over paths that are specified in terms of maps may be developed by a process that treats a wrong path as a virtual obstacle on the screen, and the robot advances in the designated direction when it reaches intersections. An autonomous f...

A long‐range and high‐resolution underwater acoustic positioning system

Abstract It is desired to track the location of an underwater data collecting platform using acoustic range data. A long‐range and high‐resolution acoustic system for underwater locating has been investigated. The system provides continuous and highly accurate tracking of a platform referenced to bottom‐mounted buoys. Each reference buoy contains an acoustic transponder, which is used to obtain ranging data from the transponder to the platform. The transponder has a signal source that is phase‐modulated by a maximal‐length binary sequence and a correlation processing unit to be capable of detecting received acoustic signals with high SNR in a noisy environment or in attenuation due to long‐range propagation, and to identify multipath acoustic signals. The acoustic system has been designed and sea tests tried. The results of that experiment have yielded capability of a submeter underwater acoustic positioning system.

Robust output tracking of a class of nonlinear time-varying uncertain systems

Abstract A new method will be proposed to design a linear time-invariant (LTI) robust controller for a nonlinear time-varying plant which is unknown but belongs to a given set. By this method, a nominal controller is first designed to achieve the desired control properties for an artificial LTI nominal plant, then a robust compensator is designed to restrain the influence on the closed-loop properties of the real plant perturbations from the nominal one. It will be shown that for any plant in the set satisfying some assumptions, the closed-loop control system with a LTI controller designed by the presented method is globally asymptotically stable and the output tracking error can be made as small as desired if the initial conditions are zeros.

Adaptive Control System Design for Stable SISO Plants with Amplitude Constraints on the Inputs

Abstract The problem of MRAC system design for stable SISO contin-uous-time plants with amplitude constraints on the inputs is dealt with. A modification is made on the basic adaptive law based on the a prior information about the desired vector. It is shown that an adaptive controller with the modified adaptive law proposed can guarantee the asymptotical convergence of the output of the plant to that of the reference model and the boundedness of all signals involved in the closed-loop control systeM for any bounded initial conditions, if some assumption which is very reasonable holds.

Development of multipaths inverted echosounder

Abstract A multipaths inverted echosounder was developed and tested for measuring vertical average currents by accurately measuring time differences for sound wave to travel in two opposite directions along a path in the ocean. The acoustic paths “sing around” vertical triangle with a base about 4 km long, and the time differences determine the horizontal component of velocity averaged through water column. The field tests were conducted by using two multipaths inverted echo sounders (MIES). Each MIES provides the function of transponder and records all data. The results of the field tests are presented and discussed.

Monitoring of the transport of the ocean current by an acoustic transceiver array

Current velocity can be determined by measuring the difference of the sound wave traveling time between two points. The multipaths inverted echo sounder (MIES) [Takeuchi et al., J. Acoust. Soc. Jpn. 49, 543–550 (1993)] was developed in order to apply this method to the measurement of the volume transport of the Kuroshio. Measurement of mean current velocity can be made with a difference of reciprocal travel times of the sound wave along two sides of a triangle in a vertical plane, which is constructed by the acoustic paths with a base side of the mooring distance when two multipath inverted echosounders were deployed 10 km apart. The measurement of volume transport was attempted by applying the above method, where three multipath inverted echosounders were deployed so as to construct a regular triangle on the sea bottom. In this paper, the result of the measurement of the volume transport of the Kuroshio over Izu Ridge from 20 March to 25 April 1995 is presented.