Hitachi, Ltd.

Other

Hitachi Cable, Inc.

The Tokyo Electric Power Company, Incorporated

Junichi Makino

Shigeru Oho

Hisao Sonobe

Yutaka Nishimura

Seiji Suda

Hiroshi Kajioka

Yuusuke Takamoto

Tatsuya Kumagai

Tomoji Inui

Masahiro Matsumoto

Takeshi Atago

Nobuo Kurihara

Junichi Ishii

Yasuhiro Gunji

Matsuo Amano

Kouji Kitano

Yoshihiro Sano

Hiroshi Araki

Yoshiteru Miki

Masami Okamura

Yoshihumi Oura

An interference sensor passes radiation from a source and a polariser to a loop of optical fiber so that radiation beams circulate in opposite directions around the loop and interfere. The loop contains an optical phase modulator which imposes an optical modulator on the radiation beams circulating on the loop. A converter detects the interfering and modulated beams and generates an interference signal which is then processed by an analyser. The interference in the loop is dependent on rotation of the loop and therefore analysis of the interference signal permits that rotation to be measured. In the present invention, the interference signal is (i) sampled at a frequency different from that of the optical modulation, or (ii) electronically modulated in the analyser at a frequency different from that of the optical modulation, or (iii) optically modulated in the loop at a second optical modulation frequency. The analysis in the analyser may be in the frequency domain (i.e. consideration being given to the frequency of the interference signal) or in the time domain (i.e. independent of frequency).

Interference sensor and method utilizing extracted alliasing frequency

Analog circuit of a thermal type intake air flow sensor for detecting a quantity of air drawn into an automotive engine is formed as a part of the input hardware of a microcomputer for control of the engine, and the analog circuit is used for operations which need to be performed at high speed, while adjustment, an output process, etc. are executed under the same operating system as is used for engine control.

Thermal type intake air flow measuring instrument

In an optical fiber gyroscope, the sensitivity thereof is optimized with a phase bias afforded by utilizing the phase characteristics of an optical branching/coupling unit. Further, the fluctuation of the intensity of a light source and the error and secular change of the phase characteristics of the optical branching/coupling unit are compensated by an electronic circuit. Moreover, an optical fiber loop is located in a heat insulation casing so as not to be affected by an ambient temperature change, thereby to prevent the drift of the optical fiber gyroscope attributed to an temperature change. Thus, the optical fiber gyroscope of high measurement accuracy is provided.

An improved optical branching/coupling unit for an optical fiber

Thermal type intake air flow measuring instrument and internal

A car control apparatus in which correction characteristics indicating whether or not various control constants are proper or not are calculated through loop control of one of the car's operation parameters, such as the air-fuel ratio, on the basis of the air-fuel ratio correction factors subjected to learning to thereby rationalize the control constants such as the fundamental injection time so as to realize proper fuel injection and proper ignition timing control.

Apparatus and method for controlling a car

An interface signal produces in a phase modulation type fiber optic gyroscope is classified into odd and even groups at a synchronous detector. An angular velocity is processed by the signals of even groups and odd groups.

Phase modulation type fiber optic gyroscope

Protection of an electric power system is attained under control of a digital computer. Voltage and current of the electric power system to be protected are subjected to sampling at a predetermined sampling frequency and are applied to the computer after being converted into digital signals. The computer computes the product of these two digital signal inputs. The signal thus obtained is added to a preceding signal representing the product of voltage and current taken at time before a predetermined period of time so that unnecessary frequency components included in these signals can be removed. Then, the level of the resultant signal (which is free from the unnecessary frequency components) is compared with the level of a reference signal. When the former is greater than the latter, there is a fault in the electric power system, and necessary protective measures are taken to protect the electric power system.

Protective relaying system

Growing community of inventors

Katsuta, Japan

Junichi Makino