Hisao Sonobe

Knocking Detection of a Gasoline Engine by Utilizing an Optical Fiber with Specific Refractive-index Composition.

Abnormal combustion of a gasoline engine is often accompanied by a sharp metallic noise called knocking. A recently proposed method of in-cylinder pressure measurement is applied to detect the knocking, where the bending power loss of a single-mode fiber with specific refractive-index composition is utilized. The high-frequency response of a prototype sensor is obtained with a small structure to utilize the bending mechanism that is installed into an engine head gasket. Knocking signals are detected in a wide range of trace- to heavy-knock conditions.

Multiplex in-cylinder pressure measurement utilizing an optical fiber with specific refractive-index composition

An approach to multiplex in-cylinder pressure measurement that utilizes a single-mode optical fiber with specific refractive-index composition has been proposed. The sensing fiber has been designed to show a certain amount of optical power loss with a small change in the fiber-local-bend radius. Along with pressure-transferring diaphragms the sensing fiber was embedded into the head gasket of a four-cylinder gasoline engine. The internal-pressure change in each combustion chamber was detected on the basis of bending power loss in the fiber. Combustion pressure peaks for each cylinder were clearly observed.

Fiber optic gyroscopes for vehicle navigation systems

Fiber optic gyroscopes (FOGs) have been developed for vehicle navigation systems and are used in Toyota Motor Corporation models Mark II, Chaser and Cresta in Japan. Use of FOGs in these systems requires high reliability under a wide range of conditions, especially in a temperature range between -40 and 85 degree(s)C. In addition, a high cost-performance ratio is needed. We have developed optical and electrical systems that are inexpensive and can perform well. They are ready to be mass-produced. FOGs have already been installed in luxury automobiles, and will soon be included in more basic vehicles. We have developed more inexpensive FOGs for this purpose.

Development of open-loop fiber optic gyroscopes for industrial and consumer use

Fiber optic gyroscopes (FOGs) are developed for industrial and consumer applications. The bias error, which is determined by electrical circuits rather than the optical system, varies between 0.01 and 36 deg/hr depending on the construction of the electrical system. The scale factor error at each input rate is less than 0.5% in the temperature range of -30 to 85 degree(s)C. These FOGs are compact, highly reliable, and need only a +12 V D.C. power source. They are ready for mass production.

Secondary-phase-modulation method for open-loop fiber-optic gyroscopes

A proposed method of secondary phase modulation for open-loop fiber-optic gyroscopes is examined in general terms. To detect the rotation rate of a system through a beat-frequency channel, we employ linearly combined signals with different frequencies for the optical phase modulation. We find that the proper combinations of the modulation frequencies can optimize the sensitivity of gyroscopes. With this method we can employ a high-frequency band for optical phase modulations while keeping relative a lower-frequency band of the detection channel. The theoretically derived result is experimentally confirmed by using a lithium-niobate (LiNbO(3)) optical phase modulator. We also discuss the combination setup with an optical integrated-circuit device and digital signal processing.

Signal processing schemes for open-loop optical fiber gyroscopes

Open-loop signal processing techniques for a phase-modulated optical fiber gyroscope are discussed and classified according to sampling or non-sampling, frequency- or time-domain, and real or equivalent time schemes. A duality theory between frequency and time for the gyroscope signal is developed. The rotation rate supplied to the gyroscope is detected from both the frequency and time signals. As examples of equivalent time signal processing, down sampling and pulse modulation techniques are proposed.

Signal distortion induced by Fresnel reflection in open-loop fiber-optic gyroscopes.

The signal distortion that is due to Fresnel reflection in open-loop fiber-optic gyroscopes was theoretically analyzed to determine the relationship between the reflection ratio and the scale factor error of the gyroscopes. The analysis showed that the in-phase component of each Fourier harmonic of the gyroscope signal deviates from the true sinusoidal function, a quadrature-phase component appears, and the pi/2 rotation rates of harmonic components disagree. We evaluated the degree of scale factor degradation by defining the harmonic distortion ratio, which can be used as a measure for the reflectional quality of the gyroscopic optical system. The theory was verified by the response of an experimental gyroscope. The Fresnel reflection was eliminated by optical and electrical means, and the signal distortion of the experimental gyroscope was suppressed.