Zexel Gmbh

Zexel USA Corporation

Zexel Corporation Diahatsu-nissan

Daihatsu-nissay

Wei-Wen Kao

Liang-Jong Huang

The invention provides a direction sensor and a method of calibrating a direction sensor having a relative heading sensor and an absolute heading sensor. The method allows calibration of both the relative heading sensor and the absolute heading sensor at the same time, by taking advantage of the known angular relationship between maxima and minima on the measurement curve of the absolute heading sensor. Such maxima and minima are found by rotating the sensors through an angle of at least 360.degree., reading the absolute and relative heading sensor outputs at numerous points and comparing each successive output. The relative heading sensor output at the minimum is subtracted from that at the maximum, and the difference divided by the known angle to arrive at a conversion constant for the relative heading sensor. The center and radii of the measurement curve of the absolute heading sensor may be found by determining the maxima and minima of the curve in two perpendicular directions.

Calibration method for a relative heading sensor

A hybrid vehicle navigation system employs both GPS and dead reckoning sensors, working in parallel, to produce a sensed and a calculated position, respectively. The sensed and the calculated positions are compared to a road data base to determine separate correction factors required to correct the sensed and the calculated positions. In one embodiment, the system employs either the sensed or calculated position for navigation depending on which has the smaller correction factor.

Correcting GPS position in a hybrid naviation system

A vehicle navigation system is used to determine the absolute position of a vehicle with improved accuracy on freeways or rural highways. First, the system stores a known vehicle position in its memory. As the vehicle moves away from the known position, the system uses a variety of means to sense external signals. These means include satellite transmission receivers and magnetic compasses. When a change in the external signals occurs, the system recognizes the presence of a landmark which can then be used to set the vehicle's position. To accomplish this, the system's data processor searches a map data base, attempting to fix the position of the sensed landmark with respect to the initially stored known position. When the system identifies the most likely landmark, the position of the vehicle is then reset to that position.

Position correction method for vehicle navigation system

An apparatus for compensating a magnetic heading as indicated by a vehicle's magnetic compass so that the magnetic heading corresponds to a true heading as indicated by signals received in the vehicle from the Global Positioning System. The apparatus includes a computer for calculating compensation factors from successive positions occupied by the vehicle as it travels.

Apparatus for correcting vehicular compass heading with the aid of the

A vehicle navigation system helps locate the vehicle on a road network by overcoming, through the use of fuzzy logic, the errors of positioning sensors and routing computers. In the system, sensors continually feed position coordinates to a processing unit that traces the vehicle's path in a road database. Fuzzy logic-based reasoning is used to determine the most probable location of the vehicle, whether off- or on-road, thereby correcting errors in its raw path as sensed or computed.

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Fremont, CA, United States of America

Wei-Wen Kao