Process for establishing the driving direction of a vehicle with

Details Process for establishing the driving direction of a vehicle with Process for establishing the driving direction of a vehicle with

1985-11-07

1988-03-08

Haroian, Harry N.

Geometrical instruments

Indicator of direction of force traversing natural media

Magnetic field responsive

33361, G01C 1738

Patent

active

047291729

DESCRIPTION:

BRIEF SUMMARY
STATE OF THE ART

The invention is based on a process for establishing the vehicle direction of a vehicle with an electronic compass in accordance with the type of the main claim. In a known navigation apparatus (DE-PS No. 27 54 888) the driving direction of a vehicle is established with a two axis magnetometer, whose output signals are fed to a correction unit for compensating magnetic interference fields in the vehicle, whereby a zero point displacement of the output signals as well as a proportional change of one of the output signals is performed. In this solution one assumes that an interference field with a permanent vector is present which is superimposed with an earth field which is more or less screened by the vehicle body depending on the alignment of the vehicle. Thereby, in light of the zero point displacement the interference field vector is taken into consideration and by the proportional changing of one of the two magnetometer signals the effect of the vehicle body on the earth field should be compensated. Thereby, a local curve is provided for the measuring values of the magnetometer on its x and y axis by turning the vehicle, whose center point is displaced from the axis cross together with the vector of the interfering field, so that an ellipse is formed due to the proportional change of the signal on one axis, whose axis extend parallel to the measuring axis. Due to the proportional change of the one output signal the ellipse should be reshaped into a circle and due to the zero position displacement the circle should be located in the axis cross which is checked by a control step in that the corrected signals are elevated to a square and must form a constant value when being computed (circle equation).
It is disadvantageous in this known solution that the correction of the values measured by the magnetometer are performed in an analog computer circuit which is rather inaccurate in light of the known technology. Furthermore, it is not known in which manner the correcting dimensions are established. Since a control step is required it is to be assumed that the correcting dimensions must be established by scanning tests, which is rather cumbersome and erroneous. Moreover, only timely constant interference fields have to be considered in this manner. A further essential disadvantage of the known process consists in that only an axis parallel displacement is taken into consideration from the zero point for the elliptical local curve of the screened earth field, whereby in reality such an elliptical local curve is turned by any amount in the vector diagram. Since this turning is not picked up in the known measuring process, a considerable deviation results for a navigation of the established drive direction from the actual drive direction.
With the subject invention it is aimed to establish the direction of the earth field or the drive direction of the vehicle rather accurately by an accurate establishing of the actual local curve of the magnetic field measured by the magnetometer.


ADVANTAGES OF THE INVENTION

The process in accordance with the invention for establishing the driving direction with the characterizing features of the main claim has the advantage that with the stored measuring points the center point displacement as well as the shape and the turning of the local curve can be calculated by the computer in the vector diagram without necessitating scan tests. A further advantage can be seen in that with a calibrated measuring the installing tolerances for the magnetometer and the so-called erroneous direction of the earth field may be compensated. In this manner, it is possible to establish and indicate the accurate direction of the earth field or the driving direction to a preestablished destination from the current measurements on the magnetometer through the established local curve.
Due to the measures stated in the subclaims advantageous further embodiments and improvements of the features stated in the main claim are made possible. It is particularly advantages with the use o

REFERENCES:
patent: 3991361 (1976-11-01), Mattern et al.
patent: 4031630 (1977-06-01), Fowler
patent: 4416067 (1983-11-01), Scherer et al.
patent: 4546550 (1985-10-01), Marchent et al.

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