Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C17/00—Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes
  • G01C17/38—Testing, calibrating, or compensating of compasses

Definitions

• the invention is based on a method for correcting angular errors when determining the direction of travel of vehicles with an electronic compass according to the preamble of the main claim.
• From DE-PS 27 54 888 it is known to determine the direction of travel of a vehicle using a two-axis magnetometer in a navigation apparatus, the output signals of which are fed to a correction unit for compensating for magnetic interference fields in the vehicle, by means of which a zero point shift of the output signals and a proportional change in one of the output signals is carried out.
• an interference field with a fixed vector is present in the vehicle and is overlaid by an earth field, which is more or less shielded by the body of the vehicle depending on the orientation of the vehicle.
• the travel is determined
• Direction only the component of the earth's field lying in the driving plane is detected by the magnetometer by arranging one axis of the magnetometer in the direction of travel and the other transverse to the direction of travel.
• the built-in electronic compass there is no measurement error as long as the vehicle is traveling horizontally.
• an angle error occurs when measuring the direction of travel on the electronic compass, which can be up to 30 depending on the uphill or downhill gradient and depending on the direction of travel.
• the magnetometer must have an elaborate and susceptible gimbal suspension, so that the axes of the magnetometer lie in a horizontal plane even when driving up and downhill.
• measurement errors occur when cornering, when accelerating or braking the vehicle.
• the aim of the present solution is to easily compensate for the angular errors which depend on the inclination of the vehicle in its longitudinal axis.
• the method according to the invention with the characterizing features of the main claim has the advantage that the measuring accuracy of the electronic compass is significantly improved by the compensation of the inclination-dependent angle error. Another advantage is that the magnetometer can now be installed with its axles stationary in the vehicle. There is no gimbal attachment.
• FIG. 1 shows a block diagram of an electronic compass for determining the direction of travel of a motor vehicle with inclination-dependent angle correction according to the invention
• FIG. 2 shows a coordinate system with a vehicle traveling uphill
• FIG. 3 shows a vehicle with the magnetic field vectors measured by the magnetometer
• FIG. 4 shows a diagram that depends
• Figure 5 shows the measured and the actual north direction in the coordinate system with respect to the vehicle's longitudinal axis
• Figure 6 shows a schematically illustrated measuring device for the angle of inclination of the vehicle
• Figures 7 and 8 show flow diagrams for the Operation of the electronic compass according to Figure 1. Description of the embodiment
• FIG. 1 shows the block diagram for an electronic compass which is permanently installed for navigation in a motor vehicle.
• the electronic compass consists of a sensor 10, an evaluation circuit 11, an inclination measuring device 12 and a display 13.
• the sensor 10 which is attached, for example, in the middle of the roof of a passenger vehicle (FIG. 3), contains a magnetometer with time coding.
• the magnetometer is provided with two probes, which are accommodated in the sensor 10 together with a power supply and a signal shaping stage for each of the magnetic field probes.
• the evaluation circuit 11 is essentially realized by a microcomputer, the input of which is supplied with the sensor signals.
• the evaluation circuit 11 is a memory stage 14, a computing stage 15 for calculating the uncorrected direction angle y is a further computing stage 16 for determining the vehicle inclination in its longitudinal axis, shown broken down into a correction stage 17 for determining a correction or calibration variable and into a further calculation stage 18 for angle correction.
• a fixed direction angle can be set via various inputs of the correction stage 17 , a fixed angle of inclination or the angle of inclination of the earth field He can be entered as a calibration variable in the evaluation circuit 11.
• the computing stage 18 is connected via an output to the display 13, on which the direction of travel of the vehicle can be displayed in addition to further information.
• FIG. 2 shows a vehicle 19 in a coordinate system on an inclined plane.
• the coordinate system has a horizontal axis x o and a vertical axis se z o .
• the inclined plane forms with the horizontal
• Axis x o an angle / Figure 2 also shows by pa parallel arrows indicated the direction of the earth field He effective in the vehicle 19.
• This earth field He forms an inclination angle to the horizontal plane that remains practically unchanged within a radius of several hundred kilometers.
• the connecting lines of the places on the earth's surface with the same inclination angles are called isoclinics. They are entered in textbooks on navigation on maps (see H. Birr, S. Kuschinsky, L. Uhlig "Guide to Navigation - Terrestrial Navigation", Transpress VEB-Verlag fürmaschineberichtmaschine Berlin, (1968).
• the vehicle 19 is shown in plan view.
• the sensor 10 is equipped with its one probe axis x to the longitudinal axis of the vehicle and with its other probe axis e y transverse to the longitudinal axis.
• the sensor 10 measures the X and Y components of the field vector H effective on it, which is composed of a fixed interference field vector Hs and the earth field vector He.
• the earth field vector He acting on the sensor 10 describes an elliptical locus curve O when the vehicle 19 is rotated by shielding in the motor vehicle, since the vector of the interference field Hs and the position and shape of the locus curve O are determined by calibration measurements and in memory 14 by constant ones Sizes are stored, the direction of the earth field He can be determined by the electronic compass using a vector equation, in that the vector of the magnetic field H is measured cyclically by the sensor 10.
• Figure 4 is a diagram for different angles of inclination the angle error ⁇ yz that occurs for the directional display as a function of the direction of travel is shown with reference direction north. Like Figure 5 shows, the angle forms the angle between the vehicle longitudinal axis x and the north direction. It can be seen from the diagram (FIG. 4) that there is no angular error in a vehicle which is traveling on a horizontal plane and that maximum angular errors occur on uphill or downhill gradients in north-west directions. In the case of a gradient of 10% (6o), angle errors of c 13 ° occur.
• the inclination measuring device 12 cyclically determines the inclination of the vehicle's longitudinal axis.
• a position sensor 20 is used for this, as is shown schematically in FIG. 6. It consists of a body 21 arranged in the vehicle, which rests on a solid base 22 and is held on the side by two pressure sensors 23, 2h.
• the base 22 is located in the driving plane of the vehicle, while the pressure sensor 23 is arranged perpendicular to it behind the body 21 and the position sensor 24 in front of the body 21, as viewed in the direction of travel. From the acceleration force parallelogram shown in FIG.
• the method for determining the direction of travel of the vehicle 19 with the correction of inclination-dependent angle errors will now be explained in more detail.
• a calibration variable E is already stored in the evaluation circuit 11. If this is not yet the case, the inclination angle is determined in a program section 27 via the correction stage 17 entered the earth field and formed a calibration quantity E, which is stored in the storage stage 14.
• the angle of inclination or the inclination value for the area in which the vehicle is being driven can be taken in a very simple manner from a map provided with inclination lines and entered into the evaluation circuit 11 via input keys.
• a further program section 28 is now with the inclination measuring device 12 measures the total acceleration a 'and the instantaneous driving speed v and the values are fed as measuring signals to the evaluation circuit 11 and temporarily stored there.
• the corrected direction angle for the vehicle 19 is determined.
• this value is now given on the display 13.
• the display 13 can indicate the direction of travel by means of an arrow or indicate the direction of travel with regard to a predetermined destination.
• the program now jumps back to the program section 18, in which the data from the inclination measuring device 12 are again read into the evaluation circuit 11 in order to determine the inclination angle y
• This program section and the subsequent sections 29 to 33 are run through cyclically by the program, so that every change in the direction of travel and the vehicle inclination in the longitudinal axis is detected and the display is corrected accordingly.
• the evaluation circuit 11 it is also possible to dispense with the input of the inclination angle and instead to carry out a calibration measurement with the vehicle 19.
• the vehicle 19 is positioned with the longitudinal axis in a certain direction, for example in the east, and with a certain slope angle, for example 10 °.
• a calibration key can be pressed for this when the vehicle has assumed the predetermined position.
• step 27b in the calibration position of the vehicle 19, the magnetic field H o effective there is measured by the sensor 10, and in step 27c the directional angle s is calculated by the computing unit 15 from this measured variable determined and stored in memory level 1 4.
• step 27d the data entered y and the measured direction angle in correction stage 17 the calibration variable E according to the functional equation:
• E f p determined and stored in the memory stage 14.
• the direction of travel is then cyclically determined and displayed in accordance with the flow chart shown in FIG. 7 with the sections 28 to 33.
• the invention is not limited to the exemplary embodiment shown, since such an electronic compass can be used to determine the direction of travel both for aircraft and for watercraft.
• the compass can not only be used to determine the direction of travel, but also very generally for the navigation of vehicles which are to be controlled, for example, from a fixed starting point to a specific destination. In such a case, for example, the signals of the vehicle speed sensor are used together with the direction of travel determined by the compass to determine the respective location of the vehicle 19.
• the respective location height of the vehicle can also be calculated and displayed with an appropriately constructed evaluation circuit together with the path signals.
• a specified altitude base must be entered from time to time.
• a pendulum or another device for measuring the inclination of the vehicle can also be used.
• the base 25 for the body 21 can also be designed as a pressure sensor. This would have the advantage that the braking or acceleration force does not act on this pressure sensor lying parallel to the driving plane, and a change in the measurement signal at this sensor could therefore be used directly to determine the vehicle inclination. It is disadvantageous, however, that such a pressure sensor must be cushioned against impacts from unevenness in the road and the like.

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• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Navigation (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=6238576

Family Applications (1)

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• 1984
  • 1984-06-16 DE DE19843422490 patent/DE3422490A1/de active Granted
• 1985
  • 1985-04-17 US US06/787,796 patent/US4725957A/en not_active Expired - Fee Related
  • 1985-04-17 EP EP85901974A patent/EP0187761A1/de not_active Ceased
  • 1985-04-17 WO PCT/DE1985/000124 patent/WO1986000129A1/de not_active Application Discontinuation
  • 1985-04-17 JP JP60501722A patent/JPS61502414A/ja active Granted

Non-Patent Citations (1)

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