US 4,791,574 AGranted

Land vehicle navigation device comprising a filter unit for determining an optimum heading from presented orientation signals, and filter unit to be used in said navigation device

AssigneeU.S. Philips Corporation

InventorsMartinus L. G. Thoone, Henricus P. M. Krukkert

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Abstract

In a navigation device for land vehicles the orientation signal which indicates the direction of movement along which the vehicle is moving is measured on the one hand by an electronic compass. A further orientation signal is produced by the variation of the vehicle orientation as determined by wheel sensors. These two orientation signals comprise measuring errors. In order to determine an optimum value for the orientation from said values a digital filter unit is used which comprises low-pass and high-pass filters. The value for the orientation signal measured by the compass is presented to the input of the low-pass filter and the further orientation signal is presented to an input of the high-pass filter. The filter unit further comprises a control unit which generates a filter parameter from received orientation signals and supplies said filter parameter to the low-pass filter and the high-pass filter.

Claims20

Dependent claims

A navigation device for a land vehicle comprising:

an electronic compass for measuring the orientation of the vehicle and adapted to produce a first orientation signal by regular sampling of the measured orientation, a measuring unit operating independently of said compass for determining variations in the orientation of the vehicle and adapted to produce second orientation signals from regularly measured samples of the variations in the orientation, and a digital filter unit adapted to filter received first and second orientation signals, wherein the filter unit comprises a first low-pass filter for filtering first orientation signals received from the electronic compass, a high-pass filter for filtering the second orientation signals received from the measuring unit, a control unit which receives the first and second orientation signals and generates and supplies a first filter parameter control signal to the first low-pass filter and to the high-pass filter to control the filter characteristics thereof, and an output unit responsive to filtered orientation output signals of the first low-pass filter and the high-pass filter to produce from said received filtered orientation signals a weighted vehicle orientation signal which indicates the direction of movement of the vehicle.

A land vehicle navigation device comprising:

an electronic compass including a first sampling device for producing first orientation signals by regular sampling of vehicle orientation measured by said electronic compass;
a measuring unit operating independently of said compass for determining variations in the vehicle orientation, said measuring unit including a second sampling device for producing second orientation signals by regular sampling of variations in the vehicle orientation determined by said measuring unit;
and
a digital filter unit comprising:
a control unit having an input for receiving said first and second orientation signals and means for producing in response to the received orientation signals a first filter parameter signal;
a first low-pass filter and a high-pass filter each having a signal input for receiving said first and second orientation signals, respectively, and having a parameter input for receiving said first filter parameter signal, said filters being operative to transform said received orientation signals into respective output signals in accordance with a frequency response characteristic controllable by said filter parameter signal;
combination means for deriving a weighted vehicle orientation signal indicating vehicle direction of movement by combining said output signals of said first low-pass filter and said high-pass filter;
and
means responsive to said weighted vehicle orientation signal for determining vehicle position coordinates.

6 more elements

Dependencies are inferred from the claim text.