Azimuth signal generator

• US 4,977,679 A
• Filed: 10/03/1989
• Issued: 12/18/1990
• Est. Priority Date: 10/28/1988
• Status: Expired due to Fees

• Current Assignee: Japan Aviation Electronics Industry Limited
• Original Assignee: Japan Aviation Electronics Industry Limited
• Inventors: Saito, Takahiro, Ito, Junichi
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Dowling, William C.
• Application Number:
  US07/416,688
• Time in Patent Office: 441 Days
• Field of Search: 33/316, 33/17 R, 33/317 D, 33/318, 33/319, 33/324, 33/326, 33/361, 33/362, 33/356, 33/355 R, 33/333, 33/357, 33/359, 364/457, 364/453, 364/449, 364/454, 73/504, 73/517 A
• US Class Current: 33/316
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

In an azimuth signal generator for an automobile navigation system a change in the rotational rate of an inertia rotary member, which has its rotary shaft held vertically and is driven at substantially a constant speed, is detected as a direction changing rate of the car and the direction changing rate is integrated by an integrator to obtain an azimuth signal. On the other hand, the azimuth of geomagnetism is detected by a geomagnetic azimuth sensor and a correcting signal is produced based on an error between the azimuth signal and the geomagnetic azimuth signal. The correcting signal is negatively feedback to the input side of the integrator, causing the azimuth signal to follow the geomagnetic azimuth signal.

Claims

1. An azimuth signal generator comprising:

a case to be fixedly mounted on the body of a vehicle;

an inertia rotary member housed in said case, with its rotary shaft held vertically;

a drive means mounted on said case, for rotating said inertia rotary member;

a relative rotational rate detecting means for detecting the rotational rate of said inertia rotary member relative to said case to provide a relative rotational rate signal;

a first subtracting means supplied with said relative rotational rate signal from said relative rotational rate detecting means and a correcting signal, for subtracting said correcting signal from said relative rotational rate signal;

an integrating means for integrating the subtracted output from said first subtracting means to provide the result of integration as an azimuth signal;

a geomagnetic azimuth detecting means for producing a geomagnetic azimuth signal in accordance with an azimuth of the geomagnetism;

a second subtracting means supplied with said azimuth signal from said integrating means and said geomagnetic azimuth signal from said geomagnetic azimuth signal detecting means, for providing the difference therebetween as an error signal;

a correcting signal generating means for creating said correcting signal in accordance with said error signal from said second subtracting means and supplying said correcting signal to said first subtracting means;

said inertia rotary member having boar codes provided at equiangular intervals on its outer peripheral surface, said relative rotational rate detecting means including a bar code sensor fixedly mounted on said case in opposed relation to said outer peripheral surface of said inertia rotary member for detecting said bar codes to produce an inertia signal containing pulses corresponding to said bar codes detected, and a counting means which receives said inertia signal, counts the number of said pulses per unit time and outputs, as said relative rotational rate signal, a signal corresponding to the count value;

and said relative rotational rate detecting means including a setting means for initializing, as a reference value, the count value of said counting means during the steady state rotation of said inertia rotary member, and a third subtracting means for obtaining a difference between said count value of said counting means and said reference value from said setting means to obtain the difference as said relative rotational rate signal.

2. The azimuth signal generator of claim 1, wherein said correcting signal generating means includes an amplifying means for amplifying said error signal from said second subtracting means, an error integrating means for integrating said error signal, and an adding means for adding together the outputs of said amplifying means and said error integrating means to obtain said correcting signal.

3. An azimuth signal generator comprising:

a case to be fixedly mounted on the body of a vehicle;

an inertia rotary member housed in said case, with its rotary shaft held vertically;

a drive means mounted on said case, for rotating said inertia rotary member;

a relative rotational rate detecting means for detecting the rotational rate of said inertia rotary member relative to said case to provide a relative rotational rate signal;

a first subtracting means supplied with said relative rotational rate signal from said relative rotational rate detecting means and a correcting signal, for subtracting said correcting signal from said relative rotational rate signal;

an integrating means for integrating the subtracted output from said first subtracting means to provide the result of integration as an azimuth signal;

a geomagnetic azimuth detecting means for producing a geomagnetic azimuth signal in accordance with an azimuth of the geomagnetism;

a second subtracting means supplied with said azimuth signal from said integrating means and said geomagnetic azimuth signal from said geomagnetic azimuth signal detecting means, for providing the difference therebetween as an error signal; and

a correcting signal generating means for creating said correcting signal in accordance with said error signal from said second subtracting means and supplying said correcting signal to said first subtracting means, said correcting signal generating means including an amplifying means for amplifying said error signal from said second subtracting means, an error integrating means for integrating said error signal, and an adding means for adding together the outputs of said amplifying means and said error integrating means to obtain said correcting signal.

4. The azimuth signal generator of claim 3 wherein said inertia rotary member has bar codes provided at equiangular intervals on its outer peripheral surface and wherein said relative rotational rate detecting means includes a bar code sensor fixedly mounted on said case in opposed relation to said outer peripheral surface of said inertia rotary member, for detecting said bar codes to produce an inertia signal containing pulses corresponding to said bar codes detected, and a counting means which receives said inertia signal, counts the number of said pulses per unit time and outputs, as said relative rotational rate signal, a signal corresponding to the count value.