Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2002-05-03
2004-12-28
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S079000, C701S121000, C702S096000, C702S150000, C340S993000
Reexamination Certificate
active
06836729
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of and an apparatus for detecting a vehicle speed pulse drop in an on-vehicle navigation system in which a current position etc. of a vehicle is displayed by using (i) a dead reckoning positioning system (i.e., a self-sustained or built-in positioning system), which is a system for measuring the current position on the basis of an output from dead reckoning positioning sensors including a vehicle speed sensor, and/or (ii) a radio wave positioning system such as a GPS (Global Positioning System), which is a system for positioning or measuring the current position on the basis of “positioning radio waves (which are radio waves or electric waves for positioning the present position)” from satellites for the radio wave positioning or measurement such as GPS satellites etc. The present invention also relates to an on-vehicle navigation system including the above-mentioned detecting apparatus, as well as a program storage device and a computer data signal embodiment in a carrier wave, which allow a computer to function as the above-mentioned detecting apparatus.
2. Description of the Related Art
Currently, there are (i) the dead reckoning positioning or measuring system and (i) the GPS, as rough categories of a system for positioning or measuring the present position of a vehicle in an on-vehicle navigation system.
The dead reckoning positioning system is intended to calculate a current position with respect to a standard position, on the basis of a moving direction, a distance and the like of a movable body obtained by dead reckoning positioning sensors such as a vehicle speed sensor, an angular velocity sensor, an acceleration sensor and the like which are equipped in the movable body. Especially, the vehicle speed sensor, among the dead reckoning positioning sensors, is intended to generate a vehicle speed pulse in response to a rotation of a vehicle shaft after detecting the rotation and is constructed to calculate a drive distance and a velocity from the cumulative number and the number per unit time of the generated vehicle speed pulse respectively.
Recently, as disclosed in Japanese Patent Application Laying Open NO. Hei 10-300509 and Japanese Patent Application Laying Open NO. Hei 10-115627 etc., for example, there has been developed a vehicle speed sensor of a magnetic field detection type, which detects a change of a magnetic field emitted from a generation source of the vehicle speed pulse additionally attached to a tire or at the vicinity thereof, or emitted from a steel belt included in the tire, to thereby generate the vehicle speed pulse. According to this type of sensor, it is possible to generate the vehicle speed pulse relatively easily in an arbitrary type of vehicle including a foreign vehicle or the like which has no generation source of the vehicle speed pulse or is uncertain about its presence.
On the other hand, the GPS is intended to receive with GPS receivers the positioning radio waves from a plurality of GPS satellites launched into the outer space and to calculate a current position and a moving velocity of a movable body by a 3D (3-dimensional) measurement or a 2D (2-dimensional) measurement based on the reception results.
Recently, as disclosed in Japanese Patent Application Laying Open NO. Hei 09-297030 and Japanese Patent Application Laying Open NO. Hei 10-307036, for example, a navigation system, which performs both of the above described dead reckoning positioning measurement and the above described GPS measurement, has been also developed. This navigation system mainly uses the dead reckoning positioning measurement or compensates the GPS measurement with the dead reckoning positioning measurement in the case that the GPS measurement is not available or cannot attain an enough accuracy, for example. On the other hand, in the case that the GPS measurement is available or can attain an accuracy as usual, the navigation system mainly uses the GPS measurement and compensates the GPS measurement with the dead reckoning positioning measurement.
However, especially as to the vehicle speed sensor which plays a key role in the dead reckoning positioning system as described above, such a situation may occur that the “vehicle speed pulse” is not generated when “the vehicle speed pulse” as a vehicle speed signal is supposed to be outputted from the vehicle speed sensor while the vehicle is actually driving,which is a problem (this situation is referred to as a “vehicle speed pulse drop”). There may be considered various causes and reasons of this vehicle speed pulse drop individually and concretely, e.g., it is difficult to produce (i) the vehicle speed sensor with a constant sensitivity and (ii) the generation source of the vehicle speed pulse with a constant output, over the whole vehicle speed, an electrical noise is generated on a line or wire through which the vehicle speed pulse is transmitted, and a sensor error is generated due to an unexpected vibration in driving.
Especially, as to the vehicle speed sensor which detects the change of the magnetic field to generate the vehicle speed pulse as mentioned above, there is a significant problem that the vehicle speed pulse drop may occur frequently depending on the driving condition because the magnetic field detected by the sensor may drastically change as much as it cannot be ignored on the detection accuracy depending on a strain of the tire, a suspension operation and so on.
When the vehicle speed pulse drop occurs, an error occurs such that the vehicle speed is drifted to its lower side to deteriorate the accuracy of the vehicle speed, and another error occurs such that the moving distance is drifted to its shorter side to deteriorate the accuracy of the moving distance based on the dead reckoning positioning system. Moreover, in addition to deteriorating the accuracy of the current position based on the dead reckoning positioning system, there is a problem that the vehicle speed pulse drop deteriorates the accuracy of the current position etc., which is finally obtained after the correction or compensation based on the dead reckoning positioning measurement with respect to the GPS measurement.
For this problem, Japanese Patent Application Laying Open NO. 2000-97713 discloses a system for calculating the moving distance and the current position with a high accuracy based on the vehicle speed pulse even in the case that the vehicle speed pulse drop is generated while driving at a low speed. However, a detection method of the vehicle speed pulse drop in this system is extremely simple. For example, in this system, the vehicle speed pulse drop is detected by a change from a condition of “the number of the vehicle speed pulse>1” to a condition of “the number of the vehicle speed pulse=0” under monitoring the vehicle speed pulse with a constant time interval. Therefore, it is hard to say that the detection accuracy of the vehicle speed pulse drop is substantially high.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of and an apparatus for detecting a vehicle speed pulse drop, in which the detection of the vehicle speed pulse drop can be performed with a high accuracy, an on-vehicle navigation system including the above mentioned detecting apparatus, as well as a program storage device and a computer data signal embodiment in a carrier wave, which allow a computer to function as the detecting apparatus.
The above object of the present invention can be achieved by a first method of detecting a vehicle speed pulse drop of a vehicle speed pulse in an on-vehicle navigation system, the system provided with a radio wave positioning apparatus and a vehicle speed sensor, by which the vehicle speed pulse is generated, for a dead reckoning positioning, the method provided with: a first calculation process of calculating a first physical quantity of a predetermined type from radio wave positioning data of the radio wave positioning apparatus; a second cal
Goto Seiji
Okamoto Tatsuya
Tanaka Kazuaki
Black Thomas G.
Donnelly Arthur D.
Pioneer Corporation
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