Data processing: measuring – calibrating – or testing – Calibration or correction system – Sensor or transducer
Reexamination Certificate
2002-05-03
2004-06-29
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Sensor or transducer
C702S146000
Reexamination Certificate
active
06757631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a method of and an apparatus for detecting an angular velocity on the basis of an output voltage of an angular velocity sensor such as a gyro or the like and to a method of and an apparatus for detecting an angle on the basis of the output voltage of the angular velocity sensor such as a gyro or the like. The present invention also relates to a navigation system including the above-mentioned apparatus for detecting an angle, a program storage device and a computer data signal embodiment in a carrier wave, which allow a computer to function as the apparatus for detecting an angle or angular velocity.
2. Description of the Related Art
Conventionally, there is an angular velocity sensor such as a gyro or the like among instruments mounted on various types of movable things, and it is mounted, for example, on a movable body such as a vehicle, an airplane, a rocket, a ship or the like for detecting an angle or an angular velocity, or on a robot for controlling its attitude, or on a video camera for correcting movement of the hand. There is also an apparatus for detecting an angle, which displays or records after calculation of an angle, and further an apparatus for detecting an angular velocity, which displays or records after calculation of an angular velocity, on the basis of an output voltage of the angular velocity sensor in this kind.
For example, an on-vehicle navigation system is equipped with the angular velocity sensor such as a vibration gyro or the like and it calculates a drive azimuth on the basis of its output voltage and displays the calculated drive azimuth on a display map in a predetermined format. Alternatively, it is constructed to calculate a current position by a dead reckoning positioning measurement by using a drive distance obtained from a drive distance sensor or the like in conjunction with the calculated drive azimuth, and to display the calculated current position in a predetermined format on the display map.
The angular velocity sensor in this kind is constructed to set a bias voltage, which is an output voltage outputted when the angular velocity is zero, as a standard voltage and to calculate an angle on the basis of this standard voltage and an output voltage of the angular velocity sensor at an arbitrary time. Alternatively, it is constructed to calculate the angular velocity by how high the output voltage of the angular velocity sensor at the arbitrary time is, including its polarity, with the standard voltage as a standard.
Especially here, as for the angular velocity sensor such as a vibration gyro or the like, its bias voltage changes stepwise by a temperature drift and a start drift. Therefore, if the bias voltage on startup is fixed as the standard voltage, the detected drive azimuth may disadvantageously change gradually in spite of direct advance of a vehicle, for example. To avoid this, Japanese Patent Application Laying Open NO. Hei 5-52578 discloses a method of decreasing effects of the temperature drift or the like by updating the bias voltage, which is the output voltage of the angular velocity sensor, as a new standard voltage when it is detected that a vehicle is stopping on the basis of a vehicle speed obtained from an apparatus for detecting a vehicle speed.
According to the above-mentioned Japanese Patent Application Laying Open NO. Hei 5-52578, the effects of the temperature drift of the bias voltage or the like can be decreased when updating the standard voltage or just after that. However, because the standard voltage is not updated but constant, considering about a period until the standard voltage is updated next time, the effects of a change by the temperature drift of the bias voltage or the like reveal themselves remarkably with time passing by. Moreover, the standard voltage is not updated as long as such a drive condition that the standard voltage can be updated is not obtained. Therefore, as such a period that the standard voltage is not updated becomes longer, the errors of an angle caused by the change by the temperature drift of the bias voltage or the like increase. Consequently, the drive azimuth of a vehicle displayed on a display map departs widely from a road direction depending on the elapsed time from when the standard voltage, which is generally unknown to a driver, is updated, for example, which is a big problem in practice.
Furthermore, a similar problem applies to a general apparatus for detecting an angular velocity equipped with an angular velocity sensor, and the angular velocity to be detected may have errors depending on the elapsed time after updating the standard voltage by the effects of the temperature drift of the bias voltage described above or the like as well.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of and an apparatus for detecting an angular velocity as well as a method of and an apparatus for detecting an angle, which can decrease the errors caused by the change by the start drift, the temperature drift or the like of the bias voltage of the angular velocity sensor such as a gyro, and further a navigation system equipped with the apparatus for detecting an angle, a program storage device and a computer data signal embodiment in a carrier wave, which allow a computer to function as the apparatus for detecting an angle or angular velocity.
The above object of the present invention can be achieved by a method of detecting an angular velocity provided with processes of: setting a bias voltage, as a standard voltage, which is an output voltage outputted from an angular velocity sensor in response to an angular velocity when a predetermined condition is satisfied as well as updating the standard voltage every time the predetermined condition is satisfied; calculating the angular velocity on the basis of the output voltage with using the set or updated standard voltage as a standard; storing time data, which indicate a time of setting or updating the standard voltage, in correspondence with standard voltage data, which indicate a value of the set or updated standard voltage; estimating a value of the bias voltage of the angular velocity sensor at each time between times of setting or updating the standard voltage, as a function of time, on the basis of a plurality of the stored standard voltage data and a plurality of the stored time data; and correcting the angular velocity calculated by the calculating process on the basis of a difference between a value of the standard voltage used in the calculating process and the estimated value of the bias voltage.
According to the method of detecting an angular velocity of the present invention, the bias voltage, which is the output voltage outputted from the angular velocity sensor such as a gyro, is firstly set as the standard voltage when such a predetermined condition that a movable body in various types such as an airplane, a rocket, a ship, a vehicle or the like, or a movable thing such as a robot, a video camera or the like, on which the angular velocity sensor is mounted, is stopping, is straightly advancing or the like is satisfied as an initial condition, for example. Then, after the method of detecting an angular velocity is started, every time this predetermined condition is satisfied, the standard voltage is updated by the setting process. Then, the angular velocity is calculated by the calculating process on the basis of the output voltage with using the set or updated standard voltage as a standard. Normally, the angular velocity is calculated in response to how high the output voltage is, including the positive and negative polarity, with respect to the standard voltage. On the other hand, the time data, which indicate a time of setting or updating the standard voltage, is stored into a memory or the like by the storing process, in correspondence to the standard voltage data, which indicate a value of the set or updated standard voltage, every time the standard voltage is set or updated. T
Endo Isao
Goto Seiji
Imada Seiji
Barlow John
Morgan & Lewis & Bockius, LLP
Pioneer Corporation
Washburn Douglas N
LandOfFree
Method of and apparatus for detecting angular velocity,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of and apparatus for detecting angular velocity,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of and apparatus for detecting angular velocity,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3347177