Offset-drift correcting device for gyro-sensor

Claim 2

An offset-drift correcting device for a gyro-sensor mounted on an object and outputting a signal representing an angular speed of the object, the device comprising: first means for detecting whether or not the object is rotating; second means connected to the gyro-sensor for smoothing the angular speed represented by the output signal of the gyro-sensor, and deriving an average angular speed of the object from the angular speed represented by the output signal of the gyro-sensor; third means connected to the second means for calculating an amount of temporal variation In the average angular speed derived by the second means, wherein the third means comprises a low pass filter processing an output signal of the second means which represents the average angular speed; fourth means connected to the third means for integrating an output signal of the third means which represents the calculated amount of temporal variation, and outputting a signal representing a result of the integrating; fifth means connected to the first means and the second means for estimating a first offset level of the output signal of the gyro-sensor in response to the average angular speed derived by the second means in cases where the first means detects that the object is not rotating, wherein the fifth means comprises an adaptive filter processing the output signal of the second means which represents the derived average angular speed; sixth means connected to the fourth means and the fifth means for combining the result of the integrating by the fourth means and the first offset level estimated by the fifth means into a second estimated offset level of the output signal of the gyro-sensor; and seventh means connected to the gyro-sensor and the sixth means for subtracting the second estimated offset level provided by the sixth means from the output signal of the gyro-sensor to convert the output signal of the gyro-sensor into an offset-free signal.

Claim 3

An offset-drift correcting device for a gyro-sensor mounted on an object and outputting a signal representing an angular speed of the object, the device comprising: first means for estimating an angular speed of the object; second means for subtracting the angular speed estimated by the first means from the angular speed represented by the output signal of the gyro-sensor, and outputting a signal representing a result of the subtracting; third means connected to the second means for smoothing the output signal of the second means, and outputting a signal representing a result of the smoothing; fourth means connected to the third means for estimating an offset level of the output signal of the gyro-sensor in response to the output signal of the third means, wherein the fourth means comprises an adaptive filter processing the output signal of the third means; and fifth means connected to the gyro-sensor and the fourth means for subtracting the offset level estimated by the fourth means from the output signal of the gyro-sensor to convert the output signal of the gyro-sensor into an offset-free signal.

Claim 4

The offset-drift correcting device of claim 2, further comprising: eighth means for detecting whether or not the gyro-sensor starts to be powered; and ninth means connected to the fourth means, the adaptive filter, and the eighth means for modifying characteristics of the integrating by the fourth means and characteristics of the adaptive filter during a predetermined time following a moment at which the eighth means detects that the gyro-sensor starts to be powered.

Claim 5

The offset-drift correcting device of claim 2, further comprising: eighth means for detecting a frequency of occurrence of updating of the first offset level estimated by the fifth means; and ninth means connected to the first means, the adaptive filter, and the eighth means for modifying characteristics of the detecting by the first means and characteristics of the adaptive filter in response to the frequency detected by the eighth means.

Claim 6

The offset-drift correcting device of claim 2, further comprising: eighth means for determining desired initial conditions of the adaptive filter in response to the output signal of the gyro-sensor; and ninth means connected to the adaptive filter and the eighth means for setting the adaptive filter into the desired initial conditions determined by the eighth means when the adaptive filter starts to operate.

Claim 7

An offset-drift correcting device for a gyro-sensor mounted on an object and outputting a signal representing an angular speed of the object, the device comprising: first means for detecting whether or not the object is rotating; second means connected to the gyro-sensor for smoothing the angular speed represented by the output signal of the gyro-sensor, and deriving an average angular speed of the object from the angular speed represented by the output signal of the gyro-sensor; third means connected to the second means for calculating an amount of temporal variation in the average angular speed derived by the second means, wherein the third means comprises a low pass filter processing an output signal of the second means which represents the average angular speed; fourth means connected to the third means for integrating an output signal of the third means which represents the calculated amount of temporal variation, and outputting a signal representing a result of the integrating; fifth means connected to the first means and the second means for estimating a first offset level of the output signal of the gyro-sensor in response to the average angular speed derived by the second means in cases where the first means detects that the object is not rotating, wherein the fifth means comprises an adaptive filter processing the output signal of the second means which represents the derived average angular speed; sixth means connected to the fourth means and the fifth means for combining the result of the integrating by the fourth means and the first offset level estimated by the fifth means into a second estimated offset level of the output signal of the gyro-sensor; seventh means connected to the gyro-sensor and the sixth means for subtracting the second estimated offset level provided by the sixth means from the output signal of the gyro-sensor to convert the output signal of the gyro-sensor into an offset-free signal; eighth means for detecting whether or not the gyro-sensor starts to be powered; ninth means connected to the fourth means, the adaptive filter, and the eighth means for modifying characteristics of the integrating by the fourth means and characteristics of the adaptive filter during a predetermined time following a moment at which the eighth means detects that the gyro-sensor starts to be powered; tenth means for detecting a frequency of occurrence of updating of the first offset level estimated by the fifth means; eleventh means connected to the first means, the adaptive filter, and the tenth means for modifying characteristics of the detecting by the first means and the characteristics of the adaptive filter in response to the frequency detected by the tenth means; twelfth means for determining desired initial conditions of the adaptive filter in response to the output signal of the gyro-sensor; and thirteenth means connected to the adaptive filter and the twelfth means for setting the adaptive filter into the desired initial conditions determined by the twelfth means when the adaptive filter starts to operate.