Apparatus and method for setting a gyroscrope zero point

• US 20070136019A1
• Filed: 10/12/2005
• Published: 06/14/2007
• Est. Priority Date: 10/12/2004
• Status: Active Grant

• Current Assignee: Intellectual Discovery Co., Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Moon, Young-Khon, Yun, Doo-Hee
• Granted Patent: US 7,565,260 B2
• Time in Patent Office: Days
• US Class Current: 702/87
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

Disclosed are an apparatus and a method for computing a position of a moving entity, and an apparatus and method for setting a gyroscope zero point or a gyroscope zero point reference value. In the apparatus for setting the gyroscope zero point, a gyroscope outputs a signal of angular velocity in the form of voltage. A global positioning system (GPS) receiver receives a GPS signal. An analog-to-digital (A/D) converter digitizes the voltage output from the gyroscope. A controller detects a speed and a direction angle of a vehicle from the received GPS signal, determines if the vehicle is traveling in a straight line, and filters the voltage output from the gyroscope to obtain a gyroscope zero point reference value if the vehicle is traveling in the straight line.

Claims

1. An apparatus for setting a gyroscope zero point reference value, comprising:

a gyroscope for outputting a signal indicating angular velocity in the form of a voltage;

a global positioning system (GPS) receiver for receiving a GPS signal;

an analog-to-digital (A/D) converter for digitizing the voltage output from the gyroscope; and

a controller for detecting a speed and a direction angle of a vehicle from the received GPS signal, determining if the vehicle is traveling in a straight line, and filtering the voltage output from the gyroscope to obtain a gyroscope zero point reference value if the vehicle is traveling in the straight line.

2. The apparatus according to claim 1, wherein the gyroscope zero point reference value is computed by

ZPT_Ref=(N−

1)/N*ZPT_Ref+1/N*Mean(Y[0 . . . 9]), where ZPT_Ref

denotes a gyroscope zero point reference value, N denotes a smoothing filter constant, and Mean(Y[0 . . . 9]) denotes a mean value of Y[0] to Y[9] values, each of the Y[0] to Y[9] values being an average of an accumulated value obtained by accumulating a mean value of gyroscope output values measured in a predetermined cycle a predetermined number of times.

3. The apparatus according to claim 2, further comprising:

a memory for storing the gyroscope zero point reference value.

4. A method for setting a gyroscope zero point reference value, comprising:

checking global positioning system (GPS) measurement in a predetermined cycle;

determining if a vehicle is traveling in a straight line from a result of the GPS measurement, incrementing a count value associated with the straight-line traveling if the vehicle is traveling in the straight line, and computing a gyroscope zero point reference value according to

ZPT_Ref=(N−

1)/N*ZPT_Ref+1/N*Mean(Y[0 . . . 9]), where ZPT_Ref

denotes a gyroscope zero point reference value, N denotes a smoothing filter constant, and Mean(Y[0 . . . 9]) is a mean value of Y[0] to Y[9] values, each of the Y[0] to Y[9] values being an average of an accumulated value obtained by accumulating a mean value of gyroscope output values measured in a predetermined cycle a predetermined number of times; and

determining the count value associated with the straight-line traveling after computing the gyroscope zero point reference value, storing the computed gyroscope zero point reference value in a memory if the count value is larger than N, and waiting for the cycle to be reached if the count value is less than or equal to N.

5. An apparatus for setting a gyroscope zero point, comprising:

a gyroscope for outputting a signal indicating angular velocity in the form of a voltage;

a global positioning system (GPS) receiver for receiving a GPS signal;

an analog-to-digital (A/D) converter for digitizing the voltage output from the gyroscope; and

a controller for analyzing the GPS signal, determining if a vehicle is traveling in a straight line, obtaining a gyroscope zero point reference value, comparing a gyroscope output range value with a noise level value in a predetermined cycle, and updating a gyroscope zero point when the gyroscope output range value is less than or equal to the noise level value.

6. The apparatus according to claim 5, wherein the gyroscope output range value is computed by Range=MAX(Y[0 . . . 9])−

MIN(Y[0 . . . 9]), where MAX(Y[0 . . . 9]) is a maximum value of Y[0] to Y[9] values, and MIN(Y[0 . . . 9]) is a minimum value of the Y[0] to Y[9] values, each of the Y[0] to Y[9] values being an average of an accumulated value obtained by accumulating a mean value of gyroscope output values measured in a predetermined cycle the predetermined number of times, and

wherein the noise level value is updated to a minimum value of computed gyroscope output range values whenever the gyroscope output range value is less than or equal to the noise level value.

7. The apparatus according to claim 5, further comprising:

a memory for storing a value of the gyroscope zero point, the noise level value, and the gyroscope zero point reference value.

8. A method for setting a gyroscope zero point using a memory storing a gyroscope zero point value, a noise level value, and a gyroscope zero point reference value, comprising:

determining if the gyroscope zero point value, the noise level value, and the gyroscope zero point reference value are present in the memory, when power is applied;

initializing a gyroscope zero point and a gyroscope zero point reference value to the stored values thereof and initializing a noise level to a predetermined multiple of the stored value thereof if the values are present, and initializing only the noise level to a value computed by taking into account a case where vibration is large, if the values are not stored;

sequentially storing, in a plurality of buffers, an average of an accumulated value obtained by accumulating a mean value of gyroscope output values measured in a second time interval for a first time period;

obtaining a gyroscope output range value whenever sequentially storing, in the plurality of buffers, an average of an accumulated value obtained by accumulating a mean value of gyroscope output values measured in the second time interval for the first time period after all the buffers are initially filled;

updating the noise level to a minimum gyroscope output range value, when the gyroscope output range value is less than or equal to the noise level value; and

summing values stored in all the buffers when the noise level is updated, and updating a new gyroscope zero point to a mean value of the stored values.

9. The method according to claim 8, wherein if the gyroscope output range value is larger than a value set by taking into account a case where vibration is large even when the gyroscope output range value is less than or equal to the noise level value, the noise level is maintained without being updated.

10. The method according to claim 8, further comprising:

checking if a condition of |Mean(Y[0 . . . 9])−

ZPT₁₃Ref|≦

ε

is satisfied before the gyroscope zero point is set, where Mean(Y[0 . . . 9]) denotes the gyroscope zero point value, ZPT_Ref denotes the gyroscope zero point reference value, and ε

denotes a half value of a true noise level of a gyroscope in a non-vibration state.

11. The method according to claim 10, further comprising:

determining if a count value associated with straight-line traveling is larger than a smoothing filter constant; and

determining if the condition is satisfied, when the count value is larger than the smoothing filter constant.

12. The method according to claim 10, further comprising:

determining if the gyroscope zero point reference value stored in advance is valid; and

determining if the condition is satisfied, when the gyroscope zero point is valid.