Apparatus and method for detecting motion with low power consumption in inertia sensor

• US 20070024581A1
• Filed: 04/12/2006
• Published: 02/01/2007
• Est. Priority Date: 08/01/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Jong, Shin, Kun, Kim, Youn, Hwang, Hyun
• Granted Patent: US 7,652,609 B2
• Time in Patent Office: Days
• US Class Current: 345/156
• CPC Class Codes: G01C 21/166 Mechanical, construction or arrangement details of inertial navigation systems
• CPC Class Codes: G01P 13/00 Indicating or recording presence, absence, or direction, of movement electric switches H01H; counting moving objects G06M7/00
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

A motion detector and method with low power consumption in an inertia sensor. The motion detector is selectively supplied with power for operation of the inertia sensor according to a power control signal. While the inertia sensor is supplied with power, three-dimensional analog signals are sampled, A/D converted, and outputted via a controller. A pulse width of the power control signal is determined by reflecting the sampling and A/D conversion period and reflecting the operation preparing period of the inertia sensor from the A/D converted value.

Claims

1. A motion detector comprising:

an inertia sensor supplied with power and generating an analog signal associated with inertia, the power selectively supplied according to a power control signal; and

a controller generating the power control signal, sampling the analog signal associated with inertia, and converting the analog signal into a digital value,

wherein a pulse width of the power control signal is determined by reflecting a sampling and digital conversion period and reflecting an operation preparing period of the inertia sensor based on the converted digital value.

2. The motion detector of claim 1, wherein:

the analog signal associated with inertia is an analog acceleration signal,

the controller samples the analog acceleration signal and converts the analog acceleration signal into a corresponding digital acceleration value within a pulse of the power control signal for which power is supplied to the inertia sensor, and

the pulse width of the power control signal is determined on the basis of digital acceleration values in a motion state and digital acceleration values in a static state where the analog acceleration signal is converted by the controller.

3. The motion detector of claim 2, wherein power to the inertia sensor is shut off after sampling the analog acceleration signal, according to the power control signal within a certain period.

4. The motion detector of claim 3, wherein the sampling of the analog acceleration signal and power shut off to the inertia sensor is performed substantially at the same time.

5. The motion detector of claim 2, wherein the pulse width of the power control signal is determined on the basis of digital acceleration values in a static state and in a motion state from another motion detector constantly supplied with power, in addition to the digital acceleration values in the static state and in the motion state from the motion detector selectively operating according to the power control signal.

6. The motion detector of claim 5, wherein a difference between a maximum peak-to-peak level of digital acceleration values of the motion detector and a maximum peak-to-peak level of digital acceleration values of the another motion detector measured for a certain period in the static state is less than a threshold value.

7. The motion detector of claim 6, wherein the threshold value is less than 0.05 g, g being an acceleration of gravity.

8. The motion detector of claim 5, wherein a correlation between digital acceleration values of the motion detector and digital acceleration values of the another motion detector measured for a certain period in the motion state is greater than a threshold value.

9. The motion detector of claim 8, wherein the motion state is a state where the motion detector and the another motion detector two-dimensionally rotate about one rotation axis.

10. The motion detector of claim 9, wherein the correlation is calculated using 180 degrees phase inverted values of digital acceleration values from the another motion detector.

11. The motion detector of claim 10, wherein the threshold value is greater than a value corresponding to 98% correlation of the digital acceleration values.

12. The motion detector of claim 1, wherein the controller operates in a standby mode for a certain period before the inertia sensor is supplied with power after the converted digital value is generated.

13. The motion detector of claim 1, wherein the inertia sensor is a gyro sensor, a geomagnetic compass sensor, or an accelerometer generating three-dimensional analog signals.

14. The motion detector of claim 13, wherein the controller generates a corresponding digital value indicating a degree of motion on the basis of the three-dimensional analog signals.

15. The motion detector of claim 1, wherein the controller measures a difference between an operation starting time of the inertia sensor when power is initially supplied according to the power control signal and a normal operation time of the inertia sensor, as the operation preparing period, and reflects the measured difference to determine the pulse width of the power control signal.

16. The motion detector of claim 15, wherein the controller determines the pulse width to be at least as long as the operation preparing period and the sampling and digital conversion period added together.

17. The motion detector of claim 15, wherein the controller measures a time when the digital value has a certain offset value greater than in the operation starting time of the inertia sensor, as the normal operation time of the inertia sensor.

18. A method of detecting motion by using an inertia sensor, the method comprising:

generating a power control signal;

selectively supplying power to the inertia sensor according to the power control signal;

generating an analog signal associated with inertia via the inertia sensor; and

sampling the analog signal and converting the same into a digital value,

wherein a pulse width of the power control signal is determined by reflecting a sampling and digital conversion period and reflecting an operation preparing period of the inertia sensor based on the converted digital value.

19. The method of claim 18, wherein the conversion comprises sampling an analog acceleration signal as the analog signal associated with inertia and converting the sampled analog acceleration signal into a corresponding digital acceleration value within a pulse width of the power control signal for which the power is supplied to the inertia sensor, and

wherein the pulse width of the power control signal is determined on the basis of digital acceleration values in a static state and digital acceleration values in a motion state.

20. The method of claim 19, wherein the power to the inertia sensor is shut off according to the power control signal within a certain period after sampling the analog acceleration signal.

21. The method of claim 20, wherein the sampling of the analog acceleration signal and the power shut off to the inertia sensor is performed substantially at the same time.

22. The method of claim 19, wherein the pulse width of the power control signal is determined on the basis of digital acceleration values corresponding to analog acceleration signals in a static state and in a motion state from an another inertia sensor constantly supplied with power, in addition to the digital acceleration values corresponding to analog acceleration signals in the static state and in the motion state from the inertia sensor selectively operating according to the power control signal.

23. The method of claim 22, wherein the difference between the maximum peak-to-peak level of corresponding digital acceleration values into which outputs of the inertia sensor are converted and the maximum peak-to-peak level of corresponding digital acceleration values into which outputs of the another inertia sensor are converted, measured, for a certain period in the static state is less than a threshold value.

24. The method of claim 23, wherein the threshold value is smaller than 0.05 g, g being an acceleration of gravity.

25. The method of claim 22, wherein a correlation between corresponding digital acceleration values into which an output of the inertia sensor is converted and corresponding digital acceleration values in which an output of the another inertia sensor is converted, measured for a certain period in the motion state is greater than a threshold value.

26. The method of claim 25, wherein the motion state is a state where the inertia sensor and the another inertia sensor two-dimensionally rotate about one rotation axis.

27. The method of claim 26, wherein the correlation is calculated using 180 degrees phase inverted values of the corresponding digital acceleration values into which an output of the another inertia sensor is converted

28. The method of claim 27, wherein the threshold value is greater than a value corresponding to 98% correlation of the digital acceleration values.

29. The method of claim 18, wherein the inertia sensor is a gyro sensor, a geomagnetic compass sensor, or an accelerometer generating three-dimensional analog signals.

30. The method of claim 18, comprising measuring a difference between an operation starting time of the inertia sensor when power is initially supplied according to the power control signal and a normal operation time of the inertia sensor as the operation preparing period, and reflecting the measured difference to determine the pulse width of the power control signal.

31. The method of claim 30, comprising determining the pulse width to be at least as long as the operation preparing period and the sampling and digital conversion period added together.

32. The method of claim 30, comprising measuring a time when the digital value has a certain offset value greater than in the operation starting time of the inertia sensor as the normal operation time of the inertia sensor.

33. A computer-readable storage medium encoded with processing instructions for causing a processor to execute a method of detecting motion by using an inertia sensor, the method comprising:

generating a power control signal;

selectively supplying power to the inertia sensor according to the power control signal;

generating an analog signal associated with inertia via the inertia sensor; and

sampling the analog signal and converting the same into a digital value,

wherein a pulse width of the power control signal is determined by reflecting a sampling and digital conversion period and reflecting an operation preparing period of the inertia sensor based on the converted digital value.