Inertial Sensing Method and System

• US 20080143675A1
• Filed: 02/05/2007
• Published: 06/19/2008
• Est. Priority Date: 12/13/2006
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Liou, Shun-Nan, Hsieh, Chin-Lin, Tsai, Ming-Jye
• Granted Patent: US 7,812,818 B2
• Time in Patent Office: Days
• US Class Current: 345/158
• CPC Class Codes: G06F 1/1626 with a single-body enclosure integrating a flat display, e.g. Personal Digital Assistants [PDAs]
• CPC Class Codes: G06F 2200/1637 Sensing arrangement for detection of housing movement or orientation, e.g. for controlling scrolling or cursor movement on the display of an handheld computer
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G08C 2201/32 Remote control based on movements, attitude of remote control device

Abstract

An inertial sensing method is disclosed, which is capable of detecting tilting of an inertial sensing apparatus with respect to a specific level surface while using the detection for defining/controlling movements of a cursor displayed on a display, In a preferred aspect, as it is capable of acting as an hand-held input device, a swing of a hand holding the inertial sensing apparatus can be detected thereby and is used for controlling a page change of a display. Operationally, a micro inertial sensing module of the aforesaid inertial sensing apparatus detects changes of gravity caused by tilts of the inertial sensing apparatus and then generates inclination signals accordingly while enabling a wireless transmitter to send the same to a micro processing unit where the inclination signals are filtered and then compared with predefined datum signals so as to enable a cursor control circuit to define/control movements of a cursor displayed on a display according to the comparison. In addition, an effect of vibration measured along an axis of a Cartesian coordinate system of X-, Y-, and Z-axes defining the inertial sensing apparatus can be eliminated by the use of variations of signals measured along other axes of the Cartesian coordinate system. Preferably, by using two Y-axis accelerometers of the micro inertial sensing module to measure a difference of centrifugal forces detected respectively thereby, the adverse affection of centrifugal forces exerting upon the Y-axis can be eliminated.

Claims

1. A three-dimensional inertial sensing method for cursor control, comprising the steps of:

using a micro inertial sensing module to detect an acceleration of gravity for generating a raw inclination signal accordingly;

low-filtering the raw inclination signal for obtaining a stabilized inclination signal;

registering an initial signal of the micro inertial sensing module;

calculating a signal variation amount basing on the raw inclination signal, the stabilized inclination signal so as to compensate the raw inclination signal using the signal variation amount;

calculating the difference between the compensated inclination signal and the initial signal; and

mapping the differences as a coordinate signal for controlling the movement of a cursor displayed on a display.

2. The method of claim 1, wherein the micro inertial sensing module is comprised of:

an X-axis accelerometer, for measuring acceleration variations of gravity caused by a rolling movement of the micro inertial sensing module with respect to an X axis of a Cartesian coordinate system of X-, Y-, and Z-axes defining the micro inertial sensing module; and

a Y-axis accelerometer, for measuring acceleration variations of gravity caused by a pitch movement of the micro inertial sensing module with respect to a Y axis of the Cartesian coordinate system.

3. The method of claim 1, wherein the calculating of the signal variation amount basing on the raw inclination signal, the stabilized inclination signal for compensating the raw inclination signal using the signal variation amount further comprises the steps of:

modifying the raw inclination signal detected by the X-axis accelerometer by subtracting an X-axis vibration signal detected by the X-axis accelerometer from the raw inclination signal detected by the X-axis accelerometer;

modifying the raw inclination signal detected by the Y-axis accelerometer by subtracting an Y-axis vibration signal detected by the Y-axis accelerometer from the raw inclination signal detected by the Y-axis accelerometer;

registering an X-axis variation as the subtraction of the initial signal detected by the X-axis accelerometer from the modified X-axis raw inclination signal; and

registering a Y-axis variation as the subtraction of the initial signal detected by the Y-axis accelerometer from the modified Y-axis raw inclination signal.

4. The method of claim 3, wherein the modifying of the raw inclination signals detected by the X-axis and Y-axis accelerometers further comprises the steps of:

registering the X-axis vibration signal as an middle value of the difference of the X-axis raw inclination signal and the stabilized X-axis inclination signal;

registering the Y-axis vibration signal as an middle value of the difference of the Y-axis raw inclination signal and the stabilized Y-axis inclination signal;

acquiring a compensated X-axis inclination signal by subtracting the X-axis vibration signal from the X-axis raw inclination signal; and

acquiring a compensated Y-axis inclination signal by subtracting the Y-axis vibration signal from the Y-axis raw inclination signal.

5. The method of claim 2, wherein the micro inertial sensing module further comprises a Z-axis accelerometer, used for detecting an acceleration of gravity with respect to the Z-axis of the Cartesian coordinate system, caused by the rolling and pitching of the micro inertial sensing module detected respectively by the X-axis accelerometer and Y-axis accelerometer, so as to obtain information relating to the positioning of the micro inertial sensing module.

6. The method of claim 2, wherein the micro inertial sensing module further comprises a second Y-axis accelerometer, spaced from the Y-axis accelerometer by a specific distance.

7. The method of claim 6, wherein the influence of centrifugal force working on the inertial sensing apparatus can be eliminated by the use of the difference between two centrifugal forces detected respectively by the two Y-axis accelerometers in terms of the following formula:

Ay=(R+R2)/R×

(Tvy−

Tvy2)

ModifiedTvy=Tvy−

Ay

wherein

Ay is the centrifugal force detected by the Y-axis accelerometer;

R is the distance spaced between the Y-axis and the second Y-axis accelerometer;

R2 is the distance between the second Y-axis accelerometer and a center of rotation;

Tvy is the inclination signal of the Y-axis accelerometer;

Tvy2 is the inclination signal of the second Y-axis accelerometer;

i.e. a modified Y-axis inclination signal can be obtained by subtracting the centrifugal force Ay from the raw Y-axis inclination signal Tvy.

8. The method of claim 1, wherein the micro inertial sensing module is coupled to a central processing unit, capable of receiving the measurements of acceleration variations and thus generating raw inclination signals accordingly;

and the central processing unit is connected to a wireless transmitter for transmitting the raw inclination signals; and

the wireless transmitter is enabled to function corresponding to a wireless receiver in a manner that the wireless receiver is able to receive the raw inclination signals transmitted by the wireless transmitter and thus send the received raw inclination signals to a micro processing unit to be low-pass filtered and processed by other posterior procedures; and

the micro processing unit is connected to a display by way of a cursor control circuit, capable of controlling the movement of a cursor displayed on the display as well as controlling a page-changing or continuous page-changing on the display.

9. A three-dimensional inertial sensing method for directing page-changing, comprising the steps of:

using a micro inertial sensing module to detect an acceleration of gravity for generating a raw inclination signal accordingly;

low-filtering the raw inclination signal for obtaining a stabilized inclination signal;

detecting whether the inclination of the micro inertial sensing module with respect to the X-axis and Y-axis is falling within a range of balance;

if so, continue the detecting;

otherwise, steps posterior to the detection is perform; and

evaluating whether an instant variation of the raw X-axis inclination signal is exceeding a threshold range;

if so, a page-changing is enabled;

otherwise, the process flow back to the foregoing mode detecting step.

10. The method of claim 9, wherein a continuous page-changing is perform while the instant variation of the raw inclination signal is exceeding a threshold range and the raw inclination signal is not transient but lastingly fixed to a detection of the micro inertial sensing module as it is tilt by a specific inclination angle.

11. The method of claim 10, wherein the continuous page-changing is stopped and the process proceeds back to the mode detecting step as soon as the raw inclination signal is not lastingly fixed to a detection of the micro inertial sensing module as it is tilt by a specific inclination angle.

12. The method of claim 9, wherein the micro inertial sensing module is comprised of:

at least an X-axis accelerometer, for measuring acceleration variations of gravity caused by a rolling movement of the micro inertial sensing module with respect to an X axis of a Cartesian coordinate system of X-, Y-, and Z-axes defining the micro inertial sensing module.

13. The method of claim 9, wherein the micro inertial sensing module is coupled to a central processing unit, capable of receiving the measurements of acceleration variations and thus generating raw inclination signals accordingly;

and the central processing unit is connected to a wireless transmitter for transmitting the raw inclination signals; and

the wireless transmitter is enabled to function corresponding to a wireless receiver in a manner that the wireless receiver is able to receive the raw inclination signals transmitted by the wireless transmitter and thus send the received raw inclination signals to a micro processing unit to be low-pass filtered and processed by other posterior procedures; and

the micro processing unit is connected to a display by way of a cursor control circuit, capable of controlling the movement of a cursor displayed on the display as well as controlling a page-changing or continuous page-changing on the display.

14. The method of claim 13, wherein the range of balance is defined in the micro processing unit so as to be used for evaluating whether the raw inclination signal is falling inside the range of balance;

if so, the micro inertial sensing module is situated in a balance status;

otherwise, the micro inertial sensing module is situated in an unbalance status.

15. The method of claim 14, wherein the range of balance is defined as 0 g±

0.3 g, and g=9.8 m/s².

16. A three-dimensional inertial sensing method, comprising the steps of:

using a micro inertial sensing module to detect an acceleration of gravity for generating a raw inclination signal accordingly;

low-filtering the raw inclination signal for obtaining a stabilized inclination signal; and

detecting whether the micro inertial sensing module is situated in a cursor-control mode or a page-changing mode so as to correspondingly select a process to be perform from the group consisting a cursor-control process and a page-change process.

17. The method of claim 16, wherein the cursor-control process comprises the steps of:

registering an initial signal of the micro inertial sensing module;

calculating a signal variation amount basing on the raw inclination signal, the stabilized inclination signal so as to compensate the raw inclination signal using the signal variation amount;

calculating the difference between the compensated inclination signal and the initial signal; and

mapping the differences as a coordinate signal for controlling the movement of a cursor displayed on a display.

18. The method of claim 16, wherein the micro inertial sensing module is comprised of:

an X-axis accelerometer, for measuring acceleration variations of gravity caused by a rolling movement of the micro inertial sensing module with respect to an X axis of a Cartesian coordinate system of X-, Y-, and Z-axes defining the micro inertial sensing module; and

a Y-axis accelerometer, for measuring acceleration variations of gravity caused by a pitch movement of the micro inertial sensing module with respect to a Y axis of the Cartesian coordinate system.

19. The method of claim 17, wherein the calculating of the signal variation amount basing on the raw inclination signal, the stabilized inclination signal for compensating the raw inclination signal using the signal variation amount further comprises the steps of:

modifying the raw inclination signal detected by the X-axis accelerometer by subtracting an X-axis vibration signal detected by the X-axis accelerometer from the raw inclination signal detected by the X-axis accelerometer;

modifying the raw inclination signal detected by the Y-axis accelerometer by subtracting an Y-axis vibration signal detected by the Y-axis accelerometer from the raw inclination signal detected by the Y-axis accelerometer;

registering an X-axis variation as the subtraction of the initial signal detected by the X-axis accelerometer from the modified X-axis raw inclination signal; and

registering a Y-axis variation as the subtraction of the initial signal detected by the Y-axis accelerometer from the modified Y-axis raw inclination signal.

20. The method of claim 19, wherein the modifying of the raw inclination signals detected by the X-axis and Y-axis accelerometers further comprises the steps of:

registering the X-axis vibration signal as an middle value of the difference of the X-axis raw inclination signal and the stabilized X-axis inclination signal;

registering the Y-axis vibration signal as an middle value of the difference of the Y-axis raw inclination signal and the stabilized Y-axis inclination signal;

acquiring a compensated X-axis inclination signal by subtracting the X-axis vibration signal from the X-axis raw inclination signal; and

acquiring a compensated Y-axis inclination signal by subtracting the Y-axis vibration signal from the Y-axis raw inclination signal.

21. The method of claim 18, wherein the micro inertial sensing module further comprises a Z-axis accelerometer, used for detecting an acceleration of gravity with respect to the Z-axis of the Cartesian coordinate system, caused by the rolling and pitching of the micro inertial sensing module detected respectively by the X-axis accelerometer and Y-axis accelerometer, so as to obtain information relating to the positioning of the micro inertial sensing module.

22. The method of claim 18, wherein the micro inertial sensing module further comprises a second Y-axis accelerometer, spaced from the Y-axis accelerometer by a specific distance.

23. The method of claim 22, wherein the influence of centrifugal force working on the inertial sensing apparatus can be eliminated by the use of the difference between two centrifugal forces detected respectively by the two Y-axis accelerometers in terms of the following formula:

Ay=(R+R2)/R×

(Tvy−

Tvy2)

ModifiedTvy=Tvy−

Ay

wherein

Ay is the centrifugal force detected by the Y-axis accelerometer;

R is the distance spaced between the Y-axis and the second Y-axis accelerometer;

R2 is the distance between the second Y-axis accelerometer and a center of rotation;

Tvy is the inclination signal of the Y-axis accelerometer;

Tvy2 is the inclination signal of the second Y-axis accelerometer;

a modified Y-axis inclination signal can be obtained by subtracting the centrifugal force Ay from the raw Y-axis inclination signal Tvy.

24. The method of claim 16, wherein the page-change process comprises the steps of:

detecting whether the inclination of the micro inertial sensing module with respect to the X-axis and Y-axis is falling within a range of balance;

if so, continue the detecting;

otherwise, steps posterior to the detection is perform; and

evaluating whether an instant variation of the raw X-axis inclination signal is exceeding a threshold range;

if so, a page-changing is enabled;

otherwise, the process flow back to the foregoing mode detecting step.

25. The method of claim 24, wherein the range of balance is defined as 0 g±

0.3 g, and g=9.8 m/s².

26. The method of claim 24, wherein a continuous page-changing is perform while the instant variation of the raw inclination signal is exceeding a threshold range and the raw inclination signal is not transient but lastingly fixed to a detection of the micro inertial sensing module as it is tilt by a specific inclination angle.

27. The method of claim 26, wherein the continuous page-changing is stopped and the process proceeds back to the mode detecting step as soon as the raw inclination signal is not lastingly fixed to a detection of the micro inertial sensing module as it is tilt by a specific inclination angle.

28. The method of claim 16, wherein the micro inertial sensing module is comprised of:

at least an X-axis accelerometer, for measuring acceleration variations of gravity caused by a rolling movement of the micro inertial sensing module with respect to an X axis of a Cartesian coordinate system of X-, Y-, and Z-axes defining the micro inertial sensing module.

29. The method of claim 25, wherein the micro inertial sensing module is coupled to a central processing unit, capable of receiving the measurements of acceleration variations and thus generating raw inclination signals accordingly;

and the central processing unit is connected to a wireless transmitter for transmitting the raw inclination signals; and

the wireless transmitter is enabled to function corresponding to a wireless receiver in a manner that the wireless receiver is able to receive the raw inclination signals transmitted by the wireless transmitter and thus send the received raw inclination signals to a micro processing unit to be low-pass filtered and processed by other posterior procedures; and

the micro processing unit is connected to a display by way of a cursor control circuit, capable of controlling the movement of a cursor displayed on the display as well as controlling a page-changing or continuous page-changing on the display.

30. A three-dimensional inertial sensing apparatus, comprising:

a micro inertial sensing module, for detecting an acceleration of gravity for generating a raw inclination signal accordingly, further comprising;

an X-axis accelerometer, for measuring acceleration variations of gravity caused by a rolling movement of the micro inertial sensing module with respect to an X axis of a Cartesian coordinate system of X-, Y-, and Z-axes defining the micro inertial sensing module;

a first Y-axis accelerometer, for measuring a first acceleration variation of gravity caused by a pitch movement of the micro inertial sensing module with respect to a Y axis of the Cartesian coordinate system; and

a second Y-axis accelerometer, for measuring a second acceleration variation of gravity caused by a pitch movement of the micro inertial sensing module with respect to a Y axis of the Cartesian coordinate system;

and

a receiving end, for receiving the raw inclination signal of the micro inertial sensing module.

31. The apparatus of claim 30, wherein the micro inertial sensing module further comprises a Z-axis accelerometer, used for detecting an acceleration of gravity with respect to the Z-axis of the Cartesian coordinate system, caused by the rolling and pitching of the micro inertial sensing module detected respectively by the X-axis accelerometer and Y-axis accelerometer, so as to obtain information relating to the positioning of the micro inertial sensing module.

32. The apparatus of claim 30, wherein the first and the second Y-axis accelerometers are spaced from each other by a specific distance.

33. The apparatus of claim 30, wherein the micro inertial sensing module is coupled to a central processing unit, capable of receiving the measurements of acceleration variations and thus generating raw inclination signals accordingly;

and the central processing unit is connected to a wireless transmitter for transmitting the raw inclination signals; and

the wireless transmitter is enabled to function corresponding to a wireless receiver in a manner that the wireless receiver is able to receive the raw inclination signals transmitted by the wireless transmitter and thus send the received raw inclination signals to a micro processing unit to be low-pass filtered and processed by other posterior procedures; and

the micro processing unit is connected to a display by way of a cursor control circuit, capable of controlling the movement of a cursor displayed on the display as well as controlling a page-changing or continuous page-changing on the display.