Inertial Sensing Input Apparatus and Method

• US 20080134783A1
• Filed: 02/14/2007
• Published: 06/12/2008
• Est. Priority Date: 12/12/2006
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Liou, Shun-Nan, Tsai, Ming-Jye, Jeng, Sheng-Wen
• Granted Patent: US 7,830,360 B2
• Time in Patent Office: Days
• US Class Current: 73/514.01
• CPC Class Codes: G01P 15/18 in two or more dimensions
• 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

Abstract

An inertial sensing input apparatus is disclosed, which includes: an accelerometer module, capable of detecting accelerations with respect to a Cartesian coordinate system of X-, Y-, and Z-axes; and a gyroscope, used for detecting a rotation measured with respect to the Z-axis. By the aforesaid input apparatus, an input method can be provided which comprises steps of: (a) zeroing each and every sensing element of the input apparatus at rest for defining base signals with respect to each of such sensing elements; (b) using a Z-axis accelerometer selected among those sensing elements to detect and determine whether Z-axis accelerations of the input apparatus measured along the Z-axis of the Cartesian coordinate system are varying; (c) enabling the input apparatus to enter a surface (2D) operating mode while no acceleration varying is detected along the Z axis, whereas an X-axis accelerometer and a Y-axis accelerometer are activated accordingly to detect an X-axis acceleration and a Y-axis acceleration in respective and thus generate an X-axis acceleration signal and a Y-axis acceleration signal correspondingly, and the same time that a gyroscope is activated to detect a rotation of the input apparatus caused when the input apparatus is moving and thus generate an angular velocity signal correspondingly for compensating the X-axis acceleration signal and the Y-axis acceleration signal; (d) enabling the input apparatus to enter a space (3D) operating mode while acceleration varying is detected along the Z axis. Hence, not only the input apparatus is freed from the limitation of operation space and is capable of compensating the unconscious rotation caused by a human operation as it is being held in a human hand, but also it is freed from the interferences caused by the electronic noises generated from the inertial sensing elements.

Claims

1. An inertial sensing input apparatus, comprising:

an accelerometer module, structured with at least three accelerometers for detecting accelerations in three perpendicular directions with respect to a Cartesian coordinate system of X-, Y-, and Z-axes; and

a gyroscope, used for detecting a rotation measured with respect to the Z-axis;

wherein, an angle of rotation is obtained by integrating the angular velocity of the rotation detected by the gyroscope while calculating a centrifugal force as well as a centripetal force exerting upon the inertial sensing input apparatus at the moment of the rotation so as to using those for compensating acceleration signals measured along the X-axis and the Y-axis and thereafter defining movements of an object displayed on a screen of an interactive computer by the use of the compensated acceleration signals.

2. The apparatus of claim 1, wherein one accelerometer of the acceleration module, referring hereinafter as a Z-axis accelerometer, is being enabled for detecting an acceleration with respect to the Z-axis while the inertial sensing input apparatus is experiencing an up-and down displacement and thus selecting an operating mode for the inertial sensing input apparatus accordingly.

3. The apparatus of claim 2, wherein the operating mode of the inertial sensing input apparatus includes:

a surface (2D) operating mode, by which two accelerometers of the acceleration module, referring hereinafter as an X-axis accelerometer and a Y-axis accelerometer, are activated accordingly to detect an X-axis acceleration and a Y-axis acceleration in respective and thus generate an X-axis acceleration signal and a Y-axis acceleration signal correspondingly; and

a space (3D) operating mode, by which the gyroscope is activated for detecting a rolling of the inertial sensing input apparatus while generating an angular velocity signal accordingly and the Y-axis accelerometer is activated for detecting a pitch of the inertial sensing input apparatus while generating another Y-axis acceleration signal accordingly.

4. The apparatus of claim 3, wherein the X-axis accelerometer is disabled when the inertial sensing input apparatus is operating in the space (3D) operating mode.

5. The apparatus of claim 1, wherein the acceleration module is a device selected from the group consisting of a modulized structure, a combined structure configuring with accelerometers for measuring three axes of a space respectively and independently, and the combination thereof.

6. An inertial sensing input method, comprising the steps of:

(a) zeroing an X-axis accelerometer, a Y-axis accelerometer, a Z-axis accelerometer and a gyroscope of an inertial sensing input apparatus at rest for defining BaseValue signals (BVs) with respect to those sensing elements, whereas the X-axis accelerometer, the Y-axis accelerometer, the Z-axis accelerometer are being arranged to detect accelerations of an inertial sensing input apparatus in three perpendicular directions with respect to a Cartesian coordinate system of X-, Y-, and Z-axes;

(b) using the Z-axis accelerometer to detect and determine whether a Z-axis acceleration of the inertial sensing input apparatus measured along the Z-axis of the Cartesian coordinate system is varying during a specified period of time;

(c) enabling the inertial sensing input apparatus to enter a surface (2D) operating mode while no acceleration varying is detected along the Z axis, whereas the X-axis accelerometer and the Y-axis accelerometer are activated accordingly to detect an X-axis acceleration and a Y-axis acceleration in respective and thus generate an X-axis acceleration signal and a Y-axis acceleration signal correspondingly; and

(d) enabling the input apparatus to enter a space (3D) operating mode while acceleration varying is detected along the Z axis, whereas the gyroscope is activated for detecting a rolling of the inertial sensing input apparatus while generating an angular velocity signal accordingly and the Y-axis accelerometer is activated for detecting a pitch of the inertial sensing input apparatus while generating another Y-axis acceleration signal accordingly.

7. The method of claim 6, wherein the step (b) of the method further comprises the step of:

defining the Z-axis acceleration of the inertial sensing input apparatus measured along the Z-axis as a motion signal and thus comparing the motion signal with the BVz of the Z-axis accelerometer so as to determine whether the acceleration of the inertial sensing input apparatus measured along the Z-axis is varying during the specified period of time.

8. The method of claim 6, wherein the step (C) of the method, in that the inertial sensing input apparatus is enabled to operate at the surface (2D) operating mode, further comprises the step of:

(c1) using the gyroscope to detect an unconscious rotation caused by a human operation as the inertial sensing input apparatus is being held to move on a planar surface in a human hand while generating an angular velocity signal accordingly, and thus using the angular signal for compensating the X-axis acceleration signal and the Y-axis acceleration signal.

9. The method of claim 8, wherein the compensating of the X-axis acceleration signal and the Y-axis acceleration signal, as that of step (c1), further comprises steps of:

(c11) integrating angular velocity of the inertial sensing input apparatus with respect to the angular velocity signal so as to obtain an angle of rotation; and

(c12) detecting a centrifugal force at a tangent direction as well as a centripetal force exerting upon the inertial sensing input apparatus at the moment of the rotation.

10. The method of claim 9, wherein the rotation angle, the centrifugal force and the centripetal force acquired by the gyroscope are used in a calculation for canceling out a rotation error contained in a combined acceleration signal integrating the X-axis and the Y-axis acceleration signals, and thus by the calculation, an rotation error caused by the unconscious rotation is compensated

11. The method of claim 10, wherein the step of compensating the X-axis acceleration signal and the Y-axis acceleration signal further comprises the steps of:

calculating the X-axis acceleration caused by an displacement of the inertial sensing input apparatus at the X-axis by subtracting effect of the centrifugal force from the acceleration detected by the X-axis accelerometer;

calculating the Y-axis acceleration caused by an displacement of the inertial sensing input apparatus at the Y-axis by subtracting effect of the centripetal force from the acceleration detected by the X-axis accelerometer; and

compensating the X-axis acceleration signal and the Y-axis acceleration signal.

12. The method of claim 11, wherein the compensating of the X-axis acceleration signal and the Y-axis acceleration signal is achieved by the following formula:

$\left[\begin{array}{c}{g}_{\mathrm{cx}}\\ g_{\mathrm{cy}}\end{array}\right]=\left[\begin{array}{cc}\cos <br><br><br><br>\mathrm{\theta <br><br>}& \sin <br><br><br><br>\mathrm{\theta <br><br>}\\ -\sin <br><br><br><br>\mathrm{\theta <br><br>}& \cos <br><br><br><br>\mathrm{\theta <br><br>}\end{array}\right]\times <br><br>\left[\begin{array}{c}{g}_{\mathrm{rx}}\\ g_{\mathrm{ry}}\end{array}\right]$

wherein

g_cx is the acceleration measured along the X-axis after being compensated;

g_cy is the acceleration measured along the Y-axis after being compensated;

θ

is the angle of rotation;

g_rx is the X-axis acceleration caused by an displacement of the inertial sensing input apparatus at the X-axis; and

g_ry is the Y-axis acceleration caused by an displacement of the inertial sensing input apparatus at the Y-axis.

13. The method of claim 8, wherein after the (c1) step, the method further comprises the step of:

double integrating the compensated X-axis and the Y-axis acceleration signals to obtain a displacement for using the same to define movements of an object displayed on a screen of an interactive computer.

14. The method of claim 6, wherein the step (C) of the method, in that the inertial sensing input apparatus is enabled to operate at the surface (2D) operating mode, further comprises the step of:

(c13) suspending the detecting based on the zeroing of step (a) and examining whether a plurality of successive X-axis and the Y-axis acceleration signals, stored in advanced in the inertial sensing input apparatus, are all fallen inside a threshold range;

(c14) averaging the plural successive X-axis and the Y-axis acceleration signals and replacing the BVs by the averaged X-axis and the Y-axis acceleration signals in respective when all of which fall inside the threshold range; and

(c15) performing no addition operation when all of which are not fallen inside the threshold range.

15. The method of claim 14, wherein the amount of the successive X-axis and the Y-axis acceleration signals being stored in the inertial sensing input apparatus is dependent upon the size of the apparatus as well as actual requirement.

16. The method of claim 14, wherein the threshold range is dependent upon the size of the apparatus as well as actual requirement.