Method and apparatus for detecting free fall of electronic device
View Patent ↗A method and apparatus for detecting a free fall of an electronic device. The method includes: sensing a falling acceleration of the electronic device using an acceleration sensor; determining whether the sensed falling acceleration is less than a predetermined threshold; when the sensed falling acceleration is less than the predetermined threshold, determining whether the falling acceleration is a statistical constant, which has a statistical significance, and is maintained for a predetermined time; and when the falling acceleration is a statistical constant and maintained for a predetermined time, determining that the electronic device falls freely. Accordingly, it is possible to exactly detect a free fall of an electronic device, irrespective of an error of the acceleration of gravity generated when a falling acceleration of the electronic device is measured, due to ambient conditions, e.g., a temperature change and a rotation acceleration generated when the electronic device rotates.
1. A method of detecting a free fall of an electronic device, comprising:
(a) sensing a falling acceleration of the electronic device using an acceleration sensor;
(b) determining whether the sensed falling acceleration is less than a predetermined threshold;
(c) if the sensed falling acceleration is less than the predetermined threshold, determining whether the falling acceleration is a statistical constant, which has a statistical significance, and is maintained for a predetermined time; and
(d) if the falling acceleration is the statistical constant and maintained for the predetermined time, determining that the electronic device falls freely.
2. The method of claim 1 , wherein the predetermined threshold is obtained by compensating for an error between a reference acceleration of gravity and a sensed acceleration of gravity, and a rotation acceleration of the electronic device generated when the electronic device rotates.
3. The method of claim 1 , further comprising operation (e) resetting the predetermined threshold to correspond to an error of acceleration of gravity, and proceeding to the operation (a).
4. The method of claim 3 , wherein the operation (e) comprises:
detecting the error of acceleration of gravity; and
resetting the predetermined threshold using the detected error of acceleration of gravity.
5. The method of claim 1 , wherein during the operation (c), the sensed falling acceleration is determined as the statistical constant if the sensed falling acceleration changes within a predetermined range and is maintained for the predetermined time.
6. The method of claim 1 , wherein during the operation (c), the sensed falling acceleration is determined as the statistical constant when a variance of the falling acceleration changing for the predetermined time is less than or equal to a predetermined value.
7. The method of claim 1 , wherein during the operation (c), the sensed falling acceleration is determined as the statistical constant when a Chi-square value of the falling acceleration sensed for the predetermined time is less than or equal to a predetermined value, the Chi-square value being obtained according to a Chi-square test.
8. An apparatus for detecting a free fall of an electronic device, comprising:
an acceleration sensor which senses a falling acceleration of the electronic device;
an acceleration comparator which determines whether the falling acceleration is less than a predetermined threshold;
an acceleration change determining unit which determines whether the falling acceleration is a statistical constant, which has a statistical significance, and is maintained for a predetermined time, according to the result of a first determination result transmitted from the acceleration comparator; and
a free fall determining unit which determines that the electronic device falls freely if a second determination result indicates that the falling acceleration is the statistical constant and is maintained for the predetermined time, wherein said second result is transmitted from the acceleration change determining unit.
9. The apparatus of claim 8 , wherein the predetermined threshold is obtained by compensating for an error between a reference acceleration of gravity and a sensed acceleration of gravity, and a rotation acceleration generated when the electronic device rotates.
10. The apparatus of claim 8 , further comprising a threshold setting unit which resets the predetermined threshold to correspond to an error of acceleration of gravity.
11. The apparatus of claim 10 , wherein the threshold setting unit comprises:
a measured error detecting unit which detects the error of acceleration of gravity; and
a setting unit which resets the predetermined threshold according to the error of acceleration of gravity.
12. The apparatus of claim 8 , wherein the acceleration change determining unit determines the sensed falling acceleration as the statistical constant if the falling acceleration sensed for the predetermined time is maintained within a predetermined range.
13. The apparatus of claim 8 , wherein the acceleration change determining unit determines the sensed falling acceleration as the statistical constant if a variance of the falling acceleration sensed for the predetermined time is less than or equal to a predetermined number.
14. The apparatus of claim 8 , wherein the acceleration change determining unit determines the sensed falling acceleration as the statistical constant when a Chi-square value of the falling acceleration sensed for the predetermined time is less than or equal to a predetermined value.