Free fall detection system for protecting hard drives in mobile devices

• US 20110215940A1
• Filed: 03/01/2011
• Published: 09/08/2011
• Est. Priority Date: 03/08/2010
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Bartholomeyczik, Julian, Scheiermann, Sergej
• Granted Patent: US 9,514,780 B2
• Time in Patent Office: Days
• US Class Current: 340/669
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G11B 19/043 by detecting a free-fall condition

Abstract

In a method for detecting free fall, a first acceleration parallel to a first axis, a second acceleration parallel to a second axis perpendicular to the first axis, and a third acceleration parallel to a third axis perpendicular to the first axis and to the second axis are measured. A sum of a first value of the first acceleration, a second value of the second acceleration, and a third value of the third acceleration is calculated, and the free fall is detected as a function of the sum.

Claims

1. A method for detecting a free fall of a mobile device, comprising:

measuring a first acceleration parallel to a first axis;

measuring a second acceleration parallel to a second axis perpendicular to the first axis;

measuring a third acceleration parallel to a third axis perpendicular to the first axis and to the second axis;

calculating a sum of a first value of the first acceleration, a second value of the second acceleration, and a third value of the third acceleration; and

detecting the free fall of the mobile device as a function of the calculated sum.

2. The method as recited in claim 1, wherein the first acceleration, the second acceleration, and the third acceleration are measured using a triple-axis acceleration sensor.

3. The method as recited in claim 2, wherein the triple-axis acceleration sensor is configured to generate digital signals.

4. The method as recited in claim 1, further comprising:

comparing the calculated sum to a predetermined threshold value.

5. The method as recited in claim 4, further comprising:

generating a warning signal if the calculated sum is below the threshold value.

6. The method as recited in claim 5, wherein the warning signal indicates that the free fall is present.

7. The method as recited in claim 6, further comprising:

locking a write-read head of a hard drive of the mobile device if the free fall is detected.

8. A device for detecting a free fall of a mobile device, comprising:

a triple-axis acceleration sensor configured to measure (i) a first acceleration parallel to a first axis, (ii) a second acceleration parallel to a second axis perpendicular to the first axis, and (iii) a third acceleration parallel to a third axis perpendicular to the first axis and to the second axis; and

an evaluation circuit configured to (a) calculate a sum of a first value of the first acceleration, a second value of the second acceleration, and a third value of the third acceleration, and (b) detect the free fall of the mobile device as a function of the calculated sum.

9. The device as recited in claim 8, wherein the device is implemented as a microelectromechanical system.

10. The device as recited in claim 9, wherein the triple-axis acceleration sensor and the evaluation circuit are integrated in a sensor housing.

11. The device as recited in claim 8, further comprising:

means for locking a write-read head of a hard drive of the mobile device if the free fall is detected.