Free fall detection system for protecting hard drives in mobile devices

• US 9,514,780 B2
• Filed: 03/01/2011
• Issued: 12/06/2016
• Est. Priority Date: 03/08/2010
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Bartholomeyczik, Julian, Scheiermann, Sergej
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): MATHEWS, CRYSTAL
• Application Number:
  US12/932,635
• Publication Number:
  US 20110215940A1
• Time in Patent Office: 2,107 Days
• Field of Search: None
• US Class Current: 1/1
• 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 absolute value of the first acceleration, a second absolute value of the second acceleration, and a third absolute 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:

recording a first acceleration of the mobile device provided by a first acceleration sensor, the first acceleration being parallel to a first axis;

recording a second acceleration of the mobile device provided by a second acceleration sensor, the second acceleration being parallel to a second axis perpendicular to the first axis;

recording a third acceleration of the mobile device provided by a third acceleration sensor, the third acceleration being parallel to a third axis perpendicular to the first axis and to the second axis;

determining first, second and third absolute values of the first, second and third accelerations, respectively;

determining a sum of the first, second and third absolute values;

detecting the free fall of the mobile device solely as a function of the sum; and

generating a warning signal responsive to detecting the free fall.

2. The method as recited in claim 1, wherein the first acceleration, the second acceleration, and the third acceleration are recorded from 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 sum to a predetermined threshold value.

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

generating the warning signal if the 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.

12. The method of claim 1, wherein the first, the second, and the third acceleration sensors are part of a single triple axis acceleration sensor.

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

a triple-axis acceleration sensor configured to generate;

a first acceleration of the mobile device parallel to a first axis,

a second acceleration of the mobile device parallel to a second axis perpendicular to the first axis, and

a third acceleration of the mobile device parallel to a third axis perpendicular to the first axis and to the second axis; and

an evaluation circuit configured to;

record the generated first, second and third accelerations,

determine first, second and third absolute values of the first, second and third accelerations, respectively,

determine a sum of the first, second and third absolute values, and

detect the free fall of the mobile device solely as a function of the 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:

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