Accelerometer signal processor comprising variable oscillators and counters

• US 6,484,577 B1
• Filed: 02/28/2002
• Issued: 11/26/2002
• Est. Priority Date: 10/31/2001
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Bennett, George J.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US10/087,893
• Time in Patent Office: 271 Days
• Field of Search: 735/10, 735/11, 735/141.6, 735/141.9, 735/142.6, 735/142.7, 73/14.1, 702/141, 702/145
• US Class Current: 73/514.26
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/093 by photoelectric pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G11B 5/5534 Initialisation, calibration, e.g. cylinder "set-up"
• CPC Class Codes: G11B 5/5582 system adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock
• CPC Class Codes: G11B 5/59694 System adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock

Abstract

An accelerometer signal processor is disclosed comprising a sensor for generating A, B, C and D sensor signals in response to a sensor excitation. Variable oscillators convert the sensor signals into oscillating signals, and the oscillating signals up-count and down-count counters. The outputs of the counters represent a linear acceleration along at least two axes, as well as a rotational acceleration.

Claims

1. An accelerometer signal processor for use in processing sensor signals generated by an accelerometer, the accelerometer comprises a sensor for generating A, B, C and D sensor signals in response to a sensor excitation, the accelerometer signal processor comprising:

(a) an A variable oscillator (VO) for generating an A oscillating signal in response to the A sensor signal;

(b) a B VO for generating a B oscillating signal in response to the B sensor signal;

(c) a C VO for generating a C oscillating signal in response to the C sensor signal;

(d) a D VO for generating a D oscillating signal in response to the D sensor signal;

(e) a first axis counter comprising an up count input responsive to the A oscillating signal and a down count input responsive to the D oscillating signal, the first axis counter for generating on output signal indicative of an acceleration along a first axis;

(f) a second axis counter comprising an up count input responsive to the B oscillating signal and a down count input responsive to the C oscillating signal, the second axis counter for generating on output signal indicative of an acceleration along a second axis; and

(g) a rotation counter comprising an up count input responsive to the A and D oscillating signals and a down count input responsive to the B and C oscillating signals, the rotation counter for generating an output signal indicative of a rotational acceleration.

2. The accelerometer signal processor as recited in claim 1, further comprising:

(a) a first summing circuit for summing frequencies of the A and D oscillating signals to generate an output signal applied to the up count input of the rotation counter; and

(b) a second summing circuit for summing frequencies of the B and C oscillating signals to generate an output signal applied to the down count input of the rotation counter.

3. The accelerometer signal processor as recited in claim 1, wherein:

(a) the sensor comprises an optical sensor; and

(b) the sensor excitation comprises light.

4. The accelerometer signal processor as recited in claim 1, further comprising an AGC counter responsive to the A, B, C and D oscillating signals and a reference oscillating signal, the AGC counter for generating an AGC signal for controlling the sensor excitation.

5. The accelerometer signal processor as recited in claim 4, further comprising a reference VO for generating the reference oscillating signal.

6. A method of processing sensor signals generated by an accelerometer, the accelerometer comprises a sensor for generating A, B, C and D sensor signals in response to a sensor excitation, the method comprising the steps of:

(a) generating an A oscillating signal in response to the A sensor signal;

(b) generating a B oscillating signal in response to the B sensor signal,

(c) generating a C oscillating signal in response to the C sensor signal;

(d) generating a D oscillating signal in response to the D sensor signal;

(e) up-counting a first-axis counter in response to the A oscillating signal and down-counting the first-axis counter in response to the D oscillating signal, the first axis counter for generating on output signal indicative of a first linear acceleration;

(f) up-counting a second axis counter in response to the B oscillating signal and down-counting the second axis counter in response to the C oscillating signal, the second axis counter for generating on output signal indicative of a second linear acceleration; and

(g) up-counting a rotation counter in response to the A and D oscillating signals and down-counting the rotational counter in response to the B and C oscillating signals, a rotation counter for generating an output signal indicative of the rotational acceleration.

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

(a) summing frequencies of the A and D oscillating signals to generate an output signal for up-counting the rotation counter; and

(b) summing frequencies of the B and C oscillating signals to generate an output signal for down-counting the rotation counter.

8. The method as recited in claim 6, wherein:

(a) the sensor comprises an optical sensor; and

(b) the sensor excitation comprises light.

9. The method as recited in claim 6, further comprising the steps of:

(a) generating a reference oscillating signal;

(b) generating a control signal in response to the A, B, C and D oscillating signals and the reference oscillating signal; and

(c) controlling the sensor excitation in response to the control signal.