Motion sensor and method of making same

• US 6,293,150 B1
• Filed: 12/02/1999
• Issued: 09/25/2001
• Est. Priority Date: 12/02/1999
• Status: Expired due to Fees

• Current Assignee: Precision Control Design Incorporated
• Original Assignee: Precision Control Design Incorporated
• Inventors: Conlan, Robert W.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/453,331
• Time in Patent Office: 663 Days
• Field of Search: 73/504.15, 73/536, 73/540, 73/545, 73/535, 73/542, 73/862.621, 73/862.627, 73/862.629, 73/862.632, 73/862.634, 73/862.636 , 73/862.637, 73/862.639, 600/595, 600/587, 600/493, 600/503
• US Class Current: 73/536
• CPC Class Codes: A61B 5/1126 using a particular sensing technique
• CPC Class Codes: G01P 13/00 Indicating or recording presence, absence, or direction, of movement electric switches H01H; counting moving objects G06M7/00

Abstract

A motion sensor for monitoring the activity of a body in motion includes a pair of force detecting sensors capable of detecting both magnitude and direction of an applied force. These sensors are configured to enable translational or rotational motion resulting from travel in a vehicle to be suppressed from any general motion signal leaving only a rotational or translational component. The active compensation of an electrical circuit is provided to aid in the calibration of a non-ideal sensor pair and reduce the leakage of translational motion into rotational motion or rotational motion into translational motion due to any differences between the pair.

Claims

1. A motion sensor for monitoring the activity of a body in motion, comprising:

a mount;

a pair of force detecting sensors capable of detecting both the magnitude and direction of an applied force, each of said sensors comprising;

a beam having a first end, a second end, a top and a bottom, said beam rigidly attached to said mount generally near said first end; and

said second end of said beam having a mass generally greater than said first end of said beam thereby providing a cantilever effect to said beam whereby when said sensor is put into general motion either said top or said bottom of said beam is stretched and produce both a voltage source effect and a capacitance effect, both of said effects corresponding to a translational motion component and a rotational motion component of said general motion; and

a means for connecting said effects of said beams whereby said rotational component or said translational component is canceled.

2. A motion sensor for monitoring the activity of a body in motion as defined in claim 1 wherein said force detecting sensors are piezoelectric bimorph beams having a mass attached near said second ends of said beams.

3. A motion sensor for monitoring the activity of a body in motion as defined in claim 2 wherein each said beam is ceramic.

4. A motion sensor for monitoring the activity of a body in motion as defined in claim 1 wherein said means for connecting include a resistive element and associated circuitry.

5. A motion sensor for monitoring the activity of a body in motion as defined in claim 1 wherein each said sensor is further connected to a means to calibrate said effects.

6. A motion sensor for monitoring the activity of a body in motion as defined in claim 5 wherein said means to calibrate is a differential amplifier.

7. A motion sensor for monitoring the activity of a body in motion, comprising:

a mount;

a first and a second piezoelectric bimorph beam, each of said beams having a first end and a second end and a top and a bottom, said beams rigidly attached to said mount generally near said first ends;

a mass attached generally near said second ends of said beams thereby providing a cantilever effect to said beams whereby when said sensor is put into general motion either said tops or said bottoms of said beams are stretched and produce both a voltage source effect and a capacitance effect, both of said effects corresponding to a translational motion component and a rotational motion component; and

a resistive element connecting said effects of said beams whereby said rotational or said translational component is canceled.

8. A motion sensor for monitoring the activity of a body in motion as defined in claim 7 wherein each said beam is ceramic.

9. A motion sensor for monitoring the activity of a body in motion as defined in claim 7 wherein said sensor is further connected to a means to calibrate said effects.

10. A motion sensor for monitoring the activity of a body in motion as defined in claim 9 wherein said means to calibrate is a differential amplifier.

11. A method of making a motion sensor capable of suppressing a rotational or translational component from any general motion signal, consisting of:

providing a mount;

providing a pair of force detecting sensors capable of detecting both the magnitude and direction of an applied force, each of said sensors comprising a beam having a first end, a second end, a top and a bottom;

attaching said beams to said mount generally near said first ends, said second ends of said beams having a mass generally greater than said first ends of said beam thereby providing a cantilever effect to said beams whereby when said sensor is put into general motion either said top or said bottom of said beam is stretched and produce both a voltage source effect and a capacitance effect, both of said effects corresponding to a translational motion component and a rotational motion component of said general motion; and

attaching a means for connecting said effects of said beams whereby said rotational component or said translational component is canceled.

12. A method of making a motion sensor capable of suppressing a rotational or translational component from any general motion signal as defined on claim 11 further consisting of:

calibrating the sensor to reduce a difference in capacitance of the beams; and

calibrating the sensor to reduce a difference in intrinsic voltage of the beams.