Multi-zone capacitive force sensing device and methods

• US 20070227257A1
• Filed: 04/03/2006
• Published: 10/04/2007
• Est. Priority Date: 04/03/2006
• Status: Active Grant

• Current Assignee: Ypoint Capital, Inc,
• Original Assignee: Loadstar Sensors Incorporated (Ypoint Capital, Inc,)
• Inventors: Harish, Divyasimha, Schultz, John, Wong, King, Dallenbach, William
• Granted Patent: US 7,343,814 B2
• Time in Patent Office: Days
• US Class Current: 73/780
• CPC Class Codes: G01G 23/3728 with wireless means
• CPC Class Codes: G01G 23/3735 using a digital network
• CPC Class Codes: G01G 7/06 by electrostatic action
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 5/0076 Force sensors associated with manufacturing machines G01L5/0066, G01L5/0071 and B23Q17/09 take precedence; for the specific machine or operation involved see relevant class, e.g. B21 - B42

Abstract

A multi-zone capacitive force sensing apparatus/method is disclosed. In one embodiment, an apparatus includes one or more capacitors each having an upper conductive surface and a lower conductive surface substantially parallel to the upper conductive surface, a housing with a top plate and a bottom plate to encompass the capacitors, and a sensor in the housing to generate a measurement based on a change in a distance between the upper conductive surface and the lower conductive surface of each of the capacitors when a contact zone of the top plate associated with the each of the plurality of capacitors is deflected by a force applied on the contact zone. The apparatus may also include a comparison module associated with the sensor to generate a signal indicating unevenness of a force applied on the top plate when there is any significant difference between measurements of the capacitors.

Claims

1. An apparatus, comprising:

a plurality of capacitors each having an upper conductive surface and a lower conductive surface substantially parallel to the upper conductive surface;

a housing with a top plate and a bottom plate to encompass the plurality of capacitors; and

a sensor in the housing to generate a measurement based on a change in a distance between the upper conductive surface and the lower conductive surface of each of the plurality of capacitors when a contact zone of the top plate associated with the each of the plurality of capacitors is deflected by a force applied on the contact zone.

2. The apparatus of claim 1 further comprising a reference capacitor having an upper reference surface and a lower reference surface in the housing to compensate an error in the measurement based on an environmental condition.

3. The apparatus of claim 2 further comprising at least one contact zone cavity formed on a bottom surface of the top plate, and wherein the upper conductive surface is formed on each of the at least one contact zone cavity.

4. The apparatus of claim 3 further comprising at least one bottom cavity formed on a top surface of the bottom plate, and wherein the lower reference surface is formed on each of the at least one bottom cavity.

5. The apparatus of claim 4 wherein the at least one contact zone cavity and the at least one bottom cavity are approximately 2/1000 inch in depth.

6. The apparatus of claim 5 further comprising a single printed circuit board to accommodate the sensor and a plurality of circuits associated with the sensor and to provide the lower conductive surface of the each of the plurality of capacitors and the upper reference surface of the reference capacitor.

7. The apparatus of claim 1 further comprising a comparison module associated with the sensor to generate a signal data indicating unevenness of a force applied on the top plate when there is any significant difference between measurements of the plurality of capacitors.

8. The apparatus of claim 7 further comprising an alarm module associated with the sensor to express a sensory data when a parameter of the signal data exceeds a threshold value.

9. The apparatus of claim 1 further comprising an aggregation module associated with the sensor to sum up the measurement of the each of the plurality of capacitors.

10. The apparatus of claim 1 further comprising a capacitance-to-frequency converter module associated with the sensor to convert the measurement to a frequency value.

11. The apparatus of claim 1 further comprising a communication module and a data processing module associated with the sensor to interface with a communication device.

12. The apparatus of claim 1 wherein the housing comprises three capacitors to form a three zone sensor to generate the measurement associated with at least one of the three capacitors.

13. A method, comprising:

producing a deflection in each of a plurality of contact zones coupled to a top plate of a housing which encompasses a plurality of capacitors each having two parallel conductive surfaces when a load is applied on the plurality of contact zones; and

automatically generating a capacitance data from each of the plurality of capacitors when a distance between the two parallel conductive surfaces of the each of the plurality of capacitors is changed due to the deflection in the each of the plurality of contact zones.

14. The method of claim 13 further comprising proportionally converting the capacitance data to a frequency data wherein the frequency data is possibly modulated to a high value.

15. The method of claim 13 further comprising comparing the capacitance data to determine a levelness of the load applied on the plurality of contact zones.

16. The method of claim 15 further comprising generating an alarm sound when the capacitance data is not substantially equal across the plurality of capacitors.

17. The method of claim 13 further comprising measuring a plurality of forces using a sensor having the plurality of capacitors when the plurality of forces are applied on the plurality of contact zones.

18. The method of claim 13 further comprising modifying at least one attribute of the housing to change a deflection characteristic of the contact zones.

19. The method of claim 13 further comprising creating a cavity on a bottom surface of the top plate opposite to each of the plurality of contact zones to form an upper conductive surface of the two parallel conductive surfaces.

20. The method of claim 13 in a form of a machine-readable medium embodying a set of instructions that, when executed by a machine, cause the machine to perform the method of claim 13.