Surface force distribution sensor by frequency-domain multiplexing

• US 8,266,971 B1
• Filed: 11/24/2009
• Issued: 09/18/2012
• Est. Priority Date: 11/25/2008
• Status: Expired due to Fees

• Current Assignee: Randall W. Jones
• Original Assignee: Randall W. Jones
• Inventors: Jones, Randall E.
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): Davis-Hollington, Octavia
• Application Number:
  US12/592,456
• Time in Patent Office: 1,029 Days
• Field of Search: 73862041-862046
• US Class Current: 73/862.046
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G10H 1/0551 using variable capacitors

Abstract

One embodiment of a surface force distribution sensor includes an elastic dielectric (108) sandwiched by a first plurality of compliant, conductive carrier elements (110) and a second plurality of conductive pickup elements (106), as well as a system for frequency-domain demultiplexing including at least a microprocessor (209). A plurality of signals is generated, each of which has a different fundamental frequency and is connected to a different carrier element. The pickup and carrier elements are arranged so that each pickup element overlaps one or more carrier elements. When forces are applied to a nonconductive compliant layer (112), the distance between one or more carrier elements and one or more pickup elements decreases at their points of overlap, increasing the amplitude of carrier signals capacitively transmitted to the pickup elements. The microprocessor demultiplexes the signals received from the pickup elements to determine the amplitude of each carrier signal received, and thereby the applied force, at each point of overlap on the surface of the compliant layer. Other embodiments are described and shown.

Claims

1. A force sensor comprising:

a dielectric;

a plurality of conductive carrier elements on one side of said dielectric;

a plurality of conductive pickup elements on the opposite side of said dielectric;

said pluralities of carrier and pickup elements being oriented to form a plurality of dielectric separated crossings;

means for applying carrier signals to said carrier elements including means for generating a plurality of signals of predetermined frequencies; and

a plurality of amplifiers each connected to one of the pickup elements for amplifying the carrier signals transmitted capacitively from multiple carrier elements to the respective pickup element at the crossings thereof; and

frequency demultiplexing means connected to said plurality of amplifiers for separating the output of each respective amplifier into a plurality of component frequencies; and

means for analyzing the amplitudes of each said component frequency to determine the distance between the carrier and pickup elements at one of the dielectric separated crossings; and

means for restoring said pluralities of conductive elements to predetermined rest positions in the absence of external forces;

whereby external forces varying the positions of said pluralities of carrier and pickup elements at each of the crossings thereof from said rest positions may be determined simultaneously and continuously.

2. The force sensor of claim 1 wherein said means for applying signals incorporate a microprocessor.

3. The force sensor of claim 1 wherein said means for frequency demultiplexing signals incorporate a microprocessor.

4. The force sensor of claim 1 wherein said dielectric includes a compressible elastic material.

5. The force sensor of claim 1 wherein said plurality of signals have frequencies between 1 kilohertz and 100 kilohertz.

6. The force sensor of claim 1 further including a computer interface.

7. A method of measuring a distribution of forces, the method comprising:

providing an elastic dielectric sandwiched between a first plurality of conductive carrier elements and a second plurality of conductive pickup elements, said pluralities of conductive elements positioned to create areas of overlap with each other; and

generating first signals of predetermined frequency and amplitude and transmitting the first signals to the first plurality of carrier elements; and

receiving second signals from the second plurality of pickup elements; and

frequency demultiplexing the second signals to determine distances separating the first plurality of carrier elements from the second plurality of pickup elements at the areas of overlap thereof, and thereby forces acting on the dielectric.

8. The method of claim 7, wherein demultiplexing the second signals comprises calculating a Fast Fourier Transform using a microprocessor.

9. The method of claim 7, wherein generating said first signals comprises executing a program on a microprocessor;

and wherein demultiplexing said second signals comprises executing an additional program on the microprocessor.