Array type pressure sensing apparatus and pressure measurement method using the same

• US 7,926,365 B2
• Filed: 02/12/2009
• Issued: 04/19/2011
• Est. Priority Date: 08/13/2008
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Yeh, Shao-Hsing, Shen, Yu-Tang
• Primary Examiner(s): NOORI, MASOUD H
• Application Number:
  US12/370,033
• Publication Number:
  US 20100037709A1
• Time in Patent Office: 796 Days
• Field of Search: 73862041-862046
• US Class Current: 73/862.046
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires

Abstract

An array type pressure sensing apparatus suitable for multi-touch sensing and pressure quantification for gray scale identification is provided. The array type pressure sensing apparatus includes a plurality of first axes, a plurality of second axes, a plurality of piezoresistive units, a third axis, a plurality of standard resistors and a control unit. The second axes are disposed crisscross with the first axes, and there is one piezoresistive unit disposed on the cross between one first axis and one second axis. The third axis is disposed crisscross with the first axes, and there is one standard resistor on the cross between one first axis and the third axis. A pressure measurement method implemented using the array type pressure apparatus is also provided. The pressure measurement method is a gray scale identification method by pressure quantification of a linear piezoresistive system.

Claims

1. A pressure measurement method suitable for pressure sensing using the array type pressure sensing apparatus comprising:

a plurality of first axes;

a plurality of second axes, being disposed crisscross with the first axes;

a plurality of piezoresistive units, one of which being disposed on the cross between one first axis and one second axis, capable of exhibiting different resistance values when being applied with different pressures;

a third axis, being disposed crisscross with the first axes;

a plurality of standard resistors, one of which being disposed on the cross between one first axis and the third axis, capable of exhibiting a constant resistance value when being applied with different pressures; and

a control unit, having a plurality of I/O ports respectively coupled to the first axes, the second axes and the third axis, through which the control unit performs a tri-state logic scanning and driving process on the first axes, the second axes and the third axis;

the pressure measurement method comprising;

measuring voltage signals of the piezoresistive units and the standard resistor corresponding to each first axis;

forming a voltage dividing matrix comprising the voltage signals of the piezoresistive units and the standard resistor corresponding to each first axis;

forming a conductance matrix comprising inverses of resistance values of the piezoresistive units and the standard resistor, resulting in a product of the voltage dividing matrix and the conductance matrix being a zero matrix to form a set of piezoresistive simultaneous equations; and

solving the set of piezoresistive simultaneous equations to acquire the resistance values of the piezoresistive units.

2. The pressure measurement method as recited in claim 1, wherein the step of measuring the voltage signals of the piezoresistive units corresponding to each first axis comprises:

performing a high impedance input on the scanned first axis and a low level output on the remaining first axes; and

performing a high level output on one second axis and the low level output on the remaining second axes and the third axis to measure the divided voltage signal of the piezoresistive unit corresponding to the second axis using the scanned first axis.

3. The pressure measurement method as recited in claim 1, wherein the step of measuring the voltage signals of the standard resistor corresponding to each first axis comprises:

performing a high impedance input on the scanned first axis and a low level output on the remaining first axes; and

performing a high level output on the third axis and the low level output on the second axes to measure the voltage signal of the standard resistor using the scanned first axis.

4. The pressure measurement method as recited in claim 2, wherein the low level output is grounding.

5. The pressure measurement method as recited in claim 1, wherein the set of piezoresistive simultaneous equations are solved by Gaussian elimination, Gaussian-Jordan elimination or iteration.

6. The pressure measurement method as recited in claim 1, wherein the number of the second axes is N−

1, the voltage dividing matrix is an N×

N matrix and the conductance matrix is an N×

1 matrix.

7. The pressure measurement method as recited in claim 3, wherein each entry in the ith row in the voltage dividing matrix is represented by A_ij with i between 1˜

N−

1,j between 1˜

N, so that entry A_ij represents the negative voltage signal of the piezoresistive unit corresponding to the second axis in the jth column when j is not equal to i and, entry A_ii represents the voltage signal of the high level output minus the voltage signal of the piezoresistive unit corresponding to the second axis in the ith column when j is equal to i.

8. The pressure measurement method as recited in claim 6, wherein each entry in the Nth row in the voltage dividing matrix is represented by A_Nj with j between 1˜

N, so that entry A_Nj represents the negative voltage signal of the standard resistor when j is not equal to N and, entry A_NN represents the voltage signal of the high level output minus the voltage signal of the standard resistor when j is equal to N.

9. The pressure measurement method as recited in claim 6, wherein each entry in the conductance matrix is represented by X_i with i between 1˜

N, so that entry X_i represents the inverse of the resistance value of the piezoresistive unit corresponding to the second axis in the ith row when i is not equal to N and, entry X_N represents the inverse of the resistance value of the standard resistor when i is equal to N.

10. The pressure measurement method as recited in claim 3, wherein the low level output is grounding.