Capacitive Deformation Sensor and Measurement System

Abstract

This invention discloses a capacitive deformation sensor and measurement system. The capacitive deformation sensor comprises at least one conductive reference layer, a deformable dielectric layer, and a signal conductor, which together form a distributed parameter transmission line and are terminated by an electrical connector. External force causes a change in the spacing between the conductor and the reference layer or the equivalent dielectric constant of the dielectric layer, resulting in measurable changes in characteristic impedance, reflection coefficient, propagation delay, or resonant position. A readout circuit applies electrical excitation to the signal conductor and measures the aforementioned electrical response. Calibration is used to estimate the magnitude of the force, and the contact position or curvature can be selectively identified. The capacitive deformation sensor can be structured as a stripline or microstrip line, and its sensitivity, linearity, and noise immunity can be improved through geometric or spacer elements.

Claims

1. A capacitive deformation sensor, comprising: A flexible substrate having a longitudinal axis; A first conductor and a second conductor are arranged adjacent to each other on the flexible substrate and electrically insulated from each other, the first conductor and the second conductor extending along at least a portion of the longitudinal axis; a drive terminal is coupled to the proximal end of the first conductor; And a sensing terminal coupled to the proximal end of the second conductor; wherein, stretching, compression or bending applied to the flexible substrate changes the lateral spacing and / or relative orientation between the first conductor and the second conductor, thereby changing their capacitive coupling, such that when an alternating excitation is applied to the driving terminal, the electrical signal at the sensing terminal will change depending on the mechanical deformation.

2. The capacitive deformation sensor as described in claim 1, wherein, The first conductor and the second conductor are flexible filaments, which are selected from a group consisting of wires, multi-strand cables and conductive yarns, and the flexible filaments are fixed to the flexible substrate by means of sewing, weaving or adhesive.

3. The capacitive deformation sensor as described in claim 1, wherein, At least a portion of the first conductor and / or the second conductor extends along a non-linear path, the non-linear path being selected from a serpentine, sawtooth, or zigzag pattern.

4. The capacitive deformation sensor as described in claim 1, wherein, The first conductor and the second conductor include multiple finger-like structures to form an interlaced finger pattern, and the extending direction of the finger-like structures is perpendicular to the longitudinal axis.

5. The capacitive deformation sensor as described in claim 1, wherein, The distal ends of the first conductor and the second conductor are each open circuits.

6. The capacitive deformation sensor as claimed in claim 1, further comprising a back adhesive layer configured to adhere the flexible substrate to a target surface, said target surface being located on clothing, belt, suspenders, seat belt, ground, or mat surface.

7. The capacitive deformation sensor as described in claim 1, wherein, The dimensions and configuration of the flexible substrate are designed for wearing on the human chest and abdomen to sense the expansion during respiration.

8. A measurement system, comprising: At least one sensor as described in claim 1; A driving circuit adapted to apply an alternating excitation to the driving terminal; a readout circuit having a high-impedance input coupled to the sensing terminal and adapted to estimate the capacitive coupling between the first conductor and the second conductor; and a processing circuit that generates at least one mechanical activity measure based on the output of the readout circuit.

9. The measurement system as described in claim 8, wherein, The number of sensors is multiple, and the multiple sensors are arranged in multiple columns and multiple rows on a platform to define a two-dimensional sensing area matrix; wherein, the driving circuit is configured to sequentially address different columns, and the readout circuit monitors the corresponding rows; and the processing circuit locates the applied pressure position to one of the sensing areas of the matrix based on the simultaneous response of a column of sensors and a row of sensors.

10. The measurement system as described in claim 8, wherein, The driving circuit is adapted to apply two or more test frequencies, and the processing circuit is adapted to use amplitude and / or phase information to distinguish between axial tensile strain and normal pressure.

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