Inductive sensing systems and methods based on multiple frequencies

Patent metadata

Field	Value
Publication number	US-9780780-B2
Application number	US-201414466530-A
Country	US
Kind code	B2
Filing date	Aug 22, 2014
Priority date	Aug 22, 2014
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

A target detection system may include a power supply and an inductor capacitor (LC) tank circuit. The LC tank circuit may include a sensing coil, a first tank capacitor, and a second tank capacitor. Further, the LC tank circuit may alternate between the first tank capacitor and the second tank capacitor, and the power supply may power the LC tank circuit. The target detection system may further include measurement circuitry to measure a first decay characteristic of a first set of free oscillations from the first tank capacitor and a second decay characteristic of a second set of free oscillations from the second tank capacitor. Additionally, the target detection system may also include processing circuitry to compare the first decay characteristic to the second decay characteristic to determine a presence and a distance of a target.

First claim

The invention claimed is:

1. A target detection system, comprising:
a power supply;
an inductor capacitor (LC) tank circuit comprising a sensing coil, a first tank capacitor enabling a first frequency free oscillation, and a second tank capacitor enabling a second frequency free oscillation different from the first frequency free oscillation, wherein the LC tank circuit alternates between connection of the same sensing coil to the first tank capacitor and to the second tank capacitor, and wherein the power supply provides a power source for the LC tank circuit;
measurement circuitry configured to measure a first decay characteristic of the first frequency free oscillation and the second frequency free oscillation; and
processing circuitry configured to compare the first decay characteristic to the second decay characteristic to determine a presence and a distance of a target;
wherein the measurement circuitry uses differences in the first frequency free oscillation and the second frequency free oscillation to create data that differentiates changes in the first decay characteristic and in the second decay characteristic as a result of environment changes from changes in the first decay characteristic and in the second decay characteristic as a result of target presence changes.

2. The target detection system of claim 1 , wherein a first capacitance of the first tank capacitor is less than a second capacitance of the second tank capacitor.

3. The target detection system of claim 1 , wherein the measurement circuitry measures the first decay characteristic and the second decay characteristic by integrating a positive half of a first decaying sine wave of the first set of free oscillations and a second decaying sine wave of the second set of free oscillations.

4. The target detection system of claim 1 , comprising a potentiometer configured to compensate for a rapid temperature change of a detection environment.

5. The target detection system of claim 4 , wherein the potentiometer is configured to change resistance values over time as the sensing coil changes temperatures.

6. The target detection system of claim 5 , wherein the potentiometer resistance decreases to provide a positive voltage compensation and increases to provide a negative voltage compensation.

7. The target detection system of claim 1 , wherein the measurement circuitry distinguishes between a ferrous target and a non-ferrous target.

8. A method for detecting a target, comprising:
transmitting a first frequency signal and a second frequency signal different from the first frequency signal toward a potential target location;
detecting a first decay characteristic of the first frequency signal and a second decay characteristic of the second frequency signal;
measuring the first decay characteristic and the second decay characteristic;
comparing the first decay characteristic to the second decay characteristic; and
detecting a presence of a target and a depth of a target based on a comparison of the first decay characteristic and the second decay characteristic;
wherein transmitting the first frequency signal and the second frequency signal comprises alternating between the first frequency signal and the second frequency signal by alternately coupling a first capacitor to a sensing coil and a second capacitor to the same sensing coil; and
wherein differences in the first frequency signal and the second frequency signal are used to create data that differentiates changes in the first decay characteristic and in the second decay characteristic as a result of environment changes from changes in the first decay characteristic and in the second decay characteristic as a result of target presence changes.

9. The method of claim 8 , comprising detecting a rapid temperature change of a target detection environment; and adjusting a potentiometer to compensate for environmental changes affecting the first decay characteristic and the second decay characteristic.

10. The method of claim 8 , comprising distinguishing target data from disturbance data related to environmental disturbances.

11. The method of claim 10 , wherein the environmental disturbances comprise at least rapid changes in temperature.

12. The method of claim 8 , comprising calibrating a detection device upon initiation based on initiation temperature readings at the detection device.

13. A target detection system, comprising:
a power supply;
driver circuitry configured to provide a power source based upon power from the power supply;
a transmitter configured to receive power from the driver circuitry and to transmit a first magnetic field at a first frequency and a second magnetic field at a second frequency, the transmitter comprising a first capacitor, a second capacitor, a coil, and a switch that alternatively couples the first capacitor to the coil and the second capacitor to the same coil to produce the first and second frequencies;
a first receiver and a second receiver, wherein the first receiver is configured to tune to the first magnetic field at the first frequency, and the second receiver is configured to tune to the second magnetic field at the second frequency;
measurement circuitry to measure a first set of oscillation characteristics of the first receiver and a second set of oscillation characteristics of the second receiver; and
processing circuitry to compare the first set of oscillation characteristics to the second set of oscillation characteristics to determine a presence and a distance of a target;
wherein the measurement circuitry uses differences in the first set of oscillation characteristics and the second set of oscillation characterisics to create data that differentiates changes in a first decay characteristic and in a second decay characteristic as a result of environment changes from changes in the first decay characteristic and in the second decay characteristic as a result of target presence changes.

14. The target detection system of claim 13 , wherein the first frequency is higher than the second frequency.

15. The target detection system of claim 13 , wherein the transmitter transmits the first signal and the second signal toward a target location at the same time.

16. The target detection system of claim 13 , wherein the transmitter alternates between transmitting the first signal and the second signal.

17. The target detection system of claim 13 , wherein the measurement circuitry is configured to distinguish between a ferrous target and a non-ferrous target.

Assignees

• Rockwell Automation Tech Inc

Inventors

• Sun James Feng
• Boutaud Frederic

Classifications

• G01D5/2006

  by influencing the self-induction of one or more coils (G01D5/22 takes precedence) · CPC title

• H03K17/9547 Primary

  with variable amplitude · CPC title

• H03K2217/952

  Detection of ferromagnetic and non-magnetic conductive targets · CPC title