Estimation of gap between a proximity sensor and target
A method is provided for sensing proximity of a target. The method includes sensing inductance associated with a magnetic field, wherein the inductance is affected by the target when the target is proximate the magnetic field. The method further includes providing the sensed inductance for processing. The processing includes determining an inductance value from at least the sensed inductance and estimating a parameter of a gap between a location of sensing the inductance and the target as a function of the inductance value and application of a nonlinear model of a relationship between the gap and inductance.
1. A system for sensing proximity of a target, the system comprising:
a sensor configured to generate a magnetic field and sense inductance and resistance, wherein the inductance is affected by the target when the target is proximate the sensor;
a sensor cable coupled to the sensor, the sensor cable being configured to provide the sensed inductance from the sensor to processing equipment; and
the processing equipment configured to receive the sensed inductance and resistance via the sensor cable, determine an inductance value from the sensed inductance as a function of an inductance model, and a resistance value from the sensed resistance as a function of a resistance model, and estimate a parameter of a gap between the sensor and the target by a lookup step as a function of the inductance value, the resistance value, the inductance model, and the resistance model,
wherein the inductance model includes a first term giving a non-linear relationship between the parameter and inductance and applies experimentally determined first coefficients, and the resistance model includes a second term giving a non-linear relationship between the parameter and resistance and applies experimentally determined second coefficients.
2. The system of claim 1 , wherein the processing equipment is further configured to use the resistance value to correct for variation in sensor temperature when estimating the parameter.
3. The system of claim 2 , wherein the processing equipment is further configured to use models of influence of cable length of the sensor cable on the inductance and resistance of the sensor to determine corrections for cable length variation.
4. The system of claim 3 , wherein the processing equipment is further configured to correct the inductance and resistance values for at least one of temperature and the cable length variation.
5. The system of claim 4 , wherein the processing equipment is further configured to estimate the parameter by using the corrected inductance and resistance values.
6. The system of claim 1 , wherein the processing equipment is further configured to estimate the parameter by—outputting a binary indication whether the parameter is acceptable or unacceptable.
7. A method for sensing proximity of a target, the method comprising:
sensing inductance and resistance associated with a magnetic field, wherein the inductance is affected by the target when the target is proximate the magnetic field; and
providing the sensed inductance for processing, wherein the processing comprises:
determining an inductance value from the sensed inductance as a function of an inductance model;
determining a resistance value from the sensed resistance as a function of a resistance model;
performing a lookup step as a function of the inductance value, the resistance value, the inductance model, and the resistance model; and
estimating a parameter of a gap between a location of sensing the inductance and the target by a result of the lookup step,
wherein the inductance model includes a first term giving a non-linear relationship between the parameter and inductance and applies experimentally determined first coefficients, and the resistance model includes a second term giving a non-linear relationship between the parameter and resistance and applies experimentally determined second coefficients.
8. The method of claim 7 , further comprising using the resistance value to correct for variation in temperature near the sensing when estimating the parameter.
9. The method of claim 8 , further comprising using models of influence of cable length on the sensed inductance and resistance to determine corrections for cable length variation, wherein cable length is a length of a cable that provides the sensed resistance and inductance for processing.
10. The method of claim 9 , further comprising correcting the inductance and resistance values for at least one of temperature and the cable length variation.
11. The method of claim 10 , wherein estimating the parameter further includes using the corrected inductance and resistance values.
12. The method of claim 7 , wherein estimating the parameter further includes outputting a binary indication whether the parameter is acceptable or unacceptable.
13. A method for sensing proximity of a target, the method comprising:
receiving a signal associated with sensing inductance and resistance associated with a magnetic field, wherein the inductance is affected by the target when the target is proximate the magnetic field;
determining an inductance value from the signal as a function of an inductance model;
determining a resistance value from the signal as a function of a resistance model;
performing a lookup step as a function of the inductance value, the resistance value, the inductance model, and the resistance model; and
estimating a parameter of a gap between a location of sensing the inductance and the target by a result of the lookup step,
wherein the inductance model includes a first term giving a non-linear relationship between the parameter and inductance and applies experimentally determined first coefficients, and the resistance model includes a second term giving a non-linear relationship between the parameter and resistance and applies experimentally determined second coefficients.
14. The method of claim 13 , further comprising using the resistance value to correct for variation in temperature near the sensing when estimating the parameter.
15. The method of claim 14 , further comprising using models of influence of cable length on the sensed inductance and resistance to determine corrections for cable length variation, wherein cable length is a length of a cable that provides the sensed resistance and inductance for processing.
16. The method of claim 15 , further comprising: correcting the inductance and resistance values for at least one of temperature and the cable length variation; and
estimating the parameter further includes using the corrected inductance and resistance values.
17. The method of claim 13 , wherein estimating the parameter includes outputting a binary indication whether the parameter is acceptable or unacceptable.