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First Claim
1. A method of determining the location of a field sensor relative to a plurality of field generators of known location, each field generator comprising a plurality of co-located field generating elements, the method comprising the steps of:
- 1) for each generator, energising each generating element and measuring the respective field generated by each generating element at the field sensor, 2) for each field generator calculating, from the measurements of the fields generated by each of its generating elements, an estimate of the distance from that particular field generator to the sensor, and 3) utilising the estimates of the distances from each of the field generators to the sensor, and the known location of the field generators to calculate the location of the sensor relative to the field generators.
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Abstract
Methods and apparatus are provided for locating the position, preferably in three dimensions, of a sensor by generating magnetic fields which are detected at the sensor. The magnetic fields are generated from a plurality of locations and, in one embodiment of the invention, enable both the orientation and location of a single coil sensor to be determined. The present invention thus finds application in many areas where the use of prior art sensors comprising two or more mutually perpendicular coils is inappropriate.
198 Citations
17 Claims
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1. A method of determining the location of a field sensor relative to a plurality of field generators of known location, each field generator comprising a plurality of co-located field generating elements, the method comprising the steps of:
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1) for each generator, energising each generating element and measuring the respective field generated by each generating element at the field sensor, 2) for each field generator calculating, from the measurements of the fields generated by each of its generating elements, an estimate of the distance from that particular field generator to the sensor, and 3) utilising the estimates of the distances from each of the field generators to the sensor, and the known location of the field generators to calculate the location of the sensor relative to the field generators. - View Dependent Claims (2, 3, 4, 5)
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6. A method of determining the location of a field sensor, comprising a plurality of co-located field sensing elements, relative to a field generator, comprising a plurality of co-located field generating elements, the method comprising the steps of:
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1) energising a single field generating element to establish a field, 2) measuring a value of the field strength at the field sensor which is dependent on the location and orientation of the sensor within the field, 3) repeating steps
1) and
2) for each field generating element,4) calculating, by utilising all the values measured in step 2 and an estimate of the location of the sensor, an estimate of the field strength B that would exist at the sensor if the axis of the field were directed towards the sensor, and 5) maximising the value of B by iteratively altering the estimate of the location of the sensor until the location of the sensor relative to the field is found to a desired level of accuracy.
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7. Apparatus for determining the location of a field sensor comprising:
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a plurality of field generators each comprising a plurality of field generating elements, energising means operable for each field generator to energise each of the Plurality of field generating elements to produce a field within which the location of the object may be determined, measurement means, connected to the field sensor, for measuring and outputting a parameter of the field at the sensor, control means for controlling the energising means, storing parameters output by the measurement means, and calculating the location of the sensor relative to the plurality of field generators. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. Apparatus for determining the location of an object relative to a field generator, the apparatus comprising
a field generator comprising a plurality of field generating elements, energising means for sequentially energising each of the field generating elements to produce a field within which the object may be located, a sensor, to be attached to the object, comprising a plurality of co-located field sensing elements, each able to sense a parameter of the field, measurement means for measuring and outputting the parameter of the field sensed by each field sensing element when each field generating element is energised, and control means for controlling the energising means, storing the parameters output by the measurement means and calculating the location of the sensor, relative to the field generator wherein the control means is operable to determine the location of the sensor by, weighting each of the parameters, sensed by the sensor, by a location dependent weighting factor, calculating from all the parameters sensed at the sensor an estimate of the field strength at the sensor, iteratively altering the location dependent weighting factors until a maximum value of the field strength is found.
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16. Apparatus for determining the location of an object substantially as hereinbefore described, with reference to, and as shown in, the accompanying drawings.
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17. A method of locating an object substantially as hereinbefore described, with reference to, and as shown in, the accompanying drawings.
Specification