Method and system for providing tolerance to interference and obstructions of line of sight

• US 8,170,830 B2
• Filed: 08/22/2007
• Issued: 05/01/2012
• Est. Priority Date: 08/22/2006
• Status: Expired due to Fees

• Current Assignee: James P. Jacobs, Mark Robert Schneider
• Original Assignee: James P. Jacobs, Mark Robert Schneider
• Inventors: Jacobs, James P., Schneider, Mark Robert
• Primary Examiner(s): Raymond, Edward
• Application Number:
  US12/438,027
• Publication Number:
  US 20100241392A1
• Time in Patent Office: 1,714 Days
• Field of Search: 702/150, 702182-185, 702/188, 600/245, 600/258, 600/262
• US Class Current: 702/150
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/3975 active
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00

Abstract

Various aspects of the present invention are shown and described, each of which has stand alone utility in a navigated medical environment. A receiver position calibration system and method facilitates calibration of a reference frame prior to each navigated procedure. A concept and application of confidence weights is introduced. Confidence weights can be applied to distance calculations to mitigate the effects of interference and increase the tolerance of the navigated medical system. Multi-path interference is minimized through the transmission of a signal having a pattern of unique frequencies and filtering of the distance calculations for each frequency to identify the “best” distance in the presence of multi-path interference. A position determination method and system that transmits a signal having multiple frequency components permits positions to be identified with high resolution over a large area.

Claims

1. A method for determining a position of an object includes the steps of:

generating a confidence weight for association with a measured distance between the object and an antenna in response to historical data associated with the antenna; and

determining a position of the object by applying the confidence weight to the measured distance to control a degree of contribution of the measured distance in a determination of the position; and

using the determined position to track the object during a navigated procedure.

2. The method of claim 1 wherein the confidence weight is provided to increase a tolerance of a positioning system to one of signal interference and signal obstruction.

3. The method of claim 2 wherein the positioning system is a navigated medical system.

4. The method of claim 1 wherein the measured distance is determined in response to a signal transmitted between the object and the antenna, and wherein the confidence weight is further generated in response to a relationship between the signal and the historical data.

5. The method of claim 4 wherein the historical data includes at least one of historical data associated with the signal, historical data associated with the measured distance and historical data associated with the position.

6. The method of claim 5 wherein the historical data associated with the signal includes at least one of signal strength, signal phase and signal noisiness.

7. The method of claim 5 wherein historical data associated with the measured distance includes distance measurements for different frequencies of the signal.

8. The method of claim 5 wherein the historical data further includes historical data associated with one or more other receivers that are used to determine the position of the object.

9. The method of claim 4 wherein the confidence weight is determined in response to a trend of the historical data and one of the signal, the measured distance or the position.

10. The method of claim 4 wherein the confidence weight is determined in response to a divergence of one of the signal, the measured distance and the position from a trend of the historical data.

11. The method of claim 8 wherein the confidence weight is determined in response to a divergence of one of the signal, the measured distance and the position from a trend of historical data of the one or more other receivers.

12. The method of claim 4 wherein the measured distance is a raw distance determined in response to a phase of the signal.

13. The method of claim 4 wherein the signal is transmitted by a transmitter coupled to the object and received by a receiver coupled to the antenna.

14. The method of claim 4 wherein the signal is transmitted by a transmitter coupled to the antenna and received by the object.

15. A method of determining a position of an object includes the steps of, for each of a plurality of antennas:

receiving a signal transmitted between the object and a respective antenna;

generating a respective confidence weight to associate with a measured distance between the object and the respective antenna using historical information associated with at least one antenna of the plurality of antennas;

comparing an estimated distance to each of the measured distances to generate a distance offset;

applying the respective confidence weight to a function of the associated distance offset for each of the plurality of receivers to provide a plurality of weighted distance offsets;

summing the weighted distance offsets and comparing a result to a threshold; and

responsive to the distance offset exceeding the threshold, adjusting the estimated distance and repeating the steps of comparing, applying and summing until the result is less than or equal to the threshold.

16. A system for determining the position of an object comprising:

a non-transitory computer readable medium having computer instructions stored therein, and coupled to a processor of the system to cause said processor to thereby perform said computer instructions;

a historical data store stored on the computer readable medium and comprising historical information associated with an antenna;

program code stored on the computer readable medium, for generating a confidence weight and associating the confidence weight with a measured distance between the antenna and the object; and

program code stored on the computer readable medium for determining a position of the object including applying the confidence weight to the measured distance to control a degree of contribution of the measured distance to the position; and

wherein processing units within the system operate on computer instructions in the program code for generating the confidence weight and the program code for determining a position to track the object during a navigated procedure.

17. The system of claim 16 wherein the confidence weight is provided to increase a tolerance of the system to one of signal interference and signal obstruction.

18. The system of claim 17 wherein the system is a navigated medical system.

19. The system of claim 16 wherein the measured distance is determined in response to a phase of a signal transmitted between the object, wherein the signal is transmitted at a plurality of frequencies and wherein the historical data includes historical data for each frequency of the plurality of frequencies.

20. A system for determining a position of an object includes:

a signal generator for generating a signal for transmission between the object and a plurality of antennas in a frame of reference;

means for determining and associating a plurality of confidence weights to a corresponding plurality of measured distances, each measured distance associated with one antenna of the plurality of antennas;

positioning logic for determining a position of the object by;

deriving an estimated distance to each of the plurality of antennas using an estimated position;

calculating a distance offset for each antenna by comparing the measured distance of the associated antenna to the associated derived distance;

applying the confidence weights to a function of corresponding distance offsets to provide a plurality of weighted distance offsets and summing the weighted distance offsets to provide a result; and

responsive to the result being outside a threshold, adjusting the estimated position and repeating the steps of deriving, calculating and applying until the result is within the threshold.