Position tracking system and method using radio signals and inertial sensing

• US 10,416,276 B2
• Filed: 08/24/2017
• Issued: 09/17/2019
• Est. Priority Date: 11/12/2010
• Status: Active Grant

• Current Assignee: Position Imaging, Inc.
• Original Assignee: Position Imaging, Inc.
• Inventors: Hill, Edward L., Schneider, Mark
• Primary Examiner(s): Phan, Dao L
• Application Number:
  US15/685,493
• Publication Number:
  US 20170350961A1
• Time in Patent Office: 754 Days
• Field of Search: 342451
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/0063 of measured values, i.e. measurement on base station and position calculation on mobile
• CPC Class Codes: G01S 5/0258 by combining or switching between measurements derived from different systems
• CPC Class Codes: G01S 5/0264 at least one of the systems being a non-radio wave positioning system
• CPC Class Codes: G01S 5/0294 Trajectory determination or predictive filtering, e.g. target tracking or Kalman filtering

Abstract

An RF position tracking system for wirelessly tracking the three-dimensional position of a tracked object. The tracked object has at least one mobile antenna and at least one inertial sensor. The system uses a plurality of base antennas which communicate with the mobile antenna using radio signals. The tracked object also incorporates the inertial sensor to improve position stability by allowing the system to compare position data from radio signals to data provided by the inertial sensor.

Claims

1. A system for tracking a position of a tracked object, the system comprising:

an inertial and magnetic detection subsystem (IMDS) attached to the tracked object, configured to determine position and orientation information of the tracked object by monitoring inertia and magnetic orientation over time;

an RF tracking system comprising;

at least one mobile antenna on the tracked object, and

at least three base antennae spaced apart from each other,

wherein the RF tracking system is adapted to calculate a distance between each of the at least one mobile antenna and each of the at least three base antennae, and calculate position and orientation of the tracked object from the calculated distances; and

a fusion algorithm processor adapted to receive the position and orientation information from the IMDS, and from the RF tracking system, and merge them into a corrected position and orientation of the tracked object.

2. The system of claim 1, wherein the at least three base antennae may be located at more than one base, that can communicate with each other by one of wired and wireless communication.

3. The system of claim 1, wherein the IMDS comprises one of the group consisting of a gyroscope, an accelerometer, and a magnetic sensor.

4. The system of claim 1, wherein the fusion algorithm processor comprises a Kalman filter configured to fuse the position and orientation information of the tracked object from the IMDS and from the RF tracking system.

5. The system of claim 4, wherein the Kalman filter communicates feedback to the fusion algorithm processor for aligning the position and orientation of the IMDS with that of the RF tracking system.

6. The system of claim 5, wherein the position and orientation information from the RF tracking system is loosely coupled with that of the IMDS.

7. The system of claim 5, wherein the position and orientation information from the RF tracking system is tightly coupled with that of the IMDS.

8. The system of claim 1, wherein the fusion algorithm processor is configured to determine an orientation of the tracked object from output of the IMDS.

9. The system of claim 1, wherein the RF tracking system comprises:

a transmitter section coupled to each of the base antennae, adapted to cause the base antennae to transmit a radio signal; and

a receiver section attached to the at least one mobile antenna, configured to receive and demodulate signals sensed by the at least o mobile antenna,

a tracking processor adapted to determine distances between the at least one mobile antenna and each of the base antennae; and

a position and orientation device to determine the location of the at least one mobile antenna, and the orientation of the tracked object, more than one mobile antenna is tracked.

10. The system of claim 1, wherein the RF tracking system comprises:

a transmitter section coupled to the at least one mobile antenna, adapted to cause the mobile antenna to transmit a radio signal; and

a receiver section attached to each of the at least three base antennae, configured to receive and demodulate the signals sensed by each of the base antennae;

a tracking processor adapted to determine distances between the at least one mobile antenna and each of the base antennae; and

a position and orientation device adapted to determine a location of the at least one mobile antenna and the tracked object, the position and orientation device also determines an orientation of the tracked object if more than one mobile antenna is tracked.

12. The system of claim 1, wherein the fusion algorithm processor is configured to calculate a position and orientation of the tracked object, and combine output of the IMDS with the calculated position and orientation to produce a weighted position of the tracked object.

13. The system of claim 1, wherein the RF tracking system is configured to measure timing data from the radio signal, calculate a position of the tracked object using the timing data, and the fusion algorithm processor combines output of the IMDS with the calculated position to produce a weighted position of the tracked object.

11. The system wherein the IMDS is configured to provide output only when the IMDS detects motion.

14. A system for tracking a position of a tracked object, the system comprising:

an inertial and magnetic detection subsystem (IMDS) attached to the tracked object, configured to determine position and orientation information of the tracked object by monitoring inertia and magnetic orientation over time;

an RF tracking system comprising;

at least one mobile antenna on the tracked object, and

at least three base antennae spaced apart from each other,

wherein the RF tracking system is adapted to calculate a distance between each of the at least one mobile antenna and each of the at least three base antennae, and calculate position and orientation of the tracked object from the calculated distances; and

a fusion algorithm processor adapted to receive the position and orientation information from the ;

PODS, and from the RF tracking system, determine a difference between them, filter this difference with a Kalman filter and employ a filtered output of the Kalman filter to adjust the position and orientation determined by the IMDS into a corrected position and orientation of the tracked object.

15. The system of claim 14, wherein the filtered output of the Kalman filter is subtracted from the position and orientation calculated by the IMDS in a feed-forward design.

16. The system of claim 14, wherein the filtered output of the Kalman filter is fed backward to the IMDS to update its position and orientation so that it will produce more accurate position and orientation determinations of the tracked object in a feedback design.

17. A method for tracking a position of a tracked object, the system comprising:

transmitting a radiofrequency (RF) signal between each of at least one mobile antenna and at least three base antennae;

calculating a distance between each of the at least one mobile antenna and the at least three base antennae from the transmitted RE signals;

determining a position and orientation of the tracked object from the calculated distances;

monitoring inertia of the tracked object over time employing an inertial/magnetic detection system (IMDS);

calculating position and orientation of he tracked object from the monitored inertia; and

using a Kalman filter to merge the position and orientation calculated from the transmitted RF signal and that calculated from the monitored inertia to result in a more accurate position and orientation of the tracked object.

18. The method of claim 17, further comprising the step of weighting the position calculated from the transmitted RF signal, and combining the weighted position with the position calculated from the monitored inertia to produce the position of the tracked object.

19. The method of claim 17 wherein the step of calculating a distance comprises:

calculating a distance between each of the at least one mobile antenna and at least three base antennae using phase differences between pairs of received RF signals.

20. The method of claim 17 wherein the step of calculating a distance comprises:

calculating a distance between each of the at least one mobile antenna and at least three base antennae using differences between time of flight of pairs of received RE signals.