Position tracking system and method using radio signals and inertial sensing

Abstract

An RF position tracking system for wirelessly tracking the three dimensional position of a device that transmits a radio signal. The device has an antenna and at least one inertial sensor. The system uses a plurality of receiver antennas to receive the device's radio signal at each antenna. The device also incorporates an inertial sensor to improve position stability by allowing the system to compare position data from radio signals to data provided by the inertial sensor.

What is claimed is: 
     
         1 . A system for tracking a position of a wireless device, the system comprising:
 a radio frequency device having at least one antenna, the radio frequency device having an inertial sensor configured to transmit inertial sensor measurements and further configured to emit a radio signal containing RF phase data;   at least three receiver antennae each configured to receive the radio signal;   a data processor; and   a receiver in communication with the at least three receiver antennae, the receiver configured to receive the radio signal from each one of the at least three receiver antennae and further configured to communicate the RF phase data to the data processor.   
     
     
         2 . The system of  claim 1 , having at least four receiver antennae. 
     
     
         3 . The system of  claim 1 , wherein the inertial sensor is selected from the group consisting of a gyroscope, an accelerometer, and a magnetic sensor. 
     
     
         4 . The system of  claim 1 , wherein the data processor comprises a Kalman filter configured to fuse the RF phase data and the inertial sensor measurements to calculate a position of the radio frequency device. 
     
     
         5 . The system of  claim 4 , wherein the Kalman filter communicates feedback to the data processor for aligning the RF phase data with the position of the radio frequency device. 
     
     
         6 . The system of  claim 5 , wherein the RF phase data is loosely coupled with the inertial sensor measurements. 
     
     
         7 . The system of  claim 5 , wherein the RF phase data is tightly coupled with the inertial sensor measurements. 
     
     
         8 . The system of  claim 1 , wherein the data processor is configured to determine an orientation of the radio frequency device from the inertial sensor measurements. 
     
     
         9 . The system of  claim 1 , wherein the radio frequency device further comprises a transmitter antenna located at a position fixed with the radio frequency device, and wherein the data processor is configured to determine an orientation of the radio frequency device from the transmitter antenna. 
     
     
         10 . The system of  claim 1 , wherein the inertial sensor is configured to transmit the inertial sensor measurements signals only when the inertial sensor detects motion. 
     
     
         11 . The system of  claim 1 , wherein the data processor is configured to filter the RF phase data, calculate a position of the radio frequency device, and combine the inertial sensor measurements with the calculated position to produce a weighted position of the radio frequency device. 
     
     
         12 . The system of  claim 1 , wherein the data processor is configured to measure timing data from the radio signal, calculate a position of the radio frequency device using the time data, and combine the inertial sensor measurements with the calculated position to produce a weighted position of the radio frequency device. 
     
     
         13 . A system for tracking a wireless device, the system comprising:
 a device including a sensor configured to detect motion or orientation of the device, the device having at least one antenna capable of emitting a radio signal, the radio signal including at least one of phase data and timing data, the radio signal further including a signal corresponding to motion or orientation of the device;   at least three receiver antennae each configured to receive the radio signal; and   a receiver in communication with the at least three receiver antennae, the receiver including a data processor that determines the position of the device using the at least one of phase data and timing data and the signal corresponding to the motion or orientation of the device.   
     
     
         14 . The system of  claim 13 , further including a time out circuit that puts the device in a lower power state when the sensor does not detect motion for a period of time. 
     
     
         15 . The system of  claim 13 , wherein the sensor is an inertial sensor. 
     
     
         16 . The system of  claim 15 , wherein the data processor is configured to process the at least one of phase data and timing data and the signal corresponding to motion or orientation of the device in a fusion algorithm to determine the position of the device. 
     
     
         17 . The system of  claim 13 , wherein the data processor uses a fusion algorithm to determine the position of the device. 
     
     
         18 . A method for tracking a position of a wireless device, the system comprising:
 obtaining radio frequency (RF) data from a RF signal transmitted by a radio frequency device and received by at least three receiver antennae;   obtaining inertial data from an inertial signal transmitted by the radio frequency device; and   determining a position of the wireless device from a combination of the RF data and the inertial data.   
     
     
         19 . The method of  claim 18 , further comprising merging the radio frequency signal with the inertial signal using a Kalman filter to produce the combination of the RF signal and inertial signal. 
     
     
         20 . The method of  claim 18 , wherein determining a position of the wireless device includes calculating a first position of the wireless device using the RF data, calculating a second position of the wireless device using the inertial data, and adjusting the second calculated position based on the first calculated position to produce the position of the wireless device. 
     
     
         21 . The method of  claim 18 , wherein determining a position of the wireless device includes calculating the position based on the RF data obtained from the RF signal, weighting the calculated position, and combining the weighted position with the inertial data to produce the position of the wireless device, wherein the RF data obtained from the RF signal is at least one of phase data and timing data.