Position-tracking device for position-tracking system
View Patent ↗A position-tracking system for tracking the position of an object is disclosed. According to various embodiments, the tracking system includes a tracking device that is connected to or otherwise affixed to the object to be tracked. The tracking device may include, among other things, an inertial sensor assembly, radio transceivers and a processor. The position tracking system may also include a host processing system that is in communication with the tracking device. The position tracking system may provide variable-resolution position information based on the environment in which the object is moving. In a “wide resolution” area, the system may compute a general position for the object based on a wireless telephone network Cell-ID/map correlation architecture. In a high-resolution area, greater position resolution may be realized from the combination of a wireless aiding system and inputs from the inertial sensors. In the high-resolution mode, the system may exploit distinct patterns of motion that can be identified as motion “signatures” that are characteristic of certain types of motion. Kinematic (or object movement) models may be constructed based on these motion signatures and the position tracking system may estimate the state of the object based on the kinematic model for the current mode of the object. Adaptive and cascaded Kalman filtering may be employed in the analysis to more accurately estimate the position and velocity of the object based on the motion pattern identified.
1. A position tracking device for use in position tracking system, wherein the position tracking device is associated with a mobile object to be tracked by the position tracking system such that the position tracking device moves with the mobile object, the position tracking device comprising:
an inertial sensor assembly;
a reference position receiver; and
a high resolution module in communication with the inertial sensor assembly and the reference position receiver, wherein the high resolution module is for computing the location of the mobile object in real-time based on a combination of input from the inertial sensor assembly and a reference position signal received by the reference position receiver when the mobile object is located in a first area requiring high position resolution, wherein the high resolution module is for computing the location of the object by:
detecting a current mode of movement for the mobile object based on the input from the inertial sensor assembly and historical information about the location of the mobile object;
determining a first estimated position of the mobile object based at least on a motion model for the current mode of movement for the mobile object:
determining a second estimated position of mobile object based on the input from the inertial sensor assembly and the historical information about the location of the mobile object; and
estimating a real-time location of the mobile object based on the first and second estimated positions.
2. The position tracking device of claim 1 , wherein the high resolution module is for estimating the real-time location of the mobile object based on the first and second estimated positions using a Kalman filter.
3. The system of claim 2 , wherein the high resolution module is further for correcting the historical information about the location of the mobile object based on corrective information.
4. The system of claim 3 , wherein the corrective information includes the reference position signal.
5. The system of claim 4 , wherein the corrective information includes detection of a transition in the mode of movement by the mobile object.
6. The system of claim 1 , wherein the inertial sensor assembly includes at least one accelerometer and at least one gyroscope.
7. The position tracking device of claim 1 , further comprising a wide area resolution module for computing the position of the mobile object when the mobile object is located in a second area requiring lesser position resolution.
8. The position tracking device of claim 7 , further comprising a wireless telephone network transceiver, and wherein the wide area resolution module is for computing the position of the mobile object when the mobile object is in the second area based on cell-ID information received by the wireless telephone network transceiver from a wireless telephone network.
9. The position tracking device of claim 7 , further comprising a receiver for receiving a signal indicating that the mobile object is moving between the first area and the second area, such that the position tracking device transitions between computing the location of the mobile object with the high resolution module and computing the location of the mobile object with the wide are resolution module in response to the signal.
10. The position tracking device of claim 1 , further comprising a power management module for determining a power level for the position tracking device based on inputs from the inertial sensor assembly.
11. A method of estimating the real-time state of a mobile object, wherein the real-time state estimate for the mobile object includes a real-time estimate of the position, velocity and heading of the mobile object, the method comprising:
detecting movement of the mobile object with an inertial sensor assembly;
determining a current mode of movement for the mobile object based on the detected movement and state estimates for the mobile object for prior instances in time;
determining a first state estimate of the mobile object based at least on a motion model for the current mode of movement for the mobile object;
determining a second state estimate of the mobile object by dead reckoning based on movement of the object detected by the inertial sensor assembly and the state estimates for the mobile object for the prior instances in time; and
computing a real-time state estimate for the mobile object based on the first and second state estimates.
12. The method of claim 11 , wherein computing the real-time state estimate for the mobile object includes using Kalman filtering techniques to compute the real-time state estimate of the mobile object based on the first and second state estimates.
13. The method of claim 11 , further comprising correcting the real-time state estimate of the mobile object based on received corrective information when the corrective information is received.
14. The method of claim 13 , wherein correcting the real-time state estimate of the mobile object includes correcting the real-time state estimate based on the state estimates of the object at the prior instances in time, information regarding the timing of the last transition in the mode of movement of the mobile object, and the received corrective information.
15. The method of claim 14 , wherein correcting the real-time state estimate of the mobile object includes correcting the velocity estimate of the mobile object at time n when corrective position information for time n is received.
16. The method of claim 15 , wherein correcting the real-time state estimate of the mobile object includes correcting the heading estimate of the mobile object at time n when corrective position information for time n is received.
17. The method of claim 16 , further comprising updating the state estimates of the object for instances in time prior to time n based on the corrected velocity estimate at time n, the corrected heading estimate at time n, the corrected position estimate at time n.