Position determination systems and methods utilizing error of multiple candidate positions
Examples of systems and methods described herein may be used to track a tagged object through a scene. Techniques are described herein to calculate a position of the tag using wireless communication with multiple anchor devices. In some examples, the anchor devices may be self-localizing, e.g., they may dynamically determine their position and relationship to one another. In some examples, position of a tag may be calculated by calculating multiple candidate positions using different localization techniques—such as geometric localization techniques and/or optimization-based techniques. An error may also be identified associated with each candidate position. A final position may be determined for the tag based on the errors associated with the candidate positions (e.g., the candidate position with the smallest error may be utilized as the position, e.g., the determined position, of the tag).
1. A method comprising:
deploying a plurality of anchor devices about a scene;
monitoring movement of a respective anchor device of the plurality of anchor devices using an inertial measurement unit of the respective anchor device to determine when the respective anchor device is stationary;
determining a position of the respective anchor device when it is stationary;
collecting a set of ranges based on wireless message transmissions, the set of ranges including a range between a particular device and the respective anchor device;
calculating a first candidate position of the particular device based on the set of ranges and one or more positions of one or more anchor devices among the plurality of anchor devices using a geometric localization technique;
estimating error associated with the first candidate position;
calculating a second candidate position of the particular device and error associated with the second candidate position using an optimization-based technique, based on residual errors relative to the one or more positions and distances for the one or more anchor devices of the plurality of anchor devices;
selecting a determined position for the particular device based on the error associated with the first candidate position and the error associated with the second candidate position.
2. The method of claim 1 , further comprising collecting a set of positions for the plurality of anchor devices, and wherein using the geometric localization technique is further based on the set of positions.
3. The method of claim 1 , further comprising selecting a subset of the plurality of anchor devices for use in the geometric localization technique based on positions of the plurality of anchor devices, noise in a respective communication channel to each of the plurality of anchor devices, or combinations thereof.
4. The method of claim 3 , further comprising utilizing positions of more anchor devices than the subset of the plurality of anchor devices to estimate the error associated with the first candidate position.
5. The method of claim 1 , wherein said using a geometric localization technique comprises using lateration.
6. The method of claim 1 , further comprising further updating the first candidate position and the second candidate position based on previous positions of the particular device to provide a smoothed first candidate position and a smoothed second candidate position.
7. The method of claim 6 , further comprising calculating error associated with the smoothed first candidate position and the smoothed second candidate position.
8. The method of claim 7 , wherein said selecting a determined position is further based on error associated with the smoothed first candidate position and the smoothed second candidate position.
9. The method of claim 1 , wherein the inertial measurement unit comprises at least one of an accelerometer or a gyroscope.
10. The method of claim 1 , further comprising:
transitioning to an initialization mode of the respective anchor device responsive to powering on of the respective anchor device; and
transitioning to a discovery mode upon determining that the respective anchor device is stationary,
wherein the said monitoring the movement of the respective anchor device of the plurality of anchor devices is performed during the initialization mode, and
wherein said collecting the set of ranges is performed with the respective anchor device in the discovery mode.