Systems and methods for controlling a density of visual landmarks in a visual simultaneous localization and mapping system
The invention is related to methods and apparatus that use a visual sensor and dead reckoning sensors to process Simultaneous Localization and Mapping (SLAM). These techniques can be used in robot navigation. Advantageously, such visual techniques can be used to autonomously generate and update a map. Unlike with laser rangefinders, the visual techniques are economically practical in a wide range of applications and can be used in relatively dynamic environments, such as environments in which people move. One embodiment further advantageously uses multiple particles to maintain multiple hypotheses with respect to localization and mapping. Further advantageously, one embodiment maintains the particles in a relatively computationally-efficient manner, thereby permitting the SLAM processes to be performed in software using relatively inexpensive microprocessor-based computer systems.
1. A method for managing content of a landmark database in a Visual Simultaneous Localization and Mapping System (VSLAM) for a mobile device, the method comprising:
visually obtaining a measurement of a landmark;
analyzing a quality of the measurement, where the quality of the measurement provides an indication of whether the measurement is an outlier;
storing an indication when the measurement has been identified as an outlier; and
removing a landmark from the map when the measurements of the landmark are repeatedly identified as outliers.
2. The method as defined in claim 1 , wherein storing the indication further comprises updating a count of how many times the measurement has been identified as an outlier.
3. The method as defined in claim 1 , wherein storing the indication further comprises updating a first count of how many times the landmark has been measured and a second count of how many times the measurements have been identified as outliers.
4. The method as defined in claim 1 , wherein storing the indication further comprises updating a count of how many consecutive times the measurement has been identified as an outlier.
5. The method as defined in claim 1 , wherein a measurement is identified as an outlier at least partly when a visual measurement suggests a pose that is inconsistent with a pose that is estimated by a large proportion of particles.
6. The method as defined in claim 1 , wherein a measurement is identified as an outlier at least partly when a difference between a pose estimated by a visual measurement and the pose estimated by a Simultaneous Localization and Mapping System (SLAM) exceeds a predetermined threshold.
7. The method as defined in claim 1 , wherein a measurement is identified as an outlier at least partly in response to a calculation of projection error.
8. The method as defined in claim 1 , wherein a measurement is identified as an outlier at least partly in response to a measurement of a slope of a floor.
9. The method as defined in claim 1 , wherein a measurement is identified as an outlier at least partly in response to a number of matching features common to an image and to a landmark.
10. A computer program embodied in a tangible medium for managing content of a landmark database in Visual Simultaneous Localization and Mapping System (VSLAM) for a mobile device, the computer program comprising:
a module with instructions configured to visually obtain a measurement of a landmark;
a module with instructions configured to analyze a quality of the measurement, where the quality of the measurement provides an indication of whether the measurement is an outlier;
a module with instructions configured to store an indication when the measurement has been identified as an outlier; and
a module with instructions configured to remove a landmark from the map when the measurements of the landmark are repeatedly identified as outliers.
11. The computer program as defined in claim 10 , wherein the module with instructions configured to store the indication further comprises instructions configured to update a count of how many times the measurement has been identified as an outlier.
12. The computer program as defined in claim 10 , wherein the module with instructions configured to store the indication further comprises instructions configured to update a first count of how many times the landmark has been measured and a second count of how many times the measurements have been identified as outliers.