Positive and negative obstacle avoidance system and method for a mobile robot

Abstract

Embodiments of the present invention provide methods and systems for ensuring that mobile robots are able to detect and avoid positive obstacles in a physical environment that are typically hard to detect because the obstacles do not exist in the same plane or planes as the mobile robot's horizontally-oriented obstacle detecting lasers. Embodiments of the present invention also help to ensure that mobile robots are able to detect and avoid driving into negative obstacles, such as gaps or holes in the floor, or a flight of stairs. Thus, the invention provides positive and negative obstacle avoidance systems for mobile robots.

Description

FIELD OF ART[0001]This invention generally relates to mobile robots. More specifically, the invention is directed to systems and methods for detecting positive and negative obstacles in physical environments through which mobile robots move and preventing the mobile robots from driving into those obstacles.BACKGROUND ART[0002]Mobile robots, including autonomously-navigating mobile robots, inertially-guided robots, remote-controlled mobile robots, and robots guided by laser targeting, vision systems, roadmaps and beacons, to name a few examples, normally use horizontally-oriented laser sensors to scan the area in the mobile robot's direction of travel and to detect potential obstacles in the mobile robot's path. The horizontally-oriented lasers, which typically scan in two-dimensional planes roughly parallel with floor, work reasonably well for detecting objects that extend from the floor in a substantially perpendicular direction, so long as the obstacle intersects the horizontally-...

AI Technical Summary

Benefits of technology

[0011]Multiple non-horizontal lasers oriented to scan the physical environment in non-horizontal planes may be used to enhance the mobile robot's ability to detect and avoid positive obstacles that do not extend vertically from the floor or intersect the mobile robot's horizontal scanning planes, and are therefore undetected by the mobile robot's horizontal lasers. Thus, in addition to the first non-horizontal laser scanning in the first plane, a second non-horizontal laser may be attached to the mobile robot and oriented to scan the physical environment in a second plane that is also not parallel to the floor of the physical environment. In such embodiments, the memory stores a second set of initial operating parameters and preferences for use by the positive obstacle avoidance engine in processing the laser readings from the second non-horizontal laser, including: (1) a second data structure of two-dimensional coordinates from the floor plan, each two dimensional coordinate in the second data structure representing another location in the physical environment to be avoided by the mobile robot, and (2) placement information for the second laser, including a second laser position and a second laser tilt. In this case, the laser controller receives a second set of laser readings from the second laser, each laser reading corresponding to a location in the physical environment where the second laser detects a physical obstacle in the second plane. The positive obstacle avoidance engine performs the same calculations for each laser reading received from the second set of laser readings in order to determine whether the detected obstacle represents the expected floor or ceiling, based on distance and angle from the robot, or otherwise represents some obstacle located between the floor and the ceiling in the physical environment that needs to be avoided. Thus, the positive obstacle avoidance engine converts each laser reading into a second three-dimensional coordinate based on the second plane angle (theta), the second plane distance (r), the second laser position and the second laser tilt. The positive obstacle avoidance engine then determines an minimum allowable ceiling height and a maximum allowable floor height for the second three-dimensional coordinate based on the x-component of the second three-dimensional coordinate, the y-component of the second three-dimensional coordinate and the tolerance profile. Then the engine determines whether the second z-component lies between the allowable floor height and the allowable ceiling height based on the z-component's distance from the robot. If so, the positive obstacle avoidance engine adds the x-component and the y-component of the second three-dimensional coordinate to the second data structure of two-di

Problems solved by technology

However, they do not work well for detecting positive physical obstacles in the mobile robot's path that are parallel to the floor and/or obstacles that are not at the same height as the horizontally-oriented scanning plane.

This means the mobile robots frequently have no way of detecting and avoiding positive obstacles, such as long tables with legs at the ends (and no legs in the middle), objects suspended from a ceiling or other structure, and obstacles that stick out from the edge of another object, like a keyboard tray.

Mobile robots that use horizontally-oriented lasers fo

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