The present invention relates to a multi sensor system for 3D mobile robot navigation, localization and mapping that combine a high-repetition rate laser range sensor and a stereo camera.
Currently, mobile robots are lacking in good peripheral vision to detect and track obstacles or plan paths in crowded or complex environments. One of the best ways to accurately sense the environment around the robot is by using laser ranging (lidar). Some lidars could be found on the market, but if they provide mapping in 3D, they are big, use lots of power and are expensive. Smaller ones provide only line scans on limited angular range (max 180° around the platform) resulting in limited view of the scene. Mobile robots moving in complex terrains need to track landmarks and obstacle all around the platform for navigation purpose.
Lars S. Nyland (IEEE Proceedings, 1998) in an article entitled Captured Dense Environmental Range Information with a Panning Scanning Laser Range Finder describes a laser range finder that uses a rotating mirror tilted at 45° that allows for range measurement in a 300° sweep and includes a digital camera where, after an environment is scanned, the laser is removed from the panning unit and replaced with the camera. The apparatus described by Lars S. Nyland obtains full-color images of a scene augmented with range data on a pixel-by-pixel basis. The apparatus described by Lars S. Nyland is built from an assembly of two commercial products (an Acquity Research AR-4000 ranging laser and a Dperception pan and titlt unit. To obtain the final result, the process requires removing the ranging laser and replacing it by a camera. The scanning process is slow.
It is an object of the present invention to provide a navigation system for mobile robots with laser volumetric sensing to provide 3D ranging and imaging on 360° around a mobile platform.
A volumetric sensor for mobile robot navigation to avoid obstacles in the robot's path comprises a laser volumetric sensor mounted on a platform with a laser and detector directed to a tiltable mirror in the transparent cylinder that is rotatable through 360° by a motor, the mirror being tiltable by a rotatable cam mechanism in the transparent cylinder driven by a motor to provide a laser scan and distance measurements of obstacles near the robot.
The invention will be described in more detail with reference to the accompanying drawings in which:
Currently, mobile robots are lacking in good peripheral vision to detect and track obstacles or plan paths in crowded or complex environments. One of the best ways to accurately sense the environment around the robot is by using laser ranging (lidar). Some lidars could be found on the market, but if they provide mapping in 3D, they are big, use lots of power and are expensive. Smaller ones provide only line scans on limited angular range (max 180° around the platform) resulting in limited view of the scene. Mobile robots moving in complex terrains need to track landmarks and obstacle all around the platform for navigation purpose.
Lars S. Nyland (IEEE Proceedings, 1998) in an article entitled Captured Dense Environmental Range Information with a Panning Scanning Laser Range Finder describes a laser range finder that uses a rotating mirror tilted at 45° that allows for range measurement in a 300° sweep and includes a digital camera where, after an environment is scanned, the laser is removed from the panning unit and replaced with a digital camera. The apparatus described by Lars S. Nyland obtains full-color images of a scene augmented with range data on a pixel-by-pixel basis but the images and range data are obtained at separate times.
The present invention uses a simple and sturdy mechanism to provide 3D ranging and imaging on 360° around a mobile platform located on a movable robot. This scanner provides good close range volumetric sensing (up to 10 m). To provide longer range data, the scanner is combined with a large baseline near IR stereo camera to track distant objects in 3D. Data from the scanner and the stereo camera are fused and provided to the robot's navigation, localization and mapping layer.
Referring to
The azimuth and elevation axes are self-synchronized by the driving mechanism. The motor drives 40 and 38 tooth gears on the same driving shaft 2. The 40 tooth gear drives the rotation of the mirror cylinder 10 and the 38 tooth gear drives the cam cylinder 6. When the mirror cylinder is ending 40 revolutions, the cam cylinder 6 will complete 38 turns, resulting in one full elevation scan for each 10 revolutions of the mirror.
The laser beam is steered by a single mirror 7 mounted on a fork 13 rotating continuously at a speed near 1800 RPM and tilted up and down 90 times a minute. Both motions of the mirror are synchronized together and are driven by a single motor. The result is a screw-like scanning pattern ranging from minus 45° to plus 10° providing a range to nearby obstacles all around the robot.
The volumetric laser scanner illustrated in
The motor 1 in
The wide base stereo camera 12 and scanning lidar concept according to the present invention is illustrated in
The prototype sensor has the following specification:
The present invention has sturdy mechanics to provide laser volumetric sensing around 360° and stereo vision on the same platform. The lidar provides short range precision measurements around the platform on which it is mounted and the stereo camera locates and tracks more distant objects.
Various modifications may be made to the preferred embodiment without departing from the spirit and scope of the invention as defined in the appended claims.
This claims benefit of Provisional Application Ser. No. 60/566,941 filed on 3 May 2004.
Number | Date | Country | |
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60566941 | May 2004 | US |