This thesis is on mobile robot navigation using range sensors. The two sensors types used are time-of-flight lasers and sheet-of-light range cameras, both giving densely spaced range measurements. Map generation and navi gation are achieved in indoor environments, even when there are lots of disturbing objects giving cluttered range measurements. The walls are observed in the range scans using the Range Weighted Hough Transform, (RWHT) and the estimates of the map and the robot position are maintained during motion using Extended Kalman Filtering (EKF). The calibration of sensor parameters during operation uses the relative motion given by the incremental encoders on the wheels as the absolute calibration reference. Matching of observations to previous estimates are performed using a deci sion directed classifier. The algorithms can be used both to build a map, or during navigation using an existing map. The algorithms have been verified in several experiment with the range sensors onboard actual mobile robots. The size of a large room was estimated with a standard deviation of 1 cm. The robot navigates autonomously through an open door detected by the laser. The accuracy during passage was 1 cm at a speed of 0.5 m/s. The trajectory is perpendicular to the wall within 0.5 degrees. In one experiment the robot created a map of its environment while moving at speeds from 0.5 to 1 m/s. The standard deviation in the esti mated map dimensions for a series of tests were 1 to 2 cm and 1 degree. The navigation system has also been used for an autonomous plastering robot with automatic planning to include doors and windows. The navigation is very robust against both outliers in the measurements and disturbing objects. It is not seriously disturbed even when most of the walls are occluded and there are several persons moving around during operation.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:ltu-17818 |
| Date | January 1995 |
| Creators | Forsberg, Johan |
| Publisher | Luleå tekniska universitet, EISLAB, Luleå |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, info:eu-repo/semantics/masterThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | Licentiate thesis / Luleå University of Technology… → 31 dec 1996, 0280-8242 ; 1995:08 |
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