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Point Cloud Gathering for an Autonomous Bucket Excavator. Robotics Research Lab University of Kaiserslautern Gregor Zolynski. Overview. System for 3D data gathering from given sensor arrangement Introduction: machine and sensors Problems and limitations Concepts

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Point cloud gathering for an autonomous bucket excavator

Point Cloud Gatheringfor an Autonomous Bucket Excavator

Robotics Research Lab

University of Kaiserslautern

Gregor Zolynski


Overview
Overview

System for 3D data gathering from given sensor arrangement

  • Introduction: machine and sensors

  • Problems and limitations

  • Concepts

  • Selected implementation details

  • Short example

Point Cloud Gathering for an Autonomous Bucket Excavator


Active scanners for safety applications
Active Scanners for Safety Applications

18t bucket excavator

  • Laser scanners on both sides of arm for safety

  • Panning: “natural” motion

  •  utilize scanners for data gathering

  •  no additional articulation necessary

Point Cloud Gathering for an Autonomous Bucket Excavator


Laser scanner scan planes
Laser Scanner & Scan Planes

  • Planar laser scanner(SICK LMS 151)

  • Coverage of 270° at 0.5° / 0.25° resolution

  • All scan points located on scan plane

Point Cloud Gathering for an Autonomous Bucket Excavator


Laser scanner scan planes1
Laser Scanner & Scan Planes

  • Planar laser scanner(SICK LMS 151)

  • Coverage of 270° at 0.5° / 0.25° resolution

  • All scan points located on scan plane

  • Two scanners mounted vertically

  • Rotational encoder

Point Cloud Gathering for an Autonomous Bucket Excavator


Problems limitations

Problems

Heavy noise

Vibrations

Undetected displacement

Resulting system limitations

Stationary vehicle

Big objects

Semi-dynamic terrain

Dynamic/moving obstacles

Problems, Limitations, …

Point Cloud Gathering for an Autonomous Bucket Excavator


Problems limitations desired behavior

Problems

Heavy noise

Vibrations

Undetected displacement

Resulting system limitations

Stationary vehicle

Big objects

Semi-dynamic terrain

Dynamic/moving obstacles

Desired Behavior

Gather all data

Maintain healthy resolution

Remember briefly covered portions

Quickly remove invalid data

Problems, Limitations, Desired Behavior

Point Cloud Gathering for an Autonomous Bucket Excavator


Concept data gathering
Concept: Data Gathering

  • Fuzzy points: Each point has a position and an uncertainty

  • Point cloud: New scan points added form each scan

  • Aging: Scan points “decay” and get discarded

  • Merging: New points are fused with close-by neighbors

Point Cloud Gathering for an Autonomous Bucket Excavator


Concept data gathering1
Concept: Data Gathering

  • Fuzzy points: Each point has a position and an uncertainty

  • Point cloud: New scan points added form each scan

  • Aging: Scan points “decay” and get discarded

  • Merging: New points are fused with close-by neighbors

Point Cloud Gathering for an Autonomous Bucket Excavator


Concept deletion volume

Sensor pose k

Sensor pose k+1

Scan plane k+1

Concept: Deletion Volume

  • Volume spanned between two consecutive scans of each scanner

  • Usually combination of translation and rotation

  • Displacement is very small

  • Assumption: Space betweenscan planes is empty

     Delete all contained points

Point Cloud Gathering for an Autonomous Bucket Excavator













Efficient implementation
Efficient Implementation

  • Deletion volume:4 planes + triangle strip

  • Naïve point-in-volume tests are expensive (20.000 points)

  • Faster:

    • Space binning

    • Signed distance to 4 planes

    • Intersection of ray from point towards sensor

Point Cloud Gathering for an Autonomous Bucket Excavator


Quick triangle intersection
Quick Triangle Intersection

  • Scan points: polar coordinates(angle ~ point index)

  • Each point in point cloud in sensor’s coordinate space

  • Intersection candidate triangles:At least one corner above and below checked point

  • Quick text for min/max distance, then intersection

Point Cloud Gathering for an Autonomous Bucket Excavator


Example
Example

Point Cloud Gathering for an Autonomous Bucket Excavator





Thank you

Point Cloud Gathering for an Autonomous Bucket Excavator


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