3D Mapping Robots: 3D Mapping Robots Intelligent Robotics School of Computer Science Jeremy Wyatt James Walker


What Are 3D Mapping Robots and Their Uses?: What Are 3D Mapping Robots and Their Uses? Robots which produce a 3-dimensional model of their environment from the data they collect They can be used by people who need to know more about the interior of a building: Architects Fire fighters Human rescue workers


Types of Sensing Techniques: Types of Sensing Techniques Stereo vision Laser range finders A combination of the two


Stereo Vision: Stereo Vision Use stereo disparities to compute depth Inaccurate in detecting the position of walls and objects especially in cluttered environments


Laser Range Finders: Laser Range Finders Very accurate in measuring distances to walls and objects in the environment Has a range of 8m with a resolution of 1mm and a statistical error of +/-10mm Can not detect any texture in the environment so can only produce single coloured models


A Combination of the Two: A Combination of the Two Laser range finders for detecting the distance of walls and objects An omni-cam for producing texture maps for a realistic visualisation of the environment


The GATech Robot: The GATech Robot Equipped with a laser range finder positioned vertically to scan perpendicular to the movement of the robot


How the Robot Builds the 3D Models: How the Robot Builds the 3D Models Collects raw data from the environment using the laser range finder Converts the raw data into Cartesian co-ordinates Converts the Cartesian co-ordinates into a mesh for the 3D model


How the Robot Collects the Raw Data: How the Robot Collects the Raw Data Laser moves through 180˚ in 0.5˚ steps from one side of the robot over the top to the other recording the distance Approximately 38 scans are completed every second Robot moves forward at 0.25m/s Therefore approximately one scan every 5cm


Transforming the Raw Data Into Co-ordinates: Transforming the Raw Data Into Co-ordinates Raw data is in the form of cylindrical co-ordinates Transformed using the pose of the robot, the angle of the scan and the height of the centre of the laser scanner


Collecting the Co-ordinates to Form Triangles: Collecting the Co-ordinates to Form Triangles Choose two scan points p1 and p2 from the same scan, taken at angles α and α + 0.5˚ Choose the two corresponding points q1 and q2 from the next scan Form two triangles p1p2q1 and q1p2q2 For each triangle calculate its normal vector


GATech Model: GATech Model


GATech Model: GATech Model


GATech Model: GATech Model


Disadvantages of This Approach: Disadvantages of This Approach The corridor appears to be slightly curved due to the way the robot moves Obstacles below a height of 0.52m can not be detected by the robot No filtering techniques were used so the model is very noisy but retains a high level of complexity because of this


Further Examples: Thrun et al: Further Examples: Thrun et al Uses two laser range finders and an omni-cam Uses a technique called expectation maximisation Processes the data to reduce the noise


Expectation Maximisation: Expectation Maximisation Estimates the number of surfaces and their location Adds and removes surfaces until it converges on the best fit model for the data


Thrun et al: Thrun et al


Thrun et al: Thrun et al


Summary: Summary Brief overview of what 3D mapping is and some uses for 3D mapping Different types of sensors used How to collect data and convert it into a 3D model Some more advanced methods for 3D mapping and processing of the data


References: References www.cc.gatech.edu/ai/robot-lab/research/3d/ www-2.cs.cmu.edu/~thrun/3d/


Processing the Data: Processing the Data Various techniques and algorithms have been used to reduce the noise in the data Smoothing is always used as a final post processing step as nearby measurements are likely to belong to the same surface


Types of 3D Mapping Robots: Types of 3D Mapping Robots Stationary Move with manual guidance Fully automated