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« Structure from motion » algorithms for the CYCAB robot

« Structure from motion » algorithms for the CYCAB robot. Guillaume CERNIER ENSIMAG - 2nd year internship 19th June - 15th September 2006. INRIA presentation. Well-known french research centre in : Computer science Control theory Applied mathematics

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« Structure from motion » algorithms for the CYCAB robot

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  1. « Structure from motion » algorithms for the CYCAB robot Guillaume CERNIER ENSIMAG - 2nd year internship 19th June - 15th September 2006

  2. INRIA presentation • Well-known french research centre in : • Computer science • Control theory • Applied mathematics • 6 research centres (Lorraine, Rennes, Rhône-Alpes, Rocquencourt, Sophia-Antipolis, Futurs) • Partner of the new research centre of Microsoft at Orsay • INRIA Rhône-Alpes unit : • 26 research teams among 8 associated with foreign laboratories • Near 500 people (engineers, researches, PhD students, interns, …) • Local partners : IMAG, UJF, INPG, CNRS, … • Member of 10 european research networks • 271 contracts among 53 with industry and 26 european • 14 start-ups created since 1998 (more than 560 jobs created) Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  3. e-Motion team presentation • “GEometry and Probability for MOtion and AcTION” • Belongs to the GRAVIR lab (INRIA, CNRS, UJF, INPG) • Goals : • Developing algorithmic models and methods allowing to build artificial systems • With capacities of perception, decision, and action • Operating in open and dynamic environments • Start-ups : Itmi (1982), Getris Images (1985), Aleph Technologies (1989), Aleph Med (1992), Probayes (2003). • Industrial collaborations : Robotsoft, Renault, PSA, AW Europe (linked to Toyota), XL-Studio, Aesculap, Teamlog, Kelkoo. Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  4. CYCAB presentation • Large R&D program between INRIA & INRETS • Autonomous vehicle intended for urban areas • Automatic taxi computer-guided • Can be adapted for blind and/or handicapped people • Autonomous + urban areas => avoiding obstacles • Before my internship : avoidance realized by a laser telemeter • Internship goal : use a video camera to estimate the structure of the whole scene in front of the vehicle • Called “structure from motion” Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  5. 3D estimation of the structure Internship goals Videos, sequence of pictures • Constraints : • Software development : C/C++ • Real-time processing • Integration to the whole platform embedded in the Cycab (plug-in format) Helps : • Use of an open-source 3D vision library : “OpenCV” Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  6. “Structure from motion” (1/3) • The problem : only one camera => unknown motion between 2 snapshots • So, structure from motion is a 2-step process : • Optical flow (vector field) computation between 2 pictures • Thanks to this optical flow, computing : • First, the motion of the camera between the 2 pictures • Finally, the 3D structure of the scene Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  7. Optical flow computation (2/3) • SPARSE Vector field • To lighten computation • Vectors tracking real points in the scene • How choose the points to track ? • GoodFeaturesToTrack algorithm • Exists in OpenCV library • Computation of the optical flow : • Pyramidal algorithms • Establishing correspondence between points of the 2 pictures • Eliminate “outliers” • Let to know the “fundamental matrix” Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  8. 3D structure computation (3/3) • 2 steps : • Find the motion between the 2 pictures : • Thanks to fundamental & intrinsic matrixes • Find the rotation and translation resulting • Here, we know the position of the camera at the 2 snapshots • Computes the 3D point for each point pair (q1,q2) in the 2 pictures : • Triangulation methods • Least-square methods (retained) • Depends of the projection matrixes P1 & P2 • Pi = KRi( I3x3 | -ti ) (4x3 matrixes) Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  9. Other development • Camera Calibration GUI Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  10. Difficulties and successes • 3D vision library OpenCV contains some bugs … • Tutors absence … • Very interesting research field ! • Reach the internship goals 2 weeks before the planned date • Research article writing for a robotics conf (ICRA 07) • Learning a GUI API (Gtk+) Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

  11. Team life • Different culture people (Italian, Brazilian, Asiatic, …) • Summer at INRIA is … Guillaume CERNIER« Structure from motion » algorithms for the CYCAB robot

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