RESEARCH ACTIVITIES

Sensor-based control of Autonomous Underwater Vehicles

My research on control design for AUVs and sensor-based control design for AUVs in particular has been started since my involvement in the thesis work of Szymon Krupinski whom I co-supervised with Tarek Hamel and Guillaume Allibert. Autonomous navigation of AUVs in an unknown or partially known and dynamically changing oceanic environment is challenging. Scientific issues are strongly related to the fact that the AUV may navigate in cluttered areas where global acoustic positioning systems are unusable or insufficiently precise for safe navigation. In this case, the AUV must rely on exteroceptive sensors and sensor-based navigation strategies. Although several types of sensors can be used, the video camera remains an excellent candidate as they are considerably cheaper than acoustic sensors and provide rich information at a high update rate. Among many applications related to vision-based control paradigm, we have investigated the two following relevant control problems of fully-actuated AUVs:
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The Girona-500 AUV (left) used by the company Cybernétix for experimental validations of our vision-based controllers for homography-based stabilization and positioning (middle) and for pipeline following (right)

  • Vision-based stabilization and positioning: This functionality is useful for AUV navigation close to underwater infrastructures in the case when high-resolution imaging is needed for inspection or intervention tasks. Using a monocular camera without the assumption of planarity of the target and knowledge of its geometry is very challenging because the pose cannot be fully reconstructed from visual data. However, monocular-vision can be sufficient to achieve stabilization. In the context of monocular-vision, we have recently proposed a novel homography-based visual servoing (HBVS) control approach for fully-actuated AUVs, using the homography matrix that encodes transformation information between two images of the same planar target. The proposed control approach has been experimentally validated by my industrial collaborator Cybernétix on the Girona-500 AUV. This work is accepted for publication in IEEE Transactions on Robotics.
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Validation of the proposed HBVS controller using a downward-looking camera: reference image and current images
 
 

  • Vision-based pipeline/cable following: Highly relevant for inspection of submerged linear infrastructures such as pipelines and cables by AUVs, this problem has often been addressed using either a monocular camera or an acoustic sensor. We have proposed an IBVS controller for fully-actuated AUVs for pipeline/cable following using a monocular camera and using Plücker coordinates for the representation of lines. Experimental validations of this control approach have been recently carried out by Cybernétix on the Girona-500 AUV.
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Validation of the proposed vision-based controller for pipeline following: Initial image and current images during convergence
 


  • Related past project: CNRS PEPS CONGRE (CONtrôle Générique de Robots mobiles en Environnement sous-marin) (2013-2015). Consortium: ISIR and I3S. I was the project coordinator.

  • PhD students:
    • Szymon KRUPINSKI (01/10/2010–10/07/2014, co-advisor with T. Hamel and G. Allibert, financed by the company Cybernétix). Subject: Offshore structure following by means of sensor servoing and sensor fusion. Thesis defended in 10 July 2014, with highest honour. PhD defense committee: L. Jaulin (Reviewer), P. Souères (Reviewer), V. Creuze, T. Hamel, G. Allibert, M.-D. Hua, A. Fidani. Actual position: research engineer at Cybernétix.
    • Lam Hung NGUYEN (01/09/2015-now, co-advisor with T. Hamel). Subject: Nonlinear control of Autonomous Underwater Vehicles.

  • Experimental platform under development: For primary experimental validations (such as vision-based control), we have purchased a mini underwater platform BlueROV, which is currently upgraded with high level functionalities such as homography estimation. An engineer (CDD until end of 2017) is involved in this development.

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