Dam wall detection and tracking using a Mechanically Scanned Imaging Sonar

Abstract

Abstract-In Dam inspection tasks, an underwater robot has to grab images while surveying the wall meanwhile maintaining a certain distance and relative orientation. This paper proposes the use of an MSIS (Mechanically Scanned Imaging Sonar) for relative positioning of a robot with respect to the wall. An imaging sonar gathers polar image scans from which depth images (Range & Bearing) are generated. Depth scans are first processed to extract a line corresponding to the wall (with the Hough Transform), which is then tracked by means of an EKF (Extended Kalman Filter) using a static motion model and an implicit measurement equation associating the sensed points to the candidate line. The line estimate is referenced to the robot fixed frame and represented in polar coordinates (ρ&θ) which directly corresponds to the actual distance and relative orientation of the robot with respect to the wall. The proposed system has been tested in simulation as well as in water tank conditions.

Autonomous Dam Surveillance Robot System Based on Multi-Sensor Fusion

“…A GPS-based surveillance robot is proposed in [12] to monitor the exterior deformation of the dam. A mechanically scanned imaging sonar (MSIS) is used for locating the underwater robot relative position for dam wall surveillance [13]. Many researchers utilized UAVs for dam image collecting and modeling, which is low-cost and convenient [14,15].…”

State feedback control of an underwater vehicle for wall following

“…To detect distance and orientation of the wall, several schemes have been proposed in the literature. One can either use sonar [6] but this high cost technique (more than 5k$) suffers from low sampling rate and high bandwidth emission, which increases significantly the risk of interference with other acoustic devices (e.g. modem).…”

“…Several control strategies have been developed for applications such as bottom hovering [3,4] or wall/ship hull following [5,6]. For instance, the horizontal motion of the Romeo ROV [13] uses a PI gain scheduling controller able to reduce the robot dynamics to a nominal characteristic equation.…”

“…Fig. 1) to monitor the state o structure (crack detection) [6]. During t vehicle performs video or sonar imaging inspection is similar and is performed to weaknesses.…”

Visual inspection of hydroelectric dams using an autonomous underwater vehicle

“…Although dam walls are generally curved to improve the structural resistance to the water pressure, they can be locally approximated by a line feature (see Figure 7). These vertical and planar structures can be efficiently detected in acoustic images (Kazmi, Ridao, Ribas, & Hernàndez, 2009). The process begins with the estimation of the initial position of the wall with respect to the vehicle.…”