12-06-2012, 03:42 PM
A Climbing-Flying Robot for Power Line Inspection
Power Line Inspection.doc (Size: 340.5 KB / Downloads: 54)
Abstract:
Our society is becoming increasingly more dependent on reliable electric power supply. Since power outages cause substantial financial losses to the producers, distributors and also to the consumers of electric power, it is in the common interest to minimize failures on power lines. To detect the defects early and to accordingly schedule the maintenance activities, the distribution networks are inspected regularly.
. Robot Requirements:
Power Line Features and Faults:
Power lines are a dangerous environment. The electric potential differences between the lines are in the order of 100 kV, yielding the electric field in the vicinity of the lines close to 15 kV/cm under normal conditions and even more in the presence of defect. Power lines are also a complex environment, difficult for robots to navigate. The simplest power lines have one conductor per phase, while others may have more.
The conductors are hung on insulator.
. Inspection with an UAV:
Inspection with an UAV is an upgrade of automated helicopter inspection so both concepts have some common problems. An evaluation of using an UAV for power line inspection indicated that this inspection method could be faster than foot patrol and would yield the same or better accuracy than costly helicopter inspection. It was concluded that the system is feasible from a technical point of view. A small electrically driven rotorcraft, which can pick up energy from power lines, was presented. This vehicle would be equipped with gyro-stabilized cameras, navigation and position regulation, a computer for image and other sensor data processing, a communication link and a system for electric power pick up. Power would be obtained from the power line using a pantograph mechanism. The most research was devoted to the development of a vision system for power line tracking and to image quality assurance. Namely, good power line tracking is important for visual position control and navigation, while image quality is of utmost importance for inspection purposes.
Position Control:
Since power lines have to be inspected from a small distance but must under no
Circumstances get damaged even in strong wind, position control of the UAV is difficult yet very important. Because conductors have to be in the field of view of the camera almost all the time, determining position of the helicopter visually from the images of the conductors seems very attractive.
Automatic Power Line Tracking:
Visual tracking of power lines with an UAV is similar to visual tracking with a helicopter.
The only major difference is that the UAV can get closer to the lines. The tracking methods are therefore a little different. Jones and Go lightly developed a simple tracking algorithm that could track the power line with three lines based on the Hough Transform in 2006. The main purpose of this tracking algorithm was to provide height and lateral displacement of the vehicle to the control system. The method was tested on a scaled model and was proven to be successful even when the background was cluttered. Another method for visual power line tracking utilized a vector-gradient Hough transform for line detection. Only one line was tracked and simultaneously inspected. The position of the helicopter with regard to the line was determined with stereo vision.