Pipe systems vary from straight, horizontal stretches with constant diameter, to complex structures with corners, T-joints, vertical branching and varying diameter. Additionaly, obstacles such as valves and measurement instruments exists, as well as known irregularities as sediments and impurities.
SINTEF ICT is currently developing a new type of pipe inspection robot, capable of handling this complex environment. The motive is to give the industry better knowledge of the condition of physical processes and systems, to be able to, simpler and at an earlier time, discover irregularities or possible causes of reduced throughput, process failure or at worst physical damage.
The robot has been named PiKo, after "Pipe inspecting Konda" - or just as well PiCo in English, and is a part of SINTEF Applied Cybernetic's third generation of snake-like robots (see Anna Konda and Aiko for previous generations).
PiKo consists of a set of identical modules connected by a set of special forks. Figure 1 shows one module.
Figure 1 Figure 2
Two modules are connected by a fork, as shown in figure 2. To move forward, each module has a motor giving propulsion to the wheel-pairs pictured. The two wheel-pairs (upper and lower pair in figure 2) turns in opposite direction of each other, allowing PiKo to "push" forward if necessary.
One of the more central aspects of the robot is the fact that each module also controls vertical and horizontal angle in relation to its neighbouring modules - we say that it has active joints with two degrees of freedom. This makes PiKo exceptionally flexible, well fit to the task of navigating the oblong shapes of pipe structures. PiKo can make sharp turns, climb vertically, avoid obstacles, and even resist potential flow in a pipe structure.
Horizontally, PiKo moves in much the same way as a train. Each module follws the previous in a row. Vertically, the motion is somewhat different. PiKo tries to push against opposing walls with alternating parts of its body, as shown in this animation. The special forks between each module are able to sense if, and how hard, PiKo is pushing with each module against a wall. After mounting itself for a vertical climb or descent, PiKo will drive forward in a normal fashion.
Structure of a module
Figure 3 shows an illustration of the inner structure of a module. It consists of three electro-motors, gears to give the wanted scale of speed and torque, and some additional drive gears to transfer torque from the motors to wheels and joint arms. Figure 5 shows a module with a complete assembly.
Figure 3 Figure 4 Figure 5
Each module also has a controller unit, as shown in figure 4. This is a circuit board controlling the various electro-motors, and reading sensor information from the outside world. All modules may communicate with other modules, and with the robot's brain, through a communication bus running through the entire robot. This communication system is similar to the one found in a modern car.
PiKo's head is the first module of its body. Here, calculations and evaluation regarding path planning and similar activities are conducted. A special camera, called a 3D-camera, is also situated here. This camera can take ordinary grey-scale images, but can also tell the distance from the camera to each pixel of the picture taken. The camera plays a central part in interpretation of the world for the robot, and may in cooperation with algorithms developed by SINTEF Optical Measurement Systems and Data Analysis describe the three-dimensional structure of the inside of a pipe, as well as construct a map of upcoming turns, branches, etc.
PiKo can also communicate with the outside world, making an operator able to control it. The operator may give PiKo commands such as select the branch going left/right, keep going forward, or stop when something unexpected is registered. Communication is handled by an IP interface. This makes it able for the operator to be situated at any desktop computer (anywhere in the world) to control PiKo.
The Complete Prototype
A fully connected and working prototype was finished in february 2009, and is shown in the image below. In its current state, the robot is able to move through both horizontal and vertical pipe structures.
The two figures below show key experiments conducted with the prototype. One shows drawn lines simulating a typical bend of a pipe. This experiment was conducted to prove that the robot was able to keep its entire body inside a structure without pushing on the sides during a turning motion. The second figure shows the robot mounting itself in a vertical pipe and then climbing inside the pipe while the pipe is being held in the air by an operator.
The concept for climbing motion is also shown in the figure below.
Follow this link to see a video of PIKo in action.
- Total length: ~1 meters
- Weight: ~6 kg
- Degrees of Freedom in total: 8
- Angle deflection: +/- 60 degrees
- Actuation: Electro-motors
- Joint angular moment per module per DoF: 11 Nm
- Operational speed: 0.2 m/s
PiKo is a research robot under development. Focus for the research has been on propulsion and path planning inside pipes. This means that challenges regarding influences by the environment, such as pressure, temperature, or humidity, have not been addressed. Currently, initial testing of prototype modules and forks are being conducted, and a complete robot with all modules and head will be ready by christmas 2008.
Contact person at SINTEF Applied Cybernetics: Aksel A. Transeth