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Active guidance system for the PIRATE pipe inspection robot tethering cable

Maks, M.H. (2015) Active guidance system for the PIRATE pipe inspection robot tethering cable.

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Abstract:The PIRATE inspection robot can travel at 80mm/s through pipe networks ranging from 51 to 120mm internal diameter; the robot is connected to the outside world with a tether cable. When traveling into the pipe network problems can occur in the cable pulling capabilities of the inspection robot. The current tested prototype can pull with a force of 14N, but the inspection robot is not always capable of delivering the 14N pull force, for instance when taking a bend. With a force of 14N a cable could be pulled 250m into a straight PVC pipe or 125m into a corroded steel pipe. These distances are based on calculations; values for friction were acquired by testing. In case of a real pipe network with radius or miter bends the pull force increases exponentially in the bend. The increase in friction becomes even worse by deformation of the cable on a sharp edge of a miter bend. Tests show forces should not exceed 3N in miter bends to prevent jamming of the cable. To aid the inspection robot in a minimal 50m traveling distance into a pipe network, with bends, cable guiding is necessary. A system operating from within the pipe network must be able to pass obstacles like miter bends; this limits the size of the system to a cylinder with a diameter of 30mm and a module length of 60mm. These sizes are for a system composed of multiple modules; in case only one module is used there are more solutions possible. To power the system the best options are to equip it with batteries or to use an inductive coupling with the tether cable. In case of the inductive coupling communications can also be performed relatively easy. If the system is incorporated into the tether cable and not only guiding it, it is possible to connect a wire directly to the system. With the results of the analysis, requirements for the system could be set up and concepts could be made that match the requirements. Five concepts were generated, of which two seem very promising. Concept 1 uses a clamping mechanism to lock itself inside a pipe at a specific point like a bend, and will then aid in cable pulling. It can pull a cable with a second system attached to it, which can then replace the first system to increase the traveling distance of the inspection robot. The concept can be powered with an inductive coupling if two tether cables are used; maximum travelling distance is more than 100m, which is adequate for the current inspection robot. Concept 4 is a propelling cable system; the tether cable is the guidance system. The cable is equipped with wheels between fixed segments of cable. The length of the cable segments can be matched to the conditions of the pipe network. The wheels on the cable are pressing against the wall of the pipe and pull and push the cable forward. Because the system is connected to the cable, power can simply be supplied; this makes it possible to travel larger distances than the clamping system. Concept 1 was chosen to elaborate because it is best suited for varying pipe conditions and multiple bends close together. The system will consist of two clamping modules, two cableT feeding modules and a power module. The guidance system is designed to pull two 30m UTP cables and a second cable guiding through a pipe network. This requires a pulling force of 12.5N and a clamping force of 15N, for safety the pulling force is increased to two modules each delivering 7.5N. The clamping mechanism is executed with a lead screw and a small motor with gearbox. The cableTfeeding module also uses a small motor with gearbox and is fitted with pulleys to apply force on the cables. Springs are placed between the modules to align linearly to prevent blocking in pipes. The modules were designed in SolidWorks and were constructed at the University with easily available materials. The finished prototypes were tested, to determine if they met set criteria. The clamping module almost reached the set clamping force of 15N, but was not able to withstand the required pulling force. The clamping force should at least be doubled, preferably tripled. Reason for lower forces than expected is the 5% efficiency of the lead screw compared to the expected 20% efficiency. The cableTfeeding module was not able to deliver the required 7.5N at a speed of 80mm/s; cause for this low outcome is the wrongly estimated efficiency of the gearing system. The efficiency was only half of the expected efficiency. Besides a more efficient gearing, a more powerful motor will be necessary to make this module work. To fit a more powerful motor, the module sizes should probably be increased by 50%.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:20 art studies
Programme:Industrial Design BSc (56955)
Link to this item:http://purl.utwente.nl/essays/66814
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