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Bats may hold the key to the development of robotic devices that can inspect built structures. Using complex coded noises, bats identify the location of prey, for example, with extraordinary accuracy. By incorporating a similar system into robotic devices, it is hoped they could locate and find faults with similar accuracy. The aim is to develop robots that can remotely inspect inaccessible or hazardous areas, such as nuclear installations or gas pipelines. 'The final product is still 10 years away,' says Markus Friedrich of the University of Strathclyde, 'but there is already a great deal of interest from industry worldwide in this approach to non-destructive evaluation'.

'Bats use echolocation to locate objects and find their way around obstacles in the dark. By emitting waveforms over a broad range of frequencies and detecting the length of time for 'echoes' to return, bats build up a clear image of their surroundings. One aspect we can incorporate in the robots is to mimic the bats sequences of waveforms and use the improvement in echolocation within the robot sensing and positioning system,' says Markus. Parts of this system have already been designed and are currently under laboratory evaluation.

'The robots are controlled by a host computer and, through two-way communication, efficient search patterns are mapped out, obstacles detected, and collisions prevented. When a robot detects a flaw, the computer can initiate a special routine to change the behaviour of all the robots in use. The computer acts like mission control, receiving information from individual robots and sending out commands to individuals and the group, so that behaviour changes according to the distribution of defects,' explains Markus. The robots also carry their own processors to enable them to travel in straight lines and to carry out specific tasks. Cameras onboard the robots carry out visual inspection. Ultrasound that uses sound waves as they 'echo' off surfaces is used to measure the thickness of structures and to detect flaws. A further system is based on changes in magnetic fields detected by the robot as it travels along a pipe surface, indicating some level of metal loss that could mean corrosion.

Research to develop the robotic devices is part of an ongoing programme funded by the Engineering and Physical Sciences Research Council (EPSRC). Six universities and a consortium of industry, including Rolls Royce and Shell, make up the Research Centre for Non-Destructive Evaluation. The work on bats is being undertaken by a four year project known as BIAS Biologically Inspired Acoustic Systems, involving a small group of universities, industry, and the British Geological Survey.

Automating inspection of inaccessible or dangerous structures is a key priority for reducing inspection costs, improving safety and preventing disasters. 'At this stage we have proved the concept of remote testing by teams of robotic devices', says Markus, 'but we have many hurdles to overcome, including size reduction, and improving power consumption'.