The rat’s whiskers

Touch technology project aims to develop sensory systems for a range of applications from helping locate disaster survivors to space exploration. Siobhan Wagner reports

Sensors that twitch their ‘whiskers’ like a rat to detect their surroundings in dark and possibly dangerous environments is the goal of a four-year EU touch sensing project.

The BIOmimetic Technology for vibrissal ACtive Touch (BIOTACT) project will include UK involvement from the Bristol Robotics Laboratory and Sheffield University.

The resulting technology could have a number of applications such as search and rescue robots that pick their way through rubble and debris, mine-clearing machines or even planetary rovers.

The technique could also be used in domestic goods such as vacuum cleaners to sense textures for optimal cleaning, or in the textile industry where long thin sensors could feel for problems within the weave of a fabric.

While vision supplies information about distant objects, touch is invaluable in sensing the nearby environment, yet has often been overlooked in system design.

‘We have predominantly focused on our own main sense which is vision,’ explained Bristol Robotics deputy director Tony Pipe, who has worked with his colleague Martin Pearson for the last few years developing a robot that uses whiskers for artificial touch technology.

‘While vision is a fantastic sensory method, it is useless in visually occluded environments, and it is only recently that research has looked at using touch,’ he said.

The team began with a government-funded project called Whiskerbot, which has provided the basic technical foundation for their projects since.

Pipe and Pearson have developed a way to build artificial whiskers that mimic rat whiskers in curvature and taper, but are four times the size.

They are constructed from carbon fibre and arranged in a group of nine on each side of a robotic head. Resistive elastomers are bonded to the periphery of each whisker to give an approximation of where the tip is in 2D space.

In use, the whiskers are moved forward and backward using a high-performance electrical motors that mimic the muscle movements inside a rat’s cheeks.

The whiskers are attached to a head and a robotic neck that moves up and down. The neck is attached to a robotic platform with three independent drive units that can drive in any direction.

As the whiskers twitch and contact an object, it generates a strain in the elastomers. The system’s artificial neuron processor, built out of a Field Programmable Gate Array, converts this strain into a series of spike trains. ‘At this point the system is copying how the brain experiences the world through a series of spikes of activity,’ said Pearson.

These spikes will allow the sensor to detect what it is touching and will help them navigate around the area it is in.

The main work ahead for the Bristol team will be to develop the system so it is ready for industrial use. There could be several different designs for the sensor depending on the application. Pipe said that British Nuclear Fuels has already expressed interest in using a BIOTACT device to investigate toxic liquids in tanks.

Pipe said that although touch is a valuable sensory method in visually restricted areas it should be used to complement vision, not replace it. ‘So if our robot thinks it sees something of interest, it can use its whiskers to sense if it is what it could half see through the dark,’ he said.

The team plans to work with sensor manufacturers after the project is finished, but Pipe said an industrial sensor is probably about 10 years away.