Elephantine actuation

It may look like something from a 1970s sci-fi series, but this terrifying creation is in fact a demonstration of an amazingly simple and effective actuator design developed by Engineers at Edinburgh’s Heriot-Watt University.

The gentle, organic movements of VORSCHT’s arms (VORSCHT stands for Versatile Original Resident Smoothly Carefully Handles Things!) are intended to demonstrate the suitability of this technology for application in deep space and sub-sea handling systems.

The appeal of the ‘Elephant’s Trunk’ or ‘flexible continuum’ actuator is its mechanically efficient design. Differing from conventional systems, where a load carrying structure is moved by an additional external device, the actuator acts as the supporting structure and provides movement.

Dr Bruce Davies, who heads up the project at the university’s department of mechanical and chemical engineering, gained his inspiration from watching bent flexible hoses straighten out under pressure. According to Davies, ‘This didn’t work very well and I moved on to the concept of starting straight and causing it to bend by using convoluted elements. I had been thinking about deformable structure before, and these were the ideas that cropped up.’

Each actuator is made of three bellows placed in a parallel arrangement forming the vertices of an equilateral triangle. The bottom of the triad is attached to an end-plate, which connects each bellow to the other two members of a particular trunk. Different pressure in each bellow is used to create a range of forces causing the trunk to bend according to the constraints provided by the end plate.

Described as ‘compliant’, the movement of the actuator is gentle and controlled. This means that any interaction with the surroundings is unlikely to produce catastrophic results.

Dr Davies believes that the continuum actuator will be ideally suited for handling, gripping and catching tasks on board the International Space Station, and is currently working on links with NASA to develop the technology.