Scientists aim to create crayfish robots for Mars mission

Australian scientists are using indigenous freshwater crayfish, known as the Yabby, as their inspiration to help build miniature robots for NASA’s exploration of Mars.

University of Melbourne zoologist, Professor David Macmillan and associates in his Melbourne laboratory and collaborating laboratories overseas are using the Yabby (Cherax destructor) to help advance research in biomimetics.

‘Invertebrates such as insects and crustaceans achieve similar movement and sensory outcomes to humans. For example, finding food and selection of appropriate mates and nesting sites. Where humans use millions of neurons to achieve such outcomes, invertebrates do it with thousands. Where humans use hundreds, invertebrates may use as few as six,’ said Professor Macmillan.

Advances in computational network modelling, and electronics are said to have permitted the development of a new class of truly biomimetic creatures. But it isn’t as easy as merely taking apart an animal or plant and copying what you see.

‘Evolution doesn’t always come up with the best solution from an engineer’s perspective,’ said Professor Macmillan.

Despite these evolutionary pitfalls, biomimetics has already produced swimming robots that achieve propulsion by whole body undulations or tail flapping and robots that walk using multiple jointed legs to mediate locomotion. Inroads are even being made in flying robots that fly by flapping mechanical wings.

Professor Macmillan has focused his research on the Yabby’s powerful tail, and it has revealed some interesting implications for future robotic design.

‘The tail of the Yabby acts like a hinged lever, changing form to act as a sail for steering or a powerful paddle for swimming. The arrangement of muscles and nerves presents an interesting case study in biological solutions to problems associated with the dynamics and control of multi-jointed levers,’ explained Professor Macmillan.

‘Such levers could be useful in design of multi-jointed legs for mobility over difficult terrain, or in activities requiring precision lifting and leverage,’ he said.

To find how the Yabby controls its tail, Professor Macmillan’s group recorded the activity from individual nerve cell sensors in the tail called muscle receptor organs, while simultaneously recording the activity in the nerves and muscles that control each tail segment.

What they discovered was a feedback system for controlling complex movements that would prove useful, although Professor Macmillan said that neither he nor his team could establish what the yabby uses this system for.

‘The system works perfectly when isolated in a dish. But when we examine the system in a freely behaving animal to try and find out what the Yabby uses it for in its natural environment, the system behaves contrary to what we or an engineer might expect. In fact, the sensors hardly fire at all during movements initiated by the animal itself,’ said Professor Macmillan

‘The implications of these experiments are particularly pertinent if the interpretations are to inform or lead robotic design.

‘Evolution does not necessarily produce an engineer’s solution to an animal’s problem. It simply produces one that works, one that is selected because its features give the individual an edge – even a slight one – over its competitors in the game of survival.

‘Biomimetic researchers also need to be aware that animals carry design features that reflect their evolutionary history as well as responses to their present situation. When we dissect them we may find features and solutions that appear inefficient or counter intuitive. The human appendix is one example of this.

‘By studying invertebrates like the Yabby and its marine relatives, it may be possible to reverse engineer their neurological systems and build miniature, lightweight and autonomous robots capable of performing the range of complex tasks needed to explore Mars and beyond,’ he concluded.