Harnessing elastic instability for power-amplification

While large animals are able to use muscles to run and jump in real-time, the power limitations of muscles at small scales mean that small creatures such as insects cannot use muscle in the same way. Despite this, the impressive jumping capabilities of insects such as the flea and locust are well known. These insects manage this feat by slowly using their muscles to store energy before releasing it suddenly to give rapid motion. This is analogous to how an archer uses a bow and arrow and is an example of 'power amplification': even doing work slowly can give rise to high power if the energy is stored slowly but released quickly.

In the example of the archer it is clear that the energy is stored in the stretching of the bow string; moreover, the vast majority of the elastic energy stored in the bow string is converted to the kinetic energy of the arrow. For insects, however, the storage and release mechanisms are not so clear, with a variety of different mechanisms proposed. Nevertheless, many engineers are developing robots that exploit similar elastic mechanisms to actuate rapid motion and thereby jump or catch falling objects.

In this proposal, we will use mathematical modelling to understand how the potential of power amplification can be harnessed in a class of insect-inspired, jumping robots. This model system has the advantage that the different components can be directly observed and controlled by our collaborators, allowing us to understand how they operate. By comparing the results of mathematical modelling with experiments performed by a collaborator, we seek to understand whether mechanisms based on 'snap-through' are in some senses 'better' than simple springs. We will also understand the key role that the geometry of the substrate that is jumped from plays with the effectiveness of these jumps.