Researchers in the Faculty of Engineering of the University of Bristol, in England, in the UK, have developed a new technology to propel micro-uncrewed air vehicles (UAVs) which, like birds and insects, use flapping wings to fly. Any aircraft, no matter how small, that uses flapping wings to fly is technically called an ornithopter. A number of micro-UAV ornithopters have been developed and demonstrated in recent years, but all have used motors, gears and other complicated transmission systems to move their wings up and down.

The new technology developed at Bristol removes the need for these motors, gears and complex transmissions, thereby simplifying and reducing the weight of such micro-ornithopters. The technology is a new form of ‘electromechanical zipping’, which is a means of directly converting electrical energy into mechanical energy.    

Inspired by flying insects, particularly bees, the Bristol engineers have developed and successfully demonstrated a direct-drive artificial muscle system. (Artificial muscles are a category of new-generation actuators.) They have dubbed this system the Liquid-amplified Zipping Actuator (Laza). It moves the wings without needing any gears or rotating parts.

“With the Laza, we apply electrostatic forces directly on the wing, rather than through a complex, inefficient transmission system,” highlighted Laza study lead author and developer Dr Tim Helps. “This leads to better performance, simpler design, and it will unlock a new class of low-cost, lightweight flapping micro-air vehicles for future applications, like autonomous inspection of offshore wind turbines.”

By simplifying the design of micro ornithopters, Laza technology allows the miniaturisation of this category of UAVs down to the size of insects. The research team has demonstrated that the technology can provide consistent wing flapping for more than one-million cycles, establishing that it can provide endurance. They have also shown that a pair of flapping wings which are powered by Laza can deliver more power than insect muscles of the same weight. In fact, Laza delivers enough power to fly a micro-ornithopter across a room at a speed of 18 body lengths per second.

“Making smaller and better performing flapping wing micro robots is a huge challenge,” pointed out research team leader and Robotics Professor Jonathan Rossiter. “Laza is an important step toward autonomous flying robots that could be as small as insects and perform environmentally critical tasks such as plant pollination and exciting emerging roles such as finding people in collapsed buildings.”

Other potential applications for the new technology include environmental monitoring and missions in hazardous environments. The results of the research have been published in the journal Science Robotics.