Electromechanical effects ensure the flapping of wings: Researchers have developed a clever drive system for fluttering flying robots that does not require conventional motor and gear technology. The lightness is not at the expense of the performance: the system can carry insect-like flying robots powerfully and energy-efficiently through the air, tests show. The developers say that the uncomplicated drive concept could pave the way for smaller, lighter and more effective micro-flying robots for environmental monitoring or rescue work.
Propeller-driven drones are currently dominating developments in small aircraft. In addition, however, there are already approaches that are more based on the model of flight technology in nature. Flying robots with flapping wings can also offer some advantages in certain application areas. Above all, very small devices, which are cheap for some purposes, can benefit from the system: With flapping wings, they achieve better maneuverability and flight stability and, in addition, operation is very quiet compared to propellers.
So far, however, there has been a catch with the technical solutions: The wings of micro flying robots are usually set in an up and down motion by motors, gears and other complex transmission systems. These concepts are associated with technical complexity, energy losses, weight and undesirable dynamic effects. The drive system thus puts a strain on the previous designs and, above all, significantly limits their ranges.
Direct instead of indirect power transmission
In order to develop better solutions, scientists working with Tim Helps from the University of Bristol have once again looked to nature as a model. In biology, as is well known, there are no cogs or rotating gear parts – instead, muscles ensure the movements of the wings. Based on bees and co, the researchers have developed a kind of artificial muscle system that can provide beating movements in an innovative way. Instead of rotating parts and gear elements, the so-called Liquid-amplified Zipping Actuator (LAZA) uses electrostatic forces to trigger the upward and downward movements. “The forces are converted directly into wing movement and not via a complex, inefficient transmission system,” says Helps.
The wing base of the LAZA system forms a negatively charged electrode rod. It lies embedded between two outwardly curved electrodes. If these now alternately receive a negative or positive charge, the wing rod in the middle is deflected upwards or downwards by the respective forces of attraction. The effect is enhanced by a drop of liquid dielectric in the base of the wing. By adjusting the frequency of the gas exchange, an impact effect can be set at different speeds.
Lightweight, uncomplicated and yet powerful
To show that this system can effectively set a wing in motion, the researchers built a dragonfly-sized prototype of a micro-flying robot: They attached transparent plastic wings to the beating LAZA elements. Evaluations of flight tests with this micro flying robot then showed: The LAZA concept can even give a flapping wing more power than insect muscles of the same weight. The researchers report that the energy-saving drive was able to propel the micro-flying robot through the air at 18 body lengths per second. The system is apparently also robust: It beats evenly and reliably even in continuous operation.
The LAZA system could now become a fundamental building block in the development of autonomous, insect-like flying robots, say the scientists. “It enables performance in a simpler design. So it could give rise to a new class of low-cost and lightweight micro-flying robots for future applications,” says Helps. Senior author Jonathan Rossiter from the University of Bristol continues: “LAZA is an important step towards autonomous flying robots that can be as small as insects. For example, they could pollinate plants at one point or perform tasks such as finding people in collapsed buildings.”
Source: University of Bristol, professional article: Science Robotics, doi: 10.1126/scirobotics.abi8189
Video © Dr Tim Helps/ University of Bristol