This paper describes the development and testing of an EAP (electroactive polymer) actuator for driving the wings of an MAV (micro air vehicle). Creating the drive system for a flapping MAV is extremely challenging because of the required combined bending/twisting of the wing during flapping. Silicone-based DEs (dielectric elastomer) were used for the actuator material. In addition, the EAP actuators were operated at resonant frequency which is an important means of producing optimal flight performance with reduced power consumption. The paper presents the optimisation of the structural and operational performance of the EAP actuator. The paper also presents the test results of the actuator driving an actual MAV wing.

There are several analogies of mechanical design between the bicycle and nature. The coasting ability of a bicycle is analogous with the coasting ability of birds ; the chain transmission has an analogy with the four-bar linkage in bird wings; the spoke-rim wheel layout has analogies with natural structures; and the tyre is analogous with some of the shock absorbing structures in animals. Comparing optimal design in the bicycle and nature demonstrates that the bicycle is very effi cient as a transport machine and as a structure. However, one key difference with nature is that coasting animals like birds avoid steep gradients by fl ying on a level course or by using thermals to gain altitude. Analysis of the energy demands of cycling show that uphill cycling has a major negative impact on journey times and energy effi ciency. Investing in dedicated cycle paths in order to avoid steep gradients could signifi cantly increase the take-up of cycling and this would have signifi cant long-term environmental advantages.