Samueli School of Engineering

Background:   Vibrational stability is a natural phenomenon where a system if vibrating at sufficiently high frequencies, can bring itself back into a stable state if perturbed. This is akin to the high frequency flapping that hummingbirds and insects employ to maintain a hovering position and fly. Micro Air Vehicles (MAV) are a subset of air vehicles that have a size restriction and are commonly used for commercial, military, and reconnaissance purposes where larger devices are not feasible. With the idea of combining vibrational stability with micro air vehicle restrictions, we aim to study and manufacture a mechanism capable of producing this flapping motion and conduct performance testing to compare a manufactured “quadflapper” with more conventional quadcopters/drones. Preliminary performance testing between a “quadflapper” utilizing a passive pitching, flapping mechanism found in a toy [insert name of toy] and a similar set-up that replaced the toy mechanism with propellors was conducted. These two set-ups differed only in their lift mechanism and a circuit board. The quadcopter had a mass of 57.51 grams and an operating time of 8 minutes whereas the quadflapper had a mass of 53.97 grams and an operating time of 6 minutes. By performing a simple lift experiment with incremental weight added to a load, we found that the quadcopter set-up could produce 119.42 grams of maximum lift while the quadflapper produced 103.32 grams. This showed that the quadcopter was able to produce more lift and maintain a longer operating time despite its heavier base mass. However, the quadflapper responded much better when faced with physical perturbances during testing such as obstacle collisions. In most cases, it was able to fix itself and maintain steady flight afterward which shows that could potentially be employing vibrational stability to correct itself without any feedback. Further experimentation must be done to quantify this otherwise inadequate measure of relative stability and maneuverability. Furthermore, we are also working on the design and manufacturing of an active pitching mechanism. The “toy” mechanism currently on the quadflapper employs passive pitching which means that only the top portion of the wing is being moved. The lower portions are affected by wind and air flow, so the pitching angle is also dependent on these factors. A new design must control both the top and bottom portion of the wing to create an active pitching angle. To create the flapping motion, we designed and modified linkages to be actuated by a crankshaft and electric motor system. The wings are then attached to the system of linkages. Two similar systems of linkages are located above and below each other, which creates the control of the pitching angle. This will reduce the effects of air flow and provide more control and lessen the variability of the flight. Future progression in the design portion of this project is focused on the redesign of the toy mechanism to employ an active pitching angle and redesign and modification of a Université Libre de Bruxelles (ULB) design. The current ULB redesign employs a motor-driven central shaft that drives a top and bottom crankshaft to control their respective portions of the wing. Mathematically, the system identification team has been working find the equations of motion and forces relevant to a model of hummingbird flight. This has evolved into the creation of a testing rig to visually record the airflow around the wings of a single flapping mechanism. A better understanding of the mathematics, physics, and fluid dynamics of the flapping system may prove useful for further optimization of the quadflapper and flapping designs in general.