Flying drone may be fun; designing them is a real engineering challenge. Drone design requires integration of many engineering branches such as solid mechanics, fluid mechanics, applied mathematics, control systems, automation and data analysis. We have already discussed the basics of drone design in another article. So without further ado, let’s explore the various engineering domains, and the software that is needed for drone design.
Drone Design
It all starts with the purpose. The design of drone primarily depends on its ultimate use. Unmanned air vehicles (or UAVs as drones are formally called) can now be seen in many applications ranging from domestic to scientific, industrial to entertainment and from research to military. Concept generation involves the initial level of design study and development of the drone structure. It can range from configurations that includes fixed wing, drones with multi rotors, adaptive wing, etc., and include both remotely piloted and autonomous modes of operation. The requirements for drones that do surveillance are different from drones that are used for video shooting, and drones that are used to deliver parcels have different requirements than drones that are used for amateur racing. As a result, there are many classes of unmanned air vehicles in existence, and many types within each class, developed by various manufacturers. Many of today's drones are capable of carrying some form of payload. In addition, most drones carry some sort of sensors (including camera sensors), and of relaying this sensor information to the ground is one of the primary purpose of drones.
Design Analysis
Drones include advanced technologies and their production cuts across several engineering disciplines that include mechanical, aeronautical, system control, electrical engineers and computer software. Drone design analysis begins with pre-processing, structural analysis, aerodynamic and stability analysis to evaluating various dynamic 'what if' scenarios. After the CAD files of the initial design are available, engineers take it for detailed validation. During the structural analysis phase, the drone structure is subjected to various forms of operational loading. Understanding the structural performance is the key to take the design development forward. The various dynamic scenarios carefully analyze the effects of adverse flight conditions, as well as probable human error in handling the drone. The drone material is typically composite, and even that needs to be modelled layer-by-layer using laminate modelling approach.
Fluid Dynamics
Fluid mechanics is the study of fluids and how forces affect them. Fluid dynamics is one of two branches of fluid mechanics that studies the motion of fluids (both gaseous and liquid). Engineers can create energy efficient drone designs that optimize air flow by making smarter choices on the form, speeds, and materials of their designs. Energy is required to move objects through fluids, for example a ship sailing in the sea. To improve aerodynamics and use less energy, engineers need to work on reducing the drag coefficient. The drag coefficient is a number that is used to model all of the complex dependencies of shape, weight, and flow conditions on a drone (or any other object that navigates through a fluid). Computational fluid dynamics (CFD) simulations can help engineers optimize designs by helping them to better understand how the design will interact with fluids. Drones fly through air and their aerodynamics matter a lot in their performance. Their range and endurance depends much on the structure and shape of the propeller. CFD simulation of drones is therefore necessary to optimize its design.
Control System for Flight Controller
Drones are controlled by a flight controller. It can be considered as the brain of the drone. A flight controller consists of an electronic circuit board and a variety of sensors that detect the movement of the drone. Primary among them are gyroscopes and accelerometer. The electronic gadgetry sees to it that the drone responds to user commands, which includes altitude, speed, and direction. A properly designed controller helps the drone operator with smoother movements and stability.
Multibody Dynamics
Drones are controlled by changing the rotation rate of one or more rotor discs in order to change its torque load and thrust / lift. Multibody dynamics is the analysis of such mechanisms that consist of interconnected rigid and deformable components. The dynamics of these large-scale multibody systems are highly nonlinear, and require numerical solutions that are possible using computer-based techniques. A multibody dynamics simulation helps in getting insights about the dynamics of the drone.
Embedded Systems
Drones are typically unstable dynamic systems. Embedded systems are used to pilot them using sensor data from the drone that includes position, orientation, or any other sensor essential for the successful completion of the task that it is supposed to perform.
Motor System
Motors are what provide thrust power to a drone. Motor design includes pre-design and detailed analysis of the motor system. The pre design of a motor is carried out by evaluating the machine design by choosing topology, winding architecture, coil composition, material, air gap, etc. And of course, the size of the motor depends on the drone frame size and the thrust to weight ratio. The torque, speed, current generated and magnetic flux of a drone motor is determined by detailed electromagnetic analysis.
Drone Design Software
We have covered the principal aspects of drone design. As can be seen from an engineering perspective, drone design needs domain knowledge of aerodynamics, fluid mechanics, material science, embedded software and system controls. Since drones are subject to highly volatile conditions like temperature, fluctuations in pressure, wind currents, etc., it is not feasible to provide proper simulation solutions using simple mathematical tools. Finite element analysis (FEA) and CFD is useful for such problems that involve complicated geometries, loads, and material properties where analytical solutions cannot be obtained. As mentioned above, CFD is the analysis of fluid flows using numerical solution methods. Using CFD, engineers are able to analyze complex problems involving fluid-fluid, fluid-solid or fluid-gas interaction. The aerodynamic loads on the drone rotors / blades are calculated using CFD tools. Altair, which is a leading engineering simulation software provider, has many tools in its arsenal that provides good FEA and CFD simulation software for drone design. While there are many software available in India and elsewhere for drone design, simulation software like Inspire™, HyperMesh™, OptiStruct™ FEA, Radioss™, Multiscale Designer™, AcuSolve™, Activate®, MotionSolve™ and Embed® are preferred by drone design companies for their reliability and efficacy.