8.10. Frame selection (student version)#
Written by Marc Budinger (INSA Toulouse), Scott Delbecq (ISAE-SUPAERO) and Félix Pollet (ISAE-SUPAERO), Toulouse, France.
8.10.1. Mechanical and Aerodynamic Functions of a drone structure#
The structure of a drone supports payloads (such as cameras, sensors and batteries) and distributes structural loads (such as weight, inertia and vibrations). For the purposes of this project, we will assume that the mechanical structure is primarily composed of carbon composite tubes. You can draw inspiration from formulas for the strength of materials (stress in beams under bending).
The drone structure also aims to minimise drag with streamlined shapes (e.g. tapered arms and enclosed fuselages) to reduce parasitic drag, and smooth surfaces to limit skin friction drag. Wing-like structures (for fixed-wing drones) generate lift. Blunt bodies (e.g. hemispheres or tubes) are dominated by pressure drag. Streamlined bodies (e.g. airfoils) are dominated by surface and lift-induced drag.
8.10.2. Design graph#
The following diagram represents the design graph of the frame selection.
Fig. 8.16 Airframe design graph#
Exercise 8.14
Give the main sizing problems you are able to detect.
Propose one or multiple solutions (which can request equation manipulation, addition of design variables, addition of constraints)
Orientate the arrows
Give equations order, inputs/outputs at each step of this part of sizing procedure
8.10.2.1. Sizing code#
import numpy as np
# Specifications
N_arm = 4.0 # [-] Number of arms
N_pro_arm = 1.0 # [-] Number of propellers per arm (1 or 2)
# Reference parameters for scaling laws
sigma_max = (
280e6 / 4.0
) # [Pa] Composite max stress (2 reduction for dynamic, 2 reduction for stress concentration)
rho_s = 1700.0 # [kg/m3] Volumic mass of aluminum
# Assumptions
D_pro = 0.3 # [m] Propeller diameter
F_pro_to = 15.0 # [N] Thrust for one propeller during take off
# Design variables
## To be completed
# Equations
## To be completed
%whos
Variable Type Data/Info
-------------------------------
D_pro float 0.3
F_pro_to float 15.0
N_arm float 4.0
N_pro_arm float 1.0
np module <module 'numpy' from '/op<...>kages/numpy/__init__.py'>
rho_s float 1700.0
sigma_max float 70000000.0
8.10.3. Lift and drag evaluation#
Based on the concept studied, propose a set of equations that can be used to evaluate the drag of your drone. Some concepts introduce wings or streamlined lifting surfaces. NACA profiles are standardized airfoil shapes developed by the National Advisory Committee for Aeronautics (NACA) to optimize lift, drag, and stall characteristics for aircraft wings. The 00xx notation (e.g., NACA 0012) defines symmetrical airfoils: “00” indicates no camber (identical upper/lower surfaces), and “xx” specifies the maximum thickness as a percentage of chord length (e.g., 12% for NACA 0012).These profiles are widely used in drones for their predictable performance and simplicity in symmetric flight conditions.
Resources that may be of interest for understanding or as reference data: