program to find velocity of a UAV

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sayooj m 2011-5-9

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编辑： Jim Riggs 2019-8-7

hi

am in need of a program to find the velocity and acceleration of a solar powered unmanned aerial vehicle (UAV) with the following specifications :

Wingspan : 48 inches
Chord : 7 inches
Wing Area : 336 square inches
Weight : 750 grams(Fully loaded)
Motor : Brushless 2212/13
Battery : 11.1 V, 1800 Mah
Propeller : 9 X 6 Electric
RPM : 9-10,000
ESC : 18 A
Channels : Rudder, Elevator, Throttle
Materials : Minimal Balsa, Corrugated Sheets

could anyone please help? its for our final year project work..

thank you!!

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Guy Rouleau 2011-5-12

Start with F=m*a and build up on that...

Walter Roberson 2011-5-12

African or European? Carrying how many coconuts?

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Answer 1

Jim Riggs 2019-8-6

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编辑：Jim Riggs 2019-8-7

This is a fun problem (aircraft design). I guess it's OK to give an answer on this, since it was homework 8 years ago!

A quick method to get the velocity of a small, electric UAV is using work/energy methods as follows:

Start with the estimated power draw from the electric motor.

Now assume that the motor is 70% efficient in converting electric power to shaft power.

A typical hobby size propeller is 70% efficient in converting shaft power to thrust. So the available power for thrust is ~50% of the electric power consumed.

This thrust is working against the aerodynamic drag. There are two primary sources of drag: Induced drag, and skin friction. The induced drag is an artifact of creating lift. It will be determined based on the wing loading (Weight/Area) and the Wing Geometry (for rectangular wing, this is mainly the aspect ratio (Area/Chord length). Using aerodynamic design tables, you can obtain an estimate for the induded drag and the skin friction drag (in terms of drag coefficient). The Drag force is = 1/2 (air density) (Drag ciefficient) (Wing Area) (Velocity)^2

Energy dissipated by drag = Drag Force x Velocity = (1/2 rho Cd A) V^3

Set the dissipated energy (Drag x V) equal to the thrust power available and solve for V. This is the horizontal speed of the aircraft at the specified electrical power consumption.

An aircraft design table will give reasonable estimates for drag values. Similarly, you can get the actual power consumption of your motor from the manufacturer or from a test bench. Some propeller manufacturers will likewise publish performance data for their products.