Calculate Your Payload Capacity
One spec that every UAV designer has to define is the payload
capacity. This is the dierence between the aircraft’s total lift
and its all up weight (AUW). The AUW is exactly what it sounds
like: the weight of the aircraft as it is outfitted for flight, with
motors, battery pack, computer, and so on. Now that we under-
stand how to calculate our total lift, we can weigh all of our
components to find our AUW and determine our aircraft’s pay-
load capacity.
Electronic Speed Controllers
Electronic speed controllers (ESCs) are small electronic circuits
that are used to independently control the speed and direction
of each motor on our quad. Four ESCs are installed on our air-
craft, each designed
specifically for use with brushless motors.
They work by converting power from the main flight battery into
a sequence of electrical signals that are sent across three dier-
ent wires to the brushless motor. That sequence controls the
speed, rotation, and even braking ability of the motor. The
required speed for each motor is communicated to each ESC
from the flight controller. We will have more on that in the next
section.
Classification: Amps and volts
There are generally two main specs you need to look for when
buying ESCs: amperage and voltage. The number of volts an
ESC is rated for determines what size battery you can use with
the ESC (we will discuss batteries in more depth in “Flight Bat-
tery” on page 50). For now, we will just point out that the unit we
will be using in our example is a three-cell battery rated at 12.6
volts. Remember the motor spec sheets we mentioned while
discussing total lift? Those same specs generally contain the
current draw in amps as well. That information is what you use
to determine what size ESCs you need for your desired motor
and props.
Power Train 49
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