Page 17 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

xvi P r e fa ce

Truly understanding how a quadcopter flies was my reason for including Chapter 2,
which covers basic flight aerodynamics. Make no mistake; quadcopters are governed by the
same flight principles that apply from the Wright brothers’ “Flyer” to the ultramodern F-35
Joint Strike Fighter ( JSF). As a real pilot, I thought it was important that readers understand
how the quadcopter can be made to fly and what aerodynamic forces are constantly in play
while it is flying. Along the way, I threw in a “little” math in terms of proportional-integral-
derivative (PID) theory to provide a basis for understanding the control protocol or algorithms
that are needed to keep the quadcopter in a steady flight pattern.
Chapter 3 contains all the build instructions for assembling and configuring the Parallax
Corporation’s Elev-8 quadcopter kit. Go no further than this chapter if you simply want to
read an expanded set of assembly instructions. However, I expect my readers to be far more
interested in what makes up the quadcopter system and will read on. I promise you that you
will not be disappointed.
The Propeller chip supplied by Parallax is the heart of the quadcopter flight-control
board. Chapter 4 explores what constitutes this fantastic technology and how you can learn
to program this chip to perform the experimental functions you can invent and desire to test.
I also introduce and explain the concept of pulse-width modulation (PWM), which is an
integral technology needed to control the quadcopter.
Chapter 5 covers all the propulsor components that make up larger-scale quadcopters,
including the motors, electronic speed controllers (ESCs) and the propellers. All of these are
essential parts of the quadcopter’s propulsion system, and it is very important that you
understand what limitations and constraints apply to each of them. “Overtaxing” your
motors will cause the quadcopter to fail, and probably at the worst time possible.
The next chapter covers radio-controlled (R/C) systems. Don’t worry, you will not be
required to build your own; however, I do want you to understand why certain R/C systems
are so much better than others that are normally much less expensive. I make the case that it
is a wise investment to acquire a high-quality R/C system to ensure that you maintain
positive control over your quadcopter at all times. There are many inexpensive systems
available, and while they may be satisfactory for toy systems, they really are not suitable for
a relatively expensive and larger-scale quadcopter like the Elev-8. I also show you how to
program a Parallax development board to measure certain key signals that transmit from
your R/C system.
Chapter 7 covers R/C grade servos, which is a bit odd, as the basic Elev-8 kit does not
contain any servos. I included this servo chapter to ensure that you are well acquainted with
this technology, as these devices are used extensively in “regular” R/C aircraft and also in a
modification to the Elev-8 for controlling the tilt of an onboard video camera. I also show
how to build an LED-flasher circuit that takes advantage of a spare servo channel that is
available on the quality R/C transmitter.
GPS is covered in Chapter 8, in which I start with what I hope is a good, but brief,
tutorial on how GPS functions and how it could be used in conjunction with quadcopter
operations. I also show you how to build a real-time GPS data-reporting system, using XBee
technology to transmit data from the quadcopter to a ground control station (GCS).
Theoretically, you could control the quadcopter using the transmitted GPS coordinates well
beyond the R/C operator’s line-of-sight (LOS); however, I strongly do not recommend this
mode of operation.
I discuss airborne video systems in Chapter 9, as that is truly a hot-topic item with
regard to quadcopters. Two types of video systems are shown, one which provides high-
quality, wide-angle views, and another which is much lower quality but still more than
adequate to be used with video-processing software, which is also discussed in the chapter.
Although not mentioned in the chapter, I do want to acknowledge that I have been involved