Analyzing and Calibrating Precision Controls on U.A.V.’s
Oscar Camacho and Jordan Gonzalez
Engineering Department, Hartnell College, Salinas, CA 93901
Dr. Mark Karpenko, NSRC Research Fellow, Control and Optimization Lab
Abstract
Method
In today’s world of advancing technology,
unmanned aerial vehicles (UAV’s) have become an
essential tool for gathering information. They have
been used for a variety of functions, such as remote
sensing, commercial and military aerial surveillance,
transportation, and scientific research. The goal of
project was to test a new autopilot device that will be
used on UAV’s. Two experiments needed to be
designed. One involved designing and building a
one-axis, free-swinging pendulum to hold a UAV and
collect data of pitch and roll. The other experimental
set up involved a controlled rotation rate table to
collect data for yaw. Both experiments included
microcontrollers and analog systems to control the
apparatus and display relevant system information.
Both experimental setups were completed and
tested according to specifications, however time did
not allow collection of data.
One of the first thing that was done was
getting familiar with embedded C coding so that
programming the microcontrollers’ would not be such
a difficult task. The essential programming
information (tutorial of embedded C along with a
code template to follow) had to be learned. The next
step was to program the PIC18 microcontroller to
manage the two experiments
Picture 1:
Jordan with UAV in the Center for
Autonomous Vehicle Research
(CAVR)
Picture 2:
Oscar and UAV in the CAVR
The pendulum set up was successfully
constructed. It was tested to make sure it was one
directional and free swinging. The encoder was
integrated into the set up. Minor changes were
made at the end to improve sturdiness of
apparatus.
Figure 1:
Microchip PIC18f45k20 board,
PICkit 3 Debugger, and MPLAB
IDE program software.
The pendulum was assembled by cutting the 2x4 to
the desired length. The next step was to drill holes in
the correct position on the 2x4 so that it will
correspond with the holes located on the pillow block
bearings. Next, each pillow block bearing was
fastened to a 2x4 in order to mount it to an A frame.
The PVC pipe was constructed in a “T” shape so that
the top ends of the pipe may be inserted and fixed
into the pillow block bushing. The remaining bottom
open end of the PVC pipe that was not attached to
the bushings was used to mount the airplane
harness to the pendulum. The harness was created
by cutting out pieces of plywood to specified
measurements.
Conclusion
Results
Picture 4:
Oscar assembling the
Pendulum experiment
The harness allowed the UAV to be mounted
in two different orientations during testing. It was
interfaced with the pendulum through angle brackets
that allowed the harness to be securely attached.
The plywood used was less than a quarter of an inch
to reduce the weight added to the UAV during
experiment.
Picture 5:
The UAV in harness
mounted on
Pendulum in pitch
testing position.
Materials
The UAV experiments incorporated mechanical,
electrical, and computer software components and
thus required a significant planning component. The
completed work spanned the full project cycle of
initial system requirements gathering, design and
prototyping using SolidWorks and other tools, parts
acquisition, construction (mechanical and software),
implementation, and testing. Both experimental
setups were completed and tested according to
specifications, however time did not allow collection
of data. The project will continue at NPS. The
information gathered will help other students and
researchers calibrate and improve the autopilot
devices that will go on future unmanned aircrafts.
Literature cited
Bates M, PIC Microcontrollers An Introduction to
Microelectronics, 2nd ed., Elsevier; 2004
Rorabaugh B, Mechanical Devices for the Electronic
Experimenter, Pennsylvania, McGraw-Hill Inc.;
1995
Microchip Database [Internet]. 2010 United States of
America: Microchip Technology Inc.[cited 2012
July 13]. Available from:
http://ww1.microchip.com/downloads/en/deviced
oc/41303g.pdf
Acknowledgments
For the pendulum design we used: two pillow
block bearings, some clamps, a cedar 2x4, PVC
pipe , PVC glue, plywood and a bracket for the
mechanical setup. The circuitry setup we used was a
PIC18 microcontroller, an absolute encoder (electromagnetic position), and a radio transmitter .
The materials we used for the rotation table
design was: ½” thick plywood, a PIC18
microcontroller, an optical encoder, and a LCD
screen.
Picture 3:
Jordan finalizing the
components for rotation
table. .
Figure 2: Dimensioned
drawing of UAV harness (Solid
Works). Completed harness
holding UAV at right.
The assembly of the actual harness was tricky
because the plane has to be completely enclosed
within the harness so it will not slide around.
The circuitry used to determine the angle of the
pendulum consists of a PIC18 microcontroller and
an absolute encoder. The microcontroller logs the
pendulum angle for reference to the inertial sensor
used to measure pitch in the UAV.
The encoder needed to be absolute (1 degree
precision) so it could use the relationship between
the encoder value and the physical position of the
UAV. The encoder accurately records changes in
position. The initial position is set at assembly.
Thank you to Dr. Mark Karpenko and Mr.
Robert Casey. Thanks to Brad Watanabe and David
Mann for programming assistance. Thank you to
Kelly Locke, Andy Newton, and Joe Welch of Hartnell
College. This internship was funded by a Title V
Strengthening Transfer Pathways Grant.
Figure 2:
The absolute
magnetic encoder
(www.usdigital.com)
The controlled rotation rate table was made
by making a plywood platform to serve as a base
on which to mount a bearing to support a turntable
that spins with minimal friction.
For further information
Picture 6:
The UAV connected
to pendulum in vertical position.
Figure 3:
Example of digital signal from
an absolute magnetic encoder.
Please contact p.rockmonkey@yahoo.com or
camachoo1399@student.hartnell.edu
More information on this and related projects can be
obtained at
http://nps.edu/Academics/Institutes/Cebrowski/STEM
/CommunityCollege3C.html