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DC Motor Control
mouse
EE 496
Advisor: Dr. Tep Dobry
Team Members
• Ikaika Ramos
– Overall Project Manager
– Chassis Fabricator
– Hardware Specialist
• Aaron Tsutsumi
– “Jack of All Trades”
– Algorithm Constructor
– Software Innovator
Brief Overview
• Another Micromouse…Zzz
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– Abide by all IEEE Regional 6 Micromouse
Rules
– In response to last years Regional 6 Winner
• Propulsion Design Difference
– DC Motors
– Control Method
Block Diagram
Power Supply
• Chose to use lithium polymer
batteries over nickel-metal
hydride because of higher
energy density
– Higher energy density = Smaller
size, less weight
• Using switching voltage
regulators because of high
efficiency
– Decided to use a self-contained
package to avoid having to
calculate values for external
components and to keep size
small.
Sensor System
• Used same components as
our previous mouse since
we were familiar with it.
– Sharp GP2D120 sensors and
Maxim MAX114 analogdigital converter.
• Decided to use a different
sensor configuration.
– Using four sensors instead of
three, two outer sensors on
outside point straight
forward to help align during
a 45 degree run.
Motor Control
• PWM
– We chose to use Pulse Width Modulation to control the
speed of the motors because it is simple to implement.
• H-Bridge
– H-bridges will be used to control the direction of the
motors.
• Encoders
– We chose to use optical encoders to help determine the
position of our mouse.
PWM
• A pulse-width modulated
signal is a rectangular
waveform with a varying
duty cycle.
• A longer duty cycle means
the voltage is on for longer
and the average voltage
applied to the motor is
higher and vice versa.
• Will be implemented using
the PWM generator on our
microcontroller.
H-Bridge
• DC motors only have two leads.
The direction it spins is
determined by which terminal
has power applied and which is
connected to ground.
• An H-bridge consists of four
switches (in our case BJTs) and
depending on which two are
closed, allow the motor to
operate in either direction
• We chose to use an L298 chip
from STMicroelectronics
because it has two H-bridges in
one package.
Encoders
• We decided to use optical
encoders over accelerometers.
– Accelerometers were harder
to implement, and may not
have been accurate enough.
– If the mouse was not
accelerating or decelerating,
we would have had to
assume and calculate our
position
• The optical encoders give us a
more definite position reading.
• We chose the HEDS-9100
encoders because of size
limitations.
Microprocessor
• Rabbit 3100 Core Module
– Uses a Rabbit 3000 microprocessor.
• Software P.I.D Controller
– A software Proportional-Integral-Derivative
controller is a feedback system that will allow
us to more accurately control our system.
Rabbit 3100
• We chose the Rabbit 3100
over other
microprocessors.
– Other models we researched
would have been harder to
implement.
– Chose the Rabbit 3100
because we could reuse our
programming cable and it
had pulse-width modulation
capability.
– Also found that it had
quadrature decoders which
help us to use the encoders.
Software P.I.D. Controller
• Motors are not a digital type of device. A sharp change in
voltage level doesn’t instantly change the speed of the
motor. We have to take this time constant into
consideration.
• We will use a PID controller to fine-tune the operation of
our motor.
• Takes readings and calculates an error value.
• Tries to get the system to settle at the correct value as
quickly as possible.
• A PID controller modifies the error signal in three ways to
determine the best correction.
• Still needs to be implemented and fine-tuned…
Proportional – Integral – Derivative
• The proportional part of the modification is simply
multiplying the error signal by a constant to adjust for the
current error.
• The integral part of the modification is multiplying the
error signal by the result of an integral to adjust for error in
the past that hasn’t been corrected yet.
• The derivative part of the modification is multiplying the
error signal by the result of a derivative to try and predict
the future error correction required.
• The sum of these corrections (once the constants have been
fine-tuned) should be a system that reaches an accurate
steady state as soon as possible.
Tracking, Mapping, Solving
• Using old code,
modified for this
mouse.
• Plan on possibly
implementing different
solving methods.
• Plan to implement a
few modified flood-fill
(Bellman) algorithms
What remains to be done…
•
•
•
•
•
Connect PCB board to external modules
Programming the mouse
Fine-tune PID controller
Troubleshooting / Debugging
Write up our 30 page paper
Gantt Chart
21-May
Research Parts
Research Software Implementation
Get Samples of Parts we can Get Samples For
Order Parts not Being Sampled
Test Microprocessor/Microcontroller
Test Motors/PWM
Test Encoder
Test Batteries
Test H Bridge
Build Chassis
Design Circuit
Assemble Circuit
Implement Straight Movement
Implement Turns
Implement Alignment
Implement PID
Tune PID
Final Troubleshooting/Debugging
Paper Write-Up
10-Jun
30-Jun
20-Jul
9-Aug
29-Aug
18-Sep
8-Oct
28-Oct
“Because this is a design review,
I will expect everyone to ask at
least TWO questions sometime
during your session.”