dc motor control mouse ee 496 advisor: dr. tep dobry
Post on 22-Dec-2015
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TRANSCRIPT
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…Zzzzz
– 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 analog-digital 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 Chart21-May 10-Jun 30-Jun 20-Jul 9-Aug 29-Aug 18-Sep 8-Oct 28-Oct
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
“Because this is a design review, I will expect everyone to ask at least TWO questions sometime
during your session.”
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