Engine Speed Control for HMMWV

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Engine Speed Control for HMMWV
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Members

• Faculty Advisor Industrial Advisor
• Dr. Marshall Molen Mr. Dan Harkins
  Picture Unavailable
• Team Members
• Team Leader
• Daniel Kennedy Patrick
  McNally Catalina Olarte
  Jarrod Fortinberry
  Overcurrent Protection Stepper Motor
  Research Website Design
  Research Signal Processing
  Power Electronics
  Simulations Microcontroller
  Interface

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Overview

• United States Army wants to deploy high-power
  intelligence gathering equipment in remote areas
• Integrating these systems into Humvees would
  allow remote deployment
• Problem
• Humvee is unable to supply required power at idle
  speeds
• Effects
• Load does not receive required power
• Increased wear and tear on the engine

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Initial Questions

• How to measure RPMs of the engine?
• How to measure electrical load?

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RPM Signal

• Magnetic Sensor on Flywheel
• Time-Consuming Installation
• 138 Pulse Per Revolution
• 2V-4V pk-pk sin wave
• Alternator
• Easy Access for Installation
• Only 16 Pulses Per Revolution
• 28 V pk-pk square wave

• Chosen to meet design constraints of
• Tachometer accurracy of /- 0.5
• Installation time of 2 to 4 hours by mechanic

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Electrical Load
Load Current ltlt Maximum Alternator Current
Load Current lt Maximum Alternator Current
Load Current gt Maximum Alternator Current
Field Current
Alternator
Load
Battery
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Load Measurement Options

• Load Current
• Direct measurement of load
• Large amounts of current
• Battery Current
• Smaller Current
• Fluctuates rapidly if RPMs are inadequate for
  load
• Field Current
• Possible indicator of load
• Alternator manufacturer recommended against using
  field current

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System Overview
Actuator
PIC
User Interface
Load Current
RPM Reading
Engine / Alternator
Battery
Load
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System Specifics
Load Current
Tach Signal
DC Current Probe
F/V Converter
Microcontroller
H-bridge
Stepper Motor
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System Overview
Actuator
PIC
User Interface
Load Current
RPM Reading
Engine / Alternator
Battery
Load
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Actuator

• Links Mechanical Part of Project with the
  Electronic Part
• Hybrid, Bipolar Stepper Motor
• 12 V, 0.4 A, 2-phase motor
• Driver circuit must be used to supply ample
  current
• Driver circuit must be able to drive positive and
  negative current through the motor (H-bridge
  circuit)
• Electromagnet
• 12 VDC
• Attached to stepper motor moves the throttle
  cable

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Actuator
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System Overview
Actuator
PIC
User Interface
Load Current
RPM Reading
Engine / Alternator
Battery
Load
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Processor

• Chosen to meet design constraints of
• Controller Accuracy /- 3.0
• Total component cost of less than 600

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System Overview
Actuator
PIC
User Interface
Load Current
RPM Reading
Engine / Alternator
Battery
Load
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User Interface
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Simulink Schematic
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Simulink Results
Simulated Load vs Time
RPMs vs Load
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Problem 1

• RPM reading from the alternator must be converted
  into RPMs for engine. But what if the engine to
  alternator pulley ratio is different?
• Solution
• Add potentiometer to F/V circuit to allow Army
  mechanics to calibrate the system.

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Problem 2

• Stepper motor does not have enough torque to
  operate the throttle.
• Solution
• Use current chopper to drive the stepper motor
• Drives the stepper motor at maximum current
  regardless of motor speed

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Test Data
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Cost Summary
Design constraint Cost of Parts lt 600
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What Works

• Manual mode functions correctly up to 1300 RPMs
  with average stabilization time of 12.5 seconds
• Auto mode has been successfully tested with loads
  of up to 250 A

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What Doesnt

• The controller is unstable at RPM values over
  1300 because the throttle is more sensitive and
  the stepper motor does not provide enough
  resolution

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Senior Design II Goals

• Improve stability at higher RPMs through use of a
  longer lever arm or by micro-stepping the
  stepper motor
• Improve stabilization times
• Design packaging

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Acknowledgement s

• Dr. Marshall Molen
• Evan Burnett
• Bill Buchanon
• Josh Lofton
• Angela Card
• Robin Kelley
• Dan Harkins
• Dr. Picone

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Questions??
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References

• P.C. Sen, Principles of Electric Machines and
  Power Electronics, John Wiley Sons, New York,
  New York, USA, 1997
• National Materials Advisory Board, Use of
  Lightweight Materials in 21st Century Army
  Trucks, National Research Council of the
  National Academies, Washington, DC, 2003.