Deployable Tactical Aircraft Training Simulator D'T'A'T'S'

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Deployable Tactical Aircraft Training Simulator
(D.T.A.T.S.)
Group 9

• Sponsored by

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GROUP 9Group Members

• Michael Geary (EE)
• James Lewis (EE)
• Guy Maness II (EE)

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WHAT IS D.T.A.TS

• Program developed for military
• It is not a true flight simulator
• Tool used to introduce pilots to surrounding
  environment, familiarize them with potential
  mission targets
• Enable rehearsal of various aspects of mission
  including details such as terrain, weather
  conditions etc.

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D.T.A.T.S PHYSICAL SPECIFICATIONS

• Trainer needs to be deployable and easily
  transportable
• Must be capable of operating under harsh
  conditions
• Able to be reconfigured to simulate multiple
  tactical aircraft (Currently based on F/A-18
  Hornet)
• Must give realistic behaviour and feedback to
  trainee
• Should be modular in design to facilitate
  maintenance
• Adequate and accurate documentation must be
  provided to operate and support system

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EXISTING D.T.A.T.S SYSTEM

• PC platform(2 PIII 600 Mhz processors)
• F/A-18 Hornet flight stick and throttle
• Four Neuro Logic systems flat panel monitors
• Pacific Scientific servo motors and controllers
  to implement force feedback
• Smart-UPS 300 RM5U
• Microsoft flightsim 98 and Windows 98 SE

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NEW COMPONENTS PROVIDED BY SENIOR DESIGN 2000
TEAM

• Mechanical Flight Stick designed by ISM
• Designed to provide realistic flight feel
  based on typical flight dynamics
• Sola power supply rated 10 amperes at 12 volts.
• 5 volt logic power supply
• Two stepper motors Part M2-3437-S
• Group built stepper motor driver system with
  gameport to USB conversions component.

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Existing System Block Diagram
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GROUP 9 SENIOR DESIGN 2000OBJECTIVES

• Create OPERATIONAL prototype
• Improve and upgrade flight operators controls
  (ie. Flight stick, throttle, rudder)
• Provide functional force feed back flight stick
  resistance (real feel flight experience)

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SENIOR DESIGN 2001 ACCOMPLISHMENTS

• Improved Flight Operators Controls Gameport to
  USB conversion
• Functional Flight Stick Force Feedback

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FLIGHT CONTROL DEVICES OBJECTIVES

• RESTORE AND IMPROVE FUNCTIONALITY
• QUICK AND ACCURATE RESPONSE TIME
• DURABLE
• CAPABLE OF OPERATING UNDER HARSH CONDITIONS
• EASILY INTEGRATED INTO DTATS MISSION TRAINER

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Methods For Improving Flight Controls

• Redesign mechanical flight stick design
• Improved flight stick position sensing
• Conversion from gameport to USB device

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Mechanical Flight Stick Design

• Designed for us by ISM inc.
• Easily integrated into existing DTATS platform
• Accurately represent flight Dynamics
• Compatible with both our design for flight stick
  force feedback and flight stick position sensing
  methods

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Mechanical Flight Stick Design
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Mechanical Flight Stick Design
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Mechanical Flight Stick Design
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Flight Stick Position Sensing
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Flight Stick Position Sensing

• Potentiometers
• Hall Effect Sensors
• Optical position sensing

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Potentiometer Based Position Sensing

• Easily Integrated into new flight stick design
• Easily obtainable
• Low Cost
• Industrial grade with high resolution and linear
  resistive output available

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USB Controls Interface
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Why USB?
Gameport
USB

• Limited Reliability
• Limited Speed
• Single device interface
• Specific single application
• Multi wire interface

• Much More Reliable
• Much Faster
• Can interface w/ up to 126 peripherals at once
• Can be used with any USB compatible device
• Simple 4 wire interface with only 2 data lines

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USB Cable at a Glance
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How Do We Do It?

• Flight stick axis potentiometers and buttons send
  out information
• Axis information is then sent through an RC
  network to create a variable ? constant
• The microcontroller systematically sends out one
  shot pulses to read the ? of each axis
• Cypress USB uC converts to serial USB protocol
• Windows recognizes device as an HID

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Flight Controls Block Diagram
RC
RC
RC
CY63000A Microcontroller
Flight Controls
CPU
RC
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USB Microcontroller Requirements

• Must have multiple ports (needs to support 4 axis
  and at least 4 buttons)
• Must have high enough resolution to support game
  interface
• Must automatically convert analog information
  into serial USB protocol
• Must be compatible with Windows HID protocol

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Cypress CY7C63000A

• Easy to use
• Development kit available from mfg.
• Commonly used in this type of application
• Cheap
• Reliable
• Stand alone does it all package

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Cypress CY7C63000A Cont
Image complements of Cypress.com
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Microcontroller pin-outs
Port 0 (Buttons)
Port 1 (Axiis)
USB Data
Image complements of Cypress.com
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Generating Force Feedback for the Flight Stick
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Real Feel Flight Experience

• The F/A-18 flight stick will resist move with 3.5
  to 4.5 pounds of force per G.
• Implemented using extension springs, redesigned
  gimbal device, and stepper motors for varying the
  extension of the springs.

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General Methodology for Implementing Force
Feedback

• Flight equations generated by the flight
  simulation software will update the required
  amount of force which needs to be applied to the
  flight stick.
• Stepper motors will be controlled via a printer
  port (each of which has 8 output pins) in order
  to rotate them in the correct direction which
  cause the preloading spring mechanism to affect
  the desired amount of force.
• Insert picture of physical flight stick on next
  slide.

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Choice of Motor Type for Actuation

• Servomotors were originally used. We replaced
  these with Stepper motors for the following
  reasons.
• Easily integrated into software because of logic
  encoded step commands. Simple physical operation
  of stator and rotor.
• The last design made use of a software program
  for updating the motor characteristics which
  could not be integrated with a flight simulator
  program.
• Cost The current stepper motors are
  approximately 1/10th the cost of the original
  servomotors.

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Bipolar Stepper Motor

• Two motor windings are enclosed which cause
  magnetic forces to attract the teeth of the
  stator and rotor to each other. A logic 1 or 0
  defines the direction of current across the
  winding.
• Disadvantage Open loop system if the torque
  pulls the stator and rotor out of position, the
  motor will rotate freely. However, if we operate
  well within the holding torque range of the motor
  this is not a problem.

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H Bridge Motor Control

• To facilitate the switching of current direction
  across the motor winding, electronic drive
  circuitry is needed.
• The Allegro Microsystems 3952 was chosen as our
  H-bridge IC.

• Conceptual drawing of H bridge.
• A, B, C, and D are switches that either conduct
  current or cut the node off from the power supply

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Reasons for Choosing the Allegro 3952 H-bridge IC

• Logic gates incorporated into the IC select fast
  decay, slow decay, or braking modes.
• It can direct up to 3.5 amperes of peak current.
• Rated for up to 55 volts.

• Incorporates internal sense circuitry for current
  detection.
• Provides a simple platform for determining the
  off time used in PWM current limiting.
• Comes in a 16 pin DIP package for easy
  breadboarding and transfer to circuit board.

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Current Utilization of the 3952 IC in DTATS Design

• Due to a physical redesign which reduced the
  amount of torque required from the motor shaft,
  we decided to use resistive current limiting
  rather than PWM current limiting.
• Currently, the H-bridge is required to switch 1.4
  Amperes through each motor winding rather than 2
  Amperes which was initially planned for.
• Much of the logic is unnecessary for our
  application. E.G., in the current design we see
  no need to either brake or disable the H-bridge.
  These inputs (brake and enable) are always tied
  to logic high and low respectively.

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Stepping the motor

• By logically encoding the motor inputs we only
  need a two bit output to step the motor through a
  full rotation.
• The printer port is being used to output the
  correct number of encoded bits to serially step
  the motor through the required rotations.
• See next slide for details.

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3952 Logic for Current Switching.

• The direction of current in the 3952 is
  controlled by one signal called phase.
• Phase high will cause current to flow from out
  A to out B (Please refer to functional diagram)

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Step Sequence (continued)

• The figure on the right is a crude representation
  of the previously described bipolar step motor.
• It is connected to the outputs of two 3952 ICs.
• In the picture both IC1 and IC2 are receiving a
  high value on their phase input pin.
• Representing this as a two bit vector with IC1 as
  the high bit and IC2 low bit we can see that the
  following decimal sequence will cause a clockwise
  rotation.
• 3, 1, 0, 2. This shall be used in a step routine
  on the PC.

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PC Step Routine in Software

• The Borland Turbo C compiler was used because
  of abundant references found in literature
  regarding the outport() function.
• This function is found in the dos.h header file.
  
• The printer port is at address 378hex or 888
  decimal. outport() will accept either form. The
  function requires two arguments port address,
  and value to write.
• We could not take on the responsibility of
  converting the Lockheed Martin flight simulator
  software, so we have not incorporated this simple
  functionality into the flight simulator program.
  It is apparent how it can be used based on the
  design methodology.

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Shortcomings of the Printer Port as Control
Signal Generator

• After the design was finalized it became apparent
  that the printer port was experiencing problems
  regarding the speed at which it could generate
  output bits.
• A possible remedy of the problem is to send basic
  signals to a Basic Stamp or other microcontroller
  from the printer port. Thus making the
  microcontroller responsible for the high speed
  loop output for motor stepping.

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Distribution of Work
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D.T.A.T.S. Milestones
Proposed
Actual
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Budget