Critical Design Review
Team RIDE
Brennan Dayberry
Adam Marrapode
James McGlynn
Ben Sufit
Chris Taylor
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Presentation Overview
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Project Visual Walkthrough
Problems and Design Revisions
Revised Mechanical Functions
Flow of Information
PC Plug-in
FPGA Game Code and Motor Control
FPGA NiosII and Controller Board
Motors, Drivers, and Power
Schedule
Division of Labor
Budget Considerations
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Visual Walkthrough
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Problems and Design Revisions
Mechanical Engineering:
• We completely underestimated the amount of mechanical
engineering knowledge required to implement our project
• Mechanical engineers have consulted with us on various topics
relevant to our project, and helped guide us in the right direction
• Due to the machining, metalwork, and welding involved, a few of us
have gained access to the ITLL machine shop, and have a
mechanical engineer with welding experience lined up to help us
with any welding needed
• We have attempted to make our mechanical design as simple as
possible while maintaining the overall goal of our project
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Problems and Design Revisions
Linear Actuators:
• Grant Immohara from
Mythbusters provided
information on actuator
suppliers
• Very hard to find exact
actuators to meet design
specifications for load forces
and actuator speeds
• Way too expensive, cannot
accommodate within our
budget
• Much harder to implement into
design than originally
perceived
• Overall: Linear actuators were
a bad idea and we wasted too
much valuable time trying to
find the perfect one
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Problems and Design Revisions
Motors:
• After researching variable AC, DC and stepper motors, we
decided to use stepper motors and salvaged two from the
previous capstone project, the BP gas line robot
• Well within our budget as they were free, and higher models are
within budget ($300-$400)
• Stepper motors much easier to implement into design, both
mechanically and electrically
• Feedback easier via step control and shaft encoders
• Use crank arm and levers to achieve 2 degrees of freedom
• Stepper motor system already has AC-DC converter power
supply
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Problems and Design Revisions
Overview:
• Tremendous amount of mechanical input was needed
from outside sources
• Calculations of Torques and Force loads proved that
linear actuators are not efficient, but proved that stepper
motors could carry out design specs by using a crank
and lever system
• Metal support frame for cockpit was deemed to heavy,
so we went with plywood instead and will improve rigidity
with perimeter molding of angle-iron
• Motion base will have 2-degrees of freedom with 2
stepper motors, both on the front edge.
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Mechanical Functions
• When motors move
in unison together,
cockpit pitches up
and down
• When motors move
opposite directions,
cockpit rolls side to
side
• Approximately 7°-12°
range of motion in
both degrees of
freedom
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Universal Joint
• Salvaged from an old
truck drive shaft
• Placed at center of
mass to support
majority of weight
• Restricts motion to
two degrees of
freedom
• Adjustable height
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Ball Joint
• Allows levers to move
freely at pivot point on
cockpit
• Prevents lever arms
from bending when
the cockpit moves
• Easily available from
local suppliers
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Torque Requirements
• Need 15 pounds-force along front edge per motor (empirically
measured)
• Crank arm is 2 inches long
• We need 30 inch-pounds, or 3.4 Newton-meters at motor shaft
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Cockpit Pitching
• Both motor crank arms
move together, so
cockpit pitches up
• The delta distance
between the cockpit
old position and new is
about 2.5 inches
• Allows pitch swing of
about 5 inch delta, or
6°
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Cockpit Rolling
• Motor crank arms
move in opposite
direction, so cockpit
rolls to the left
• Delta distance
between old and new
position is 2 inches
• Provides roll swing of
about 4 inch delta, or
12°
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Information Flow
• PC Plug-in filters game data
into movements then sends to
FPGA Game Code Module
• Game Code Module considers
current positions, evaluates
new desired positions based
on feedback, then sends data
to FPGA Motor Code Module
• Motor Code Module converts
simple movement commands
into pulses and directions for
each motor
• Motor Drivers take PWM
signals and drive motors
correspondingly
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PC Plug-In: Overview
• Dynamically-Linked Library
• Routines run in real-time when race is
started
• Telemetry data held in game data
structures (C++ classes)
• Telemetry updates at 91 FPS
• Telemetry converted to “motion profiles”
• Structures -> Filter -> Serial Port
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PC Plug-In: Raw Data
• Data polled on frame update and sent to
filter functions
• Data sent in three types:
– Acceleration: forces created by car movement
– Impact: forces created by impact with
environmental hazards (walls, other cars)
– Pitch/Roll: forces created by movement of car
in relation to normal (includes bumps, jumps)
• Data in Cartesian coordinates
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PC Plug-In: Filters
• Filter for each type of data
• Data sampled and converted at ~5 Hertz
– rate variables held as constants to allow for
easy optimization with hardware
• Each filter converts data to simple motion
profile
• Simple motion profiles sent to
superposition function
• Superposition function sends final profile to
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serial port
PC Plug-In: System Functions
• initialize
– Initializes communication with controller board
• log
– logs any pertinent data (meant for
development, debugging)
• send_profile
– sends direction and magnitude of motor arm
motion
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FPGA Game Decode
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Inputs from PC
Feedback via variables and optical encoders
Output to Motor Control
cmdmov values (command move)
Magnitude and Feedback
Sample Code
Early feedback
Output
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Flow of Code in Neos II
Input from plug in
Decode motor movement
Is movement possible?
Input from feedback
No
Yes
Calculate possible movement
Execute movement
Execute movement
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Inputs, Feedback and Outputs
• The input to the FPGA will be a set of two
integers corresponding to the desired
movement and magnitude.
• The feedback is the current position of the
motor, provided by shaft encoders and
known variables.
• The output gives the command to the
motor based on the input and feedback
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(command move) cmdmov values
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1= front (brake)
2 = back (acceleration)
3 = front right
4 = front left
5 = back right
6 = back left
7 = CRASH or rumble strip (depending on
magnitude)
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Magnitude and Feedback
• Magnitude is a value of one to ten
determined by the PC plug-in.
• Feedback is a number between zero and
two hundred (200 steps per revolution)
that contains the current position
information.
• The code calculates which movements to
make and determines if the movement is
possible based on the feedback
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Sample Code Nested Switch
or Lookup Table
switch(cmdmove){
case 1: //pitch front
swich(mag){
case 1: // magnitude of one
if ((fdbk - mag) <= 0)//check pos
then mag = fdbk;
movemoter1(cmdmov, mag);
movemoter2(cmdmov, mag);
break;//moves motor as far as pos
case 2: // magnitude of two
if ((fdbk + mag) >= 200)//check
……………………
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FPGA Game Output
• The FPGA Game Code module sends
basic movement information to the FPGA
Motor Control module to be converted into
real movement
• The Game Code module handles all
feedback decisions, so that the Motor
Control module only has to translate basic
movements into motor rotation
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FPGA Motor Control
• Translates fundamental movements into
number of steps and direction of rotation of
both motor shafts.
• Only provided with the changes in movement
from the last position, to make translation fast
and simple.
• Relates desired cockpit behavior into
necessary motor behavior through basic
physics
• Controls logic driving the PWM and direction
circuits on FPGA
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Altera Nios II Softcore Design Flow
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SOPC Builder
Nios II IDE
(C/C++)
(“System-on-aProgrammable-Chip”)
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Quartus II
(VHDL/Verilog)
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FPGA
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Position
Feedback
RS232
Logic
PC
UART
Cyclone FPGA
Motor
Driver
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Control Board Overview
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Breakout Board from
www.devboards.de
• Connects FPGA to
PCB with headers
• Simplifies FPGA
mating to PCB
• Provides JTAG and
Serial Programming
Interfaces
• Allows for easy
replacement of FPGA
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Some Schematics
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Some Schematics
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Slo-Syn Stepper Motor
• 5.44 N-m Minimum
Holding Torque
• 2 phase
• 1.8° per step (200
steps)
• Controlled via MD808
motor driver
• We will be operating at
60-100 rpm, at 5 N-m
continuous torque
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MD808 Motor Driver
• Opto-isolated control
• 80VDC, 4A power
• Control via pulse
signal; one rising
edge is one motor
step
• Direction control;
high-low signals CCW
or CW rotation
direction
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Feedback
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Because we made the
design choice to go with
stepper motors instead of
liner actuators we can get
some early feedback by
keeping track of the
approximate position of
the motors.
• We anticipate that this will
not be sufficient for the
finished product and plan
on using optical shaft
encoders to provide the
exact position of the
motor.
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Motor Power Circuit
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Converts 120VAC to 80VDC
Transformer converts 120Vrms to 60Vrms
Full wave rectifier supplies 80Vpeak full wave
Filter capacitor turns full wave into 80VDC output
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Revised Schedule
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Deliverables
Milestone 1
• Mechanical assembly partially complete
• PC Plug-in nearly finished
• FPGA Game Code and Motor Control functional
• PCB Layout revision 1 ordered
Milestone 2
• System integration partially complete
• Mechanical construction and assembly finished
• Modules functioning independently
• PCB revision 2 ordered
Expo
• System integration complete
• Cockpit moving with respect to simulation
• All technical documentation complete
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Division of Labor
Brennan
Chris
James
Adam
Ben
Mechanical Design
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Mechanical Assembly
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Motor Control
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Motor Feedback
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Programming PC Driver
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FPGA Game Code
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FPGA Logic
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FPGA NiosII Softcore
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Communications
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Analog Circuits
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PCB Layout
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Power
Budget
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X
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Budget Overview
New Investors:
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Joseph Brennan, owner of Southern Lending LLC Investment Firm
– Invested $1000.00 towards project through CU Foundation
– www.southernlendingllc.com
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DENT Sport Garage
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National Pro Rally team and automotive upgrade shop
Will support safety of project
7-point safety belt harness system neck collar
Better and newer seat for larger individuals
www.dentsport.com
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Budget Overview
Overview of Materials and Parts:
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NEOS II FPGA
– Devboard (free!)
– Breakout + FPGA ($180)
Two DC Stepper motors and drivers
– (free!)
– If unable to repair defective driver, new one will cost $365
AC-DC Converter Power Supply
– (free!)
Miscellaneous scrap materials purchased thus far
– U-bolts, plywood, driveshaft for center pivot
– $150.00
Total Spent: $330.00
– Well within budget requirements for now
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Questions?
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