Motion Control: Modeling, Design and Implementation

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Motion ControlModeling, Design and
Implementation

• Wayne J. Book
• HUSCO/Ramirez Chair in Fluid Power and Motion
  Control
• G.W. Woodruff School of Mechanical Engineering
• Georgia Institute of Technology

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Introduction Why Motion?

• A key aspect of many engineering problems
• Of particular relevance to mechanical engineering
• Excellent representation of other engineering
  control problems
• Visually engaging

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What you should learn through this course

• Areas where motion is an important aspect and
  unique aspect of those areas
• Aspects of motion system design performance,
  constraints and specifications.
• Modeling representation of the physical system
• Identification from physical example to model
• Control achieving what you want
• Relevance of mathematical constructs
• Hands-on confidence in electrical and hydraulic
  drives
• But what you DO learn depends on YOU!

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Example areas

• Manufacturing
• Material and Materials Handling
• Mobile equipment
• Transportation
• Medical and scientific
• Human interfaces
• Consumer and entertainment
• Office products
• Military

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Manufacturing

• Machine tool spindle and tool axes
• Die casting
• Extrusion (plastic and metal)
• Wafer Stepper
• Stereo Lithography
• Spot welding
• Seam welding
• Custom equipment for automation

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Vulcan Paint Inspection Systemby CAMotion, Inc.
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Material Handling

• Packaging case packers
• Fork lift truck
• Automated Guided Vehicles (AGV)
• Conveyors
• Robots
• Cranes
• Form, fill and seal machines

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Want 120 Bags of Chips/Minute? See Kliklok
Woodman
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Mobile Equipment

• Cranes
• Loaders
• Back hoes
• Forestry equipment
• Pavers
• Lifts

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Mobile equipment (construction)
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Transportation

• Automobile active suspensions, wipers, windows,
  antennas, HVAC, locks oh yes the engine
• Aircraft airfoils, landing gear, support
  equipment
• Trains
• Elevators
• Segway http//www.howstuffworks.com/ginger2.htm

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Dean Kamens Segway
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Medical and Scientific

• RoboDoc hip joint replacement surgery
• Minimally invasive remote surgery (Zeus, Aesop
  and daVinci systems (teleoperated)
• Diagnostics and rehabilitation of muscles
• Artifical heart
• Scanning Probe Microscopes
• Instrument stages

The daVinci System by Intuitive Surgical
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Human Interface

• Haptic display manipulators
• Joysticks
• Teleoperator masters
• Digital clay
• Automobile steering
• Active Seat (John Deere)

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Phantom Haptic Display
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Consumer Entertainment

• Washing machines
• Cameras
• Can openers
• Ice dispensers
• Video players
• DVD and CD players
• Amusement parks

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Outdoor Show in Las VegasShip sinks and is
raised repeatedly by hydraulic actuation
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Office Equipment

• Copiers
• Scanners
• Printers
• Shredders
• Fax machines

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Military

• See all of the above application areas, plus
• Radar
• Guns
• Guided munitions
• Loading munitions

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Design Tradeoffs(you dont get something for
nothing)
Performance Measures (soft limits)

• Speed
• Bandwidth
• Accuracy
• Payload
• Range
• Cost
• .

Tradeoffs (speed vs. cost for example) Constraint
rules, laws or equations Dictated by
technologies used
Performance Specifications (hard limits)
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Simple Tradeoff Examples

• Cost f(speed)
• Dollars are applied to use lighter materials,
  stronger motors, lower friction.
• Gross motion speed f(inertia) f(drive cross
  section)
• Bandwidth or fine motion speed g(stiffness)
  g(drive cross section)
• So Gross motion speed h(Bandwidth)

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Constraints

• Consider constraints on shaft size, radius r,
  with torque T, shear modulus G and length L.
• Yield stress
• Fatigue
• Compliant rotation
• Buckling
• One of these may occur at a lower shaft radius
  and thus be the active constraint.
• Which constraint is active depends on the
  technology used, e.g. material technology may
  affect G and hence ? or affect ?y

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Need a Balanced Mass InvestmentIf constant total
mass is split between shaft beam
torque
shaft (JG)
beam (EI(r))
log(nat. freq.)
rotation
rmax
rigid beam
rigid shaft
beam radius r
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TradeoffsTwo or more performance measures are
coupled by constraints

• Performance (max or min)
• Speed
• Bandwidth
• Payload
• Accuracy (static, dynamic, tracking)
• Weight
• Space
• Cost
• Energy
• Disturbance rejection

• Physical Constraints
• Yield
• Fatigue
• Buckling modes
• Deflection
• Vibration
• Temperature rise
• Electromagnetic interference
• Efficiency
• other

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Motion ControlClass 2

• Recall from last class many applications
• Manufacturing, Material and Materials Handling,
  Mobile equipment, Transportation, Medical and
  scientific, Human interfaces, Consumer and
  entertainment, Office products, Military
• Design tradeoffs balance two measures of
  performance by adjusting a design parameter.
• Physical constraints on a parameter may be active
  or inactive.
• Which constraint is active may change with a
  change in design specification (application).

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Homework 1 Discussion

• Design specifications for a forklift truck
• Payload weight capacity
• Vehicle weight
• Engine type I.C. or electric
• Maximum lift height
• As the weight to be lifted increases structural
  mass increases as does the other drive component
  capacity.

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Specifications Cross Plot
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Motion System Overview(hydraulic example)
Volts-amp
Electric or IC prime mover
Transmission line valve
Motor or cylinder
Flow-press.
Rpm-torque or force
Rpm-torque
Flow-press.
Pump

• The system consists of a series of transformation
  of power variables
• Power is either converted to another useful form
  or waste heat
• Impedance is modified (unit force/unit flow)
• Power is controlled
• Function is achieved

Coupling mechanism
Rpm-torque or force
Load
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Generic Components
GENERAL
EXAMPLE

• Power source
• Power transformer
• Power modulation
• Impedance matching
• Motion transformation
• Load
• Environment

• Fuel
• Motor
• Throttle
• Gear box
• Drive shaft, differential
• Inertia, friction
• Gravity, wind

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Additional considerations

• Parasitic Effects
• Compliance
• Friction
• Resistance
• Heat

• Environment
• Gravity
• Mass
• Spring
• Power dissipation
• Power input

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Energy or Power Domains

• Energy is required to move any thing (mass) in
  its environment of friction and stiffness.
• Power d(energy)/dt (effort) x (flow)
• Various domains are useful for causing motion
• Mechanical T and R (translation and rotation)
• Fluid
• Electrical (and magnetic)
• These domains are complementary in some ways
• Transformation between domains is critical
• Electrical (volt x amp) -gt motor -gt Mechanical R
  (torque x rotational speed)
• Mechanical -gt pump -gt Fluid (pressure x flow)
• Fluid -gt cylinder -gt Mechanical T (force x speed)

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Transformersalso scale effort and flow in the
power product

• Gear box ratio n (N-m / N-m)
• Torque out (Torque in) x n
• Speed out (Speed in) / n
• Lever ratio n (N / N)
• Force out (Force in) x n
• Speed out (Speed in) /n
• Motor pump cylinder ratio n (N/Amp)
• Force out (Current in) x n
• Speed out (Voltage in) / n
• Losses reduce power out energy dissipated

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Choice of power domains

• Given a motion, what power domains should you
  use?
• What power is required?
• What is the ratio of speed to force?
• What control is needed? (manual, remote,
  bandwidth, )
• Where can you locate the power source?
• What degrees of freedom separate the motion from
  the source?
• Heat dissipation, space, noise, environment?

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Actuators are Transformers

• Standard examples
• Electromagnetic (motors, solenoids, voice coils)
• Hydraulic (motors, cylinders)
• Pneumatic (motors, cylinders)

• More exotic
• Piezoelectric
• Electrostatic
• Shape memory alloy
• Electro/magneto rheological fluids
• Magnetic particle clutches
• Thermal

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Issues in Actuator Selection
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Piezoelectric (Crystal) Actuators

• The piezoelectric effect produces charge across x
  for strain in y
• Alternatively, charge produces strain
• Hence sensors and actuators result
• Popular materials
• PZT lead zirconium titanate
• PVDF polyvinylidene flouride
• Barium titanate
• LS lithium sulfate
• Motions are small but precise, high resolution.
  Forces can be high, must be compressive in
  practice.
• See .pdf file for example of inch worm
• Ref Shetty Kolk, Mechatronic Systems, PSW
  Publishing

Quartz Example
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Shape Memory Alloys

• Based on phase transformation in metals between
  austinitic (stiff) and martensitic (pliable)
• Material is deformed in martensitic
• Upon heating it returns to austinitic
• Difference in modulus causes force to be exerted
  and return to original shape
• Upon cooling the martensitic state and shape
  results, completing the cycle
• Practical materials NiTinol a nickle-tin alloy
• See following web page http//www.aerofit.com/sma/
  memory.htm