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Using Pulse-Width Modulation
Fluid Power Fluid Power ControlControl
The TeamThe Team Andy the Red Ranger Shelley the Blue Ranger Anna the Yellow Ranger Robert the Green Ranger Nathan the Black Ranger Jack the Pink Ranger Alex the White Ranger J. Newlin – The Science Museum of Minnesota Forrest Price – The Science Museum of Minnesota Professor William Durfee – The University of Minnesota Professor Perry Li – The University of Minnesota
World… meet Fluid World… meet Fluid PowerPower
GoalsGoals Explain Fluid Power to the Public Connect PWM and Fluid Power Explain the New Research Done by
the University Have 3 Interactive and Educational
Exhibits Have At Least One Site Visit to the
Science Museum Before Design Show Have Multiple Levels of Complexity
ExhibitsExhibits Fluid Power Experiment Bench
“Build It Yourself” Hydraulic Circuits
PWM and Duty Cycle Test BedBoth Electrical and Hydraulic PWM Circuits
Hydraulic PWM Valve Poster and PrototypeWorking Model of PWM Valve
Science Museum Science Museum Exhibit BasicsExhibit Basics What makes a good exhibit?
Educational Engaging Appeal to many age levels Multiple users Multi-sensory Visible moving parts Explanation/Exploration of familiar phenomena Average time a person spends at an exhibit is
2-3 minutes!
Experiment BenchExperiment Bench One concept Several variables, many outcomes
Do it yourself Early assured success (EAS) One to three users Ownership
Fluid Power Fluid Power Experiment BenchExperiment Bench Concept: Fluid Power Variables: dump truck, sprinkler, carousel, valves and pumps
Users plumb it themselves EAS: simple circuit Designed for 1-3 users Ownership: jelly bean shaped bench
Fluid Power Fluid Power Experiment BenchExperiment Bench Our vision
Base Circuit and LoadsBase Circuit and Loads
The Experiment BenchThe Experiment BenchPrototype
Landscape tubingWorking Exhibit
Clear PVC Clear tubing
PWM DemonstrationPWM Demonstration Make workings of PWM visible to viewers
Demonstrate Improved Efficiency
Compare similar usage of PWM in an Electrical and Fluid circuit
Electrical Electrical DemonstrationDemonstration Demonstrate PWM with two light dimmersPower Source – Hand Cranked Generator
Load – Light BulbPWM Signal generated by large optical encoder
Comparison in energy usage:Power resistors vs. Power semiconductors
Visitor will feel difference in power demands
System LayoutSystem Layout
A Second Identical A Second Identical ExhibitExhibit Make a parallel exhibit using fluid components:Generator → Pump with reservoirResistors → Throttling valvesTransistors for PWM → High speed solenoid valve
Light bulb → Fan connected to fluid motor
Power meter → TachometerSwitching transistors → 3-way solenoid valves
Fluid CircuitFluid Circuit
Fluid CircuitFluid Circuit
Fluid CircuitFluid Circuit
Fluid CircuitFluid Circuit
Fluid CircuitFluid Circuit
Fluid CircuitFluid Circuit
Fluid CircuitFluid Circuit
Fluid CircuitFluid Circuit
User Inputs for Both User Inputs for Both ExhibitsExhibits A start button
Spins the duty cycle wheel for 30 seconds Crank
The user can spin the crank to deliver power
Toggle switch Activates duty cycle or divider/throttler
system Load power selector
Varies the duty cycle and selects divider/throttler
The ActivityThe Activity
1. Hit start to spin wheel
2. Turn crank to deliver power
3. Switch between the parallel
systems
4. Repeat at different duty cycles
5. Watch the system as the wheel
slows down
Desired ResultsDesired Results Understanding of PWM power efficiency
User gets brighter bulb / faster fan using PWM system for a given power input
Understanding of electrical and fluid power The user feels the power input and sees the
output Understanding of pulse-width modulation
The dim bulb becomes a flashing bulb at the end
Fun and interactive The user enjoys experimenting with the
exhibits
Current DesignCurrent Design Designed for user accessibilityUsers of 40 to 70 inches tallWheelchair accessible
Designed for user friendlinessFew user inputsExhibits are back-to-back
Dimensions (inches)Dimensions (inches)
Current Design
UMN Research PosterUMN Research Poster
Inform
ImprovementsControlPump optimization
Display
Purpose of the ProjectPurpose of the Project Relay Knowledge
Common Applications of Fluid Power and PWM
Current Research at the University of Minnesota
Encourage Interest Theories of PWM and Fluid Power Control
Attraction of Target Group Attract a 4th Grade Audience Hold Attention of Target Audience
ReviewReview Three Exhibits
Fluid Power Experiment Laboratory
PWMElectrical PortionFluid Portion
Poster and Model
Tasks Left to CompleteTasks Left to Complete Fluid Power Experiment Lab PWM Exhibit Poster/Model Science Museum Testing Adjustments to the Exhibits Before the Design Show