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