Disturbance Rejection:Disturbance Rejection:Final PresentationFinal Presentation

Group 2:Group 2:Nick FronzoNick FronzoPhil GaudetPhil Gaudet

Sean SenicalSean SenicalJustin TurnierJustin Turnier

OverviewOverview

Introduction and ObjectivesIntroduction and Objectives Design Process:Design Process:

Motor / Sensor SelectionMotor / Sensor Selection Testing SystemTesting System Controller DesignController Design

Project Build and Functional TestsProject Build and Functional Tests PerformancePerformance Success and ChallengesSuccess and Challenges RecommendationsRecommendations

IntroductionIntroduction

Problem Statement:Problem Statement:

The transmission of line of sight The transmission of line of sight communication devices aboard a ship are communication devices aboard a ship are broken from the disturbances caused by broken from the disturbances caused by waves.waves.

Goal:Goal:

Stabilize communication devices that Stabilize communication devices that

are on unstable platforms via a pan-tilt are on unstable platforms via a pan-tilt

mechanism.mechanism.

ObjectivesObjectives

Use pan-tilt mechanism with mounted laser Use pan-tilt mechanism with mounted laser pointer to simulate line of sight communications pointer to simulate line of sight communications link.link.

Disturbances will be added to pan-tilt system via Disturbances will be added to pan-tilt system via mechanical spring mount designed to simulate mechanical spring mount designed to simulate motion induced by waves.motion induced by waves.

Use inclinometers to sense disturbance in order Use inclinometers to sense disturbance in order to perform the necessary correction.to perform the necessary correction.

Design SpecificationsDesign Specifications

Desired OutputDesired Output: Have output point on ceiling within a 2” : Have output point on ceiling within a 2” square box (x,y) centered around desired output point square box (x,y) centered around desired output point for a laser pointer that is mounted 4’ away.for a laser pointer that is mounted 4’ away.

Maximum Pan Motion:Maximum Pan Motion: 2 2oo Maximum Tilt Motion:Maximum Tilt Motion: 2 2oo

Maximum Torque Induced:Maximum Torque Induced: .1 N-m .1 N-m

Disturbance Frequency:Disturbance Frequency: 0 - 1.5Hz 0 - 1.5Hz

Disturbance Detection:Disturbance Detection: Detect rotations about X and Y axisDetect rotations about X and Y axis

Design Process: Initial ConcernsDesign Process: Initial Concerns

Budget ConstraintsBudget Constraints

Mathematical ModelMathematical Model

Motion SensingMotion Sensing

Testing ProceduresTesting Procedures

Design Process: Choosing a MotorDesign Process: Choosing a Motor

Key Parameters:Key Parameters: TorqueTorque Gear RatioGear Ratio Peak VelocityPeak Velocity

Iterative Process:Iterative Process: Select MotorSelect Motor Run SimulationsRun Simulations Analyze ResultsAnalyze Results

CostCost

Design Process: Choosing a motorDesign Process: Choosing a motor

Final Decision:Final Decision:

Pittman GM8712-21Pittman GM8712-21

19.5:1 Gear Ratio19.5:1 Gear Ratio

Very Low CostVery Low Cost

$75$75

No Performance SacrificeNo Performance Sacrifice

Design Process: Sensor SelectionDesign Process: Sensor Selection

NeedsNeeds Initial Solutions:Initial Solutions:

Rate GyroRate Gyro AccelerometerAccelerometer

ProblemsProblems CostsCosts

Design Process: Sensor SelectionDesign Process: Sensor Selection

Solution:Solution:

US Digital T-4 Incremental InclinometerUS Digital T-4 Incremental Inclinometer

Specifications:Specifications: 300 CPR300 CPR Encoded OutputEncoded Output Low CostLow Cost

Trade OffsTrade Offs Low ResolutionLow Resolution Slow ReactionSlow Reaction

Design Process: Testing MountDesign Process: Testing Mount

Determine desired motions to be implementedDetermine desired motions to be implemented

Design a system to incorporate these motionsDesign a system to incorporate these motions

Assemble systemAssemble system

Integrate with pan/tilt mechanismIntegrate with pan/tilt mechanism

Design Process: Testing MountDesign Process: Testing Mount• A universal yoke assemble will support the pan tilt base. The yoke will provide two rotational degrees of freedom to simulate ocean wave action

•Pan-Tilt will be clamped to mounting plates.

•Springs will stabilize the mount

•Construction: steel tube and plate

•Smooth Motion

Design Process: Controller DesignDesign Process: Controller Design

Specifications:Specifications: 1% Overshoot1% Overshoot .5 Second Settling Time.5 Second Settling Time

Linearized about (0,0)Linearized about (0,0) Used MATLAB RLTOOLUsed MATLAB RLTOOL Simulation ResultsSimulation Results

Design Process: SimulationsDesign Process: Simulations

Pan Motor Linearized Step Response

Design Process: SimulationsDesign Process: Simulations

Tilt Motor Linearized Step Response

Design Process: SimulationsDesign Process: Simulations

Non-Linear Step Response

Friction compensation:Friction compensation:

The friction of the uncontrolled system is The friction of the uncontrolled system is very large due to a large internal gear ratio very large due to a large internal gear ratio (19.5:1).(19.5:1).

The positive and negative coulomb friction The positive and negative coulomb friction values cannot be averaged because they values cannot be averaged because they differ greatly. differ greatly.

Dead zone improved by tightening loose Dead zone improved by tightening loose set screw and adding controller set screw and adding controller compensation.compensation.

Friction (Simulink):Friction (Simulink):

Design Process: Total CostDesign Process: Total Cost

Project BuildProject Build

Sensor MountingSensor Mounting Used ARCS Board Encoder PortsUsed ARCS Board Encoder Ports Aligned Sensors with Axis of MotionAligned Sensors with Axis of Motion Re-aligned Sensors with Axis of Pan/TiltRe-aligned Sensors with Axis of Pan/Tilt

Fix Pan/Tilt to Testing MountFix Pan/Tilt to Testing Mount Calibrate Laser to Show PositionCalibrate Laser to Show Position

Functional TestsFunctional Tests

Simulated Waves with Vertical MountSimulated Waves with Vertical Mount Low Frequency / Amplitude DisturbancesLow Frequency / Amplitude Disturbances Mid Frequency / Amplitude DisturbancesMid Frequency / Amplitude Disturbances High Frequency / Amplitude DisturbancesHigh Frequency / Amplitude Disturbances

Simulated Satellite Simulated Satellite Laser pointer represents communication linkLaser pointer represents communication link 2”x2” Box represents satellite to be linked to2”x2” Box represents satellite to be linked to

PerformancePerformance

DemonstrationDemonstration

No ControlNo Control Pan / Tilt ControlPan / Tilt Control

ResultsResults

Goals vs. ResultsGoals vs. Results

SuccessesSuccesses

Sensor and Motor IntegrationSensor and Motor Integration Acceptable Disturbance RejectionAcceptable Disturbance Rejection Friction CompensationFriction Compensation

Increased Point to Point AccuracyIncreased Point to Point Accuracy .17 radians error to .03 radians.17 radians error to .03 radians

Practical Value of Previous CoursesPractical Value of Previous Courses

FailuresFailures

Look Up Table Implementation Look Up Table Implementation At Low FrequenciesAt Low Frequencies

not very smoothnot very smooth

At High FrequenciesAt High Frequencies Poor compensationPoor compensation StabilityStability

““Dead Zone”Dead Zone” Due to friction (?)Due to friction (?) Due to loose set screw (?)Due to loose set screw (?)

RecommendationsRecommendations

Implement Look-Up TableImplement Look-Up Table Detect Translational MovementDetect Translational Movement Better MotorsBetter Motors Velocity EstimationVelocity Estimation

Questions?Questions?