Disturbance Rejection: Final Presentation Group 2: Nick Fronzo Phil Gaudet Sean Senical Justin Turnier

Overview  Introduction and Objectives  Design Process:  Motor / Sensor Selection  Testing System  Controller Design  Project Build and Functional Tests  Performance  Success and Challenges  Recommendations

Introduction  Problem Statement: The transmission of line of sight communication devices aboard a ship are broken from the disturbances caused by waves.  Goal: Stabilize communication devices that are on unstable platforms via a pan-tilt mechanism.

Objectives  Use pan-tilt mechanism with mounted laser pointer to simulate line of sight communications link.  Disturbances will be added to pan-tilt system via mechanical spring mount designed to simulate motion induced by waves.  Use inclinometers to sense disturbance in order to perform the necessary correction.

Design Specifications Desired Output: Have output point on ceiling within a 2” square box (x,y) centered around desired output point for a laser pointer that is mounted 4’ away. Maximum Pan Motion: 2 o Maximum Tilt Motion: 2 o Maximum Torque Induced:.1 N-m Disturbance Frequency: Hz Disturbance Detection: Detect rotations about X and Y axis

Design Process: Initial Concerns  Budget Constraints  Mathematical Model  Motion Sensing  Testing Procedures

Design Process: Choosing a Motor  Key Parameters:  Torque  Gear Ratio  Peak Velocity  Iterative Process:  Select Motor  Run Simulations  Analyze Results  Cost

Design Process: Choosing a motor  Final Decision: Pittman GM :1 Gear Ratio 19.5:1 Gear Ratio  Very Low Cost $75  No Performance Sacrifice

Design Process: Sensor Selection  Needs  Initial Solutions:  Rate Gyro  Accelerometer  Problems  Costs

Design Process: Sensor Selection  Solution: US Digital T-4 Incremental Inclinometer  Specifications:  300 CPR  Encoded Output  Low Cost  Trade Offs  Low Resolution  Slow Reaction

Design Process: Testing Mount  Determine desired motions to be implemented  Design a system to incorporate these motions  Assemble system  Integrate with pan/tilt mechanism

Design 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 Design  Specifications:  1% Overshoot .5 Second Settling Time  Linearized about (0,0)  Used MATLAB RLTOOL  Simulation Results

Design Process: Simulations Pan Motor Linearized Step Response

Design Process: Simulations Tilt Motor Linearized Step Response

Design Process: Simulations Non-Linear Step Response

Friction compensation:  The friction of the uncontrolled system is very large due to a large internal gear ratio (19.5:1).  The positive and negative coulomb friction values cannot be averaged because they differ greatly.  Dead zone improved by tightening loose set screw and adding controller compensation.

Friction (Simulink):

Design Process: Total Cost

Project Build  Sensor Mounting  Used ARCS Board Encoder Ports  Aligned Sensors with Axis of Motion  Re-aligned Sensors with Axis of Pan/Tilt  Fix Pan/Tilt to Testing Mount  Calibrate Laser to Show Position

Functional Tests  Simulated Waves with Vertical Mount  Low Frequency / Amplitude Disturbances  Mid Frequency / Amplitude Disturbances  High Frequency / Amplitude Disturbances  Simulated Satellite  Laser pointer represents communication link  2”x2” Box represents satellite to be linked to

Performance  Demonstration  No Control  Pan / Tilt Control  Results

Goals vs. Results

Successes  Sensor and Motor Integration  Acceptable Disturbance Rejection  Friction Compensation  Increased Point to Point Accuracy .17 radians error to.03 radians  Practical Value of Previous Courses

Failures  Look Up Table Implementation  At Low Frequencies  not very smooth  At High Frequencies  Poor compensation  Stability  “Dead Zone”  Due to friction (?)  Due to loose set screw (?)

Recommendations  Implement Look-Up Table  Detect Translational Movement  Better Motors  Velocity Estimation

Questions?