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Disturbance Rejection: Final Presentation

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

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Disturbance Rejection: Final Presentation

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

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

  3. 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.

  4. 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.

  5. 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: 2o Maximum Tilt Motion: 2o Maximum Torque Induced: .1 N-m Disturbance Frequency: 0 - 1.5Hz Disturbance Detection: Detect rotations about X and Y axis

  6. Design Process: Initial Concerns • Budget Constraints • Mathematical Model • Motion Sensing • Testing Procedures

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

  8. Design Process: Choosing a motor • Final Decision: Pittman GM8712-21 19.5:1 Gear Ratio • Very Low Cost $75 • No Performance Sacrifice

  9. Design Process: Sensor Selection • Needs • Initial Solutions: • Rate Gyro • Accelerometer • Problems • Costs

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

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

  12. 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

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

  14. Design Process: Simulations Pan Motor Linearized Step Response

  15. Design Process: Simulations Tilt Motor Linearized Step Response

  16. Design Process: Simulations Non-Linear Step Response

  17. 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.

  18. Friction (Simulink):

  19. Design Process: Total Cost

  20. 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

  21. 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

  22. Performance • Demonstration • No Control • Pan / Tilt Control • Results

  23. Goals vs. Results

  24. 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

  25. 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 (?)

  26. Recommendations • Implement Look-Up Table • Detect Translational Movement • Better Motors • Velocity Estimation

  27. Questions?

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