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Ground Control

Andrew Bourgeois Aaron M inard. Ground Control. Contents. Background Problem Statement Solution Mechanical Design System Diagram Electrical Design Programming Schedule Budget. Background. VTC developing CubeSat , transmits data Have to follow CubeSat to receive data

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Ground Control

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  1. Andrew Bourgeois Aaron Minard Ground Control

  2. Contents • Background • Problem Statement • Solution • Mechanical Design • System Diagram • Electrical Design • Programming • Schedule • Budget

  3. Background • VTC developing CubeSat, transmits data • Have to follow CubeSat to receive data • Existing 3-meter parabolic dish antenna • Low orbit satellite revolves around earth in minutes, seen for short time per orbit • Existing solutions • EGIS Bi-axial antenna positioning system

  4. EGIS Rotor and Control • Equipment-GesellschaftfürInternationaleElektronikSysteme • Cost: • Software $400 • Data Interface $1,100 • Hardware $2,700 (EL-40°, AZ-180°) • Extension $2,200 (EL-90°, AZ-360°) • Rotor Hardware Mount $400 • Satellite Dish Mount $400 • Total $7,200

  5. SatPC32 • A free software available online for tracking satellites. Updates on screen and controls rotor to point to position satellite • Uses orbit of satellite and observer position • Many types of rotors to select for output • Uses Serial port or Parallel port on PC

  6. SatPC32 WinListen predicts path Screen Shot of SatPC32 in use

  7. Problem • Track a low orbit satellite such as a CubeSat from horizon to horizon is as little as 30 seconds 180°/30 seconds=6°/sec • Move a 3 meter satellite dish • 360° Azimuth (left/right) • 90° Elevation (up/down) • Interface to PC running SatPC32

  8. Solution • Gears and motors, motor controllers • FreescaleColdfire 32-bit Microcontroller • Serial interface with SatPC32 using EGIS controls and a serial port • Position sent as ASCII Characters • :P AZ=123.45 • :P EL=009.87 • Magnetic Encoders measure position of dish • Use/Modify existing designs for elevation and azimuth control

  9. System Diagram SatPC32 EL - Motor Controller RS232 AZ - Motor Controller Micro- controller Position Encoders Limit Switches

  10. Mechanical Concepts • Azimuth • A left to right angle measurement from a fixed point (north in navigation) • Worm Gears • Speed (Gear Ratio) • Torque • Modify existing designs

  11. Azimuth Design

  12. Elevation Design

  13. Analysis

  14. Position Sensing Specified previously • 1° step size = at least nine bit resolution 29 = 512 steps 360 deg/512 steps = .7 deg/step • 6°/sec = 1 rpm 180°/30sec=6°/sec=360°/60sec • Magnetic shaft encoder • Max 15,000 rpm • Absolute position sensing • Small size, large operating temperature range • Analog output from 10-bit DAC • 1024 steps or .35°/step

  15. Power Distribution A Micro- controller Position Encoders PC Running SatPC32 E 5Vdc regulator 12Vdc 10Amp Limit Switch Motor Controller Circuit Protection FUSE AC 12Vdc 10Amp FUSE Limit Switch Motor Controller

  16. Micro Controller

  17. Programming • Read new position from serial port • Stores values when they come in • Read actual position from encoders • Measure periodically • Decide where to turn, how fast • Always checking limit switches • If ever activated, stop motors New Serial? Read Serial Check Encoders? Read Encoders Controller (Set Outputs)

  18. Check-Serial Code

  19. Schedule

  20. Cost

  21. Thank You • VTC Mechanical Department • Ordering Parts, answer construction questions • Professor John Murphy • Controller software design, test equipment • Professor Samuel Colwell • Programming support • LEDdynamics Inc. of Randolph, VT • Electrical Supplies & Microcontrollers • Erich Eichmann • SatPC32 Support

  22. Questions?

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