Ground Control

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?