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Andrew Bourgeois Aaron M inard. Ground Control. Contents. Background Satellite Tracking SatPC32 Problem Statement Solution Mechanical Design System Diagram Electrical Design Software Schedule Budget. Background. VTC developing Cubesat , transmits data
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Andrew Bourgeois Aaron Minard Ground Control
Contents • Background • Satellite Tracking • SatPC32 • Problem Statement • Solution • Mechanical Design • System Diagram • Electrical Design • Software • Schedule • Budget
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 • Many existing solutions • EGIS Bi-axial antenna positioning system • BIG-RAS Azimuth and Elevation Rotator
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
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
SatPC32 WinListen predicts path Screen Shot of SatPC32 in use
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 • Integrate/improve previous design
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
Mechanical Stuffffffffffffffffff • Maybe some Azimuth (talk about using last years stuff that was good?) • Maybe a whole slide summarizing last years model and then discussing what we liked (Azimuth) and what we thought needed improvement (Elevation) • We liked work gears for both… why? (speed) • Discuss around here about the wind force calculations….? Angular acceleration…. ?
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 (6°/sec)(60sec/1min)(1rev/360deg) • Magnetic shaft encoder • Absolute position sensing • Small size, large operating temperature range • Analog output from 10-bit DAC • 1024 steps or .35°/step
System Diagram SatPC32 EL - Motor Controller RS232 AZ - Motor Controller Micro- controller Position Encoders Limit Switches
Electrical Flow 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
Software (Microcontroller) • Decide where to turn, how fast • Read new position from serial port • Stores values when they come in • Read actual position from encoders • Measure periodically • Always checking limit switches • If ever activated, stop motors Controller (Set Outputs) New Serial? Read Serial Check Encoders? Read Encoders