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Ground Control

Ground Control. Jordan Hodge Jordan Lyford Wilson Schreiber. Contents. Background Problem Statement Solution Mechanical Azimuth Elevation Concepts Static and Dynamics of System Software SatPC32 Interpolation Programming Electrical/Controls Position Sensing Controller

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Ground Control

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  1. Ground Control Jordan Hodge Jordan Lyford Wilson Schreiber

  2. Contents • Background • Problem Statement • Solution • Mechanical • Azimuth • Elevation • Concepts • Static and Dynamics of System • Software • SatPC32 • Interpolation • Programming • Electrical/Controls • Position Sensing • Controller • System Diagram • Timeline • Responsibilities • Questions

  3. Background • VTC developing CubeSat, transmits data • Continuing where previous groups have left off • 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

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

  5. Solution • Gears and motors, motor controllers • Freescale Coldfire 32-bit Microcontroller • Serial interface with SatPC32 simulating the functions of EGIS controls • Magnetic Encoders sense rotor/dish position • Use/Modify existing designs for elevation and azimuth control

  6. Mechanical Areas of Interest • Axis orientation (EL/AZ or AZ/EL) • Weight of dish and Center of Mass • Moment of Inertia of the dish • Torque needed to spin/flip the Dish

  7. Available Solution • EGIS- Current market solution • 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

  8. Azimuth and Elevation • Azimuth • A left to right angle measurement from a fixed point (north in navigation) • Elevation • Angle between the flat plane and the object in the sky (satellite).

  9. Axis MountingDesign • Probable AZ/EL Configurations: • Fork Mount • Same simple left-right/up/down characteristics • Allows the dish to go over backwards if it needs to.

  10. Axis Mounting Design • Equatorial Mount: • The movement of the Azimuth (here the Declination Axis) makes an arc in the sky. • The Elevation (a) is set parallel to the earths axis of rotation. This system is much more accurate than the Fork and needs a much less complicated control system.

  11. Choosing Design Choosing a Solution: • If there is a polar orbit, or strange orbit all together: • Adish with the fork configuration may be the best choicebecause it can track any satellite.

  12. Proposed Fork Design EL Axis AZ Axis

  13. Forces and Foot Pounds • Balance (RoM = Rm) • Reduce driving torque that the motor has to produce

  14. Mechanical Design Statics and Dynamics: Key Points of Interest: • Dynamic Torque- The torque encountered by a system that is not only in motion, but accelerating. • Static Torque- The torque produced at constant velocity (rest or running). • Center of Mass- The mean location of all system masses. • Moment of Inertia- A measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation.

  15. Center of Mass: Solid Works

  16. Mechanical Design Torque Calculations: • TStarting= KrunningTrunning Krunning = Running Torque Multiplier • To= [ 5250 x HP ] / N To = Operating or running Torque ( ft-lbs ) | • HP = Horsepower delivered by electric motor **Note: Values switch from N = Rotational velocity ( rpm)| metric to English Units 5250 = Constant converting horsepower to ft-lbs/minute and work/revolution to torque • T = [ N x WR2 ] / [ Ta x 308 ] T  = Time ( seconds )|N = Velocity at load (rpm ) Ta = Average Torque During start ( ft-lbs ) WR2 =  Rotating Inertia (lbs-ft3)|W =Weight (lbs) R = Radius of Gyration (ft2)| 308 = Constant derived converting minutes to seconds, mass from weight, and radius to circumference

  17. SolidWorks Motion Analysis

  18. Torque Curves (Elevation)

  19. Torque Curves (Azimuth)

  20. Mechanical Design Methods of Determining and Modeling Physical System Parameters: • SolidWorks - COMSOL • Scaling system down and measure accordingly • Placement of Ballast • Forces Involved

  21. System Diagram SatPC32 RS232 EL - Motor Controller Micro-Controller AZ - Motor Controller Limit Switches Position Encoders 21

  22. Timeline (Rev 1.0)

  23. Areas of Reasonability Hodge CAD and FEA Torque Calculations/Measurements Ballast Implementation Motor Specifications Lyford Sensors and Electrical Mounting Motors Drive Mechanisms and Implementation Material Manager/ Budget Schreiber Project Manager Mechanical Analysis and FEA Interpolation Implementation Communications Motor Controllers

  24. Questions?

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