 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 2

 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 3

 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 4

 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 5

 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 6

 Azimuth › A left to right angle measurement from a fixed point (north in navigation) 7  Elevation › Angle between the flat plane and the object in the sky (satellite).

8 Probable Azimuth/ Elevation Configurations:  Fork Mount Same simple left- right/up/down characteristics Allows the dish to go over backwards if it needs to.

9  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.

10 Choosing a Solution:  Knowing the Satellite path ultimately determines what setup is best. › If the Satellite orbit is not a polar orbit, then the Equatorial Mount might be the best choice.

11 Choosing a Solution:  If there is a polar orbit, or strange orbit all together:  The Dish with the Fork configuration may be the best choice.

12  Balance (R o M = Rm) › Reduce driving torque that the motor has to produce

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. 13

14  Worm Gears › Speed (Gear Ratio) › Torque › Modify existing designs

15 Torque Calculations:  T Starting = K running T running K running = Running Torque Multiplier  T o = [ 5250 x HP ] / N T o = 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 WR 2 ] / [ T a x 308 ] T = Time ( seconds )|N = Velocity at load (rpm ) T a = Average Torque During start ( ft-lbs ) WR 2 = Rotating Inertia (lbs-ft 3 )|W =Weight (lbs) R = Radius of Gyration (ft 2 )| 308 = Constant derived converting minutes to seconds, mass from weight, and radius to circumference

Methods of Determining and Modeling Physical System Parameters:  SolidWorks - COMSOL  Scaling system down and measure accordingly › Placement of Ballast › Forces Involved 16

 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 17

18 Screen Shot of SatPC32 in use WinListen predicts path

Main Loop Interpolator Encoder Check SatPC32 Limit Check

 Read new position from serial › 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 20 Controller (Set Outputs) New Serial ? Check Encoder s? Read Serial Read Encoders

G 1 T AccelerationVelocity 1 T 1 s 1 s SatPC32 Data Summing Junction Operation

24 Micro- controller EL - Motor Controller AZ - Motor Controller Limit Switches RS232 SatPC32 Position Encoders

 1° step size = at least 9-bit res.  2 9 = 512 steps  360 deg/512 steps =.7 o /step  Magnetic Shaft Encoder › 15,000rpm max › Absolute Position Sensing › Analog output from 10-bit DAQ  1024 Steps = 0.35 o /step

27 Micro- controller EL - Motor Controller AZ - Motor Controller Limit Switches RS232 SatPC32 Position Encoders

 Hodge › CAD and FEA › Torque Calculations/Measurements › Ballast Implementation  Lyford › Sensors › Mounting Motors › Drive Mechanisms and Implementation  Schreiber › Project Manager › Interpolation Implementation › Communications › Motor Controllers