Gimbal Control and Design for Tracking of a

Gimbal Control and Design for Tracking of a Solar Eclipse Matthew Plewa and Brent Scharlau

Introduction Two part system • Gimbal • Flight characteristics • Pointer • Two methods commonly used • Mathematical method • Imaging method

Gimbal • What is the typical motion of balloons? • Pendulum motion • Rotation • What is required to compensate for this motion?

Gimbal Requirements • 3 axis are required • Pitch • ± 90 degrees • Roll • ± 90 degrees • Yaw • Due to rotation this axis needs as much freedom as possible

Electronics • Gimbal controller • storm 32 -BGC • Compact • Contains brushless motor controllers • Variety of input pins • Closed source firmware causes issues for modifications

Electronics • RFD-900 • Needed a way to send Sun’s current azimuth and zenith angle • The gimbal controller allows for PWM input for setting values • RFD-900 acts as a serial port and using a chipkit allows the string to be converted and then transmitted using PWM

Pointing Analytic • Developed for solar array pointing • Angles can then be transmitted via RFD 900 link

Pointing Imaging • Using a low resolution camera • Filter required to prevent sensor damage • Look for the brightest object • Even during an eclipse arcs of the Sun will still be present • It is possible using simple geometry to find the center of an arc. • Point toward the center of the circle or arc

Manufacturing • Mostly off the shelf parts • It was necessary to manufacture the adapter plates between of the shelf components and the gimbal motors

Testing • RFD-900 link testing to verify strings where being decoded properly • Axis rotation had to be tested • Yaw axis was limited due to the large number of wiring going to the camera • Would be necessary to unwind the cables periodically

Flight • Cables led to more issues • Since it was a cold spring day the cables were incredibly stiff • This meant that the motors had to work harder to compensate for this stiffness. • During the flight this caused the gimbal controller to time out since the requested angles were not achievable

Future Work (Gimbal) • Cable management • Yaw location change • It may be possible to make the yaw axis not have to compensate for the cables • Using a “Weather vane” to limit the amount of rotation (Hopefully eliminating the rotation)

Future Work (Pointer) • Hybrid system • Instead of using an imaging or analytic method by itself using them together can eliminate many of the issues • This will also help to eliminate any error that accumulates in the gimbal controller • A fully automatic system is possible through a hybrid system

Questions? Matthew Plewa Email: mplewa@iastate. edu