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despin platform

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wjpremerlani
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Last seen: 8 months 6 days ago
Joined: 2022-03-30 20:44
Posts: 11
despin platform

Hi,

A Flipsky 7070 110 KV motor and a miniFSESC6.7 Pro ESC were two key components in a "despin" platform that I built to help out a friend who flies large model rockets.

The mission of the platform is to provide a stationary platform for taking videos from the top of a large, spin-stabilized model rocket that might be spinning at up to 600 RPM CW or CCW, and flying at speeds of up to mach 6. He and I are calling it a "despin" platform, because it counteracts the spin.

The motor, battery, ESC and controller are mounted on the stabilized platform, which is attached to the nose of the rocket by the motor shaft, and supported by a combination of a thrust bearing and the motor bearings themselves. There are two, 2-cell Lipo batteries in series. Everything is arranged to preserve inertial symmetry, because even though the platform will not be spinning, it is desired to maintain the overall inertial symmetry of the rocket.

I built the controller myself from scratch, including hardware and software. The interface between the controller and VESC is PWM.

The VESC was ideally suited for the application, particularly being able to operate with zero dead band in duty cycle mode, since the the controller itself was doing the outer loop speed control. The VESC programming tool was easy to use and very useful.

Here is a video of a ground test that I performed on the system by spinning it up at 78 rpm on a very old Radio Shack record player: https://drive.google.com/file/d/1VwiN_7uSeQDj43A4TpVVFm6f6OTuM0Z9/view?u...

The VESC and motor were sized to provide enough transient torque to handle the significant inertia of the platform. The actual current draw on the battery is almost zero, because the only significant continuous torque loading on the motor is due to the friction of the thrust bearing and the motor bearing, which is very small.

I have sent the system off to my friend who plans to do ground testing at 600 rpm, either with a lathe, or perhaps with a NASA spin table that he has access to as a NASA employee.

An actual flight is planned for later on this year.

Best regards to all, Bill Premerlani