FLIGHT HARDWARE IMPLEMENTATION OF A FEED FORWARD VIBRATION CONTROL SYSTEM FOR SPACEFLIGHT CRYOCOOLERS

Edward James &Stuart Banks McDonnell Douglas Corp. Seabrook, MD, USA 20706

Johnathon Wilmot Hughes-STX Greenbelt, MD USA 20770

A simple control system using force sensors and non-real time signal processing has been designed and tested which reduces vibration levels by as much as 50dB at the fundamental drive frequency and 30dB for the 2nd through the 20th harmonics. The NASA/GSFC control algorithm is briefly discussed.

A proven radiation hardened flight microprocessor card designed and built for the Cosmic Ray Upset Experiment (CRUX) was adapted for use with NASA/GSFC's feed forward, non-real time, vibration control algorithm. The card design consists of a Intel 8085 microprocessor running at 2 Mhz with 8k of PROM and 8k of RAM. It has one serial RS-422 UART and a 12 bit analog to digital converter. An auxiliary circuit board was fabricated which contains dual port memory I/O and digital to analog converters. The CRUX and auxiliary circuit card designs are discussed in detail.

This vibration control hardware & software system will then be tested on a variety of cryocoolers including a Magnavox, Texas Instrument, Hughes tactical cryocoolers followed by TRW, Lockheed & Ball long-life cryocoolers. Test results will be presented. Conclusions and lessons learned from the GSFC test experience will be presented.

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