ANALOG ADAPTIVE VIBRATION CANCELLATION SYSTEM FOR STIRLING CRYOCOOLERS

The vibration produced by Stirling cryocoolers is incompatible with pr ecision-pointing imaging instruments. This paper examines a vibration cancellation system that was designed for the expander of a Hughes tac tical cooler. This system uses a custom-designed multi-axis counterbal ance and an analogue implementation of an adaptive feedforward compens ator. A non-linearity associated with the counterbalance is modelled, and its effect on the closed-loop system is assessed. In an initial te st, the third harmonic of the expander's axial force was cancelled by 22-38 dB over a wide range of drive frequencies, with little effect on the other harmonics or the lateral vibrations.