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.