Fuzzy control on the phase and stroke of a linear compressor of a split-Stirling cryocooler

A new dual fuzzy controller for the linear compressor of a split-Stirling cryocooler is proposed in this paper. In addition to the stroke, the phase of the working fluid, circulating from the compressor to the split regenerator, is an important parameter to the cooling efficiency. The non-linearities and uncertainties of a cryocooler make it impossible to use a conventional controller over a wide range of operation. This fuzzy controller is designed to consist of a fuzzy stroke control and phase control without any explicit system models, but driven in the human thinking mechanism. Computer simulations and experiments showed that the compressor piston in the displacement tracking control failed to catch up with the periodic sinusoidal command. However, the dual fuzzy controller can successfully drive the piston to follow the stroke as well as the phase of the reference command. This new fuzzy control methodology can be employed with split-type cryocoolers, whose stroke and phase both contribute to the refrigeration performance. (C) 1998 Elsevier Science Ltd. All rights reserved.