System Dynamics and Control of a Linear Compressor for Stroke and Frequency Adjustment

Abstract

This paper presents results of an investigation on the system dynamics and the controller design of a linear compressor for stroke and frequency adjustment. A system dynamics model was derived and identified experimentally. A control system was designed based on the system dynamics model. The control system used a PDF (Pseudo-Derivative-Feedback) algorithm. The results of step response test for stroke regulation show that, it takes about 0.2 s for the regulation with small overshoot and negligible steady-state error. For the step change of operating frequency, it takes about 0.4 s to reach steady state with small tracking error. The control system also has very good performance for disturbance rejection. The transient periods are about 0.2 s with stroke variation to within 10%. The controller is shown to have the capability to replace the conventional crank-shaft mechanism as in a reciprocating compressor. The controller can also be used to regulate both stroke and frequency of the compressor during operation. The performance can thus be very flexible and efficient for a system using the linear compressor and the present control system.