The fuzzy control of an electrohydraulic fatigue testing system

Electrohydraulic control systems have been widely used for material testing. But, because of the variety of parameter and high–order parameter identification, the design of a suitable controller is not easy. In this paper, the fuzzy logic controller and linguistic approach self–organising fuzzy controller are implemented for fatigue position and force testings. Experiments have been carried out at between 0.1–10 Hz. The results indicate that the fuzzy logic controller with a fixed fuzzy rule is valid only for a narrow frequency range. The linguistic approach self–organising fuzzy controller has a learning mechanism to adjust the fuzzy rule. Thus it can be implemented for a wider frequency range, and the peak–peak magnitude errors of both position and force testings are within 3% for 0.1–10 Hz sinusoidal commands.