Suljetun hydraulijärjestelmän digitaalinen asemasäätö

摘要

The design of safe and reliable digital control systems requires understanding phenomena that do not exist in continuous-time control systems. Neglecting this in the design process may cause significant unwanted behavior or even instability. In this thesis, the digital position control of an existing closed-loop hydraulic system is studied by means of simulation. Models are developed for the hydraulic system, based on mathematical models of the system components, and for the digital controller based on the properties of digital control systems. The aim is to take into account the most important aspects of digital control. Previously, the system has been successfully controlled by an analog controller. This thesis focused on the study of digital controllers with sample rates between 5 and 20 Hz. The performances of the analog and digital controllers were compared in various conditions, including model parameter variations and the presence of measurement noise. It was found that by an appropriate filtering and selection of simple control equations, the performances of the two controllers were practically equivalent.