PLC implementation of fractional PI controller in positioning of electrohydraulic servodrive

The article describes the implementation of fractional order PI controller with the Programmable Logic Controller (PLC). The control system proposed is used for positioning of an electrohydraulic drive with Bosch Rexroth servo valve. The controller is based on PLC, working under real time operating system Automation Runtime. User interface is equipped with the touch panel of Power Panel 500 type. In the first part of the paper the fractional order calculus theory is introduced. In addition, some examples of fractional controller implementations in different kinds of objects are presented. The subsequent section focuses on author’s own research. The Oustaloup’s method description is recalled along with its computer implementation. Further, the impact of finite order of the approximation function is verified. The article includes the description of test stand structure, code generation and implementation of PI controller on the dedicated PLC.