A Fractional Order Fuzzy PID Controller for An Electro-Hydraulic Rotary Actuator

Abstract

Nowadays, hydraulic systems play an important role in modern industry for the reason that hydraulic systems have many advantages over other technologies with electric motors, as they possess high durability and the ability to produce large forces at high speed. However, most previous hydraulic actuators contain a valve-controlled hydraulic system (VHSs) that utilizes an open loop control which is results in low efficiency and loss the energy. To solve these disadvantages of conventional hydraulic system, electro-hydraulic actuator (EHA) systems have been developed and widely used. The electro-hydraulic rotary actuator (EHRA) is known as one kind of EHA system where the hydraulic rotary is the end-effector of system. The EHRA has inherited the advantages of EHA system. Hence it is popularly implemented in the systems wherever high torque is required. However, the main disadvantages of EHRA system are complicated dynamic, non-linearity and large uncertainties in hydraulic systems due to unstableness of some hydraulic parameter such as bulk modulus, the compressibility of oil or viscosity of oil which lead to the control problems become a difficulty. This thesis presents a fractional order fuzzy PID (FOFPID) controller for position control of an EHRA system. The proposed control is a combination between the fractional order PID controller and a fuzzy logic rule. Fractional order PID controller with two extra parameters changes the integer order of integral and derivative functions in conventional PID to non-integer order. Therefore, they help to improve tracking performance. Three fuzzy rules are designed to adjust the parameters of FOPID. The Kp, Ki, Kd gains are adjusted during the operation process. To verify the performance of the proposed system and controller, some simulations and experiments are carried out in different conditions. The results demonstrate that the proposed fractional order fuzzy PID controller achieves the better performance with high accuracy in various working conditions supporting strongly the applicability of the proposed control method in modern hydraulic applications.