A study on force control of electric-hydraulic load simulator using an online tuning Quantitative Feedback Theory

Nowadays, hydraulic actuators play an important role in a modern industry where controlled force or position with high accuracy is the most significant demand. This paper presents a new kind of electric-hydraulic load simulator (HLS) for conducting performance and stability test in the bench system where force control is important. The system model consists of a hybrid hydro-electric actuator and another hydraulic circuit generating disturbances. For the purpose of improving force control performance of hydraulic hybrid systems, an online tuning force controller based Quantitative Feedback Theory (QFT) technique is applied to the load simulator and also proposed in this paper. The controller is firstly designed to satisfy the robust performance requirement, tracking performance specification, and disturbance attenuation despite uncertainties of the load simulator system. Secondly, by using gradient descent method it becomes an online tuning QFT controller during the system operation process to adapt with a wide range of working conditions including perturbations. Experiments are carried out to evaluate the effectiveness of the proposed control method applied for the electric-hydraulic load simulator systems.