Modelling and experimental verification of pressure relief synchronous control for small trapped fluid volumes

This paper presents a pressure relief synchronous control method for four small entrapped high-pressure fluid volumes on a huge hydraulic machine. Firstly, as the existing pressure relief methods cannot behave well for small entrapped high-pressure fluid volumes, a novel electrohydraulic proportional pressure relief circuit is proposed. The electrohydraulic proportional pressure relief circuit is composed of a proportional pressure relief valve, a damping orifice and a constant pressure source, through which the pressure can be relieved proportionally to the command signal. Secondly, as the machine is a manned hydropower carrier, a very safety-critical application, a simple and easy to implement hybrid control scheme consisting of a synchronization controller and a pressure tracking controller is developed. As the pressure relief circuit has a wide range of operating conditions and parameter uncertainties, a practical self-tuning fuzzy proportion integration (PI) pressure tracking controller with feedforward is proposed, and a master–slave PI synchronization pressure controller with dead band is employed for the four entrapped fluid volumes. Finally, the experimental verification is implemented on a test stand to demonstrate the effectiveness of the proposed synchronous control system. The experimental results confirm that the pressure deviations among the four small entrapped high-pressure fluid volumes are bound within ± 0 . 18 MPa .