Decoupling control of radial 4 degree of freedom system of magnetic-liquid double suspension bearing based on generalized extended state observer.

As the novel suspension bearing, Magnetic-Liquid Double Suspension Bearing (MLDSB) is mainly supported by magnetic suspension and supplemented by a liquid hydrostatic bearing. Due to its great bearing capacity and stiffness, rapid response, great active control, and so on, MLDSB is suitable for medium speed heavy loads and has a large carrying capacity and high operating stability. In addition, the radial inertia coupling and gyroscopic coupling between radial 4-DOF control channels can reduce control precision, operation stability, and reliability of MLDSB. Therefore, a mathematical model of radial 4-DOF rotor-dynamics of MLDSB is established in this paper, and the inherent coupling mechanism is explored. Taking inertial coupling, gyroscopic coupling, and external disturbance loads as lumped disturbances, a decoupled controller based on Generalized Extended State Observer (GESO) is established. The influence of the GESO controller on the decoupling and control performance of radial 4-DOF control channels is simulated. The results indicate that the decoupling effect of the GESO controller is great. Under the action of step signal, the steady displacement, maximum displacement, adjustment time, and peak time of the rotor after decoupling are all reduced, among which the steady displacement and maximum displacement are the most obvious. Under the sinusoidal signal, the steady displacement and maximum displacement are reduced by 90%, which can effectively avoid the "gap-impact" fault. Under the pulse signal, the steady displacement, maximum displacement, adjustment time, and peak time are all reduced, among which the maximum displacement is the most obvious. The research in this paper can provide a theoretical reference for the stable support and decoupling control of MLDSB.

Research on Identification Method of Wear Degradation of External Gear Pump Based on Flow Field Analysis.

As a kind of hydraulic power component, the external gear pump determines the performance of the entire hydraulic system. The degradation state of gear pumps can be monitored by sensors. Based on the accelerated life test (ALT), this paper proposes a method to identify the wear degradation state of external gear pumps based on flow field analysis. Firstly, the external gear pump is theoretically analyzed. Secondly, dynamic grid technology is used to simulate the internal flow field of the gear pump in detail. Finally, the theoretical and simulation results are verified by the ALT. The results show that this method can effectively identify the wear degradation status of four sample pumps. The results of the work not only provide a solution to the research on the wear degradation of external gear pumps, but also provide strong technical support for the predictive maintenance of hydraulic pumps.