RESUMO
As an alternative way to lubricating oil of oil-film bearing, a new type of nano-scale magnetic fluid oil for oil-film bearing was developed, which could be targeted to improve the lubrication performance of oil-film bearing and improve the load-carrying capacity. A new type of nano-scale magnetic fluid oil-film bearing oil was prepared by the co-precipitation technique based on industrial S-220 lubricating oil as the base carrier. The characterization of the prepared oxide was performed on powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). The stability of nano-scale magnetic fluid oil was checked by magnetic sedimentation and centrifugation. Based on the modified Einstein formula, the viscosity of the magnetic fluid is analyzed from the temperature and magnetic field strength using an unifactor experiment method. The results show that the smaller the magnetic particle size in the magnetic fluid, the better the magnetic energy, dispersion and stability. The viscosity-temperature characteristic of nanoscale magnetic fluid is consistent with the theoretical analysis. Compared with the basic liquid, the viscosity-temperature characteristic of the magnetic fluid is obviously improved, which helps improve the lubrication performance of oil-film bearing and provides the basis for continuous lubrication.
RESUMO
In this paper, a control method for a hydraulic loading system of an electromechanical platform based on a fractional-order PID (Proportion-Integration-Differentiation) controller is proposed, which is used to drive the loading system of a mechatronic journal test rig. The mathematical model of the control system is established according to the principle of the electro-hydraulic system. Considering the indetermination of model parameters, the method of parameter identification was used to verify the rationality of the theoretical model. In order to improve the control precision of the hydraulic loading system, the traditional PID controller and fractional-order PID controller are designed by selecting appropriate tuning parameters. Their control performances are analyzed in frequency domain and time domain, respectively. The results show that the fractional-order PID controller has better control effect. By observing the actual control effect of the fractional-order PID controller on the journal test rig, the effectiveness of this control algorithm is verified.