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Abstract
More and harsher operational environment of spindle puts forward higher requirements for the performance of bearings. It is no longer suitable for the traditional journal bearing to work in the conditions above. In order to meet the requirements of high speed and heavy haul operation, the article presents servo-valve active compensation to realize accurate control of spindle position accuracy and improve the behavior of hydrostatic journal bearings. By regarding the journal bearing as an automatic control system in the process of modeling, the dynamic equation and flow continuity equation for the proposed bearing were derived. The dynamic characteristics of the proposed journal bearings and the traditional journal bearings were studied in the operational environment of high speed and heavy duty. The numerical results indicate that the proposed hydrostatic active journal bearing has good performances, including good controllability and stability, fast response, high stiffness, strong resistance, etc., compared to traditional journal bearings. The use of active lubrication with servo-valve controller results in a significant amount of amplitude reduction and greatly improves the positional accuracy of the spindle. Therefore, it has the potential application in heavy-haul and high-speed machinery.
NOMENCLATURE
| b | = | Width of recess (m) |
| b1 | = | Width of land (m) |
| Cd | = | Discharge coefficient of servo-valve |
| D | = | Diameter of bearing (m) |
| d | = | Servo-valve core diameter (m) |
| hi | = | Thickness of the oil film (m) |
| h0 | = | Initial thickness of the oil film (m) |
| L | = | Length of the bearing (m) |
| l | = | Length of the recess (m) |
| l1 | = | Length of the land (m) |
| m | = | Mass of the spindle (kg) |
| Pi | = | Oil pressure of the oil recess (Pa) |
| Ps | = | Oil supply pressure (Pa) |
| r | = | Spindle radius (m) |
| s | = | Maximal displacement of the servo-valve (m) |
| u | = | Linear velocity of the rotor surface (m/s) |
| Ve | = | Effective volume (m3) |
| w | = | Servo-valve area gradient, w = π d |
| xv | = | Servo-valve core displacement (m) |
| β | = | Oil bulk modulus (N·s/m) |
| η | = | Oil viscosity (Pa·s) |
| ρ | = | Oil density (kg/m3) |