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Modeling, simulation, and identification of the hydrostatic pumps and motors
Published in Nicolae Vasiliu, Daniela Vasiliu, Constantin Călinoiu, Radu Puhalschi, Simulation of Fluid Power Systems with Simcenter Amesim, 2018
Nicolae Vasiliu, Daniela Vasiliu, Constantin Călinoiu, Radu Puhalschi
The modern hydrostatic transmissions requiring a continuously variable motor shaft speed are based on the electrohydraulic proportional control of a bent axis axial pistons motor displacement (Figure 7.5.1) [6,7]. The servovalve is governed by a DC solenoid attached to the control cover. When the solenoid current increases above the threshold current, the servopiston starts to move from the max toward the minimum displacement position. The shaft speed versus current relation is a nonlinear one. In order to minimize hysteresis, a pulse-width modulated control signal of 70–90 Hz has to be utilized [8]. This type of hydraulic motor has gained widespread acceptance in closed-loop industrial systems because they do not need an auxiliary pump: a three-way selector takes the small control oil flow from the motor power ports. The overall motor size is small enough to fit the driving wheels, winches, and so on. The swashplate variable displacement motors are heavier and expensive because they need an external servovalve, and an additional medium-pressure gear pump. They are promoted especially in high-performance applications such as aerospace and military ones. The main problem of these servomotors dynamics is the control stability generated by the low-stiffness feedback spring.
A hybrid of CFD and PSO optimization design method of the integrated slipper/swashplate structure in seawater hydraulic axial piston pump
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Ruidong Hong, Hui Ji, Songlin Nie, Hao He, Ming Guo, Fanglong Yin, Xiaopeng Yan
The configuration of a traditional SHAPP is illustrated in Figure 2. The rotating kit mainly includes a cylinder which is connected to the drive shaft and piston/slipper assembly. A slipper is coupled to the piston through a pair of ball and socket joint to form a ball joint friction pair. When the shaft rotates, the piston/slipper assembly slides on the swashplate, and forces each piston to make a periodic linear reciprocating motion inside the cylinder. Generally, the main lubrication interfaces of SHAPP would adopt the ‘soft-to-hard’ material combination of corrosion-resistant metals and engineering materials, such as PEEK/17-4PH (Huang et al., 2020; Nie et al., 2019). However, those underwater equipment would be subject to the increased working pressure and rotational speed in some specific occasions, which will lead to the abnormal work of SHAPP. The high-working pressure significantly would be inclined to cause the deformation of softer material and increase the lateral force on the piston, bend the piston and accelerate its wear, especially in poorly lubricated seawater (Nie et al., 2021; Yin et al., 2021a,b; Zhu et al., 2020); the high shaft speed would make the slipper generate considerable centrifugal force due to its own structure causing severe sliding wear (Bergada et al., 2010; Suo et al., 2021).