Abstract
Digital hydraulic technology as an emergent and important branch of fluid power offers good prospects for intelligence, integration, and energy saving of hydraulic systems. The high-speed on-off valve (HSV) that is a critical component of digital hydraulics has the drawbacks of specific design, narrow scope of application and high price compared to the commercial solenoid screw-in cartridge valve (SCV) widely used in the hydraulic industry at present. In this paper, a hybrid voltage control strategy composed of the preloading voltage, positive pulse voltage, holding voltage and negative pulse voltage is proposed to enhance the dynamic characteristics of the SCV, which makes it meet the demands of the digital hydraulics and achieve the end of replacing the HSV. Based on the structural analysis of the SCV, a mathematical model of the SCV is deduced. Subsequently, the simulation model of the SCV is developed in AMESim and validated by experimental measurements. The effects of the different duty ratios of the preloading voltage and holding voltage on the dynamic characteristics of SCV are studied, and the dynamic responses of the SCV under the normal voltage, positive and negative pulse and hybrid voltage control strategies are compared. The simulation results indicate that the increment of the preload voltage duty ratio and the reduction of the holding voltage duty ratio are conducive for decreasing the total opening and closing time of the SCV, especially the opening delay and closing delay time. The hybrid voltage control proposed has a better effect in dynamic characteristics than the other two strategies, using which the total opening time of the SCV reduces by 74.24% (from 29.5 ms to 7.60 ms), and the total closing time is drastically squeezed by 92.06% (from 136 ms to 10.8 ms). This provides a technical reference for improving the dynamic response speed of SCVs and popularizing digital hydraulic technology.
Highlights
The conventional electro-hydraulic proportional/servo system (EHPSS) has been widely used in robotics, aerospace, and precision machining, etc., because of its advantages such as high power mass rate and favorable dynamic performance [1]
The opening and closing times are the most important index to evaluate the dynamic performance of the high-speed on-off valve (HSV) in the digital hydraulic field, which directly affects the performance of a digital hydraulic system
The hybrid voltage control method consisting of preloading voltage, positive pulse voltage, holding voltage and negative pulse voltage is put forward and applied to the usual commercial screw-in cartridge valve to raise its dynamic response so that the SCV
Summary
The conventional electro-hydraulic proportional/servo system (EHPSS) has been widely used in robotics, aerospace, and precision machining, etc., because of its advantages such as high power mass rate and favorable dynamic performance [1]. Most of the existing relevant research has improved the dynamic response characteristics by optimizing the structure and parameters of HSV. In reference [4], the effects of the structural parameters (the valve spool diameter and the conical seat angle) on the linear control performance of HSV were researched by the method of computational fluid dynamics (CFD). This research provides a theoretical basis for the application of hybrid voltage control method in improving the dynamic characteristics of the SCV, and has important significance for expanding the application of digital hydraulic technology. When the coil is de-energized, the solenoid does not produce electromagnetic force, and the spool only contacts closely with the valve seat under the action of spring force
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