Abstract
Pump-controlled hydraulic circuits are more efficient than valve-controlled circuits, as they eliminate the energy losses due to flow throttling in valves and require less cooling effort. Presently existing pump-controlled solutions for single rod cylinders encounter an undesirable performance during certain operating conditions. This paper investigates the performance issues in common pump-controlled circuits for the single rod actuators. Detailed analysis is conducted that identifies these regions in a load-velocity plane and the factors affecting them. The findings are validated by experimental results. A new design is then proposed that employs a limited throttling valve alongside two pilot operated check valves for differential flow compensation to improve the performance. The valve is of the flow control type and is chosen to have a throttling effect over critical regions; it has the least throttling over other operating regions, thus maintaining efficiency. Experimental work demonstrates improved performance in a full operating range of the actuator as compared to a circuit that uses only the pilot-operated check valves. This circuit is energy efficient and capable of recuperating energy.
Highlights
It has been seen that pump-controlled hydraulic circuits have better efficiency compared to valve-controlled circuits
Throttling losses in valves represent one of the main energy losses in hydraulic circuits presently used in these machines
It was shown that how cylinder area ratio, operated check valves was analyzed and the regions in the load-velocity plane that show poor
Summary
It has been seen that pump-controlled hydraulic circuits have better efficiency compared to valve-controlled circuits. Rahmfeld and Ivantysynova [11] introduced a circuit that comprises a variable displacement piston pump and two pilot-operated check valves (POCVs) to compensate for the differential flow in single-rod cylinders. To compensate for the differential flow Jalayeri et al [21] used an on/off solenoid valve and a check valve, while Altare and Vacca [15] utilized a special form of shuttle valve, which they called a dual-pressure valve Both designs are more energy efficient as compared to conventional valve-controlled alternatives and accurate enough for many industrial applications. From the above discussion it is seen that in spite of the large amount of studies on the topic, throttle-less actuation technology for single rod cylinders has not been fully explored, compared to valve-controlled actuation, in terms of dynamic performance [22]. The trade-off between energy efficiency and performance is investigated
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