Investigation of New Servo Drive Concept Utilizing Two Fixed Displacement Units

Pedersen, Henrik C.; Schmidt, Lasse; Andersen, Torben Ole; Brask, Morten H.

doi:10.5739/jfpsij.8.1

Cited by 17 publications

(19 citation statements)

References 1 publication

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“…Here the uneven cylinder flows are compensated by the pumps, as the displacement ratio of the pumps ideally matches the cylinder area ratio. However, as pointed out by [70], anti-cavitation valves and pressure-relief valves are generally required, because the pressure dependent pump leakages make it impossible to achieve proper matching of the pump displacement ratio and the cylinder area ratio under all operating conditions. To limit a potential pressure increase [70] uses two proportional valves shown as the blue components to bleed off oil to the reservoir.…”

Section: Class B-variable-speed Single Prime Mover With Multiple Pumpsmentioning

confidence: 99%

Classification and Review of Pump-Controlled Differential Cylinder Drives

et al. 2019

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Pump-controlled hydraulic cylinder drives may offer improved energy efficiency, compactness, and plug-and-play installation compared to conventional valve-controlled hydraulic systems and thus have the potential of replacing conventional hydraulic systems as well as electro-mechanical alternatives. Since the late 1980s, research into how to configure the hydraulic circuit of pump-controlled cylinder drives has been ongoing, especially in terms of compensating the uneven flow requirements required by a differential cylinder. Recently, research has also focused on other aspects such as replacing a vented oil tank with a small-volume pressurized accumulator including the consequences of this in terms of thermal behavior. Numerous references describe the advantages and shortcomings of pump-controlled cylinder drives compared to conventional hydraulic systems or electro-mechanical drives. This paper presents a throughout literature review starting from the earliest concepts based on variable-displacement hydraulic pumps and vented reservoirs to newer concepts based on variable-speed electric drives and sealed reservoirs. By classifying these drives into several proposed classes it is found that the architectures considered in the literature reduce to a few basic layouts. Finally, the paper compares the advantages and shortcomings of each drive class and seek to predict future research tasks related to pump-controlled cylinder drives. IntroductionWith an increased industrial focus on energy efficiency, plug-and-play installation, and compactness, conventional valve-controlled hydraulic cylinder drives are increasingly being replaced by electro-mechanical alternatives, such as roller or ball screws [1], especially for small power classes. This happens despite the well-known advantages of hydraulic linear actuation such as large force/power densities, reliability, and robustness. Hydraulic actuation is, however, still the preferred solution for many applications such as industrial presses, large mobile machinery, crane manipulators, primary aircraft control etc. [2][3][4]. Among other reasons this is due to certain limitations for the electro-mechanical alternatives, such as limited reliability (e.g., shock loads damage), the difficulties of implementing overload/failure protection and/or limited force capabilities [5][6][7]. To strengthen the position regarding these applications and to make hydraulic cylinder drives competitive with electro-mechanical drives for low power applications, there is a need to enhance both the energy efficiency and the overall flexibility of hydraulic cylinder drives.The flexibility of a hydraulic system may be related to how power is being distributed between the prime mover and the actuator(s). As illustrated in Figure 1, at least three different power distribution topologies exist: hydraulic, mechanical, and electrical distribution.

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Section: Class B-variable-speed Single Prime Mover With Multiple Pumpsmentioning

confidence: 99%

Classification and Review of Pump-Controlled Differential Cylinder Drives

et al. 2019

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“…In the case of a non-vented valve ( Figure 6 depicts alternative designs), an opening pilot pressure lower than the inlet pressure is the prerequisite for "normal flow" (i.e., p x < p In ). The poppet lift always results from the force equilibrium that is expressed differently and is contingent on "normal flow" (16) or "reverse flow" (17).…”

Section: The Dynamic Modeling Of the Systemmentioning

confidence: 99%

“…It is based on multiple fixed-displacement pumps/motors driven by a common variable-speed prime mover. Alternatives with two hydraulic units [6,[16][17][18] or with three hydraulic units [19][20][21] exist.…”

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A Self-Contained Electro-Hydraulic Cylinder with Passive Load-Holding Capability

et al. 2019

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Self-contained electro-hydraulic cylinders have the potential to replace both conventional hydraulic systems and the electro-mechanical counterparts enhancing energy efficiency, plug-and-play installation, and reduced maintenance. Current commercial solutions of this technology are limited and typically tailor-made, whereas the research emphasis is primarily on cost efficiency and power applications below five [kW]. Therefore, there is the need of developing more flexible systems adaptable to multiple applications. This research paper offers a contribution in this regard. It presents an electro-hydraulic self-contained single-rod cylinder with passive load-holding capability, sealed tank, capable of recovering energy, and scalable up to about eighty [kW]. The system implementation on a single-boom crane confirms its feasibility: The position tracking error remains well within ±2 [mm], oscillations are limited, and the overall energy efficiency is about 60 [%] during actuation. Concerning the passive load-holding devices, it is shown that both vented and non-vented pilot-operated check valves achieve the desired functioning and can hold the actuator position without consuming energy. Additional observations about the size and the arrangement of the load-holding valves are also provided. In conclusion, this paper demonstrates that the proposed self-contained cylinder can be successfully extended to several practical applications, especially to those characterized by overrunning external loads and the need of securing the actuator position.

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“…Consequently, compact and self-contained electro-hydraulic cylinders (SCCs) have received considerable attention in the last decade [3][4][5][6][7][8][9][10], showing the potential to replace both conventional hydraulics and linear electro-mechanical systems [11]. SCCs can in fact enhance energy efficiency, modular design, plug-and-play installation, and reduced maintenance [12].…”

Section: Introductionmentioning

confidence: 99%

A Comparison Study of a Novel Self-Contained Electro-Hydraulic Cylinder versus a Conventional Valve-Controlled Actuator—Part 2: Energy Efficiency

2019

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This research paper presents the second part of a comparative analysis of a novel self-contained electro-hydraulic cylinder with passive load-holding capability against a state of the art, valve-controlled hydraulic system that is typically used in load-carrying applications. After addressing the control design and motion performance in the first part of the study, the comparison is now focused on the systems’ energy efficiency. It is experimentally shown that the self-contained solution enables 62% energy savings in a representative working cycle due to its throttleless and power-on-demand nature. In the self-contained drive, up to 77% of the energy taken from the power supply can be used effectively if the recovered energy is reused, an option that is not possible in the state of the art hydraulic architecture. In fact, more than 20% of the consumed energy may be recovered in the self-contained system during the proposed working cycle. In summary, the novel self-contained option is experimentally proven to be a valid alternative to conventional hydraulics for applications where passive load-holding is required both in terms of dynamic response and energy consumption. Introducing such self-sufficient and completely sealed devices also reduces the risk of oil spill pollution, helping fluid power to become a cleaner technology.

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Investigation of New Servo Drive Concept Utilizing Two Fixed Displacement Units

Cited by 17 publications

References 1 publication

Classification and Review of Pump-Controlled Differential Cylinder Drives

Classification and Review of Pump-Controlled Differential Cylinder Drives

A Self-Contained Electro-Hydraulic Cylinder with Passive Load-Holding Capability

A Comparison Study of a Novel Self-Contained Electro-Hydraulic Cylinder versus a Conventional Valve-Controlled Actuator—Part 2: Energy Efficiency

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