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

Abstract

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.

Classification and Review of Pump-Controlled Differential Cylinder Drives

“…Commercial products based on the pilot-operated check valve solution has been introduced lately by Bosch Rexroth AG [45,61]. In [3] the authors proposed to include a passive load-holding subsystem (Blue components in Figure 5b) for actuating a single link crane manipulator. The load-holding subsystem passively holds the load in case of emergency e.g., power shutdown but it may also be enabled by the operator during standstill to enhance energy efficiency.…”

“…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].…”

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

“…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]. Current commercial solutions of the SCC technology are limited and typically tailor-made, whereas the research emphasis is primarily on different electro-hydraulic configurations [13][14][15][16], energy-efficiency [17][18][19][20][21], thermal analysis [22][23][24], and low-power servo applications [25].…”

“…Hence, this research paper aims to experimentally evaluate and compare the energy consumption and the energy efficiency of a self-contained electro-hydraulic cylinder versus a conventional approach. A SCC concept able to operate in four quadrants, including passive load holding, and suitable for power levels above 5 kW was proposed in [10] and implemented on a singleboom crane in [12]. A further analysis of this solution is presented in the first part of this research [28], including the control design and the motion performance comparison against the valvecontrolled cylinder (VCC) discussed in [29].…”

Experimental Study on Fast and Energy-Efficient Direct Driven Hydraulic Actuator Unit

“…In recent years, several researchers have published work comparing closed-circuit displacementcontrolled and valve-controlled single-actuator systems, in some cases including electro-mechanical actuators in the comparisons [6][7][8][9][10][11]. The researchers have found pump systems based on speed-control or a combination of speed control and displacement control to reach equal, or even superior, performance when considering the aspects of energy efficiency and dynamics.…”