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.
Highlights
Linear actuators capable of delivering high forces to perform heavy-duty operations are commonplace in many fields of industry
Plug-and-play installation, and reduced maintenance are becoming crucial characteristics in these areas, there is an ongoing tendency to replace standard valve-controlled hydraulic cylinders with the electro-mechanical counterparts
An alternative approach makes use of self-contained electro-hydraulic cylinders (SCCs). They are, according to the definition used in this paper, self-sufficient linear hydraulic actuators controlled by a local hydraulic unit that is driven by a dedicated electric motor
Summary
Linear actuators capable of delivering high forces to perform heavy-duty operations are commonplace in many fields of industry. Plug-and-play installation, and reduced maintenance are becoming crucial characteristics in these areas, there is an ongoing tendency to replace standard valve-controlled hydraulic cylinders with the electro-mechanical counterparts (e.g., roller-screw actuators directly driven by electric motors [1]). These electro-mechanical solutions are unsuitable in several applications such as offshore oil drilling [2], mainly due to the limited reliability (i.e., unexpected impact forces and overloads damage the screw).
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