Dear Colleagues,

The topic of this Special Issue concerns the latest developments and advances in the field of electro-hydraulic actuators for mechatronic systems, with a particular focus devoted to design solutions developed with the aim of increasing their performance, mainly in terms of energy efficiency, mechanical strength, duration and production costs.

As is well known, an electro-hydraulic actuator is a modular combination of a high-performance hydraulic actuator, a power unit consisting of a hydraulic pump driven by an electric motor, a dedicated electronic or electro-mechanical system, used to control and manage all the actuator functions, and some other additional but fundamental components, including hydraulic tanks, control valves, accumulators, filters, manifolds, pipes and fittings. Electro-hydraulic actuators usually combine simplicity and lower purchase costs, due to the presence of the electric power supply, with the high operating speeds and mechanical failsafe of fluid powered actuators. They typically offer the benefits of energy accumulation for emergency operation (as an alternative to spring return), high-torque and high-speed capabilities, easy operating time adjustment and high flexibility of control systems. Other fundamental features include the use of AC or DC electric power and, thus, no polluting emissions to the atmosphere, smart control, diagnostics and wireless communication, and compliance with all the worldwide standards and legislations.

During the last three decades, the requirements commonly applied for designing electro-hydraulic actuators for mechatronic systems have been focused on a continuous increase of their overall efficiency, mainly in terms of actuation times, power losses, and weight and volume reductions. Moreover, a considerable growth of the incoming and outgoing flow rates and of the supply pressure targets has been constantly registered.

Following this trend, innovative, miniaturized and more efficient components and subsystems, with advanced features, additional functions and complex control strategies, have been developed and applied in order to comply with the increased power density and stringent safety regulations. Furthermore, the achievement of a combined reduction of vibrations and emitted noise is another fundamental challenge for the present design engineers.

The research activities concerning the design and optimization of electro-hydraulic actuators for mechatronic systems are characterized by a highly multi-disciplinary approach, including mechanical engineering, materials science, fluid power applications and theoretical, computational and experimental fluid dynamics. If all these activities are successfully completed, potential benefits in terms of improved performance, affordability, fuel consumption reduction and environmental compliance can be easily reached and maintained.

Moreover, in recent years, innovative manufacturing processes, techniques and materials have been studied, set up and applied with the aim of developing components, subsystems and micro-electro-mechanical systems that are simultaneously lighter and more resistant. In this field, additive manufacturing and rapid prototyping certainly represent two examples of key technologies for this purpose. Another very interesting and promising topic is the integration of new types of sensors for pressure, temperature, mass flow and speed measurements, which can be very useful for the diagnosis, control and monitoring of their operating conditions and performance parameters.

We invite investigators to contribute their original research and review articles dealing with innovative design solutions and advances in electro-hydraulic actuators, developed and applied for standard mechatronic systems or leading to new horizons and fields of application.

Potential topics include, but are not limited to:

• New design solutions useful for increasing the efficiency of the electro-hydraulic actuators;
• Study of the dynamic interaction between the actuator and connected mechatronic systems;
• Adoption of new materials and manufacturing technologies;
• New and innovative applications, broadening their use in different technical fields;
• Development and validation of lumped and distributed numerical models;
• Modeling and optimization;
• Innovative setups and sensors for experimental characterization;
• Condition monitoring and predictive maintenance

Dr. Fabrizio Paltrinieri
Dr. Matteo Venturelli
Guest Editors

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