Workshop on Innovative Engineering for Fluid Power

A Novel Multi-Pump System for Hydraulic Actuation in Electric Mobile Machinery

Artur Tozzi de Cantuaria Gama — 2023-03-23

An observable trend nowadays is the change in the prime movers of mobile heavy machinery to electric alternatives to achieve more eco-friendly equipment. These solutions often require large and heavy batteries with limited capacity, making the research of more efficient components and the development of different system architectures an important topic of study. Hydraulic actuation is still a relevant application for these vehicles because of its reliability, controllability, and high power density. The electrification and digitalization of mobile machinery allow for innovative designs and control strategies to be implemented that take advantage of electro-hydraulic systems and their characteristics. Similar research has shown that a higher number of degrees of freedom allow for the system to operate with higher total efficiency. This paper introduces a novel actuation architecture that combines multiple fixed displacement hydraulic pumps and on/off directional valves to control the position and force of two hydraulic actuators for the working functions of a mobile machine. Each pump is powered by a variable speed electric drive so that each one can be operated independently, and together with the set of directional valves, allows the selection of different combinations of pumps and flow sharing between the actuators’ chambers to achieve the desired flow and pressure on each cylinder. The multi-pump system favours the use of smaller pumps, and the possibility of combining their flows reduces the need to operate the components at lower efficiency points such as partial displacement. At the same time, controlling the pumps’ flow through the variable-speed electric motors means that throttling valves are not needed. The development of this architecture will allow for its use in mathematical models to analyse its behaviour and efficiency and to obtain insights regarding points of improvement in the system architecture.

Digital Hydraulic Actuators: An Alternative for Aircraft Control Surfaces

Dimitri Oliveira e Silva — 2023-03-23

In the last decades, digital hydraulics has emerged as a new alternative for the development of more efficient hydraulic systems, where the effects of throttling losses and internal leakages are minimized through the use of conventional hydraulic components associated in parallel or through switching hydraulics. In the aviation industry, hydraulic systems are commonly applied to control highly relevant systems, such as landing gear and flight control surfaces. In this context, digital hydraulics can be used as an alternative solution to improve the energy efficiency of aircraft hydraulic systems. Based on that, this paper aims to present three new hydraulic actuators for application on aircraft flight control surfaces using digital hydraulics. The actuators are being studied by the Laboratory of Hydraulic and Pneumatic Systems - LASHIP of the Federal University of Santa Catarina - UFSC and are called Digital Hydraulic Actuator - DHA, Digital Electro Hydrostatic Actuator - DEHA and Variable Speed Digital Electro Hydrostatic Actuator - VSDEHA. The simulation results show that the actuators developed can be 23 times more efficient than conventional servo-hydraulic actuators, with equivalent dynamic characteristics, demonstrating the potential for application of these new actuators in aeronautical systems.

Energy Efficiency Analysis and Experimental Test of a Closed-Circuit Pneumatic System

Fedor Nazarov — 2023-03-23

In a closed-circuit pneumatic system the air from the pneumatic cylinder is not exhausted directly in the atmosphere, as done in traditional open-circuit systems, but is captured and fed to the compressor inlet. This provides an opportunity to increase the compressor inlet pressure above the atmospheric and consequently enables both higher compression efficiency and volumetric flow rate. Until the present, the advantages of the closed-circuit pneumatics were assessed only within theoretical studies without being verified experimentally due to uncertainties in performance of a real compressor under oscillating pressure and flow rate, as well as due to a risk of mutual cylinder interference caused by differences in load and required pressure profiles. Hence, this study focuses on experimental investigation of energy efficiency and practicability issues of the closed-circuit pneumatics. It is shown that simultaneous operation of two pneumatic cylinders of different size (Ø32×200 and Ø50×200) performing different tasks (high-dynamic mass handling and extension against the constant force) does not have any negative effect neither on the cylinder dynamics nor on the compressor performance. Inlet pressure increase up to 1.5 barrel leads to by factor 2.5 higher volumetric flow rate and total efficiency gain of 72 % (increase from 10.7 % to 18.4 %). The experimentally obtained results show a great potential of the closed-loop pneumatics and indicate the need in further research into design and control methods of such systems to enable technology deployment to the industry. Industrial applications can profit from the reduced energy consumption especially in case of pneumatic systems with decentralized air supply.

An Estimator for Aircraft Actuator Characteristics Using Singular Value Decomposition

Felix Larsson — 2023-03-23

This paper illustrates how a Singular Value Decomposition (SVD) and regression analyses can be used to create estimation models for aircraft actuator components by use of industrial data. The estimation models are at the end used to show how an electromechanical actuator´s weight and size will evolve with respect to output force. An essential step in the early design of aircraft is to be able to predict the weight and size of a resulting concept. This weight and size typically include contributions of main components such as wing and fuselage. Weight and size estimations at this stage can also range down to components at a sub-system level, for example, the aircraft actuators. The weight and size of an actuator depends on many parameters, and it is desirable to understand any underlying relationship to make qualified estimations of an actuator’s characteristics. However, the knowledge about a design is often limited at an early design stage and the required information is not always available. Consequently, estimations must be made from limited information and desired properties of the actuator. One way to approach this problem is to use SVD. An SVD analysis determines the most influential parameters in a data set and uses these to create an estimation model that only requires a few inputs for estimating the remaining parameters in the data set. An SVD can thereby be used for both identifying the driving parameters in a statistical dataset of existing solutions and to estimate the characteristics of new designs to be developed.

Thermohydraulic Modeling of An Electro-Hydraulic Servo Actuator on Damped Mode

Marina Brasil Pintarelli — 2023-03-23

Hydraulically powered flight control systems are widely used in aviation, especially for commercial aircraft, which require significant forces from system actuators to control the applicable surfaces as demanded. These systems are being studied and are evolving to become smaller, lighter, and more efficient. These improvements bring several advantages, such as payload increase and drag reduction. However, as these systems are optimized, and their dimensions are reduced, the thermal effects of fluid flow become more relevant. Especially when the working fluid passes through small orifices, excessive heat can eventually compromise the equipment's performance and damage its internal subcomponents. When we analyze the damped mode operation of actuation systems presented on some commercial aircraft, these restrictions become even more relevant – knowing that the damping orifice diameter can be significantly reduced to provide the desired performance for the operation. Therefore, the main goal of this study is to analyze and evaluate the thermal impact on an Electro-Hydraulic Servo Actuator (EHSA) while in damped mode operation, contributing to the industry and the literature in this kind of assessment. Through the research presented, it's possible to estimate the temperature of the system's components and, consequently, avoid malfunctions caused by overheating. Furthermore, developing a model allows the simulation of various environmental conditions, reducing rig costs or in-flight tests. The modeling approach was conducted on the MATLAB/Simulink platform. It was based on two main points that improved model comprehension during its development and minimized errors: the building blocks philosophy of segregating each component's influence and model, and the continuous validation of the model through a comparison with a physics-integrated software (AMESim).

Frugal Approach for The Design of a Rehabilitation Physical System

Ruben Dario Solarte Bolaños — 2023-03-23

In the rehabilitation process, robotic structures can support the different medical-surgical actions. These recovery process activities often involve repetitive movements that must be performed several times at various amplitudes. Robotic structures for rehabilitation can be driven by three types of active drives, namely electric, pneumatic and hydraulic actuators. Pneumatic systems have become increasingly present in various market segments and are widely used in the industry, mainly due to their ease of maintenance, low cost, safety and applicability in various processes. Currently, the concept of Frugal Innovation is being discussed, which emerges as a way to produce effective and affordable products using fewer resources to reach less-served customers. Frugal Innovation is centered on saving resources, is characterized by simplicity and clarity and aims to reach the low-income market. This article proposes the application of Frugal development methods in the design of a lower limb rehabilitation system. With the application of frugal concepts, pneumatic actuators were chosen. The choice of the pneumatic cylinder is presented from the required pneumatic force. The application of the Frugal Innovation approach in the design of this type of products demonstrates the relevance of applying these methods in efforts to mitigate or reduce the growth of the technological gap between underdeveloped and developed countries.

The History and Future of Fluid Power Pumps and Motors

Samuel Kärnell — 2023-03-23

Positive displacement pumps have been around for thousands of years, but it was first in the beginning of the 19th century they started to be used for power transmission purposes. At that time, the fluid was water, and the applications were primarily presses. During the century, the technology developed and towards its end, fluid power systems were used to transmit power to hundreds or even thousands of consumers within several cities. However, in the 20th century, these large-scale fluid power transmission systems were outcompeted by the electric grid. But at the same time, the focus for fluid power was shifted towards self-contained, oil-based systems, which were suitable in many mobile applications powered by combustion engines. Once again, fluid power systems are now undergoing a transition. This especially apply to mobile applications, where combustion engines are being replaced by electric motors. This puts new requirements on the hydraulic systems as well as the pumps and motors that are to be used. Electrification means increased focus on energy efficiency, and speed-control becomes more relevant than before. New system designs are therefore highly relevant. Depending on the architecture that is chosen, different requirements will be set on the pumps and motors. Aspects such as multi-mode operation, high- and low-speed performance, and displacement control will be discussed in this paper.

Optimization of Pressure Relief Grooves for Multi-Quadrant Hydraulic Machines in Different System Architectures

Thomas Heeger — 2023-03-23

In hydraulic axial piston machines, each chamber switches between the high-pressure and the low-pressure port with every revolution. How this process, the commutation, is done, is an essential part of pump design. The commutation typically targets a smooth pressure transition to minimize compressible flow pulsations. However, an ideal pressure match is not possible over the whole operating range of the machine. Thus, pressure relief grooves are considered a “necessary evil” in the state of the art, which can reduce flow pulsations over a wide operating range on the expense of slightly increased losses. Depending on the drive cycle and especially the number of quadrants a hydraulic machine is used in, the optimal pressure relief groove design differs. The increased losses and pulsations for enabling 4-quadrant operation of hydraulic machines are shown.

Pump-controlled systems lead to hydraulic machines running in different drive cycles than in conventional valve-controlled systems, affecting ideal groove design. This paper focuses on how to optimize pressure relief grooves and thus presents the methodology incl. the simulation model, formulation of the objective function, and choice of optimization algorithm. Optimizations are carried out for 1-, 2- and 4-quadrant operation. Pareto fronts for a trade-off between flow pulsations and losses are presented, for both a valve-controlled system and a pump-controlled system carrying out the same task in an excavator boom application.

Development of Pneumatic Technology for Automation and Control of Small Hydropower Plants

Vinícius Vigolo — 2023-03-23

Small hydropower plants have been seen as a more sustainable source of energy in comparison with large hydropower plants due to the smaller required flooding area. However, every source of energy production has, inevitably, an impact on the environment. Aiming to reduce the usage of fossil-based products, such as hydraulic oil, a joint effort has been made between the Laboratory of Hydraulic and Pneumatic systems and the companies Reivax Automation and Control and China Three Gorges, in order to introduce the pneumatic technology to the hydrogeneration sector. Characteristics such as easy installation and maintenance, low acquisition costs, and mainly, low environmental impact, make the pneumatic technology an excellent candidate to replace the hydraulic servo actuators that have been traditionally used for automation and control in hydropower plants, which use large quantities of hydraulic oil and provide a high risk of a river bed contamination due to possible leakages or incorrect disposal of hydraulic oil. This paper presents two cycles of development of a pneumatic solution to automate and control the generating unit of small hydropower plants. It includes the first proposed solutions, proof of concepts and drawbacks that were faced, as well as the new challenges and achievements that rose during the design process. The paper also presents the most up-to-date results from a pilot project where a fully pneumatic solution was applied for a generating unit with 438 kVA of generating capacity and a model of development that was identified based on common activities performed during the first two cycles of development.