An integrated compact digital hydraulic converter prototype for hydraulic transmission

Digital hydraulic converters are innovative devices that enable efficient regulation and control of hydraulic fluid flow and pressure. Unlike conventional methods that employ flow throttling and power dissipation, digital hydraulic converters use digital control signals to create highly efficient hydraulic fluid power systems. In this study, a new, compact, highly efficient, and high-bandwidth digital hydraulic converter prototype was developed and investigated. The new converter comprises a high-flowrate, low-resistance, and high-speed rotary valve, inertance and capacitive components, and real-time programmable logic controllers (PLCs) to form an integrated digital hydraulic device. Analytical models of the prototype were developed to investigate converter performance and energy efficiency, followed by experimental validations. Analytical and experimental results showed that the new hydraulic converter has very good pressure dynamics, performance, and energy efficiency. This work contributes to the design and development of high-performance digital hydraulic components for sustainable hydraulic machinery

An integrated compact digital hydraulic converter prototype for hydraulic transmission

Digital hydraulic converters are innovative devices that enable efficient regulation and control of hydraulic fluid flow and pressure. Unlike conventional methods that employ flow throttling and power dissipation, digital hydraulic converters use digital control signals to create highly efficient hydraulic fluid power systems. In this study, a new, compact, highly efficient, and high-bandwidth digital hydraulic converter prototype was developed and investigated. The new converter comprises a high-flowrate, low-resistance, and high-speed rotary valve, inertance and capacitive components, and real-time programmable logic controllers (PLCs) to form an integrated digital hydraulic device. Analytical models of the prototype were developed to investigate converter performance and energy efficiency, followed by experimental validations. Analytical and experimental results showed that the new hydraulic converter has very good pressure dynamics, performance, and energy efficiency. This work contributes to the design and development of high-performance digital hydraulic components for sustainable hydraulic machinery

Efficient Control of a Switched Inertance Hydraulic Converter With a Time-Varying Load

Switched inertance hydraulic converters (SIHC) are new digital hydraulic devices which provide an alternative to conventional proportional or servo valve-controlled systems in hydraulic fluid power. SIHCs can adjust and control flow and pressure by means of using digital control signals that do not rely on throttling the flow and dissipation of power, and provide hydraulic systems with high-energy efficiency, good controllability, and insensitivity to contamination. A flow booster is one configuration of SIHCs which can deliver more flow than the supply flow. In this article, the loading effects of SIHCs are investigated by applying a time-varying load on the flow booster. A control system consisting of a PI controller and a switching frequency optimizer was designed to operate a flow booster at its optimal switching frequencies and switching ratios to maximize system efficiency when the load varies. Simulated results showed that the flow booster with the proposed controller has very good dynamic response and can be operated at an average efficiency of 70% with a time-varying load. Compared with only using a PI controller, the proposed controller can improve the overall efficiency by up to 20%. As time-varying loading conditions are commonly found in hydraulic applications, this work constitutes an important contribution to the design and development of high-efficiency SIHCs

Efficient control of a switched inertance hydraulic converter with a time-varying load

Digital hydraulics is a novel alternative to proportional or servo-valve-controlled systems in fluid power engineering, providing hydraulic systems with high-energy efficiency, good controllability, and insensitivity to contamination. Switched inertance hydraulic converters (SIHCs) are new digital hydraulic devices that can adjust flow and pressure by digital switching instead of throttling the flow. In this paper, an efficient closed-loop control system is proposed for SIHCs subject to time-varying loading conditions in which the load pressure and/or flow varies with time. The control system is designed to operate SIHCs at optimized switching frequencies and ratios that maximize system efficiency when the load varies. With the proposed controller, the SIHC can effectively adapt to the time-varying load and has achieved up to 10% efficiency improvement and up to 65% pressure ripple reduction without affecting the system’s dynamic responses, compared with using a non-optimized controller. The work shows the feasibility and advantages of simultaneously controlling the switching ratio and switching frequency of SIHCs with a time-varying load. As time-varying loading conditions are commonly found in hydraulic applications, the research outcomes constitute an important aspect in the design and development of highly efficient SIHCs and their practical use in hydraulic machinery

Efficient control of a switched inertance hydraulic converter with a time-varying load

Digital hydraulics is a novel alternative to proportional or servo-valve-controlled systems in fluid power engineering, providing hydraulic systems with high-energy efficiency, good controllability, and insensitivity to contamination. Switched inertance hydraulic converters (SIHCs) are new digital hydraulic devices that can adjust flow and pressure by digital switching instead of throttling the flow. In this paper, an efficient closed-loop control system is proposed for SIHCs subject to time-varying loading conditions in which the load pressure and/or flow varies with time. The control system is designed to operate SIHCs at optimized switching frequencies and ratios that maximize system efficiency when the load varies. With the proposed controller, the SIHC can effectively adapt to the time-varying load and has achieved up to 10% efficiency improvement and up to 65% pressure ripple reduction without affecting the system’s dynamic responses, compared with using a non-optimized controller. The work shows the feasibility and advantages of simultaneously controlling the switching ratio and switching frequency of SIHCs with a time-varying load. As time-varying loading conditions are commonly found in hydraulic applications, the research outcomes constitute an important aspect in the design and development of highly efficient SIHCs and their practical use in hydraulic machinery

MODAL ANALYSIS OF FLUID-STRUCTURE INTERACTION IN A BENT PIPELINE

ABSTRACT Fluid-structure interaction in a bent pipeline is investigated by modal methods. Measured frequency response functions between flow rate excitation and pressure response indicate a coupling effect near the third pipeline resonance. Using modal coordinates for the hydraulic and the mechanical subsystems, a two-degrees-of-freedom study of resonance coupling is carried out. An experimental modal analysis of the coupled hydraulicmechanical system confirms the predicted resonance splitting; it illustrates the coupling mechanism and shows the relevant mechanical part. An analytical fluid-structure interaction model succeeds in reproducing the measured coupling effect. This model is also used for modification prediction; it demonstrates that an appropriate assembly of mass and damping on the pipeline can help to reduce hydraulic resonance amplitudes. INTRODUCTION Dynamic laminar flow is well understood for hydraulic pipelines with rigid walls; frequency response functions between hydraulic states exhibit a number of single resonance peaks. If fluid-structure interaction plays a role, individual resonance peaks will change. In [1], theory and measurements show the splitting of a pipeline resonance by the influence of structural vibration. Calculated frequency response functions from water-filled pipeline systems were compared in [2] and show an increase in the number of resonances if fluid-structure interaction is taken into account. Theoretical studies of fluidstructure interaction in liquid-filled pipeline systems indicate the importance of the coupling mechanism at dead ends, elbows, and junctions Fluid-structure interaction is essential at the origin of vibrations and noise in fluid power systems. For drives that ar

Modelling and analysis of hydraulic step-down switching converters

In this study, a steady state analysis of step-down converter systems, considering the load losses in the inertance tube and switched valve, is presented. The model describes the behaviour of the average load pressure as a function of the pulse-width modulated duty cycle. The steady state expressions for the load flow rate, high and low supply flow rates, and system efficiency are also discussed. A system prototype was developed and tested to evaluate the model accuracy. The system parameters (e.g. tube diameter and length and switching frequency) were analysed to predict the best system configuration. The study describes how the system efficiency is influenced by these parameters. The model presented allows the ideal parameter combination for maximum efficiency to be determined. It can be used for the preliminary design of switching converters, and a further time or frequency analysis can be performed for system optimization