Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

Rannow, Michael B.; Li, Perry Y.

doi:10.1115/1.4006620

Cited by 29 publications

(20 citation statements)

References 7 publications

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“…Through numerical studies, Rannow and Li found that the soft switch approach can theoretically reduce throttling and compressibility losses by 81% and combined system losses by 64% when operating at 20 Hz. Alternatively, the use of a soft switch that is 4.4 times slower than a baseline PWM circuit yields the same circuit efficiency [30]. The single soft switch proposed by Rannow and Li has two phases, the first phase is when it displaces to the lock point while the tank valve closes, and the second phase is when the lock releases during the opening of the tank valve.…”

Section: Soft Switchingmentioning

confidence: 99%

Design and Validation of a Soft Switch for a Virtually Variable Displacement Pump

Beckstrand

Ven

2017

Journal of Dynamic Systems, Measurement, and Control

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Switch-mode hydraulic control is a compact and theoretically efficient alternative to throttling valve control or variable displacement pump control. However, a significant source of energy loss in switch-mode circuits is due to throttling during valve transitions. Hydraulic soft switching was previously proposed as a method of reducing the throttling energy loss, by absorbing, in a small variable volume chamber, the flow that would normally be throttled across the transitioning high-speed valve. An active locking mechanism was previously proposed that overcomes the main challenge with soft switching, which is a lock mechanism that releases quickly and with precise timing. This prior work demonstrated a reduction in energy losses by 66% compared to a control circuit. In this paper, a numerical model is developed for a switch-mode virtually variable displacement pump (VVDP) circuit, utilizing the proposed soft switch. The model is then used as a means of designing a proof of concept prototype to validate the model. The prototype design includes methods for controlling the soft switch spring preload, travel distance, piston displacement required to unlock the soft switch, valve command duty cycle, switching cycle period, and load pressure. Testing demonstrated that the soft switch circuit performed as expected in a baseline condition. The operating region for this prototype was found to be quite narrow. However, the model does a good job of predicting the displacement of the soft switch.

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Section: Soft Switchingmentioning

confidence: 99%

Design and Validation of a Soft Switch for a Virtually Variable Displacement Pump

Beckstrand

Ven

2017

Journal of Dynamic Systems, Measurement, and Control

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“…In this way, the inside circumference of the sleeve and thus diameter of the spool becomes a function of the number and diameter of ports in a particular row: . (10) where d spool is the diameter of the spool. As the number and diameter of sleeve ports increases, the pressure drop across the valve for a given spool position is decreased.…”

Section: Design Processmentioning

confidence: 99%

“…Increasing N and d o also increases the required diameter of the spool per Eq. (10) which comes at the cost of increased leakage flow through the clearance seal between the sleeve and the spool based on a parallel plate approximation of the annulus:…”

Section: Design Processmentioning

confidence: 99%

“…Second, each switching event results in throttling across the partially-open transitioning valve. This energy loss can be minimized through soft switching [10,11] or by reducing the valve transition time, at the expense of increasing the velocity of the switching element. Finally, each switching cycle incurs losses due to compressing and decompressing the fluid in the switched volume.…”

Section: Introductionmentioning

confidence: 99%

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Crank-Slider Spool Valve for Switch-Mode Circuits

Yudell

Koktavy

Ven

2015

ASME/BATH 2015 Symposium on Fluid Power and Motion Control

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A key component of switch-mode hydraulic circuits is a high-speed two-position three-way valve with a variable duty cycle. This paper presents a new valve architecture that consists of two valve spools that are axially driven by crank-slider mechanisms. By phase shifting the two crank links, which are on a common crankshaft, the duty cycle of the valve is adjusted. The two spools split and re-combine flow such that two switching cycles occur per revolution of the crankshaft. Because the spools move in a near-sinusoidal trajectory, the peak spool velocities are achieved at mid-stroke where the valve land transitions across the ports, resulting in short valve transition times. The spool velocity is lower during the remainder of the cycle, reducing viscous friction losses. A dynamic model is constructed of this new valve operating at 120 Hz switching frequency in a switch-mode circuit. The model is used to illustrate design trade-offs and minimize energy losses in the valve. The resulting design solution transitions to the on-state in 5% of the switching period and the combined leakage and viscous friction in the valve dissipate 1.7% of the total power at a pressure of 34.5MPa and volumetric flow rate of 22.8L/min.

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“…Also, the throttling losses increase with the fraction of entrained air and flow ripples. The 'SoftSwitching' concept is proposed to eliminate the energy losses during the switching transition [16].…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Studies of a Switched Inertance Hydraulic System in a Four-Port High-Speed Switching Valve Configuration

2017

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Abstract:The switched inertance hydraulic system (SIHS) is a novel high-bandwidth and energy-efficient digital device which can adjust or control flow and pressure by a means that does not rely on throttling the flow and dissipation of power. An SIHS can provide an efficient step-up or step-down of pressure or flow rate by using a digital control signal. In this article, analytical models of an SIHS in a four-port high-speed switching valve configuration are proposed, and the system dynamics and performance are investigated theoretically and experimentally. The flow responses, system characteristics, and power consumption can be predicted effectively and accurately by using the proposed models, which were validated by comparing with experiments and with numerical simulation. The four-port configuration is compared with the three-port configuration, and it is concluded that the former one is less efficient for valves of the same size, but provides a bi-direction control capability. As bi-direction control is a common requirement, this constitutes an important contribution to the development of efficient digital hydraulics.

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Soft Switching Approach to Reducing Transition Losses in an On/Off Hydraulic Valve

Cited by 29 publications

References 7 publications

Design and Validation of a Soft Switch for a Virtually Variable Displacement Pump

Design and Validation of a Soft Switch for a Virtually Variable Displacement Pump

Crank-Slider Spool Valve for Switch-Mode Circuits

Theoretical and Experimental Studies of a Switched Inertance Hydraulic System in a Four-Port High-Speed Switching Valve Configuration

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