Experimental Investigation of a Displacement-controlled Hydrostatic Pump/Motor by Means of Rotating Valve Plate

Interest in the control of variable fluid power pumps/motors has increased in recent years.The actuators used are inefficient and expensive and this reduces the variable units’ usability.This paper introduces displacement control of pumps/motors by means of a rotating valveplate. By changing the angle of the valve plate, the effective use of the stroke is changed. Therotating valve plate is experimentally verified by a modified in-line pump. In the prototype,the valve plate is controlled with a worm gear connected to an electric motor. The resultsshow potential for this kind of displacement control. However, the rotating valve plate createspressure pulsations at part-displacement due to the commutation being performed at highpiston speeds. If the piston speed and hence the flow from each piston is low, the pressurepulsation is acceptable

Designing Irreversible Inhibitors—Worth the Effort?

This is the peer-reviewed version of the following article: González-Bello, C. (2016). Designing Irreversible Inhibitors-Worth the Effort?. Chemmedchem, 11(1), 22-30, which has been published in final form at https://doi.org/10.1002/cmdc.201500469. This article may be used for non-commercial purposes in accordance with Wiley-VCH Terms and Conditions for Self-ArchivingDespite the unquestionable success of numerous irreversible drugs that are currently in clinical use, such as acetylsalicylic acid (Aspirin) and penicillin, the number of such approved drugs is much lower than that of noncovalent drugs. Over the years, the potential off‐target effects of these types of compounds have been the primary concern that has hampered their development. However, their remarkable advantages over noncovalent drugs and a better analysis of the risks have decreased the widespread skepticism surrounding them. The design of irreversible inhibitors is a challenge, particularly considering that in some cases their efficacy is due to complex and unexpected mechanisms of action. In this review the main advantages of irreversible inhibition are summarized, and the complexity of certain covalent modification mechanisms is highlighted with selected examplesSpanish Ministry of Economy and Competitiveness. Grant Number: SAF2013-42899-R Xunta de Galicia. Grant Number: GRC2013-041 European Regional Development Fund (ERDF)S

Fluid Power Pumps and the Electrification : With a Focus on Discrete Displacement Control in Load Handling Applications

More and more vehicles are being electrified. Mobile working machines and heavy trucks are not excluded, and these machines are often hydraulically intense. Electrification entails new requirements for the hydraulic system and its components, and these requirements must be taken into consideration. Hydraulic systems have looked similar for a long time, but now there is an opportunity to advance. Many things change when a diesel engine is replaced with an electric motor. For example, variable-speed control becomes more relevant, electric regeneration becomes possible, and the use of multiple prime movers becomes an attractive alternative. The noise from the hydraulic system will also be more noticeable when the diesel engine is gone. Furthermore, the introduction of batteries to the system makes the energy more valuable, since batteries are heavy and costly compared to a diesel tank. Therefore, it is commercially viable to invest in the hydraulic system. This thesis revolves around the heart of the hydraulic system, that also is the root of all evil. That is the pump. Traditionally, a pump has had either a fixed displacement or a continuously variable displacement. Here, the focus is on something in between, namely a pump with discrete displacement. The idea of discrete displacement is far from unique, but has not been investigated in detail in combination with variable speed before. In this thesis, a novel design for a quiet pump with discrete displacement is presented and analysed. The results show that discrete displacement is relevant from an energy perspective for machines working extensively at high pressure levels and with low flow rates, and that a few discrete values are enough to make a significant difference. However, for other cycles, the possible energy gains are very limited, but the discrete displacement can be a valuable feature if downsizing the electric machine is of interest

Hysteresis Control in Pump-Controlled Systems—A Way to Reduce Mode-Switch Oscillations in Closed and Open Circuits

There is growing interest in using electric motors as prime movers in mobile hydraulic systems. This increases the interest in so-called pump-controlled systems, where each actuator has its own drive unit. Such architectures are primarily appealing in applications where energy efficiency is important and electric recuperation is relevant. An issue with pump-controlled systems is, however, mode-switch oscillations which can appear when the pressure levels in the system are close to the switching condition. In this paper, the mode-switching behavior of different generalized closed and open circuit configurations is investigated. The results show that the choice of where to sense the pressures has a huge impact on the behavior. They also show that, if the pressure sensing components are properly placed, closed and open circuits can perform very similarly, but that mode-switch oscillations still can occur in all circuits. Active hysteresis control is suggested as a solution and its effectiveness is analyzed. The outcome from the analysis shows that active hysteresis control can reduce the risk for mode-switch oscillations significantly

An Experimental Analysis of Valve Plate Control : a New Approach to Displacement Control for Hydraulic Piston Machines

Displacement control of a pump means controlling the amount of fluid that is pumped per rotation. This is used to increase the efficiency or controlling the flow in a system and currently there is almost exclusively one type of displacement control available for piston machines on the market. With this method, the stroke length of the pistons can be varied by changing the angle of the so-called swashplate. There are however drawbacks with this principle that mainly concern in stability or efficiency. In this thesis, an unconventional approach to displacement control has been experimentally evaluated. The principle of this method is to vary the effective use of the stroke length by rotating the valve plate, which is a component that separates the inlet from the outlet. This can be done with an electric motor and the problems concerning efficiency and stability can be avoided. The main drawback with this type of control is however the high noise level caused by pressure ripple in the cylinders. This thesis treats the characteristics of this type of control, both theoretically and experimentally, and describes the analysed prototype. It also deals with new conceptual designs for this type of control. How-ever, in summary it can be said that the prototype behaved as expected but had problems with leakage

On Electrified Fluid Power Systems in Mobile Machinery

High power density in combination with flexible power distribution possibilities and extreme robustness are reasons why fluid power has been the preferred technology in mobile machinery, such as excavators and cranes, since the mid-20th century. In principle, the machines have been powered by a combustion engine which powers a pump, with the output from the pump being distributed to different functions via valves. However, a transformation is currently underway. Combustion engines are being replaced by electric motors, and batteries able to store energy corresponding to several hours of operation are often desired. Since batteries tend to be heavy and expensive, reducing the energy consumption is getting higher priority than ever before. There are applications where electrification means that hydraulic components are replaced by electric counterparts, but fluid power has characteristics that are highly desirable in mobile machinery. Therefore, many hydraulic actuators will remain. Conventional hydraulic systems, which are known for their inefficiency, should, however, be adapted to the new conditions brought about by electrification. The question, and the overall subject of this thesis, is: how? The research has focused on two main topics: pump-controlled systems, which are systems where each actuator has its own supply unit, and the use of variable displacement pumps in electrified systems. A large proportion of the losses in many conventional hydraulic systems is due to the simultaneous operation of functions that require different pressure levels. One way to avoid these losses is to use pump-controlled systems. How these systems should be designed is, however, far from obvious. In this thesis, different types of pump-controlled systems are compared, both statically and dynamically. Regarding variable displacement pumps, they have had a natural place in many conventional systems, but electrification may change this, since speed-control can now also be used for flow- and pressure control. However, there are still aspects relating to energy consumption and component dimensioning, among other things, that makes variable pumps relevant. These aspects are investigated here, and different types of variable pumps are reviewed.2022-09-05: The PDF has been replaced by one witch color. </p

Hysteresis Control in Pump-Controlled Systems : A Way to Reduce Mode-Switch Oscillations in Closed and Open Circuits

There is growing interest in using electric motors as prime movers in mobile hydraulic systems. This increases the interest in so-called pump-controlled systems, where each actuator has its own drive unit. Such architectures are primarily appealing in applications where energy efficiency is important and electric recuperation is relevant. An issue with pump-controlled systems is, however, mode-switch oscillations which can appear when the pressure levels in the system are close to the switching condition. In this paper, the mode-switching behavior of different generalized closed and open circuit configurations is investigated. The results show that the choice of where to sense the pressures has a huge impact on the behavior. They also show that, if the pressure sensing components are properly placed, closed and open circuits can perform very similarly, but that mode-switch oscillations still can occur in all circuits. Active hysteresis control is suggested as a solution and its effectiveness is analyzed. The outcome from the analysis shows that active hysteresis control can reduce the risk for mode-switch oscillations significantly.Funding: Swedish Energy AgencySwedish Energy AgencyMaterials &amp; Energy Research Center (MERC) [44427-3]</p

Digital pumps in speed-controlled systems – an energy study for a loader crane application

Imagine a system with a pump driven by a speed-controlled electric motor. What and how much can be gained by using a pump with discretely variable displacement instead of a conventional fixed pump in such a system? This question is the focus in this paper, in which a simulation study based on a drive cycle for a loader crane is presented. The results indicate that the system efficiency from inverter input to pump output can increase by a few percentages. This might be considered small in relation to the increasing complexity that comes with discrete displacement. However, the results also show that a system with discrete displacement substantially reduces torque and cooling requirements on the electric motor. The required maximum torque can be reduced by 30 to 50 % and the motor can generate up to 40 % less heat since it can work in more efficient conditions. These potential benefits will be obtained with only a few discrete displacement settings available