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On optimal design of hydrostatic machines
Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
2008 (English)In: Proceedings of the 6th International Fluid Power Conference, IFK, Vol WS, 2008, 273-286Conference paper (Refereed)
Abstract [en]

Noise is a well known challenge for hydraulic systems and hydrostatic machines is one of the largest noise contributors in a hydraulic system. The noise from the machine originates from flow pulsations in the discharge and suction ports, as well as pulsations in piston forces and bending moments. To the design a quite hydraulic machine is a difficult task where many different objectives need to be considered. This paper presents a generic method for how optimization based on simulation models could be used to design quieter hydraulic machines. In order to stay competitive on a global market an efficient product development process is essential for all manufacturing industries. By using simulation-s tools in the design process, the product can be analysed before the actual product is manufactured. Furthermore, in order to find an optimal design of the machine with respect to noise, a comprehensive dynamic simulation model is needed. The model contains all important noise contributors. In the paper, the simulation models are used together with a non-gradient optimization method in order to find the best possible design. A vital part when using optimization to support design is always to formulate the objective function. As mentioned above, noise is generated from different sources and all these sources need to be considered when the objective function is formulated. For example a design that minimizes flow pulsations in the suction port will surely perform badly in some other objective. Therefore noise minimization could be looked upon as a typical multi-objective optimization problem. It is also not evident how the different objective should be ranked because the observed noise level is strongly depending on the system in which the machine is to be used. The paper also considers whether the objective function should be formulated in time or frequency domain. Traditionally, simulation of machine performance is conducted in the time domain, but the human ear hears noise in the frequency domain and perceives high and low frequencies differently. Furthermore, transformation from piston forces into emitted noise is much higher at high-frequency content than low-frequency content. This makes it natural to formulate the objective function in frequency domain, which raises the question of how the different harmonic should be ranked. In the paper a number of different approaches to formulate the objective function is presented and evaluated. The objectives considered are flow pulsation in both discharge and suction ports, as well as pulsation in piston forces and bending moments. Furthermore, the objectives are studied in both time and frequency domain. The design application is a variable hydraulic machine of bent axis type with nine pistons, which is operated both as a pump and a motor. However, the methods presented in the paper could be applied to other types of hydraulic machines as well. 

Keyword [en]
Fluid power, pump, motor, noise, optimisation
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-42260Local ID: 62133OAI: diva2:263116
6th International Fluid Power Conference, March 31-April 2, Dresden, Germany
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2012-01-18Bibliographically approved
In thesis
1. On Fluid Power Pump and Motor Design: Tools for Noise Reduction
Open this publication in new window or tab >>On Fluid Power Pump and Motor Design: Tools for Noise Reduction
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Noise and vibration are two of the main drawbacks with fluid power  systems. The increasing requirements concerning working environment as well as machines' impact on surroundings put components and systems to harder tests. The surrounding machines, e.g. combustion engines, have made considerable progress regarding the radiated noise. This allows the fluid power system's noise to become more prominent. Noise from fluid power systems has been a research topic for several decades and much improvement has been achieved. However, considerable potential for improvement still remains.

In addition to the legislation governing working environment, the machines tend to be used as more multi-quadrant machines, which require more flexible noise reduction features. One of the main benefits with fluid power is the high power density. To increase this value even more, the system's working pressure increases, which correlates with increased noise level.

The main source of noise is considered to be the pump and motor unit in the fluid power system. The noise can be divided into two parts: fluid-borne noise and structure-borne noise. The fluid borne noise derives from flow pulsation which is subsequently spread through pipeline systems to other parts of the fluid power systems. The flow pulsation is created due to the finite stiffness of oil and the limited number of pumping elements. The structure-borne noise generates directly from pulsating forces in the machine. The pulsating forces are mainly created by the pressure differences between high and low pressure ports.

Effective and accurate tools are needed when designing a quiet pump/motor unit. In this thesis simulation based optimisation is used with different objective functions including flow pulsation and pulsating forces as well as audible noise. The audible noise is predicted from transfer functions derived from measurements. Two kinds of noise reduction approaches are investigated; cross-angle in multi-quadrant machines and non-uniform placement of pistons. The simulation model used is experimentaly validated by source flow measurements. Also, source flow measurements with the source admittance method are investigated.

In addition, non-linear flow through a valve plate restrictor is investigated and the steady state restrictor equation is proposed to be extended by internal mass term.

Publisher, range
Linköping: Linköping University Electronic Press, 2012. 130 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1417
National Category
Engineering and Technology
urn:nbn:se:liu:diva-73981 (URN)978-91-7519-994-8 (ISBN)
Public defence
2012-01-20, Sal A35, Hus A, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2012-01-18 Created: 2012-01-18 Last updated: 2012-01-18Bibliographically approved

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