MODEL AND EXPERIMENTAL VALIDATION OF A LOAD SENSING SYSTEM WITH A CRITICALLY LAPPED REGULATOR SPOOL

Authors

  • Duqiang Wu Lead Engineer, Eaton Corp, Minneapolis
  • Greg Schoenau Department of Mechanical Engineering, University of Saskatchewan 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9
  • Richard Burton Department of Mechanical Engineering, University of Saskatchewan 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9
  • Doug Bitner Department of Mechanical Engineering, University of Saskatchewan 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Keywords:

load sensing, stability, linearization, operating point, energy efficiency

Abstract

A load sensing (LS) system is one in which the pump flow is regulated to keep the pressure drop across an orifice constant and independent of any variation in the load pressure. This ensures that the pressure loss across the orifice is kept to a minimum, thereby increasing efficiency. An LS regulator spool is used to sense the pressure drop across the orifice to control pump delivery. The spool can be underlapped, critically lapped or overlapped. As a trade-off between efficiency and dynamic response, the LS spool is usually critically lapped. This results in a nonlinear model that is sensitive to operating regions.

In this paper, a review of published literature on LS systems is briefly summarized. An LS system model is developed and linearized. Procedures to solve these very complex equations are introduced. Because load sensing systems require pressure feedback, stability can often be an issue. Analysis of these systems to determine the steady state and dynamic performance is very difficult to do because of the dependency of the models on the operating point. Linearized models which reflect a methodology to account for changing operating conditions have been developed and have established three distinct regions of operation (labeled “Conditions I, II, and III”). This paper presents the experimental nature of these conditions and provides experimental evidence that the models so derived are valid over certain frequency ranges. The objective of this paper, then, was to establish confidence in the models by examining frequency response performance under these three distinct conditions. The results show that good agreement does exist between the models and their physical counterparts and establishes limitations thereof.

This research can assist in the design or optimization of an LS system and help in the development of advanced control strategies for obtaining further efficiency within certain dynamic performance constraints.

Downloads

Download data is not yet available.

Author Biographies

Duqiang Wu, Lead Engineer, Eaton Corp, Minneapolis

Duqiang Wu Received his M.Sc from Nanjing University of Science and Technology in China, 1984 and his PhD from the University of Saskatchewan in 2003. He was an Engineer (1986) at Shaanxi Mechanical and Electrical Institute in China, and a Visiting Scholar (1997) at University of Illinois at Urbana-Champaign. He is now a research engineer with Eaton Corp, Minneapolis.

Greg Schoenau, Department of Mechanical Engineering, University of Saskatchewan 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Greg Schoenau Professor of Mechanical Engineering at the University of Saskatchewan. He was head of that Department from 1993 to 1999. He obtained B.Sc. and M. Sc. Degrees from the University of Saskatchewan in mechanical engineering in 1967 and 1969, respectively. In 1974 he obtained his Ph.D. from the University of New Hampshire in fluid power control systems. He continues to be active in research in this area and in the thermal systems area as well. He has also held positions in numerous outside engineering and technical organizations.

Richard Burton, Department of Mechanical Engineering, University of Saskatchewan 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Richard Burton P.Eng, Ph.D, FASME, Burton is a Professor of Mechanical Engineering, University of Saskatchewan He is involved in research pertaining to the application of intelligent theories to control and monitoring of hydraulics systems, component design, and system analysis. He is a Fellow of ASME, a member of the executive of ASME, FPST Division, a member of the hydraulics' advisory board of SAE and NCFP and a convenor for FPNI.

Doug Bitner, Department of Mechanical Engineering, University of Saskatchewan 57 Campus Drive, Saskatoon, Saskatchewan, Canada, S7N 5A9

Doug Bitner MSc. Departmental Assistant Mechanical Engineering, University of Saskatchewan. Manager Fluid Power Laboratory and Control Systems Laboratory University of Saskatchewan.

References

Bitner, D. and Burton, R. T. 1984(1). Experimental

Measurement of Load Sensing Pump Parameters.

Proceeding of the 40th National Conference on Fluid

Power, Chicago, pp. 153-161.

Bitner, D. and Burton, R. T. 1984(2). Small Signal

Model of a Load Sensing Pump. Proceeding of the

th National Conference on Fluid Power, Chicago,

pp. 107-112.

Bitner, D. 1986. Analytical and Experimental Analysis

of a Load Sensing Pump. M. Sc. thesis, University

of Saskatchewan, Canada.Book, R. and Goering, C. E. 1997. Load Sensing Hydraulic

System Simulation. Applied Engineering in

Agriculture. ASAE Vol.13 (1), pp.17-25.

Erkkila, M. 1999. Practical Modelling of Load-

Sensing Systems. Proceeding of the Sixth Scandinavian

International Conference on Fluid Power,

SICFP'99, Tampere, Finland, pp. 445.

Kappl, T.J. 2001. Semiempirical Model for Variable

Displacement Pump with Load Sensing Regulator

and Power Restrictor. Proceedings of 2001 ASME

International Mechanical Engineering Congress

and Exposition. New York, NY, USA. Nov. 11.

Kavanagh, G. P., Schoenau, G.J. and Burton, R.T.

Dynamic Analysis of a Variable Displacement

Pump. ASME Journal of Dynamic Systems

Measurement and Control, Vol.112, No.1, pp.122.

Kim, S. D. and Cho, H. S. 1988. Stability Analysis of

a Load-Sensing Hydraulic System. Proceedings of

the Institute of Mechanical Engineering. Part A.

Vol. 202, pp. 79-88.

Krus, P. 1988. On Load Sensing Fluid Power Systems.

Dissertation No.198. Linkoping University, Sweden.

Lantto, B., Palmberg, J.O. and Krus, P. 1990. Static

and Dynamic Performance of Mobile Load-sensing

Systems with Two Different Types of Pressure-

Compensated Valves. SAE Technical Paper Series.

SAE. Sept. 10-13, pp. 251.

Lantto, B., Krus, P. and Palmberg, J.O. 1991. Interaction

between Loads in Load-sensing Systems. Proceeding

of the 2nd Tampere International Conference

on Fluid Power. Linkoping, Sweden, pp. 53.

Merritt, H.E. 1967. Hydraulic Control Systems. John

Wiley & Sons, Inc.

Palmberg, J. O., Krus, P. and Ding, K. 1985. Dynamic

Response Characteristics of Pressure-Control

Pumps. The First International Conference on Fluid

Power Transmission and Control. Zhejiang University,

Hangzhou, China, pp. 110.

Sakurai, Y. and Takahashi, K. 1997. Modelling and

Simulation of a Load Sensing System by Bond-

Graph Method. Proceedings of the Fifth

Scandinavian International Conference on Fluid

Power. Linkoping University. Vol. 3, pp.187-198.

Wu, D. 2003. Modeling and Experimental Evaluation

of a Load -Sensing and Pressure Compensated Hydraulic

System, PhD Thesis, University of Saskatchewan.

Wu, D., Burton, R., Schoenau, G. and Bitner, D.

(1). Establishing Operating Points for a Linearized

Model of a Load Sensing System. International

Journal of Fluid Power. Vol. 3, No. 2, pp. 47-54.

Wu, D., Burton, R., and Schoenau, G. 2002(2). An

Empirical Discharge Coefficient Model for Orifice

Flow. International Journal of Fluid Power. Vol. 3,

No. 3.

Wu, D., Burton, R., Schoenau, G. and Bitner, D.

Modeling of Orifice Flow Rate at Very Small

Openings. International Journal of Fluid Power.

Vol. 4, No. 1.

Zarotti, L. G. and Nervegna, N. 1988. Saturation

Problems in Load Sensing Architectures. Proceeding

of the 43rd National Conference on Fluid Power,

NCFP, Chicago, pp. 393.

Downloads

Published

2005-11-01

How to Cite

Wu, D., Schoenau, G., Burton, R., & Bitner, D. (2005). MODEL AND EXPERIMENTAL VALIDATION OF A LOAD SENSING SYSTEM WITH A CRITICALLY LAPPED REGULATOR SPOOL. International Journal of Fluid Power, 6(3), 5–18. Retrieved from https://journals.riverpublishers.com/index.php/IJFP/article/view/563

Issue

2005: Vol 06 Iss 3

Section

Original Article