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Displacement Control Strategies of an In-Line Axial-Piston Unit
Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-2315-0680
2017 (English)In: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Ericson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, p. 244-253Conference paper, Published paper (Refereed)
Abstract [en]

The need for efficient propulsion in heavy vehicles has led to an increased interest in hybrid solutions. Hydraulic hybrids rely on variable hydraulic pumps/motors to continuously convert between hydraulic and mechanical power. This process is carried out via the implementation of secondary control which, in turn, is dependent on a fast displacement controller response. This paper reports on a study of a prototype axial piston pump of the in-line type, in which the displacement is measured with a sensor and controlled using a software-based controller. A pole placement control approach is used, in which a simple model of the pump is used to parametrise the controller using desired resonance and damping of the closed loop controller as input. The controller’s performance is tested in simulations and hardware tests on the prototype unit. The results show that the pole placement approach combined with a lead-compensator controller architecture is flexible, easy to implement and is able to deliver a fast response with high damping. The results will in the future be used in further research on full-vehicle control of heavy hydraulic hybrids.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. Vol. 144, p. 244-253
Series
Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 144
Keywords [en]
Hydraulic hybrids, displacement control, pole placement
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-139854DOI: 10.3384/ecp17144244ISBN: 9789176853696 (print)OAI: oai:DiVA.org:liu-139854DiVA, id: diva2:1134012
Conference
The 15th Scandinavian International Conference on Fluid Power, SICFP’17, June 7-9, 2017, Linköping, Sweden
Available from: 2017-08-17 Created: 2017-08-17 Last updated: 2019-08-21Bibliographically approved
In thesis
1. Control Aspects of Complex Hydromechanical Transmissions: with a Focus on Displacement Control
Open this publication in new window or tab >>Control Aspects of Complex Hydromechanical Transmissions: with a Focus on Displacement Control
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with control aspects of complex hydromechanical transmissions. The overall purpose is to increase the knowledge of important aspects to consider during the development of hydromechanical transmissions to ensure transmission functionality. These include ways of evaluating control strategies in early design stages as well as dynamic properties and control aspects of displacement controllers, which are key components in these systems.

Fuel prices and environmental concerns are factors that drive research on propulsion in heavy construction machinery. Hydromechanical transmissions are strong competitors to conventional torque-converter transmissions used in this application today. They offer high efficiency and wide speed/torque conversion ranges, and may easily be converted to hybrids that allow further fuel savings through energy recuperation. One challenge with hydromechanical transmissions is that they offer many different configurations, which in turn makes it important to enable evaluation of control aspects in early design stages. In this thesis, hardware-in-the-loop simulations, which blend hardware tests and standard software-based simulations, are considered to be a suitable method. A multiple-mode transmission applied to a mid-sized construction machine is modelled and evaluated in offline simulations as well as in hardware-in-the-loopsimulations.

Hydromechanical transmissions rely on efficient variable pumps/motors with fast, accurate displacement controllers. This thesis studies the dynamic behaviour of the displacement controller in swash-plate axial-piston pumps/motors. A novel control approach in which the displacement is measured with an external sensor is proposed. Performance and limitations of the approach are tested in simulations and in experiments. The experiments showed a significantly improved performance with a controller that is slightly more advanced than a standard proportional controller. The implementation of the controller allows simple tuning and good predictability of the displacement response.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. p. 55
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1781
National Category
Control Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering Robotics Computer Engineering Vehicle Engineering
Identifiers
urn:nbn:se:liu:diva-139855 (URN)10.3384/lic.diva-139855 (DOI)978-91-7685-483-9 (ISBN)
Presentation
2017-09-08, ACAS, Campus Valla, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2017-08-17 Created: 2017-08-17 Last updated: 2018-01-13Bibliographically approved
2. Control of Hybrid Hydromechanical Transmissions
Open this publication in new window or tab >>Control of Hybrid Hydromechanical Transmissions
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with control aspects of complex hybrid hydromechanical transmissions for heavy mobile working machines. Control problems are identified and solved to facilitate the implementation and use of these systems.

Fuel prices and environmental concerns have increased the interest in hybrid hydromechanical transmissions for heavy mobile working machines. Hybridisation, the introduction of a secondary energy source in the transmission, offers attractive improvements in terms of both fuel efficiency and performance. These improvements are, in turn, enabled by software control. A complex transmission architecture has several components that need to interact in a stable manner. In addition, optimal utilisation of the added energy source is required to maximise fuel savings. Meanwhile, there is a strong trend towards automation, where many of the operator’s difficult control tasks need to be managed by computers. Sophisticated control strategies are therefore needed, along with a deeper understanding of dynamic properties.

Previous research on the control of hybrid hydromechanical transmissions has primarily focussed on on-road applications. The working conditions of heavy working machines place different requirements on the transmission, which is also reflected in the control strategy.

This thesis highlights the importance of fast response of the variable displacement pump/motors used in hybrid hydromechanical transmissions. Their central position in the interface between hydraulics and mechanics makes their dynamic performance a limiting factor both for the stability of the transmission control loops and in the realisation of smooth mode shifts in multiplemode transmissions. Dynamic models and control strategies for displacement actuators are derived and validated in simulation and experiments. A linear model for dynamic analysis of a general hybrid hydromechanical transmission for heavy working machines is derived and a powertrain control strategy based on decoupled control is proposed. The strategy is verified in simulations and experiments in hardware-in-the-loop simulations, and may be used in a working machine with or without a human operator.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. p. 106
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1992
National Category
Control Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-159771 (URN)10.3384/diss.diva-159771 (DOI)9789176850510 (ISBN)
Public defence
2019-09-20, ACAS, Building A, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2019-08-21 Created: 2019-08-21 Last updated: 2019-09-05Bibliographically approved

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Larsson, L. ViktorKrus, Petter

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