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Control Aspects of Complex Hydromechanical Transmissions: with a Focus on Displacement Control
Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
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: urn:nbn:se:liu:diva-139855DOI: 10.3384/lic.diva-139855ISBN: 978-91-7685-483-9 (print)OAI: oai:DiVA.org:liu-139855DiVA, id: diva2:1134028
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
List of papers
1. Simulation Aided Design and Testing of Hydromechanical Transmissions
Open this publication in new window or tab >>Simulation Aided Design and Testing of Hydromechanical Transmissions
2014 (English)In: The 9th JFPS International Symposium on Fluid Power, Matsue, 2014, 2014Conference paper, Published paper (Refereed)
Abstract [en]

This paper demonstrates the use of high-speed simulation in transmission conceptual design and presents a transmission test bed for hardware-in-the-loop simulations of hydromechanical transmission concepts. Complex transmissions, such as multiple-mode hydromechanical transmissions and hydraulic hybrid transmissions, present new difficulties and costs in the development process. There is today a greater demand for more efficient product development and more work has shifted towards simulation. The Hopsan simulation package allows robust, high-speed simulations suitable for both offline and hardware-in-the-loop simulation. New simulation models for hydromechanical transmissions are developed and used to simulate a known two-mode transmission concept. The same concept is also tested in hardware-in-the-loop simulations in the proposed transmission test bed. Results show good agreement with the hardware tests and highlight the proficiency of the simulation tools.

Keywords
Hydromechanical Transmission, Hardware-in-the-loop, Hopsan
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:liu:diva-126561 (URN)4-931070-10-8 (ISBN)
Conference
the 9th JFPS International Symposium on Fluid Power in Matsue, Shimane Japan, on October 28-31, 2014
Available from: 2016-03-30 Created: 2016-03-30 Last updated: 2018-03-21
2. Mode Shifting in Hybrid Hydromechanical Transmissions
Open this publication in new window or tab >>Mode Shifting in Hybrid Hydromechanical Transmissions
2015 (English)In: ASME/BATH 2015 Symposium on Fluid Power and Motion Control, ASME Press, 2015, p. 13-Conference paper, Published paper (Refereed)
Abstract [en]

Demands for low cost sustainable solutions have increased the use of and interest in complex hydromechanical transmissions for heavy off-road vehicles. In transmissions with multiplemodes, an important condition is to maintain the tractive force during the mode shifting event. For hybrid hydromechanical transmissions, with a direct connection to a hydraulic accumulator, the impressed system pressure caused by the hydraulic accumulator has not yet been observed to interfere with this condition. In this paper, a black box model approach is used to modify the hydraulic system after obtaining knowledge regarding how it is affected by a mode shift. A comparative study is carried out where a full vehicle model of a mobile working machine is simulated with two different hydraulic systems. The results show that different system solutions imply different demands on the included components, and that the mode shifting event is not a negligible factor in heavy hydraulic hybrid vehicles.

Place, publisher, year, edition, pages
ASME Press, 2015
Keywords
Mode shifting, hydromechanical transmissions, fluid power, heavy construction machinery
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-126556 (URN)10.1115/FPMC2015-9583 (DOI)000373970500045 ()978-0-7918-5723-6 (ISBN)
Conference
ASME/BATH 2015 Symposium on Fluid Power and Motion Control, Chicago, Illinois, USA, October 12–14, 2015
Projects
Research on Hydromechanical Transmissions and Hybrid Motion systems, RHYTHM
Funder
Swedish Energy Agency, P39367-1
Available from: 2016-03-30 Created: 2016-03-30 Last updated: 2017-11-09
3. Modelling of the Swash Plate Control Actuator in an Axial Piston Pump for a Hardware-In-the-Loop Simulation Test Rig
Open this publication in new window or tab >>Modelling of the Swash Plate Control Actuator in an Axial Piston Pump for a Hardware-In-the-Loop Simulation Test Rig
2016 (English)In: Proceedings of the 9th FPNI Ph.D. Symposium on Fluid Power, FPNI2016, ASME Press, 2016, article id UNSP V001T01A044Conference paper, Published paper (Refereed)
Abstract [en]

Hydraulic hybrid system solutions are promising in the quest for energy efficiency in heavy construction machines. Hardware-in-the-loop simulations, where hardware is included in software simulations in real time, may be used to facilitate the development process of these systems without the need to build expensive prototypes. In this paper, the displacement actuator of a prototype pump used in a hardware-in-the-loop simulation test rig is modelled and validated against hardware, in order to draw conclusions regarding its dynamic behaviour in a future control design. The results show that the dynamic response of the modelled displacement actuator is mainly determined by the system pressure as well as the response and geometry of the control valve.

Place, publisher, year, edition, pages
ASME Press, 2016
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-133328 (URN)10.1115/FPNI2016-1570 (DOI)000398986900044 ()978-0-7918-5047-3 (ISBN)
Conference
The 9th FPNI Ph.D. Symposium on Fluid Power
Projects
Research on Hydromechanical Transmissions and Hybrid Motion systems, RHYTHM
Funder
Swedish Energy Agency, P39367-1
Note

The authors would like to thank the Swedish Energy Agency for contributing funds for the research project. Thanks also go to Bosch Rexroth for providing the prototype machines.

Available from: 2016-12-20 Created: 2016-12-20 Last updated: 2017-09-12
4. Displacement Control Strategies of an In-Line Axial-Piston Unit
Open this publication in new window or tab >>Displacement Control Strategies of an In-Line Axial-Piston Unit
2017 (English)In: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Krus, Petter; Liselott Ericson; Magnus Sethson, Linköping: Linköping University Electronic Press, 2017Conference 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
Series
Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 144
Keywords
Hydraulic hybrids, displacement control, pole placement
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:liu:diva-139854 (URN)978-91-7685-369-6 (ISBN)
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: 2018-04-17Bibliographically approved

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