| 1. |
- Pettersson, Karl, 1983-, et al.
(författare)
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Simulation Aided Design and Testing of Hydromechanical Transmissions
- 2014
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Ingår i: The 9th JFPS International Symposium on Fluid Power, Matsue, 2014. - 4931070108
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 2. |
- Braun, Robert, 1984-, et al.
(författare)
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Hopsan: An Open-Source Tool for Rapid Modelling and Simulation of Fluid and Mechatronic Systems
- 2020
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Ingår i: Proceedings of the BATH/ASME 2020 Symposium on Fluid Power and Motion Control (FPMC2020). - : American Society of Mechanical Engineers (ASME). - 9780791883754
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Konferensbidrag (refereegranskat)abstract
- Hopsan is an open-source simulation package developed as a collaboration project between industry and academia. The simulation methodology is based on transmission line modelling, which provides several benefits such as linear model scalability, numerical robustness and parallel simulation. All sub-models are pre-compiled, so that no compilation is required prior to starting a simulation. Default component libraries are available for hydraulic, mechanic, pneumatic, electric and signal domains. Custom components can be written in C++ or generated from Modelica and Mathematica. Support for simulation-based optimization is provided using population-based, evolutionary or direct-search algorithms. Recent research has largely focused on co-simulation with other simulation tools. This is achieved either by using the Functional Mock-up Interface standard, or by tool-to-tool communications. This paper provides a description of the program and its features, the current status of the project, and an overview of recent and ongoing use cases from industry and academia.
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| 3. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
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A General Approach to Low-Level Control of Heavy Complex Hybrid Hydromechanical Transmissions
- 2018
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Ingår i: BATH/ASME 2018 Symposium on Fluid Power and Motion Control. - : ASME Press. - 9780791851968
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on the low-level control of heavy complex hydraulic hybrids, taking stability and the dynamic properties of the included components into account. A linear model which can describe a high number of hybrid configurations in a straightforward manner is derived and used for the development of a general multiple input multiple output (MIMO) decoupling control strategy. This strategy is tested in non-linear simulations of an example vehicle and stability requirements for the low-level actuators are derived. The results show that static decoupling may be used to simplify the control problem to three individual loops controlling pressure, output speed and engine speed. In particular, the pressure and output speed loops rely on fast displacement controllers for stability. In addition, it was found that the decoupling is facilitated if the hydrostatic units have equal response. The low-level control of heavy complex hydraulic hybrids may thus imply other demands on actuators than what is traditionally assumed.
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| 4. |
- Larsson, L. Viktor, 1990-
(författare)
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Control of Hybrid Hydromechanical Transmissions
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 5. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
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Control Optimisation of a Pump-Controlled Hydraulic System using Digital Displacement Pumps
- 2021
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Ingår i: Proceedings of the 17:th Scandinavian International Conference on Fluid Power, SICFP’21, June 1-2, 2021, Linköping, Sweden. - : Linköping University Electronic Press. - 9789179290139
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Konferensbidrag (refereegranskat)abstract
- When dealing with electrification of working machines, energy-efficient operation is key to maximise the usage of the limited capacity of on-board batteries. Previous research indicate that plenty is gained by reducing component and system losses by means of design. In contrast, this paper focuses on how to maximise energy efficiency by means of control optimisation. Dynamic programming with backward-facing simulationis used to find the optimal electric motor speed trajectory for a scooptram machine equipped with pump control, using digital displacement pumps with dynamic flow sharing as enabling technology. The results show that low shaft speed is preferred to minimise drag losses from parasitic components, partly facilitated by the relatively high and operation point-independent efficiencies of the pumps and electricmotor. The results indicate energy reduction of 5 - 9 %, where higher figures could beexpected for other, more hydraulic-intense applications, such as excavators.
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| 6. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
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Displacement Control Strategies of an In-Line Axial-Piston Unit
- 2017
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Ingår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden. - Linköping : Linköping University Electronic Press. - 9789176853696 ; , s. 244-253
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 7. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
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Hardware-in-the-loop Simulation of Complex Hybrid Hydromechanical Transmissions
- 2018
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Ingår i: WIEFP2018 – 4th Workshop on Innovative Engineering for Fluid Power, November 28-30, Sao Paulo, Brazil. - Linköping : Linköping University Electronic Press. - 9789176851364 ; , s. 69-73
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Konferensbidrag (refereegranskat)abstract
- Fuel efficiency and environmental concerns are factors that drive the development of complex solutions for propulsion in heavy working machines. Although these solutions, such as power-split hydromechanical transmissions and hydraulic hybrids, indeed are promising in terms of energy efficiency, they also tend to increase the dependency on accurate, stable control. The realization of this aspect, in turn, relies on continuous testing throughout the development process, usually carried out on expensive, time-consuming prototypes. To lower the development costs and time, hardware-in-the-loop (HWIL) simulations may be introduced as a middle-way between pure prototyping and computer-based simulations. In this concept, some parts of the transmission are represented as hardware while others are included as mathematical models running in real-time in a data acquisition system. This mix of hardware and software allows for high versatility while maintaining a high level of reliability of the results. This paper reports on parts of a study on HWIL simulations of heavy complex hybrid hydromechanical transmissions. Control algorithms for the hardware/model interface in a test rig are derived and their performance are evaluated in HWIL simulations of a mid-sized wheel loader. The results show the importance of fast rig controllers to capture the fast dynamics of the software simulations. It was also found that an important aspect of HWIL simulations is that they are well aligned with their purpose. If so, the simulation yields more reliable knowledge, which is of higher use in the design process of these complex systems. To summarize, HWIL simulations may, if implemented properly, be an important asset in the development of heavy complex hybrid hydromechanical transmissions.
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| 8. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
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Low-Level Control of Hybrid Hydromechanical Transmissions for Heavy Mobile Working Machines
- 2019
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- Fuel efficiency has become an increasingly important property of heavy mobile working machines. As a result, Hybrid Hydromechanical Transmissions (HMTs) are often considered for the propulsion of these vehicles. The introduction of hybrid HMTs does, however, come with a number of control-related challenges. To date, a great focus in the literature has been on high-level control aspects, concerning optimal utilization of the energy storage medium. In contrast, the main topic of this article is low-level control, with the focus on dynamic response and the ability to realize requested power flows accurately. A static decoupled Multiple-Input-Multiple-Output (MIMO) control strategy, based on a linear model of a general hybrid HMT, is proposed. The strategy is compared to a baseline approach in Hardware-In-the-Loop (HWIL) simulations of a reference wheel loader for two drive cycles. It was found that an important benefit of the decoupled control approach is that the static error caused by the system’s cross-couplings is minimized without introducing integrating elements. This feature, combined with the strategy’s general nature, motivates its use for multiple-mode transmissions in which the transmission configuration changes between the modes.
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| 9. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
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Mode Shifting in Hybrid Hydromechanical Transmissions
- 2015
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Ingår i: ASME/BATH 2015 Symposium on Fluid Power and Motion Control. - : ASME Press. - 9780791857236 ; , s. 13-
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 10. |
- Larsson, L. Viktor, 1990-
(författare)
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Modellering och simulering av en hydraulmekanisk power-splittransmission med två moder
- 2015
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Konferensbidrag (refereegranskat)abstract
- Strängare krav på lägre bränsleförbrukning och miljöpåverkan har lett till att tillverkare av tunga arbetsmaskiner i allt högre utsträckning ser sig om efter mer energieffektiva transmissioner. Som en konsekvens har komplexa hydraulmekaniska power-splittransmissioner blivit allt mer intressanta som alternativ till de mer traditionella koncepten. Genom att kombinera den klassiska hydrostaten med en mekanisk länk höjs verkningsgraden samtidigt som en kontinuerligt varierbar utväxling kan realiseras. Införandet av olika växelsteg (moder) gör transmissionen än mer mångsidig, samtidigt som designrymden utvidgas. Detta medför att modellering och simulering har blivit ett viktigt verktyg under utvecklingsprocessen, eftersom transmissionernas egenskaper kan studeras i detalj utan att behöva tillverka dyra prototyper. På så sätt kan viktiga beslut fattas, och slutsatser dras, i ett tidigt skede i utvecklingen. I denna artikel beskrivs hur både linjäriserade och olinjära modeller av en power-splittransmission med två moder för en traktorgrävare tagits fram. De olinjära modellerna har implementerats och simulerats i det Flumes-utvecklade simuleringsprogrammet Hopsan. Förslag ges på en enkel reglerstrategi, och ett antal viktiga slutsatser om konceptet kan dras och stå till grund för hur konceptet skall tas vidare i utvecklingsprocessen.
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| 11. |
- Larsson, L. Viktor, 1990-, et al.
(författare)
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Modelling of the Swash Plate Control Actuator in an Axial Piston Pump for a Hardware-In-the-Loop Simulation Test Rig
- 2016
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Ingår i: Proceedings of the 9th FPNI Ph.D. Symposium on Fluid Power, FPNI2016. - : ASME Press. - 9780791850473
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Konferensbidrag (refereegranskat)abstract
- 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.
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