| 1. |
- Larsson, L. Viktor, et al.
(författare)
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Optimisation of a Pump-Controlled Hydraulic System using Digital Displacement Pumps
- 2022
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Ingår i: International Journal of Fluid Power. - : RIVER PUBLISHERS. - 1439-9776 .- 2332-1180. ; 23:1, s. 53-78
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Tidskriftsartikel (refereegranskat)abstract
- When electrifying working machines, energy-efficient operation is key to maximise the use of the limited capacity of on-board batteries. Previous research indicate high energy savings by means of component and system design. In contrast, this paper focuses on how to maximise energy efficiency by means of both design and control optimisation. Simulation-based optimisation and dynamic programming are used to find the optimal electric motor speed trajectory and component sizes for a scooptram machine equipped with pump control, enabled by digital displacement pumps with dynamic flow sharing. The results show that a hardware configuration and control strategy that enable low pump speed minimise drag losses from parasitic components, partly facilitated by the relatively high and operation point-independent efficiencies of the pumps and electric motor. 5-10% cycle energy reductions are indicated, where the higher figure was obtained for simultaneous design and control optimisation. For other, more hydraulic-intense applications, such as excavators, greater reductions could be expected.
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| 2. |
- Nostrani, Marcos Paulo, et al.
(författare)
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Multi-Chamber Actuator Using Digital Pump for Position and Velocity Control Applied in Aircraft
- 2023
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Ingår i: International Journal of Fluid Power. - : RIVER PUBLISHERS. - 1439-9776 .- 2332-1180. ; 24:1
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a multi-chamber hydraulic actuator controlled by digital pumps and on/off valves, in order to improve the efficiency of hydraulic systems applied in aircraft for flight control. Hydraulic positioning systems are used in many different applications, such as mobile machinery, industry and aerospace. In aircraft, the hydraulic actuators are used at flight control surfaces, cargo doors, steering, landing gear and so one. However, the mas-sive use of resistive control techniques, which throttles the passages of the hydraulic fluid, associated with internal leakage of the hydraulic components, make these systems low energy efficient. In order to improve their energy efficiency, digital hydraulics emerges as a promising solution mainly for mobile applications. In this paper a hydraulic positioning system for aircraft control surfaces using a multi-chamber actuator controlled by on/off valves and a digital pump is proposed. The use of a digital pump with three fixed displacement pumps can provide eight different volumetric displacement out-puts. The multi-chamber actuator with four areas can operate in two different modes, normal or regenerative, resulting in six different equivalent areas. The regenerative mode allows the actuator to achieve higher actuation velocity values with smaller pumps. These equivalent areas combined with the dif-ferent supplied flow rates can deliver 43 different discrete output velocity values for the actuator, in steady-state. For the system dynamic analyses, three mathematical simulation models were developed using MATLAB/Simulink and Hopsan, one for the digital system, and two for the conventional solutions applied in aircraft (Servo Hydraulic Actuators (SHA) and Electro Hydrostatic Actuator (EHA)). The simulation results demonstrate that the digital actuator can achieve, for position control, a maximum position error, in a steady-state, of 0.7 mm. From the energy consumption point of view, the digital circuit consumes 31 times less energy when compared with the SHA and 1.7 when compared to the EHA, resulting in an energy efficiency of 54%.
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| 3. |
- Raduenz, Henrique, et al.
(författare)
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Energy Management Based on Neural Networks for a Hydraulic Hybrid Wheel Loader
- 2022
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Ingår i: International Journal of Fluid Power. - : RIVER PUBLISHERS. - 1439-9776 .- 2332-1180. ; 23:3, s. 411-432
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a method to derive optimised energy management strate-gies for a hydraulic hybrid wheel loader. Energy efficiency is a key aspect for the sustainability of off-road mobile machines. Energy management strategies for on-road hybrid vehicles cannot be directly applied to off-road hybrid machines. One significant reason is that there are added degrees of freedom with respect to how power can be recovered, exchanged and reused in the different functions, such as drivetrain or work functions. This results in more complex energy management strategies being derived. This paper presents an analysis and preliminary conclusions for a proposed method to derive optimised online energy management strategies for a hydraulic hybrid wheel loader. Dynamic programming is used to obtain optimal offline energy management strategies for a series of drive cycles. The results are used as examples to train a neural network. The trained neural network then implements the energy management strategy and is used to make optimised control decisions. Through simulation, the neural networks ability to learn the dynamic programming decision-making process is shown, resulting in the machine operating with fuel consumption similar to that of the offline optimal energy management strategy. Aspects of simplicity to model these machines for dynamic programming optimisation, the data necessary to train the network, the training process, variables used to learn the dynamic pro-gramming decision-making process and the robustness of the network when facing unseen operational conditions are discussed. The paper demonstrates the simplicity of the method for taking into account variables that affect the control decisions, therefore achieving optimised solutions.
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| 4. |
- Raduenz, Henrique, et al.
(författare)
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Extended Analysis of a Valve-Controlled System with Multi-Chamber Actuator
- 2022
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Ingår i: International Journal of Fluid Power. - : RIVER PUBLISHERS. - 1439-9776 .- 2332-1180. ; 23:1, s. 79-108
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Tidskriftsartikel (refereegranskat)abstract
- This paper outlines an extended analysis on how multi-chamber actuators can improve the efficiency of valve-controlled systems. Resistive control is a major source of energy losses in valve-controlled systems that share the same pump to drive multiple loads. By combining different chambers, the load on multi-chamber actuators can be transformed into different pressure and flow rate levels. This allows the adaptation of its load to the loads on other actuators. This can lead to a reduction of resistive control energy losses that occur between pump and actuators when driven simultaneously. As a case study to highlight how the system efficiency can be improved, a load sensing system with a conventional and a multi-chamber actuator is analysed. The equations that describe the system steady state behaviour are presented to evaluate the effect of the load transformations on the system efficiency. A disadvantage of such architecture is the fact that load transformations result in different actuator speeds. To reduce this effect, a compensation factor for the command signal to the proportional valve is presented. The highlight from this paper is the potential for efficiency improvement enabled by the adoption of multi-chamber actuators in a valve-controlled architecture. Further research is required for the selection of number of chambers and their areas since they directly affect the system efficiency.
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| 5. |
- Axin, Mikael, 1984-, et al.
(författare)
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A Flexible Working Hydraulic System for Mobile Machines
- 2016
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Ingår i: International Journal of Fluid Power. - : Taylor & Francis. - 1439-9776 .- 2332-1180. ; 17:2, s. 79-89
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper proposes a novel working hydraulic system architecture for mobile machines. Load sensing, flow control and open-centre are merged into a generalized system description. The proposed system is configurable and the operator can realize the characteristics of any of the standard systems without compromising energy efficiency. This can be done non-discretely on-the-fly. One electrically controlled variable displacement pump supplies the system and conventional closed-centre spool valves are used. The pump control strategies are explained in detail. Experimental results demonstrate one solution to the flow matching problem and the static and dynamic differences between different control modes.
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| 6. |
- Baer, Katharina, 1984-, et al.
(författare)
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Framework for simulation-based simultaneous system optimization for a series hydraulic hybrid vehicle
- 2019
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Ingår i: International Journal of Fluid Power. - : Taylor & Francis. - 1439-9776 .- 2332-1180. ; 20:1, s. 27-51
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Tidskriftsartikel (refereegranskat)abstract
- Hybridisation of hydraulic drivetrains offers the potential of efficiency improvement for on – and off-road applications. To realise the advantages, a carefully designed system and corresponding control strategy are required, which are commonly obtained through a sequential design process. Addressing component selection and control parameterisation simultaneously through simulation-based optimisation allows for exploration of a large design space as well as design relations and trade-offs, and their evaluation in dynamic conditions which exist in real driving scenarios. In this paper, the optimisation framework for a hydraulic hybrid vehicle is introduced, including the simulation model for a series hybrid architecture and component scaling considerations impacting the system’s performance. A number of optimisation experiments for an on-road light-duty vehicle, focused on standard-drive-cycle-performance, illustrate the impact of the problem formulation on the final design and thus the complexity of the design problem. The designs found demonstrate both the potential of energy storage in series hybrids, via an energy balance diagram, as well as some challenges. The framework presented here provides a base for systematic evaluation of design alternatives and problem formulation aspects.
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| 7. |
- Dell'Amico, Alessandro, et al.
(författare)
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Modelling and experimental validation of a nonlinear proportional solenoid pressure control valve
- 2016
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Ingår i: International Journal of Fluid Power. - : River Publishers. - 1439-9776 .- 2332-1180. ; 17:2, s. 90-101
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the static and dynamic behaviour of a pressure control valve with nonlinear negative characteristics. The pressure control valve has both reducing and relieving capability and is actuated by a solenoid. The static characteristics have been measured over the entire working range, covering the dynamic response of the solenoid, as well as the complete valve. A model is proposed that considers the flow as a mix of laminar and turbulent flow and flow forces with a flow angle that varies with the stroke of the spool. The model shows good agreement with measurements. The investigations show that the flow forces decrease with higher flow rates as a result of a flow angle that tends to go towards a vertical angle. This results in an increase in pressure with flow during pressure reducing mode. A linear analysis is also presented, explaining this as a negative spring constant in the low frequency range. Stability is, however, maintained.
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| 8. |
- Isaksson, Ove
(författare)
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Particle counter and neural network used to detect sliding wear and pitting in a radial hydraulic motor
- 2010
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Ingår i: International Journal of Fluid Power. - : River Publishers. - 1439-9776 .- 2332-1180. ; 11:2, s. 5-13
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Tidskriftsartikel (refereegranskat)abstract
- A particle counter was used to detect sliding wear and pitting in a low-speed hydraulic motor. The features used by a neural network were accumulated mass, number of particles and time above threshold. The diagnostic tool was experimentally evaluated by collecting data from a test rig running under heavy-duty conditions in a laboratory.Accumulated time above a threshold value seems to be an adequate feature to detect severe damage to a low speed motor at constant operating conditions. Using a neural network to combine the three features gives earlier and more reliable detection of which wear mode is prevailing than when only using the features singly.
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| 9. |
- Pettersson, Karl, 1983-, et al.
(författare)
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A novel hydromechanical hybrid motion system for construction machines
- 2017
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Ingår i: International Journal of Fluid Power. - Abingdon, UK : Taylor & Francis. - 1439-9776 .- 2332-1180. ; 18:1, s. 17-28
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with a novel type of hybrid motion system for construction machines based on a common pressure rail shared between a hydromechanical power-split transmission and secondary controlled work hydraulics. A construction machine with driveline and work functions is a complex coupled motion system and the design of an effective hybrid system needs to take both subsystems into account. Studies on energy efficient hybrid systems for construction machines have hitherto principally focused on one subsystem at a time - work hydraulics or driveline. The paper demonstrates a use case with a specific transmission concept proposal for a medium-sized wheel loader. The system is modelled and simulated using an optimal energy management strategy based on dynamic programming. The results show the benefits of a throttle-free bidirectional link between the machine's subsystems and the energy storage, while taking advantage of the complex power flows of the power-split transmission.
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| 10. |
- Kärnell, Samuel, 1993-, et al.
(författare)
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Classification and Review of Variable Displacement Fluid Power Pumps and Motors
- 2023
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Ingår i: International Journal of Fluid Power. - : River Publishers. - 1439-9776. ; 24:2, s. 207-246
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Tidskriftsartikel (refereegranskat)abstract
- Displacement control of positive displacement machines has been a part of fluid power since the early days. Some of the early hydraulic presses already used two different displacement settings, though this was realised by using two different pumps rather than changing the displacement. Later, radial motors with variable stroke length appeared, followed by other designs of variable machines, such as swashplate machines, bent-axis machines, and variable vane machines. All these solutions control the displacement by varying the volume difference of the displacement element – but there are other ways of achieving this. Most have not passed the research state, but some are commercially available. In this paper, different ways of varying the displacement are presented and classified. The classification divides concepts into either control of displaced fluid or control of usage of displaced fluid. In turn, these concepts can be either on system level or displacement element level. This results in four main classes, which to some extent can describe the characteristics of the control.
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