Rafael Åman

Computationally efficient two-regime flow orifice model for real-time simulation

In fluid power system simulation, orifice flow is, in the main, clearly in the turbulent area. Only when a valve is closed or an actuator driven against an end stopper does the flow become laminar as pressure drop over the orifice approaches zero. So, in terms of accuracy, the description of laminar flow is hardly necessary. Unfortunately, when a purely turbulent description of the orifice is used, numerical problems occur when pressure drop becomes close to zero since the first derivative of flow with respect of pressure drop approaches infinity when pressure drop approaches zero. Furthermore, the second derivative becomes discontinuous, which causes numerical noise and an infinitely small integration step when a variable step integrator is used. In this paper, a numerically efficient model for the orifice flow is proposed using a cubic spline function to describe the flow in the laminar and transition areas. Parameters for the cubic spline are selected such that its first derivative is equal to the first derivative of the pure turbulent orifice flow model in the boundary condition. The key advantage of this model comes from the fact that no geometrical data is needed in calculation of flow from the pressure drop. In real-time simulation of fluid power circuits, a trade-off exists between accuracy and calculation speed. This investigation is made for the two-regime flow orifice model. The effect of selection of transition pressure drop and integration time step on the accuracy and speed of solution is investigated.

Energy saving in working hydraulics of long booms in heavy working vehicles

Abstract Hybridization of heavy off-highway working vehicles brings considerable energy savings in the form of a downsized internal combustion engine (ICE) by means of reduced no-load losses. In this paper, a novel energy saving opportunity in working hydraulics at the end of long booms of working vehicles is proposed. In traditional off-highway working vehicles, the working hydraulics is supplied through pipes, hoses, and valves by a hydraulic pump located near the main engine. A significant amount of energy is lost in long pipelines and hoses as well as in valve throttles. A new topology is introduced to supply the power along the long boom; the power for a hydraulic actuator is supplied by an integrated electro-hydraulic energy converter (IEHEC), which is located at the boom end. The electrical energy to the converter is supplied through electrical cables, which have negligible losses compared with a conventional fluid power supply with long pipelines. The converter transforms the electrical energy into hydraulic energy at the end of the boom, and may also recover energy for additional energy savings.

Towards a better energy efficiency through a systems approach in an industrial forklift system

The purpose of this study is to improve the potential energy recovery to electric energy in an electrohydraulic forklift system. The initial result achieved for the energy saving ratio after structural optimization is 40%. Component optimization is applied to the tested drive; this consists of an electric servomotor with direct torque control which is directly running a reversible hydraulic pump. According to the study, the energy efficiency and the energy recovery from the electrohydraulic forklift system can be increased by 11%. New ideas and directions for further research were obtained during the study.

Novel ICT-Enabled Collaborative Design Processes and Tools for Developing Non-Road Mobile Machinery

The improvement of the energy efficiency is an important topic for non-road mobile machinery developers and manufacturers. These machines normally use fluid power transmission in drivelines and working actuators. New energy efficient technologies, e.g. a hybrid power transmission with an energy recovery feature, have been introduced. Currently most of the manufacturers are still using conventional technologies in their product development process. Human operators have an effect on the overall efficiency of the machines. Taking into account the human effects is difficult and expensive using the conventional design processes and tools.The objective of this study is to provide international machine manufacturers instrumental, yet novel, community and simulation-based (ICT-enabled) tools/methods for the strategic and cost effective development of their product practices and design processes. The development of models and methods will allow for rapid real-time virtual prototyping of complex machines and machine fleets that operate within a number of worksites or geographical conditions. The introduction of this state-of-the art (and going beyond) advancement in real-time virtual technology, simulation, internet based design technologies and software, cyber-physical and big data processing systems, will present a holistic approach to improve the entire product life. Targeted user groups are manufacturers of non-road mobile machinery (i.e. excavators, wheel loaders, etc.). These machines and production systems share the following key features: 1) They are complex mechatronic systems with several interconnections between hydraulic drives; mechanics, electronics, software and 2) they include autonomous, semiautonomous and human driven operated systems. Methods developed will enable machine manufacturers’ access to technologies that will lead to a more cost effective consumer ordinated, life cycle optimization process.This paper will introduce the method of developing customized products in a fast, agile and networked way that will lead to significantly reduced life-cycle costs.Copyright

Tool for Studying Effects of Human Operators on Energy Consumption of Working Hydraulics of Off-Highway Working Vehicle

The improvement of the energy efficiency is an important topic for off-highway working vehicle developers and manufacturers. New energy efficient technologies, e.g. a hybrid power transmission with an energy recovery feature, have been introduced. However, currently most of the working vehicles are using more conventional technologies. Human operators have an effect on the overall efficiency of the vehicles. The research of the human effect is difficult and expensive using the conventional research methods. A real-time simulation and virtual reality (VR) technology have developed fast recently. A VR-based real-time simulator is a powerful low-cost tool and enables a several novel research methods. The aim of this study is to find the suitability of the VR-based simulator to find the effect of a human operator on the energy consumption of the working hydraulics of off-highway working vehicles. Experimental tests are carried out using human-in-the-loop simulation in an immersive VR-environment. The vehicle used for the case study is an underground mining loader. The results show that the proposed method is valid to find the values for the energy consumption and energy efficiency of a working hydraulics. A variation in the energy efficiency of the working hydraulics was found. The variation correlates with the operator’s driving style. With a larger group of operators the effect of a human operator on the energy consumption can be defined.© 2014 ASME

Experimental Analysis of Electro-Hydraulic Hybrid Actuator System for Off-Highway Working Vehicles

Electro-hydraulic hybrid power transmission system can save energy and thus reduce the pollution while maintaining the same performance in comparison to the conventional fluid power system in off-highway working vehicles. This paper introduces experimental analysis of an electro-hydraulic hybrid actuator system specially developed for the recuperation of the potential and kinetic energy in off-highway working vehicles. In this compact assembly all the components are located near each other to save space. Proposed hybrid actuator system can be controlled directly by an electrical frequency converter which allows the replacement of long lossy fluid power transmission lines with electrical cables. Integrated electro-hydraulic energy converter (IEHEC) is the principal component of the proposed hybrid actuator system. The energy converter consists of a fixed-displacement hydraulic pump-motor and an integrated electrical permanent magnet synchronous motor-generator. IEHEC unit can be driven in four quadrants to produce the mechanical power required for the hydraulic actuator, or to recover the energy released by the actuator mechanism and supply it back to electrical circuit. Suitable places for this application are all actuators that carry out work cycle in which the kinetic and potential energy is available for recovery, e.g. lifting cylinders in cranes, fork lift trucks, etc.The test rig allows the experimental analysis of behavior of real power transmission system in two modes while using simulated loads. The first mode is the work cycle mode using IEHEC as motor connected to the hydraulic pump. The other mode is the energy recovery mode while direction of operation is reversed. The real-time simulated loads, which are carried out by simulating typical work cycle of a mechanism, enable the loading in the work cycle and provide the recoverable energy in the recovery mode. The forces acting in actuator connection point are implemented in the test rig by a hydraulic cylinder which is controlled by bandwidth proportional cartridge valves and a dSpace Real-time Control system.The electro-hydraulic hybrid actuator system was simulated in a certain loading case using virtual simulation and also hardware-in-the-loop (HIL) simulation in the test rig. The responses were compared. Experimental analysis of the dynamic behaviour of a real electro-hydraulic hybrid actuator system has been carried out by using HIL simulation.Copyright