An extended tractor model was developed by means of the Multi Body System program SIMPACK for simulating the dynamic loads at transport tasks with implements and trailers on rigid road. Therefore an improved tire model with measured parameters was presented. The tractor model includes a detailed description of the front and rear three point hitch with hydraulic and hydropneumatic elements, free play and elasticity. Further the trailer coupling is modeled with different trailers. Time histories, root mean square values and load spectra of simulated curves are compared with measured curves. The experiments were made on a single obstacle and on the "smooth track".(ISO 5008, 100 m length). The results of simulation and measurement have a high conformity.
This thesis documents the studies carried out in order to investigate the possibilities to implement flow simulation of turbulent flows in pneumatic valves, improve the quality of information about flow fields inside valves and insure the results by means of experiments. For this purpose, various steady-state flow conditions in pneumatic valve models have been analysed, calculated and measured on a test rig.
The studies deal with two-dimensional basic geometries of pneumatic valves: "orifice/throttle", "flapper/nozzle" and "cross-sectional deflection". The flow through components is characterised by local sub- and supersonic areas, very high gradients of pres-sure and turbulence. The investigation have been carried out with varied parameters (geometry, boundary conditions, mesh, turbu-lence models, CFD-codes). The Finite-Volume programmes with adaptive adjustment of computing grids have proven advantageous for physically meaningful and stable solutions by acceptable computing times.
In addition to force and flow measurement, the flow has been experimentally visualised by means of hydraulic analogy and schlieren method. The emphasis was conception and testing of a laser-schlieren apparatus for acquisition of air flow under friction in typical pneumatic models. The test rig technique enabled the acquiring of the real flow characteristics, as well as the stating of bene-fit and limits of CFD simulation.
A closer attention was paid to investigation of parameter variations, such as form of nozzle or area and length ratio. A pneumatic flapper-nozzle combination showed e.g. high total pressure losses depending on the valve stroke, as result of shock waves. The flow simulation renders details and tendencies of a real flow at control cross section well and reproduces the volume rate and the flow force precisely enough. The principle immanent discrepancies between calculation and measurement have been detected in areas of high turbulence far away from control cross section.
A hydrostatic transmission system transfers mechanical power from the prime mover through the hydraulic system back to me-chanical power. The purpose of this thesis was to find out an effective control system for the hydrostatic transmission system. First, a non-linear simulation model for the hydrostatic transmission system was developed. The model consisted of sub-models for a diesel engine, a hydraulic pump, hydraulic pipelines, a hydraulic motor and a control system. The efficiency of the hydraulic pump and motor was calculated using simulation models.
The simulation models were verified by comparing the measured data from the real hydrostatic transmission system to the simu-lated data from the simulation models. The control strategies for the diesel engine, hydraulic pump and hydraulic motor were com-pared with the help of the simulation models. The investigated control strategies were the following: traditional control, secondary control and adaptive control.
The main objective of this thesis was to compare the control strategies taking into consideration efficiencies of the hydraulic pump and motor. It was discovered that at high loads all control strategies gave satisfactory results, which means that the overall efficiency is quite high. However, the load is often changing during the operation of the hydrostatic transmission system. At low loads the differences between different control strategies are bigger in terms of efficiency.
In this study the diesel engine, the hydraulic pump and the hydraulic motor are controlled at the same time. The result of this the-sis was that at low loads it is possible to improve the efficiency of the hydraulic pump and motor in the hydrostatic transmission system by using an adaptive control system.
This thesis focuses on reducing the fluid-borne noise by developing high performance new hydraulic silencers. At the first half part, in order to develop this effectively, measuring method of transfer matrix parameters of system components and investigation on the pulsation attenuation characteristics of hydraulic silencer in practical fluid power systems are described. The knowledge of above investigation is crucial for the design of quieter fluid power systems as well as the design of high performance silencer.
Development research of two kinds of new multiple volume resonators, called a "variable resonance-mode type side-branch" resonator and a "multi degree of freedom type Helmholtz" resonator, are presented in the last half part. These are devised in order to reduce the successive several harmonics of the fixed discrete-frequency pressure pulsation such as those generated by a fixed speed hydraulic pump in a hydraulic excavator or an injection-molding machine. Unlike a conventional side-branch or Helmholtz resonator, these can make up the desired plural resonance modes freely with a single closed-end tube configuration. It is shown that the present silencer has proven to be very successful in application to a real hydraulic excavator for reducing audible noise as well as pressure pulsation.
Today’s engineering design processes require the use of simulation in order to meet high requirements on for example cost, per-formance, efficiency or environmental emissions. This type of simulation is enabled by software available from different vendors. However, the technique has not yet fully matured in the industry and clear standards are not yet established. By tradition, different tools are used in different engineering domains, for example electrical, mechanical hydraulic and control, and every tool uses specific formats for the model representation. This means that different tools and model representations are used at different companies and departments within a company.
It is now becoming more and more important to integrate simulation models from several engineering domains in order to simu-late the total behaviour of complex systems. Multi-domain simulation in large projects is a difficult task with several problems to solve. For example the following questions need to be raised: How should we handle the large amount of information that the simu-lation models are associated with? How can we handle the exchange of simulation models between companies, for example in proj-ects with one system integrator and several suppliers? How can proprietary information be protected and model quality guaranteed regardless of the simulation tool?
In this thesis, a background to system modeling and simulation in general is presented. Then a new modeling approach is intro-duced based on a combination of the object-oriented modeling language Modelica and the so-called distributed modeling technique. With this approach it is possible to design parts of the system in a general high-level modeling language based on equations. The parts are then automatically transformed to enable distributed simulation. Each part is a complete executable component with its own equation solver and can be plugged into a system model as a black box if desired. The approach is evaluated in two different projects where an electro-hydrostatic actuation system for aircraft is modelled and simulated: First for evaluation of dynamic performance of the whole system and secondly for analysis of the thermal properties of the system.
In the last part of the thesis, it is shown how simulation models can be stored in an object-oriented database that is directly con-nected to the simulation software package. With this approach, it is more straightforward to handle large models and information associated with the models. Cooperative work can be managed and integration facilitated. It is also observed that the programming effort in designing simulation software applications is significantly reduced if information is managed by a database system.
The PhD thesis deals with the design of a Direct Drive Valve (DDV) based on its static performance and its sensitivity analysis in loop with the actuator. This work can be divided into five parts. In the first part, a mathematical model of flow and flow forces along with transfer function models of the spool valve is presented. In the second part, mathematical model of electro-magnetic flux in the linear force motor along with transfer function models of the motor have been presented. The third part deals with the development of the computer-aided design methodology of the DDV. The fourth part presents a static performance simulation algorithm of the DDV and its sensitivity analysis. Finally, the fifth part studies the sensitivity of the static performance of the DDV in loop with an actuator are presented.
The major contribution of the present dissertation is development of a systematic design algorithm of a DDV, and study of the ef-fect coupling between the static performance of DDV and an actuator in loop. Exploitation of the force-stroke diagram for constant current in formulating important design constraints is the major criterion of the present exposition. The other contribution of the work is development of a computer-aided tool to simulate the static performance of the DDV with actuator in loop and carry out a detail sensitivity analysis. The present investigation involving sensitivity study of some geometric sizes on the no-load and locked actuator static performances has a bearing on the tolerance identification of the critical sizes. The major theoretical achievement of the present analysis lies in obtaining the pressure-discharge relationship in the leakage path. This analysis can also be applied in case of laminar flow through transmission line of short length.
This thesis aims at using advanced modeling and simulation techniques, distributed artificial intelligence, virtual reality, and fa-cilities for e-commerce to enhance the virtual prototyping process for hydraulic systems. The new design paradigms: "integrated virtual model", "plug-in + simulate + visualize", "intelligent and interactive virtual workbench" are proposed to address the current problems in virtual prototyping.
The methodologies and implementation techniques for the proposed design paradigms are explored as follow:
- A virtual model structure and the component-based topology is defined for the integrated representation of components that make up a hydraulic system;
- A simple but effective Fuzzy Neural Network (FNN) approach is proposed to model the hydraulic components' behaviour;
- An agent-based composable simulation for system behaviour evaluation is proposed along with the definition of communi-cation architecture;
- An internet-based interactive and intelligent virtual prototyping process is developed.
This thesis work constitutes initial efforts towards the development of an intelligent workbench for the virtual prototyping of hy-draulic systems over the Internet. It also has the potential application in other manufacturing design areas.
A variable delivery axial piston pump is a key component of hydraulic transmission systems. The problem to suppress the vibra-tion in transmission line systems driven by this kind of pump has not been throughout solved for a long time. In this paper serve control system performance of the pump is studied, the problem to prevent the pair of frictional surfaces for the flow divider pintle from sinter due to overheat is tackled. The vibration mechanism is analyzed in theory, and the vibration sources are eliminated in practice. Besides, the control of electro hydraulic Servo Control System is also studied.
New ideas and techniques, some of which were first proposed by the author, are presented. The electro hydraulic direct acting proportional feedback with a displacement sensor is used in the pump. A control loop is closed through the pressure control valve and the load-sensing valve. The constant pressure regulation of the load-sensing pump is accomplished by using the direct pressure measure method. The improved radial force balance method is used in the design of the flow divider pintle. The pressure compensa-tor is added in the hydrostatical balance system. All that are beneficial for the flow divider pintle suffering from the sinter due to over heat. The Outside features and the ways by which both the energy transfer and the couple effect take place between adjacent parts are found. The cause of the vibration in the oil circuit is mainly the couple effect between the pipe and the liquid in it. The oil tank is not a vibration absorber but a vibration source, which should not be ignored. The Control is proposed for improving the vibration of electro hydraulic servo pump Systems. Simulations Show That the Controller has good robustness. The new GA algorithm for get-ting optimal weight matrices if Control is proposed.
A water hydraulic fire-fighting robot with wavy movement is proposed in this research. The proposed robot can run along flat ground, climb stairs and enter fire places. A new type of movement called wavy movement, which is realized by rotating 12 crosses, was proposed to build the robot. A robot with wavy movement is able to ascend and descend stairs with simple structure, easy control method and high speed by covering edges of stairs within separate wave shapes between touching points. Two water hydraulic mo-tors, which are controlled by 2 water hydraulic servo valves, are used to rotate 12 crosses via chains and sprockets. Two water hy-draulic cylinders, which are controlled by 2 water hydraulic directional valves, are used to adjust the posture of the robot so that it can keep a right angle to stairs while climbing. The cross phase synchronous control is used to keep the phase difference between right and left side to minimum. In this dissertation, the followings will be discussed: the principle of wavy movement, the mechanical design of the robot, the water hydraulic drive system, the speed and position control of motors, the cross phase synchronous control, the posture adjustment, and the experimental result of the developed robot.
Starting at January 2002 the PhD will take 3 years. The student will be paid around 1100 Euro net per month. For further infor-mation please contact:
Contact: Jean-Charles Maré, Email: jean-charles.mare@insa-tlse.fr
by J. Johnson
448 pages
Publisher: Delmar Publishers
ISBN 0766823652
Featuring easy-to-understand explanations of theory and underlying mathematics principles, this book provides readers with a complete introduction to fluid power, including hydraulics and pneumatics. The differences and similarities between hydraulics and pneumatics are identified, allowing readers to leverage their knowledge en route to new skills. Detailed color illustrations, photo-graphs, and color-enhanced schematics are used effectively to add clarity to discussion of the construction and function of compo-nents. A dedicated section on component specifications is featured in each chapter, while realistic numbers are used and problems are stated in such a way as to develop practical system design skills. Knowledge of college-level algebra is assumed, but no trigonometry or calculus is required, making this book ideal for the technologist. Nomenclature, metric prefixes and conversion factors, equations, and graphic symbols are located in handy appendices for use by readers as they progress through the book. An introduction to the industry, plus a comprehensive glossary, is also included for the benefit of those who are just beginning their study of fluid power.