The dissertation focused on the flow and cavitation characteristics of non-commercial water hydraulics seat valve structures. Experimental measurements and computational fluid dynamics were used as research methods. The main goal in the work was to clarify the effect of individual details on flow and the occurrence of cavitation, which in the fluid dynamics simulations were examined in a typically engineering fashion. Some possible error sources of modelling are also discussed. The work was primarily basic research with no substantial development of the valve structure. Four different basic structured were examined in terms of pressure conditions, flow rate, fluid temperature and cavitation noise. Flow direction through the valve and valve opening served as variables. Occurrence of cavitation was observed visually through a transparent structure.
    The results emphasize the differences in the valve structures. Orifices with a surface along the flow stream had a higher discharge coefficient than the other shapes; on the other hand, they were more sensitive to cavitation. The sensitivity depends on the flow rate rather than the pressure conditions over the orifice. The noise produced by the cavitating flow depends on the flow direction and the fluid space where cavitation bubbles collapse. In general, the model predicted the flow well. Potential error sources were the theoretical sharpness of the geometry and the modelling of the mass transfer between liquid and vapour phases, that is, cavitation modelling

    This thesis is an analysis and usability study of open code and implementation development methods for software to be used in the controller of a hydraulic boom. Both operating system and application software are studied. The usability study concentrates on questions important to automation, mechatronics and hydraulic engineers. The criteria considered are the configurability of the system, usability and implementation of mathematical algorithms, hiding of software complexity, testing and debugging and the clarity of the software. This study compares the usability of C, C++, UML and DSM development methods. The controller software exploit open source software libraries. The controller software contains RT, LAPACK, BLAS and FFTW libraries. These libraries, applicable in general Linux distributions, and used, for example, in Matlab. Also, C++ matrix libraries such as IT++ are studied but not used in the software. In this context licensing of open source code is discussed and the reasons for proprietary code contamination are studied. The usability of a Linux operating system is estimated, where the criteria are stability, ability for real-time operation, clarity of implementation and other factors. The aim of this study is estimation of the potential for implementing controller software with open methods and determining how it fulfills all requirements of industry. Used as an example in this study is Intelligent Machine Control project wherein software for a boom controller was implemented. The controller software was implemented with all four methods where this was possible. All data from the project were analyzed, forming the basis for the usability study. The operating system was standard Linux 2.6.18; only the CAN driver kernel module was added. The software includes an implementation of floating average filters and Kalman estimators for inputs. For hydraulic valves, the software contains pre-configured curves, self-learning valve controllers and speed feedback control for valve/cylinder combinations. For control of actuators, the software features vibration damping and the shaping of the set value to avoid vibration stimulus are included. With the software implemented, it was possible to
drive the hydraulic boom in joint and world coordination.
    The contributions of the thesis relate to usability and efficiency of different software development methods. Important contributions are also made to the literature on usability and the problems, that arise when open source code and Linux are used as a foundation for an embedded system.
    The results of this thesis are a usability study of four different methods and conclusions concerning the usability and viability of a Linux operating system in the controller for hydraulic systems. The main conclusion of the thesis is that DSM hides the complexity of the software components. Also the result can be used in other technology domains of the same scale.

        The research on efficiency optimization and control for dredging slurry pipeline transport system (DSPTS) is the main objective of the thesis. The main achievements include the contents as follow. The mathematic model of DSPTS was established. It puts forward an efficiency optimization evaluation method of DSPTS, which makes accurate continuous on-line evaluation of the system’s working state, benefits the safe on-line adjustment of the system working points and leads to the optimal system efficiency. The working points on-line dynamic optimization method was put forward for DSPTS, which makes the system’s working points change with the working state and approach the optimum by dynamic adjustment, thus to improve the system’s efficiency as well as the safety of DSPTS. It presents a multi-pump coordinated control method, which aims at optimizing the integrated efficiency of the unit, uses genetic algorithm to make on-line rotation speed coordination and optimization of the pumps, thus to approach the highest workingefficiency of the unit.

      In this paper, the flow simulation, high-speed observation and spectrum measurement methods are adopted to investigate the relationships of valve port structure, pressure gradient, flow pattern and cavitation characteristic from the microscopic point of view. Against the complex shape, small size, high velocity and dramatic change of flow structure, we studied the effect of structure and flow parameters on the state of cavitation, as well as the relations of cavitation distribution, flow discharge and noise characteristics from analyzing the cavitation status under various forms of valve port. The conclusions are that, the generation and development of cavitation are affected by both shear flow and eddy current. When the two states of flow occur simultaneously, cavitation is more susceptible to the vortex. Valve port transportation will cause dramatic change of the pressure gradient inside flow channel, thereby the cavitation inception location and cavitation type will transfer correspondingly. Through multi-parameter optimization method, we get the modified formula of discharge in the state of cavitation. At the same time, through the visualization and spectrum analysis of flow field, we found that the frequency of bubble flow’s cyclical fluctuation is in coincidence with the high frequency of noise. The results are of great theoretical and practical values for the design of high-efficiency, low energy loss and low-noise hydraulic valves and piping system.

The study on real-time measuring method of concrete pump discharge is the main objective of the thesis. The main achievements include the contents as follow. The mathematic model of the concrete pump discharge is established. The measuring methods based on pressure, pressure and displacement, pressure change trend, pressure change trend and displacement are proposed. The pressure of the pumping hydraulic system and the piston displacement of the concrete pump are measured on site. The data processing for the pressure and displacement signals are carried out using median filtering, moving average filtering, wavelet filtering, adaptive filtering as well as wavelet adaptive filtering. The hardware component and assembly structure of the real-time measuring instrument , the intelligent monitoring and control system of the concrete pump discharge are introduced, and the hardware and software of the instrument are designed. Each measuring method is realized by analyzing the pressure and displacement signals, calculating the realtime pumping efficiency factor and actual discharge in each pumping stroke, accumulating the actual discharge in all pumping stroking,and obtaining the total actual discharge. By field experiment, comparing with the current measuring methods, the measuring methods proposed in this paper improve the measuring accuracy.

The fluidic flowmeter with feedback passages induces fluid vibration by Coanda effect. The frequency of the the vibration is proportional with the flow rate to a large extent. The fluidic flowmeter has a favourable future because of its extremely low lower limit in theory, however the present fluidic flowmeter has some shortcomings in engineering applications: lower limit much higher than theoretical; low signal to noise ratio; lack of criteria for structural parameters design and performance optimization, which limited the popularization of this flowmeter. In this dissertation, basic theory and design method of hydrodynamic vibration induced by jet alternating are researched to counter the defects of high lower limit and low signal to noise ratio in fluidic flowmeter. Fluidic flowmeter with vertical inlet passage and double outlets structure is schemed out, prototype is developed and performance test is carried out. Criteria for structural parameters design and performance optimization of the fluidic flowmeter are established. Design method of improving the anti-interference ability of fluidic flowmeter by vertical inlet passage structure is schemed out, which makes the fluid vibraion plane depart from the pipe axis to reduce the interference of the upstream flow pulse to the flow field in fluidic oscillator, therefore induces stable jet attachment and alternate vibration even at low flow rate, improves the anti-interference ability, decreases the lower limit of the fluidic flowmeter; the double outlets design method is schemed out, which improves the performance of attachment and switching in fluidic flowmeter, strengthen the pressure in the feedback passage, therefore decreases the lower limitand improves the signal to noise ratio.

    Energy is consuming up and pollution is more and more serious nowadays, so research on energy saving of hydraulic excavators has great significance because of their large application quantities, high energy consumption and bad exhaust. As hydraulic excavator is one typical construction machinery, such research can also provide solutions for other construction machines which have the same characteristics to achieve energy saving.
    In one hydraulic excavator, all exhaust and most components which have low energy conversion efficiency are in the power system. So the research on energy saving and exhaust reduction of hydraulic excavators should concentrate in the power system. Generally, the main factors affecting the efficiency and exhaust of the power system are the structure, parameter matching and control strategy.
    In this dissertation, the corresponding energy saving methods are proposed and the structure of hybrid system is presented based on the analyses of energy consumption of hydraulic excavators. The corresponding control strategy of the hybrid system is developed according to the working condition of hydraulic excavators. And parameter matching of this hybrid system is studied. Then a design method of hybrid system in hydraulic excavators is proposed based on the above research. This dissertation can provide some theoretical and experimental references for the further research on energy saving of power system in hydraulic excavators.

    The research on motion control of Humanoid Leg Joints Actuated by Pneumatic Artificial Muscles is the main objective of the thesis. The main achievements include the contents as follow. The multi-DOF joints based on human physiological structure of low limb was established. The performance of the hardware system was analyzed. The mathematic model of multi-DOF joint actuated by PWM high speed valves was built. The experimental results demonstrated the correct of the mathematic model. The influence of working pressure, temperature, internal volume and friction can be researched through simulation. Considering the strongly nonlinear of pneumatic muscles joint and difficult to build a precise model, a sliding variable structure robust controller was designed. Experimental results showed that the steady state error is less than 0.005 rad, low frequency tracking error is less than 0.06 rad. A robust adaptive control (ARC) strategy based on robust control was designed to improve the control performance. The steady state error is less than 0.003 rad, the low frequency tracking error is less than 0.01 rad, and high frequency is less than 0.05 rad. In order to reduce the cost of practical application, the saturation robust adaptive controller (SARC) was developed using the position feedback only. It’s still on the basis of robust control and adaptive control. The low frequency tracking error is less than 0.01 rad, high frequencytracking error is less than 0.03 rad.

    The dissertation aims at a φ6.3m earth pressure balance shield machine (EPB) and a φ1.8m test SM, proposes three new hydraulic drive modes including the multi-variable pumps built-up drive with closed hydraulic circuit, the variable displacement pump control and the variable speed pump control with closed loop control; proposes an accurate Tc calculate model for EPB; proposes a brainpower control method of the cutter head speed. In this paper, the research aiming at the hydraulic systems with different drive modes is taken by the principle analyse, test and simulation which the models are highly alike with the real systems by taking advantage of the AMESim fully and especially considing the change of the out load. The reaserch includes the hydraulic system efficiency, the cutter head speed, time domain analyse, frequency domain analyse and the hydraulic system performances in the changed load, hydraulic motor failure, or the cutter head binding conditions. This paper also analises Tc’s constitution of EPB, and studies on Tc of the φ1.8m test SM by simulation and test including Tc and the relationship of Tc with other parameters, and proposes the accurate calculate model of Tc, furthermore, proposes a brainpower control method of the cutter head speed based on the earth condition recognition and the index of drive power efficiency, the statistical classified method of the tunneling earth layer and the expert systemhave been firstly researched.

Bramah Award 2007

Exceptional innovation in the field of fluid power engineering 

Awarded to

Dr. ir Peter A. J. Achten


Dr. ir Peter A. J. Achten  was presented with the Joseph Bramah Medal at the ASME Symposium on Fluid Power
and Motion Control (FPMC 2008) at Bath University, Bath, UK, on 10 September 2008.

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