To simulate the zero-gravity environment for dynamic testing of low frequency space structures, a high precision pneumatic suspension system (PSS) is developed and some pneumatic key technological problems in design of the suspension system are solved. First of all, a type of air-suspending frictionless cylinders is designed based on inner gas pressure supporting by orifice restrictors, and a multi-objective optimization design method of the cylinders is proposed to optimize the structural parameters. Then a high precision pneumatic proportional pressure valve is developed by adopting plunger-type structure with two-stage poppet, and the steady-state precision of pressure control is no less than 0.25KPa. A mathematical model of the PSS is built, and the effects of main system parameters on static/dynamic characteristics, control performance and plunge suspension frequency of the PSS are analyzed. After that a constant pressure control method based on a high precision pressure sensor and proportional valves is proposed to achieve high precision of pressure control. Experimental results show that the total friction force of the PSS is less than 0.0098N, and the steady-state pressure fluctuation is less than 25Pa, which meet the demand of no friction and high precision, and verify the feasibility and validity of the system scheme.

   This study shows how modeling and simulation can be used as a development tool for the analysis and design of power-split drivelines.
Based on publicly available knowledge of power-split theory and its applications, a steady-state calculation model was developed. The model calculates the drive diagram and prints it out as traction effort versus vehicle velocity. The drive diagram is a function of engine torque and speed, power-split design and parameters, main gear transmission rate and driving wheel radius. It calculates also the system pressure of the hydrostatics and torques and the running speeds for all system components.
The steady-state calculation model was used to analyze the basic characteristics: input- and output-coupled power-split designs and to assess current power-split drives. It is a powerful tool for developing new driveline concepts. The thesis presents two industrial applications: a variable speed compressor drive for drilling equipment and a tractor CVT transmission, both designed using the steady state calculation model.
A dynamic model of the complete power-train, including the engine and vehicle dynamics, was developed to examine power- split driveline characteristics. Separate independent models were developed for all the power-train components, easy editing, replacement and testing. Some simulation results are presented. Based on the same dynamic model, a hardware-in-the-loop (HIL) system was developed as a platform for controller development. Additional functions, such as power shuttle, range gear, and Power Take Off (PTO) controls, were added to create a complete powertrain.
Simulation-aided design tools, steady state, dynamic and HIL simulation models make it possible to cut down design time and cost. More time and effort can then be used for virtual and field testing and for increasing the functionality and reliability of the machines.

       The research on the HAMCT (horizontal axis marine current turbine) is the main objective of the thesis. The research work includes turbines blade design, and power transmission design that includes the mechanical method and hydraulic method, and the stability of power output and the maximum of the captured energy. By theory analysis, simulation methods and field tests, the following achievements are achieved. The three-split-power three-merging-power transmission and gearbox-generator/pump incorporated structure are adopted in the 25kW semi-direct-driven unit. The hydraulic system with the reservoir is used to stabilize the power, and the hydraulic pitch control system is used to adapt the dual-direction ocean flow. The hydraulic volume timing control method is adopted to realize the variable speed run and maximum power capture in the research of the 20kW unit. At last the field tests of the 5 kW prototypes and the 25 kW prototypes are introduced, and the device’s efficiency and system performances are analyzed.

     Conventional gasoline engine drives intake valve and exhaust valve by using mechanical camshaft. This kind of engine cannot adapt to different distributing programs in various working conditions.
Therefore, a variable valve actuator system with adoption of high-speed electro-hydraulic valve and single rod hydraulic cylinder is proposed to offset the disadvantages of present distributing mechanism. In order to solve the valve shock problem, a high-speed valve buffer structure characterized by its multiple openings throttle and spring buffer is well proposed in this paper. In the purpose of addressing the problem of low dynamic response of present electro-hydraulic valve, a drive for high-speed electro-hydraulic valve was successful developed. Finally, in order to solve the problem of low dynamic response of the electro-hydraulic variable valve, a high-speed large flow electro-hydraulic valve of without spring, pressure feedback structure was proposed. The experimental results show that the maximum dynamic response frequency of the optimized proportional actuator system can reach to 50Hz and it can be used to control 1500r/min engine valve and the maximum dynamic response frequency of the optimized on/off actuator system can reach to 133Hz and it can be used to control 4000r/min engine valve.

    Hydrostatic displacement units as well as other technical devices are subject to a continuous development process. Due to common rising energy costs demands on efficient machines also in the field of hydraulics gain weight. The testing of measures, which contribute to raise power and efficiency of hydrostatic displacement units, is presented in this thesis. In this field the accuracy of investigation plays a crucial role. Thus the uncertainty of tests is discussed first and determined exemplarily for the measurement of an axial piston pump’s coefficient of efficiency. Tests in tribological contacts are made to determine the friction of PVD-coated surfaces to derive improvement possibilities for the entire unit. The investigation of efficiency coefficients shows the effects of some improvements at a running machine. By means of the capacity determination the efficiency coefficient can be divided into different parts in order to get more detailed information about the pump’s behaviour. The simulation is used to investigate the efficiency of a vane pump. The coupling of tribological and kinematical models allows the calculation of friction and leakage in the gap between vane and contour ring.

In this dissertation, the steady heat transfer of the micro thermal airflow sensor is systematically studied. Firstly, the thin film thermal conductivity measurement method is studied. A heat transfer model of the thin film-substrate structure is built to extend the original Raman method for the thermal conductivity measurement of the sub-micrometer- or nanometer-scale thin films. The extended Raman method is applied to the thin films used in the micro thermal airflow sensor to obtain their thermal conductivities. Secondly, based on the obtained material thermal parameters, the conjugate conduction-convection heat transfer of the micro thermal airflow sensor is studied, a steady heat transfer model is built and the numerical analysis is performed. Based on the analysis results, the optimal design criteria are proposed to enhance the steady performance of the micro thermal airflow sensor. Thirdly, based on the proposed optimal design criteria, the operation mode of the micro thermal airflow sensor is designed, the materials of the micro thermal airflow sensor are chosen and the structure of the micro thermal airflow sensor is designed to enhance the steady performance of the micro thermal airflow sensor. Fourthly, according to the present experimental devices and techniques of the lab, the applicable fabrication processes of the micro thermal airflow sensor are chosen, and the designed micro thermal airflow sensors are fabricated with the achievements of the fabrication processes experiments. The obtained micro thermal airflow sensors are test for their steady performance, and the test results have confirmed the validity of the proposed optimal design criteria.

In this paper, an arc welding robot named “Qianjiang I” is designed, theoretical research and experimental verification are carried out systematically and deeply on serial robot, especially serial robot with six degrees of freedom. The research aims to finding the constraints on domestic robot industrialization, as well as obtaining an effective solution of theory and technology for the development and application of serial robots. A set of real-time algorithm is obtained, which can solve the inverse kinematics problem of serial robots with six rotate joints and various geometries efficiently, and C++ programming language is adopted to realize the set of algorithms. B-spline is utilized to generate joint trajectory, time-optimal and jerk-continuous trajectory is generated, and smoothness- optimal trajectory by setting the cumulative jerk as the goal of optimization is planned. Optimal parameters of PID controller are searched using sequential quadratic programming method, and fuzzy adaptive PID controller and PID controller with compensation of gravitational moment are designed. Further on, an adaptive iterative learning controller is proposed and an input-type iterative learning strategy is discussed, both of them can improve the trajectory tracking accuracy. At last, further research and domestic industrialization of serial robot are prospected, which provides a reference for the following research and design.

In hydraulic power steering systems of motor vehicles, often unintended acoustic phenomena can result from certain driving situations. The acoustic phenomenon known as “rattling” is generated by impacts on the steering cylinder, if the car rides over bumps, kerb stones or similar obstacles. In special friction conditions between tire and road surface during parking, a phenomenon called “shuddering” occurs and leads to strong vibrations. These are audible by the driver as noise, and sensory through shaky steering wheel torque. In this PhD thesis the reasons for rattling and shuddering are analyzed. The design of two test benches affords easy access to the steering systemś components and allows measurement equipment to be easily installed. Furthermore, the development of simulation models are used to study different hydraulic line designs of the steering system. With the simulation models, physical data can be calculated, which can not be measured at the test benches. A comparison between measured and simulated data then verifies the simulation models. To evaluate measured and simulated data of different hydraulic line designs, characteristic numbers are calculated and compared. Active components, to eliminate both phenomena, are worked out systematically and structured in a matrix of principle solutions. The choice of an intelligent switch element out of the matrix leads to the design of three prototype valves, which are installed in the hydraulic lines of the power steering system and analyzed at the two test benches. Characteristic numbers of the three valve lines are calculated and compared to the hydraulic line of the series. With the designed valve lines the rattling and shuddering problem can be solved.

The steam valve regulating system of modern steam turbine units has transmitted from mechanical hydraulic regulation to digital electro-hydraulic (DEH) regulation, which improves the quality of adjusting, realize the complex control algorithm, strengthen the system security and enhance the regulating quality of power and frequency. However, there is no fast control valving function in most DEH systems of our country. Fast control valving is an effective measure that kept the electric power system running stably. Especially when it is applied in area where the electric network structure is weak, the transient stabilization ability of electric power system can be enhanced obviously. In this paper, regulating system in 200MW steam turbine is studied. The protection principle of fast valving under the malfunction of electric network, devise of fast control system and optimization operation tactic are all analyzed and experiment research are made. At the same time, the faults such as internal leakage, plugging and jam in DEH system and fault tolerant control of the system are studied deeply.

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Li Xin

In this work, a new pneumatic non-contact handling device named vortex cup is studied theoretically and experimentally. The vortex cup mainly consists of a circular vortex room, annular flat skirt and a tangential nozzle. Compressed air is blown into the vortex room through the tangential nozzle to form swirling air flow. Swirling air flow gives rise to negative pressure and thus applies a lifting force to a work piece placed under the vortex cup so that the work piece can levitate with a very thin gap away from the vortex cup, through which supplied air is discharged to atmosphere. In case of steady-state condition, the lifting force is dependent upon the gap thickness between the vortex cup and the work piece, which results in an important fact that there is a considerable narrow stable levitation region below the vortex cup where the work piece can levitate stably. Furthermore, in order to enhance the understanding of swirling flow inside the vortex cup, a numerical study was conducted by means of computational fluid dynamics (CFD). The flow field including flow pattern, spatial pressure and velocity distributions were clarified through CFD results. Next, in dynamical cases where the gap thickness varies with time, it is found that lifting force has a very rapid responsibility, and a squeeze damping force is caused by the thin air layer entrapped between the annular flat skirt of the vortex cup and the work piece. Accordingly, a non-linear spring-damper model is proposed to express the dynamical characteristics and proved to be valid by experiments. Finally, some practical issues including the air power consumption of the vortex cup and its pipe system, bending calculation of the work piece and comparison with the Bernoulli non-contact handling chuck were discussed, based on which assessment methods and the advantages of the vortex cup were made clear.

Beuth-Innovationspreis 2009

 The Beuth-Innovationpreis 2009 

Awarded to

Dr. Ing. Matthias Liermann

for his PhD thesis titled “Self-energizing Electro-Hydraulic Brake”

Books & Proceedings Published in 2009