Applied Mechanics and Materials Vols. 220-223

Abstract: As a new type of controllable rheological smart material, Magneto-rheological Fluids (MRF) are widely used in the field of vibration control. This article investigated their integrated dynamic characteristics in squeeze mode and shear mode. Two prototypes were designed and fabricated. The dynamic test for the two prototypes was performed on a simply supported beam vibrating device with the methods of drop-hammering and sweep-frequency measuring. The experimental results demonstrate that the damping ratio of the prototype in squeeze effect presents linearly and widely controllable from 0.0948 to 0.2268 with the increase of the coils’ excitation current, behaving as a variable MR damper. However, its natural frequency remains unchanged. It is also shown that the natural frequency of the prototype in shear effect increases significantly from 18Hz to 24 Hz, acting as a semi-active dynamic vibration (SDVA) absorber with broadband vibration absorption for the maximum attenuation of up to 74.3%. This study provides guidance for engineering applications of MRF.

Abstract: Aircraft hydraulic power carts are important aviation support equipment. Because of their complex structure they have high failure rate. Therefore fault diagnosis system for hydraulic power carts is necessary to ensure high reliability and maintainability for hydraulic power carts. This paper presents a diagnosis method based on fuzzy diagnosis theory in the developing process of a new type of hydraulic power carts. The fault Symptom, critical value and fault causes are established based on the research of fault mode for hydraulic power carts. And also the mathematical model of fault diagnosis for hydraulic power carts is established based on fuzzy diagnosis theory. The practical test results and fault diagnosis instances show that with this fault diagnosis system fast fault diagnosis for hydraulic power carts was carried out successfully.

Abstract: A new type of hydrostatic journal gas bearing with axial slot of tangential gas entry for miniature air turboexpander is firstly developed in this paper. This bearing configuration is presented and constructed to fit manufacture simplicity. The experimental investigations are carried out to reveal the relationship between bearing parameters and instability threshold speed. It is feasible to increase the stability of hydrostatic journal gas bearing by adopting this kind of configuration with axial slot of tangential gas entry. Some valuable tested results are obtained to reveal the optimum slot height and radial clearance for this miniature air turboexpander.

Abstract: It is presented that a new adaptive dual-voltage method to improve the control performance of high-speed solenoid valve and a control device of high-speed solenoid switch valve that could adapt to the pressure change of supply inlet is developed. Based on AMESim, this paper has processed the static and dynamic performance simulation of adaptive dual-voltage method to improve the performance of high-speed solenoid valve. This paper has built an experiment platform of adaptive dual-voltage method to improve the control performance of high-speed solenoid valve, and carried out corresponding experiments. Both simulation and experiment have proved that the method had obviously effect to improve the control performance of high-speed solenoid switch valve and the developed high-speed solenoid switch valve can effectively control the system

Abstract: With the characteristics of non-stationarity, non-linearity, time-lag of refrigeration/ heating supplying in minds, load forecasting of central air-conditioning system is carried using time sequence analysis method. Firstly, acquisition sample data of central air-conditioning system is pretreated, and random time sequence AR model of system is formulated. Then, forecasting of AR refrigeration/heating load based on Yule-walker method is conducted. In order to enhance forecasting accuracy, crossover forecasting is introduced into the load forecasting, that is, to use vertical forecasting to follow household demands for load and horizontal forecasting to track changes of weather. Then, weight cross is made to vertical and horizontal forecasting results. Finally, refrigeration/heating load forecasting software of central air-conditioning system is developed, which is used in energy-saving monitoring and control of central air-conditioning system.

Abstract: One series of cone welding workpiece is a key part of certain critical equipment;we detected the weld quality and geometric error to ensure the high quality. This paper we research the straight weld, the girth weld ultrasonic testing equipment and geometric errors laser automatic testing equipment. Since the testing equipments have a certain degree of correlation, this article also draws on product family design thought, the modular and parametric technique to design the different testing equipments. The kind of design greatly improves the quality, reduces the manufacturing costs, shortens the research and development cycle, receives very nice results.

Abstract: A new scheme of deadbeat direct torque control (DTC) of surface permanent magnet synchronous motor (SPM) is proposed in this paper. The main ideal is choosing the reference voltage vector in two phase stator reference frame previously and real-time calculating the pulse width of the reference voltage vector which diminish the error of torque. With the new scheme, the torque ripples were greatly reduced when compared with those of the basic DTC and the quick dynamic torque response of the basic DTC was still retained. Fixed switching frequency at different operating conditions becomes possible by this new structure. Simulation results verify the correctness and feasibility of this method.

Abstract: This paper analyzes the principle and properties of the traditional direct power control (DPC) system for the three-phase grid-connected voltage source inverter based on its mathematical model. Hysteresis comparators in power loop of DPC control system, leading to the switching frequency not fixed .the fluctuation of power and DC voltage in temporary state. This paper brought an improved program. The active and reactive powers are calculate by estimating the virtual flux. The AC side voltage sensors could be replaced. The SVPWM has been utilized instead of the power hysteresis and switching table of the traditional DPC system.

Abstract: Coalmines’ productive activity demands safety, comfortability, efficiency and economy, which are just the features of advanced human-machine engineering. Then current situation of advanced human-machine engineering’s application in coalmine is summarized, including: operating devices of coalmine machinery are man-beneficial; “safe color” in coal mining machinery is applied; signals under coalmine are effectively released; noise environment in coalmine are improved. Finally, the future trends of advanced human –engineering are discussed: coalmine safe human-machine engineering, coalmine green human-machine engineering, coalmine virtual human-machine engineering, coalmine intelligentized human-machine engineering, and coalmine digital human-machine engineering, etc.

Abstract: In order to predict the evolutionary potential and the technological development direction of the loader, the combination of the maturity prediction and the technology evolutionary mode and the evolutionary line in TRIZ (Theory of the Solution of Inventive Problems, Invention Problem Solving Theory) determines the technological maturity of the loader, and analyzes the location of the loader’s evolutionary route along the different evolutionary mode, finally put forward the possible future development direction of the loader according to the current evolutionary potential .