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Digital current regulator for proportional electro-hydraulic valves with unknown disturbance rejection 总被引:1,自引:0,他引:1
Solenoid current regulation is well-known and standard in any proportional electro-hydraulic valve. The goal is to provide a wide-band transfer function from the reference to the measured current, thus making the solenoid a fast and ideal force actuator within the limits of the power supplier. The power supplier is usually a Pulse Width Modulation (PWM) amplifier fixing the voltage bound and the Nyquist frequency of the regulator. Typical analog regulators include three main terms: a feedforward channel, a proportional feedback channel and the electromotive force compensation. The latter compensation may be accomplished by integrative feedback. Here the problem is faced through a model-based design (Embedded Model Control), on the basis of a wide-band embedded model of the solenoid which includes the effect of eddy currents. To this end model parameters must be identified. The embedded model includes a stochastic disturbance dynamics capable of estimating and correcting the electromotive contribution together with parametric uncertainty, variability and state dependence. The embedded model which is fed by the measured current and the supplied voltage becomes a state predictor of the controllable and disturbance dynamics. The control law combines reference generator, state feedback and disturbance rejection to dispatch the PWM amplifier with the appropriate duty cycle. Modeling, identification and control design are outlined together with experimental result. Comparison with an existing analog regulator is also provided. 相似文献
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Characterization of modified thick thermal barrier coatings 总被引:1,自引:0,他引:1
Ahmaniemi S. Tuominen J. Vippola M. Vuoristo P. Mäntylä T. Cernuschi F. Gualco C. Bonadei A. Di Maggio R. Ahmaniemi S. 《Journal of Thermal Spray Technology》2004,13(3):361-369
In gas turbines and diesel engines, there is a demand for thick thermal barrier coatings (TTBCs) due to the increased process
combustion temperatures. Unfortunately, the increased thickness of plasma-sprayed thermal barrier coatings (TBCs) normally
leads to a reduced coating lifetime. For that reason, the coating structures have to be modified. When modifying the structure
of TTBCs, the focus is normally on elastic modulus reduction of the thick coating to improve the coating strain tolerance.
On the other hand, coating structural modification procedures, such as sealing treatments, can be performed when increased
hot-corrosion resistance or better mechanical properties are needed. In this article, several modified zirconia-based TTBC
structures with specific microstructural properties are discussed. Coating surface sealing procedures such as phosphate sealing,
laser glazing, and sol-gel impregnation were studied as potential methods for increasing the hot-corrosion and erosion resistance
of TTBCs. Some microstructural modifications also were made by introducing segmentation cracks into the coating structures
by laser glazing and by using special spraying parameters. These last two methods were studied to increase the strain tolerance
of TTBCs. The coating microstructures were characterized by optical microscopy, a scanning electron microscopy (SEM), transmission
electron microscopy (TEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). The effect of sealing procedures
on the basic thermal and mechanical properties of the coatings was studied. In addition, some correlations between the coating
properties and microstructures are also presented, and the advantages and drawbacks of each modification procedure are discussed. 相似文献
3.
S. Ahmaniemi P. Vuoristo T. Mntyl C. Gualco A. Bonadei R. Di Maggio 《Surface & coatings technology》2005,190(2-3):378-387
The thermal cycling properties of several modified thick thermal barrier coatings (TTBC) were studied in three test series in which the maximum coating temperature was fixed to 1000, 1150 and 1300 °C. The modified coating structures were all segmentation-cracked coatings and some of these coatings were surface-sealed. The segmentation-cracked coatings were produced by laser glazing or by using appropriate plasma spray parameters. The sealing treatments were made by using aluminium phosphate or sol–gel-based sealant. In this paper, it was demonstrated that regardless of whether the segmentation-cracked TTBCs were made by using specific plasma spray parameters or by laser glazing, the strain tolerance of the coating improved significantly. Instead, both sealing treatments reduced the thermal cycling resistance of the TTBCs to some degree, especially in the case of aluminium phosphate sealing. Coating microstructures, their mechanical and elastic properties and residual stresses were taken into consideration when estimating the thermal cycling properties and failure modes of the coatings. 相似文献
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