In order to solve the problem of performance analysis and optimal design of flexible suspension structure for displacement measurement probing sensors, a novel theoretical model of stiffness with high accuracy is proposed. Both displacements constraint and angle constraint of elastic diaphragms are considered during modeling, and a stiffness equation including all dimensional parameters and material characteristics of elastic diaphragms is obtained. Thus the stiffness of the flexible suspension structure is modeled theoretically and accurately, and the influence on performance of probing sensors by each parameter can be analyzed. Simulations results show that the theoretical model of stiffness proposed is more accurate than existing models, and performance analysis and optimal design of probing sensors can be carried out based on it.
With the fast development of the advanced equipment manufacturing toward precision and ultra-precision trend, especially with the continuously improving of the aviation engine’s performance, the problem of high displacement resolution for the large-load two-dimension adjusting and positioning worktable used for the aeroengine assembling become evident. A method was proposed which is based on the invariable restoring force, and the adjusting and positioning physical model was established. The experiment results indicate that under the occasion of a load with 508 kilogram, the worktable has got a displacement resolution of 0.3μm after using the improved method compared to 1.4μm of the traditional method. The improved method could meet the requirements of aviation engine assembling worktable.
KEYWORDS: Sensors, Spherical lenses, Chemical elements, Algorithm development, Environmental sensing, Control systems, Thermal energy technology, Temperature metrology, Structural design, Fluctuations and noise
In order to solve the problem of thermal drift and further improve the performance for sensors with extreme demand for precision, based on analysis of shortcomings of existing compensation methods and characteristics of thermal drift, a novel active suppression technology against thermal drift is proposed. Considering the change of properties of reference elements in sensors caused by temperature variation is the most major factor that introduces thermal drift error, a special thermal structure is designed to provide a small environmental chamber with sub-structure design of high performance heat isolation, heat conduction and homogenization of temperature, and the temperature in the environmental chamber is controlled with high precision based on bilateral temperature adjusting with thermo electronic cooler (TEC) devices, and a compound control algorithm of Bang-Bang and anti-windup PID. Experimental results with an ultra-precision spherical capacitive sensor show thermal drift error is significantly eliminated and the precision of the sensor can reach the level of several resolutions.
KEYWORDS: Sensors, Electrodes, Signal processing, Integrated circuits, Capacitance, Digital electronics, Wireless communications, Calibration, Data communications, Digital signal processing
In order to solve the problem of noncontact, wireless and nonmagnetic displacement sensing with nanometer resolution within critical limited space for ultraprecision displacement monitoring in the Joule balance device, a novel wireless digital capacitive displacement sensor (WDCDS) is proposed. The WDCDS is fabricated with brass and other nonmagnetic material and powered with a small battery inside, a small integrated circuit is assembled inside for converting and processing of capacitive signal, and low power Bluetooth is used for wireless signal transmission and communication. Experimental results show that the WDCDS proposed has a resolution of better than 1nm and a nonlinearity of 0.077%, therefore it is a delicate design for ultraprecision noncontact displacement monitoring in the Joule balance device, meeting the demand for properties of wireless, nonmagnetic and miniaturized size.
Using the diamond turning lathe and mono crystalline diamond tool, the aluminum alloy of 2A12 was cut under different cutting parameters including cutting speed, feed rate and depth of cut and the mirror surfaces were made. The surface roughness, micro hardness and residual stress of the mirror surface were tested by the surface profiler, the universal hardness tester and X-stress Robot. The influences of the cutting parameters on the mirror quality were studied. The research results have theoretical and practical significance to the selection of the optimal cutting parameters in ultraprecision diamond turning.
In the respect of ultra-precision manufacturing of axisymmetric surface, the machine tool with tool swing feeding which has less interpolation error sources compared to the conventional ultra-precision diamond turning machine tool with T-structureis worth studying.Therefore,based on the dynamic simulation modeling and multi-body dynamics theory,in this paper, we establish the control model,and tool path for Ultra-precision machine.Then we got the model for surface topography with differentinput parameters like spindle speed, feedrate, tool parameters and so on. Taking the spherical optics part with diameter of 300 mm, for example, we input the process parameters and get its surface topography, then evaluate its surface quality by surface roughness value (Ra) and surface shape accuracy(PV) .
The anisotropy of material removal rate for diamond gives a method to control the lapping rate of diamond specimen, i.e. changing the lapping direction. This requires comprehension on the relationship of the material removal rate and the lapping direction for diamond. This paper provides a method to figure out the diamond lapping direction. By preprocessing a straight edge formed by lapping a surface intersects with the required machining surface, the diamond lapping direction can be figured out under the Confocal Scanning Laser Microscope only if the crystal directions of the two surfaces are determined at first. The advantage of our method is that there is no need to consider the position and posture of the diamond specimen fixed on the holder.
Non-rotational symmetric surface machining requires at least three numerically controlled axes, so there exists a desperately need of an ultra-precision vertical linear axis for ultra-precision machine tools. Based on the above consideration, a vertical ultra-precision linear axis has been developed to satisfy the need for non-rotational symmetric surface ultra-precision machining. The paper discusses the design challenges of the vertical ultra-precision linear axis and presents the mechanical structure designed with dual linear motor drive. A guide component and a gravity compensation mechanism have been designed. Finite element models for the vertical ultra-precision were established to evaluate the dynamic performance of the vertical ultra-precision linear axis. Analysis results show that the configuration of the vertical ultra-precision linear axis is reasonable with good dynamic performance.
The requirement of the vibration isolation system for ultra-precision machine tool was extremely stringent. However, most of the isolation systems currently cannot meet the requirement. Therefore, it is urgently needed to design a new vibration isolation system to fulfill the strict vibration capability required by ultra-precision machine tool. In this paper the structure and principle of the conventional vibration isolation systems composed of air springs were first elucidated thoroughly. Based on these knowledge, we have designed a vibration isolation system with the function of auto-leveling adjustment for a home-made ultra-precision machine tool. The capability of vibration isolation system was validated by an experimental method, in which acceleration-frequency curves were recorded. And post data processing including the analyzing the cut-off frequency and amplitude attenuation were followed. The experimental results demonstrated that the air spring vibration isolation system designed in this paper has the capability to effectively isolate the vibration from the ground: it has a higher attenuation ratio for vibration with a frequency beyond 3 Hz, which preferably meet the vibration isolation requirement of the ultra-precision machine tool.
It is quite difficult to manufacturing optical components, the combination of high gradient ellipsoid and hyperboloid,
with high machining surface requirements. To solve the problem, in this paper we present a turning and forming method
via oscillating feed of R-θ layout lathe, analyze machining ellipsoid segment and hyperboloid segment separately through
oscillating feed. Also calculate parameters on each trajectory during processing respectively and obtain displacement,
velocity, acceleration and other parameters. The simulation result shows that this rotary turning method is capable of
ensuring that the cutter is on the equidistance line of meridian cross section curve of work piece during processing high
gradient aspheric surface, which helps getting high quality surface. Also the method provides a new approach and a
theory basis for manufacturing high quality aspheric surface and extending function of the available twin-spindle lathe as
well.
In the non-rotational symmetrical microstrcture surfaces generation using turning method with Fast Tool Servo(FTS), non-uniform distribution of the interpolation data points will lead to long processing cycle and poor surface quality. To improve this situation, nearly arc-length tool path generation algorithm is proposed, which generates tool tip trajectory points in nearly arc-length instead of the traditional interpolation rule of equal angle and adds tool radius compensation. All the interpolation points are equidistant in radial distribution because of the constant feeding speed in X slider, the high frequency tool radius compensation components are in both X direction and Z direction, which makes X slider difficult to follow the input orders due to its large mass. Newton iterative method is used to calculate the neighboring contour tangent point coordinate value with the interpolation point X position as initial value, in this way, the new Z coordinate value is gotten, and the high frequency motion components in X direction is decomposed into Z direction. Taking a typical microstructure with 4μm PV value for test, which is mixed with two 70μm wave length sine-waves, the max profile error at the angle of fifteen is less than 0.01μm turning by a diamond tool with big radius of 80μm. The sinusoidal grid is machined on a ultra-precision lathe succesfully, the wavelength is 70.2278μm the Ra value is 22.81nm evaluated by data points generated by filtering out the first five harmonics.
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