Surface Profile Error Research Articles

インフレータブルリフレクタ膜の最適膜厚

The purpose of this paper is to obtain an optimum thickness distribution of an inflatable membrane reflector which consists of two circular membranes attached at their edges. The deflection analysis of the membrane is based on the large deflection theory of plate. In numerical simulation, the finite element method is used. In the optimization, the objective function is the surface profile error between the paraboloid and the inflated shape of membrane, and the discrete distribution of optimum thickness is obtained. In addition, the simulation for experiment is performed under a restricted condition in thickness. Based on this result, a circular membrane with optimized thickness profile is produced and the shape measurement experiment is performed.

Panel gap cover for millimetre-wave antenna

The reflector of the 10 m diameter, millimetre-wave, South Pole Telescope has been equipped with reflecting covers over the gaps between panels. The covers are thin metal strips that lie on the surface of the panels, with spring clip retainers that engage steps in the panel edges. Covering the gaps reduces thermal noise from the reflector by ∼2 K at the expense of increasing the surface profile error by ∼11 µm rms.

Wheel curve generation error of aspheric microgrinding in parallel grinding method

In aspheric grinding of hard brittle material, in-process wheel wear is a crucial factor affecting the profile error of the ground surface. To suppress wheel wear, parallel grinding is adopted. Since the wheel and workpiece contact point changes during parallel grinding, geometric wheel error influences machining accuracy significantly. In the wheel truing process with a cup truer, the wheel radius is determined by the angle and distance between the wheel and the truer. Through geometric analysis, this paper presents a new equation of wheel radius, which enables process parameters, such as setup error or thermal error, to be determined easily. Simulation results show that wheel radius error is predominantly affected by vertical deviation between the wheel rotation center and the truer center. Experimental results show that wheel radius errors match those from simulation well.

Measurement of the Straightness of a Leadscrew-Driven Precision Stage

This paper describes a multi-probe method for measuring the straightness error of a leadscrew-driven stage. Two displacement probes are employed to scan a flat artifact mounted on the stage. The surface profile error of the flat artifact is separated from the straightness error of the stage in a differential output of the probes. The straightness error can thus be obtained accurately from an integration operation of the differential output without the influence of the surface profile error. An improved technique of data processing is adopted for measurement of straightness error components with periodicity shorter than the probe spacing. The influence of the angular error of the stage is compensated for by using the result measured by an autocollimator. Experiments of straightness measurement of a leadscrew-driven stage with a lead of 1 mm were carried out by using two flat artifacts with different degrees of precision. The successful detection of the short-periodicity component of the straightness error with a periodicity equal to the lead indicated the feasibility of the multi-probe method.

超精密非球面加工機の運動誤差測定(第2報) : 運動誤差の機上測定実験(G13-2 機械加工および工作機械(2),G13 生産加工・工作機械部門)

A capacitance probe-based system is developed for measurement of carriage Straightness and roll error motions. The system, which is added to a conventional laser interferometer, consists of a probe-unit and an auxiliary flat surface. The profile error of the flat surface, which is moved by the carriage, is first measured with the X-probes accurately through separating the carriage lateral Straightness error (Z-error). The auxiliary flat surface is then used as an accurate reference for carriage lateral Straightness error measurement. The roll error of the carriage can be measured by dividing the difference of the Y-probes by the probe distance between the Y-probes. The developed system has been applied to the measurement of an ultra-precision aspheric grinding machine. The Straightness error and roll error were measured to be 120nm and 2.4arcsec over a stroke of 80mm, respectively.

A study on enhancement of grinding accuracy by an active tool control

An approach to enhance dimensional accuracy of the grinding process has been presented, and grinding of a glass material with a metal-bonded diamond wheel has been studied. In this study, a grinding tool is suspended flexibly and controlled by an electromagnetic actuator. During grinding, profile error of a ground surface is indirectly measured and fed back to a control system. A model of grinding error has been suggested on which the indirect measurement has been based. An optimal PID control is adopted and effectiveness of the in-process feedback control has been verified experimentally.

Intelligent shape control for precision membrane antennae and reflectors in space

After a brief history of use in space about two decades ago, a resurgence of interest in membrane structures in space is developing, motivated in large part by a great potential for reduced launch mass and stowed volume. Applications for such structures range from planar configurations in solar sails, concentrators and shields, to inflatable lenticulars for radar, radio and optics. Three key factors are paramount for the success and user acceptance of this technology: deployment, longevity and performance. The performance hinges critically on the precision of the membrane surface. The amount of precision is highly mission dependent and may entail one or more of the following issues: surface smoothness, deviation from desired surface profile and slope error. Surface precision is often estimated to be between 1/50 to 1/20 of the wavelength of interest; thus values on the order of a micron (or less) to a millimeter root mean square (RMS) are often presented. It is unlikely that such surface precision can be achieved through purely passive means. This paper addresses the problem of modeling and controlling a class of nonlinear systems that can be considered as highly compliant structures. We consider specifically planar and inflatable membranes, which are represented by complex nonlinear multi-variable models. Boundary perturbations and thermal gradients are demonstrated to be potential actuation schemes for improving the reflector profile. Nonlinear controllers developed to improve performance are often dependent on state estimation and parameter identification procedures. The existence of these procedures, within the control strategy, increases the size of the algorithms, limiting the system performance in real-time. This research has as a main objective to create an intelligent controller based on feedback error learning, which is capable of extracting performance information from precision large membrane deployables and subsequently using this information to achieve maximum surface precision.

Accuracy Optimisation for Mould Surface Profile Milling

In the profile milling process for mould surfaces, for any type of curve combination, when implementing the milling process on a CNC machine, the surface can be produced from straight lines or curves in a piecewise or continuous milling process. This work employs the features of a CNC machine: 1. To divide the various sizes of curve at different slopes. 2. To use with different milling spindle speeds. 3. To use cutting feeds for actual milling experimentation. The results of the profile dimension accuracy and profile surface roughness from these experiments are then used in a neural network to establish an experiment result and a model for the milling variables. The neural network is composed of a number of functional nodes. Once the milling parameters (spindle speed, feed speed and milling angle) are given, the milling processing performance (the surface roughness, the surface profile-error) can be accurately predicted by the network developed. The optimal milling processing parameters can be searched for by a simulation annealing (SA) optimisation algorithm with a performance index to obtain a satisfactory mould surface. The experiment is then used to show that improved conditions for mould profile processing can indeed be obtained.

Measurement of 2-D Surface Profile and Motion Errors by Using Software Datum.

In this paper, the asymmetric 2-D mixed method (A2DMM) was proposed to measure 2-D surface profile and scanning errors of the scanning stages.Two phasemodulated fiber interferometric displacement sensors and two angular sensors are developed to construct a measuring probe to realize the method.Zero adjustment errors caused by misalignment of the sensor's zero outputs are also analyzed, and a self-correction method for compensating zero adjustment errors is presented.2-D surface profile of a silver-coated glass plate is measured using this measuring head.The measurement results are evaluated and compared with those obtained by other differential methods.The z-directional translation motion, roll and pitch are accurately evaluated.

Quantitative Evaluation of Cutting Resistance in the Finishing Process of End Milling.

This paper deals with the quantitative evaluation of cutting resistance in the finishing process of end milling to develop a computer-aided precision machining system which can control the surface profile error by varying the combination between the machine tool, tool specifications and cutting conditions. The cutting resistance generated under the finishing process of end milling is divided into cutting force, flank force and edge force through the measurement of total summed force and flank force. Also, A machining equation is developed to clarify the relation between cutting force and the removed chip area ; the flank force and contact area between the work surface and the flank face ; and the edge force and contact edge length. It is shown that the variation of cutting force, produced by the difference of work material and the progress of tool wear, can be evaluated through the specific cutting force and the force ratio between radial force and principal force. The same evaluation can be carried out on the flank force and the edge force in terms of the coefficient of friction and the specific edge force, respectively.

Compact-scan, plane-polar microwave holographic technique for reflector antenna profile measurement

The simulation and practical results of a short range microwave holographic technique for the measurement of reflector antenna surface profile are presented. The technique uses a linearly scanned transmit/receive CW probe located on-axis at approximately two focal lengths from the reflector vertex. A compact plane polar data set is obtained and used to reconstruct the surface profile error map. A comparison is made between the microwave measurement technique and a more traditional mechanical measurement of the reflector surface. It is shown that synthetic aperture holographic principles can be employed in a non-anechoic environment. The method is aimed primarily at reflectors up to 5 m in diameter, but with suitable scanning systems it can be applied equally well to larger antennas.

Development and evaluation of a fine finishing end mill with high rigidity. The effect of a helix angle on the cutting force.

The mechanics of oblique cutting indicate that the magnitude of radial force orthogonal to the machined surface can be reduced by increasing the angle of inclination. This paper deals with the experimental research to clarify the relation between the helix angle and the cutting performance of a helical end mill. The performance of an one-fluted end mill with various helix angles is verified through the measurement of cutting force, ploughing force and the surface profile error in the micro milling. It is shown that the radial force is dramatically reduced by increasing the helix angle, restricted within the cutting condition where the single tooth is engaged in the cutting operation. Also, it is made clear that the optimum helix angle which can reduce the surface profile error to the minimum value can be simulated from the measured relation between the radial force and the helix angle, even if the number of flutes engaged in the operation is shifted in each applied condition.

A study of the crowning method for the type 3 worm gear. (5th report. An analysis of the relationship between the resharpening of the worm hob and the tooth bearing).

A precise analysis has been made on the relationship between the resharpening of the type 3 worm hob and the tooth bearing of the type 3 worm gear. Firstly, a calculation method, which is used to calculate the axial profile of a new basic thread surface formed by the resharpened cutting edge of the worm hob, is obtained. Secondly, considering the new basic thread surface of the worm hob as a new thread surface of the type 3 worm, a caluclation method for the dimensions of the cone-shaped cutter, which is used to cut the new thread surface, is obtained. Thirdly, by applying these calculation methods to numerical examples of the worm hob, the profile error of the basic thread surface owing to the radius reduction made by the resharpening of the worm hob is clarified numerically, and the new dimensions of the resharpened worm hob and the cone-shaped cutter are obtained. Finally, the variation of the tooth bearing between the new wheel tooth surface cut by the resharpened worm hob and the thread surface of the original worm is discussed.

A Portable Holographic Antenna Measurement System

AbstractInterferometrics has developed a portable holographic antenna measurement system. The system is comprised of a small interferometer which uses satellite signals to measure the complex beam pattern of the antenna under test. A PC controls all aspects of data collection and analysis. The system produces maps of surface profile errors and the illumination power in reflector antennas.

Development and evaluation of a fine finishing end mill with high rigidity. Cutting edge geometry and ploughing force.

Experimental research to clarify the relation between cutting edge geometry and plastic sliding on a four-fluted end mill is performed. Also, an edge, which can reduce dimensional inaccuracy and surface profile error in the finishing process of end milling, is presented. The performance of a newly performed cutting edge is verified through the measurement of chip geometry and cutting force variation in the face milling. It is shown that the sum of the rubbing and ploughing forces can be reduced by making the edge sharp as well as the margin width small. Both surface profile error and surface roughness can be improved in the case where the margin face is polished and protected from the flank wear by TiN coating. It is expected that a finer finished work surface can be derived by polishing the rake face along with the margin face.

Development and evaluation of finishing end mill with high rigidity.

Finishing end mills which can reduce dimensional inaccuracy and surface profile error in the finish process of end milling are presented. Computer simulation against chip geometry and variable distance from work surface to cutter axis are performed for the design of cutter shape with high rigidity. The performance of newly developed end mills are verified through the measurement of spiral chip diameter, cutting force variation and surface profile error in the face milling. it is shown that the magnitude of surface profile error can be reduced from 60% to 70% by the newly developed end mills, compared with the standard type. While the characteristic of surface profile error remains unchanged, for the cutter geometry with standard pitch was adopted. The cutter also possess a sufficient space to extrude chips which are produced in the finish process of end milling.

Microwave holographic technique for reflector antenna profile measurement

A short-range microwave holographic technique for the measurement of reflector antenna surface profile is described. The technique uses a linearly scanned transmit/receive CW probe located on-axis at approximately two focal lengths from the reflector vertex. Rotation of the reflector provides a plane-polar data set which can be reconstructed by a fast algorithm to provide a surface profile error map. No special precautions are required with regard to the reflectivity of the environment. Practical results are provided to illustrate the performance of the system.

Microwave holographic metrology of large reflector antennas

A microwave holographic technique for the determination of amplitude and phase of the principal and cross-polarized aperture fields of large reflector antennas is described. The hologram formation process utilizes the elevation over azimuth scanning system normally associated with these antennas, and, in this respect, appears to be unique among other proposed methods of field probing. The present work describes the means used to obtain vital information on the antenna structure such as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> - and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</tex> -plane phase centers of the feed, and rms values of the reflector surface profile errors. Accurate prediction of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> - and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</tex> -plane radiation patterns in the near- and far-field is also demonstrated.

Reflector surface error compensation in cassegrain antennas

Two focal plane parabolic reflectors 2.8 m in diameter were used to test the feasibility of compensating for reflector surface profile errors by figuring the surface of a Cassegrain mirror. The paraboloids had been designed originally for frequencies less than 7 GHz, and therefore the surface errors had a significant effect on the antenna performance in the 27-40 GHz range. For these frequencies a template could be used to measure the surface profile. The first reflector had a prominent axially symmetrical surface error component. Compensating for this alone simplified the construction of the subreflector and improved the overall aperture efficiency at 34 GHz from 12 percent to 24 percent. The second reflector had a more random distribution of surface errors. Its efficiency was improved from 35 percent to 48 percent at 34 GHz, the improvement in gain varying from 1.1 dB at 28 GHz to 2.3 dB at 40 GHz, the shortfall being within 1 dB of the possible improvement predicted from the measured surface errors. For both reflectors the illumination efficiency set by the feed horn was about 50 percent. The linear cross polarization discrimination on axis increased from 29 dB to 38 dB at 34 GHz. The sidelobe levels and gain improvement obtained suggest that effective rms errors of about 0.45 mm with correlation distances of about 30 cm remained on the reflector surface after compensation, consistent with the estimated accuracy of the measuring and construction techniques adopted.

Some results of electronic compensation for surface profile errors in parabolic reflectors

This letter describes the basic principles of a proposed system for compensating for the effect of surface profile errors in parabolic reflectors. It also describes some experimental results which verify the technical feasibility of the proposals and discusses some implications of its future development.