Compensation method for complex optics considering the arc grinding wheel profile error.

This paper proposes a method for improving the performance of a position sensorless control system for a slotless surface permanent magnet synchronous motor (SPMSM) in a very low-speed region. In position sensorless control based on a motor model, accurate motor parameters are required because parameter errors would affect position estimation accuracy. Therefore, online parameter identification is used. The error between the reference voltage and the voltage applied to the motor is compensated to ensure accuracy and stability of the sensorless control system. In this study, two voltage error compensation methods are used: compensation method 1, which is the conventional method and compensation method 2, which is the proposed method. In the proposed method, online parameter identification and compensation method 2 are used. The proposed method is evaluated by experimental results.

Most of disk drives suffer from various disturbances that degrade read–write performances. As the track density rapidly increases, basic drive functions may fail even with a small scale disturbance in a normal operating environment. For the reason, an accurate identification of the repeatable runout (RRO) of a hard disk drive has been one of the most important tasks for the successful servo designs in modern hard disk drive integration. Extensive research efforts have been dedicated for the compensation of the runouts and produced many successful strategies to minimize the influences to the critical basic drive functions. Primarily for the simple implementation and the cost reduction in the actual drive development and manufacturing, most of the developed methods being used in the actual drive integration are preferred to be formulated on time domain or frequency domain with very basic limited functions. The primitive frequency domain approaches usually require extensive calculations and large physical memories. In the present work, a RRO compensation method that combines advantages of the transient Fourier coefficients (TFC) and the least mean square (LMS) update is introduced. Combining the two methods in a proper fashion, the present work provides many benefits for the drive design and outperforms the previous compensation methods. The proposed method requires significantly less amount of computational work and physical memories compared to the conventional runout compensation methods. And it also provides effective frequency component selectivity so that the compensation resources are to be concentrated to a specific problem reason. Comprehensive frequency domain formulation of the method followed by a series of experimental test results is provided in the present article.

The conventional dynamic capacitance compensation (DCC) method applied to the 3D LCD display has difficulty having the low crosstalk level encouraged for optimal 3D image qualities. The bit-expandable DCC method is proposed in this paper to make the crosstalk compensation more accurate by offering a larger number of DCC lookup table (LUT) value candidates. The bit-expandable DCC method includes DCC LUT with larger bits of data than the input data of the display, and modified bilinear interpolation to reduce the crosstalk over all the gray-level transitions between the previous and current frames. Next, the multitoning method restores the bit numbers lengthened by LUT, minimizing the data loss and the multitoning artifacts. Finally, based both on the crosstalk simulation result and the hardware utilization, it can be concluded that the bit numbers of DCC LUT expanded to 12 bit is optimal, and the experiment showed that the crosstalk corresponding to all the gray-to-gray data transitions decreased to below 1%.

High precision synchronous vibration suppression for a MSFW subject to phase lag influence

An output-capacitorless low-dropout regulator (OCL-LDO) using a dual-active feedback frequency compensation (DAFFC) scheme with both transient and stability enhancement has been presented in this paper. The DAFFC scheme consists of two parallel active feedback paths, which creates two pole-zero pairs to effectively enhance the stability and transient response for the proposed OCL-LDO. Compared to the conventional single-path active-feedback frequency compensation method, the proposed DAFFC technique has provided one more design freedom with one more active feedback loop deployed and has been proved to be capable of obtaining better compensation effects with the same capacitor budget. Besides, the induced extra ac currents by the two active feedback loops have also enhanced the transient response of the proposed OCL-LDO. To substantiate the proposed DAFFC, a telescopic cascode output stage for error amplifier, and two on-chip compensation capacitors (5 and 1 pF, respectively) are needed. The proposed OCL-LDO has been implemented in 65-nm CMOS technology and the active chip area is 0.0105 mm2. The output voltage is 0.8 V, and the minimum input voltage is 0.95 V at 100-mA loading current. The proposed OCL-LDO can work stably in a load range of 0 to 100 mA with 14-μA quiescent current.

An artificial neural network-based error compensation method is proposed for improving the accuracy of resolver-based 16-bit encoders by compensating for their respective systematic error profiles. The error compensation procedure, for a particular encoder, involves obtaining its error profile by calibrating it on a precision rotary table, training the neural network by using a part of these data and then determining the corrected encoder angle by subtracting the ANN-predicted error from the measured value of the encoder angle. Since it is not guaranteed that all the resolvers will have exactly similar error profiles because of the inherent differences in their construction on a micro scale, the ANN has been trained on one error profile at a time and the corresponding weight file is then used only for compensating the systematic error of this particular encoder. The systematic nature of the error profile for each of the encoders has also been validated by repeated calibration of the encoders over a period of time and it was found that the error profiles of a particular encoder recorded at different epochs show near reproducible behaviour. The ANN-based error compensation procedure has been implemented for four encoders by training the ANN with their respective error profiles and the results indicate that the accuracy of encoders can be improved by nearly an order of magnitude from quoted values of ∼ ±6 arc-min to ∼ ±0.65 arc-min when their corresponding ANN-generated weight files are used for determining the corrected encoder angle.

Curing‐induced distortion (CID) in carbon fiber‐reinforced polymer (CFRP) composite parts presents a significant challenge in the manufacturing of high‐precision parts. While mold compensation techniques have been widely employed for relatively simple geometries like C‐shaped or V‐shaped parts, their applicability to more complex forms, particularly enclosed, rotational structures, remains inadequately investigated. The intricate CID behavior of these geometries poses substantial challenges to effective mold compensation. This study investigates a global mesh‐based mold compensation strategy tailored for enclosed and rotational CFRP parts. The global mesh‐based compensation (GMC) method is defined as a global deviation correction technique, enabling precise and continuous adjustment of each mesh node via a global compensation factor, k . To address the frequent issue of coordinate system reference drift during the compensation of such geometries, an iterative closest point algorithm is integrated into the GMC framework. Numerical simulations and mold compensation procedures are conducted across several representative configurations, demonstrating notable reductions in CID. Further experimental validation on an air‐intake part confirms the method's efficacy, yielding a 69.4% reduction in maximum CID when compared to an uncompensated mold. The results substantiate the proposed mesh‐based compensation method as a robust, accurate, and practical solution for manufacturing high‐precision enclosed and rotational CFRP parts.

The paper shows that it is possible to compensate for the effects of mechanical profile errors in large parabolic reflectors, by means of a specially designed multielement feed array situated in the focal plane of the reflector. The factors relating the magnitude and period of these profile errors to the size and complexity of the compensating feed are discussed, and a novel method is described for achieving this compensation by controlling the phasing of the array. The system employs a spatial Fourier-transforming device, and its use is mainly restricted to long-period profile errors. Experimental results of this process, derived from a small-scale laboratory system employing a 1-dimensional 5ft parabolic reflector incorporating an 8-element feed, are presented. These results demonstrate compensation for profile errors up to π/2 radians. The possible application of this technique to existing and new reflectors is discussed.

Aspheric surfaces are important to the optical systems and need high precision surface metrology. Stylus profilometry is currently the most common approach to measure axially symmetric elements. However, if the asphere has the rotational alignment errors, the wrong cresting point would be located deducing the significantly incorrect surface errors. This paper studied the simulated results of an asphere with rotational angles around X-axis and Y-axis, and the stylus tip shift in X, Y and Z direction. Experimental results show that the same absolute value of rotational errors around X-axis would cause the same profile errors and different value of rotational errors around Y-axis would cause profile errors with different title angle. Moreover, the greater the rotational errors, the bigger the peak-to-valley value of profile errors. To identify the rotational angles in X-axis and Y-axis, the algorithms are performed to analyze the X-axis and Y-axis rotational angles respectively. Then the actual profile errors with multiple profile measurement around X-axis are calculated according to the proposed analysis flow chart. The aim of the multiple measurements strategy is to achieve the zero position of X-axis rotational errors. Finally, experimental results prove the proposed algorithms achieve accurate profile errors for aspheric surfaces avoiding both X-axis and Y-axis rotational errors. Finally, a measurement strategy for aspheric surface is presented systematically.

The form error reduction in side wall machining using successive down and up milling

The thermo-mechanical model of the deformable mirror based on ANSYS multiphysics is provided and calculated. High energy laser radiation results in a mirror deformation of about 0.9 m. Therefore, according to the characteristic distribution of the thermally-induced deformation, a compensation method is proposed. The compensation mirror, placed in the optical path after the deformable mirror, is composed of a thin mirror and some restriction parts. By contrast with the poles of the deformable mirror, the restriction parts of the compensation mirror are installed in a staggered order. Three types of compensation mirrors with different shapes of restriction parts are calculated. The results show that the values of the thermal deformation reduce to 0.35 m, 0.32 m and 0.40 m. Using the BPF (beam propagation factor) to evaluate the compensation effect, the results indicate that the BPF value increases from 0.906 to 0.966, 0.971 and 0.957. Further calculations show that the size of the restriction parts has little effect on the compensation effect.

Precision modeling of form errors for cylindricity evaluation using genetic algorithms

Error analysis and compensation method of displacement measurements based on reflection projection imaging

In this study, efficient polishing processes with inspection procedures for a large convex hyperbolic mirror of Cassegrain optical system are presented. The polishing process combines the techniques of conventional lapping and CNC polishing. We apply the conventional spherical lapping process to quickly remove the sub-surface damage (SSD) layer caused by grinding process and to get the accurate radius of best-fit sphere (BFS) of aspheric surface with fine surface texture simultaneously. Thus the removed material for aspherization process can be minimized and the polishing time for SSD removal can also be reduced substantially. The inspection procedure was carried out by using phase shift interferometer with CGH and stitching technique. To acquire the real surface form error of each sub aperture, the wavefront errors of the reference flat and CGH flat due to gravity effect of the vertical setup are calibrated in advance. Subsequently, we stitch 10 calibrated sub-aperture surface form errors to establish the whole irregularity of the mirror in 160 mm diameter for correction polishing. The final result of the In this study, efficient polishing processes with inspection procedures for a large convex hyperbolic mirror of Cassegrain optical system are presented. The polishing process combines the techniques of conventional lapping and CNC polishing. We apply the conventional spherical lapping process to quickly remove the sub-surface damage (SSD) layer caused by grinding process and to get the accurate radius of best-fit sphere (BFS) of aspheric surface with fine surface texture simultaneously. Thus the removed material for aspherization process can be minimized and the polishing time for SSD removal can also be reduced substantially. The inspection procedure was carried out by using phase shift interferometer with CGH and stitching technique. To acquire the real surface form error of each sub aperture, the wavefront errors of the reference flat and CGH flat due to gravity effect of the vertical setup are calibrated in advance. Subsequently, we stitch 10 calibrated sub-aperture surface form errors to establish the whole irregularity of the mirror in 160 mm diameter for correction polishing. The final result of the Fabrication of ф160 mm Convex Hyperbolic Mirror for Remote Sensing Instrument160 mm convex hyperbolic mirror is 0.15 μm PV and 17.9 nm RMS.160 mm convex hyperbolic mirror is 0.15 μm PV and 17.9 nm RMS.

Based on the homogeneous coordinate transformation method and finite element simulation method of a whole hobbing machine, this paper proposes a highly applicable force-induced error model for a high-speed dry hobbing machine. The number of parameters needed in the error estimation can be effectively reduced by using this model, which has great value in industry application. According to the engagement features of the conjugating surface and the principle of two-degrees-of-freedom hobbing, the meshing equation was deduced and the force-induced errors of the system were mapped to the normal errors of gear surface. In this way, the mapping relationship between different kinds of force-induced errors and hobbing precision can be obtained. Then, the theoretical tooth surface and the real tooth surface under the influence of force-induced errors were respectively calculated by using a numerical simulation method. Based on numerical simulation results, the mathematical relationship between the tooth profile root-mean-square error (RMSE) and the compensation variables was obtained, as well as the optimal value of the compensation variables. The following experimental results validate the feasibility and accuracy of this error compensation method. This study has an important guiding role in the improvement of dry gear hobbing precision.