290 results about "Linearity error" patented technology

The invention relates to a PMSM servo system control method based on fuzzy and active disturbance rejection control. A position signal is given by a differential tracker to arrange a transition process so that the contradiction between rapidness and overshoot of a system is solved, and uncertainty, friction torques and external disturbance due to modeling errors of the system are observed via an expansion state observer; according to the error between the differentials generated by the differential tracker and state variation generated by the expansion state observer, a fuzzy inference rule is obtained with application of experimental experience of technical staff, so that a fuzzy rule control table of an error proportion coefficient, a differential coefficient and an integration coefficient is established; accurate control amount is obtained after de-fuzzification, so that parameter self-adaptive adjustment of a nonlinear error feedback control law is realized; and compensation amounts of the nonlinear error feedback control law and the expansion state observer to the total disturbance forms the control amount, thereby realizing optimal control for an controlled object. The method of the invention improves both tracking precision and disturbance rejection capability of the system.

A method and apparatus for correcting the offset and linearity error of a data acquisition system. A charge redistribution digital to analog convertor (CDAC) is connected to one of the differential inputs of a comparator whose second input comes from a function CDAC. The calibration algorithm is built into a digital control unit. The digital control unit detects the offset and capacitor mismatch errors sequentially, stores the calibration codes for each error in calibration mode and provides the input-dependent error correction signals synchronized with the binary search timing to adjust the differential input of the comparator and compensate the input-dependent errors present at the output of the non-ideal function CDAC during normal conversions.

The present invention discloses a single-frequency laser interferometer non-linear error compensation device. The single-frequency laser interferometer non-linear error compensation device is characterized in that after a light beam emitted by a laser is split by a polarization splitting prism, the transmitted light is projected to a rectangular prism and is returned to the polarization splitting prism to form the reference light S; the reflected light is projected to a plane mirror and is returned to the polarization splitting prism to form the measurement light P; a linear polaroid along an S direction is placed in a reference light path, and a linear polaroid along a P direction is arranged in a measurement light path, thereby realizing the nonorthogonal error compensation; the semi-transparent and semi-reflective mirrors are arranged in the emergent light paths of the linear polaroids, so that the reference light and the measurement light are combined and then are split by a depolarization splitting prism evenly, the transmitted light generates the interference signals I1 and I2 via a quarter-wave plate and the polarization splitting prism, the reflected light generates the interference signals I3 and I4 via the polarization splitting prism, and the mutual phase difference of the signals I1, I2, I3 and I4 is 90 degrees. According to the present invention, a non-linear error of the single-frequency laser interferometer is compensated effectively.

The invention provides a rapid measuring and error compensation method for linearity error of a linear guide rail, and aims at solving the problems of small measurement method, large error and complex data treatment in the prior art. The method comprises the steps of measuring and acquiring a plurality of data points on the linear guide rail through a laser interference instrument; analyzing the linearity measurement result for the data of the acquired points through a linearity data analyzing module in an XD laser measurement system so as to obtain the linearity error of the guide rail. With the adoption of the method, the mounting error, environmental error, delay error and the error caused by thermal expansion of a measured object in measuring can be analyzed; an error correcting model is built.

A triaxial magnetic electronic compass error compensation method based on depth learning. An implicit error model is trained for compensating non-linear error in magnetic compass measurement and improving the orientation accuracy of the magnetic compass. The error model training consists of two stages: a first stage is pre-training, and a second stage is reverse trimming by using a back-propagation algorithm for fine-tuning all layers of the network, and reducing the error of model training. The magnetic compass calibration and compensation procedure is to use depth learning algorithm training to obtain a non-linear error model, and the distorted measurement magnetic field is inversed back to a true magnetic field value, thereby reducing the calculation error of course angle. The invention aims at nonlinear error of magnetic compass and provides the error training method based on depth learning; compared to random initialization of a traditional neural network, the weight of each layer locates in a better position of parameter space, so as help to improve the convergence of the algorithm and model training accuracy and achieve high-precision orientation of magnetic compass.

The invention discloses a method for controlling accuracy of the shape of an ultrahigh-strength steel thin-wall cylinder. The method comprises the following steps of: 1) detecting the appearance of a cylinder; 2) mounting a special shape correction clamp; 3) tempering for stable shape; 4) discharging and cooling; 5) removing the special shape correction clamp and detecting the appearance; and 6) performing repeated shape correction. In the method, after a cylinder shell is quenched, the special shape correction clamp performs shape correction of the cylinder shell, and then the corrected shape is stabilized by tempering. The shape accuracy of the obtained cylinder shell is relatively high, and the requirement on the product design accuracy is completely met, wherein after the shape correction, the linearity error is not greater than 2.5 mm, and difference between large and small diameters is not greater than 1.5 mm. The processing method disclosed by the invention can be applied to the shape accuracy control on the cylinder shell of a secondary combustion chamber of a solid rocket ramjet.

The invention discloses a measuring-compensating device and method for a single-frequency interference linearity error and position thereof. After passing a half-wave plate, the polarization direction of a linearly polarized light beam output by a single-frequency laser is adjusted to 45 degree relative to the paper surface, the modulated linearly polarized light beam is split by a first depolarization splitting prism, a transmitted light beam enters a Wollaston prism type laser single-frequency interferometer, a reflected light beam enters a Michelson type laser single-frequency interferometer, the Wollaston prism type laser single-frequency interferometer serves as a sensing unit to process formed circularly polarized and linearly polarized interference signals, and a linearity error and a position thereof are measured. An error detection and compensation part uses the Michelson type laser single-frequency interferometer as a sensing unit, formed thickness-equivalent interference fringe images are analyzed, swing and pitch angles are measured, a measuring result of the linearity error and the position thereof is compensated according to the measured pitch angle, and the measuring precision of the linearity error and the position thereof is improved.

A SAR ADC includes capacitors, a comparator, and a SAR logic circuit. The capacitors include a first set of capacitors and an error-detection capacitor. The first set of capacitors generates a first set of voltage signals that are compared with a common-mode voltage signal (V_CM) by the comparator during a first set of comparison cycles. The comparator generates a first set of control signals that is used by the SAR logic circuit to successively approximate the first set of voltage signals and generate a first set of bits. An error-detection capacitor generates an error-detection signal that is compared with the common-mode voltage signal V_CM by the comparator to generate an error-detection control signal. The SAR logic circuit compensate for an error in the first set of bits based the logic state of the error-detection control signal.

The invention discloses a nonlinear-error-free laser heterodyne interferometer system for angle measurement, wherein the nonlinear-error-free laser heterodyne interferometer system comprises a single-frequency laser source, an acousto-optical frequency shift unit, an optical interference device, a planar mirror which moves along with the movement of a measured member, and a phase detecting device, wherein the single-frequency laser source and the acousto-optical frequency shift unit can operate for generating an incident light beam which has no frequency aliasing and has certain frequency difference and is spatially separated. Under the function of the optical interference device, the incident light beam is reflected twice by the planar mirror. Finally the reflected incident light beam is input to the phase detecting device. The yaw angle of the measured member is determined by means of change amount of the phase difference. Between generation of a measuring light beam with certain frequency difference from the acousto-optical frequency shift unit and interference, the transmission paths are separated and are spatially independent. The nonlinear-error-free laser heterodyne interferometer system prevents a periodical nonlinear error which is caused by polarized light with two frequencies in the interference optical path, thereby effectively improving measurement accuracy. The nonlinear-error-free laser heterodyne interferometer system can be widely used for geometric quantity precise measurement in the fields of numerical control machine tools, military industry, spaceflight, etc.

The invention discloses a device for comprehensively measuring linear guide rail friction force and manufacturing and mounting errors, and belongs the technical fields of measurement. The device for comprehensively measuring the linear guide rail friction force and the manufacturing and mounting errors mainly comprises a linear feeding system, a guide rail and sliding block friction force measuring device, a guide rail linearity error measuring device and a guide rail mounting parallelism error measuring device. The guide rail and sliding block friction force measuring device drives a sliding block to move through a servo motor to achieve measurement of the dynamic friction force of the sliding block at different running speed and under different loading effects, and the value of the friction force can be obtained by utilizing a pull pressure sensor. The guide rail mounting parallelism error measuring device converts parallelism errors among guide rails into internal stress of a connecting rod, and the values of the parallelism errors can be obtained through measurement of the pull pressure sensor. A standard straight gauge block is utilized by the guide rail linearity error measuring device as a reference of measurement, the linearity error of the guide rails is converted into changes of compression amount of a spring, a least square method is utilized for processing, measurement is convenient, and measurement accuracy is high.

A method and associated apparatus determine an overlay error on a substrate. A beam is projected onto three or more targets. Each target includes first and second overlapping patterns with predetermined overlay offsets on the substrate. The asymmetry of the radiation reflected from each target on the substrate is measured. The overlay error not resultant from the predetermined overlay offsets is determined. The function that enables calculation of overlay from asymmetry for other points on the wafer is determined by limiting the effect of linearity error when determining the overlay error from the function.

Provided is a polarization resistance single line polarization interference and single Woodward prism spectral homodyne laser vibrometer, belonging to the laser interference measuring field. An interference portion utilizes a half-wave plate, a quarter-wave plate and an NBS to generate +/-45 DEG linear polarization reference light and linear polarization measuring light orthorhombic in a one way polarization direction and having light paths overlapped; the reference light and measuring light of a detection portion are split and generate four paths of optoelectronic signals with a phase position difference of 90 DEG through a same Woodward prism, thereby restraining outstanding features of non-linear errors from an optical path structure and principle. The vibrometer realizes four channel homodyne orthogonal laser interference measurement, effectively solves the problems that, in the prior art, polarization leakage and polarization aliasing exist in the optical path, output signals exist direct current biased errors and nonopiate errors, and non-linear errors of measuring results are obvious, and possesses significant technical advantages in an ultra-precision vibration measuring field.

The invention relates to a direct measurement method, especially a rapid measurement method for the parallelism error of linear guide rails. Data points on the linear guide rails are measured and collected via a laser interferometer; linearity measurement result analysis is carried out on data of the collection points via a linearity data analysis module in an XD laser measurement system to obtain the linearity errors of the guide rails; and a parallelism error analysis module in the XD laser measurement system fits the linearity errors of the two guide rails to obtain the parallelism error of the guide rails. The method can be used to solve the problems including low efficiency, large error and complex data processing of a present measurement method.

The invention discloses a frequency modulated continuous wave linear array amplitude-phase error correction method based on a single dominant scattering center. The method includes the steps: firstly, correcting frequency modulated nonlinear error signals in echo waves; secondly, separating frequency modulated nonlinear errors from multichannel amplitude-phase errors by the aid of RVP (residual video phase) filter processing; finally, respectively correcting signals obtained after RVP filter processing of the frequency modulated nonlinear errors and the influence of the multichannel amplitude-phase errors to correct overall amplitude-phase errors of the echo waves received by a system. The method solves the problem that the quality of a reconstructed radar image is degraded due to direct imaging as a frequency modulated continuous wave linear array imaging radar system has the frequency modulated nonlinear errors and the multichannel amplitude-phase errors.

The invention belongs to the field of laser interference measurement, and relates to a quadrature error-free double-path polarization interference and double-Wollaston prism light-splitting type homodyne laser vibration meter. An interference part generates double paths of linear polarization reference light and linear polarization measurement light whose polarization directions are orthogonal and light paths are overlapped through a quarter-wave plate and a polarization-eliminating beam splitter NBS, and in a detection part, reference light and measurement light generate four paths of photoelectric signals with a phase difference of 90 degrees through two Wollaston prisms whose spatial rotation angles around light beams form a specific relation, thereby obtaining an outstanding characteristic of inhibiting a nonlinear error from a light path structure and in principle. The quadrature error-free double-path polarization interference and double-Wollaston prism light-splitting type homodyne laser vibration meter provided by the invention adopts less optical elements to realize four-channel homodyne quadrature laser interference measurement, can effectively solve the problems in an existing technical scheme that polarization leakage and polarization aliasing exist in the light paths, a direct current biased error and a non-quadrature error exist in an output signal, and a nonlinear error of a measurement result is obvious, and thus has remarkable technical advantages in the field of ultra-precise vibration measurement.

A multi-stage variable gain amplifier is disclosed that utilizes overlapping gain curves to compensate for log-linear errors. Each gain stage is configured to approximate a log-linear response with a sinusoidal error term such that a portion of the curve has positive errors and a portion of the curve has negative errors. In operation, the control signal inputs for the gain stages are driven such that the gain curves overlap and positive errors in each stage are offset by negative errors in the adjacent stage. The resulting combined gain is a more log-linear response.

A method and system for correcting alignment and linearity errors in devices using a finger or stylus input device with a display device interactively coupled to a digitizer is disclosed. Touching intersections in a calibration grid on the display device may be performed to create a linearity map. Subsequently, detected stylus input is mapped to a sector in the linearity map, and resultant screen coordinates are calculated using ratios within a reference rectangle corresponding to the detected stylus input and the mapped sector.

A feedback divider in a mixed-signal circuit is modulated by a frequency control word controlling a delta-sigma modulator. An accumulated quantization error from the delta-sigma modulator is compared to a residual error in the circuit by a Least-Mean Square (LMS) correlator for gain calibration to adjust for linear errors. Upper bits of the accumulated quantization error access a lookup table to find two outputs of the compensation function that are interpolated between using lower bits of the accumulated quantization error. The interpolated result is an adjustment subtracted from the loop to compensate for non-linear errors. A set of orthogonal kernels is generated from the accumulated quantization error and calibrated using another LMS correlator and inverse transformed to generate updates to the non-linear compensation function in the lookup table. The kernels can be Walsh Hadamard (WH) and the inverse transformer an inverse WH transformer.

The invention discloses a modified coherence peak demodulation method for fiber end face detection, and belongs to the technical field of a fiber end face measuring instrument. The demodulation method comprises quickly limiting phase extraction in a zero order stripe through a modified extremum method, and reducing the random error caused by environment disturbance and CCD shot noise; and performing phase correction for the extracted light intensity maximum based on a Carre phase shift algorithm, and eliminating the influence of the linear phase shift error on the fiber end face height value. During the process for calculating the fiber end face height value, the modified coherence peak demodulation method has no demand for performing phase unwrapping operation, thus improving the calculating speed, and has the advantages of being insensitive to the linear error Epsilon of a phase shifter, and being high in precision.

The invention discloses a quadratic overload term test method for a flexible gyroscope based on optical fiber monitoring and a centrifuge with a two-axis turntable, which belongs to the technical field of inertia. The test method includes the steps: firstly, mounting an optical fiber gyroscope and the flexible gyroscope on the centrifuge with the two-axis turntable, electrifying the flexible gyroscope and the optical fiber gyroscope and acquiring static output data after preheating stabilization; secondly, synchronously rotating the centrifuge along with an outer turntable and an inner turntable of the two-axis follow-up turntable and acquiring overload output data after rotation speed stabilization; and finally, calculating secondary overload term coefficient. The test method has the advantages that the relationship between a quadratic term of a specific force-sensitive error and environmental overload acceleration in a static drift model of the flexible gyroscope can be calibrated, a quadratic polynomial model of specific force-sensitive error terms can be established, and a test scheme is provided for calculating and determining the influence of nonlinear errors of the flexible gyroscope on system errors.