Encoder error measurement method and system based on angular domain resampling iteration

Abstract

The present invention belongs to the technical field of encoder error measurement and specifically discloses an encoder error measurement method and system based on angular domain resampling iteration. The method includes the following steps: S1, obtaining a time-domain analytical signal of an encoder; S2, obtaining an instantaneous angular velocity signal of the encoder containing an error component; S3, performing time-domain synchronous averaging on the instantaneous angular velocity signal of step S2; S4, integrating and calibrating the signal of step S3; S5, obtaining an encoder angular domain signal; S6, obtaining an instantaneous angular velocity signal of the encoder containing an error component; S7, performing angular domain synchronous averaging on the instantaneous angular velocity signal of step S6; S8, integrating and calibrating the angular domain synchronously averaged signal; S9, performing angular domain nonlinear resampling on the integrated and calibrated encoder signal; S10, performing angular domain iterative correction on the encoder angular domain signal, determining whether convergence has occurred, and outputting the encoder error if convergence has occurred; otherwise, returning to step S6. Using this technical solution, error measurement is more accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of encoder error measurement, and relates to an encoder error measurement method and system based on angular domain resampling iteration. Background Art

[0002] Encoders are primarily used for speed measurement and positioning, and are widely used in precision manufacturing, automotive engineering, railways, and shipbuilding. Encoder error is a key performance metric. Encoder measurement error is closely related to instantaneous angular velocity measurement and is crucial for fault diagnosis of rotating machinery. Encoder self-calibration enables precise encoder measurement and enhances weak characteristic signal components, thereby improving the accuracy of true operating conditions and fault diagnosis of rotating machinery.

[0003] A photoelectric encoder is a device or apparatus that converts an angle signal into a signal (typically an electrical signal) that is easily collected, transmitted, and processed, in order to determine angular displacement or azimuth. It is an important sensor widely used in instrumentation, industrial automation, signal detection, robotics, aviation, and navigation. Currently, photoelectric encoders are categorized into two types based on the nature of their output signal: analog and digital. Analog encoders are further divided into synchronizers, resolvers, potentiometers, and inductive sensors; digital encoders are categorized into pulse disks, contact encoders, photoelectric encoders, electromagnetic encoders, and inductive synchronizers. With technological advancements and application needs, photoelectric encoders are required to achieve higher accuracy while maintaining cost-effectiveness. Therefore, reducing interference and improving sensor output accuracy is a critical issue in engineering applications. Accurately measuring the error of the photoelectric encoder is crucial for subsequent error correction. Summary of the Invention

[0004] The purpose of the present invention is to provide an encoder error measurement method and system based on angular domain resampling iteration to accurately obtain the error of a photoelectric encoder.

[0005] In order to achieve the above object, the basic scheme of the present invention is: an encoder error measurement method based on phase difference angular domain resampling iteration, comprising the following steps:

[0006] S1, obtain the encoder pulse analysis signal through multiple probes and obtain the encoder's time domain analysis signal;

[0007] S2, performing signal differentiation based on the encoder time domain analysis signal obtained in step S1 to obtain the encoder instantaneous angular velocity signal containing error components;

[0008] S3, performing time domain synchronous averaging on the instantaneous angular velocity signal containing the error component obtained in step S2;

[0009] S4, integrating and calibrating the time-domain synchronously averaged signal obtained in step S3;

[0010] S5, performing angular domain nonlinear resampling on the encoder signal after integration and calibration in step S4 to obtain an encoder angular domain signal;

[0011] S6, performing signal differentiation on the encoder angular domain signal to obtain the encoder instantaneous angular velocity signal containing error components;

[0012] S7, performing angular domain synchronous averaging on the instantaneous angular velocity signal containing the error component obtained in step S6;

[0013] S8, integrating and calibrating the angular domain synchronously averaged signal obtained in step S7;

[0014] S9, performing angular domain nonlinear resampling on the encoder signal after integration and calibration in step S8;

[0015] S10, performing iterative correction in the angular domain on the encoder angular domain signal after the angular domain nonlinear resampling in step S9, that is, re-entering the angular domain signal into steps S6 to S9 for signal processing to determine whether it converges; if it converges, output the encoder error; otherwise, return to step S6.

[0016] The working principle and beneficial effects of this basic solution are: using a probe to achieve self-measurement of encoder error under variable speed conditions, effectively improving encoder measurement accuracy. The time-domain analytical signal is first processed, followed by the angular-domain signal. The integral property of the Fourier transform is then used to integrate the instantaneous angular velocity error after synchronous averaging to obtain the encoder's instantaneous angular error. This allows for effective error measurement and has promising application prospects for accurately measuring the instantaneous angular velocity of low-cost, low-precision encoders.

[0017] Furthermore, the method for obtaining the time domain analysis signal in step S1 is as follows:

[0018] The modulation phase λ′ value obtained by measuring demodulation includes the shaft rotation phase λ and the phase deviation λ caused by the encoder error d ;

[0019] Encoder error deviation λ measured by two probes d1 (λ) and λ d2 (λ) There is an angle difference δ, corresponding to a phase difference Nδ in the pulse modulation signal, where N is the number of lines of the encoder, that is, the number of pulses emitted in one revolution;

[0020] The relationship between the encoder error components in the modulation phase is:

[0021]

[0022] Among them, λd (λ) is the encoder error;

[0023] The time domain analysis signal a(t) of the encoder square wave is measured as:

[0024]

[0025] Where p(t) is the encoder square wave function, H is the Hilbert transform, i is the imaginary unit, A(t) is the amplitude function, λ′(t) is the modulated phase, is the measured shaft angle function, e is a natural constant;

[0026] The time domain analysis signals P1(t) and P2(t) obtained by the two probes are:

[0027]

[0028] Wherein, λ′1(t) and λ′2(t) are the time domain phases of the measured pulse signal with time t as the independent variable; n is the order of the modulation frequency, and the order values ​​are 0, 1, 2, ... n.

[0029] The calculation is simple and easy to use.

[0030] Furthermore, the method for obtaining the instantaneous angular velocity signal in step S2 is as follows:

[0031] Perform center difference and frequency domain demodulation on the analytical signal, and the encoder interval angle Δθ can be approximately estimated as The instantaneous angle containing only the encoder error is approximately calculated based on the center difference as:

[0032]

[0033] in, is the instantaneous angular velocity of the error component, N is the number of lines of the encoder, a d (t) is the analytical differential signal of the dual-probe encoder pulse signal:

[0034]

[0035] a1(t) is the analytical signal of probe #1, a2(t) is the analytical signal of probe #2, is the differential analytical signal of the error component.

[0036] Obtaining the instantaneous angular velocity signal in the time domain is beneficial for subsequent use.

[0037] Furthermore, in step S3, the method for performing time-domain synchronous averaging on the instantaneous angular velocity signal containing the error component is:

[0038] The instantaneous angular velocity signal containing error components is averaged in the time domain synchronously, with the axis rotation period as the average period. After the time domain synchronous averaging process, the instantaneous angular velocity error of the encoder is for:

[0039]

[0040] n=N1-M+1,N1-M+2,...,N1

[0041] Where N is the number of lines of the encoder; M is the length; m k is the approximate value of kt / Δt; k represents the number of times; t is the characteristic period of the encoder's instantaneous angular velocity error; Δt is the sampling interval; n is the order of the modulation frequency, and the order value is 0, 1, 2, ... n; N1 is the number of sampling points, It is the sampling sequence of the encoder instantaneous angular velocity error without time domain synchronous averaging processing.

[0042] The instantaneous angular velocity signal containing error components is enhanced by time domain synchronous averaging to facilitate subsequent use.

[0043] Furthermore, the method for integrating and calibrating the signal after time-domain synchronous averaging in step S4 is as follows:

[0044] Using the integral property of Fourier transform, the instantaneous angular velocity error after time domain synchronous averaging is integrated to obtain the encoder instantaneous angular error θ e (t) is:

[0045]

[0046] in, is the inverse Fourier transform, is the frequency domain expression of the instantaneous angular velocity of the encoder error, j is the imaginary unit, and f is the frequency.

[0047] The integration property of Fourier transform is used to integrate the instantaneous angular velocity error after time domain synchronous averaging, which is simple to operate.

[0048] Furthermore, the method for obtaining the encoder angle domain signal in step S5 is:

[0049] In the time domain: Based on spline interpolation and the obtained encoder angle error θ e (t), perform cubic spline interpolation to obtain a linear and equiangularly spaced time series t in the angular domain inter (n):

[0050] t inter (m) = spline(θ carrier (n),t(n),θ inter (m))

[0051] Among them, spline is cubic spline interpolation, θ carrier (n) is the angular sequence of the carrier signal with equal time intervals, θ inter (m) is an equiangularly spaced sequence, and t(n) is an equiangularly spaced sequence of source signals;

[0052] The t obtained by the difference inter (m) and θ inter (m) mapping relationship, for time domain signal Perform linear angular domain resampling and reconstruction to obtain the angular domain signal of the encoder signal, that is,

[0053] The angular domain analytical signal a(θ) of the encoder square wave is:

[0054]

[0055] Where P(θ) is the real part of the analytical signal, H is the Hilbert transform, i is the imaginary unit, A(θ) is the amplitude function of the encoder square wave signal, and λ′(θ) is the phase function of the encoder square wave signal. is the angle function of the encoder square wave signal;

[0056] The angular domain analysis signals obtained by the two probes are:

[0057]

[0058] Wherein, λ′1(θ) and λ′2(θ) are the angular domain phases of the measured pulse signal with the shaft rotation angle θ as the independent variable, and n is the order of the modulation frequency, with the order values ​​being 0, 1, 2, ..., n.

[0059] The operation is simple and easy to use.

[0060] Furthermore, in step S6, the instantaneous angular velocity signal containing the error component of the encoder is obtained as:

[0061]

[0062] in, is the instantaneous angular velocity signal of the encoder containing error components, the subscript q is the qth iteration, a d (θ) is the angular domain of the analytical differential signal of the dual-probe encoder pulse signal:

[0063]

[0064] Where a1(θ) is the angular domain expression of the analytical signal of the first probe; a2(θ) is the angular domain expression of the analytical signal of the second probe. It is the differential analytical signal in the angular domain of the analytical differential signal.

[0065] In the angular domain, the instantaneous angular velocity signal of the encoder containing error components is obtained, which is beneficial for subsequent use.

[0066] Furthermore, in step S7, the method for performing angular domain synchronous averaging on the instantaneous angular velocity signal containing the error component is:

[0067]

[0068] n=N θ1 -M+1,N θ1 -M+2,...,N θ1

[0069] Among them, M is the length; N is the number of lines of the encoder; N θ1 is the average number of segments; m θk is the approximate value of kθ / Δθ; is the instantaneous angular velocity signal containing error components after synchronous averaging in the angular domain; is the sampling sequence of the encoder instantaneous angular velocity error without time domain synchronous averaging processing, the subscript q is the qth iteration, n is the order of the modulation frequency, and the order value is 0, 1, 2, ... n.

[0070] The instantaneous angular velocity signal containing error components is enhanced by synchronous averaging in the angular domain to facilitate subsequent use.

[0071] Furthermore, the method for integrating and calibrating the signal after synchronous averaging in the angular domain in step S8 is as follows:

[0072]

[0073] in, is the inverse Fourier transform, θ qe (θ) is the angular domain expression of the encoder’s instantaneous angular error, is the angular domain expression of the encoder’s instantaneous angular velocity, f θ is the frequency expression in the angular domain, the subscript q is the qth iteration, and j is the imaginary unit.

[0074] The instantaneous angular velocity error after synchronous averaging in the angular domain is integrated using the integral property of Fourier transform.

[0075] Furthermore, the method for performing angular domain nonlinear resampling on the integrated and calibrated encoder signal in step S9 is as follows:

[0076] Time domain-angle domain transformation nonlinear interpolation reconstruction:

[0077] t q_inter (m θ )=spline(θ q-1_carrier (nθ ),t q-1_inter (m θ ),θ inter (m θ ))

[0078] Nonlinear angular domain reconstruction and resampling of analytical signals based on the time domain-angular domain transformation relationship:

[0079] α q_inter (m θ )=spline(α q-1 (m θ ),θ q-1_inter (m θ ),θ inter (m θ ))

[0080] Where spline is cubic spline interpolation, subscript q is the qth iteration, θ q-1_carrier (n θ ) is the angular sequence of the carrier signal with equal time intervals in the q-1th iteration, t q_inter (m θ ) is the time series with linear and equiangular intervals in the angular domain in the qth iteration, t q-1_inter (m θ ) is the linear and equiangularly spaced time series in the angular domain in the q-1th iteration; α q_inter (m θ ) is the encoder square wave analytical signal interpolated in the qth iteration in the angular domain; α q-1 (m θ ) is the encoder square wave analytical signal in the q-1th iteration in the angular domain; θ q-1_inter (m θ ) is the equiangular interval sequence of interpolation in the q-1th iteration; θ inter (m θ ) is a sequence of equal angular intervals in the angular domain.

[0081] Simple operation and easy to use.

[0082] Furthermore, based on the obtained encoder error, the encoder error component obtained by measuring the angle signal is subtracted from the encoder pulse output angle signal to eliminate it, and finally the encoder error correction is achieved.

[0083] Obtaining more accurate encoder error is beneficial to realizing encoder self-calibration and improving encoder measurement accuracy.

[0084] The present invention also provides an encoder error measurement system based on phase differential angular domain resampling iteration, comprising a code disk, at least two probes arranged on the code disk, and a processor, wherein the input end of the processor is connected to the output end of the probe, and the processor executes the method of the present invention to perform encoder error measurement.

[0085] This system can be used to accurately measure encoder errors, which is beneficial for encoder calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 1 is a flow chart of an encoder error measurement method based on angular domain resampling iteration according to the present invention;

[0087] Figure 2 Schematic diagram of the structure of the encoder error measurement system based on angular domain resampling iteration of the present invention;

[0088] Figure 3 It is a curve diagram of the encoder signal angular domain nonlinear resampling of the encoder error measurement method based on angular domain resampling iteration of the present invention. DETAILED DESCRIPTION

[0089] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0090] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0091] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal communication between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0092] The present invention addresses the problem that encoder manufacturing and installation errors affect measurement accuracy and discloses an encoder error measurement method based on phase differential angular domain resampling iteration, which can effectively realize encoder self-calibration and improve encoder measurement accuracy. It has good application prospects in the precise measurement of instantaneous angular velocity of low-cost and low-precision encoders. Figure 1 As shown, the method includes the following steps:

[0093] S1, obtain the encoder pulse analysis signal through multiple probes and obtain the encoder's time domain analysis signal;

[0094] S2, performing signal differentiation based on the encoder time domain analysis signal obtained in step S1 to obtain the encoder instantaneous angular velocity signal containing error components;

[0095] S3, performing time domain synchronous averaging on the instantaneous angular velocity signal containing the error component obtained in step S2;

[0096] S4, integrating and calibrating the time-domain synchronously averaged signal obtained in step S3;

[0097] S5, performing angular domain nonlinear resampling on the encoder signal after integration and calibration in step S4 to obtain an encoder angular domain signal;

[0098] S6, performing signal differentiation on the encoder angular domain signal to obtain the encoder instantaneous angular velocity signal containing error components;

[0099] S7, performing angular domain synchronous averaging on the instantaneous angular velocity signal containing the error component obtained in step S6;

[0100] S8, integrating and calibrating the angular domain synchronously averaged signal obtained in step S7;

[0101] S9, performing angular domain nonlinear resampling on the encoder signal after integration and calibration in step S8;

[0102] S10, perform angular domain iterative correction on the encoder angular domain signal after angular domain nonlinear resampling in step S9, that is, re-enter the angular domain signal into steps S6 to S9 for signal processing to determine whether it has converged; specifically, if the ratio of the absolute value of the difference between the two iterative results to the absolute value of the previous result is less than 0.1%, it is determined to be converged, and if converged, the encoder error is output; otherwise, return to step S6.

[0103] In a preferred embodiment of the present invention, the method for obtaining the time domain analysis signal in step S1 is as follows:

[0104] The modulation phase λ′ value obtained by measuring demodulation includes the shaft rotation phase λ and the phase deviation λ caused by the encoder error d ;

[0105] Encoder error deviation λ measured by two probes d1 (λ) and λ d2 (λ) There is an angle difference δ, corresponding to a phase difference Nδ in the pulse modulation signal, where N is the number of lines of the encoder, that is, the number of pulses emitted in one revolution;

[0106] The relationship between the encoder error components in the modulation phase is:

[0107]

[0108] Among them, λ d (λ) is the encoder error;

[0109] The time domain analysis signal a(t) of the encoder square wave is measured as:

[0110]

[0111] Where p(t) is the encoder square wave function, H is the Hilbert transform, i is the imaginary unit, A(t) is the amplitude function, λ′(t) is the modulated phase, is the measured shaft angle function, e is a natural constant;

[0112] The time domain analysis signals P1(t) and P2(t) obtained by the two probes are:

[0113]

[0114] Wherein, λ′1(t) and λ′2(t) are the time domain phases of the measured pulse signal with time t as the independent variable; n is the order of the modulation frequency, and the order values ​​are 0, 1, 2, ... n.

[0115] In a preferred embodiment of the present invention, the method for obtaining the instantaneous angular velocity signal in step S2 is as follows:

[0116] Perform center difference and frequency domain demodulation on the analytical signal, and the encoder interval angle Δθ can be approximately estimated as The instantaneous angle containing only the encoder error is approximately calculated based on the center difference as:

[0117]

[0118] in, is the instantaneous angular velocity of the error component, N is the number of lines of the encoder, a d (t) is the analytical differential signal of the dual-probe encoder pulse signal:

[0119]

[0120] Where a1(t) is the analytical signal of probe #1, a2(t) is the analytical signal of probe #2, is the differential analytical signal of the error component.

[0121] In a preferred embodiment of the present invention, the method for performing time-domain synchronous averaging on the instantaneous angular velocity signal containing the error component in step S3 is:

[0122] The instantaneous angular velocity signal containing error components is subjected to time domain synchronous averaging (TSA), with the axis rotation period as the averaging period. After time domain synchronous averaging processing, the instantaneous angular velocity error of the encoder is for:

[0123]

[0124] n=N1-M+1,N1-M+2,...,N1

[0125] Where N is the average number of segments; M is the length; m k is the approximate value of kt / Δt; k represents the number of times; t is the characteristic period of the encoder's instantaneous angular velocity error; Δt is the sampling interval; n is the order of the modulation frequency, and the order value is 0, 1, 2, ... n; N1 is the number of sampling points, It is the sampling sequence of the encoder instantaneous angular velocity error without time domain synchronous averaging processing.

[0126] In a preferred embodiment of the present invention, the method for integrating and calibrating the signal after time-domain synchronous averaging in step S4 is as follows:

[0127] Using the integral property of Fourier transform, the instantaneous angular velocity error after time domain synchronous averaging is integrated to obtain the encoder instantaneous angular error θ e (t) is:

[0128]

[0129] in, is the inverse Fourier transform, is the frequency domain expression of the instantaneous angular velocity of the encoder error, j is the imaginary unit, and f is the frequency.

[0130] In a preferred embodiment of the present invention, Figure 3 As shown, the method for obtaining the encoder angle signal in step S5 is:

[0131] An ideal error-free encoder measures the rotation angle as the shaft rotates, containing only the true rotation component, i.e., θ carrier (t) = θ r (t), and the measured rotation angle has a linear relationship with the rotation speed or time, that is, θ carrier (t) = ω ct, the modulation frequency of the encoder pulse signal is constant and only affects the encoder resolution and speed ω c Linear correlation.

[0132] In actual applications, due to the influence of manufacturing and installation errors, the rotation angle measured by the encoder contains not only the actual rotation component but also the encoder error component, that is, θ carrier (t) = θ r (t)+θ e (t), due to the encoder error component θ e The random characteristics of (t), the measured angle and encoder resolution and speed ω c The encoder pulse signal carrier frequency is unstable due to the nonlinear relationship between the program and the encoder.

[0133] Based on spline interpolation (to interpolate given multiple points to obtain a smooth curve, spline interpolation data processing method is used) and the encoder angular error θ obtained e (t), perform cubic spline interpolation to obtain a linear and equiangularly spaced time series t in the angular domain inter (n), provides a bridge for converting time domain signals to angle domain signals:

[0134] t inter (m) = spline(θ carrier (n),t(n),θ inter (m))

[0135] Among them, spline is cubic spline interpolation, θ carrier (n) is the angular sequence of the carrier signal with equal time intervals, θ inter (m) is an equiangularly spaced sequence, and t(n) is an equiangularly spaced sequence of source signals;

[0136] The t obtained by the difference inter (m) and θ inter (m) mapping relationship, for time domain signal Perform linear angular domain resampling and reconstruction to obtain the angular domain signal of the encoder signal, that is,

[0137] The angular domain analytical signal a(θ) of the encoder square wave is:

[0138]

[0139] Where P(θ) is the real part of the analytical signal, H is the Hilbert transform, i is the imaginary unit, A(θ) is the amplitude function of the encoder square wave signal, and λ′(θ) is the phase function of the encoder square wave signal. is the angle function of the encoder square wave signal;

[0140] The angular domain analysis signals obtained by the two probes are:

[0141]

[0142] Wherein, λ′1(θ) and λ′2(θ) are the angular domain phases of the measured pulse signal with the shaft rotation angle θ as the independent variable.

[0143] In a preferred embodiment of the present invention, the instantaneous angular velocity signal containing an error component of the encoder obtained in step S6 is:

[0144]

[0145] in, is the instantaneous angular velocity signal of the encoder containing error components, the subscript q is the qth iteration, a d (θ) is the angular domain of the analytical differential signal of the dual-probe encoder pulse signal:

[0146]

[0147] Where a1(θ) is the angular domain expression of the analytical signal of the first probe; a2(θ) is the angular domain expression of the analytical signal of the second probe. It is the differential analytical signal in the angular domain of the analytical differential signal.

[0148] In a preferred embodiment of the present invention, the method for performing angular domain synchronous averaging on the instantaneous angular velocity signal containing the error component in step S7 is:

[0149]

[0150] n=N θ1 -M+1,N θ1 -M+2,...,N θ1

[0151] Among them, M is the length; N is the number of lines of the encoder; N θ1 is the average number of segments; m θk is the approximate value of kθ / Δθ; is the instantaneous angular velocity signal containing error components after synchronous averaging in the angular domain; is the sampling sequence of the encoder instantaneous angular velocity error without time domain synchronous averaging processing, the subscript q is the qth iteration, n is the order of the modulation frequency, and the order value is 0, 1, 2, ... n.

[0152] In a preferred embodiment of the present invention, the method for integrating and calibrating the signal after synchronous averaging in the angular domain in step S8 is as follows:

[0153]

[0154] in, is the inverse Fourier transform, θ qe (θ) is the angular domain expression of the encoder’s instantaneous angular error, is the angular domain expression of the encoder’s instantaneous angular velocity, f θ is the frequency expression in the angular domain, the subscript q is the qth iteration, and j is the imaginary unit.

[0155] In a preferred embodiment of the present invention, the method for performing angular domain nonlinear resampling on the integrated and calibrated encoder signal in step S9 is as follows:

[0156] Time domain-angle domain transformation nonlinear interpolation reconstruction:

[0157] t q_inter (m θ )=spline(θ q-1_carrier (n θ ),t q-1_inter (m θ ),θ inter (m θ ))

[0158] Nonlinear angular domain reconstruction and resampling of analytical signals based on the time domain-angular domain transformation relationship:

[0159] α q_inter (m θ )=spline(α q-1 (m θ ),θ q-1_inter (m θ ),θ inter (m θ ))

[0160] Where spline is cubic spline interpolation, subscript q is the qth iteration, θ q-1_carrier (n θ ) is the angular sequence of the carrier signal with equal time intervals in the q-1th iteration, t q_inter (m θ ) is the time series with linear and equiangular intervals in the angular domain in the qth iteration, t q-1_inter (m θ ) is the linear and equiangularly spaced time series in the angular domain in the q-1th iteration; α q_inter (m θ ) is the encoder square wave analytical signal interpolated in the qth iteration in the angular domain; α q-1 (m θ ) is the encoder square wave analytical signal in the q-1th iteration in the angular domain; θ q-1_inter (m θ ) is the equiangular interval sequence of interpolation in the q-1th iteration; θ inter(m θ ) is a sequence of equal angular intervals in the angular domain.

[0161] In a preferred embodiment of the present invention, the encoder error is obtained and the encoder error component obtained by measuring the angle signal is subtracted from the encoder pulse output angle signal to finally achieve encoder error correction.

[0162] like Figure 2 As shown, the present invention also provides an encoder error measurement system based on phase differential angular domain resampling iteration, including a code disk, at least two probes arranged on the code disk, and a processor. The probe includes a light source and a photosensitive element. The photosensitive element converts the light on / off signal caused by the rotation of the code disk into a high-level and low-level signal. The modulation phase λ′ value obtained by the measurement demodulation includes the shaft rotation phase λ and the phase deviation λ caused by the encoder error. d . The input end of the processor is connected to the output end of the probe, and the processor executes the method of the present invention to measure the encoder error. This technical solution realizes self-measurement of the encoder error under variable speed conditions by setting two probes at arbitrary angles. Multiple probes can be set at the factory to realize error measurement and self-calibration of the encoder throughout its life cycle. It is also possible to realize error measurement and self-calibration of encoders used on site by adding a temporary second probe. This method can improve the accuracy of the encoder with a slight increase in cost, especially for low-cost Hall-type geared encoders with obvious error components.

[0163] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0164] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for measuring encoder error based on phase difference angle domain resampling iteration, characterized in that: The steps include: S1, obtain the encoder pulse analysis signal through multiple probes and obtain the encoder's time domain analysis signal; S2, performing signal differentiation based on the encoder time domain analysis signal obtained in step S1 to obtain the encoder instantaneous angular velocity signal containing error components; S3, performing time domain synchronous averaging on the instantaneous angular velocity signal containing the error component obtained in step S2; S4, integrating and calibrating the time-domain synchronously averaged signal obtained in step S3; S5, performing angular domain nonlinear resampling on the encoder signal after integration and calibration in step S4 to obtain an encoder angular domain signal; S6, performing signal differentiation on the encoder angular domain signal to obtain the encoder instantaneous angular velocity signal containing error components; S7, performing angular domain synchronous averaging on the instantaneous angular velocity signal containing the error component obtained in step S6; S8, integrating and calibrating the angular domain synchronously averaged signal obtained in step S7; S9, performing angular domain nonlinear resampling on the encoder signal after integration and calibration in step S8; S10, performing iterative correction on the encoder angle domain signal after the angle domain nonlinear resampling in step S9, i.e., re-submitting the angle domain signal to steps S6 to S9 for signal processing to determine whether it converges; if so, outputting the encoder error; otherwise, returning to step S6; The method for obtaining the encoder angle signal in step S5 is: Based on spline interpolation and the obtained encoder angular error θ e (t), perform cubic spline interpolation to obtain a linear and equiangularly spaced time series t in the angular domain inter (n): t inter (m)=spline(θ carrier (n),t(n),θ inter (m)) Among them, spline is cubic spline interpolation, θ carrier (n) is the angular sequence of the carrier signal with equal time intervals, θ inter (m) is an equiangularly spaced sequence, and t(n) is an equiangularly spaced sequence of source signals; The t obtained by the difference inter (m) and θ inter (m) mapping relationship, for time domain signal Perform linear angular domain resampling and reconstruction to obtain the angular domain signal of the encoder signal, that is, The angular domain analytical signal a(θ) of the encoder square wave is: Where P(θ) is the real part of the analytical signal, H is the Hilbert transform, i is the imaginary unit, A(θ) is the amplitude function of the encoder square wave signal, and λ′(θ) is the phase function of the encoder square wave signal. is the angle function of the encoder square wave signal; The angular domain analysis signals obtained by the two probes are: Wherein, λ′1(θ) and λ′2(θ) are the angular domain phases of the measured pulse signal with the shaft rotation angle θ as the independent variable, and n is the order of the modulation frequency, with the order values ​​being 0, 1, 2, ..., n.

2. The encoder error measurement method based on phase differential angular domain resampling iteration according to claim 1, characterized in that: The method for obtaining the time domain analysis signal in step S1 is as follows: The modulation phase λ′ value obtained by measuring demodulation includes the shaft rotation phase λ and the phase deviation λ caused by the encoder error d ; Encoder error deviation λ measured by two probes d1 (λ) and λ d2 (λ) There is an angle difference δ, corresponding to a phase difference Nδ in the pulse modulation signal, where N is the number of lines of the encoder, that is, the number of pulses emitted in one revolution; The relationship between the encoder error components in the modulation phase is: Among them, λ d (λ) is the encoder error; The time domain analysis signal a(t) of the encoder square wave is measured as: Where p(t) is the encoder square wave function, H is the Hilbert transform, i is the imaginary unit, A(t) is the amplitude function, λ′(t) is the modulated phase, is the measured shaft angle function, e is a natural constant; The time domain analysis signals P1(t) and P2(t) obtained by the two probes are: Wherein, λ′1(t) and λ′2(t) are the time domain phases of the measured pulse signal with time t as the independent variable; n is the order of the modulation frequency, and the order values ​​are 0, 1, 2, ... n.

3. The encoder error measurement method based on phase differential angle domain resampling iteration according to claim 1, characterized in that: The method for obtaining the instantaneous angular velocity signal in step S2 is as follows: Perform center difference and frequency domain demodulation on the analytical signal, and the encoder interval angle Δθ can be approximately estimated as The instantaneous angle containing only the encoder error is approximately calculated based on the center difference as: in, is the instantaneous angular velocity of the error component, N is the number of lines of the encoder, a d (t) is the analytical differential signal of the dual-probe encoder pulse signal: Where a1(t) is the analytical signal of probe #1, a2(t) is the analytical signal of probe #2, is the differential analytical signal of the error component.

4. The encoder error measurement method based on phase differential angular domain resampling iteration according to claim 1, characterized in that: The method for performing time-domain synchronous averaging on the instantaneous angular velocity signal containing the error component in step S3 is: The instantaneous angular velocity signal containing error components is averaged in the time domain synchronously, with the axis rotation period as the average period. After the time domain synchronous averaging process, the instantaneous angular velocity error of the encoder is for: Where N is the number of lines of the encoder; M is the length; m k is the approximate value of kt / Δt; k represents the number of times; t is the characteristic period of the encoder's instantaneous angular velocity error; Δt is the sampling interval; n is the order of the modulation frequency, and the order value is 0, 1, 2, ... n; N1 is the number of sampling points, It is the sampling sequence of the encoder instantaneous angular velocity error without time domain synchronous averaging processing.

5. The encoder error measurement method based on phase differential angular domain resampling iteration according to claim 1, characterized in that: The method for integrating and calibrating the signal after time-domain synchronous averaging in step S4 is as follows: Using the integral property of Fourier transform, the instantaneous angular velocity error after time domain synchronous averaging is integrated to obtain the encoder instantaneous angular error θ e (t) is: Among them, F -1 [] is the inverse Fourier transform, is the frequency domain expression of the instantaneous angular velocity of the encoder error, j is the imaginary unit, and f is the frequency.

6. The encoder error measurement method based on phase differential angular domain resampling iteration according to claim 1, characterized in that: The instantaneous angular velocity signal containing the error component of the encoder obtained in step S6 is: in, is the instantaneous angular velocity signal of the encoder containing error components, the subscript q is the qth iteration, a d (θ) is the angular domain of the analytical differential signal of the dual-probe encoder pulse signal: Where a1(θ) is the angular domain expression of the analytical signal of the first probe; a2(θ) is the angular domain expression of the analytical signal of the second probe. It is the differential analytical signal in the angular domain of the analytical differential signal.

7. The encoder error measurement method based on phase differential angular domain resampling iteration according to claim 1, characterized in that: The method for performing angular domain synchronous averaging on the instantaneous angular velocity signal containing error components in step S7 is: Among them, M is the length; N is the number of lines of the encoder; N θ1 is the average number of segments; m θk is the approximate value of kθ / Δθ; is the instantaneous angular velocity signal containing error components after synchronous averaging in the angular domain; is the sampling sequence of the encoder instantaneous angular velocity error without time domain synchronous averaging processing, the subscript q is the qth iteration, n is the order of the modulation frequency, and the order value is 0, 1, 2, ... n.

8. The encoder error measurement method based on phase differential angular domain resampling iteration according to claim 1, characterized in that: The method for integrating and calibrating the signal after synchronous averaging in the angular domain in step S8 is as follows: Among them, F -1 [] is the inverse Fourier transform, θ qe (θ) is the angular domain expression of the encoder’s instantaneous angular error, is the angular domain expression of the encoder’s instantaneous angular velocity, f θ is the frequency expression in the angular domain, the subscript q is the qth iteration, and j is the imaginary unit.

9. The encoder error measurement method based on phase differential angular domain resampling iteration according to claim 1, characterized in that: The method for performing angular domain nonlinear resampling on the integrated and calibrated encoder signal in step S9 is as follows: Time domain-angle domain transformation nonlinear interpolation reconstruction: t q_inter (m θ )=spline(θ q-1_carrier (n θ ),t q-1_inter (m θ ),θ inter (m θ )) Nonlinear angular domain reconstruction and resampling of analytical signals based on the time domain-angular domain transformation relationship: a q_inter (m θ )=spline(α q-1 (m θ ),θ q-1_inter (m θ ),θ inter (m θ )) Where spline is cubic spline interpolation, subscript q is the qth iteration, θ q-1_carrier (n θ ) is the angular sequence of the carrier signal with equal time intervals in the q-1th iteration, t q_inter (m θ ) is the time series with linear and equiangular intervals in the angular domain in the qth iteration, t q-1_inter (m θ ) is the linear and equiangularly spaced time series in the angular domain in the q-1th iteration; α q_inter (m θ ) is the encoder square wave analytical signal interpolated in the qth iteration in the angular domain; α q-1 (m θ ) is the encoder square wave analytical signal in the q-1th iteration in the angular domain; θ q-1_inter (m θ ) is the equiangular interval sequence of interpolation in the q-1th iteration; θ inter (m θ ) is a sequence of equal angular intervals in the angular domain.

10. The encoder error measurement method based on phase differential angle domain resampling iteration according to claim 1, characterized in that: According to the obtained encoder error, the encoder error component obtained by measuring the angle signal is subtracted from the encoder pulse output angle signal to eliminate it, and finally the encoder error correction is achieved.

11. An encoder error measurement system based on phase differential angular domain resampling iteration, characterized in that: The device comprises a code disk, at least two probes arranged on the code disk, and a processor, wherein the input end of the processor is connected to the output end of the probe, and the processor executes the method according to any one of claims 1 to 10 to measure the encoder error.

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