Demodulation method and device of inductive encoder, control system, medium and product

Abstract

The invention discloses a demodulation method and device of an inductive encoder, a motor control system, a storage medium and a computer program product, and the method comprises the steps: outputting a preset excitation signal to an excitation coil, and generating an induction signal capable of inducing the displacement of a rotor part on a receiving coil; acquiring an induction signal on the receiving coil to obtain a DSB signal of the receiving coil; performing ADC sampling on the DSB signal of the receiving coil at a sampling rate with the same frequency as the preset excitation signal to obtain a sampling signal of the receiving coil; correcting the sampling signal of the receiving coil, compensating the deviation of the sampling rate when ADC sampling is carried out on the DSB signal of the receiving coil, and obtaining a correction signal of the receiving coil; and demodulating the correction signal of the receiving coil to obtain a detection value of the displacement of the rotor part. According to the scheme, through sine and cosine correction, frequency domain correction and time interpolation, ADC sampling rate deviation is compensated, and demodulation quality and resolving accuracy of induction signals are improved.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, specifically relating to a demodulation method, device, motor control system, storage medium, and computer program product for an inductive encoder, and particularly to a demodulation method, device, motor control system, storage medium, and computer program product for an inductive encoder based on intelligent real-time compensation sampling rate. Background Technology

[0002] Inductive encoders are widely used in industrial automation, robotics, and precision measurement due to their superior oil and vibration resistance compared to photoelectric encoders, lower assembly difficulty, and higher positional accuracy compared to magnetoelectric encoders. Inductive encoders generate an alternating magnetic field through an excitation coil, which in turn induces a displacement signal through a receiving coil. Furthermore, by demodulating the induced signal from the receiving coil, the rotor angular position signal of the motor is output and calculated.

[0003] However, in operations such as demodulation of the induced signal from the receiving coil, the sampling accuracy of the induced signal from the receiving coil cannot be guaranteed, which affects the demodulation quality of the induced signal from the receiving coil, and thus affects the measurement accuracy of the rotor angle position signal of the motor.

[0004] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a demodulation method, device, motor control system, storage medium, and computer program product for an inductive encoder, in order to solve the problem that the sampling accuracy of the received coil induced signal cannot be guaranteed in operations such as demodulation of the received coil induced signal, which affects the demodulation quality of the received coil induced signal and thus affects the measurement accuracy of the rotor angle position signal of the motor. The invention achieves the effect of compensating for the sampling rate deviation of the ADC module by using sine and cosine correction, frequency domain correction, and time interpolation processing, thereby improving the demodulation quality of the displacement signal induced by the received coil and the accuracy of position calculation.

[0006] This invention provides a demodulation method for an inductive encoder, the inductive encoder having a stator and a rotor, the stator having an excitation coil and a receiving coil; the demodulation method for the inductive encoder includes: outputting a preset excitation signal to the excitation coil to generate an induction signal on the receiving coil capable of sensing the displacement of the rotor; acquiring the induction signal on the receiving coil to obtain a DSB signal of the receiving coil; performing ADC sampling on the DSB signal of the receiving coil at a sampling rate of the same frequency as the preset excitation signal to obtain a sampled signal of the receiving coil; correcting the sampled signal of the receiving coil to compensate for the deviation of the sampling rate when performing ADC sampling on the DSB signal of the receiving coil to obtain a corrected signal of the receiving coil; and demodulating the corrected signal of the receiving coil to obtain a detected value of the displacement of the rotor.

[0007] In some embodiments, a preset excitation signal is output to the excitation coil to generate an induction signal on the receiving coil that can sense the displacement of the rotor portion. This includes: outputting a square wave signal at a preset fixed frequency and a fixed duty cycle; performing power amplification and RLC series resonance processing on the square wave signal to obtain a sine signal with a preset fixed frequency, which is used as the preset excitation signal; and outputting the preset excitation signal to the excitation coil.

[0008] In some embodiments, acquiring the induced signal on the receiving coil to obtain the DSB signal of the receiving coil includes: acquiring the induced signal on the receiving coil; performing signal amplification processing on the induced signal on the receiving coil to obtain an amplified induced signal on the receiving coil, which is used as the DSB signal of the receiving coil.

[0009] In some embodiments, the sampling signal of the receiving coil is corrected to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by an ADC, thereby obtaining a corrected signal for the receiving coil. This includes: performing sine and cosine correction on the sampling signal of the receiving coil to obtain a sine and cosine correction signal for the receiving coil; and performing correction processing based on frequency domain correction and time interpolation on the sine and cosine correction signal of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by an ADC, thereby obtaining the corrected signal for the receiving coil.

[0010] In some embodiments, the sine and cosine correction signals of the receiving coil are subjected to correction processing based on frequency domain correction and time interpolation to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, thereby obtaining a correction signal for the receiving coil. This includes: performing frequency domain correction on the sine and cosine correction signals of the receiving coil to obtain a frequency domain correction signal for the receiving coil; performing time interpolation processing on the frequency domain correction signal of the receiving coil to obtain a time interpolation signal for the receiving coil; determining the difference between the time interpolation signal of the receiving coil and a preset target signal, and determining whether the difference is within a set error range; if the difference is determined to be within the set error range, then determining the time interpolation signal of the receiving coil as the correction signal for the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC; if the difference is determined to be outside the set error range, then returning to the previous step to re-perform frequency domain correction on the sine and cosine correction signals of the receiving coil.

[0011] In some embodiments, frequency domain correction is performed on the sine and cosine correction signals of the receiving coil to obtain a frequency domain correction signal for the receiving coil. This includes: performing FFT processing on the sine and cosine correction signals of the receiving coil to obtain a frequency domain signal of the receiving coil; filtering the frequency domain signal of the receiving coil using a filtering module with a cutoff frequency of half a preset target sampling rate to obtain a filtered signal of the receiving coil; and performing an inverse FFT transform on the filtered signal of the receiving coil to obtain a time domain signal of the receiving coil, which serves as the frequency domain correction signal of the receiving coil.

[0012] In some embodiments, time interpolation processing is performed on the frequency domain correction signal of the receiving coil to obtain the time interpolation signal of the receiving coil, including: interpolating the frequency domain correction signal of the receiving coil by the Sinc function according to a preset target sampling period to correct the sampling rate, thereby obtaining the time interpolation signal of the receiving coil.

[0013] In conjunction with the above method, another aspect of the present invention provides a demodulation apparatus for an inductive encoder, the inductive encoder having a stator portion and a rotor portion, the stator portion having an excitation coil and a receiving coil; the demodulation apparatus for the inductive encoder includes: a control unit configured to output a preset excitation signal to the excitation coil to generate an induction signal on the receiving coil capable of sensing the displacement of the rotor portion; an acquisition unit configured to acquire the induction signal on the receiving coil to obtain a DSB signal of the receiving coil; the control unit is further configured to perform ADC sampling on the DSB signal of the receiving coil at a sampling rate of the same frequency as the preset excitation signal to obtain a sampled signal of the receiving coil; the control unit is further configured to correct the sampled signal of the receiving coil to compensate for the deviation of the sampling rate when performing ADC sampling on the DSB signal of the receiving coil to obtain a corrected signal of the receiving coil; the control unit is further configured to demodulate the corrected signal of the receiving coil to obtain a detected value of the displacement of the rotor portion.

[0014] In some embodiments, the control unit outputs a preset excitation signal to the excitation coil to generate an induction signal on the receiving coil that can sense the displacement of the rotor portion, including: outputting a square wave signal at a preset fixed frequency and a fixed duty cycle; performing power amplification and RLC series resonance processing on the square wave signal to obtain a sine signal with a preset fixed frequency as the preset excitation signal; and outputting the preset excitation signal to the excitation coil.

[0015] In some embodiments, the acquisition unit acquires the induced signal on the receiving coil to obtain the DSB signal of the receiving coil, including: acquiring the induced signal on the receiving coil; performing signal amplification processing on the induced signal on the receiving coil to obtain an amplified induced signal on the receiving coil, which is used as the DSB signal of the receiving coil.

[0016] In some embodiments, the control unit corrects the sampled signal of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by an ADC, thereby obtaining a corrected signal for the receiving coil. This includes: performing sine and cosine correction on the sampled signal of the receiving coil to obtain a sine and cosine correction signal for the receiving coil; and performing correction processing based on frequency domain correction and time interpolation on the sine and cosine correction signal of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by an ADC, thereby obtaining the corrected signal for the receiving coil.

[0017] In some embodiments, the control unit performs frequency-domain correction and time interpolation-based correction processing on the sine and cosine correction signals of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by an ADC, thereby obtaining a correction signal for the receiving coil. This includes: performing frequency-domain correction on the sine and cosine correction signals of the receiving coil to obtain a frequency-domain correction signal for the receiving coil; performing time interpolation processing on the frequency-domain correction signal of the receiving coil to obtain a time interpolation signal for the receiving coil; determining the difference between the time interpolation signal of the receiving coil and a preset target signal, and determining whether the difference is within a set error range; if the difference is determined to be within the set error range, then determining the time interpolation signal of the receiving coil as the correction signal for the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by an ADC; if the difference is determined to be outside the set error range, then returning to the previous step to re-perform frequency-domain correction on the sine and cosine correction signals of the receiving coil.

[0018] In some embodiments, the control unit performs frequency domain correction on the sine and cosine correction signals of the receiving coil to obtain a frequency domain correction signal for the receiving coil, including: performing FFT processing on the sine and cosine correction signals of the receiving coil to obtain a frequency domain signal of the receiving coil; filtering the frequency domain signal of the receiving coil using a filtering module with a cutoff frequency of half a preset target sampling rate to obtain a filtered signal of the receiving coil; and performing an inverse FFT transform on the filtered signal of the receiving coil to obtain a time domain signal of the receiving coil, which serves as the frequency domain correction signal of the receiving coil.

[0019] In some embodiments, the control unit performs time interpolation processing on the frequency domain correction signal of the receiving coil to obtain the time interpolation signal of the receiving coil, including: performing sampling rate correction on the frequency domain correction signal of the receiving coil by interpolation using the Sinc function according to a preset target sampling period to obtain the time interpolation signal of the receiving coil.

[0020] In conjunction with the above-described device, the present invention further provides a motor control system, including: the demodulation device for the inductive encoder described above.

[0021] In conjunction with the above method, the present invention further provides a storage medium comprising a stored program, wherein, when the program is executed, the device on which the storage medium is located executes the steps of the demodulation method of the inductive encoder described above.

[0022] In conjunction with the above method, the present invention further provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the demodulation method for the inductive encoder described above.

[0023] Therefore, the solution of this invention targets the excitation coil and receiving coil of the stator section of an inductive encoder. An excitation signal obtained by outputting a PWM signal with a fixed frequency and fixed duty cycle from the PWM module of the main chip acts on the excitation coil, generating an alternating magnetic field. The receiving coil then senses the displacement signal of the stator section of the inductive encoder. After sampling the DSB signal of the receiving coil through the ADC module of the main chip, the sampled DSB signal undergoes sine and cosine correction, frequency domain correction, and time interpolation to obtain a correction signal. The qualified correction signal is then calculated to obtain the position calculation result of the rotor section of the inductive encoder. Thus, by utilizing sine and cosine correction, frequency domain correction, and time interpolation, compensation for the sampling rate deviation of the ADC module is achieved, improving the demodulation quality of the displacement signal sensed by the receiving coil and the accuracy of the position calculation.

[0024] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of an embodiment of the demodulation method for the inductive encoder of the present invention;

[0027] Figure 2 This is a flowchart illustrating an embodiment of the method of the present invention, in which the excitation coil outputs a preset excitation signal.

[0028] Figure 3 This is a flowchart illustrating an embodiment of the method of the present invention for obtaining the induced signal on the receiving coil;

[0029] Figure 4 This is a schematic flowchart of an embodiment of the method of the present invention for correcting the sampling signal of the receiving coil;

[0030] Figure 5 This is a schematic flowchart of an embodiment of the correction processing based on frequency domain correction and time interpolation in the method of the present invention;

[0031] Figure 6 This is a schematic flowchart of an embodiment of the method of the present invention for frequency domain correction of the sine and cosine correction signals of the receiving coil;

[0032] Figure 7 This is a schematic diagram of the structure of an embodiment of the demodulation device for the inductive encoder of the present invention;

[0033] Figure 8 This is a schematic diagram of the stator section of an inductive encoder.

[0034] Figure 9 This is a schematic diagram of the code disk portion of an inductive encoder.

[0035] Figure 10 This is a schematic diagram of the waveform of the original modulated DSB signal;

[0036] Figure 11 This is a schematic diagram of the waveform of the demodulated signal (10s period length) obtained under ideal sampling rate;

[0037] Figure 12 This is a schematic diagram of the waveform of the demodulated signal (100s period length) obtained under ideal sampling rate;

[0038] Figure 13 A schematic diagram of the waveform of the demodulated signal (10s period length) obtained with a 1% deviation from the ideal sampling rate;

[0039] Figure 14 A schematic diagram of the waveform of the demodulated signal (100s period length) obtained with a 1% deviation from the ideal sampling rate;

[0040] Figure 15 A flowchart illustrating the method for real-time compensation of sampling rate deviation;

[0041] Figure 16 This is a schematic diagram of the excitation processing circuit.

[0042] Referring to the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows:

[0043] 102 - Acquisition unit; 104 - Control unit. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0045] Considering that the sampling accuracy of the received coil's induced signal cannot be guaranteed during demodulation operations, affecting the demodulation quality and thus the accuracy of measuring the motor's rotor angle position signal, specifically... Figure 8 This is a schematic diagram of the stator section of an inductive encoder. Figure 9This is a schematic diagram of the code disk section of an inductive encoder. The structure of an inductive encoder is as follows: Figure 8 and Figure 9 As shown, Figure 8 This is the stator section of the inductive encoder. Figure 9 This refers to the code disk (rotor) part of the inductive encoder. When the position of the inductive encoder needs to be obtained, an alternating current (excitation signal) is supplied to the excitation coil of the stator part of the inductive encoder, thereby generating an alternating magnetic field in the excitation coil. When the inductive encoder rotates, the rotor generates an electromagnetic field of varying intensity due to the eddy current effect, which affects the phase, amplitude, and other attributes of the induced signal of the receiving coil. Through demodulation and other operations of the induced signal of the receiving coil, a precise angular position signal is output and calculated.

[0046] Figure 10 This is a schematic diagram of the waveform of the original modulated DSB signal. Figure 11 This is a schematic diagram of the waveform of the demodulated signal (10s period length) obtained under ideal sampling rate. Figure 12 This is a schematic diagram of the waveform of the demodulated signal (100s period length) obtained at an ideal sampling rate. In the demodulation process of the receiving coil inductive encoder, to reduce reliance on hardware circuits such as analog filtering and lock-in amplification, and to lower computational complexity, related solutions can use a sampling rate at the same frequency as the carrier signal, and then use an ADC module (i.e., an analog-to-digital converter) to process the signal. Figure 10 The modulated DSB signal (i.e., suppressed-carrier double-sideband amplitude modulation signal) shown is directly sampled to achieve signal demodulation. The sampling result is as follows: Figure 11 and Figure 12 As shown, the envelope extraction and demodulation of the carrier signal are excellent.

[0047] Figure 13 This is a schematic diagram of the waveform of the demodulated signal (10s period length) obtained with a 1% deviation from the ideal sampling rate. Figure 14 This is a schematic diagram of the waveform of the demodulated signal (100s period length) obtained with a 1% deviation from the ideal sampling rate. However, the actual sampling rate of an ADC module is affected by various factors, such as clock source fluctuations, temperature changes, power supply jitter, and electromagnetic interference, all of which can affect the accuracy of the ADC module's sampling rate. Furthermore, this demodulation method places very high demands on the sampling rate of the ADC module. Figure 13 and Figure 14 The image shows the results of sampling the signal using a sampling rate that deviates from the carrier signal frequency by 1%. The signal amplitude shows a significant deviation, and the demodulated signal after multiple cycles shows significant distortion. Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14In the graph, the horizontal axis represents time in seconds (s), and the vertical axis represents voltage in volts (V).

[0048] Therefore, there is an urgent need for a method that can intelligently and in real-time compensate for the sampling rate deviation of the ADC module, so as to improve the demodulation quality and the accuracy of position calculation in operations such as demodulation of the received coil induction signal of inductive encoder.

[0049] Therefore, the present invention proposes a demodulation method for an inductive encoder, specifically an inductive encoder demodulation method based on intelligent real-time compensation sampling rate. It uses an optimized correction method based on frequency domain correction and time interpolation to compensate the sampling rate of the ADC module during inductive demodulation, thereby improving the demodulation quality and accuracy of position calculation for operations such as demodulation of the received coil induction signal of the inductive encoder.

[0050] According to embodiments of the present invention, a demodulation method for an inductive encoder is provided, such as... Figure 1 The diagram shows a flowchart of an embodiment of the method of the present invention. The inductive encoder has a stator portion and a rotor portion. The stator portion has an excitation coil and a receiving coil, and the rotor portion has a code disk. Upon receiving an excitation signal, the excitation coil generates an electromagnetic field, causing the code disk to rotate, and the receiving coil generates an induction signal for sensing the displacement of the rotor portion. In the solution of the present invention, as... Figure 1 As shown, the demodulation method of the inductive encoder includes steps S110 to S150.

[0051] Step S110: Output a preset excitation signal to the excitation coil to generate an induction signal on the receiving coil that can sense the displacement of the rotor portion.

[0052] Step S120: Obtain the induced signal on the receiving coil to obtain the DSB signal of the receiving coil.

[0053] Step S130: The DSB signal of the receiving coil is sampled by an ADC at a sampling rate that is the same as the preset excitation signal to obtain the sampled signal of the receiving coil.

[0054] Step S140: Correct the sampling signal of the receiving coil to compensate for the deviation in sampling rate when the DSB signal of the receiving coil is sampled by ADC, and obtain the corrected signal of the receiving coil.

[0055] Step S150: Demodulate the correction signal of the receiving coil to obtain the detected value of the displacement of the rotor part, that is, obtain the position calculation result of the rotor part.

[0056] This invention proposes an inductive encoder demodulation algorithm based on intelligent real-time compensation sampling rate. This algorithm compensates for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC, thereby reducing the dependence on hardware circuits such as analog filtering and lock-in amplification, reducing computational complexity, and reducing the stringent requirements on clock, power supply, electromagnetic, etc. in hardware processing to control the sampling rate of the ADC module.

[0057] In some embodiments, the specific process of outputting a preset excitation signal to the excitation coil in step S110 to generate an induction signal on the receiving coil that can sense the displacement of the rotor portion is described in the following exemplary description.

[0058] The following is combined Figure 2 The flowchart shown is a schematic diagram of an embodiment of the method of the present invention in which the excitation coil outputs a preset excitation signal. It further illustrates the specific process of the excitation coil outputting the preset excitation signal in step S110, including steps S210 to S220.

[0059] Step S210: Output a square wave signal at a preset fixed frequency and fixed duty cycle.

[0060] Step S220: After power amplification and RLC series resonance processing of the square wave signal, a sinusoidal signal with a preset fixed frequency is obtained as a preset excitation signal; and the preset excitation signal is output to the excitation coil.

[0061] Figure 15 This is a flowchart illustrating a method for real-time compensation of sampling rate deviation. Figure 15 In the example shown, the excitation processing circuit can be adopted as follows: Figure 16 The circuit shown. Figure 16 This is a schematic diagram of the excitation processing circuit. (Example:) Figure 16 As shown, the excitation processing circuit consists of a power amplifier circuit and an RLC series resonant circuit. The power amplifier circuit uses a Class AB complementary power amplifier output circuit composed of N-MOS and P-MOS transistors, enabling the drain outputs of both to produce a square wave signal with a large current output capability. The RLC series resonant circuit maximizes the excitation signal power, and by adjusting the resonant frequency for matching, it outputs a sine / cosine excitation signal with the largest possible voltage. Figure 16 In the example shown, the square wave signal with a fixed frequency and duty cycle generated by the PWM module is output as a sine wave signal with a fixed frequency after passing through the power amplifier circuit and the RLC series resonant circuit.

[0062] In the present invention, a preset excitation signal is output to the excitation coil to generate an induction signal on the receiving coil that can sense the displacement of the rotor. Then, an ADC module is used for ADC sampling. The DC deviation, amplitude deviation, and phase deviation of the analog signal sampled by the ADC module are compensated and corrected by sine and cosine correction. This reduces the stringent requirements on the hardware processing such as clock, power supply, and electromagnetics for controlling the sampling rate of the ADC module, greatly improves the demodulation quality of the signal obtained by the receiving coil by the sampling method of the ADC module, prevents nonlinear distortion of the demodulated signal, and ensures the accuracy of position calculation.

[0063] In some embodiments, the specific process of obtaining the induced signal on the receiving coil and obtaining the DSB signal of the receiving coil in step S120 is described in the following exemplary description.

[0064] The following is combined Figure 3 The schematic diagram shown is a flowchart of an embodiment of the method of the present invention for obtaining the induced signal on the receiving coil. The specific process of obtaining the induced signal on the receiving coil in step S120 is further explained, including steps S310 to S320.

[0065] Step S310: Obtain the induced signal on the receiving coil.

[0066] Step S320: The induced signal on the receiving coil is amplified to obtain the amplified induced signal on the receiving coil, which is used as the DSB signal of the receiving coil.

[0067] exist Figure 15 In the example shown, a signal amplification circuit is used to amplify the modulated DSB signal generated on the receiving coil, resulting in an amplified DSB signal, which is then used as the DSB signal of the receiving coil. The signal amplification circuit can employ a voltage operational amplifier or a differential operational amplifier to amplify the original signal by 2 to 3 times.

[0068] In the present invention, the induced signal on the receiving coil is obtained to obtain the DSB signal of the receiving coil, and then the ADC module is used for ADC sampling. Frequency domain correction and time interpolation are used to compensate for the sampling rate deviation of the ADC module, correct the sampling rate deviation of the ADC module, and greatly improve the demodulation quality and position calculation accuracy of the signal obtained by the receiving coil by the sampling method of the ADC module.

[0069] In some embodiments, the specific process of correcting the sampled signal of the receiving coil in step S140 to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, and obtaining the corrected signal of the receiving coil, is described in the following exemplary description.

[0070] The following is combined Figure 4 The schematic diagram shown is a flowchart of an embodiment of the method of the present invention for correcting the sampling signal of the receiving coil. It further illustrates the specific process of correcting the sampling signal of the receiving coil in step S140, including steps S410 to S420.

[0071] Step S410: Perform sine and cosine correction on the sampled signal of the receiving coil to obtain the sine and cosine correction signal of the receiving coil.

[0072] Step S420: The sine and cosine correction signals of the receiving coil are corrected based on frequency domain correction and time interpolation to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, so as to obtain the corrected signal of the receiving coil.

[0073] like Figure 15 As shown, the process of the real-time compensation method for sampling rate deviation includes:

[0074] Step 1: ADC module and sine / cosine correction:

[0075] DSB (Double Sideband Amplitude Modulation) signal is a linear modulation technique that achieves spectrum shifting by multiplying a baseband signal with a sinusoidal carrier. Its core feature is the complete suppression of the carrier component, retaining only the upper and lower sideband signals. By sampling the DSB signal at the same sampling rate as the excitation signal, a preliminary demodulated sine and cosine waveform is obtained, corresponding to… Figure 10 The signal shown is the modulated DSB signal obtained by the receiving coil. The acquired data is input into the sine and cosine correction module to correct deviations in DC, amplitude, and phase, eliminating the influence of signal deviations on subsequent corrections.

[0076] In step 1, the main chip outputs a PWM signal with a fixed high frequency (f0) and fixed duty cycle. This PWM signal passes through the excitation processing circuit, ultimately obtaining a sine and cosine excitation signal with a fixed frequency and high amplitude voltage. This signal then passes through the excitation coil on the stator of the inductive encoder, ultimately generating a high-frequency electromagnetic field. At this time, the moving disk of the inductive encoder rotates, and according to the eddy current effect, a high-frequency electromagnetic field is received at the receiving coil of the inductive encoder. Figure 10 The original modulated DSB signal is shown. This signal is amplified by a signal amplification circuit to obtain an amplified DSB signal, which is then input into the ADC module of the main chip. The main chip is configured to sample the signal at a sampling rate f0, which is the same frequency as the output PWM wave, for demodulation processing.

[0077] Since the sampling rate of the main chip's ADC module may have deviations, real-time correction and compensation of the sampling rate are required. Subsequently, in the main chip, sine and cosine correction, frequency domain correction, time interpolation, and signal evaluation methods according to the present invention are performed sequentially. When the sampled signal meets the requirements, the adjusted sampled signal is output, and position calculation is performed.

[0078] In step 1, sine and cosine correction compensates for the DC deviation, amplitude deviation, and phase deviation of the analog signal sampled by the ADC module, thereby improving the accuracy of the sampled values ​​and reducing the impact on subsequent compensation calculations. In the solution of this invention, by compensating for the DC deviation, amplitude deviation, and phase deviation of the analog signal sampled by the ADC module through sine and cosine correction, the stringent requirements on hardware processing such as clock, power supply, and electromagnetic parameters for controlling the sampling rate of the ADC module are reduced.

[0079] In some embodiments, the specific process of performing frequency domain correction and time interpolation-based correction processing on the sine and cosine correction signals of the receiving coil in step S420 to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, and to obtain the correction signal of the receiving coil, is described in the following exemplary description.

[0080] The following is combined Figure 5 The schematic diagram shows an embodiment of the correction processing based on frequency domain correction and time interpolation in the method of the present invention. It further illustrates the specific process of the correction processing based on frequency domain correction and time interpolation in step S420, including steps S510 to S550.

[0081] Step S510: Perform frequency domain correction on the sine and cosine correction signals of the receiving coil to obtain the frequency domain correction signal of the receiving coil.

[0082] Step S520: Perform time interpolation processing on the frequency domain correction signal of the receiving coil to obtain the time interpolation signal of the receiving coil.

[0083] Step S530: Determine the difference between the time interpolation signal of the receiving coil and the preset target signal, and determine whether the difference is within the set error range.

[0084] Step S540: If it is determined that the difference is within the set error range, then the time interpolation signal of the receiving coil is determined as the correction signal of the receiving coil to compensate for the deviation of the sampling rate when the DSB signal of the receiving coil is sampled by ADC.

[0085] Step S550: If it is determined that the difference is not within the set error range, return to the previous step to re-correct the frequency domain of the sine and cosine correction signal of the receiving coil.

[0086] like Figure 15 As shown, the process of the real-time compensation method for sampling rate deviation also includes:

[0087] Step 2, frequency domain correction.

[0088] Step 3: Time interpolation.

[0089] Step 4, Signal Evaluation:

[0090] The corrected signal is analyzed in the time and frequency domains to evaluate the correction result. If the deviation is too large, the process returns to step 2, i.e., looping back to the frequency domain correction step, and re-corrects until the requirements are met before proceeding to step 5. After frequency domain conversion, the frequency spectrum can be analyzed to determine the frequency deviation between the analog signal frequency corresponding to the current actual rotational speed and the actual sampled value, thus identifying whether there is a deviation in the actual sampled value. The time and frequency domain analysis of the corrected signal to evaluate the correction result mainly involves frequency domain conversion. After conversion, the frequency of the actual sampled signal result can be compared with the ideal sampling frequency to evaluate and compare their deviations. This is specifically described in steps 21 and 22 below, but the evaluation and comparison do not require filtering; only analysis is performed.

[0091] Step 5, Output the results:

[0092] After the calibration is passed, the position is finely calculated to obtain the precise position value. There are many methods for position fine-grained calculation. Since one revolution of the encoder consists of several cycles of sine and cosine signals, the main logic is to perform calculations such as arctangent on the compensated sine and cosine signals to obtain a unique angle value for one cycle, which is used as the result of the position fine-grained calculation.

[0093] This invention proposes an intelligent real-time compensation scheme for sampling rate deviation. It uses frequency domain correction and time interpolation to compensate for the sampling rate deviation of the ADC module, significantly improving the demodulation quality of the signal obtained from the receiving coil by the ADC module's sampling method. This prevents nonlinear distortion of the demodulated signal and ensures the accuracy of position calculation. Simultaneously, it effectively reduces the stringent requirements on hardware processing such as clock, power supply, and electromagnetic parameters.

[0094] In some embodiments, the specific process of performing frequency domain correction on the sine and cosine correction signals of the receiving coil in step S510 to obtain the frequency domain correction signal of the receiving coil is described in the following exemplary description.

[0095] The following is combined Figure 6The schematic diagram shown is a flowchart of an embodiment of the method of the present invention for frequency domain correction of the sine and cosine correction signals of the receiving coil. It further illustrates the specific process of frequency domain correction of the sine and cosine correction signals of the receiving coil in step S510, including steps S610 to S630.

[0096] Step S610: Perform FFT processing on the sine and cosine correction signals of the receiving coil to obtain the frequency domain signal of the receiving coil.

[0097] Step S620: A filtering module with a cutoff frequency of half the preset target sampling rate is used to filter the frequency domain signal of the receiving coil to obtain the filtered signal of the receiving coil.

[0098] Step S630: Perform an inverse FFT transform on the filtered signal of the receiving coil to obtain the time-domain signal of the receiving coil, which serves as the frequency-domain correction signal of the receiving coil.

[0099] like Figure 15 As shown, the flow of the real-time compensation sampling rate deviation method also includes: in step 2, frequency domain correction, as follows:

[0100] Step 21: Perform Fast Fourier Transform (FFT) processing on the above sampled values ​​to convert them from the time domain to the frequency domain for further processing.

[0101]

[0102] Where N is the number of sampled values, x[n] is the sampled value, and e is a natural number. Since spectrum analysis is required, the default number of sampled values ​​N is 100. Each correction uses the most recent 100 sampled values ​​for frequency domain analysis. n is the corresponding time signal in the time domain. k is the frequency after frequency domain conversion, and x[k] is the spectrum of the sampled value x[n] after Fast Fourier Transform. For details, refer to the parameter definitions of Fourier Transform and Laplace Transform. This converts the result to the frequency domain, allowing for processing of the sampled values ​​in the frequency domain, using filters and other methods to achieve high-frequency suppression and sampling frequency correction.

[0103] Step 22: Design a low-pass filter with a cutoff frequency of half the ideal sampling rate to filter the spectrum x[k], suppress the high-frequency aliasing components of the spectrum x[k], and align the sampling rate of the spectrum x[k] with the ideal sampling rate.

[0104] Let the filter be H(k), then the corrected spectrum y[k] is:

[0105] y[k]=H[k]*x[k] (2).

[0106] The corrected signal is subjected to an inverse fast fourier transform (IFFT) to recover the time-domain signal y[n].

[0107] In the solution of this invention, the sampling rate of the ADC module during inductor demodulation is compensated based on frequency domain correction, thereby improving the sampling rate accuracy of the ADC module and thus improving the demodulation quality of the signal obtained from the receiving coil.

[0108] In some embodiments, step S520 involves performing time interpolation processing on the frequency domain correction signal of the receiving coil to obtain the time interpolation signal of the receiving coil, including: performing sampling rate correction on the frequency domain correction signal of the receiving coil by interpolation using the Sinc function according to a preset target sampling period to obtain the time interpolation signal of the receiving coil.

[0109] like Figure 15 As shown, the process of the real-time compensation sampling rate deviation method also includes: In step 3, the time interpolation is as follows:

[0110] The time-series signal y[n] after frequency domain correction is subjected to signal time interpolation.

[0111] Assuming an ideal sampling period of T = 10, the latest three sampled values ​​before the current frequency domain correction time difference are:

[0112]

[0113] In formula (3), result is the sampled value at the corresponding time point n, that is, 1401 is the sampled value of y

[20] . The sampling rate correction is achieved by interpolation using the Sinc function. The sampled value at time point 30 (that is, with a sampling period of 10, the next time point 30 after the time point 20 after the previous round of compensation) is inserted. The calculation method is as follows:

[0114] ①Calculation of the sinc function:

[0115] By interpolating the two most recent sampled values ​​from formula (4), we obtain the values ​​shown in formulas (5) and (6):

[0116]

[0117] t is the time point to be inserted. That is, when n1 = 20, its sampled value T1 is 1401. If interpolation is needed at time point t = 30, then t needs to be substituted with 30 and the following calculation is performed.

[0118] ② Coefficient normalization:

[0119] Since interpolation is generally performed based on the sampled values ​​from the two most recent time points, n can be obtained respectively. k and n k-1 The sinc values ​​at time points, such as 0.936 and 0.234 in the above text, can be calculated using the formula:

[0120] Q = 1 / (sinc((tn)) k ) / T)+sinc((tn k-1 ) / T)).

[0121] Q is the normalization factor of 0.8547, and the other parameters are the same as in formula (4); T is the ideal sampling period of 10, t is the time point to be inserted, and n k These are the two latest time points.

[0122] The normalization factor is calculated to obtain formula (7):

[0123]

[0124] The coefficients obtained after normalization are as follows:

[0125] ω k =sinc((tn) k ) / T)*Q;

[0126] ω k-1 =sinc((tn) k-1 ) / T)*Q;

[0127] ω 28 =0.936*0.8547≈0.8 (8);

[0128] ω 38 =0.234*0.8547≈0.2 (9).

[0129] ω k-1 and ω k n k-1 and n k The normalization coefficient of the sinc value at the corresponding time point.

[0130] ③ Weighted summation:

[0131] y[t]=ω k *y[n k ]+ω k-1 *y[n k-1 ];

[0132] y

[30] =ω 28 *y

[28] +ω 38 *y

[38] =0.8*1923+0.2*2522≈2043 (10).

[0133] y[t] is the sampled value at time t, y[n k ] is n k The sampled value at time point y[n k-1 ] is n k-1 The sampled values ​​at time points. Verification showed that after correction, the relative error with the ideal value of 2048 at time point 30 was only 0.25%, significantly improving accuracy. In this implementation, the results were obtained from the analysis of the actual measured experimental data. A 12-bit ADC module was used for sampling, obtaining the sampled values ​​at t(20), t(28), and t(38), respectively. After compensation and correction, the sampled value at time t(30) could be obtained. Generally, the sampled values ​​from the previous and next periods of the value to be inserted can be selected for calculation; the formula n above can be referenced. k and n k-1 .

[0134] This process is repeated to correct the sampling rate deviation of the ADC module. By correcting the sampling rate deviation of the ADC module, thus... Figure 14 The demodulated signal shown has a bias, which can be compensated to become Figure 12 The ideal signal waveform is shown.

[0135] In the solution of this invention, the time interpolation-based optimization correction method compensates for the sampling rate of the ADC module during inductor demodulation, effectively avoiding nonlinear distortion of the demodulated signal and ensuring the accuracy of position calculation.

[0136] like Figure 15As shown, in the main chip, the signal output from the first output terminal of the ADC module is synthesized by adaptive frequency and then output to the PWM module. The signal output from the second output terminal of the ADC module undergoes sine and cosine correction, frequency domain correction, time interpolation, signal evaluation, and result output to obtain the position calculation result. Since the excitation signal is obtained by processing the PWM wave output from the main chip through a corresponding excitation processing circuit, the frequency of the excitation signal is directly related to the frequency of the PWM wave. Furthermore, the amplitude and other related parameters of the modulated DSB signal induced by the receiving coil are closely related to the frequency of the excitation signal. Therefore, the sampling results can be analyzed in the above process to verify its linearity, peak-to-peak value, and other signal quality parameters, thereby dynamically adjusting the PWM module frequency and thus the excitation signal frequency. For example, a default value can be given initially, typically around 1MHz, and then dynamically adjusted subsequently. The PWM module in the main chip outputs a square wave signal with a fixed frequency and duty cycle to the excitation processing circuit. The excitation processing circuit outputs a sine wave signal with a fixed frequency as the excitation signal and outputs it to the excitation coil. The excitation coil outputs a signal to the receiving coil through the eddy current effect. The receiving coil outputs the modulated DSB signal to the signal amplification processing circuit. The signal amplification processing circuit outputs the amplified DSB signal to the ADC module in the main chip.

[0137] In the present invention, an optimized correction method based on frequency domain correction and time interpolation is used to compensate the sampling rate of the ADC module during inductive demodulation, thereby improving the demodulation quality and position calculation accuracy of operations such as demodulation of the received coil induced signal of the inductive encoder. This solves the problem of high sampling rate requirements of the ADC module in related solutions, thus improving the demodulation quality of the signal obtained from the received coil by the ADC module's sampling method, effectively avoiding nonlinear distortion of the demodulated signal, and ensuring the accuracy of position calculation.

[0138] The technical solution of this embodiment uses an excitation signal obtained by outputting a PWM signal with a fixed frequency and fixed duty cycle from the PWM module of the main chip to the excitation coil and receiving coil of the stator part of the inductive encoder. The excitation coil generates an alternating magnetic field, which is then sensed by the receiving coil to induce the displacement signal of the stator part of the inductive encoder. After sampling the DSB signal of the receiving coil by the ADC module of the main chip, the sampled DSB signal is processed by sine and cosine correction, frequency domain correction, and time interpolation to obtain a correction signal. The qualified correction signal is then calculated to obtain the position calculation result of the rotor part of the inductive encoder. Thus, by using sine and cosine correction, frequency domain correction, and time interpolation, the sampling rate deviation of the ADC module is compensated, improving the demodulation quality of the displacement signal induced by the receiving coil and the accuracy of the position calculation.

[0139] According to embodiments of the present invention, a demodulation apparatus for an inductive encoder corresponding to a demodulation method for an inductive encoder is also provided. See also Figure 7 The diagram shows a structural schematic of an embodiment of the device of the present invention. The inductive encoder has a stator portion and a rotor portion. The stator portion has an excitation coil and a receiving coil, and the rotor portion has a code disk. The excitation coil generates an electromagnetic field upon receiving an excitation signal, causing the code disk to rotate. An induction signal is generated on the receiving coil for sensing the displacement of the rotor portion. In the embodiment of the present invention, as... Figure 7 As shown, the demodulation device of the inductive encoder includes: an acquisition unit 102 and a control unit 104.

[0140] The control unit 104 is configured to output a preset excitation signal to the excitation coil to generate a sensing signal on the receiving coil capable of sensing the displacement of the rotor portion. The specific functions and processing of the control unit 104 are described in step S110.

[0141] The acquisition unit 102 is configured to acquire the induced signal on the receiving coil to obtain the DSB signal of the receiving coil. The specific functions and processing of the acquisition unit 102 are described in step S120.

[0142] The control unit 104 is further configured to perform ADC sampling on the DSB signal of the receiving coil at a sampling rate that is the same as the preset excitation signal, to obtain the sampled signal of the receiving coil. The specific functions and processing of the control unit 104 are further described in step S130.

[0143] The control unit 104 is further configured to correct the sampled signal of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC, thereby obtaining a corrected signal for the receiving coil. The specific functions and processing of this control unit 104 are further described in step S140.

[0144] The control unit 104 is further configured to demodulate the correction signal of the receiving coil to obtain the detected value of the displacement of the rotor portion, that is, to obtain the position calculation result of the rotor portion. The specific functions and processing of the control unit 104 are further described in step S150.

[0145] This invention proposes an inductive encoder demodulation algorithm based on intelligent real-time compensation sampling rate. This algorithm compensates for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC, thereby reducing the dependence on hardware circuits such as analog filtering and lock-in amplification, reducing computational complexity, and reducing the stringent requirements on clock, power supply, electromagnetic, etc. in hardware processing to control the sampling rate of the ADC module.

[0146] In some embodiments, the control unit 104 outputs a preset excitation signal to the excitation coil to generate a sensing signal on the receiving coil capable of sensing the displacement of the rotor portion, including:

[0147] The control unit 104 is further configured to output a square wave signal at a preset fixed frequency and a fixed duty cycle. The specific functions and processing of the control unit 104 are further described in step S210.

[0148] The control unit 104 is further configured to perform power amplification and RLC series resonance processing on the square wave signal to obtain a sinusoidal signal with a preset fixed frequency, which serves as a preset excitation signal; and to output the preset excitation signal to the excitation coil. The specific functions and processing of the control unit 104 are further described in step S220.

[0149] Figure 15 This is a flowchart illustrating a method for real-time compensation of sampling rate deviation. Figure 15 In the example shown, the excitation processing circuit can be adopted as follows: Figure 16 The circuit shown. Figure 16 This is a schematic diagram of the excitation processing circuit. (Example:) Figure 16 As shown, the excitation processing circuit consists of a power amplifier circuit and an RLC series resonant circuit. The power amplifier circuit uses a Class AB complementary power amplifier output circuit composed of N-MOS and P-MOS transistors, enabling the drain outputs of both to produce a square wave signal with a large current output capability. The RLC series resonant circuit maximizes the excitation signal power, and by adjusting the resonant frequency for matching, it outputs a sine / cosine excitation signal with the largest possible voltage. Figure 16 In the example shown, the square wave signal with a fixed frequency and duty cycle generated by the PWM module is output as a sine wave signal with a fixed frequency after passing through the power amplifier circuit and the RLC series resonant circuit.

[0150] In the present invention, a preset excitation signal is output to the excitation coil to generate an induction signal on the receiving coil that can sense the displacement of the rotor. Then, an ADC module is used for ADC sampling. The DC deviation, amplitude deviation, and phase deviation of the analog signal sampled by the ADC module are compensated and corrected by sine and cosine correction. This reduces the stringent requirements on the hardware processing such as clock, power supply, and electromagnetics for controlling the sampling rate of the ADC module, greatly improves the demodulation quality of the signal obtained by the receiving coil by the sampling method of the ADC module, prevents nonlinear distortion of the demodulated signal, and ensures the accuracy of position calculation.

[0151] In some embodiments, the acquisition unit 102 acquires the induced signal on the receiving coil to obtain the DSB signal of the receiving coil, including:

[0152] The acquisition unit 102 is further configured to acquire the induced signal on the receiving coil. The specific functions and processing of the acquisition unit 102 are further described in step S310.

[0153] The acquisition unit 102 is further configured to amplify the induced signal on the receiving coil to obtain the amplified induced signal on the receiving coil, which serves as the DSB signal of the receiving coil. The specific function and processing of the acquisition unit 102 are further described in step S320.

[0154] exist Figure 15 In the example shown, a signal amplification circuit is used to amplify the modulated DSB signal generated on the receiving coil, resulting in an amplified DSB signal, which is then used as the DSB signal of the receiving coil. The signal amplification circuit can employ a voltage operational amplifier or a differential operational amplifier to amplify the original signal by 2 to 3 times.

[0155] In the present invention, the induced signal on the receiving coil is obtained to obtain the DSB signal of the receiving coil, and then the ADC module is used for ADC sampling. Frequency domain correction and time interpolation are used to compensate for the sampling rate deviation of the ADC module, correct the sampling rate deviation of the ADC module, and greatly improve the demodulation quality and position calculation accuracy of the signal obtained by the receiving coil by the sampling method of the ADC module.

[0156] In some embodiments, the control unit 104 corrects the sampling signal of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC, thereby obtaining a corrected signal for the receiving coil, including:

[0157] The control unit 104 is further configured to perform sine and cosine correction on the sampled signal of the receiving coil to obtain the sine and cosine correction signal of the receiving coil. The specific functions and processing of the control unit 104 are further described in step S410.

[0158] The control unit 104 is further configured to perform frequency domain correction and time interpolation-based correction processing on the sine and cosine bias correction signals of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC, thereby obtaining the correction signal of the receiving coil. The specific functions and processing of this control unit 104 are further described in step S420.

[0159] like Figure 15As shown, the process of the real-time compensation method for sampling rate deviation includes:

[0160] Step 1: ADC module and sine / cosine correction:

[0161] DSB (Double Sideband Amplitude Modulation) signal is a linear modulation technique that achieves spectrum shifting by multiplying a baseband signal with a sinusoidal carrier. Its core feature is the complete suppression of the carrier component, retaining only the upper and lower sideband signals. By sampling the DSB signal at the same sampling rate as the excitation signal, a preliminary demodulated sine and cosine waveform is obtained, corresponding to… Figure 10 The signal shown is the modulated DSB signal obtained by the receiving coil. The acquired data is input into the sine and cosine correction module to correct deviations in DC, amplitude, and phase, eliminating the influence of signal deviations on subsequent corrections.

[0162] In step 1, the main chip outputs a PWM signal with a fixed high frequency (f0) and fixed duty cycle. This PWM signal passes through the excitation processing circuit, ultimately obtaining a sine and cosine excitation signal with a fixed frequency and high amplitude voltage. This signal then passes through the excitation coil on the stator of the inductive encoder, ultimately generating a high-frequency electromagnetic field. At this time, the moving disk of the inductive encoder rotates, and according to the eddy current effect, a high-frequency electromagnetic field is received at the receiving coil of the inductive encoder. Figure 10 The original modulated DSB signal is shown. This signal is amplified by a signal amplification circuit to obtain an amplified DSB signal, which is then input into the ADC module of the main chip. The main chip is configured to sample the signal at a sampling rate f0, which is the same frequency as the output PWM wave, for demodulation processing.

[0163] Since the sampling rate of the main chip's ADC module may have deviations, real-time correction and compensation of the sampling rate are required. Subsequently, in the main chip, sine and cosine correction, frequency domain correction, time interpolation, and signal evaluation methods according to the present invention are performed sequentially. When the sampled signal meets the requirements, the adjusted sampled signal is output, and position calculation is performed.

[0164] In step 1, sine and cosine correction compensates for the DC deviation, amplitude deviation, and phase deviation of the analog signal sampled by the ADC module, thereby improving the accuracy of the sampled values ​​and reducing the impact on subsequent compensation calculations. In the solution of this invention, by compensating for the DC deviation, amplitude deviation, and phase deviation of the analog signal sampled by the ADC module through sine and cosine correction, the stringent requirements on hardware processing such as clock, power supply, and electromagnetic parameters for controlling the sampling rate of the ADC module are reduced.

[0165] In some embodiments, the control unit 104 performs frequency domain correction and time interpolation-based correction processing on the sine and cosine bias correction signals of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC, thereby obtaining the corrected signal of the receiving coil, including:

[0166] The control unit 104 is further configured to perform frequency domain correction on the sine and cosine correction signals of the receiving coil to obtain the frequency domain correction signal of the receiving coil. The specific functions and processing of the control unit 104 are further described in step S510.

[0167] The control unit 104 is further configured to perform time interpolation processing on the frequency domain correction signal of the receiving coil to obtain the time interpolation signal of the receiving coil. The specific functions and processing of the control unit 104 are further described in step S520.

[0168] The control unit 104 is further configured to determine the difference between the time interpolation signal of the receiving coil and a preset target signal, and to determine whether the difference is within a set error range. The specific functions and processing of the control unit 104 are further described in step S530.

[0169] The control unit 104 is further configured to, if it is determined that the difference is within a set error range, determine the time interpolation signal of the receiving coil as the correction signal of the receiving coil, so as to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC. The specific functions and processing of the control unit 104 are further described in step S540.

[0170] The control unit 104 is further configured to return if it is determined that the difference is not within the set error range, so as to re-perform frequency domain correction on the sine and cosine correction signals of the receiving coil. The specific functions and processing of the control unit 104 are further described in step S550.

[0171] like Figure 15 As shown, the process of the real-time compensation method for sampling rate deviation also includes:

[0172] Step 2, frequency domain correction.

[0173] Step 3: Time interpolation.

[0174] Step 4, Signal Evaluation:

[0175] The corrected signal is analyzed in the time and frequency domains to evaluate the correction result. If the deviation is too large, the process returns to step 2, i.e., loops back to the frequency domain correction step, and is repeated until the requirements are met before proceeding to step 5. After frequency domain conversion, the spectrum can be analyzed to determine the frequency deviation between the analog signal frequency corresponding to the current actual rotational speed and the actual sampled value, thus revealing whether there is a deviation in the actual sampled value.

[0176] Step 5, Output the results:

[0177] After the calibration is passed, the position is finely calculated to obtain the precise position value. There are many methods for position fine-grained calculation. Since one revolution of the encoder consists of several cycles of sine and cosine signals, the main logic is to perform calculations such as arctangent on the compensated sine and cosine signals to obtain a unique angle value for one cycle, which is used as the result of the position fine-grained calculation.

[0178] This invention proposes an intelligent real-time compensation scheme for sampling rate deviation. It uses frequency domain correction and time interpolation to compensate for the sampling rate deviation of the ADC module, significantly improving the demodulation quality of the signal obtained from the receiving coil by the ADC module's sampling method. This prevents nonlinear distortion of the demodulated signal and ensures the accuracy of position calculation. Simultaneously, it effectively reduces the stringent requirements on hardware processing such as clock, power supply, and electromagnetic parameters.

[0179] In some embodiments, the control unit 104 performs frequency domain correction on the sine and cosine correction signals of the receiving coil to obtain a frequency domain correction signal for the receiving coil, including:

[0180] The control unit 104 is further configured to perform FFT processing on the sine and cosine correction signals of the receiving coil to obtain the frequency domain signal of the receiving coil. The specific functions and processing of the control unit 104 are further described in step S610.

[0181] The control unit 104 is further configured to use a filtering module with a cutoff frequency of half the preset target sampling rate to filter the frequency domain signal of the receiving coil, thereby obtaining the filtered signal of the receiving coil. The specific functions and processing of the control unit 104 are further described in step S620.

[0182] The control unit 104 is further configured to perform an inverse FFT transform on the filtered signal of the receiving coil to obtain the time-domain signal of the receiving coil, which serves as the frequency-domain correction signal for the receiving coil. The specific functions and processing of the control unit 104 are further described in step S630.

[0183] like Figure 15As shown, the flow of the real-time compensation sampling rate deviation method also includes: in step 2, frequency domain correction, as follows:

[0184] Step 21: Perform Fast Fourier Transform (FFT) processing on the above sampled values ​​to convert them from the time domain to the frequency domain for further processing.

[0185]

[0186] Where N is the number of sampled values, x[n] is the sampled value, and e is a natural number. Since spectrum analysis is required, the default number of sampled values ​​N is 100. Each correction uses the most recent 100 sampled values ​​for frequency domain analysis. n is the corresponding time signal in the time domain. k is the frequency after frequency domain transformation, and x[k] is the spectrum of the sampled value x[n] after Fast Fourier Transform. For details, please refer to the parameter definitions of Fourier Transform and Laplace Transform.

[0187] Step 22: Design a low-pass filter with a cutoff frequency of half the ideal sampling rate to filter the spectrum x[k], suppress the high-frequency aliasing components of the spectrum x[k], and align the sampling rate of the spectrum x[k] with the ideal sampling rate.

[0188] Let the filter be H(k), then the corrected spectrum y[k] is:

[0189] y[k]=H[k]*x[k] (2).

[0190] The corrected signal is subjected to an inverse fast fourier transform (IFFT) to recover the time-domain signal y[n].

[0191] In the solution of this invention, the sampling rate of the ADC module during inductor demodulation is compensated based on frequency domain correction, thereby improving the sampling rate accuracy of the ADC module and thus improving the demodulation quality of the signal obtained from the receiving coil.

[0192] In some embodiments, the control unit 104 performs time interpolation processing on the frequency domain correction signal of the receiving coil to obtain the time interpolation signal of the receiving coil. Specifically, the control unit 104 is further configured to perform sampling rate correction on the frequency domain correction signal of the receiving coil by interpolation using the Sinc function according to a preset target sampling period to obtain the time interpolation signal of the receiving coil.

[0193] like Figure 15 As shown, the process of the real-time compensation sampling rate deviation method also includes: In step 3, the time interpolation is as follows:

[0194] The time-series signal y[n] after frequency domain correction is subjected to signal time interpolation.

[0195] Assuming an ideal sampling period of 10, the latest three sampled values ​​before the current frequency domain corrected time difference are:

[0196]

[0197] In formula (3), result is the sampled value at the corresponding time point n, that is, 1401 is the sampled value of y

[20] . The sampling rate correction is achieved by interpolation using the Sinc function. The sampled value at time point 30 (that is, with a sampling period of 10, the next time point 30 after the time point 20 after the previous round of compensation) is inserted. The calculation method is as follows:

[0198] ①Calculation of the sinc function:

[0199] By interpolating the two most recent sampled values ​​from formula (4), we obtain the values ​​shown in formulas (5) and (6):

[0200]

[0201] ② Coefficient normalization:

[0202] The normalization factor is calculated to obtain formula (7):

[0203]

[0204] The coefficients obtained after normalization are as follows:

[0205] ω 28 =0.936*0.8547≈0.8 (8);

[0206] ω 38 =0.234*0.8547≈0.2 (9).

[0207] ③ Weighted summation:

[0208] y

[30] =ω 28 *y

[28] +ω 38 *y

[38] =0.8*1923+0.2*2522≈2043 (10).

[0209] Verification showed that after correction, the relative error with the ideal value of 2048 at time 30 was only 0.25%, indicating a significant improvement in accuracy. In this embodiment, the results were obtained by analyzing the actual measured experimental data. A 12-bit ADC module was used for sampling, and the sampled values ​​were obtained at t(20), t(28), and t(38), respectively. After compensation and correction, the sampled value at time t(30) could be obtained.

[0210] This process is repeated to correct the sampling rate deviation of the ADC module. By correcting the sampling rate deviation of the ADC module, thus... Figure 14 The demodulated signal shown has a bias, which can be compensated to become Figure 12 The ideal signal waveform is shown.

[0211] In the solution of this invention, the time interpolation-based optimization correction method compensates for the sampling rate of the ADC module during inductor demodulation, effectively avoiding nonlinear distortion of the demodulated signal and ensuring the accuracy of position calculation.

[0212] like Figure 15 As shown, in the main chip, the signal output from the first output terminal of the ADC module is synthesized by adaptive frequency and then output to the PWM module. The signal output from the second output terminal of the ADC module is subjected to sine and cosine correction, frequency domain correction, time interpolation, signal evaluation, and result output to obtain the position calculation result. The PWM module in the main chip outputs a square wave signal with a fixed frequency and duty cycle to the excitation processing circuit. The excitation processing circuit outputs a sine signal with a fixed frequency as the excitation signal and outputs it to the excitation coil. The excitation coil outputs a signal modulated by the eddy current effect to the receiving coil. The receiving coil outputs the modulated DSB signal to the signal amplification processing circuit. The signal amplification processing circuit outputs the amplified DSB signal to the ADC module in the main chip.

[0213] In the present invention, an optimized correction method based on frequency domain correction and time interpolation is used to compensate the sampling rate of the ADC module during inductive demodulation, thereby improving the demodulation quality and position calculation accuracy of operations such as demodulation of the received coil induced signal of the inductive encoder. This solves the problem of high sampling rate requirements of the ADC module in related solutions, thus improving the demodulation quality of the signal obtained from the received coil by the ADC module's sampling method, effectively avoiding nonlinear distortion of the demodulated signal, and ensuring the accuracy of position calculation.

[0214] Since the processing and functions implemented by the device in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned methods, any details not covered in the description of this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0215] According to an embodiment of the present invention, a motor control system corresponding to a demodulation device for an inductive encoder is also provided. This motor control system may include the demodulation device for the inductive encoder described above.

[0216] Since the processing and functions implemented by the motor control system in this embodiment are basically the same as those in the embodiments, principles and examples of the aforementioned device, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0217] According to an embodiment of the present invention, a computer program product corresponding to the demodulation method for an inductive encoder is also provided, comprising a computer program that, when executed by a processor, implements the steps of the demodulation method for the inductive encoder described above.

[0218] Since the processing and functions implemented by the product in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned methods, any details not covered in the description of this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0219] According to an embodiment of the present invention, a storage medium corresponding to a demodulation method for an inductive encoder is also provided. The storage medium includes a stored program, wherein, when the program is executed, the device where the storage medium is located executes the steps of the demodulation method for the inductive encoder described above.

[0220] Since the processing and functions implemented by the storage medium in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned methods, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0221] In summary, it is readily understood by those skilled in the art that, without conflict, the aforementioned advantageous methods can be freely combined and superimposed.

[0222] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A demodulation method for an inductive encoder, characterized in that, The inductive encoder has a stator section and a rotor section, and the stator section has an excitation coil and a receiving coil; The demodulation method of the inductive encoder includes: A preset excitation signal is output to the excitation coil to generate an induction signal on the receiving coil that can sense the displacement of the rotor portion; The induced signal on the receiving coil is acquired to obtain the DSB signal of the receiving coil; The DSB signal of the receiving coil is sampled by an ADC at a sampling rate that is the same as the preset excitation signal to obtain the sampled signal of the receiving coil. The sampled signal of the receiving coil is corrected to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, and the corrected signal of the receiving coil is obtained. The correction signal of the receiving coil is demodulated to obtain the detected value of the displacement of the rotor section.

2. The demodulation method for an inductive encoder according to claim 1, characterized in that, Outputting a preset excitation signal to the excitation coil to generate an induction signal on the receiving coil capable of sensing the displacement of the rotor portion, including: Output a square wave signal at a preset fixed frequency and fixed duty cycle; After power amplification and RLC series resonance processing of the square wave signal, a sinusoidal signal with a preset fixed frequency is obtained as a preset excitation signal; and the preset excitation signal is output to the excitation coil.

3. The demodulation method for an inductive encoder according to claim 1, characterized in that, Acquiring the induced signal on the receiving coil to obtain the DSB signal of the receiving coil includes: Acquire the induced signal on the receiving coil; The induced signal on the receiving coil is amplified to obtain the amplified induced signal on the receiving coil, which is used as the DSB signal of the receiving coil.

4. The demodulation method for an inductive encoder according to any one of claims 1 to 3, characterized in that, The sampled signal of the receiving coil is corrected to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by the ADC, resulting in a corrected signal for the receiving coil, including: The sampling signal of the receiving coil is subjected to sine and cosine correction to obtain the sine and cosine correction signal of the receiving coil; The sine and cosine correction signals of the receiving coil are subjected to correction processing based on frequency domain correction and time interpolation to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, so as to obtain the correction signal of the receiving coil.

5. The demodulation method for an inductive encoder according to claim 4, characterized in that, The sine and cosine bias correction signals of the receiving coil are subjected to correction processing based on frequency domain correction and time interpolation to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, resulting in a corrected signal for the receiving coil, including: The sine and cosine correction signals of the receiving coil are frequency domain corrected to obtain the frequency domain corrected signal of the receiving coil. The frequency domain correction signal of the receiving coil is subjected to time interpolation processing to obtain the time interpolation signal of the receiving coil; Determine the difference between the time interpolation signal of the receiving coil and the preset target signal, and determine whether the difference is within the set error range; If the difference is determined to be within the set error range, then the time interpolation signal of the receiving coil is determined to be the correction signal of the receiving coil to compensate for the deviation of the sampling rate when the DSB signal of the receiving coil is sampled by ADC. If it is determined that the difference is not within the set error range, the process returns to perform frequency domain correction on the sine and cosine correction signals of the receiving coil again.

6. The demodulation method for an inductive encoder according to claim 5, characterized in that, The frequency domain correction signal of the receiving coil is obtained by performing frequency domain correction on the sine and cosine bias correction signals of the receiving coil, including: The sine and cosine correction signals of the receiving coil are processed by FFT to obtain the frequency domain signal of the receiving coil. A filtering module with a cutoff frequency of half the preset target sampling rate is used to filter the frequency domain signal of the receiving coil to obtain the filtered signal of the receiving coil. The filtered signal of the receiving coil is subjected to an inverse FFT to obtain the time-domain signal of the receiving coil, which is used as the frequency-domain correction signal of the receiving coil.

7. The demodulation method for an inductive encoder according to claim 5, characterized in that, The frequency domain correction signal of the receiving coil is subjected to time interpolation processing to obtain the time interpolation signal of the receiving coil, including: According to the preset target sampling period, the sampling rate of the frequency domain correction signal of the receiving coil is corrected by interpolation using the Sinc function to obtain the time interpolation signal of the receiving coil.

8. A demodulation device for an inductive encoder, characterized in that, The inductive encoder has a stator section and a rotor section, and the stator section has an excitation coil and a receiving coil; The demodulation device for the inductive encoder includes: The control unit is configured to output a preset excitation signal to the excitation coil to generate a sensing signal on the receiving coil that can sense the displacement of the rotor portion. The acquisition unit is configured to acquire the induced signal on the receiving coil to obtain the DSB signal of the receiving coil; The control unit is further configured to perform ADC sampling on the DSB signal of the receiving coil at a sampling rate with the same frequency as the preset excitation signal, so as to obtain the sampling signal of the receiving coil. The control unit is further configured to correct the sampling signal of the receiving coil to compensate for the sampling rate deviation when the DSB signal of the receiving coil is sampled by ADC, so as to obtain the corrected signal of the receiving coil. The control unit is further configured to demodulate the correction signal of the receiving coil to obtain the detected value of the displacement of the rotor portion.

9. A motor control system, characterized in that, include: The demodulation device for the inductive encoder as described in claim 8.

10. A storage medium, characterized in that, The storage medium includes a stored program, wherein, when the program is executed, it controls the device containing the storage medium to perform the demodulation method of the inductive encoder as described in any one of claims 1 to 7.

11. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the demodulation method of the inductive encoder as described in any one of claims 1 to 7.

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