Wireless communication phase-locked double-point sampling rotary transformer decoding system

Abstract

The invention discloses a wireless communication phase-locked double-point sampling rotary transformer decoding system, and relates to a software decoding method, a decoding circuit and an online monitoring system of a rotary transformer, and the system comprises an MCU controller, an excitation amplification circuit, a power amplification circuit, a voltage raising and voltage reducing and dividing circuit, a signal conditioning circuit and an NB-IoT communication module. The system has the following functions: a phase compensation scheme is adopted to achieve phase locking of sine and cosine wave cluster modulation signals and excitation signals, so that the information sampling position is more accurate; a double-point sampling enhanced decoding method is adopted, so that the influence of offset fluctuation of sine and cosine envelope signals on position estimation can be eliminated, and the amplitude of an effective signal is increased; on-line monitoring of the electrical angle information of the motor rotor is realized by adopting NB-IoT communication. According to the system, the MCU is matched with a common circuit for software decoding, the defects that a special decoding chip is high in cost and poor in universality are overcome, the decoding precision of the rotary transformer is improved, and online data monitoring is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of rotary transformers, and in particular to a phase-locked dual-point sampling rotary transformer decoding system for wireless communication. Background Art

[0002] With the rapid development of the automotive electronics industry, industrial robots, smart medical and other industries, the applications involved are aimed at high precision, low cost and high stability to achieve the integration of sensing and control of the sensing unit and the execution unit. Therefore, it is crucial to design a high-precision, online monitoring angle sensing system. Commonly used angle sensing systems include photoelectric encoders, Hall encoders and resolvers. Among them, resolvers are widely used due to their strong vibration resistance and high detection accuracy. At present, the usual decoding solution for resolvers is to use a dedicated decoding chip, which integrates excitation generation, signal conditioning and signal decoding. It is widely used, but this part of the dedicated chip is often out of supply and has a high price. Therefore, this design uses separate devices to build a decoding system, but while reducing costs, there are also the following problems:

[0003] In the decoding system built with separate devices, due to the existence of filtering and amplitude modulation circuits, phase lag is inevitably introduced, which will cause a phase difference between the excitation signal of the rotary transformer and the sine and cosine wave cluster modulation signal, and then the sampling point deviates from the peak or valley when the ADC of the MCU is sampled, resulting in insufficient solution accuracy. Therefore, a phase compensation solution is needed to adaptively adjust the phase compensation reference signal of an analog excitation signal according to the output signal, and lock the peak and valley positions of the sine and cosine wave cluster modulation signals through the phase compensation reference signal without affecting the input of the excitation signal.

[0004] Secondly, in the decoding system built with separate devices, the sine and cosine envelopes containing the rotor position information are usually extracted by performing a single peak sampling in a high-frequency excitation cycle, and then subtracting the bias measured before power-on to obtain the envelope. However, there are a lot of errors in this process, including bias drift, amplitude difference, and harmonic interference. Therefore, a method needs to be designed to avoid errors as much as possible and improve the signal-to-noise ratio and data sampling accuracy.

[0005] Finally, since rotary transformers are all wired products in actual use, there are space limitations for reading the measured angle information, and it is difficult to save historical data and implement over-limit warning functions. At the same time, as a type of electromagnetic sensor, the rotor winding as the secondary side of the transformer will inevitably cause electromagnetic interference to wireless communication during operation. Therefore, how to deal with the interference between wireless communication and rotary transformers is an important direction.

[0006] In view of the above, it is necessary to propose a solution to improve one or more problems existing in the above-mentioned related technical solutions.

[0007] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0008] In view of the defects existing in the prior art, the purpose of the present invention is to achieve the above purpose. The present invention provides a phase-locked dual-point sampling rotary transformer decoding system for wireless communication, which involves a software decoding method, a decoding circuit and an online monitoring system for a rotary transformer. The system includes an MCU controller, an excitation amplifier circuit, a power amplifier circuit, a voltage boost and voltage-down divider circuit, a signal conditioning circuit and an NB-IoT communication module. The system functions include: a phase compensation scheme is adopted to achieve phase locking between the sine and cosine wave cluster modulation signals and the excitation signal, thereby making the information sampling position more accurate; a dual-point sampling enhanced decoding method is adopted to eliminate the influence of the bias fluctuation of the sine and cosine envelope signals on the position estimation, and to increase the amplitude of the effective signal; and NB-IoT communication is used to realize online monitoring of the electrical angle information of the motor rotor. The system disclosed in the present invention uses MCU in conjunction with common circuits for software decoding, which solves the shortcomings of high cost and weak versatility of dedicated decoding chips, improves the decoding accuracy of rotary transformers, and achieves online data monitoring.

[0009] The purpose of the present invention is achieved through the following technical solutions, in conjunction with the accompanying drawings:

[0010] A phase-locked dual-point sampling rotary transformer decoding system for wireless communication, characterized by comprising:

[0011] MCU controller, used for the generation of SPWM excitation signal and phase compensation reference signal, phase difference detection and phase compensation, signal sampling and decoding, and configuration of wireless communication module;

[0012] The excitation amplifier circuit is used to perform low-pass filtering, signal amplification, limit protection and buffering on the dual-channel SPWM signals output by the MCU;

[0013] A power amplifier circuit is used to amplify the power of the excitation signal in the form of sine and cosine to meet the needs of the rotary transformer;

[0014] The voltage boost and voltage-down divider circuit is used to boost the voltage and scale the amplitude of the two sets of dual-channel differential signals output by the rotary transformer to reach the ADC acquisition range of the MCU;

[0015] The signal conditioning circuit is used to perform low-pass filtering on the differential signal and convert the differential signal into a stable single-ended signal.

[0016] The NB-IoT communication module is connected to the MCU through the serial port, which is used to upload the decoded information to the OneNET cloud platform and provide visual monitoring and early warning functions.

[0017] Preferably, the excitation amplifier circuit comprises:

[0018] R1, R2 and C1 form an RC low-pass filter to remove the high-frequency components of the SPWM excitation signal and convert it into a smooth sine wave form;

[0019] Operational amplifier IC1A and its surrounding resistors R3, R4, R5 and R6 form a signal amplifier and apply a voltage offset to amplify the input signal;

[0020] The circuit protection is provided by two double diodes D1 and D2 to prevent T1A and T1B from being turned on at the same time and causing the tube to explode;

[0021] The totem pole output stage formed by T1A and T1B further buffers the current of the excitation signal, ensuring that the signal remains stable when driving the load.

[0022] Preferably, the signal conditioning circuit comprises:

[0023] The common-mode interference filter circuit composed of R21, C22 and R22, C21, and the differential-mode interference filter circuit composed of R21, R22 and C23 together form an RC filter network, which can effectively filter out high-frequency common-mode and differential-mode interference signals;

[0024] The next circuit consists of R23, R24, R25, R26, C24, C25 and an operational amplifier, which is used for differential-to-single-ended subtraction operations, and converts the sine and cosine differential signals into single-ended outputs through differential ratio calculations;

[0025] The positive input of the op amp is connected in parallel by R25 and R24 and then combined with C24 to form a first-order RC low-pass filter, which further low-passes the input signal and reduces noise interference in the output;

[0026] The output of the op amp is connected to a resistor divider and filter circuit consisting of R27, R28 and C26. Its main function is to further accurately control the single-ended signal within the ADC sampling range of 0 to 3.3V, thereby obtaining the final sine-cosine wave cluster modulation signals sin_out and cos_out. The expressions are as follows:

[0027]

[0028] Where U sin_out , U cos_outU is a sine and cosine signal containing rotor position information. Its frequency is consistent with the excitation signal frequency, and its amplitude is in a sine and cosine relationship with the rotor position. e is the signal amplitude after the conditioning circuit processes; u na 、u nb They are the sum of the bias of the positive and cosine signals respectively. The bias comes from the bias of the transformer itself during installation and use, the circuit bias caused by the non-isolated circuit structure, and the common-mode interference between the positive and cosine input signals.

[0029] Preferably, the MCU controller includes a phase compensation module and a decoding module; the phase compensation module captures the rising edge information of the input square wave signal through the MCU's ADC2_CH2, and then compares it with the rising edge information of the phase compensation reference signal captured through the MCU's ADC2_CH1 to obtain the phase difference, and compensates the phase difference information to the phase compensation reference signal of TM1_CH4 to achieve the phase locking function; the decoding module is responsible for A / D sampling of the sine and cosine wave cluster modulation signals sin-out / cos-out using a dual-point sampling enhanced decoding method, extracting its envelope information, and then calculating the rotor mechanical angle information through the signal demodulation algorithm of the second-order state observer, and converting it into rotor electrical angle information.

[0030] Preferably, the phase compensation module comprises an operational amplifier in comparison mode, which is used to convert the sine wave cluster modulation signal sin-out into a square wave signal and provide it to ADC2_CH2 of the MCU for capture.

[0031] Preferably, the decoding module includes a two-point sampling enhanced decoding method and a signal demodulation algorithm based on a second-order state observer; the two-point sampling enhanced decoding method is used to track and sample the sine and cosine wave cluster modulation signal information and extract its envelope; the signal demodulation algorithm based on the second-order state observer is used to calculate the position information from the envelope.

[0032] Preferably, the dual-point sampling enhanced decoding method comprises:

[0033] In order to suppress the influence of bias voltage fluctuation on position decoding, the peak and trough of the sine and cosine wave cluster modulation signals are sampled within the phase compensation reference signal period after phase locking. The double-point sampling enhanced decoding method samples the sine and cosine signals at the peak as follows:

[0034]

[0035] Where, t max Indicates the fixed peak sampling time in each cycle;

[0036] The sine and cosine signals sampled at the trough are:

[0037]

[0038] The peak and trough phases differ by half a period of the phase compensation reference signal, so:

[0039]

[0040] Where, T compensate is the phase compensation reference signal period after phase locking;

[0041] By trigonometric transformation we can get:

[0042] A ADC = sin(ωt max )=-sin(ωt min )

[0043] After the difference processing of the peak and trough signals of the two collected sine and cosine signals, we can get:

[0044]

[0045] Preferably, the signal demodulation algorithm based on the second-order state observer includes:

[0046] by is the state equation, is the measurement equation, then the basic form of the second-order state observer is:

[0047]

[0048] In the formula, and is the estimated value of the motor rotor position and speed; k θ , k ω are all observer gains greater than zero;

[0049] set up Then there is an error equation:

[0050]

[0051] By first approximation at the origin of the coordinate system, the Jacobian coefficient matrix of the linearized system can be obtained as:

[0052]

[0053] The characteristic equation of matrix A is:

[0054] λ 2 +k θ λ+k ω =0

[0055] Because k θ , kω are all greater than zero, and it is clear that the eigenvalues ​​of A all have negative real parts. According to Lyapunov's first method, the zero solution of the error equation is asymptotically stable, that is, the output of the second-order state observer can approach the true value with zero error. According to the requirements of stability and rapidity, the two characteristic roots of the characteristic equation are selected as λ1 and λ2, and the observer gain coefficient can be determined as In order to enable MCU to solve the problem, T compensate is the sampling period, the basic form of the observer can be discretized as:

[0056]

[0057] In the formula, and t = jT compensate Angle and angular velocity estimates at time instant.

[0058] Preferably, the NB-IoT communication module includes a BC20 module and a OneNET cloud platform; the BC20 module is configured through the serial port of the MCU, and the device is connected to the OneNET cloud platform using relevant AT commands and data is reported; the OneNET cloud platform provides data visualization View 3.0 service, and the present invention completes the display application construction through this service to realize the visualization display function of the web and mobile terminals.

[0059] On the basis of the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0060] The present invention provides a phase-locked dual-point sampling rotary transformer decoding system for wireless communication, which abandons the dedicated decoding chip solution, adopts separation devices to build the decoding system, takes MCU as the main control, and is supplemented by conditioning circuits and communication modules to realize online detection of angle information, thereby solving the shortcomings of high cost and weak versatility of dedicated decoding chips, improving the decoding accuracy of the rotary transformer, and achieving online data monitoring.

[0061] A phase compensation scheme is adopted to achieve phase locking between the sine and cosine wave cluster modulation signals and the excitation signal, thereby making the information sampling position more accurate.

[0062] The dual-point sampling enhanced decoding method is adopted to eliminate the influence of the bias fluctuation of the sine and cosine envelope signals on the position estimation and increase the amplitude of the effective signal.

[0063] NB-IoT communication is used to realize online monitoring of the electrical angle information of the motor rotor. Thanks to the narrow bandwidth and extremely low signal-to-noise ratio of NB-IoT communication, the electromagnetic interference of the rotor winding as the secondary side of the transformer on the wireless communication data transmission during operation is avoided to the greatest extent, and the historical data preservation and over-limit warning functions are realized based on the OneNET cloud platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0065] Figure 1 It is a structural schematic block diagram of a phase-locked dual-point sampling rotary transformer decoding system for wireless communication according to the present invention;

[0066] Figure 2 It is an excitation amplification circuit diagram of an implementation scheme of the present invention;

[0067] Figure 3 A power amplifier circuit diagram of an implementation scheme of the present invention;

[0068] Figure 4 A voltage boosting and voltage reducing circuit diagram of an implementation scheme of the present invention;

[0069] Figure 5 A signal conditioning circuit diagram for an embodiment of the present invention;

[0070] Figure 6 A block diagram of a second-order state observer according to an embodiment of the present invention;

[0071] Figure 7 It is a schematic diagram of the single sampling method and the double-point sampling enhanced decoding method;

[0072] Figure 8 The waveform diagram of the phase compensation reference signal and the sine and cosine wave cluster modulation signal obtained in the present invention in this solution;

[0073] Fig. 9 The envelope waveform diagram obtained by the double-point sampling enhanced decoding method measured in the experiment of the present invention; DETAILED DESCRIPTION

[0074] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0075] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0076] It should be noted that the parameter data of the components involved in the circuit should be specifically set according to the actual application requirements and are not specifically limited in this application.

[0077] like Figures 1 to 6 As shown, a phase-locked dual-point sampling rotary transformer decoding system for wireless communication includes:

[0078] MCU controller, used to generate dual complementary SPWM signals and one PWM signal with the same frequency and phase as the excitation signal exc-out, which are used as output dual excitation signals and one phase compensation reference signal respectively. It is also used for phase compensation, signal sampling and decoding, and configuration of wireless communication module;

[0079] The excitation amplifier circuit is used to perform low-pass filtering, signal amplification, limit protection and buffering on the dual-channel SPWM signals output by the MCU to generate dual-channel smooth and stable excitation signals in the form of sine and cosine;

[0080] The power amplifier circuit is used to amplify the excitation signal in the form of sine and cosine to meet the input requirements of the rotary transformer. The first-level voltage amplification is completed by the in-phase proportional amplifier circuit composed of the operational amplifier LM324, and the amplification factor is (1+RF / R11). The second-level power amplification is completed by the voltage follower composed of the power amplifier OPA547, which not only improves the load capacity, but also isolates the load circuit from the front-end circuit, so that the front-end circuit is not interfered by the load;

[0081] The voltage boost and voltage-down divider circuit is used to scale the amplitude of the two sets of dual-channel differential signals output by the resolver, increase the center voltage from 0V to 1.8V, and scale the amplitude to the classic value of about 3.3V to reach the ADC acquisition range of the MCU;

[0082] The signal conditioning circuit is used to perform low-pass filtering on the differential signal and convert the differential signal into a stable single-ended signal.

[0083] The NB-IoT communication module is connected to the MCU through the serial port, which is used to upload the decoded information to the OneNET cloud platform and provide visual monitoring and early warning functions.

[0084] Furthermore, the excitation amplifier circuit comprises:

[0085] R1, R2 and C1 form an RC low-pass filter to remove the high-frequency components of the SPWM excitation signal and convert it into a smooth sine wave form;

[0086] Operational amplifier IC1A and its surrounding resistors R3, R4, R5 and R6 form a signal amplifier and apply a voltage offset to amplify the input signal;

[0087] The circuit protection is provided by two double diodes D1 and D2 to prevent T1A and T1B from being turned on at the same time and causing the tube to explode;

[0088] The totem pole output stage formed by T1A and T1B further buffers the current of the excitation signal, ensuring that the signal remains stable when driving the load.

[0089] Furthermore, the signal conditioning circuit comprises:

[0090] The common mode interference filter composed of R21, C22 and R22, C21, and the differential mode interference filter composed of R21, R22 and C23 together constitute an RC filter circuit, which can filter out high-frequency common and differential mode interference signals;

[0091] The latter stage consists of R23, R24, R25, R26, C24, C25 and an op amp to form a differential-to-single-ended subtraction circuit, which converts the sine and cosine differential signals into single-ended signals through differential proportional operations;

[0092] The positive terminal of the operational amplifier is connected in parallel by R25 and R24, and then forms an RC first-order low-pass filter circuit with C24 to perform a low-pass filter on the input signal again, further reducing the output signal noise;

[0093] The output of the op amp is connected to a resistor divider circuit and a filter circuit composed of R27, R28, and C26. Its function is to further stabilize the single-ended signal within the ADC sampling range of 0 to 3.3V, and finally obtain the sine and cosine wave cluster modulation signal sin_out / cos_out, which is expressed as follows:

[0094]

[0095] Where U sin_out , U cos_out U is a sine and cosine signal containing rotor position information. Its frequency is consistent with the excitation signal frequency, and its amplitude is in a sine and cosine relationship with the rotor position. e is the signal amplitude after the conditioning circuit processes; u na 、u nbThey are the sum of the bias of the positive and cosine signals respectively. The bias comes from the bias of the transformer itself during installation and use, the circuit bias caused by the non-isolated circuit structure, and the common-mode interference between the positive and cosine input signals.

[0096] Furthermore, the MCU controller includes a phase compensation module and a decoding module; the phase compensation module captures the rising edge information of the input square wave signal through the ADC2_CH2 of the MCU, and then compares it with the rising edge information of the phase compensation reference signal captured through the ADC2_CH1 of the MCU to obtain the phase difference, and compensates the phase difference information to the phase compensation reference signal of TM1_CH4 to achieve the phase locking function; the decoding module is responsible for A / D sampling of the sine and cosine wave cluster modulation signals sin-out / cos-out using the dual-point sampling enhanced decoding method, extracting its envelope information, and then calculating the rotor mechanical angle information through the signal demodulation algorithm of the second-order state observer, and converting it into rotor electrical angle information.

[0097] Furthermore, the phase compensation module includes an operational amplifier in comparison mode, which is used to convert the sine wave cluster modulation signal sin-out into a square wave signal and provide it to ADC2_CH2 of the MCU for capture.

[0098] Furthermore, the decoding module includes a two-point sampling enhanced decoding method and a signal demodulation algorithm based on a second-order state observer; the two-point sampling enhanced decoding method is used to track the sampled sine and cosine wave cluster modulation signal information and extract its envelope; the signal demodulation algorithm based on the second-order state observer is used to calculate the position information from the envelope.

[0099] Furthermore, the dual-point sampling enhanced decoding method includes:

[0100] In order to suppress the influence of bias voltage fluctuation on position decoding, the peak and trough of the sine and cosine wave cluster modulation signals are sampled within the phase compensation reference signal period after phase locking. The double-point sampling enhanced decoding method samples the sine and cosine signals at the peak as follows:

[0101]

[0102] Where, t max Indicates the fixed peak sampling time in each cycle;

[0103] The sine and cosine signals sampled at the trough are:

[0104]

[0105] The peak and trough phases differ by half a period of the phase compensation reference signal, so:

[0106]

[0107] Where, T compensate is the phase compensation reference signal period after phase locking;

[0108] By trigonometric transformation we can get:

[0109] A ADC = sin(ωt max )=-sin(ωt min )

[0110] After the difference processing of the peak and trough signals of the two collected sine and cosine signals, we can get:

[0111]

[0112] Furthermore, the signal demodulation algorithm based on the second-order state observer includes:

[0113] by is the state equation, is the measurement equation, then the basic form of the second-order state observer is:

[0114]

[0115] In the formula, and is the estimated value of the motor rotor position and speed; k θ , k ω are all observer gains greater than zero;

[0116] set up Then there is an error equation:

[0117]

[0118] By first approximation at the origin of the coordinate system, the Jacobian coefficient matrix of the linearized system can be obtained as:

[0119]

[0120] The characteristic equation of matrix A is:

[0121] λ 2 +k θ λ+k ω =0

[0122] Because k θ , k ωare all greater than zero, and it is clear that the eigenvalues ​​of A all have negative real parts. According to Lyapunov's first method, the zero solution of the error equation is asymptotically stable, that is, the output of the second-order state observer can approach the true value with zero error. According to the requirements of stability and rapidity, the two characteristic roots of the characteristic equation are selected as λ1 and λ2, and the observer gain coefficient can be determined as In order to enable MCU to solve the problem, T compensate is the sampling period, the basic form of the observer can be discretized as:

[0123]

[0124] In the formula, and t = jT compensate Angle and angular velocity estimates at time instant.

[0125] Furthermore, the NB-IoT communication module includes a BC20 module and a OneNET cloud platform; the BC20 module is configured through the serial port of the MCU, and the device is connected to the OneNET cloud platform using relevant AT commands, and the LwM2M protocol is used in conjunction with the OneNET API to implement relevant functions, including adding / deleting objects, sending / reading data, and responding to subscription / reading / writing / execution requests; the OneNET cloud platform provides a data visualization View 3.0 service, and the present invention completes the display application construction through this service. First, the uploaded data is configured with a data filter, and then the component is bound to the data source and the warning value is configured. After completion, the display application generates a static URL code, and the visualization display function of the web and mobile terminals can be realized.

[0126] Example

[0127] A wireless communication phase-locked dual-point sampling rotary transformer decoding system can replace the decoding system composed of a dedicated decoding chip, and achieve online monitoring and over-limit warning with data visualization. In addition, in view of the insufficient accuracy of the existing decoding system based on separation devices, a phase compensation scheme and a dual-point sampling enhanced decoding algorithm are proposed to make the sampling more accurate and minimize the influence of bias fluctuations on the sampling results.

[0128] The specific process of decoding using the decoding system of the present invention is as follows:

[0129] Based on the pulse impulse area equivalence principle, the MCU generates dual SPWM signals to form the input excitation signal form of the resolver. Because it is generated by the MCU timer, it is convenient for us to adjust the frequency according to the actual needs of the resolver. At the same time, the MCU generates a phase compensation reference signal, which is a sinusoidal signal with the same frequency as SPWMp. Because it is generated by the same timer, the phase can be kept consistent.

[0130] The dual-channel SPWM signal is connected to the excitation amplifier circuit, which performs low-pass filtering on the SPWM waveform, removes the high-frequency part to obtain a smooth sinusoidal excitation signal, and then amplifies and buffers the signal to obtain exc-out+ / exc-out-;

[0131] exc-out+ / exc-out- are connected to a power amplifier circuit, and after a primary voltage amplification and a secondary power amplification, exc+ / exc- are obtained, which improves the load capacity and meets the input requirements of the rotary transformer.

[0132] At this time, differential signals sin+ / sin- and cos+ / cos- will be obtained at the output winding end of the rotary transformer. The four signals first enter the voltage boost and voltage step-down divider circuit to increase the center voltage and scale the amplitude to reach the ADC voltage acquisition range of the MCU.

[0133] The processed signal will then enter the signal conditioning circuit, and after filtering, it will be converted from differential to single-ended signal to obtain sin-out and cos-out, and further voltage stabilization will be performed here to ensure that the signal level range at this time is within the ADC voltage acquisition range of the MCU and will not damage the main control hardware.

[0134] At the same time, sin-out will be divided into one path and enter the comparator. The setting of the comparator reference voltage is the same as the center voltage set in the voltage boost and step-down voltage divider circuit. After processing, sin-out will be converted into a square wave signal and provided to the MCU for capture. The MCU will measure the phase of this signal and the phase compensation reference signal to obtain the phase difference, and compensate this phase difference value to the phase compensation reference signal to achieve the phase locking function.

[0135] Inside the MCU, the system uses a dual-point sampling enhanced decoding method to sample the peak and valley values ​​of sin-out and cos-out according to the period of the phase compensation reference signal after phase compensation, and obtain the information of the envelope signal, thereby solving the sin-solve and cos-solve containing the rotor position information. The signal information will then be substituted into the signal demodulation algorithm based on the second-order state observer, and the rotor electrical angle will be obtained after calculation.

[0136] After that, the rotor electrical angle will be sent to the BC20 module through the serial port of the MCU. The BC20 module connects to the OneNET cloud platform through AT commands, creates objects based on the LwM2M protocol and sends data. At this time, the electrical angle information can be seen on the OneNET cloud platform.

[0137] Finally, since this embodiment needs to realize the online viewing function of the mobile terminal, a data visualization View 3.0 service is created on the OneNET cloud platform, and relevant data filters are configured, data sources are bound, over-limit thresholds are set, and interface styles are set. Finally, the display application generates a static URL code, thereby realizing the visualization display function of the web and mobile terminals.

[0138] Figure 1 The system block diagram is given, which can be simply seen as four parts: communication part, MCU controller, level conversion part, and rotary transformer. The MCU controller is responsible for signal generation, software decoding and phase compensation functions, and the level conversion part includes Figures 2 to 5 The four circuits are responsible for excitation signal filtering, excitation signal power amplification, resolver feedback signal voltage boosting and voltage reduction and resolver feedback signal signal conditioning.

[0139] Figure 2 A circuit is given to convert an SPWM waveform into a smooth sine wave. The circuit takes SPWMp as input, passes it through a low-pass filter (set by R2 and C1), amplifies the voltage (set by resistors R1 and R2), applies a voltage offset (set by resistors R3 and R4), and finally uses a totem pole output stage (composed of T1A and T1B) to buffer the current of the excitation signal. The SPWMn signal is processed in the same way as the SPWMp signal, and the circuit structure used is the same.

[0140] Figure 3 It is a typical power amplifier circuit. The first-stage voltage amplifier composed of LM324 is responsible for amplifying the voltage by (1+RF / R11) times, so that the peak-to-peak value of the excitation signal reaches the input requirement of the rotary transformer; the second-stage power amplifier composed of OPA547 is responsible for improving the current driving capability, and its maximum output current can reach 1A. In addition, this part can also be used as a signal buffer to prevent the previous stage circuit from interfering with the load.

[0141] Figure 4 It is a typical level-lifting and voltage-dropping circuit, which raises the center voltage of the feedback signal of the rotary transformer to a suitable voltage value (set by the voltage-divider network composed of R15, R16 and R17 for the +5V power supply), and then R18 and R19 form a resistor divider to reduce the voltage by R19 / (R19+R18) times.

[0142] Figure 5A composite circuit structure is given to realize common mode interference suppression, low-pass filtering, differential to single-ended conversion and voltage division, which ensures that the ADC can collect a relatively pure sinusoidal signal. The processing method of cos+ / cos- signal is the same as that of sin+ / sin- signal, and the circuit structure used is the same.

[0143] In the embodiment, the relationship between the phase compensation reference signal processed inside the MCU and the sine and cosine wave cluster modulation signal is as follows: Figure 8 As shown, the MCU obtains the envelope waveform through the dual-point sampling enhanced decoding method as shown in Fig. 9 shown.

[0144] It should be pointed out that the excitation signal parameters used in this embodiment are 400Hz / 26Vrms, the rotary transformer transformation ratio is 0.5, and the pole pair number is 1:16, but this does not mean that the present invention is only applicable to this type of rotary transformer. Figures 2 to 6 The parameters and component selection should be configured according to actual needs, and thus be applicable to all forms of rotary transformers. Finally, the above embodiments and drawings do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the scope of the patent of the present invention.

Claims

1. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication, characterized in that: include: MCU controller, used for the generation of SPWM excitation signal and phase compensation reference signal, phase difference detection and phase compensation, signal sampling and decoding, and configuration of wireless communication module; The excitation amplifier circuit is used to perform low-pass filtering, signal amplification, limit protection and buffering on the dual-channel SPWM signals output by the MCU; A power amplifier circuit is used to amplify the power of the excitation signal in the form of sine and cosine to meet the needs of the rotary transformer; The voltage boost and voltage-down divider circuit is used to boost the voltage and scale the amplitude of the two sets of dual-channel differential signals output by the rotary transformer to reach the ADC acquisition range of the MCU; A signal conditioning circuit is used to perform low-pass filtering on the differential signal and convert the differential signal into a stable single-ended signal; The NB-IoT communication module is connected to the MCU through the serial port, which is used to upload the decoded information to the OneNET cloud platform and provide visual monitoring and early warning functions.

2. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 1, characterized in that: The excitation amplifier circuit comprises: R1, R2 and C1 form an RC low-pass filter to remove the high-frequency components of the SPWM excitation signal and convert it into a smooth sine wave form; Operational amplifier IC1A and its surrounding resistors R3, R4, R5 and R6 form a signal amplifier and apply a voltage offset to amplify the input signal; The circuit protection is provided by two double diodes D1 and D2 to prevent T1A and T1B from being turned on at the same time and causing the tube to explode; The totem pole output stage formed by T1A and T1B further buffers the current of the excitation signal, ensuring that the signal remains stable when driving the load.

3. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 1, characterized in that: The signal conditioning circuit comprises: The common-mode interference filter circuit composed of R21, C22 and R22, C21, and the differential-mode interference filter circuit composed of R21, R22 and C23 together form an RC filter network, which can effectively filter out high-frequency common-mode and differential-mode interference signals; The next circuit consists of R23, R24, R25, R26, C24, C25 and an operational amplifier, which is used for differential-to-single-ended subtraction operations, and converts the sine and cosine differential signals into single-ended outputs through differential ratio calculations; The positive input of the op amp is connected in parallel by R25 and R24 and then combined with C24 to form a first-order RC low-pass filter, which further low-passes the input signal and reduces noise interference in the output; The output of the op amp is connected to a resistor divider and filter circuit consisting of R27, R28 and C26. Its main function is to further accurately control the single-ended signal within the ADC sampling range of 0 to 3.3V, thereby obtaining the final sine-cosine wave cluster modulation signals sin_out and cos_out. The expressions are as follows: Where U sin_out , U cos_out U is a sine and cosine signal containing rotor position information. Its frequency is consistent with the excitation signal frequency, and its amplitude is in a sine and cosine relationship with the rotor position. e is the signal amplitude after the conditioning circuit processes; u na 、u nb They are the sum of the bias of the positive and cosine signals respectively. The bias comes from the bias of the transformer itself during installation and use, the circuit bias caused by the non-isolated circuit structure, and the common-mode interference between the positive and cosine input signals.

4. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 1, characterized in that: The MCU controller includes a phase compensation module and a decoding module; the phase compensation module captures the rising edge information of the input square wave signal through the MCU's ADC2_CH2, and then compares it with the rising edge information of the phase compensation reference signal captured through the MCU's ADC2_CH1 to obtain the phase difference, and compensates the phase difference information to the phase compensation reference signal of TM1_CH4 to achieve the phase locking function; the decoding module is responsible for A / D sampling of the sine and cosine wave cluster modulation signals sin-out / cos-out using a dual-point sampling enhanced decoding method, extracting its envelope information, and then calculating the rotor mechanical angle information through the signal demodulation algorithm of the second-order state observer, and converting it into rotor electrical angle information.

5. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 4, characterized in that: The phase compensation module includes an operational amplifier in comparison mode, which is used to convert the sine wave cluster modulation signal sin-out into a square wave signal and provide it to ADC2_CH2 of the MCU for capture.

6. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 4, characterized in that: The decoding module includes a dual-point sampling enhanced decoding method and a signal demodulation algorithm based on a second-order state observer; the dual-point sampling enhanced decoding method is used to track and sample the sine and cosine wave cluster modulation signal information and extract its envelope; The signal demodulation algorithm based on the second-order state observer is used to calculate the position information from the envelope.

7. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 6, characterized in that: The dual-point sampling enhanced decoding method comprises: In order to suppress the influence of bias voltage fluctuation on position decoding, the peak and trough of the sine and cosine wave cluster modulation signals are sampled within the phase compensation reference signal period after phase locking; the double-point sampling enhanced decoding method samples the sine and cosine signals at the peak as follows: Where, t max Indicates the fixed peak sampling time in each cycle; The sine and cosine signals sampled at the trough are: The peak and trough phases differ by half a period of the phase compensation reference signal, so: Where, T compensate is the phase compensation reference signal period after phase locking; By trigonometric transformation we can get: A ADC =sin(ωt max )=-sin(ωt min ) After the difference processing of the peak and trough signals of the two collected sine and cosine signals, we can get:

8. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 5, characterized in that: The signal demodulation algorithm based on the second-order state observer includes: by is the state equation, is the measurement equation, then the basic form of the second-order state observer is: In the formula, and is the estimated value of the motor rotor position and speed; k θ , k ω are all observer gains greater than zero; set up Then there is an error equation: By first approximation at the origin of the coordinate system, the Jacobian coefficient matrix of the linearized system can be obtained as: The characteristic equation of matrix A is: l 2 +k θ λ+k ω =0 Because k θ , k ω are all greater than zero, and it is obvious that the eigenvalues ​​of A all have negative real parts; according to Lyapunov's first method, the zero solution of the error equation is asymptotically stable, that is, the output of the second-order state observer can approach the true value with zero error; according to the requirements of stability and rapidity, the two characteristic roots of the characteristic equation are selected as λ1 and λ2, and the observer gain coefficient can be determined as In order to enable MCU to solve the problem, T compensate is the sampling period, the basic form of the observer can be discretized as: In the formula, and t = jT compensate Angle and angular velocity estimates at time instant.

9. A phase-locked dual-point sampling rotary transformer decoding system for wireless communication as claimed in claim 1, characterized in that: The NB-IoT communication module includes a BC20 module and a OneNET cloud platform; the BC20 module is configured through the serial port of the MCU, and the device is connected to the OneNET cloud platform using relevant AT commands and data is reported; the OneNET cloud platform provides a data visualization View 3.0 service, and the present invention completes the display application construction through this service to realize the visualization display function of the web and mobile terminals.

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