Speed signal processing methods and systems
By connecting a magnetoresistive speed sensor to a capacitor, zero-crossing harmonics in the magnetoresistive speed measurement system are eliminated, generating a stable square wave signal. This solves the problem of speed jumps and achieves signal stability and efficient energy utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUIZHONG POWER GENERATION CO LTD
- Filing Date
- 2022-11-02
- Publication Date
- 2026-05-26
AI Technical Summary
In harsh environments, magnetoresistive speed measurement systems are prone to zero harmonic fluctuations, which can cause speed jumps and affect the normal operation of rotating machinery. Existing solutions, such as replacing gears or using eddy current sensors, are costly or ineffective, and the resistive elements cause energy loss.
By connecting a magnetoresistive speed sensor to a first capacitor, the capacitor is used to remove zero-crossing harmonics and generate a square wave signal to avoid signal loss. A signal shaping module and a controller are used for speed monitoring. The capacitor capacity is determined based on the parameters of the speed measuring gear and the sensor.
It effectively eliminates zero-crossing harmonics, ensures stable speed signals, avoids signal loss, reduces energy loss, requires minimal modification and is easy to implement, and is suitable for magnetoresistive speed measurement systems.
Smart Images
Figure CN115754336B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of thermal automatic control, and more specifically, to a speed signal processing method and system. Background Technology
[0002] Magnetoresistive speed measurement is a common method for measuring rotational speed. Because magnetoresistive sensors have strong output signals and good anti-interference performance, they can be used in harsh environments such as smoke, oil, and water vapor. Therefore, magnetoresistive speed measurement systems account for a large proportion of industrial production in my country. Determining rotational speed using a speed-measuring gear is another common method. However, due to various issues such as the tooth profile of the speed-measuring gear, the harmonic amplitude at the zero-crossing point may exceed the threshold dead zone, leading to speed jumps. These speed jumps can cause rotating machinery (such as steam turbine units) to malfunction. Summary of the Invention
[0003] The purpose of this disclosure is to provide a speed signal processing method and system to eliminate zero-crossing harmonics, so that the speed signal of the input signal shaping module is a sine wave, thereby avoiding speed jumps; and the first capacitor does not cause energy loss, and can avoid signal loss when the speed measuring gear speed is low.
[0004] To achieve the above objectives, the first aspect of this disclosure provides a speed signal processing method, comprising:
[0005] When the speed measuring gear rotates, a speed signal is generated. The speed measuring gear and the magnetoresistive speed sensor are arranged adjacent to each other and separated by an air gap threshold. The magnetoresistive speed sensor is connected to both ends of the first capacitor.
[0006] The zero-crossing harmonics in the rotational speed signal are removed by the first capacitor to correct the rotational speed signal, wherein;
[0007] Based on the corrected rotational speed signal, a square wave signal is generated to monitor the rotational speed of the speed measuring gear;
[0008] The capacitance of the first capacitor is such that the corrected rotational speed signal does not contain zero-crossing harmonics.
[0009] Optionally, generating a square wave signal based on the corrected rotational speed signal includes:
[0010] The corrected rotation speed signal is clipped according to a preset amplitude threshold to generate a first waveform signal;
[0011] The first waveform signal is subjected to low-pass filtering to generate the second waveform signal;
[0012] Remove the portion of the second waveform signal whose amplitude is less than the threshold level to generate the third waveform signal;
[0013] The third waveform signal is converted into a square wave signal.
[0014] Optionally, converting the third waveform signal into a square wave signal includes:
[0015] Based on the third waveform signal, determine the level information;
[0016] Upon receiving a strobe signal from the controller, a square wave signal is generated based on the level information, and the square wave signal is transmitted to the controller, wherein the controller is used to monitor the rotational speed of the speed measuring gear.
[0017] Optionally, the capacitance of the first capacitor is determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor.
[0018] Optionally, the capacitance of the first capacitor can be determined in the following way:
[0019] The theoretical capacity of the first capacitor is determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor.
[0020] If the speed signal passes through the first capacitor of the theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is greater than the threshold level, then the size of the first capacitor is increased based on the theoretical capacity according to the preset capacity adjustment step size until the corrected speed signal does not contain zero-crossing harmonics.
[0021] If the speed signal passes through a first capacitor of the theoretical capacity and the resulting corrected speed signal contains a zero-crossing harmonic, and the amplitude of the zero-crossing harmonic is less than the threshold level, then the size of the first capacitor is reduced based on the theoretical capacity according to a preset capacity adjustment step size until the corrected speed signal does not contain a zero-crossing harmonic.
[0022] Optionally, the speed measuring gear is a non-involute gear or a large module gear, wherein the gear module of the large module gear is greater than the module threshold.
[0023] To achieve the above objectives, a second aspect of this disclosure provides a speed signal processing system, comprising: a speed measuring gear, a magnetoresistive speed sensor, a first capacitor, a signal shaping module, and a controller;
[0024] The speed measuring gear and the magnetoresistive speed sensor are arranged adjacent to each other and separated by an air gap threshold. The magnetoresistive speed sensor is connected to both ends of the first capacitor and is used to generate a speed signal when the speed measuring gear rotates.
[0025] The first capacitor is used to remove zero-crossing harmonics from the speed signal when the speed measuring gear rotates, so as to correct the speed signal;
[0026] The first and second ports of the input terminal of the signal shaping module are respectively connected to the two ends of the first capacitor, and are used to generate a square wave signal based on the corrected rotation speed signal.
[0027] The controller is used to receive the square wave signal to monitor the rotational speed of the speed measuring gear;
[0028] The capacitance of the first capacitor is such that the corrected rotational speed signal does not contain zero-crossing harmonics.
[0029] Optionally, the signal shaping module includes a limiting module, a filtering module, a threshold level module, and a signal conversion module connected in sequence;
[0030] The amplitude limiting module is used to clip the corrected speed signal according to a preset amplitude threshold to generate a first waveform signal.
[0031] The filtering module is used to perform low-pass filtering on the first waveform signal to generate a second waveform signal;
[0032] The threshold level module is used to remove the portion of the second waveform signal whose amplitude is less than the threshold level in order to generate the third waveform signal;
[0033] The signal conversion module is used to convert the third waveform signal into a square wave signal.
[0034] Optionally, the signal conversion module is used to convert the third waveform signal into a square wave signal, including: determining level information based on the third waveform signal; generating a square wave signal based on the level information when a strobe signal is received from the controller, and transmitting the square wave signal to the controller, wherein the controller is used to monitor the rotational speed of the speed measuring gear.
[0035] Optionally, the capacitance of the first capacitor is determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor.
[0036] Optionally, the capacitance of the first capacitor can be determined in the following way:
[0037] The theoretical capacity of the first capacitor is determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor.
[0038] If the speed signal passes through the first capacitor of the theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is greater than the threshold level, then the size of the first capacitor is increased based on the theoretical capacity according to the preset capacity adjustment step size until the corrected speed signal does not contain zero-crossing harmonics.
[0039] If the speed signal passes through a first capacitor of the theoretical capacity and the resulting corrected speed signal contains a zero-crossing harmonic, and the amplitude of the zero-crossing harmonic is less than the threshold level, then the size of the first capacitor is reduced based on the theoretical capacity according to a preset capacity adjustment step size until the corrected speed signal does not contain a zero-crossing harmonic.
[0040] Optionally, the speed measuring gear is a non-involute gear or a large module gear, wherein the gear module of the large module gear is greater than the module threshold.
[0041] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects:
[0042] The magnetoresistive speed sensor is connected to both ends of the first capacitor. When the speed measuring gear rotates, the magnetoresistive speed sensor generates a speed signal. The first capacitor selects the frequency of the speed signal, intercepting zero-crossing harmonics outside the passband and repairing distorted speed waveforms, ensuring the corrected speed signal waveform meets the sine wave requirements of the shaping module. Furthermore, there is no physical resistive element between the magnetoresistive speed sensor and the first capacitor, and the capacitor itself does not lose energy. Therefore, signal loss is avoided at low speeds of the speed measuring gear, thus ensuring the accuracy of speed monitoring. The modification to existing equipment is minimal, making implementation convenient and feasible.
[0043] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description
[0044] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:
[0045] Figure 1 This is a schematic diagram showing the positional relationship between a linear gear and a magnetoresistive speed sensor in related technologies.
[0046] Figure 2 This is a waveform diagram of a speed signal that experiences a jump in speed, as described in related technologies.
[0047] Figure 3 This is a schematic diagram of a parallel resistor voltage divider circuit in related technologies.
[0048] Figure 4 This is a structural block diagram of a speed signal processing system provided in an exemplary embodiment of the present disclosure.
[0049] Figure 5 This is a correction circuit equivalent to the circuit formed by the coil of the first capacitive and magnetoresistive speed sensor provided in an exemplary embodiment of this disclosure.
[0050] Figure 6 This is a waveform diagram showing the input voltage and output voltage of the correction circuit provided in an exemplary embodiment of this disclosure.
[0051] Figure 7 This is the amplitude-frequency response curve of the correction circuit provided in an exemplary embodiment of this disclosure.
[0052] Figure 8 This is the phase frequency response curve of the correction circuit provided in an exemplary embodiment of this disclosure.
[0053] Figure 9 This is a circuit diagram of a signal shaping module provided in an exemplary embodiment of this disclosure.
[0054] Figure 10 This is a flowchart of a speed signal processing method provided in an exemplary embodiment of the present disclosure.
[0055] Explanation of reference numerals in the attached figures
[0056] 1. Speed measuring gear; 2. Signal shaping module; 3. Controller
[0057] 21 Limiting module 22 Filtering module 23 Threshold level module
[0058] 24 Signal conversion module 4 Magnetoresistive speed sensor C1 First capacitor
[0059] C2 is the second capacitor, R1 is the first resistor, and R2 is the second resistor.
[0060] R3 is the third resistor, R4 is the fourth resistor, and R5 is the fifth resistor.
[0061] R6 is the sixth resistor, R7 is the seventh resistor, and R8 is the eighth resistor.
[0062] D1 is the first diode; D2 is the second diode; and D3 is the third diode.
[0063] D4, fourth diode; U1, comparator; U2, inverter.
[0064] U3 NAND gate 11 First gear vertex 12 Second gear vertex Detailed Implementation
[0065] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.
[0066] A magnetoresistive speed sensor includes a frequency-to-voltage converter, which receives the output frequency pulse signal from the magnetoresistive speed sensor and converts this frequency pulse signal into a corresponding DC voltage signal for output. In other words, the frequency-to-voltage converter is equivalent to a digital-to-analog converter. After obtaining the corresponding DC voltage, it is input as the speed signal into the conditioning circuit to convert the sine wave of the speed signal into a square wave.
[0067] The capacitors in the conditioning circuit have an integral function in the time domain, which can filter out the glitches and noise in the speed signal waveform. However, they do not have the function of distinguishing the operating range of the speed signal frequency.
[0068] Therefore, while the conditioning circuit is versatile, it cannot repair severely distorted waveforms. Specifically, the conditioning circuit can convert input speed signals that are sinusoidal or quasi-sinusoidal, but it cannot convert speed waveforms with zero-crossing harmonics. However, the speed signal waveform input to the conditioning circuit often contains zero-crossing harmonics, meaning the speed waveform output by the magnetoresistive speed sensor is distorted.
[0069] Figure 1 This is a schematic diagram illustrating the positional relationship between a linear gear and a magnetoresistive speed sensor in related technologies. For example... Figure 1 As shown, there is a certain distance between the linear gear and the magnetoresistive speed sensor 4 (i.e., there is an air gap).
[0070] by Figure 1 Taking an example, when the tooth apex (highest point) passes the yoke of the magnetoresistive speed sensor 4, the magnetic resistance is at its minimum, the magnetic flux reaches its maximum, the rate of change of magnetic flux is 0, the induced electromotive force of the coil is 0, and the speed signal waveform returns to zero. Because the thickness of the straight tooth tip is more than twice the diameter of the yoke of the magnetoresistive speed sensor 4, the signal waveform cannot quickly cross zero when transitioning from the positive half-wave to the negative half-wave. During the transition from the first gear apex 11 to the second gear apex 12, there will be some slight changes in the air gap, causing changes in the magnetic flux passing through the coil, resulting in harmonics near the zero point. When the tooth groove (lowest point) passes the yoke of the magnetoresistive speed sensor 4, because the tooth groove width is much smaller than the tooth tip thickness, the time it takes to pass through the magnetoresistive speed sensor 4 is shorter, so there is no zero-crossing hysteresis when the waveform transitions from the negative half-wave to the positive half-wave.
[0071] When the turbine speed is low, the speed signal amplitude is small, and the shaft vibration amplitude is also relatively small. The air gap change of the magnetoresistive speed sensor 4 is relatively stable, the coil magnetic flux fluctuation is small, and the harmonic amplitude generated when the signal crosses zero is low, not exceeding the peak-to-peak value of the speed measuring module threshold. Therefore, the comparator will not be falsely triggered. Thus, when the yoke of the magnetoresistive speed sensor 4 passes through one tooth, the comparator only outputs one speed pulse signal, indicating that the speed is normal.
[0072] When the turbine speed is high (e.g., greater than 500 rpm), especially during acceleration, the amplitude of the speed signal increases with the increase in gear speed. Furthermore, mechanical factors such as exceeding the critical speed, oil film whirl, and shaft misalignment cause an increase in shaft vibration amplitude. This leads to increased fluctuations in the air gap of the magnetoresistive speed sensor 4 due to the vibration amplitude, resulting in greater fluctuations in the coil magnetic flux. This further increases the amplitude of interference harmonics when the speed signal crosses zero. If one or more harmonic peaks exceeding the threshold value cross the threshold dead zone in each speed waveform, it will falsely trigger the comparator to output one or more corresponding speed pulses, causing a speed jump. The waveform of the corresponding speed signal at this time can be seen as follows: Figure 2 As shown. Figure 2 As shown, when the speed signal waveform crosses zero, it slowly transitions from positive to negative zero, accompanied by high-frequency harmonics, which are the zero-crossing harmonics.
[0073] Currently, the problem of speed jumps can be solved in the following ways:
[0074] (1) Replace the speed measuring gear or process the speed measuring gear to re-process its tooth profile into an involute tooth profile.
[0075] However, reprocessing into involute gears requires a long construction period, affecting the commissioning of the turbine unit; the financial cost is also high. In addition, the formation of zero-crossing harmonics is not solely due to the linear gear design, thus the effectiveness is difficult to guarantee.
[0076] (2) Replace the magnetoresistive speed sensor with an eddy current sensor.
[0077] However, in addition to configuring an eddy current sensor, a preamplifier, an eddy current speed signal detection module, a terminal unit, and other components are also required, which is very expensive; in addition, the preamplifier has poor resistance to high-temperature environments.
[0078] (3) Connect a resistor Rx in parallel at the input end of the speed signal channel to shunt and reduce voltage (e.g., ...). Figure 3 As shown in the figure, the zero-crossing harmonic amplitude is reduced to within the threshold dead zone. To prevent excessive sensitivity loss, the resistance value of resistor Rx usually needs to take into account the impedance RS of the magnetoresistive speed sensor. Generally, the condition that RS is much smaller than RX is met, where RL is the load.
[0079] However, since resistor Rx is an energy-consuming component, it reduces the amplitude of both the zero-crossing harmonic and the signal, resulting in a large loss of the effective part of the signal. This leads to a weak signal at low speeds, which can easily cause loss of speed at low speeds. Furthermore, this method is only effective when the zero-crossing harmonic is small, and ineffective when the zero-crossing harmonic is large.
[0080] To address the aforementioned problems, this disclosure provides a speed signal processing system.
[0081] Figure 4 This is a structural block diagram of a speed signal processing system provided in an exemplary embodiment of this disclosure. Figure 4 As shown, the speed signal processing system includes a speed measuring gear 1, a first capacitor C1, a signal shaping module 2, a controller 3, and a magnetoresistive speed sensor 4;
[0082] Among them, the speed measuring gear 1 and the magnetoresistive speed sensor 4 are arranged adjacent to each other and separated by an air gap threshold. The magnetoresistive speed sensor 4 is connected to both ends of the first capacitor C1 and is used to generate a speed signal when the speed measuring gear 1 rotates.
[0083] The first capacitor C1 is used to remove zero-crossing harmonics from the speed signal when the speed measuring gear 1 rotates, so as to correct the speed signal;
[0084] The first and second ports of the input terminal of the signal shaping module 2 are respectively connected to the two ends of the first capacitor C1, and are used to generate a square wave signal based on the corrected speed signal;
[0085] The controller 3 is used to receive square wave signals to monitor the rotational speed of the speed measuring gear 1;
[0086] The capacitance of the first capacitor C1 is such that the corrected speed signal does not contain zero-crossing harmonics.
[0087] For example, the circuit consisting of the magnetoresistive speed sensor 4 and the first capacitor C1 can be equivalent to... Figure 5 The calibration circuit shown is illustrated, where R is the internal resistance of the magnetoresistive speed sensor 4. Analyzing it from a time-domain perspective is as follows: taking the voltage across the first capacitor C1 as the response, then... Figure 5 The differential equation corresponding to the correction circuit in the equation can be expressed as shown in equation (1):
[0088]
[0089] Among them, u s(t) The rotational speed signal (converted from a frequency pulse signal into a corresponding DC voltage signal), u s This is the induced voltage, u c1 R is the voltage across the first capacitor C1, C is the capacitance of the first capacitor C1, R is the internal resistance of the magnetoresistive speed sensor 4, and t is time.
[0090] Solving for formula (1) yields:
[0091]
[0092] Where u0 is the output voltage, which is numerically equivalent to the voltage u across the first capacitor C1. c1 From formula (2), we can obtain that if u s(t) It is a step signal (equivalent to a sufficiently short segment of rotational speed signal). As time increases, the voltage u across the first capacitor C1 increases. c1 Approaching the induced voltage u s .
[0093] If the time constant RC is large enough, when an external step signal is applied, the voltage u across the first capacitor C1 will be... c1 The voltage u across the first capacitor C1 rises slowly, and when the time constant RC is much larger than the pulse width, the voltage u rises slowly. c1 Smaller, induced voltage u s The voltage drop mainly occurs on the internal resistance R of the magnetoresistive speed sensor 4, and the output voltage u0 can be expressed by the following formula (3):
[0094]
[0095] Among them, i c1 The current corresponding to the first capacitor C1. From formula (3), we know that the induced voltage u... s The voltage is approximately integrally related to the output voltage u0. The longer the integration time, the lower the cutoff frequency, and the greater the induced voltage u0 in the correction circuit. s The waveform of the output voltage u0 is as follows Figure 6 As shown. Figure 6 As shown, u s(t) After the waveform is corrected by the correction circuit, the abnormal abrupt changes in the output voltage u0 signal waveform are smoothed out, and the mixed u s(t) The shorter the duration of the spike pulse in the waveform, the smaller the integral quantity obtained, and the spike pulse can be effectively suppressed.
[0096] From the perspective of frequency domain analysis, the transfer function A(jω) of the correction circuit can be expressed as shown in equation (4):
[0097]
[0098] Where C is the capacitance of the first capacitor C1, R is the internal resistance of the magnetoresistive speed sensor 4, f is the frequency of the induced voltage change, ω is the angular frequency, and |A(jω)| is the circuit amplitude frequency. This refers to the phase frequency of the circuit.
[0099] From formula (4), the formula (5) corresponding to the circuit amplitude frequency |A(jω)| is:
[0100]
[0101] According to formula (5), we can obtain, as follows Figure 7 The amplitude-frequency response curve of the equivalent circuit is shown. (From...) Figure 7 It can be determined that as the frequency f increases, |A(jω)| gradually and smoothly decays, that is... Gradually and smoothly decays.
[0102] The phase frequency of the circuit can be obtained from formula (4). The corresponding formula (6) is:
[0103]
[0104] From formula (6), we can obtain, as follows Figure 8 The phase frequency response curve of the equivalent circuit shown is given. Figure 8 It can be determined that as the frequency f increases, the voltage U across the first capacitor C1 increases. c1 Lagging behind the induced voltage U s The greater the phase angle difference, Figure 7 In this context, f0 is the cutoff frequency of the correction circuit's passband. Where f = f0, If f < f0, then the frequency is within the passband.
[0105] Therefore, the equivalent circuit has a phase shift effect, with a maximum hysteresis of up to 90°. At this time, the amplitude of the output voltage u0 also decays to 0, and the normal induced voltage u s The frequencies of the signals are all within the passband and are almost unaffected when passing through the correction circuit, while zero-crossing harmonics are strongly suppressed, and the phase shift effect corrects the distorted waveform. That is, in the frequency domain, the first capacitor C1 can precisely control the frequency and waveform of the rotational speed pulse.
[0106] In other words, by setting the first capacitor C1, the frequency of the rotation speed signal can be selected. Signals with frequencies within the passband can pass without restriction, while signals outside the passband are not allowed to pass. Since the frequency of the zero-crossing harmonic exceeds the allowable passband range, the zero-crossing harmonic is intercepted. The distorted rotation speed signal waveform is then corrected to restore it to a sine wave.
[0107] In this circuit, the first capacitor C1 is connected to the signal shaping module 2, which is equivalent to the first capacitor C1 being connected in parallel with the load in the equivalent circuit. The passband gain decreases under load, while the cutoff frequency f0 increases, meaning the passband gain and cutoff frequency of the correction circuit change with the load. Combining formulas (5) and (6), it can be seen that the load can affect... The controllable quantities of |A(ω)| include the capacitance of the first capacitor C1, meaning the size of the first capacitor C1 is related to the degree of speed distortion. Therefore, by controlling the capacitance of the first capacitor C1, the corrected speed signal can be made free of zero-crossing harmonics.
[0108] Furthermore, the first capacitor C1 itself does not consume energy, and the resistor in the correction circuit can be obtained by using the internal resistance R of the coil of the magnetoresistive speed sensor 4. That is, there may be no physical resistor element in the actual circuit. Therefore, the correction circuit can correct the zero-crossing harmonics without consuming energy.
[0109] For example, in Figure 4 In the planar direction shown, the first port of the input terminal of the signal shaping module 2 is the upper end, and the second port is the lower end. Since square waves are more stable than sine waves during transmission, the speed signal can be converted into a square wave signal by the signal shaping module 2. The controller 3 can be a microcontroller unit (MCU) used to receive the square wave signal for speed monitoring of the speed measuring gear 1. It can convert the square wave signal into a digital quantity, which is then sent to the turbine electro-hydraulic control system (DEH) via the I / O bus to control the turbine. Alternatively, the digital quantity can be sent via the I / O bus to the steam-driven feedwater pump turbine electro-hydraulic control system (MEH), turbine protection devices, or a local tachometer for corresponding control operations.
[0110] The magnetoresistive speed sensor is connected to both ends of the first capacitor. When the speed measuring gear rotates, the magnetoresistive speed sensor generates a speed signal. The first capacitor selects the frequency of the speed signal, intercepting zero-crossing harmonics outside the passband and repairing distorted speed waveforms, ensuring the corrected speed signal waveform meets the sine wave requirements of the shaping module. Furthermore, there is no physical resistive element between the magnetoresistive speed sensor and the first capacitor, and the capacitor itself does not lose energy. Therefore, signal loss is avoided at low speeds of the speed measuring gear, thus ensuring the accuracy of speed monitoring. The modification to existing equipment is minimal, making implementation convenient and feasible.
[0111] Optionally, the signal shaping module 2 may include a limiting module 21, a filtering module 22, a threshold level module 23, and a signal conversion module 24 connected in sequence;
[0112] The limiting module 21 is used to clip the corrected speed signal according to a preset amplitude threshold to generate a first waveform signal;
[0113] The filtering module 22 is used to perform low-pass filtering on the first waveform signal to generate the second waveform signal;
[0114] The threshold level module 23 is used to remove the portion of the second waveform signal whose amplitude is less than the threshold level in order to generate the third waveform signal;
[0115] The signal conversion module 24 is used to convert the third waveform signal into a square wave signal.
[0116] For example, the preset amplitude threshold can be pre-set, for instance, to 10V. When the amplitude limiting module 21 receives the corrected rotational speed signal, it can remove the portion of the signal exceeding ±10V, retaining only the portion within the 20Vp-p peak-to-peak range to generate the first waveform signal. This preprocessing of the input signal ensures signal stability and reduces signal distortion.
[0117] The clipped first signal can be low-pass filtered by the filtering module 22 to remove high-frequency noise and generate a filtered second waveform signal. The threshold level module 23 can be used to remove the portion of the second waveform signal with an amplitude lower than the threshold level to generate a third waveform signal, thus avoiding interference from noise. The signal conversion module 24 can be used to convert the third waveform signal into a square wave signal. Since square wave signals are more stable, waveform conversion can ensure signal stability.
[0118] Optionally, the limiting module 21 may include a first resistor R1, a second resistor R2, a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4;
[0119] The first end of the first resistor R1 is connected to the first port, and the second end of the first resistor R1 is connected to the positive terminal of the first diode D1 and the negative terminal of the second diode D2 to form the first junction point. The negative terminal of the first diode D1 is connected to the positive terminal of the first DC power supply, and the positive terminal of the second diode D2 is connected to the negative terminal of the first DC power supply.
[0120] The first end of the second resistor R2 is connected to the second port, and the second end of the second resistor R2 is connected to the positive terminal of the third diode D3 and the negative terminal of the fourth diode D4 to form the second junction point. The negative terminal of the third diode D3 is connected to the positive terminal of the first DC power supply, and the positive terminal of the fourth diode D4 is connected to the negative terminal of the first DC power supply.
[0121] For example, the first resistor R1 and the second resistor R2 are used to limit the surge current. Figure 9In the planar orientation shown, the first end of the first resistor R1 is the left end, and the second end is the right end; the first end of the second resistor R2 is the left end, and the second end is the right end. The first DC power supply can be 10V. The cathodes of the first diode D1 and the third diode D3 can be connected to the positive terminal of the 10V DC power supply, and the anodes of the second diode D2 and the fourth diode D4 can be connected to the negative terminal of the 10V DC power supply. The circuit composed of the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 can be used for clipping to ensure signal stability and reduce signal distortion.
[0122] Optionally, the filter module 22 may include a second capacitor C2, with a first end of the second capacitor C2 connected to a first junction point and a second end of the second capacitor C2 connected to a second junction point.
[0123] For example, in Figure 9 In the planar orientation shown, the first end of the second capacitor C2 is the upper end, and the second end is the lower end. For example, the filter module 22 can also be an RC filter circuit.
[0124] Optionally, the threshold level module 23 may include a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8;
[0125] The first terminal of the third resistor R3 is connected to the first terminal of the second capacitor C2. The second terminal of the third resistor R3 is connected to the first terminals of the fifth resistor R5 and the seventh resistor R7. The second terminal of the fifth resistor R5 is grounded.
[0126] The first terminal of the fourth resistor R4 is connected to the second terminal of the second capacitor C2. The second terminal of the fourth resistor R4 is connected to the first terminal of the sixth resistor R6 and the eighth resistor R8. The second terminal of the sixth resistor R6 is grounded, and the second terminal of the eighth resistor R8 is connected to the positive terminal of the second DC power supply.
[0127] For example, in Figure 9 In the planar orientation shown, the first end of the third resistor R3 is the left end, and the second end is the right end; the first end of the fourth resistor R4 is the left end, and the second end is the right end; the first end of the fifth resistor R5 is the top end, and the second end is the bottom end; the first end of the sixth resistor R6 is the bottom end, and the second end is the top end; the first end of the seventh resistor R7 is the left end, and the second end is the right end; and the first end of the eighth resistor R8 is the left end, and the second end is the right end. The second DC power supply can be 5V.
[0128] When the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the eighth resistor R8 are connected, they can form the following: Figure 9The threshold level circuit shown in the threshold level module 23 can be configured to achieve a threshold level of ±150mV by selecting the values of the third resistor R3, fourth resistor R4, fifth resistor R5, sixth resistor R6, seventh resistor R7, and eighth resistor R8. This allows the portion of the second waveform signal with an amplitude lower than ±150mV to be removed, thus avoiding interference from noise.
[0129] Optionally, the signal conversion module 24 can be used to convert the third waveform signal into a square wave signal in the following manner:
[0130] Based on the third waveform signal, the level information is determined; upon receiving the strobe signal from the controller 3, a square wave signal is generated based on the level information and transmitted to the controller 3, whereby the controller is used to monitor the speed of the speed measuring gear.
[0131] Specifically, the signal conversion module 24 may include a comparator U1, an inverter U2, and a NAND gate U3. The positive input terminal of the comparator U1 is connected to the first terminal of the fifth resistor R5 and the seventh resistor R7. The negative input terminal of the comparator U1 is connected to the first terminal of the sixth resistor R6 and the eighth resistor R8. The output terminal of the comparator U1 is connected to the second terminal of the seventh resistor R7. The comparator U1 is used to determine the level information based on the third waveform signal.
[0132] The input terminal of inverter U2 is connected to controller 3, and the output terminal of inverter U2 is connected to the first input terminal of NAND gate U3. Inverter U2 is used to output a conduction signal when it receives a strobe signal from controller 3. The second input terminal of NAND gate U3 is connected to the output terminal of comparator U1, and the output terminal of NAND gate U3 is connected to controller 3. NAND gate U3 is used to generate a square wave signal according to the level information when it receives the conduction signal, and transmit the square wave signal to controller 3.
[0133] For example, comparator U1 can be an operational amplifier of model LM311. When the voltage at the positive input terminal (pin 2 of the LM311 operational amplifier) is greater than the voltage at the negative input terminal (pin 3 of the LM311 operational amplifier), the output terminal of comparator U1 (pin 7 of the LM311 operational amplifier) outputs a high level; when the voltage at the positive input terminal is less than the voltage at the negative input terminal, the output terminal of comparator U1 outputs a low level. Here, pin 1 of the LM311 operational amplifier is grounded, and the high and low levels are the level information.
[0134] exist Figure 9In the planar orientation shown, the first input terminal of NAND gate U3 is at the lower left, and the second input terminal is at the upper left. The second input terminal receives the level information sent by the output terminal of comparator U1, and the first input terminal receives the conduction signal sent by the output terminal of inverter U2. Inverter U2 can be a 74HC14 chip, and NAND gate U3 can be a 74HC00 chip. Inverter U2 and NAND gate U3 provide a gating function. Without a gating signal, the output terminal of NAND gate U3 does not output a signal. When the controller is ready to process data and count from the field, the controller sends a gating signal. The conduction signal sent by the output terminal of inverter U2 then turns on NAND gate U3. The level information sent by the output terminal of comparator U1 can be used by NAND gate U3 to generate a TTL level digital signal (square wave signal), and this digital signal is input to the controller.
[0135] Optionally, the capacitance of the first capacitor C1 can be determined based on the rated speed and number of teeth of the speed measuring gear 1 and the DC impedance of the coil of the magnetoresistive speed sensor 4.
[0136] Specifically, the capacitance of the first capacitor C1 can be determined in the following way:
[0137] The theoretical capacity of the first capacitor C1 is determined based on the rated speed and number of teeth of the speed measuring gear 1 and the DC impedance of the coil of the magnetoresistive speed sensor 4.
[0138] If the speed signal passes through the first capacitor C1 of theoretical capacity, and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is greater than the threshold level, then the size of the first capacitor C1 is increased according to the preset capacity adjustment step size, based on the theoretical capacity, until the corrected speed signal does not contain zero-crossing harmonics.
[0139] If the speed signal passes through the first capacitor C1 of theoretical capacity, and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of these zero-crossing harmonics is less than the threshold level, then the size of the first capacitor C1 is reduced based on the theoretical capacity according to the preset capacity adjustment step size, until the corrected speed signal does not contain zero-crossing harmonics.
[0140] For example, the theoretical capacitance C0 of the first capacitor C1 can be determined by formula (7):
[0141]
[0142] Where f0 is the cutoff frequency, C0 is the theoretical capacitance of the first capacitor C1, and R is the internal resistance of the magnetoresistive speed sensor 4, i.e., the DC impedance of the coil. The cutoff frequency f0 can be determined by formula (8):
[0143]
[0144] Where n is the rated speed of the shaft being measured by the speed measuring gear 1, in revolutions per minute, and z is the number of teeth of the speed measuring gear 1.
[0145] However, in practical applications, the signal may be affected by many factors such as the distributed parameters in the rotation speed channel, ambient temperature, air gap fluctuation, and the equivalent impedance of the signal shaping module 2. For example, the capacitance of the first capacitor C1 is positively correlated with the air gap fluctuation, while the equivalent impedance of the signal shaping module 2 is negatively correlated with the capacitance of the first capacitor C1.
[0146] Therefore, in order to ensure that the capacitance of the first capacitor C1 is such that the speed signal does not contain zero-crossing harmonics, the theoretical capacitance C0 can be used as a base value, and the capacitance of the first capacitor C1 can be adjusted based on the theoretical capacitance C0.
[0147] For example, if the corrected speed signal obtained by passing the speed signal through a first capacitor C1 of theoretical capacity contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is greater than the threshold level, then the size of the first capacitor C1 is increased according to a preset capacity adjustment step, based on the theoretical capacity. If the zero-crossing harmonics disappear during the increase, the adjustment is stopped; or if the amplitude of the zero-crossing harmonics decreases below the threshold level during the increase, then the capacity adjustment step can be reduced, and the size of the first capacitor C1 can be reduced, so that the frequency of the zero-crossing harmonics continuously decreases, so that the corrected speed waveform no longer contains zero-crossing harmonics.
[0148] If the corrected speed signal obtained by passing the speed signal through the theoretically sized first capacitor C1 contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is less than the threshold level, then the size of the first capacitor C1 is controlled to decrease according to a preset capacity adjustment step, based on the theoretical capacity, until the zero-crossing harmonics disappear, and the adjustment stops.
[0149] A steam turbine can be equipped with multiple magnetoresistive speed sensors 4. The coil impedances of different sensors are different. Therefore, the resistance value of each magnetoresistive speed sensor 4 must be measured one by one; the capacitance of the corresponding first capacitor C1 must be determined separately.
[0150] Optionally, the speed measuring gear 1 can be a non-involute gear or a large module gear.
[0151] Among them, the gear module of a large module gear is greater than a module threshold, which can be preset, for example, set to 4. Non-involute gears can be as follows: Figure 1 The linear gear shown.
[0152] Based on the same inventive concept, this disclosure also provides a speed signal processing method. Figure 10This is a flowchart of a speed signal processing method provided in an exemplary embodiment of this disclosure. Figure 1 As shown, the method may include S101 to S103.
[0153] S101 generates a speed signal when the speed measuring gear rotates.
[0154] The speed measuring gear and the magnetoresistive speed sensor are arranged adjacent to each other and separated by an air gap threshold. The magnetoresistive speed sensor is connected to both ends of the first capacitor.
[0155] S102 removes zero-crossing harmonics from the speed signal through the first capacitor to correct the speed signal.
[0156] S103 generates a square wave signal based on the corrected rotational speed signal to monitor the rotational speed of the speed measuring gear.
[0157] The capacitance of the first capacitor is such that the corrected speed signal does not contain zero-crossing harmonics.
[0158] The magnetoresistive speed sensor is connected to both ends of the first capacitor. When the speed measuring gear rotates, the magnetoresistive speed sensor generates a speed signal. The first capacitor selects the frequency of the speed signal, intercepting zero-crossing harmonics outside the passband and repairing distorted speed waveforms, ensuring the corrected speed signal waveform meets the sine wave requirements of the shaping module. Furthermore, there is no physical resistive element between the magnetoresistive speed sensor and the first capacitor, and the capacitor itself does not lose energy. Therefore, signal loss is avoided at low speeds of the speed measuring gear, thus ensuring the accuracy of speed monitoring. The modification to existing equipment is minimal, making implementation convenient and feasible.
[0159] Optionally, in S103, generating a square wave signal based on the corrected rotational speed signal may include:
[0160] The corrected speed signal is clipped according to a preset amplitude threshold to generate the first waveform signal;
[0161] The first waveform signal is low-pass filtered to generate the second waveform signal;
[0162] Remove the portion of the second waveform signal whose amplitude is less than the threshold level to generate the third waveform signal;
[0163] The third waveform signal is converted into a square wave signal.
[0164] Thus, preprocessing the signal by clipping ensures signal stability and reduces signal distortion. Low-pass filtering of the first waveform signal removes high-frequency noise. Removing the portion of the second waveform signal with amplitude below the threshold level avoids noise interference. Since square wave signals are more stable, waveform conversion can ensure signal transmission stability.
[0165] Optionally, converting the third waveform signal into a square wave signal may include:
[0166] Determine the level information based on the third waveform signal;
[0167] Upon receiving a strobe signal from the controller, a square wave signal is generated based on the level information and transmitted to the controller.
[0168] The controller is used to monitor the rotational speed of the speed measuring gear.
[0169] Optionally, the capacitance of the first capacitor can be determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor.
[0170] Specifically, the capacitance of the first capacitor can be determined in the following way:
[0171] The theoretical capacity of the first capacitor is determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor.
[0172] If the speed signal passes through the first capacitor of theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is greater than the threshold level, then the size of the first capacitor is increased according to the preset capacity adjustment step size, based on the theoretical capacity, until the corrected speed signal does not contain zero-crossing harmonics.
[0173] If the speed signal passes through the first capacitor of theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of these zero-crossing harmonics is less than the threshold level, then the size of the first capacitor is reduced based on the theoretical capacity according to the preset capacity adjustment step size, until the corrected speed signal does not contain zero-crossing harmonics.
[0174] This ensures the accuracy of the determined capacitance value of the first capacitor.
[0175] Optionally, the speed measuring gear can be a non-involute gear or a large module gear.
[0176] Among them, the gear module of the large module gear is greater than the module threshold.
[0177] The specific manner of each step in the methods described in the above embodiments has been described in detail in the embodiments of the relevant systems, and will not be elaborated here.
[0178] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.
[0179] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.
[0180] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.
Claims
1. A method for processing rotational speed signals, characterized in that, include: When the speed measuring gear of the steam turbine rotates, a speed signal is generated. The speed measuring gear and the magnetoresistive speed sensor are arranged adjacent to each other and separated by an air gap threshold. The magnetoresistive speed sensor is connected to both ends of the first capacitor. The zero-crossing harmonics in the rotational speed signal are removed by the first capacitor to correct the rotational speed signal, wherein; Based on the corrected rotational speed signal, a square wave signal is generated to monitor the rotational speed of the speed measuring gear; The capacitance of the first capacitor is such that the corrected rotational speed signal does not contain zero-crossing harmonics. The capacitance of the first capacitor is determined in the following way: The theoretical capacity of the first capacitor is determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor. If the speed signal passes through the first capacitor of the theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is greater than the threshold level, then the size of the first capacitor is increased based on the theoretical capacity according to the preset capacity adjustment step size until the corrected speed signal does not contain zero-crossing harmonics. If the speed signal passes through the first capacitor of the theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is less than the threshold level, then the size of the first capacitor is reduced based on the theoretical capacity according to the preset capacity adjustment step size until the corrected speed signal does not contain zero-crossing harmonics. The step of generating a square wave signal based on the corrected rotational speed signal includes: The calibration speed signal is clipped using a limiting module according to a preset amplitude threshold to generate a first waveform signal. The first waveform signal is low-pass filtered using a filtering module to generate the second waveform signal; The threshold level module is used to remove the portion of the second waveform signal whose amplitude is less than the threshold level in order to generate the third waveform signal; The third waveform signal is converted into a square wave signal using a signal conversion module. The limiting module includes a first resistor, a second resistor, a first diode, a second diode, a third diode, and a fourth diode. The first end of the first resistor is connected to the first port, and the second end of the first resistor is connected to the positive terminal of the first diode and the negative terminal of the second diode to form a first junction point. The negative terminal of the first diode is connected to the positive terminal of the first DC power supply, and the positive terminal of the second diode is connected to the negative terminal of the first DC power supply. The first end of the second resistor is connected to the second port, and the second end of the second resistor is connected to the positive terminal of the third diode and the negative terminal of the fourth diode to form a second junction point. The negative terminal of the third diode is connected to the positive terminal of the first DC power supply, and the positive terminal of the fourth diode is connected to the negative terminal of the first DC power supply.
2. The method according to claim 1, characterized in that, The step of converting the third waveform signal into a square wave signal includes: Based on the third waveform signal, determine the level information; Upon receiving a strobe signal from the controller, a square wave signal is generated based on the level information, and the square wave signal is transmitted to the controller, wherein the controller is used to monitor the rotational speed of the speed measuring gear.
3. The method according to any one of claims 1-2, characterized in that, The speed measuring gear is a non-involute gear or a large module gear, wherein the gear module of the large module gear is greater than the module threshold.
4. A steam turbine speed signal processing system, characterized in that, include: Speed measuring gear, magnetoresistive speed sensor, first capacitor, signal shaping module, and controller; The speed measuring gear and the magnetoresistive speed sensor are arranged adjacent to each other and separated by an air gap threshold. The magnetoresistive speed sensor is connected to both ends of the first capacitor and is used to generate a speed signal when the speed measuring gear rotates. The first capacitor is used to remove zero-crossing harmonics from the speed signal when the speed measuring gear rotates, so as to correct the speed signal; The first and second ports of the input terminal of the signal shaping module are respectively connected to the two ends of the first capacitor, and are used to generate a square wave signal based on the corrected rotation speed signal. The controller is used to receive the square wave signal to monitor the rotational speed of the speed measuring gear; The capacitance of the first capacitor is such that the corrected rotational speed signal does not contain zero-crossing harmonics. The capacitance of the first capacitor is determined in the following way: The theoretical capacity of the first capacitor is determined based on the rated speed and number of teeth of the speed measuring gear and the DC impedance of the coil of the magnetoresistive speed sensor. If the speed signal passes through the first capacitor of the theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is greater than the threshold level, then the size of the first capacitor is increased based on the theoretical capacity according to the preset capacity adjustment step size until the corrected speed signal does not contain zero-crossing harmonics. If the speed signal passes through the first capacitor of the theoretical capacity and the resulting corrected speed signal contains zero-crossing harmonics, and the amplitude of the zero-crossing harmonics is less than the threshold level, then the size of the first capacitor is reduced based on the theoretical capacity according to the preset capacity adjustment step size until the corrected speed signal does not contain zero-crossing harmonics. The signal shaping module includes a limiting module, a filtering module, a threshold level module, and a signal conversion module connected in sequence. The amplitude limiting module is used to clip the corrected speed signal according to a preset amplitude threshold to generate a first waveform signal. The filtering module is used to perform low-pass filtering on the first waveform signal to generate a second waveform signal; The threshold level module is used to remove the portion of the second waveform signal whose amplitude is less than the threshold level in order to generate the third waveform signal; The signal conversion module is used to convert the third waveform signal into a square wave signal; The limiting module includes a first resistor, a second resistor, a first diode, a second diode, a third diode, and a fourth diode. The first end of the first resistor is connected to the first port, and the second end of the first resistor is connected to the positive terminal of the first diode and the negative terminal of the second diode to form a first junction point. The negative terminal of the first diode is connected to the positive terminal of the first DC power supply, and the positive terminal of the second diode is connected to the negative terminal of the first DC power supply. The first end of the second resistor is connected to the second port, and the second end of the second resistor is connected to the positive terminal of the third diode and the negative terminal of the fourth diode to form a second junction point. The negative terminal of the third diode is connected to the positive terminal of the first DC power supply, and the positive terminal of the fourth diode is connected to the negative terminal of the first DC power supply.
5. The system according to claim 4, characterized in that, The signal conversion module is used to convert the third waveform signal into a square wave signal, including: determining level information based on the third waveform signal; generating a square wave signal based on the level information when a strobe signal is received from the controller, and transmitting the square wave signal to the controller, wherein the controller is used to monitor the rotational speed of the speed measuring gear.
6. The system according to any one of claims 4-5, characterized in that, The speed measuring gear is a non-involute gear or a large module gear, wherein the gear module of the large module gear is greater than the module threshold.