A speed measurement system and method

Abstract

The application discloses a kind of speed measurement system and speed measurement method, belong to the technical field of industrial automation speed measurement.Speed sensing unit signal output terminal is coupled signal input terminal of signal processing unit, signal output terminal of signal processing unit is coupled signal input terminal of standard signal output unit, and constitutes speed measurement signal positive transmission link;Signal input terminal of closed-loop control unit is coupled signal feedback terminal of standard signal output unit, signal output terminal of closed-loop control unit is coupled control input terminal of signal processing unit, and forms closed-loop regulation link.The application solves the problem that speed measurement and signal conversion are separated in the prior art, and multiple modules are cooperatively debugged complicatedly.No need to write special PLC processing program for different brands and models of sensors, reduces system development cycle and labor cost, significantly improves the compatibility and adaptability of the system in different rotating equipment and different industrial scenarios.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial automation speed measurement, and in particular relates to a speed measurement system and speed measurement method. Background Technology

[0002] In the field of industrial production automation, rotational speed is a core indicator reflecting the operating status of rotating equipment. Various rotating equipment such as motors, water pumps, fans, conveyors, and machine tool spindles need to be equipped with speed measuring devices to convert mechanical speed signals into electrical signals and transmit them to the PLC control system. This enables real-time monitoring of rotational speed, process control, and fault early warning, and is a key link in ensuring the continuous and stable operation of industrial production.

[0003] Currently, the mainstream speed measurement solution in the industrial field is the pulse speed sensor solution based on the proximity switch principle. Its core working principle is: the speed sensor senses the rotation of the object being measured, outputting several discrete pulse speed signals for each revolution. These pulse signals are transmitted to the PLC control system, where technicians write a dedicated pulse signal processing program to indirectly obtain the rotational speed data by calculating the pulse frequency or number. In addition, some existing technologies separate speed measurement and signal conversion, using an independent pulse speed sensor to collect signals and then connecting an external signal conversion module to attempt to convert the pulse signals into analog signals. However, this does not form an integrated speed measurement and signal conversion architecture and still requires multi-module collaborative debugging. Furthermore, the pulse signals output by pulse speed sensors are non-standard signals, lacking a unified industrial processing standard, and the number of pulses output per week varies significantly between different brands and models of sensors. This necessitates that PLCs must be programmed with dedicated processing methods for the pulse output characteristics of specific sensors. Furthermore, when changing sensors or adjusting speed measurement requirements, the core parameters of the PLC program must be modified. This not only increases the development cycle and manpower costs of industrial measurement and control systems but also reduces the system's compatibility and adaptability across different devices and scenarios.

[0004] Meanwhile, the inherent time delay in the counting and processing of pulse signals by the PLC causes a deviation between the speed detection result and the actual operating state of the equipment. In addition, some existing signal conversion schemes lack a targeted closed-loop adjustment mechanism, making it impossible to calibrate the output signal in real time, which further aggravates the accuracy loss and makes it difficult to meet the high requirements of speed measurement accuracy in industrial scenarios such as precision machining and precise fluid control. Summary of the Invention

[0005] To address the technical problems existing in the background art described above, the present invention provides a speed measurement system and a speed measurement method.

[0006] The present invention employs the following technical solution to realize a speed measurement system, comprising: a speed sensing unit, a signal processing unit, a standard signal output unit, and a closed-loop control unit; The signal output terminal of the speed sensing unit is coupled to the signal input terminal of the signal processing unit, and the signal output terminal of the signal processing unit is coupled to the signal input terminal of the standard signal output unit, thus forming a forward transmission link for the speed measurement signal. The signal input terminal of the closed-loop control unit is coupled to the signal feedback terminal of the standard signal output unit, and the signal output terminal of the closed-loop control unit is coupled to the control input terminal of the signal processing unit, forming a closed-loop regulation link.

[0007] In a further embodiment, it also includes: a graded power supply unit, which provides a stable power supply adapted to the operating voltage of the speed sensing unit, the signal processing unit, the standard signal output unit and the closed-loop control unit respectively.

[0008] In a further embodiment, the rotation speed sensing unit includes: a sensing chip U13; the sensing chip U13 is used to sense changes in the magnetic signal on the rotating component under test, generate an original rotation speed electrical signal, and after internal filtering and optimization processing of the original rotation speed electrical signal, output a stable rotation speed electrical signal to the signal processing unit through the OUT signal terminal.

[0009] In a further embodiment, the signal processing unit includes: a main control MCU unit, a signal protection unit, and a PWM to voltage conversion unit; The main control MCU unit's calculation sampling input terminal is coupled to the output terminal of the speed sensing unit, and the PWM output terminal is coupled to the input terminal of the PWM-to-voltage unit. The signal protection unit is connected in series between the feedback signal link of the closed-loop control unit and the calculation and sampling terminal of the main control MCU unit, and is used to perform electrostatic protection and noise filtering on the feedback signal. The output terminal of the PWM to voltage conversion unit is coupled to the control input terminal of the standard signal output unit, and is used to convert the PWM signal into an analog voltage signal to drive a 4-20mA current output.

[0010] In a further embodiment, the standard signal output unit includes: a power transistor Q1, a current-limiting resistor R4, and a sampling resistor R5; The base of the power transistor Q1 is coupled to the output of the signal processing unit via a current-limiting resistor R4. The emitter of the power transistor Q1 is coupled to one end of the sampling resistor R5, and the other end of the sampling resistor R5 is coupled to the input terminal of the closed-loop control unit; the voltage signal across the sampling resistor R5 is output to the closed-loop control unit as a feedback signal.

[0011] In a further embodiment, the closed-loop control unit includes: a current detection chip and a filter capacitor C4; The input terminal of the current detection chip is coupled to both ends of the sampling resistor R5 in the standard signal output unit, and is used to collect the voltage signal corresponding to the output current. The output terminal of the current detection chip is coupled to the control input terminal of the signal processing unit via a filter capacitor C4, which is used to output the current feedback signal to the signal processing unit to realize closed-loop regulation.

[0012] In a further embodiment, the hierarchical power supply unit includes: a first power supply unit and a second power supply unit; The first power supply unit supplies power to the speed sensing unit, the signal protection unit, and the main control MCU unit. The second power supply unit supplies power to the PWM to voltage conversion unit, the standard signal output unit, and the closed-loop control unit.

[0013] A speed measurement method based on the speed measurement system described above includes the following steps: The original rotational speed electrical signal of the object under test is acquired using the sensing chip U13; the original rotational speed electrical signal is filtered to output a stable rotational speed electrical signal. Based on the stable rotational speed electrical signal, the main control chip U11 is used to perform calculations and sampling to obtain digital sample values, and the actual rotational speed of the measured object is calculated. The actual speed value is linearly mapped to the corresponding PWM duty cycle. The main control chip U11 generates a PWM signal, which is converted into an analog control voltage by the PWM to voltage conversion unit, and outputs a 4~20mA industrial standard current signal. The voltage feedback signal corresponding to the 4~20mA industrial standard current is acquired using the current detection chip U2, and the voltage feedback signal is filtered. Based on the deviation between the processed voltage feedback signal and the target value, the main control chip U11 fine-tunes the PWM duty cycle to ensure that the 4~20mA industrial standard current stably corresponds to the current actual speed value.

[0014] In a further embodiment, the conversion process of the 4~20mA industrial standard current signal is as follows: The actual rotational speed value is calculated using a linear formula. Convert to PWM duty cycle ; The main control chip U11 outputs a PWM signal, which is then converted into an analog control voltage by the operational amplifier U3. ; The analog control voltage Linear conversion to 4~20mA industrial standard current .

[0015] The beneficial effects of this invention are as follows: This invention integrates a speed sensing unit, a signal processing unit, a standard signal output unit, and a closed-loop control unit to form an integrated speed measurement and signal conversion architecture. It eliminates the need for external signal conversion modules, solving the problems of separate speed measurement and signal conversion, and cumbersome multi-module collaborative debugging in existing technologies. Simultaneously, through the unified processing of the speed signal and PWM linear mapping by the main control MCU unit, discrete pulse signals are converted into 4~20mA industrial standard current signals, adapting to common PLC control systems in the industrial field. This eliminates the need to write dedicated PLC processing programs for different brands and models of sensors, reducing system development cycle and labor costs, and significantly improving the system's compatibility and adaptability in different rotating equipment and industrial scenarios.

[0016] This invention sets up a hierarchical power supply unit, with the first power supply unit and the second power supply unit providing appropriate operating voltages for each module of the system, avoiding operational failures caused by voltage mismatch between different modules and ensuring long-term stable operation of the system; the units are connected by a clear signal coupling relationship to form a complete forward transmission link and closed-loop regulation link, which is logically rigorous and structurally compact, reducing signal loss and interference during signal transmission and improving the system's operational reliability and anti-interference capability.

[0017] The speed measurement method of this invention has a clear process. From speed signal acquisition, processing, conversion to closed-loop fine-tuning, the entire process is completed automatically without manual intervention. Each module of the system uses standardized components (such as sensing chip U13, power transistor Q1, current detection chip, etc.), which are convenient to purchase and replace. When it is necessary to adjust the speed measurement range, only the linear mapping parameters of the PWM duty cycle need to be fine-tuned. There is no need to modify the system hardware or core program again, which greatly reduces the system maintenance cost and the difficulty of later debugging. Attached Figure Description

[0018] Figure 1 This is a topology diagram of the speed measurement system in Example 1.

[0019] Figure 2 This is a circuit diagram of the speed sensing unit in Embodiment 1.

[0020] Figure 3 This is a circuit diagram of the main control MCU unit in Example 1.

[0021] Figure 4 This is a circuit diagram of the signal protection unit, PWM to voltage conversion unit, closed-loop control unit, standard signal output unit, and closed-loop control unit in Example 1. Detailed Implementation

[0022] The present invention will now be further described with reference to the accompanying drawings and embodiments.

[0023] Example 1 like Figure 1 As shown, this embodiment discloses a speed measurement system, including a speed sensing unit, a signal processing unit, a standard signal output unit, and a closed-loop control unit; The signal output terminal of the speed sensing unit is coupled to the signal input terminal of the signal processing unit, and the signal output terminal of the signal processing unit is coupled to the signal input terminal of the standard signal output unit, thus forming a forward transmission link for the speed measurement signal. The signal input terminal of the closed-loop control unit is coupled to the signal feedback terminal of the standard signal output unit, and the signal output terminal of the closed-loop control unit is coupled to the control input terminal of the signal processing unit, forming a closed-loop regulation link.

[0024] In this embodiment, the forward transmission link and the closed-loop control link cooperate and work together to ensure the efficient conversion of the speed signal from mechanical quantity to industrial standard electrical signal, and to achieve precise control of the output signal through closed-loop feedback, which greatly improves the accuracy and stability of the speed measurement system.

[0025] To achieve the above technical solution, the rotation speed sensing unit described in this embodiment includes: a sensing chip U13, used to sense changes in magnetic signals on the rotating component under test, generate an original rotation speed electrical signal, and after filtering and optimizing the original rotation speed electrical signal, output a stable rotation speed electrical signal to the signal processing unit.

[0026] Specific connection relationships are as follows Figure 2 For example, it includes: sensor chip U13, external Hall switch / proximity switch QZ, bias resistor R15, bias resistor R19, current limiting resistor R18, status indicator LED2, and filter capacitor C13. The sensor chip U13 is model HAL253UA, and its pin connections are as follows: VDD terminal: Electrically connected to the +5V power supply network, and simultaneously connected in parallel with a 100nF filter capacitor C13 to system ground (GND) to filter out power supply ripple and high-frequency interference, and stabilize the chip power supply voltage.

[0027] GND terminal: Directly connected to system ground (GND) to form a complete power supply loop and provide a signal reference ground. This avoids common-mode interference introduced by ground potential differences and ensures the accuracy of signal acquisition and processing.

[0028] OUT terminal: Coupled to the signal processing unit, and electrically connected to one end of bias resistor R15, one end of bias resistor R19, and one end of current-limiting resistor R18. The other end of bias resistor R15 is connected to the +5V power supply, forming a pull-up bias branch. The other end of bias resistor R19 is connected to the anode of status indicator LED2. The other end of current-limiting resistor R18 is connected to the signal output terminal of the external Hall effect switch / proximity switch QZ.

[0029] The status indicator LED2 used in this embodiment is model LTST-C190KSKT, with its cathode connected to system ground (GND), and bias and current limiting are provided by R19.

[0030] By setting the status indicator LED2, the LED2 is turned on and off by the level change of the OUT signal terminal, so as to visually reflect the presence and status of the speed signal.

[0031] When the rotation of the object being measured is detected, a raw rotation speed pulse signal with periodic high and low level changes is output. This signal is transmitted to the OUT terminal of the sensing chip U13 via the current limiting resistor R18. The sensing chip U13 internally performs filtering and optimization processing on the raw pulse signal to eliminate noise and glitches, and outputs a regular rotation speed pulse signal.

[0032] The other end of the bias resistor R19 is connected to the anode of the status indicator LED2, and the cathode of LED2 is connected to system ground (GND). R19 provides both bias and current limiting. When the OUT terminal outputs a high level, current flows through R19 to LED2 to light it up. When the OUT terminal outputs a low level, LED2 turns off. The periodic on and off of LED2 provides a visual feedback on the presence and pulse status of the speed signal, which is convenient for on-site debugging and troubleshooting.

[0033] In a further embodiment, the signal processing unit includes: a main control MCU unit, a signal protection unit, and a PWM to voltage conversion unit; The main control MCU unit's calculation sampling input terminal is coupled to the output terminal of the speed sensing unit, and the PWM output terminal is coupled to the input terminal of the PWM-to-voltage unit. The signal protection unit is connected in series between the feedback signal link of the closed-loop control unit and the calculation and sampling terminal of the main control MCU unit, and is used to perform electrostatic protection and noise filtering on the feedback signal. The output terminal of the PWM to voltage conversion unit is coupled to the control input terminal of the standard signal output unit, and is used to convert the PWM signal into an analog voltage signal to drive a 4-20mA current output.

[0034] Combination Figure 3 The main control MCU unit described in this embodiment includes: a main control chip U11, a power supply filter circuit, a reset circuit, a status indicator circuit, a calculation sampling terminal, and a PWM output terminal connected thereto. The main control chip U11 is a PY32F002BF15U6TR, and its power supply pin is electrically connected to the +5V power network.

[0035] The power supply filtering circuit includes two filter capacitors, C2 and C14, connected in parallel. The filter capacitors C2 and C14 are connected in parallel between the power supply pin and system ground (GND) to filter out power supply ripple and high-frequency interference, providing a clean power supply for stable chip operation.

[0036] The reset circuit includes a reset resistor R1 and a filter capacitor C1. One end of the reset resistor R1 is electrically connected to the +5V power supply network, and the other end is electrically connected to the PC0-NRST reset pin of the main control chip U11. At the same time, the filter capacitor C1 is connected in parallel to the system ground (GND) at this node, forming a power-on reset and manual reset circuit to ensure normal system startup and abnormal reset.

[0037] The status indication circuit includes a status indicator LED1 (XL-1005UGC) and a current-limiting resistor R16. The anode of LED1 is connected to the +5V power network via the current-limiting resistor R16, and the cathode is connected to system ground (GND) to visually indicate the system power status.

[0038] In this embodiment, the calculation sampling terminal is the PA7 pin of the main control chip U11, which is used to receive the speed pulse signal or current feedback signal after signal processing; the PWM output terminal is the PB1 pin of the main control chip U11, which is used to output a PWM signal with adjustable duty cycle.

[0039] Correspondingly, the signal protection unit described in this embodiment includes: an electrostatic discharge (ESD) protection device U4 (model PESD3V3L1UB), a current-limiting resistor R6, and a filter capacitor C4. Combined with... Figure 4 The specific connection relationships are as follows: One end of the current-limiting resistor R6 is coupled to the OUT pin of the current detection chip U2 in the closed-loop control unit to receive the processed current feedback signal; The other end of the current-limiting resistor R6 is simultaneously coupled to the signal input terminal of the electrostatic protection device U4, one end of the filter capacitor C4, and the PA7 pin (calculation sampling terminal) of the main control chip U11. The grounding terminal of the electrostatic discharge protection device U4 is directly connected to the system ground (GND) to discharge static electricity and surge interference introduced into the industrial field and prevent high voltage from damaging the main control MCU unit; The other end of the filter capacitor C4 is connected to system ground (GND), forming an RC low-pass filter network with the current-limiting resistor R6 to filter out high-frequency noise and interference in the feedback signal, providing a stable and clean feedback signal for the MCU.

[0040] The PWM to voltage conversion unit described in this embodiment includes: operational amplifier U3 (model LM321DTR), resistor R2, resistor R3, resistor R17, and filter capacitors C3 and C5.

[0041] The specific connection relationship of the PWM to voltage conversion unit is as follows: The non-inverting input terminal (pin 1) of the operational amplifier U3 is coupled to the PB1 pin (PWM output terminal) of the main control MCU unit through resistor R17 to receive the PWM pulse signal with adjustable duty cycle; at the same time, capacitor C5 is connected in parallel to the system ground (GND) to form an RC low-pass filter network to perform preliminary smoothing of the PWM signal and convert the pulse waveform into an analog voltage that is approximately DC.

[0042] The inverting input terminal (pin 3) of operational amplifier U3 is connected to system ground (GND) via series resistor R2, and simultaneously connected to the output terminal (pin 4) of operational amplifier U3 via series resistor R3, forming a proportional negative feedback loop to achieve voltage regulation of the input analog voltage.

[0043] The power supply terminal (pin 5) of operational amplifier U3 is connected to the +12V power supply network, and a filter capacitor C3 (100nF / 25V) is connected in parallel to the system ground (GND) to filter out power supply ripple and high-frequency interference, providing a clean power supply for stable operation of the op-amp; the ground terminal (pin 2) of operational amplifier U3 is directly connected to the system ground (GND).

[0044] The output terminal (pin 4) of operational amplifier U3 serves as the analog control voltage output terminal of the PWM to voltage conversion unit. It is coupled to the base of power transistor Q1 in the standard signal output unit and outputs the linearly corresponding analog voltage signal to drive the generation of subsequent 4~20mA industrial standard current.

[0045] In a further embodiment, the standard signal output unit described in this embodiment includes: a power transistor Q1, a current-limiting resistor R4, and a sampling resistor R5; In this embodiment, the base of the power transistor Q1 is coupled to the output terminal of the signal processing unit via a current-limiting resistor R4. The power transistor Q1 used in this embodiment is a BCP56-16, and the current-limiting resistor R4 is used to limit the base drive current to prevent the power transistor from being damaged due to overcurrent and to ensure stable operation of the device.

[0046] The emitter of the power transistor Q1 is coupled to one end of the sampling resistor R5, and the other end of the sampling resistor R5 is coupled to the input terminal of the closed-loop control unit. The voltage signal across the sampling resistor R5 is output to the closed-loop control unit as a feedback signal. It should be noted that the voltage signal across the sampling resistor R5 is linearly proportional to the output 4~20mA current. This voltage signal is output to the closed-loop control unit as a current feedback signal, providing a precise signal basis for subsequent current output closed-loop calibration.

[0047] In a further embodiment, the closed-loop control unit includes: a current detection chip U2 (model INA199A1DCKR) and a filter capacitor C4.

[0048] The current detection chip U2, as the core device for current sampling and amplification, has its REF terminal connected to the +5V power network, its GND terminal directly connected to the system ground (GND), and its V+ terminal connected to the +12V power network, providing adaptive power supply and reference level for stable chip operation.

[0049] The IN+ and IN- pins of the current detection chip U2 are respectively coupled to the two ends of the sampling resistor R5 in the standard signal output unit to collect the voltage feedback signal on the sampling resistor R5. This voltage signal is linearly proportional to the 4~20mA output current.

[0050] The OUT terminal of the current detection chip U2 is the signal output terminal of the closed-loop control unit. The filter capacitor C4 is connected in parallel to the system ground (GND) to filter out high-frequency noise in the feedback signal. The filtered feedback signal is coupled to the input terminal of the signal protection unit in the signal processing unit, and the processed current feedback signal is transmitted to the subsequent link to provide a reliable signal basis for the main control MCU unit to fine-tune the PWM duty cycle.

[0051] Furthermore, to ensure that each unit operates stably and independently under its appropriate voltage, and to avoid signal interference or device damage caused by voltage mismatch issues, this embodiment also includes a hierarchical power supply unit, which provides stable power to the speed sensing unit, signal processing unit, standard signal output unit, and closed-loop control unit respectively, adapted to their operating voltages. The hierarchical power supply unit includes a first power supply unit and a second power supply unit. The first power supply unit supplies power to the speed sensing unit, the signal protection unit, and the main control MCU unit. The second power supply unit supplies power to the PWM to voltage conversion unit, the standard signal output unit, and the closed-loop control unit.

[0052] The first power supply unit outputs a stable +5V voltage to power the speed sensing unit, the signal protection unit in the signal processing unit, and the main control MCU unit. Its power supply pins are electrically connected to the corresponding +5V power supply terminals of each unit, and each unit's power supply terminal is connected in parallel with a filter capacitor to system ground (GND) to filter out power supply ripple. The second power supply unit outputs dual stable voltages of +12V and +24V. The +12V voltage powers the PWM to voltage conversion unit and the closed-loop control unit in the signal processing unit, while the +24V voltage powers the main power supply of the power drive circuit of the standard signal output unit. Each voltage output terminal is electrically connected to the corresponding unit's adapter power supply terminal to form an independent power supply link that does not interfere with each other.

[0053] In summary, the speed sensing unit in this embodiment filters and optimizes the original speed electrical signal through the sensing chip U13, effectively filtering out noise interference and ensuring that the speed signal input to the signal processing unit is stable and reliable. The signal protection unit of the signal processing unit performs electrostatic protection and noise filtering on the closed-loop feedback signal, further ensuring the stability of signal transmission. The closed-loop control unit collects the output current feedback signal through the current detection chip and, combined with the PWM duty cycle proportional fine-tuning mechanism, calibrates the 4~20mA current output deviation in real time. This solves the problems of time delay and accuracy loss caused by the lack of closed-loop adjustment in PLC processing in the prior art, significantly improving the speed measurement accuracy and the stability of current output. It can meet the requirements of industrial scenarios with high speed measurement accuracy, such as precision machining and precise fluid control.

[0054] Example 2 Based on the speed measurement system disclosed in the embodiments, this embodiment discloses a speed measurement method, including the following steps: Signal acquisition and preprocessing: The original rotational speed electrical signal of the object under test is acquired using the sensing chip U13; the original signal is internally filtered and optimized to remove noise and glitches from the industrial environment, and a stable rotational speed pulse signal is output through the OUT terminal. At the same time, the status is visually fed back to the signal status via the status indicator LED2, providing a reliable signal source for subsequent processing.

[0055] Rotational speed calculation and PWM signal generation: A stable rotational speed pulse signal is transmitted to the main control MCU unit of the signal processing unit. The main control chip U11 samples this signal through the PA7 pin (calculation sampling terminal), converting the analog signal into a digital sample value. Then, the sample value is calculated using an internal algorithm to calculate the actual rotational speed of the object being measured. A linear formula is used to convert the actual rotational speed value... Convert to PWM duty cycle It generates and outputs a PWM pulse signal with an adjustable duty cycle through the PB1 pin (PWM output terminal).

[0056] PWM Converter and Standard Current Output: The PWM signal output by the main control chip U11 is transmitted to the PWM converter unit of the signal processing unit. The circuit consisting of operational amplifier U3, resistors R2 / R3 / R17, and filter capacitors C3 / C5 converts the PWM signal into an analog control voltage. The analog voltage is transmitted to the base of the power transistor Q1 in the standard signal output unit via the current-limiting resistor R4, driving the power transistor Q1 to work. Combined with the +24V power supply and the sampling resistor R5, the analog control voltage is converted into a 4~20mA industrial standard current signal, which is then output to industrial control equipment such as PLC.

[0057] Current feedback and signal processing: The sampling resistor R5 of the standard signal output unit converts the 4~20mA output current into a linearly corresponding voltage feedback signal, which is transmitted to the closed-loop control unit. The current detection chip U2 acquires the voltage feedback signal, filters out high-frequency noise through the filter capacitor C4, and then transmits the feedback signal to the signal protection unit. The protection and filtering circuit composed of the electrostatic protection device U4, the current limiting resistor R6, and the filter capacitor C4 performs electrostatic protection and noise filtering on the feedback signal to avoid interference in the industrial field from damaging the main control MCU. Finally, the processed feedback signal is transmitted to the calculation and sampling end of the main control chip U11.

[0058] Closed-loop calibration and precise control: The main control chip U11 compares the received feedback signal with the target voltage value, calculates the deviation value, and then uses a proportional correction algorithm to fine-tune the PWM duty cycle in real time. The fine-tuned PWM signal is then converted into a calibrated 4~20mA current through the PWM to voltage unit and the standard signal output unit, so as to achieve a precise and stable correspondence between the output current and the actual speed, forming a complete closed-loop regulation link.

[0059] Throughout the process, the tiered power supply unit provides the appropriate voltage for each module: the first power supply unit outputs +5V to power the speed sensing unit, the main control MCU unit, and the signal protection unit; the second power supply unit outputs +12V to power the PWM to voltage conversion unit and the closed-loop control unit; and outputs +24V to power the power drive circuit of the standard signal output unit, ensuring that each module operates independently and stably without voltage crosstalk or signal interference.

[0060] Furthermore, the actual speed value in the speed calculation and PWM signal generation steps. The calculation formula is as follows: ; In the formula, The number of pulses per revolution For statistical purposes, For the basis.

[0061] Digital sampling values ​​count the number of pulses per unit time.

[0062] Correspondingly, the linear formula is: ; In the formula, and These are the lower and upper limits of the speed measurement range, respectively. This represents the PWM duty cycle.

[0063] In the PWM voltage conversion and standard current output, the following formula is used to convert the PWM signal into an analog control voltage. : ; Finally, the analog control voltage Linear conversion to 4~20mA industrial standard current .

[0064] To facilitate understanding, this embodiment further provides the implementation method of closed-loop calibration and precise control, such as: The closed-loop control unit acquires the voltage feedback signal across the sampling resistor R5 via the current detection chip U2. This voltage is correlated with the output current. The feedback signal exhibits a linear proportional relationship; after electrostatic discharge protection and RC filtering by the signal protection unit, the processed feedback signal is transmitted to the calculation and sampling terminal of the main control MCU unit. The main control MCU unit converts this feedback signal into the actual output current value. , and the target current value Compare and calculate the deviation value. ; A proportional correction algorithm is used to fine-tune the PWM duty cycle in real time. ； in, The fine-tuned PWM duty cycle This is the proportional adjustment coefficient, used to control the adjustment speed and stability. The fine-tuned PWM signal is then converted back into an analog control voltage by the PWM-to-voltage unit, driving the standard signal output unit to output a calibrated 4~20mA current until the deviation ΔI approaches 0, achieving a precise and stable correspondence between the output current and the actual speed, forming a complete closed-loop adjustment chain.

Claims

1. A speed measuring system, characterized in that, include: Speed ​​sensing unit, signal processing unit, standard signal output unit, and closed-loop control unit; The signal output terminal of the speed sensing unit is coupled to the signal input terminal of the signal processing unit, and the signal output terminal of the signal processing unit is coupled to the signal input terminal of the standard signal output unit, thus forming a forward transmission link for the speed measurement signal. The signal input terminal of the closed-loop control unit is coupled to the signal feedback terminal of the standard signal output unit, and the signal output terminal of the closed-loop control unit is coupled to the control input terminal of the signal processing unit, forming a closed-loop regulation link.

2. The speed measuring system according to claim 1, characterized in that, It also includes a tiered power supply unit, which provides a stable power supply adapted to the operating voltage of the speed sensing unit, signal processing unit, standard signal output unit and closed-loop control unit respectively.

3. The speed measuring system according to claim 1, characterized in that, The rotation speed sensing unit includes a sensing chip U13; the sensing chip U13 is used to sense changes in magnetic signals on the rotating component under test, generate an original rotation speed electrical signal, and after filtering and optimizing the original rotation speed electrical signal, output a stable rotation speed electrical signal to the signal processing unit.

4. The speed measuring system according to claim 1, characterized in that, The signal processing unit includes: a main control MCU unit, a signal protection unit, and a PWM to voltage conversion unit; The main control MCU unit's calculation sampling input terminal is coupled to the output terminal of the speed sensing unit, and the PWM output terminal is coupled to the input terminal of the PWM-to-voltage unit. The signal protection unit is connected in series between the feedback signal link of the closed-loop control unit and the calculation and sampling terminal of the main control MCU unit, and is used to perform electrostatic protection and noise filtering on the feedback signal. The output terminal of the PWM to voltage conversion unit is coupled to the control input terminal of the standard signal output unit, and is used to convert the PWM signal into an analog voltage signal to drive a 4-20mA current output.

5. A speed measuring system according to claim 1, characterized in that, The standard signal output unit includes: a power transistor Q1, a current-limiting resistor R4, and a sampling resistor R5; The base of the power transistor Q1 is coupled to the output of the signal processing unit via a current-limiting resistor R4. The emitter of the power transistor Q1 is coupled to one end of the sampling resistor R5, and the other end of the sampling resistor R5 is coupled to the input terminal of the closed-loop control unit; the voltage signal across the sampling resistor R5 is output to the closed-loop control unit as a feedback signal.

6. A speed measuring system according to claim 1, characterized in that, The closed-loop control unit includes: a current detection chip and a filter capacitor C4; The input terminal of the current detection chip is coupled to both ends of the sampling resistor R5 in the standard signal output unit, and is used to collect the voltage signal corresponding to the output current. The output terminal of the current detection chip is coupled to the control input terminal of the signal processing unit via a filter capacitor C4, which is used to output the current feedback signal to the signal processing unit to realize closed-loop regulation.

7. A speed measuring system according to claim 2, characterized in that, The hierarchical power supply unit includes: a first power supply unit and a second power supply unit; The first power supply unit supplies power to the speed sensing unit, the signal protection unit, and the main control MCU unit. The second power supply unit supplies power to the PWM to voltage conversion unit, the standard signal output unit, and the closed-loop control unit.

8. A speed measurement method based on a speed measurement system as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The original rotational speed electrical signal of the object under test is acquired using the sensing chip U13; the original rotational speed electrical signal is filtered to output a stable rotational speed electrical signal. Based on the stable rotational speed electrical signal, the main control chip U11 is used to perform calculations and sampling to obtain digital sample values, and the actual rotational speed of the measured object is calculated. The actual speed value is linearly mapped to the corresponding PWM duty cycle. The main control chip U11 generates a PWM signal, which is converted into an analog control voltage by the PWM to voltage conversion unit, and outputs a 4~20mA industrial standard current signal. The voltage feedback signal corresponding to the 4~20mA industrial standard current is acquired using the current detection chip U2, and the voltage feedback signal is filtered. Based on the deviation between the processed voltage feedback signal and the target value, the main control chip U11 fine-tunes the PWM duty cycle to ensure that the 4~20mA industrial standard current stably corresponds to the current actual speed value.

9. A speed measurement method according to claim 8, characterized in that, The conversion process of the 4~20mA industrial standard current signal is as follows: The actual rotational speed value is calculated using a linear formula. Convert to PWM duty cycle ; The main control chip U11 outputs a PWM signal, which is then converted into an analog control voltage by the operational amplifier U3. ; The analog control voltage Linear conversion to 4~20mA industrial standard current .

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