A pin-type force sensor

Abstract

This invention belongs to the field of force sensor technology and discloses a pin-type force sensor. The sensor includes a pin body, a magnetic circuit system, and a control circuit. The control circuit has a measurement mode and a calibration mode, and switches modes via a mode switching detection circuit connected to a signal output port. When an external device applies a voltage command higher than the normal signal range to the signal output port, the mode switching detection circuit triggers the microprocessor (MCU), causing the sensor to switch from measurement mode to calibration mode. In calibration mode, the MCU can use the same signal output port to perform bidirectional data communication with the external device, thereby achieving online calibration. This invention solves the problems of high cost and inability to calibrate online in existing pin-type force sensors. Through ingenious circuit multiplexing design, it greatly simplifies the sensor calibration and maintenance process, reduces costs, and improves measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the field of force sensor technology, and particularly relates to a pin-type force sensor based on magnetostrictive effect that can be calibrated online. Background Technology

[0002] A pin-type force sensor is a sensor that combines a traditional mechanical connecting pin with a force measuring element. It is commonly used in electro-hydraulic lifting systems of hoisting equipment, traction equipment, and construction machinery. It not only serves as a connector and load-bearing device, but also measures the tensile or compressive load borne by the pin in real time.

[0003] Currently, pin-type force sensors on the market are mainly divided into two categories:

[0004] The first type is a sensor based on resistance strain gauges, which detects stress deformation by attaching strain gauges to specific positions on the pin shaft. The manufacturing process of this type of sensor is relatively complex, requiring precise patching and temperature compensation. Furthermore, the analog signal generated by the strain gauge is weak and easily affected by electromagnetic interference, resulting in weak anti-interference capability.

[0005] The second type is based on the magnetostrictive effect, which uses the principle that the permeability of ferromagnetic materials changes when subjected to force to measure force. These sensors usually have better overload capacity and anti-interference ability.

[0006] However, existing magnetostrictive sensors, especially imported products, often use dedicated integrated circuits (ASICs) for their internal control circuits, which makes them expensive and difficult to replace once damaged.

[0007] Regardless of the type of sensor, it must undergo a complex multi-point calibration process before leaving the factory. During use, the accuracy of the sensor may decrease due to zero-point drift caused by changes in installation conditions, environment, or long-term use.

[0008] However, existing sensors generally lack the function of online calibration based on actual working conditions. Once recalibration is required, they must be disassembled and returned to the factory for processing, which greatly affects the ease of use and the working efficiency of the equipment. Utility Model Content

[0009] The purpose of this invention is to provide a pin-type force sensor, which aims to solve the technical problems of high sensor cost, reliance on dedicated chips, and inability to perform online calibration in the prior art.

[0010] To achieve the above objectives, this utility model provides the following technical solution:

[0011] A pin-type force sensor includes: a pin body, a magnetic circuit system disposed inside the pin body, and a control circuit for driving and processing signals; the magnetic circuit system includes an excitation coil and an induction coil; the control circuit includes a microprocessor (MCU), a signal output port, and a mode switching detection circuit connected to the signal output port.

[0012] The control circuit has at least two operating modes: measurement mode and calibration mode;

[0013] In the measurement mode, the control circuit drives the excitation coil to generate an alternating magnetic field, calculates the measured value corresponding to the load on the pin body based on the output signal of the induction coil, and outputs a standard signal corresponding to the measured value through the signal output port.

[0014] The mode switching detection circuit is configured to output a trigger signal to the MCU when the signal output port receives an externally applied mode switching command signal with a voltage value higher than the normal range of the standard signal.

[0015] After receiving the trigger signal, the MCU switches the control circuit from measurement mode to calibration mode. In calibration mode, the MCU communicates bidirectionally with an external calibration device through the signal output port to execute an online calibration program.

[0016] Furthermore, the mode switching detection circuit includes a first diode connected to the signal output port, and the inverting terminal of the first diode is connected to the analog-to-digital converter (ADC) input pin of the MCU; when the mode switching command signal is received, the first diode is reverse-biased and cut off, so that the ADC input pin detects a high-level signal as the trigger signal.

[0017] Furthermore, in the calibration mode, the MCU functionally connects its own Universal Asynchronous Receiver Transmitter (UART) transmit pin TXD and receive pin RXD to the signal output port to realize data transmission and reception.

[0018] Furthermore, the control circuit also includes a first digital-to-analog converter DAC1 for generating an excitation signal and a second digital-to-analog converter DAC2 for outputting a standard signal; when entering calibration mode, the MCU controls DAC2 to output a preset low level to avoid interference with data communication.

[0019] Furthermore, the control circuit also includes a sampling control circuit synchronized with the excitation signal of the excitation coil; the sampling control circuit includes a voltage comparator, which is used to compare the excitation signal with a reference voltage and output an interrupt trigger signal to the interrupt pin of the MCU; the MCU synchronously starts the ADC to sample the output signal of the induction coil according to the interrupt trigger signal.

[0020] Furthermore, the excitation signal is a sine wave signal; the sampling control circuit generates the interrupt trigger signal at the peak or trough of the sine wave signal to ensure that data sampling is performed when the excitation energy is at its maximum, thereby improving the signal-to-noise ratio.

[0021] Furthermore, the control circuit also includes a non-volatile memory for storing multi-point nonlinear calibration parameters obtained through an online calibration program; in measurement mode, the MCU uses the multi-point nonlinear calibration parameters to correct the measurement results to improve measurement accuracy.

[0022] Furthermore, the components of the control circuit are all general-purpose electronic components and do not include dedicated integrated circuits (ASICs).

[0023] Compared with the prior art, this utility model has the following advantages:

[0024] 1. This utility model has an original design of a mechanism for mode switching and data communication through a single signal output line; the user only needs to apply a high-level signal to the signal output line to put the sensor into calibration mode, and then communicate with the sensor through the line to complete the online calibration of data without disassembling the sensor, which greatly simplifies the maintenance process and improves the ease of use.

[0025] 2. The control circuit of this utility model uses only general-purpose MCUs and peripheral components, avoiding reliance on expensive and difficult-to-procure dedicated chips and significantly reducing hardware costs. At the same time, the online calibration function simplifies the calibration process during production.

[0026] 3. This utility model adopts a sampling technology that is synchronized with the sine wave excitation signal to ensure that the acquisition is carried out at the moment when the signal energy is strongest, which effectively improves the signal-to-noise ratio; combined with multi-point nonlinear calibration, it can accurately compensate for the nonlinear error of the sensor and improve the measurement accuracy across the entire range. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the sensor appearance according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the cross-sectional structure of the sensor according to an embodiment of the present invention;

[0029] Figure 3 This is a block diagram of the electrical control principle of an embodiment of this utility model;

[0030] Figure 4 This is a waveform diagram of the relevant signal of the sensor in the embodiment of this utility model under no-force conditions;

[0031] Figure 5 This is a waveform diagram of the relevant signal of the sensor under pressure in an embodiment of this utility model;

[0032] Figure 6 This is a waveform diagram of the relevant signal of the sensor under tensile force in an embodiment of this utility model;

[0033] Figure 7 This is a flowchart illustrating the sensor operation of an embodiment of this utility model;

[0034] Figure 8 This is a schematic diagram of the sensor calibration software interface that accompanies this utility model embodiment. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0036] like Figure 1 and Figure 2 As shown, this utility model discloses a pin-type force sensor, whose main structure includes a sensor housing 1 as the pin body, an iron core support 2, an excitation coil 3 and an induction coil 4 wound on the iron core support 2, a control board 5, and a signal output line 6. The sensor housing 1 is a hollow structure used to accommodate and protect the internal magnetic circuit system and electronic components. Its two ends can have the required slots or holes for installation. When in use, it replaces ordinary pins and plays the role of structural connection and load transmission.

[0037] The working principle of the sensor is based on the magnetostrictive effect, such as Figure 3 As shown, the MCU on control board 5 outputs a digitized sine wave sequence through the DAC1 port. This sequence is amplified by power amplifier PA and then drives the excitation coil E0, which corresponds to... Figure 2 The excitation coil 3 generates an alternating, symmetrical magnetic field around the iron core support 2, and the induction coil E1 corresponds to this magnetic field. Figure 2 The induction coil 4 in the middle is composed of multiple symmetrically arranged coils.

[0038] When the sensor housing 1 is not under force, the magnetic field is symmetrical, so the total electromotive force induced in the induction coil E1 is zero. When the sensor housing 1 is subjected to tension or pressure, it undergoes a slight deformation. This deformation is transmitted to the iron core support 2, causing a change in the permeability of the iron core support 2, thereby disrupting the symmetry of the original magnetic field. This asymmetrical magnetic field will induce a non-zero voltage signal in the induction coil E1. The amplitude and phase of this signal are proportional to the magnitude and direction of the force applied.

[0039] The weak signal output from induction coil E1 is amplified and conditioned by coupling capacitor C2 and operational amplifier OP2, and then sent to the ADC1 port of the MCU for analog-to-digital conversion.

[0040] To accurately capture the signal amplitude, this embodiment employs a synchronous sampling mechanism. The drive signal of the excitation coil E0 is simultaneously fed into a voltage comparator composed of operational amplifier OP1 and reference voltage Vref1; when the sinusoidal excitation signal reaches its... Figure 4 When the peak value is reached at time T1, the output state of comparator OP1 will flip, generating a rising or falling edge signal. This signal is sent to the MCU as an interrupt signal INT1. After receiving the interrupt INT1, the MCU immediately starts ADC1 to sample, thereby ensuring that the induced signal value is always captured at the moment when the excitation energy is the maximum and the signal response is the most significant, which effectively improves the signal-to-noise ratio and anti-interference capability of the measurement. Figure 4 , Figure 5 and Figure 6 The timing relationship between the DAC1 excitation signal, INT1 interrupt signal, and ADC1 sampling signal is shown under three states: no force, pressure, and tension.

[0041] After the MCU acquires the value of ADC1, it performs data processing such as digital filtering. In measurement mode, the MCU calculates the ADC value into an actual force value such as Newton or kilonewton by looking up a table or performing function operations based on the calibration parameters stored in the internal non-volatile memory EEPROM. Then, according to the sensor's range, the MCU converts the force value into a standard analog voltage signal, specifically, for example, 0-5V, and outputs it through the DAC2 port. This output signal is then buffered and driven by a follower circuit composed of operational amplifier OP3, and finally output through the signal output port OUT to output line 6.

[0042] The key design feature of this utility model lies in its online calibration function, the implementation of which is detailed in [link to details]. Figure 3 and Figure 7 The flowchart, in Figure 3In the output circuit, a first diode D1 is connected between the output port OUT and the output terminal V1 of DAC2. In normal measurement mode, the voltage range of DAC2 output is 0-5V. At this time, D1 is conducting, and the voltage of V1 is basically equal to the voltage of V2. An ADC detection pin of the MCU continuously monitors the voltage at point V2.

[0043] When online calibration of the sensor is required, an external calibration device, such as a PC connected to a serial port tool, will apply a voltage higher than the normal operating voltage range of the sensor, such as 12V, to the OUT port through output line 6. At this time, the high voltage will cause the first diode D1 to be reverse cut off, thereby protecting the DAC2 and OP3 of the preceding stage. At the same time, the voltage at point V2 will rise rapidly. After the MCU's ADC pin detects this high level far exceeding 5V, it will determine that it has received a command to enter calibration mode.

[0044] like Figure 7 As shown in the flowchart, once the ADC detects a high voltage, the program will enter the calibration mode branch from the main loop. The MCU will immediately control DAC2 to output 0V to clear the output bus. Subsequently, the MCU will logically connect its internal UART serial port function pins TXD and RXD to the OUT port.

[0045] Specifically, when data needs to be received, such as when TXD outputs 0V and RXD is set to serial port receive mode, the MCU receives serial data sent from an external calibration device via the OUT line through the RXD pin; when data needs to be sent, such as when RXD outputs 0V and TXD is configured to serial port send mode, the MCU sends data to the OUT line through the TXD pin.

[0046] Running on external calibration equipment, such as Figure 8 The calibration software shown allows operators to apply a series of standard loads to the sensor, such as through weights or a standard force gauge, and input the corresponding standard value (KN) on the software interface. After each standard value is input, the operator clicks the calibration button, and the calibration software sends the instructions and data to the sensor via the OUT line. After receiving the data, the sensor MCU records the original AD value under the current load and pairs it with the received standard force value.

[0047] By collecting multiple linear calibration points, the MCU can generate a non-linear, piecewise force-AD value correspondence table internally. This table will be burned into the MCU's EEPROM as new calibration parameters. After calibration, the external device sends an exit calibration command, or after a timeout, the sensor will automatically exit the calibration mode, RXD and TXD will return to the high-resistance state, and the sensor will return to the measurement mode.

[0048] In subsequent measurement work, the MCU will use this new, online calibrated parameter table to calculate the force value, so that the sensor's measurement results can accurately reflect its actual working condition and compensate for errors caused by installation, environment and other factors.

[0049] In summary, this utility model, through ingenious circuit design and software flow, utilizes a single signal output line to multiplex three functions: analog signal output, mode switching trigger, and bidirectional digital communication. It achieves powerful online calibration functionality at extremely low hardware cost, solves the pain points of existing technologies, and has high practical value.

[0050] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A pin-on force sensor, characterized by include: The pin body, a magnetic circuit system disposed inside the pin body, and a control circuit for driving and processing signals; the magnetic circuit system includes an excitation coil (E0) and an induction coil (E1); the control circuit includes a microprocessor (MCU), a signal output port OUT, and a mode switching detection circuit connected to the signal output port OUT; the control circuit has a measurement mode and a calibration mode. In the measurement mode, the control circuit drives the excitation coil (E0) to generate an alternating magnetic field, and calculates the measured value corresponding to the load on the pin body based on the output signal of the induction coil (E1), and outputs a standard signal corresponding to the measured value through the signal output port OUT; The mode switching detection circuit is configured to output a trigger signal to the MCU when the signal output port OUT receives an externally applied mode switching command signal with a voltage value higher than the normal range of the standard signal. After receiving the trigger signal, the MCU switches the control circuit from measurement mode to calibration mode. In calibration mode, the MCU communicates bidirectionally with an external calibration device through the signal output port OUT to execute an online calibration program.

2. A pin-bus type force sensor according to claim 1, wherein The mode switching detection circuit includes a first diode (D1) connected to the signal output port OUT. The inverting terminal of the first diode (D1) is connected to the analog-to-digital converter (ADC) input pin of the MCU. When the mode switching command signal is received, the first diode (D1) is reverse-biased and cut off, so that the ADC input pin detects a high-level signal as the trigger signal.

3. A pin-bus type force sensor according to claim 2, wherein In the calibration mode, the MCU functionally connects the transmit pin TXD and receive pin RXD of its Universal Asynchronous Receiver Transceiver (UART) to the signal output port OUT to enable data transmission and reception.

4. A pin-bus type force sensor according to claim 3, wherein The control circuit also includes a first digital-to-analog converter (DAC1) for generating an excitation signal and a second digital-to-analog converter (DAC2) for outputting a standard signal; when entering calibration mode, the MCU controls the second digital-to-analog converter (DAC2) to output a preset low level.

5. The pin shaft load cell of claim 1, wherein, The control circuit also includes a sampling control circuit that is synchronized with the excitation signal of the excitation coil (E0); the sampling control circuit includes a voltage comparator (OP1), which is used to compare the excitation signal with a reference voltage Vref1 and output an interrupt trigger signal (INT1) to the interrupt pin of the MCU; the MCU synchronously starts the ADC to sample the output signal of the induction coil (E1) according to the interrupt trigger signal (INT1).

6. A pin-bus type force sensor according to claim 5, wherein The excitation signal is a sine wave signal; the sampling control circuit generates the interrupt trigger signal (INT1) at the peak or trough of the sine wave signal.

7. The pin shaft load cell of claim 1, wherein, The control circuit also includes a non-volatile memory for storing multi-point nonlinear calibration parameters obtained through an online calibration program; In the measurement mode, the MCU corrects the measurement result by using the multi-point non-linear calibration parameter.

8. The pin shaft load cell of claim 1, wherein, The components of the control circuit are all general electronic components, and do not contain special integrated chips.

Images