Gantry crane weighing and overload protection terminal and control method thereof

Abstract

The invention provides a gantry crane weighing and overload protection terminal and a control method thereof, and relates to the technical field of gantry crane weighing and safety protection. According to the invention, a high-precision ADC chip is matched with an AC excitation circuit and a six-wire system sensor to directly sample sensor signals. The ADC adopts excitation voltage feedback from a six-wire system weighing sensor as reference voltage instead of fixed reference voltage generated by a circuit, so that the influence of power supply fluctuation is eliminated. The alternating current excitation circuit can generate excitation sources with positive and negative voltages, and the common zero drift problem in direct current excitation can be eliminated by sampling the conversion result of positive excitation and negative excitation for processing, so that the temperature stability is improved. Through the channel selection function of the ADC chip, one ADC chip can perform time division multiplexing and read data of the two sensors. Through direct sampling of sensor signals, a transmitter link is eliminated, and conversion errors generated by a transmitter are directly reduced.

Description

Technical Field

[0001] This invention relates to the field of weighing and safety protection technology for gantry cranes, and in particular to a weighing and overload protection terminal for gantry cranes and its control method. Background Technology

[0002] Gantry cranes (hereinafter referred to as gantry cranes) are the main equipment in bulk cargo terminals. Overload limiting is one of the essential safety features of gantry cranes, preventing accidents caused by exceeding the maximum lifting capacity. Weighing function is another important function of gantry cranes, used to collect data such as workload, providing data support for terminal operation and management.

[0003] The lifting capacity of gantry cranes is typically measured indirectly, with a force-taking device transmitting the weight proportionally to a load cell for load monitoring. The load cell operates on the principle of strain gauges; the force acting on it causes a slight change in resistance. By measuring this change in resistance, the magnitude of the force acting on the load cell can be calculated.

[0004] PLCs and other actuators cannot directly measure minute changes in resistance. A signal conditioning circuit needs to be installed after the sensor to amplify and convert the weak resistance signal into a signal that the PLC can process. Currently, gantry cranes typically use four-wire load cells paired with a 4-20mA load transmitter to convert the resistance change of the load cell into a 4-20mA current signal, which is then sent to the PLC and other devices. This architecture can only be used with four-wire load cells. Four-wire load cells have only one pair of signal lines and are easily affected by errors in the measurement circuit and the resistance of the sensor wires, leading to inaccurate measurement results.

[0005] Furthermore, the 4-20mA weighing transmitter performs analog-to-analog conversion, which is susceptible to temperature changes and electromagnetic interference, leading to errors in the conversion results. The 4-20mA current signal output is also an analog output. The cable length from the transmitter to devices such as PLCs is typically quite long, and the transmission is easily affected by line voltage drops and external electromagnetic interference, resulting in distortion of the output signal.

[0006] Furthermore, when receiving 4-20mA current signals, devices such as PLCs need to perform analog-to-digital conversion (also known as analog-to-digital conversion or AD conversion), which not only requires additional hardware but also introduces new conversion errors. 4-20mA weighing transmitters have limited functionality, typically only providing basic zeroing and lacking functions such as calibration, fusion calculation, and overload signal output; further processing by devices like PLCs is required after receiving the signal.

[0007] The invention patent CN112027917B proposes an intelligent gateway for overload protection of lifting equipment. In this scheme, sensors rely on transmitters for signal amplification and conversion. The transmitter performs analog-to-analog conversion, which is susceptible to temperature changes and electromagnetic interference, leading to errors in the conversion results. Due to the large size of cranes, the wires from the transmitter output to the MCU input are typically long, making the analog signal output by the transmitter susceptible to electromagnetic interference and transmission distortion. Furthermore, this scheme uses the MCU's integrated analog-to-digital converter (ADC) for analog-to-digital conversion. The ADC integrated within the microcontroller has low resolution, is susceptible to internal noise, and has poor accuracy; the reference power supply depends on the microcontroller's power supply. It lacks multi-channel multiplexing functionality, requiring a separate transmitter for each sensor, resulting in high costs. Weight data processing is relatively simple, only performing zero-point compensation and sensitivity correction, failing to consider the sensor's nonlinear characteristics, temperature drift, and data jitter. Summary of the Invention

[0008] Purpose of the invention: To propose a gantry crane weighing and overload protection terminal and its control method to solve the above-mentioned problems existing in the prior art.

[0009] In a first aspect, the present invention provides a gate operator weighing and overload protection terminal, comprising: a power supply module, a microcontroller module, an Ethernet communication module, a button and screen module, an external Flash ROM module, an AC excitation generation module, a weighing sensor, a low-pass filter module, and an AD acquisition module;

[0010] The weighing sensor is provided in multiple parts, and each pair of sensors requires two low-pass filter modules, one AC excitation generation module, and one AD acquisition module.

[0011] The power module is used to generate various voltages required for the operation of each component in the circuit.

[0012] The microcontroller module coordinates the work of each sub-module to realize the functions of sensor data acquisition, processing, and output;

[0013] The Ethernet communication module implements the standard TCP / IP protocol, enabling the microcontroller module to communicate with other host computers.

[0014] The buttons and screen module can be configured with various parameters;

[0015] The external Flash ROM module stores various parameters and firmware;

[0016] The AC excitation generation module is controlled by the microcontroller module and is used to generate positive or negative excitation voltages.

[0017] Each of the weighing sensors receives an AC excitation voltage and provides a feedback voltage and an output signal;

[0018] Each of the low-pass filter modules performs hardware filtering on the feedback voltage and output signal given by the gravity sensor;

[0019] Each AD acquisition module uses the feedback voltage given by the sensor as a reference voltage, converts the sensor output signal into a digital quantity, and sends it to the microcontroller module; each AD acquisition module can time-division multiplex the signals of two weighing sensors.

[0020] In a further embodiment of the first aspect, the microcontroller module consists of a microcontroller U1 of model STM32H743VG and its peripheral circuitry.

[0021] Each AD acquisition module can time-division multiplex the signals of two weighing sensors, including sensor I and sensor II, both of which are six-wire weighing sensors.

[0022] In a further embodiment of the first aspect, the power module includes a DC-DC step-down chip U2, a first low-dropout linear regulator chip U3, a second low-dropout linear regulator chip U4, and their peripheral circuitry.

[0023] 12V_EXT is the external power input. After being protected by the reverse polarity protection diode D1, the self-resetting fuse FR1, and the varistor RV1, the output is the first standard voltage. The DC-DC step-down chip U2 is model SCT2432STER, and its input is the first standard voltage.

[0024] The DC-DC step-down chip U2 starts working when the voltage at its EN pin is higher than 1.18V; R1 and R2 are voltage divider resistors used to set the start-up voltage V of the DC-DC circuit. s V s =1.18·(R1+R2) / R1;

[0025] The resistor R3 connected to pin 4 of U2 is used to set the operating frequency f of the DC-DC circuit. sw f sw =1·10 11 / R3; Capacitor C1 is the bootstrap capacitor for U2; R4 and R5 are used to generate feedback voltage, setting the output voltage V of the DC-DC circuit. o V o =0.8·(R4+R5) / R4; Inductor L1, capacitors C2, C3, C4 and U2 together form a Buck step-down circuit;

[0026] The first low-dropout linear regulator chip U3 is model TPS7A2050PDBVR;

[0027] The second low-dropout linear regulator chip, U4, is model AP7365-33.

[0028] In a further embodiment of the first aspect, the AC excitation generation module is composed of two dual-channel single-pole single-throw analog switch chips TS5A21366, with two digital signal input ports N1AIN8 and N1AIN9, an excitation voltage + output port N1EXC0 and an excitation voltage - output port N1EXC1;

[0029] The microcontroller U1 controls the AD acquisition module to provide signals N1AIN8 and N1AIN9. This circuit can output a 5V excitation voltage or a -5V excitation voltage.

[0030] In a further embodiment of the first aspect, in the low-pass filter module, each weighing sensor has a pair of voltage feedback signals REF0, REF1 and a pair of weight output signals BR_O+, BR_O-; since each AD acquisition module acquires data from two weighing sensors, each low-pass filter module has two weight output signal filters and voltage feedback signal filters of the same specifications; the low-pass filter is composed of a resistor connected in series with each pair of signals, a differential capacitor connected in parallel between each pair of signals, and a common-mode capacitor connected in parallel between each pair of signals and GND, used to filter high-frequency interference in the signal lines.

[0031] In a further embodiment of the first aspect, the AD acquisition module consists of an ADC chip U9 of model ADS1262 and its peripheral circuitry;

[0032] The ADC chip U9 has eight channels as analog signal input ports, configured as four differential signal inputs. The differential input channels N1AIN0 and N1AIN1 are connected to the feedback output port of sensor I, the differential input channels N1AIN6 and N1AIN7 are connected to the signal output port of sensor I, the differential input channels N1AIN2 and N1AIN3 are connected to the feedback output port of sensor II, and the differential input channels N1AIN4 and N1AIN5 are connected to the signal output port of sensor II.

[0033] N1AIN8 and N1AIN9 are configured as GPIO output mode and controlled by microcontroller U1. The output signals are connected to the AC excitation generation module to generate excitation voltage.

[0034] The ADC chip U9 communicates with the microcontroller U1 via the SPI bus, receives the configuration parameters and control signals given by the microcontroller U1, and returns the AD conversion result.

[0035] A second aspect of the present invention provides a control method for the above-mentioned gantry crane weighing and overload protection terminal, comprising the following steps:

[0036] The microcontroller module reads the output of each sensor through AC excitation technology and performs zero-point compensation to correct the output deviation of the sensor under no-load conditions.

[0037] Nonlinear sensitivity correction is performed by interpolation to compensate for the difference between the theoretical and actual sensitivity of the sensor. Then, Kalman filtering is performed to calculate the optimal estimate that is closer to the true value.

[0038] After obtaining the optimal estimates from all sensors, multi-sensor fusion is performed based on the characteristics of the door operator to obtain a final weight output, and an alarm signal is output according to preset rules.

[0039] In a further embodiment of the second aspect, the microcontroller module reads the outputs of each sensor using AC excitation technology, specifically including:

[0040] Initialize the ADC chip, set the PGA gain and switch to single-trigger mode, and the following conditions must be met:

[0041] V REF / Gain·(2 32-1 -1) / 2 32-1 ≥V REF ·K s

[0042] Among them, V REF K is the ADC reference voltage. s For sensor sensitivity;

[0043] The output signals of the two weighing sensors under positive excitation are measured separately. First, the AC excitation generation circuit is controlled to output positive excitation voltage to the sensor. The reference channel of the ADC chip is set as the feedback voltage output channel N1AIN0 and N1AIN1 of sensor I, and the signal input channel of the ADC chip is set as the signal output channel N1AIN6 and N1AIN7 of sensor I.

[0044] Initiating a single conversion yields the positive excitation conversion result R from sensor I. s1+ Then, keeping the positive excitation output unchanged, the reference channels of the ADC chip are set to the sensor II feedback voltage output channels N1AIN2 and N1AIN3, and the signal input channels of the ADC chip are set to the sensor II signal output channels N1AIN4 and N1AIN5. A single conversion is then initiated to obtain the sensor II positive excitation conversion result R. s2+ ;

[0045] After the positive excitation measurement is completed, the AC excitation generation circuit outputs a negative excitation voltage to the sensor, sets the reference channel of the ADC chip to the sensor I feedback voltage output channels N1AIN0 and N1AIN1, and flips the reference input channel to set the signal input channel of the ADC chip to the sensor I signal output channels N1AIN6 and N1AIN7. A single conversion is then initiated, yielding the sensor I negative excitation conversion result R. s1- After completion, the reference channels of the ADC chip are set to the sensor II feedback voltage output channels N1AIN2 and N1AIN3, and the reference input channels are flipped. The signal input channels of the ADC chip are set to the sensor II signal output channels N1AIN4 and N1AIN5, and a single conversion is started to obtain the sensor II negative excitation conversion result R. s2- .

[0046] In a further embodiment of the second aspect, under a positive excitation voltage, the positive output of the sensor's equivalent bridge is connected to the positive input channel of the ADC chip, and the negative output of the sensor's equivalent bridge is connected to the negative input channel of the ADC chip; therefore, under a positive excitation voltage, R... s+ =Gain·(V) out +V os ), where R s+ For the positive excitation equivalent input voltage, V out V is the output voltage of the sensor bridge. os For various drift voltages, including ADC drift error and parasitic thermocouple drift in the circuit, Gain is the PGA gain of the ADC chip;

[0047] Under a negative excitation voltage, because the polarity of the excitation voltage is reversed and the ADC signal input channel remains unchanged, the positive output of the sensor's equivalent bridge is connected to the negative input channel of the ADC chip, and the negative output of the sensor's equivalent bridge is connected to the positive input channel of the ADC chip; therefore, under a negative excitation voltage, R... s- =Gain·(-V) out +V os ), where R s- For the negative excitation equivalent input voltage, V out V is the output voltage of the sensor bridge. os For various drift voltages, Gain is the PGA gain of the ADC chip;

[0048] By measuring the equivalent input voltages under positive and negative polarity excitations respectively, the fused input voltage R can be calculated using the following formula. s :

[0049]

[0050] By integrating R s+ With Rs- Eliminate drift error V os .

[0051] In a further embodiment of the second aspect, the sensitivity of the weighing sensor is first corrected before reading the output of each sensor:

[0052] Prepare n standard weights of known weight, whose weights in ascending order are W. s1 W s2 ,…,W sn Place standard weights sequentially onto the weighing sensor and record the corresponding sensor output value V. s1 V s2 ,…,V sn V s0 =W s0 =0; Calculate the sensor sensitivity G of the nth segment of the curve. n ,:

[0053]

[0054] Each sensor is calibrated independently;

[0055] When the unknown weight W o When applying load to the load cell, first determine its sensitivity interval n, and then obtain the corresponding segmented sensitivity G. n The sensor outputs V using the following formula. o Calculate W o :W o =W s(n-1) +G n ·(V o -V s(n-1) ).

[0056] In a further embodiment of the second aspect, the multi-sensor fusion based on the characteristics of the door operator specifically includes:

[0057] The user pre-inputs the force coefficients c1, c2, ..., c of n weighing sensors. n ;

[0058] The formula for calculating the fusion weight is as follows: Where W is the calculated total weight, W i Let c be the weight reading of the i-th weighing sensor. i is the force coefficient of the i-th weighing sensor.

[0059] Compared with the prior art, the present invention has significant technical advantages in the following aspects:

[0060] A high-precision ADC chip is used in conjunction with an AC excitation circuit and a six-wire sensor for direct sampling of sensor signals. The ADC uses the excitation voltage feedback from the six-wire load cell as the reference voltage, rather than a fixed reference voltage generated by the circuit, eliminating the influence of power supply fluctuations. An independent high-precision ADC conversion chip is used, instead of the MCU's built-in ADC conversion, reducing conversion errors and noise. The AC excitation circuit can generate positive and negative voltage excitation sources. By sampling and processing the conversion results of positive and negative excitations, the zero-point drift problem common in DC excitation can be eliminated, improving temperature stability. Through the ADC chip's channel selection function, a single ADC chip can be time-division multiplexed to read data from two sensors, reducing hardware costs. Direct sampling of sensor signals eliminates the transmitter stage, directly reducing conversion errors caused by the transmitter.

[0061] The equipment uses the industrial standard protocol Modbus TCP to transmit data over the network, eliminating signal distortion during transmission. It is compatible with mainstream industrial equipment and can be directly integrated.

[0062] This invention incorporates algorithms such as zero-point compensation, sensitivity correction, nonlinear interpolation correction, and Kalman filtering, which significantly correct various errors in the sensor and improve data accuracy.

[0063] This invention uses fewer discrete analog devices and extensively integrates devices to reduce drift problems caused by temperature effects. Attached Figure Description

[0064] Figure 1 This is an architecture diagram of the gantry crane weighing and overload protection terminal in the embodiment.

[0065] Figure 2 This is a flowchart of the control method used for the terminal in the embodiment.

[0066] Figure 3 This is the circuit diagram of the power module in the terminal.

[0067] Figure 4 This is the circuit schematic of the AC excitation voltage generation module in the terminal.

[0068] Figure 5 This is the circuit schematic of the low-pass filter module in the terminal.

[0069] Figure 6 This is the circuit diagram of the AD acquisition module in the terminal.

[0070] Figure 7 This is the circuit schematic of the microcontroller module in the terminal.

[0071] Figure 8This is the circuit schematic of the external Flash ROM module in the terminal.

[0072] Figure 9 This is the circuit diagram of the Ethernet communication module in the terminal.

[0073] Figure 10 This is the circuit diagram of the button and screen modules in the terminal.

[0074] Figure 11 This is a flowchart illustrating the multi-channel AC excitation reading of sensor output in this embodiment.

[0075] Figure 12 This is a circuit diagram of the ADC chip under positive excitation voltage in the embodiment.

[0076] Figure 13 This is a circuit diagram of the ADC chip under negative excitation voltage in the embodiment.

[0077] Figure 14 This is a graph showing the relationship between the force on the sensor and its output when the sensitivity of the weighing sensor is corrected in the embodiment.

[0078] Figure 15 This is a flowchart of the network upgrade procedure performed on the terminal in the embodiment. Detailed Implementation

[0079] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0080] Before describing the embodiments in detail, some terms used below will be explained.

[0081] ADC: Analog-to-Digital Converter (ADC) is used to convert analog signals into digital signals.

[0082] AD conversion: The conversion action that transforms analog signals into digital signals, which relies on the ADC.

[0083] The following embodiments will elaborate on this solution from both hardware and software design perspectives.

[0084] I. Hardware Design

[0085] The hardware design schematic diagram of this invention is as follows: Figure 1As shown. The power supply module generates various voltages required for the operation of each component in the circuit. The microcontroller module coordinates the work of each submodule, realizing sensor data acquisition, processing, and output functions. The Ethernet communication module implements the standard TCP / IP protocol, upon which the microcontroller communicates with other host computers. The button and screen modules allow setting various parameters. The external Flash ROM module stores various parameters and firmware, enabling in-application upgrades. The AC excitation generation module, controlled by the microcontroller, generates positive or negative excitation voltages. The six-wire load cell receives the AC excitation voltage and provides a feedback voltage and output signal. The low-pass filter module performs hardware filtering on the feedback voltage and output signal from the load cell to reduce interference. The six-wire load cell AD acquisition module uses the feedback voltage from the sensor as a reference voltage, converts the sensor output signal into a digital quantity, and sends it to the microcontroller. The microcontroller processes the data in software and outputs the result. Each six-wire load cell AD acquisition module can acquire signals from two six-wire load cells through time-division multiplexing. The module within the dashed box in the hardware design diagram has two instances in this invention, thus it can handle four six-wire weighing sensor inputs.

[0086] 1. Power Module

[0087] The power module in this invention features diode reverse polarity protection, a resettable fuse, and varistor protection against overvoltage and overcurrent. It accepts a 9-36V DC input, first stepping it down to a 5.5V intermediate voltage via a DC-DC converter, then further stepping it down to 5.0V and 3.3V via two LDOs respectively. The 5.0V supplies power to the ADC chip, and the 3.3V supplies power to the remaining digital circuits. The circuit schematic of the power module is shown below. Figure 3 As shown.

[0088] 12V_EXT is the external power input. After protection by the reverse polarity protection diode D1, the resettable fuse FR1, and the varistor RV1, the output is 12V. U2 is a DC-DC step-down chip SCT2432STER, with a 12V input. U2 starts operating when the voltage at its EN pin is higher than 1.18V. R1 and R2 are the start-up voltage divider resistors, used to set the start-up voltage V of this DC-DC circuit. s V s = 1.18·(R1+R2) / R1. Resistor R3 connected to pin 4 of U2 is used to set the operating frequency f of the DC-DC circuit. sw f sw =1·10 11 / R3. Capacitor C1 is the bootstrap capacitor for U2. R4 and R5 are used to generate the feedback voltage, setting the output voltage V of the DC-DC circuit. o V o=0.8·(R4+R5) / R4. Inductor L1, capacitors C2, C3, C4, and U2 together form a Buck step-down circuit. 5V5 is the output voltage of the DC-DC step-down circuit formed by U2, and its typical value is 5.5V.

[0089] U3 is a low-dropout linear regulator chip TPS7A2050PDBVR, which accepts a 5.5V input voltage and outputs a 5.0V voltage. U4 is a low-dropout linear regulator chip AP7365-33, which accepts a 5.5V input voltage and outputs a 3.3V voltage.

[0090] Specifically, the circuit module includes an external power input interface 12V_EXT, a reverse polarity protection diode D1 (50V 1A), a resettable fuse FR1 (500mA), a varistor RV1 (10D330), a DC-DC step-down chip U2 (SCT2432STER), a low dropout linear regulator chip U3 (TPS7A2050PDBVR), a low dropout linear regulator chip U4 (AP7365-33), and resistors R1, R2, R3 (200K), R4 (10K), and R5 (59K). R6 (100K), inductor L1 (18uH), capacitors C1, C2 (47uF), C3 (100nF), C4 (100nF), C5 (10nF), C6 (100nF 50V), C8 (4.7uF 50V), C9 (10uF), C10 (100nF), C11 (100nF), C12 (10uF), C13 (10nF), C14 (10uF), C15 (100nF), C16 (10uF), C17 (100nF).

[0091] The connection relationships of the above components are as follows:

[0092] The external power supply 12V_EXT passes through the reverse polarity protection diode D1, the self-resetting fuse FR1, and the varistor RV1 in sequence to output a 12V voltage. This 12V voltage is connected to the VIN pin (pin 2) of the DC-DC step-down chip U2.

[0093] Resistors R1 and R2 form a start-up voltage divider resistor, which is connected to the EN pin (pin 3) of U2 to set the start-up voltage of the DC-DC circuit; resistor R3 is connected to the RT / CLK6 pin (pin 6) of U2 to set the circuit operating frequency; resistors R4 and R5 are connected to the FB pin (pin 5) of U2 to generate a feedback voltage to set the output voltage.

[0094] Capacitor C1 is the bootstrap capacitor of U2 and is connected to the relevant pin of U2; Inductor L1, capacitors C2, C3, and C4 together with U2 form a Buck step-down circuit, and the output of U2 is 5.5V (5V5).

[0095] A 5V5 voltage is connected to the VIN pin of U3, and the VOUT pin (pin 5) of U3 outputs a 5.0V voltage (5V0). The EN pin (pin 2) of U3 is connected to resistor R6, and capacitors C9, C10, C11, C12, and C13 are connected around U3. At the same time, a 5V5 voltage is connected to the IN pin (pin 3) of U4, and the OUT pin (pin 1) of U4 outputs a 3.3V voltage (3V3). Capacitors C14, C15, C16, and C17 are connected around U4.

[0096] Each capacitor is connected between its corresponding chip pin and GND to achieve the filtering function. One end of inductor L1 is connected to the output terminal of U2, and the other end is connected to the capacitor and other filtering components.

[0097] 2. Communication and Incentive Generation Module

[0098] Figure 4 This is the circuit schematic of the AC excitation voltage generation module. The circuit consists of two dual-channel single-pole single-throw analog switch chips, TS5A21366. The circuit has two digital signal input ports, N1AIN8 and N1AIN9, and two output ports: excitation voltage + N1EXC0 and excitation voltage - N1EXC1. The input and output correspondence of this circuit is shown in Table 1.

[0099] Table 1 Input / Output Comparison Table of the AC Excitation Generation Module

[0100]

[0101] The circuit can output a 5V excitation voltage or a -5V excitation voltage by using the N1AIN8 and N1AIN9 signals provided by the microcontroller.

[0102] Specifically, the AC excitation generation module includes a dual-channel single-pole single-throw analog switch chip U7 (TS5A21366), a dual-channel single-pole single-throw analog switch chip U8 (TS5A21366), digital signal input ports N1AIN8 and N1AIN9, excitation voltage output ports N1EXC0 and N1EXC1, capacitors C45 (1uF) and C48 (1uF), a 5V0 power supply interface, and a GND interface.

[0103] The connection relationships of the above components are as follows:

[0104] The 5V0 power supply is connected to the VCC pin of U7 and the VCC pin of U8 respectively; the GND is connected to the GND pin of U7 and the GND pin of U8 respectively.

[0105] Digital signal input ports N1AIN8 are connected to the IN2 pin of U7 and the IN2 pin of U8, respectively; digital signal input ports N1AIN9 are connected to the IN1 pin of U7 and the IN1 pin of U8, respectively.

[0106] The COM1 pin of U7 is connected to the excitation voltage output port N1EXC1, and the NO1 and NO2 pins of U7 are connected to the relevant lines respectively; the COM1 pin of U8 is connected to the excitation voltage output port N1EXC0, and the NO1 and NO2 pins of U8 are connected to the relevant lines respectively.

[0107] One end of capacitor C45 is connected to the relevant pin of U7, and the other end is connected to GND; one end of capacitor C48 is connected to the relevant pin of U8, and the other end is connected to GND, thus achieving the filtering function.

[0108] 3. Low-pass filter module

[0109] Figure 5 This is a circuit diagram of a low-pass filter module. Each sensor has a pair of voltage feedback signals REF0 and REF1 and a pair of weight output signals BR_O+ and BR_O-. Since each sensor acquisition module can acquire data from two sensors, the low-pass filter module has two identical weight output signal filters and voltage feedback signal filters. The low-pass filter consists of a resistor connected in series with each pair of signals, a differential capacitor connected in parallel between each pair of signals, and a common-mode capacitor connected in parallel between each pair of signals and GND, used to filter high-frequency interference in the signal lines.

[0110] Specifically, the low-pass filter module includes resistors R40 (47R), R41 (47R), R42 (0R), R43 (0R), R44 (47R), R45 (47R), R48 (0R), R53 (0R), and capacitors C44 (100nF), C46 (100nF), C47 (100nF), C49 (100nF), C50 (100nF), C51 (100nF), C52 (100nF), C53 (100nF), C55 (100nF), and C5... 7 (100nF), C58 (100nF), C60 (100nF), signal interfaces N1S1_BR_O+, N1S1_BR_O-, N1S1_REF0, N1S1_REF1, N1S2_BR_O+, N1S2_BR_O-, N1S2_REF0, N1S2_REF1, AD acquisition module interfaces N1AIN0, N1AIN1, N1AIN2, N1AIN3, N1AIN4, N1AIN5, N1AIN6, N1AIN7, GND interface.

[0111] The connection relationships of the above components are as follows:

[0112] For the N1S1 sensor signal: N1S1_BR_O+ is connected to N1AIN6 through resistor R40, and N1S1_BR_O- is connected to N1AIN7 through resistor R41; N1S1_REF0 is connected to N1AIN0 through resistor R42, and N1S1_REF1 is connected to N1AIN1 through resistor R43.

[0113] For the N1S2 sensor signal: N1S2_BR_O+ is connected to N1AIN4 through resistor R44, and N1S2_BR_O- is connected to N1AIN5 through resistor R45; N1S2_REF0 is connected to N1AIN2 through resistor R48, and N1S2_REF1 is connected to N1AIN3 through resistor R53.

[0114] One end of capacitor C44 is connected to the N1S1_BR_O+ line, and the other end is connected to GND; one end of C46 is connected to the N1S1_BR_O- line, and the other end is connected to GND; one end of C47 is connected between N1S1_BR_O+ and N1S1_BR_O- to achieve differential filtering; one end of C49 is connected to the N1S1_REF0 line, and the other end is connected to GND; one end of C50 is connected to the N1S1_REF1 line, and the other end is connected to GND; one end of C51 is connected between N1S1_REF0 and N1S1_REF1 to achieve differential filtering.

[0115] One end of capacitor C52 is connected to the N1S2_BR_O+ line, and the other end is connected to GND; one end of C53 is connected to the N1S2_BR_O- line, and the other end is connected to GND; one end of C55 is connected between N1S2_BR_O+ and N1S2_BR_O- to achieve differential filtering; one end of C57 is connected to the N1S2_REF0 line, and the other end is connected to GND; one end of C58 is connected to the N1S2_REF1 line, and the other end is connected to GND; one end of C60 is connected between N1S2_REF0 and N1S2_REF1 to achieve differential filtering.

[0116] 4. Six-wire load cell AD acquisition module

[0117] Figure 6This is a circuit diagram of a six-wire load cell AD acquisition module. U9 in this module is a high-precision differential ADC chip, ADS1262. The ADS1262 has eight channels as analog signal input ports, configured as four differential signal inputs. The differential input channels N1AIN0 and N1AIN1 are connected to the feedback output port of load cell 1; the differential input channels N1AIN6 and N1AIN7 are connected to the signal output port of load cell 1; the differential input channels N1AIN2 and N1AIN3 are connected to the feedback output port of load cell 2; and the differential input channels N1AIN4 and N1AIN5 are connected to the signal output port of load cell 2. N1AIN8 and N1AIN9 are configured as GPIO outputs, controlled by a microcontroller, and their output signals are connected to an AC excitation generation module to generate an excitation voltage.

[0118] In this module, the ADS1262 communicates with the microcontroller via the SPI bus, receives configuration parameters and control signals from the microcontroller, and returns the AD conversion results.

[0119] Specifically, this six-wire weighing sensor AD acquisition module includes a high-precision differential ADC chip U9 (ADS1262), resistors R46 (100K), R47 (100K), R50 (47R), R51 (47R), R52 (47R), R54 (47R), R55 (47R), R56 (47R), capacitors C54 (1uF), C56 (4.7nF), C59 (1uF), C62 (100nF), C61 (1uF), C63 (100nF), C64 (1uF), crystal oscillator X, and analog signal input ports N1AIN0, N1AIN1, N1AIN2, N1AIN3, N1AIN4, and N1AIN. IN5, N1AIN6, N1AIN7, N1AIN8, N1AIN9, N1AINCOM, AD reference voltage output port N1ADCREFOUT, microcontroller pins PE0, PB3, PB5, PB4, PE1, PB8, 5V0 power supply interface, 3V3 power supply interface, GND interface, SPI bus interface (CS, SCLK, DIN, DOUT / DRDY, DRDY), BYPASS interface, RESET / PWDN interface, START interface, AVDD interface, AVSS interface, DVDD interface, DGND interface, XTAL1 / CLKIN interface, XTAL2 interface, CAPP interface, CAPN interface.

[0120] The connection relationships of the above components are as follows:

[0121] The analog signal input ports of ADC chip U9 are as follows: the differential input channel consisting of N1AIN0 and N1AIN1 is connected to the feedback output port of weighing sensor 1; the differential input channel consisting of N1AIN6 and N1AIN7 is connected to the signal output port of weighing sensor 1; the differential input channel consisting of N1AIN2 and N1AIN3 is connected to the feedback output port of weighing sensor 2; the differential input channel consisting of N1AIN4 and N1AIN5 is connected to the signal output port of weighing sensor 2; N1AIN8 and N1AIN9 are configured as GPIO output mode and connected to the AC excitation generation module.

[0122] Power connections: 5V0 power supply is connected to the AVDD pin (pin 7) and related lines of U9, and 3V3 power supply is connected to the DVDD pin (pin 19) and related lines of U9; GND is connected to the AVSS pin (pin 8), DGND pin (pin 18) and other ground lines of U9 respectively.

[0123] Resistor connections: R46 and R47 are connected to the relevant pins of U9 at one end and to GND at the other end; R50, R51, R52, R54, R55, and R56 are connected to the corresponding pins of U9 and the microcontroller pins PE0, PB3, PB5, PB4, PE1, and PB8 respectively, with a resistance value of 47R.

[0124] Capacitor connections: C54 is connected between the relevant pin of the SPI bus and GND; C56 is connected between the CAPP pin (pin 5) and the CAPN pin (pin 6) of U9; C59, C62, C61, C63, and C64 are connected between the relevant pin of U9 and GND respectively to achieve the filtering function.

[0125] The crystal oscillator X is connected to the XTAL1 / CLKIN pin (pin 15) and XTAL2 pin (pin 16) of U9; U9 communicates with the microcontroller via the SPI bus (CS, SCLK, DIN, DOUT / DRDY, DRDY), receives configuration parameters and control signals, and returns the AD conversion result; the BYPASS interface, RESET / PWDN interface, START interface, etc. are connected to the corresponding lines according to the circuit requirements.

[0126] 5. Microcontroller module

[0127] Figure 7 This is a circuit diagram of the microcontroller module. U1 in this module is an STM32H743VG microcontroller. The microcontroller connects to the various hardware modules in this invention, executes algorithms to process data, and outputs the results.

[0128] Specifically, the microcontroller module includes a microcontroller U1 (STM32H743VG, divided into three parts: U1A, U1B, and U1C), resistors R11 (10K), R12 (10K), R13 (1K), inductor L2 (600R), and capacitors C18 (12pF), C19 (12pF), C20 (100nF), C21 (2.2uF), C22 (100nF), C23 (2.2uF), C24 (100nF), C25 (100nF), C26 (100nF), C27 (100nF), and C28 (100nF). C29 (100nF), C30 (100nF), Crystal X1 (8MHz), Buttons S1 and S2, BOOT0 interface, OSCIN interface, OSCOUT interface, NRST interface, various I / O pins (such as PA0-WKUP, PA1, PA2, ..., PB0-PB15, PC0-PC15, PD0-PD15, PE0-PE15, etc.), 3V3 power supply interface, GND interface, VDD interface, VSS interface, VDDA interface, VSSA interface, VCAP1 interface, VCAP2 interface, VREF+ interface, VBAT interface.

[0129] The connection relationships of the above components are as follows:

[0130] Power connection: Connect the 3V3 power supply to the microcontroller's VDD pin (e.g., pins 27, 50, 75, 100), VDDA pin (pin 21), VBAT pin (pin 6), and related lines; connect GND to the microcontroller's VSS pin (e.g., pins 10, 26, 49, 74, 99), VSSA pin (pin 19), and other ground lines.

[0131] Crystal and Capacitors: One end of crystal X1 (8MHz) is connected to the OSCIN interface, and the other end is connected to the OSCOUT interface. Both ends of the crystal are connected to GND through capacitors C18 and C19 respectively. Capacitor C20 is connected between the NRST pin and GND. C21 is connected between the VCAP1 interface (pin 48) and GND. C22 is connected between the VREF+ interface (pin 20) and GND. C23 is connected between the VCAP2 interface (pin 73) and GND. C24-C30 are connected between the VDD and VSS pins of the microcontroller respectively to realize the filtering function.

[0132] Resistor connections: R11 is connected to the 3V3 power supply at one end and to the relevant pin at the other end; R12 is connected to GND at one end and to the BOOT0 interface at the other end; R13 is connected to the 3V3 power supply at one end and to the relevant pin at the other end; Inductor L2 is connected in the relevant power supply line.

[0133] Buttons and Interfaces: Button S1 is connected to the relevant lines of the NRST pin; button S2 is connected to a specific I / O pin line; the BOOT0 interface is connected to GND through resistor R12 for boot mode selection; each I / O pin (such as PA0_LAN_NRST, PA1_RMII_CLK, PA2_LAN_MDIO, PB11_RMII_TXEN, PB12_RMII_TXD0, PB13_RMII_TXD1, PE0, PE1, etc.) is connected to the corresponding interfaces of other modules (such as Ethernet communication module, AD acquisition module, etc.) to realize data transmission and control.

[0134] 6. External Flash ROM module

[0135] Figure 8 This is the circuit schematic of an external Flash ROM module. U5 is an SPI Flash chip W25Q64JV, used to save various program parameters when power is off and for remote firmware upgrades. U5 is connected to the microcontroller U1, which reads and writes data as needed.

[0136] Specifically, the external FlashROM module includes an SPI Flash chip U5 (W25Q64JV), a capacitor C31 (100nF), microcontroller pins PD11_QSPIB1_IO0, PD12_QSPIB1_IO1, PB10_QSPIB1_NCS, PB2_QSPI_CLK, PE2_QSPIB1_IO2, PD13_QSPIB1_IO3, a 3V3 power supply interface, and a GND interface.

[0137] The connection relationships of the above components are as follows:

[0138] Power connection: Connect the 3V3 power supply to the VCC pin (pin 8) of U5; connect GND to the GND pin (pin 4) of U5; connect one end of capacitor C31 to the VCC pin of U5 and the other end to GND to achieve filtering.

[0139] Data and control connections: The microcontroller's PD11_QSPIB1_IO0 pin is connected to the U5's DI (IO0) pin (pin 5); the PD12_QSPIB1_IO1 pin is connected to the U5's DO (IO1) pin (pin 6); the PB10_QSPIB1_NCS pin is connected to the U5's CS pin (pin 1); the PB2_QSPI_CLK pin is connected to the U5's CLK pin (pin 7); the PE2_QSPIB1_IO2 pin is connected to the U5's IO2 pin (pin 2); and the PD13_QSPIB1_IO3 pin is connected to the U5's IO3 pin (pin 3), enabling the microcontroller to perform read / write control and data transmission to the U5.

[0140] 7. Ethernet communication module

[0141] Figure 9 This is the circuit schematic of the Ethernet communication module. U6 is the LAN8742A Ethernet PHY chip, which connects to the microcontroller via the RMII interface. The microcontroller can establish TCP / UDP connections as needed. J1 is a 100Mbps RJ45 connector with a built-in network transformer.

[0142] Specifically, the Ethernet communication module includes an Ethernet PHY chip U6 (LAN8742A), a 100Mbps RJ45 connector J1 (HR913129A) with a built-in network transformer, and resistors R21 (49R9), R22 (49R9), R23 (49R9), R24 (49R9), R25, R28 (33R), R29 (33R), R30 (33R), R31 (10K), and R32 (3 3R), R34(10K), R35(1.5K), R36(12.1K, 10K), R37(10K), R38(330R), R39(330R), capacitor C32(470p F), C33(1uF), C34(100nF), C35(100nF), C36(1uF), C37(100nF), C38(100nF), C39(100nF), C4 0 (12pF), C41 (100nF), C42 (12pF), C43 (12pF), Crystal X2 (25MHz), 3V3 power supply interface, GND interface, LANAVDD interface, LAN_TX_P interface, LAN_TX_N interface, LAN_RX_P interface, LAN_RX_N interface, LAN_LED1 interface, LAN_LED2 interface, LANXTAL1 interface, LANXTAL2 interface, Microcontroller pins PB11_RMII_TXEN, PB12_RMII_TXD0, PB13_RMII_TXD1, PA7_RMII_CRS_DV, PC4_RMII_RXD0, PC5_RMII_RXD1, PA0_LAN_NRST, PA1_RMII_CLK, PC1_LAN_MDC, PA2_LAN_MDIO.

[0143] The connection relationships of the above components are as follows:

[0144] Power Connections: Connect the 3V3 power supply to the VDDIO pin (pin 9), VDD1A pin (pin 19), VDD2A pin, VDDCR pin, and LANAVDD interface of U6; connect GND to the GND pin, EP pin, and other ground lines of U6; connect one end of capacitor C33 to the LANAVDD interface and the other end to GND; connect one end of C34 to the VDDIO pin and the other end to GND; connect one end of C35 to the VDD1A pin and the other end to GND; connect one end of C36 to the VDD2A pin and the other end to GND; connect one end of C37 to the VDDCR pin and the other end to GND; connect one end of C38 to the LANAVDD interface and the other end to GND; connect one end of C39 to the LANAVDD interface and the other end to GND; connect one end of C41 to the relevant pins of the RJ45 connector and the other end to GND, all of which perform filtering functions.

[0145] Crystal and capacitors: One end of crystal X2 (25MHz) is connected to the LANXTAL1 interface and the other end is connected to the LANXTAL2 interface. Both ends of the crystal are connected to GND through capacitors C40 and C42 respectively. One end of C43 is connected to the LANXTAL1 interface and the other end is connected to GND.

[0146] Resistor connections: R21, R22, R23, and R24 (all 49R9) are connected between the LANAVDD interface and the relevant lines, respectively; R25 is connected in a specific signal line; R28, R29, R30, and R32 (all 33R) are connected between the signal input / output pins of U6 and the corresponding interfaces (such as LAN_RX_P, LAN_RX_N, LAN_TX_P, LAN_TX_N), respectively; one end of R31 (10K) is connected to the LAN_LED2 interface, and the other end is connected to GND; one end of R34 (10K) is connected to PA1_RMI. The I_CLK pin is connected to a 3V3 power supply at one end; R35 (1.5K) is connected to the PA2_LAN_MDIO pin at one end and to a 3V3 power supply at the other end; R36 (12.1K) is connected between the RBIAS pin (pin 24) of U6 and GND; R36 (10K) is connected in a specific line; R37 (10K) is connected to the nINT / REFCLKO pin (pin 14) of U6 at one end and to GND at the other end; R38 and R39 (both 330R) are connected between the LAN_LED1 and LAN_LED2 interfaces and GND respectively.

[0147] Chip to connector and microcontroller connection: The TXEN pin (pin 16) of U6 connects to the PB11_RMII_TXEN pin of the microcontroller; the TXD0 pin (pin 17) connects to the PB12_RMII_TXD0 pin of the microcontroller; the TXD1 pin (pin 18) connects to the PB13_RMII_TXD1 pin of the microcontroller; the CRS_DV / MODE2 pin (pin 11) connects to the PA7_RMII_CRS_DV pin of the microcontroller; the RXD0 / MODE0 pin (pin 8) connects to the PC4_RMII_RXD0 pin of the microcontroller; the RXD1 / MODE1 pin (pin 7) connects to the PC5_RMII_RXD1 pin of the microcontroller; the nRST pin (pin 15) connects to the PA0_LAN_NRST pin of the microcontroller; the MDC pin (pin 13) connects to the PC1_LAN_MDC pin of the microcontroller; the MDIO pin (pin 12) connects to the PA... 2_LAN_MDIO pin; U6's TXN pin (pin 21) and TXP pin (pin 20) are connected to the LAN_TX_N and LAN_TX_P interfaces respectively; RXN pin (pin 23) and RXP pin (pin 22) are connected to the LAN_RX_N and LAN_RX_P interfaces respectively; RJ45 connector J1's TD+ pin is connected to the LAN_TX_P interface, TD- pin is connected to the LAN_TX_N interface, RD+ pin is connected to the LAN_RX_P interface, and RD- pin is connected to the LAN_RX_N interface; LAN_LED1 interface is connected to J1's YLEDA pin (pin 12), and LAN_LED2 interface is connected to J1's GLEDA pin (pin 9); J1's YLEDK pin (pin 11) and GLEDK pin (pin 10) are connected to GND respectively; J1's SHELL pins (pins 13 and 14) are connected to GND; J1's CHSGND pin is connected to GND.

[0148] 8. Button and screen module

[0149] Figure 10 This is the circuit diagram for the button and screen module. S3 to S7 are five independent buttons, and connector H2 connects to an SPIOLED screen. Various parameters can be set via the buttons and screen menus.

[0150] Specifically, the button and screen module includes buttons S3, S4, S5, S6, and S7; resistors R14 (10K), R15 (10K), R16 (10K), R17 (10K), and R18 (10K); an SPIOLED screen connector H2 (HDR-7); microcontroller pins PD0_KEY1, PD3_KEY2, PD4_KEY3, PD6_KEY4, PD7_KEY5; PE12_SPI4SCK; PE14_SPI4MOSI; PE11_LEDDC; PE13_LEDRST; PE15_LEDCS; a 3V3 power interface; and a GND interface.

[0151] The connection relationships of the above components are as follows:

[0152] Button and Resistor Connections: Button S3 is connected to the microcontroller's PD0_KEY1 pin at one end and to GND at the other end; resistor R14 (10K) is connected to the PD0_KEY1 pin at one end and to a 3V3 power supply at the other end. Button S4 is connected to the microcontroller's PD3_KEY2 pin at one end and to GND at the other end; resistor R15 (10K) is connected to the PD3_KEY2 pin at one end and to a 3V3 power supply at the other end. Button S5 is connected to the microcontroller's PD4_KEY3 pin at one end and to GND at the other end; resistor R16 (10K) is connected to the PD4_KEY3 pin at one end and to a 3V3 power supply at the other end. Button S6 is connected to the microcontroller's PD6_KEY4 pin at one end and to GND at the other end; resistor R17 (10K) is connected to the PD6_KEY4 pin at one end and to a 3V3 power supply at the other end. One end of button S7 is connected to the PD7_KEY5 pin of the microcontroller, and the other end is connected to GND; one end of resistor R18 (10K) is connected to the PD7_KEY5 pin, and the other end is connected to the 3V3 power supply.

[0153] Screen connector connection to microcontroller: Pin 2 of the SPIOLED screen connector H2 is connected to the PE12_SPI4SCK pin of the microcontroller, pin 3 is connected to the PE14_SPI4MOSI pin, pin 4 is connected to the PE11_LEDDC pin, pin 5 is connected to the PE13_LEDRST pin, pin 6 is connected to the PE15_LEDCS pin, and pin 7 is connected to GND, realizing the microcontroller's control and data transmission of the SPIOLED screen.

[0154] II. Software Design

[0155] The software algorithm diagram of this invention is shown below. Figure 2As shown, the microcontroller first reads the outputs of each sensor using AC excitation technology, then performs zero-point compensation to correct the output deviation of the sensors under no-load conditions. Next, it uses interpolation to correct nonlinear sensitivity, compensating for the difference between the theoretical and actual sensor sensitivity. Finally, it performs Kalman filtering to calculate the optimal estimate that is closer to the true value. After obtaining the optimal estimates for all sensors, multi-sensor fusion is performed based on the characteristics of the door operator to obtain a final weight output, and an alarm signal is output according to preset rules.

[0156] 1. Multi-channel AC excitation reading sensor output

[0157] This program controls the ADC chip to switch to the specified sensor input channel, sets the excitation source polarity, starts and waits for the conversion result, and stores the data in a buffer for use by other programs. The specific process is as follows: Figure 11 As shown:

[0158] When the program starts, it initializes the ADC chip, sets the PGA gain, and switches to single-trigger mode. The maximum PGA gain is 32, and the following conditions must be met:

[0159] V REF / Gain·(2 32-1 -1) / 2 32-1 ≥V REF ·K s

[0160] Among them, V REF The ADC reference voltage is fixed at 5V in this design. s The value represents the sensor sensitivity, expressed in mV / V.

[0161] After initialization, the output signals of the two sensors under positive excitation are measured respectively. First, the AC excitation generation circuit is controlled to output positive excitation voltage to the sensors. The reference channels of the ADC chip are set to the feedback voltage output channels N1AIN0 and N1AIN1 of sensor 1, and the signal input channels of the ADC chip are set to the signal output channels N1AIN6 and N1AIN7 of sensor 1. After the settings are completed, a single conversion is started to obtain the positive excitation conversion result R of sensor 1. s1+ Then, keeping the positive excitation output unchanged, the reference channels of the ADC chip are set to the feedback voltage output channels N1AIN2 and N1AIN3 of sensor 2, and the signal input channels of the ADC chip are set to the signal output channels N1AIN4 and N1AIN5 of sensor 2. A single conversion is then initiated to obtain the positive excitation conversion result R of sensor 2. s2+After the positive excitation measurement is completed, the control AC excitation generation circuit outputs a negative excitation voltage to the sensor, sets the reference channel of the ADC chip to the sensor 1 feedback voltage output channels N1AIN0 and N1AIN1, and flips the reference input channel to set the ADC chip's signal input channel to the sensor 1 signal output channels N1AIN6 and N1AIN7. A single conversion is then initiated, obtaining the negative excitation conversion result R of sensor 1. s1- After completion, the reference channels of the ADC chip are set to the feedback voltage output channels N1AIN2 and N1AIN3 of sensor 2, and the reference input channels are flipped to set the signal input channels of the ADC chip to the signal output channels N1AIN4 and N1AIN5 of sensor 2. A single conversion is then initiated to obtain the negative excitation conversion result R of sensor 2. s2- .

[0162] The circuit diagram under positive excitation voltage is as follows: Figure 12 As shown, the positive output of the sensor's equivalent bridge is connected to the positive input channel of the ADC, and the negative output of the sensor's equivalent bridge is connected to the negative input channel of the ADC. os This represents the drift error in the circuit, including the drift error of the ADC, the drift of parasitic thermocouples in the circuit, etc. Therefore, under a positive excitation voltage, R has s+ =Gain·(V) out +V os ), where R s+ For the positive excitation equivalent input voltage, V out V is the output voltage of the sensor bridge. os For various drift voltages, Gain is the PGA gain of the ADC chip.

[0163] The circuit diagram under negative excitation voltage is as follows: Figure 13 As shown, due to the polarity reversal of the excitation voltage and the unchanged ADC signal input channel, the positive output of the sensor's equivalent bridge is connected to the negative input channel of the ADC, and the negative output of the sensor's equivalent bridge is connected to the positive input channel of the ADC. Therefore, under a negative excitation voltage, R... s- =Gain·(-V) out +V os ), where R s- For the negative excitation equivalent input voltage, V out V is the output voltage of the sensor bridge. os For various drift voltages, Gain is the PGA gain of the ADC chip.

[0164] By measuring the equivalent input voltages under positive and negative polarity excitations respectively, the fused input voltage R can be calculated using the following formula. s :

[0165]

[0166] By integrating R s+ With R s- This eliminates the drift error V. os This eliminates the need for frequent circuit calibration, improving measurement accuracy.

[0167] 2. Zero-point compensation

[0168] When the load cell is not under load, the output signal should theoretically be zero. However, due to manufacturing errors, installation stress, or environmental factors, there may be an initial offset, i.e., zero drift, which needs to be adjusted by software to return the output to zero under no-load conditions.

[0169] The steps for zero-point compensation are as follows:

[0170] (1) When the sensor is not under force, the zero-point output result is measured multiple times using the method in the previous section, and the average value of the result is taken and stored in the Flash memory as the zero-point correction parameter.

[0171] (2) During normal operation, subtract the previously saved zero-point correction parameters from the output measured by the ADC.

[0172] 3. Sensitivity Correction

[0173] The sensitivity of a weighing sensor refers to the relationship between its output signal and the input load. In practical applications, due to manufacturing tolerances, differences in wire resistance, drift caused by temperature effects, and the influence of signal conditioning circuits, the actual sensitivity of the sensor will deviate from its nominal value. Sensitivity correction can make the output signal correspond to the actual load. This invention uses a standard weight loading method to calibrate the sensitivity coefficient of each sensor, and then uses interpolation compensation to improve accuracy. The specific steps are as follows:

[0174] (1) As Figure 14 As shown, prepare n standard weights of known weight, whose weights from smallest to largest are W... s1 W s2 ,…,W sn Place standard weights sequentially onto the weighing sensor and record the corresponding sensor output value V. s1 V s2 ,…,V sn V s0 =W s0 =0. Calculate the sensor sensitivity G for the nth segment of the curve. n Its expression is For multiple sensors, each sensor needs to be calibrated independently.

[0175] (2) When the unknown weight W oWhen applying load to the load cell, first determine its sensitivity interval n, and then obtain the corresponding segmented sensitivity G. n The sensor outputs V using the following formula. o Calculate W o :

[0176] W o =W s(n-1) +G n ·(V o -V s(n-1) 4. Kalman Filter

[0177] Weighing sensor measurements are susceptible to interference from various noise sources, such as mechanical vibration and electronic noise, under complex operating conditions, leading to data fluctuations. This invention uses a Kalman filter algorithm to suppress noise and improve the accuracy, stability, and reliability of the weighing system. In the filtering program, the state variable x is set as the load weight. The state prediction equation of the filtering algorithm is as follows:

[0178] in, For the estimation of the prior state at the current moment, Let A be the posterior state estimate of the previous time step, and let A be the state transition matrix. Since the load cell is mainly used for weighing gantry cranes, and the load weight does not change in a short period of time, A is set to 1.

[0179] The covariance prediction equation of the filtering algorithm is:

[0180] in Let P be the covariance estimated prior at the current time. k-1 Q is the covariance estimated posteriorly from the previous time step, and Q is the process noise covariance. Q is a preset parameter, obtained by the user from documents such as the sensor manual, and written into the terminal via keyboard or network.

[0181] The Kalman gain equation for the filtering algorithm is:

[0182] Where K k H represents the Kalman gain at the current moment, H is the observation matrix, and R is the measurement noise covariance. Since the sensor directly measures the weight of the object or there is only a linear relationship, H is set to 1 by default, and the user can modify this parameter according to the actual situation. R is a preset parameter, which is obtained by the user according to the sensor manual and other documents, and written into the terminal via keyboard or network.

[0183] The state update equation of the filtering algorithm is as follows:

[0184] in The posterior state estimate at the current time, i.e., the filtered result, z kThis is the measurement value at the current moment.

[0185] The covariance update equation of the filtering algorithm is:

[0186] Where P k Let I be the posterior covariance at the current time step, and let I be the identity matrix.

[0187] The filtering algorithm executes the prediction-gain calculation-update sequence for the output value of each sensor. First, it obtains the prior estimate through the state prediction equation and the covariance prediction equation. Then, it calculates the weights using the Kalman gain equation. Finally, it obtains the posterior estimate through the state update equation and the covariance update equation, thus completing one filtering operation.

[0188] 5. Multi-sensor fusion

[0189] The lifting capacity of gantry cranes is typically measured indirectly, with a force take-off (FTO) device transferring the weight to the load cells at a certain ratio. Multiple FTO devices are usually used, each with a different transfer ratio. A multi-sensor fusion algorithm combines the measurements from each sensor with the user-input ratio coefficients to calculate the actual load weight. Depending on the characteristics of the FTO devices, the user needs to pre-input the force take-off coefficients c1, c2, ..., c of n sensors. n .

[0190] The formula for calculating the fusion weight is as follows: Where W is the calculated total weight, W i For the weight reading of the i-th sensor, c i Let be the force coefficient of the i-th sensor.

[0191] 6. Output weight and alarm

[0192] The terminal stores the readings from each sensor and the calculated total weight into the Modbus TCP holding register. PLCs and other devices write the intermediate amplitude signal into the terminal's Modbus TCP holding register to determine the currently used rule group. When the intermediate amplitude signal is valid, the alarm rule uses rule group A; when the intermediate amplitude signal is invalid, the alarm rule uses rule group B.

[0193] The format of the rule group file is as follows:

[0194] <comparison operator>, <number>, <register address>: <bits>

[0195] The comparison operators can be >, <, >=, and <=. When the calculated total weight meets the conditions specified by the comparison operator, a 1 is written to the specified bit at the register address; otherwise, a 0 is written. Each rule group file can contain multiple rules, one rule per line. The name of the rule group A file is rulesListA, and the name of the rule group B file is rulesListB. Users can upload the files to the terminal using the TFTP protocol.

[0196] PLCs and other devices can read specified register addresses and bits to determine whether an alarm has been triggered.

[0197] 7. Keyboard settings

[0198] Upon initial use, the terminal requires manual configuration of network and parameter information. The terminal features five independent buttons and an OLED display, along with a configuration menu. Users can set the IP address, subnet mask, default gateway, and various constant configuration parameters in applications via the menu.

[0199] 8. In-app program upgrade

[0200] To reduce the frequency of on-site maintenance by upgrading programs via the network, the terminal has an in-application program upgrade function. For example... Figure 15 As shown, after the device powers on, it first runs the BootLoader program to check if the firmware file to be upgraded (update) and the CRC32 checksum file to be upgraded (upCRC) exist in the external Flash memory. If both exist, it first checks if the CRC32 checksum of the currently used firmware matches the content of the CRC32 checksum file to be upgraded (upCRC). If they match, no upgrade is needed, and the system jumps to the application. If they don't match, it calculates the CRC32 checksum of the firmware file to be upgraded (update) and compares it with the CRC32 checksum file to be upgraded (upCRC). If they match, the application-level upgrade begins, burning the content of the update file to the internal Flash program memory, and the system jumps to the application. If they don't match, the firmware file to be upgraded is corrupted, the upgrade is not performed, and the system jumps directly to the application.

[0201] The application implements a TFTP server, allowing users to update files in the external Flash via the TFTP protocol and send a restart command to the debug port via the TCP protocol to re-enter the BootLoader program.

[0202] In summary, the technical solution proposed in this invention has the following advantages:

[0203] Significantly improves measurement accuracy. By employing a six-wire sensor, direct ADC sampling, AC excitation, and network transmission, interference and errors during conversion and transmission are reduced.

[0204] High degree of functional integration. A single device can meet the needs of gantry crane overload protection and weighing functions. It has multiple intelligent algorithms, is user-friendly, and can be set up through the screen. Subsequent upgrades and maintenance can be completed via the network without the need for on-site visits.

[0205] It supports multiple sensor access, reducing hardware costs. One acquisition circuit can support time-division multiplexing of two sensors, and multiple acquisition circuits can exist on the circuit board at the same time, so one circuit board can meet the acquisition needs of multiple sensors.

[0206] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A weighing and overload protection terminal for a gantry crane, characterized in that, include: Power supply module, microcontroller module, Ethernet communication module, button and screen module, external Flash ROM module, AC excitation generation module, weighing sensor, low-pass filter module, AD acquisition module; The weighing sensor is provided in multiple parts, and each pair of sensors requires two low-pass filter modules, one AC excitation generation module, and one AD acquisition module. The power module is used to generate various voltages required for the operation of each component in the circuit. The microcontroller module coordinates the work of each sub-module to realize the functions of sensor data acquisition, processing, and output; The Ethernet communication module implements the standard TCP / IP protocol, enabling the microcontroller module to communicate with other host computers. The buttons and screen module can be configured with various parameters; The external Flash ROM module stores various parameters and firmware; The AC excitation generation module is controlled by the microcontroller module and is used to generate positive or negative excitation voltages. Each of the weighing sensors receives an AC excitation voltage and provides a feedback voltage and an output signal; Each of the low-pass filter modules performs hardware filtering on the feedback voltage and output signal given by the gravity sensor; Each AD acquisition module uses the feedback voltage given by the sensor as a reference voltage, converts the sensor output signal into a digital quantity, and sends it to the microcontroller module; each AD acquisition module can time-division multiplex the signals of two weighing sensors.

2. The gantry crane weighing and overload protection terminal according to claim 1, characterized in that, The microcontroller module consists of a microcontroller U1 of model STM32H743VG and its peripheral circuits. Each AD acquisition module can time-division multiplex the signals of two weighing sensors, including sensor I and sensor II, both of which are six-wire weighing sensors.

3. The gantry crane weighing and overload protection terminal according to claim 1, characterized in that, The power module includes a DC-DC step-down chip U2, a first low-dropout linear regulator chip U3, a second low-dropout linear regulator chip U4, and their peripheral circuits. 12V_EXT is the external power input. After being protected by the reverse polarity protection diode D1, the self-resetting fuse FR1, and the varistor RV1, the output is the first standard voltage. The DC-DC step-down chip U2 is model SCT2432STER, and its input is the first standard voltage. The DC-DC step-down chip U2 starts working when the voltage at its EN pin is higher than 1.18V; R1 and R2 are voltage divider resistors used to set the start-up voltage V of the DC-DC circuit. s V s =1.18·(R1+R2) / R1; The resistor R3 connected to pin 4 of U2 is used to set the operating frequency f of the DC-DC circuit. sw f sw =1·10 11 / R3; Capacitor C1 is the bootstrap capacitor for U2; R4 and R5 are used to generate feedback voltage, setting the output voltage V of the DC-DC circuit. o V o =0.8·(R4+R5) / R4; Inductor L1, capacitors C2, C3, C4 and U2 together form a Buck step-down circuit; The first low-dropout linear regulator chip U3 is model TPS7A2050PDBVR; The second low-dropout linear regulator chip, U4, is model AP7365-33.

4. The gantry crane weighing and overload protection terminal according to claim 2, characterized in that, The AC excitation generation module consists of two dual-channel single-pole single-throw analog switch chips TS5A21366, with two digital signal input ports N1AIN8 and N1AIN9, an excitation voltage + output port N1EXC0 and an excitation voltage - output port N1EXC1. The microcontroller U1 controls the AD acquisition module to provide signals N1AIN8 and N1AIN9. This circuit can output a 5V excitation voltage or a -5V excitation voltage.

5. The gantry crane weighing and overload protection terminal according to claim 1, characterized in that, In the low-pass filter module, each weighing sensor has a pair of voltage feedback signals REF0 and REF1 and a pair of weight output signals BR_O+ and BR_O-. Since each AD acquisition module acquires data from two weighing sensors, each low-pass filter module has two weight output signal filters and voltage feedback signal filters of the same specifications. The low-pass filter consists of a resistor connected in series with each pair of signals, a differential capacitor connected in parallel between each pair of signals, and a common-mode capacitor connected in parallel between each pair of signals and GND, used to filter high-frequency interference in the signal lines.

6. The gantry crane weighing and overload protection terminal according to claim 2, characterized in that, The AD acquisition module consists of an ADS1262 ADC chip U9 and its peripheral circuitry. The ADC chip U9 has eight channels as analog signal input ports, configured as four differential signal inputs. The differential input channels N1AIN0 and N1AIN1 are connected to the feedback output port of sensor I, the differential input channels N1AIN6 and N1AIN7 are connected to the signal output port of sensor I, the differential input channels N1AIN2 and N1AIN3 are connected to the feedback output port of sensor II, and the differential input channels N1AIN4 and N1AIN5 are connected to the signal output port of sensor II. N1AIN8 and N1AIN9 are configured as GPIO output mode and controlled by microcontroller U1. The output signals are connected to the AC excitation generation module to generate excitation voltage. The ADC chip U9 communicates with the microcontroller U1 via the SPI bus, receives the configuration parameters and control signals given by the microcontroller U1, and returns the AD conversion result.

7. The control method for the weighing and overload protection terminal of the gantry crane according to any one of claims 1 to 6, characterized in that, include: The microcontroller module reads the output of each sensor through AC excitation technology and performs zero-point compensation to correct the output deviation of the sensor under no-load conditions. Nonlinear sensitivity correction is performed by interpolation to compensate for the difference between the theoretical and actual sensitivity of the sensor. Then, Kalman filtering is performed to calculate the optimal estimate that is closer to the true value. After obtaining the optimal estimates from all sensors, multi-sensor fusion is performed based on the characteristics of the gantry crane to obtain a final weight output, and an alarm signal is output according to preset rules.

8. The control method according to claim 7, characterized in that, The microcontroller module reads the outputs of each sensor through AC excitation technology, specifically including: Initialize the ADC chip, set the PGA gain and switch to single-trigger mode, and the following conditions must be met: V REF / Gain·(2 32-1 -1) / 2 32-1 ≥V REF ·K s Among them, V REF K is the ADC reference voltage. s For sensor sensitivity; The output signals of the two weighing sensors under positive excitation are measured separately. First, the AC excitation generation circuit is controlled to output positive excitation voltage to the sensor. The reference channel of the ADC chip is set as the feedback voltage output channel N1AIN0 and N1AIN1 of sensor I, and the signal input channel of the ADC chip is set as the signal output channel N1AIN6 and N1AIN7 of sensor I. Initiating a single conversion yields the positive excitation conversion result R from sensor I. s1+ Then, keeping the positive excitation output unchanged, the reference channels of the ADC chip are set to the sensor II feedback voltage output channels N1AIN2 and N1AIN3, and the signal input channels of the ADC chip are set to the sensor II signal output channels N1AIN4 and N1AIN5. A single conversion is then initiated to obtain the sensor II positive excitation conversion result R. s2+ ; After the positive excitation measurement is completed, the AC excitation generation circuit outputs a negative excitation voltage to the sensor, sets the reference channel of the ADC chip to the sensor I feedback voltage output channels N1AIN0 and N1AIN1, and flips the reference input channel to set the signal input channel of the ADC chip to the sensor I signal output channels N1AIN6 and N1AIN7. A single conversion is then initiated, yielding the sensor I negative excitation conversion result R. s1- After completion, the reference channels of the ADC chip are set to the sensor II feedback voltage output channels N1AIN2 and N1AIN3, and the reference input channels are flipped. The signal input channels of the ADC chip are set to the sensor II signal output channels N1AIN4 and N1AIN5, and a single conversion is started to obtain the sensor II negative excitation conversion result R. s2- .

9. The control method according to claim 8, characterized in that, Under a positive excitation voltage, the positive output of the sensor's equivalent bridge is connected to the positive input channel of the ADC chip, and the negative output of the sensor's equivalent bridge is connected to the negative input channel of the ADC chip; therefore, under a positive excitation voltage, R... s+ =Gain·(V) out +V os ), where R s+ For the positive excitation equivalent input voltage, V out V is the output voltage of the sensor bridge. os For various drift voltages, including ADC drift error and parasitic thermocouple drift in the circuit, Gain is the PGA gain of the ADC chip; Under a negative excitation voltage, because the polarity of the excitation voltage is reversed and the ADC signal input channel remains unchanged, the positive output of the sensor's equivalent bridge is connected to the negative input channel of the ADC chip, and the negative output of the sensor's equivalent bridge is connected to the positive input channel of the ADC chip; therefore, under a negative excitation voltage, R... s- =Gain·(-V out +V os ), where R s- For the negative excitation equivalent input voltage, V out V is the output voltage of the sensor bridge. os For various drift voltages, Gain is the PGA gain of the ADC chip; By measuring the equivalent input voltages under positive and negative polarity excitations respectively, the fused input voltage R can be calculated using the following formula. s : By integrating R s+ With R s- Eliminate drift error V os .

10. The control method according to claim 7, characterized in that, Before reading the output of each sensor, the sensitivity of the weighing sensor is first corrected: Prepare n standard weights of known weight, whose weights in ascending order are W. s1 W s2 ,…,W sn Place standard weights sequentially onto the weighing sensor and record the corresponding sensor output value V. s1 V s2 ,…,V sn V s0 =W s0 =0; Calculate the sensor sensitivity G of the nth segment of the curve. n ,: Each sensor is calibrated independently; When the unknown weight W o When applying load to the load cell, first determine its sensitivity interval n, and then obtain the corresponding segmented sensitivity G. n The sensor outputs V using the following formula. o Calculate W o :W o =W s(n-1) +G n ·(V o -V s(n-1) ); The multi-sensor fusion based on the characteristics of the gantry crane specifically includes: The user pre-inputs the force coefficients c1, c2, ..., c of n weighing sensors. n ; The formula for calculating the fusion weight is as follows: Where W is the calculated total weight, W i Let c be the weight reading of the i-th weighing sensor. i is the force coefficient of the i-th weighing sensor.

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