An automatic weighing device for electric fork-lift trucks and a method for weighing

Abstract

The application discloses an automatic weighing device of an electric forklift and a weighing method thereof, and relates to the technical field of forklift weighing. The device is based on the existing forks, lifting mechanism and execution unit of the forklift, and comprises an integrated operation and display control display unit, a sensing unit for detecting the weight of goods, a processing unit connected with the sensing unit and used for receiving and processing signals, and a transmission unit for transmitting the signals of the processing unit. The sensing unit, the processing unit, the transmission unit and the control display unit are electrically connected. The application adopts multiple weighing modes to solve the problem of inaccurate weighing caused by the random factor of the load center position in forklift weighing. The electronic weighing system can realize network communication function, can realize real-time information transmission between external host computers, instruments and cloud platforms, and can integrate the carrying capacity, weighing and network communication function of ordinary forklifts.

Description

Technical Field

[0001] This invention relates to the field of forklift weighing technology, specifically to an automatic weighing device and weighing method based on existing electric forklifts. Background Technology

[0002] Automatic forklift weighing devices are a crucial component of modern logistics. With the rapid development of logistics, higher demands are being placed on the efficiency of logistics equipment. The foundation for improving the efficiency of logistics equipment lies in its ability to collect and transmit information about goods. The development and application of new automatic forklift weighing devices enable forklifts and other logistics equipment to have a wider range of functions. Firstly, they can help users manage goods more efficiently, such as accurately measuring the weight of goods in the warehouse, assessing losses during production, and collecting information multiple times. Secondly, they can reduce investment in equipment such as floor scales and improve transportation efficiency by completing many weighing operations during transportation.

[0003] Existing forklift weighing devices suffer from inaccurate weighing due to random factors affecting the center of gravity of the load, resulting in unnecessary losses. Furthermore, the weight data is often collected manually, which can lead to data loss and hinder traceability in later stages. In addition, manual data collection is prone to errors and is inefficient, significantly impacting the normal transport process of forklifts. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic weighing device and weighing method for electric forklifts, so as to solve the problems of inaccurate weighing caused by the random center of gravity of the load on the forklifts and the high error rate and slow efficiency of manual weight data collection in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an automatic weighing device for electric forklifts, which is based on the existing forklift forks, lifting mechanism, and execution unit, comprising: a control and display unit integrating operation and display; a sensing unit for detecting the weight of goods; a processing unit connected to the sensing unit for receiving and processing signals; and a transmission unit for transmitting signals from the processing unit; the sensing unit, the processing unit, the transmission unit, and the control and display unit are electrically connected.

[0006] The control display unit is connected to the transmission unit;

[0007] The processing unit is connected to a storage unit for storing the processed signal;

[0008] The sensing unit includes an inclination sensor installed between the forklift forks and the mast to measure the angle between them, a load cell installed on the forks, and a pressure sensor installed on the lifting mechanism cylinder.

[0009] Preferably, the control display unit is a display and / or a cloud platform.

[0010] Preferably, the display and / or the cloud platform include an integrated input unit for transmitting operator instructions and an output unit for displaying weighing data.

[0011] Preferably, the processing unit includes an A / D conversion module for converting signals from the sensing unit and a data acquisition module connected to the A / D conversion module, wherein the data acquisition module is used to compare and analyze the signals converted by the A / D conversion module.

[0012] Preferably, the transmission unit is connected to the execution unit for controlling the lifting and tilting of the forks.

[0013] Preferably, the tilt sensor and / or load cell are further equipped with an alarm unit, which is electrically connected to the transmission unit. The transmission unit analyzes the signal sent by the processing unit and powers on the alarm unit.

[0014] An automatic weighing method for an electric forklift, based on the aforementioned automatic weighing device, involves issuing commands through a control and display unit, a sensing unit measuring the goods on the forklift forks, receiving and processing the measured signal through a processing unit, and then transmitting the converted signal to the control and display unit for display. The method includes steps S1 (initialization setting), S2 (mode selection), S3 (weighing), S4 (data processing), and S5 (data uploading). Specifically, it is as follows:

[0015] S1 Initialization Setup Steps: After the device is powered on, the weight value in the storage unit is reset to zero through the processing unit.

[0016] S2 mode selection steps: Select the operating mode through the input unit. There are four operating modes.

[0017] S3 Weighing Procedure: Weighing measurement is performed through the sensing unit;

[0018] S4 Data Processing Step: The processing unit receives and calculates the signal from step S3 and converts the analog signal from the sensing unit into a digital signal.

[0019] S5 Data Upload Step: Upload the digital signal from step S4 to the output unit via the transmission unit.

[0020] Preferably, the four working modes in the S2 mode selection step are as follows:

[0021] In the first working mode, the load cell weighs the goods, and the processing unit receives, calculates, and converts the data, which is then transmitted to the output unit by the transmission unit.

[0022] In the second working mode, the load cell weighs the goods and the tilt sensor measures the angle between the forks and the mast. The processing unit receives, calculates and converts the data, and the transmission unit transmits it to the output unit.

[0023] In the third working mode, the weighing sensor weighs the goods during the lifting process of the lifting mechanism, and the pressure sensor measures the pressure of the lifting mechanism's hydraulic cylinder. The data is then received, calculated, and converted by the processing unit, and transmitted to the output unit by the transmission unit.

[0024] During the lifting process, the pressure on the load cell increases gradually. The analog signals output by the suspension displacement sensors on both sides of the lifting mechanism are digitally acquired, and the displacement data is compared with the actual weight measured by the load cell using a fusion algorithm.

[0025] In the fourth working mode, the instructions for working mode one, working mode two, or working mode three are terminated through the operation input unit, and the weight value is stored and accumulated through the storage unit and transmitted to the output unit through the transmission unit.

[0026] Preferably, when the processing unit compares the weight of the loaded goods in step S4 and finds that it exceeds the maximum load of the forklift, the comparison signal is output to the alarm unit through the transmission unit.

[0027] Preferably, when weight is detected in step S3, the forklift lifting mechanism and tilting mechanism are prohibited from operating simultaneously.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This invention solves the problem of inaccurate weighing caused by random factors such as the position of the load center of gravity in forklift weighing by adopting multiple weighing modes. The forklift weighing device designed using this method can reduce weighing errors, has high control precision, and strong resistance to vibration and interference. At the same time, the electronic weighing system of this invention can realize network communication function, enabling real-time information transmission between external host computers, instruments, and cloud platforms. This allows ordinary forklifts to integrate handling capacity, weighing, and network communication functions into one, completing forklift handling, weighing, and data management in one go, reducing human error rate, and achieving a high degree of intelligence. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of an automatic weighing device for an electric forklift according to the present invention;

[0031] Figure 2 This is a schematic diagram of the weighing process of an automatic weighing device for an electric forklift according to the present invention;

[0032] Figure 3 This is a schematic diagram of the working process of the transmission unit of the automatic weighing device for electric forklifts according to the present invention.

[0033] Figure 4 This is a schematic diagram of the overall circuit structure of an automatic weighing device for an electric forklift according to the present invention;

[0034] Figure 5 This is a schematic diagram of the processing unit circuit structure of an automatic weighing device for an electric forklift according to the present invention.

[0035] Figure 6 This is a schematic diagram of the alarm unit circuit structure of an automatic weighing device for an electric forklift according to the present invention.

[0036] In the diagram: 1. Execution unit; 2. Transmission unit; 3. Storage unit; 4. Tilt sensor; 5. Weighing sensor; 6. Pressure sensor; 7. A / D conversion module; 8. Data acquisition module; 9. Display; 10. Cloud platform; 11. Input unit; 12. Output unit; 13. Alarm unit. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example

[0039] Please see Figure 1 An automatic weighing device for electric forklifts, based on the existing forklift forks, lifting mechanism and execution unit 1, consists of a control display unit integrating operation and display, a sensing unit for detecting the weight of goods, a processing unit connected to the sensing unit for receiving and processing signals, a transmission unit 2 for transmitting signals from the processing unit, and an alarm unit 13 electrically connected to the transmission unit 2.

[0040] In practice, the sensing unit measures the angle by installing an angle sensor 4 between the forklift forks and the mast, two sets of load cells 5 are installed on the forks to measure the weight of the goods, and a set of pressure sensors 6 is installed on the lifting mechanism cylinder to measure the pressure signal when the goods are lifted.

[0041] The processing unit consists of an A / D conversion module 7 (model HX711AD) for converting signals from the sensing unit, a data acquisition module 8 connected to the A / D conversion module 7, and a storage unit 3 for storing the processed signals. The data acquisition module 8 is used to compare and analyze the signals converted by the A / D conversion module 7.

[0042] The mass measured by the HX711AD converter is converted into a digital signal. The HX711 is a 24-bit A / D converter chip designed specifically for high-precision electronic scales, featuring simple programming, fast response, no need for external components, and automatic power-on reset. This chip has two analog input channels and an internal 128x gain programmable amplifier, offering advantages such as high accuracy, low error, and low cost. The HX711 can be connected to a microprocessor via four microprocessor-powered connectors.

[0043] The data acquisition module uses the HX711 chip as its core component. For example... Figure 5 As shown, the circuit connected to the left of P2 is a bridge circuit. The HX711's regulated power supply powers the sensor's bridge through its AVDD and AGND ports. Since the HX711 uses channel A internally, the bridge output signal is only connected to the HX711's INA- and INA+ ports via interfaces 3 and 4 on P2. The bridge output signal is then converted into a digital value by the HX711's internal A / D converter and output through the HX711's DOUT port.

[0044] The transmission unit 2 is a microcontroller, connected to the execution unit 1 on the existing forklift, used to control the lifting and tilting of the forks. An alarm unit 13 is installed on the tilt sensor 4 and the load cell 5. The alarm unit 13 is electrically connected to the transmission unit 2. The processing unit sends a signal, which the transmission unit 2 analyzes and powers on the alarm unit 13.

[0045] like Figure 6 As shown, alarm unit 13 is implemented by using a PNPS8550 transistor to drive a buzzer. Combined with... Figure 4 As shown, the I / O port of transmission unit 2 is connected to the base of the transistor through resistor R7. When the output of the I / O port of transmission unit 2 is low, the transistor will conduct, the positive terminal of the buzzer will be connected to the power supply, and the negative terminal will be connected to GND, and the buzzer will be powered on and emit an alarm sound. When the output of the I / O port of transmission unit 2 is high, the transistor will be cut off, the buzzer cannot form an effective circuit, the buzzer will not work, and the alarm will stop.

[0046] The display 9 of the control display unit and the cloud platform 10 are connected to the transmission unit 2. The display 9 can adopt the forklift onboard instrument in the prior art. The working mode is selected through the input unit 11 on the display 9 or the cloud platform 10. The output unit 12 displays the weight of the goods on the forklift, the fork tilt angle and the hydraulic oil pressure.

[0047] In this embodiment, the tilt sensor 4 is a KM1-LVT518T type, the pressure sensor 6 is a hydraulic sensor GZY40 type, and the weighing sensor 5 is an electromagnetic force weighing sensor Z6FC3 / 3t with a range of 3 tons. However, it is not limited to the models in the above embodiment. Those skilled in the art can set it according to the actual working conditions, and it will not be listed one by one here.

[0048] Please see Figure 2 The automatic weighing method for electric forklifts involves issuing commands through a control and display unit, with a sensing unit measuring the goods on the forklift forks. The measured signal is received, calculated, and converted by a processing unit, and then transmitted to the control and display unit for display via a transmission unit 2. The steps are as follows: S1 initialization setting, S2 mode selection, S3 weighing, S4 data processing, and S5 data upload.

[0049] S1 Initialization Setting Steps: After the device is powered on, the weight value in storage unit 3 is cleared and initialized by the processing unit.

[0050] S2 Mode Selection Steps: Select the operating mode via input unit 11. There are four operating modes:

[0051] In working mode one, the load is weighed by the load sensor 5, and the data is received, calculated and converted by the processing unit, and transmitted to the output unit 12 by the transmission unit 2. Working mode one is selected when the load being transported by the forklift is between 1.5 and 3.5 tons and the load does not need to be tilted.

[0052] In the second working mode, the load is weighed by the load cell 5 and the angle between the forks and the mast is measured by the tilt sensor 4. The data is received, calculated and converted by the processing unit and transmitted to the output unit 12 by the transmission unit 2. The second working mode is selected when the forklift is carrying goods at a certain tilt angle.

[0053] In practice, the relationship between the weight of the detected cargo and its angle is first established. The weighing device undergoes at least three statically determinate force analyses to derive the conversion function of the cargo weight with respect to the sensor signal. Fuzzy correction is then used to correct and compensate for the weight value. After weighing, the processed sensor signal is converted back into a weight value using the conversion function. Specifically, as follows:

[0054] Based on the analysis results of the fork angle model, actual vehicle tests were conducted under eccentric and uniform load conditions. The mass on both sides was calculated according to Formula 1 based on the linear relationship between displacement and load.

[0055]

[0056]

[0057] In the formula: W1 and Wr are the frontal and offset suspension loads, respectively; Wa and Wb are the load values ​​calibrated by the digital displacement of the frontal and offset sides, respectively; DR and DL are the calibration values ​​of the digital displacement sensor values ​​of the frontal and offset sides, respectively; Da and Db are the digital displacement sensor values ​​of the frontal and offset sides, respectively.

[0058] To address the measurement errors caused by off-center loading, a Kalman fusion model for displacement and angle was established.

[0059] (1) First, the prior state is estimated using Formula 2.

[0060]

[0061]

[0062] In the formula: The Kalman prior estimates of the vehicle's load at time k are the frontal and offset sides, respectively; W 1(k-1) W r(k-1) The Kalman posterior estimates of the load at time (k-1) for the frontal and offset sides are respectively.

[0063] (2) Using the prior error covariance matrix in Formula 3

[0064]

[0065] In the formula: The prior covariances at time k for the frontal and offset loads, respectively; P 1(k-1) P r(k-1) These are the posterior covariances at time (k-1) for the frontal and offset side loads, respectively.

[0066] (3) Kalman gain is calculated using Formula 4

[0067]

[0068] In the formula: K1 and Kr are the Kalman gains of the front and offset loads, respectively.

[0069] (4) Perform posterior state estimation using Formula 5

[0070]

[0071]

[0072] In the formula: W l(k) W r(k) The Kalman posterior estimates of the load at time k are the frontal and offset sides of the vehicle, respectively.

[0073] (5) Update the covariance matrix using Formula 6

[0074]

[0075] In the formula: P 1(k) P r(k) Let be the posterior covariances of the loads on the left and right sides of the vehicle at time k.

[0076] The algorithm reduces weighing errors when the load is uneven, is applicable when the load is even, and can smooth axle load fluctuations during dynamic weighing.

[0077] In the third working mode, the forklift uses its own hydraulic system and lifting chain to lift the lifting rod and lift the rack upwards. During the upward lifting motion, the pressure on the load cell 5 increases gradually, requiring the travel contact to obtain a more accurate value from the load cell 5. The load cell 5 weighs the goods during the lifting process, combined with pressure sensor 6 measuring the hydraulic cylinder pressure. The data acquisition module 8 digitally acquires the analog signals from the suspension displacement sensors on both sides of the forklift lifting mechanism, outputting the load data corresponding to the displacement data. The measured displacement and weight data from 1.5 to 3.5T are calculated using a data fusion algorithm and compared with the measured values ​​from the suspension displacement sensors on both sides. Through a Kalman data fusion algorithm of displacement, acceleration, and weight, the maximum load deviation of the left and right masts can be controlled within 50kg. Furthermore, under heavy loads, the compensation effect for a 1.8T load is 3.21% less than that for a light load of 500kg, demonstrating better compensation under heavy load conditions. Finally, the data is transmitted to the output unit 12 via the transmission unit 2; when a certain amount of goods being transported by the forklift needs to be counted by piece or when the goods being transported by the forklift are less than 1.5T, the working mode 3 is selected.

[0078] In operating mode four, the instructions for operating mode one, two, or three are terminated via the operation input unit 11, and the weight value is stored and accumulated via the storage unit 3, and then transmitted to the output unit 12 via the transmission unit 2. Operating mode four is selected when the forklift has moved a certain amount of goods and the total weight needs to be calculated.

[0079] S3 Weighing Procedure: After selecting the working mode, weighing is performed according to the sensor unit set by the working mode.

[0080] When weight is detected, the forklift lifting mechanism and tilting mechanism are prohibited from working simultaneously via transmission unit 2.

[0081] S4 Data Processing Steps: The processing unit receives and calculates the signal in step S3 and collects the analog signal from the sensing unit through the data acquisition module 8. The A / D conversion module converts the signal into a digital signal and performs calculations according to the corresponding working mode. When the weight of the loaded goods exceeds the maximum load of the forklift, the processing unit outputs the comparison signal to the alarm unit 13 through the transmission unit 2.

[0082] S5 Data Upload Step: The processed digital signal from step S4 is uploaded to the display 9 and cloud platform 10 of the output unit 12 via the transmission unit 2. Both the display 9 and cloud platform 10 can select the weighing mode and display parameters such as the weight of the goods carried by the forklift, the fork tilt angle, and the hydraulic oil pressure. Simultaneously, the cloud platform can statistically analyze and output bar charts and line graphs of the forklift weighing data. Based on the forklift weighing data table, and by obtaining the total weight of goods transported by each forklift per workday from the MySQL database, specific data graphs of three days, one week, half a month, and one month's workload are generated in real time on a plane coordinate system. A switching button is provided, allowing the weighing data to dynamically switch between line graphs and bar charts. The bar chart effectively reflects the total workload of the forklift, while the line graph predicts the trend of changes in the electric forklift's workload, thereby understanding the working efficiency of the electric forklift and improving its utilization efficiency.

[0083] The workflow of transmission unit 2 is as follows: Figure 3 As shown, the main process requires enabling the CAN controller's receive interrupt before receiving interrupt-controlled messages. After the acceptance filter accepts the message to be received, it places it in the FIFO memory. A receive interrupt is then generated, and the main control chip, upon response, stores the message in its own message memory and sets the release buffer in the command register. The receiving sequence is: interrupt-driven reception, disabling processing unit interrupts, determining if a receive interrupt is needed, determining if it's a remote frame or a data buffer, reading the data, and enabling interrupts.

[0084] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An automatic weighing method for an electric fork truck, characterized by: The signal measured by the sensing unit on the goods on the forklift fork is transmitted to the control display unit for display through the processing unit receiving calculation conversion; including S1 initialization setting step, S2 mode selection step, S3 weighing step, S4 data processing step and S5 data uploading step; specifically as follows: S1 initialization setting step: after the device is started and powered on, the weight value in the storage unit (3) is initialized to zero by the processing unit; S2 mode selection step: select the working mode through the input unit (11), which includes four modes; S3 weighing step: weighing measurement is performed by the sensing unit; S4 data processing step: the signal in step S3 is received, calculated and converted into a digital signal by the processing unit; S5 data uploading step: the digital signal in step S4 is uploaded to the output unit (12) through the transmission unit (2); The four working modes in the S2 mode selection step are as follows: Working mode one: the weighing sensor (5) weighs the goods, and the processing unit receives calculation conversion, and the transmission unit (2) transmits to the output unit (12); Working mode two: the weighing sensor (5) weighs the goods in combination with the angle measurement between the fork and the gantry by the inclination sensor (4), and the processing unit receives calculation conversion, and the transmission unit (2) transmits to the output unit (12); The processing unit receives calculation conversion in working mode two includes: establishing the relationship between the detected goods weight and the angle, performing static force analysis on the weighing device more than three times, obtaining the conversion function of the goods weight about the sensing signal, and using fuzzy correction to correct and compensate the weight value, and after weighing, the processed sensing signal is converted into a weight value by the conversion function; specifically as follows: According to the analysis result of the fork angle model, the real vehicle test is performed on the uneven load and even load state, and the mass of the two sides is calculated according to the linear relationship between displacement and load according to the following formula: ； In the formula: W1 and Wr are the front and offset side suspension loads respectively; Wa and Wb are the front and offset side displacement digital calibration load values respectively; DR and DL are the front and offset side calibration values of the displacement sensor digital measurement values respectively; Da and Db are the front and offset side displacement sensor digital measurement values respectively; A Kalman data fusion model of displacement and angle is established; The prior state estimation is performed by the following formula: ； In the formula: respectively, the vehicle k time front and offset side of the Kalman prior estimate load; respectively the Kalman posterior estimation of the load at the instant of time (k-1) for the front and offset side of the vehicle; The prior error covariance matrix is calculated by the following formula: ； In the formulae: are the prior covariances at time k for the front and offset side loads, respectively; are the posterior covariances at time (k-1) for the front and offset side loads, respectively; The Kalman gain is calculated by the following formula: ； In the formula: K1 and Kr are the Kalman gains of the front and offset side loads respectively; The posterior state estimation is performed by the following formula: ； In the formulae: respectively are the Kalman posterior estimation of the vehicle k at the moment of the front and offset side load; The covariance matrix is updated by the following formula: ； In the formula: respectively, the left and right sides of the vehicle k at the time of the load of the posterior covariance; Working mode three: the weighing sensor (5) weighs the goods during the lifting of the lifting mechanism in combination with the pressure sensor (6) for measuring the oil cylinder pressure of the lifting mechanism, and the processing unit receives calculation conversion, and the transmission unit (2) transmits to the output unit (12); The pressure received by the weighing sensor (5) during lifting is a process from small to large, and the analog output of the suspension displacement sensor on both sides of the lifting mechanism is digitally collected. The displacement data and the actual weight of the weighing sensor (5) are compared through fusion algorithm; The fourth working mode is to end the instructions of the first working mode, the second working mode or the third working mode through the operation input unit (11), and to store and accumulate the weight value through the storage unit (3), and to transmit the weight value to the output unit (12) through the transmission unit (2).

2. The automatic weighing method of the electric forklift according to claim 1, characterized in that: When the processing unit compares the weight of the loaded goods in the S4 step and finds that the weight exceeds the maximum load of the forklift, the comparison signal is output to the alarm unit (13) through the transmission unit (2).

3. The motorized fork truck automatic weighing method of claim 1, wherein: The S3 step detects the weight and prohibits the simultaneous operation of the forklift lifting mechanism and the inclination.

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