A method and system for braking an automated door machine

Abstract

The application discloses a brake method and system of an automatic portal crane, and the method comprises the following steps: setting a target position of a grab bucket when braking is needed; and cyclically executing the following steps a to e until a difference between an actual position of the grab bucket and a stopping position is less than or equal to a threshold value, and outputting a frequency converter shutdown instruction and a brake starting instruction: a. collecting a real-time frequency of the frequency converter; b. calculating the actual position of the grab bucket; c. calculating a theoretical stopping distance under a current real-time frequency; d. compensating the theoretical stopping distance by considering a load; and e. calculating the stopping position based on the target position of the grab bucket and the compensated stopping distance. The application solves a long-existing problem of 'incompatibility between speed and accuracy' in the field of crane positioning by means of a trinity of non-linear modeling, dynamic calculation and data driving, and provides high-efficiency automatic operation for port automation.

Description

Technical Field

[0001] This invention relates to the field of crane positioning, and more specifically to a braking method and system for an automated gantry crane. Background Technology

[0002] Automated gantry cranes, also known as automated gantry cranes, mainly consist of a slewing mechanism, a hoisting mechanism, and a luffing mechanism. The slewing mechanism drives the crane to rotate, the hoisting mechanism controls the lifting and lowering of the grab bucket, and the luffing mechanism adjusts the horizontal amplitude of the grab bucket.

[0003] In the bulk cargo handling process of automated gantry cranes, precise positioning of the mechanism is crucial. Excessive deviation can lead to material spillage or even collisions during grabbing and unloading. Traditional automated gantry cranes using fixed braking point control have inherent drawbacks: at low speeds, premature braking causes the mechanism to fail to reach the target position, requiring secondary fine-tuning and reducing operational efficiency. At high speeds, late braking causes the mechanism to overshoot the target position. In variable-speed operations, the stopping deviation of the same braking point is inconsistent at different speeds, resulting in poor control robustness.

[0004] Existing crane braking methods generally assume a linear relationship between braking distance and speed, and do not take into account factors such as load changes and mechanical wear. Therefore, the errors generated in each operation are different, and they cannot adapt to changes in load and other factors. Summary of the Invention

[0005] To address the problem of precise positioning of the variable frequency drive mechanism of a crane under variable speed operation in automatic mode, this invention provides a braking method and system for an automated gantry crane. By establishing a quantitative relationship model between frequency and braking distance in the automated operation mode of the gantry crane, adaptive and precise braking across the entire speed domain is achieved, eliminating the impact of speed and load changes on positioning accuracy.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A braking method for an automated gantry crane is proposed, which establishes a quantitative relationship model between the real-time frequency of the frequency converter and the braking distance in the automated operation mode of the gantry crane, and performs automated gantry crane braking through the following steps:

[0008] When braking is required, set the target position for the grab bucket;

[0009] Repeatedly execute steps a to e until the difference between the actual position of the grab bucket and the braking position is less than or equal to the threshold, then output the inverter stop command and the brake start command:

[0010] a. Acquire the real-time frequency of the frequency converter;

[0011] b. Calculate the actual position of the grab bucket;

[0012] c. Calculate the theoretical braking distance at the current real-time frequency based on the quantitative relationship model between the real-time frequency and braking distance of the inverter;

[0013] d. Consider load to compensate for the theoretical braking distance;

[0014] e. Calculate the braking position based on the target position of the grab bucket and the compensated braking distance.

[0015] To optimize the above technical solution, the specific measures also include:

[0016] Furthermore, the specific process for calculating the actual position of the grab bucket is as follows:

[0017] The number of drum rotations is monitored in real time and converted into the actual position of the grab bucket using the following formula:

[0018] P current = P be +S= P be +N×π×d;

[0019] In the formula, P current Indicates the actual position of the grab bucket. P be S represents the position of the grab bucket before the drum rotates, N represents the number of rotations of the drum, and d represents the diameter of the drum.

[0020] Furthermore, the calculation of the theoretical braking distance at the current real-time frequency based on the quantitative relationship model between the real-time frequency and the braking distance of the inverter is specifically as follows:

[0021] D = af 2 + bf + c;

[0022] In the formula, D represents the theoretical braking distance, f represents the real-time frequency of the inverter, a is the coefficient of the quadratic term, b is the coefficient of the linear term, and c is the constant term. The values ​​of a, b, and c are obtained by fitting a quadratic function to the historical data pair (f, D) sample set using the least squares method.

[0023] Furthermore, the consideration of load to compensate for the theoretical braking distance specifically refers to:

[0024] D adj = D · (1 + α·Δm / m0);

[0025] In the formula, D adjThe value represents the compensated braking distance, D represents the theoretical braking distance, α represents the load sensitivity coefficient, Δm represents the difference between the actual load and the rated load, and m0 is the rated load.

[0026] Furthermore, the calculation of the braking position based on the target position of the grab bucket and the compensated braking distance specifically involves:

[0027] Read the motion direction signal of the mechanism from the PLC;

[0028] Calculate the braking position using the following formula:

[0029] P brake = P target - D adj × V sign

[0030] In the formula, P brake Indicates the braking position, P target Indicates the target location of the grab, D adj V represents the compensated braking distance. sign It is the signal for the direction of the mechanism's movement. A value of +1 indicates forward movement, and a value of -1 indicates reverse movement.

[0031] The present invention also proposes a crane braking system, comprising:

[0032] The host computer is used to set the target position of the grab bucket;

[0033] The sensing module is used to calculate the actual position of the grab bucket;

[0034] The decision module is used to collect the real-time frequency of the frequency converter, calculate the theoretical braking distance at the current real-time frequency based on the quantitative relationship model between the real-time frequency of the frequency converter and the braking distance, and consider the load to compensate for the theoretical braking distance; calculate the braking position based on the target position of the grab bucket and the compensated braking distance; compare the actual position of the grab bucket with the braking position, and if the difference between the actual position of the grab bucket and the braking position is less than or equal to the threshold, output the frequency converter stop command and the brake start command.

[0035] The execution module responds to the decision module by cutting off the inverter enable based on the inverter stop command and starting the brake based on the brake start command.

[0036] To optimize the above technical solution, the specific measures also include:

[0037] Furthermore, the sensing module includes a mechanism encoder, a displacement calculation unit, and a PLC controller;

[0038] The mechanism encoder is installed on the output shaft side of the hoisting mechanism drum of the crane to monitor the number of drum rotations in real time.

[0039] The displacement calculation unit converts the number of drum rotations into the actual position of the grab bucket, using the following formula:

[0040] P current = P be +S= P be +N×π×d;

[0041] In the formula, P current Indicates the actual position of the grab bucket. P be S represents the position of the grab bucket before the drum rotates, N represents the number of rotations of the drum, and d represents the diameter of the drum.

[0042] The actual position of the grab bucket is transmitted to the PLC controller via fieldbus; the PLC controller inputs the actual position and target position of the grab bucket into the decision module.

[0043] Furthermore, the decision-making module includes a frequency acquisition unit, a dynamic model calculation unit, a braking point generator, a position comparator, and a control command generation unit;

[0044] The frequency acquisition unit obtains the real-time frequency f of the frequency converter via the Profibus bus;

[0045] The dynamic model calculation unit calculates the theoretical braking distance at the current real-time frequency, specifically as follows:

[0046] D = af 2 + bf + c;

[0047] In the formula, D represents the theoretical braking distance, f represents the real-time frequency of the inverter, a is the coefficient of the quadratic term, b is the coefficient of the linear term, and c is the constant term. The values ​​of a, b, and c are obtained by fitting a quadratic function to the historical data pair (f, D) sample set using the least squares method.

[0048] To compensate for the theoretical braking distance, the load is considered, specifically:

[0049] D adj = D · (1 + α·Δm / m0);

[0050] In the formula, D adj The value represents the compensated braking distance, D represents the theoretical braking distance, α represents the load sensitivity coefficient, Δm represents the difference between the actual load and the rated load, and m0 is the rated load.

[0051] The braking point generator calculates the braking position based on the target position of the grab bucket and the compensated braking distance;

[0052] The position comparator continuously compares the actual position of the grab bucket with its braking position;

[0053] The control command generation unit in P current - P brake When ≤δ, a frequency converter stop command and a brake start command are generated, where, P current Indicates the actual position of the grab, P brake This indicates the braking position, and δ is the threshold.

[0054] Furthermore, the execution module includes a frequency converter control unit, a three-phase asynchronous motor, a hydraulic push rod brake, and a mechanical feedback loop;

[0055] The inverter control unit outputs a 0-50Hz rotation frequency signal to the inverter during normal operation, and disconnects the inverter enable when it receives an inverter stop command.

[0056] The three-phase asynchronous motor receives the PWM drive signal output by the frequency converter and drives the drum to rotate;

[0057] The hydraulic push rod brake locks the drum after receiving the brake start command.

[0058] The mechanical feedback loop feeds back the motion state of the rotating mechanism to the encoder via a mechanical connection.

[0059] Furthermore, the calculation of the braking position based on the target position of the grab bucket and the compensated braking distance specifically involves:

[0060] Read the motion direction signal of the mechanism from the PLC;

[0061] Calculate the braking position using the following formula:

[0062] P brake = P target - D adj × V sign

[0063] In the formula, P brake Indicates the braking position, P target Indicates the target location of the grab, D adj V represents the compensated braking distance. sign It is the signal for the direction of the mechanism's movement. A value of +1 indicates forward movement, and a value of -1 indicates reverse movement.

[0064] The beneficial effects of this invention are:

[0065] This invention demonstrates through experimental data that actual braking distance is dominated by friction in the low-speed range, exhibiting near-linearity, while in the high-speed range it is dominated by inertia (D ∝ This exhibits strong nonlinearity. For the first time, a nonlinear mapping relationship D = af between frequency and braking displacement is established. 2 + bf + c, replacing the traditional fixed delay / fixed distance mode. In high-altitude conditions, the quadratic term af... 2 The primary phase (bf) dominates, significantly increasing the braking distance (D) to avoid under-braking and overtravel. Under low-speed conditions, the primary phase (bf) dominates, automatically reducing the braking distance (D) to avoid over-braking and premature stopping, thus solving speed adaptability defects and achieving automatic and precise positioning across the entire speed range.

[0066] A self-calibration mechanism for design parameters is introduced, and a load adaptive model D is introduced. adj = D · (1 + α·Δm / m0), which reduces debugging costs, shifts from manual testing to automatic calibration, and automatically updates model parameters according to equipment status, thus reducing maintenance costs.

[0067] It achieves adaptive and precise automatic braking of the automated gantry crane across the entire speed range, eliminating the impact of speed and load changes on positioning accuracy.

[0068] This invention fundamentally solves the long-standing problem of "speed and accuracy being mutually exclusive" in the field of crane positioning through a three-pronged innovation of nonlinear modeling, dynamic calculation, and data-driven approach, providing highly efficient automated operations for port automation. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the braking method for the automated gantry crane proposed in this invention.

[0070] Figure 2 This is an architecture diagram of the braking system of the automated gantry crane proposed in this invention. Detailed Implementation

[0071] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0072] Example 1

[0073] This invention proposes a braking method for an automated door operator, such as... Figure 1 As shown, a quantitative relationship model between the real-time frequency of the frequency converter and the braking distance of the gantry crane in the automated operation mode is established, and the automated gantry crane braking is carried out through the following steps:

[0074] When braking is required, the target position of the grab bucket is set on the host computer;

[0075] Repeatedly execute steps a to e until the difference between the actual position of the grab bucket and the braking position is less than or equal to the threshold, then automatically output the inverter stop command and the brake start command:

[0076] a. Acquire the real-time frequency of the frequency converter;

[0077] b. Calculate the actual position of the grab bucket; the specific process is as follows:

[0078] The number of drum rotations is monitored in real time and converted into the actual position of the grab bucket using the following formula:

[0079] P current = P be +S= P be +N×π×d;

[0080] In the formula, P current Indicates the actual position of the grab bucket. P be S represents the position of the grab bucket before the drum rotates, N represents the number of rotations of the drum, and d represents the diameter of the drum.

[0081] c. Calculate the theoretical braking distance at the current real-time frequency based on a quantitative relationship model between the inverter's real-time frequency and braking distance; specifically:

[0082] D = af 2 + bf + c;

[0083] In the formula, D represents the theoretical braking distance, f represents the real-time frequency of the inverter, a is the coefficient of the quadratic term, b is the coefficient of the linear term, and c is the constant term. The values ​​of a, b, and c are obtained by fitting a quadratic function to the historical data pair (f, D) sample set using the least squares method.

[0084] d. Consider the load to compensate for the theoretical braking distance; specifically:

[0085] D adj = D · (1 + α·Δm / m0);

[0086] In the formula, D adj The value represents the compensated braking distance, D represents the theoretical braking distance, α represents the load sensitivity coefficient, Δm represents the difference between the actual load and the rated load, and m0 is the rated load.

[0087] e. Automatically calculate the braking position based on the target position of the grab bucket and the compensated braking distance. Specifically:

[0088] Read the motion direction signal of the mechanism from the PLC;

[0089] Calculate the braking position using the following formula:

[0090] P brake = P target - D adj × V sign

[0091] In the formula, P brake Indicates the braking position, P target Indicates the target location of the grab, D adj V represents the compensated braking distance. sign It is the signal for the direction of the mechanism's movement. A value of +1 indicates forward movement, and a value of -1 indicates reverse movement.

[0092] Example 2

[0093] This invention proposes a braking system for an automated door operator corresponding to the method in Embodiment 1, such as... Figure 2 As shown, it includes:

[0094] The host computer is used to set the target position of the grab bucket;

[0095] The sensing module is used to calculate the actual position of the grab bucket;

[0096] The decision module is used to collect the real-time frequency of the frequency converter, calculate the theoretical braking distance at the current real-time frequency based on the quantitative relationship model between the real-time frequency of the frequency converter and the braking distance, and consider the load to compensate for the theoretical braking distance; calculate the braking position based on the target position of the grab bucket and the compensated braking distance; compare the actual position of the grab bucket with the braking position, and if the difference between the actual position of the grab bucket and the braking position is less than or equal to the threshold, output the frequency converter stop command and the brake start command.

[0097] The execution module responds to the decision module by cutting off the inverter enable based on the inverter stop command and starting the brake based on the brake start command.

[0098] The sensing module includes a mechanism encoder, a displacement calculation unit, and a PLC controller;

[0099] The mechanism encoder is installed on the output shaft side of the hoisting mechanism drum of the crane to monitor the number of drum rotations in real time;

[0100] The displacement calculation unit converts the number of drum rotations into the actual position of the grab bucket, using the following formula:

[0101] P current = P be +S= P be +N×π×d;

[0102] In the formula, P current Indicates the actual position of the grab bucket. P be S represents the position of the grab bucket before the drum rotates, N represents the number of rotations of the drum, and d represents the diameter of the drum.

[0103] The actual position of the grab bucket is transmitted to the PLC controller via fieldbus; the PLC controller inputs the actual position and target position of the grab bucket into the decision module.

[0104] The decision module includes a frequency acquisition unit, a dynamic model calculation unit, a braking point generator, a position comparator, and a control command generation unit;

[0105] The frequency acquisition unit obtains the real-time frequency f of the inverter via the Profibus bus;

[0106] The dynamic model calculation unit calculates the theoretical stopping distance at the current real-time frequency, specifically:

[0107] D = af 2 + bf + c;

[0108] In the formula, D represents the theoretical braking distance, f represents the real-time frequency of the inverter, a is the coefficient of the quadratic term, b is the coefficient of the linear term, and c is the constant term. The values ​​of a, b, and c are obtained by fitting a quadratic function to the historical data pair (f, D) sample set using the least squares method.

[0109] To compensate for the theoretical braking distance, the load is considered, specifically:

[0110] D adj = D · (1 + α·Δm / m0);

[0111] In the formula, D adj The value represents the compensated braking distance, D represents the theoretical braking distance, α represents the load sensitivity coefficient, Δm represents the difference between the actual load and the rated load, and m0 is the rated load.

[0112] The braking point generator calculates the braking position based on the target position of the grab bucket and the compensated braking distance; specifically:

[0113] Read the motion direction signal of the mechanism from the PLC;

[0114] Calculate the braking position using the following formula:

[0115] P brake = P target - D adj × V sign

[0116] In the formula, P brakeIndicates the braking position, P target Indicates the target location of the grab, D adj V represents the compensated braking distance. sign It is the signal for the direction of the mechanism's movement. A value of +1 indicates forward movement, and a value of -1 indicates reverse movement.

[0117] The position comparator continuously compares the actual position of the grab bucket with its braking position;

[0118] The control command generation unit is in P current - P brake When ≤δ, a frequency converter stop command and a brake start command are generated, where, P current Indicates the actual position of the grab, P brake This indicates the braking position, and δ is the threshold.

[0119] The execution module includes a frequency converter control unit, a three-phase asynchronous motor, a hydraulic push rod brake, and a mechanical feedback loop;

[0120] When the inverter control unit is working normally, it outputs a 0-50Hz rotation frequency signal to the inverter. When it receives a shutdown command from the inverter, it cuts off the inverter enable.

[0121] The three-phase asynchronous motor receives the PWM drive signal output by the frequency converter and drives the drum to rotate;

[0122] After receiving the brake start command, the hydraulic push rod brake locks the drum.

[0123] The mechanical feedback loop feeds back the motion state of the rotating mechanism to the encoder via a mechanical connection.

[0124] Braking distance model and experimental verification, test conditions are shown in Table 1:

[0125] Table 1

[0126]

[0127] The gantry crane includes a slewing mechanism, a hoisting mechanism, and a luffing mechanism. This invention supports fault isolation and reconfiguration: when a single mechanism malfunctions, the parameters of the remaining mechanisms are automatically adjusted. The experimental verification below uses the slewing mechanism as an example.

[0128] Model formula: Quadratic function model D = af 2 + bf + c (a≠0)

[0129] In the formula, D represents the braking distance, and f is the output frequency of the inverter.

[0130] The experimental procedure is as follows:

[0131] 1) Baseline setting: Fix the target position P target = 112.25°

[0132] 2) Data collection is shown in Table 2:

[0133] Table 2

[0134]

[0135] 3) Model fitting:

[0136] The least squares method was used to fit a quadratic function to 40 sets of (f, D) data points, with coefficients ranging from a to [0.005, 0.006], b to [0.28, 0.30], and c to [-1.6, -1.5] (preferred values: a: 0.0058, b: 0.29, c: -1.55). The formula for the rotating mechanism model is as follows:

[0137] D = 0.0058f 2 + 0.29f - 1.55

[0138] 4) Validate the data

[0139] The results of the frequency effect test (40t rated load) are shown in Table 3:

[0140] Table 3

[0141]

[0142] Error analysis:

[0143] Maximum absolute error: 0.22° (corresponding to 30Hz operating conditions)

[0144] Average relative error: 0.06%.

[0145] The results of the load effect test (20Hz fixed frequency) are shown in Table 4:

[0146] Table 4

[0147]

[0148] The error was controlled within 0.03° after compensation, proving the effectiveness of the compensation mechanism.

[0149] 5) Comparison of experimental results, see Table 5:

[0150] Table 5

[0151]

[0152] 6) Extreme operating condition verification:

[0153] Scenario 1: High-speed emergency stop (45Hz→0)

[0154] Target position: 180.0°

[0155] Actual measurement stop: 179.86° (error 0.14°)

[0156] Braking time: 2.8s (compliant with EN 13001 safety standards)

[0157] Scenario 2: Low-frequency fine-tuning (5Hz→0)

[0158] Target position: 90.0°

[0159] Actual measurement stop: 90.02° (error 0.02°)

[0160] Minimum control accuracy verified: 0.01°

[0161] Scenario 3: Continuous Directional Change

[0162] Cumulative error: 0.31° (total displacement of four segments: 405°)

[0163] Maximum error per segment: 0.15° (occurring in the 180°→0° segment)

[0164] 7) Verification conclusions

[0165] Accuracy verification: Positioning error across the entire frequency band ≤ 0.22°;

[0166] Robustness verification: When the load varies by 20-40t, the error after compensation is ≤0.03°;

[0167] Safety verification: Reduced impact during high-speed braking, extending equipment lifespan;

[0168] Economic benefits: Reduces the time spent on fine-tuning positions and improves operational efficiency.

[0169] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0170] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A braking method for an automated gantry crane, characterized in that, Establish a quantitative relationship model between the real-time frequency of the inverter and the braking distance in the automated operation mode of the gantry crane, and implement automated gantry crane braking through the following steps: When braking is required, set the target position for the grab bucket; Repeatedly execute steps a to e until the difference between the actual position of the grab bucket and the braking position is less than or equal to the threshold, then output the inverter stop command and the brake start command: a. Acquire the real-time frequency of the frequency converter; b. Calculate the actual position of the grab bucket; c. Calculate the theoretical braking distance at the current real-time frequency based on the quantitative relationship model between the real-time frequency and braking distance of the inverter; specifically, the calculation of the theoretical braking distance at the current real-time frequency based on the quantitative relationship model between the real-time frequency and braking distance of the inverter is as follows: D = off 2 + bf + c; In the formula, D represents the theoretical braking distance, f represents the real-time frequency of the inverter, a is the coefficient of the quadratic term, b is the coefficient of the linear term, and c is the constant term. The values ​​of a, b, and c are obtained by fitting a quadratic function to the historical data pair (f, D) sample set using the least squares method. d. Consider the load to compensate for the theoretical braking distance; specifically, considering the load to compensate for the theoretical braking distance means: D adj = D · (1 + α·Δm / m0); In the formula, D adj The value represents the compensated braking distance, D represents the theoretical braking distance, α represents the load sensitivity coefficient, Δm represents the difference between the actual load and the rated load, and m0 is the rated load. e. Calculate the braking position based on the target position of the grab bucket and the compensated braking distance.

2. The braking method of the automated gantry crane as described in claim 1, characterized in that, The specific process for calculating the actual position of the grab bucket is as follows: The number of drum rotations is monitored in real time and converted into the actual position of the grab bucket using the following formula: P current = P be +S= P be +N×π×d; In the formula, P current Indicates the actual position of the grab bucket. P be S represents the position of the grab bucket before the drum rotates, N represents the number of rotations of the drum, and d represents the diameter of the drum.

3. The braking method for the automated gantry crane as described in claim 1, characterized in that, The calculation of the braking position based on the target position of the grab bucket and the compensated braking distance is specifically as follows: Read the motion direction signal of the mechanism from the PLC; Calculate the braking position using the following formula: P brake = P target - D adj × V sign ; In the formula, P brake Indicates the braking position, P target Indicates the target location of the grab, D adj V represents the compensated braking distance. sign It is the signal for the direction of the mechanism's movement. A value of +1 indicates forward movement, and a value of -1 indicates reverse movement.

4. A braking system for an automated gantry crane, characterized in that, include: The host computer is used to set the target position of the grab bucket; The sensing module is used to calculate the actual position of the grab bucket; The decision module is used to collect the real-time frequency of the frequency converter, calculate the theoretical braking distance at the current real-time frequency based on the quantitative relationship model between the real-time frequency of the frequency converter and the braking distance, and consider the load to compensate for the theoretical braking distance; calculate the braking position based on the target position of the grab bucket and the compensated braking distance; compare the actual position of the grab bucket with the braking position, and if the difference between the actual position of the grab bucket and the braking position is less than or equal to the threshold, output the frequency converter stop command and the brake start command. The decision-making module includes a frequency acquisition unit, a dynamic model calculation unit, a braking point generator, a position comparator, and a control command generation unit. The frequency acquisition unit obtains the real-time frequency f of the frequency converter via the Profibus bus; The dynamic model calculation unit calculates the theoretical braking distance at the current real-time frequency, specifically as follows: D = off 2 + bf + c; In the formula, D represents the theoretical braking distance, f represents the real-time frequency of the inverter, a is the coefficient of the quadratic term, b is the coefficient of the linear term, and c is the constant term. The values ​​of a, b, and c are obtained by fitting a quadratic function to the historical data pair (f, D) sample set using the least squares method. To compensate for the theoretical braking distance, the load is considered, specifically: D adj = D · (1 + α·Δm / m0); In the formula, D adj The value represents the compensated braking distance, D represents the theoretical braking distance, α represents the load sensitivity coefficient, Δm represents the difference between the actual load and the rated load, and m0 is the rated load. The braking point generator calculates the braking position based on the target position of the grab bucket and the compensated braking distance; The position comparator continuously compares the actual position of the grab bucket with its braking position; The control command generation unit in P current - P brake When ≤δ, a frequency converter stop command and a brake start command are generated, where, P current Indicates the actual position of the grab, P brake This indicates the braking position, and δ is the threshold value. The execution module responds to the decision module by cutting off the inverter enable based on the inverter stop command and starting the brake based on the brake start command.

5. The braking system of the automated gantry crane as described in claim 4, characterized in that, The sensing module includes a mechanism encoder, a displacement calculation unit, and a PLC controller; The mechanism encoder is installed on the output shaft side of the hoisting mechanism drum of the gantry crane to monitor the number of drum rotations in real time; The displacement calculation unit converts the number of drum rotations into the actual position of the grab bucket, using the following formula: P current = P be +S= P be +N×π×d; In the formula, P current Indicates the actual position of the grab bucket. P be S represents the position of the grab bucket before the drum rotates, N represents the number of rotations of the drum, and d represents the diameter of the drum. The actual position of the grab bucket is transmitted to the PLC controller via fieldbus; the PLC controller inputs the actual position and target position of the grab bucket into the decision module.

6. The braking system of the automated gantry crane as described in claim 4, characterized in that, The execution module includes a frequency converter control unit, a three-phase asynchronous motor, a hydraulic push rod brake, and a mechanical feedback loop; The inverter control unit outputs a 0-50Hz rotation frequency signal to the inverter during normal operation, and disconnects the inverter enable when it receives an inverter stop command. The three-phase asynchronous motor receives the PWM drive signal output by the frequency converter and drives the drum to rotate; The hydraulic push rod brake locks the drum after receiving the brake start command. The mechanical feedback loop feeds back the motion state of the rotating mechanism to the encoder via a mechanical connection.

7. The braking system of the automated gantry crane as described in claim 4, characterized in that, The calculation of the braking position based on the target position of the grab bucket and the compensated braking distance is specifically as follows: Read the mechanism's motion direction signal from the PLC controller; Calculate the braking position using the following formula: P brake = P target - D adj × V sign ; In the formula, P brake Indicates the braking position, P target Indicates the target location of the grab, D adj V represents the compensated braking distance. sign It is the signal for the direction of the mechanism's movement. A value of +1 indicates forward movement, and a value of -1 indicates reverse movement.

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