A dynamic operation control method of a ship electric telescopic ladder

Abstract

The application discloses a kind of dynamic operation control methods of ship electric telescopic ladder, comprising: S1, by three-dimensional force sensor, rotary encoder, millimeter wave radar / laser ranging sensor and six-axis inertial measurement unit respectively acquisition equivalent concentrated load force, extension length, end vertical distance and end vertical swing speed;S2, establish dynamic bending moment safety calculation model, according to the comparison result of real-time bending moment and the safety bending moment threshold value varying with extension length, execute overrun protection;S3, establish end soft landing compensation model under wave disturbance, when end vertical distance is less than or equal to trigger threshold, switch to wave compensation peristalsis mode, according to wave speed feedforward compensation output speed instruction;S4, when overrun protection and soft landing compensation are triggered simultaneously, overrun protection is given priority to, execute hierarchical deceleration micro shrinkage action, restore soft landing mode after retraction;Eliminate the overload judgment blind area of traditional weighing method in long cantilever structure, realize smooth docking under complex sea conditions.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology for ship deck machinery, and in particular to a safety control method for ship electric telescopic ladders (gang ladders / pilot ladders) in dynamic maritime operating environments. Specifically, it is a method for coordinated control of telescopic ladder load torque management and end soft landing. Background Technology

[0002] Electric telescopic ladders are indispensable access equipment for large engineering vessels (such as rescue and salvage vessels). Taking a certain type of vessel involved in this application (such as the Qunli ship) as an example, the stainless steel electric telescopic ladder it is equipped with has a maximum extension length of 30 meters and a rated maximum static load of 907.5 kg (equivalent to 11 people), and is driven by an electric winch (lifting speed 8.09 m / min).

[0003] However, in actual marine engineering operations, existing telescopic ladder control systems suffer from the following two independent but jointly threatening operational safety, and no solution has been found in the existing technology to address these two issues collaboratively: Defect 1: Static overload assessment based on total weight fails (risk of bending moment overload): Current technology relies solely on whether the total weight exceeds 907.5 kg to determine overload. However, when the ladder's extension length dynamically changes, the load moment (i.e., bending moment) equals the product of the load force and the lever arm. When personnel or materials are concentrated in the lower part of the ladder (near the end), even if the total weight does not exceed the rated value, the resulting dynamic bending moment may far exceed the design limit of the upper ladder, leading to structural yielding deformation or winch brake disc slippage. Current technology lacks a dynamic monitoring and response mechanism for the mapping relationship between "extension length and real-time bending moment".

[0004] Defect 2: Rigid impact at the end of the wave under wave disturbance (risk of hard landing): When operating at sea, the mother ship experiences six degrees of freedom motion with the waves (especially heave and roll). In existing technology, during the descent of the telescopic ladder to the target platform (such as a dock or the deck of a rescue vessel), it is often forcibly lowered at a constant mechanical speed (e.g., 8.09 m / min). At the moment the ladder tip contacts the target surface, the superposition of relative velocities caused by the waves generates a violent instantaneous impact force far exceeding the static load. This impact can easily damage the ladder end pulleys or anti-slip pads, and may even cause the steel cable to break at the peak of the impact.

[0005] In summary, there is an urgent need for a dynamic operation control method that can simultaneously address both "internal torque overload" and "external wave impact" in order to improve the intrinsic safety level of the equipment under all sea conditions. Summary of the Invention

[0006] This invention provides a dynamic operation control method for a ship's electric telescopic ladder. Its core objective is to construct a unified dynamic safety model that, when performing telescopic and retracting actions, can actively avoid structural overload based on the ladder's real-time attitude (length and bending moment) and actively compensate for wave disturbances when approaching the target interface, thereby achieving a "soft landing" at the end. This expands the telescopic ladder's operating scenario from "still water / ideal working conditions" to "dynamic working conditions in sea states of level four and below".

[0007] This invention adopts the following technical solution: a dynamic operation control method for a ship's electric telescopic ladder, wherein the electric telescopic ladder consists of an upper ladder, a middle ladder, a lower ladder, and an electric winch, as follows: Figure 2 As shown, the control method includes the following steps: S1, Constructing the sensing information perception layer: like Figure 1 As shown, a three-dimensional force sensor is installed at the fixed end of the upper ladder (where it connects to the hull) to acquire in real time the force components of the ladder on the fixed end in three orthogonal directions, including the vertical component. Horizontal component force and horizontal longitudinal component The controller performs vector synthesis of the three orthogonal components, and takes the projected component of the synthesized force along the axis of the trapezoid as the equivalent concentrated load force. Its mathematical expression is = ,in The resultant force vector, Let be the unit vector along the axis of the trapezoid. The scalar value obtained by the dot product of and is the equivalent concentrated load force.

[0008] An absolute rotary encoder is installed at the end of the winch drum drive shaft to obtain the current extension length of the ladder in real time; a millimeter-wave radar / laser range sensor and a six-axis inertial measurement unit (IMU) are installed at the end of the lower ladder to obtain the real-time vertical distance from the end to the target surface and the real-time triaxial acceleration and angular velocity of the end, respectively.

[0009] S2, Establish the dynamic bending moment safety calculation model and judgment logic: Define the current extension length of the ladder as L (unit: m), and define the equivalent concentrated load force acting on the fixed end as measured by the three-dimensional force sensor. (Unit: N), this value is obtained by synthesizing three orthogonal force vectors from a three-dimensional force sensor and projecting them onto the axis of the trapezoid. Due to the uneven load distribution along the trapezoid's length, a dynamic bending moment is introduced. (Unit: N·m), its expression is: ; in This is a correction factor (dimensionless, ranging from 0.45 to 0.65) for the center of gravity position, which is estimated in real time based on the current load distribution along the ladder length. Its default value is based on the mass distribution of the upper / middle / lower ladder. In actual operation, it is dynamically updated by the controller according to the changes in the load distribution of each ladder section during the ladder extension process (for example, the load distribution is calculated by the total force obtained by the three-dimensional force sensor and the strain signal of each ladder section). It can also be used as a fixed value after factory calibration.

[0010] Simultaneously, based on the yield strength and section modulus of the ladder material, a safe bending moment threshold curve varying with the extension length is pre-stored in the controller. To ensure absolute safety, a dynamic safety factor is introduced. (With a value range of 1.2 ~ 1.6), the threshold expression is: ; Where W is the flexural modulus of the trapezoid section (m). 3 ), The yield strength (Pa) of the material (316 stainless steel) is typically 205 × 10⁻⁶. 6 Pa), The maximum design extension length (m).

[0011] like Figure 6 As shown, the safe bending moment threshold decreases monotonically with the increase of the extension length L, reflecting the physical law of the decrease in load-bearing capacity under long cantilever conditions.

[0012] Real-time determination ≥ When this happens, the over-limit protection subroutine is entered.

[0013] S3, Establish a terminal soft landing compensation model under wave disturbance: Let H (in meters) be the real-time vertical distance between the end of the lower ladder and the target surface, and let H be the vertical swing velocity of the end (i.e., the approach velocity of the target surface relative to the end) calculated by the IMU. (Unit: m / s, downward direction is positive).

[0014] Assume the rated drive speed of the winch is (Unit: m / s, positive values ​​represent a decrease). When detected ( When the soft landing trigger distance threshold (typically 2.0 ~ 3.0 m) is reached, the system switches from "high-speed operation mode" to "wave-compensated creep mode". In this mode, the controller's final output speed command... Determined by the following formula: ; in The set low-speed creep base velocity (unit: m / s, value range: 0.1 ~ 0.5 m / min, i.e. 0.0016 ~ 0.0083 m / s). The wave compensation gain coefficient (dimensionless, ranging from 0.6 to 1.0) is calibrated manually or automatically by the control panel according to the sea state level.

[0015] In particular, when When the calculation result is negative, it indicates that the wave's upward speed is greater than its downward speed. The controller instructs the winch to briefly brake or slightly reverse its direction to maintain a "non-contact following" state between the end point and the target surface. And when... When the value is negative, its absolute value does not exceed the set maximum micro-lift speed limit. (In this embodiment, we take) = This is to avoid the ladder moving too quickly in the reverse direction, causing it to detach significantly from the target surface.

[0016] S4, Collaboration between priority arbitration and enforcement agencies: like Figure 5 As shown, when the over-limit protection in step S2 and the soft landing compensation in step S3 are triggered simultaneously, the over-limit protection has a higher priority than the soft landing compensation. At this time, the controller immediately interrupts the current descent command and forcibly executes a graded deceleration miniaturization maneuver. The graded maneuver strategy is as follows: Level 1 Response: Triggers audible and visual alarm (buzzer + flash), duration... =2s; Level 2 response: Execute motor braking to decelerate to zero speed, duration... =1s; Level 3 Response: If the bending moment remains within the danger zone, the hydraulic buffer release circuit is activated, causing the ladder to automatically retract slightly. The amount of slight retraction... The controller determines the deviation of the current real-time bending moment from the safety threshold. = - The calculation formula is derived from the proportional-integral (PI) control law: ; in , Preset proportional gain and integral gain coefficients. , The value is obtained by the controller through a step response test based on the response characteristics of the ladder retraction hydraulic system. Specifically, under the rated working pressure of the hydraulic system, a step opening command is input to the hydraulic valve, the retraction displacement response curve is recorded, and the value is calculated using the Ziegler-Nichols critical proportional method. and The initial value for tuning typically ranges from 1 to 1. =0.5~2.0, =0.1~0.5, which can be adaptively adjusted by those skilled in the art according to the actual flow-opening characteristics of the hydraulic valve; To control the cycle, and The maximum amplitude limit is 0.5 meters; the controller calculates accordingly. Output hydraulic valve opening command until detected < Stop retracting at that time.

[0017] After performing the above-mentioned shrinking and retraction action, if the vertical distance H between the end and the target surface becomes greater than the specified value again due to the retraction... If the wave compensation mode in step S3 is automatically restored, the system continues to perform a soft landing descent. If the over-limit protection is triggered again during the descent, the graded deceleration and miniaturization action is repeated until the ladder safely retracts to within the bending moment safety range. During the above reciprocating execution process, The single-time limit and cumulative protection logic remain unchanged.

[0018] Compared with the prior art, the beneficial effects of the present invention include: (1) Eliminate the blind spot of “false overload”: By introducing the lever arm-bending moment dynamic model, the failure problem of traditional weighing method in long cantilever structure is solved, and the safety monitoring dimension is improved from “scalar weight” to “vector moment”, which effectively prevents structural buckling in long state.

[0019] (2) Achieve precise docking under complex sea conditions: By introducing wave velocity feedforward compensation, the resultant velocity at the end of the ladder is narrowed from the uncontrollable "8.09m / min" to the controllable "≤0.1m / s" low-speed and stable contact, which greatly reduces the peak value of the impact load (theoretically calculated to reduce the impact load by more than 70%).

[0020] (3) High system integration, no need for major hardware modifications: all sensors are commercially available standard parts, and the control logic can be embedded into the existing PLC control system, resulting in low implementation costs and facilitating batch technical upgrades of the existing fleet. Attached Figure Description

[0021] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0022] Figure 1 A schematic diagram of the system structure of the electric telescopic ladder provided by the present invention; Figure 2 This is a flowchart illustrating the overall process of the dynamic operation control method for the electric telescopic ladder of the present invention. Figure 3 for Figure 2The detailed control flowchart of the dynamic bending moment over-limit protection step (S2) in the middle; Figure 4 for Figure 2 The detailed control flow chart for the wave-compensated soft landing step (S3); Figure 5 A time sequence logic diagram for priority arbitration of over-limit protection and wave compensation; Figure 6 This is a characteristic curve showing the change of the safety bending moment threshold involved in this invention with the ladder extension length; the threshold reaches its maximum value when the extension length L approaches 0. When L approaches When the threshold approaches 0, it reflects the physical law of reduced load-bearing capacity under long cantilever conditions. Detailed Implementation

[0023] To enable those skilled in the art to better understand and implement the present invention, the method of the present invention will be described in detail below with reference to specific parameters and working conditions.

[0024] (I) System hardware configuration example: This embodiment uses a specific ship conversion project as an example: Maximum length of retractable ladder =30 m; The winch motor has a power of 3.7kW and a rated descent speed of [missing information]. =8.09 m / min ≈ 0.135 m / s; The controller uses a Siemens S7-1200 programmable logic controller (PLC), paired with an analog input module to acquire force sensor (range 0~10V) and encoder (synchronous serial interface, SSI), and uses high-speed pulse capture IMU serial port data (baud rate 115200).

[0025] The six-axis IMU is installed at the bottom of the lower ladder near the end pulley. Its power supply and data communication are achieved using a flexible drag chain cable laid along the side of the ladder, with sufficient cable slack to accommodate the full extension and retraction of the ladder; alternatively, a built-in battery power supply and wireless data transmission module can be used to avoid cable interference. All of the above installation methods are conventional choices in the art, and the specific selection does not constitute a limitation of the present invention.

[0026] (II) Specific implementation example of step S2 (bending moment protection): like Figure 3 As shown, in this embodiment, step S2 is executed according to the following process: 1. Sensor data preprocessing: The raw signal output by the three-dimensional force sensor is , , The voltage signals from the three channels are converted into force values ​​(unit: N) by the controller after analog-to-digital (AD) conversion. Based on the factory-calibrated sensor mounting matrix, the controller combines the three component forces into an equivalent concentrated load force on the fixed end. Specifically, let the unit vector along the axis of the trapezoid be... The resultant force vector is ,but = (i.e., dot product operation), the scalar value is the equivalent concentrated load force used in the bending moment calculation in the subsequent step S2.

[0027] 2. Data Sampling and Filtering: The controller cycles =50 ms (20Hz) acquisition and encoder angle The extension length L is calculated from the number of turns n of the wire rope released from the drum: ; in This is the average winding diameter of the drum (m). To prevent malfunctions caused by noise, [the following is specified]. Perform a first-order low-pass filter. Define... The bending moment value is obtained after low-pass filtering. The filtering formula is as follows: ; Where k is the sampling sequence number, and the filter coefficient 0.2 corresponds to the cutoff frequency. ≈ ≈0.637Hz ( =50ms), the continuous domain transfer function of the filter is ,in It is a time constant and satisfies = Those skilled in the art can adjust the filter coefficients according to the actual noise level; such adjustments require no creative effort.

[0028] In this embodiment, the bending modulus of the trapezoidal section is taken as W = 1.2 × 10⁻⁶. -3 m 3 The yield strength of 316 stainless steel is taken as =205×10 6 Pa, after substituting into the above threshold formula, can be obtained for different stretch lengths. The specific values ​​are calculated based on this set of parameters in the following action examples.

[0029] 3. Action Examples: Assuming the ladder currently extends L = 25 m, the three-dimensional force sensor measures... =2.5 kN, center of gravity correction factor =0.6. Calculate the real-time bending moment: =2.5×10 3 ×25×0.6=37500 N·m=37.5 kN·m; according to =1.6 and formula = Substituting L=25m and W=1.2×10 -3 m 3 , =205×10 6 Pa was calculated to obtain (25)≈25.6kN·m (This value already includes the overall safety margin).

[0030] Judgment: 37.5 > 25.6, indicating the condition is in the over-limit zone, triggering over-limit protection (if there is no concentrated load at the end). =1.7kN =25.5 < 25.6, within the safe zone). If at this time, the personnel at the end suddenly gather down the ladder, If the voltage jumps to 2.0 kN, then =30 kN·m ≥ 25.6 kN·m, the degree of exceeding the limit is further aggravated, triggering the over-limit protection. At this time, the PLC outputs a signal, on the one hand disconnecting the motor main contactor coil, and on the other hand, the PI controller determines the deviation based on the value of the deviation. = - Calculate the initial retraction amount. For example, in... Under the condition of 2.0kN, =30-25.6=4.4kN·m, the controller calculates the initial value based on this. The value is then used to activate the hydraulic buffer valve, causing the ladder to begin retracting; if the deviation continues to increase, then... The bending moment increases dynamically according to the PI law until it falls back to its original value. The following limits the retraction to stop, and the total retraction amount in a single instance shall not exceed 0.5m.

[0031] (III) Specific implementation example of step S3 (wave soft landing): like Figure 4 As shown, in this embodiment, step S3 is executed according to the following process: 1. Calculation of wave velocity: Let the vertical acceleration output by the six-axis IMU in the ship's coordinate system be... (Unit: m / s) 2 Since wave motion is approximately low-frequency simple harmonic motion, the controller... The vertical velocity is obtained by performing discrete integration.

[0032] To avoid integral drift, a bandpass filter (cutoff frequency 0.05–0.5 Hz, corresponding to the dominant wave frequency) is used, and its continuous domain transfer function is: ; in The center frequency of the bandpass filter (take) =2π×0.1rad / s), The damping ratio is set to 0.707 (the standard value of the Butterworth response is used in this embodiment), with upper and lower cutoff frequencies of 0.05Hz and 0.5Hz, respectively. The acceleration signal processed by this bandpass filter is then discretely integrated to suppress the interference of low-frequency zero drift and high-frequency noise on the velocity calculation.

[0033] Then, the discrete integral formula is used: ; The wave period is detected in real time by the controller: when vertical acceleration... When the sign changes from positive to negative or from negative to positive (i.e., when it crosses zero), record the time interval between two adjacent zero crossings. This interval is the current wave cycle. Every time two adjacent zero-crossing points are detected (i.e., one complete cycle), the controller performs an integral zero-crossing correction. The filter output value is reset and integration restarts to eliminate the cumulative integration error caused by accelerometer zero drift. The frequency of the zero-correction adaptively varies with the actual wave period, typically between 0.05 Hz and 0.5 Hz (corresponding to a period of 2 s to 20 s).

[0034] 2. Example of coordinated speed control in the final stage: Set soft landing trigger threshold =2.0 m. When the ranging radar detects H=1.8 m, it enters wave compensation mode.

[0035] Set low-speed creep base velocity =0.3 m / min = 0.005 m / s. Wave compensation gain =0.8.

[0036] The current IMU-calculated hull heave rate is =+0.02 m / s (meaning the target surface rapidly impacts the ladder upwards).

[0037] Calculation output: =0.005-0.8×0.02=0.005-0.016=-0.011 m / s; A negative result indicates that the controller does not output a descent command, but instead outputs a micro-ascent command of 0.011 m / s, causing the ladder end to rise synchronously with the target surface, thus avoiding hard contact. When the wave falls... When = -0.02 m / s, the calculated value is: =0.005 + 0.016 = 0.021 m / s. At this point, the controller allows for relatively fast tracking of the descent to compensate for the gap in the wave trough. With this compensation, the relative velocity at end-point contact is strictly controlled within ±0.005 m / s, achieving a true "soft landing".

[0038] (iv) Overall machine workflow: Throughout the entire process of ship berthing operations: 1. Extension Phase: The operator presses the "Lower / Extend" button, and the winch lowers the cable. During this phase, step S2 is monitored throughout. The value is set to trigger protection once it approaches the limit.

[0039] 2. Approaching stage: When H≤2m, step S3 will automatically intervene. Regardless of whether the button is in the "high speed" position, the controller will automatically block the high speed signal and force a switch to the wave compensation creep mode.

[0040] 3. Sudden Large Wave Overload Phase: Assume that an abnormally large wave suddenly occurs during the approach phase, causing distortion of the IMU integral velocity and additional hydrodynamic load on the ladder. Exceeding limits. At this point, the priority arbitration in step S4 takes effect, immediately forcibly exiting the wave compensation mode and performing an emergency miniaturization pullback to ensure that the structure is not permanently damaged.

[0041] It should be further noted that those skilled in the art should understand that the sensor selection (such as three-dimensional force sensor, millimeter-wave radar, IMU), specific filtering algorithms (such as low-pass filtering, band-pass filtering), specific programming implementation of the PLC controller, and execution actions of the winch hydraulic buffer mechanism mentioned in this specification are all prior art known in the art or can be conventionally selected and adaptively adjusted by those skilled in the art according to actual working conditions. Their specific models and implementation codes do not constitute a limitation on the core protection scope of this invention. Any modifications, equivalent substitutions, improvements (especially equivalent substitutions for various sensor data fusion algorithms), and reasonable adjustments to the execution order of each step, if they do not depart from the overall inventive concept of this invention and can be conceived without creative effort, should be included within the protection scope of this invention.

Claims

1. A dynamic operation control method for a ship's electric telescopic ladder, wherein the electric telescopic ladder comprises an upper ladder, a middle ladder, a lower ladder, and an electric winch, characterized in that, Includes the following steps: S1, Construct a sensing information perception layer: Install a three-dimensional force sensor at the fixed end of the upper ladder to obtain the force components of the ladder in three orthogonal directions on the fixed end; A rotary encoder is installed at the end of the winch drum drive shaft to obtain the current extension length of the ladder; a distance measuring sensor and an inertial measurement unit are installed at the end of the lower ladder to obtain the real-time vertical distance of the end from the target surface and the real-time vertical swing speed of the end, respectively. S2, Establish a dynamic bending moment safety calculation model and judgment logic: Calculate the equivalent concentrated load force based on the force components of the three-dimensional force sensor. Define the current extension length of the ladder as L, and introduce dynamic bending moment. ,in The center of gravity position correction coefficient is used; simultaneously, a safe bending moment threshold curve varying with the extension length is established. When real-time judgment ≥ When this happens, the over-limit protection subroutine is entered; S3, Establish a soft landing compensation model for the terminal under wave disturbance: Define the real-time vertical distance between the terminal and the target surface as H, and the vertical swing velocity of the terminal as... When H≤ At this time, the system switches to wave-compensated creep mode, and the controller's final output speed command... ,in The base velocity is the low-speed creeping velocity. This is the wave compensation gain coefficient; S4, Coordinated Priority Arbitration and Execution Agency Linkage: When the over-limit protection in step S2 and the soft landing compensation in step S3 are triggered simultaneously, the over-limit protection has a higher priority than the soft landing compensation, and the controller immediately interrupts the current descent command and forcibly executes the graded deceleration and miniaturization action.

2. The method according to claim 1, characterized in that, In step S1, the force components acquired by the three-dimensional force sensor include the vertical component. Horizontal component force and horizontal longitudinal component The controller performs vector synthesis of the three orthogonal components and takes the projected component of the resultant force along the axis of the trapezoid as the equivalent concentrated load force. Its mathematical expression is = ,in The resultant force vector, It is the unit vector along the axis of the trapezoid.

3. The method according to claim 1, characterized in that, In step S2, the safe bending moment threshold curve The expression is: ； Where W is the flexural modulus of the trapezoidal section. For the material's yield strength, For dynamic safety factor, This is the maximum design extension length.

4. The method according to claim 1, characterized in that, In step S2, the center of gravity position correction coefficient The value range is 0.45~0.

65. Its default value is based on the mass distribution of the upper, middle and lower ladders. In actual operation, the controller dynamically updates the value according to the changes in the load distribution of each ladder section during the extension process.

5. The method according to claim 1, characterized in that, In step S3, the low-speed creep base velocity The value range is 0.0016~0.0083 m / s, and the wave compensation gain coefficient is... The value ranges from 0.6 to 1.0, and is calibrated manually or automatically via the control panel according to the sea state level.

6. The method according to claim 1, characterized in that, In step S3, when the final output speed command When the value is negative, the controller instructs the winch to slightly rise in the reverse direction, and the absolute value of the reverse rising speed does not exceed the set maximum rising speed limit. , = .

7. The method according to claim 1, characterized in that, In step S4, the graded deceleration and miniaturization action includes: Level 1 Response: Triggers audible and visual alarm, duration... =2s; Level 2 response: Execute motor braking to decelerate to zero speed, duration... =1s; Level 3 Response: If the bending moment remains within the danger zone, activate the hydraulic buffer release circuit to automatically retract the ladder slightly. The controller determines the amount of deviation. = - The results are obtained from the proportional-integral control law: ； in This is the proportional gain coefficient. This is the integral gain coefficient. To control the cycle, and The maximum amplitude is 0.5 meters.

8. The method according to claim 7, characterized in that, The proportional gain coefficient The value range is 0.5 to 2.0, and the integral gain coefficient is... The value ranges from 0.1 to 0.5, and is obtained by the controller through step response test based on the response characteristics of the ladder retraction hydraulic system.

9. The method according to claim 1, characterized in that, In step S4, after performing the shrinking and retraction action, if the vertical distance H between the end and the target surface becomes greater than the specified value again due to the retraction... If the wave compensation mode in step S3 is automatically restored, the system will continue to perform a soft landing descent. If the over-limit protection is triggered again during the descent, the graded deceleration and miniaturization action will be repeated until the ladder is safely retracted to the bending moment safety range.

10. The method according to claim 1, characterized in that, In step S2, the real-time bending moment After first-order low-pass filtering, the filtering formula is: ； Where k is the sampling sequence number. This is the filtered bending moment value; In step S3, the vertical acceleration output by the inertial measurement unit The vertical swing velocity of the end is obtained by discrete integration after processing with a bandpass filter. The transfer function of the bandpass filter is: ； in The center frequency of the bandpass filter. is the damping ratio.

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