A method for online identification of the thrust of a stem of a waterjet propeller

Abstract

The present application relates to the technical field of power control, and discloses a mooring column thrust online identification method of a water jet propeller, which comprises the following steps: establishing a ship longitudinal dynamics model; establishing a water jet propeller mooring column thrust model containing parameters to be identified, which represents the influence of rotating speed, rudder angle and reverse bucket angle on thrust; constructing a state observer, cutting off the feedback of a position sensor after issuing an identification action instruction, and calculating a calculated motion result in an open loop mode depending on the dynamics model; synchronously acquiring actual measurement results of the ship; physically isolating each parameter to be identified by setting multiple groups of control action sequences, and iteratively adjusting the parameters to be identified in sequence online with the goal of reducing the deviation between the calculated motion result and the actual measurement result. The present application realizes online real-time adjustment of thrust parameters, avoids the problem of algorithm non-convergence caused by strong coupling of multiple parameters, and greatly saves the on-site debugging time of the ship.

Description

Technical Field

[0001] This invention relates to the field of power control technology, and in particular to a method for online identification of bollard thrust in a waterjet propulsion system. Background Technology

[0002] The main function of a dynamic positioning system is to automatically control a vessel's longitudinal, lateral, and heading degrees of freedom, enabling the vessel to maintain its set position, heading, and trajectory. Dynamically positioned vessels are typically equipped with thrusters such as side thrusters, azimuth thrusters, and propeller-rudder thrusters. In recent years, to simultaneously meet the requirements of fixed-point positioning control performance and high-speed navigation capability, waterjet propulsion has been increasingly applied to various types of dynamically positioned vessels or offshore platforms. Modeling and identifying the bollard thrust of waterjet propulsion has become the foundation for the motion control of such dynamically positioned vessels.

[0003] Waterjet propulsion typically has three control variables: motor speed, rudder angle, and bucket angle. Different combinations of these three variables can generate thrusts in different directions and magnitudes acting on the ship. Establishing a mathematical model that is easy to use in engineering is the foundation for identifying its bollard thrust, and the design of the identification process and actions is key to identifying the bollard thrust of a waterjet propulsion system.

[0004] Therefore, there is an urgent need in this field for an online identification method for the bollard thrust of waterjet propulsion systems that is more accurate and has higher recognition accuracy. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in related technologies. To this end, the present invention provides a method for online identification of bollard thrust in a waterjet propulsion system.

[0006] A method for online identification of bollard thrust in a waterjet propulsion system includes: A dynamic model of the longitudinal motion of a ship is established to characterize the relationship between the forces acting on the ship and its motion state in the longitudinal motion. A mathematical model of the bollard thrust of a waterjet propulsion system was established to determine the thrust parameters to be identified for the waterjet propulsion system under different control variables. Set corresponding identification action commands for the thrust parameters to be identified; A state observer is constructed, and the reception of position information is paused after the identification action command is issued. The position information is measured and fed back through position sensors. Based on the ship's longitudinal motion model and the current thrust parameters to be identified, an open-loop calculation is performed to obtain the ship's calculated motion result. During the process of the water jet propulsion unit executing the identification action command, the actual measurement results of the position sensor are acquired simultaneously. The motion deviation is obtained based on the calculated motion results and the actual measurement results; The thrust parameters to be identified are iteratively adjusted according to the motion deviation until convergence is achieved, thus obtaining the target thrust parameters that have been identified. The establishment of the bollard thrust mathematical model for the waterjet propulsion system is used to determine the thrust parameters to be identified for the waterjet propulsion system under different control variables, including: Establish extreme value models of forward and reverse bollard thrust to determine the basic thrust parameters; Establish thrust models under different bucket tilting angles and determine bucket tilting adjustment parameters; Establish a thrust attenuation model caused by rudder angle and determine the rudder angle attenuation parameters; The basic thrust parameters, the bucket-turning adjustment parameters, and the rudder angle attenuation parameters together constitute the thrust parameters to be identified.

[0007] Furthermore, the establishment of a dynamic model for the longitudinal motion of the ship, used to characterize the relationship between the ship's forces and its motion state, includes: To obtain the ship's longitudinal moment of inertia, longitudinal damping coefficient, longitudinal speed, longitudinal current velocity, longitudinal thrust, and longitudinal wind force; Based on the longitudinal moment of inertia, longitudinal damping coefficient, longitudinal speed, longitudinal current velocity, longitudinal thrust, and longitudinal wind force, a differential equation with the ship's longitudinal acceleration as the output variable is established, and the differential equation is used as the ship's longitudinal motion model.

[0008] Furthermore, the state observer is constructed, and after issuing the identification action command, it pauses receiving position information. The position information is measured and fed back through a position sensor. Based on the ship's longitudinal motion model and the current thrust parameters to be identified, an open-loop calculation is performed to obtain the ship's calculated motion result, including: Before issuing the identification action command, the state observer is made to run in state estimation mode, and closed-loop correction is performed using the measurement value of the position sensor to obtain an initial estimated state synchronized with the real state. After issuing the identification action command, the state observer is switched to the model calculation mode. The position sensor measurement feedback is cut off by inputting a state signal representing that the position sensor is unavailable to the state observer. Starting from the initial estimated state, pure kinematic calculations are performed over time using only the ship's longitudinal motion model and the current thrust parameters to be identified, to obtain the predicted longitudinal motion displacement, which is then used as the calculated motion result.

[0009] Furthermore, the identification action command includes multiple sets of control commands for physically decoupling the thrust parameter to be identified; the control commands include rudder angle command, bucket angle command, and speed command; When identifying the basic thrust parameters, the identification action commands issued include zero-degree rudder angle command, full-capacity bucket tilt angle command, and set rotational speed command. When identifying the bucket tilting adjustment parameters, the issued identification action commands include a zero-degree rudder angle command, a bucket tilting angle command with a specific value, and a set speed command; when identifying the rudder angle attenuation parameters, the issued identification action commands include a rudder angle command with a specific value, a full-value bucket tilting angle command, and a set speed command.

[0010] Further, the basic thrust parameters include the forward bollard thrust coefficient and the reverse bollard thrust coefficient; the iterative adjustment of the corresponding thrust parameters to be identified based on the motion deviation includes: When the identified action command includes a zero-degree rudder angle command, a positive full-capacity bucket angle command, and a maximum speed command, if the longitudinal displacement in the calculated motion result is greater than the longitudinal displacement in the actual measurement result, then the current positive bollard thrust coefficient is reduced in the next iteration; otherwise, the current positive bollard thrust coefficient is increased. When the identification action command includes a zero-degree rudder angle command, a reverse full-capacity bucket angle command, and a maximum speed command, if the absolute value of the longitudinal displacement in the calculated motion result is greater than the absolute value of the longitudinal displacement in the actual measurement result, then the current reverse bollard thrust coefficient is reduced in the next iteration; otherwise, the current reverse bollard thrust coefficient is increased.

[0011] Furthermore, the bucket-tumbling adjustment parameters include zero-thrust bucket-tumbling parameters; the iterative adjustment of the corresponding thrust parameter to be identified based on the motion deviation further includes: When the identification action command includes a zero-degree rudder angle command, a bucket angle command with a value set to zero, and an idle speed command as the set speed command, the longitudinal speed when the ship's motion state tends to be stable is obtained. If the longitudinal velocity is positive, then decrease the current inverted angle value; if the longitudinal velocity is negative, then increase the current inverted angle value. The bucket tilting angle value corresponding to the zero longitudinal velocity after the motion state stabilizes is determined as the zero-thrust bucket tilting parameter for which the identification is completed.

[0012] Furthermore, the bucket-tumbling adjustment parameters include power parameters for the forward bucket-tumbling curve and power parameters for the reverse bucket-tumbling curve; the iterative adjustment of the corresponding thrust parameter to be identified based on the motion deviation further includes: When the identification action command includes a zero-degree rudder angle command, a mid-tumbling angle command, and a maximum speed command: If the acceleration direction is positive and the calculated longitudinal displacement is greater than the actual measured longitudinal displacement, then increase the current power parameter of the positive bucket-tumbling curve; otherwise, decrease it. If the direction of acceleration is reversed, and the calculated absolute value of the longitudinal displacement is greater than the actual measured absolute value of the longitudinal displacement, then the power parameter of the current reverse bucket-turning curve is increased; otherwise, it is decreased.

[0013] Furthermore, the rudder angle attenuation parameter includes a thrust attenuation coefficient parameter and a power parameter of the attenuation thrust rudder angle curve; the iterative adjustment of the corresponding thrust parameter to be identified based on the motion deviation further includes: When the identification action command includes the limit rudder angle command, the full bucket tilt angle command, and the maximum speed command, the current thrust attenuation coefficient parameter is adjusted in reverse iteratively based on the relationship between the calculated longitudinal displacement and the actual measured longitudinal displacement. When the identification action command includes an intermediate rudder angle command between zero degrees and the extreme rudder angle, a full-capacity bucket angle command, and a maximum speed command, the power parameter of the current attenuation thrust rudder angle curve is adjusted in reverse iteratively based on the relationship between the calculated longitudinal displacement and the actual measured longitudinal displacement.

[0014] Furthermore, the convergence condition is: After a preset time has elapsed since the issuance and execution of the single identification action command, the motion deviation between the calculated motion result and the actual measurement result is less than a set distance threshold.

[0015] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: 1. Traditional offline extended-dimensional filtering typically solves for multiple parameters to be identified as a unified state vector. However, in the extremely complex fluid physics environment of a waterjet propulsion system, the strong coupling of multiple parameters can easily lead to filter divergence. This solution innovatively employs a method of "dual-mode switching of the state observer" combined with "manually set limit decoupling actions" to successfully reduce the dimensionality of the complex multivariate equations and isolate them into a univariate adjustment logic, effectively ensuring the convergence of the identification of various core parameters (such as the basic thrust coefficient, bucket attenuation, and rudder angle attenuation).

[0016] 2. Unlike traditional hysteresis modeling methods that rely on water tank towing tests or offline data acquisition, this system uses sensors to acquire real displacement and performs real-time rolling comparisons with the virtual displacement predicted by the open-loop model. Qualitative adjustments are immediately made as soon as the deviation exceeds a threshold, achieving "trial-and-error" adjustment of the thrust model and significantly lowering the barrier to model building.

[0017] 3. For field engineers, this set of sequential standard test procedures (such as testing full bucket emptying, idling to zero, and extreme full rudder) has strong operability and automation potential. It avoids meaningless and invalid data collection, significantly saves calibration and debugging time of the ship system in the field, and ultimately outputs an accurate and convenient underlying mathematical model for motion control of the ship's dynamic positioning system.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the online identification method for bollard thrust of the waterjet propulsion device of the present invention; Figure 2 This is a comparison chart showing that forward motion observation is faster than measurement during the identification process of this invention; Figure 3 This is a comparison chart showing that forward motion observation is slower than measurement during the identification process of this invention; Figure 4 This is a synchronous comparison diagram of forward motion observation and measurement during the identification process of this invention; Figure 5 This is a comparison chart showing that negative motion observation is faster than measurement during the identification process of this invention; Figure 6 This is a comparison chart showing that the observation of negative motion is slower than the measurement during the identification process of this invention; Figure 7 This is a synchronous comparison diagram of negative motion observation and measurement during the identification process of this invention; Figure 8 This is a comparison chart of experimental data for the b0 adjustment process of this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but cannot be used to limit the scope of this invention.

[0022] like Figure 1 The diagram illustrates the flow of the online identification method for bollard thrust of the waterjet propulsion system of the present invention.

[0023] A method for online identification of bollard thrust in a waterjet propulsion system, comprising the following steps: S1: Establish a dynamic model of the ship's longitudinal motion; The dynamic model is as shown in equation (1): (1) In the formula, m is the longitudinal moment of inertia of the ship, typically taken as 1.1 to 1.2 times the displacement. d is the longitudinal damping coefficient, obtained through CFD calculations or towing tank tests. u is the longitudinal speed of the ship. For the longitudinal acceleration of the ship; Longitudinal flow velocity; For longitudinal thrust, when the ship is operating in dynamic positioning mode, It is the sum of the longitudinal components of the bollard thrust of each propeller; This refers to longitudinal wind force.

[0024] The calculation is as shown in equation (2): (2) in: The longitudinal dimensionless wind load coefficient of the ship hull is generally obtained through wind tunnel testing or CFD simulation analysis. Relative wind direction angle; air density; Relative wind speed; This represents the projected area of ​​the ship's hull facing the wind.

[0025] S2: Establish a mathematical model of the bollard thrust of the waterjet propulsion system and determine the parameters to be identified; Includes the following steps: S21: Establishment of extreme value models for forward and reverse bollard thrust: (3) In the formula, This refers to the motor speed. This represents the positive bollard thrust at a given rotational speed. This represents the reverse bollard thrust at a given rotational speed. r represents the rudder angle; b represents the bucket tilting state, with 100% being the maximum forward thrust and -100% being the maximum reverse thrust. , These are the forward and reverse bollard thrust coefficients, respectively, and are parameters to be identified.

[0026] S22: Establishment of thrust models under different bucket angles: (4) In the formula, This represents the bucket-tumbling state corresponding to 0 thrust, and is the parameter to be identified. and They represent The positive thrust corresponding to the above tomb raiding The following are the negative thrusts corresponding to tomb raiding; and These are the powers of the forward and reverse thrusts with respect to the bucket-tumbling curve, respectively, and are the parameters to be identified. (The condition is met.) , , and They are generally not equal and need to be identified separately.

[0027] S23: Establishment of a thrust attenuation model caused by rudder angle: (5) In the formula, and They represent , Regarding thrust after rudder angle decay; Maximum rudder angle; and , respectively, are the thrust attenuation coefficients for forward and reverse thrust, and are parameters to be identified; and These are the powers of the forward and reverse attenuation thrust curves with respect to the rudder angle, respectively, and are the parameters to be identified. , They represent , The direction is 0° (0 radians) pointing towards the bow and 90° (90 degrees) pointing towards the starboard side. / 2 radians). Satisfies , , and They are generally not equal and need to be identified separately.

[0028] S24: Based on the above models, establish a mathematical model of the bollard thrust of the waterjet propulsion system: (6) In the formula, , These represent the magnitude and direction of the thrust when digging a bucket from zero or more. , These represent the magnitude and direction of the thrust when the bucket is moved below zero.

[0029] S3: Design the identification process and actions to complete the online identification of each parameter in sequence.

[0030] The specific steps include: S31: Design a state observer to estimate the longitudinal motion of the ship: System state equations: (7) In the formula, Indicates longitudinal displacement; , All are zero-mean Gaussian white noise; longitudinal speed The noise amplitude of the model, Longitudinal flow velocity The noise amplitude of the model.

[0031] , , These represent the rate of change of longitudinal displacement (i.e., velocity), the rate of change of longitudinal speed (i.e., acceleration), and the rate of change of longitudinal flow velocity, respectively. For the longitudinal speed of the ship, Longitudinal flow velocity; For longitudinal thrust, For longitudinal wind force; The longitudinal moment of inertia of the ship; Longitudinal damping coefficient Longitudinal thrust The calculation is as follows: (8) In the formula, For the total number of waterjet propulsion units, The number of waterjet propulsion units that generate positive thrust.

[0032] System measurement equations: (9) In the formula, y represents the longitudinal displacement measurement. To measure the noise amplitude for longitudinal displacement, Zero-mean Gaussian white noise, This represents longitudinal displacement.

[0033] Based on the model formed by the system state equation (7) and the system measurement equation, a state observer is designed using the extended Kalman filter algorithm to estimate the longitudinal motion of the ship. Before identification begins, the state estimation mode of the state observer is used so that the estimated motion can follow the motion measured by the sensor; after identification begins, the model extrapolation mode is used, that is, the model extrapolation result is used as the state estimation result, and the model extrapolation motion is compared with the actual motion measured by the sensor to obtain the thrust used in model (7). Whether the thrust is greater or less than the actual bollard thrust to be identified, and then based on the longitudinal thrust model (8), further refine the single waterjet propeller bollard thrust model (6). , , , , , , , , Adjustments will be made.

[0034] We assume that the state equation of the nonlinear system is used in the system recursive model, and its specific form is as follows: ; in, Let k be the system state vector at time k. Let the system state vector at time k-1 take values. Let f represent the system input at time k-1. and , The functional relationship, This represents the value of the system noise at time k-1.

[0035] The observation equations are defined for the measurement model, and their specific form is as follows: ; in, Let h represent the measured value at time k, and h represent the ratio of the measured value to h'. The functional relationship, This represents the value of the measurement noise at time k.

[0036] Noise is defined as follows: System noise It follows a Gaussian distribution with zero mean. , The system noise covariance matrix; Noise measurement It follows a Gaussian distribution with zero mean. , To measure the noise covariance matrix; The two types of noise are independent of each other and are unrelated to the initial state of the system.

[0037] The EKF filtering formula is as follows: C1: State Prior Prediction Based on the optimal state at the previous moment Predict the current state : .

[0038] C2: Covariance Prior Prediction Update the predicted value of the state error covariance : ; in, Let be the error covariance matrix at time k-1. Let k be the system noise covariance matrix at time k-1. The state transition Jacobian matrix is ​​obtained by substituting the partial derivative of f with respect to x. Obtain its value.

[0039] C3: Calculate Kalman gain The model adaptively adjusts the weights to balance the prediction error and the observation error of the sensors. : ; in, To measure the Jacobian matrix, we substitute the partial derivative of h with respect to x into the equation. Obtain its value. Let be the measurement noise covariance matrix at time k.

[0040] C4: Post-hoc state update By correcting the predicted state using the current measurements, we obtain the optimal state estimate for the current time. : .

[0041] C5: Covariance Posterior Update Update the error covariance of the current optimal state In preparation for the next iteration: in: It is an identity matrix.

[0042] The state observer used in this identification method employs the standard extended Kalman filter formula in the state estimation mode, following steps 1 to 5 above.

[0043] The extended Kalman filter formula used by the state observer in this identification method in the model extrapolation mode is as follows: L1: State Prior Prediction Based on the optimal state at the previous moment Predict the current state : L2: Covariance Prior Prediction Update the predicted value of the state error covariance Unlike the standard formula, this only relies on the model. Take 0: L3: Post-hoc state update Current optimal state estimation Use the predicted values ​​directly : L4: Covariance Posterior Update Error covariance Use the predicted values ​​directly : Unlike offline identification using the extended-dimensional EKF filtering algorithm, this patent employs an online identification method, avoiding the predicament of unusable data or inability to converge the parameters to be identified in offline identification. The identification process can continue until a satisfactory result is obtained. Twenty seconds after the start of a single identification action, if the deviation between the model-calculated motion and the actual motion measured by the sensor is less than 2 meters, the identification result for the parameter to be identified is deemed reasonable.

[0044] Taking a ship equipped with two waterjet propulsion units as an example, the identification process and actions are designed to complete the online identification of the parameters to be identified.

[0045] S32: , Identify: 1) With two waterjet propulsion units at a given rudder angle of 0° and the vessel fully tilted, and the maximum rotational speed of both propulsion units, the ship accelerates forward from 0 speed. At this point, a spurious signal indicating that no position sensor is available is given to the state observer, causing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed.

[0046] 2) With a rudder angle of 0° and the vessel tilting at -100%, and the maximum rotational speed of both waterjet propellers, the ship accelerates backward from 0 speed. At this point, a spurious signal indicating no available position sensors is given to the state observer, prompting it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed.

[0047] S33: , , Identify: 1) With two waterjet propulsion units, a rudder angle of 0°, bucket tilting of 0°, and idle speed, if the ship has a positive longitudinal velocity after stabilizing, the velocity should be gradually decreased from 0 until the stabilized longitudinal velocity is 0; if the ship has a negative longitudinal velocity after stabilizing, the velocity should be gradually increased from 0. This continues until the longitudinal velocity reaches zero after stabilization. This method is used to complete the parameter calculation. The identification results were confirmed.

[0048] 2) Two waterjet propulsion units are given a rudder angle of 0°. Between 100% and 100%, the ship is given its maximum rotational speed at both waterjet propulsion units, causing it to accelerate forward from 0 speed. At this point, a spurious signal indicating no available position sensors is provided to the state observer, prompting it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared to the actual measured motion. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is increased. Otherwise, turn it down. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed.

[0049] 3) Two waterjet propulsion units provide a rudder angle of 0°, -100%~ The ship is tossed about between two waterjet propulsion units at their maximum speeds, accelerating backward from 0 speed. A spurious signal indicating no available position sensors is provided to the state observer, prompting it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared to the actual measured motion. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, the speed is increased. Otherwise, turn it down. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed.

[0050] S34: , , , Identify: 1) Two waterjet propellers are given their maximum negative and maximum positive rudder angles respectively, with the bucket tilted at 100%. The maximum rotational speed of both waterjet propellers is also given, causing the ship to accelerate forward from 0 speed. At this point, a spurious signal indicating no available position sensors is given to the state observer, causing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is increased. Otherwise, turn it down. Repeat the above steps, iterating several times, to finalize the parameters. The identification results were confirmed.

[0051] 2) The two waterjet propellers are given their negative and positive maximum rudder angles respectively, with the bucket tilted at -100%. The maximum rotational speed of both waterjet propellers is also given, causing the ship to accelerate backward from 0 speed. At this point, a spurious signal indicating that no position sensor is available is given to the state observer, allowing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, then the speed is increased. Otherwise, turn it down. Repeat the above steps, iterating several times, to finalize the parameters. The identification results were confirmed.

[0052] 3) The two waterjet propellers are given negative maximum to 0° rudder angle and 0° to positive maximum rudder angle respectively, with the bucket tilted at 100%. The maximum rotational speed of both waterjet propellers is given, causing the ship to accelerate forward from 0 speed. At this point, a false signal indicating no available position sensors is given to the state observer, allowing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion result is compared with the actual measured result. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, iterating several times, to finalize the parameters. The identification results were confirmed.

[0053] 4) The two waterjet propellers are given negative maximum to 0° rudder angle and 0° to positive maximum rudder angle respectively, with the bucket tilted at -100%. The maximum rotational speed of both waterjet propellers is given, causing the ship to accelerate backward from 0 speed. At this point, a false signal indicating no available position sensors is given to the state observer, allowing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, iterating several times, to finalize the parameters. The identification results were confirmed.

[0054] Experimental Example Based on the above technical solution, the following is a specific embodiment of completing the online identification of the parameters to be identified, taking a ship equipped with two waterjet propulsion units as an example.

[0055] D32: , Identify: 1) With two waterjet propulsion units at a given rudder angle of 0° and the vessel fully tilted, and the maximum rotational speed of both propulsion units, the ship accelerates forward from 0 speed. At this point, a spurious signal indicating that no position sensor is available is given to the state observer, causing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. The adjustment process is as follows Figures 2-4 As shown. The actual identification process requires repeated actions until the calculated longitudinal displacement is approximately equal to the measured longitudinal displacement. The adjustment process for other parameters to be identified also involves continuous corrections until the reasonable conditions for the results of each identification parameter are met. These will not be described in detail below.

[0056] 2) With a rudder angle of 0° and the vessel tilting at -100%, and the maximum rotational speed of both waterjet propellers, the ship accelerates backward from 0 speed. At this point, a spurious signal indicating no available position sensors is given to the state observer, prompting it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. The adjustment process is as follows Figures 5-7 As shown.

[0057] D33: , , Identify: 1) With two waterjet propulsion units, a rudder angle of 0°, bucket tilting of 0°, and idle speed, if the ship has a positive longitudinal velocity after stabilizing, the velocity should be gradually decreased from 0 until the stabilized longitudinal velocity is 0; if the ship has a negative longitudinal velocity after stabilizing, the velocity should be gradually increased from 0. This continues until the longitudinal velocity reaches zero after stabilization. This method is used to complete the parameter calculation. The identification results were confirmed. Parameters to be identified. The adjustment process is as follows Figure 8 As shown.

[0058] 2) With a rudder angle of 0° and the bucket tilted at 70%, and the two waterjet propellers at their maximum speeds, the ship accelerates forward from 0 speed. At this point, a spurious signal indicating no available position sensors is given to the state observer, prompting it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is increased. Otherwise, turn it down. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. Adjustment process and Figures 2-4 Similar to the example shown.

[0059] 3) With a rudder angle of 0° and a bucket tilt of -70% set for both waterjet propellers, and maximum rotational speed for both propellers, the ship accelerates backward from 0 speed. At this point, a spurious signal indicating no available position sensors is given to the state observer, prompting it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, the speed is increased. Otherwise, turn it down. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. Adjustment process and Figures 5-7 Similar to the example shown.

[0060] D34: , , , Identify: 1) Two waterjet propellers are given their maximum negative and maximum positive rudder angles, i.e., -30° and 30° respectively, with the bucket tilted 100%. The maximum rotational speed of both waterjet propellers is given, causing the ship to accelerate forward from 0 speed. At this point, a spurious signal indicating no available position sensors is given to the state observer, allowing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is increased. Otherwise, turn it down. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. Adjustment process and Figures 2-4 Similar to the example shown.

[0061] 2) The two waterjet propellers are given their maximum negative and maximum positive rudder angles, i.e., -30° and 30° respectively, and a -100% bucket tilt. The maximum rotational speed of the two waterjet propellers is also given, causing the ship to accelerate backward from 0 speed. At this point, a spurious signal indicating that no position sensor is available is given to the state observer, allowing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion result is compared with the actual measured result. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, then the speed is increased. Otherwise, turn it down. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. Adjustment process and Figures 5-7 Similar to the example shown.

[0062] 3) With rudder angles of -20° and 20° respectively assigned to the two waterjet propellers, and the bucket fully tilted, the ship is accelerated forward from 0 speed by its maximum rotational speed. At this point, a spurious signal indicating no available position sensors is given to the state observer, prompting it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the calculated longitudinal displacement is greater than the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. Adjustment process and Figures 2-4 Similar to the example shown.

[0063] 4) The two waterjet propellers are given rudder angles of -20° and 20° respectively, and the bucket is tilted to -100%. The maximum rotational speed of both waterjet propellers is set, causing the ship to accelerate backward from 0 speed. At this point, a spurious signal indicating that no position sensor is available is given to the state observer, allowing it to calculate the ship's longitudinal motion based on the dynamic model. The calculated motion is compared with the actual measured motion. If the absolute value of the calculated longitudinal displacement is greater than the absolute value of the measured longitudinal displacement, the speed is reduced. Otherwise, increase the size. Repeat the above steps, and after several iterations, complete the parameter calculation. The identification results were confirmed. Parameters to be identified. Adjustment process and Figures 5-7 Similar to the example shown.

[0064] This invention proposes an online identification method for the bollard thrust of a waterjet propulsion system, establishes a reliable and convenient mathematical model for the bollard thrust of a waterjet propulsion system, and designs a series of identification processes and actions to achieve the identification of the bollard thrust of the waterjet propulsion system, providing an accurate and reliable control mathematical model for the motion control of dynamically positioned ships equipped with waterjet propulsion systems.

[0065] This invention is based on a dynamic model of ship motion. During the identification process, by comparing the relationship between the motion results calculated by the model and the actual motion measurement results, the parameters to be identified for the waterjet propulsion bollard thrust can be adjusted online in real time, which greatly saves debugging time.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for online identification of bollard thrust in a waterjet propulsion system, characterized in that, include: A dynamic model of the longitudinal motion of a ship is established to characterize the relationship between the forces acting on the ship and its motion state in the longitudinal motion. A mathematical model of the bollard thrust of a waterjet propulsion system was established to determine the thrust parameters to be identified for the waterjet propulsion system under different control variables. Set corresponding identification action commands for the thrust parameters to be identified; A state observer is constructed, and the reception of position information is paused after the identification action command is issued. The position information is measured and fed back through position sensors. Based on the ship's longitudinal motion model and the current thrust parameters to be identified, an open-loop calculation is performed to obtain the ship's calculated motion result. During the process of the water jet propulsion unit executing the identification action command, the actual measurement results of the position sensor are acquired simultaneously. The motion deviation is obtained based on the calculated motion results and the actual measurement results; The thrust parameters to be identified are iteratively adjusted according to the motion deviation until convergence is achieved, thus obtaining the target thrust parameters that have been identified. The establishment of the bollard thrust mathematical model for the waterjet propulsion system is used to determine the thrust parameters to be identified for the waterjet propulsion system under different control variables, including: Establish extreme value models of forward and reverse bollard thrust to determine the basic thrust parameters; Establish thrust models under different bucket tilting angles and determine bucket tilting adjustment parameters; Establish a thrust attenuation model caused by rudder angle and determine the rudder angle attenuation parameters; The basic thrust parameters, the bucket-turning adjustment parameters, and the rudder angle attenuation parameters together constitute the thrust parameters to be identified.

2. The online identification method for bollard thrust of a waterjet propulsion system according to claim 1, characterized in that, The aforementioned dynamic model for the longitudinal motion of the ship, used to characterize the relationship between the ship's forces and its motion state, includes: To obtain the ship's longitudinal moment of inertia, longitudinal damping coefficient, longitudinal speed, longitudinal current velocity, longitudinal thrust, and longitudinal wind force; Based on the longitudinal moment of inertia, longitudinal damping coefficient, longitudinal speed, longitudinal current velocity, longitudinal thrust, and longitudinal wind force, a differential equation with the ship's longitudinal acceleration as the output variable is established, and the differential equation is used as the ship's longitudinal motion model.

3. The online identification method for bollard thrust of a waterjet propulsion system according to claim 1, characterized in that, The state observer is constructed, and after issuing the identification action command, it pauses receiving position information. The position information is measured and fed back through position sensors. Based on the ship's longitudinal motion model and the current thrust parameters to be identified, an open-loop calculation is performed to obtain the ship's calculated motion result, including: Before issuing the identification action command, the state observer is made to run in state estimation mode, and closed-loop correction is performed using the measurement value of the position sensor to obtain an initial estimated state synchronized with the real state. After issuing the identification action command, the state observer is switched to the model calculation mode. The position sensor measurement feedback is cut off by inputting a state signal representing that the position sensor is unavailable to the state observer. Starting from the initial estimated state, pure kinematic calculations are performed over time using only the ship's longitudinal motion model and the current thrust parameters to be identified, to obtain the predicted longitudinal motion displacement, which is then used as the calculated motion result.

4. The online identification method for bollard thrust of a waterjet propulsion system according to claim 1, characterized in that, The identification action command includes multiple sets of control commands for physically decoupling the thrust parameter to be identified; the control commands include rudder angle command, bucket angle command, and speed command. When identifying the basic thrust parameters, the identification action commands issued include zero-degree rudder angle command, full-capacity bucket tilt angle command, and set rotational speed command. When identifying the bucket tilting adjustment parameters, the issued identification action commands include a zero-degree rudder angle command, a bucket tilting angle command with a specific value, and a set speed command; when identifying the rudder angle attenuation parameters, the issued identification action commands include a rudder angle command with a specific value, a full-value bucket tilting angle command, and a set speed command.

5. The online identification method for bollard thrust of a waterjet propulsion system according to claim 4, characterized in that, The basic thrust parameters include the forward bollard thrust coefficient and the reverse bollard thrust coefficient; the iterative adjustment of the corresponding thrust parameters to be identified based on the motion deviation includes: When the identified action command includes a zero-degree rudder angle command, a positive full-capacity bucket angle command, and a maximum speed command, if the longitudinal displacement in the calculated motion result is greater than the longitudinal displacement in the actual measurement result, then the current positive bollard thrust coefficient is reduced in the next iteration; otherwise, the current positive bollard thrust coefficient is increased. When the identification action command includes a zero-degree rudder angle command, a reverse full-capacity bucket angle command, and a maximum speed command, if the absolute value of the longitudinal displacement in the calculated motion result is greater than the absolute value of the longitudinal displacement in the actual measurement result, then the current reverse bollard thrust coefficient is reduced in the next iteration; otherwise, the current reverse bollard thrust coefficient is increased.

6. The online identification method for bollard thrust of a waterjet propulsion system according to claim 4, characterized in that, The bucket-tumbling adjustment parameters include zero-thrust bucket-tumbling parameters; the iterative adjustment of the corresponding thrust parameter to be identified based on the motion deviation further includes: When the identification action command includes a zero-degree rudder angle command, a bucket angle command with a value set to zero, and an idle speed command as the set speed command, the longitudinal speed when the ship's motion state tends to be stable is obtained. If the longitudinal velocity is positive, then decrease the current inverted angle value; if the longitudinal velocity is negative, then increase the current inverted angle value. The bucket tilting angle value corresponding to the zero longitudinal velocity after the motion state stabilizes is determined as the zero-thrust bucket tilting parameter for which the identification is completed.

7. The online identification method for bollard thrust of a waterjet propulsion system according to claim 4, characterized in that, The bucket-tumbling adjustment parameters include power parameters for the forward bucket-tumbling curve and power parameters for the reverse bucket-tumbling curve; the iterative adjustment of the corresponding thrust parameter to be identified based on the motion deviation further includes: When the identification action command includes a zero-degree rudder angle command, a mid-tumbling angle command, and a maximum speed command: If the acceleration direction is positive and the calculated longitudinal displacement is greater than the actual measured longitudinal displacement, then increase the current power parameter of the positive bucket-tumbling curve; otherwise, decrease it. If the direction of acceleration is reversed, and the calculated absolute value of the longitudinal displacement is greater than the actual measured absolute value of the longitudinal displacement, then the power parameter of the current reverse bucket-turning curve is increased; otherwise, it is decreased.

8. The online identification method for bollard thrust of a waterjet propulsion system according to claim 4, characterized in that, The rudder angle attenuation parameters include thrust attenuation coefficient parameters and power parameters of the attenuation thrust rudder angle curve; the iterative adjustment of the corresponding thrust parameters to be identified based on the motion deviation further includes: When the identification action command includes the limit rudder angle command, the full bucket tilt angle command, and the maximum speed command, the current thrust attenuation coefficient parameter is adjusted in reverse iteratively based on the relationship between the calculated longitudinal displacement and the actual measured longitudinal displacement. When the identification action command includes an intermediate rudder angle command between zero degrees and the extreme rudder angle, a full-capacity bucket angle command, and a maximum speed command, the power parameter of the current attenuation thrust rudder angle curve is adjusted in reverse iteratively based on the relationship between the calculated longitudinal displacement and the actual measured longitudinal displacement.

9. The online identification method for bollard thrust of a waterjet propulsion system according to claim 1, characterized in that, The convergence condition is: After a preset time has elapsed since the issuance and execution of the single identification action command, the motion deviation between the calculated motion result and the actual measurement result is less than a set distance threshold.

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