A method for maintaining a ship's course considering rudder performance

Abstract

This invention relates to the field of ship heading control technology, and provides a ship heading control method considering steering gear performance. The method includes: establishing a nonlinear model of the ship's heading; designing a virtual controller based on the ship's nonlinear model; introducing an event-triggered mechanism; constructing an event-triggered rule based on a hybrid threshold to achieve adaptive adjustment of threshold parameters; obtaining intermediate control inputs by calculating the actuator gain adaptive compensation law and the radial basis function neural network weight update law; obtaining event-triggered control inputs based on the event-triggered rules; and automatically inputting the event-triggered control inputs into the heading control system for ship heading control. This invention enables adaptive adjustment of threshold parameters, avoids frequent control signal transmissions in the initial stage of the control system, thereby reducing the steering gear execution frequency, and constructs an adaptive compensation law to weaken the nonlinear influence of the actuator gain function on the heading control system.

Description

Technical Field

[0001] This invention relates to the field of ship course maintenance control technology, and in particular to a ship course maintenance control method that takes into account steering gear performance. Background Technology

[0002] Ship course maintenance control is one of the most fundamental tasks during navigation. Research on this topic has yielded numerous beneficial results, including PID control, adaptive neural network control, model predictive control, sliding mode control, and dynamic surface control. These control algorithms offer significant advantages in improving course maintenance accuracy. However, they neglect the issue of servo motor energy efficiency. High-precision course maintenance control algorithms increase the number of servo motor maneuvers, leading to additional servo motor energy losses. Furthermore, in existing technologies, course maintenance accuracy is easily affected by the nonlinear gain function of the actuators. Therefore, the main shortcomings of existing technologies for course maintenance control can be summarized as follows:

[0003] (1) In the prior art, there are two main types of heading-keeping control algorithms. One is a continuous-time control algorithm, which requires real-time updates of control commands. The other is a heading-keeping method based on static event triggering. In this method, the event triggering threshold parameter needs to be set manually and remains fixed, which still results in excessive control command updates in the initial stage of the control system. Moreover, the control commands in both of the above methods need to be transmitted to the servo system in real time, causing frequent servo operation, which is not conducive to saving servo energy.

[0004] (2) In the heading control system, there is an unknown limitation on the actuator gain. In the prior art, it is usually assumed that the actuator gain is known and can be fed back in real time in the control system, which is different from the actual engineering. Moreover, after the event triggering mechanism is introduced, a nonlinear term, the threshold parameter, will be added to the actuator gain function, which will increase the nonlinear effect of the heading control system. Summary of the Invention

[0005] This invention primarily addresses the technical problems of existing technologies where control commands need to be transmitted to the steering gear system in real time, resulting in frequent steering gear manipulation and hindering energy conservation. It also addresses the technical issue that existing technologies typically assume actuator gain is known and can provide real-time feedback within the control system, which differs from practical engineering scenarios. The invention proposes a ship heading-keeping control method that considers steering gear performance. This method aims to achieve adaptive adjustment of threshold parameters, further avoid frequent control signal transmissions in the initial stage of the control system, thereby reducing the steering gear's execution frequency. Additionally, it constructs an adaptive compensation law to weaken the nonlinear influence of the actuator gain function on the heading-keeping control system.

[0006] This invention provides a ship course-keeping control method considering steering gear effectiveness, comprising:

[0007] Establish a nonlinear model of the ship's heading; the nonlinear model of the ship is shown in equation (1):

[0008]

[0009] A virtual controller is designed based on the ship's nonlinear heading model.

[0010] ,include:

[0011]

[0012]

[0013]

[0014] The intermediate control input is obtained by calculating the actuator gain adaptive compensation law and the radial basis function neural network weight update law. The event-triggered control input is then obtained from the intermediate control input according to the event triggering rule.

[0015] The event-triggered control inputs are automatically entered into the heading control system for ship heading maintenance control.

[0016] Further, the step of obtaining intermediate control input by calculating the actuator gain adaptive compensation law and the radial basis function neural network weight update law, and obtaining event-triggered control input based on the intermediate control input according to the event triggering rule, includes:

[0017]

[0018] This invention provides a ship heading control method that considers rudder performance. It designs a virtual controller using a ship's heading model, constructs event-triggered rules based on hybrid thresholds, and then designs a heading control law that considers rudder performance based on these rules. This achieves the following two beneficial technical effects:

[0019] (1) Construct an event triggering mechanism based on hybrid threshold in the heading control system. Compared with the static event triggering mechanism, the hybrid threshold adjustment mechanism can achieve adaptive adjustment of threshold parameters, which can further avoid the frequent transmission of control signals in the initial stage of the control system, thereby further reducing the execution frequency of the servo motor.

[0020] (2) Due to the introduction of the event triggering mechanism, the threshold parameter will be combined with the actuator function, which increases the nonlinear term of the heading hold control system. To address this limitation, an adaptive compensation law is constructed to weaken the nonlinear effect of the actuator gain function on the heading hold control system. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the implementation of the ship course-keeping control method considering steering gear performance provided by the present invention.

[0022] Figure 2 This is a logic diagram of the ship course-keeping control method that takes into account the performance of the steering gear in this invention.

[0023] Figure 3 This is a control output curve diagram in the embodiment;

[0024] Figure 4 This is a control input curve graph in the embodiment;

[0025] Figure 5 This is an event triggering control interval diagram in the embodiment;

[0026] Figure 6 This is a diagram of the neural network weight update parameters in the embodiment;

[0027] Figure 7 This is the actuator gain adaptive compensation law diagram in the embodiment. Detailed Implementation

[0028] To make the technical problems solved by this invention, the technical solutions adopted, and the technical effects achieved clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings, not all of them.

[0029] like Figure 1 , Figure 2 As shown, the ship heading control method considering steering gear effectiveness provided in this embodiment of the invention includes:

[0030] 101. Establish a nonlinear model of the ship's heading;

[0031] Specifically, the nonlinear model of the ship is shown in equation (1):

[0032]

[0033]

[0034] 103. Introduce an event triggering mechanism and construct event triggering rules based on hybrid thresholds to achieve adaptive adjustment of threshold parameters;

[0035] Specifically, continuous control commands will greatly increase the execution frequency of the servo system and overuse servo energy. Therefore, in order to achieve step control signals, thereby reducing the frequent operation of the servo system and reducing servo energy consumption, we introduce an event triggering mechanism and construct event triggering rules based on hybrid thresholds.

[0036] Based on the control input prior to the event trigger:

[0037]

[0038]

[0039] 105. Automatically input event-triggered control inputs into the heading control system for ship heading maintenance control.

[0040] Simulation experiment:

[0041] To verify the effectiveness of the proposed control algorithm, a heading mathematical model of an unmanned vessel (mass 23.8 kg, length 1.255 m, beam 0.29 m) was selected as the controlled object. The proposed control algorithm, along with existing technologies 1 and 2, were numerically simulated on a MATLAB platform. The continuous sampling time interval was 0.01 seconds. Existing technology 1 is a robust adaptive sliding mode control algorithm, characterized by its continuous-time control mechanism. Existing technology 2 is a ship event-triggered control algorithm, characterized by its static threshold parameter triggering. In this simulation experiment, the neural network weight update parameters are as follows: Figure 6 As shown, the actuator gain adaptive compensation law is as follows: Figure 7 As shown.

[0042] Simulation results are as follows Figures 3-5 As shown. From Figure 3 It can be observed that the control algorithm of this invention, prior art 1, and prior art 2 can all achieve the control objective. However, the accuracy of the algorithm of this invention is lower than that of prior art 1. Figure 4 As can be seen, the control commands of the control algorithm of this invention are in a step-like manner, which can reduce the transmission frequency from the controller to the actuator, thereby reducing the steering frequency of the actuator. Furthermore, from... Figure 5 As can be seen, the maximum trigger interval of the algorithm of this invention can reach 4.03 seconds, and the number of triggers in this invention is 155, while the number of triggers in prior art 2 is 350, and the number of triggers in prior art 1 is 10,000. To further describe the advantages of the algorithm of this invention, we constructed the following servo energy efficiency function:

[0043]

[0044]

[0045] According to the servo motor energy efficiency function, the energy efficiency of the algorithm of this invention is 64.5, the energy efficiency of prior art 2 is 28.6, and the energy efficiency of prior art 1 is 1.

[0046] This indicates that the algorithm of the present invention can greatly reduce the transmission frequency of control commands and reduce the energy consumption of servo operation.

[0047] 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 to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some or all of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ship course-keeping control method considering rudder performance, characterized in that, The method includes: Establish a nonlinear model of the ship's heading; the nonlinear model of the ship is shown in equation (1): ； In the formula, These represent the ship's forward speed, drift speed, and bow roll rate, respectively. This represents the uncertainty term in the forward model. Represents the actuator gain function; These represent the Coriolis centripetal coefficients in the forward and lateral directions, respectively. These represent the hydrodynamic damping coefficients in the lateral drift direction and the yaw direction, respectively. Indicates unmodeled dynamics; Indicates external disturbance. Indicates the coefficient of inertia; Representation function The derivative with respect to time, Indicates the ship's actual heading angle; Representing variables r The derivative with respect to time; parameters δr Indicates servo control input; A virtual controller is designed based on the ship's nonlinear heading model. ,include: Assume the ship's desired course is Furthermore, it is twice differentiable, and the heading error is defined. And by differentiating it, we get equation (3); ； In the formula, Indicates the ship's actual heading angle; Introducing an event-triggered mechanism and constructing event-triggered rules based on hybrid thresholds to achieve adaptive adjustment of threshold parameters includes: The event triggering rules based on hybrid thresholds include: Based on the control input prior to the event trigger: ； ； In the formula, For the model's uncertainties, It is used as a weighting coefficient to adjust the contribution of the "robust correction term" to the total control output; The intermediate control input is obtained by calculating the actuator gain adaptive compensation law and the radial basis function neural network weight update law. The event-triggered control input is then obtained from the intermediate control input according to the event triggering rule. The event-triggered control inputs are automatically entered into the heading control system for ship heading maintenance control.

2. The ship course-keeping control method considering steering gear effectiveness according to claim 1, characterized in that, The process of obtaining intermediate control input by calculating the actuator gain adaptive compensation law and the radial basis function neural network weight update law, and obtaining event-triggered control input based on the intermediate control input according to the event triggering rule, includes: 。

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