A method and system for dynamic positioning control of a diesel engine driven vessel

Abstract

The application relates to the technical field of ship power positioning, and particularly discloses a ship power positioning control method and system suitable for diesel engine driving, which comprises the following steps: S1: acquiring environment data, calculating total environment load force, determining upper limit of propeller thrust and corresponding upper limit of diesel engine rotating speed; S2: determining lower limit of theoretical rotating speed of the diesel engine according to the upper limit of the diesel engine rotating speed, combining with the lowest stable rotating speed of the diesel engine, calculating lower limit of the diesel engine rotating speed and corresponding lower limit of the propeller thrust; S3: acquiring original thrust demand of the propeller, determining final thrust of the propeller according to the original thrust demand of the propeller, the upper limit of the propeller thrust and the lower limit of the propeller thrust, and driving the propeller through the diesel engine according to the final thrust of the propeller, so as to realize ship positioning control. The application can fully exert the large-thrust advantage of the diesel engine, avoid the defect of slow rotating speed adjustment, and balance the thrust size demand and response speed without changing hardware.

Description

Technical Field

[0001] This invention relates to the field of ship dynamic positioning technology, and in particular to a dynamic positioning control method and system suitable for diesel engine driven ships. Background Technology

[0002] With the increasing demand for marine engineering operations, dynamic positioning (DP) systems have become core equipment for deep-sea platforms, engineering vessels, and other vessels. They use thrusters to adjust thrust in real time to counteract environmental disturbances such as wind, waves, and currents, thereby maintaining the vessel's position and course.

[0003] As the actuator of a dynamic positioning system, the response characteristics of the ship's propulsion unit directly determine the dynamic positioning control performance. Currently, the mainstream propulsion systems for ships include diesel engine drive and electric drive. While electric-driven propulsion offers a fast response, its maximum thrust is often limited, failing to meet the thrust requirements for positioning in harsh sea conditions. Diesel-driven propulsion, although capable of handling various sea conditions, typically suffers from large speed adjustment inertia (response time ranging from tens of seconds to minutes), making it difficult to meet the demands of dynamic positioning for rapid (second-level) speed response and precise thrust adjustment of the propulsion unit. Summary of the Invention

[0004] This invention aims to solve the problem of reduced performance in traditional dynamic positioning control caused by slow diesel engine speed regulation. To this end, this invention provides a dynamic positioning control method and system for diesel-powered ships, applicable to dynamic positioning control systems for diesel engine-driven propellers. It fully leverages the high thrust of diesel engines while avoiding the drawback of slow speed regulation, balancing thrust requirements and response speed without altering the hardware.

[0005] This invention provides a dynamic positioning control method for diesel engine-driven ships, the technical solution of which includes: S1: Acquire environmental data, calculate the total environmental load force, and determine the upper limit of the thruster thrust and its corresponding upper limit of the diesel engine speed based on the total environmental load force; S2: Determine the theoretical lower limit of the diesel engine speed based on the upper limit of the diesel engine speed, and calculate the lower limit of the diesel engine speed in combination with the lowest stable speed of the diesel engine; obtain the corresponding lower limit of the thrust of the propeller based on the lower limit of the diesel engine speed. S3: Obtain the initial thrust requirement of the propeller, determine the final thrust of the propeller based on the initial thrust requirement, the upper limit of the thruster and the lower limit of the thruster, and drive the propeller through the diesel engine according to the final thrust of the propeller to achieve ship positioning control; The process of determining the final thrust of the thruster includes: When the initial thrust requirement of the thruster is less than the lower limit of the thruster, multiple thrusters generate offset thrusts that cancel each other out. Based on the offset thrust of each thruster and the initial thrust requirement of the thruster, the final thrust of the thruster that is greater than or equal to the lower limit of the thruster is calculated.

[0006] Furthermore, when the original thrust requirement of the propeller is less than the lower limit of the propeller thrust, for the two propellers in the same group, they generate offset thrusts of the same magnitude but opposite directions; the resultant force of the two offset thrusts is zero, and has no effect on the overall ship force.

[0007] Furthermore, for the original thrust requirements of two thrusters in the same group, when the original thrust requirements of one or both thrusters are less than the lower limit of thruster thrust, the two thrusters in the same group will generate an offset thrust.

[0008] Furthermore, the process of determining the final thrust of the thruster also includes: When the initial thrust requirement of the thruster is less than or equal to the upper limit of the thruster's thrust and greater than or equal to the lower limit of the thruster's thrust, the initial thrust requirement of the thruster will be taken as the final thrust of the thruster. When the initial thrust requirement of the thruster exceeds the upper limit of the thruster, the upper limit of the thruster is taken as the final thrust of the thruster.

[0009] Furthermore, the lower limit of the theoretical speed of diesel engines The calculation formula is: in, This is the upper limit of diesel engine speed. This represents the maximum rate of change of diesel engine speed. The dynamic response time is determined by the performance of the diesel engine itself and the current sea state fluctuations.

[0010] Furthermore, dynamic response time The calculation formula is: in, This is the minimum stable speed of the diesel engine. This is the default requirement for the thrust response time of the dynamic positioning system. These are the adjustment parameters for the diesel engine speed regulation characteristics. These are adjustment parameters for sea state fluctuation characteristics. For the environmental demand force envelope diameter, This is a reference value for the environmental demand force envelope diameter corresponding to standard operating sea conditions.

[0011] Furthermore, the calculation process for the total environmental load includes: S1.1: Acquire environmental data and expand it to obtain an expanded range of environmental data; the environmental data includes wind speed, wind direction, current speed, current direction, wave height, and wave direction; S1.2: For the extended environmental data range, a cyclic traversal method is used for sampling to calculate multiple sets of wind loads, flow loads, and wave loads; S1.3: Perform traversal sampling of wind load, flow load and wave load respectively, and linearly superimpose the sampling results to obtain the total environmental load force.

[0012] Furthermore, the calculation process for the upper limit of the thruster and its corresponding upper limit of the diesel engine speed includes: The total environmental load force is used to distribute the thrust of the thrusters using the pseudo-inverse method to obtain the pre-distributed thrust value for each thruster, and then the upper limit of the thruster is calculated. The upper limit of diesel engine speed is obtained based on the upper limit of thrust and the thrust-speed characteristic curve of the thruster.

[0013] Furthermore, at preset intervals, steps S1 and S2 are repeated to update the upper limit of thruster thrust, the upper limit of diesel engine speed, the lower limit of diesel engine speed, and the lower limit of thruster thrust to adapt to changes in sea conditions.

[0014] This invention also provides a dynamic positioning control system for diesel-powered ships, the technical solution of which includes: The data acquisition and thrust limit calculation unit is used to acquire environmental data, calculate the total environmental load force, and determine the upper limit of the thruster and its corresponding upper limit of the diesel engine speed based on the total environmental load force. The thrust lower limit calculation unit is used to determine the theoretical lower limit of the diesel engine speed based on the upper limit of the diesel engine speed, and calculate the lower limit of the diesel engine speed in combination with the lowest stable speed of the diesel engine; and obtain the corresponding lower limit of the thrust of the propeller based on the lower limit of the diesel engine speed. The final thrust calculation unit is used to obtain the original thrust requirement of the thruster, determine the final thrust of the thruster based on the original thrust requirement, the upper limit of thruster and the lower limit of thruster, and drive the thruster through the diesel engine based on the final thrust of the thruster to achieve ship positioning control; The process of determining the final thrust of the thruster includes: When the initial thrust requirement of the thruster is less than the lower limit of the thruster, multiple thrusters generate offset thrusts that cancel each other out. Based on the offset thrust of each thruster and the initial thrust requirement of the thruster, the final thrust of the thruster that is greater than or equal to the lower limit of the thruster is calculated.

[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. This invention utilizes dynamic range control of propeller thrust and diesel engine speed for dynamic positioning control, effectively avoiding problems such as slow diesel engine speed adjustment, slow propeller thrust response, and deterioration of dynamic positioning control accuracy, while fully leveraging the high thrust advantage of the diesel engine. By dynamically setting the upper and lower limits of propeller thrust and utilizing the pre-allocation of the diesel engine speed range, a balance between high thrust and rapid response of the diesel-driven propeller is achieved in dynamic positioning.

[0016] 2. By limiting the thrust range of the propeller, the present invention enables the diesel engine to cover the entire required speed range adjustment (i.e., all thrust requirements) within the acceptable time range of dynamic positioning, which significantly improves the real-time response of dynamic positioning and thus enhances the system control accuracy.

[0017] 3. This invention calculates the dynamic thrust range by using environmental load extreme value calculation and margin expansion, and reserves a safety margin to ensure that sufficient thrust can still be provided under extreme sea conditions such as sudden winds and waves, and can meet the high thrust requirements of high-level sea state control.

[0018] 4. This invention proposes the concept of virtual idling speed, which determines the lower limit of the theoretical speed of the diesel engine based on its own performance and the current sea state fluctuations, thereby realizing the accurate calculation of the lower limit of the thrust of the propeller.

[0019] 5. This invention designs a bias force control strategy, which achieves intuitive control by using a bias thrust grouping and offsetting strategy to ensure the lower limit for small demands and the upper limit for large demands.

[0020] 6. The thrust range hard cutoff of this invention prevents diesel engine overspeed or propeller overload, reducing the risk of equipment failure; the bias force control strategy can also reduce the frequent turning of the propeller by changing the thrust magnitude, which is beneficial to the safety of underwater operations.

[0021] 7. This invention recalculates the thrust range every 30-60 minutes and automatically adapts to changes in wind, waves and currents (such as transitioning from calm sea conditions to rough sea conditions); at the same time, this strategy fully utilizes the high thrust characteristics of diesel engines, thereby improving the operational capability boundary in high sea states.

[0022] 8. The diesel engine and propulsion device of the present invention operate within a specific speed range, avoiding frequent and large-scale thrust and speed fluctuations, significantly reducing mechanical shock and wear, and helping to extend the service life of the diesel engine and propulsion device.

[0023] 9. Currently, most ships use a hybrid system of diesel engine-driven main propeller (tail rotor) and electric-driven auxiliary propeller (side thruster). This invention can achieve multi-power mode switching of ships without hardware modification, thus improving the ship's operational adaptability.

[0024] 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

[0025] 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.

[0026] Figure 1 This is a flowchart of the method provided by the present invention.

[0027] Figure 2 This is a schematic diagram of the bias force distribution provided by the present invention.

[0028] Figure 3 This is the fixed-point hovering trajectory diagram provided by the present invention.

[0029] Figure 4 This is the control time-history curve provided by the present invention.

[0030] Figure 5 This is a thruster response time-history curve provided by the present invention. Detailed Implementation

[0031] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but should not be used to limit the scope of this invention.

[0032] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0033] The following is combined Figures 1 to 5 The present invention will be further described in detail below, providing a method and system for dynamic positioning control of diesel-powered ships: In this embodiment, as Figure 1 As shown, a dynamic positioning control method for diesel-powered ships is provided, comprising the following steps: S1: Dynamic capability analysis and speed limit determination: Obtain environmental data, calculate the total environmental load force, and determine the upper limit of the thruster thrust and its corresponding upper limit of the diesel engine speed based on the total environmental load force.

[0034] This step combines measured data of wind, waves, and currents, and through environmental load calculations, environmental force superposition, total thrust calculations required for dynamic positioning, single-thrust distribution, and correlation with the upper limit of diesel engine speed, determines the upper limit of thrust for the thruster and the corresponding upper limit of diesel engine speed. Specifically, it includes the following steps: S1.1: Environmental Parameter Measurement and Margin Extension: Acquiring environmental data, primarily wind, wave, and current data, including wind speed. ,wind direction Flow rate Flow direction High waves and waves Typically, data is collected through shipboard sensors.

[0035] To ensure sufficient margin for dynamic positioning control, the environmental data is expanded, extending each data point from a single point value to a range. In this embodiment, expansion is performed at 20% and 20°, resulting in the following expanded environmental data range: wind speed range. Wind direction range Flow velocity range Flow range Wave height range Wave direction range .

[0036] S1.2: Environmental Load Traversal Calculation: For the extended environmental data range, a cyclic traversal method is used for sampling to calculate multiple sets of wind loads. Flow load and wave load ; in, The wind load force in the longitudinal direction of the ship on the water. The wind load force in the sway direction of a ship on the water. The wind load force in the bow direction of a surface vessel. The flow load force in the longitudinal direction of the ship on the water surface. The flow load force in the sway direction of a ship on the water surface. The current load force in the bow direction of a surface vessel. The wave load force in the longitudinal direction of a surface vessel. The wave load force in the sway direction of a ship on the water surface. This refers to the wave load force in the bow direction of a surface vessel.

[0037] Assuming: wind load is Interval at ,by Interval at By sampling through interval traversal, we can obtain... From the wind sampling data, 45 sets of wind load data can be calculated.

[0038] S1.3: Total Environmental Force Superposition: Wind load, flow load, and wave load are sampled sequentially, and the sampling results are linearly superimposed to obtain the total environmental load force. in, For total environmental load, The total environmental load force in the longitudinal direction of the vessel on the water. The total environmental load force in the sway direction of a surface vessel. The total environmental load force in the bow direction of the surface vessel.

[0039] If, in step S1.2, there are 45 sets of sampled data for wind load, flow load, and wave load, then in step S1.3, there are a total of Total environmental load of the group.

[0040] S1.4: Thruster Thrust Upper Limit Allocation: Based on the total environmental load force obtained in step S1.3, thrust is allocated to the thrusters using a pseudo-inverse method to obtain the pre-allocated thrust value for each thruster. , ,in, The thrust pre-allocation value for the first thruster. The thrust pre-allocation value for the second thruster. The pre-allocated thrust value for the nth thruster. Assign matrix to thrust The pseudo-inverse matrix, This represents the total number of thrusters. Then, the maximum value of the pre-allocated value for each thruster is taken to obtain the maximum thrust of each thruster. , , This is the upper limit of the thrust of the first thruster. This is the upper limit of the thrust of the second thruster. This represents the upper limit of the thrust of the nth thruster.

[0041] S1.5: Corresponding Diesel Engine Speed ​​Limit: For propellers driven by diesel engines, the corresponding diesel engine speed limit is obtained by looking up the table one by one based on the propeller thrust limit and the diesel engine's propeller thrust-speed characteristic curve. , ,in, This is the upper speed limit for the first diesel engine. This is the upper speed limit for the second diesel engine. Let m be the upper limit of the rotational speed of the m-th diesel engine. This refers to the number of diesel engines on board, typically. When multiple thrusters share a single diesel engine, the maximum speed limit is set to the larger value.

[0042] S2: Virtual Idle Speed ​​Setting and Propeller Thrust Lower Limit Calculation: Determine the theoretical lower limit of the diesel engine speed based on the upper limit of the diesel engine speed, and then calculate the lower limit of the diesel engine speed by combining it with the lowest stable speed of the diesel engine; obtain the corresponding lower limit of the propeller thrust based on the lower limit of the diesel engine speed.

[0043] This step, based on the rapid response requirements of dynamic positioning control and the diesel engine's response characteristics, determines the lower speed limit (virtual idle speed) by extending a preset time downwards from the upper limit of diesel engine speed. Then, it obtains the corresponding lower thrust limit of the propeller through mapping the thrust-speed characteristic curve. Specifically, it includes the following steps: S2.1: Calculation of the lower limit of the theoretical speed of a diesel engine: based on the maximum rate of change of diesel engine speed. Diesel engine speed limit and dynamic response time Calculate the lower limit of the theoretical speed of a diesel engine The calculation formula is: .

[0044] Dynamic response time The calculation formula is determined by the diesel engine's own performance and the current sea state fluctuations: in, This is the minimum stable speed of the diesel engine. This is the default requirement for the thrust response time of the dynamic positioning system. These are the adjustment parameters for the diesel engine speed regulation characteristics. These are adjustment parameters for sea state fluctuation characteristics. For the environmental demand force envelope diameter, This is a reference value for the environmental demand force envelope diameter corresponding to standard operating sea conditions.

[0045] It reflects the diesel engine's own speed regulation performance.

[0046] Typically, 10-20 seconds are taken; in this embodiment, It lasts for 15 seconds.

[0047] This reflects the severity of fluctuations in the current environmental load.

[0048] This characterizes the fluctuation of the current sea state environmental force demand. Based on the total environmental load force calculation results in S1.3, it is calculated according to the following formula: in, This represents the change in the total environmental load force along the longitudinal direction of the vessel on the water. This represents the change in the total environmental load force in the sway direction of a surface vessel. This represents the change in the total environmental load force in the bow direction of a surface vessel. To obtain the maximum value, To obtain the minimum value.

[0049] Provides a normalized benchmark.

[0050] , The typical range of values ​​is , The worse the current diesel engine's speed regulation performance and the more drastic the sea state changes, the more likely it is to cause problems. It will then increase adaptively.

[0051] S2.2: Lower speed limit correction: based on the theoretical lower speed limit of the diesel engine. and the minimum stable speed of diesel engines Calculate the feasible lower limit of diesel engine speed. , .

[0052] S2.3: Correlation of Lower Thruster Thrust Limit: Based on the lower limit of diesel engine speed and the thrust-speed characteristic curve of the diesel engine's thruster, the lower limit of thruster thrust corresponding to the lower limit of diesel engine speed is mapped to obtain the lower limit of diesel engine thrust. .

[0053] S3: Thrust Range Limitation: Obtain the original thrust requirement of the propeller, determine the final thrust of the propeller based on the original thrust requirement, the upper limit of the thruster and the lower limit of the thruster, and drive the propeller through the diesel engine according to the final thrust of the propeller to achieve ship positioning control.

[0054] The process for determining the final thrust of the thruster is as follows: When the initial thrust requirement of the thruster is less than the lower limit of the thruster, multiple thrusters generate offset thrusts that cancel each other out; based on the offset thrust of each thruster and the initial thrust requirement of the thruster, the final thrust of the thruster that is greater than or equal to the lower limit of the thruster is calculated. When the initial thrust requirement of the thruster is less than or equal to the upper limit of the thruster's thrust and greater than or equal to the lower limit of the thruster's thrust, the initial thrust requirement of the thruster will be taken as the final thrust of the thruster. When the initial thrust requirement of the thruster exceeds the upper limit of the thruster, the upper limit of the thruster is taken as the final thrust of the thruster.

[0055] In the real-time control of dynamic positioning, an offset force control strategy is adopted to ensure that the final thrust of the thruster is within the range specified in the thrust command. This range ensures that the diesel engine operates within a specific speed range. It balances thrust and speed.

[0056] S3.0: Calculation of the initial thrust requirement of the propeller: In the real-time control of dynamic positioning, the control module can adopt existing methods such as PID, optimal control, and model predictive control, such as the methods disclosed in Chinese invention patents with application publication numbers CN116627043A or CN115826606A, to calculate the 3D control resultant force of the entire ship based on the current environmental load, position, and heading control deviation; the thrust distribution module can adopt existing methods such as sequential quadratic programming and particle swarm optimization, such as the method disclosed in Chinese invention patent application publication number CN108845576A, to optimally distribute the 3D control resultant force to all actuators to obtain the initial thrust requirement of the propeller. , , For the initial thrust requirement of the first thruster, For the original thrust requirements of the second thruster, This represents the initial thrust requirement for the nth thruster.

[0057] S3.1: Based on the original thrust requirement of the thruster, the upper limit of thruster thrust, and the lower limit of thruster thrust, determine the relationship between the original thrust requirement of the thruster and the upper and lower limits of thruster thrust, and determine the final thrust of the thruster based on this relationship.

[0058] S3.11: When the original thrust requirement of the thruster is less than the lower limit of the thruster, an offset force control strategy is adopted to make multiple thrusters generate offset thrusts that cancel each other out. Based on the offset thrust of each thruster and the original thrust requirement of the thruster, the final thrust of the thruster is calculated. The final thrust of the thruster must meet the requirement of being greater than or equal to the lower limit of the thruster.

[0059] In ships, diesel-powered propellers are typically used in groups. For two propellers in the same group, they generate paired, identical, but opposite bias thrusts. Since the resultant force of the two bias thrusts is zero, it has no effect on the overall force of the ship.

[0060] like Figure 2 As shown, the stern of the ship is equipped with thrusters #2 and #3, which are grouped laterally. Figure 2 Image (a) shows the initial thrust requirement of thruster #2. and the original thrust requirements of thruster #3 .when , If any one of the values ​​is less than the lower limit of the thruster, or if both values ​​are simultaneously less than the lower limit of the thruster, the offset thrust is calculated according to the following formula: Figure 2 (b)

[0061] in, For the original thrust requirement of the i-th thruster, for The longitudinal component of force, for The lateral component of force, Let the working deflection angle of the i-th thruster be , This is the lower limit of the thrust of the i-th thruster. The lateral component of the thrust after adding offset thrust to the i-th thruster, Let be the bias thrust of the i-th thruster.

[0062] For the original thrust requirements of two thrusters in the same group, when the original thrust requirements of one or both thrusters are less than the lower limit of thrust, the two thrusters in the same group will generate an offset thrust.

[0063] like If the thrust is less than the lower limit of the thruster, it needs to be decomposed into... longitudinal component and lateral component of force Then according to and the lower limit of the third thruster Calculate the lateral component of the third thruster after adding offset thrust. and the bias thrust of the third thruster At this point, the final thrust of the third thruster... equal .

[0064] Because of the No. 3 thruster Thruster #2 needs to generate power for offsetting. of , For the bias thrust of the second thruster, and They are equal in size but opposite in direction. Then, Combination longitudinal component and lateral component of force Calculate the final thrust of the second thruster. .

[0065] If the initial thrust requirements of both thrusters are less than the lower limit of thruster thrust, then the corresponding offset thrust needs to be calculated separately, the larger value is selected, and then the final thrust of the two thrusters is calculated separately.

[0066] Two thrusters grouped laterally produce offset thrust that cancels each other out. Similarly, two thrusters grouped longitudinally produce offset thrust that cancels each other out.

[0067] In this case, the working angle corresponding to the final thrust of the thruster is different from the original working angle (which corresponds to the original thrust requirement of the thruster).

[0068] By traversing and calculating all thrusters, the goal is to ensure that all thrusters satisfy the following conditions. Minimum thrust limit. For the final thrust of the i-th thruster, This represents the lower limit of the thrust of the i-th thruster.

[0069] In diesel engine-driven applications, the difference between the upper and lower limits of the thruster is significant. Applying a bias force control strategy, this difference is almost negligible. Greater than In the event of... Greater than In such cases, refer to S3.13 for details. Truncate it to... . This represents the upper limit of the thrust of the i-th thruster.

[0070] S3.12: When the initial thrust requirement of the thruster is less than or equal to the upper limit of the thruster's thrust and greater than or equal to the lower limit of the thruster's thrust, the initial thrust requirement of the thruster shall be taken as the final thrust of the thruster. That is, when At that time, keep .

[0071] S3.13: Thrust Over-Limit Cutoff: When the initial thrust requirement of the thruster exceeds the upper limit of the thruster, the upper limit of the thruster is used as the final thrust of the thruster. That is, in the real-time control of dynamic positioning, when... At that time, it was truncated to .

[0072] S3.2: Based on the final thrust of the propeller, the propeller is driven by a diesel engine to achieve ship positioning control.

[0073] S4: Dynamic Update: Every preset period, steps S1 and S2 are repeated to update the upper limit of thruster thrust, the upper limit of diesel engine speed, the lower limit of diesel engine speed, and the lower limit of thruster thrust. This adjusts the dynamic range of thruster thrust and diesel engine speed to adapt to changes in sea state. Preferably, the preset period is 30-60 minutes. That is, the upper limit of thruster thrust, the upper limit of diesel engine speed, the lower limit of diesel engine speed, and the lower limit of thruster thrust are updated once every preset period. Within each preset period, step S3 is executed in real time to obtain the original thrust requirement of the thruster and calculate the thrust required at sea state. The final thrust of the propellers within the zone is used for ship positioning control.

[0074] In this embodiment, as Figure 2 As shown, a typical dynamically positioned vessel is selected: the bow is equipped with one ducted thruster (1#), which is directly driven by an electric motor to improve the bow control capability of the vessel; the stern is equipped with two azimuth thrusters (2# and 3#), which are driven by two diesel engines and can achieve 360° power output.

[0075] In the simulation test, the parameters are set as follows: 1) Wind speed 8m / s, wave height 2m, current speed 3 knots, wind, wave and current directions are all 90°; 2) Bow thrusters, bidirectional thrust, with a thrust of ±10kN; 3) Axle-mounted azimuth thruster, 360° power output, rated thrust of 100kN.

[0076] Based on calculations in steps S1-S2, under the current sea conditions, considering factors such as thrust magnitude and response speed, the single-propeller thrust range of the stern azimuth thruster is limited to a dynamic range of [25kN, 50kN].

[0077] The principle of limiting the offset force of the stern azimuth thruster is as follows: when the original thrust requirement is less than 25kN, by adding an additional mutually canceling lateral offset force to the two thrusters, the actual thrust of the thrusters is kept within the dynamic range of [25kN, 50kN].

[0078] Under the target sea state, a fixed-point hovering test was conducted based on the target position and heading set by the user. The simulation time was 600 seconds, and the hovering trajectory was as follows: Figure 3 As shown, the control time-history curve is as follows: Figure 4 As shown, the thruster response time-history curve is as follows: Figure 5 As shown.

[0079] Depend on Figure 5It is evident that the thrust of the two azimuth thrusters is consistently limited to the range of [25kN, 50kN], balancing thrust magnitude and rapid response. Figure 3 , Figure 4 As can be seen, the positioning control effect is excellent. During the 600-second hovering control period, the position error is no greater than 0.3665m and the heading error is no greater than 0.7005°.

[0080] This embodiment also provides a dynamic positioning control system for diesel-powered ships, the technical solution of which is as follows: including: The data acquisition and thrust limit calculation unit is used to acquire environmental data, calculate the total environmental load force, and determine the upper limit of the thruster and its corresponding upper limit of the diesel engine speed based on the total environmental load force. The thrust lower limit calculation unit is used to determine the theoretical lower limit of the diesel engine speed based on the upper limit of the diesel engine speed, and calculate the lower limit of the diesel engine speed in combination with the lowest stable speed of the diesel engine; and obtain the corresponding lower limit of the thrust of the propeller based on the lower limit of the diesel engine speed. The final thrust calculation unit is used to obtain the original thrust requirement of the thruster, determine the final thrust of the thruster based on the original thrust requirement, the upper limit of thruster and the lower limit of thruster, and drive the thruster through the diesel engine based on the final thrust of the thruster to achieve ship positioning control; The process of determining the final thrust of the thruster includes: When the initial thrust requirement of the thruster is less than the lower limit of the thruster, multiple thrusters generate offset thrusts that cancel each other out; based on the offset thrust of each thruster and the initial thrust requirement of the thruster, the final thrust of the thruster that is greater than or equal to the lower limit of the thruster is calculated. When the initial thrust requirement of the thruster is less than or equal to the upper limit of the thruster and greater than or equal to the lower limit of the thruster, the initial thrust requirement of the thruster shall be taken as the final thrust of the thruster. When the initial thrust requirement of the thruster exceeds the upper limit of the thruster, the upper limit of the thruster is taken as the final thrust of the thruster.

[0081] 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 dynamic positioning control method for diesel-powered ships, characterized in that, include: S1: Acquire environmental data, calculate the total environmental load force, and determine the upper limit of the thruster thrust and its corresponding upper limit of the diesel engine speed based on the total environmental load force; S2: Determine the theoretical lower limit of the diesel engine speed based on the upper limit of the diesel engine speed, and calculate the lower limit of the diesel engine speed in combination with the lowest stable speed of the diesel engine; obtain the corresponding lower limit of the thrust of the propeller based on the lower limit of the diesel engine speed. Theoretical lower limit of diesel engine speed The calculation formula is: in, This is the upper limit of diesel engine speed. This represents the maximum rate of change of diesel engine speed. The dynamic response time is determined by the diesel engine's own performance and the current sea state fluctuations. Dynamic response time The calculation formula is: in, This is the minimum stable speed of the diesel engine. This is the default requirement for the thrust response time of the dynamic positioning system. These are the adjustment parameters for the diesel engine speed regulation characteristics. These are adjustment parameters for sea state fluctuation characteristics. For the environmental demand force envelope diameter, This is a reference value for the environmental demand force envelope diameter corresponding to standard operating sea states; S3: Obtain the initial thrust requirement of the propeller, determine the final thrust of the propeller based on the initial thrust requirement, the upper limit of the thruster and the lower limit of the thruster, and drive the propeller through the diesel engine according to the final thrust of the propeller to achieve ship positioning control; The process of determining the final thrust of the thruster includes: When the initial thrust requirement of the thruster is less than the lower limit of the thruster, multiple thrusters generate offset thrusts that cancel each other out. Based on the offset thrust of each thruster and the initial thrust requirement of the thruster, the final thrust of the thruster that is greater than or equal to the lower limit of the thruster is calculated.

2. The dynamic positioning control method for diesel-powered ships as described in claim 1, characterized in that, When the original thrust requirement of the propeller is less than the lower limit of the propeller thrust, for the two propellers in the same group, they generate offset thrust of the same magnitude but opposite direction; the resultant force of the two offset thrusts is zero and has no effect on the overall force of the ship.

3. The dynamic positioning control method for diesel-powered ships as described in claim 2, characterized in that, For the original thrust requirements of two thrusters in the same group, when the original thrust requirements of one or both thrusters are less than the lower limit of thrust, the two thrusters in the same group will generate an offset thrust.

4. A dynamic positioning control method for diesel-powered ships as described in any one of claims 1-3, characterized in that, The process of determining the final thrust of the thruster also includes: When the initial thrust requirement of the thruster is less than or equal to the upper limit of the thruster's thrust and greater than or equal to the lower limit of the thruster's thrust, the initial thrust requirement of the thruster will be taken as the final thrust of the thruster. When the initial thrust requirement of the thruster exceeds the upper limit of the thruster, the upper limit of the thruster is taken as the final thrust of the thruster.

5. The dynamic positioning control method for diesel-powered ships as described in claim 1, characterized in that, The calculation process for total environmental load includes: S1.1: Acquire environmental data and expand it to obtain an expanded range of environmental data; the environmental data includes wind speed, wind direction, current speed, current direction, wave height, and wave direction; S1.2: For the extended environmental data range, a cyclic traversal method is used for sampling to calculate multiple sets of wind loads, flow loads, and wave loads; S1.3: Perform traversal sampling of wind load, flow load and wave load respectively, and linearly superimpose the sampling results to obtain the total environmental load force.

6. A dynamic positioning control method for diesel-powered ships as described in claim 1 or 5, characterized in that, The calculation process for the upper limit of the thruster and the corresponding upper limit of the diesel engine speed includes: The total environmental load force is used to distribute the thrust of the thrusters using the pseudo-inverse method to obtain the pre-distributed thrust value for each thruster, and then the upper limit of the thruster is calculated. The upper limit of diesel engine speed is obtained based on the upper limit of thrust and the thrust-speed characteristic curve of the thruster.

7. The dynamic positioning control method for diesel-powered ships as described in claim 1, characterized in that, Every preset period, steps S1 and S2 are repeated to update the upper limit of thruster thrust, the upper limit of diesel engine speed, the lower limit of diesel engine speed, and the lower limit of thruster thrust to adapt to changes in sea state.

8. A dynamic positioning control system for diesel-powered ships, characterized in that, A method for performing dynamic positioning control of a diesel-powered ship as described in any one of claims 1 to 7, comprising: The data acquisition and thrust limit calculation unit is used to acquire environmental data, calculate the total environmental load force, and determine the upper limit of the thruster and its corresponding upper limit of the diesel engine speed based on the total environmental load force. The thrust lower limit calculation unit is used to determine the theoretical lower limit of the diesel engine speed based on the upper limit of the diesel engine speed, and calculate the lower limit of the diesel engine speed in combination with the lowest stable speed of the diesel engine; and obtain the corresponding lower limit of the thrust of the propeller based on the lower limit of the diesel engine speed. The final thrust calculation unit is used to obtain the original thrust requirement of the thruster, determine the final thrust of the thruster based on the original thrust requirement, the upper limit of thruster and the lower limit of thruster, and drive the thruster through the diesel engine based on the final thrust of the thruster to achieve ship positioning control; The process of determining the final thrust of the thruster includes: When the initial thrust requirement of the thruster is less than the lower limit of the thruster, multiple thrusters generate offset thrusts that cancel each other out. Based on the offset thrust of each thruster and the initial thrust requirement of the thruster, the final thrust of the thruster that is greater than or equal to the lower limit of the thruster is calculated.

Images