Method, system and medium for heading motion control of catamaran under single propeller intact

Abstract

The application discloses a kind of for single propeller intact under catamaran heading movement control method, system and medium, belong to ship movement control field.It includes: S1, the line of the position of catamaran in failure and the designated target point is selected as the to-be-tracked straight line, obtain the direction angle θ of catamaran expected spiral advance;S2, control the remaining propeller of catamaran to first speed and second speed alternate switching, calculate the correction term of current switching time, including: obtaining the position of catamaran at adjacent switching time, with the distance of the midpoint of two positions from the to-be-tracked straight line approaching to 0 as control target, by PI control, output correction term;S3, with the correction term corrects the switching angle of the time of current switching, so that the running track of catamaran and the to-be-tracked straight line are perpendicular when switching speed;S4, whether catamaran reaches designated target point, if not, repeat S2 and S3, if yes, end control.The application can make the reliability of catamaran control under failure condition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ship motion control, and more particularly relates to a method and system for controlling the heading motion of a catamaran with one intact propeller, and a medium. BACKGROUND

[0002] In recent years, unmanned vehicles have received more and more attention, and the growing emphasis on the ocean economy has made waterborne unmanned vehicles and their research a hot topic. A catamaran refers to a "ship" connected by a reinforcing frame on the upper part of two separate underwater hulls, with two rudders and two propellers, and is widely used in the field of ship research. The underwater environment is complex and changeable, full of time-varying wind, waves, and currents, which brings potential faults to the actuators of the catamaran. When the actuators fail, how to quickly recover the failed ship for maintenance has important scientific and economic significance.

[0003] When only one propeller is available in the entire power system of the catamaran, i.e., both the rudders and one of the propellers of the ship have been damaged, the power system of the ship cannot normally control the heading and speed of the ship, and the ship has lost its normal navigation capability. Due to the asymmetric distribution of the propellers of the catamaran, the ship will perform circular motion in one direction. In the prior art, the method for controlling the catamaran with only one propeller to navigate to a specified target point is an open-loop control method. This method does not consider the influence of the large inertia of the ship itself, and there will be a large deviation in controlling the navigation trajectory, so that the failed ship cannot reach the specified target point, and the control method has low reliability. SUMMARY

[0004] In view of the defects and improvement needs of the prior art, the present application provides a method and system for controlling the heading motion of a catamaran with one intact propeller, and a medium, which aims to enable the catamaran to stably and safely run to a specified target point when only one propeller is available in the power system of the catamaran, thereby improving the reliability of the control.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, a method for controlling the heading motion of a catamaran with one intact propeller is provided, comprising:

[0006] S1, selecting a line connecting the position of the catamaran at the time of failure and the specified target point as a to-be-tracked straight line, to obtain a desired direction angle θ of the catamaran propelling forward;

[0007] S2, controlling the remaining propeller of the catamaran to alternately switch between a first rotation speed n rb and a second rotation speed n rs , and calculating a correction term at the current switching time , comprising: obtaining the positions c i-1 and ci , the midpoint of c i-1 and c i is away from the straight line to be tracked L i tends to 0 as the control target, and the output of the correction term is controlled by PI control

[0008] S3, the switching angle at the current switching time is corrected by the correction term to switch the speed when the running track of the catamaran is perpendicular to the straight line to be tracked;

[0009] S4, it is judged whether the catamaran reaches the specified target point, if not, the S2 and the S3 are repeated, and if yes, the control is ended.

[0010] Further, in the S2, the correction term at the current switching time is :

[0011]

[0012] wherein K P and K I are the proportional and integral coefficients respectively, L i is the distance of the midpoint of c i-1 and c i away from the straight line to be tracked, is the integral term at the current switching time.

[0013] Further, the integral term at the current switching time is :

[0014]

[0015] wherein, are the upper and lower limit values of the integral term at the previous switching time respectively.

[0016] Further, the running track of the catamaran is perpendicular to the straight line to be tracked when

[0017]

[0018] wherein ψ i is the catamaran heading angle at the current switching time, and θ is the direction angle of the catamaran expected to spiral forward.

[0019] Further, the distance L i-1 of the midpoint of c i away from the straight line to be tracked is i :

[0020]

[0021] wherein c i-1 = [x i-1 , y i-1 ], c i = [x i , y i ], and the equation of the straight line to be tracked is denoted as Ax+By+C=0.

[0022] According to a second aspect of the present application, a heading motion control system for a catamaran with a single propeller under failure is provided, comprising: a desired heading calculation module, a rotating speed switching module, a correction term design module, and a judgment module.

[0023] The desired heading calculation module is configured to select a line connecting a position of the catamaran under failure and a specified target point as a straight line to be tracked, and obtain a direction angle θ of a desired helical advance of the catamaran.

[0024] The rotating speed switching module is configured to control the only remaining propeller of the catamaran to switch between a first rotating speed n rb and a second rotating speed n rs alternately, and correct a switching angle at a current switching time by a correction term output by the correction term design module, so that the catamaran switches the rotating speed when a running track of the catamaran is perpendicular to the straight line to be tracked.

[0025] The correction term design module is configured to calculate the correction term at the current switching time, comprising: obtaining positions c i-1 and c i of the catamaran at a previous switching time and the current switching time, and taking a distance L i-1 between a midpoint of c i and c i and the straight line to be tracked as a control target, and outputting the correction term

[0026] The judgment module is configured to judge whether the catamaran reaches the specified target point, and if not, repeat the rotating speed switching module and the correction term design module, and if yes, end the control.

[0027] Further, in the correction term design module, the correction term at the current switching time is:

[0028]

[0029] wherein K P and K I are coefficients of proportion and integration respectively, and L i is the distance between the midpoint of c i-1 and c i and the straight line to be tracked. is an integral term of the previous switching time.

[0030] Further, the integral term of the current switching time is

[0031]

[0032] wherein, ψ are respectively upper and lower limit values of the integral term of the previous switching time.

[0033] Further, in the rotating speed switching module, the running track of the catamaran is perpendicular to the straight line to be tracked, and the following is satisfied:

[0034]

[0035] wherein, ψ i is a catamaran heading angle at a current switching time, and θ is a direction angle of the catamaran expected to spiral forward.

[0036] According to a third aspect of the present application, a computer readable storage medium is provided, and a computer program is stored on the computer readable storage medium, and the program is executed by a processor to implement the control method according to any one of the first aspect.

[0037] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0038] (1) The control method designed in the present application is for the control of the catamaran to follow the track under the condition that only a single propeller is intact. Different speeds are used on both sides of the track to be followed by the catamaran, so that the ship can spiral forward. The correction term is added to the speed switching condition, and based on PI control, the distance L i between the midpoint of the line connecting the positions of the catamaran at two adjacent switching times and the straight line to be tracked is taken as an error term. The switching angle at the current switching time is corrected by the designed correction term to make the error converge, so that the running track of the catamaran follows the direction of the expected spiral forward, and the catamaran can also run safely to the specified target point under the failure condition, thereby improving the reliability of the control of the catamaran under the damage of the power system.

[0039] (2) Since the angle at the speed switching time is adjusted by the correction term, a certain margin is left between the ideal switching point and the actual switching point, which maximally reduces the influence of the large inertia of the catamaran itself on the heading, and since the actual control time of the ship is discrete, the problem that the actual switching point does not intersect with the straight line to be tracked is avoided, and the stability and reliability of the heading control are further improved.

[0040] ​(3) Further, the integral term is limited by an amplitude, which can avoid integral saturation.

[0041] In summary, the application is suitable for fault-tolerant motion control of a catamaran under the condition that only a single propeller is intact, and can enable the catamaran to stably and safely sail to a specified target point under a fault condition, thereby improving the reliability of control. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a flow chart of catamaran heading control provided by the application under the condition that only a single propeller is intact.

[0043] Figure 2 is a trajectory simulation experiment curve diagram of single propeller screw propulsion control of a catamaran by an Otter ship according to Embodiment 1 of the application.

[0044] Figure 3 is an error curve diagram of single propeller screw propulsion of Embodiment 1 of the application.

[0045] Figure 4 is a curve diagram of actual physical experiment of a catamaran unmanned ship HUSTER-30 according to Embodiment 2 of the application. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the application clearer, the application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as they do not conflict with each other.

[0047] In the application, the terms "first", "second", etc. in the application and the drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0048] As shown in Figure 1 , the application provides a catamaran heading motion control method under the condition that only a single propeller is intact, which comprises the following steps:

[0049] S1, selecting a line connecting a position of the catamaran under a fault condition and a specified target point as a to-be-tracked straight line, to obtain a direction angle θ of screw propulsion of the expected ship; wherein, the equation of the to-be-tracked straight line is Ax+By+C=0;

[0050] S2, controlling the rotation speed of the remaining propeller of the catamaran to alternately switch between a first rotation speed n rb and a second rotation speed n rs ; and calculating a correction term at the current switching time, which comprises: obtaining the position c of the catamaran at the previous switching time and the current switching timei-1 and c i , with c i-1 and c i The distance L from the midpoint of the line to be tracked i The control objective is to approach 0; this is achieved through PI control, which outputs a correction term.

[0051] S3, with corrections Correct the switching angle at the current switching moment so that the catamaran's running trajectory is perpendicular to the straight line to be tracked before switching the rotation speed;

[0052] S4. Determine if the catamaran has reached the designated target point. If not, repeat S2 and S3. If yes, end control.

[0053] Specifically, in S2, the correction term at the current switching moment. for:

[0054]

[0055] Among them, K P With K I The coefficients for proportionality and integral are respectively, L i For c i-1 and c i The distance from the midpoint of the line to be tracked. The integral term at the current switching moment is equal to the integral term at the previous switching moment and L. i sum.

[0056] c i-1 and c i The distance L from the midpoint of the line to be tracked i for:

[0057]

[0058] Among them, c i-1 =[x i-1 ,y i-1 ]、c i =[x i ,y i The distance can be positive or negative. If the position coordinate of the ship on one side of the line to be tracked is positive, then the position coordinate on the other side of the line to be tracked is negative.

[0059] Furthermore, the integral of the current switching moment designed in this invention is:

[0060]

[0061] The integral term designed in this invention has a limit. To avoid integral saturation, respectively are upper and lower limit values of the integral term at the current switching time.

[0062] Specifically, in S3, the running track of the catamaran is perpendicular to the straight line to be tracked, and the following is satisfied:

[0063]

[0064] In the formula, ψ i is the heading angle of the catamaran at the current switching time, and θ is the direction angle of the desired helical advance of the catamaran, is the correction term at the current switching time, which is used to correct the switching angle at the current switching time.

[0065] The initial value of the correction term is 0, and at each time of controlling the switching of the propeller speed, the correction term at the current switching time is changed to adjust the overall heading ψ i of the ship helically advancing so that the ship advances along the direction angle θ of the desired helical advance.

[0066] Specifically, in S2, the first turning radius of the catamaran helically advancing corresponds to the first speed n rb of the propeller, and the second turning radius corresponds to the second speed n rs of the propeller, wherein the first turning radius is greater than the second turning radius, and different speeds of the propeller correspond to different turning radii so that the ship can advance in a helical manner.

[0067] Specifically, in the embodiment of the application, the propeller speed, the position and the heading of the catamaran at the current switching time are measured by a sensor.

[0068] The control method designed in the application is for the control of the catamaran to follow the track under the condition that only the single propeller is intact. Based on the relationship between the track radius and the speed, different speeds are used on both sides of the track to be followed by the catamaran, and under different speeds of the propeller, the turning radius of the ship is different, so that the ship advances in a helical manner. Based on PI control, the correction term at the current switching time is added to the speed switching condition, so that the distance L i between the midpoint of the line connecting the positions of the catamaran at two adjacent switching times and the straight line to be tracked is taken as an error term, and the correction term is designed to correct the switching angle at the current switching time so as to make the error converge, and thus the running track of the catamaran follows the direction of the desired helical advance, so that the catamaran can also operate safely to the specified target point under the fault condition, and the reliability of the control of the catamaran under the damage of the power system is improved.

[0069] Meanwhile, by adjusting the angle of the speed switching time with the correction term, a certain margin is left between the ideal switching point and the actual switching point, which minimizes the impact of the ship's large inertia on the course and ensures that the actual control time of the ship is discrete, thus avoiding the problem that the actual switching point does not intersect with the line to be tracked, and further improving the stability and reliability of the course control.

[0070] According to another aspect of the present invention, the present invention also provides a catamaran heading motion control system with a single propeller intact, which mainly includes: a desired forward direction calculation module, a speed switching module, a correction term design module and a judgment module;

[0071] The desired forward direction calculation module is used to select the line connecting the position of the catamaran during the malfunction and the specified target point as the straight line to be tracked, and obtain the desired spiral forward direction angle θ of the ship; where the equation of the straight line to be tracked is denoted as Ax+By+C=0.

[0072] The speed switching module is used to control the remaining propeller of the catamaran to operate at a first speed n. rb Second speed n rs Alternate switching between correction items output by the correction item design module. Correct the switching angle at the current switching moment so that the catamaran's running trajectory is perpendicular to the straight line to be tracked before switching the rotation speed;

[0073] The correction term design module is used to calculate the correction term at the current handover moment. Includes: obtaining the positions of the catamaran at the previous and current switching times. i-1 and c i , with c i-1 and c i The distance L from the midpoint of the line to be tracked i The control objective is to approach 0; this is achieved through PI control, which outputs a correction term.

[0074] The judgment module is used to determine whether the catamaran has reached the designated target point. If not, the speed switching module and correction item design module are executed repeatedly. If yes, the control ends.

[0075] In the correction item design module, the correction item at the current switching moment. for:

[0076]

[0077] Among them, K P With K I The coefficients for proportionality and integral are respectively, L i For c i-1 and c ithe midpoint of the two straight lines is away from the straight line to be tracked, is the integral term at the current switching time.

[0078] Specifically, the integral term at the current switching time is

[0079]

[0080] wherein, are the upper and lower limit values of the integral term at the previous switching time.

[0081] Specifically, in the rotating speed switching module, the running track of the catamaran is perpendicular to the straight line to be tracked, and the following condition is met

[0082] wherein, ψ i is the heading angle of the catamaran at the current switching time, and θ is the direction angle of the catamaran in the desired spiral advancing.

[0083] The catamaran heading motion controller for single propeller intactness designed in the application is used to execute the catamaran heading motion control method for single propeller intactness shown above.

[0084] The application further provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the catamaran heading motion control method for single propeller intactness shown above.

[0085] The method of the application is further described below by taking two specific embodiments.

[0086] Embodiment 1

[0087] As shown in Figs. Figure 2 and Figure 3 In the embodiment, the Otter ship is used to simulate the catamaran single propeller spiral advancing controller. Since the Otter ship has no rudder, only one side propeller is stopped to simulate the fault of single propeller intactness. The straight line equation is set as x+y=0. The closed loop controller designed by the method and the open loop controller under ideal conditions are simulated. The ideal controller does not use the correction term, and the rotating speed of the propeller is switched when ψ i -θ=±90°. For the closed loop controller, in the embodiment, K P =0.2, K I =0.12, the integral limit is ±20, and the correction limit is ±30. Figure 2 The ship navigation track of single propeller spiral advancing is given. It can be seen that the closed loop path curve is corrected by the correction term according to the error, the closed loop path curve in the figure passes through the straight line to be tracked, and spirally advances along the given path straight line, while the open loop path curve deviates from the given straight line.​

[0088] Figure 3 The error curve of single propeller helical forward is given by Figure 3 It can be seen that the error is measured by the distance between the midpoint of ci and ci-1 and the tracking straight line. The error of the closed-loop controller is basically within 0.5m, while the error of the open-loop controller gradually increases with time. In fact, the open-loop controller helically forward along the straight line x+3y=0, and the angle deviation from the set tracking straight line is about 26°. Due to the angle deviation, the open-loop controller is farther and farther away from the set straight line. While the closed-loop controller helically forward along the given straight line x+y=0. This result proves the effectiveness of the controller designed by the method.

[0089] Embodiment 2

[0090] As shown in Figure 4 , in this embodiment, the double-hull unmanned surface vehicle HUSTER-30 independently developed by the unmanned surface vehicle team of Huazhong University of Science and Technology is used. All the rudders of HUSTER-30 are fixed, and one side propeller is stopped, and only one side propeller is kept working. The proportional coefficient K P =24, the integral coefficient K I =3, and the single propeller speed of 2000rpm corresponds to a larger turning radius (i.e. the first turning radius), and the speed of 4000rpm corresponds to a smaller turning radius (i.e. the second turning radius). In addition to the closed-loop controller, the control effect of the open-loop controller is also given as a comparison. Due to the limitation of the experimental site, the line connecting the fixed point at the center of the lake and the initial position of the double-hull vehicle is the tracking straight line, which is different from the tracking straight line in embodiment 1. Such setting also conforms to the actual application, that is, the ship needs to return to a fixed port after a random point failure, at this time, the sailing direction of the ship is the line connecting the current position and the port. It can be seen from Figure 4 that the open-loop control strategy cannot achieve the goal of normally controlling the helical forward of the ship, while the closed-loop controller designed by the method basically helically forward along the given straight line, and achieves good control effect.

[0091] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for controlling the course motion of a catamaran under single propeller intactness, characterized by, The control method comprises the following steps: S1, a line connecting a position of the selected catamaran at the time of failure and a designated target point is a to-be-tracked straight line, and a direction angle θ of expected spiral advancement of the catamaran is obtained; S2, controlling the remaining propeller of the catamaran to a first rotation speed n rb and a second rotation speed n rs alternately switching, calculating a correction term at the current switching time comprising: obtaining the position c i-1 and c i of the catamaran at the previous switching time and the current switching time i-1 and c i of the midpoint of c i-1 and c i from the distance L i tending to 0 as a control target, outputting the correction term through PI control S3、with the correction item The switching angle of the current switching time is corrected, and the switching of the speed is performed when the running track of the catamaran is perpendicular to the straight line to be tracked. S4, whether the catamaran reaches the designated target point is judged, if not, the S2 and the S3 are repeated, and if yes, the control is ended.

2. The control method according to claim 1, characterized by, In the S2, the correction term of the current switching time is is: where K P and K I are the proportional and integral coefficients, respectively, L i is the distance between the midpoint of c i-1 and c i and the straight line to be tracked, is the integral term at the current switching instant.

3. The control method according to claim 2, characterized by, the integral term of the current switching instant is: wherein are the upper and lower limit values of the integral term of the pre-switching instant, respectively.

4. The control method according to claim 1, characterized by, When a running track of the catamaran is perpendicular to the to-be-tracked straight line, the following condition is met: where ψ i is the current switching time of the catamaran heading angle, θ is the catamaran desired direction of the screw forward angle.

5. The control method according to any one of claims 1 to 4, characterized by, The c i-1 and c i midpoint of the distance L i from the straight line to be tracked is: where c i-1 = [x i-1 ,y i-1 ], c i = [x i ,y i ], and the equation of the straight line to be tracked is denoted as Ax + By + C = 0.

6. A system for controlling the course motion of a catamaran under single propeller intactness, characterized by, The control method comprises the following steps: An expected advancement direction calculation module, a rotating speed switching module, a correction term design module and a judging module are comprised; The expected advancement direction calculation module is used for obtaining a direction angle θ of expected spiral advancement of the catamaran by taking a line connecting a position of the selected catamaran at the time of failure and a designated target point as a to-be-tracked straight line; The rotation speed switching module is used for controlling the remaining propeller of the catamaran to switch between the first rotation speed n rb and the second rotation speed n rs alternately, and the correction term output by the correction term design module The switching angle of the current switching moment is corrected, and the rotation speed switching is performed when the running track of the catamaran is perpendicular to the to-be-tracked straight line. The correction term design module is used for calculating a correction term at a current switching time The method comprises: acquiring a position c of the catamaran at a previous switching time i-1 And c i The midpoint of c i-1 And c i The distance L between the midpoint of c i And the to-be-tracked straight line approaches 0 as a control target, and the correction term is output through PI control The judging module is used for judging whether the catamaran reaches the designated target point, if not, the rotating speed switching module and the correction term design module are repeatedly executed, and if yes, the control is ended.

7. The control system of claim 6, wherein, In the correction term design module, the correction term at the current switching time is is: where K P and K I are the proportional and integral coefficients, respectively, L i is the distance between the midpoints of c i-1 and c i and the straight line to be tracked, is the integral term at the current switching instant.

8. The control system of claim 7, wherein, the integral term of the current switching instant is: wherein respectively the upper and lower limit values of the integral term of the pre-switching instant.

9. The control system of claim 6, wherein, When a running track of the catamaran is perpendicular to the to-be-tracked straight line, the following condition is met: where ψ i is the current switching time of the catamaran heading angle, θ is the catamaran desired direction of the screw forward angle.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to realize the control method in any one of claims 1-5.

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