CN112148026A - Thrust distribution method of underwater robot dynamic positioning system - Google Patents

Thrust distribution method of underwater robot dynamic positioning system Download PDF

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Publication number
CN112148026A
CN112148026A CN202010827818.6A CN202010827818A CN112148026A CN 112148026 A CN112148026 A CN 112148026A CN 202010827818 A CN202010827818 A CN 202010827818A CN 112148026 A CN112148026 A CN 112148026A
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thrust
distribution method
rov
thrusters
moment
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李志刚
尹汉军
黄福祥
李新飞
刘飞龙
吴朝晖
喻龙
袁利毫
邬博文
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Harbin Engineering University
Offshore Oil Engineering Co Ltd
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Offshore Oil Engineering Co Ltd
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course or altitude of land, water, air, or space vehicles, e.g. automatic pilot
    • G05D1/10—Simultaneous control of position or course in three dimensions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63C—LAUNCHING, HAULING-OUT, OR DRY-DOCKING OF VESSELS; LIFE-SAVING IN WATER; EQUIPMENT FOR DWELLING OR WORKING UNDER WATER; MEANS FOR SALVAGING OR SEARCHING FOR UNDERWATER OBJECTS
    • B63C11/00—Equipment for dwelling or working underwater; Means for searching for underwater objects
    • B63C11/52—Tools specially adapted for working underwater, not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/001—Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/08—Propulsion
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
    • G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
    • G05B13/04—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators
    • G05B13/042—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators in which a parameter or coefficient is automatically adjusted to optimise the performance
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
    • B63G8/00—Underwater vessels, e.g. submarines; Equipment specially adapted therefor
    • B63G8/001—Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations
    • B63G2008/002—Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations unmanned

Abstract

The invention discloses a thrust distribution method of an overdrive operation type remote control underwater robot power positioning system, which divides 7 hydraulic thrusters into two groups according to a target propulsion system and arrangement characteristics, selects a thrust distribution objective function and a thrust constraint condition, and solves the optimal thrust of each thruster by adopting a sequential quadratic programming optimization algorithm. And finally, the expected output thrust of the 7 thrusters outputs the six-freedom-degree thrust and the thrust moment under the action of a thrust synthesis matrix, so that the six-freedom-degree motion control of the operation type ROV is realized, and the three-dimensional space dynamic positioning process of the operation type ROV is completed. The thrust distribution method effectively solves the optimal solving limitation of the non-convex problem in the over-driving thrust distribution system, reasonably distributes the thrust for each propeller, meets the output limitation of the propeller and the optimization result of the objective function, and ensures that the ROV can safely operate in the actual engineering.

Description

Thrust distribution method of underwater robot dynamic positioning system
Technical Field
The invention relates to the technical field of motion control of unmanned underwater robots, in particular to a thrust distribution method of an over-drive operation type remote control underwater robot (ROV-removed Operated Vehicle) six-degree-of-freedom motion control system.
Background
Generally, when the working type ROV is subjected to motion control, an input command is mainly from a control room, and an electric signal is transmitted to a target ROV through an umbilical cable. However, in actual engineering work, both disturbance of deep sea currents and wave disturbance in the vicinity of shallow water affect the actual operation state of workers, and the work state cannot be maintained with high accuracy. It is very necessary that the ROV has a Dynamic Positioning (DP) function, which can appropriately reduce the burden on the operator and is advantageous to improve the underwater working efficiency.
The thrust distribution unit in the DP function reasonably distributes six-degree-of-freedom thrust (moment) instructions provided by the controller to each thruster of the ROV to resist various external forces, thereby realizing the control of the position and attitude of the ROV. In order to improve the stability of the operation type ROV in deep sea operation and prevent the robot from being out of control due to faults, a plurality of propellers are arranged on the horizontal plane and the vertical plane respectively so as to ensure the safe operation of the robot. However, the thrust distribution module is used for reasonably controlling the thrust distribution of the thruster according to actual conditions, so that the thrust distribution module has a higher engineering value.
The thrust distribution unit is used as an execution unit for the movement of a controlled object, the thrust distribution problem is more and more widely concerned by researchers, and the corresponding thrust distribution method is used for researches of aerospace systems, aircraft systems, vehicle systems, ship and ocean engineering control systems, underwater robot movement control systems and the like. As far as present, the main thrust distribution methods are: a direct distribution method, a Pseudo-Inverse (Pseudo Inverse) thrust distribution method, a Nonlinear Optimization (Nonlinear Optimization) method, and a Dynamic Control distribution (Dynamic Control Allocation) method, and the like. The ROV under study has the number of propellers larger than the number of degrees of freedom, so the ROV belongs to the problem of controlling an overdrive motion system. This means that there are many ways of distributing the thrust (torque) required to achieve the target control command to each propeller. Therefore, the thrust allocation problem of the overdrive ROV belongs to a nonlinear optimization problem, wherein an objective function in the optimization problem can contain various optimization items, and constraints are that the magnitude of the thrust and the change rate are limited. By combining the form of the objective function, it can be found that it is very suitable to select a sequential quadratic programming method to solve the problem of operational ROV thrust distribution.
The working type ROV researched by the invention is provided with 7 hydraulic propeller thrusters in a vector arrangement mode, needs to realize a three-dimensional space dynamic positioning function, namely 6-degree-of-freedom motion control, and is a typical over-drive motion control system. The difficulty of the thrust distribution method of the control system mainly comprises the following four aspects:
(1) the general underwater robot only needs to control 3 (advancing/retreating, pitching and turning) degrees of freedom to move, while the operation type ROV needs to control 6 degrees of freedom to move simultaneously, so that the system has high control dimension and great design difficulty.
(2) The ROV is provided with 7 vector arrangement type hydraulic thrusters, the 7 thrusters are required to act simultaneously for realizing ROV six-degree-of-freedom motion control, the problem of thrust distribution of a typical overdrive system is solved, and how to reasonably distribute 6 control quantities to the 7 thrusters is difficult.
(3) The thruster of the operation type ROV is a servo valve control hydraulic propeller thruster, is a typical inertia link, the execution of a thrust command has a large hysteresis characteristic, and if no proper thrust distribution method of an overdrive system exists, the motion response of 7 hydraulic thrusters of the operation type ROV can be caused to have phase difference, and even the ROV can generate a steady oscillation phenomenon.
(4) The hydraulic thruster has the limit of thrust threshold and response speed, and the problem of over-driving ROV thrust distribution under the constraint condition of the thruster is realized, so that the hydraulic thruster is one of the main difficulties in the design of an ROV control system. Therefore, the thrust force distribution method of the overdrive system becomes one of the key technologies for developing a working type ROV simulation training simulator and actual ROV working equipment.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an optimized thrust distribution method for an operation type ROV simulator or actual equipment, better solve the problem of multi-propeller thrust distribution in an ROV dynamic positioning working mode, realize ROV six-degree-of-freedom dynamic positioning under the physical constraint condition of a propeller through a sequence quadratic programming optimization distribution algorithm, and meet the requirements of reducing energy consumption and propeller abrasion.
In order to solve the technical problem, the invention provides a thrust distribution method of an underwater robot dynamic positioning system, which comprises the following steps:
s1: the ROV receives a pose instruction of an operator, and transmits the pose instruction to the underwater robot 6-degree-of-freedom motion controller to calculate expected longitudinal thrust, transverse thrust, vertical thrust, longitudinal thrust moment, transverse thrust moment and yaw thrust moment;
s2: establishing a thrust distribution objective function for a plurality of thrusters to perform thrust distribution optimization;
s3: setting the thrust output constraint conditions of each propeller, wherein the thrust output constraint conditions are divided into equality constraint and inequality constraint, and one of the total thrust or the torque output by the controller is equal to the result after the thrust is synthesized;
s4: initializing a target function, a constraint condition and parameters of a sequence quadratic programming algorithm;
s5: setting an energy consumption weight matrix and an error weight matrix in the objective function according to actual requirements, setting maximum iteration times and initial values of calculation results, and preparing for subsequent thrust distribution solving;
s6: solving a nonlinear thrust distribution problem consisting of the objective function and a constraint equation by using a sequential quadratic programming algorithm to obtain optimal thrust output;
s7: and transmitting the solved optimal thrust to the ROV through the propelling device, thereby realizing the power positioning function.
Preferably, the thrust force distribution objective function in step S2 is:
Figure BDA0002636867870000031
in the formula: the first term is used to optimize energy consumption, W is an energy consumption weight matrix in the form of a diagonal matrix, u ═ u1u2 u3 u4 u5 u6 u7]TA vector matrix is input for the control of 7 thrusters; the second term belongs to a penalty term, wherein s is a column matrix which is used as a relaxation variable of the optimization term and represents the difference between the thrust input by the controller and the thrust output by the thrust synthesis; q is also a diagonal matrix, and the weight of the input and output error values in the objective function can be determined by changing the value of Q; the third item is to avoid the strange structure of the propeller, which is largeAt number 0, ρ is the weight of the optimization term to avoid denominator of 0.
Preferably, the step S3 is written as a mathematical expression:
s＝τ-B(β)u
umin≤u≤umax
Δumin≤u-u0≤Δumax；
for the equation, the left side of the equation is a relaxation variable, the controller is allowed to output thrust or thrust moment and an actual resultant thrust or thrust moment to have an error, and tau on the right side of the equation is [ X ═ XT YT ZT KT MT NT]TAre respectively as follows: longitudinal thrust generated by 7 propellers, transverse thrust generated by 7 propellers, vertical thrust generated by 7 propellers, transverse moment generated by 7 propellers, longitudinal moment generated by 7 propellers, yawing moment generated by 7 propellers and B (beta) is a propulsion system arrangement matrix;
Figure BDA0002636867870000041
in the formula: beta is ahO of 4 horizontal thrusters and a body coordinate system { n }bzbAn included angle; beta is avO of 3 vertical thrusters and a body coordinate system { n }bzbThe included angle of the axes; x is the number ofh、yh、zhRespectively is the distance o between 4 horizontal propellersbxb、obyb、obzbDistance of the shaft; x is the number ofv、yv、zvRespectively 3 vertical thrusters are respectively spaced by a distance obxb、obyb、obzbDistance of the shaft; the symbol c is the cosine function cos (·); the symbol s is a sine function sin (·).
Preferably, the quadratic programming algorithm in step S4 is:
Figure BDA0002636867870000042
Figure BDA0002636867870000043
Figure BDA0002636867870000044
solving the optimal solution d in the formulak。
Preferably, the if dkIf | | is less than or equal to the original problem, stopping calculation to obtain an approximate KT point (x) of the original problemk,μk,λk)。
Preferably, for a certain cost function phi (x, sigma), a penalty function sigma is chosenkSo that d iskIs that the function is at xkIn the descending direction of (c).
Preferably, said is mkTo satisfy the minimum non-negative integer m of the following inequality:
φ(xk+ρmdk,σk)-φ(xk,σk)≤ηρmφ′(xk,σk；dk)
order to
Figure BDA0002636867870000051
xk+1＝xk+αkdk。
Preferably, the first and second electrodes are formed of a metal,
Figure BDA0002636867870000052
Figure BDA0002636867870000053
Figure BDA0002636867870000054
and least squares
Figure BDA0002636867870000055
Preferably, the correction matrix BkIs Bk+1Let us order
sk＝αkdk
Figure BDA0002636867870000056
Figure BDA0002636867870000057
In the formulak＝θkyk+(1-θk)Bksk，
Parameter thetakIs defined as:
Figure BDA0002636867870000058
let k be k +1 and go to the beginning of the step to make the calculation.
The invention has the technical effects that: the invention discloses a thrust distribution method of an over-drive operation type remote control underwater robot power positioning system. Aiming at the application requirements of an operation type ROV power positioning system in practical engineering, 7 hydraulic thrusters are divided into two groups according to a target propulsion system and arrangement characteristics, a thrust distribution objective function and a thrust constraint condition are selected, and the optimal thrust of each thruster is solved by adopting a Sequential Quadratic Programming (SQP) optimization algorithm. And finally, outputting the thrust and the thrust moment of six degrees of freedom by the expected output thrust of the 7 thrusters under the action of a thrust synthesis matrix, and obtaining the magnitude of the longitudinal force, the transverse force, the vertical force, the pitching moment, the rolling moment and the yawing moment required in the dynamic positioning process. And applying a sequential quadratic programming optimization algorithm to the thrust distribution problem through the established propulsion system model of the propeller and the physical constraint limiting conditions of each propeller, thereby obtaining thrust output capable of meeting the requirements. The optimal solution of the thrust distribution problem is obtained, the energy consumption is reduced, the abrasion of the propeller is reduced, the reliability of the ROV in deep sea operation is improved, and the method has important value and significance for actual engineering.
Drawings
FIG. 1 illustrates the working principle of an operating type ROV dynamic positioning system;
FIG. 2 is a schematic diagram of the arrangement of 4 horizontal thrusters in a work-type ROV;
FIG. 3 is a schematic diagram of the arrangement of 3 vertical thrusters in a work-type ROV;
FIG. 4 is a technical schematic diagram of the thrust allocation module solving for optimal thrust;
FIG. 5 operational type ROV motion response results;
fig. 6 shows a simulation result of the working ROV thrust distribution.
Detailed Description
The present invention is further described with reference to the following drawings and specific examples so that those skilled in the art can better understand the present invention and can practice the present invention, but the examples are not intended to limit the present invention.
When the working type ROV distributes the thrust of a plurality of propellers in a power positioning working state, the adopted method is as follows: according to the information of the position appointed by the operator, the longitudinal force, the transverse force, the vertical force, the pitching moment, the rolling moment and the yawing moment required in the dynamic positioning process are obtained through calculation of the controller. And applying a sequential quadratic programming optimization algorithm to the thrust distribution problem through the established propulsion system model of the propeller and the physical constraint limiting conditions of each propeller, thereby obtaining thrust output capable of meeting the requirements. And finally, synthesizing the thrust output by each propeller, thereby realizing the power positioning function of the operation type ROV. The method comprises the following steps:
the method comprises the following steps of firstly, selecting a thrust distribution model objective function, wherein the thrust distribution optimization objective mainly aims at reducing the energy consumption of a propeller and realizing the control function of six-degree-of-freedom motion errors under the condition of reducing the abrasion of the propeller. Secondly, it is also to avoid the singular structure of the ROV during the operation, therefore, the thrust distribution objective function can be established as:
Figure BDA0002636867870000071
in the formula: the first item is used for optimizing energy consumption, W is an energy consumption weight matrix in a diagonal matrix form, the weight of the energy consumption in each optimization target can be changed by changing the size of the energy consumption weight matrix, and the optimization item can also reduce the abrasion degree of a propeller so that the propeller can work reliably for a long time. Wherein u ═ u1 u2 u3 u4 u5 u6 u7]TThe vector matrix is input for the control of 7 thrusters.
The second term belongs to the penalty term, where s is a column matrix, which is the slack variable of the optimization term, representing the difference between the thrust input by the controller and the thrust output by the thrust combination. Q is also a diagonal matrix, and the weight of the input and output error values in the objective function can be determined by changing the magnitude of Q.
The third term is set to avoid the singular structure of the propeller, wherein the third term is a number larger than 0, and p is the weight of the optimized term to avoid the denominator being 0.
And secondly, setting thrust output constraint conditions of each propeller, wherein the thrust output constraint conditions are divided into equality constraint and inequality constraint. The thrust limit of the propeller output and the thrust output change rate limit are mainly considered. Besides, the total thrust or torque output by the controller is ensured to be equal to the combined result of the thrust as much as possible. Written as a mathematical expression:
s＝τ-B(β)u (2)
umin≤u≤umax (3)
Δumin≤u-u0≤Δumax (4)
for equation (1), the left side of the equation is the slack variable, allowing the controller to output a thrust (moment) that is in error with the actual resultant thrust (moment) in order to better accomplish the dynamic positioning task. τ on the right of the equation ═ XT YT ZT KT MT NT]TAre respectively as follows: the longitudinal thrust generated by the 7 thrusters, the transverse thrust generated by the 7 thrusters, the vertical thrust generated by the 7 thrusters, the transverse inclination moment generated by the 7 thrusters, the longitudinal inclination moment generated by the 7 thrusters and the yawing moment generated by the 7 thrusters. B (β) is a propulsion system layout matrix in which the thrust limit and rated output power of each propeller are as shown in table 1.
Figure BDA0002636867870000081
In the formula: beta is ahO of 4 horizontal thrusters and a body coordinate system { n }bxbThe included angle of the axes; beta is avO of 3 vertical thrusters and a body coordinate system { n }bzbThe included angle of the axes; x is the number ofh、yh、zhRespectively is the distance o between 4 horizontal propellersbxb、obyb、obzbDistance of the shaft; x is the number ofv、yv、zvRespectively 3 vertical thrusters are respectively spaced by a distance obxb、obyb、obzbDistance of the shaft; the symbol c is the cosine function cos (·); the symbol s is a sine function sin (·). Among them, the arrangement position of each of the 7 pushers is shown in table 2.
TABLE 2
Figure BDA0002636867870000082
And thirdly, initializing the objective function, the constraint condition and the parameters of the sequential quadratic programming algorithm. Namely, the energy consumption weight matrix and the error weight matrix in the objective function are set according to actual requirements, and the maximum iteration times and the initial value of the calculation result are set to prepare for subsequent thrust distribution solving.
And fourthly, solving the nonlinear thrust distribution problem formed by the objective function and the constraint equation by using a sequential quadratic programming algorithm to obtain the optimal thrust output. The sequence quadratic programming algorithm solving method comprises the following steps:
step 1: solving quadratic programming subproblems by smooth Newton method
Figure BDA0002636867870000091
Figure BDA0002636867870000092
Figure BDA0002636867870000093
Obtain the optimal solution dk。、
Step 2: if | dkIf | | is less than or equal to the original problem, stopping calculation to obtain an approximate KT point (x) of the original problemk,μk,λk)。
And step 3: for a certain cost function phi (x, sigma), a penalty function sigma is chosenkSo that d iskIs that the function is at xkIn the descending direction of (c).
And 4, step 4: let mkTo satisfy the minimum non-negative integer m of the following inequality:
φ(xk+ρmdk,σk)-φ(xk,σk)≤ηρmφ′(xk,σk；dk) (7)
order to
Figure BDA0002636867870000094
xk+1＝xk+αkdk。
And 5: computing
Figure BDA0002636867870000095
Figure BDA0002636867870000096
Figure BDA0002636867870000097
And least squares
Figure BDA0002636867870000101
Step 6: correction matrix BkIs Bk+1Let us order
sk＝αkdk (12)
Figure BDA0002636867870000102
Figure BDA0002636867870000103
Z herek＝θkyk+(1-θk)Bksk。
Parameter thetakIs defined as:
Figure BDA0002636867870000104
and 7: and (5) enabling k to be k +1, and turning to the step 1.
And fifthly, transmitting the solved optimal thrust to the ROV through a propelling device, thereby realizing the function of dynamic positioning.
The invention is further described below with reference to the accompanying drawings.
Fig. 1 is a schematic diagram of the operation of a power positioning system for a working ROV. Firstly, the ROV receives a pose command of an operator, transmits the command to the motion controller, and the controller can calculate the size of longitudinal force, transverse force, vertical force, pitching moment, rolling moment and yawing moment required by reaching a target pose according to a related algorithm. The instructions search the most suitable output thrust of each propeller through the established new thrust system module and the constraint of each actual propeller on the thrust by a sequential quadratic programming optimization algorithm, so that the dynamic positioning function is realized.
As shown in fig. 1, the present invention includes: the system comprises an ROV hydrodynamic model, an ROV kinematic model, a six-degree-of-freedom motion controller, an overdrive thrust distribution module, a thrust synthesis module and a target pose input module. The invention can simulate how to reasonably distribute longitudinal thrust, transverse thrust and yaw thrust moment to 4 horizontal thrusters in real time; the method can simulate how to reasonably distribute vertical thrust, longitudinal moment and transverse moment to 3 vertical thrusters in real time; the simulation method can simulate how to combine the thrust of 7 propellers into a thrust vector with six degrees of freedom to act on the operation type ROV body model; and the process of achieving the target pose in the dynamic positioning process can be simulated by the ROV.
Fig. 2 and 3 are schematic layout views of 4 horizontal thrusters and 3 vertical thrusters, respectively, in which the coordinate position of each thruster in space is shown as the main technical parameters of the thruster in table 1.
TABLE 1
Figure BDA0002636867870000111
Fig. 4 is a technical schematic diagram of the thrust allocation module for solving the optimal thrust, and the specific steps include:
the method comprises the following steps that firstly, a thrust distribution model objective function is selected, and the thrust distribution optimization aims to reduce the output power and the energy consumption of a propeller as far as possible and reduce the abrasion of the propeller and control errors. Secondly, the singular structure of the ROV in the operation process is also avoided, so that the thrust distribution objective function can be established as shown in the formula (1).
In the formula: the first term is used to optimize energy consumption, and W is an energy consumption weight matrix, which is a diagonal matrix, and the weight of energy consumption in each optimization objective can be changed by changing the size of the matrix. The wear degree of the propeller can be reduced by optimizing the item, so that the propeller can work more safely and stably. Wherein u ═ u1 u2 u3 u4 u5 u6 u7]TThe vector matrix is input for the control of 7 thrusters.
The second term belongs to the penalty term, where s is a column matrix, which is the slack variable of the optimization term, representing the difference between the thrust input by the controller and the thrust output by the thrust combination. Q is also a diagonal matrix, and the weight of the input and output error values in the objective function can be determined by changing the magnitude of Q.
The third term is set to avoid the singular structure of the propeller, wherein the third term is a number larger than 0, and p is the weight of the optimized term to avoid the denominator being 0.
And secondly, setting thrust output constraint conditions of each propeller, wherein the thrust output constraint conditions are divided into equality constraint and inequality constraint. The main problems to be considered are the limit of the thrust output by the propeller and the limit of the change rate of the thrust output. Besides, the total thrust or torque output by the controller is ensured to be equal to the combined result of the thrust as much as possible. The mathematical expressions are shown in formulas (2) to (4).
For the first equality constraint, the left side of the equality is the slack variable, allowing the controller output thrust (moment) to be in error from the actual resultant thrust (moment) in order to better accomplish the dynamic positioning task. τ on the right of the equation ═ XT YT ZT KT MTNT]TAre respectively as follows: longitudinal thrust generated by 7 propellers, transverse thrust generated by 7 propellers and 7 propellersThe vertical thrust generated by the device, the transverse inclination moment generated by 7 thrusters, the longitudinal inclination moment generated by 7 thrusters and the yawing moment generated by 7 thrusters. B (beta) is a propulsion system arrangement matrix, and is shown as a formula (5).
And thirdly, initializing the objective function, the constraint condition and the parameters of the sequential quadratic programming algorithm. In the invention, the energy consumption weight matrix is set to W ═ diag (1,1,1,1,1,1,1), the error weight matrix is set to Q ═ diag (1000,1000,1000,1000,1000,1000), and the maximum iteration number is k in each iteration calculation processmax150, the thruster deployment matrix B (β) is:
Figure BDA0002636867870000121
and fourthly, solving the nonlinear thrust distribution problem formed by the objective function and the constraint equation by using a sequential quadratic programming algorithm to obtain the optimal thrust output.
And fifthly, transmitting the solved optimal thrust to the ROV through a propelling device, thereby realizing the function of dynamic positioning.
With reference to the working principle schematic diagram of the working type ROV power positioning system in fig. 1, after the thrust distribution optimization method used in the working type ROV power positioning system is compiled into a Simulink simulation model, the working effect is subjected to simulation verification. The simulation environment and the calculation condition are as follows: the initial position is (0m, 0m, 0m) in the northeast coordinate system, and the initial roll angle, the initial pitch angle, and the yaw angle are all 0 °. The positioning target is (10m, 10m, 5m) in a northeast coordinate system, the roll angle and the pitch angle are always kept at 0 degrees, and the target value of the yaw angle is set to be 10 degrees. The simulation time is set to 100s, the calculation step size is 0.1s, the motion response of the ROV is shown in FIG. 5, and the thrust variation of each propeller is shown in FIG. 6.
The above-mentioned embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.

Claims (9)

1. A thrust distribution method of an underwater robot dynamic positioning system is characterized by comprising the following steps:
s1: the ROV receives a pose instruction of an operator, and transmits the pose instruction to the underwater robot 6-degree-of-freedom motion controller to calculate expected longitudinal thrust, transverse thrust, vertical thrust, longitudinal thrust moment, transverse thrust moment and yaw thrust moment;
s2: establishing a thrust distribution objective function for a plurality of thrusters to perform thrust distribution optimization;
s3: setting the thrust output constraint conditions of each propeller, wherein the thrust output constraint conditions are divided into equality constraint and inequality constraint, and one of the total thrust or the torque output by the controller is equal to the result after the thrust is synthesized;
s4: initializing a target function, a constraint condition and parameters of a sequence quadratic programming algorithm;
s5: setting an energy consumption weight matrix and an error weight matrix in the objective function according to actual requirements, setting maximum iteration times and initial values of calculation results, and preparing for subsequent thrust distribution solving;
s6: solving a nonlinear thrust distribution problem consisting of the objective function and a constraint equation by using a sequential quadratic programming algorithm to obtain optimal thrust output;
s7: and transmitting the solved optimal thrust to the ROV through the propelling device, thereby realizing the power positioning function.
2. The thrust force distribution method according to claim 1, wherein the thrust force distribution objective function in step S2 is:
Figure FDA0002636867860000011
in the formula: the first term is used to optimize energy consumption, W is a diagonal matrixForm of energy consumption weight matrix, u ═ u1 u2 u3u4 u5 u6 u7]TA vector matrix is input for the control of 7 thrusters; the second term belongs to a penalty term, wherein s is a column matrix which is used as a relaxation variable of the optimization term and represents the difference between the thrust input by the controller and the thrust output by the thrust synthesis; q is also a diagonal matrix, and the weight of the input and output error values in the objective function can be determined by changing the value of Q; the third term is set to avoid the singular structure of the propeller, wherein the third term is a number larger than 0, and p is the weight of the optimized term to avoid the denominator being 0.
3. The thrust force distribution method according to claim 1, wherein said step S3 is written as a mathematical expression:
s＝τ-B(β)u
umin≤u≤umax
Δumin≤u-u0≤Δumax；
for the equation, the left side of the equation is a relaxation variable, the controller is allowed to output thrust or thrust moment and an actual resultant thrust or thrust moment to have an error, and tau on the right side of the equation is [ X ═ XT YT ZT KT MT NT]TAre respectively as follows: longitudinal thrust generated by 7 propellers, transverse thrust generated by 7 propellers, vertical thrust generated by 7 propellers, transverse moment generated by 7 propellers, longitudinal moment generated by 7 propellers, yawing moment generated by 7 propellers and B (beta) is a propulsion system arrangement matrix;
Figure FDA0002636867860000021
in the formula: beta is ahO of 4 horizontal thrusters and a body coordinate system { n }bzbAn included angle; beta is avO of 3 vertical thrusters and a body coordinate system { n }bzbOf shaftsAn included angle; x is the number ofh、yh、zhRespectively is the distance o between 4 horizontal propellersbxb、obyb、obzbDistance of the shaft; x is the number ofv、yv、zvRespectively 3 vertical thrusters are respectively spaced by a distance obxb、obyb、obzbDistance of the shaft; the symbol c is the cosine function cos (·); the symbol s is a sine function sin (·).
4. The thrust force distribution method according to claim 1, wherein the quadratic programming algorithm in step S4 is:
Figure FDA0002636867860000031
Figure FDA0002636867860000032
Figure FDA0002636867860000033
solving the optimal solution d in the formulak。
5. The thrust force distribution method according to claim 4, wherein if | | | dkIf | | is less than or equal to the original problem, stopping calculation to obtain an approximate KT point (x) of the original problemk,μk,λk)。
6. Thrust force distribution method according to claim 5, characterized in that for a certain cost function φ (x, σ), a penalty function σ is chosenkSo that d iskIs that the function is at xkIn the descending direction of (c).
7. The thrust force distribution method according to claim 6,characterized in that m is setkTo satisfy the minimum non-negative integer m of the following inequality:
φ(xk+ρmdk,σk)-φ(xk,σk)≤ηρmφ′(xk,σk；dk)
order to
Figure FDA0002636867860000034
xk+1＝xk+αkdk。
8. The thrust force distribution method according to claim 7,
Figure FDA0002636867860000035
Figure FDA0002636867860000036
Figure FDA0002636867860000037
and least squares
Figure FDA0002636867860000038
9. Thrust force distribution method according to claim 8, characterized in that the correction matrix BkIs Bk+1Let us order
sk＝αkdk
Figure FDA0002636867860000041
Figure FDA0002636867860000042
In the formulak＝θkyk+(1-θk)Bksk，
Parameter thetakIs defined as:
Figure FDA0002636867860000043
let k be k +1, go to the claim 2 for calculation.
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