CN114967714A - Anti-interference motion control method and system for autonomous underwater robot - Google Patents

Anti-interference motion control method and system for autonomous underwater robot Download PDF

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CN114967714A
CN114967714A CN202210728589.1A CN202210728589A CN114967714A CN 114967714 A CN114967714 A CN 114967714A CN 202210728589 A CN202210728589 A CN 202210728589A CN 114967714 A CN114967714 A CN 114967714A
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state
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边有钢
杨静心
徐彪
秦洪懋
胡满江
秦兆博
秦晓辉
谢国涛
王晓伟
丁荣军
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Hunan University
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Abstract

The invention discloses an anti-interference motion control method of an autonomous underwater robot, which comprises the following steps: step 1, establishing an autonomous underwater robot dynamics and kinematics simplified linear model; step 2, establishing a system nominal model; step 3, constructing a disturbance observer; step 4, designing a nominal model predictive controller; step 5, designing an auxiliary model predictive controller; and 6, measuring the system state at the next moment, taking the moment as a new current moment, and returning to the step 3. According to the control method for the disturbance rejection motion of the autonomous underwater robot, the double-layer model prediction control framework is established, the influence caused by uncertainty can be effectively responded, the reference value can be tracked, and the control effect is better.

Description

Anti-interference motion control method and system for autonomous underwater robot
Technical Field
The invention belongs to the technical field of autonomous underwater robot control, and particularly relates to an autonomous underwater robot anti-interference motion control method and system.
Background
An underwater robot is underwater equipment which replaces human beings to finish various complex operations in a marine environment. The autonomous underwater robot is increasingly used in the fields of marine science investigation, rescue and salvage, submarine resource survey and the like by virtue of the characteristics of flexibility, autonomy, intelligence and the like. In various application scenes, the autonomous underwater robot can realize the position and posture control of depth setting, submerging and surfacing, hovering and positioning and the like in a high-quality manner, which is a necessary condition for accurately and efficiently completing tasks.
The control technology of the autonomous underwater robot is the core technology of the autonomous underwater robot. The autonomous underwater robot has the characteristics of high nonlinearity, strong coupling and the like, so that the autonomous underwater robot is more difficult to apply to motion control. In addition, the motion control of the underwater robot is greatly influenced by common complex environments such as dynamic ocean currents, storms, deep water pressure and the like in the marine environment. Based on the characteristics, an accurate control model of the autonomous underwater robot is difficult to establish, and some un-modeled dynamic establishment simplified models are often ignored, so that the established models are not matched with the reality, and the control accuracy is influenced.
At present, the research on the motion control method of the autonomous underwater robot mainly comprises various methods such as PID control, fuzzy control, sliding mode control, neural network control, adaptive control and the like, and also has the technology of combining two or more control methods such as fuzzy sliding mode variable structure control, adaptive neural network control and the like. The patent ' a depth interval control method and system of an underwater robot ' (patent number: 202010310143.8) owned by Huazhong university of science and technology ' discloses a depth interval control method and system of an underwater robot under the constraint of rudder angle and rudder speed, which is beneficial to reducing the frequency and amplitude of rudder striking, but the method does not consider disturbance in the optimization process, only depends on the robustness of a controller, and may not ensure the control effect when large disturbance exists. The patent 'an underwater robot path tracking control method based on model predictive control' (patent number: 201811383664.5) owned by Qinghua university discloses an underwater robot path tracking control method based on model predictive control, which is realized by online numerical optimization and rolling time domain, processes the constraint of control input, has certain robustness, but is still insufficient to process model uncertainty and external interference. Therefore, a robust prediction control method capable of effectively processing disturbance is needed to be provided, so that the autonomous underwater robot system can strictly meet constraint conditions under the condition of uncertainty, and meanwhile, the robustness of the system is effectively improved.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to solve the problem of motion control of an autonomous underwater robot under unknown bounded disturbance, and provides a control method and a control system with robustness.
In order to realize the purpose, the invention provides the following technical scheme: an anti-interference motion control method for an autonomous underwater robot comprises the following steps:
step 1, establishing an autonomous underwater robot dynamics and kinematics simplified linear model, converting the model into a continuous time model in a state space, and discretizing the model to obtain a discrete time model of a system;
step 2, establishing a system nominal model used as a prediction equation of a nominal model prediction controller, and converting the system state and control input constraint into a tightened state and control input constraint of a nominal system;
step 3, constructing a disturbance observer, taking a disturbance variable as an expanded state quantity, estimating a system disturbance value, and sending the estimated value to an auxiliary prediction controller;
designing a nominal model predictive controller, constructing a cost function, and solving a finite time domain optimization problem to obtain a nominal optimal control input and a corresponding nominal state;
step 5, designing an auxiliary model prediction controller, receiving nominal prediction input and output signals and a disturbance signal provided by a disturbance observer, solving optimal control aiming at an actual system model, and acting the first control quantity of a control sequence on the autonomous underwater robot system;
and 6, measuring the system state at the next moment, taking the moment as a new current moment, and returning to the step 3.
As a further improvement of the present invention, the tightened state and control input constraints of the nominal system in step 2 are specifically expressed as:
Figure BDA0003711798770000021
Figure BDA0003711798770000031
wherein α and γ represent a reduction coefficient in the range of (0, 1).
As a further improvement of the present invention, the specific steps of constructing the disturbance observer in step 3 are as follows:
step 31, regarding the disturbance as a newly added state quantity, adding the newly added state quantity into an uncertain system, and establishing a linear state observer as follows:
Figure BDA0003711798770000032
wherein the state estimate is
Figure BDA0003711798770000033
Outputting the estimated value
Figure BDA0003711798770000034
L, H is a matrix of the gains of the observer,
Figure BDA0003711798770000035
for disturbance estimation, β is an auxiliary variable;
step 32, calculating a state estimation error and a disturbance error:
Figure BDA0003711798770000036
Figure BDA0003711798770000037
then to e x The derivation yields:
Figure BDA00037117987700000313
obtaining the first derivative of the disturbance estimate:
Figure BDA0003711798770000038
wherein the estimate of the derivative of the disturbance
Figure BDA0003711798770000039
Step 33, the state estimation error and the disturbance estimation error are combined into an estimation error system as follows:
Figure BDA00037117987700000310
wherein G ═ e x T e w ] T
Figure BDA00037117987700000311
An estimation error representing the derivative of the disturbance.
As a further improvement of the present invention, the specific steps of designing a nominal model predictive controller in step 4, constructing a cost function, and solving a finite time domain optimization problem to obtain a nominal optimal control input and a corresponding nominal state are as follows:
step 41, designing an optimal control input for each sampling time, driving the nominal system state to a target point and minimizing a cost function, wherein the constructed cost function is as follows:
Figure BDA00037117987700000312
wherein x ref Is a target state vector, N p Q, R respectively represent positive definite weighting matrixes of a prediction state and control input for predicting a time domain, P is a terminal weighting matrix, and the positive definite weighting matrix is obtained by solving a Riccati equation;
step 42, the nominal prediction model constraints and the nominal state constraints and nominal control constraints are satisfied, and the nominal states and nominal controls are respectively constrained within the subsets of the actual constraints:
Figure BDA0003711798770000041
Figure BDA0003711798770000042
and (3) state constraint to be met by the model in the last prediction interval in the prediction time domain:
Figure BDA0003711798770000043
terminal constraints
Figure BDA0003711798770000044
Satisfy the requirement of
Figure BDA0003711798770000045
And the like. Wherein A is K =A+BK,
Figure BDA0003711798770000046
Is a robust invariant set;
step 43, representing the optimal control problem at any time k in a limited time domain:
Figure BDA0003711798770000047
Figure BDA0003711798770000048
Figure BDA0003711798770000049
Figure BDA00037117987700000410
Figure BDA00037117987700000411
wherein,
Figure BDA00037117987700000412
the linear feedback gain K is determined by a linear quadratic regulator.
As a further improvement of the present invention, the method for solving the optimal control for the actual system model in step 5 is to solve the following optimization problem:
Figure BDA00037117987700000413
Figure BDA00037117987700000414
Figure BDA00037117987700000415
Figure BDA00037117987700000416
Figure BDA00037117987700000417
wherein
Figure BDA0003711798770000055
Estimated by a disturbance observer.
As a further improvement of the present invention, the specific steps of establishing an autonomous underwater robot dynamics and kinematics simplified linear model in step 1, converting the model into a continuous time model in a state space, and discretizing the model to obtain a discrete time model of the system are as follows:
step 11, defining a required coordinate system: the system comprises an inertial coordinate system and a satellite coordinate system, wherein the inertial coordinate system is fixed on the ground, the satellite coordinate system is fixed on the autonomous underwater robot, the E-xi eta zeta represents the inertial coordinate system, and the O-xyz represents the satellite coordinate system;
step 12, defining six-freedom-degree speed V ═ u V l p q r of the autonomous underwater robot in the satellite coordinate system] T And the position and attitude angle eta relative to the fixed coordinate system [ x y z phi theta phi DEG] T The autonomous underwater robot motion equation is as follows:
MV+C(V)V+D(V)V+g(η)=τ
Figure BDA0003711798770000052
wherein M is the sum of rigid mass and additional mass matrix, C (V) is Coriolis force and centripetal force matrix, D (V) is damping matrix, g (eta) is restoring moment, tau is propulsion system input matrix, J (eta) is Jacobian transformation matrix between inertial coordinate system and random coordinate system;
step 13, assuming that the transverse velocity v, the course angular velocity p, the roll angular velocity r and the roll angle phi of the relevant state quantities of the horizontal plane are all approximate to 0, the change of the longitudinal velocity u is smooth and stable, u is approximate to a constant, the model is decoupled only by considering the motion of the autonomous underwater robot in the vertical x-z plane, and the simplified vertical three-order depth control model is established as follows:
Figure BDA0003711798770000053
wherein z is the vertical depth under the inertial coordinate system, theta is the longitudinal inclination angle, q is the longitudinal inclination angle speed, delta is the rudder angle, I y For moment of inertia about the y-axis, M q 、M δ
Figure BDA0003711798770000054
To add a mass matrix, W is gravity, B 1 Is buoyancy, Δ q Representing the uncertainty part of the model, τ q Representing external time-varying disturbances caused by ocean currents and wind waves;
step 14, collecting position information and attitude information of the autonomous underwater robot by using a sensor, taking z, theta and q as state quantities, taking a rudder angle delta as a control input, and taking x as [ z, theta, q ]] T For describing the depth control problem of autonomous underwater robots. Converting the model into a state space equation:
Figure BDA0003711798770000061
wherein the state transition matrix
Figure BDA0003711798770000062
Input matrix
Figure BDA0003711798770000063
Discretizing a continuous time state space equation according to sampling time delta T to obtain:
x k+1 =Ax k +Bδ k +w k
therein, state
Figure BDA0003711798770000064
Control input
Figure BDA0003711798770000065
As a further improvement of the present invention, in step 14, it is assumed that the perturbation is bounded, and the bounded set is a convex set, which is represented as:
Figure BDA0003711798770000066
wherein w max Is the perturbation upper bound.
The invention also provides a system applying the method, which comprises a data acquisition device, a calculation unit, an execution mechanism and a driving mechanism, wherein the calculation unit is used for carrying the method and controlling the execution mechanism and the driving mechanism after the method is executed, the data acquisition device comprises a posture sensor and a depth sensor, the posture sensor is used for acquiring underwater information, robot posture and inertial navigation information and carrying out mean value filtering on the information, and the depth sensor is used for measuring the height distance to the water surface.
The invention has the beneficial effects that:
(1) according to the invention, a double-layer model predictive control framework is established, so that the influence caused by uncertainty can be effectively coped with and a reference value can be tracked, and a better control effect is achieved;
(2) the method estimates the prediction error caused by the uncertainty of the autonomous underwater robot system by using the disturbance observer, and compensates the estimated disturbance, so that the actual state track is close to the nominal system state track, and the control precision is improved;
(3) the invention explicitly processes the state and the control constraint, strictly ensures the constraint to be satisfied, keeps the state of the autonomous underwater robot system in a pipeline taking a nominal state track as a center, and improves the control robustness of the system.
Drawings
FIG. 1 is an inertial coordinate system and a satellite coordinate system of autonomous underwater robot motion in accordance with the present invention;
fig. 2 is a block diagram of autonomous underwater robot depth control in an embodiment provided by the present invention.
Detailed Description
The invention will be further described in detail with reference to the following examples, which are given in the accompanying drawings.
Taking the depth control of an autonomous underwater robot as an example, the method comprises the following specific steps:
the method comprises the following steps: and establishing a simplified prediction model according to the kinematics and dynamics model of the autonomous underwater robot.
First, the required coordinate system is defined: the system comprises an inertial coordinate system and a body-following coordinate system, wherein the inertial coordinate system is fixed on the ground, the body-following coordinate system is fixed on the autonomous underwater robot, and as shown in figure 1, E- ξ η ζ represents the inertial coordinate system, and O-xyz represents the body-following coordinate system.
And then defining the speed V ═ u V l p q r of the autonomous underwater robot with six degrees of freedom in the satellite coordinate system] T And the position and attitude angle eta relative to the fixed coordinate system [ x y z phi theta phi DEG] T The autonomous underwater robot motion equation is as follows:
MV+C(V)V+D(V)V+g(η)=τ
Figure BDA0003711798770000071
wherein M is the sum of the rigid body mass and the additional mass matrix, C (V) is a Coriolis force and centripetal force matrix, D (V) is a damping matrix, g (eta) is a restoring moment, tau is a propulsion system input matrix, and J (eta) is a Jacobian transformation matrix between an inertial coordinate system and a random coordinate system.
Assuming that the transverse velocity v, the course angular velocity p, the roll angular velocity r and the roll angle phi of the relevant state quantities of the horizontal plane are all approximate to 0, the change of the longitudinal velocity u is gentle and stable, u is approximate to a constant, the model is decoupled only by considering the movement of the autonomous underwater robot in the vertical x-z plane, and the simplified vertical three-order depth control model is established as follows:
Figure BDA0003711798770000072
wherein z is the vertical depth under the inertial coordinate system, theta is the longitudinal inclination angle, q is the longitudinal inclination angle speed, delta is the rudder angle, I y For moment of inertia about the y-axis, M q 、M δ
Figure BDA00037117987700000810
To add a mass matrix, W is gravity, B 1 Is buoyancy, Δ q Representing the uncertainty part of the model, τ q Representing external time-varying disturbances caused by ocean currents and waves.
The unmodeled dynamics of the system is internal disturbance, and various uncertainties brought by ocean currents, storms and the like are external disturbance, and the internal disturbance delta is converted into q External disturbance τ q Are all considered as bounded disturbances and are equivalent to the total disturbance Δ of the system w
The position information and the attitude information of the autonomous underwater robot are acquired by using a sensor, z, theta and q are used as state quantities, a rudder angle delta is used as control input, and x is [ z, theta and q ]] T For describing the depth control problem of autonomous underwater robots. Converting the model into a state space equation:
Figure BDA0003711798770000081
wherein the state transition matrix
Figure BDA0003711798770000082
Input matrix
Figure BDA0003711798770000083
Discretizing a continuous time state space equation according to sampling time delta T to obtain:
x k+1 =Ax k +Bδ k +w k
wherein the state
Figure BDA0003711798770000084
Control input
Figure BDA0003711798770000085
Due to the complexity and time variability of the underwater environment, it is difficult to obtain an accurate value of the disturbance through a model or a sensor, and it can be assumed that the disturbance is bounded, and the bounded set is a convex set, which can be expressed as:
Figure BDA0003711798770000086
wherein w max Is the perturbation upper bound.
Step two: and establishing a nominal model of the autonomous underwater robot system and calculating nominal constraints.
The state and control input constraints are first set according to the actual physical conditions of the system and the saturation constraints of the mechanism. The submergence speed of the autonomous underwater robot is related to the pitch angle and the torque, and the large pitch angle and the large torque enable the autonomous underwater robot to submerge rapidly but are not suitable to be too large. In order to ensure the safety and stability of the sports, certain pitching constraint conditions must be met to avoid the phenomena of rolling and the like. Thus, the given state constraints include constraints on pitch angle and pitch angular velocity, and the control input constraints refer to the range of rudder angle changes that allow for input:
Figure BDA0003711798770000087
Figure BDA0003711798770000088
wherein, aggregate
Figure BDA0003711798770000089
Are all tight convex sets, x, containing the origin min 、x max 、δ min 、δ max Is a known constant.
Nominal model means a virtual but precisely known model built in the control system, written in the form of a state space, ignoring all uncertainties of the system:
Figure BDA0003711798770000091
wherein,
Figure BDA0003711798770000092
is the nominal state at the time of k,
Figure BDA0003711798770000093
is the nominal control input at time k.
Part of the phase difference between the actual model and the nominal model:
Figure BDA0003711798770000094
and calculating the state and input constraint of the nominal system according to the state and control constraint of the autonomous underwater robot system. Due to neglecting the system uncertainty, the nominal system has more compact constraints compared with the actual system, and the nominal state constraint and the nominal control constraint are calculated and tightened on the basis of the actual constraints, which are respectively expressed as:
Figure BDA0003711798770000095
Figure BDA0003711798770000096
wherein α and γ represent a reduction coefficient in the range of (0, 1).
Step three: the system disturbance is estimated using a disturbance observer. Firstly, taking the disturbance as an extended state quantity to be added into an uncertain system, and establishing a linear state observer as follows:
Figure BDA0003711798770000097
wherein the state estimate is
Figure BDA0003711798770000098
Outputting the estimated value
Figure BDA0003711798770000099
L, H is a matrix of observer gains which,
Figure BDA00037117987700000910
for disturbance estimation, β is an auxiliary variable.
The state estimation error and the disturbance estimation error are as follows:
Figure BDA00037117987700000911
Figure BDA00037117987700000912
then to e x The derivation yields:
Figure BDA00037117987700000913
the first derivative of the disturbance estimate can then be expressed as:
Figure BDA00037117987700000914
wherein the estimated value of the derivative of the disturbance
Figure BDA00037117987700000915
The state estimation error and the disturbance estimation error constitute an estimation error system as follows:
Figure BDA0003711798770000101
wherein G ═ e x T e w ] T
Figure BDA0003711798770000102
An estimation error representing the derivative of the disturbance.
Through designing a proper observer gain matrix, the characteristic values of the error system are all positioned on a left half complex plane, so that the estimation error of the error system is converged to zero, and the stability of the disturbance observer is ensured. The obtained disturbance estimation value is fed back to the auxiliary prediction controller, and the influence of the disturbance on the controlled object is counteracted as much as possible.
Step four: and designing a nominal model prediction controller, and calculating the optimal nominal control input in a prediction time domain.
An optimal control input is designed for each sampling instant, driving the nominal system state to the target point and minimizing the cost function. The control target is to design a nominal input rudder angle under the condition of not considering system uncertainty and unknown time-varying external disturbance, so that the error between a nominal state and a given reference state value in a prediction time domain is minimum, a cost function reflects the control requirement of the system on the state and input of each prediction stage, and the cost function adopts the following form:
Figure BDA0003711798770000103
wherein x is ref Is a target state vector, N p For the prediction horizon Q, R represents the positive definite weighting matrix of the prediction states and control inputs, respectively. And P is a terminal weight matrix and is obtained by solving the Riccati equation.
Solving the optimal problem requires satisfying the nominal prediction model constraints as well as the nominal state constraints and the nominal control constraints. In the finite time domain, the optimal control problem at any time k is represented as:
Figure BDA0003711798770000104
Figure BDA0003711798770000105
Figure BDA0003711798770000106
Figure BDA0003711798770000107
Figure BDA0003711798770000108
wherein,
Figure BDA0003711798770000109
the linear feedback gain K is determined by a linear quadratic regulator.
The nominal state and nominal control inputs are constrained within a subset of the actual constraints, respectively:
Figure BDA0003711798770000111
Figure BDA0003711798770000112
and (3) state constraint to be met by the model in the last prediction interval in the prediction time domain:
Figure BDA0003711798770000113
terminal constraints
Figure BDA0003711798770000114
Satisfy the requirement of
Figure BDA0003711798770000115
And the like. Wherein A is K =A+BK,
Figure BDA0003711798770000116
Is a robust invariant set.
The optimization problem is intended to predict the state as close to the target state value as possible and the rudder angle input as small as possible. Solving the optimization problem to obtain a nominal optimal control sequence
Figure BDA0003711798770000117
And corresponding nominal state sequence
Figure BDA0003711798770000118
And sent to the controller of the lower layer as a reference instruction for assisting the predictive controller.
Step five: and designing an auxiliary predictive controller, and designing a control strategy based on the actual predictive model.
Since autonomous underwater robotic systems may be affected by disturbances, future state trajectories may differ from nominal predicted trajectories. To counteract the effects of the disturbance, the auxiliary predictive controller is designed so that the system state and control inputs are close to the nominal sequence. Solving the following optimization problem:
Figure BDA0003711798770000119
Figure BDA00037117987700001110
Figure BDA00037117987700001111
Figure BDA00037117987700001112
Figure BDA00037117987700001113
wherein
Figure BDA00037117987700001114
Estimated by a disturbance observer.
Final control signal
Figure BDA00037117987700001115
Solving two optimization problems through the fourth step and the fifth step to obtain a first control signal of the sequence
Figure BDA00037117987700001116
And acts as a rudder angle signal to the controlled object.
Step six: and measuring the system state at the next moment, taking the moment as the new current moment, and returning to the step three.
In another aspect, the present embodiment provides a system, including a data acquisition device, a calculation unit, an execution mechanism, and a driving mechanism, where the calculation unit is configured to carry the above method and control the execution mechanism and the driving mechanism after executing the method, the data acquisition device includes a posture sensor and a depth sensor, the posture sensor is configured to acquire underwater information, robot posture and inertial navigation information and perform mean filtering on the information, the depth sensor is configured to measure a height distance to a water surface, and under consideration of unknown disturbance caused by unmodeled dynamic and dynamic ocean currents, storms, and the like, a system model satisfying state and control constraints is established, and a double-layer model prediction controller is designed in combination with a disturbance observer. The upper layer designs a nominal predictive controller for a nominal model, and finds the nominal input and the nominal state so that the error between the nominal state and a reference value is minimum. And the lower layer designs an auxiliary prediction controller aiming at the actual model, and solves the control input actually acting on the autonomous underwater robot so as to compensate the error between the nominal state and the actual state. The method can ensure that the state of the autonomous underwater robot system is strictly kept in a small neighborhood of a target state to fluctuate so as to accurately realize motion control.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims (8)

1. An anti-interference motion control method of an autonomous underwater robot is characterized by comprising the following steps: the method comprises the following steps:
step 1, establishing an autonomous underwater robot dynamics and kinematics simplified linear model, converting the model into a continuous time model in a state space, and discretizing the model to obtain a discrete time model of a system;
step 2, establishing a system nominal model used as a prediction equation of a nominal model prediction controller, and converting the system state and control input constraint into a tightened state and control input constraint of a nominal system;
step 3, constructing a disturbance observer, taking a disturbance variable as an expanded state quantity, estimating a system disturbance value, and sending the estimated value to an auxiliary prediction controller;
designing a nominal model predictive controller, constructing a cost function, and solving a finite time domain optimization problem to obtain a nominal optimal control input and a corresponding nominal state;
step 5, designing an auxiliary model prediction controller, receiving nominal prediction input and output signals and a disturbance signal provided by a disturbance observer, solving optimal control aiming at an actual system model, and acting the first control quantity of a control sequence on the autonomous underwater robot system;
and 6, measuring the system state at the next moment, taking the moment as a new current moment, and returning to the step 3.
2. The autonomous underwater vehicle disturbance rejection motion control method according to claim 1, characterized in that: the tightened state of the nominal system and the control input constraints in step 2 are specifically represented as:
Figure FDA0003711798760000011
Figure FDA0003711798760000012
wherein α and γ represent a reduction coefficient in the range of (0, 1).
3. The autonomous underwater robot disturbance rejection motion control method according to claim 1 or 2, characterized in that: the specific steps of constructing the disturbance observer in the step 3 are as follows:
step 31, adding the disturbance as a newly added state quantity into an uncertain system, and establishing a linear state observer as follows:
Figure FDA0003711798760000013
wherein the state estimate is
Figure FDA0003711798760000014
Outputting the estimated value
Figure FDA0003711798760000015
L, H is a matrix of the gains of the observer,
Figure FDA0003711798760000016
for disturbance estimation, β is an auxiliary variable;
step 32, calculating a state estimation error and a disturbance error:
Figure FDA0003711798760000021
Figure FDA0003711798760000022
then to e x The derivation yields:
Figure FDA0003711798760000023
obtaining the first derivative of the disturbance estimate:
Figure FDA0003711798760000024
wherein the estimate of the derivative of the disturbance
Figure FDA0003711798760000025
Step 33, the state estimation error and the disturbance estimation error are combined into an estimation error system as follows:
Figure FDA0003711798760000026
wherein G ═ e x T e w ] T
Figure FDA0003711798760000027
Representing the estimation error of the derivative of the disturbance.
4. The autonomous underwater vehicle disturbance rejection motion control method according to claim 3, characterized in that: the specific steps of designing a nominal model predictive controller, constructing a cost function, solving a finite time domain optimization problem, and obtaining a nominal optimal control input and a corresponding nominal state in the step 4 are as follows:
step 41, designing an optimal control input for each sampling time, driving the nominal system state to a target point and minimizing a cost function, wherein the constructed cost function is as follows:
Figure FDA0003711798760000028
wherein x ref Is a target state vector, N p For predicting the time domain, Q, R represents positive definite weighting matrix of prediction state and control input respectively, P is terminal weighting matrix, and is obtained by solving Riccati equation;
step 42, the nominal prediction model constraints and the nominal state constraints and nominal control constraints are satisfied, and the nominal state and nominal control are respectively constrained in the subsets of the actual constraints:
Figure FDA0003711798760000029
Figure FDA00037117987600000210
the state constraint to be satisfied by the last prediction interval in the prediction time domain is as follows:
Figure FDA00037117987600000211
terminal constraints
Figure FDA00037117987600000212
Satisfy the requirement of
Figure FDA00037117987600000213
And the like. Wherein A is K =A+BK,
Figure FDA0003711798760000031
Is a robust invariant set;
step 43, representing the optimal control problem at any time k in a limited time domain:
Figure FDA0003711798760000032
Figure FDA0003711798760000033
Figure FDA0003711798760000034
Figure FDA0003711798760000035
Figure FDA0003711798760000036
wherein,
Figure FDA0003711798760000037
the linear feedback gain K is determined by a linear quadratic regulator.
5. The autonomous underwater vehicle disturbance rejection motion control method according to claim 4, characterized in that: in the step 5, the following optimization problem is solved in a manner of solving the optimal control for the actual system model:
Figure FDA0003711798760000038
Figure FDA0003711798760000039
Figure FDA00037117987600000310
Figure FDA00037117987600000311
Figure FDA00037117987600000312
wherein
Figure FDA00037117987600000313
Figure FDA00037117987600000314
Estimated by a disturbance observer.
6. The autonomous underwater vehicle disturbance rejection motion control method of claim 5, characterized in that: the specific steps of establishing an autonomous underwater robot dynamics and kinematics simplified linear model in the step 1, converting the model into a continuous time model in a state space, and discretizing the model to obtain a discrete time model of the system are as follows:
step 11, defining a required coordinate system: the system comprises an inertial coordinate system and a satellite coordinate system, wherein the inertial coordinate system is fixed on the ground, the satellite coordinate system is fixed on the autonomous underwater robot, the E-xi eta zeta represents the inertial coordinate system, and the O-xyz represents the satellite coordinate system;
step 12, defining six-freedom-degree speed V ═ u V l p q r of the autonomous underwater robot in the satellite coordinate system] T And the position and attitude angle eta relative to the fixed coordinate system [ x y z phi theta phi DEG] T The autonomous underwater robot motion equation is as follows:
MV+C(V)V+D(V)V+g(η)=τ
Figure FDA0003711798760000041
wherein M is the sum of rigid mass and additional mass matrix, C (V) is Coriolis force and centripetal force matrix, D (V) is damping matrix, g (eta) is restoring moment, tau is propulsion system input matrix, J (eta) is Jacobian transformation matrix between inertial coordinate system and random coordinate system;
step 13, assuming that the transverse velocity v, the course angular velocity p, the roll angular velocity r and the roll angle phi of the relevant state quantities of the horizontal plane are all approximate to 0, the change of the longitudinal velocity u is smooth and stable, u is approximate to a constant, the model is decoupled only by considering the motion of the autonomous underwater robot in the vertical x-z plane, and the simplified vertical three-order depth control model is established as follows:
Figure FDA0003711798760000042
wherein z is the vertical depth under the inertial coordinate system, theta is the longitudinal inclination angle, q is the longitudinal inclination angle speed, delta is the rudder angle, I y For moment of inertia about the y-axis, M q 、M δ
Figure FDA0003711798760000048
To add a mass matrix, W is gravity, B 1 Is buoyancy, Δ q Representing the uncertainty part of the model, τ q Representing external time-varying disturbances caused by ocean currents and wind waves;
step 14, collecting position information and attitude information of the autonomous underwater robot by using a sensor, taking z, theta and q as state quantities, taking a rudder angle delta as a control input, and taking x as [ z, theta, q ]] T For describing the depth control problem of autonomous underwater robots. Converting the model into a state space equation:
Figure FDA0003711798760000043
wherein the state transition matrix
Figure FDA0003711798760000044
Input matrix
Figure FDA0003711798760000045
Discretizing a continuous time state space equation according to sampling time delta T to obtain:
x k+1 =Ax k +Bδ k +w k
wherein the state
Figure FDA0003711798760000046
Control input
Figure FDA0003711798760000047
7. The autonomous underwater vehicle disturbance rejection motion control method of claim 6, characterized in that: in step 14, it is assumed that the perturbation is bounded, and the bounded set is a convex set, which is expressed as:
Figure FDA0003711798760000051
wherein w max Is the perturbation upper bound.
8. A system to which the disturbance rejection motion control method of the autonomous underwater robot of any of claims 1 to 7 is applied, characterized in that: the system comprises a data acquisition device, a calculation unit, an execution mechanism and a driving mechanism, wherein the calculation unit is used for carrying the method, and controls the execution mechanism and the driving mechanism after the method is executed, the data acquisition device comprises a posture sensor and a depth sensor, the posture sensor is used for acquiring underwater information, robot posture and inertial navigation information and carrying out mean value filtering on the information, and the depth sensor is used for measuring the height distance to the water surface.
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