CN115291622A - Obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method - Google Patents

Obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method Download PDF

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CN115291622A
CN115291622A CN202210595527.8A CN202210595527A CN115291622A CN 115291622 A CN115291622 A CN 115291622A CN 202210595527 A CN202210595527 A CN 202210595527A CN 115291622 A CN115291622 A CN 115291622A
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unmanned aerial
aerial vehicle
vector
obstacle
sliding mode
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钱默抒
吴柱
刘国勇
展凤江
马传焱
葛贤坤
诸庆生
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Nanjing Tech University
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Abstract

The invention discloses an obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method based on an artificial potential field method and a cerebellum model neural network, which is used for unmanned aerial vehicle formation obstacle avoidance control and processing the influence of external interference and internal parameter uncertainty. The adverse effect of lumped interference is approximately estimated and compensated by introducing a cerebellum model neural network, and a self-adaptive fractional order sliding mode controller is designed based on an artificial potential field method. The method realizes the stability and good obstacle avoidance performance of the unmanned aerial vehicle formation closed-loop tracking control system, and verifies that the method has certain effectiveness and good performance through a simulation example.

Description

Obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method
Technical Field
The invention relates to the field of control of aerial unmanned aerial vehicles, in particular to a distributed formation fractional order sliding mode control problem of an obstacle avoidance unmanned aerial vehicle considering lumped interference influence.
Background
In recent years, with the development of unmanned aerial vehicles becoming mature, a single unmanned aerial vehicle can not meet the requirements of some complex tasks gradually, and researchers begin to research the formation cooperative control of multiple unmanned aerial vehicles. Compared with a single unmanned aerial vehicle, the unmanned aerial vehicle formation has great advantages in military or civil fields such as loading and transportation, wildfire monitoring, disaster relief, battlefield reconnaissance, attack and the like. The unmanned aerial vehicle formation cooperative control also becomes more complex and difficult due to the influence of complex factors such as external interference, obstacles and uncertainty of internal parameters. Therefore, under the conditions of external interference, uncertainty of internal parameters and existence of obstacles, the rapid tracking control and obstacle avoidance problem of unmanned aerial vehicle formation causes extensive attention of scholars.
Aiming at the problem of obstacle avoidance of unmanned aerial vehicle formation, numerous scholars at home and abroad propose various algorithms. Patent CN112180954A invented an unmanned aerial vehicle obstacle avoidance method based on artificial potential field, and the main contribution is to provide additional transverse obstacle avoidance control force, so as to solve the adverse effect of local minimum value on unmanned aerial vehicle obstacle avoidance, but the method can not make unmanned aerial vehicle get back to the desired position immediately after avoiding the obstacle. Patent CN111290429A discloses an unmanned aerial vehicle formation and obstacle avoidance control method thereof based on a consistency algorithm and an artificial potential field method, and the influence of a local minimum value can be eliminated by introducing auxiliary traction acceleration information perpendicular to the moving direction of an obstacle. However, in the obstacle avoidance process, the unmanned aerial vehicle position tracking error and the speed tracking error based on the method fluctuate greatly, and the stability of formation is influenced. Furthermore, neither of the above two approaches takes into account the effect of lumped disturbances (external disturbances and internal parameter uncertainties) on the formation control system.
In view of the problem that the external interference and the parameter uncertainty affect the control performance of the nonlinear system, a great deal of research has been carried out by many scholars, and the research results show that the neural network can well estimate and compensate the external interference and the parameter uncertainty. Meanwhile, the improved artificial potential field method can solve the problem of local minimum values and realize formation cooperative obstacle avoidance. In addition, the designed fractional order sliding mode controller can ensure the stability and the global robustness of a closed-loop formation control system, and solves the problem that the traditional obstacle avoidance algorithm cannot return to the expected position immediately after avoiding the obstacle.
Disclosure of Invention
In view of the defects in the prior art, the invention provides a distributed formation fractional order sliding mode control method for an obstacle avoidance unmanned aerial vehicle, which mainly comprises the following steps:
step 1, establishing an ith unmanned aerial vehicle dynamics model as follows:
Figure BSA0000273886590000011
wherein i is the number of unmanned aerial vehicles in the formation, i =1 i ,ψ i
Figure BSA0000273886590000012
Respectively representing the airspeed, the pitch angle, the course angle and x of the unmanned aerial vehicle i ,y i And z i Is the three-dimensional coordinate of the unmanned plane, m i Is the fuselage mass, g is the gravitational acceleration, and the control inputs to the system are
Figure BSA0000273886590000021
θ i Showing the roll angle, T i Is engine thrust, u xi ,u yi ,u zi Control inputs in the X, Y, Z-axis directions, respectively, n i Is the coefficient of dynamic load, D i Is the resistance;
step 2, converting the unmanned aerial vehicle dynamics model in the step 1 into a state space equation, and describing a nonlinear model considering lumped interference as follows:
Figure BSA0000273886590000022
wherein p is i =[x i ,y i ,z i ] T In the form of a position vector, the position vector,
Figure BSA0000273886590000023
is a velocity vector, d si For lumped interference, G and R i Can be obtained by the following formula:
G=[0 0 -g] T
Figure BSA0000273886590000024
step 3, utilizing a cerebellum model neural network to realize the online estimation of the lumped interference, and the specific process is as follows:
the architecture of the cerebellum model neural network comprises an input space, an association memory space, a receiving domain space, a weight memory space and an output space. The specific introduction is as follows:
(1) Input space: for input I = [ ] 1 ,I 2 ,...,I q ] T ∈R q I is a continuous and q-dimensional input space;
(2) Associating memory space: several different elements are stacked into a block, and each block performs an accept domain basis function, here a gaussian function is used as the basis function, which can be expressed as:
Figure BSA0000273886590000025
wherein,
Figure BSA0000273886590000026
is the jth input I j The gaussian function corresponding to the k-th block,
Figure BSA0000273886590000027
and σ jk Respectively corresponding mean value and variance of the Gaussian function, and M is the number of blocks;
(3) Receiving a domain space: within this space, the multidimensional receive domain basis function is defined as:
Figure BSA0000273886590000028
wherein, L represents the L-th receiving domain base function, N is the number of the receiving domain base functions, and the multidimensional receiving domain base function is represented by a vector as follows:
Figure BSA0000273886590000029
wherein,
Figure BSA00002738865900000210
and σ can be represented by the following vector:
Figure BSA00002738865900000211
σ=[σ 11 ,...,σ q1 ,σ 12 ,...,σ q2 ,...,σ 1M ,...,σ qM ] T
(4) Weight memory space: the N components of the weight memory space that receive each location of the domain space to a particular adjustable value can be represented as:
W=[w 1 ,...,w L ,...,w N ] T
wherein w L Representing the connection weight of the L-th receiving domain basis function;
(5) An output space: the output of the entire cerebellar model neural network can be expressed as:
Figure BSA0000273886590000031
the output of the cerebellar model neural network can be expressed as:
Figure BSA0000273886590000032
cerebellum model neural network on-line approximation lumped interference d si The expression of (a) is:
Figure BSA0000273886590000033
wherein epsilon is an approximation error,
Figure BSA0000273886590000034
W *T and phi * The optimal parameter vectors of W and phi respectively,
Figure BSA0000273886590000035
and σ * Are respectively as
Figure BSA0000273886590000036
Optimal parameter vector of sum σ, d si * Is d si The optimal vector of (2);
the cerebellum model neural network estimation error can be expressed as:
Figure BSA0000273886590000037
wherein,
Figure BSA0000273886590000038
Figure BSA0000273886590000039
and
Figure BSA00002738865900000310
the estimated values of W and phi respectively;
in order to achieve a good estimate of the lumped interference, taylor expansion linearization technique is used to transform the nonlinear function into a partially linear form, i.e.:
Figure BSA00002738865900000311
wherein,
Figure BSA00002738865900000312
Figure BSA00002738865900000313
and
Figure BSA00002738865900000314
are respectively as
Figure BSA00002738865900000315
And σ, H is a higher order term, and has:
Figure BSA00002738865900000316
Figure BSA00002738865900000317
and is
Figure BSA00002738865900000318
And
Figure BSA00002738865900000319
is defined as:
Figure BSA00002738865900000320
Figure BSA00002738865900000321
according to the formula:
Figure BSA00002738865900000322
wherein the uncertainty term
Figure BSA00002738865900000323
Representing an approximation error term and assuming it is bounded, i.e., | | Δ | | < δ, δ being a positive constant, | | | Δ | | being the Euclidean norm of Δ;
The cerebellum model neural network self-adaptation law is obtained by a Lyapunov stability analysis method as follows:
Figure BSA0000273886590000041
Figure BSA0000273886590000042
Figure BSA0000273886590000043
wherein λ is max Is a matrix
Figure BSA0000273886590000044
L is the laplacian matrix, Λ is the adjacency matrix of the leader,
Figure BSA0000273886590000045
is the product of Crohn's disease, I 3 Is a 3 x 3 identity matrix, s is a fractional order global integral sliding mode as designed herein,
Figure BSA0000273886590000046
η σ ,ζ 1 ,ζ 2 and ζ 3 Are all normal numbers, W 0
Figure BSA0000273886590000047
σ 0 Are each W *
Figure BSA0000273886590000048
σ * The initial estimate of (a);
step 4, designing a self-adaptive fractional order sliding mode controller based on an artificial potential field method;
firstly, it needs to be explained that the implementation of the control system of the present invention requires that the formation of unmanned aerial vehicles meets the designed formation configuration during the flight process, and therefore, the expected position of the ith unmanned aerial vehicle should meet:
Figure BSA0000273886590000049
wherein
Figure BSA00002738865900000410
A virtual leader position is represented by a virtual leader location,
Figure BSA00002738865900000411
representing a desired position of each drone relative to the virtual leader;
the graph theory is one of the important components in formation flight, and the invention adopts an undirected graph
Figure BSA00002738865900000412
Wherein
Figure BSA00002738865900000413
A set of nodes of the graph G is represented,
Figure BSA00002738865900000414
a set of edges is represented that is,
Figure BSA00002738865900000415
representing an adjacency matrix; in an undirected graph, we can get:
Figure BSA00002738865900000416
Figure BSA00002738865900000417
and a ij =a ji (ii) a When the ith unmanned aerial vehicle can receive the information of the jth unmanned aerial vehicle, there are (j, i) epsilon and a ij =1, otherwise, a ij =0; definition of
Figure BSA00002738865900000418
Is a degree matrix, wherein
Figure BSA00002738865900000419
Thus, the Laplacian matrix is
Figure BSA00002738865900000420
Figure BSA00002738865900000421
For a communication topology with one leader 0 and n followers, this can be represented as:
Figure BSA00002738865900000422
wherein
Figure BSA00002738865900000423
Representing a set of nodes; the adjacency matrix for the leader is Λ = diag { λ 1 ,...,λ n }. λ if the ith follower can receive the leader's information i > 0, otherwise, λ i =0;
An adaptive fractional order sliding mode controller u designed based on an artificial potential field method is composed of a track tracking controller and a collaborative obstacle avoidance controller, namely:
u=u α +u β
wherein u is an adaptive fractional order sliding mode controller α For trajectory tracking controllers u β A cooperative obstacle avoidance controller;
(1) Trajectory tracking controller design
Position tracking error vector e of the ith unmanned aerial vehicle i (t) and velocity tracking error vector
Figure BSA00002738865900000424
Comprises the following steps:
Figure BSA00002738865900000425
wherein p is i (t) and
Figure BSA00002738865900000426
respectively actual position vector and expected position vector of the unmanned plane, v i (t) and
Figure BSA00002738865900000427
respectively an actual speed vector and an expected speed vector of the unmanned aerial vehicle, and t is time;
distributed coupled position tracking error of unmanned aerial vehicle formation
Figure BSA00002738865900000428
Can be described as:
Figure BSA00002738865900000429
wherein λ i Elements of the adjacency matrix Λ, a, being the leader ij Is a contiguous matrix
Figure BSA00002738865900000430
Element of (e) j (t) is a position tracking error vector of the jth unmanned aerial vehicle, j is the number of the unmanned aerial vehicle, and j = 1.
The above formula can be rewritten as:
Figure BSA0000273886590000051
wherein l ii And l ij Are all elements of the laplace matrix L;
thus, the distributed coupled position tracking error vector is:
Figure BSA0000273886590000052
wherein,
Figure BSA0000273886590000053
distributed coupled velocity tracking error vector from above
Figure BSA0000273886590000054
Comprises the following steps:
Figure BSA0000273886590000055
error vector for distributed coupled velocity tracking
Figure BSA0000273886590000056
Designing a fractional order global integral sliding mode:
Figure BSA0000273886590000057
wherein s is fractional order global integral sliding mode, D Representing distributed coupled velocity tracking error vectors
Figure BSA0000273886590000058
Is a fractional order, c is a normal number, and h (t) can be expressed as:
Figure BSA0000273886590000059
where k is a normal number, where k is,
Figure BSA00002738865900000510
h (0) is the initial value of h (t),
Figure BSA00002738865900000511
is the initial distributed coupled velocity tracking error vector,
Figure BSA00002738865900000512
is a fractional order integral value at time t =0;
and (5) obtaining the following by derivation of s:
Figure BSA00002738865900000513
in order to effectively reduce the chattering problem in the sliding mode control and improve the rate of tracking error convergence, the approach law used herein is:
Figure BSA00002738865900000514
wherein eta 1 ,η 2
Figure BSA00002738865900000517
Are all design parameters and are all normal numbers, and tanh (·) is a hyperbolic tangent function;
according to the above, the trajectory tracking controller is designed to:
Figure BSA00002738865900000515
wherein,
Figure BSA00002738865900000516
lumped interference estimated for a cerebellar model neural network;
(2) Design of cooperative obstacle avoidance controller
Unlike the conventional artificial potential field method, the controller provided herein designs a virtual agent β on the surface of the obstacle, and keeps the speed of the drones in the formation consistent with the speed of the virtual agent β. In addition, a repulsion function is designed between the unmanned aerial vehicle and the virtual agent beta, and an obstacle avoidance prediction mechanism and a concave-convex function are introduced into the controller;
assume that the obstacle has a radius r o The center of the sphere is O β Thus, the state information of the virtual agent β can be derived by the following equation:
p i,β =τp i +(I-τ)O β ,v i,β =τPv i
wherein p is i,β ,v i,β Are respectively the ithThe position and speed of the virtual agent beta corresponding to the unmanned aerial vehicle,
Figure BSA0000273886590000061
Figure BSA0000273886590000062
I 3 is a 3 × 3 identity matrix, and | l | · | |, is the euclidean norm;
in formation flight, the ith drone not only shares detected obstacle information, but also receives obstacle information from neighboring drones. Comparing the obtained obstacle information, and selecting a pair of obstacle information, wherein the specific selection principle is as follows:
1) When the speed values of a plurality of pairs of obstacle information are different, according to the maximum speed value max (| | v) i,β | |) to select corresponding obstacle information;
2) When the speed values of a plurality of pairs of obstacle information are the same, according to the minimum distance value min (| | p) i -p i,β | |) to select corresponding obstacle information;
3) If the two conditions are not met, randomly selecting a pair of obstacle information;
therefore, the cooperative obstacle avoidance controller is designed as follows:
Figure BSA0000273886590000063
wherein,
Figure BSA0000273886590000064
represents a cooperative obstacle avoidance controller, belongs to β ,c p ,c v Are all normal numbers, p γ,β And v γ,β Is the position and velocity, k, of the virtual agent beta selected according to the above principles β For an obstacle avoidance prediction mechanism, whether the unmanned aerial vehicle needs to avoid the obstacle when detecting the obstacle is determined,
Figure BSA0000273886590000065
is a continuous lightSmooth concave-convex function, which can change the degree of influence of repulsion on the drone, k β And
Figure BSA0000273886590000066
can be obtained by the following formula:
Figure BSA0000273886590000067
Figure BSA0000273886590000068
wherein r is i Radius of unmanned plane, r d Is the detection radius of the unmanned aerial vehicle, r o Radius of obstacle, O β Is the center of the obstacle, d io Distance between unmanned aerial vehicle and obstacle, d io =||p i -O β ||,
Figure BSA0000273886590000069
Figure BSA00002738865900000610
Determining the maximum range of the unmanned aerial vehicle influenced by the repulsive force field,
Figure BSA00002738865900000611
and 5, verifying the stability of the unmanned aerial vehicle formation closed-loop control system.
According to the adaptive fractional order sliding mode controller, the stability of a formation closed-loop control system under the influence of lumped interference needs to be proved.
Defining a lyapunov function V:
Figure BSA00002738865900000612
deriving V as:
Figure BSA00002738865900000613
Figure BSA0000273886590000071
after equivalent transformation, the method is easy to obtain:
Figure BSA0000273886590000072
Figure BSA0000273886590000073
the above formula can be described as:
Figure BSA0000273886590000074
wherein χ and b are normal numbers, and are obtained by the following formula:
Figure BSA0000273886590000075
Figure BSA0000273886590000076
we can obtain from the above equation:
Figure BSA0000273886590000077
the following is obtained from the above equation: according to the Lyapunov stability condition, all error signals are bounded, and therefore the closed loop control system is asymptotically stable.
Compared with the prior art, the beneficial effects of the invention are embodied in the following aspects:
(1) The obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method based on the artificial potential field method and the cerebellum model neural network has the advantages of being high in tracking speed, control accuracy and the like, and ensures that formation can be quickly restored to an expected position after obstacle avoidance is completed;
(2) According to the distributed formation fractional order sliding mode control method of the obstacle avoidance unmanned aerial vehicle based on the artificial potential field method and the cerebellum model neural network, the adverse effect of lumped interference is considered;
(3) According to the distributed formation fractional order sliding mode control method of the unmanned aerial vehicle for avoiding the obstacles based on the artificial potential field method and the cerebellum model neural network, the problem of local minimum values can be solved, and formation obstacle avoidance can be successfully realized.
Drawings
In order to better embody the advantages of the method designed by the invention, aiming at the problem of obstacle avoidance of the unmanned aerial vehicle, the obstacle avoidance method of the traditional artificial potential field method is selected to be compared with the distributed formation fractional order sliding mode control method of the obstacle avoidance unmanned aerial vehicle designed by the invention, and the result shows that the method provided by the invention has better tracking performance and obstacle avoidance performance.
Fig. 1 is a communication topology diagram of formation of unmanned aerial vehicles according to the present invention;
FIG. 2 is a comparison graph of three-dimensional trajectory simulation;
FIG. 3 is a comparison graph of x-axis position tracking error simulation;
FIG. 4 is a comparison graph of position tracking error simulation in the y-axis;
FIG. 5 is a comparison graph of position tracking error simulation for the z-axis.
Detailed Description
The present invention will be explained in further detail below with reference to the drawings and embodiments. The specific embodiments described herein are merely illustrative of the invention and do not delimit the invention.
In order to enable people in the research field to better understand the implementation of the method, matlab2017a software is used for carrying out unmanned aerial vehicle formation tracking control and obstacle avoidance simulation so as to verify the reliability of the unmanned aerial vehicle formation tracking control and obstacle avoidance simulation. The simulation results of a formation consisting of one virtual leader and four identical drones are presented. The laplacian matrix L of the unmanned aerial vehicle formation communication topological graph is as follows:
Figure BSA0000273886590000081
herein, the initial velocity and position of the virtual navigator are respectively: v. of L (0)=50m/s,
Figure BSA0000273886590000082
Flight path is [50t,200, 400 ]] T And m is selected. The maximum speed of the unmanned aerial vehicle is 60m/s, and the maximum acceleration is 10m/s 2 Acceleration of gravity g =9.8m/s 2 . The initial state of the unmanned aerial vehicle is shown in table 1, and each design parameter of the controller is selected as follows: k =0.01, η 1 =η 2 =1,
Figure BSA0000273886590000083
β =1,c v =6,c p =5,c=1,λ i =1,
Figure BSA0000273886590000086
r o =60,r d =100, the expected position of each drone relative to the virtual pilot is:
Figure BSA0000273886590000084
to simplify the shape of the obstacle, we assume the obstacle to be a radius r d =60m centered on O β =[1000,200,400] T m, a spherical object. Meanwhile, let the lumped interference be: d is a radical of si =0.12[sin0.5t,sin0.5t,sin0.5t] T The simulation step size is 0.1s.
Table 1 initial state of unmanned plane
Figure BSA0000273886590000085
The result shows that the distributed formation fractional order sliding mode control method for the obstacle avoidance unmanned aerial vehicle can realize the rapid tracking of the expected track within 0-5 s, and can immediately recover to the expected track after the obstacle avoidance is finished. Compared with the traditional artificial potential field method, the method provided by the invention not only considers the adverse effect of lumped interference, but also can solve the problem of local minimum value and realize obstacle avoidance. Through comparison of the simulation results, the effectiveness and feasibility of the distributed formation fractional order sliding mode control method for the obstacle avoidance unmanned aerial vehicle are verified, and the method is in line with expectation.
Finally, it is recognized that the invention is not limited to the specific embodiments described above, but rather is intended to cover all modifications, equivalents, improvements, and equivalents falling within the spirit and scope of the invention.

Claims (3)

1. A distributed formation fractional order sliding mode control method of an obstacle avoidance unmanned aerial vehicle based on an artificial potential field method and a cerebellum model neural network comprises the following steps:
step 1, establishing an ith unmanned aerial vehicle dynamics model:
Figure FSA0000273886580000011
wherein i is the number of the unmanned aerial vehicles in the formation, i =1, \ 8230, n, n is the number of the unmanned aerial vehicles in the formation, V i ,ψ i
Figure FSA0000273886580000012
Respectively representing the airspeed, pitch angle, course angle, x of the unmanned aerial vehicle i ,y i And z i Three-dimensional coordinates for unmanned aerial vehicles, m i Is the fuselage mass, g is the gravitational acceleration, and the control inputs to the system are
Figure FSA0000273886580000013
θ i Showing the roll angle, T i Is hairThrust of motive machine u xi ,u yi ,u zi Control inputs in the X-axis, Y-axis, Z-axis directions, n i Is the dynamic load coefficient, D i Is a resistance force;
step 2, converting the unmanned aerial vehicle dynamic model in the step 1 into a state space equation, and simultaneously considering modeling of lumped interference:
definition of p i =[x i ,y i ,z i ] T And
Figure FSA0000273886580000014
for the position vector and velocity vector of the ith drone, respectively, the nonlinear dynamical model considering lumped interference can be expressed as:
Figure FSA0000273886580000015
wherein d is si For lumped interference, G and R i Obtained by the following formula:
G=[0 0 -g] T
Figure FSA0000273886580000016
and 3, estimating the lumped interference by using the cerebellum model neural network according to the step 2, wherein the specific steps are as follows:
the relation between the input and the output of the cerebellum model neural network is as follows:
Figure FSA0000273886580000017
wherein y is the output vector, I is the input vector, W is the connection weight vector of the receiving domain, phi is the multi-dimensional receiving domain basis function vector,
Figure FSA0000273886580000018
and σ are each a Gaussian functionA value and a variance;
cerebellum model neural network on-line approximation lumped interference d si The expression of (c) is:
Figure FSA0000273886580000019
where ε is the approximation error, W * ,φ *
Figure FSA00002738865800000110
σ * Are respectively W, phi,
Figure FSA00002738865800000111
optimum parameter vector of sigma, W *T Is W * Transpose of (d) si * Is d si The optimal vector of (2);
the cerebellum model neural network estimation error can be expressed as:
Figure FSA00002738865800000112
wherein,
Figure FSA0000273886580000021
are respectively W, phi, d si An estimated value of (d);
and (3) converting the nonlinear function into a partial linear form by using a Taylor expansion linearization technique, namely:
Figure FSA0000273886580000022
wherein,
Figure FSA0000273886580000023
and
Figure FSA0000273886580000024
are respectively as
Figure FSA0000273886580000025
And σ, H is a higher order term, and has:
Figure FSA0000273886580000026
Figure FSA0000273886580000027
and is
Figure FSA0000273886580000028
And
Figure FSA0000273886580000029
is defined as:
Figure FSA00002738865800000210
Figure FSA00002738865800000211
according to the formula:
Figure FSA00002738865800000212
wherein the uncertainty term
Figure FSA00002738865800000213
Representing an approximation error term and assuming that the approximation error term is bounded, namely | | | delta | is less than or equal to delta, delta is a normal number, and | | | delta | is an Euclidean norm of delta;
the cerebellum model neural network self-adaptation law is obtained by a Lyapunov stability analysis method as follows:
Figure FSA00002738865800000214
Figure FSA00002738865800000215
Figure FSA00002738865800000216
wherein λ is max Is a matrix
Figure FSA00002738865800000217
L is the laplacian matrix, a is the adjacency matrix of the leader,
Figure FSA00002738865800000218
is the product of Crohn's disease, I 3 Is a 3 x 3 identity matrix, s is a fractional order global integral sliding mode as designed herein,
Figure FSA00002738865800000219
η σ ,ζ 1 ,ζ 2 and ζ 3 Are all normal numbers, W 0
Figure FSA00002738865800000220
σ 0 Are each W *
Figure FSA00002738865800000221
σ * The initial estimate of (a);
step 4, designing a self-adaptive fractional order sliding mode controller based on an artificial potential field method according to the step 2;
and 5, verifying the stability of the unmanned aerial vehicle formation closed-loop control system.
2. The obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method according to claim 1, characterized in that the step 4 of designing an adaptive fractional order sliding mode controller based on an artificial potential field method comprises the following steps:
an adaptive fractional order sliding mode controller designed based on an artificial potential field method is composed of a track tracking controller and a collaborative obstacle avoidance controller, namely:
u=u α +u β
wherein u is an adaptive fractional order sliding mode controller α For trajectory tracking controllers u β A cooperative obstacle avoidance controller;
(1) Trajectory tracking controller design
Position tracking error vector e of ith unmanned aerial vehicle i (t) and velocity tracking error vector
Figure FSA0000273886580000031
Comprises the following steps:
Figure FSA0000273886580000032
wherein p is i (t) and
Figure FSA0000273886580000033
respectively actual position vector and expected position vector of the unmanned plane, v i (t) and
Figure FSA0000273886580000034
respectively an actual speed vector and an expected speed vector of the unmanned aerial vehicle, and t is time;
distributed coupled position tracking error of unmanned aerial vehicle formation
Figure FSA0000273886580000035
Can be described as:
Figure FSA0000273886580000036
wherein λ i Elements of the adjacency matrix Λ, a, being the leader ij To follow up a neighbor matrix
Figure FSA0000273886580000037
Element of (e) j (t) is a position tracking error vector of a jth unmanned aerial vehicle, j is the number of the unmanned aerial vehicle, and j =1, \ 8230;, n;
the above formula can be rewritten as:
Figure FSA0000273886580000038
wherein l ii And l ij Are all elements of the laplace matrix L;
thus, the distributed coupled position tracking error vector may be described as:
Figure FSA0000273886580000039
wherein,
Figure FSA00002738865800000310
distributed coupled velocity tracking error vector from above
Figure FSA00002738865800000311
Comprises the following steps:
Figure FSA00002738865800000312
error vector for distributed coupled velocity tracking
Figure FSA00002738865800000313
Designing a fractional order global integral sliding mode:
Figure FSA00002738865800000314
wherein s is a fractional order global integral sliding mode, D Representing distributed coupled velocity tracking error vectors
Figure FSA00002738865800000315
Is given by a fractional integral of (a), α ∈ (0, 1) is the fractional order, c is a positive number, and h (t) can be expressed as:
Figure FSA00002738865800000316
where k is a normal number, where k is,
Figure FSA00002738865800000317
h (0) is the initial value of h (t),
Figure FSA00002738865800000318
is the initial distributed coupling velocity tracking error vector,
Figure FSA00002738865800000319
is a fractional order integral value at time t =0;
in order to effectively reduce the buffeting problem in sliding mode control and improve the rate of tracking error convergence, the approach law used herein is as follows:
Figure FSA00002738865800000320
wherein eta 1 ,η 2
Figure FSA00002738865800000321
Are all normal numbers, and tanh (·) is a hyperbolic tangent function;
according to the above, the trajectory tracking controller is designed to:
Figure FSA0000273886580000041
wherein,
Figure FSA0000273886580000042
lumped interference estimated for a cerebellar model neural network;
(2) Design of cooperative obstacle avoidance controller
Different from the traditional artificial potential field method, the controller provided by the invention designs a virtual intelligent body beta on the surface of the barrier, keeps the speed of the unmanned aerial vehicle in formation consistent with that of the virtual intelligent body beta, designs a repulsion function between the unmanned aerial vehicle and the virtual intelligent body beta, and introduces an obstacle avoidance prediction mechanism and a concave-convex function into the controller;
assume that the obstacle has a radius r o The center of the sphere is O β The state information of the virtual agent β can therefore be derived from the following equation:
p i,β =τp i +(I 3 -τ)O β ,v i,β =τPv i
wherein p is i,β ,v i,β Respectively the position and the speed of the virtual agent beta corresponding to the ith unmanned aerial vehicle,
Figure FSA0000273886580000043
Figure FSA0000273886580000044
I 3 is a 3 × 3 identity matrix, and | | · | | is an euclidean norm;
in formation flight, the ith unmanned aerial vehicle not only needs to share detected obstacle information, but also receives obstacle information from adjacent unmanned aerial vehicles, and a pair of obstacle information is selected by comparing the obtained obstacle information, wherein the specific selection principle is as follows:
1) When the speed values of a plurality of pairs of obstacle information are different, according to the maximum speed value max (| | v) i,β | |) to select corresponding obstacle information;
2) When the speed values of a plurality of pairs of obstacle information are the same, according to the minimum distance value min (| | p) i -p i,β | |) to select corresponding obstacle information;
3) If the two conditions are not met, randomly selecting a pair of obstacle information;
therefore, the cooperative obstacle avoidance controller is designed as follows:
Figure FSA0000273886580000045
wherein i is the number of the unmanned aerial vehicle,
Figure FSA0000273886580000046
a cooperative obstacle avoidance controller is shown,
Figure FSA00002738865800000411
c p ,c v are all normal numbers, p γ,β And v γ,β Is the position and velocity, k, of the virtual agent beta selected according to the above principles β For an obstacle avoidance prediction mechanism, which determines whether the unmanned aerial vehicle needs to avoid an obstacle when detecting an obstacle, ρ (z) is a continuous smooth concave-convex function which can change the influence degree of repulsion on the unmanned aerial vehicle, k β And ρ (z) can be obtained by the following formula:
Figure FSA0000273886580000047
Figure FSA0000273886580000048
wherein r is i Radius of unmanned plane, r d Radius of detection for unmanned aerial vehicle, r o Radius of obstacle, O β Is the center of the obstacle, d io Is the distance between the drone and the obstacle, d io =||p i -O β ||,
Figure FSA0000273886580000049
Determining the maximum range of the unmanned aerial vehicle influenced by the repulsive force field,
Figure FSA00002738865800000410
3. the obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method according to claim 1, wherein the process of verifying the stability of the unmanned aerial vehicle formation closed-loop control system in step 5 is as follows:
defining the Lyapunov function V as:
Figure FSA0000273886580000051
deriving V as:
Figure FSA0000273886580000052
after equivalent transformation, it is easy to obtain:
Figure FSA0000273886580000053
Figure FSA0000273886580000054
the above formula can be described as:
Figure FSA0000273886580000055
wherein χ and b are normal, and can be obtained by the following formula:
Figure FSA0000273886580000056
Figure FSA0000273886580000057
the above inequality equation can be rewritten as:
Figure FSA0000273886580000058
the following is obtained from the above equation: according to the Lyapunov stability condition, all error signals are bounded, and therefore the closed loop control system is asymptotically stable.
CN202210595527.8A 2022-05-27 2022-05-27 Obstacle avoidance unmanned aerial vehicle distributed formation fractional order sliding mode control method Pending CN115291622A (en)

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