Disclosure of Invention
The invention aims to provide a robust trajectory planning scheme of an unmanned aerial vehicle in a non-deterministic interference environment aiming at the defects of the prior art, so that the unmanned aerial vehicle reduces the interference of an external radiation source on the premise of meeting the flight speed/acceleration constraint and the maximum flight energy consumption constraint, and reasonably plans the flight trajectory of the unmanned aerial vehicle, thereby improving the reliability of received signals.
In order to realize the purpose of the invention, the technical scheme is as follows:
an unmanned aerial vehicle robust trajectory planning method under a non-determined interference environment is characterized by comprising the following steps:
s1: establishing an unmanned aerial vehicle trajectory planning system model;
s2: defining an unmanned aerial vehicle robust trajectory planning problem P1 according to a system model;
s3: introducing base station distance vectors
Wherein the nth element represents the distance of the drone from the control station at time n; interference power vector
Wherein the nth element represents the total power of the drone interfered by the ground radiation source at time n; interference distance matrix
Wherein the (m, n) th element represents the distance of the drone from the mth ground radiation source at time instant n. Problem P1 is transformed into equivalent problem P2;
s4: converting the problem P2 into an equivalent problem P3 by using an S-Procedure algorithm;
s5: converting the problem P3 approximation process into a convex problem P4;
s6: and solving an optimization target based on the unmanned aerial vehicle trajectory planning model P4 to obtain the optimal flight trajectory of the unmanned aerial vehicle.
S1 specifically includes:
s1.1, setting the flying height of the unmanned aerial vehicle as H and the flying time as T, and using a preset starting point { xI,yI,H}(xI,yIAbscissa and ordinate representing start point) to a specified end point { xF,yFH flight (x)F,yFAbscissa and ordinate representing the endpoint); the ground has 1 control station with height of 0 and horizontal position of ws=[xs,ys](xs,ysHorizontal and vertical coordinates representing a control station); the ground has M radiation sources, the height is 0, and the horizontal position is wj,m=[xj,m,yj,m](xj,m,yj,mHorizontal and vertical coordinates representing a ground radiation source); the relationship between the estimated position/power and the actual position/power of the radiation source is expressed as:
wherein
And
indicating the estimated position and power of the m-th radiation source, Δ w
j,mAnd Δ p
j,mRepresenting the estimated error of the mth radiation source position and power,
and xi
mRepresents the upper error bound, A, of the mth radiation source
j,mAnd psi
j,mIndicating the error range of the position and power of the mth radiation source.
S1.2, the flight time T is averagely divided into N moments, and the length delta of the adjacent moments is equal to T/N; let the minimum flying speed of the unmanned aerial vehicle be uminMaximum flying speed of umaxMaximum acceleration of amax(ii) a At time n, the horizontal coordinate of the unmanned aerial vehicle is q [ n ]]=[x[n],y[n]](x[n],y[n]Abscissa and ordinate representing position), and a velocity u [ n ]]=[ux[n],uy[n]](ux[n],uy[n]Transverse and longitudinal components of velocity), and acceleration is a [ n ]]=[ax[n],ay[n]](ax[n],ay[n]Is the lateral and longitudinal components of acceleration); the flight constraints of a drone are expressed as:
u[n]=u[n-1]+a[n-1]δ,n=2,3,...,N, (3b)
q[N]=qF,u[N]=uF, (3d)
wherein q isI、uIAnd aIRespectively representing the position, the speed and the acceleration of the unmanned aerial vehicle at the initial moment; q. q.sFAnd uFRespectively representing the final position and the final speed of the unmanned aerial vehicle;
s1.3 at the nth moment, the distances from the unmanned aerial vehicle to the control station and the ground radiation source are respectively expressed as
Then the channel gain from the drone to the ground control station and the ground radiation source is:
wherein beta is0Expressed as the channel gain when the distance is 1;
s1.4 the total energy consumption required by the unmanned aerial vehicle in the flight process is as follows:
wherein c is
1And c
2Represents the relevant constant of the hardware of the unmanned aerial vehicle, g represents the gravity acceleration,
representing the consumption of flight kinetic energy of the drone, J represents the mass of the drone.
S2 specifically includes:
at the nth moment, the received signal-to-noise ratio under the worst condition of the unmanned aerial vehicle is as follows:
where M is the number of ground radiation sources, p0Uplink transmission power, sigma, for ground control station to drone2Representing additive white gaussian noise. The method is popularized to the whole flight process, the maximum average signal-to-noise ratio of the unmanned aerial vehicle receiving the worst condition is taken as a target, and the trajectory planning problem is expressed as follows:
u[n]=u[n-1]+a[n-1]δ,n=2,3,...,N, (8d)
q[N]=qF,u[N]=uF, (8f)
wherein Γ is the maximum flight energy consumption constraint of the drone.
S3 specifically includes:
power p of radiation source
j,mGet
To eliminate Δ p in the objective function
j,mAnd (4) variable quantity. Introducing base station distance vector by adopting redundancy variable method
Wherein the nth element represents the distance of the drone from the control station at time n; interference power vector
Wherein the nth element represents the total power of the drone interfered by the ground radiation source at time n; interference distance matrix
Wherein the (m, n) th element represents the distance of the drone from the mth ground radiation source at time instant n. Problem P1 is transformed into equivalent problem P2 as follows:
(8b)-(8i) (9e)
s4 specifically includes:
using S-Procedure algorithm (algorithm existing in the field), reference constraint matrix
Wherein the (m, n) th element represents the constraint of the drone at time instant n with respect to the mth ground radiation source. The semi-infinite constraint (9d) is equivalently converted into the following constraint:
wherein
And is
Wherein
And
a horizontal and vertical coordinate representing the estimated position of the mth radiation source;
reintroducing n-dimensional velocity vector
Wherein the nth element represents the speed of the drone at time n; the trajectory plan P2 translates into an equivalence problem P3 as follows:
(8c)-(8h),(9b),(9c),(10),(11)(12f)
s5 specifically includes:
at a given kth iteration point (I [ n ])](k),L[n](k)) And (3) performing first-order Taylor expansion on the non-convex function to obtain a global lower boundary value:
at a given kth iteration point u n](k)In the non-convex constraint (12c), (12d) | | u [ n |)]||2The first order Taylor expansion is used as follows:
at a given kth iteration point (x n)](k),y[n](k)),Non-linear term c in non-convex constraint (10)m[n]The first order Taylor expansion is used as follows:
the trajectory plan P3 translates into an approximately convex problem P4 as follows:
(8c)-(8h),(9b),(9c),(11),(12b),(12e) (13e)
wherein
At this point, the optimal solution for the trajectory is solved by the CVX toolset.
S6 specifically includes the following steps:
s6.1, initializing the position, the speed and the acceleration of the unmanned aerial vehicle to be q respectively
(0)、u
(0)And a
(0)The objective function is
The iteration number K is 0, and the maximum iteration number K is set
maxIterative precision threshold θ
1;
S6.2, giving the position, the speed and the acceleration of the k-th iteration unmanned aerial vehicleDegree q of(k)、u(k)And a(k)Substituting the optimal solution into a trajectory planning optimization model P1 to solve to obtain the optimal solution q of the position, the speed and the acceleration of the unmanned aerial vehicle after the k +1 iteration(k+1)、u(k +1)And a(k+1);
S6.3, judging whether K is more than or equal to K
maxOr is or
If yes, obtaining optimized position, speed and acceleration q
(*)、u
(*)And a
(*)(ii) a If not, the number of iterations k is updated to k +1 and steps S6.2 and S6.3 are repeated.
The invention provides a robust trajectory planning method for an unmanned aerial vehicle under a non-deterministic interference environment, which is used for maximizing the average signal-to-noise ratio under the worst condition in the flight process, thereby realizing reasonable planning of the flight trajectory of the unmanned aerial vehicle.
The invention has the beneficial effects that: the robust trajectory planning method for the unmanned aerial vehicle comprises the steps of firstly constructing an optimization model about the flight trajectory of the unmanned aerial vehicle in a non-determined interference environment, then introducing a redundancy variable based on model characteristics, and iteratively solving the problems by adopting an S-Procedure algorithm and a continuous convex optimization algorithm until the algorithms are converged. The method realizes reasonable planning of the flight trajectory on the premise of improving the reliability of the control signal received by the unmanned aerial vehicle and meeting the system flight speed/acceleration constraint and the maximum flight energy consumption constraint.
Detailed Description
The objects and effects of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The embodiment provides an unmanned aerial vehicle robust trajectory planning method under a non-deterministic interference environment, which comprises the following steps:
s1: establishing an unmanned aerial vehicle trajectory planning system model;
as shown in fig. 1, consider a three-dimensional coordinate system. Let the flying height of the unmanned aerial vehicle be H and the flying time be T, and use a preset starting point { xI,yI,H}(xI,yIAbscissa and ordinate representing start point) to a specified end point { xF,yFH flight (x)F,yFAbscissa and ordinate representing the endpoint); the ground has 1 control station with height of 0 and horizontal position of ws=[xs,ys](xs,ysHorizontal and vertical coordinates representing a control station); the ground has M radiation sources, the height is 0, and the horizontal position is wj,m=[xj,m,yj,m](xj,m,yj,mHorizontal and vertical coordinates representing a ground radiation source); the relationship between the estimated position/power and the actual position/power of the radiation source is expressed as:
wherein
And
denotes the m-thPosition and power, Δ w, of individual radiation source estimates
j,mAnd Δ p
j,mRepresenting the estimated error of the mth radiation source position and power,
and xi
mRepresents the upper error bound, A, of the mth radiation source
j,mAnd psi
j,mIndicating the error range of the position and power of the mth radiation source.
Dividing T into N moments on average, wherein the length delta of adjacent moments is T/N; let the minimum flying speed of the unmanned aerial vehicle be uminMaximum flying speed of umaxMaximum acceleration of amax(ii) a At time n, the horizontal coordinate of the unmanned aerial vehicle is q [ n ]]=[x[n],y[n]](x[n],y[n]Abscissa and ordinate representing position), and a velocity u [ n ]]=[ux[n],uy[n]](ux[n],uy[n]Transverse and longitudinal components of velocity), and acceleration is a [ n ]]=[ax[n],ay[n]](ax[n],ay[n]Is the lateral and longitudinal components of acceleration); the flight constraints of a drone are expressed as:
u[n]=u[n-1]+a[n-1]δ,n=2,3,...,N, (3b)
q[N]=qF,u[N]=uF, (3d)
wherein q isI、uIAnd aIRespectively representing the position, the speed and the acceleration of the unmanned aerial vehicle at the initial moment; q. q.sFAnd uFRespectively representing the final position and the final speed of the unmanned aerial vehicle;
at the nth moment, the distances from the unmanned aerial vehicle to the control station and the ground radiation source are respectively expressed as
Then the channel gain from the drone to the ground control station and the ground radiation source is:
wherein beta is0Expressed as the channel gain when the distance is 1;
the total energy consumption required by the unmanned aerial vehicle in the flight process is as follows:
wherein c is
1And c
2Represents the relevant constant of the hardware of the unmanned aerial vehicle, g represents the gravity acceleration,
representing the consumption of flight kinetic energy of the drone, J represents the mass of the drone.
S2: defining an unmanned aerial vehicle robust trajectory planning problem P1 according to a system model;
at the nth moment, the received signal-to-noise ratio under the worst condition of the unmanned aerial vehicle is as follows:
where M is the number of ground radiation sources, p0Uplink transmission power, sigma, for ground control station to drone2Representing additive white gaussian noise. The method is popularized to the whole flight process, the maximum average signal-to-noise ratio of the unmanned aerial vehicle receiving the worst condition is taken as a target, and the trajectory planning problem is expressed as follows:
u[n]=u[n-1]+a[n-1]δ,n=2,3,...,N, (8d)
q[N]=qF,u[N]=uF, (8f)
wherein Γ is the maximum flight energy consumption constraint of the drone.
S3: power p of radiation source
j,mGet
To eliminate Δ p in the objective function
j,mAnd (4) variable quantity. Introducing base station distance vectors
Wherein the nth element represents the distance of the drone from the control station at time n; interference power vector
Wherein the nth element represents the total power of the drone interfered by the ground radiation source at time n; interference distance matrix
Wherein the (m, n) th element represents the distance of the drone from the mth ground radiation source at time instant n. Problem P1 is transformed into equivalent problem P2 as follows:
(8b)-(8i) (9e)
s4: converting the problem P2 into an equivalent problem P3 by using an S-Procedure algorithm;
adopting S-Procedure algorithm, and using constraint matrix
Wherein the (m, n) th element represents the constraint of the drone at time instant n with respect to the mth ground radiation source. The semi-infinite constraint (9d) is equivalently converted into the following constraint:
wherein
And is
Wherein
And
a horizontal and vertical coordinate representing the estimated position of the mth radiation source;
reintroducing n-dimensional velocity vector
Wherein the nth element represents the speed of the drone at time n; the trajectory plan P2 translates into an equivalence problem P3 as follows:
(8c)-(8h),(9b),(9c),(10),(11) (12f)
s5: converting the problem P3 approximation process into a convex problem P4;
at a given kth iteration point (I [ n ])](k),L[n](k)) And (3) performing first-order Taylor expansion on the non-convex function to obtain a global lower boundary value:
at a given kth iteration point u n](k)In the non-convex constraint (12c), (12d) | | u [ n |)]||2The first order Taylor expansion is used as follows:
at a given kth iteration point (x n)](k),y[n](k)) The non-linear term c in the non-convex constraint (10)m[n]The first order Taylor expansion is used as follows:
the trajectory plan P3 translates into an approximately convex problem P4 as follows:
(8c)-(8h),(9b),(9c),(11),(12b),(12e) (13e)
wherein
At this point, the optimal solution for the trajectory is solved by the CVX toolset.
S6: and solving an optimization target based on the unmanned aerial vehicle trajectory planning model P4 to obtain the optimal flight trajectory of the unmanned aerial vehicle. As shown in fig. 2, the specific steps are as follows:
s6.1, initializing the position, the speed and the acceleration of the unmanned aerial vehicle to be q respectively
(0)、u
(0)And a
(0)The objective function is
The iteration number K is 0, and the maximum iteration number K is set
maxIterative precision threshold θ
1;
S6.2, giving the position, the speed and the acceleration q of the k iteration unmanned aerial vehicle(k)、u(k)And a(k)Substituting the optimal solution into a trajectory planning optimization model P1 to solve to obtain the optimal solution q of the position, the speed and the acceleration of the unmanned aerial vehicle after the k +1 iteration(k+1)、u(k +1)And a(k+1);
S6.3, judging whether K is more than or equal to K
maxOr is or
If yes, obtaining optimized position, speed and acceleration q
(*)、u
(*)And a
(*)(ii) a If not, the number of iterations k is updated to k +1 and steps S6.2 and S6.3 are repeated.
Fig. 3 compares the performance of the inventive solution with the performance of the reference trajectory planning solution, and simulates the designed solution by Matlab. The parameters are specifically set as: flight height H is 100m, and starting point coordinate is q
I(100) m, end point q
F(800) m; the coordinate and power of the ground control unit are (0,0,0) m and p respectively
010W; 3 radiation sources to
Has a power distribution coordinate of
On the ground; error of radiation source power is xi
m0.02W; the total time of flight T is 30 s. Other parameters are shown in table 1:
TABLE 1 simulation parameters
Fig. 3 shows a flight trajectory diagram of the drone, wherein the abscissa and ordinate are expressed as flight coordinates of the drone. As can be seen from the figure: for the same network scene, the unmanned aerial vehicle trajectory planning path provided by the method can be skillfully far away from the radiation source, and the distance between the unmanned aerial vehicle trajectory planning path and the radiation source is greater than that of a reference trajectory planning scheme.
Fig. 4 shows the average worst-case signal-to-noise ratio during the flight of the drone, where the abscissa is the flight energy consumption upper limit of the drone and the ordinate is the average worst-case signal-to-noise ratio. It can be seen that for the same network scenario, the system performance of the method of the present invention is superior to that of the reference trajectory planning scheme.
Through the performance simulation comparison, the method of the invention not only can meet the flight speed/acceleration constraint of the system and the maximum flight energy consumption limitation, but also can improve the communication performance of the network so as to realize the reasonable planning of the flight path. The method can be well adapted to the future mobile communication technology based on the unmanned aerial vehicle, so that the performance of the unmanned aerial vehicle is improved.
The present invention is not limited to the above-described embodiments, and those skilled in the art can implement the present invention in other various embodiments based on the disclosure of the present invention. Therefore, the design of the invention is within the scope of protection, with simple changes or modifications, based on the design structure and thought of the invention.