使用要点
- 创建决策变量
- 设置目标函数
- 添加约束条件
- 参数配置
- 求解问题
问题描述
假设M个无人机的任务是尽快覆盖一组由 P 顶点表示的多边形凸区域,假设每架无人机的最大飞行时间是有限的,并且是预先知道的。每架无人机的都配备了一个指向下方的机载摄像头,无人机需要使用它来感知 P 指定的整个区域。具体问题如下:
- 最大限度减少覆盖区域 P 所需时间的无人机数量 m <= M
- 以最短完成任务时间为目标规划每个 UAV 路径
变量定义
C
i
j
C_{ij}
Cij represents the traversing cost of the edge
(
i
,
j
)
(i,j)
(i,j) between nodes
i
i
i and
j
j
j.
for i=1:numberOfVertices
for j=1:numberOfVertices
if i~=j
C(i,j)=norm(V(i,:)-V(j,:))/(uavSpeed*1000/60);
end
end
end
X
i
j
k
∈
{
0
,
1
}
{X_{ij}^{k}}\in\{0,1\}
Xijk∈{0,1} represents whether or not the
k
k
k-th UAV is going to fly from vertex
i
i
i to vertex
j
j
j.
V
i
j
k
∈
R
{V_{ij}^{k}}\in\R
Vijk∈R represent the flight speed of the
k
k
k-th UAV while flying from vertex
i
i
i to vertex
j
j
j.
t
s
∈
R
{t_{s}}\in\R
ts∈R be the individual setup time.
L
k
{L_k}
Lk be the battery duration of UAV number
k
k
k.
m
∈
N
{m}\in\N
m∈N be the variable that represents the number of UAVs designed for a mission
M
∈
N
{M}\in\N
M∈N be the total number of UAVs available.
O
∈
N
{O}\in\N
O∈N be the constant number of UAV operators.
N
∈
N
{N}\in\N
N∈N be the number of nodes of the graph.
d
k
d_{k}
dk represents the extra time necessary to launch UAV
k
k
k.
每个无人机的最短时间可表示为:
T
k
=
∑
i
=
1
N
∑
j
=
1
N
C
i
j
V
i
j
k
X
i
j
k
+
d
k
T_{k}=\sum_{i=1}^{N} \sum_{j=1}^{N} \frac{C_{i j}}{V_{i j}^{k}} X_{i j}^{k}+d_{k}
Tk=i=1∑Nj=1∑NVijkCijXijk+dk
线性规划问题定义:
m
i
n
(
V
)
min(\mathcal{V})
min(V)
∑
i
=
1
N
∑
j
=
1
N
C
i
j
V
i
j
k
X
i
j
k
+
d
k
≤
V
,
k
=
1
,
…
,
M
\sum_{i=1}^{N} \sum_{j=1}^{N} \frac{C_{i j}}{V_{i j}^{k}} X_{i j}^{k}+d_{k} \leq \mathcal{V}, k =1, \ldots, M
i=1∑Nj=1∑NVijkCijXijk+dk≤V,k=1,…,M
t
s
⌈
k
O
⌉
∑
j
=
1
N
X
1
j
k
=
d
k
,
k
=
1
,
…
,
M
t_{s} {\lceil\frac{k}{O}\rceil \sum_{j=1}^{N} X_{1 j}^{k}=d_{k}, k=1, \ldots, M }
ts⌈Ok⌉j=1∑NX1jk=dk,k=1,…,M
01 | 创建决策变量
变量设置常用的三种形式:
- sdqvar() 设置实型变量
- intvar() 设置整型变量
- binvar() 设置0-1变量
举例:P = sdqvar(n,m) 表示用 n 行 m 列定义一个矩阵(或标量)P
v = sdpvar(1,1);
X = binvar(numberOfVertices,numberOfVertices,uavNumber,'full');
u = sdpvar(numberOfVertices,1);
m = intvar(1,1);
for k = 1:uavNumber
for i = 1:numberOfVertices
X(i,i,k) = 0;
end
if uav(k) == 0
X(:,:,k) = zeros(numberOfVertices);
end
end
02 | 设置目标函数
YALMIP 默认求解最小值问题,如果问题的目标函数是求解最大值,则需要在目标函数前加负号
目标函数即求最小值 v
03 | 添加约束条件
先初始化约束条件为空,再逐个将约束条件添加
constraints = [];
% 限制1 - 总成本
for k = 1:uavNumber
sum1 = 0;
for i = 1:numberOfVertices
for j = 1:numberOfVertices
if i ~= j
sum1 = sum1 + C(i,j)*sum(X(i,j,k));
end
end
end
constraints = [constraints, v >= sum1 + sum(X(1,:,k))*ceil(k/O)*uavSetupTime];
% 限制9 - 飞行时间
constraints = [constraints, sum1 <= uavFlightTime];
end
% 限制2 - 每个顶点必须被访问一次
for j = 2:numberOfVertices
constraints = [constraints, sum(sum(X(:,j,:))) == 1];
end
% 限制3 - 到达给定节点的节点与离开该节点的节点相同。
for k = 1:uavNumber
for p = 1:numberOfVertices
constraints = [constraints, sum(X(:,p,k)) - sum(X(p,:,k)) == 0];
end
end
% 限制4&5 - 无人机数量
constraints = [constraints, sum(sum(X(1,:,:))) == m];
constraints = [constraints, m <= sum(uav)];
% 限制7 - 循环
for i = 2:numberOfVertices
for j = 2:numberOfVertices
if i ~= j
constraints = [constraints, u(i) - u(j) + numberOfVertices*sum(X(i,j,:)) <= numberOfVertices - 1];
end
end
end
% 限制 8 - 强制每条线路仅由一架无人机沿一个方向穿越
for i = 2:2:numberOfVertices
constraints = [constraints, 1 == sum(X(i,i+1,:)) + sum(X(i+1,i,:))];
end
% 限制 10 - 避免 UA Vs 沿着不平行于覆盖范围的边缘穿过覆盖区域行
for i = 2:2:numberOfVertices
constraints = [constraints, sum(X(i,i+1,:)) == sum(sum(X(i,3:2:numberOfVertices,:)))];
constraints = [constraints, sum(X(i+1,i,:)) == sum(sum(X(i+1,2:2:numberOfVertices,:)))];
end
04 | 参数设置
使用 sdpsetting() 函数进行参数设置
% 使用 gurobi 最小化 v 受限于约束变量中包含的约束
options = sdpsettings('verbose',1,'gurobi.Threads',4);
05 | 求解问题
首先使用 solvesdp() 函数求解
再使用 double() 函数将求解的变量转换为实数
solvesdp(constraints,v,options);
X = round(double(X));
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