线性方程组系数直接提取问题

张泽俊

我用MATLAB求解19个线性方程组，想直接提取方程组系数 具体代码如下
clc

A_yuan=[103 350 142]';
B_yuan=[-127 350 128]';
C_yuan=[-12 491 104]';
D_yuan=[-12 589 127]';
E_yuan=[122 345 -80]';
F_yuan=[-108 345 -80]';
G_yuan=[7 620 -89]';
H_yuan=[-156 545 178]';
P_yuan=[0 678 -265]';
I_yuan=[-15 500 540]';
J_yuan=[-156 317 186]';
R_AB=A_yuan-B_yuan;
R_EF=E_yuan-F_yuan;
FA=[x1 x2 x3]';
FB=[x4 x5 x6]';
R_JH=J_yuan-H_yuan;
FH=x19*R_JH;
R_CI=C_yuan-I_yuan
FC=x20*R_CI;
FE=[x7 x8 x9]';
FF=[x10 x11 x12]';
FD=[x13 x14 x15]';
FG=[x16 x17 x18]';
FP=[0 0 10000]';
EG_bj=(E_yuan-G_yuan) %E,G铰接点矢量半径
FG_bj=F_yuan-G_yuan%F,G铰接点矢量半径
AD_bj=A_yuan-D_yuan;%A,D铰接点矢量半径
BD_bj=B_yuan-D_yuan;%B,D铰接点矢量半径
CD_bj=C_yuan-D_yuan;%C,D铰接点矢量半径
PG_bj=P_yuan-G_yuan;%P,G铰接点矢量半径
DG_bj=D_yuan-G_yuan;%D,G铰接点矢量半径
HG_bj=H_yuan-G_yuan;%H,G铰接点矢量半径
M_EG=cross(EG_bj,FE)
M_FG=cross(FG_bj,FF)
M_AD=cross(AD_bj,FA)
M_BD=cross(BD_bj,FB)
M_CD=cross(CD_bj,FC)
M_PG=cross(PG_bj,FP)
M_DG=cross(DG_bj,FD)
M_HG=cross(HG_bj,FH)

f1=FE(1,1)+FF(1,1)+FG(1,1)==0%下叉形臂平衡
f2=FE(2,1)+FF(2,1)+FG(2,1)
f3=FE(3,1)+FF(3,1)+FG(3,1)
f4=M_EG(1,1)+M_FG(1,1)%对G点取矩
f5=M_EG(2,1)+M_FG(2,1)
f6=M_EG(3,1)+M_FG(3,1)
f7=FA(1,1)+FB(1,1)+FC(1,1)+FD(1,1)%上叉形臂平衡
f8=FA(2,1)+FB(2,1)+FC(2,1)+FD(2,1)
f9=FA(3,1)+FB(3,1)+FC(3,1)+FD(3,1)
f10=M_AD(1,1)+M_BD(1,1)+M_CD(1,1)%对D点取矩
f11=M_AD(2,1)+M_BD(2,1)+M_CD(2,1)
f12=M_AD(3,1)+M_BD(3,1)+M_CD(3,1)
f13=FP(1,1)-FD(1,1)-FG(1,1)-FH(1,1)%转向节平衡
f14=FP(2,1)-FD(2,1)-FG(2,1)-FH(2,1)
f15=FP(3,1)-FD(3,1)-FG(3,1)-FH(3,1)
f16=M_PG(1,1)-M_DG(1,1)-M_HG(1,1)%对G点取矩
f17=M_PG(2,1)-M_DG(2,1)-M_HG(2,1)
f18=M_PG(3,1)-M_DG(3,1)-M_HG(3,1)
f19=FA'*R_AB     
A = equationsToMatrix([f1,f2,f3,f4,f5,f6,f7,f8,f9,f10,f11,f12,f13,f14,f15,f16,f17,f18,f19],[x1,x2,x3,x4,x5,x6,x7,x8,x9,x11,x12,x13,x14,x15,x16,x17,x18,x19,x20])
但提取的结果是
A =

[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     3]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,    -9]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,  -436]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0, 42521]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,   -69]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,   294]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,    228,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,     -8,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -60276,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  -1304,     0]
[   0, 0,  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, -37164,     0]
[ 230, 0, 14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,      0,     0]
很显然是不对，但不知道问题在哪里？求哪位大侠能指点下？