MATLAB带符号的expm函数一直计算不出

Question

这是程序代码：

E=10;
L1=15e-6;
C1=100e-6;
L2=15e-6;
C2=100e-6;
R=20;
r=10e-3;
Iref1=1.3;
Ton=0.3e-6;
Iref2=1.5;
T2=0.88e-6;
Pcpl=8;
I=[1,0,0,0;0,1,0,0;0,0,1,0;0,0,0,1];
syms Vo1 Vo2 iL1 iL2
for i=1:100
        Pcpl=8+(i-1)*0.02;%变化的参数
        Id=iL1+Ton*(E-Vo1)/L1;
        iL2=Pcpl/Vo1;
        d1=Ton/(Ton+(Id-Iref1)*L1/Vo1);
        d2=(Iref2-iL2)*L2/((Vo1-Vo2)*T2);
        %d1(d1>=1)=0.99;d1(d1<=0)=0.01;
        %d2(d2>=1)=0.99;d2(d2<=0)=0.01;
       % A1=[0,-1/L1,0,0;r+1/C1,0,0,0;0,0,0,-1/L2;0,0,1/C2,-1/(R*C2)];
        A1=[0,-1/L1,0,0;r+1/C1,0,(-r-1/C1),0;0,1/L2,0,-1/L2;0,0,1/C2,-1/(R*C2)];  %←←←←
        B1=[d1/L1,0,0,0]';
        A2=[0,-1/L1,0,0;r+1/C1,0,0,0;0,0,0,-1/L2;0,0,1/C2,-1/(R*C2)];
        B2=[d1/L1,0,0,0]';
        Xn=[iL1;Vo1;iL2;Vo2];
        X=expm(A2*(1-d2)*T2)*expm(A1*d2*T2)*Xn+expm(A2*(1-d2)*T2)*(expm(A1*d2*T2)-I)*inv(A1)*B1*E+(expm(A2*(1-d2)*T2)-I)*inv(A2)*B2*E;%  非线性函数系统
        f=Xn-X;
        fixed_point=fsolve(f,[1 1 1 1]);%平衡点                                                      % ←←←←
        jacobian_mat=jacobian(X,[iL1;Vo1;iL2;Vo2]);%雅可比矩阵
        %n=length(fixed_point.iL1);%n为平衡点组数，即n组平衡点[x1 x2]
        n=size(fixed_point,1);
    for j=1:n
        fixed(j).jacobian=subs(jacobian_mat,Xn,{fixed_point.Xn(j)});%每个平衡点的雅可比矩阵
        fixed(j).eig=eig(fixed(j).jacobian);%平衡点的特征值
        eig_max=max(double(real(fixed(j).eig)));
        if eig_max<=0
            plot(Pcpl,double(fixed_point.Xn(j)),'.')
            hold on
        else
             plot(Pcpl,double(fixed_point.Xn(j)),'+')%鞍点用+标出
             hold on
        end;
    end;
end

经过试验发现是矩阵A1无法带指数e计算，一直正忙，后来我尝试换成上面带%位置的A1矩阵又可以了，请问应该如何解决？
求各位帮忙分析分析，感谢