看了薛定宇老师的《MATLAB控制系统辅助设计》相关章节，有个语句不明白

看了薛定宇老师的《MATLAB控制系统辅助设计》相关章节，有些语句不明白。代码如下：

function [sys,x0,str,ts]=nnbp_pid(t,x,u,flag,T,nh,xite,alfa,kF1,kF2)

switch flag,

   case 0, [sys,x0,str,ts] = mdlInitializeSizes(T,nh);

   case 3, sys = mdlOutputs(t,x,u,T,nh,xite,alfa,kF1,kF2);

    case {1, 2, 4, 9},sys = [];

   otherwise, error(['Unhandled flag =',num2str(flag)]);

end;

% 初始化函数

function [sys,x0,str,ts] = mdlInitializeSizes(T,nh)

sizes = simsizes; % 读入模板，得出默认的控制量

sizes.NumContStates = 0;sizes.NumDiscStates = 0;

sizes.NumOutputs = 4+7*nh;sizes.NumInputs = 7+14*nh;

sizes.DirFeedthrough = 1;sizes.NumSampleTimes = 1;

sys = simsizes(sizes); x0 = [];str = []; ts = [T 0];

% 系统输出计算函数

function sys = mdlOutputs(t,x,u,T,nh,xite,alfa,kF1,kF2)

wi_2=reshape(u(8:7+4*nh),nh,4);

wo_2=reshape(u(8+4*nh:7+7*nh),3,nh);

wi_1=reshape(u(8+7*nh:7+11*nh),nh,4);

wo_1=reshape(u(8+11*nh:7+14*nh),3,nh);

xi=[u([6,4,1])', 1];xx=[u(1)-u(2); u(1); u(1)+u(3)-2*u(2)];

I=xi*wi_1';Oh=non_transfun(I,kF1); K=non_transfun(wo_1*Oh',kF2);

uu=u(7)+K'*xx;dyu=sign((u(4)-u(5))/(uu-u(7)+0.0000001));

dK=non_transfun(K,3);delta3=u(1)*dyu*xx.*dK;

wo=wo_1+xite*delta3*Oh+alfa*(wo_1-wo_2)+alfa*(wo_1-wo_2);

dO=2*non_transfun(I,3);

wi=wi_1+xite*(dO.*(delta3'*wo))'*xi+alfa*(wi_1-wi_2);

sys=[uu; K;wi(:);wo(:)];

% 激活函数近似

function W1=non_transfun(W,key)

switch key

   case 1, W1=(exp(W)-exp(-W))./(exp(W)+exp(-W));

   case 2, W1=exp(W)./(exp(W)+exp(-W));

   case 3, W1=2./(exp(W)+exp(-W)).^2;

[size=13.3333px]想知道这里的xi=[u([6,4,1])', 1];中的1是什么意思 为什么有1？