diff --git a/GA_PID/fitness.m b/GA_PID/fitness.m
new file mode 100644
index 0000000..14c355a
--- /dev/null
+++ b/GA_PID/fitness.m
@@ -0,0 +1,24 @@
+function fit=fitness(Kp,Ki,Kd)
+
+assignin('base','Kp',Kp);
+assignin('base','Ki',Ki);
+assignin('base','Kd',Kd);
+[~,~,y_out]=sim('thetapid',[0,50]);
+z=(y_out(end,1));   %%表示 取这个 矩阵的第一列最后一行的数据。
+t0=yy.time;
+y=yy.signals.values;
+% res=yy;
+% ymax=find(y>=1);
+% tr=t0(ymax(1));%计算上升时间tr
+[ym,tp]=max(y);
+% tp=t0(tp);%计算峰值时间tp
+Mp=ym-1;%计算超调量Mp
+s0=length(t0);
+while y(s0)>0.98&&y(s0)<1.02
+    s0=s0-1;
+end
+ts=t0(s0);%计算调整时间ts
+% error=sum(abs(yy1.signals.values-9));
+w=[0.8 0.1 0.1];
+zhibiao=[z ts Mp];
+fit=1/(zhibiao*w');