fmincon函数求解过程中出现无解的情况

求最优解问题的抛出：

求这个函数的最小值 function f = myfun(x)

                        f = (pi*(x(3)+2)*x(2)*x(1)^2)/4;
运行后返回（约束在最后面有写）
Warning: Trust-region-reflective method does not currently solve this type of problem,
 using active-set (line search) instead. 
> In fmincon at 439
Solver stopped prematurely.
fmincon stopped because it exceeded the function evaluation limit,
options.MaxFunEvals = 300 (the default value).
x =
    4.0499
   14.0013
    1.0013
FVAL =
  541.3289

说是这个trust……解不了这个问题，那么该怎么改一下?help过没发现怎么改……

非线性约束 function [c,ceq] = mycon(x)
         k=1.6*(x(1)/x(2))^0.14;     %曲度系数
         F=13;                       %最大力
         f=20.2416;                  %气门最大升程
         G=8100;                     %切变模量
         w=1500;                     %凸轮轴转速
         c(1) =8*k*F*x(2)/(pi*x(1)^3)-51;   %切应力
         c(2) =((x(3)+2-0.5)+1.2*f)/x