用MAPLE解BVP遇到newton iteration not converging

lambeef

具体代码如下：
# U  q2 W1 }; m; t/ k: g1 ]$ z% ^& K: g4 `l := 1000*10^(-9);
w := 50*10^(-9);
k := (1/12)*w^3;
% E: X3 Y* f- m. h7 S$ ]2 `E := 150*10^9;
6 v8 q7 \' G4 P; [d := 20*10^(-9);
' a9 b' D% R) |$ ^ v := 2.3;
# h3 q- X8 ?+ O7 a8 helectrostatic := 8.854*10^(-12)*v^2*(1/2);
1 ]2 Q4 v* T/ d; ^3 l2 }ode := diff(y(x), x$4) = electrostatic/((d-y(x))^2/E/k);
. ]) ^4 h/ F# ^$ G% V* ~bcs1 := y(0) = 0, (D(y))(0) = 0, (D(D(y)))(l) = 0, (D(D(D(y))))(l) = 0;
  T2 k, ]& @1 w! b+ z" j/ U3 gansl1 := dsolve({ode, bcs1}, numeric, method = bvp, abserr = 28)
问题是求在静电场作用下，梁的弯曲问题。v是电压,当电压很小时，可以算出结果，但是电压大于1V时出现‘newton iteration not converging’. 想了很长时间做不出来，请各位帮个忙！谢谢！