我试了一下用if和Piecewise构造分段函数，用FindMinimum，NMinimize求最小值都没有结果，是最优化函数本身不支持分段函数，还是我的代码出了问题

\[Epsilon] = 0.01;
a = 0
act = 1.5
\[Lambda]1 = 0;
f1 = 1;
f22[t] = Piecewise[{{0,
Abs[(x2[t] - x1[t])] <=
b}, {c*(x2[t] - x1[t] - (x2[t] - x1[t])/Abs[x2[t] - x1[t]]),
Abs[(x2[t] - x1[t])] > b}}];
f21[t] = Piecewise[{{0,
Abs[(x2[t] - x1[t])] <=
b}, {c*(x1[t] - x2[t] - (x1[t] - x2[t])/Abs[x1[t] - x2[t]]),
Abs[(x2[t] - x1[t])] > b}}];
FindMinimum[{t, \[Epsilon]*a == \[Epsilon]*\!\(
\*SubscriptBox[\(\[PartialD]\), \({t, 2}\)]\(x2[
t]\)\) + \[Epsilon]*\[Lambda]2*(D[x2[t], t] -
D[x1[t], t]) + \[Epsilon]*f22[t],
a == D[x1[t], {t, 2}] + \[Lambda]1*D[x1[t], t] +
f1*x1[t] + \[Epsilon]*\[Lambda]2*(D[x1[t], t] -
D[x2[t], t]) + \[Epsilon]*f21[t],
0.5*f1*x1[t]^2 + 0.5*Derivative[1][x1][t]^2 - 0.01 ==
0}, { \[Lambda]2, 0.1}, {b, 1}, {c, 1.5}]

你是要vp吗，你设置了陌生人无法回复信息