为什么“der()"Modelica 中的运算符仅适用于时间变量? [英] Why does the "der()" operator in Modelica apply to the time variable only?

问题描述

我在 Dymola 中构建了一个简单的模型，但我对 der() 运算符感到困惑，为什么 der() 运算符仅适用于时间变量?如果我想对其他变量使用导数怎么办

I build a simple to model in Dymola, but I got confused about the der() operator, why does the der() operator apply to the time variable only? What if I want to use the derivate to other variables

在下面的代码中，如果我想计算dy/dx(y到x的导数)，我该怎么做?

In the following code, if I want to calculate dy/dx(derivative of y to x), how should I do this?

model A
  Real x, y, z;
equation
  x=10;
  y=sin(x);
  z=der(y);
end A;

推荐答案

通过函数支持偏导数.请参阅 Modelica Spec 3.4:函数的偏导数中的第 12.7.2 章.

Partial derivatives are supported via functions. See chapter 12.7.2 in Modelica Spec 3.4: Partial Derivatives of Functions.

您必须将感兴趣的方程移到函数的算法部分.您的示例可能如下所示:

You have to move the equation of interest into the algorithm section of a function. Your example could look as follows:

model A
  Real x, z;

  function f1
    input Real a;
    output Real b;
  algorithm 
    b :=sin(a);
  end f1;

  function der_f1 = der(f1, a);

equation 
  x = 10;
  z = der_f1(x);
end A;

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