Question

我有一个人为的Modelica模型，其中有一个由多个when语句操纵的状态机变量：

model WhenExample
  type State = enumeration(first, second, third);

  State   state;
initial equation
  state = State.first;

equation
  when sample(0, 1) then
    state = State.second;
  end when;

  when sample(0, 3) then
    state = State.third;
  end when;
end WhenExample;

在OpenModelica OMC下编译时，出现以下错误：

[1] 16:46:39 Symbolic Error
Too many equations, over-determined system. The model has 2 equation(s) and 1 variable(s).

这有点意义，因为我做我的单state变量有两个方程式。但是，这些方程仅适用于离散时间点，对吗？

我是否需要确保特定变量的所有“操作”仅在单个when语句中发生？

Answer 1

请参阅Modelica规范，第8.5节“事件和同步”： https://www.modelica.org/documents/ModelicaSpec33Revision1.pdf

就在第8.6节之前，有一个例子可以帮助你。基于此的一些代码如下：

model WhenExample
  parameter Integer multiplySample = 3;
  Boolean fastSample, slowSample;
  Integer ticks(start=0);
  type State = enumeration(first, second, third);
  State state(start = State.first);
equation
  fastSample = sample(0,1);
algorithm
  when fastSample then
    ticks := if pre(ticks) < multiplySample then pre(ticks)+1 else 0;
    slowSample := pre(ticks) == 0;
    state := State.second;
  end when;
  when slowSample then
    state := State.third;
  end when;
end WhenExample;

Modelica中when语句中离散状态机变量的公式太多

1 个答案: