Modelica

Question

我正在 Wolfram System Modeler 中创建一个 Max Per Interval 模块。

为了便于解释，我将最大值设置为 10。

block HighWaterMarkPerInterval
  extends Modelica.Blocks.Interfaces.SISO;
protected
  Integer index;
  Real currentMax;
  Real endTimes[1, 45] = [30812532.2, 32037805, 33265581.8, 34493233.8, 35720861.5, 36948483, 38176307.7, 39426940.6, 40654485.4, 41882212.1, 43109672.7, 44337076, 45564265.7, 46793039.6, 48045130.9, 50749960.3, 52040090.6, 53558507.7, 54814537.3, 56331978.2, 57587753.3, 59105952.9, 60362517.8, 61879307.8, 63136031.5, 64363411.4, 65590464.3, 67738027.40000001, 84725789.8, 87831338.09999999, 89030965.40000001, 90258821.8, 91486663.5, 92714210.3, 93941727.7, 95166770.3, 97283519, 99434222.90000001, 100658067.1, 102807019, 104030032.7, 106179193, 107402090, 109550214.2, 110771545.3];
algorithm
  if endTimes[1, index] < time then
    index := pre(index) + 1;
    currentMax := 0;
  else
    currentMax := 10; // Constant to until I get logic working
  end if;
initial algorithm
  index := 0;
equation
  y = currentMax;
end HighWaterMarkPerInterval;

当运行时，索引立即递增到无穷大。我觉得我的逻辑有问题，但我想不通。

代码应该检查我们是否仍在间隔时间，当我们进入下一个间隔时间时，它会将 "currentMax" 值设置为零。这将重置我在另一个块中实现的最大值。

如有任何帮助，我们将不胜感激。谢谢

编辑：代码部分表单示例。

model HighWaterMarkPerInterval
  annotation(Diagram(coordinateSystem(extent = {{-148.5, -105}, {148.5, 105}}, preserveAspectRatio = true, initialScale = 0.1, grid = {5, 5})));
  extends Modelica.Blocks.Interfaces.SISO;
  Modelica.Blocks.Math.Max maxblock(u1 = currentMax, u2 = u);
  Real flybyEnds[1, 45] = [30813151,32038322,33266015, truncated for space saving...];
  Integer index;
  Real currentMax;
initial equation
  index = 1;
  currentMax = 0;  
algorithm
  // When we are in the interval continually grab max block output and output currentMax
  when {time>=flybyEnds[1, index-1], time <=flybyEnds[1,index]} then 
    currentMax := pre(maxblock.y);
    y := currentMax;
  end when;
  // When we move to the next interval reset current max and move to the next interval
  when time > flybyEnds[1, index] then
    currentMax := 0;
    index := pre(index) + 1;
  end when;
end HighWaterMarkPerInterval;

Answer 1

您需要使用 when，而不是 if。您可以在 Modelica by Example.

中找到关于两者以及它们之间差异的讨论

SO 上也讨论了这个问题 here and here。

这是一个例子（完全未经测试，但它展示了基本思想）：

model HighWaterMarkPerInterval
  extends Modelica.Blocks.Interfaces.SISO;
  parameter Modelica.SIunits.Time sample_rate=3600;
  Real flybyEnds[45] = {30813151,32038322,33266015,...};
  Integer index;
  Real currentMax;
initial algorithm
  // Specify the first time we are interested in...
  index := 1;
algorithm 
  // At the start of the simulation, the initial max for the current
  // interval [0,30813151] is whatever u is.  The initial output value
  // is also the initial value for u
  when initial() then
    currentMax := u
    y := u;
  end when;

  // Check at some sample rate (faster than the flyby interval!)
  // if u > currentMax...
  when sample(sample_rate, sample_rate) then
    // New currentMax is the larger of either currentMax or u
    // when the sample took place
    currentMax := max(pre(currentMax), pre(u));
  end when;

  // At the end of the "flyby", record the maximum found since
  // the last flyby and specify the next flyby index.
  when time>=flybyEnd[index] then
    // New output is the value of currentMax from this interval
    y := pre(currentMax);
    // Now reset currentMax
    currentMax := pre(u);
    // Increment index up to the length of flybyEnd
    index := min(pre(index)+1, size(flybyEnd,1));
  end when;
end HighWaterMarkPerInterval;

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