2

Following this question, I modified my code to:

model test
  // types
  type Mass = Real(unit = "Kg", min = 0);
  type Length = Real(unit = "m");
  type Area = Real(unit = "m2", min = 0);
  type Force = Real(unit = "Kg.m/s2");
  type Pressure = Real(unit = "Kg/m/s2");
  type Torque = Real(unit = "Kg.m2/s2");
  type Velocity = Real(unit = "m/s");
  type Time = Real(unit = "s");

  // constants
  constant Real pi = 2 * Modelica.Math.asin(1.0);
  parameter Mass Mp = 0.01;
  parameter Length r1 = 0.010;
  parameter Length r3 = 0.004;
  parameter Integer n = 3;
  parameter Area A = 0.020 * 0.015;
  parameter Time Stepping = 1.0;
  parameter Real DutyCycle = 1.0;
  parameter Pressure Pin = 500000;
  parameter Real Js = 1;
  //parameter Real Muk = 0.0;
  parameter Real Muk = 0.158;

  // variables
  Length x[n];
  Velocity vx[n];
  Real theta;
  Real vt;
  Pressure P[n];
  Force Fnsp[n];
  Torque Tfsc;

initial equation
  theta = 0;
  vt = 0;

algorithm
  for i in 1:n loop
    if noEvent((i - 1) * Stepping < mod(time, n * Stepping)) and noEvent(mod(time, n * Stepping) < Stepping * ((i - 1) + DutyCycle)) then
      P[i] := Pin;
    else
      P[i] := 0;
    end if;
  end for;
  Tfsc := -r3 * Muk * sign(vt) * abs(sum(Fnsp));

equation
  vx = der(x);
  vt = der(theta);
  x = r1 * {sin(theta + (i - 1) * 2 * pi / n) for i in 1:n};
  Mp * der(vx) + P * A = Fnsp;
  Js * der(theta) = Tfsc - r1 * Fnsp * {cos(theta + (i - 1) * 2 * pi / n) for i in 1:n};
  // Js * der(theta) = - r1 * Fnsp * {cos(theta + (i - 1) * 2 * pi / n) for i in 1:n};

  annotation(
    experiment(StartTime = 0, StopTime = 30, Tolerance = 1e-06, Interval = 0.03),
    __OpenModelica_simulationFlags(lv = "LOG_STATS", outputFormat = "mat", s = "dassl"));
end test;

However, I get the preprocessing warning of

[1] .... Translation Warning

Iteration variables with default zero start attribute in torn nonlinear equation system:

     Fnsp[3]:VARIABLE(unit = "Kg.m/s2" )  type: Real  [3]
     Fnsp[2]:VARIABLE(unit = "Kg.m/s2" )  type: Real  [3]
     Fnsp[1]:VARIABLE(unit = "Kg.m/s2" )  type: Real  [3]
     $DER.vt:VARIABLE()  type: Real

which doesn't make sense but I assume I can safely ignore, and the compiling error of:

Matrix singular!

under-determined linear system not solvable

which had also been previously reported here. if I remove the lines

Torque Tfsc;

and

Tfsc := -r3 * Muk * sign(vt) * abs(sum(Fnsp));

and changing

Js * der(theta) = - r1 * Fnsp * {cos(theta + (i - 1) * 2 * pi / n) for i in 1:n};

works perfectly fine. However, setting Muk to zero, which theoretically the same thing leads to the same error as above! I would appreciate if you could help me know what is the problem and how I can resolve it.

P.S.1. On the demo version of Dymola the simulation test finishes with no errors, only the warning:

Some variables are iteration variables of the initialization problem:
but they are not given any explicit start values. Zero will be used.
Iteration variables:
der(theta, 2)
P[1]
P[2]
P[3]

P.S.2. Using JModelica, removing the noEvent and using the python code:

model_name = 'test'
mo_file = 'test.mo'

from pymodelica import compile_fmu
from pyfmi import load_fmu

my_fmu = compile_fmu(model_name, mo_file)

myModel = load_fmu('test.fmu')
res = myModel.simulate(final_time=30)

theta = res['theta']
t = res['time']

import matplotlib.pyplot as plt
plt.plot(t, theta)
plt.show()

it solves the model blazingly fast for small values (e.g. 0.1) of Muk. But again it gets stuck for bigger values. The only warnings are:

Warning at line 30, column 3, in file 'test.mo':
  Iteration variable "Fnsp[2]" is missing start value!
Warning at line 30, column 3, in file 'test.mo':
  Iteration variable "Fnsp[3]" is missing start value!
Warning in flattened model:
  Iteration variable "der(_der_theta)" is missing start value!
4

2 回答 2

1

您不需要使用算法来分配方程(即使它们在 for 循环和 if 中)。我将它们移至方程式部分并完全删除了您的算法部分:

model test
  // types
  type Mass = Real(unit = "Kg", min = 0);
  type Length = Real(unit = "m");
  type Area = Real(unit = "m2", min = 0);
  type Force = Real(unit = "Kg.m/s2");
  type Pressure = Real(unit = "Kg/m/s2");
  type Torque = Real(unit = "Kg.m2/s2");
  type Velocity = Real(unit = "m/s");
  type Time = Real(unit = "s");

  // constants
  constant Real pi = 2 * Modelica.Math.asin(1.0);
  parameter Mass Mp = 0.01;
  parameter Length r1 = 0.010;
  parameter Length r3 = 0.004;
  parameter Integer n = 3;
  parameter Area A = 0.020 * 0.015;
  parameter Time Stepping = 1.0;
  parameter Real DutyCycle = 1.0;
  parameter Pressure Pin = 500000;
  parameter Real Js = 1;
  //parameter Real Muk = 0.0;
  parameter Real Muk = 0.158;

  // variables
  Length x[n];
  Velocity vx[n];
  Real theta;
  Real vt;
  Pressure P[n];
  Force Fnsp[n];
  Torque Tfsc;

initial equation
  theta = 0;
  vt = 0;
equation

  for i in 1:n loop
    if noEvent((i - 1) * Stepping < mod(time, n * Stepping)) and noEvent(mod(time, n * Stepping) < Stepping * ((i - 1) + DutyCycle)) then
      P[i] = Pin;
    else
      P[i] = 0;
    end if;
  end for;
  Tfsc = -r3 * Muk * sign(vt) * abs(sum(Fnsp));

  vx = der(x);
  vt = der(theta);
  x = r1 * {sin(theta + (i - 1) * 2 * pi / n) for i in 1:n};
  Mp * der(vx) + P * A = Fnsp;
  Js * der(theta) = Tfsc - r1 * Fnsp * {cos(theta + (i - 1) * 2 * pi / n) for i in 1:n};
  // Js * der(theta) = - r1 * Fnsp * {cos(theta + (i - 1) * 2 * pi / n) for i in 1:n};
end test;

这使得编译器更容易为强组件找到合理的排序和撕裂。这仍然会在 19 岁时中断,但在此之前它可能正是您正在寻找的。牛顿求解器在该阈值之后发散,因为我真的不知道你在这里做什么,很遗憾我无法提供任何结果分析。

于 2019-09-11T14:59:15.307 回答
1

此外,您的 if 方程触发的事件似乎可以被Sample运算符完全替换。你可能想看看那个。

于 2019-09-11T15:02:47.727 回答