id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
6171	Invalid evaluation of auxiliary wrapFunctionCalls variable in conditional equations/expressions	anonymous	Karim Adbdelhak	"I was advised by sjoelund.se on Stackoverflow to report an error i had with ""acos(variable) outside domain -1.0 <= -1 <= +1.0""

The error occured with OM version 1.13, but is also present with 1.16. 

I dont have enough knowledge to determine if it is something to fix/ if it is already handled the appropriate way.

I'd like to add, that since i've been doing a few trigonometry calculation models, that it can be common to run into asin/acos out of domain blockers, despite equations that can mathematically never get out of domain (only numerically,  i guess). 

In his words ""[...]OpenModelica added a bad equation for common subexpression elimination someTmpVar = acos(cosbeta) which always runs regardless of the if-equations you use to guard this[...]"", see:

[https://stackoverflow.com/questions/55064752/math-acos-out-of-domain-error-when-combined-with-backlash-element]

Detailed description of the model/purpose, see stack overflow link.
For convenience repeated: 
Model Diagram: [https://i.stack.imgur.com/IjOS4.jpg]
Model code is:
{{{
package test  
  model LD_Abwickel_ZF_VAL  
     Modelica.Blocks.Sources.Ramp ramp2(duration = 1.24, height = 122, offset = -2);
     Modelica.Mechanics.Rotational.Components.ElastoBacklash2 elastoBacklash(b = 1.85005, c = 1e4, d = 1e2, phi_rel0 = -0.925025);
     Modelica.Mechanics.Rotational.Components.Fixed fixed2;
     Modelica.Mechanics.Rotational.Sources.Position position1(exact = true);
     Modelica.Blocks.Math.UnitConversions.From_deg from_deg1;
     test.LD_Pendelarm_ZugfederF2 lD_Pendelarm_ZugfederF21;
  equation
     connect(position1.flange, lD_Pendelarm_ZugfederF21.flange);
     connect(elastoBacklash.flange_a, lD_Pendelarm_ZugfederF21.flange);
     connect(ramp2.y, from_deg1.u);
     connect(from_deg1.y, position1.phi_ref);
     connect(elastoBacklash.flange_b, fixed2.flange);
  end LD_Abwickel_ZF_VAL;


    model LD_Pendelarm_ZugfederF2  
      Modelica.Mechanics.Rotational.Interfaces.Flange_a flange;
      .Modelica.SIunits.Angle phi(displayUnit = ""deg"");
      .Modelica.SIunits.Torque M;
      parameter .Modelica.SIunits.Length a(displayUnit = ""mm"") = 25.49e-3;
      parameter .Modelica.SIunits.Length b(displayUnit = ""mm"") = 23.38e-3;
      parameter .Modelica.SIunits.Length d(displayUnit = ""mm"") = 43.89e-3;
      parameter .Modelica.SIunits.Length L0(displayUnit = ""mm"") = 59.5e-3 ""Ungespannte Laenge d. Feder"";
      parameter .Modelica.SIunits.Length Lk(displayUnit = ""mm"") = 47.19e-3 ""Laenge unbelasteter Federkörper"";
      parameter .Modelica.SIunits.Force F0 = 4.1 ""innere Vorspannkraft Feder"";
      parameter .Modelica.SIunits.TranslationalSpringConstant R(displayUnit = ""N/mm"") = 0.868e+3 ""Federkonstante"";
      parameter Integer z = 2 ""Anzahl Federn"";
      .Modelica.SIunits.Length c(displayUnit = ""mm"");
      .Modelica.SIunits.Angle delta(displayUnit = ""deg"", min = -2 * .Modelica.Constants.pi, max = 2 * .Modelica.Constants.pi, nominal = 0);
      .Modelica.SIunits.Angle alpha(displayUnit = ""deg"", min = -2 * .Modelica.Constants.pi, max = 2 * .Modelica.Constants.pi, nominal = 0.5 * .Modelica.Constants.pi);
      .Modelica.SIunits.Angle beta(displayUnit = ""deg"", min = -4 * .Modelica.Constants.pi, max = 4 * .Modelica.Constants.pi, nominal = .Modelica.Constants.pi);
      .Modelica.SIunits.Angle psi(displayUnit = ""deg"", min = -4 * .Modelica.Constants.pi, max = 4 * .Modelica.Constants.pi, nominal = 0);
      .Modelica.SIunits.Length L_gerade(displayUnit = ""mm"");
      .Modelica.SIunits.Length L_bogen(displayUnit = ""mm"") = 46.1e-3;
      .Modelica.SIunits.Length L_c(displayUnit = ""mm"") ""rel. Federlaenge (gesamt)"";
      .Modelica.SIunits.Force F_c ""Summe Federkraft"";
      Real cosalpha(min = -1, max = 1, nominal = 0);
      Real cosdelta(min = -1, max = 1, nominal = 0);
      Real cosbeta(min = -1, max = 1, nominal = 0);
    equation
      flange.phi = phi;
      flange.tau = M;
      if noEvent(phi <= 0) then
         c = a - b;
         cosdelta = 1;
         delta = 0;
         L_gerade = sqrt(c ^ 2 + d ^ 2);
         cosalpha = -1;
         alpha = .Modelica.Constants.pi;
      else
         c = sqrt(a ^ 2 + b ^ 2 - 2 * a * b * cos(phi));
         cosdelta = (b ^ 2 - a ^ 2 - c ^ 2) / (-2 * a * c);
         if noEvent(cosdelta <= 0.999999 and cosdelta >= (-0.999999)) then
            cos(delta) = cosdelta;
         else
            delta = if noEvent(sign(cosdelta) > 0) then 0 else .Modelica.Constants.pi;
         end if;
         L_gerade = sqrt(c ^ 2 + d ^ 2 - 2 * c * d * cos(delta + .Modelica.Constants.pi * 0.5));
         cosalpha = (a ^ 2 - b ^ 2 - c ^ 2) / (-2 * b * c);
         if noEvent(cosalpha <= 0.999999 and cosalpha >= (-0.999999)) then
            cos(alpha) = cosalpha;
         else
            alpha = if noEvent(sign(cosalpha) > 0) then 0 else .Modelica.Constants.pi;
         end if;
      end if;
      cosbeta = (d ^ 2 - c ^ 2 - L_gerade ^ 2) / (-2 * c * L_gerade);
      if noEvent(cosbeta <= 0.999999 and cosbeta >= (-0.999999)) then
         cos(beta) = cosbeta;
      else
         beta = if noEvent(sign(cosbeta) > 0) then 0 else .Modelica.Constants.pi;
      end if;
      psi = alpha - beta;
      L_c = L_gerade + L_bogen - (L0 - Lk) - Lk;
      F_c = z * (R * L_c + F0);
      M = F_c * sin(psi);
    end LD_Pendelarm_ZugfederF2;
end test;
{{{

}}}

}}}



"	defect	closed	high	1.18.0	Backend	v1.16.0-dev	fixed		Andreas Heuermann Philip Hannebohm