function theForce = getQfForce_X(x_position)
%It is presumed that QuickField is already started, the QuickField problem is opened.
%x_position is an absolute position of the plunger (vertex "anchor")

%1. Move the plunger to proper position (x_position)
%2. Calculate the force
%3. Move the plunger back to zero position


  qf = actxserver('QuickField.Application'); %get link to QuickField
  pbm = qf.Problems.Item(1);      %get link to the problem
  pbm.LoadModel();                  %load model
  mdl = pbm.Model;                %get link to the model

%1. Move the plunger to proper position (x_position)
%get current position of plunger (vertex "anchor")
  theShape = mdl.Shapes.LabeledAs('anchor','',''); %returns a collection of objects
  theVertex = theShape.Vertices.Item(1); %take first object in collection (normally there is only one vertex there)

%displacement vector
  oldX = theVertex.Point.X;
  theVector = qf.PointXY(x_position - oldX, 0); %displacement vector between desired position and current position



%select the object to move, i.e. "insulation"
%(the plunger core is attached to plunger insulation and would be moved automatically)
  theShape = mdl.Shapes.LabeledAs('','','insulation');
%move the selected Shape
  theShape.Move(0, theVector); %QuickField constant qfShift = 0
  mdl.Shapes.BuildMesh();         %build mesh in the model
  mdl.Save();                       %save model file


  pbmState = pbm.SolveProblem(1); %1=NoWait, solve the problem asynchronously
  pause (2); %pause for 2 seconds to let the pbmState to be updated



  start_time = time();
  do
%wait till the problem is solved, but no more then 60 seconds
    v = pbmState.IsActive;
    p = time()-start_time;
  until ((!v) | (p>60)) 

%problem not solved - cannot continue
  if (!pbm.Solved) disp("cannot solve"); break; endif  
  
%check the state
  pbm.AnalyzeResults();             %load results
  res = pbm.Result;               %get link to the result
%to calculate the force we should build integration contour
%we build the contour in the field window
  theFieldWindow = res.GetFieldWindow(1); %open the field window
  theContour = theFieldWindow.Contour;    %get link to the contour
  theContour.AddBlock1('plunger_core');       %add "plunger" block to contour
%calculate the magnetic force integral
  theMagneticForce = res.GetIntegral(15, theContour).Value; % QuickField constant 'qfInt_MaxwellForce' = 15

  theForce = theMagneticForce.X;  %plunger is moved by the X-component of the force
endfunction