Building/Coding A Custom Clutch in Simscape

Hi All,

I am trying to build a custom clutch using in simscape based on the code from the rotational hard-stop in the foundation library of simscape.

I am trying to alter the code so that under certain circumstances in the system when the rotational hard-stop is disconnected via a clutch the position of the slider in the rotational hard-stop is reset to 0. I have added an output port to show the position of the slider and an input port to trigger the reset of the angle of the slider. (see code below)

nodes 
    R = foundation.mechanical.rotational.rotational % R:left
    C = foundation.mechanical.rotational.rotational % C:right
  end

    inputs

        X = { 0, 'N'}; %Reset voltage
    end

    outputs
        A = { 0 ,'rad'}; %A:right
    end

    variables
        t = { 0, 'N*m'};      %torque through
        phi = { 0, 'rad'};
        w = { 0, 'rad/s'};
        Z = { 1, 'N' };       % Voltage switch point      
    end

    parameters
      upper_bnd = { 0.1, 'rad' };         % Upper bound
      lower_bnd = { -0.1, 'rad' };        % Lower bound
      stiff_up = { 1e6, 'N*m/rad' };      % Contact stiffness at upper bound
      stiff_low = { 1e6, 'N*m/rad' };     % Contact stiffness at lower bound
      D_up = { 0.01, 'N*m*s/rad' };       % Contact damping at upper bound
      D_low = { 0.01, 'N*m*s/rad' };      % Contact damping at lower bound
      initial_angle = { 0, 'rad' };       % Initial angular position

    end 

    function setup
      if lower_bnd > upper_bnd
        pm_error('simscape:LessThanOrEqual','Lower bound','Upper bound')
      end
      if stiff_up < 0
        pm_error('simscape:GreaterThanOrEqualToZero','Contact stiffness at upper bound')
      end
      if stiff_low < 0
        pm_error('simscape:GreaterThanOrEqualToZero','Contact stiffness at lower bound')
      end
      if D_up < 0
        pm_error('simscape:GreaterThanOrEqualToZero','Contact damping at upper bound')
      end
      if D_low < 0
        pm_error('simscape:GreaterThanOrEqualToZero','Contact damping at lower bound')
      end

      across( w, R.w, C.w);
      through( t, R.t, C.t);
      phi = initial_angle;
    end

    equations
      if (phi > upper_bnd)
          % Slider hits upper bound
          t == stiff_up * (phi - upper_bnd) + D_up * w;
      elseif (phi < lower_bnd)
          % Slider hits lower bound
          t == stiff_low * (phi - lower_bnd) + D_low * w;
      else
          % Slider is between hard stops
          t == {0, 'N*m'}; 
      end

      if (X > Z)
          phi == 0;
      else
          phi.der == w;
      end

      A == phi;
    end

end

I have tried adding an extra if function at the end of the equations section but when ever I try to run the model it comes up with an error basically saying if you have a differential on one branch of an if function you have to have one on the other....

I realise this is a long post and a lot to ask but I don't have much time to get this done. Does anyone have any suggestions on how to reset the angle of rotational hard stop???

A separate question, are there any books anyone can recommend on programming in simscape of just simscape in general???

Many thanks in advance for any help. Regards Nick

[Sergey Omeliantchuck]

I make this code for my custom electromagnetic clutch

component elclutch2
% Electromagnetic clutch Merobel
% Copyright 2017 NPP VIUS, Inc.

nodes
    p = foundation.electrical.electrical; % +:top
    n = foundation.electrical.electrical; % -:bottom
    R = foundation.mechanical.rotational.rotational; % R:top
    C = foundation.mechanical.rotational.rotational; % C:bottom
end

parameters
    K = { 0.1, 'V/(rad/s)' }; % Constant v == K*w;
    S = { 0.1, '(N*m)/A' }; % Constant t == -S*i;
    m = { 0.1, 'N*m' }; % Minimal torque
    vel_thr = { 1e-4, 'rad/s' };        % Linear region velocity threshold    
end

variables
    i = { 0, 'A' };     % Current
    v = { 0, 'V' };     % Voltage
    t = { 0, 'N*m' };   % Torque
    w = { 0, 'rad/s' }; % Angular velocity
end

branches
    i : p.i -> n.i;
    t : R.t -> C.t;
end

equations
    v == K*w;
    v == p.v - n.v;
    w == R.w - C.w;
    %t == -m-S*i;
%     if (w <= vel_thr)
%         % Linear region
%         t == -m;
%     else
        t == -m-S*i;
%     end    
end

end