An error: Undefined function 'mrdivide' for input arguments of type 'NetworkEn​gine.Compo​nentVariab​leCompileD​ata'.

    I'm trying to build an engine model in simscape. Here is my code;*

component engine_cylinders 
% ine :0.1
% Provides an interface between the pneumatic, liquid and mechanical rotational
% domains. 
%    
% Eta is the conversion efficiency.
%
% If the pneumatic pressure drops from Port A to port B, then the
% resulting torque is positive acting from the mechanical C to S ports.

% Copyright 2014 SK.

nodes
    A = foundation.pneumatic.pneumatic; % A:right
    B = foundation.pneumatic.pneumatic; % B:right
    F = foundation.thermal_liquid.thermal_liquid; % F:left
    S = foundation.mechanical.rotational.rotational; % S:left
    C = foundation.mechanical.rotational.rotational; % C:left
end

parameters
    H_L = { 1, 'J/kg' };     % Fuel lower heating value
    rev_cy = { 1, '1'};      % 1 for two stroke and 2 for four stroke engines
    V_d = { 1, 'm^3' };      % Displacement volume
    R_AF_high = { 27, '1'};  % Higher R_AF limit (typically 20-27 for HFO)
    R_AF_low = {  5, '1'};   % Lower R_AF limit (typically 5-8)

end

parameters(Access = private)

      gam = { 1.4, '1' };                 % Ratio of specific heats
      c_p = { 1005 , 'J/kg/K' };          % Specific heat at constant pressure
      c_v = { 717.86 , 'J/kg/K' };        % Specific heat at constant volume
      R   = { 287.05, 'J/kg/K' };         % Specific gas constant
      viscosity = { 18.21e-6, 'Pa*s' };   % Dynamic viscosity
      kin_viscosity = { 15.11e-6, 'm^2/s'};    % Kinematic viscosity
      Pa  = { 101325, 'Pa' };             % Ambient pressure
      Ta  = { 293.15, 'K' };              % Ambient temperature
      range_error = {2, '1' };            % Pressure or temperature below absolute zero
      K_z1 = {0.0105e-5, '1'};            % Const. for fuel chem. energy prop. in exh gas
      K_z0 = {0.3120, '1' };              % Const. for fuel chem. energy prop. in exh gas
  end

variables
    mdot_F = { 1, 'kg/s' };    % Fuel mass flow
    mdot_A = { 1, 'kg/s' };    % Air mass flow
    R_AF = {1, '1'};           % Air to fuel ratio
    eta_c = { 1, '1' };        % Combustion Efficiency
    p_i = {1, 'N/m^2' };       % Indicated mean effective pressure (IMEP)
    x_r = {1, '1' };           % Fuel index position
    p_imax = {1, 'N/m^2' };    % Maximum IMEP
    p_b = {1, 'N/m^2' };       % Brake mean effective pressure (BMEP)
    p_f = {1, 'N/m^2' };       % Friction mean effective pressure (FMEP)
    zeta_a = {1, '1' };        % Fuel chemical energy proportion in exh gas
    % Pneumatic through variables
    G   = { 0, 'kg/s' };       % Mass flow rate 
    Q_A = { 0, 'J/s' };        % Heat flow into port A
    Q_B = { 0, 'J/s' };        % Heat flow into port B
    % Mechanical through and across variables
    t = { 0, 'N*m' };           % Torque
    w = { 0, 'rad/s' };         % Angular velocity
    BSFC = {0, 'kg/W' };        % Brake specific fuel consumption
    pr_t = {0, '1'};            % Pressure ratio P_B/P_A
    lambda_e = {0, '1'};        % Specific heat ratio 
    eta_b = {0, '1' };          % Brake efficiency   
    mdot = {0, 'kg/s'};         % Fuel mass flow
end

function setup
    mdot_F == F.mdot;
    mdot_A == A.G;
    R_AF == mdot_A/mdot_F;

      if R_AF>=R_AF_high
          eta_c == 1;
      elseif R_AF<=R_AF_low
          eta_c == 0;
      else
          eta_c == (R_AF-R_AF_low)/(R_AF_high-R_AF_low);
      end

      if eta <= 0
          pm_error( 'simscape:GreaterThanZero', 'Efficiency' )
      end
      if eta > 1
          pm_error( 'simscape:LessThan', '1' )
      end
  end

branches
    G   : A.G -> B.G;
    Q_A : A.Q -> *;
    Q_B : B.Q -> *;
    t   : S.t -> C.t;
    mdot: F.mdot -> *;
end

equations

      let
          % Logs of absolute pressures and temperatures. Extrapolate
          % linearly for pressures below p_min.
          P_A = if A.p < p_min, p_unit*exp(p_offset_min + p_gradient_min*(A.p - p_min)) else A.p end;
          P_B = if B.p < p_min, p_unit*exp(p_offset_min + p_gradient_min*(B.p - p_min)) else B.p end;
          % Efficiency from pneumatic to mechanical domains. Will be greater than one if pumping, and
          % less than one if motoring.

      in
          w == S.w - C.w;
          p_i == eta_c*p_imax*x_r;
          p_b == p_i - p_f; 
          p_b == (p_imax - K_f3)*x_r-K_f0;
          zeta_a == K_z1 * p_b + K_z0;
          t == p_b*V_d/(2*pi*rev_cy);
          p_b == pi*N_E*t/30;
          BSFC == mdot_F/p_b;
          eta_b == p_b/mdot_F/H_L;

          if G>=0
              Q_A == G*A.c_p*A.T;            
          else
              Q_B == -G*A.c_p*B.T;
          end
      end
  end

end

But I'm getting an error:

Failed to generate 'MySimscape_lib'

Caused by: Error using MySimscape.pneumatic/engine_cylinders>setup (line 73) Undefined function 'mrdivide' for input arguments of type 'NetworkEngine.ComponentVariableCompileData'.

What does this mean, and how can I get over that problem.

I'll appreciate if anyone can help?

Answer 1

[Steve Miller]

The documentation page for equations in Simscape tells you which equations you can use and what the requirements are. mrdivide is permitted, but the second element must be a scalar.

https://www.mathworks.com/help/simscape/lang/equations.html

--Steve