Error occurring while solving odes using ode15s

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Telema Harry 2021-8-1

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评论： Telema Harry 2021-8-3

Hello,

I am trying to solve a systems of nonlinear ODE using ODE15s but I keep getting an error after about 29 seconds and I can't figure out what is causing the error.

see a screen shot of the error.

What could be the likely cause of this error.

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Telema Harry 2021-8-2

编辑：Telema Harry 2021-8-2

在 MATLAB Online 中打开

@Walter RobersonThank you once again for your feedback.

what is class() of the result? I am not sure. Please how can I check this?
have you configured Mass Matrix? I am not sure but I have included a sample of the code. The I variables are all constant while the Q_.. variables are computed at some point using the different input data.
Have you configured any special functions such as for estimation of the gradient? No. The functions only computes input variables required for further computation. The functions are shown in the sample code
Is it possible that you passed in your time as single precision? I only used time (t) once, to compute the local time. Local_time = DATE.tLST * 3600 + t;
your boundary conditions as single precision? I have not set boundary condition.

   options = [];
     In0 = [loc.lat; loc.lon; In.T_gas; In.T_film; In.M_gas; In.Uz; In.Z]';
      [t,output] = ode15s(@dynamics,tspan,In0, options, wind);
function dxdt = dynamics(t,y,wind)
%% VARIABLES DECLARATION
    global I DATE B
%     persistent TT
%% TRANSFER VALUES FROM y VARIABLE TO THE ACTUAL VARIABLE NAMES
      lat       = y(1);
      lon       = y(2);
      T_gas     = y(3);
      T_film    = y(4);
      M_gas     = y(5);
      Uz        = y(6);
      Z         = y(7);  
 
       [t,y']
    
    [P_air, T_air, rho_air] = atmospheremodel(Z); 
    [Uw, Vw] = interpolateWindVelocity(P_air, lon, lat, wind);
    
    Local_time = DATE.tLST * 3600 + t;
    Local_time = Local_time/3600; 
    
    [day_number, ELV] = solarangle_function(DATE, Local_time,lat,lon);
    
    dlat = M* Uw; 
    dlon = (M* Vw)/ (cos(lat*(pi/180)));
    dT_film = (Q_sun + Q_Albedo + Q_IR_planet + Q_IR_film + Q_con_ext -  Q_con_int - Q_IR_out)/(I.c_film * B.M_film);    
    alt = 25000;
    if Z > alt
        dM_gas =  -mass_flow;
    else
        dM_gas =  0;
    end
    
    
    
    dUz = (GI - B.M_gross*I.g  -  Drag_Z)/M_virtual;
    dZ = Uz;
    
      RoC =  -Uz;    
      dT_gas = Q_con_int/(I.Ye*M_gas*I.Cv) - (((I.Ye - 1)*rho_air*I.g * RoC)/(I.Ye * rho_gas*I.R_gas));
     dxdt = [dlat, dlon, dT_gas, dT_film, dM_gas, dUz, dZ]';

Telema Harry 2021-8-3

Thank you once again for your help. Please see below output of the code.

class(tspan) = 'double'

class(In0) = double

class (wind) = struct

class (I) = struct

class(B) = struct

class(DATE) = struct

class (test_output) = double

Telema Harry 2021-8-3

在 MATLAB Online 中打开

@Walter Roberson Thank you so much for the recommendation on how to pass additional variables to the ode*().

I have removed all the global variables and I have re-written my function as shown below.

In0 = [loc.lat; loc.lon; In.T_gas; In.T_film; In.M_gas; In.Uz; In.Z]; 
[t, output] = Balloondynamics(tspan,In0,wind, DATE, I, B);
 
function [time, dxdt] = dynamics(tspan,y0,wind, DATE, I, B)
    [time, dxdt] = ode23(@solve_ode,tspan,y0);
    
    function dxdt = solve_ode(t,y)
      %% TRANSFER VALUES FROM y VARIABLE TO THE ACTUAL VARIABLE NAMES
      lat       = y(1);
      lon       = y(2);
      T_gas     = y(3);
      T_film    = y(4);
      M_gas     = y(5);
      Uz        = y(6);
      Z         = y(7);  
 
       [t,y']
        ....  
          
    end
    
end

I am a step closer to solving my next challenge.

So, my wind data for 1 hour is about 6.5 G and loading it takes a lot of time. Idealy, I will like to run my simulation using 1 week worth of wind data. This would mean, discarding the wind data after 1 hour simulation time (3600 seconds) and loading the next hour wind data.

e.g. load new wind data after every 3600 seconds.

I can read the wind data one after the other but I am not sure how to pass it to the ode function.

However, I was able to pass the multiple wind data to my own Runge Kutta function.

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Answer 1

Sulaymon Eshkabilov 2021-8-1

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编辑：Sulaymon Eshkabilov 2021-8-1

The computed solution might be "nan" or "inf" only. Briefly speaking the size mismatch.

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Walter Roberson 2021-8-1

I do not understand how this could explain the error message about trying to mix sparse and single in a * operation ?

Telema Harry 2021-8-2

Thank you for your input @Sulaymon Eshkabilov

I initially thought that maybe one of the computed solution is "nan" or infinity, so I tried to debug the code just before it crashed and I discovered that all the computed solutions were all real numbers.

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Error occurring while solving odes using ode15s

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