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sjoelund.se wrote:
For me, the first one succeeds and the second one fails.
If I make M,m and D constant, it succeeds. So something in initialization seems to go wrong. Note that using simulate(rocket, method = "euler") works fine regardless.
But the first falied and the second true.I can't explain,
So something in initialization seems to go wrong
??????
Please tell me!!!!!!!!
thanks for all!!!!!!!!!!!!!
ok
I will write to clean my problem!!!!!!!11
The first i have a ODE : => x’’ = G*M* /(x2) + G*m*/( (D-x)2 ) , x(0) = R , x'(0) = V
G = 6.67*(10^(-11)) "gravity constant";
M = 59736*(10^(20)) "mass of earth";
m = 7.347*(10^(22)) "mass of mooth";
D = 384400.0 "distance betwen earth and mooth(mean)";
V = 50.0 "velocity of rocket";
After i write this on modelica (**********)
Code:
model rocket
parameter Real G = 6.67*(10^(-11)) "gravity constant";
parameter Real M = 59736*(10^(20)) "mass of earth";
parameter Real m = 7.347*(10^(22)) "mass of mooth";
parameter Real D = 384400.0 "distance betwen earth and mooth(mean)";
parameter Real V = 50.0 "velocity of rocket";
Real x(start = 6400.0) "distance bettwen rocket and earth";
Real y(start = V) "der of x";
Real temp1;
Real temp2;
equation
temp1 = G*M;
temp2 = G*m;
der(y)*(D-x)*(D-x)*x*x = -1*temp1*(D-x)*(D-x) + temp2*x*x ;
der(x) = y;
end rocket;
i simulator it -> error
But where i change it by : y(t) = Rx(t) và u(a) = y(a*T) với t = a*T with T2 = R/g
I have new ODE : u’’ = -1/(u2) + 0.012/((60 - u)2); u(0) = 1 ;u’(0) = V*T/R
I write on modelica
Code:
model rocket
parameter Real G = 6.67*(10^(-11)) "gravity constant";
parameter Real M = 59736*(10^(20)) "mass of earth";
parameter Real m = 7.347*(10^(22)) "mass of mooth";
parameter Real D = 384400.0 "distance betwen earth and mooth(mean)";
parameter Real V = 50.0 "velocity of rocket";
Real x(start = 1.0);
Real y(start = (V/7.92));
Real temp1 ;
Real temp2;
equation
temp1 = m/M;
temp2 = D/6400;
der(y)*((temp2-x)^2)*x*x = -1*((temp2-x)^2) + temp1*x*x ;
der(x) = y;
end rocket;
-> it is ok
So , why the first(**********) way was error
Thanks for all!
But I can't fix it.plz help me.
I get a other solution by ODE :
Code:
model rocket
parameter Real G = 6.67*(10^(-11)) "gravity constant";
parameter Real M = 59736*(10^(20)) "mass of earth";
parameter Real m = 7.347*(10^(22)) "mass of mooth";
parameter Real D = 384400.0 "distance betwen earth and mooth(mean)";
parameter Real V = 50.0 "velocity of rocket";
Real x(start = 1.0);
Real y(start = (V/7.92));
Real temp1 ;
Real temp2;
equation
temp1 = m/M;
temp2 = D/6400;
der(y)*((temp2-x)^2)*x*x = -1*((temp2-x)^2) + temp1*x*x ;
der(x) = y;
end rocket;
it excute good and can switch to
Code:
model rocket
parameter Real G=6.67*(10^(-11)) "gravity constant";
parameter Real M = 59736*(10^(24)) "mass of earth";
parameter Real m = 7.347*(10^(22)) "mass of mooth";
parameter Real D = 384400 "distance bettwen earth and mooth(mean)";
parameter Real V = 100000.0 "velocity of rocket";
Real x(start = 0.0) "distance bettwen rocket and earth";
Real y(start = V) "der of x";
equation
der(x) = y;
der(y)*((D-x)^2)*x = (-1)*G*M*((D-x)^2) + G*m*x ;
end rocket;
(************)
so why (************) don't run when i simulate??????It can error of modelica??????
Thanks
hi all
I have GUI in java and input some parameter example (a) .I want process in openmodelica example(ODE :
Code:
der(x) = ax
)and show result back java.
Plz give me solution.
thanhks
Ok thanks
plz help me again
Code:
model rocket
parameter Real G=6.67*(10^(-11)) "gravity constant";
parameter Real M = 59736*(10^(24)) "mass of earth";
parameter Real m = 7.347*(10^(22)) "mass of mooth";
parameter Real D = 384400 "distance bettwen earth and mooth(mean)";
parameter Real V = 100000.0 "velocity of rocket";
Real x(start = 0.0) "distance bettwen rocket and earth";
Real y(start = V) "der of x";
equation
der(x) = y;
der(y)*((D-x)^2)*x = (-1)*G*M*((D-x)^2) + G*m*x ;
end rocket;
where i sinulate -> error:
Code:
simulate(rocket,stopTime = 5)
record SimulationResult
resultFile = "Simulation failed.
"
end SimulationResult;
plz .I need it soon.I don 't know what is error
adrpo,
so,how to get a solution for it????????
y'' - (y'/(x-1)) = x*(x-1) with y'(2) = -1 and y(2) = 1;
@All : I am .... so i not good at English
i have a problem ưhen i try to describe ODE
I HAVE A ODE :
y'' - (y'/(x-1)) = x*(x-1) with y'(2) = -1 and y(2) = 1;
how way to get a solution?????
my code:
Code:
model DAEexample
Real x;
Real y(start = 1.0);
Real u(start = -1.0);
equation
der(y) = u;
der(u) - (u/(x-1)) = x*(x-1);
end DAEexample;
--------
Code:
loadFile("C:/OpenModelica1.5.0/test/test1.mo")
true
>> simulate(test1,startTime = 2.0,stopTime = 20.0)
record SimulationResult
resultFile = "Simulation failed.
Error: Too few equations, underdetermined system. The model has 1 equation(s) and 2 variable(s)
"
end SimulationResult;
thanks for all
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