Matlab 为什么我只能在八度音阶的ODE45模拟中得到NaN och Inf？
我用ODE45的倍频程来模拟一个ODE方程组。但问题是ODE模拟给出了错误的值。看看这个倍频程代码：Matlab 为什么我只能在八度音阶的ODE45模拟中得到NaN och Inf？,matlab,octave,nan,openmodelica,ode45,Matlab,Octave,Nan,Openmodelica,Ode45,我用ODE45的倍频程来模拟一个ODE方程组。但问题是ODE模拟给出了错误的值。看看这个倍频程代码： function dx = dynamik(t, x) b1 = 1000; b2 = 2000; m1 = 10; m2 = 7; M = 2000; g = 9.82; mu = 0.3; L = 0.1; Ap = 0.004; Am = 0.002; Pp = 2*10^6; Pm = 2.1*10^6; k1 = 1.78e+4; k2 = 4.04e+4; k3 = 8.86e+3;
function dx = dynamik(t, x)
b1 = 1000;
b2 = 2000;
m1 = 10;
m2 = 7;
M = 2000;
g = 9.82;
mu = 0.3;
L = 0.1;
Ap = 0.004;
Am = 0.002;
Pp = 2*10^6;
Pm = 2.1*10^6;
k1 = 1.78e+4;
k2 = 4.04e+4;
k3 = 8.86e+3;
dx= [ x(2);
-k1/m1*x(1) + k1/m1*x(3) - b1/m1*x(4) + b1/m1*x(4) + Ap/m1*Pp - Pm*Am/m1*x(2);
x(4);
k1/M*x(1) - k1/M*x(3) + b1/M*x(2) - b1/M*x(4) - g*mu*x(4) - k2/M*x(3) + k3*L/M*sin(x(5));
x(6);
3*k2/(m2*L)*x(3) - 3*k2/m2*sin(x(5)) - 3*k3/(m2*L^2)*x(5) - 3*b2/(m2*L^2)*x(6) + 3*g/(2*L)*sin(x(5))];
endfunction
tspan = 0:0.5:10;
init = [0, 0, 0, 0, 0, 0];
[t, y] = ode45(@dynamik, tspan, init);
>> y
y =
0.0000e+00 0.0000e+00 0.0000e+00 0.0000e+00 0.0000e+00 0.0000e+00
1.6659e+08 -6.9253e+10 -1.9336e+05 8.0380e+07 -4.4787e+07 3.8388e+12
5.9331e+18 -2.4665e+21 -6.8864e+15 2.8628e+18 -1.3333e+32 1.1428e+37
2.1131e+29 -8.7843e+31 -2.4526e+26 1.0196e+29 -3.9691e+56 3.4019e+61
7.5258e+39 -3.1286e+42 -8.7350e+36 3.6313e+39 -1.1816e+81 1.0127e+86
2.6803e+50 -1.1142e+53 -3.1110e+47 1.2933e+50 -3.5174e+105 3.0148e+110
9.5460e+60 -3.9684e+63 -1.1080e+58 4.6060e+60 -1.0471e+130 8.9747e+134
3.3998e+71 -1.4134e+74 -3.9461e+68 1.6404e+71 -3.1171e+154 2.6717e+159
1.2109e+82 -5.0337e+84 -1.4054e+79 5.8425e+81 -9.2794e+178 7.9533e+183
4.3125e+92 -1.7928e+95 -5.0054e+89 2.0808e+92 -2.7624e+203 2.3676e+208
1.5359e+103 -6.3849e+105 -1.7827e+100 7.4109e+102 -8.2234e+227 7.0482e+232
5.4701e+113 -2.2740e+116 -6.3491e+110 2.6394e+113 -2.4480e+252 2.0982e+257
1.9482e+124 -8.0989e+126 -2.2612e+121 9.4003e+123 -7.2875e+276 6.2461e+281
6.9386e+134 -2.8844e+137 -8.0534e+131 3.3479e+134 -2.1694e+301 1.8594e+306
NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN
NaN NaN NaN NaN NaN NaN
model Hydraulik_System_1
// Types for variables
type PositionCylinder = Real(unit="m");
type Position = Real(unit="m");
type Velocity = Real(unit="m/s");
type DegreesPosition = Real(unit="rad");
type DegreesVelocity = Real(unit="rad/s");
type pressure = Real(unit="Pa");
type flows = Real(unit="l/min", min=0.0);
// Types for parameters
type spring = Real(unit="N/m");
type damper = Real(unit="Ns/m");
type mass = Real(unit="kg");
type friction = Real(unit="%");
type length = Real(unit="m");
type gravitation = Real(unit="m/s^2");
type area = Real(unit="cm^2");
// Parameters
parameter spring k1 = 1.78*10^4;
parameter spring k2 = 4.04*10^4;
parameter spring k3 = 8.86*10^3;
parameter mass m1 = 10;
parameter mass m2 = 7;
parameter mass M = 2000;
parameter damper b1 = 1000;
parameter damper b2 = 2000;
parameter gravitation g = 9.82;
parameter friction mu = 0.3;
parameter area Am = 0.002;
parameter area Ap = 0.004;
parameter length L = 0.1;
parameter pressure Pp = 2*10^6;
parameter pressure Pm = 2.1*10^6;
// Variables
PositionCylinder x1;
Position x3;
Velocity x2 , x4;
DegreesPosition x5;
DegreesVelocity x6;
initial equation
x1 = 0;
x2 = 0;
x3 = 0;
x4 = 0;
x5 = 0;
x6 = 0;
equation
der(x1) = x2;
der(x2) = - k1/m1*x1 + k1/m1*x3 - b1/m1*x4 + b1/m1*x4 + Ap/m1*Pp - Pm*Am/m1*x2;
der(x3) = x4;
der(x4) = k1/M*x1 - k1/M*x3 + b1/M*x2 - b1/M*x4 - g*mu*x4 - k2/M*x3 + k3*L/M*sin(x5);
der(x5) = x6;
der(x6) = 3*k2/(m2*L)*x3 - 3*k2/m2*sin(x5) - 3*k3/(m2*L^2)*x5 - 3*b2/(m2*L^2)*x6 + 3*g/(2*L)*sin(x5);
end Hydraulik_System_1;
你能告诉我为什么我的模拟会发生这种情况吗？OpenModelica模拟结果和倍频程模拟结果之间存在巨大差异。为什么？我是否更改ODE解算器并不重要。结果几乎是一样的。我使用了lsode，也得到了正确的答案，但通话参数必须切换，tspan更小 首先，交换函数中的参数：
function dx = dynamik(x, t)
tspan = 0:0.0625:2;
lsode[y,t] = lsode(@dynamik, init, tspan );
更新：已安装
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