How do I keep f as a variable in a state space model, as f is supposed to be the input variable??
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m1=1;
m2=1;
l1=1;
l2=1;
M=5;
g=10;
A_motor=[0,1,0,0,0,0;0,0,(-m1*g)/M,0,(-m2*g/M),0;0,0,0,1,0,0;0,0,(g/l1)-(-m2*g)/(M*l1),0,(-m2*g)/(M*l2),0;0,0,0,0,0,1;0,0,(-m1*g)/(M*l2),0,(g/l2)-(m2*g)/(M*l2),0];
B_motor=[0;f/M;0;-f/(M*l1);0;-f/(M*l2)];
C_motor=[0,1,0,1,0,1];
D_motor=[0];
When I input this as my code I recieve an error stating that f is not defined, however I need to keep f as the input variable.
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Star Strider
le 5 Mai 2022
Since ‘f’ is only defined in ‘B_motor’ simply create an anonymous function from it, and then from ‘motor_ss’ (to keep with the existing names).
m1=1;
m2=1;
l1=1;
l2=1;
M=5;
g=10;
A_motor=[0,1,0,0,0,0;0,0,(-m1*g)/M,0,(-m2*g/M),0;0,0,0,1,0,0;0,0,(g/l1)-(-m2*g)/(M*l1),0,(-m2*g)/(M*l2),0;0,0,0,0,0,1;0,0,(-m1*g)/(M*l2),0,(g/l2)-(m2*g)/(M*l2),0];
B_motor= @(f) [0;f/M;0;-f/(M*l1);0;-f/(M*l2)];
C_motor=[0,1,0,1,0,1];
D_motor=[0];
motor_ss = @(f) ss(A_motor, B_motor(f), C_motor, D_motor)
figure
step(motor_ss(0.0000001))
figure
step(motor_ss(0.0001))
I considered Create State-Space Model with Both Fixed and Tunable Parameters, however that has the tunable parameters only in the ‘A’ matrix (appropriately), so that would not appear to apply here.
.
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Paul
le 5 Mai 2022
Hi Star,
Tunable parameters work fine anywhere in the model
m1=1;
m2=1;
l1=1;
l2=1;
M=5;
g=10;
f = realp('f',0); % default value of 0
A_motor=[0,1,0,0,0,0;0,0,(-m1*g)/M,0,(-m2*g/M),0;0,0,0,1,0,0;0,0,(g/l1)-(-m2*g)/(M*l1),0,(-m2*g)/(M*l2),0;0,0,0,0,0,1;0,0,(-m1*g)/(M*l2),0,(g/l2)-(m2*g)/(M*l2),0];
B_motor=[0;f/M;0;-f/(M*l1);0;-f/(M*l2)];
C_motor=[0,1,0,1,0,1];
D_motor=[0];
sys = ss(A_motor,B_motor,C_motor,D_motor)
step(sampleBlock(sys,'f',0.0001));
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Paul
le 4 Mai 2022
Hello Arya,
Assuming that f(t) is the input to the system, it is not included in the B-matrix. Rathe, the B-matrix should be:
B_motor=[0;1/M;0;-1/(M*l1);0;-1/(M*l2)];
and the state space model of the system is:
xdot = A_motor * x + B_motor * f
y = C_motor * x + D_motor * f
If f(t) is not the input to the system, further clarification is needed on what f actually is.
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