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Naveshin Jawaheer

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Error, (in plots/odeplot) input is not a...

Answered: Naveshin Jawaheer 15

September 12 2022

0 0

@tomleslie Thanks for your help. For some reason when I run it, the same error Error, (in plots/odeplot) input is not a valid dsolve/numeric solution) still pops up. All I have changed is the mass values. I ahve attached the code below. Also for some reason, why is the code for the plot in text mdoe rather than math mode?

Thanks for your time and thanks

restart:

>	(x[1],y[1]):= l[1]~(sin,-cos)(theta(t)); (x[2],y[2]):= l[2]~(-sin,cos)(theta(t)); (x[4],y[4]):= (x[1],y[1])+~l[4]~(-sin,cos)((theta+phi)(t)); (x[3],y[3]):= (x[2],y[2])+~l[3]~(sin,-cos)((theta-psi)(t)); R:= table([seq](k= [x[k],y[k]], k= 1..4)); dR:= diff~(R, t);

table( [( 1 ) = [l[1]*sin(theta(t)), -l[1]*cos(theta(t))], ( 2 ) = [-l[2]*sin(theta(t)), l[2]*cos(theta(t))], ( 3 ) = [-l[2]*sin(theta(t))-l[3]*sin(-theta(t)+psi(t)), l[2]*cos(theta(t))-l[3]*cos(-theta(t)+psi(t))], ( 4 ) = [l[1]*sin(theta(t))-l[4]*sin(theta(t)+phi(t)), -l[1]*cos(theta(t))+l[4]*cos(theta(t)+phi(t))] ] )

(1)

>	F:= [theta, phi, psi](t): V:= [l[1], l[2], l[3], l[4], m[1], m[2], diff(F, t)[], (cos,sin)(psi(t)), g]:

>	T:= combine(simplify(collect(m[1]/2inner(dR[4]$2)+m[2]/2inner(dR[3]$2), V)), trig);

(2)

>	U:= collect(simplify(expand(gm[1]y[4] + gm[2]y[3])), V);

-g*m[1]*l[1]*cos(theta(t))+g*m[2]*l[2]*cos(theta(t))+(-g*cos(theta(t))*cos(psi(t))-g*sin(theta(t))*sin(psi(t)))*m[2]*l[3]+g*(cos(theta(t))*cos(phi(t))-sin(theta(t))*sin(phi(t)))*m[1]*l[4]

(3)

>	L:= simplify(collect(T-U, V));

(4)

>	Eul:= remove(has, VariationalCalculus:-EulerLagrange(L, t, F), K[1]);

${sin(phi(t))*l[1]*l[4]*m[1]*(diff(theta(t), t))^2-g*(-sin(phi(t))*l[4]*m[1]*cos(theta(t))-sin(theta(t))*cos(phi(t))*l[4]*m[1])+l[4]*m[1]*(cos(phi(t))*l[1]-l[4])*(diff(diff(theta(t), t), t))-m[1]*l[4]^2*(diff(diff(phi(t), t), t)), sin(psi(t))*l[2]*l[3]*m[2]*(diff(theta(t), t))^2-g*(sin(psi(t))*l[3]*m[2]*cos(theta(t))-sin(theta(t))*cos(psi(t))*l[3]*m[2])-l[3]*m[2]*(cos(psi(t))*l[2]-l[3])*(diff(diff(theta(t), t), t))-m[2]*l[3]^2*(diff(diff(psi(t), t), t)), -g*(-(cos(phi(t))*l[4]*m[1]-cos(psi(t))*l[3]*m[2]-l[1]*m[1]+l[2]*m[2])*sin(theta(t))-cos(theta(t))*(sin(phi(t))*l[4]*m[1]+sin(psi(t))*l[3]*m[2]))-(2*(diff(phi(t), t))*sin(phi(t))*l[1]*l[4]*m[1]+2*(diff(psi(t), t))*sin(psi(t))*l[2]*l[3]*m[2])*(diff(theta(t), t))-(-2*cos(phi(t))*l[1]*l[4]*m[1]-2*cos(psi(t))*l[2]*l[3]*m[2]+(l[1]^2+l[4]^2)*m[1]+m[2]*(l[2]^2+l[3]^2))*(diff(diff(theta(t), t), t))-l[4]*m[1]*(diff(phi(t), t))^2*sin(phi(t))*l[1]+l[4]*m[1]*(cos(phi(t))*l[1]-l[4])*(diff(diff(phi(t), t), t))-(diff(diff(psi(t), t), t))*l[3]*m[2]*(cos(psi(t))*l[2]-l[3])+(diff(psi(t), t))^2*l[3]*m[2]*sin(psi(t))*l[2]}$

(5)

>	INITS:= phi(0) = Pi/4, psi(0) = Pi/4, theta(0) = (3*Pi)/4, D(phi)(0) = 0, D(psi)(0) = 0, D(theta)(0) = 0 :

>	PARAM:= [g = 9.8, l[1] = 10, l[2] = 100, l[3] = 100, l[4] = 21, m[1] = 35000, m[2] = 350]:

>	sys:= eval(Eul, PARAM)[]:

>	sol:= dsolve([sys, INITS], numeric):

plots:-odeplot(
    sol, [t, diff(psi(t), t)], 1..3, numpoints= 1000,
    labels= ["times(sec)", "Psi’(deg/s)"],
    labeldirections= [horizontal, vertical], font= [TIMES, ROMAN, 20]
);
plots:-odeplot(
    sol, [t, diff(theta(t), t)], t= 1..3, numpoints= 1000,
    labels= ["time(sec)", "Theta’(deg/s)"],
    labeldirections= [horizontal, vertical], font = [TIMES, ROMAN, 20]);

Error, (in plots/odeplot) input is not a valid dsolve/numeric solution

Download Naveshin.mw

Same dsolve issue...

Answered: Naveshin Jawaheer 15

September 12 2022

0 0

@Carl Love Thanks for the help on the missing parenthesis. However for some reason it can be seen that I still have the issue with the dsolve part which gives me the error, Error, (in dsolve/numeric/process_input) system must be entered as a set/list of expressions/equations. The code with the update is below. Do you mind taking a look?