Advanced Search

C_R

1461 Reputation

19 Badges

4 years, 9 days
Contact C_R

MaplePrimes Activity


These are questions asked by C_R

Why can't isolate not isolate theta(q) b...

C_R 1461 Maple
isolate
May 16 2023
3 1

[6600.0*theta(q)-17000.0*theta(q-1)+14400.0*theta(q-2)-4000.0*theta(q-3) = v(q)-.20*theta(q)+.20*theta(q-1)]

[6600.0*theta(q)-17000.0*theta(q-1)+14400.0*theta(q-2)-4000.0*theta(q-3) = v(q)-.20*theta(q)+.20*theta(q-1)]

 (1)

isolate([6600.0*theta(q)-17000.0*theta(q-1)+14400.0*theta(q-2)-4000.0*theta(q-3) = v(q)-.20*theta(q)+.20*theta(q-1)], theta(q))

Error, (in isolate) invalid arguments for isolate

  

solve([6600.0*theta(q)-17000.0*theta(q-1)+14400.0*theta(q-2)-4000.0*theta(q-3) = v(q)-.20*theta(q)+.20*theta(q-1)], theta(q))[]

theta(q) = 0.1515105603e-3*v(q)+2.575709827*theta(q-1)-2.181752068*theta(q-2)+.6060422411*theta(q-3)

 (2)

It works for h(x)  in help(isolate)


Download no_isolation.mw

How to replace Y(z)/z^i terms in z-trans...

C_R 1461 Maple
substitution z-transform
May 14 2023
2 2

Is it even possible to use a replacement list as attempted below to convert a z-transform to a finite difference expression?

z-transformed impulse response (`sampletime = 1/20`)

(10*exp(3/10)-7*exp(1/5)-3*exp(2/5))*exp(1/10)*U(z)/z+(exp(1/10)*(-3+10*exp(1/10)-7*exp(1/5))-(10*exp(3/10)-7*exp(1/5)-3*exp(2/5))*exp(1/10))*U(z)/z^2-(-3+10*exp(1/10)-7*exp(1/5))*exp(1/10)*U(z)/z^3 = 8*Y(z)*exp(1/10)*exp(3/10)*exp(1/5)+(8*((-exp(1/5)-exp(3/10))*exp(1/10)-exp(3/10)*exp(1/5)))*Y(z)/z+(8*(exp(1/10)+exp(1/5)+exp(3/10)))*Y(z)/z^2-8*Y(z)/z^3

(10*exp(3/10)-7*exp(1/5)-3*exp(2/5))*exp(1/10)*U(z)/z+(exp(1/10)*(-3+10*exp(1/10)-7*exp(1/5))-(10*exp(3/10)-7*exp(1/5)-3*exp(2/5))*exp(1/10))*U(z)/z^2-(-3+10*exp(1/10)-7*exp(1/5))*exp(1/10)*U(z)/z^3 = 8*Y(z)*exp(1/10)*exp(3/10)*exp(1/5)+8*((-exp(1/5)-exp(3/10))*exp(1/10)-exp(3/10)*exp(1/5))*Y(z)/z+8*(exp(1/10)+exp(1/5)+exp(3/10))*Y(z)/z^2-8*Y(z)/z^3

 (1)

deg_mx := 3

3

 (2)

Replacements to get finite difference equation

[seq(U(z)/z^i = U[q+1-i], i = deg_mx .. 0, -1), seq(Y(z)/z^i = Y[q+1-i], i = deg_mx .. 0, -1)]

[U(z)/z^3 = U[q-2], U(z)/z^2 = U[q-1], U(z)/z = U[q], U(z) = U[q+1], Y(z)/z^3 = Y[q-2], Y(z)/z^2 = Y[q-1], Y(z)/z = Y[q], Y(z) = Y[q+1]]

 (3)

Attempt to replace

algsubs([U(z)/z^3 = U[q-2], U(z)/z^2 = U[q-1], U(z)/z = U[q], U(z) = U[q+1], Y(z)/z^3 = Y[q-2], Y(z)/z^2 = Y[q-1], Y(z)/z = Y[q], Y(z) = Y[q+1]][1], (10*exp(3/10)-7*exp(1/5)-3*exp(2/5))*exp(1/10)*U(z)/z+(exp(1/10)*(-3+10*exp(1/10)-7*exp(1/5))-(10*exp(3/10)-7*exp(1/5)-3*exp(2/5))*exp(1/10))*U(z)/z^2-(-3+10*exp(1/10)-7*exp(1/5))*exp(1/10)*U(z)/z^3 = 8*Y(z)*exp(1/10)*exp(3/10)*exp(1/5)+8*((-exp(1/5)-exp(3/10))*exp(1/10)-exp(3/10)*exp(1/5))*Y(z)/z+8*(exp(1/10)+exp(1/5)+exp(3/10))*Y(z)/z^2-8*Y(z)/z^3)

Error, (in algsubs) cannot compute degree of pattern in z

  

NULL

Download replace_Y_of_z_by_Y_of_q.mw

How to apply initial conditions to a fle...

C_R 1461 MapleSim
beam
May 09 2023
0 0

I was not able to apply ICs (initial conditions) using the advanced parameter settings of the flexible beam component in the attached file. My intention is to have a beam moving at t=0s (velocity of end frame <> 0). The computed initial values for the elastic coordinates (see output console for the disabled component below encircled in red) indicate that the flexible beam has no kinetic energy at t=0s.

A workaround is to attach a rigid body to the end frame and apply the ICs to the body. (Inertia and mass of the rigid body can be set to zero.)

How to apply initial conditions to the disabled component so that it moves as the workaround?

Imposing_IC_v.msim

How get all solutions of this "periodic"...

C_R 1461 Maple
rootfinding numeric rootof
April 30 2023
2 2

Ideally, I would like to find all roots of this RootOf expression for a given interval.

I tried defining a function from the argument of the RootOf expression and using fsolve to find solutions, but could not get all of them.

What I managed to do skips the interval, is not really elegant and raises additional questions.
I would be grateful for any hints and improvements.

RootOf(_Z*cos(_Z)-sqrt(sin(_Z)^2))

RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))

 (1)

allvalues(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2)))

Error, (in RootOf/sort1) cannot numerically evaluate the argument

  

RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), index = i)

RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2), index = i)

 (2)

evalf(subs(i = 3, RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2), index = i)))

RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2), index = 3)

 (3)

evalf(RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 3))

-4.493409458

 (4)

rt := ''RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), i)''

'RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), i)'

 (5)

subs(i = 3, rt)

RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 3)

 (6)

evalf(RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 3))

-4.493409458

 (7)

seq(subs(i = k, rt), k = 1 .. 5)

RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 1), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 2), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 3), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 4), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 5)

 (8)

evalf(%)

0., 0., -4.493409458, 4.913180439, 4.913180439

 (9)

{-4.493409458, 0., 4.913180439}[]

-4.493409458, 0., 4.913180439

 (10)

seq(evalf(subs(i = k, rt)), k = 1 .. 5)

Error, (in evalf/RootOf) numeric exception: division by zero

  

evalf(seq(subs(i = k, rt), k = 1 .. 5))

Error, (in evalf/RootOf) numeric exception: division by zero

  

NULL

seq(subs(i = k, rt), k = -5 .. 5)

RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), -5), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), -4), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), -3), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), -2), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), -1), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 0), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 1), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 2), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 3), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 4), RootOf(op(RootOf(_Z*cos(_Z)-(sin(_Z)^2)^(1/2))), 5)

 (11)

evalf(%)

-4.493409458, -4.493409458, -2.028757845, -2.028757838, 4.913180439, 0., 0., 0., -4.493409458, 4.913180439, 4.913180439

 (12)

NULL

NULL

Download RootOf_a_periodic_function.mw

Can some suppress (i.e. ignore) the warn...

C_R 1461 MapleSim 2023
warning
April 27 2023
1 1

I cannot. If I right click on the warning I get only a copy option

Double_Pendulum_warning.msim

2 3 4 5 6 7 8 Last Page 4 of 18