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AndreaAlp

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11 years, 122 days
University of Verona
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These are questions asked by AndreaAlp

dsolve/numeric cannot solve if known pro...

AndreaAlp 30 Maple
dsolve numeric differential-equations
January 18 2018
0 1

Dear bright people of MaplePrimes, 

I'm stuck in a problem with dsolve.

I have a ODE system that I would like to solve numerically (because it's huge) in vars: var1(t), var2(t), var3(t), etc... Inside the ODE there are procedures with arguments like proc(f(x,y), a, b, c, etc...) where f(x,y) is a function for a curve (so x and y are variables) and a,b,c are numeric. 
Procedures have been written as indicated in the help page, i.e. differentiating whether the procedures are called with symbolic arguments or numeric arguments. So I call dsolve specifying the "known" procedures and a numeric method. Maple sets the problem correctly. However, when it tries to solve the equations numerically it points out that in the ODE ys there are some undefined parameters. Specifically, those parameters are x, y. But, again, x and y are not parameters but variables that are used in the procedures within the ODEs. 

I tried to include x and y as parameters and solve the system. However, before retrieving the solution, a numerical value must be given to all the parameters. 

What should I do if I need to keep f(x,y) symbolic in my procedures but I want to solve my ODE numerically? 

Thank you for supporting me. 
Thank you so much. 

Andrea



 

 

How can I find the intersection between ...

AndreaAlp 30 Maple 18
surface intersection implicitplot3d
December 21 2017
6 18

Hello everyone, 

please need some brain power here to help me with this problem. I'm stacked here and I cannot find a solution. 

I would like to find the intersection between a plane and a quadric surfaces. Please notice that the two equations are written like f(x,y) and g(x,z) respectively. My first problem is that I cannot visualize the two surfaces correctly as implicitplot3d of the quadric surfaces displays nothing in return. 

I want then to find the centre of the ellipse and plot the point and the two surfaces all together in the same 3d plot. Somehow I canont make it. What is wrong with me? 

I am pasting here my MWE. 

Any kind of help would be really appreciated. Thank you so much. 

Andrea

MWE_maple_help.mw
 

> 

restart:
> 

with(plottools):
with(plots):
> 

with(Student:-MultivariateCalculus):
with(Student:-Precalculus):
with(geometry):
> 

with( Optimization ):

> 

my_plane := 2024.30587449691-.341275505799078*x-3.89936179341114*y;
my_quadric := -10595.4104931095+6.73749956241827*x+42.1022818380012*z-0.654818649508000e-1*x^2-0.421174257681115e-1*z^2;

2024.30587449691-.341275505799078*x-3.89936179341114*y

  

-10595.4104931095+6.73749956241827*x+42.1022818380012*z-0.654818649508000e-1*x^2-0.421174257681115e-1*z^2

 (1)
> 

my_quadric_plot_3d := implicitplot3d(my_quadric, x=-10000..10000,
                                       y = -100..100,
                                      z=-10000..10000,color="DodgerBlue"):
my_plane_plot_3d := implicitplot3d(my_plane, x=-10000..10000,
                                       y = -100..100,
                                      z=-10000..10000,color="DarkOrange"):
> 

my_ellipse := CompleteSquare( subs(y = solve(z = my_plane, y), my_quadric));

-0.4211742577e-1*(z-499.8202178)^2-0.6548186495e-1*(x-51.44553815)^2+99.68250

 (2)
> 

ellipse(e1, my_ellipse, [x,z]):
XY_centre_e1     := coordinates(center(o,e1)):
my_center_point := [XY_centre_e1[1],XY_centre_e1[2],
                       subs(x=XY_centre_e1[1], y=XY_centre_e1[2], my_plane)]:
my_center_point_plot := pointplot3d(my_center_point, color = "red"):
> 

display(my_center_point_plot, my_plane_plot_3d, my_quadric_plot_3d);

 


 

Download MWE_maple_help.mw

 

 

Maple CodeGeneration[Matlab] array eleme...

AndreaAlp 30 Maple
July 05 2013
2 4

Dear all

i am writing some differential equations with Maple. I'd like now to generate the Matlab code and let them run. Unfortunately I need the closed form but Maple does not distinguish (at first sight, of course) between time functions and parameters. But what in Maple is a time function, will be an array in Matlab. Unfortunately in Matlab environment the array product is carried out by the meaning of the element-by-element command: ".* " .

Using CodeGeneration[Matlab...

Optimal control ODE or DAE formulation...

AndreaAlp 30 Maple 12
June 06 2013
0 0

Further tags : implicit form, Matlab codegen for GPOPS purposes

Hi there,

I would like to introduce my self and ask you for an advice. 

I have a four linked robot that i would really like to control by the meaning of the optimal control theory. The arm has 4 actuators (giving torques U) in corrispondence of 4 rotational joints. P parameters describe the system.

I got ht edynamic system with the Lagrangian method and now I have 4 2nd order...

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