Skip to main content

graphics - Animating a rotating disk


I have a system with 3 degrees of freedom that I want to know if it is possible to visualise with Mathematica in the two-dimensional $X-Y$ plane. I have a plane circular object rotating at its set speed say $10$ deg/s. This object is not rotating at the $(0, 0)$ origin point but is displaced from the origin $(0, 0)$ coordinates and its motion path is described by


$x=x_0 + a \times \cos(\omega \: t)$ and $y=a \times \sin(\omega \: t)$


Some values: $x_0 = 1$ mm; $a=0.25$ mm, $\omega=10$ deg/s (same as the rotating speed of the circular object). The radius of the circular object can be taken to be a couple of cm say $2$ cm.


The time parameter $t$ in the parametric equations can be discretised in $20$ steps as follows:


$\mathrm{step}= \frac{360 \; \mathrm{deg}}{\omega \times 20} = \frac{360}{10 \times 20}=1.8$ s


so that $\mathrm{step}$ will take values $0$, $1.8$, $3.6$, $\ldots$, $34.2$ s.


Thus the product $\omega \: t$ as the cosine and sine arguments of the parametric path can be written as



$\omega \: t = \omega \times \frac{\mathrm{step \times \pi}}{180}$


which in units gives $\frac{\mathrm{deg}}{\mathrm{seconds}} \times \frac{\mathrm{seconds} \times \mathrm{radians}}{\mathrm{deg}} = \mathrm{radians}$.


Any help will be appreciated to this Mathematica newbie on how to go about to simulate this kind of motion. Desired animation fatures:




  1. Perhaps the circular object can have hatched shading so that its rotating motion can be seen on top of its following the parametric circular path;




  2. The $x-$ and $y-$axes should be visible;





  3. The parametric path given by the parametric equations in $x$ and $y$ should be visible as a circle.





Answer



Lets start with some parameters (note that I've chosen larger values for a and x0 here to actually see the movement of the centre)


radius = 20;
x0 = 10;
a = 5;
om1 = 10 Degree;

om2 = 10 Degree;

The centre of the rotating object at time t is given by


centre[t_] := {x0 + a Cos[om1 t], a Sin[om1 t]};

I'm using RegionPlot to create an image of the disk centred at the origin


circ = RegionPlot[x^2 + y^2 <= radius^2, {x, -radius, radius}, 
{y, -radius, radius},
Mesh -> 20, MeshStyle -> {{Red}, {Blue}}, BoundaryStyle -> Black,
PlotStyle -> None]


Mathematica graphics


Next, we're defining a function for creating the plot at time t. I'm using Rotate and Translate to get the orientation and position of the disk. The path of the centre is plotted using ParametricPlot


plot[t_] := Show[Graphics[
Translate[Rotate[{circ[[1]], Point[{0, 0}]}, om2 t], centre[t]]],
If[Abs[t] <= $MachineEpsilon, {},
ParametricPlot[centre[s], {s, 0, t}, PlotStyle -> {Black}]],
PlotRange -> {{-2 radius, 2 radius}, {-2 radius, 2 radius}},
Axes -> True]


Plugging this function into Animate will create an animation of this function:


Animate[plot[t], {t, 0, 36}]

Mathematica graphics


Comments

Popular posts from this blog

front end - keyboard shortcut to invoke Insert new matrix

I frequently need to type in some matrices, and the menu command Insert > Table/Matrix > New... allows matrices with lines drawn between columns and rows, which is very helpful. I would like to make a keyboard shortcut for it, but cannot find the relevant frontend token command (4209405) for it. Since the FullForm[] and InputForm[] of matrices with lines drawn between rows and columns is the same as those without lines, it's hard to do this via 3rd party system-wide text expanders (e.g. autohotkey or atext on mac). How does one assign a keyboard shortcut for the menu item Insert > Table/Matrix > New... , preferably using only mathematica? Thanks! Answer In the MenuSetup.tr (for linux located in the $InstallationDirectory/SystemFiles/FrontEnd/TextResources/X/ directory), I changed the line MenuItem["&New...", "CreateGridBoxDialog"] to read MenuItem["&New...", "CreateGridBoxDialog", MenuKey["m", Modifiers-...

How to thread a list

I have data in format data = {{a1, a2}, {b1, b2}, {c1, c2}, {d1, d2}} Tableform: I want to thread it to : tdata = {{{a1, b1}, {a2, b2}}, {{a1, c1}, {a2, c2}}, {{a1, d1}, {a2, d2}}} Tableform: And I would like to do better then pseudofunction[n_] := Transpose[{data2[[1]], data2[[n]]}]; SetAttributes[pseudofunction, Listable]; Range[2, 4] // pseudofunction Here is my benchmark data, where data3 is normal sample of real data. data3 = Drop[ExcelWorkBook[[Column1 ;; Column4]], None, 1]; data2 = {a #, b #, c #, d #} & /@ Range[1, 10^5]; data = RandomReal[{0, 1}, {10^6, 4}]; Here is my benchmark code kptnw[list_] := Transpose[{Table[First@#, {Length@# - 1}], Rest@#}, {3, 1, 2}] &@list kptnw2[list_] := Transpose[{ConstantArray[First@#, Length@# - 1], Rest@#}, {3, 1, 2}] &@list OleksandrR[list_] := Flatten[Outer[List, List@First[list], Rest[list], 1], {{2}, {1, 4}}] paradox2[list_] := Partition[Riffle[list[[1]], #], 2] & /@ Drop[list, 1] RM[list_] := FoldList[Transpose[{First@li...

plotting - How to draw lines between specified dots on ListPlot?

I would like to create a plot where I have unconnected dots and some connected. So far, I have figured out how to draw the dots. My code is the following: ListPlot[{{1, 1}, {2, 2}, {3, 3}, {4, 4}, {1, 4}, {2, 5}, {3, 6}, {4, 7}, {1, 7}, {2, 8}, {3, 9}, {4, 10}, {1, 10}, {2, 11}, {3, 12}, {4,13}, {2.5, 7}}, Ticks -> {{1, 2, 3, 4}, None}, AxesStyle -> Thin, TicksStyle -> Directive[Black, Bold, 12], Mesh -> Full] I have thought using ListLinePlot command, but I don't know how to specify to the command to draw only selected lines between the dots. Do have any suggestions/hints on how to do that? Thank you. Answer One possibility would be to use Epilog with Line : ListPlot[ {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {1, 4}, {2, 5}, {3, 6}, {4, 7}, {1, 7}, {2, 8}, {3, 9}, {4, 10}, {1, 10}, {2, 11}, {3, 12}, {4, 13}, {2.5, 7}}, Ticks -> {{1, 2, 3, 4}, None}, AxesStyle -> Thin, TicksStyle -> Directive[Black, Bold, 12], Mesh -> Full, Epilog -> { Line[ ...