one man

Alexey Ivanov

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10 years, 20 days

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One way to show all solutions of a polynomial in one variable.
The root is the intersection of curves representing the imaginary part of the equation (red) and the real part (blue). These equations are obtained after representing the variable as the sum of its imaginary and real parts. The circle limits the area where all the roots are located (according to theory).
Example      -15*x^7+x^2+I*x+2=0;

As always, it's just about drawings.
The parametric equation of a circle has 3 variables and two equations. In 3-dimensional space, a circle is a spiral, but we only need one projection of this spiral into 2-dimensional space, and we also know how  the rest 2 it's projections on flat space look.
If we look at the equation of the sphere in parametric form, we will see that these are 3 equations and 5 variables:
x1 = sin(x4)*cos(x5); 
x2 = sin(x4)*sin(x5); 
x3 = cos(x4);
And so I wanted to see how the remaining 9 projections of the sphere onto 3-dimensional space look. It is very easy to do this with Maple.

 Pictures on the theme of Klein bottle.  Wikipedia article

A manipulator, in which 3 degrees of freedom are provided by changing the length of the links and one degree of freedom, is provided by turning. Only 4 degrees of freedom. Solved using Draghilev's method. In one case, the length of the manipulator link could be expressed through the value of the 3rd coordinate. The lengths of the other two links are considered generalized coordinates. In this case, it is still obtained polynomial equations, as for the usual coordinates.
I was asked to make an example of the movement of such a manipulator using Maple. (Automatically, this is an example of solving an inverse kinematics problem.)

As a continuation of the posts:
But this time without Draghilev's method.
Motion along straight lines can replace motion along any spatial path (with any practical precision), which means that solving the inverse problem of the manipulator's kinematics can be reduced to solving the movement along a sequential set of segments. Thus, another general method for solving the manipulator inverse problem is proposed.
An example of a three-link manipulator with 5 degrees of freedom. Its last link, like the first link, geometrically corresponds to the radius of the sphere. We calculate the coordinates of the ends of its links when passing a straight line segment. We do this in a loop for interior points of the segment using the procedure for finding real roots of polynomial systems of equations RootFinding [Isolate]. First, we “remove” two “extra” degrees of freedom by adding two equations to the system. There can be an infinite set of options for additional equations - if only they correspond to the technical capabilities of the device. In this case, two maximally easy conditions were taken: one equation corresponds to the perpendicularity of the last (third) link directly to the segment of the trajectory itself, and the second equation corresponds to the perpendicularity to the vector with coordinates <1,1,1>. As a result, we got four ways to move the manipulator for the same segment. All of these ways are selected as one of the RootFinding [Isolate] solutions (in text  jj=1,2,3,4).
In this text jj=4       

As you can see, everything is very simple, there is practically no programming and is performed exclusively by Maple procedures.


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