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Line/Circle-Tracking Motions

Tracking a directed line or circle for a robot is a useful capacity in a number of applications. This technology is one of MotionLab's most valuable motion-control technology. With this algorithm, Swan can track a path consisting of multiple lines and circles by switching from one line/circle to the next line/circle. The roundness of switching (transient) motions is controlled by a parameter called smoothness. With a larger smoothness, the transition curve becomes larger and smoother.

(1) The first line-tracking example is the regular polygon function. Given a positive integer n, the function generates n+1 lines, where the first and the last one are the same. Swan tracks a path consisting of the n+1 lines to make a regular n-gon and stops at the end.. By giving n = 4, Swan makes a counterclockwise (ccw) square. Watch the video, Square. Here, another grandson of the founder, Andrew, is harassing Swan. See the trajectory. The user program of this regular polygon function is shown HERE.

In this line-tracking function, Swan tracks a specific line at every moment. When the time comes, Swan switches the current line being tracked into the next one. The timing of this switch between lines is crucial; if the switching takes place too early or too late, the resulting turning motion is not ideal, as this demo and trajectory illustrate. In this trajectory diagram, each switching point from one line to the next is explicitly displayed by an arrowhead. The best switching time is computed by the line-tracking algorithm using the smoothness.

(2) The next example is a pentagon. In this case, we give n = -5 instead of +5. Then the user program makes a clockwise pentagon instead of a counterclockwise pentagon. Watch the video, Pentagon. In this pentagon execution, Swan turns -72º at each vertex. See the trajectory.

(3) By changing the regular-polygon user program a little, we can make a star shape with five points. Watch the video, Star. See the trajectory. In this motion, Swan turns -144º at each vertex.

We also possess a circle-tracking algorithm, in which Swan tracks a given oriented circle, counterclockwise (ccw) or clockwise (cw), with a given smoothness.

(4) The first circle-tracking example is called the CircleTrain. The number n (>1) of circles is given first. The circles are aligned on one line, detached from each other. The first circle is ccw and the second cw, and so forth. Swan starts from a point on the first circle, and tracks all of them in a row, and comes back to the first one. The robot stops at the starting point. Watch the video, Circle Train. Seethe trajectory. In this example n = 3. See the user program of this function HERE.

(5) The next circle-tracking example is called the CircleRing, in which eight small circles detached from each other are placed on a big circle. Swan tracks the small circles sequentially and stops when it comes back to the starting point. Watch the video, Circle Ring. See the trajectory. In this case, eight circles are positioned on a bigger circle with alternate orientations, ccw and cw. Although this motion looks similar to the prior closed serpentine, it is very different.

(6) A path can be defined by a mixed sequence of lines and circles. The Hamburger function is an example. Players for this function are a circle C and an oriented diameter L of the circle; L divides C into a pair, of a ccw half circle CU and a cw half circle CL. Swan tracks L, CU, L, CL, and L in this order and stops at the circle center. Watch the video, Hamburger. See the trajectory.

We can define a path with any number of directed lines and oriented circles in a user program. Therefore, we can program an unlimited number of distinct motions in this category.

 
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