ROBOT MOTION PLANNING
"Efficiency Analysis and Software Implementation "

David Urrabazo Jr, Arie Litosky, Yuh-Jen (Mindy) Feng
Advising Professor: Sergey Bereg
Erik Johnson School of Engineering and Computer Science
University of Texas at Dallas, USA

Supported by a grant from the
Computer Research Association
Committee on the Status of Women in Computing Research
and the
National Science Foundation


DATA ANALYSIS

In order to complete comparative analysis between the algorithms, RandomMotion and Dominance, two algorithm applets were created. Both applets allowed the programmer to control three parameters: size of robot, number of robots, and size of the applet. Along with controlling parameters, the engine running the applet indicates that total time and number of collisions allotted to complete simulation. A fail-safe mechanism was then added to limit the amount of run time for a simulation, at which if run time met the limit, the time would then be coded as being an infinite loop.  But in order to accurately compare the two algorithms, multiple simulations were required, thus a Data Analysis program was written to run the applet a specified amount of times with varying parameters and would simultaneously record the data into text files.
After completing approximately three hundred simulations for both algorithms, the following data was recorded.

Table I.

 

Simulations Completed (out of 300)

Simulations Failed (out of 300)

Average Time (size 20)

Average # of Collisions (size 20)

RandomMotion

248

52

5.7

29

Weights

240

60

5.3

54

 

Time

  1. The randomness involved in RandomMotion makes an observer inclined to believe this algorithm may not come to end (infinite) or may take extensive amount of time to complete. But rather than being infinite, this algorithm when tested completed almost 248 out of 300 simulations with varying sizes ranging from 10-50 units (increments by 10) and ranging from 1- 30 robots. RandomMotion averaged 5.7 seconds per simulation for robots of size 20. The diagram below demonstrates the Time (secs) vs. Number of Robots of Random Motion.

RM1

*Colors correspond to incremental size of the robots blue
beginning at 10 and green at 50.*

  1. The diminished random quality of Dominance makes an observer inclined to believe it will be a more efficient algorithm. But the increase efficiency proved only to occur in the time domain. On average it took robots of size 20 ranging from 1 to 30 robots to complete simulation in 5.3 seconds. The diagram below demonstrates the Time (secs) vs. Number of Robots of Dominance.

W1

*Colors correspond to incremental size of the robots blue
beginning at 10 and green at 50.*

 

Comparison:

As expected, entropy increased as the size increased due to a higher number of collisions. The randomness became more and more of a problem, causing the steepness of the trend lines to increase exponentially as time increased. Thus there will be a breakdown point which occurs when the multitude of robots size encompasses more than ¼ of the size of the applet. But on average with respect to time, Dominance holds to be more effective by a margin of a couple of seconds, which can be quantified by the reasoning: Dominance required fewer robots to be in a random phase unlike the constant randomness involved in RandomMotion.
The graph below shows the results. Pay close attention to the purple lines (RandomMotion) above the green lines (Dominance), which proves that RandomMotion on average requires more time to complete than Dominance.

TC

*The purple lines correspond to RandomMotion and green line
 corresponds to weights*

 

Collisions

  1. The randomness involved in RandomMotion makes an observer inclined to believe that this algorithm may accumulate an excessive amount of collisions. The diagram below demonstrates the Number of Collisions vs. Number of Robots of RandomMotion.

RM2

*Colors correspond to incremental size of the robots blue
beginning at 10 and green at 50.*

 

 

  1. The diminished random quality of Dominance proved to hold a negative effect on the total number of collisions, which is in contrast to the effect held in the time domain. Rather than having both robots moving away from collision, the higher ranking robot insists on staying on its path. Theoretically in effect, the probability of the higher ranking robot colliding with the same lower ranking robot (attempting to move away from collision) increases. This makes the amount of collisions rise significantly. The diagram below demonstrates the Number of Collisions vs. Number of Robots of Dominance.

W2

*Colors correspond to incremental size of the robots blue
beginning at 10 and green at 50.*

 

Comparison:

As expected as the size of the robot increased the probability of secondary collision for Dominance. The build of second collisions became more and more of a problem causing the steepness of the exponential trend lines to increase. On average with respect to collisions, RandomMotion holds to be more effective by a ratio of 2 to 1. The ratio can be quantified again by the reasoning that Dominance tends be more aggressive thus more careless with respect to collisions but more efficient in time.

CC

*The purple lines correspond to RandomMotion and green line
 corresponds to weights*