[robocup-small] Proposal for energy budget

Patrick Dingle pdingle at gmail.com
Tue Sep 13 18:34:37 EDT 2005


Hi everyone,

I have not been involved in robocup for over a year, but feel I have 
something to offer to this conversation.

>From what I have read there are several desires of SSL teams. The desire I 
would like to talk about is the desire to move towards more "real" 
soccer/football games... which have much more passing and teamwork and less 
individual effort. I would also like to address the concern that robots 
should need not be re-engineered and rebuilt (at least in the short term, 
for '06).

I have heard two main ideas for accomplishing the goal of encouraging better 
team play (e.g. passing) in the SSL.
1. Larger field and/or smaller robots
2. Energy budget or speed limits

While I am a big fan of #1, I leave it to active teams to decide whether it 
is reasonable to increase the field size. I would like to address #2, which 
can be accomplished in the short term simply using software, and without 
forcing teams to redesign robots. There are two possible implementations 
that I can think of offhand:

a) Set a cap on velocities, and possibly also a cap on accelerations. This 
should be trivial for teams to implement into their systems. Teams can 
continue to use their existing robots. A "referee camera" could be set up on 
each field, and track robot positions vs. time. This camera would exist for 
the purpose of measuring robot velocities and accelerations, and checking 
that they remain below legal limits. If a robot goes to fast, play could 
halt and a yellow card could be issued or whatnot.

b) Simulate an energy budget. A "referee camera" would be set up similar to 
proposal (a), but more complex algoritms would be used to track how much 
energy each team has used. Consider that the referee camera can see every 
robot and the ball throughout the entire game. From this, it can record 
location history (and also calculate velocity and acceleration histories). 
Given the mass of the robots and the ball (teams would be required to 
weigh-in before each game), the energy required to achieve these 
accelerations can be calculated. Friction could also be taken into 
consideration, but this would have to be approximated with an emperical 
formula (e.g. power = 0.2 * mass * sqrt(speed)). Of course, a better formula 
could be derived that should closely match what really happens. Finally, the 
ball speed could be calculated and similarly related to a power function. 
However, the camera probably wouldn't be able to see the ball at the speed 
that many teams fire at. Rotational accelerations can be ignored - the 
energy required is almost always insignificant.

I would like to suggest that (a) is a simple short term method to accomplish 
what many teams are asking for. Proposal (b) also does the job, but is 
harder to implement. Both of these methods place artificial energy limits, 
(b) being more accurate than (a). In reality, these methods are inaccurate 
because they do not take into account the efficiency of a given robot 
design. However, in the short term I think it is the right thing to do. In 
the longer term, teams can be expected to adhere to an actual battery energy 
limit (and teams will have to face the inevitability of redesigning 
effecient robots).

Finally, I would like to point out that energy is not strictly the quantity 
of interest. A small, thin and agile athlete needs less energy than a large, 
muscular athlete to accomplish the same tasks. However, both athletes can 
play a full soccer game at the same intensity because the larger athlete has 
the capacity to produce much more energy (and eat a lot more before the 
game). Therefore, one might reason that if an energy budget is implemented, 
the energy storage that a given robot can have should be a function of its 
mass (albeit, probably not linear).
 
Patrick Dingle
Cornell Big Red '03 '04
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