Thread: Proposed New Rule M11
View Single Post
  #7   Spotlight this post!  
Unread 20-01-2003, 08:35
Dodd Dodd is offline
Registered User
#0095 (Lebanon/Upper Valley Robotics Team)
  
Join Date: Jun 2001
Location: Lebanon, New Hampshire
Posts: 16
Dodd is an unknown quantity at this point
Joe's proposal
I think Joe's proposal for revising M11 is quite reasonable. I ran a couple of numbers in coming to this conclusion.

The power or rate of release criterion is no problem for applications of counterbalancing the weight of a mechanism, since the mechanism's motor does a reasonable job of defining and limiting the speed of motion. I was curious though about applications with less controlled rates of release - like flinging a container - so I looked at that.

Launching a container from the edge of one ramp at an angle of about 54 degrees above the horizontal at a velocity of about 26 ft/sec will allow the container to just clear a 5' tall 'bot on top of the platform and hit the field just at the end of the opposite ramp. The flight time is about 1.3 seconds. These numbers ignore aerodynamic effects and are idealized and approximate (but close).

I assumed the robot exerted a constant force (a la gas spring) on the container to accelerate it up to 26 ft/sec from rest along a 3' long path. The force required in this scenario is about 14 lbf, and the energy input (work done) is 42 ft-lbf. The time required to accelerate a 4 lbm container to 26 ft/sec with a 14 lbf net force is about 0.23 sec, so the rate of energy transfer to the container by the mechanism is 42 / 0.23 = 183 ft-lbf/sec ~ 250 w. I didn't check these numbers very well, but I think they are reasonable.

The point of all this is, I don't think that Joe's proposed numbers are restrictive of some crowd-pleasing robot design possibilities, while the original M11 numbers are onerously restrictive. BTW, I realize that M11 deals with energy stored at the beginning of the match, whereas any spring-powered multi-shot container launcher would have to recock itself by motor or pneumatic means during the match. I also realize that the rules restrict launcher powering to the use of elastic tubing, whereas I assumed constant force gas springs in my example for calculation ease. This was just to make sure that clever sheep on 47 wasn't slipping anything past all the rest of us.

Dodd