My match strategy priorities would be sorted by highest (estimated) points-per-second value, in that each discreet objective takes X time and nets N points. It doesn't take repetition within a single match into account, but does assume consistency between matches.
I'll also add that every team should lay out ALL stretch objectives, how to meet ALL objectives and then decide how much they can accomplish in a given season. Teams often grossly underestimate how much time it takes to build something, which is the root cause of why their robots do not work properly on the field.
Strategy to seed high: Autonomous points + Coopertition points. If at least 8 points can be achieved consistently in autonomous and Coopertition points achieved in most matches, then the rules of the ranking system put the achieving team higher than those who do only one or the other (given the same win/loss/tie record).
Minimum Objectives to meed the High-Seed Strategy
- Minimum objectives to net autonomous points: 2 balls go into a basket.
- Minimum objectives to net coopertition points: Bot gets onto the coopertition bridge via driving.
- Robot can also minimize opponents' teleop points by blocking the inbounder lane as best as possible (realized at first competition)
If achieved each match, average contributing score is 8-12 points + 2 coopertition points. In hindsight, that wasn't enough for a win in an average match (depending on which week is played) yet that WAS enough for a seed higher than 8 at most Regionals, given an equal win/loss ratio. These are particularly true of Regionals in which there were relatively few teams (30-50) in the first few weeks.
Stretch Objectives for higher effectiveness, in order of highest to lowest priority:
- Robot lowers the coopertition bridge
- Robot drives onto coopertition bridge after it is lowered
- Robot gets 2 balls in autonomous into at least the middle basket. Driving straight may be required, depending on the mechanism.
- Robot is able to collect balls and deliver them to the mechanisms that scored the 2 autonomous points, in order to potentially score some teleop points
- Given #1 and #4 in this list, traversal of the field and active delivery of balls also becomes a realized strategy
- Given #4 in this list, the robot may also reverse the intake to feed another robot in autonomous also becomes a realized strategy
Assumptions
From here we will assume that the robot will perform stretch objectives 1-3, given only a drill press, band saw, hand tools, the KOP, no automated machining support and a ~$1000 budget. We'll assume moderate quality with the hand tools (i.e. the students actually do measure twice/cut once). We'll also assume no CAD on the robot
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There may be some extra cost/time associated with individual mechanisms for each team, yet I reduce that down to each team's knowledge about materials and their own capabilities. This is how I would estimate it given the assumptions above, what I personally know about materials, and what I know about time for 3-4 students on my team to prototype & build the mechanisms.
Drive Train
2-CIMs through CIMple Box transmissions, default gear ratio. Configuration is a 4WD wide-drive with default KOP wheels. Victors/Jags are in 'brake' mode.
Satisfies: Stretch Objective #2.
Cost: $0.00
Time to Build: 6 hours. Could be done by the end of Day 2 depending on how much strategy happens, and it's only done so early so that there is
something to mount other things to right away.
Bridge Lowering Mechanism
2 arms that are linked together in the middle via a cross bar. At the ends, the arms have a passive angled inverse-ramp. Powered by 2 KOP window motors via 2 Spikes. Mounted via the Igus rods/bearings. The leverage on the rotating provides the majority of the downward force in most situations,
Satisfies: Stretch Objective #1
Cost: ~$150 for 2 spikes, some 3/4" plywood, some sandpaper, a small 1/16" Teflon sheet, some glue, 2 #35 48T sprockets, 2 12T #35 sprockets. There should also be some left over for 2-4 limit switches.
Time to Build: 24 hours (1-2 weeks depending on how often a team is allowed to meet)
Autonomous Scoring Mechanism
A single-sided shooter wheel utilizing the remaining KOP wheels, 1 CIM motor, and a $15 AM CIM hub. Wheel is positioned relative to the front of the robot such that it allows room for the bridge lowering device, and is positioned at roughly the maximum allowed height. If its gravity fed, the wheels are on the top, putting a forward spin on the ball. If the feeding mechanism is used, the wheel is on the bottom putting a backspin on the ball. For manufacturing, the wheels are spun on a drill, and using a chisel the nubs of the tread are cut off such that the wheel becomes ~5.5" diameter and has a smooth tread finish. Assume a 45-degree fixed launch angle. Using the $30 Banebots voucher, 1 RS-550 is affixed to the rotating shaft such that its back EMF current can be utilized as a speed sensor on an analog port. The max amount of Banebot RS-550's is purchased on the vouchers since they might also be used in future years.
Satisfies: Stretch Objective #3 & #5.
Cost: ~$350 for wiring, Jags/Victors, 1 CIM motor, framing, mounting structure, nuts/bolts, shaft & adapter for the BB550. May be offset via FIRST Choice.
Time to Build: 20-30 hours (1-3 weeks, depending on how often the team meets)
Ball Gathering Mechanism
Premise: A single conveyor feeds directly from the ground to the spinning wheel. The conveyor is single-sided and has guide rails, with ~1" compression.
Materials: Hollow round Urethane belts from McMaster, some 1.5-2" PVC pipe, strips of rubber (keeps the belts inline), glue (keeps the rubber on), steel axles from Lowes (or wherever), 1 CIM motor, 2 AM hubs as shaft adapters (from CIM to the steel axles), some 1" Aluminum tubing and some plywood for framing & structure (also from Lowes... or wherever), 1 Victor/Jag, some wiring, 4 pillow blocks that allow for misaligment
Satisfies: Stretch Objective #4, #5, & #6.
Cost: ~$350 -- may be offset somewhat via FIRST Choice
Time to Build: ~20 hours (1-2 weeks, depending on how often the team meets)
Programming:
The programmers would need diligence and a methodical approach to calibrating autonomous. We were able to sit on a corner of the key and get >90% accuracy after calibration at championships, so it's definitely possible. They'd also need to calibrate the conveyor speed.