Quote:
Originally Posted by JamesCH95
... but I would rather see smaller diameter wheels to control speed because they're smaller and lighter and will recover after a shot more quickly which will improve consistency.
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Not exactly true. Conservation of energy: Power In = Power Out + Losses. Then there's angular momentum and the flywheel effect. I'll describe it from a software control perspective. The two greatest factors in controlling a shooter wheel are (1) Ball Contact Time and (2) Power Available.
Greater contact time = greater Tau for your PID, meaning your software has more cycles to aggressively ramp up the motor. Smaller diameter = less contact time. Combined with angular momentum concepts, your wheel has to spin much
faster than you think to start with because it will lose more speed %-wise than a greater diameter wheel.
Greater power = less time that your software
needs to ramp up the motors because they give more output per time. This simply means that small diameter wheels and recovery time will be on par with a large-diameter flywheel, because if you put the same amount of power into each, then each will return to their respective speeds at the same time. The flywheel lost
less speed than the smaller wheel.
The rest is just angular momentum and how you engineer the wheel itself (entry point, entry speed, entry angular velocity, tread characteristics of the wheel, moment of inertia of the wheel, etc). These have more effect on the ball than wheel diameter.
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23-01-2012, 09:57
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