Shooter Lag

[Ether]

Originally Posted by Ninja_Bait

What point in the motor curve would you go for; max efficiency or max power? Or somewhere in between?

You want to select a gear ratio such that, with the wheel(s) spun up to their desired speed and no balls being launched:

1) The motor is spinning at a speed slightly greater than 50% of its 12V free speed, and

2) The motor voltage required to hold that speed is sufficiently less than 12 volts, and

3) The waste power (input watts minus output watts) is not too much greater than the waste power at max efficiency at 12 volts.

These three conditions are somewhat mutually exclusive, and you may have to sacrifice here and there to find a happy medium. Or you may have to use a more powerful motor, or more than one motor.


Rationale:

#1 is so that when a ball is launched and slows the wheel down, your motor speed will be near the value required to get maximum power from the motor (when your closed-loop controller senses the error and jacks up the voltage).

#2 is so that your closed-loop speed controller has some "headroom" to apply more power (increase the applied voltage) to get the wheel back up to speed quickly

#3 is because you are going to be spinning your wheel for the entire match and you don't want to burn out your motor.

[fox46]

Also remember that the available voltage will not always be 12V and will vary depending on your battery condition and how much power the rest of the robot is drawing.

[PriyankP]

I think the best way to go at this problem is by combining the efforts of both the mechanical and the programming sub teams. If a shooter was designed in way such that only 85% - 90% of its power will ever be needed, then you could shoot your first ball at the "full" speed (say it's 85%) then second shot could be shot immediately by changing the shooter speed via programming to 90% and so on...

I would imagine that due to the loss of momentum, running at 90% would be similar to running at 85% when the time between two successive shots is small. Yes?

[roystur44]

Best bet would be to delay the balls till the motor hit your ideal speed and your aim angle is correct. If you fire up 3 rapid balls that had the aim angle/motor speed off you have wasted 3 balls. Take a shot and see if it goes in then take another.

[Ether]

Originally Posted by fox46

Also remember that the available voltage will not always be 12V and will vary depending on your battery condition and how much power the rest of the robot is drawing.

That was the intent of the bolded portions below:

Originally Posted by Ether

2) The motor voltage required to hold that speed is sufficiently less than 12 volts...

#2 is so that your closed-loop speed controller has some "headroom" to apply more power (increase the applied voltage) to get the wheel back up to speed quickly