pic: Recycle Rush Re-design Part 2

[GeeTwo]

Originally Posted by Cash4587

If using only pneumatics for a thethered robot you will probably need more air tanks than it is worth to try to reduce the losses from long runs of wire. Lifting a tote with pistons requires a lot of air because of the weight of the totes in addition to the amount of stroke needed to lift them high enough. To stack at the feeder station you need to lift them considerably higher than the usual of about 13-14"

I haven't done the math, but I was thinking of a single large aluminum tank like this. Ten pounds of tank, but 7 gal (about 7 scf at 120 psi) of air.

[Cash4587]

Originally Posted by GeeTwo

I haven't done the math, but I was thinking of a single large aluminum tank like this. Ten pounds of tank, but 7 gal (about 7 scf at 120 psi) of air.

It might be doable. It would be hard to do, but doable. At some point though I think going the pneumatic route to try reduce weight on your physical tether would be the heavier option. The additional weight the tank and large piston or pistons would add in my opinion would be far more than a couple pounds of wire plus a versa planetary and chain loops.

[asid61]

Originally Posted by Cash4587

If using only pneumatics for a thethered robot you will probably need more air tanks than it is worth to try to reduce the losses from long runs of wire. Lifting a tote with pistons requires a lot of air because of the weight of the totes in addition to the amount of stroke needed to lift them high enough. To stack at the feeder station you need to lift them considerably higher than the usual of about 13-14"

If designed properly, perhaps 16" would be enough. As long as the bottom tote just sits at the bottom and you only lift totes 2-6, you just need it to clear the chute- which is doable with 13-14" if you raise the bottom tote a bit, or just 16"ish.

[Cash4587]

Originally Posted by asid61

If designed properly, perhaps 16" would be enough. As long as the bottom tote just sits at the bottom and you only lift totes 2-6, you just need it to clear the chute- which is doable with 13-14" if you raise the bottom tote a bit, or just 16"ish.

I would have to see it to believe it. I mean I don't doubt that it could be done but given the angle that the totes are entering the field, my team had to have a travel of about 25 inches in order for the tote being lifted to not interfere with the tote coming in through the chute. If we didn't lift it high enough the tote above it would be pushed past the point of being locked in place with the lip on the tote below it.

[pilleya]

In long distance power transmission, a transformer is used to increase voltage to crazy high amounts. This reduces the power-loss and means that a less thick wire is required.

Obviously no custom circuitry can generate voltages greater than 24 volts, but is there anything stopping a transformer being used to increase the voltage at the motor controller, to compensate for the voltage lost during transmission. As long as it decreased down to 12 volts at the motor, it would still be being fed by 12 volts thus one motor controller

"R44 CUSTOM CIRCUITS shall not directly alter the power pathways between the ROBOT battery, PDP, motor controllers, relays,
motors, or other elements of the ROBOT control system (items explicitly mentioned in R55). "

Does increasing voltage alter the power pathways?

[GeeTwo]

Let's start with a 7 gal (1617 cu in) charged to 117.6 psig (that's +8atm, selected to simplify the math). As we regulate this down to 58.8 psig (+4 atm), we are making 1617 * 4 = 6,468 scfm, or 1,293 cu in at +4 atm (58.8 psig). Multiplying this out, I show a potentially usable energy of over 76,000 lb-in. A tote weighs 7.8 lb, so that's about 9,750 tote-inches, or 5 totes times 1950 inches. If each lift is 25", this is still a total of 78 lifts. That's 78 lifts of 5 totes 25 inches. There were only 30 totes behind the walls, so even without doing any optimization beyond not pressurizing the down stroke, there is more than twice the required energy in one 7 gal tank to stack all of the totes behind the wall. (Though I haven't done any flow calculations to determine if it can be done in 2:15!)

With a 10 pound air tank, this obviously won't get down to 15 pounds, but I expect that it can be done for well under the available 35 pounds, including tank, cylinders, frame, tether, and electronics.

[GeeTwo]

Originally Posted by pilleya

In long distance power transmission, a transformer is used to increase voltage to crazy high amounts. This reduces the power-loss and means that a less thick wire is required.

Obviously no custom circuitry can generate voltages greater than 24 volts, but is there anything stopping a transformer being used to increase the voltage at the motor controller, to compensate for the voltage lost during transmission. As long as it decreased down to 12 volts at the motor, it would still be being fed by 12 volts thus one motor controller

"R44 CUSTOM CIRCUITS shall not directly alter the power pathways between the ROBOT battery, PDP, motor controllers, relays,
motors, or other elements of the ROBOT control system (items explicitly mentioned in R55). "

Does increasing voltage alter the power pathways?

Originally Posted by 2015 Game Manual

R30 Any active electrical item not explicitly listed in R18 or R55 is considered a CUSTOM CIRCUIT. CUSTOM CIRCUITS may not produce voltages exceeding 24V.

R18 is the list of motors, so that assemblies including motors do not fall under the CUSTOM CIRCUIT rules. Motor controllers are required to be connected directly to the PDP. I am 99+% certain that the GDC would consider a switching power supply which steps up from ~9V to ~12V would constitute "directly altering the power pathway". (OBTW, a transformer cannot be used to step up DC voltage; that's why Tesla's AC power distribution system eventually won out over Edison's DC system.) Consider the exceptions named in the second sentence of R44:

Originally Posted by 2015 Game Manual

R44, cont: Custom high impedance voltage monitoring or low impedance current monitoring circuitry connected to the ROBOT’S electrical system is acceptable, if the effect on the ROBOT outputs is inconsequential.

Stepping up the voltage is definitely consequential.

[pilleya]

Originally Posted by GeeTwo

I am 99+% certain that the GDC would consider a switching power supply which steps up from ~9V to ~12V would constitute "directly altering the power pathway"

Thanks for clarifying the meaning of Power pathway. I thought that it meant that must be a direct pass-through without being interrupted by a sensor or relay etc. I was taking it in a rather literal sense.

[Ari423]

Originally Posted by GeeTwo

Let's start with a 7 gal (1617 cu in) charged to 117.6 psig (that's +8atm, selected to simplify the math). As we regulate this down to 58.8 psig (+4 atm), we are making 1617 * 4 = 6,468 scfm, or 1,293 cu in at +4 atm (58.8 psig). Multiplying this out, I show a potentially usable energy of over 76,000 lb-in. A tote weighs 7.8 lb, so that's about 9,750 tote-inches, or 5 totes times 1950 inches. If each lift is 25", this is still a total of 78 lifts. That's 78 lifts of 5 totes 25 inches. There were only 30 totes behind the walls, so even without doing any optimization beyond not pressurizing the down stroke, there is more than twice the required energy in one 7 gal tank to stack all of the totes behind the wall. (Though I haven't done any flow calculations to determine if it can be done in 2:15!)

With a 10 pound air tank, this obviously won't get down to 15 pounds, but I expect that it can be done for well under the available 35 pounds, including tank, cylinders, frame, tether, and electronics.

We went the pneumatics route this year, so I have some first hand results as to how our testing went. Not powering the downstroke sounds like a good idea until you learn that most solenoids need 20 psi minimum on each side to open and close properly. We eventually decided on 15 psi, and it was still very slow going down. Also, don't forget that once your tank drops below 60 psi, you will see decreased performance. For this reason, we went with slightly bigger cylinders at 30 psi so we wouldn't see that effect until later in the match. No matter the size of your air tanks, at 60 psi you will see that effect halfway through your lifts.

Also, if you did what many teams did this year and let the second tote fall into the first one without lifting the first one, you will only need to lift 4 totes per 6 stack, not 5. You also won't need to lift them as high, only from 1 tote high to above the chute instead of from the ground. IIRC that's less than 25". Or you could do what we did and build a ramp attached to our stacker for the totes to slide to (almost) ground level, then you only need to lift the height of one tote.

[GeeTwo]

Originally Posted by Ari423

We went the pneumatics route this year, so I have some first hand results as to how our testing went. Not powering the downstroke sounds like a good idea until you learn that most solenoids need 20 psi minimum on each side to open and close properly. We eventually decided on 15 psi, and it was still very slow going down.

I agree that powering the down stroke with 15psi is probably worse than not powering it at all, but relying on a spring return or (if there's enough weight) gravity. Alternately, the two sides of the lift cylinders could be controlled through a 3-state solenoid or controlled separately so that you don't need to fill the upper chamber of the cylinders to 60psi, even though the supply is that high.

Originally Posted by Ari423

Also, don't forget that once your tank drops below 60 psi, you will see decreased performance. For this reason, we went with slightly bigger cylinders at 30 psi so we wouldn't see that effect until later in the match. No matter the size of your air tanks, at 60 psi you will see that effect halfway through your lifts.

Yes, if you read more closely you can see that I was calculating based on the air in the tank above 60 psi.

Originally Posted by Ari423

Also, if you did what many teams did this year and let the second tote fall into the first one without lifting the first one, you will only need to lift 4 totes per 6 stack, not 5. You also won't need to lift them as high, only from 1 tote high to above the chute instead of from the ground. IIRC that's less than 25". Or you could do what we did and build a ramp attached to our stacker for the totes to slide to (almost) ground level, then you only need to lift the height of one tote.

That would make it even better on several counts - fewer than half as many lifts, as well as a lighter peak lift. The lift would have to be more than 25", however. Each six-stack would involve lifting 6 totes about 30", which is much less than lifting 15 totes 25". With a bit of optimization and some sensors, I estimate that five six-stacks would take about 3 gallons, or 3 six-stacks would need about 2 gallons of tank.

[Ari423]

Originally Posted by GeeTwo

That would make it even better on several counts - fewer than half as many lifts, as well as a lighter peak lift. The lift would have to be more than 25", however. Each six-stack would involve lifting 6 totes about 30", which is much less than lifting 15 totes 25". With a bit of optimization and some sensors, I estimate that five six-stacks would take about 3 gallons, or 3 six-stacks would need about 2 gallons of tank.

I think you're misunderstanding what I'm suggesting. The bottom of the piston's travel would be at the lip of the second tote on the stack. The piston would then travel up so the bottom of the second tote would just clear the top of the chute. Granted this is more than 25" of travel, but it's 12" less than it would be otherwise, you have to lift one less tote per 6 stack, and you only ever have to lift 4 totes at a time instead of 5. Therefore, since air consumption is lift force * lift height, you can decrease both lift force and height for an overall decrease in air consumption.

[GeeTwo]

Originally Posted by Ari423

I think you're misunderstanding what I'm suggesting. The bottom of the piston's travel would be at the lip of the second tote on the stack. The piston would then travel up so the bottom of the second tote would just clear the top of the chute. Granted this is more than 25" of travel, but it's 12" less than it would be otherwise, you have to lift one less tote per 6 stack, and you only ever have to lift 4 totes at a time instead of 5. Therefore, since air consumption is lift force * lift height, you can decrease both lift force and height for an overall decrease in air consumption.

No, I understood, that you never need to lift more than four totes at a time. Perhaps I took your strategy even farther than you meant. Here's what I'm thinking as "making a stack":

• Drop two totes through the chute. The first lands on the floor, the second on top of the first.
• Lift those two totes high enough for the next step (about 30-36") (2 totes lifted)
• Drop two more totes through the chute.
• Lower the raised stack onto the stack on the floor, and continue to the low end of the stroke.
• Lift the four totes high enough for the next step (4 totes lifted).
• Drop two more totes through the chute.
• Lower the raised stack onto the stack on the floor, and continue down at least far enough to disengage from any totes.
• Open the release gate for the main robot to score it.

Six totes per stack when doing pairs is 2 for the first lift and 4 for the second lift; 2 + 4 = 6. Fifteen totes on single-stacking is 1 + 2 + 3 + 4 + 5. It doesn't matter where the lift engages the tote; the length of stroke must be as high as the bottom of the tote moves up plus the "engagement distance", that is the amount of motion between the bottom of the stroke and the tote being lifted off the floor. I'm estimating that to clear a 2-stack with a few inches for free entry of the second tote would be about 30-36".

If you were thinking of leaving a tote on the floor the whole time, that would be lifting 10 totes a bit over half as far as the six above. It's probably a wash in terms of air, but two lifts should take less time than four.

[EricH]

Originally Posted by GeeTwo

No, I understood, though perhaps I took your strategy even farther than you meant. Here's what I'm thinking as "making a stack":

• Drop two totes through the chute. The first lands on the floor, the second on top of the first.
• Lift those two totes high enough for the next step (about 30-36") (2 totes lifted)
• Drop two more totes through the chute.
• Lower the raised stack onto the stack on the floor, and continue to the low end of the stroke.
• Lift the four totes high enough for the next step (4 totes lifted).
• Drop two more totes through the chute.
• Lower the raised stack onto the stack on the floor, and continue down at least far enough to disengage from any totes.
• Open the release gate for the main robot to score it.

Six totes per stack when doing pairs is 2 for the first lift and 4 for the second lift; 2 + 4 = 6. Fifteen totes on single-stacking is 1 + 2 + 3 + 4 + 5. It doesn't matter where the lift engages the tote; the amount of lift must be as high as the bottom of the tote moves up plus the "engagement distance", that is the amount of motion between the bottom of the stroke and the tote being lifted off the floor. I'm estimating that to clear a 2-stack with a few inches for free entry of the second tote would be about 30-36".

That second bullet is where you missed him. The floor-level tote stays there to act as a catcher/ramp until the stack is complete.

[mman1506]

Originally Posted by Ari423

We went the pneumatics route this year, so I have some first hand results as to how our testing went. Not powering the downstroke sounds like a good idea until you learn that most solenoids need 20 psi minimum on each side to open and close properly. We eventually decided on 15 psi, and it was still very slow going down. Also, don't forget that once your tank drops below 60 psi, you will see decreased performance. For this reason, we went with slightly bigger cylinders at 30 psi so we wouldn't see that effect until later in the match. No matter the size of your air tanks, at 60 psi you will see that effect halfway through your lifts.

Also, if you did what many teams did this year and let the second tote fall into the first one without lifting the first one, you will only need to lift 4 totes per 6 stack, not 5. You also won't need to lift them as high, only from 1 tote high to above the chute instead of from the ground. IIRC that's less than 25". Or you could do what we did and build a ramp attached to our stacker for the totes to slide to (almost) ground level, then you only need to lift the height of one tote.

Why didn't you just leave a port on one side of the pneumatic cylinder open and put a plug on the unused port of solenoid?

[GeeTwo]

Originally Posted by mman1506

Why didn't you just leave port one side of the pneumatic cylinder open and put a plug on the unused port of solenoid?

That would be "leaving the downstroke unpowered", which has been considered and largely discarded. Unless you have a separate mechanism to engage and disengage from the tote, your downstroke will have to work against some sort of spring action to get around the top edge of the tote. For reliable action, either the down stroke needs to be powered, or a spring return is needed, or the carriage must be heavy enough to force through the ratcheting action.