Has anybody researched the advantages and disadvantages of doing a ball handler using motors versus pneumatics?
To handle the big ball your motors going to have to constantly run to hold the ball along its circumfrence.
Using pneumatics to hold the ball, the piston would apply a constant force to hold up the ball so you wouldn’t have to run your motor constantly.
I would use pneumatics.
If your mechanism is designed properly, you should NOT have to continuously run a motor to hold a big ball.
I would not use pnuematics for this task if it was the only thing I was using the pneumatics for. It takes 2 or 3 functions (IMO) before adding the pneumatics to the robot starts to make sense.
Also, with the pneumatics you should be careful with how easy it is to release the ball. In 2001, many teams dropped the big ball because they had a hair trigger on their pneumatic claw. The cylinders can be adjusted (I think) to have slower action. I would definitely do this if I were using one to grasp the big balls.
I wouldn’t be so quick to make this decision. Whether to use a motor or pneumatics requires a number of considerations…
- Are you planning to use pneumatics elsewhere on the robot? (the cost of using pneumatics is at least 10 lbs). This, in my opinion, is the main reason you may choose not to use pneumatics.
- How easy will it be to run pneumatic tubing vs. wires to the place of application? Tubing is generally more difficult since it can not make sharp turns like wire can.
- Do you want precise control over the posisition of the ball handler? Perhaps to use your component for some other function as well? If so, then a motor would be advantagous because you can stop at intermediate positions.
- A motor would not necessarily have to apply a constant load. If you use a worm gear or screwdrive-based design, the device will stop when you turn off power, and not move. The ball will remain deflected by a constant amount while it is in your possession, and the force will be transferred to the screwdrive, not the motor.
Pneumatics is almost definately easier, but the easy solution is not always the best solution.
I’d tend to agree with Patrick. Pneumatics is a serious weight commitment, especially the onboard pump. Properly geared motors with lead screws could possibly do the same thing for compareable weight after your run all the brass fittings, pump, tank… I have a hunch that we won’t be using them this year. In order to justify them, you really need to ask, "After I throw all these pneumatics and the pump, and the gauges and the storage tanks and the tubing, is this really going to be lighter than a motor and a gearbox with a lead screw?
I’d imagine you’d need to use at least 3 pneumatics before having a justified weight trade off.
However, if you can remove the pump from the system and be careful about calculating how much you’ll use pneumatics over the course of the a match, you could probably make a fair trade off with a pair of short 3/4" bore pneumatics (perhaps for shifting).
Just a few thoughts,