Trying to figure out ways to reduce losses down the tether, I came up with a concept for the stacker that allows a very light tether; it would only need to carry signal-level information.
- The mobile robot is all-electric (that is, has no pneumatics components apart from the PCB).
- A large (probably aluminum) air tank and all of the “on board” portions of the pneumatic system except the PCB are on the tether/stacker bot. All of the actuators on the stacker are pneumatic (probably just a lifter and a hold/release to access the stack.
- The compressor is located “off board” the robot. When filling the tanks, the electrical connections are run “short” from the PCB and the air connections are run “short” to the air tank.
To conserve air when lifting short stacks, I would recommend a limit switch on the lift and either a 3-state pneumatic solenoid (pressurize, closed center, vent) or a separate “keeper” pneumatic cylinder that holds a lifted stack.
Presuming that the tank will store air at/near 120psi (making it half as large as if it stored 60psi), and using a 3-state solenoid valve for the lift and a single solenoid valve for the release, I count 5 pairs of signal wires down the tether:
- Pressure switch
- Lift Limit Switch
- Pneumatic Lift
- Pneumatic Lower or Hold
- Pneumatic Release
Edit: Of course, additional sensors (tote presence, state of release, state of hold/lower) would add a bit more to the tether.