Autotote Charging - apps4work/co.a4w GitHub Wiki

Autototes run on batteries. The size of the battery (and therefore the weight) is a critical design parameter.

The smaller the battery the more often it needs to be charged, which means the more time an autotote spends idle at the charger.

And the charging mechanism is a necessary part of the Autotote design (and cost).

Avoiding unique Docking Mechanism for Charging

To avoid extra cost in the autotote for a mechanism for docking to a charging station, the design is to re-use the tote docking and picking mechanism.

A tote is picked up by it's lip, using the top of an H shape. The resting state of a tote is hanging from a fixed H shape (a hanger), and the traveling state is hanging from an H shape on the autotote.

To perform charging the tops of the H shape on the autotote are metallic and are the conductors for charging. A modified tote, a "charging tote", has conductors in its lip, so that when autotote docks as if it is going to pick up the "charging" tote, the conductors make conduct and the autotote charges. The contacts on the front lip are wired to corresponding contacts on the back lip, and the hanger's H delivers charging power to the back, to be feed to the front, to feed the autotote.

Obviously the charging tote is wired to a electricity source as so can't be moved away. It is fixed to it's hanger. And therefore the autotote has to stay idle while it is charging.

In the limit every tote could be so wired, and every every hanger could be a live charging station, so an autotote could get some recharge whenever it delivered a tote, waiting there, charging, until it needs to go elsewhere. This may reduce autotote travel significantly. It does not have to go to a charging station (and consume battery power to go there). It cannot afford to go there for just for a brief period since it which might cost it more in battery consumption than it gained in charging.

Charging on-the-go

The usuage time to recharge time ratio is an important design parameter. The LiPo battary on my cheap drone lasts for 5 minutes and takes two hours to charge. The means the drone spends 95% of its life idle, waiting for charging to complete. Extra batteries can improve this, but, for an autotote, this requires an automated mechanism for swapping out batteries.

Instead we propose to use the one piece of mechanics we already have: the tote pickup/put down mechanism.

Batteries (at least LiOn and LiPo batteries) are sufficiently small and light (and arguably cheap enough), for a tote to be modified so that it contains a battery.

Using lip contacts on the "live" static hanger, the tote could be wired so that its on-board battery can be charged while it hangs on the hanger, and with little electrical trickery, could charge autototes battery when picked up and in transit to another location, and/or drained for transport power instead of the autotote's battery.

In the limit every tote hanger could be a charging hanger and every tote could have a battery. This would minimize the battery capacity that the autotote had to carry around (but trading it for the battery in the tote), but with the effect minimizing the out-of-use time for the autotote to be idle being charged.

In effect this is a mechanism for the autotote to swap out its battery, but without requiring an extra physical mechanism to do the swap. It mitigates the effect of long charge times since totes spend 80% or more of their time hanging from a hanger. And it permits smaller batteries, since the battery-in-the-tote needs to hold little more that the energy required for the autotote to move the tote to the next station, and the battery in the autotote needs to hold little more than the energy to move, without a tote, to the next tote source.

Tote Traffic Management would already be attempting to eliminate non-loaded autotote movements as much as possible, and to minimize station-to-station distances, since both consume time and battery power. This would also minimize the necessary size of the battery, which reduces the weight of the autotote, which reduces the required size of the motor, which reduces the necessary size of the battery. So, in this case, we have beneficial feedback mechanism.

The extra cost of the battery in the totes would be migrated by the reduced size battery in the autotote, and the higher utilization of the autototes, especially if the autotote operated 24x7, meaning that less autototes are required.

In an non-24x7 operation, say single shift, without on-the-go-charging autototes might be required to recharge out-of-shift to avoid in-shift idle time. This means the batteries have to be big enough to last the whole shift, and therefore require big enough motors, which requires bigger batteries. This is a vicious amplification we can avoid with on-the-go charging.

Depending on the economics and charging specifications of the batteries, it would be possible for only some of the totes to carry batteries and/or only some of the hangers to be charging hangers, with the Traffic Management software handling the details to keep autototes having power.