Integrator, water side. A client has three small wheeled inspection robots that patrol a pump hall on a fixed route and go back to a charging dock each. Each robot runs on a Pi with a motor controller and reports battery, state and position zone to Hermetry over MQTT. The hall and its rooms are already set up as assets in Hermetry Twin.
Two things. Docking: the robot drives back using an IR emitter on the dock, but maybe 3 times a day one of them stops a few centimetres short or slightly crooked, the contacts don’t touch, and it sits there until the battery dies. Then someone walks over in the morning.
And the operators want to see on the site view when a robot is in trouble, not dig into telemetry. What do people do for both?
Could you just make the contacts bigger? Like wide copper strips on the dock.
Does the robot check that it’s actually charging after it thinks it docked?
No. It declares „docked“ when the IR signal is strongest and stops.
Aoife put her finger on it. We run AGVs in a pharma warehouse and had the same failure until we changed three things.
Mechanical: let the dock do the final alignment. A V-shaped funnel or two angled guide rails that steer the robot into position in the last 15 cm, with spring-loaded contacts that have some travel. IR only has to get it into the funnel. Michael’s wider contacts help, but the funnel is what fixes the crooked case.
Logic: „docked“ means charging current flows, not „IR is strongest“. After stopping, wait 2 s and read the charge current. If it’s not there, back off 30 cm, approach again, up to 3 tries. After 3 failures stop trying and report it.
Twin side: place each dock (if it reports anything) on the room asset it sits in, and place the robots on the site, since they move between zones and report their zone in telemetry. Then derive a status key for the robots, either on the Pi or in the root flow: critical after 3 failed docking tries or battery under 15 %, warning while it’s retrying, ok otherwise. Site status takes the worst status of everything placed under it, so a stuck robot turns the hall red on the site view without anyone opening telemetry. Also store a numeric copy (0/1/2), because text keys have no chart history. How the status rolls up: Site status and the status key.
Add a low battery alarm with a notification too, so someone hears about it before the morning walk.
Client’s mechanic welded simple guide rails onto the docks, and I changed the robot code to check charge current with 3 retries. Two weeks, one failed dock, and that one showed up red on the site view within a minute, so someone went over. Added Rachel’s battery alarm too.
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