Battery Power Supply Status for Magni Robot

vuwij · November 9, 2018, 2:29am

Hello I noticed from ubiquitymotor repository on github that it publishes a voltage for the battery but it doesn’t tell us whether the robot is plugged in or not. Notably

github.com

UbiquityRobotics/ubiquity_motor/blob/c084edfc796ed05224765634dd18618d019014c9/src/motor_hardware.cc

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Line 154 shows that the battery power supply status is always marked as unknown.

It would be very helpful if it is possible to indicate the battery power supply status of the robot. This can be especially helpful for automating robots and putting a safety for when the robot is charged or not. If we were to use the robot in a delivery scenario for example. It is also helpful for a UI to know if the robots are being charged or not.

rohbotics · November 9, 2018, 2:41am

That sounds like an excellent feature!

I am not entirely sure if the hardware supports sensing that right now. Can you please open an issue on that repo and we will look into it.

Rohan

anfederman · November 9, 2018, 5:18am

Also, I am uncertain if the calibration is correct, since the the battery voltage reported by the ROS Topic always seems to be one volt above the voltage I get off ny cheapo Harbor Freight ‘free’ VOM. I believe the latest version of the charger being shipped has a red/green LED that indicates if the batteries are being charged, but I am not sure if that model of charger was sent out on the first batch of shipped machines.

jonovos · November 9, 2018, 2:08pm

Calibration wrong ~ Yes, we concur that the Ubiquity’s battery-state topic measures voltage higher than the actual voltage, by an average of 1.5-volts measured from our reliable volt-meters, directly measured off the battery. But, it looks like their measurement seems to be consistent across the operating range.

davecrawley · November 9, 2018, 11:00pm

The robot publishes the battery state as rostopic battery_state. Regrettably there is inter-batch production variation on the battery voltage on the order of a volt or two plus or minus so this is really only useful (and really only intended) to give a general sense for the battery condition.

Our charger will increase the voltage by about 1-2V so detecting a jump in voltage is a pretty good way to sense when the battery gets plugged in.

vuwij · November 10, 2018, 6:34pm

I’ve created an issue for this in the repository. Thank you guys