Power management for 6 axis robotic arm

Thread Starter

HDJG

Joined Oct 14, 2023
2
Hello Guys,
Im currently in the process of designing and then building a robotic arm. And now im designing the electronics for it. They should be pretty simple "i hope". I've attached a picture of the circuit that I am currently designing on, and maybe you notice im not an electrical engineer xD.
I now need some advice on safety precautions that I have to implement into my system to really make it safe and reliable. I'm thinking about fuses that I'd need, circuit breakers and all this good stuff. Maybe also to know using very expensive components is not really an option because i have some limited budget, but I want to make it as safe as possible with my possibilities, but let me now if there is somthing expensive where there is now way around.
Quickly what circuit I have currently planned:
I would like to have the main power supply which is controlled by a switch that is connectet to pins on the PSU that allow for easy turning on and off. Then I have my 36v dc voltage that my motorcontrollers use. In order to implement a emergency stop I would use a simple one pole contactor that is NO and when 36V from the NC of the emergency stop is connected it should allow for current to flow to the motorcontrollers. Else it would stop current to all Motorcontrollers. For the controll of the robot I use CAN bus with an adapter to my laptop, but I think this part is okay, its more with the powersupply and emergency stop that I need help with.
Thanks a lot in advance for your help!
Regards Jonas
 

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MisterBill2

Joined Jan 23, 2018
17,833
"E-STOP" by switching off the mail power for a robot is a poor choice because it will cause unintended motions. The robot controllers use the "drive enable" signal to enable and disable motions. Your drives should all include a "drive enable" circuit, that is the way to go.
 

strantor

Joined Oct 3, 2010
6,778
These ODrive controllers apparently don't have a STO/Enable input. How weird. There is a 3rd party firmware you can use though, which turns one of the GPIO into an e-stop input. See reply #11 on this page:
https://discourse.odriverobotics.com/t/e-stop-with-odrive/1608/11

I doubt this fulfills requirements of IEC or other governing bodies. Is something you intend to sell? If not then I would not worry too much about it. If so then I would recommend don't waste time ODrive but get a real industrial drive.
 

MaxHeadRoom

Joined Jul 18, 2013
28,515
The N.A. regulation is that in an emergency stop, all motive power be removed from all motors, the control section can remain active however.
There are three classifications, One of which states that power can be removed in an orderly fashion if immediate removal it should result in damage to either machine or personnel.
The regulations are covered in NFPA79, Electrical Standard for Industrial Machinery.
 

Thread Starter

HDJG

Joined Oct 14, 2023
2
These ODrive controllers apparently don't have a STO/Enable input. How weird. There is a 3rd party firmware you can use though, which turns one of the GPIO into an e-stop input. See reply #11 on this page:
https://discourse.odriverobotics.com/t/e-stop-with-odrive/1608/11

I doubt this fulfills requirements of IEC or other governing bodies. Is something you intend to sell? If not then I would not worry too much about it. If so then I would recommend don't waste time ODrive but get a real industrial drive.
Thanks for all your answers, I don't intend to sell this its just for a hobby project. I found out the odrives have some sort of e stop functionality over can bus but I think that cant be 100% reliable. I think im going to go with removing power from all odrives as the gearboxes have quite a bit of resistance and arent backdriveable, means if I remove power it pretty quickly comes to a stop and holds position.
 
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