I have an application where the robot should slow to a safe speed when the operator approaches. I was talking with a Fanuc rep a while ago about our application, and (I thought) he said I just need to drop the SFSPD signal when the robot needs to slow down. However, when I drop the SFSPD signal the robot just stops. What am I missing?
Safe speed when operator is near robot
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ConnorAlbright -
January 27, 2017 at 9:09 PM -
Thread is marked as Resolved.
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If SFSPD is turned off while in auto, the robot WILL stop.
Are you using a collaborative robot? -
No, using a normal yellow Fanuc. The advice I got from the Fanuc rep was from me asking him about using a collaborative robot for the application, and he suggested just slowing the robot instead.
I just found the Override Select feature. I think that this should do what I want.
Setup -> Ovrd Select -
I was wrong Override Select does not quite do what I need.
It works great for when I want to slow the robot on a signal.
However, Override Select allows exactly four speeds to be set, selected by two Digital Inputs [00, 01, 10, 11].
Unfortunately, if I use this feature it seems that I can only use these four speeds. I wouldn't be able to set the custom speeds for each recipe.So now I'm back where I started.
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My new solution:
In background logic:
If DI[30:Safe] == Off Then
$MCR_GRP[1].$prgoverride = 20%
Else
$MCR_GRP[1].$prgoverride = 100%.
EndIt seems to work great. Are there any best practices that I am violating?
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well now you are down to only 2 speeds.
are you using an aria scanner?
there are safety concerns here, 20 % of 100% joint moves can still be fast.
is your payload set correctly so that crash detect will work correctly?
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My new solution:In background logic:
If DI[30:Safe] == Off Then
$MCR_GRP[1].$prgoverride = 20%
Elsel
$MCR_GRP[1].$prgoverride = 100%.
End ItIt seems to work great. Are there any best practices that I am violating?
If someone gets hurt, you'll probably lose your lawsuit for not following RIA practices. That's far from being safety rated. If you want to be safe, and have a robot work next to a person, get a collaborative robot.
At the very least, set your safe speed to ten percent, that somewhat approaches RIA standards.
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Using light curtains.
What would be a safer speed? 10%? 20% was just a preliminary number.
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Sorry to say Conner you CANNOT do what you are describing.
You are creating an unsafe condition. Unless it is a collaborative robot, the robot MUST STOP and have the motion disabled when a person is within the robots envelope unless they have a teach pendant or enabling device. -
Provided you've done the stopping distance calculations and setup the light curtains at the appropriate distances so that the robot always stops by the time a human reaches it, you are fine. But Racer mike is right, the robot must stop if a human can reach it.
Usually these are calculations are done in a risk assessment. The new RIA specs require that a risk assessment is done before a cell goes into production.
If you do that, the robot falls into the collaborative robot definition.
We do this at our facility with safety scanners. Human enters warning area 1, slow robot to 10%, warning area 2, hold robot, violation area, Estop robot. To do this with light screens, you would need 3 sets.
There could be some improvements to your code. Here is what I do:
Code: IF (GI[1:PLC SPEED]>0 AND GI[1:PLC SPEED]<=100 AND UO[8:TP Enabled]=OFF), $MCR_GRP[1].$prgoverrid=(GI[1:PLC SPEED]) ;
We use the a group input to dynamically change the robot's speed. Also I look at the TP enabled bit, so I am not fighting the PLC when in teach mode.
Here is a video illustrating the concepts talked about above:
https://www.youtube.com/watch?v=F96_eUk_06g -
You should use Speed/Pos Check Option (DCS). This is what the Shuttleworth video is demonstrating, and it will maintain at least a CATIII rating (if I remember correctly).
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I think we are on a similar page, though I only have two zones:
1 - human enters warning area (10% speed).
2 - violation area - estop robot.
And yes, DCS is being used.Thanks for the TP enable bit suggestion, I will use that.