Robot interference

Hi Everyone,

I am new to plc programming. I need some assistance in my project. I am using rslogix 5000 software. Here is the scenario :

Robot A picks up the welded part from station 1 and drops to the part rack. Part rack has 5 shelves. Robot B from station 2 will pick up the part from the rack continue the process further.

Now, there is collision detect but it only happens once in a while. The interlocks are also there. Do I need to put priority for 1 robot and if so how can I do that ?

Thanks.

Can you list the interlocks? I'm assuming the PLC is the cell controller and that the robots are slaves?

For each robot a interlock should exist that is true when the respective robot is clear of the interference zone. Before entering the zone, each robot requests permission from the PLC to enter the interference zone. The PLC then grants permission to enter if the other robot is clear. When the robot clears, it flags the PLC and that allows the other robot to gain permission. This facilitates a first-come-first-served scenario.

Are the robots colliding into the fixture or into one another? Also, what type of interlocks are you using...robot base limit switches, in-cell light curtains...which are both tied into the PLC as well.
If they are colliding into one another, then it sounds like the communication between the robots and the PLC is dropping out (for some reason) for just enough time to cause failure. It only takes one-tenth of a second for a catastrophe to happen.
Another scenario could be, a request(input) from robot 1 has come in too late and robot 2 is thinking its still supposed to be in the work area because the PLC hasn't cleared it yet. This is basically the same answer [Highlight]jstolaruk[/Highlight] gave you....didn't mean to step on your toes. If you are using base limit switches as interlocks, then maybe look and see if they may be a little out of position, a loose wire dropping out every now and then.
It could also be the software limits in one of the robots needs tweaking a bit (just spurting things off the top of my head)
I don't know if I've helped at all, but I hope we've at least pointed you in the right direction.

The OP sent me his file and it turns out that they are using Fanuc Robots in PNS mode. There exists a timing problem in the PLC that a robot is said to be not using a zone until the task acknowledgement is received from the robot that the task it is running will access the interference area. The PLC logic does a little bit to protect for it but there is that short amount of time where the task number is issued to the robot and the acknowledgement has not yet been received. This is the trouble time where both robots could start their respective interfering tasks at the same time. So some changes need to be added to protect for that and some fault logic to flag the condition whenever that condition exists.

It appears that once the robot is started on its task, there is no other communication with the PLC until the task is complete. So the entire responsibility is on the PLC to make sure everything syncs correctly.

There is the Intelligent Interference Check option in Fanuc for interlock between moving robot arms.
Or the Basic Interference Check, which interlocks robot with only static zones or obstacles.

In this application, the robots are not intermingling closely. Just some logic cleanup to better cover these short periods not having everything condition covered will fix the issue.

To RogerF089, I don't look at the other robot code to see there is similar interference conditions but if so, I would recommend the same attention to detail and faults.

It appears that once the robot is started on its task, there is no other communication with the PLC until the task is complete. So the entire responsibility is on the PLC to make sure everything syncs correctly.

Click to expand...

This is one of the major errors we have at my job. Very seldom do we have an interference fault come up, but man do we have a whole bunch of dirty programs that cause numerous outputs not to make. Its really more aggravating than anything (in my case of course)