Author Topic: NX100 SRCH-instruction  (Read 125 times)

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Offline gpunkt

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NX100 SRCH-instruction
« on: October 16, 2018, 07:14:55 AM »
Hi!

I need some help as I have come across a few different answers as to what the argument "T" stands for in a SRCH-instruction.
For instance:
MOVL P007 V=50.0 PL=0 SRCH RIN#(1)=OFF T=0.20 DIS=10
As far as I have understood the above line means that a linear move against p-variable P007 with position level 0 is made at a speed of 50.0mm/s, until the Direct input (RIN) #1 goes low. The DIS-argument allows the robot to exceed P007 with 10mm in the direction of the linear movement (in my case that would be straight down or Z minus).
But WHAT does the T-argument does? Some say that this is a delay before the movement is started, others say that it's a delay before the RIN's status i being monitored. I'm clueless as to why one would want to delay the movement (and why not just make a wait-instruction before the move-instruction?), and I don't get why you would want to delay the start of the monitoring of the RIN.

Also, when I had the robot up and running and could test my programs, I didn't have the search-sensor connected to a Direct input. Instead it went via Profibus to a PLC, and then back to the robot (via Profibus), and the instruction looked like this:
MOVL P007 V=50.0 PL=0 UNTIL IN#(45)=OFF
When performing the "search", even at the speed of 50.0mm/s the robot overshot by approximately 20-25mm (I recon that it had to do with the time it took for the signal to go all the way to the PLC, be processed, and then back to the robot). That's when I heard of the SRCH-instruction and the benefits of using Direct inputs while doing this.
So, what is the recommended top speed for a search with a RIN? The tool can cope with 40mm overshoot before it crashes and potentially breaks, and the distance of the movement will vary between 150mm and 1400mm. Given that the application is time-critical, you can see why I would want to speed up the search-movement.

And finally, I've been told to change parameter FD13 to value 2 for a softer stop and reverse. What exactly does this do? And what are the other options for this parameter?

Thanks in advance!

Offline Trek552

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Re: NX100 SRCH-instruction
« Reply #1 on: October 16, 2018, 07:24:29 AM »
T means time to search, time how long robot should wait for the input RIN.

Search speed I think you should find at your own, run as fast as you can, but not crash.

Stop end reverse you can adjust with ACC, DEC acceleration and deceleration in every motion step.

Some fast answers, hope it helps,
Have a nice day!
Have a nice day!

Offline Reintz

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Re: NX100 SRCH-instruction
« Reply #2 on: October 16, 2018, 10:28:25 AM »
As I understand the robot takes the inertia values for each axis into consideration when going through a MOV instruction. With the SRCH instruction the stop is sudden (with inertia values not taken into consideration) in order to read in the robot's position with greater accuracy after the stop. A few years ago I made a search for a DX200 gantry where the base axis moved and the robot hold it's posture. It was a long search with a speed 50mm/sec. Took about 4 months to break one of the base axis bearings because of the abrupt stops.
I have not heard of the parameter you mentioned, but softer stop would mean losing accuracy. You will over shoot it a bit before coming to a stop. So does using higher speed.
I still use long searches but now I use higher speed to find the approximate location and then use slower speed with a short search (with the SHIFT from the long search active) to get the accurate location.
The DX200 had Yaskawa own SEARCH JOBs on when they arrived. They all had the SRCH MOV with V=20.0mm/s. I made my own search JOBs but stuck with the same speed.
How much are you willing to trade accuracy for speed is totally up to you.

Offline gpunkt

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Re: NX100 SRCH-instruction
« Reply #3 on: October 16, 2018, 10:58:20 AM »
As I understand the robot takes the inertia values for each axis into consideration when going through a MOV instruction. With the SRCH instruction the stop is sudden (with inertia values not taken into consideration) in order to read in the robot's position with greater accuracy after the stop. A few years ago I made a search for a DX200 gantry where the base axis moved and the robot hold it's posture. It was a long search with a speed 50mm/sec. Took about 4 months to break one of the base axis bearings because of the abrupt stops.
I have not heard of the parameter you mentioned, but softer stop would mean losing accuracy. You will over shoot it a bit before coming to a stop. So does using higher speed.
I still use long searches but now I use higher speed to find the approximate location and then use slower speed with a short search (with the SHIFT from the long search active) to get the accurate location.
The DX200 had Yaskawa own SEARCH JOBs on when they arrived. They all had the SRCH MOV with V=20.0mm/s. I made my own search JOBs but stuck with the same speed.
How much are you willing to trade accuracy for speed is totally up to you.

Hi!
The tool is suspended down from the tool-flange, with an inflatable bellow between the flange and the tool, and has a stroke of approximately 50mm, which means that I can overshoot the target by this amount (given that the bellow is de-pressurized, of course). When I hit the target (doesn't matter if it's dead on, or if it overshot, as long as it's not more than 50mm) I start the vacuum and then move up again. Once on a comfortably height, I re-pressurize the bellow so that the tool wont jiggle or swing when I move across the robot cell.
So accuracy isn't really the case.
But maybe I'll just have to do trial and error with materials that are hard enough to be able to perform a search on, and fragile enough to break if I overshoot the target position too much.