KSS01074 Command motor torque on multiple axis while doing a linear motion in AUT mode at 75% programmed velocity

Hello,

Sorry for the long thread, I didn't want you guys to have to guess anything.

Here's what I am working with:

Robot Model: KR 210 R2700-2
Controller Model: KR C4 8.6.8 NA UL

Tool: Custom gripper

Product: Cylindrical shape with length from 300 mm to 2700 mm, diameter from 63.5mm to 255 mm and weight from a few kg to 110kg that we have to estimate with an average density multiplied by an estimated volume.

Problem: (video of the issue:

I am currently trying to run the robot in AUT mode after many many successful runs in T1 at full speed. When running the program in AUT at 10% - 30% and 50% of the programmed velocity, I have no issue. But when I tried at 75%, the robot stopped during a linear motion with a few acknowledgement messages (KSS01138 Dynamic braking triggered)(KSS01074 Command motor torque on A5, A3 and A2) (see picture below for the error message and the LOAD_DATA of the active tool)

My questions:

1. I do not change any value for axis velocity but I do change de linear velocity in the program depending on what task the robot is doing. So $VEL.CP can either be set to fast_vel, mid_vel or low_vel where fast_vel = 2.0, mid_vel = 1.0 and low_vel = 0.1. Note that I changed the $CP_VEL_TYPE to #VAR_ALL in STEU/Mada/custom.dat file to make sure that linear velocity would slow down if any axis could not keep up. With the right LOAD_DATA set on the active tool, is the robot supposed to manage its own acceleration to ensure that no error like KSS01074 and/or KSS01138 pops up no matter what the linear speed ($VEL.CP and the velocity % at which AUT mode is set)?

2. If answer to question 1 is yes, I would have think that at some part of the motion the only thing that could happen is that the robot do not reach the desired linear velocity (which is not an issue to me) because the maximum acceptable acceleration is not high enough. But it wouldnt trigger an overtorque. Is this caused by a bad LOAD_DATA. I double (triple, if not quadruple) checked it by manual calculations and compared it with a CAD and it looks fine (if anything, I am probably over guessing the mass and thus all inertia values since I am using an average density over all products and this particular product has a density under that average). The product the gripper had at this moment is considered quite light compared to what it could eventually face. The gripper has a mass of 71 kg, the product it gripped while having this issue has a mass of 28.11 kg and the maximum product the robot would lift is 110 kg. Before using the right LOAD_DATA, I already ran the robot in AUT mode with only a value of -1 in the mass box and everything else empty in the LOAD_DATA at 100% velocity with the heaviest product and I didn't have any issue. What would be the downside of using -1 as the mass for every product? To my knowledge, it only means that the robot consider that it has the heaviest load it can handle. Am I right? Would that mean that it would only slow down my cycle time? Here's a link towards a video at full speed with the heaviest product:

3. If answer to question 1 is no, is the only fix is to try the sequence with the heaviest payload and tune the desired velocity so it does not trigger any overtorque?

I could provide parts of the code if needed, I didn't want the thread to be to long for nothing. Let me know.

Thanks a lot for your time!

Quote from panic mode

seriously...?

what is the downside to driving a car by only stepping on gas and brake pedals with full force? imagine city commute while driving so that engine is always screaming to 6000RPM and then suddenly hitting brakes to get to a full stop. wash, rinse and repeat for the life of the car.

Clearly, my understanding of what -1 does to the motion is wrong. I thought it did the exact opposite. By thinking it is working with a much larger load than it is, I thought the robot would accelerate and brake much slower. I do understand though that it is not a good way to solve this problem...

Quote from panic mode

clearly your load data is wrong. the messages complain about dynamic load which is inertia. and your motion is not smooth (wide radius) - robot does unnecessarily tight turns (small radius) when it trips.

So, just to be sure I understood correctly, no matter what $VEL.CP is set to and the motion I'm trying to achieve (that does work properly in manual mode T1) if the LOAD_DATA is spot on, the robot should be able to achieve it (maybe by slowing down on its own if needed)? The motion and/or the linear velocity asked is not the issue here but really the LOAD_DATA?

Thanks,

Quote from Fubini

What you expect you would get when using spline lin slin instead of old lin. Spline would always try to limit to maximal torques according to the robots dynamic model a feature not available for old lins. The dynamic model to limit the robots trajectories to its physical boundaries with classic motion commands is only supported for classic ptp.

All my motions or either SLINs or SPTPs without using any SPLINE blocks. So it should try to limit to maximal torques according to the model right? Which would also mean that my LOAD_DATA is wrong? Do you know if errors like KSS01138 and KSS01074 are more eager to appear if the LOAD_DATA is under or over estimated?

Thanks Fubini,

Quote from Fubini

Actually if load data is wrong you would see different messages without the "command" (message number 1138)

Are you sure about that message number? Because I do have that message number and it is "Dynamic braking triggered" as shown on the screenshot in the original thread.

Thanks,