Hi there, I am designing a linear moving platform stand for a UR20. Basically a motorized carriage with four bearings on 2 rails. We have to stay under a weight limit for the whole thing, and that means light rails, light supports.
At this point the maximum load applied to the stand/carriage is the one transmitted to the stand by the UR when it performs a category 0 stop under a worst-case scenario, per the UR20 manual (p50). (Dimensioning the Stand)
Physically, it means that when the UR has a maximum momentum mass*velocity in kg.m/s and stops in a very short time (s), it transmits all of its mechanical energy to the base, applying a mean force equal to mass*velocity/time in kg.m/s² (Newtons).
The question is : Can I cut the maximum loads applied to the stand by using the momentum limit function? Would the power limit be more adequate? Since the momentum limit in the least restricted safety mode is 200 kg.m/s, would setting it at 100 kg.m/s allow me to cut the design loads in half?
That setting will not affect the safety stops, no.
Especially category stop 0 will be difficult, since it’s an immediate cutting of all power to the robot arm and hence an activation of the mechanical brakes within each joint.
But it will definitely affect the torque transmitted to the base during a safety stop, right ? Pulling a category 0 stop while the robot velocity is 0m/s should apply 0 torque to the base, no?
The safety setting is determining the stop momentum exerted when the robot is stopping with a safety stop. I am not sure about the category 0 stop, though, since it’s an emergency stop and just locks up the brakes.
The momentum setting should tell the robot how fast it can move while still being able to stop with that momentum by motor power - is what I understand from it.
