Dynamic Power Limiting


What would the best way to implement a dynamic power limting move be?

We have a system that will be compressing a load over a pretty long distance. We won’t know in advance what the compression rate will be but we will have pressure / force information from the cylinder. My hope is to be able to run a full speed until we see the force build up and then slow the cylinder down dynamically to keep the power required under the HP of the pump motor. I noticed in the Move Absolute that is warns against sending commands in rapid succession which was my first thought.

Has this been done before and if so, is there a prefered method for continually changing the velocity on the fly?


If you set the Move Absolute command to use a trapezoidal velocity profile instead of an s-curve velocity profile, then you can send the Move Absolute command in rapid succession. To choose trapezoidal velocity profile, in the Axis Parameters, on the All tab, in the Target section, set the Requested Jerk to zero.

Another option is to use a dual-loop axis and use the RMC’s force limit feature, except of course, it would actually be power limit. The secondary feedback, instead of being the force, can be Custom, and you would have a user program continually calculating the power, and that would be the secondary feedback value.

Thanks Jacob.

It is actually 4 cylinders moving together so the trapazoidzl move thing will be best.


Could our synchronized position-force method work? See Synchronized Position-Force

Thanks Jacob. I’ll look into that. Unfortunately I think the project is dead so I won’t get to try it soon.