control the speed of end effector precisely

[Lior]

Hi Johannes,

with our KR 10 we want to follow a curve that we designed in Grasshopper. Now we are wondering how we can perfectly control the speed of the end effector - especially at sections where the curve has very small radiuses. Is the speed actually handled via the Robot or via PRC?

Best
Lior

[Johannes @ Robots in Architecture]

Hello Lior,

Constant speed is always difficult with the robot. There are several things that can slow down a robot, first of all positions that are close to singularities, e.g. when A5 is close to 0. Also, if the point-density is too high, the robot will also slow down. Another thing is that in my experience you get the most constant speed if you run the robot in AUT mode with 100% OV - this means that you should set the speed exactly as you want it in KUKA|prc. Of course, as always, be careful in AUT and T2 and only use 100% OV speed once you've tested it in T1.

In KUKA|prc you can set the speed for every movement through the VEL input - m/sec for e.g. LIN, % for PTP. You can right-click a movement component and set it from C_DIS to C_VEL, where it will aim to keep a constant speed Also very relevant are the Interpolation and Acceleration options in the KUKA|prc settings / Advanced tab. For LIN movements, the higher you set CDIS/CVEL the earlier the robot will leave the programmed path - so the path will get less accurate.
Sometimes it helps to divide a curve completely equally to make the speed more even. This makes the file unnecessarily large - as there are e.g. points on straight lines - but may help as well.

Unfortunately there is no perfect way to achieve constant movement. For e.g. extrusion processes we have actually coupled the extruder speed to the speed of the tooltip and thereby compensated for the changing speed of the robot.
But the above hints should give you some pointers!

Best,
Johannes