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i have trouble interpreting the joint speed profiles my robot produces.

Setup:

  • ROS2 Humble
  • Robot: Yaskawa HC10 + YRC1000
  • Motion Planner: Moveit2 + Pilz Industrial Motion Planner

Image Descriptions:
The images show the Joint Speed Profiles of all the joints SLURBT of my robot during one movement in a movement sequence. In all cases the robot was able to finish this particular movement of the sequence, however, afterwards the trajectory is interrupted. I have tried adjusting the acceleration scaling factors as seen in the images below, but i am having trouble interpreting the results and what i consequently need to adjust. In my experience lowering the acceleration should improve the robots ability to execute a smooth movement, but the joint speed profiles don´t seem to show that.
Image 1:
Vel. scaling factor:1.0 Acc. scaling factor: 1.0
The robot visibly jerks in the beginning but reaches the full speed eventually so i am assuming the speed is not the problem. But maybe I am interpreting it wrong...
Image 2:
Vel. scaling factor:1.0 Acc. scaling factor: 0.3
Image 3:
Vel. scaling factor:1.0 Acc. scaling factor: 0.1
Image 4:
Legend
Vel.: 1.0 Acc.: 1.0 Vel.: 1.0 Acc.: 0.3 Vel.: 1.0 Acc.: 0.1 Legend

Can anyone help me figure out the problem and maybe a solution?

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  • $\begingroup$ Welcome to Robotics, Ten. Do you have plots which also show the command speed profiles? I've done a lot of work on commercial sway control systems and the speed profiles here, with the "knee" on the way up and down, looks like what I would expect with a sway control algorithm. This leaves me wondering if what you're seeing is a flaw with a standard trapezoidal speed profile or if there's some other controller. Apart from the rising transient, the first plot looks good. Images 2 and 3 show acceleration changing during what looks like a pretty smooth transient. $\endgroup$ Commented Jul 11 at 12:44
  • $\begingroup$ Could you please clarify what you mean by command speed profiles? I'm giving my robot a MaxVelocityScalingFactor() and a MaxAccelerationScalingFactor() and plot the resulting joint speed profiles via plotjuggler. Could Motoros2 have a built in sway control that is conflicting with the Moveit trajectory execution? $\endgroup$ Commented Jul 15 at 9:12
  • $\begingroup$ What tells the motors to move, and what tells them how fast to move? Is this just an on/off control where the trapezoidal profile is set by a combination of the velocity and acceleration scaling factors, or is there some speed profile issued by a controller? Whatever the case, something must be telling the motors to move, so can you plot that motion command (on/off, or some other command speed profile) along with the speed feedback? $\endgroup$ Commented Jul 15 at 12:31

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