sudden "motion aborted by reflex"

[Drorness]

Hello,
I'm experiencing some issues related to reflexive motion aborts in my experimental setup.
I'm running a looped sequence in which the robotic arm moves between 4 to 5 positions using CartesianMotion. In each iteration, the poses are slightly modified—both in position and orientation. The sequence is repeated multiple times.
However, after several iterations, I encounter a ControlException error. It appears to occur unpredictably—at random poses and during different iterations. The error message indicates the motion is being aborted by a reflex due to "cartesian_motion_generator_joint_acceleration_discontinuity".
I would appreciate any insight into the likely causes of this and suggestions on how to ensure trajectory smoothness and avoid such discontinuities.

• examples error:

Exception has occurred: ControlException
libfranka: Move command aborted: motion aborted by reflex! ["cartesian_motion_generator_joint_acceleration_discontinuity"]
control_command_success_rate: 0.96

franky._franky.ControlException: Motion finished commanded, but the robot is still moving! ["cartesian_motion_generator_acceleration_discontinuity", "cartesian_motion_generator_joint_acceleration_discontinuity"]
control_command_success_rate: 0.97

• code logic:

standby_pose = CartesianMotion(RobotPose(Affine([x_standby, y_standby, z_standby], normal_orientation)))
stop = CartesianStopMotion(relative_dynamics_factor=0.9)

robot.relative_dynamics_factor = RelativeDynamicsFactor(velocity=0.05, acceleration=0.01, jerk=0.01)
robot.move(standby_pose)

for run in range(runs):
  p1= CartesianMotion(Affine([x1, y1, z1], rot1))
  p2= CartesianMotion(Affine([x2, y2, z2], rot2)) 
  p3= CartesianMotion(Affine([x3, y3, z3], rot3))
  p4= CartesianMotion(Affine([x4, y4, z4], rot4)) 

  robot.move(p1)
  time.sleep(1)
  robot.move(p2)
  robot.relative_dynamics_factor = RelativeDynamicsFactor(velocity=0.001, acceleration=0.05, jerk=0.05)
  robot.move(p3, asynchronous=True)
  
  while (trigger > threshold):
      trigger = getValue()
      time.sleep(0.01)
  
  robot.move(stop)
  robot.join_motion()
  time.sleep(1)
  robot.relative_dynamics_factor = RelativeDynamicsFactor(0.001)
  robot.move(p4)

[TimSchneider42]

Hi,

This is a common problem with the Franka controllers. I would suggest reducing the dynamics of the stop motion a little bit. Other than that, you can try tuning acceleration and jerk a bit more. Is the issue occurring in all of these motions?

One more thing that might also be an issue is that if the CPU is very busy, it might miss a couple of frames from time to time, which also reduces control quality. Could you check if there are any spikes in CPU usage while you are running this script? Especially, excessive syscalls from other threads (e.g., printing) may impact the control thread.

Best,
Tim