New: Calculate elapsed time in ctrl_loop #92
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- ros_control expects the actual time difference - Did not use the actually measured time in safety checks and vel. calculation yet - ros::Time::now() is not realtime safe. However realtime_tools' clock limited to 750Hz right now: ros-controls/realtime_tools#23
costashatz
reviewed
Nov 29, 2022
| @@ -321,23 +322,23 @@ namespace iiwa_ros { | |||
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| for (int i = 0; i < _num_joints; i++) { | |||
| _joint_position[i] = _robot_state.getMeasuredJointPosition()[i]; | |||
| _joint_velocity[i] = filters::exponentialSmoothing((_joint_position[i] - _joint_position_prev[i]) / elapsed_time.toSec(), _joint_velocity[i], 0.2); | |||
| _joint_velocity[i] = filters::exponentialSmoothing((_joint_position[i] - _joint_position_prev[i]) / ctrl_duration.toSec(), _joint_velocity[i], 0.2); | |||
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Why not elapsed_time here? I guess you have good reasons, but I'd like to have them documented.
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well, one of them is that we should handle interruptions then. That leads to very large values for the measured elapsed time. Like seconds.
The second reason is that when we implemented the controller for the IROS 2021 paper, you told me that we should not use the actual time when integrating, but only the expected time. I applied the same reasoning on the derivative here.
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Good enough! Merging... Thanks again! :)
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Here are some measurements of the elapsed time (wrongly labelled "ctrl_duration" in the plot) running a 1 kHz FRI connection (#90) together with this Cartesian impedance controller:
(Green and blue (covered by green) are the controller calculations)