DH Parameter Calibration with April Tags.
Currently, the seeds are configured for the ST R17 Arm, but the implementation is universal for all robot arms.
Currently Depends on the apriltags2_ros package for fiducial detection.
Nominal:
| α | a | d | Δq |
|---|---|---|---|
| π | 0 | -0.355 | 0 |
| π/2 | 0 | 0 | -π/2 |
| 0 | 0.375 | 0 | 0 |
| 0 | 0.375 | 0.024 | π/2 |
| π/2 | 0 | 0.042 | 1.176 |
| 0 | -0.012 | 0.159 | π |
Initial:
| α | a | d | Δq |
|---|---|---|---|
| 3.17e+00 | 2.06e-02 | -3.86e-01 | 7.46e-04 |
| 1.67e+00 | -6.00e-02 | -5.33e-02 | -1.55e+00 |
| -8.37e-04 | 3.41e-01 | 3.31e-03 | -8.81e-02 |
| -2.76e-03 | 3.80e-01 | -6.73e-03 | 1.51e+00 |
| 1.57e+00 | -4.57e-02 | 4.83e-02 | 1.13e+00 |
| -2.32e-02 | 6.54e-03 | 1.61e-01 | 3.12e+00 |
Calibrated:
| α | a | d | Δq |
|---|---|---|---|
| 3.14e+00 | 3.81e-03 | -3.59e-01 | -1.60e-03 |
| 1.57e+00 | 1.38e-03 | -2.30e-02 | -1.55e+00 |
| -1.92e-03 | 3.66e-01 | 2.89e-02 | -1.01e-02 |
| -1.67e-03 | 3.68e-01 | 1.23e-02 | 1.56e+00 |
| 1.57e+00 | -8.20e-03 | 8.51e-02 | 1.14e+00 |
| 1.47e-03 | 7.82e-03 | 1.35e-01 | 3.18e+00 |
Mean Absolute Error over 1000 Samples:
| x (m) | y (m) | z(m) | R (deg) | P (deg) | Y (deg) |
|---|---|---|---|---|---|
| 1.55e-2 | 1.45e-2 | 1.69e-2 | 2.49e-1 | 1.78e-1 | 2.37e-1 |
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Run the perception stack for detecting target markers.
The below node publishes a virtual target at a fixed offset from
base_link:roscore roslaunch st_r17_description urdf.launch use_kinect:=false rosrun st_r17_calibration target_publisher.py _num_markers:=4 _zero:=false _rate:=100 rviz -d $(rospack find st_r17_description)/rviz/dh.rviz -
Run the Calibrator.
roslaunch st_r17_calibration calibrate.launch num_markers:=4 slop:=0.001
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Setup the World:
roscore roslaunch st_r17_gazebo gazebo.launch roslaunch st_r17_gazebo spawn_tags.launch tag_size:=0.5 rosrun st_r17_calibration gazebo_target_initializer _num_markers:=4 tag_size:=0.5 _min_Y:=-1.0 _max_Y:=1.0
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Setup the Controls:
roslaunch st_r17_description control.launch roslaunch st_r17_moveit_config move_group.launch allow_trajectory_execution:=true fake_execution:=false info:=true debug:=false roslaunch st_r17_moveit_config moveit_rviz.launch
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Start perception stack and calibration:
ROS_NAMESPACE=/left rosrun image_proc image_proc roslaunch st_r17_calibration apriltags.launch roslaunch st_r17_calibration calibrate.launch num_markers:=4 slop:=0.01 roslaunch st_r17_calibration scouter.launch
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Evaluate Performance:
rosrun st_r17_calibration evaluate_dh.py