The HapticGlove coupling matrix regression can silently fail causing the retargeting to not work

[S-Dafarra]

We recently noticed that sometimes the retargeting does not start on one hand.

Checking the log, we noticed that the corresponding learnt coupling matrices contained nan

28860   4781,924201             RobotController::RightHand:: [axes-joints coupling] Bias-A matrix:

28861   4781,924221                     -nan         -nan         -nan         -nan         -nan         -nan   1.6839e-14 -3.24393e-15 -5.14172e-15

28862   4781,924253                     -nan         -nan         -nan         -nan         -nan         -nan -9.47293e-05  0.000150101  0.000174336

28863   4781,924278                     -nan         -nan         -nan         -nan         -nan         -nan  3.77637e-06 -3.20999e-06 -9.53803e-06

28864   4781,934221                     -nan         -nan         -nan         -nan         -nan         -nan            0            0            0

28865   4781,944277                     -nan         -nan         -nan         -nan         -nan         -nan -0.000181851 -1.43075e-05 -7.10659e-06

28866   4781,944302                     -nan         -nan         -nan         -nan         -nan         -nan            0            0            0

28867   4781,944315                     -nan         -nan         -nan         -nan         -nan         -nan            0            0            0

28868   4781,944327                     -nan         -nan         -nan         -nan         -nan         -nan      1.00008 -3.99134e-05   9.0291e-06

28869   4781,944344                     -nan         -nan         -nan         -nan         -nan         -nan    -0.225956     0.371033  -0.00728537

28870   4781,954345                     -nan         -nan         -nan         -nan         -nan         -nan     0.225943     0.477995   0.00723945

28871   4781,954390                     -nan         -nan         -nan         -nan         -nan         -nan   0.00176532    0.0119013     0.337929

28872   4781,954435                     -nan         -nan         -nan         -nan         -nan         -nan   -0.0173964   -0.0204783     0.418089

28873   4781,964412                     -nan         -nan         -nan         -nan         -nan         -nan   0.00629571   0.00288404     0.226472

28874   4781,964451                     -nan         -nan         -nan         -nan         -nan         -nan   0.00327127    0.0106662     0.303892

28875   4781,964474                     -nan         -nan         -nan         -nan         -nan         -nan  -0.00992028   -0.0174625     0.270478

28876   4781,964497                     -nan         -nan         -nan         -nan         -nan         -nan   0.00547984    0.0047442     0.267673

28877   4781,964520             RobotController::RightHand:: [axes-joints coupling] A (coupling) matrix:

28878   4781,974469                     -nan         -nan         -nan         -nan         -nan   1.6839e-14 -3.24393e-15 -5.14172e-15

28879   4781,974497                     -nan         -nan         -nan         -nan         -nan -9.47293e-05  0.000150101  0.000174336

28880   4781,974515                     -nan         -nan         -nan         -nan         -nan  3.77637e-06 -3.20999e-06 -9.53803e-06

28881   4781,974532                     -nan         -nan         -nan         -nan         -nan            0            0            0

28882   4781,974546                     -nan         -nan         -nan         -nan         -nan -0.000181851 -1.43075e-05 -7.10659e-06

28883   4781,974565                     -nan         -nan         -nan         -nan         -nan            0            0            0

28885   4781,974649                     -nan         -nan         -nan         -nan         -nan            0            0            0

28886   4781,984538                     -nan         -nan         -nan         -nan         -nan      1.00008 -3.99134e-05   9.0291e-06

28887   4781,984570                     -nan         -nan         -nan         -nan         -nan    -0.225956     0.371033  -0.00728537

28888   4781,984591                     -nan         -nan         -nan         -nan         -nan     0.225943     0.477995   0.00723945

28889   4781,984613                     -nan         -nan         -nan         -nan         -nan   0.00176532    0.0119013     0.337929

28890   4781,994607                     -nan         -nan         -nan         -nan         -nan   -0.0173964   -0.0204783     0.418089

28891   4781,994645                     -nan         -nan         -nan         -nan         -nan   0.00629571   0.00288404     0.226472

28892   4781,994668                     -nan         -nan         -nan         -nan         -nan   0.00327127    0.0106662     0.303892

28893   4781,994690                     -nan         -nan         -nan         -nan         -nan  -0.00992028   -0.0174625     0.270478

28894   4781,994712                     -nan         -nan         -nan         -nan         -nan   0.00547984    0.0047442     0.267673

28895   4782,004669             RobotController::RightHand:: [axes-joints coupling] B (bias) vector:

28896   4782,004705             -nan

28897   4782,004717             -nan

28898   4782,004727             -nan

28899   4782,004737             -nan

28900   4782,014737             -nan

28901   4782,014767             -nan

28902   4782,014783             -nan

28903   4782,014809             -nan

28904   4782,014820             -nan

28905   4782,024805             -nan

28906   4782,024834             -nan

28907   4782,024839             -nan

28908   4782,024845             -nan

28909   4782,024849             -nan

28910   4782,024855             -nan

28911   4782,034877             -nan

28912   4782,034915              QP control coefficient matrix:

28913   4782,034928             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

28914   4782,034949             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

28915   4782,034968             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

28916   4782,034982             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

28917   4782,034997             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

28918   4782,044936             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

28919   4782,045010             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

28920   4782,045031             -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan -nan

Full log: log_icub-head_HapticGloveModule_3407_nan.txt

[S-Dafarra]

By checking the log, it also appeared that rank of the input data matrix was 8, while it was 9 for the other (working) hand.

Indeed, if the input matrix is not full row rank, its inverse may fail: https://github.com/robotology/walking-teleoperation/blob/354e41613a8cb0c3de961e12a84ac4c30b7a54ea/modules/HapticGlove_module/src/LinearRegression.cpp#L29

I suspect this was due to a joint not moving during the calibration phase. This might happen often if some finger goes to HF unnoticed. I would expect the module to print a meaningful error, or even better, to try to react ignoring the faulty joint.

cc @GiulioRomualdi @lrapetti @EhsanRanjbari