Table 4.

Calculated relative optimal iterative learning gain values K_l,opt,exp/K_l,opt through curve-fitting experimental data.

Stiffness combination (desired, passive)	RMS tracking errors		Normalized RMS tracking errors
	Absolute	Relative	Absolute	Relative
(D1, S1)	0.3923	0.3047	0.5667	0.4823
(D2, S1)	0.7779	0.6472	1.1623	0.9884
(D3, S1)	0.7307	0.6726	0.5850	0.3731
(D1, S2)	0.8006	0.8374	0.7524	0.7738
(D2, S2)	0.7472	0.8150	1.0389	1.0767
(D3, S2)	1.0377	0.9533	1.3639	1.1933
(D1, S3)	1.4233	1.1708	1.6885	1.3190
(D2, S3)	0.6286	0.6147	0.6616	0.5767
(D3, S3)	0.9768	1.0023	1.1173	1.1332
Average	0.8350 ± 0.2892	0.7798 ± 0.2547	0.9929 ± 0.3846	0.8796 ± 0.3398