A Response to the Reply Presented in "A Fair Comparison of Sliding-Mode and Immersion-and-Invariance Observers"

arXiv:2610.20815v1 Announce Type: new Abstract: In response to the reply presented in [Mu\~noz-V\'azquez and S\'anchez-Torres(2026)], this technical report extends the experimental evaluation of position-feedback velocity observers and adaptive tracking controllers for a pendular system with nonlinear friction reported in [Cervantes-P\'erez et al.(2026)]. The immersion and invariance (I&I) adaptive control scheme proposed in [Romero et al.(2025)], whose gains are tuned according to the guidelines presented in [Ortega et al.(2025)], is compared with a control scheme employing the adaptive modi?ed super-twisting observer of [D\'avila et al.(2006)], whose observer gains are selected according to the guidelines proposed in [Mu\~noz-V\'azquez and S\'anchez-Torres(2026)]. Although these "tuning guidelines" attenuate chattering in certain scenarios, the experimental results reported here show that they do not eliminate it in general.