Evaluation of adaptive control methods for friction in pendulum systems
A Response to the Reply Presented in "A Fair Comparison of Sliding-Mode and Immersion-and-Invariance Observers"
Robotics
Summary
This report looks at how two types of controllers help manage a pendulum's movement when friction is involved. The researchers compared a method called immersion and invariance (I&I) adaptive control with another that uses a special observer to estimate movement. They tested tuning rules designed to reduce unwanted vibrations, called chattering, but found these rules don't fully stop the problem in all cases. Their work helps understand which approaches work better under certain conditions.
What this means in practice
- •For industrial automation engineers: Improve control of mechanical systems with nonlinear friction to enhance stability and reduce vibration.
- •For robotics developers: Refine robot joint controllers by selecting adaptive observer gains that better handle friction-induced disturbances.
Authors
Luis Cervantes-Pérez, Víctor Santibáñez, Jesús Sandoval, Romeo Ortega, José Guadalupe Romero
Abstract
In response to the reply presented in [Muñoz-Vázquez and Sánchez-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-Pérez 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 [Dávila et al.(2006)], whose observer gains are selected according to the guidelines proposed in [Muñoz-Vázquez and Sánchez-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.