Evaluating the Equivalence between Nonlinear Friction and Backlash in Two-Inertia Systems

Nonlinear friction and backlash are recurrent issues in control objectives characterized by two-inertia systems, such as geared robot joints and drivetrains. Intensive analysis and research has been conducted on the compensation for these two phenomenon, but usually separately. This study evaluates the equivalence of nonlinear friction and backlash when analyzed from motor-side velocity and torsion torque, respectively. This equivalence is evaluated by inspecting the zero-crossing time and slip (reengagement impact in the case of backlash) for both cases. It is found that for both phenomenons, zero-crossing time and slip/impact can be improved by a similar methodology. Analyses are validated by experimental results.