A Parameter Identification Method for Two-Mass Systems With Friction and Limited Motion Range

This paper presents a novel Disturbance Observer (DOB)-based method for identifying mechanical parameters in two-mass systems. Unlike most traditional methods, it uses a load-side measurement, which is available in many modern devices. The method estimates parameters in a single experiment by leveraging the equivalent disturbances from two DOBs and orthogonal behaviors imposed on the kinematic variables through a closed-loop position experiment. The orthogonality facilitates the derivation of a system of linearly independent equations, which account for the mass, damping, Coulomb friction of both masses, and stiffness components, solvable with low computational complexity. The position profile avoids nearzero velocities to mitigate nonlinear friction effects and is suitable for systems with limited motion range. Simulation results under varying sensor noise levels, along with experimental validation, demonstrate the proposed method's effectiveness compared to conventional approaches.