Estimating Minimal Parameters of a Manipulator for Gravity Load and Friction

Abstract

This paper presents an identification method to estimate the minimal parameters of a manipulator for the gravity load and the friction. These parameters are required by the set-point control to ensure zero steady-state response. In the identification, the motor torque constants are unknown. The friction force is modeled by the nonsymmetric Coulomb friction and viscous friction. The crucial feature of the present method is to identify the torque constants, the friction and the gravity parameters at the same time. A theory addresses the minimal parameters composed of these three groups of parameters. The proposed identification procedure for the minimal parameters is conducted by moving one joint with a constant velocity at a time. The persistently exciting trajectories for the identification are also suggested. The experiment on the three-link PUMA robot verifies the identification method.