A disturbance observer for robot manipulators with application to electronic components assembly

The success of robotic assembly for odd form electronic components depends heavily on the ability to monitor and control the insertion force. For this purpose, a joint disturbance observer for robot manipulators is presented to estimate the reaction force due to component misinsertion. The derivation is presented in the time domain for a multi-degree-of-freedom manipulator without making the SISO linear system assumption. Based on the internal model control (IMC) concept, this observer is simple in structure. It is in the form of an integral controller and only requires measurements of joint position and velocity signals to be implemented. The observed perturbation signal includes the effects of model uncertainties as well as reaction force against the environment. Careful trajectory planning and detailed friction modeling are performed to enhance accuracy of the deduced reaction force. Experiments conducted on a SCARA robot for the insertion of PCB components demonstrated the performance of the proposed disturbance observer