Assembly automation using perturbation/correlation

In the traditional force-guided control schemes, the contact force measured by a force sensor is directly fed back to a feedback controller to generate a motion correction signal. The issue central to force guided robot control is how to obtain reliable, consistent and copious force signals and extract useful information in order to successfully guide the robot while keeping the contact force at a desired level. In this paper, instead of simply measuring contact forces, we take positive actions by giving perturbation to the end effector and observing the reaction forces to the perturbation in order to obtain much richer and more reliable information. By taking the correlation between the input perturbation and the resultant reaction forces, we can determine the gradient of the force profile and guide the part correctly. This algorithm is applied to a pipe insertion task, and connector assembly task. Based on the process model and stability analysis using the Popov stability criterion, conditions for stable, successful insertion despite nonlinearities and uncertainties in the environment are obtained. The theoretical results are verified using the experimental data.