Unwieldy Object Delivery With Nonholonomic Mobile Base: A Free Pushing Approach

This letter explores the problem of delivering unwieldy objects using nonholonomic mobile bases. We propose a new approach called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">free pushing</i> to address this challenge. Unlike previous <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">stable pushing</i> methods which maintain a stiff robot-object contact, our approach allows the robot to maneuver around the object while pushing it. It aims to execute continuous pushes without losing contact for improved pushing maneuverability. Additionally, to ensure the feasibility of the planned pushes, a robot-object contact model is developed to account for the shape and kinematics of the robot in pushing modeling and planning. A Model Predictive Controller solves the pushing planning problem in real time. Experimental results show that the proposed method achieves an average success rate of 83% with an accuracy of 0.085 m when pushing to the selected goals. Compared to the baselines, this approach improves the agility and efficiency of mobile pushers. Furthermore, it is robust in achieving the task while tolerating modeling errors.