Toward the Next Generation of Robotic Waiters

Abstract

In this paper, the problem of suppressing sloshing dynamics in liquid handling robotic systems has been faced by designing a dynamic filter that starting from the desired motion of the liquid container calculates the complete position/orientation trajectory for the robot end-effector. Specifically, a design philosophy mixing a filtering technique that suppresses the frequency contributions of the reference motion that may cause liquid oscillations and an active compensation of lateral accelerations by a proper container reorientation has been adopted. In principle, the latter contribution requires the knowledge of acceleration of the reference trajectory, but because of the use of an harmonic smoother that performs a shaping of the original motion, it is possible to obtain the value of the acceleration in runtime. In this way, the proposed methods can be applied also to reference motions that are not known in advance, e.g. commands directly provided by a human operator. This possibility has been demonstrated by means of a number of experimental tests in which the user teleoperates the robot carrying the container with the liquid by simply moving the hand in the free space whose 3D position is detected by a motion capture system.

A Plug-In Feed-Forward Control for Sloshing Suppression in Robotic Teleoperation Tasks

“…The first question that arises when analyzing all the aforementioned approaches for non-prehensile transportation, especially the last one, is whether an expression of feedforward compensation can be found that does not depend on friction parameters. This doubt arises because the approach we proposed for sloshing suppression, based on tilting compensation, only requires knowledge of linear accelerations [4].An experimental application to a waiter task suggests that the same control is able to maintain an object in equilibrium on a tray even when very fast motions are applied (see the video [3]). Additionally, while many researchers agree on the application of orientation compensation to prevent slipping, the problem of determining the optimal location of the center of rotation has not been addressed yet.…”

“…respectively, the constraint (30) for a triangular velocity trajectory becomes, in the worst case 3 ,…”