Object Gathering with a Tethered Robot Duo

TL;DR

This paper presents a novel cooperative planning framework for a tethered robot duo to efficiently gather scattered objects using optimized trajectories and net length estimation, validated through simulation and real-world experiments.

Contribution

It introduces the first method to estimate the optimal net length for a tethered robot duo and develops an iterative optimization scheme for trajectory planning.

Findings

U-shape cost function improves cooperation

Task efficiency is not proportional to net length

Framework accurately estimates optimal net length

Abstract

We devise a cooperative planning framework to generate optimal trajectories for a tethered robot duo, who is tasked to gather scattered objects spread in a large area using a flexible net. Specifically, the proposed planning framework first produces a set of dense waypoints for each robot, serving as the initialization for optimization. Next, we formulate an iterative optimization scheme to generate smooth and collision-free trajectories while ensuring cooperation within the robot duo to efficiently gather objects and properly avoid obstacles. We validate the generated trajectories in simulation and implement them in physical robots using Model Reference Adaptive Controller (MRAC) to handle unknown dynamics of carried payloads. In a series of studies, we find that: (i) a U-shape cost function is effective in planning cooperative robot duo, and (ii) the task efficiency is not always proportional to the tethered net's length. Given an environment configuration, our framework can gauge the optimal net length. To our best knowledge, ours is the first that provides such estimation for tethered robot duo.