Distributed Hierarchical Shared Control for Flexible Multirobot Maneuver Through Dense Undetectable Obstacles

When teleoperating a multirobot system (MRS) in outdoor environments, human operators can often detect obstacles that are not detected by robots and spot emergencies faster than robots do. However, the lack of efficient methods for operators to manipulate an MRS has limited the number of robots in a human–robot team. To handle this problem, a distributed hierarchical shared control scheme is proposed, aiming to provide a safe and flexible control interface for a few human operators to interact with a large MRS. The proposed hierarchical control scheme employs a two-layered structure. In the upper layer, intention field networks are designed to generate virtual human control signals. Two functionalities for human teleoperation, called: 1) group management and 2) motion intervention, are realized using intention fields, allowing the operators to split the robot formation into different groups and steer individual robots away from immediate danger. In parallel, a blending-based shared control algorithm is designed in the lower layer to resolve the conflict between human intervention inputs and autonomous formation control signals. The input-to-output stability (IOS) of the proposed distributed hierarchical shared control scheme is proved by exploiting the properties of weighting functions. Results from a usability testing experiment and a physical experiment are also presented to validate the effectiveness and practicability of the proposed method.

I. Introduction

Multirobot systems (MRSs) have attracted lots of attention over the past decades for their broad applications in cooperative manipulation [1], object transportation [2], search and rescue [3], etc. To develop an MRS for complex environments and tasks, human supervision and interventions are necessary as robots have limited cognitive and decision-making capabilities. It is still challenging to build an efficient human–robot team in which a few operators can master a large group of robots. Many problems need to be solved, including the design of a suitable interaction interface, the proper assignment of roles, the analysis of human factors, etc. [4]–[6]. Among such problems, we consider in this article the problem of developing a distributed flexible shared control scheme.