Inspection-on-the-fly using Hybrid Physical Interaction Control for Aerial Manipulators

TL;DR

This paper introduces a hybrid physical interaction control method enabling aerial manipulators to perform on-the-fly structural inspections, estimating surface properties during manipulation with improved transition and reduced lag.

Contribution

It presents a novel three-stage hybrid control paradigm and an operational space manager for real-time structural property estimation during aerial manipulation.

Findings

Effective estimation of surface stiffness and restitution coefficient during manipulation

Robust transition from motion to force control with reduced lag

Successful experiments in a mock-up exhaust shaft environment

Abstract

Inspection for structural properties (surface stiffness and coefficient of restitution) is crucial for understanding and performing aerial manipulations in unknown environments, with little to no prior knowledge on their state. Inspection-on-the-fly is the uncanny ability of humans to infer states during manipulation, reducing the necessity to perform inspection and manipulation separately. This paper presents an infrastructure for inspection-on-the-fly method for aerial manipulators using hybrid physical interaction control. With the proposed method, structural properties (surface stiffness and coefficient of restitution) can be estimated during physical interactions. A three-stage hybrid physical interaction control paradigm is presented to robustly approach, acquire and impart a desired force signature onto a surface. This is achieved by combining a hybrid force/motion controller with a model-based feed-forward impact control as intermediate phase. The proposed controller ensures a steady transition from unconstrained motion control to constrained force control, while reducing the lag associated with the force control phase. And an underlying Operational Space dynamic configuration manager permits complex, redundant vehicle/arm combinations. Experiments were carried out in a mock-up of a Dept. of Energy exhaust shaft, to show the effectiveness of the inspection-on-the-fly method to determine the structural properties of the target surface and the performance of the hybrid physical interaction controller in reducing the lag associated with force control phase.