Versatile Airborne Ultrasonic NDT Technologies via Active Omni-Sliding with Over-Actuated Aerial Vehicles

TL;DR

The problem addressed is enabling ultrasonic non-destructive testing from aerial platforms by achieving true omnidirectional sliding and dynamic scanning. The approach integrates an over-actuated UAV (Voliro T) with an omni-sliding payload that combines three omniwheels, a compliant interface, and an EMAT UT sensor to gather multi-point measurements without re-contact. Key contributions include deriving system constraints for active sliding, validating wall sliding, and demonstrating dynamic EMAT-based UT scanning that yields A-scan data and the potential for B- and C-scan representations, all while maintaining stable surface contact. The findings reveal important design trade-offs in weight, friction, and contact forces, and provide practical guidelines for deploying aerial UT systems in industrial inspections with reliable, omnidirectional data acquisition.

Abstract

This paper presents the utilization of advanced methodologies in aerial manipulation to address meaningful industrial applications and develop versatile ultrasonic Non-Destructive Testing (NDT) technologies with aerial robots. The primary objectives of this work are to enable multi-point measurements through sliding without re-approaching the work surface, and facilitate the representation of material thickness with B and C scans via dynamic scanning in arbitrary directions (i.e. omnidirections). To accomplish these objectives, a payload that can slide in omnidirections (here we call the omni-sliding payload) is designed for an over-actuated aerial vehicle, ensuring truly omnidirectional sliding mobility while exerting consistent forces in contact with a flat work surface. The omni-sliding payload is equipped with an omniwheel-based active end-effector and an Electro Magnetic Acoustic Transducer (EMAT). Furthermore, to ensure successful development of the designed payload and integration with the aerial vehicle, a comprehensive studying on contact conditions and system dynamics during active sliding is presented, and the derived system constraints are later used as guidelines for the hardware development and control setting. The proposed methods are validated through experiments, encompassing both the wall-sliding task and dynamic scanning for Ultrasonic Testing (UT), employing the aerial platform - Voliro T.

Figures (7)

• Figure 1: Voliro T: an over-actuated aerial vehicle equipped with a payload.
• Figure 2: Wheel (motor) layout, work surface frame $\mathcal{F}_S$, end-effector frame $\mathcal{F}_E$.
• Figure 3: Compliant Component: front view and side view.
• Figure 4: Active Sliding, {B}: body frame, {I}: inertial frame, $\bm{f}_N$: normal force, $\bm{f}_R$: rolling friction, $\bm{f}_w$: friction force to drive the wheels, $\bm{\tau}_w$: total wheel motor torque.
• Figure 5: Omni-Sliding Payload Prototype.