Design and Control of an Ultra-Slender Push-Pull Multisection Continuum Manipulator for In-Situ Inspection of Aeroengine

TL;DR

The paper tackles the challenge of conducting in-situ aeroengine blade inspections through restricted ports by introducing an ultra-slender push-pull multisection continuum manipulator actuated via tendons. It develops a piecewise constant curvature (PCC) kinematic model with a decoupling method to enable real-time, low-complexity control in teleoperation, validated on a three-section concentric-tube prototype. Key contributions include the PPCM design, a decoupled kinematic framework, and a closed-loop PID control that accounts for tendon tension, with experimental demonstrations of blade inspections through tight gaps. This approach offers a potential replacement for traditional industrial endoscopes by enabling thorough, single-port inspection in confined aerospace environments, and sets the stage for portable or in-pipe deployment.

Abstract

Since the shape of industrial endoscopes is passively altered according to the contact around it, manual inspection approaches of aeroengines through the inspection ports have unreachable areas, and it's difficult to traverse multistage blades and inspect them simultaneously, which requires engine disassembly or the cooperation of multiple operators, resulting in efficiency decline and increased costs. To this end, this paper proposes a novel continuum manipulator with push-pull multisection structure which provides a potential solution for the disadvantages mentioned above due to its higher flexibility, passability, and controllability in confined spaces. The ultra-slender design combined with a tendon-driven mechanism makes the manipulator acquire enough workspace and more flexible postures while maintaining a light weight. Considering the coupling between the tendons in multisection, a innovative kinematics decoupling control method is implemented, which can realize real-time control in the case of limited computational resources. A prototype is built to validate the capabilities of mechatronic design and the performance of the control algorithm. The experimental results demonstrate the advantages of our continuum manipulator in the in-situ inspection of aeroengines' multistage blades, which has the potential to be a replacement solution for industrial endoscopes.

Figures (10)

• Figure 1: Conceptual illustration of the PPCM.
• Figure 2: a) Turbine inspection scenario; b) Compressor inspection scenario.
• Figure 3: Schematic of the continuum manipulator: It is assembled by three single sections, of which three backbones form a concentric tube structure, and tendons between the three sections are coupled to each other.
• Figure 4: Schematic of the backbone actuation: It features a pneumatic system comprising three fixed pneumatic grippers and one movable gripper.
• Figure 5: Prototype of the PPCM. a) Continuum manipulator; b) A set of tendon actuation units comprising a winding unit and a force measurement unit; c) Backbone actuation; d) Architecture of the mechatronic system.