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To inspect aircraft engines for flaws and potential safety risks, they typically need to be completely dismantled, which involves cost and disruption to airlines.
Drawing on robotics technology from minimally invasive surgery, Arnau Garriga Casanovas has developed a “snake robot” capable of performing on-wing inspections without the need for disassembly, potentially leading to substantial cost savings while ensuring safety. Casanovas is a Royal Commission for the Exhibition of 1851 Industrial Fellow, and is doing the work as part of a research project with Imperial College London and Rolls-Royce.
The robot will deploy mini probes inside the aircraft engine to inspect it for potential cracks using ultrasonic sensors.
The snake robot is composed of a set of serially stacked segments, based on the concept known as flexible micro actuator (FMA), originally proposed by Koichi Suzumori from the University of Tokyo.
Each of these FMA segments consists of a cylinder with three equal longitudinal chambers. The outer surface is made of a composite of silicone with circumferential fibres that prevent radial expansion while enabling longitudinal extension. So when a differential pressure is applied in the chambers, the segment bends.
Casanovas can control the pressure at the chambers of the different segments to create a “serial manipulator” – a series of links connected by motor-actuated joints that extend from a base to an end-effector.
So far, the focus of the work has been on the research necessary to fabricate a robot. However, Casanovas has manufactured various segments of the device using a preliminary design similar to the traditional FMA, which displayed “significant dexterity, but limited force, highlighting the need for design optimisation”.
The main challenge for this project is to be able to create accurate robot control and maximise the force of the segments of the device. “In this regard, I have been investigating the optimal design, mechanical modelling, and control,” says Casanovas. “Now I believe I have found the most suitable design, I have derived closed-form solutions to the kinematics, and I’m making progress on the mechanical modelling to achieve an accurate control.”
The next stages of the project will see Casanovas complete his work on mechanical modelling and integrate it with the research carried out on kinematics to develop control laws. He will then be able to fabricate a preliminary prototype.
Casanovas says: “If everything goes well, I will then start working on the incorporation of the probe, a deployment mechanism, and a feedback system on the robot, hopefully leading to a complete prototype by the end of the project.”
The ultimate hope for the “snake robots” is to help the aerospace industry to be more efficient by streamlining the inspection process and increasing productivity. “Still, I’m conscious that the fast introduction of automation technologies poses an interesting challenge in terms of macroeconomic dynamics, so I hope we are prepared to manage the transition,” says Casanovas.
Rolls-Royce is developing a wider suite of technologies specifically designed for on-wing inspection and maintenance, supporting multiple projects. This includes work at the Rolls-Royce University Technology Centre at the University of Nottingham.
Researchers at the centre have developed in-house robotic systems, including a walking machine tool and a series of continuum robots that can be coupled to create hybrids that can walk and navigate in crammed and hazardous environments. They can perform inspection and active operations such as machining with the use of end-effectors attached to the robots.
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