The ultimate goal of the project iGear (Intelligent Gearbox for Endurance Advanced Rotorcraft) is the development of an on-the-fly Structural Health Monitoring (SHM) system, applied to the lateral rotor gearboxes and engine to main gearbox reduction stages, in the framework of...
The ultimate goal of the project iGear (Intelligent Gearbox for Endurance Advanced Rotorcraft) is the development of an on-the-fly Structural Health Monitoring (SHM) system, applied to the lateral rotor gearboxes and engine to main gearbox reduction stages, in the framework of the compound rotorcraft demonstrator for the Fast Rotorcraft IADP. Further to the inherent challenges of extreme environments, data acquisition, mining, and fault detection, the project is mandated to develop an advanced monitoring concept adapted to innovative materials (such as ceramic). These materials are planned to be used in the next generation of aircraft efficient components and add to the uncertainty of the monitoring system, due to the lack of related track records.
The iGear project proposes a dual concept approach that minimizes the technology risk while allowing enough room for the exploitation of novel, less mature, technologies:
- a first conservative approach focused in reaching the objectives with minimal risk, using high TRL technologies and sensors;
- and, a parallel second approach consisting in a research branch aligned with the development and maturation of lower TRL solutions that are crucial for the success future SHM systems, namely operation in harsh environments and acquisition of sensory information directly in the relevant spots, such as rotating elements of the gearbox.
SHM systems in rotorcrafts are being researched since 1950s and have been used quite often in helicopters in the past couple of decades. However, the innovative concept proposed for iGear will have to deal with unknown behaviours of the gearboxes, driven by the usage of new materials (mostly ceramics), but also the
impact of downsizing and weight reduction solutions. This new generation of gearboxes will bring about several challenges to iGear, such as:
- The innovative design of gearboxes, namely the size reduction, might difficult the integration process of sensors and electronic systems in the gearboxes. On the other hand, it is a critical success factor, that the integrated system does not have any negative impact on the reliability and efficiency of the gearbox;
- The unknown behaviour of new materials and innovative gearbox concepts will increase the uncertainty of the SHM results. This will require several test runs and a consolidated test campaign to reduce the uncertainty of the algorithm, and improve the reliability of the fault detection;
- In order to minimize the signal to noise ratio of the sensors, it is likely that some conditioning sensor electronics need to be installed very close to the sensors. This issue will require miniaturization of electronics and using components rated to high temperatures (usually between 180 and 200 ÂºC);
- Minimization of overall complexity, number of sensors, and system cost, while keeping an effective and reliable structural health monitoring of gearboxes are the main drivers for the success of innovative SHM solutions.
Having started by performing a deep study on the state of the art of health monitoring systems, searching not only for their specifications and capabilities, but mainly for their implemented technical solutions, despite the enormous difficulties in acquiring such information with sufficient level of detail, each partner dedicated its main focus to its area of participation in the consortium, having been covered both the state of the art of those systems regarding their employed sensing technologies and regarding the algorithms implemented. On a second stage, a study on the state of the art of candidate technologies that could be exploited to improve the capabilities of health monitoring systems for the aeronautical industry was conducted, in the several applicable fields, namely innovative physical parameters to be sensed, sensing technologies and data processing algorithms. The outputs generated triggered a deep analysis of all the applicable technical information relative to the lateral rotor gearbox, leading to establish the HMS specifications. The document issued for that purpose details the required functions and sensing technologies, the required data processing outputs, and details the system constraints, namely, regarding operating environment and mechanical interfaces.
In order to establish a well informed and technically suitable sensors selection, a thorough market search aiming at listing the best commercially available implementations of the sensing technologies identified was conducted, followed by a meticulous classification of each identified product against the criteria relevant for the iGear system success. The roadmap for bringing the low TRL sensors (the innovative branch) to a status which could enable its integration into the lateral rotor gearbox was defined. This roadmap included the design, plan and description of a testing campaign aiming at validating, in a relevant laboratory environment, the applicability of the innovative sensors for measuring the desired physical parameters. Regarding the data processing algorithms, the development of algorithms techniques to apply to the iGear was deepened, both established and innovative concepts, aiming at taking the gearbox health diagnosis beyond the current implementations.
Simultaneously, the full system architecture was defined, followed by the complete detailed design of the HMS. The conditioning electronics to apply to each sensor signal path, the full acquisition system and the electronics system for executing data processing and storage, and the complete data processing algorithms were designed. Also, the validation test rig with the goal of validating not only sensors signal acquisition, but mainly the data processing algorithms was designed. The validation test rig is composed of an industrial gearbox with replaceable gears and bearings, two electric motors for driving the GB with controlled speed and breaking it with controlled torque, and an oil circulation and heating system, all assembled in a dedicated bench. Simultaneously, the maturation tests to the innovative sensors in laboratory environment was conducted as planned.
At CDR, the iGear consortium and the Topic Manager concluded that the tests results shown the proposed innovative sensing technologies to be promising for aeronautic mechanical structures health monitoring, particularly for monitoring gears. Thus, the identified sensors were accepted to proceed their implementation in the iGear HMS.
Following the HMS and respective validation rig design approval, both were manufactured, assembled and individually subjected to a set of preliminary electrical and functional tests. Finally leading to the sensors integration into the validation test rig and preliminary signal acquisition tests to verify operation.
With achieving successful TRR, the iGear HMS validation tests started. For the following months, the approved Validation Tests Plan was executed, which included a vast set of tests incl