As part of the FLAPsense project, a sensor system for the non-contact measurement of movement (in particular flapping and cross-axis flapping) of the NGCTR's prorotor hub was developed from scratch. Based on the given requirements, a total of five concepts were evaluated and a favoured solution, Concept 1, which is based on camera sensors, was further developed through the System Requirements Review (SRR), the Preliminary Design Review (PDR) and the Critical Design Review (CDR) up to the updated final design. All development steps were documented in the form of project results and scientific publications. Unfortunately, the project encountered several major delays. In order to maximize the possible outcome of the project it was decided after the 3rd reporting period to amend the project contract and rescope FLAPsense from the initial plan to completely develop an airborne system towards a two-lane approach with the development of the airborne system up to the CDR and in parallel building and testing a research demo sensor system made of COTS parts. The first lane, i.e. the final design of the airborne sensor system has fully been achieved within the project duration. The second lane regarding the demonstration of the system was nearly completed as only the demonstration test on the rotating test rig has not been completed in within the project.
Due to the fact, that the FLAPsense sensor concept is very promising and most of the extensive work for this test still has been done, i.e. design and manufacturing of the Marty test rig, planning of the test, design and manufacturing of the preliminary model of the sensor system (= the research demo sensor system), it has been agreed to perform this demonstration test after the end of the project at on own costs and risk. Results of this Demo-Test will be used for further maturation of the system and realization of the CDR sensor design.
With regards to the exploitation the achievements made within the FLAPsense project have valuable potential for other future applications. In general, the FLAPsense technology and the Constance wireless data transfer, can be applied to other rotary or propeller aircraft.
The contactless sensing potentially has large benefits for reliability and maintenance as far as it enables more accurate measurements on a huge surface area (not only single probes) without impact to the measured object (i.e. no sensor installation on the investigated surface, that could disturb the flow) or by the measured object (i.e. no mechanical linkage that would cause unwanted coupling of several degrees of freedom).
Additionally, the different sensor concepts and lessons learnt from the system design can be used for further applications on rotor or propeller deformation measurement systems. The capabilities gained on structural analyses, heat exchange calculations and investigations on EMC and HIRF protection are valuable for future airborne sensor developments.
The real time marker detection algorithm can be used for other position, shape and deformation measurements, where the results are required directly during the running test. Presently such results are only available after the later performed postprocessing. It has to be mentioned, that the first application of the fiducial markers for highly accurate measurements that was done in FLAPsense now is pushing their development further and could improve the automatic marker processing also for other optical measurement techniques were presently a certain amount of manual marker detection is included.
The lessons learnt for the 3D printing of the enclosure can be used for future rapid prototyping actions and the software algorithms for the trigger evaluation and the ARINC data conversation can be used for next applications where a robust additional method for the RPM determination for avionics is wanted. The method can directly be implemented in the flapping sensor, avoiding additional RPM or azimuth sensor systems. Alternatively, the novel sensor system can be used as an additional one in order to increase redundancy.
