Overview
Current aircraft monitoring systems use sensors that are hard-wired to their electronic acquisition unit:
- it precludes acquisition of major parameters where wires cannot be installed;
- it results in complex installation;
- it very often results in increased weight.
Current wireless technologies enable an easy and flexible installation, but their design does not match aircraft monitoring needs as:
- autonomy is limited and re-charging is required;
- compatibility is not reached in the harsh aircraft environment.
Matching aircraft constraints and power autonomy are targets to be met by wireless monitoring systems operating at low data rates.
WISE investigated ways to integrate wireless technologies in the aircraft systems environment, for which the sensor power supply has to be autonomous.
WISE technologies will be usable in any fixed-wing aircraft or rotorcraft.
- To enhance aircraft system monitoring by developing concepts based on new wireless technologies and integrated sensing solutions, which have autonomous sensor power and low consumption, and are compatible with the harsh environment of aircraft systems;
- To allow the monitoring of new parameters, or replace/simplify complex existing solutions with physical links (wire, fluid);
- To allow continuous monitoring or improve redundancy when the link with the physical solutions would have been severed or turned off to improve information segregation.
All this will lead to improvements in aircraft design, maintainability, availability and the associated costs, reduced weight, fuel consumption and emissions.
The results expected are to have proven technology available for future programmes and products and to export to the non-aeronautical industry.
WISE intended to contribute to the standardisation of wireless technology usage in the aircraft.
The objective of the work was to develop three kinds of technologies:
- a Radio Frequency (RF) transmission through the open air medium that can remotely power the sensing element.
- a RF transmission through a complex environment comprising a metallic or composite aircraft structure. This technique should allow communication coverage through the air within the complete aircraft. Self-power generation will be investigated and could be integrated at the sensor level.
- a technique capable of energy and data transmission through a close metallic envelope. Non-RF techniques, such as the ultrasonic technique, will be investigated, including coupling with power generation techniques.
The performances of these technologies were verified by simulation, laboratory testing and finally by ground measurements on an iron bird for RF technologies.
Funding
Results
WISE achieved the following project objectives:
- improve aircraft monitoring by developing concepts based on new wireless technologies and integrated sensing solutions with autonomous sensor powering and low consumption: this has been achieved for each technologies;
- allow to monitor parameters not available or hardly available by physical link (wire or fluid);
- replace or simplify wiring solutions, fluid connections;
- information still available after wire cut (by design!).
WISE partially achieved the following project objectives:
- improve aircraft monitoring by developing concepts based on new wireless technologies and integrated sensing solutions compatible of harsh environment of aircraft systems:
- for RF remote powering: for EMI/HIRF tests: all passed, except that for HIRF radiated test the external temperature sensor wiring acts as an antenna and therefore the system is vulnerable to V/UHF emission: a correct shielding of the cabling plus filtering in the W/S would solve this issue. Also the DC power is not a full metallic box.
For Electrical tests that involved insulation, bonding and power input tests, WISE set passed successfully through all them.
For the Environmental tests per DO-160E requirements: the qualification test performed showed that the system is compliant with the vibration requirements. During altitude testing, the WISE set did not present any signs of malfunction. Temperature tests presented problems in high and low temperatures. During high temperature tests, when the test chamber temperature was 125oC, the WISE set operated for a short while, then the sensor accuracy presented degradation and finally the set stopped. It is suspected that this was due to the fact that certain components are commercial grade and thus the problem can be overcome by more careful components selection. At low temperatures, the set operated normally at the lowest extreme (-40oC) but communication with the remote sensor (WS) was lost or erroneous at temperatures between the extremes during temperature variation test with some partial recovering at some temperatures range.
This problem is not due to components rating, but is most probably related to the RF power transfer from the DC MAIN to the remote sensor module and can be resolved by updating the DC MAIN microcontroller software. Inadequate thermal management and thermal lag in the W/S sensor is also suspected. - for Ultrasonic: verification
Innovation aspects
The main gains identified are as follow:
- reduce aircraft operating cost and installation costs: WISE allows a simplification of installation and/or layout in the aircraft, it also allows a maintenance on condition that reduces direct maintenance costs;
- improve availability & dispatch rate through a simplification in system maintenance (cancellation of interconnection wiring for moving or removable parts, or simplification in maintenance see below);
- reduce cost of ground and flight tests installation thanks to wire removal;
- improve rotorcraft performance (thank to improvement in air intake temperature sensing accuracy).
- improve Man Machine Interface thanks to:
- a better situation awareness, as WISE allows to access to the exact energy status of the aircraft systems;
- a simplification of AFM/maintenance procedures: when WISE technology allows to access to the exact energy or status of the system which is not currently available with a wire solution, preventive maintenance actions or pre-flight checks are removed
- reduce incident or accident rate thanks to:
- removal of sensitive/moving wiring routines;
- reduction of incident due to gas or fluid leakage by cancellation of derivation/access used for aircraft system monitoring;
- improving fire protection by removing of holes to pass the wiring through rotorcraft composite sections.
Technical Implications
The specification phase of WISE project showed that, whatever the applications, most of the time, common requirements and design drivers are requested for each technology.
Readiness
Use of energy scavenging methods promises implementation in application scenarios with stable source conditions (e.g. vibration, light, air flow or similar) or using combination of one or more of these sources with a conventional battery operation in cases where wired installation is too complicated. WISE demonstrated energy density of vibration based energy scavenging that is on top of present state-of-the art performances. Further investigation in material use and size reduction can make this technology everyday thing in future applications.
Future research or application in aircraft product for an aircraft systems application shall address these items to make WISE a reality on board of an aircraft.
- for RF remote powering: for EMI/HIRF tests: all passed, except that for HIRF radiated test the external temperature sensor wiring acts as an antenna and therefore the system is vulnerable to V/UHF emission: a correct shielding of the cabling plus filtering in the W/S would solve this issue. Also the DC power is not a full metallic box.