Periodic Reporting for period 2 - SMARTWISE (Smart Miniaturized and Energy Autonomous Regional Aircraft Wireless Sensor)
Okres sprawozdawczy: 2022-01-01 do 2023-06-30
The SMARTWISE project developed a smart, miniaturized and energy autonomous wireless sensor platform dedicated to data collection for the Structural Health Monitoring System (SHMS) of future multi mission regional aircrafts. The aim of the SHMS is to assess and provide prognosis on the airframe integrity in real time, which allows the application of condition-based maintenance. This capability increases the aircraft availability and allows the optimisation of maintenance scheduling and cost.
Three use cases were considered (the first was prioritised):
- Usage and operational loads monitoring: 50 to 250 SPS continuous acquisition of strain gauges, accelerometers and temperature sensors.
- Damage detection using high rate accelerometers and piezo-electric diaphragms, with up to 250 KSPS acquisition rate.
- Damage diagnosis with active interrogation of piezo-electric sensors during short time windows at very high rate (2 MSPS).
At completion, the project has delivered TRL4 prototypes for the OLM use case, with the following performance:
- The energy harvester supplies 13 mW continuously, as long as there is at least 6A, 300 Hz on the main power line. This is enough to power the sensor node continuously when it is associated, in sleep mode and acquiring a temperature signal at 10 SPS. This is however not sufficient to power the sensor node when it is acquiring a strain gauge. With an at least twice larger harvester, a sensor node could be powered continuously, at the cost of a small weight increase (max 85g).
- According to Airbus data, a single wired strain sensor adds between 1 and 2 kg to the aircraft mass. The overall weight of the wireles sensor node is below 150 grams depending on configuration, including 85g for the energy harvester, and it can accommodate several strain and temperature sensors. Therefore, it is reasonable to expect from 800 to 1800g weight reduction per sensor node compared to their wired counterparts.
- The weight of the data concentrator cabling should be taken into account though. Depending on sensor location, 4 to 5 WDCs should be sufficient to cover a regional aircraft.
SMARTWISE has also experienced embedded acquisition and signal generation on piezo-electric sensors. In the future, this use case should be further explored to define duty cycling opportunities and integration with ultra-low power technology, especially in H2020 project GENEX.
Another important deliverable is a wireless data concentrator with embedded TCP/IP and micro-second synchronization with an implementation of the IEEE1588 protocol (PTP).
Three use cases were considered (the first was prioritised):
- Usage and operational loads monitoring: 50 to 250 SPS continuous acquisition of strain gauges, accelerometers and temperature sensors.
- Damage detection using high rate accelerometers and piezo-electric diaphragms, with up to 250 KSPS acquisition rate.
- Damage diagnosis with active interrogation of piezo-electric sensors during short time windows at very high rate (2 MSPS).
At completion, the project has delivered TRL4 prototypes for the OLM use case, with the following performance:
- The energy harvester supplies 13 mW continuously, as long as there is at least 6A, 300 Hz on the main power line. This is enough to power the sensor node continuously when it is associated, in sleep mode and acquiring a temperature signal at 10 SPS. This is however not sufficient to power the sensor node when it is acquiring a strain gauge. With an at least twice larger harvester, a sensor node could be powered continuously, at the cost of a small weight increase (max 85g).
- According to Airbus data, a single wired strain sensor adds between 1 and 2 kg to the aircraft mass. The overall weight of the wireles sensor node is below 150 grams depending on configuration, including 85g for the energy harvester, and it can accommodate several strain and temperature sensors. Therefore, it is reasonable to expect from 800 to 1800g weight reduction per sensor node compared to their wired counterparts.
- The weight of the data concentrator cabling should be taken into account though. Depending on sensor location, 4 to 5 WDCs should be sufficient to cover a regional aircraft.
SMARTWISE has also experienced embedded acquisition and signal generation on piezo-electric sensors. In the future, this use case should be further explored to define duty cycling opportunities and integration with ultra-low power technology, especially in H2020 project GENEX.
Another important deliverable is a wireless data concentrator with embedded TCP/IP and micro-second synchronization with an implementation of the IEEE1588 protocol (PTP).
The three use cases were analysed by the consortium, and the actual sensor types and models were selected for each use case. The selected elements include ARINC429 bus tapping, COLUMBIA strain gauges, digital accelerometers, analogue accelerometers, thermistors and piezo-electric diaphragms. The sensor operations procedures for the whole data transmission chain were established.
On the hardware side, the architecture of an acquisition PCB meant to be plugged to the wireless communication electronics was proposed. It includes performant ADCs for the acquisition of analogue sensors and the digital high range accelerometer. The PCB was produced and successfully interfaced to the communication board. A housing was created for the sensor node and the tests showed that the sensors can be acquired with the required data rate and accuracy.
The wireless data concentrator (WDC) manages groups of wireless sensors and interconnects them with the avionics over the aircraft wired network. The WDC design was proposed and its implementation realised. It includes a powerful STM32H743 MCU to withstand the high throughput and implement communication over Ethernet. Synchronisation between several WDC's is done by a Precise Time Protocol (PTP) implementation. After integration, synchronisation was evaluated at the whole network scale (wired plus wireless parts): as the synchronisation error on the wireless part of the network is around 12 µs, the total synchronisation error between two sensor nodes is in the order of 15 µs. assuming variability between samples of the same components and environmental effects, and taking some margin, a synchronisation accuracy of 100 µs is achievable. A housing was also realised for the WDC.
The wireless communication protocol was implemented over the u111 real-time operating system which provides best-in-class energy consumption.
A theoretical assessment of inductive power line harvesting from the aircraft main power supply harnesses was performed, revealing that adequate power density can potentially be achieved, to address the power requirements of use case 1 when the duty cycle is low (100 mW). Therefore, the inductive energy harvesting method was selected. A new flux funneling approach was developed and adopted, offering a substantial increase of power density. A first energy harvesting power supply design was developed during the first period and then improved during the second. It was delivered to Airbus for integration into the full SMARTWISE system and tests. The results demonstrate the power supply functionality with power line currents as low as 6 A, 300 Hz. Indicatively, the cold starting time at 10 A, 500 Hz is around 10 minutes. The average power can support the functionality of the SMARTWISE sensor nodes at low sampling rates. Higher power line currents are expected to provide higher power flows, indicatively up to 100 mW at 40 A, 500 Hz.
An architecture was also proposed for the active interrogation of up to 7 piezo-electric sensors, with an 8th one used to generate high voltage excitation signals. An embedded demonstrator based on evaluation kit was realised. Signals from the pizoeelectric sensors were acquired and also the active piezo sensor could be sucessfully driven by the embedded platform. This result was passed on to H2020 GENEX during which the system TRL will be increased.
The project has successfully submitted three peer reviewed publications, including a journal paper. The project was also advertised at the 2023 Paris Air Show and also demonstrated to students.
On the hardware side, the architecture of an acquisition PCB meant to be plugged to the wireless communication electronics was proposed. It includes performant ADCs for the acquisition of analogue sensors and the digital high range accelerometer. The PCB was produced and successfully interfaced to the communication board. A housing was created for the sensor node and the tests showed that the sensors can be acquired with the required data rate and accuracy.
The wireless data concentrator (WDC) manages groups of wireless sensors and interconnects them with the avionics over the aircraft wired network. The WDC design was proposed and its implementation realised. It includes a powerful STM32H743 MCU to withstand the high throughput and implement communication over Ethernet. Synchronisation between several WDC's is done by a Precise Time Protocol (PTP) implementation. After integration, synchronisation was evaluated at the whole network scale (wired plus wireless parts): as the synchronisation error on the wireless part of the network is around 12 µs, the total synchronisation error between two sensor nodes is in the order of 15 µs. assuming variability between samples of the same components and environmental effects, and taking some margin, a synchronisation accuracy of 100 µs is achievable. A housing was also realised for the WDC.
The wireless communication protocol was implemented over the u111 real-time operating system which provides best-in-class energy consumption.
A theoretical assessment of inductive power line harvesting from the aircraft main power supply harnesses was performed, revealing that adequate power density can potentially be achieved, to address the power requirements of use case 1 when the duty cycle is low (100 mW). Therefore, the inductive energy harvesting method was selected. A new flux funneling approach was developed and adopted, offering a substantial increase of power density. A first energy harvesting power supply design was developed during the first period and then improved during the second. It was delivered to Airbus for integration into the full SMARTWISE system and tests. The results demonstrate the power supply functionality with power line currents as low as 6 A, 300 Hz. Indicatively, the cold starting time at 10 A, 500 Hz is around 10 minutes. The average power can support the functionality of the SMARTWISE sensor nodes at low sampling rates. Higher power line currents are expected to provide higher power flows, indicatively up to 100 mW at 40 A, 500 Hz.
An architecture was also proposed for the active interrogation of up to 7 piezo-electric sensors, with an 8th one used to generate high voltage excitation signals. An embedded demonstrator based on evaluation kit was realised. Signals from the pizoeelectric sensors were acquired and also the active piezo sensor could be sucessfully driven by the embedded platform. This result was passed on to H2020 GENEX during which the system TRL will be increased.
The project has successfully submitted three peer reviewed publications, including a journal paper. The project was also advertised at the 2023 Paris Air Show and also demonstrated to students.
The measurable benefits of the project is a weight reduction compared to a comparable section of wired SHMS system: 150g for a wireless sensor node that can accommodate several sensors, including energy harvester and storage, compared to between 1 and 2 kg of cabling weight for a single wired sensor. Therefore the objective of a 60% weight reduction is reached, even after including the weight of the wireless data concentrators (4 to 5 would cover a whole regional aircraft. The objective of reducing installation and maintenance costs by at least 50% could not be formally evaluated due to the small scale of the prototype delivered.
SMARTWISE results and the following work will allow the acquisition of further knowledge on the strain applied to airframes in operations, opening some potential for lower use of material leading to lower weight and emissions. Once they reach their operational maturity, wireless SHM will help decrease the costs of large scale ground tests and of flight tests and enable predictive maintenance on regional aircraft where the use of cabled sensor would cause a problematic weight increase and an overwhelming installation burden.
The components developed in SMARTWISE are already exploited in industrial projects in the area of aeronautics, sports, and large battery systems.
SMARTWISE results and the following work will allow the acquisition of further knowledge on the strain applied to airframes in operations, opening some potential for lower use of material leading to lower weight and emissions. Once they reach their operational maturity, wireless SHM will help decrease the costs of large scale ground tests and of flight tests and enable predictive maintenance on regional aircraft where the use of cabled sensor would cause a problematic weight increase and an overwhelming installation burden.
The components developed in SMARTWISE are already exploited in industrial projects in the area of aeronautics, sports, and large battery systems.