Periodic Reporting for period 1 - SMARTWISE (Smart Miniaturized and Energy Autonomous Regional Aircraft Wireless Sensor)
Reporting period: 2020-07-01 to 2021-12-31
The SMARTWISE project develops 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 are considered:
- 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).
- The whole SHMS use cases presented by the topic manager will be analysed to expose SHMS sections and use cases for which energy autonomous and wireless sensors are feasible given the energy harvesting potential near the sensor location and the bandwidth available for wireless communications in the aircraft. Back-up solutions will be sketched for locations and use cases where self-powering and/or wireless communications are not possible.
Three use cases are considered:
- 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).
- The whole SHMS use cases presented by the topic manager will be analysed to expose SHMS sections and use cases for which energy autonomous and wireless sensors are feasible given the energy harvesting potential near the sensor location and the bandwidth available for wireless communications in the aircraft. Back-up solutions will be sketched for locations and use cases where self-powering and/or wireless communications are not possible.
The three use cases were analysed by the consortium, then reworked with the topic manager. Among the aspects considered were sensor acquisition, data communication, power consumption, and energy harvesting potential. The analysis exhibited the challenges of continuous acquisition in general and of the high rate passive and active piezo-electric sensors interrogation. Formal requirements were derived for each sub-system and also for the integration and environmental constraints.
Then 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 (strain gauges and thermistors) and the digital high range accelerometer. 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.
The wireless data concentrator (WDC) design was proposed. The WDC manages groups of wireless sensors and interconnects them with the avionics over the aircraft wired network. The most important requirements are the high throughput and the tight synchronisation needed to accurately timestamp sensor data. The part over the wireless network is inherited from the AMPWISE project. Synchronisation between several WDC's is done by a Precise Time Protocol (PTP) implementation, which was realised at the end of this period. From the implementation, accuracy in the order of 100ns was measured. The WDC includes a powerful STM32H743 MCU to withstand the high throughput and implement communication over Ethernet.
The wireless communication protocol was implemented over the u111 real-time operating system, which brings appreciated modularity to the system. Power consumption measurements show that this implementation does not consume more than the OS-less implementation realised in AMPWISE.
Three different energy harvesting options were assessed against the requirements of SMARTWISE use cases. Estimated power availability from measured vibration data provided by the topic manager show that the power availability is several orders of magnitude smaller than the intended power requirements of the use cases. For thermo-electric energy harvesting, the power density computed from temperature gradients and fluctuations is again considerably smaller than the intended application requirements. 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. Preliminary experimental results confirmed the modelling predictions, showing a power output in the range of 1 mW from a transducer of of approximate mass 12.5 g and a 0.9 A, 400 Hz power line current. Furthermore, a power management architecture with a novel, two-stage capacitive energy storage system was introduced, aiming at providing a fast cold starting capability. Based on these results and methods, the overall SMARTWISE power supply design was carried out. It comprises a semi-circular flux concentration structure, a coil and core system optimised for maximum power density and a power management PCB with cold-starting and energy autonomy capability.
Then 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 (strain gauges and thermistors) and the digital high range accelerometer. 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.
The wireless data concentrator (WDC) design was proposed. The WDC manages groups of wireless sensors and interconnects them with the avionics over the aircraft wired network. The most important requirements are the high throughput and the tight synchronisation needed to accurately timestamp sensor data. The part over the wireless network is inherited from the AMPWISE project. Synchronisation between several WDC's is done by a Precise Time Protocol (PTP) implementation, which was realised at the end of this period. From the implementation, accuracy in the order of 100ns was measured. The WDC includes a powerful STM32H743 MCU to withstand the high throughput and implement communication over Ethernet.
The wireless communication protocol was implemented over the u111 real-time operating system, which brings appreciated modularity to the system. Power consumption measurements show that this implementation does not consume more than the OS-less implementation realised in AMPWISE.
Three different energy harvesting options were assessed against the requirements of SMARTWISE use cases. Estimated power availability from measured vibration data provided by the topic manager show that the power availability is several orders of magnitude smaller than the intended power requirements of the use cases. For thermo-electric energy harvesting, the power density computed from temperature gradients and fluctuations is again considerably smaller than the intended application requirements. 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. Preliminary experimental results confirmed the modelling predictions, showing a power output in the range of 1 mW from a transducer of of approximate mass 12.5 g and a 0.9 A, 400 Hz power line current. Furthermore, a power management architecture with a novel, two-stage capacitive energy storage system was introduced, aiming at providing a fast cold starting capability. Based on these results and methods, the overall SMARTWISE power supply design was carried out. It comprises a semi-circular flux concentration structure, a coil and core system optimised for maximum power density and a power management PCB with cold-starting and energy autonomy capability.
SMARTWISE helps to fill the gap between heavy laboratory equipment and fight test installation on the one side, and low footprint, low power electronics and sensors on the other side. This will hopefully increase the possibilities to integrate permanent SHM installations with minimal weight and installation impacts.
The measurable benefits expected at the end of the project are:
- Weight reduction compared to a comparable section of wired SHMS system: at least 60% for applicable use cases.
- With respect to comparable wired solutions, the developed system is expected to reduce installation and maintenance costs by at least 50%.
The impact of the online SHM system SMARTWISE intends to contribute to will be two-fold:
- Reduced maintenance-related costs, reduce unscheduled Aircraft On Ground (AOG) occurrence, resulting in cheaper aircraft operations which would directly impact airlines.
- An new added value for “smart” composite structure components, benefiting all actors involved in the airframe manufacturing and maintenance chain.
SMARTWISE hopes to have an environmental impact by indirectly reducing energy consumption and emissions in future aircrafts by allowing 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.
The measurable benefits expected at the end of the project are:
- Weight reduction compared to a comparable section of wired SHMS system: at least 60% for applicable use cases.
- With respect to comparable wired solutions, the developed system is expected to reduce installation and maintenance costs by at least 50%.
The impact of the online SHM system SMARTWISE intends to contribute to will be two-fold:
- Reduced maintenance-related costs, reduce unscheduled Aircraft On Ground (AOG) occurrence, resulting in cheaper aircraft operations which would directly impact airlines.
- An new added value for “smart” composite structure components, benefiting all actors involved in the airframe manufacturing and maintenance chain.
SMARTWISE hopes to have an environmental impact by indirectly reducing energy consumption and emissions in future aircrafts by allowing 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.