Autonomous electrical current monitoring system for aircraft

Aircraft monitoring systems offer enhanced safety, reliability, reduced maintenance cost and improved overall flight efficiency. Advancements in wireless sensor networks (WSN) are enabling unprecedented data acquisition functionalities, but their applicability is restricted by power limitations, as batteries require replacement or recharging and wired power adds weight and detracts from the benefits of wireless technology. In this paper, an energy autonomous WSN is presented for monitoring the structural current in aircraft structures. A hybrid inductive/hall sensing concept is introduced demonstrating 0.5 A resolution, < 2% accuracy and frequency independence, for a 5 A – 100 A RMS, DC-800 Hz current and frequency range, with 35 mW active power consumption. An inductive energy harvesting power supply with magnetic flux funnelling, reactance compensation and supercapacitor storage is demonstrated to provide 0.16 mW of continuous power from the 65 μT RMS field of a 20 A RMS, 360 Hz structural current. A low-power sensor node platform with a custom multi-mode duty cycling network protocol is developed, offering cold starting network association and data acquisition/transmission functionality at 50 μW and 70 μW average power respectively. WSN level operation for 1 minute for every 8 minutes of energy harvesting is demonstrated. The proposed system offers a unique energy autonomous WSN platform for aircraft monitoring

Energy Harvesting Powered Wireless Sensor Nodes With Energy Efficient Network Joining Strategies

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordThis paper presents strategies for batteryless energy harvesting powered wireless sensor nodes based on IEEE 802.15.4e standard to join the network successfully with minimal attempts, which minimizes energy wastage. This includes using a well-sized capacitor and different duty cycles for the network joining. Experimental results showed a wireless sensor node that uses a 100 mF energy storage capacitor can usually join the network in one attempt but multiple attempts may be needed if it uses smaller capacitances especially when the harvested power is low. With a duty-cycled network joining, the time required to form a network is shorter, which reduces the overall energy usage of the nodes in joining the network. An energy harvesting powered wireless sensor network (WSN) was successfully formed in one attempt by using the proposed methods.Engineering and Physical Sciences Research Council (EPSRC

Development of efficient energy storage and power management for autonomous aircraft structural health monitoring systems

This thesis investigates the development of an efficient energy storage and power management system for aircraft structural health monitoring (ASHM) applications, powered by specific thermoelectric energy harvesting. For efficient power management, commercially available DC-DC converters are critically analysed. A novel switched-energy storage system is proposed that can be used to extend the run-time of a typical wireless ASHM sensor. Experimental characterisation of a range of different batteries and supercapacitors has been performed, followed by a critical performance analysis of a simple parallel combination of a battery and supercapacitor for run-time extension of a wireless sensor node (WSN). The problems associated with such a simple parallel hybrid system are identified, and a new switched architecture is presented that overcomes these disadvantages

Vibration energy harvesters for wireless sensor networks for aircraft health monitoring

Traditional power supply for wireless sensor nodes is batteries. However, the application of batteries in WSN has been limited due to their large size, low capacity, limited working life, and replacement cost. With rapid advancements in microelectronics, power consumption of WSN is getting lower and hence the energy harvested from ambient may be sufficient to power the tiny sensor nodes and eliminate batteries completely. As vibration is the widespread ambient source that exists in abundance on an aircraft, a WSN node system used for aircraft health monitoring powered by a piezoelectric energy harvester was designed and manufactured. Furthermore, simulations were performed to validate the design and evaluate the performance. In addition, the Z-Stack protocol was migrated to run on the system and initial experiments were carried out to analyse the current consumption of the system. A new approach for power management was reported, the execution of the operations were determined by the amount of the energy stored on the capacitor. A novel power saving interface was also developed to minimise the power consumption during the voltage measurement

Power management for energy harvesting

The use of wireless sensor networks in aircraft health management grew exponentially over the past few decades. Wireless sensor networks provide technology that reduces the amount of wiring for aircraft, thereby reducing the weight and cost of aircraft. One of the most significant limitations in the use of wireless sensor networks in aircraft health management systems is the availability of power sources. Developing Wireless Sensor Network nodes that can generate and harvest their autonomous power supply continuously is a bottleneck that has been the preoccupation of engineers for many years. The amount of energy a network of Wireless Sensors can harvest fluctuates and is difficult to predict. As a result, existing predictors of energy harvesting are prone to errors. Models-free schemes such as expert systems are thus preferred for energy management strategies. The main aim of this thesis is to propose expert-based systems for energy harvesting in aircraft to enhance wireless sensor nodes life span by improving energy harvesting, energy storage and packet loss probability. In this context, a novel integrated approach based on the Markov chain was proposed for energy harvesting in aircraft. Simulation results and quantitative analysis showed that the integration of Piezoelectric and Thermoelectric harvesters with stochastic scheduling had a better performance in terms of energy storage, energy harvesting and packet loss probability. There was also an increase in energy storage with five Markov states compared to that of two Markov states. The packet loss probability of the integrated approach with five Markov states was better than that of two Markov states. The results also showed that the integrated approach with five Markov states harvested more energy than two Markov states. The novel integration of LTspice and NS-3 simulators was proposed. The LTspice and NS-3 integration was validated by deploying the Fuzzy logic control approach in energy harvesting. Simulation results and quantitative analysis based on Fuzzy control logic expert system indicated that the integration of LTspice and NS-3 was found to be better in energy harvesting compared to non-fuzzy control systems. The downtime ratio and energy utilization efficiency of the wireless sensor nodes were also found to be better than non-fuzzy control. The power management based LEACH routing protocol was also proposed. The simulation results and quantitative analysis showed that the average harvested energy based on the LEACH routing protocol deployed with fuzzy logic and Markov chain was better compared to those with direct communication based on Markov chain and fuzzy logic systems.Aerospac

Power supply based on inductive harvesting from structural currents

Monitoring infrastructure offers functional optimisation, lower maintenance cost, security, stability and data analysis benefits. Sensor nodes require some level of energy autonomy for reliable and cost-effective operation, and energy harvesting methods have been developed in the last two decades for this purpose. Here, a power supply that collects, stores and delivers regulated power from the stray magnetic field of currentcarrying structures is presented. In cm-scale structures the skin effect concentrates current at edges at frequencies even below 1 kHz. A coil-core inductive transducer is designed. A fluxfunnelling soft magnetic core shape is used, multiplying power density by the square of funnelling ratio. A power management circuit combining reactance cancellation, voltage doubling, rectification, super-capacitor storage and switched inductor voltage boosting and regulation is introduced. The power supply is characterised in house and on a full-size industrial setup, demonstrating a power reception density of 0.36 mW/cm3, 0.54 mW/cm3 and 0.73 mW/cm3 from a 25 A RMS structural current at 360 Hz, 500 Hz and 800 Hz respectively, corresponding to the frequency range of aircraft currents. The regulated output is tested under various loads and cold starting is demonstrated. The introduced method may enable power autonomy to wireless sensors deployed in current-carrying infrastructure

Energy savvy network joining strategies for energy harvesting powered TSCH nodes

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordThis paper presents methods that enable batteryless energy harvesting powered Time Synchronized Channel Hopping (TSCH) wireless sensor nodes to join a network with less energy wastage. Network joining of TSCH nodes is a very power hungry yet inevitable process to form a working wireless sensor network (WSN). Since the energy level from energy harvesting is scarce, energy passive methods are essential. A duty-cycled network joining process in combination with an appropriate capacitor size is proposed here as they are among the factors that can be easily controlled without extra energy. When a node joins the network in a duty-cycled manner, other nodes may join the network during the gap time, which reduces energy wastage of the nodes in waiting. With an appropriate capacitor size, the capacitor can be charged up within a reasonable time and power up the node for a sufficiently long time, which increases the probability to complete the network joining process of the node. With the combination of a join duty cycle of 50% with a 100 mF capacitor, a WSN was successfully formed by two energy harvesting powered wireless sensor nodes in one network joining attempt.Engineering and Physical Sciences Research Council (EPSRC

Development Of Low Voltage Management Circuit For Low Frequency Vibration Energy Harvesting

Kajian ini membentangkan pembangunan tenaga penuai getaran berfrekuensi rendah menggunakan penjana electromagnet dan litar pengurusan voltan untuk membekalkan kuasa kepada penderia tanpa wayar. Tujuan kajian ini adalah untuk menyelesaikan masalah apabila penderia kehabisan bekalan tenaga terutamanya pada unit yang dipasang pada struktur yang sukar diakses dan diselenggara. Memandangkan voltan dan kuasa yang dihasilkan bergantung pada frekuensi masuk, maka litar pengurusan voltan yang khusus diperlukan untuk mengawal dan menyimpan tenaga elekrik. Penjana elektromagnet difabrikasi menggunakan empat penggerak gegelung suara yang dibuat daripada magnet neodimium dan gegelung tembaga. Kuasa maksimum sebanyak 0.94, 3.3, 6.4 dan 15.5 mW dijana oleh penjana elektromagnet pada frekuensi 4 Hz, 6 Hz, 8 Hz dan 10 Hz pada tahap pecutan 3.5 m/s2. Nod penderia iaitu penganding suhu NI-WSN 3212 menggunakan sebanyak 9.5 mW ketika mod siap sedia, 42.1 mW ketika mod mengesan suhu dan 105.3 mW ketika mod menghantar data. Sumbangan utama kajian ini ialah pembinaan litar yang berupaya menukar voltan rendah serendah 0.24 V dan menjana kuasa sendiri tanpa memerlukan bekalan kuasa luar. Litar tersebut terdiri daripada pengganda voltan berambang rendah, LTC3105 penukar peningkat dan kapasitor besar sebagai penyimpan tenaga. Tenaga yang disimpan berupaya untuk membekalkan tenaga kepada penderia tanpa wayar ketika mod penghantaran data iaitu sebanyak 3300 dan 2100 kitaran bagi setiap bacaan sampel 5 saat dan 1 saat. Kesimpulannya, integrasi antara penjana elektromagnet dan litar pengurusan voltan yang dibina berjaya membekalkan tenaga untuk menghidupkan NI-WSN 3212. ________________________________________________________________________________________________________________________ This research presents a development of a low frequency vibration energy harvesting based on electromagnetic harvester with voltage management circuit to power up wireless sensor nodes. This is important for cases where the sensors have no consistent energy supply especially at installations where access is difficult. Since the generated voltage and power are strongly dependent on the input frequency, it is necessary to have specific low voltage management circuit to condition and store the electrical energy. The electromagnetic harvester consists of four voice coil actuators made of neodymium magnet and copper coils. Maximum power output of 0.94, 3.3, 6.4 and 15.5 mW were generated by the harvester for frequency of 4 Hz, 6 Hz, 8 Hz and 10 Hz at acceleration level of 3.5 m/s2. The sensor node based on NI-WSN thermocouple input consumed 9.5 mW during standby mode, 42.1 mW when temperature sensing and 105.3 mW during data transmission mode. The main contribution of this research is the circuit which can rectify low voltage as low as 0.24 V and requires no external power supply to operate. It comprises of low threshold diode voltage multiplier, LTC3105 boost converter and supercapacitor as storage energy. The stored energy was enough to power up the sensor node transmission for 3300 and 2100 cycles when connected to sensor node for every 5 s and 1 s reading samples. The integration of the electromagnetic harvester and voltage management circuit constructed has successfully powered the NI-WSN 3212

Wireless Sensor Networks for Condition Monitoring in the Railway Industry : a Survey

In recent years, the range of sensing technologies has expanded rapidly, whereas sensor devices have become cheaper. This has led to a rapid expansion in condition monitoring of systems, structures, vehicles, and machinery using sensors. Key factors are the recent advances in networking technologies such as wireless communication and mobile adhoc networking coupled with the technology to integrate devices. Wireless sensor networks (WSNs) can be used for monitoring the railway infrastructure such as bridges, rail tracks, track beds, and track equipment along with vehicle health monitoring such as chassis, bogies, wheels, and wagons. Condition monitoring reduces human inspection requirements through automated monitoring, reduces maintenance through detecting faults before they escalate, and improves safety and reliability. This is vital for the development, upgrading, and expansion of railway networks. This paper surveys these wireless sensors network technology for monitoring in the railway industry for analyzing systems, structures, vehicles, and machinery. This paper focuses on practical engineering solutions, principally,which sensor devices are used and what they are used for; and the identification of sensor configurations and network topologies. It identifies their respective motivations and distinguishes their advantages and disadvantages in a comparative review