Battery and wireless network communication sensor units based on new technologies that can be used in special conditions have been developed by the Institute of Technical Physics and Materials Science (EK MFA) of the ELKH Energy Science Research Center and BHE Bonn Hungary Consortium formed in cooperation with Elektronikai Kft. The devices developed under the project are powered by environmental thermal and vibration sources and communicate with a new type of ultra-low power radio frequency transmission. The new tools can be used, among other things, to monitor the condition of various machines and transport infrastructures, to test bicycle traffic and in vehicle control systems.

More and more sensors are providing relevant information in many areas of life, such as in factories, in the vicinity of transport infrastructures or in agricultural areas. However, these devices often need to be installed in locations where wired power or, in the case of a wireless device, battery replacement is not feasible or the operation is very expensive. The solution to this is the “energy harvesting” (EV) method, which uses environmental energy sources. However, the available energy density is typically low, and its intensity varies greatly depending on location and time. The aim of the consortium project was therefore to develop solutions that would nevertheless work reliably in the given circumstances, but would be extremely cost-effective.

EC MFA researchers have been working on MEMS technology (micro- electro-mechanical-systems), and the institute has a cleanroom, microtechnological scale sample production and material testing infrastructure, as well as research expertise that is unique in Hungary (www.nems.hu). Another pillar of the project’s success is the highly cost-effective electronic unit for energy collection and radio frequency (RF) communication, developed by BHE Bonn Hungary Elektronikai Kft. (BHE), a Hungarian-owned company that excels internationally in microwave innovation. The consortium participants carried out both basic and industrial research as well as experimental development under the project

The basic research aimed at the design and implementation of new types of vibration energy collectors and multi-frequency selective accelerometers. Although traditional non-resonant accelerometers detect a wide range of frequencies at once, their sensitivity is not always sufficient and their operation requires power. The solution for EC researchers was a 30-step, two-point, suspended Fermat helical membrane tape based on silicon technology (Si technology) with an eight-segment upper electrode. The correctness of the multielectrode operating principle has been verified by shaker tests by experts. ScAlN (scandium aluminum nitride) layers with high piezoelectric constant compatible with Si technology were also investigated to obtain a higher sensor signal and electrical power. By optimizing the atomization parameters, they managed to increase the longitudinal piezoelectric coefficient on a standard silicon substrate compared to aluminum nitride (AlN) fivefold (~ 6 pC / N). In the case of nickel sheet metal substrate, with similar parameters, the same value was 10.0 pC / N, which is a high value in international comparison.

Two types of broadband antenna structures have been developed by the researchers for the electromagnetic energy extraction application. . In the 0.7-18 GHz range, they are suitable for utilizing signals from GSM, UMTS, LTE, or even 5th generation mobile phone systems, as well as digital terrestrial television systems and wireless networks as widespread sources of electromagnetic energy. A 2.4 GHz pulse receiver circuit has also been developed and built to receive pulses from multiple pulse transmitters and transmit data using a state-of-the-art IP-based data transmission method.

The project has undergone three significant developments.

Vibration diagnostic sensor (VibrAn): The purpose of vibration diagnostics is to examine the condition of machines with rotating parts based on the vibration spectrum. These measurements are usually made occasionally, but there is a growing need for continuous monitoring of components with retrofitted systems. The networkable device developed by the consortium has an extremely low power consumption (~ 1 mW) capable of measuring vibrations in the direction of all three axes in the range from 10 Hz to 2 kHz. The energy collection function was implemented with both a vibratory energy collector (VEH) and a thermoelectric generator (TEG). The system sends the measured data to the receiver hardware prepared by BHE, encrypted according to the radio protocol developed jointly with Ante Kft (www.ante.hu/hu/), from where it is transmitted via the collector (eg PC or Rasberry Pi, etc.). finally into the cloud. To this end, the researchers developed a small wireless pulse transmitter circuit operating in the 2.4 GHz ISM band, which is capable of transmitting sensor data with electromagnetic pulses of less than microseconds and very low average power consumption. The pulse receiver circuit was also developed by them – it can even receive pulses from several pulse transmitters and then transmit the data using a modern IP-based data transmission method.

Schematic operation of the sensor system (middle) and the implemented transmitter (left side) and the receiver (right side)

TireForce (TireForce): The 3D force gauge has been under development in EC MFA for more than 10 years. In addition to measuring the perpendicular load, the sensor is also able to determine the lateral forces very precisely. The project focused on the use of a force sensor with a rubber sensor. The researchers started from the assumption that a force gauge could detect faster and more directly than any current method if a tire slips due to braking or a change in road surface quality (e.g., icing). The developed test system consists of a force gauge mounted on the sidewall of the tire, a charging coil, a processing circuit and a communication module. The application for design protection for the “Vehicle tire dynamics measuring device” was recently accepted by the National Intellectual Property Office. The EC MFA Nano-sensors group, in cooperation with the ELKH Research Institute of Computer Science and Automation, performed a number of dynamic measurements using a new Nissan Leaf test car equipped with conventional sensors, including the ZalaZone test track and the Hungarian Car Club’s jerking track. The researchers used a neural network of 38 buried layers, consisting of 38 neurons per layer, to compare on-board data and rubber sensor data. Based on their results, it can be stated that the neural network they use estimates the lateral and longitudinal acceleration and the signals of the vortex sensor with high accuracy, so all these physical parameters can be determined with the self-developed sensor built into the rubber.

The system mounted inside the tire (left side cyclists) and the test car during the bench measurement (right side)

Bicycle traffic monitoring (LogLine): Traffic The main advantage of the system, developed according to the needs of professionals – and much more advanced than available on the market – is that in addition to the number and direction of passage, it can determine their speed and location of each pass, and the sensor is easier to install. The solar-powered system sends key traffic data over a long-range, narrowband LoRaWAN network protocol. The researchers examined the passage of nearly 270,000 cyclists with the measuring units located in Budapest

The project “Modern functional materials for networkable autonomous sensors” was implemented with the support of the Hungarian Government and the Research and Technological Innovation Fund.

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