Thomas Jager

Harvesting raindrop energy: experimental study

At present, the energy autonomy of a microsystem is limited by the lifespan of the battery. Hence the development of the energy harvesting concept, whereby the energy needed to power the sensor is taken from the operating environment. However, there is no single solution suitable for all types of environment. In this paper, we look at a still unexploited source of energy: rain. Our system scavenges the vibration energy from a piezoelectric flexible structure impacted by a water drop. We present an experimental device that validates the aforementioned theoretical results.

Harvesting raindrop energy: theory

At present, the energy autonomy of a microsystem is limited by the lifespan of the battery. Hence the development of an energy harvesting concept, whereby the energy needed to power the sensor is taken from the operating environment. However, there is no single solution suitable for all types of environment. In this paper, we look at a still unexploited source of energy: rain. Our system recovers the vibration energy from a piezoelectric flexible structure impacted by a water drop. This paper describes in detail the theoretical study undertaken to optimize the mechanical system.

Endogenous noradrenaline impairs the prostaglandin-induced inhibition of noradrenaline release

SummaryThe effects of prostaglandin E2 (PGE2) on electrically evoked noradrenaline release in rat brain cortex were studied under conditions under which autoinhibition of release was avoided. When stimulation was carried out with 36 pulses at 3 Hz, 1 μmol/1 PGE2, produced about 50% inhibition of release. In the presence of the α2-adrenoceptor antagonist yohimbine (1 gmol/1) the effect of PGE2 was markedly increased. When release was elicited by 3 pulses/100 Hz the period of stimulation was too short to permit development of autoinhibition by released noradrenaline. Then the concentration-response-curve for PGE2 was very similar to that obtained under the above conditions (36 pulses/3 Hz, in the presence of yohimbine). These data suggest that both the α2-adrenoceptor and the PGE2-receptor are linked to a common pathway. Since indometacin (10 μmol/1) did not enhance evoked transmitter release, an influence of endogenous PGs on in vitro release of noradrenaline from rat brain cortex slices can be excluded.

Wireless Power Transmission for Autonomous Sensors in Removable Vehicle Seats

This work proposes the use of magnetic coupling for powering autonomous sensors in space-constrained applications, such as occupancy and belt detection in removable vehicle seats. The power demand of the autonomous sensor is considered between tens and hundreds of milliwatts. A theoretical analysis first highlights the critical parameters in order to achieve a large powering range and high efficiency. Series-resonant tanks are considered for both the primary and secondary networks. Because the intended application is space-constrained, small coils have to be used. In order to increase their quality factor, commercial ferrite-core coils are used. A class D power amplifier is proposed for the primary network. Experimental results show that a power of tens of milliwatts can be transferred to a 100 §U load placed at the secondary network up to a distance of 2cm, near seven times the radius of the coils (3mm). The addition of a rectifier and a voltage regulator at the secondary network in order to properly power an autonomous sensor (3V@30mA) limits the powering range to 1cm. Overall power efficiencies around 45% and 20% are achieved respectively at distances of 5mm and 1cm.

Mechanical vibrations energy harvesting and power management

We present in this paper our different steps to develop an efficient integrated mechanical vibration energy harvesting system. We start with a macroscopic structure having a 100 g of moving mass to demonstrate the feasibility of a fully functional electrostatic transduction. An available output power of 16 muW per gram of mobile mass and per Hz over a large frequency band (20-100 Hz) has been obtained with a global efficiency of 60 %. A relative displacement close to the gap value increases the efficiency. To approach that, we introduce a non-linearity in the beams used as springs and guidance with the property to be very flexible for low displacements in order to amplify them and to be very hard for high displacements in order to reduce them. We developed a 10 g structure to validate it. Finally we present the design of an integrated structure able to multiply and maximize the capacitance variation independently of the vibration source. To finish, we present our concept in term of power management.

Swarm's absolute magnetometer experimental vector mode, an innovative capability for space magnetometry

European Space Agency’s Swarm satellites carry a new generation of 4He absolute magnetometers (ASM), designed by CEA-Leti and developed in partnership with Centre National d’Etudes Spatiales. These instruments are the first ever spaceborne magnetometers to use a common sensor to simultaneously deliver 1 Hz independent absolute scalar and vector readings of the magnetic field. Since launch, these ASMs provided very high-accuracy scalar field data, as nominally required for the mission, together with experimental vector field data. Here we compare geomagnetic field models built from such ASM-only data with models built from the mission’s nominal 1 Hz data, combining ASM scalar data with independent fluxgate magnetometer vector data. The high level of agreement between these models demonstrates the potential of the ASM’s vector mode for data quality control and as a stand-alone magnetometer and illustrates the way the evolution of key field features can easily be monitored from space with such absolute vector magnetometers

In-flight performance of the Absolute Scalar Magnetometer vector mode on board the Swarm satellites

The role of the Absolute Scalar Magnetometer (ASM) in the European Space Agency (ESA) Swarm mission is to deliver absolute measurements of the magnetic field’s strength for science investigations and in-flight calibration of the Vector Field Magnetometer (VFM). However, the ASM instrument can also simultaneously deliver vector measurements with no impact on the magnetometer’s scalar performance, using a so-called vector mode. This vector mode has been continuously operated since the beginning of the mission, except for short periods of time during commissioning. Since both scalar and vector measurements are perfectly synchronous and spatially coherent, a direct assessment of the ASM vector performance can then be carried out at instrument level without need to correct for the various magnetic perturbations generated by the satellites. After a brief description of the instrument’s operating principles, a thorough analysis of the instrument’s behavior is presented, as well as a characterization of its environment in flight, using an alternative high sampling rate (burst) scalar mode that could be run a few days during commissioning. The ASM vector calibration process is next detailed, with some emphasis on its sensitivity to operational conditions. Finally, the evolution of the instrument’s performance during the first year of the mission is presented and discussed in view of the mission’s performance requirements for vector measurements.

A 2015 International Geomagnetic Reference Field (IGRF) candidate model based on Swarm's experimental absolute magnetometer vector mode data

Each of the three satellites of the European Space Agency Swarm mission carries an absolute scalar magnetometer (ASM) that provides the nominal 1-Hz scalar data of the mission for both science and calibration purposes. These ASM instruments, however, also deliver autonomous 1-Hz experimental vector data. Here, we report on how ASM-only scalar and vector data from the Alpha and Bravo satellites between November 29, 2013 (a week after launch) and September 25, 2014 (for on-time delivery of the model on October 1, 2014) could be used to build a very valuable candidate model for the 2015.0 International Geomagnetic Reference Field (IGRF). A parent model was first computed, describing the geomagnetic field of internal origin up to degree and order 40 in a spherical harmonic representation and including a constant secular variation up to degree and order 8. This model was next simply forwarded to epoch 2015.0 and truncated at degree and order 13. The resulting ASM-only 2015.0 IGRF candidate model is compared to analogous models derived from the mission’s nominal data and to the now-published final 2015.0 IGRF model. Differences among models mainly highlight uncertainties enhanced by the limited geographical distribution of the selected data set (essentially due to a lack of availability of data at high northern latitude satisfying nighttime conditions at the end of the time period considered). These appear to be comparable to differences classically observed among IGRF candidate models. These positive results led the ASM-only 2015.0 IGRF candidate model to contribute to the construction of the final 2015.0 IGRF model.

Integrated low-power RFID-S-system for online temperature and high-resolution displacement monitoring on high speed spindle rotors

This paper presents a low-power RFID-S-system for condition monitoring in high-speed motor spindles. In modern metal cutting machine tools the machining result strongly depends on the motor spindles accuracy. Latest developments on high-speed cutting (hsc) and high-performance cutting (hpc) are leading to substantial increasing temperatures and mechanical elongations of the machine parts, which are resulting in decreasing machining precision. Beside wired sensors on stationary parts, temperature- and displacement-measuring systems on fast rotational dynamic shafts like the spindles rotor are very important, since this is the direct interface between the machine tool and the work piece. Different approaches for laboratory setups are known from literature [1], [2]. In this work, a fully spindle-integrated and tested solution suitable for mass production is presented.

Development and space qualification of the swarm Absolute Scalar Magnetometer

The Absolute Scalar Magnetometer will be flown on the three Swarm satellites to be launched by ESA in 2012. It will offer the best resolution and absolute accuracy ever attained in space. Since this instrument is essential to fulfill the projects scientific objectives, its reliability and availability have to be guaranteed over the lifetime of the four year mission. To achieve these ambitious goals, the instrument is at the cutting edge of technology. It implements an innovative fiber laser used for the optical pumping of a helium 4 gas cell located within a non magnetic rotating sensor. This led us to use specific parts, materials and processes which had to be previously space qualified. The success of the Proto-Flight Model qualification was a major achievement this year. The testing of the flight models is now in progress. This paper illustrates the long way to reach the required Technology Readiness Level starting from a concept which had already been validated on a prototype.