Energy harvesting from human body motion has been investigated extensively in the last two decades due to the increasing demand for Smart Wearables. Smart Wearables are beneficial in terms of daily monitoring of vital parameters and early recognition of diseases. However, continuous and close-meshed monitoring in daily life is often facing the obstacle of limited energy storage. Integrated sensors and electronics of Smart Wearables may be powered in a conventional manner by energy storage. But energy storage such as battery is subject to restrictions as limited lifetime and charging process. Thus, the development of self-powering Smart Wearables is highly promising. The conversion of human body motion into electrical energy is significant for the identification of medical application areas. Investigations on energy harvesting from human body motion is facing limitations such as low frequency range of body motion, low accelerations as well as wearing comfort. Numerous studies address the use of piezoelectric ceramics for energy harvesting. However, the high mass density and the high modulus of elasticity limit energy harvester designs based on piezoelectric ceramics to rather heavy wearables. In terms of lightweight designs, polymers such as PVDF (polyvinylidene fluoride) have been considered as functional materials in several researches but these materials are disadvantageous regarding energy efficiency. Auspicious functional materials for energy harvesting from body motion are piezoelectric electrets (piezoelectrets, also referred to as ferroelectrets) due to their high piezoelectric coefficients and low mass density. Piezoelectrets facilitate the implementation of lightweight energy harvester designs with high output power that is advantageous for applications in context of Smart Wearables. In particular, fluorethylpolypropylene (FEP) piezoelectrets with parallel-tunnel structures are promising generators for energy harvesting. Within the present work, a novel design of parallel-tunnel FEP energy harvester in 31-mode is introduced and validated by means of an experimental setup.

In this publication the application of novel piezoelectric materials for energy harvesting on vibrating aircraft structures is investigated. These materials have significant advantages over conventional piezoelectric transducer materials like piezoceramics. In particular, biogenic materials in the form of wood-based materials and ferroelectrets in the form of irradiation cross-linked polypropylene are the subject of the investigation. The material characterization in terms of mechanical and electromechanical properties is shown for both material types. For the wood materials a compression test is used as the material has load-bearing properties. The ferroelectrets provide high compliances and are therefore investigated in a tensile test for material characterisation as well as in a four-point flexural test regarding its behaviour when glued to a dynamically bending surface. Additionally an FE-model of the material model for ferroelectrets is presented, which is validated by experimental results. An estimation of the power output is given for different concepts with both kinds of materials.

This work covers a novel concept for piezoelectric energy harvesting for the use in lightweight design. It is motivated by a structural strain excitation in an aircraft wing caused by a dynamic pressure. The concept uses piezoelectric electrets, also called ferroelectrets. Ferroelectrets are piezoelectric polymers that show a higher ecological compatibility and a much higher structural flexibility than piezoceramics. The used ferroelectret material for piezoelectric energy conversion is fluorinated ethylene propylene (FEP) assembled in a parallel-tunnel structure that provides high transversal piezoelectric δ31-coefficients. The transformation of strain energy is realized by a metallic mechanism converting a low strain amplitude with a high structural stress to a desired high strain amplitude. Due to low stresses required in the ferroelectret material, the metallic mechanism is designed in a very light way. An analytical model is presented to show the main design parameters and a finite element model is used with the goal of investigating the power output per total energy harvester mass. The model is eventually validated with experimental results. A power output of 344.2 nW and a ratio of power per mass of 302.6 μWkg−1 can be reached for a single harvester under a realistic quasistatic load. For a suggested cluster this can be increased up to 2.6 mW/m2 which is enough to power many devices with a low power consumption.

In this work, a simulation framework for virtual testing of autonomous driving functions under the influence of a fault occurring in a component is presented. The models consist of trajectory planning, motion control, models of actuator management, actuators and vehicle dynamics. Fault-handling tests in a right-turn maneuver are described, subject to an injected fault in the steering system. Different scenarios are discussed without and with a fault and without and with counteractions against the fault. The results of five scenarios for different criticality metrics are discussed. In the case of a fault without a counteraction, a pronounced lateral position deviation of the ego vehicle from the reference curve is observed. Furthermore, the minimal and hence most critical time-to-collision (TTC) and post-encroachment time (PET) values are calculated for each scenario together with a parameter variation of the initial position of a traffic agent. The minimum TTC values are lowest in the case of a fault without counteraction. For the lateral position deviation and the TTC, the counteractions cause reduced criticality that can become even lower than in the case without a fault, corresponding to a decrease in the dynamic behavior of the vehicle. For the PET, only in the case of a fault without counteraction, a non-zero value can be calculated. With the implemented testing toolchain, the automated vehicle and the reaction of the HAD function in non-standard conditions with reduced performance can be investigated. This can be used to test the influence of component faults on automated driving functions and help increase acceptance of implemented counteractions as part of the HAD function. The assessment of the situation using a combination of metrics is shown to be useful, as the different metrics can become critical in different situations.

<div class="section abstract"><div class="htmlview paragraph">Aircraft traffic causes a significant amount of greenhouse gas emissions. Since modern aircrafts are highly electrified, the total weight is affected by cables within the components. Piezoelectric energy harvesting appears to be a reasonable option for reducing cables in certain parts of the aircraft and hence reducing fuel consumption. The proposed work covers energy harvesting in lightweight design with transmission mechanisms using so-called ferroelectrets. The energy harvester (EH) design is motivated by a strain-excitation in an aircraft wing caused by a quasi-stationary dynamic pressure. Ferroelectrets are piezoelectric polymers that show a higher ecological compatibility and a much higher structural flexibility than piezoceramics. Furthermore they provide charge constants in the same order of magnitude as piezoceramics. As a novelty compared to previous studies the energy harvesters are arranged in a cluster in the concept presented herein to increase the power output within a certain area. A central research question is, if and to what extent energy harvesting is possible using a cluster of ferroelectret EHs without and with additional seismic masses to increase the power output and the power output per total cluster mass. This question is answered with the help of a numerical simulation of a modally reduced finite element beam structure subject to a force excitation. The applied cluster is simulated using simplified, yet validated EH models. They are coupled to the structure using only a set of node numbers. In this way the suitability of the ferroelectret transmission mechanisms as vibroacoustic metamaterials for energy harvesting in aircrafts is estimated as the final result of the work.</div></div>