Alexander Lehnert

Mr. Alexander Lehnert


Research Focus & Metrics

Academic Career Length

4Years (2023-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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5 January 2023 in IEEE Access
Verified
Journal Article
Open access
ALAlexander Lehnert
Alexander Lehnert
PHPhilipp Holzinger
Philipp Holzinger
SPSimon Pfenning
Simon Pfenning
RMRalf R. Müller
Ralf R. Müller
MRMarc Reichenbach
Marc Reichenbach
Fast and resource-efficient inference in artificial neural networks (ANNs) is of utmost importance and drives many new developments in the area of new hardware architectures, e.g., by means of systolic arrays or algorithmic optimization such as pruning. In this paper, we present a novel method for lowering the computation effort for ANN inference utilizing ideas from information theory.Weight matrices are sliced into submatrices of logarithmic aspect ratios. These slices are then factorized. This reduces the number of required computations without compromising on fully parallel processing. We create a new hardware architecture for this dedicated purpose. We also provide a tool to map these sliced and factorized matrices efficiently to reconfigurable hardware. By comparing to the state of the art FPGA implementations, we can prove our claim by lowering hardware resources measured in look-up-tables (LUTs) by a factor of three to six. Our method does not rely on any particular property of the weight matrices of the ANN. It works for the general task of multiplying an input vector with a constant matrix and is also suitable for digital signal processing beyond ANNs.

Verified
Journal Article
Open access
PDF file
ALAlexander Lehnert
Alexander Lehnert
Falko GawantkaFalko Gawantka
Falko Gawantka
JDJonas During
Jonas During
FJFranz Just
Franz Just
MRMarc Reichenbach
Marc Reichenbach
Wild and forest fires pose a threat to forests and thereby, in extension, to wild life and humanity. Recent history shows an increase in devastating damages caused by fires. Traditional fire detection systems, such as video surveillance, fail in the early stages of a rural forest fire. Such systems would see the fire only when the damage is immense. Novel low-power smoke detection units based on gas sensors can detect smoke fumes in the early development stages of fires. The required proximity is only achieved using a distributed network of sensors interconnected via 5G. In the context of battery-powered sensor nodes, energy efficiency becomes a key metric. Using AI classification combined with XAI enables improved confidence regarding measurements. In this work, we present both a low-power gas sensor for smoke detection and a system elaboration regarding energy-efficient communication schemes and XAI-based evaluation. We show that leveraging edge processing in a smart way combined with buffered data samples in a 5G communication network yields optimal energy efficiency and rating results.

16 September 2023
Verified
Book Chapter
Closed access
PDF file
JKJohannes Knödtel
Johannes Knödtel
HHHector Gerardo Muñoz Hernandez
Hector Gerardo Muñoz Hernandez
ALAlexander Lehnert
Alexander Lehnert
GTGia Bao Thieu
Gia Bao Thieu
SGSven Gesper
Sven Gesper
MRMarc Reichenbach
Marc Reichenbach

16 September 2023
Verified
Book Chapter
Closed access
PDF file
ALAlexander Lehnert
Alexander Lehnert
HRHans Rosenberger
Hans Rosenberger
RMRalf R. Müller
Ralf R. Müller
MRMarc Reichenbach
Marc Reichenbach

16 July 2026 in SSRN Electronic Journal
Verified
Preprint
Open access
RSRicardo Cardoso Soares
Ricardo Cardoso Soares
Alisson BritoAlisson Brito
Alisson Brito
JSJulio Silva
Julio Silva
AFAbel Lima Filho
Abel Lima Filho
ALAlexander Lehnert
Alexander Lehnert
DGDiana Goehringer
Diana Goehringer
Condition monitoring of multirotor drones is challenging due to slight motor asynchrony and variations in rotational speed, which can cause detectors to misclassify states despite unchanged operating conditions. This work proposes a semi-supervised pipeline for anomaly detection in drone vibration signals, designed to attenuate the effect of rotational speed. Vibration data from nine signals (five healthy and four faulty) were collected at different speeds. The pipeline includes signal envelope extraction, computation of 51 features, detrending, and feature selection, yielding four key attributes. Six anomaly detectors were evaluated: a fuzzy ensemble (Meta-Fuzzy), Isolation Forest (IF), One-Class SVM (OCSVM), Extended-IF 1, Autoencoder (AE) and Variational Autoencoder (VAE). IF achieved the best accuracy (94% for the three-class setup and 93.6% for the two-class setup), followed by Meta-Fuzzy (92.81% and 93.64%). The main contribution lies in developing an integrated, lightweight, and experimentally validated methodology that unifies signals from multiple speeds into a single healthy class, maintaining high accuracy and paving the way for future onboard implementations.