M. Sc. Johannes Hoffmann Room: C-01.016 (ZEVS) Kaiserstraße 2, 24143 Kiel, Germany Phone: +49 431 880-6130 E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. ORCID: 0000-0001-8170-8147 Google scholar: Link

Research: Real-time Movement Analysis

Parkinson's disease (PD) is a neurodegenerative disease related to various movement disorders including tremor. Patients often experience a reduced quality of life due to degradation of motoric abilities like speech and gait. While the symptoms can be relieved by dopamine medication, PD itself is an incurable disease. Improvements in treatment are of vital interest in our increasingly aging society. This includes the assessment of motoric markers for an earlier and more specific diagnosis as well as regular monitorings to ensure appropriate medication in therapy. The medical examination is usually done in a clinical motor lab using stationary and highly accurate sensor systems.

Symptoms vary in severity over time, which drives the motivation for daily life measurements using body worn sensor technology. These techniques offer the potential for a more quantitative and reliable approach in comparison to self-assessment using questionnaires. The "DSS Movement Jacket" is designed as a wearable sensor system combining different sensor types to achieve highly accurate, non-stationary analyses of various movements including arm swing as an early marker for PD. The setup includes medical grade Inertial Measurement Units (IMUs) comprised of accelerometers (gravity, motion), gyroscopes (rotation) and magnetometers (geomagnetic reference). Some drawbacks are limitations for magneting sensing in distorted areas (buildings) and deviations through numeric integration (drift). Motion capturing using these sensors requires sophisticated digital signal processing approaches like Extended Kalman Filters (EKF). This includes a priori knowledge comprised in a state space representation of the human body.

Novel magnetoelectric (ME) sensors from the Collaborative Research Center CRC 1261 in combination with excitation coils are suitable for the indirect measurement of non-magnetic quantities such as movements. These sensor-coil-systems are highly sensitive and therefore low power (< 200 mW) as well as robust regarding magnetic distortions (AC field). It was recently shown that movement parameters like frequency and distance can be extracted from the measured signals. These reference data points can potentially be included into the EKF to improve the overall performance. Multiple sensor-coil-systems with optimized access schemes like Code Division Multiple Access (CDMA) are interoperable. This promises a quadratic relation between systems and data points and hence further accuracy improvements.

Related topics:

• IMU sensors
• Magnetoelectic sensors
• Sensor fusion
• Pattern recognition

Further interests:

• Real-time digital signal processing
• Wearable sensors
• Hardware development

Short CV

Publications

1. E. Engelhardt, E. Elzenheimer, J. Hoffmann, T. Schmidt, A. Zaman, N. Frey, G. Schmidt: A Concept for Myocardial Current Density Estimation with Magnetoelectric Sensors, Current Directions in Biomedical Engineering, vol. 9, no. 1, 2023, pp. 89-92, doi: 10.1515/cdbme-2023-1023

2. H. Wolframm, J. Hoffmann, R. Burgardt, E. Elzenheimer, G. Schmidt, M. Höft: PCB Coil Enables In Situ Calibration of Magnetoelectric Sensor Systems, Current Directions in Biomedical Engineering, vol. 9, no. 1, 2023, pp. 567-570, doi: 10.1515/cdbme-2023-1142

3. J. Hoffmann, C. Bald, T. Schmidt, M. Boueke, E. Engelhardt, K. Krüger, E. Elzenheimer, C. Hansen, W. Maetzler, G. Schmidt: Designing and Validating Magnetic Motion Sensing Approaches with a Real-time Simulation Pipeline, Current Directions in Biomedical Engineering, vol. 9, no. 1, 2023, pp. 455-458, doi: 10.1515/cdbme-2023-1114

4. M. Boueke, J. Hoffmann, T. Schmidt, C. Bald, R. Bergholz, G. Schmidt: Model-based Tracking of Magnetic Sensor Gloves in Real Time, Current Directions in Biomedical Engineering, vol. 9, no. 1, 2023, pp. 85-88, doi: 10.1515/cdbme-2023-1022 , open access

5. T. Schmidt, J. Hoffmann, L. Klinkenbusch, R. Bergholz and G. Schmidt: An Iterative Algorithm for Magnetic Motion Tracking, Biomedical Engineering / Biomedizinische Technik, Volume 68, Number 4, 2023

6. M. Gerhardt, L. Zimoch, C. Dorn, E. Elzenheimer, C. Bald, T. Lerg, J. Hoffmann, S. Kaps, M. Höft, G. Schmidt, S. Wulfinghoff, R. Adelung: Self-powered Elementary Hybrid Magnetoelectric Sensor, Nano Energy, Volume 115, July 2023, doi: 10.1016/j.nanoen.2023.108720

7. J. Hoffmann, S. Roldan-Vasco, K. Krüger, F. Niekiel, C. Hansen, W. Maetzler, J. Orozco-Arroyave, G. Schmidt: Pilot Study: Magnetic Motion Analysis for Swallowing Detection Using MEMS Cantilever Actuators, Sensors 2023, 23(7), 3594, doi: 10.3390/s23073594, open access

8. J. Arbustini, J. Muñoz, H. Wang, E. Elzenheimer, J. Hoffmann, L. Thormaehlen, P. Hayes, F. Niekiel, H. Heidari, M. Höft, E. Quandt, G. Schmidt, A. Bahr: MEMS Magnetic Field Source for Frequency Conversion Approaches for ME Sensors, Current Directions in Biomedical Engineering, vol. 8, no. 2, 2022, pp. 309-312, doi: 10.1515/cdbme-2022-1079 , open access

9. J. Hoffmann, C. Hansen, W. Maetzler, G. Schmidt: A Concept for 6D Motion Sensing with Magnetoelectric Sensors, Current Directions in Biomedical Engineering, vol. 8, no. 2, 451-454, 2022, doi: 10.1515/cdbme-2022-1115, open access

10. E. Elzenheimer, C. Bald, E. Engelhardt, J. Hoffmann, P. Hayes, J. Arbistin, A. Bahr, E. Quandt, M. Höft, G. Schmidt: Quantitative Evaluation for Magnetoelectric Sensor Systems in Biomagnetic Diagnostics, Sensors 2022, 22(3), 1018, doi: 10.3390/s22031018 , open access

11. J. Hoffmann, E. Elzenheimer, C. Bald, C. Hansen, W. Maetzler, G. Schmidt: Active Magnetoelectric Motion Sensing: Examining Performance Metrics with an Experimental Setup, Sensors 2021, 21(23), 8000, doi: 10.3390/s21238000, open access

12. J. Hoffmann, E. Elzenheimer, C. Bald, C. Hansen, W. Maetzler, G. Schmidt: Magnetoelektrische Sensoren zur Bewegungsdetektion und -analyse, Biosignale Workshop, 2020, Kiel, Germany