Threshold based reduction of EMS stimulation artifacts in the electromyogram when stimulation intensity increases. - In: Engineering for a changing world, (2023), 3.2.144, S. 1-10
To investigate muscular strain, it is possible to record an electromyogram (EMG) during electromyostimulation (EMS). However, stimulation artifacts make it difficult to examine evoked compound muscle action potentials (M-waves). The aim of this work was to algorithmically remove stimulation artifacts from the EMG signal when the stimulation intensity increases. For this purpose, EMG signals were recorded on four subjects who underwent a 30-second EMS of the right M. triceps surae. Afterwards we conducted offline signal processing to reduce stimulation artifacts. We implemented a two-stage threshold algorithm, adapted from O'Keeffe et al. (2001), to remove signal segments passing the thresholds in a defined sequence. Here, the thresholds in the first iteration are two constants, while the algorithm uses linearly or exponentially increasing thresholds in the second iteration. After empirically adjusting the threshold parameters, the stimulation artifacts were successfully reduced. This allows further investigations of the M-waves with respect to muscular fatigue.
https://doi.org/10.22032/dbt.59139
Control for non-linear compliant actuation of an upper arm exoskeleton. - In: Engineering for a changing world, (2023), 3.2.088, S. 1-15
Musculoskeletal diseases of the back and upper extremities are one of the main causes of sick leave in Europe. Exoskeletons are one possible approach to preventive measures. The Biomechatronics Group at Technische Universität Ilmenau is developing an antagonistically actuated exoskeleton with non-linear compliance to support flexion and extension of the elbow in repetitive tasks like in assembly. Here, we present a control strategy to achieve joint stiffness control while benefitting from the advantages of non-linear compliant actuation. We use a decentralized control approach, combining two PID controllers to control joint position and string force and thus, joint stiffness, in the antagonistically acting drive. We show limitations and benefits of this approach through simulation and measurement.
https://doi.org/10.22032/dbt.58877
Concept for the measurement of vital parameters during the use of an infrared cabin to investigate physiological effects and to individualize the sauna session. - In: Engineering for a changing world, (2023), 3.2.050, S. 1-20
Infrared sauna bathing has positive effects on body and mind. Quantifying these effects helps to make sauna use more efficient and safer and to increase the user-observed wellness effects. Currently, there are no practical solutions for a comprehensive and user-friendly monitoring of the physical impact of sauna bathing. This paper focuses on the concept development to investigate which measurement setups are suitable to record and evaluate changes in vital parameters. Based on prioritized vital parameters and requirements a pre-selection of devices in form of wearables is made, which is going to be examined in detail for their suitability. An investigation with ten test persons is planned, in which the wearables’ measurement accuracy and the user acceptance outside and inside the infrared cabin are quantified. The result is a concept for the test procedure and the evaluation of the wearables in order to integrate a suitable device into the overall system.
https://doi.org/10.22032/dbt.58880
Extending teleoperated driving using a shared X-in-the-loop environment. - In: Engineering for a changing world, (2023), 3.1.092, S. 1-14
The strong progress in modern vehicle system technology requires new methodological approaches for the development and validation of new vehicle systems. In particular, due to increasing automation, classical development methods and testing scenarios need to be evolved. Consequently, the publication focuses on an extension of teleoperated driving by the X-in-the-loop (XIL) approach. Within this framework, the classical concept based on VPN-LTE networking is analyzed and discussed at first. With this implementation, the remote control of a real vehicle is presented based on the use of a dynamic driving simulator. Especially for the development and validation of such concepts, an extension with the XIL methodology can improve this process. For this reason, the architecture of teleoperated driving is subsequently extended by networking with additional system components. The feasibility, the functionalities as well as the challenges that arise with such an extension based on the XIL methodology are shown. Within the scope of this study, the achieved transmission times for the control variables and for the video data stream are demonstrated. Based on different driving maneuvers, the achievable repeatability is discussed.
https://doi.org/10.22032/dbt.58870
Self-adapting motion cueing algorithm based on a kinematics reference model. - In: Engineering for a changing world, (2023), 3.1.085, S. 1-9
Due to a number of advantages over traditional development methods, the importance of dynamic driving simulators in automotive research and development has grown continuously in recent years. Motion simulation via motion cueing algorithms contributes significantly to the driving experience and provides the driver with valuable information about the current driving dynamics. The adaptation and tuning process of these algorithms can be difficult and timeconsuming tasks. It needs to be repeated after changes to the vehicle or driving scenario. This paper discusses and presents an adaptive or rather self-adapting motion cueing algorithm (MCA) concept. The approach is based on the integration of a kinematic reference model to dynamically and adaptively adjust the motion behavior dynamically and adaptively. This concept allows to reduce the parameter tuning effort drastically in long term, since the algorithm can adapt itself to different conditions such as vehicle type, driving situation, or driver behavior. In the following, the proposed algorithm structure is explained and illustrated. The advantages of the proposed MCA are demonstrated by an experimental comparison with a classical algorithm. Thereby it is shown how a self-adaptation of the algorithm can proceed and how to avoid violation of workspace boundaries.
https://doi.org/10.22032/dbt.58871
Comparison of the properties of biogenic wine by-products stabilized biocomposites compounded with a miniaturized single-screw extruder and a co-rotating twin-screw extruder. - In: Engineering for a changing world, (2023), 2.3.010, S. 1-13
Bioplastics research is hindered by high material prices and limited availability of biopolymers. For conventional compounding, even on lab-scale, large quantities of material are required. In this study, an alternative process for compounding biocomposites was evaluated to investigate the potential of wine-derived biogenic by-products as functional fillers. Formulations based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and wine grape pomace (WP) with filler contents up to 10 wt.-% were prepared. The materials were processed with a modified miniaturized single-screw extruder (MSE) and compared to a lab-scale twin-screw extruder (TSE). Thermal and rheological properties of the materials were determined using GPC, MFR, DSC, TGA and OIT. The mixing quality of both extruders was evaluated by optical microscopy imaging. The results revealed that the MSE represents an efficient alternative for research purposes, but differences in the dominant degradation mechanisms during processing must be considered. Thermal analysis showed that WP successfully suppressed the thermo-oxidative degradation of PHBV.
https://doi.org/10.22032/dbt.58862
Influence of the recycling process parameters on CFRTP waste properties. - In: Engineering for a changing world, (2023), 2.3.002, S. 1-12
Nowadays, the combination of continuous fibers and thermoplastic polymers as the matrix to continuous fiber-reinforced thermoplastics (CFRTP) is receiving increasing attention due to their potential advantages such as excellent weight-specific mechanical properties, short cycle times, storability, repeated meltability, good formability and the use of alternative joining processes enabling automated large volume manufacturing processes which allow various applications in different industries including transportation, construction among others. As the production rate of these materials increases, the amount of waste for disposal increases, for which recycling strategies need to be established to ensure the sustainability of CFRTP. Hence, these recycling strategies must be developed and evaluated economically and ecologically to close the loop and achieve a circular economy to process recycled fiber-reinforced pellets from CFRTP waste to valuable products e.g., by injection molding. This study presents a mechanical recycling approach from CFRTP waste to injection molded test specimens and evaluates the impact of the individual recycling steps along the recycling chain on the fiber length as the fiber length is detrimental to the resulting mechanical properties. First, the CFRTP waste processability is investigated and conditions for size reduction by cutting and shredding into feedstock for extrusion are defined. Second, fiber-reinforced pellets are produced by twin-screw extrusion. The fiber volume content and the process parameters screw speed and temperature during compounding are varied and the influence of these parameters on the fiber length is determined. Third, the extruded pellets are further processed by injection molding. Here, the influence of screw speed, back pressure, and processing temperature as well as the initial fiber length in the extruded granules on the resulting properties is investigated. Quantitative correlations between material properties and processing parameters are presented and suggestions for gentle processing during recycling are given.
https://doi.org/10.22032/dbt.58866
Influence of microstructure and microgeometry of the probe on friction stir welding of AA 6060 T66. - In: Engineering for a changing world, (2023), 2.1.114, S. 1-2
https://doi.org/10.22032/dbt.58854
Investigation of a quantified sound probe for stud weld quality measurement with numerical simulation data. - In: Engineering for a changing world, (2023), 2.1.065, S. 1-8
Drawn arc stud welding with ceramic ferrules is a widely used joining process for joining sheet metal to studs, which can be threaded or sheared. During the welding process, various irregularities can occur which adversely affect the resulting mechanical properties. Arc blowing is one of the most common process defects. Arc blowing can result in an asymmetric weld bead which can increase the failure rate of the stud. An approach to stud testing is given in DIN ISO EN 14555. A sound probe carried out by an experienced welder provides qualitative information about the weld bead. The sound probe causes the stud to vibrate at its natural frequencies. If the eigenfrequencies can be calculated for each weld bead shape, the sound probe can be quantified. To this end, a new simulation approach is presented which allows the rapid calculation of the eigenfrequencies of the stud with different weld bead shapes. A data set is also generated and analyzed.
https://doi.org/10.22032/dbt.58853
Directed energy deposition-arc (DED-Arc) and numerical welding simulation as a method to determine the homogeneity. - In: Engineering for a changing world, (2023), 2.1.036, S. 1-17
This research presents a hybrid approach to for the prediction of the homogeneity of mechanical properties in 3D metal parts manufactured using directed energy deposition-arc (DED-Arc). DED-Arc is an additive manufacturing process which can offer a cost-effective way to manufacture 3D metal parts, due to high deposition rate of up to 8 kg/h. Regression equations developed in a previous study were used to predict the mechanical properties of a wall structure using only the cooling time t8/5 calculated in a numerical welding simulation. The new approach in this research paper contains the prediction of the homogeneity of the mechanical properties, especially hardness, in 3D metal parts, which can vary due to localized changes in t8/5 cooling time provoked by specific geometrical features or general changes in dimensions. In this study a method for the calculation of the hardness distribution on additively manufactured parts was developed and shown.
https://doi.org/10.22032/dbt.58852