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Technologies, Volume 7, Issue 4 (December 2019) – 18 articles

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Cover Story (view full-size image) Coatings play a pivotal role in not only combating premature degradation of components that operate [...] Read more.
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Open AccessArticle
Minimum MOS Transistor Count Fractional-Order Voltage-Mode and Current-Mode Filters
Technologies 2019, 7(4), 85; https://doi.org/10.3390/technologies7040085 - 06 Dec 2019
Viewed by 537
Abstract
Voltage-mode and current-mode fractional-order filter topologies, which are capable of realizing various types of transfer functions, are introduced in this paper. Thanks to the employment of the transconductance parameter of the MOS transistors, the derived filter structures offer the benefit of the electronic [...] Read more.
Voltage-mode and current-mode fractional-order filter topologies, which are capable of realizing various types of transfer functions, are introduced in this paper. Thanks to the employment of the transconductance parameter of the MOS transistors, the derived filter structures offer the benefit of the electronic adjustment of their frequency characteristics. With regards to the literature, the number of MOS transisitors is minimized leading to significant reduction of the circuit complexity and power dissipation. Simulation results, derived using the Design Kit of the 0.35 μm Austria Mikro Systeme CMOS process and the Cadence IC design suite, confirm the correct operation of the presented filter structures. Full article
(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)
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Open AccessArticle
An Inverse Pheromone Approach in a Chaotic Mobile Robot’s Path Planning Based on a Modified Logistic Map
Technologies 2019, 7(4), 84; https://doi.org/10.3390/technologies7040084 - 06 Dec 2019
Viewed by 461
Abstract
One major topic in the research of path planning of autonomous mobile robots is the fast and efficient coverage of a given terrain. For this purpose, an efficient method for covering a given workspace is proposed, based on chaotic path planning. The method [...] Read more.
One major topic in the research of path planning of autonomous mobile robots is the fast and efficient coverage of a given terrain. For this purpose, an efficient method for covering a given workspace is proposed, based on chaotic path planning. The method is based on a chaotic pseudo random bit generator that is generated using a modified logistic map, which is used to generate a chaotic motion pattern. This is then combined with an inverse pheromone approach in order to reduce the number of revisits in each cell. The simulated robot under study has the capability to move in four or eight directions. From extensive simulations performed in Matlab, it is derived that motion in eight directions gives superior results. Especially, with the inclusion of pheromone, the coverage percentage can significantly be increased, leading to better performance. Full article
(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)
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Open AccessArticle
Compensation for Geometrical Deviations in Additive Manufacturing
Technologies 2019, 7(4), 83; https://doi.org/10.3390/technologies7040083 - 02 Dec 2019
Viewed by 510
Abstract
The design of additive manufacturing processes, especially for batch production in industrial practice, is of high importance for the propagation of new additive manufacturing technology. Manual redesign procedures of the additive manufactured parts based on discrete measurement data or numerical meshes are error [...] Read more.
The design of additive manufacturing processes, especially for batch production in industrial practice, is of high importance for the propagation of new additive manufacturing technology. Manual redesign procedures of the additive manufactured parts based on discrete measurement data or numerical meshes are error prone and hardly automatable. To achieve the required final accuracy of the parts, often, various iterations are necessary. To address these issues, a data-driven geometrical compensation approach is proposed that adapts concepts from forming technology. The measurement information of a first calibration cycle of manufactured parts is the basis of the approach. Through non-rigid transformations of the part geometry, a new shape for the subsequent additive manufacturing process was derived in a systematic way. Based on a purely geometrical approach, the systematic portion of part deviations can be compensated. The proposed concept is presented first and was applied to a sample fin-shaped part. The deviation data of three manufacturing cycles was utilised for validation and verification. Full article
(This article belongs to the Special Issue Reviews and Advances in Materials Processing)
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Open AccessArticle
3D Model Generation on Architectural Plan and Section Training through Machine Learning
Technologies 2019, 7(4), 82; https://doi.org/10.3390/technologies7040082 - 15 Nov 2019
Viewed by 600
Abstract
Machine learning, especially the GAN (Generative Adversarial Network) model, has been developed tremendously in recent years. Since the NVIDIA Machine Learning group presented the StyleGAN in December 2018, it has become a new way for designers to make machines learn different or similar [...] Read more.
Machine learning, especially the GAN (Generative Adversarial Network) model, has been developed tremendously in recent years. Since the NVIDIA Machine Learning group presented the StyleGAN in December 2018, it has become a new way for designers to make machines learn different or similar types of architectural photos, drawings, and renderings, then generate (a) similar fake images, (b) style-mixing images, and (c) truncation trick images. The author both collected and created input image data, and specially made architectural plan and section drawing inputs with a clear design purpose, then applied StyleGAN to train specific networks on these datasets. With the training process, we could look into the deep relationship between these input architectural plans or sections, then generate serialized transformation images (truncation trick images) to form the 3D (three-dimensional) model with a decent resolution (up to 1024 × 1024 × 1024 pixels). Though the results of the 3D model generation are difficult to use directly in 3D spatial modeling, these unexpected 3D forms still could inspire new design methods and greater possibilities of architectural plan and section design. Full article
(This article belongs to the Special Issue Computer-Aided Architectural Design)
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Open AccessLetter
Facile Fabrication of Macroscopic Self-Standing Ni or Co-doped MnO2 Architectures as Catalysts for Propane Oxidation
Technologies 2019, 7(4), 81; https://doi.org/10.3390/technologies7040081 - 11 Nov 2019
Viewed by 545
Abstract
The fabrication of macroscopic self-standing architectures plays a key role in the practical applications of nanomaterials. A facile strategy to assemble MnO2 nanowires into macroscopic self-standing architectures via hydrothermal reaction followed by ambient pressure drying was developed. The obtained sample was robust [...] Read more.
The fabrication of macroscopic self-standing architectures plays a key role in the practical applications of nanomaterials. A facile strategy to assemble MnO2 nanowires into macroscopic self-standing architectures via hydrothermal reaction followed by ambient pressure drying was developed. The obtained sample was robust and showed excellent mechanical strength with a Young’s modulus of 127 MPa, which had the possibility for practical applications. In order to promote the catalytic activity for propane oxidation, Ni or Co doping into MnO2 was studied. The results showed that the obtained macroscopic self-standing Ni-MnO2 and Co-MnO2 architectures exhibited enhanced catalytic activities for propane oxidation. Specifically, the conversions of propane over Co-MnO2 and Ni-MnO2 samples at 400 °C were 27.3% and 25.7% higher than that over pristine MnO2 sample. Full article
(This article belongs to the Special Issue Reviews and Advances in Materials Processing)
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Open AccessCommunication
AFM Characterization of Stir-Induced Micro-Flow Features within the AA6082-T6 BFSW Welds
Technologies 2019, 7(4), 80; https://doi.org/10.3390/technologies7040080 - 07 Nov 2019
Cited by 1 | Viewed by 650
Abstract
Bobbin Friction Stir Welding (BFSW) is a thermomechanical process containing severe plastic deformation by mechanical stirring and Dynamic Recrystallization (DRX) during recooling. Here we report the three-dimensional characteristics of the micro-flow patterns within the aluminium weld structure. The Surface topography observations by Atomic [...] Read more.
Bobbin Friction Stir Welding (BFSW) is a thermomechanical process containing severe plastic deformation by mechanical stirring and Dynamic Recrystallization (DRX) during recooling. Here we report the three-dimensional characteristics of the micro-flow patterns within the aluminium weld structure. The Surface topography observations by Atomic Force Microscopy (AFM) show the stirred-induced microstructural evolution where the rearrangement of dislocations at the sub-grain scale, and the subsequent High- and Low-Angle Grain Boundaries (HAGBs, LAGBs) exhibit specific alterations in grain size and morphology of the weld texture. The dislocations interaction in different regions of the weld structure also was observed in correlation to the thermomechanical behaviour of the BFSW process. These micro-flow observations within the weld breadth give a new insight into the thermomechanical characteristics of the FSW process during the stirring action where the plastic flow has a key role in the formation of the weld region distinct from the base metal. Full article
(This article belongs to the Special Issue Reviews and Advances in Materials Processing)
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Open AccessFeature PaperReview
Advanced Coatings by Thermal Spray Processes
Technologies 2019, 7(4), 79; https://doi.org/10.3390/technologies7040079 - 01 Nov 2019
Viewed by 661
Abstract
Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of [...] Read more.
Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of other in-chamber processes. Consequently, TS techniques like high-velocity oxy-fuel (HVOF) and atmospheric plasma spray (APS) are industrially well-accepted. However, they have reached limits of their capabilities while expectations from coatings progressively increase in pursuit of enhanced efficiency and productivity. Two emerging TS variants, namely high-velocity air-fuel (HVAF) and liquid feedstock thermal spraying, offer attractive pathways to realize high-performance surfaces superior to those hitherto achievable. Supersonic HVAF spraying provides highly adherent coatings with negligible porosity and its low processing temperature also ensures insignificant thermal ‘damage’ (oxidation, decarburization, etc.) to the starting material. On the other hand, liquid feedstock derived TS coatings, deposited using suspensions of fine particles (100 nm–5 µm) or solution precursors, permits the production of coatings with novel microstructures and diverse application-specific architectures. The possibility of hybrid processing, combining liquid and powder feedstock, provides further opportunities to fine tune the properties of functional surfaces. These new approaches are discussed along with some illustrative examples. Full article
(This article belongs to the Special Issue Processing and Fabrication of Advanced Materials)
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Open AccessArticle
From Undesired Flaws to Esthetic Assets: A Digital Framework Enabling Artistic Explorations of Erroneous Geometric Features of Robotically Formed Molds
Technologies 2019, 7(4), 78; https://doi.org/10.3390/technologies7040078 - 31 Oct 2019
Viewed by 612
Abstract
Until recently, digital fabrication research in architecture has aimed to eliminate manufacturing errors. However, a novel notion has just been established—intentional computational infidelity. Inspired by this notion, we set out to develop means than can transform the errors in fabrication from an undesired [...] Read more.
Until recently, digital fabrication research in architecture has aimed to eliminate manufacturing errors. However, a novel notion has just been established—intentional computational infidelity. Inspired by this notion, we set out to develop means than can transform the errors in fabrication from an undesired complication to a creative opportunity. We carried out design experiment-based investigations, which culminated in the construction of a framework enabling fundamental artistic explorations of erroneous geometric features of robotically formed molds. The framework consists of digital processes, assisting in the explorations of mold errors, and physical processes, enabling the inclusion of physical feedback in digital explorations. Other complementary elements embrace an implementation workflow, an enabling digital toolset and a visual script demonstrating how imprecise artistic explorations can be included within the computational environment. Our framework application suggests that the exploration of geometrical errors aids the emergence of unprecedented design features that would not have arisen if error elimination were the ultimate design goal. Our conclusion is that welcoming error into the design process can reinstate the role of art, craft, and material agency therein. This can guide the practice and research of architectural computing onto a new territory of esthetic and material innovation. Full article
(This article belongs to the Special Issue Computer-Aided Architectural Design)
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Open AccessArticle
An Improved Calculation Model for the Prediction of the Wear of Coated Electrical Contacts
Technologies 2019, 7(4), 77; https://doi.org/10.3390/technologies7040077 - 31 Oct 2019
Viewed by 520
Abstract
To connect terminals in a cyber–physical system, large quantities of electrical contacts are used. In order to guarantee a high reliability of the system, the lifetime of the electrical contacts should be very long. Thus, it is of great importance to understand the [...] Read more.
To connect terminals in a cyber–physical system, large quantities of electrical contacts are used. In order to guarantee a high reliability of the system, the lifetime of the electrical contacts should be very long. Thus, it is of great importance to understand the failure mechanism and then to predict the lifetime of the electrical contacts. For the applications under high thermal and/or mechanical loads, noble plating is a good choice, considering its inertness to oxidation. For noble plating, one of the most critical failure mechanisms is the fretting wear. Wear debris generated in the contact area, acting as the third bodies, will greatly influence the further wear behavior and electrical performance. In this study, the state of the art regarding third bodies is firstly reviewed, and then the influence of the third bodies on the wear and electrical performance is investigated, from the aspects of lifetime and the element distributions in contact area. Finally, an example of prediction of the wear of noble plating is shown with the consideration of the third bodies. Based on this study, by involving the third bodies, the wear of noble plating can be predicted with a higher accuracy. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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Open AccessArticle
Analysis of a Chaotic System with Line Equilibrium and Its Application to Secure Communications Using a Descriptor Observer
Technologies 2019, 7(4), 76; https://doi.org/10.3390/technologies7040076 - 24 Oct 2019
Viewed by 695
Abstract
In this work a novel chaotic system with a line equilibrium is presented. First, a dynamical analysis on the system is performed, by computing its bifurcation diagram, continuation diagram, phase portraits and Lyapunov exponents. Then, the system is applied to the problem of [...] Read more.
In this work a novel chaotic system with a line equilibrium is presented. First, a dynamical analysis on the system is performed, by computing its bifurcation diagram, continuation diagram, phase portraits and Lyapunov exponents. Then, the system is applied to the problem of secure communication. We assume that the transmitted signal is an additional state. For this reason, the nonlinear system is rewritten in a rectangular descriptor form and then an observer is constructed for achieving synchronization and input reconstruction. If we assume some rank conditions (on the nonlinearities and the solvability of a linear matrix inequality (LMI)) on the system matrices then the observer synchronization can be feasible. We evaluate and demonstrate our approach with specific numerical results. Full article
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Open AccessReview
Towards Safer Primers: A Review
Technologies 2019, 7(4), 75; https://doi.org/10.3390/technologies7040075 - 18 Oct 2019
Viewed by 754
Abstract
Primers are used to reliably initiate a secondary explosive in a wide range of industrial and defence applications. However, established primer technologies pose both direct and indirect risks to health and safety. This review analyses a new generation of primer materials and ignition [...] Read more.
Primers are used to reliably initiate a secondary explosive in a wide range of industrial and defence applications. However, established primer technologies pose both direct and indirect risks to health and safety. This review analyses a new generation of primer materials and ignition control mechanisms that have been developed to address these risks in firearms. Electrically or optically initiated metal, oxide and semiconductor-based devices show promise as alternatives for heavy metal percussive primers. The prospects for wider use of low-cost, safe, reliable and non-toxic primers are discussed in view of these developments. Full article
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Open AccessArticle
Open Source Waste Plastic Granulator
Technologies 2019, 7(4), 74; https://doi.org/10.3390/technologies7040074 - 14 Oct 2019
Viewed by 965
Abstract
In order to accelerate deployment of distributed recycling by providing low-cost feed stocks of granulated post-consumer waste plastic, this study analyzes an open source waste plastic granulator system. It is designed, built, and tested for its ability to convert post-consumer waste, 3D printed [...] Read more.
In order to accelerate deployment of distributed recycling by providing low-cost feed stocks of granulated post-consumer waste plastic, this study analyzes an open source waste plastic granulator system. It is designed, built, and tested for its ability to convert post-consumer waste, 3D printed products and waste into polymer feedstock for recyclebots of fused particle/granule printers. The technical specifications of the device are quantified in terms of power consumption (380 to 404 W for PET and PLA, respectively) and particle size distribution. The open source device can be fabricated for less than $2000 USD in materials. The experimentally measured power use is only a minor contribution to the overall embodied energy of distributed recycling of waste plastic. The resultant plastic particle size distributions were found to be appropriate for use in both recyclebots and direct material extrusion 3D printers. Simple retrofits are shown to reduce sound levels during operation by 4dB-5dB for the vacuum. These results indicate that the open source waste plastic granulator is an appropriate technology for community, library, maker space, fab lab, or small business–based distributed recycling. Full article
(This article belongs to the Section Innovations in Materials Processing)
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Open AccessArticle
Psychosocial Impact of Powered Wheelchair, Users’ Satisfaction and Their Relation to Social Participation
Technologies 2019, 7(4), 73; https://doi.org/10.3390/technologies7040073 - 10 Oct 2019
Viewed by 711
Abstract
Several studies showed positive effects of assistive technologies on psychosocial impact and participation of adults with mobility impairments. The purpose of this study was to assess the psychosocial and participation impact of powered wheelchairs. Participants were thirty persons with disabilities who use powered [...] Read more.
Several studies showed positive effects of assistive technologies on psychosocial impact and participation of adults with mobility impairments. The purpose of this study was to assess the psychosocial and participation impact of powered wheelchairs. Participants were thirty persons with disabilities who use powered wheelchairs with diverse medical conditions. The Quebec User Evaluation of Satisfaction with Assistive Technology, the Psychosocial Impact of Assistive Devices Scale and the Activities and Participation Profile Related to Mobility were used, in addition to demographic, clinical and wheelchair related questions. The participants were satisfied with both the assistive technology and related services, with the lowest satisfaction scores belonging to those who had been using their wheelchairs for a longer period of time. We noticed significant restrictions in participation mostly among persons with longer wheelchair utilization. The most satisfied were the ones with better performance in terms of social participation. Psychosocial scores showed a positive impact with higher adaptability among persons who transitioned from a manual compared to those who already had a powered wheelchair. There was a positive psychosocial impact and therefore an increase in quality of life of its users. Full article
(This article belongs to the Section Assistive Technologies)
Open AccessArticle
Convolution of Barker and Golay Codes for Low Voltage Ultrasonic Testing
Technologies 2019, 7(4), 72; https://doi.org/10.3390/technologies7040072 - 10 Oct 2019
Viewed by 625
Abstract
Ultrasonic Testing (UT) is one of the most important technologies in Non-Detective Testing (NDT) methods. Recently, Barker code and Golay code pairs as coded excitation signals have been applied in ultrasound imaging system with improved quality. However, the signal-to-noise ratio (SNR) of existing [...] Read more.
Ultrasonic Testing (UT) is one of the most important technologies in Non-Detective Testing (NDT) methods. Recently, Barker code and Golay code pairs as coded excitation signals have been applied in ultrasound imaging system with improved quality. However, the signal-to-noise ratio (SNR) of existing UT system based on Barker code or Golay code can be influenced under high high attenuation materials or noisy conditions. In this paper, we apply the convolution of Barker and Golay codes as coded excitation signals for low voltage UT devices that combines the advantages of Barker code and Golay code together. There is no need to change the hardware of UT system in this method. The proposed method has been analyzed theoretically and then in extensive simulations. The experimental results demonstrated that the main lobe level of the code produced by convolution of Barker code and Golay code pairs is much higher than the simple pulse and the main lobe of the combined code is higher than the traditional Barker code, sidelobe is the same as the baker code that constitutes this combined code. So the peak sidelobe level (PSL) of the combined code is lower than the traditional Barker code. Equipped with this, UT devices can be applied in low voltage situations. Full article
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Open AccessFeature PaperArticle
Control Limits for an Adaptive Self-Starting Distribution-Free CUSUM Based on Sequential Ranks
Technologies 2019, 7(4), 71; https://doi.org/10.3390/technologies7040071 - 01 Oct 2019
Viewed by 716
Abstract
Since their introduction in 1954, cumulative sum (CUSUM) control charts have seen a widespread use beyond the conventional realm of statistical process control (SPC). While off-the-shelf implementations aimed at practitioners are available, their successful use is often hampered by inherent limitations which make [...] Read more.
Since their introduction in 1954, cumulative sum (CUSUM) control charts have seen a widespread use beyond the conventional realm of statistical process control (SPC). While off-the-shelf implementations aimed at practitioners are available, their successful use is often hampered by inherent limitations which make them not easily reconcilable with real-world scenarios. Challenges commonly arise regarding a lack of robustness due to underlying parametric assumptions or requiring the availability of large representative training datasets. We evaluate an adaptive distribution-free CUSUM based on sequential ranks which is self-starting and provide detailed pseudo-code of a simple, yet effective calibration algorithm. The main contribution of this paper is in providing a set of ready-to-use tables of control limits suitable to a wide variety of applications where a departure from the underlying sampling distribution to a stochastically larger distribution is of interest. Performance of the proposed tabularized control limits is assessed and compared to competing approaches through extensive simulation experiments. The proposed control limits are shown to yield significantly increased agility (reduced detection delay) while maintaining good overall robustness. Full article
Open AccessArticle
A Cold-Pressing Method Combining Axial and Shear Flow of Powder Compaction to Produce High-Density Iron Parts
Technologies 2019, 7(4), 70; https://doi.org/10.3390/technologies7040070 - 24 Sep 2019
Viewed by 770
Abstract
Highly performance methods for cold pressing (cold die forging) of preforms from iron powder with subsequent heat treatment and producing ready parts made of powder are described in the paper. These methods allow fabricating parts with smooth surfaces and improved mechanical characteristics—porosity, tensile [...] Read more.
Highly performance methods for cold pressing (cold die forging) of preforms from iron powder with subsequent heat treatment and producing ready parts made of powder are described in the paper. These methods allow fabricating parts with smooth surfaces and improved mechanical characteristics—porosity, tensile strength. Application of the traditional design set-up with a single-axial loading is restricted to high stresses in the dies to deform the preforms that lead to cracks formation. New powder compaction schemes by applying active friction forces (shear-enhanced compaction) make it possible to unload dies and produce high-quality parts by cold pressing. The scheme allows moving the die in the direction of the material flow with a velocity that exceeds the material flow velocity. Full article
(This article belongs to the Special Issue Processing and Fabrication of Advanced Materials)
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Open AccessArticle
Transient Contact Opening Forces in a MEMS Switch Using Au/MWCNT Composite
Technologies 2019, 7(4), 69; https://doi.org/10.3390/technologies7040069 - 23 Sep 2019
Viewed by 717
Abstract
Most failures in micro electromechanical system (MEMS) switches can be attributed to the degradation of contact surfaces and sticking contacts. A wear-tolerant composite contact material, composed of a Au film supported by multi walled carbon nanotubes (Au/MWCNT), has been engineered to provide wear [...] Read more.
Most failures in micro electromechanical system (MEMS) switches can be attributed to the degradation of contact surfaces and sticking contacts. A wear-tolerant composite contact material, composed of a Au film supported by multi walled carbon nanotubes (Au/MWCNT), has been engineered to provide wear resistance and enhanced switching lifetime with conductive properties close to pure Au. Switching lifetimes of billions of cycles have been demonstrated, representing greatly increased performance over thin film Au. Below the arcing threshold (~12 V) the wear mechanism has been shown to be a combination of the fine transfer of contact material by the molten metal bridge (MMB) phenomenon and a delamination of the Au. In this study, the composite contact is hot switched at low current DC conditions (4 V DC and 20 mA) while the contact force is measured at the micro Newton scale in nanosecond resolution. The characteristic voltage waveform associated with the MMB is observed with forces detected as the contact softens, melts, and separates. The presence of a delamination event (DE) is also observed, where the contact opens abruptly with no MMB phenomenon apparent. The DE contact openings are associated with a transient peak force of 21.6 ± 2.3 µN while the MMBs are linked to a lower peak force of 18.1 ± 2.5 µN. Full article
(This article belongs to the Special Issue Microswitching Technologies)
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Open AccessArticle
Validation of Different Filters for Center of Pressure Measurements by a Cross-Section Study
Technologies 2019, 7(4), 68; https://doi.org/10.3390/technologies7040068 - 20 Sep 2019
Viewed by 742
Abstract
The measurement of the center of pressure (CoP) is one of the most frequently used quantitative methods for quantifying postural performance. Due to the complexity and the high biological variability of the postural control loop, a large number of different methods and parameters [...] Read more.
The measurement of the center of pressure (CoP) is one of the most frequently used quantitative methods for quantifying postural performance. Due to the complexity and the high biological variability of the postural control loop, a large number of different methods and parameters have been established to describe the CoP process. Furthermore, the methodological conditions such as the foot position, visual condition, sampling duration, and the data processing also have a relevant influence on the measurement results. In addition, there are various methods for recording the pressure curve, which differ in particular with regard to the filters used, the frequencies, and measurement times. The aim of the present study was the methodical comparison between different digital filters, measurement frequencies and times, and their effects on the CoP process based on a healthy reference group. The data acquisition was done with LabVIEW and the data storage was organized in a subject oriented data structure. Based on the presented results it could be seen that with a different dominant frequency in the spectrum of the group of test persons, certain filter types are required for the processing of CoP data. In the sampling range from 300 Hz to 1 kHz in the bipedal stand and 600 Hz to 1 kHz in the monopedal stand, the choice of measurement frequency had no influence on the filter result. Full article
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