Multichannel Feedback Research Articles

A narrowband active noise control system with coarse frequency estimator and spectrum shifter

The frequency of an internal synthetic reference signal that is inconsistent with that of the noise signal is a serious problem in narrowband active noise control (NANC) system. This is called frequency mismatch (FM), which severely deteriorates the performance of the system. To alleviate this problem, a multichannel feedback NANC system with a coarse frequency estimator and spectrum shifter is proposed in this paper. Rough estimations of multiple tones are provided by a coarse frequency estimator based on discrete Fourier transform (DFT) coefficients and fed into the spectrum shifter. Splitting the noise signal into several individual orthogonal reference signals by the spectrum shifter rather than internal generation can avoid FM problem. Because estimated frequency errors can be tolerated in the spectrum shifter but cannot be compensated by signal generators. Compared with existing methodologies, the proposed method relaxes the demand on the precision of the frequency estimator, and reduces the undesired delay in the frequency estimation by using smaller fast Fourier transform (FFT) blocks. Moreover, a computational complexity analysis of the proposed method indicates that the proposed method is advantageous in terms of computational complexity. Extensive simulations and real-time experiments were conducted to verify the superior noise reduction performance and faster convergence speed of the proposed method under different FM situations.

Cosmic Ray Processes in Galactic Ecosystems

Galaxy evolution is an important topic, and our physical understanding must be complete to establish a correct picture. This includes a thorough treatment of feedback. The effects of thermal–mechanical and radiative feedback have been widely considered; however, cosmic rays (CRs) are also powerful energy carriers in galactic ecosystems. Resolving the capability of CRs to operate as a feedback agent is therefore essential to advance our understanding of the processes regulating galaxies. The effects of CRs are yet to be fully understood, and their complex multi-channel feedback mechanisms operating across the hierarchy of galaxy structures pose a significant technical challenge. This review examines the role of CRs in galaxies, from the scale of molecular clouds to the circumgalactic medium. An overview of their interaction processes, their implications for galaxy evolution, and their observable signatures is provided and their capability to modify the thermal and hydrodynamic configuration of galactic ecosystems is discussed. We present recent advancements in our understanding of CR processes and interpretation of their signatures, and highlight where technical challenges and unresolved questions persist. We discuss how these may be addressed with upcoming opportunities.

Exploration and Practice of Cultivating Multidimensional Design Innovation Ability

This paper relies on the background of the "National Medium and Long-Term Science and Technology Development Program (2006-2020)" and "National Medium- and Long-term Education Reform and Development Program (2010-2020)" issued by the State Council . The document emphasizes the importance and urgency of cultivating innovative talents. This article takes the "Product Development and Design" course as a carrier to explore the multi-dimensional and jointly driven innovative talent training methods such as goal orientation, school-enterprise collaboration, science and education integration, and competition platform. Through: ① Build a three-tier progressive curriculum project system to help students internalize the theory and lay the foundation for practice. ②Create a school-enterprise mutual-feeding joint training method , supported by enterprise projects, and form classroom and project mutual-feeding. ③Set up the second classroom of scientific and technological innovation , with the precise drive of the four-in-one team + project + platform (competition platform) + innovation (Internet +, rural revitalization, etc.), to build a five-level integration of teaching, production, competition, research, and theoretical practice for improvement way . ④ Construct a process-based, output-oriented, quantifiable and controllable, multi-channel feedback capability achievement evaluation standard . Multi-dimensional innovative ways to explore the training mode of applied innovative talents. It is hoped that it can solve the problem of connecting the innovation ability of students and the innovation level required by enterprises.

Does Public Service Motivation Affect Teacher Satisfaction From the Perspective of Urban and Rural Dual Structure? Empirical Analysis Based on Estonia TALIS 2018 Data.

In recent years, basic education in Estonia has achieved balanced development despite the imbalance of structure and regional factors, and this phenomenon has made the Estonian educational system a general interest of international scholars. Based on the data from the 2018 Teacher Teaching International Survey (TALIS) database, this research divides 3,004 respondents in Estonia into rural teachers and urban teachers and explores the impact of public service motivation on teacher satisfaction from the perspective of urban-rural dual structure through the grouping and comparison of ordered regression models. The study finds that the three dimensions of public service motivations in Estonia will positively affect teacher satisfaction and that the influence coefficient of contribute to the society and the tendency to participate in education policies on teacher satisfaction is higher in rural areas than in urban areas. In addition, the satisfaction of rural teachers in Estonia will decrease with the age of teachers, and the satisfaction of male teachers will be significantly lower than the satisfaction of female teachers, while the satisfaction of urban teachers will decrease with the improvement of academic qualifications. In terms of the implications, on the one hand, Estonia's education policy attempts to solve the imbalance between the regional and teacher structure through subsidies and incentives; on the other hand, Estonia's education policy uses measures such as multidimensional evaluation, multichannel feedback, and local democratization to increase the teacher's participation as well as their satisfaction.

Study on the Design of a Water Dispenser for Visually Impaired Families

In visually impaired families, there are different needs in terms of the access to drinking water, and the existing research on the design of water dispensers is insufficient. In order to solve this problem, a diverse analysis, based on the inclusive design concept, of household users’ operating abilities and water dispenser preferences was carried out. Subsequently and guided by the analysis, a new water dispenser product was developed. The methods used to extrapolate the needs of visually impaired families were observation and interviews, while the questionnaire research was used to understand the user preferences. Secondly, the accessibility of the existing water dispenser was tested for visually impaired, elderly, middle-aged, and young users in the visually impaired family. Three design strategies were proposed that combine the needs and product preferences of the users: the multimode simplification of steps, water quality detection, and adaptive multichannel feedback. The water dispenser was redesigned on the basis of these. On the premise of meeting the different abilities of the users in visually impaired families, the design practice improves the users’ experience of water dispensers, and provides a practical method reference that has value for related product designs.

Exploration of the Innovative Multi-dimensional Talents Training for Mechanical Engineering Specialty in China

In view of the current engineering personnel, innovative personnel training mode and teaching system was difficult to adapt to the new needs of the industry. This paper put forward multi-dimensional co-driven innovative personnel training concept based on the goal oriented education, school-enterprise cooperation education, science and education integration education, and competition platform education. Three-level progressive curriculum project system, three-level and five-link university-enterprise complementary joint training model, and a four-level extracurricular science and technology innovation platform were established. A capability achievement evaluation standard was also established based on concepts of process-based, output-oriented, quantifiable, controllable and multi-channel feedback. A research capability model of transforming engineering problems into scientific problems was built with the help of high-end teams and provincial and ministerial platforms. The deep integration of society, school and innovation team was promoted by construction of achievement transformation mode, with market demand as the leading role and practice incubation as the carrier. With the precise drive of team, project, platform, innovation and entrepreneurship, the training mode of application-oriented innovative talents has been established, which integrates theory and practice with the five-step promotion of teaching, production, competition, research and application. The teaching reform was carried out in Qingdao university of technology and collection data comes from student of mechanical engineering major in the past three years. The achievements of teaching reform was discussed from five aspects including ‘teaching’, ‘production’, ‘competition’, ‘research’ and ‘application’. The analysis shows that the reform has achieved remarkable results. Keywords: Mechanical Engineering, Multidimensional culture, Goal-driven, Process control.

Adjustable Structure for Feedback Active Headrest System Using the Virtual Microphone Method

Active headrest is an essential application for active noise control, capable of reducing low-frequency disturbance around an error microphone. However, in most cases, attaching microphones to ears is not feasible and noise attenuation performance is vulnerable to plant response variations. This paper presents a multichannel feedback active headrest system combined with the virtual microphone method and a manually adjustable headrest structure for users. Applying the virtual microphone method can transfer the attenuation target from the distant microphone to the ear. The proposed adjustable headrest structure allows for secondary loudspeakers and the corresponding microphone to be moved as a single unit while maintaining the relative distances between the secondary loudspeakers and microphones constant to ensure that the related plant responses are consistent. Experiments were conducted to validate the performance against multi-sinusoidal machine noise. The results demonstrate the benefits of the proposed structure over conventional structures. Additionally, the applicability of the three commonly used virtual sensing methods (the auxiliary filter method, remote microphone method, and virtual microphone method) in various practical conditions was verified when using the proposed adjustable headrest structure. Furthermore, 10 volunteers were involved in the evaluation, and the robustness of the proposed system for various users was confirmed.

Optimal Filter Design of a Virtual Mechanical Impedance Control System for Multifrequency Active Sound Power Reduction of Enclosure Panels

An optimal filter design method for a virtual mechanical impedance (VMI) control system is presented in this report. Existing passive methods for reducing machinery noise have limited applications because of weight reduction, cooling, and appearance problems. The VMI control method, which does not require a sensor and can be implemented using a small number of actuators, is an active approach that can be used to replace passive methods when mechanical tuning is difficult. However, VMI control methods can only reduce single-tone noise. In this regard, we improved the VMI control system to reduce the radiated sound power of the enclosure panel at multiple frequencies. To achieve this, we propose an optimal filter design method for a multichannel feedback controller. Unlike conventional VMI control, the presented technique is capable of multifrequency control and considers the radiation efficiency, damping, and estimates the errors of the structural-acoustic system. The controller designed using the proposed method satisfies the required robustness and minimum steady-state error in the target frequency band. Thus, this filter design method facilitates the quantitative determination of several criteria that are needed to evaluate system parameter changes such as radiation efficiency, damping, and estimation error, which are overlooked in a standard active structural acoustic controller. The results obtained using a finite element-based model and experimental investigations show that the radiated sound power of the enclosure panel is reduced at multiple target frequencies after the implementation of control.

Sub-Nyquist Sampling of BPSK Signals via Feedback Structure

We consider the problem of sampling binary phase shift keying (BPSK) signals, which are widely used in communications and radar systems. Although sub-Nyquist sampling of such signals has been treated in various works, giant samples were needed. In this brief, a new sub-Nyquist sampling method based on a multichannel feedback structure is proposed for BPSK signals, which requires fewer samples. BPSK signals can be characterized by a finite number of parameters, namely, the carrier frequency, amplitude, locations of discontinuities, and phase of each symbol. Our feedback structure consists of a main channel and a feedback channel. The carrier frequency and amplitude can be estimated by the estimation of signal parameters by a rotational invariance technique algorithm in the main channel, while the phases and locations of discontinuities can be estimated by the annihilating filter in the feedback channel. The effectiveness of the proposed method is verified via simulations. In a noiseless situation, for a seven-segment BPSK signal lasting $1~{\mu } {s}$ with a 500-MHz carrier frequency, the equivalent sampling rate of the proposed method is only 3.8% of the carrier frequency, and much less than the Nyquist sampling rate of the signal. Finally, we analyze the effect of noise and present a robust reconstruction algorithm. Simulation results show that the proposed method exhibits better noise robustness than previous approaches.

Effect of dual-channel optical feedback on self-mixing interferometry system

Laser feedback interference is widely used for displacement measurement of non-cooperative targets due to its ultra-high sensitivity. However, by the same token, laser feedback interferometry (LFI) suffers from multi-channel optical feedback, which compromises measurement stability and accuracy. We perform both simulations and experiments to study the effect of dual-channel optical feedback on LFI systems based displacement measurement. Dual-channel optical feedback interference is the simplest and most representative form of multi-channel feedback interference. We evaluate system performance by varying which is the ratio of feedback level in the primary channel to the one in the secondary channel. The results indicate that the measured displacement curve is a linear line superimposed with nonlinear periodic errors when the target in the primary channel moves linearly and the target in the secondary channel stays stationary. Whereas, the curve is a periodic curve instead of a linear one, for the case when the target in the secondary channel moves linearly while the one in the primary channel stays stationary. Furthermore, the amplitude and shape of the periodic curves also depend on the parameter When is much less than 1, the displacement curve is sinusoidal, whereas the curve has a saw-tooth shape with larger amplitude for close to 1. In view of this situation, a new displacement measurement method, counting the cycles of the periodic displacement curves, is proposed. The current work can provide theoretical and experimental suggestions for improving the performance of existing self-mixing interferometry systems, and implementing ones with multi-channel optical feedback channels.

Simulating an isolated dwarf galaxy with multichannel feedback and chemical yields from individual stars

In order to better understand the relationship between feedback and galactic chemical evolution, we have developed a new model for stellar feedback at grid resolutions of only a few parsecs in global disk simulations, using the adaptive mesh refinement hydrodynamics code Enzo. For the first time in galaxy scale simulations, we simulate detailed stellar feedback from individual stars including asymptotic giant branch winds, photoelectric heating, Lyman-Werner radiation, ionizing radiation tracked through an adaptive ray-tracing radiative transfer method, and core collapse and Type Ia supernovae. We furthermore follow the star-by-star chemical yields using tracer fields for 15 metal species: C, N, O, Na, Mg, Si, S, Ca, Mn, Fe, Ni, As, Sr, Y, and Ba. We include the yields ejected in massive stellar winds, but greatly reduce the winds' velocities due to computational constraints. We describe these methods in detail in this work and present the first results from 500~Myr of evolution of an isolated dwarf galaxy with properties similar to a Local Group, low-mass dwarf galaxy. We demonstrate that our physics and feedback model is capable of producing a dwarf galaxy whose evolution is consistent with observations in both the Kennicutt-Schmidt relationship and extended Schmidt relationship. Effective feedback drives outflows with a greater metallicity than the ISM, leading to low metal retention fractions consistent with observations. Finally, we demonstrate that these simulations yield valuable information on the variation in mixing behavior of individual metal species within the multi-phase interstellar medium.

Формування та функціонування територіальних центрів комплектування та соціальної підтримки: проблеми і шляхи їх вирішення

The development of the Armed Forces of Ukraine in accordance with Western standards and the reform of the state system of mobilization and mobilization training on the basis of basic European approaches provides for reforming and ensuring the effective functioning of local military command and control agencies (MCCA), which are currently military commissariats (MC). The article reveals and analyzes the main problems in the formation and functioning of the territorial centers of recruitment and social support (TCRSP) and suggests ways of their solution. Для реализации концептуальных положений по эффективному функционированию ТЦКСП предложены пути преодоления выявленных проблем, а именно: To implement the conceptual provisions on the effective functioning of the TCRSP, ways of overcoming the identified problems are proposed, namely: 1. Introduction of advanced world experience in the activities of the shopping center. 2. Transition from the administrative-compulsory to the socio-service content of the activities of territorial centers. 3. Development of a functional structure, definition of functions, authorities and optimal number of TCRSP 4. Development of a management system and control mechanisms that make it impossible to make corrupt decisions by TCRSP officials. 5. Technical equipment TCRSP modern automated information, telecommunications and other systems and technologies. 6. Introduction of modern professional standards of professional activity and professional training of personnel of the TCRSP. 7. The introduction of effective forms and methods of control over the performance of official duties by the staff of the TCRSP and the precise regulation of its official activities. 8. Providing multi-channel feedback to various segments of the population (correspondence, personal tricks, social networks, electronic correspondence, telephone consultations, hotlines, etc.), which will ensure the legitimacy and transparency of the TCRSP. 9. Creation of favorable conditions for the widest possible involvement of the population and civil society institutions in the adoption of managerial decisions and in the development of democratic civil control. In the future it is advisable to study the system of military-professional orientation and conduct activities to select candidates for the armed forces of the leading countries of the world and mechanisms for their implementation to improve the recruitment and staffing systems of the Armed Forces of Ukraine in accordance with the needs of the troops (forces).

Multichannel control systems for the attenuation of interior road noise in vehicles

This paper considers the active control of road noise in vehicles, using either multichannel feedback control, with both headrest and floor positioned microphones providing feedback error signals, or multichannel feedforward control, in which reference signals are provided by the microphones on the vehicle floor and error signals are provided by the microphones mounted on the headrests. The formulation of these control problems is shown to be similar if the constraints of robust stability, limited disturbance enhancement and open-loop stability are imposed. A novel formulation is presented for disturbance enhancement in multichannel systems, which limits the maximum enhancement of each individual error signal. The performance of these two systems is predicted using plant responses and disturbance signals measured in a small city car. The reduction in the sum of the squared pressure signals at the four error microphones for both systems is found to be up to 8dB at low frequencies and 3dB on average, where the sound level is particularly high from 80 to 180Hz. The performance of both systems is found to be robust to measured variations in the plant responses. The enhancements in the disturbance at higher frequencies are smaller for the feedback controller than for the feedforward controller, although the performance of the feedback controller is more significantly reduced by the introduction of additional delay in the plant response.

Adaptive Feedback Active Noise Control for Yacht Environments

In a yacht cabin, high-quality absorbing materials can reduce in a good way medium and high-frequency noises, but they are completely inefficient in the case of low-frequency noises. In this brief, a detailed analysis of low-frequency noises in a yacht environment is presented; several boat conditions, depending on the presence of different noise sources (e.g., air conditioning, engines) and various navigation velocities are investigated. In this context, a specific multichannel feedback active noise control system, derived from the well-known filtered-x approach, is designed and installed in a bedroom of a yacht in order to reduce the acoustical annoyance using four error microphones and two sub-woofers for antinoise generation. The results of practical experiments are shown in order to demonstrate the effectiveness of the proposed system.

State observers and Kalman filtering for high performance vibration isolation systems

There is a strong scientific case for the study of gravitational waves at or below the lower end of current detection bands. To take advantage of this scientific benefit, future generations of ground based gravitational wave detectors will need to expand the limit of their detection bands towards lower frequencies. Seismic motion presents a major challenge at these frequencies and vibration isolation systems will play a crucial role in achieving the desired low-frequency sensitivity. A compact vibration isolation system designed to isolate in-vacuum optical benches for Advanced Virgo will be introduced and measurements on this system are used to present its performance. All high performance isolation systems employ an active feedback control system to reduce the residual motion of their suspended payloads. The development of novel control schemes is needed to improve the performance beyond what is currently feasible. Here, we present a multi-channel feedback approach that is novel to the field. It utilizes a linear quadratic regulator in combination with a Kalman state observer and is shown to provide effective suppression of residual motion of the suspended payload. The application of state observer based feedback control for vibration isolation will be demonstrated with measurement results from the Advanced Virgo optical bench suspension system.

Ultra high benefits system for electric energy saving and management of lighting energy in buildings

This paper presents a smart system, including a multi channel dimmer and a central process unit (CPU) together with an exact multi channel feedback mechanism, which automatically regulates and manages lighting in buildings. Based on a multi channel luminance feedback, a high benefits technique is utilized to convert the electric energy to lighting energy. Saving a lot of the electric energy which should be converted to lighting energy in buildings, managing the lighting energy in buildings, providing desired constant and adjustable luminance for each room (location), and the capability of working with all AC electric power sources regardless of frequency and voltage amplitude are some advantages of using the proposed system and technique, thus it will be widely used in buildings. An experimental prototype of the proposed smart system has been constructed to validate the theoretical results and to carry out the experimental tests. Experimental results earned by utilizing the proposed smart system in a sample building are presented to prove the benefits of using the system. The experimental results explicitly show a considerable electric energy saving (about 27%) in the sample building while the proposed system has provided desired constant and adjustable luminance for each location of the building.

Multichannel feedback control of interior road noise

Active noise control systems offer a potential method of reducing the weight of passive acoustic treatments and, therefore, increasing a vehicles’ fuel efficiency. The active control of engine noise can be implemented cost-effectively by using the car audio loudspeakers as control sources and an array of low-cost microphones as error sensors. Such systems have been commercially implemented, but without also controlling road noise their subjective benefits may be limited. The active control of road noise using a feedforward control strategy has also been practically demonstrated, but these systems require a number of accelerometers to be mounted to the vehicle’s structure to obtain a coherent reference signal and, therefore, lead to a significant implementation cost. This paper proposes a multichannel feedback system for the active control of road noise, which uses an array of microphones and car audio loudspeakers, which is common to a feedforward engine noise control system. The design of the multichannel feedback controller is described and its performance is validated using offline simulations employing data measured in a small city car.

Performance analysis of decentralized multi-channel feedback systems for active noise control in free space

This paper investigates the performance of decentralized multi-channel feedback analog control systems, which are flexible and economic for practical applications of active noise control. The generalized Nyquist theorem and Gerschgorin circle theorem are used to derive a sufficient stability condition in terms of the predefined maximum noise amplification and the geometrical configuration of the independent controllers, and the noise reduction performance of the multi-channel system is predicted with the design and geometrical configuration of the independent controllers. Simulation and experimental results are presented to illustrate the effectiveness of the proposed analysis.

Transcranial Contralateral Routing of the Signal as a Fitting Option for Patients with Single-Sided Deafness

Patients with single-sided deafness (SSD) often report difficulty recognizing speech when the signal is on the side of the poorer ear. As discussed in this issue of Seminars in Hearing, several fitting options are available for patients with SSD. One option that could take on greater interest due to advancements in multichannel feedback management, noise reduction, and directional microphones is the transcranial contralateral routing of the signal (TCROS). This article reviews previous reports on performance with the TCROS. This article also focuses on the advances in hearing aid technology and how these advances could improve TCROS as a fitting option for patients with SSD. Finally, this article provides information on factors that audiologists should take into consideration for patient and hearing aid selection for TCROS and outlines a procedure to verify performance of TCROS using the real-ear-aided response (REAR) and other real-ear measures (REM).

A multi-channel feedback algorithm for the development of active liners to reduce noise in flow duct applications

The present paper deals with the design and development of the active part of a hybrid acoustic treatment combining porous material properties and active control techniques. Such an acoustic system was developed to reduce evolutionary tones in flow duct applications. Attention was particularly focused on the optimization process of the controller part of the hybrid cell. A piezo-electric transducer combining efficiency and compactness was selected as a secondary source. A digital adaptive feedback control algorithm was specially developed in order to operate independently cell by cell, and to facilitate a subsequent increase in the liner surface. An adaptive bandpass filter was used to prevent the development of instabilities due to the coupling occurring between cells. Special care was taken in the development of such systems for time-varying primary signals. An automatic frequency detection loop was therefore introduced in the control algorithm, enabling the continuous adaptation of the bandpass filtering. The multi-cell structure was experimentally validated for a four-cell system located on a duct wall in the presence of flow. Substantial noise reduction was obtained throughout the 0.7–2.5 kHz frequency range, with flow velocities up to 50 m/s.