Gain Shape Research Articles

Submarine depth and pitch control based on closed-loop gain shaping algorithm

Submarine depth and pitch control based on closed-loop gain shaping algorithm

Dynamic Positioning Control of Large Ships in Rough Sea Based on an Improved Closed-Loop Gain Shaping Algorithm

In order to solve the problem of the dynamic positioning control of large ships in rough sea and to meet the need for fixed-point operations, this paper proposes a dynamic positioning controller that can effectively achieve large ships’ fixed-point control during Level 9 sea states (wind force Beaufort No. 10). To achieve a better control effect, a large ship’s forward motion is decoupled to establish a mathematical model of the headwind stationary state. Meanwhile, the closed-loop gain shaping algorithm is combined with the exact feedback linearization algorithm to design the speed controller and the course-keeping controller. This effectively solves the problem of strong external interferences impacting the control system in rough seas and guarantees the comprehensive index of robustness performance. In this paper, three large ships—the “Mariner”, “Taian kou”, and “Galaxy”—are selected as the research objects for simulation research and the final fixing error is less than 10 m. It is proven that the method is safe, feasible, practical, and effective, and provides technical support for the design and development of intelligent marine equipment for use in rough seas.

Dynamic Gain Decomposition Reveals Functional Effects of Dendrites, Ion Channels, and Input Statistics in Population Coding.

Modern, high-density neuronal recordings reveal at ever higher precision how information is represented by neural populations. Still, we lack the tools to understand these processes bottom-up, emerging from the biophysical properties of neurons, synapses, and network structure. The concept of the dynamic gain function, a spectrally resolved approximation of a population's coding capability, has the potential to link cell-level properties to network-level performance. However, the concept is not only useful but also very complex because the dynamic gain's shape is co-determined by axonal and somato-dendritic parameters and the population's operating regime. Previously, this complexity precluded an understanding of any individual parameter's impact. Here, we decomposed the dynamic gain function into three components corresponding to separate signal transformations. This allowed attribution of network-level encoding features to specific cell-level parameters. Applying the method to data from real neurons and biophysically plausible models, we found: (1) The encoding bandwidth of real neurons, approximately 400 Hz, is constrained by the voltage dependence of axonal currents during early action potential initiation. (2) State-of-the-art models only achieve encoding bandwidths around 100 Hz and are limited mainly by subthreshold processes instead. (3) Large dendrites and low-threshold potassium currents modulate the bandwidth by shaping the subthreshold stimulus-to-voltage transformation. Our decomposition provides physiological interpretations when the dynamic gain curve changes, for instance during spectrinopathies and neurodegeneration. By pinpointing shortcomings of current models, it also guides inference of neuron models best suited for large-scale network simulations.

"Unlock a better life: Here's how!": A critical inquiry into how life coaches gain capital and shape legitimacy using Instagram's affordances

Instagram has become a primary platform via which life coaches establish a relationship with potential clients and advertise their professional services. In this study, we draw from Bourdieu’s work on taste and capital to unravel how life coaches capitalize on the affordances of Instagram to generate legitimacy and credibility for their profession. Drawing from a one-month observation of 1,650 posts collected from 20 Instagram profiles of life coaches, our analysis provides insight into how these professionals strategically display and integrate cultural practices, tastes, and preferences that align with neoliberal ideals of self-improvement and self-responsibility to set themselves apart as experts within their field. They then use this distinctiveness as a marketing technique, thereby feeding off their cultural and social capital, among others by rationalizing their expertise by appealing to their own experiences, embedding client testimonials, and driving the narrative by combining hashtags or images that refer to self-entrepreneurism, self-responsibility, and the good life. We reflect on the potentially harmful implications of these legitimization techniques on individuals and society.

417 W, 2.38 mJ Innoslab amplifier compressible to a high pulse quality of 406 fs.

We demonstrate a 417 W, 175 kHz Innoslab chirped pulse amplification laser compressible to short and clean 406 fs pulse duration. A spectral bandwidth (full width at half maximum, FWHM) of ∼3 nm was maintained at full pump power, and the pulses exhibited good pulse quality in a wide tunable pulse energy range from 1.7 mJ to a maximum of 2.38 mJ. At the maximum output power, the compressed pulses were nearly pedestal free. The comprehensive effects of residual high-order dispersion from the front end, the gain shaping effects of the amplifier, and the slight mismatch of third-order dispersion (TOD) between the stretcher (CFBG) and the gating compressor, along with the small nonlinear phase shift accumulated in the amplifier, could have facilitated the high pulse quality. To the best of our knowledge, this is the shortest pulse duration from the Innoslab amplifiers at hundreds of watts average power in the millijoule energy regime.

On the generation of high-quality Nyquist pulses in mode-locked fiber lasers

Nyquist pulses have wide applications in many areas, from electronics to optics. Mode-locked lasers are ideal platforms to generate such pulses. However, how to generate high-quality Nyquist pulses in mode-locked lasers remains elusive. We address this problem by managing different physical effects in mode-locked fiber lasers through extensive numerical simulations. We find that net dispersion, linear loss, gain and filter shaping can affect the quality of Nyquist pulses significantly. We also demonstrate that Nyquist pulses experience similariton shaping due to the nonlinear attractor effect in the gain medium. Our work may contribute to the design of Nyquist pulse sources and enrich the understanding of pulse shaping dynamics in mode-locked lasers.

Ship longitudinal stabilization control based on CGSA and nonlinear switch modification

To further improve the ship's longitudinal motion stabilization control effect and the energy saving and robustness of the control method, this paper takes the training ship “YuKun” of Dalian Maritime University as the controlled plant. It analyzes the causes of the severe longitudinal motion of “YuKun”. In ship longitudinal pitch reduction control, the unstable controlled plant is transformed into a stable generalized controlled plant by Nyquist shaping, using the introduced mathematical tool of power function and gain adjustment. The controller is designed with a third-order closed-loop gain shaping algorithm (CGSA) and a switch nonlinear modification function. In the verification process, the performance index, Nyquist stability analysis, model perturbation simulation, and comparative.simulation experiments are used to prove that the designed control method has the advantages of stability, robustness, and improvement. The simulation results show that when the model is perturbed, the improved control method has the advantages of more energy saving, stability, and robustness.

Bidirectional Cladding-Pumped Multicore EDFA and its Optimization for Energy Efficiency by Tuning Pump Condition

This work investigates the feasibility of improving the energy efficiency of a cladding-pumped multicore (MC) EDFA by utilizing bidirectional (BD) pumping. We combined a conventional forward-cladding-pumped MC-EDFA with backward cladding pumping and tuned the pump-gain characteristics and gain shape by controlling the optical pump power ratio of its forward and backward pumps. Since EDFAs have wavelength dependence, output power equalization by each wavelength channel is extremely important for amplifying the wavelength division multiplexing (WDM) signal. The standard method of current equalization is to adjust the attenuation by the output power of each wavelength channel. The main issue with the current standard equalization is the indispensable optical power loss caused the reduced optical amplification efficiency of the EDFA. Our previous work demonstrated that the optical power loss due to equalization can be reduced by controlling the optical power ratio of the forward and backward pumps. This leads to improved energy efficiency of the signal amplification and equalization of both the WDM and spatial division multiplexing (SDM). <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this paper, we report our detailed investigation into the tuning amplification characteristics of the BD-MC-EDFA. Our main focus was the gain, noise figure (NF), and gain shape of a 7-core BD-MC-EDFA prototype when forward and backward optical pump power was changed. Under 8 W of total optical pump power, the percentage of 60% forward cladding optical pump power was found to be optimal for efficiency considering the minimum output optical power loss due to equalization. This condition translates into a 1.7% pump conversion efficiency (PCE) improvement, which corresponds to a 24% reduction of the total optical pump power compared to conventional MC-EDFA with only forward cladding pumping. Although the NF deteriorated by 1.0 dB in wavelength average in the 4.5-THz signal bandwidth in exchange for the efficiency improvement, degradation of the 34.2-GBaud polarization multiplexed 16 quadrature amplitude modulation (PM-16QAM) signal amplified by the BD-MC-EDFA operated under the optimized condition was negligible.

Course keeping control for very large ship using hyperbolic tangent function based on nonlinear decoration technique

To solve the problems of difficult course keeping, high energy output, and large wear of very large ships under different sea conditions, a robust controller combining the closed-loop gain shaping algorithm and nonlinear decoration is proposed in this paper. Firstly, a linear controller is designed by using the third-order closed-loop gain shaping algorithm and takes the hyperbolic tangent function as the nonlinear decoration of the controller output, and the robustness of the system is proved by H∞ robust control theory. Secondly, taking ‘Vale Brasil’, an ore carrier with a displacement of 400,000 tons, as the test plant. The nonlinear Nomoto model and nonlinear Norrbin model were established, which were compared with the control effect from the existing controller. Thirdly, simulation experiments were carried out under normal sea state and heavy sea state to prove the effectiveness. The results indicate that the proposed control strategy can achieve the required course faster, and enhances the smoothness of rudder angle actuation compared with the existing controller. It can maintain good control ability under different sea conditions. The proposed controller has the advantages of simple parameter adjustment, better robustness, less energy consumption, and reduced rudder angle. It is more in line with engineering practice and increases ship operation benefits.

Eating Competence among Brazilian College Students

Eating competence (EC) is a biopsychosocial concept related to a healthier eating pattern. Studies have shown that weight gain and body shape and weight dissatisfaction are typical among college students, contributing to low self-esteem, risky eating behaviors, and a propensity to develop eating disorders. As eating habits are determinant factors for food choices that can be modified by eating behavior, this study aimed to evaluate EC in college students from Brazil, using the Brazilian version of the EC Satter Inventory (ecSI2.0™BR), and EC's association with health data. This cross-sectional study was conducted using an online survey spread using the snowball method. The self-report instrument was divided into three parts (socioeconomic and demographic data; health data; and ecSI2.0™BR). Recruitment took place through social networks, and 593 students from public and private universities from all five regions of Brazil participated in the survey. The EC average was 29.46 ± 8.67, and 46.2% of the sample were considered competent eaters. Total EC did not differ among gender and Brazilian region. Younger participants (up to 20 y/o) presented higher scores for total EC, contextual skills and food acceptance. The total EC and contextual skills of health sciences students did not differ from those of students in other areas, except for agricultural sciences in which students had lower total EC. Obese individuals and the participants who perceived themselves to be overweight had low scores for EC. This study confirmed the hypothesis that college students have low EC, causing worse health outcomes related to BMI, perceived body weight, and occurrence of hypertension and dyslipidemia.

Gestão de atrativos culturais: O Museu Ferroviário de Juiz de Fora, Minas Gerais [Brasil

The theme heritage management appeared at first time in American museums and gain shape and importance over the years. In Brazil, mainly through tourism, it has an important role in socioeconomic development, but unfortunately the lack of diagnosis and planning, which are effective, is a detrimental factor. The museums, as cultural attractions, do not escape from this reality, and that is why one of the key pieces in museum management is the Museological Planning. Thus, the purpose of this work was to perform the initial stages of the Museological Planning process of the Railway Museum of Juiz de Fora, State of Minas Gerais, namely the Diagnosis and the Vocation, to then analyze how they relate to museological management and management of cultural attractions. In 2018, an action-research was conducted in loco, consisting of two central parts: a diagnosis of the museum, based on a survey aiming to identify the profile of the visiting public, and on the analysis of its resources and potentialities; and, a vocational study of the equipment. The work resulted in a conclusive detailed diagnosis that will be a material for the better future development of the Museum, as well as in intervention strategies, which were partially implemented, already in the period immediately after the action research was carried out.

Green energy-saving robust control for ship course-keeping system based on nonlinear switching feedback

To further save energy and reduce carbon emissions, a simple and robust green energy-saving control algorithm was proposed under the premise that the ship achieved an excellent course-keeping effect. To this end, the controller is designed by employing the third-order closed-loop gain shaping algorithm, and the final control law is obtained via the nonlinear switching feedback technique. The robustness of the system is proved by the Nyquist stability criterion. An evaluation model is carefully established for energy-saving and carbon-reduction of the course-keeping controller. The nonlinear Nomoto and Norrbin models for MV “Yukun” are implemented for simulating and further assessing under normal and heavy sea conditions. Compared with the nonlinear decoration controller, the proposed controller enhances the ship's course-keeping accuracy, shortens the delay time and settling time of the controller, lessens the steering angle and steering frequency of the rudder, increases the robustness of the system, and reduces the comprehensive energy-saving index by 26.1% under normal sea conditions. Meanwhile, good controller performance and green energy-saving effects are more in line with the requirements of navigation practice, which is essential for ships to achieve safe, economical, green, and low-carbon navigation.

Optical gain reduction caused by nonrelevant subbands in narrow-period terahertz quantum cascade laser designs

The recent designs of terahertz quantum cascade lasers usually employ the short periodic length and also the tall barriers for high-temperature operation. In this work, the effect of high-energy lying non-relevant subbands is studied based on nonequilibrium Green’s function formalisms model, demonstrating those subbands are probable to play a minor role on the population inversion, but play a major role on the optical gain at high temperatures. The phenomenon can be ascribed to the appearance of leakages crossing neighboring periods via sequential resonant tunneling, and those leakages are inherently created by the specific features of the two-well configuration in this design that the phonon well should be wide enough for performing the phonon scattering to depopulate the lower-laser subband. The narrower periodic length design can strengthen this inter-period leakage. A parasitic absorption between the first high-lying nonrelevant subbands from two laser wells can closely overlap the gain shape and thus significantly reduce the peak gain.

Nonlinear Decoration Control Based on Perturbation of Ship Longitudinal Motion Model

This paper proposes a nonlinear decoration control based on perturbation of the ship longitudinal Motion Model to reduce energy loss by achieving a good anti-pitch control effect. Even when the model is perturbed, it can continue to maintain a good robust performance and energy-saving effect for multiple-input multiple-output (MIMO) unstable systems. This proposed method uses the root locus shaping technology and the weighting matrix of mathematical tools to pull the root locus of the transfer function mathematical model with unstable zero-pole and zero-pole processes to the left half-plane of the teaching practice ship "YUKUN" of Dalian Maritime University used as the research object. The closed-loop gain shaping algorithm used to design the controller is then introduced, followed by the introduction of the first-order closed-loop gain shaping algorithm to design the robust controller with the shaped model. Finally, the nonlinear power function to decorate and improve the robust controller is presented. The simulation results show that when the model is perturbed, the nonlinear decoration control improves the control effects of the ship's heave and pitch, reduces control energy, and is critical for the ship's smooth and efficient navigation.

Autonomous ship deck landing of a quadrotor UAV using feed-forward image-based visual servoing

Autonomous takeoff and landing are crucial for unmanned aerial vehicles (UAVs) to perform various missions automatically. However, navigation sensors with low accuracy such as global positioning system (GPS) are limited in autonomous takeoff and landing for marine applications when ships are moving fast and oscillating by sea waves. In this study, an image-based visual servoing (IBVS) technique, which was originally used to land a UAV on a static target, is extended for a moving target. In particular, the ship velocity is estimated and used as a feed-forward term in the IBVS controller. To accurately estimate the velocity of the ship, velocity data from the GPS on the ship, image information obtained from the camera in the UAV, and dynamic model of the ship are combined using the Kalman filter framework. Besides, considering the under-actuated nature of the UAV and oscillation of the ship, a virtual plane concept, adaptive IBVS gain and feature shape compensation are introduced. Lastly, to apply the IBVS controller to the moving ship deck landing, a robust and safe autonomous landing procedure, starting from the approach to the touchdown phase, is also developed. The proposed autonomous landing system is validated via simulations and various real-world flight experiments simulating situations in which the ship is moving fast and oscillated by sea waves. In the flight experiments, the UAV lands successfully on the landing pad with the average touchdown error of 0.2m while the ship is oscillating at the Sea State 4 and is moving faster than 5m/s.

Modulation instability gain and modulated wave shape incited by the acoustic longitudinal vibrations in molecular chain model

The propagation of the modulated wave (MW) pattern and its instability in the nonlinear medium is an important study from where experimental results are obtained. In this work, we use the nonlinear Schrödinger equation (NLSE) with saturation nonlinearity (SN) which describes the solitonic waves in the molecular chain (MC) model. We set our study on the effectiveness of the acoustic longitudinal velocity (ALV) which is related to the acoustic longitudinal vibration to investigate the behavior of the MW patterns as well as the modulation instability (MI) gain. Its results are that the ALV creates instability zones, increases MI bands, and shortens the transition regime of the MW pattern. For a long time of simulation and a great enough value of the ALV, the MWs feature chaos-like motion. Alongside these results the ALV obvious itself as a tool control of MWs as well as an energy source for the propagation of diverse MW-shaped in the MC.

Ship Steering Adaptive CGS Control Based on EKF Identification Method

In recent years, marine autonomous surface vessels (MASS) have grown into a ship research issue to increase the level of autonomy of ship behavior decision-making and control while sailing at sea. This paper focuses on the MASS motion control module design that aims to improve the accuracy and reliability of ship steering control systems. Nevertheless, the stochastic sea and wind environment have led to the extensive use of filters and state observers for estimating the ship-motion-related parameters, which are important for ship steering control systems. In particular, the ship maneuverability Nomoto index, which primarily determines the designed ship steering controller’s performance, cannot be observed directly due to the model errors and the external environment disturbance in the process of sailing. Hence, an adaptive robust ship steering controller based on a closed-loop gain shaping (CGS) scheme and an extended Kalman filter (EKF) on-line identification method is explored in this paper. To verify the effectiveness of the proposed steering controller design scheme, the motor vessel YUKUN was taken as the control plant and a series of simulation experiments were carried out. The results show the advantages of the dynamic response performance of the proposed steering controller compared with the classical PD and traditional CGS controllers. Therefore, the proposed adaptive CGS steering controller would be a good solution for MASS motion control module design.

Grating-free 2.8 μm Er:ZBLAN fiber chirped pulse amplifier

Abstract We report on a grating-free fiber chirped pulse amplifier (CPA) at 2.8 μm for the first time. The CPA system adopted Er:ZBLAN fiber with large anomalous dispersion as the stretcher and germanium (Ge) rods as the compressor with a compact structure. High-energy picosecond pulses of 2.07 μJ were generated at the repetition rate of 100 kHz. Using highly dispersive Ge rods, the amplified pulses were compressed to 408 fs with a pulse energy of 0.57 μJ, resulting in a peak power of approximately 1.4 MW. A spectral broadening phenomenon in the main amplifier was observed, which was caused by the special gain shape of the Er:ZBLAN fiber amplifier in operation and confirmed by our numerical simulation. This compact fiber CPA system at 2.8 μm will be practical and meaningful for application fields.

Course keeping control strategy for large oil tankers based on nonlinear feedback of swish function

In order to solve the problem of the course instability and massive energy consumption of large oil tankers in navigation, a simple control strategy is proposed. Regard the large oil tanker as an unstable plant with zero points and poles in the right half plane, map its Nomoto model into the corresponding minimum phase system，then the final control law can be derived based on the closed-loop gain shaping algorithm. In this paper, to realize the purpose of energy saving, a nonlinear feedback link of swish function is applied in the system. According to the theoretical analysis above, take the large oil tanker KARASEA as a test plant, the simulation experiments are carried out in both the general sea conditions and severe sea conditions to verify if the controller is effective. Furthermore, for further test of the robustness of the controller, the Norrbin model of ship motion is also used to carry out the simulation experiments. According to the simulation results, it can be known that the control effect is satisfactory and has great ability in anti-interference. After adding the nonlinear feedback link, the average rudder angle decreases by 15%–20%，the change range of rudder angle decreases by 19%–30%, which means the decrease of the wear and energy consumption of steering engine, so the control strategy proposed in this paper has certain engineering practical significance.

A Coordination System between Decision Making and Controlling for Autonomous Collision Avoidance of Large Intelligent Ships

Large ships are typically with large inertia and longtime delay in motion, in prevailing collision avoidance methods, their maneuverability is generally neglected, there could be a dangerous situation if the system fails to control the ship course as ordered in a timely manner. This paper proposes a coordination system which consists of two algorithms for avoiding risk and then returning to scheduled waypoint. The avoiding risk algorithm are based on VO (velocity obstacle) method, the returning algorithm is derived from LOS (light of sight) guidance. For better performance, the ship model for simulation is a nonlinear Norrbin Model, with the controller improved by CGSA (closed loop gain shaping algorithm) method from traditional PID control, COLREGS (Convention on the International Regulations for Preventing Collisions at Sea) constrains are considered. To test the effectiveness of the proposed system, a series of complex scenarios including Imazu problem are applied.