Moment Disturbance Research Articles

A novel six-dimensional disturbance force and moment simulator for simulation of space micro-vibration environment

A novel six-dimensional disturbance force and moment simulator was developed because of the lack of a suitable vibration source for use in ground experiments. First, the dynamic relationship between the disturbance force, the disturbance moment generated at the center of the simulator platform, and the excitation forces of the six uniaxial actuators was established using the equivalent principle of force system. Then, the simulator structure was introduced and a modal analysis of this structure was performed. Finally, the simulator system was tested experimentally in both single-frequency experiments and multi-frequency experiments. The results obtained showed that the maximum error between the experimental values and the target values was 2.96%, which verified the correctness of the theoretical model of the six-dimensional disturbance force and moment simulator. Additionally, the multi-dimensional micro-vibration generation performance of the new simulator was verified. The proposed six-dimensional disturbance force and moment simulator can provide a micro-vibration environment to replace the real disturbance sources used in ground experiments and solve the problems caused by the lack of a vibration source for use in ground-based experiments.

A Robust Electric Power-Steering-Angle Controller for Autonomous Vehicles with Disturbance Rejection

This paper addresses the challenges associated with steering-angle control of electric power steering for autonomous vehicles, including steering model parameter uncertainty, dependency of self-aligning moment disturbance estimation on tire parameters, and compensation for the asymmetrical hysteresis behavior in the steering system caused by backlash in gears and static friction. A variable gain-sliding mode steering-angle controller is developed to deal with these challenges. Replacing the fixed gain with variable gain in the sliding mode controller solves two problems: it eliminates chattering, and it allows for automatic gain adjustment based on the maneuver and the size of the error, which eliminates the need for gain scheduling. Both fixed and variable gain-sliding mode controllers are derived and compared in simulations to prove the superiority of the variable gain controller. A sliding mode observer is developed to estimate the self-aligning moment disturbance without required information about the tire parameters, which makes it vehicle independent. The observer also treats the static friction as disturbance and estimates it along with any other disturbance, such as driver torque disturbance. The stability of both the controller and the observer is proven using Lyapunov stability theory. Simulation and experimental results proved the robustness of the presented methods to the above challenges.

Analysis of the Performance of Artificial Intelligence Algorithms in Dynamic Security Assessment

Electrical power systems around the world are currently operating near the limits of security and stability design, due to economic considerations and high rates of demand for electrical energy. During their operation, these systems are exposed to various types of disturbances, which in severe cases lead to their complete loss and complete shutdown. Dynamic security assessment is one of the most important tools used in evaluating the performance of electrical power systems after these disturbances occur. The traditional mathematical methods for evaluating dynamic security require complex computations and computational time so that they are not suitable for evaluating dynamic security in real time. To address these challenges, this research was conducted to provide new tools based on advanced techniques of artificial intelligence techniques capable of building a classifier to evaluate its dynamic behavior in real time. The research methodology in this study relied on the use of artificial intelligence techniques, including back propagation artificial neural network, decision tree algorithms (J48) and logistic model tree (LMT). Which was applied to the emergency database of the electrical power system (IEEE 14 Bus) test model after applying the most common types of electrical disturbances. The results of the artificial neural network technology showed high classification accuracy (98.958%) and a lower error rate compared to the decision tree (J48) and (LMT) algorithms. The results of this research are very important to improve the accuracy of the results of the dynamic security assessment classifier for the electrical power system, which makes it easier for the network operator to take appropriate protective measures in the moment of disturbances in the network.

Passive hydrodynamic interactions in minimal fish schools

It is a long-held perception that schooling swimming of fish can provide individuals in a group with additional hydrodynamic benefits. However how fish maintain a stable schooling formation, and the underlying interaction bases, are still unknown. This study aims to investigate effects of pure passive hydrodynamic interactions on schooling swimming and deal with whether fish can solely rely on the interactions to maintain a stable formation. The study is a pure numerical investigation based on a two-dimensional 3-DoF self-propelled model. Three two-fish formations, namely, tandem, side-by-side, and staggered formation, are investigated to explore the effects of the interactions. The study presents that the passive interactions do bring performance benefits to individuals, but swimmers cannot maintain the benefits for a long time when only relying on the pure passive interactions. The work also discusses different effects induced by the hydrodynamic interactions in some detail, including effects of deflection, wake, phase, attraction and repulsion. Essentially the hydrodynamic effects can be explained by considering time-varying pressure field. Due to the effects, a small disturbance or unbalanced moment may cause a large difference in the swimming directions of individuals in a group. The findings could offer some insights into understanding the schooling swimming mechanism.

Data-Driven Distributionally Robust MPC for Constrained Stochastic Systems

In this letter we introduce a novel approach to distributionally robust optimal control that supports online learning of the ambiguity set, while guaranteeing recursive feasibility. We introduce conic representable risk, which is useful to derive tractable reformulations of distributionally robust optimization problems. Specifically, to illustrate the techniques introduced, we utilize risk measures constructed based on data-driven ambiguity sets, constraining the second moment of the random disturbance. In the optimal control setting, such moment-based risk measures lead to tractable optimal controllers when combined with affine disturbance feedback. Assumptions on the constraints are given that guarantee recursive feasibility. The resulting control scheme acts as a robust controller when little data is available and converges to the certainty equivalent controller when a large sample count implies high confidence in the estimated second moment. This is illustrated in a numerical experiment.

A Structure-inspired Disturbance Observer for an Underwater Vehicle*

An observer is designed to estimate the disturbance force and moment acting on an underwater vehicle. The observer design leverages the structure of the nonlinear dynamic model. Provided the dynamics are sufficiently slow, the designer may choose observer parameters to ensure that the estimate error is locally, ultimately bounded and converges to an arbitrarily small neighborhood of the origin.

On Structural Parameter Optimization Method for Quad Tilt-Wing UAV Based on Indirect Size Estimation of Domain of Attraction

To deal with the flexibility in the electric aircraft design, this study develops a structural parameter optimization method. The quad tilt-wing aircraft exhibits rotary-wing flight and fixed-wing flight modes by tilting its wings. This study focuses on the domain of attraction, which is a class of state vectors that converge to a static equilibrium point after infinite time. The method indirectly estimates the size of domain of attraction of an aircraft by calculating the radius of a sphere that is encompassed by the domain. In addition, after investigating the relationship between change in structural parameters and the size of the domain of attraction, the structural parameters that maximize the size of the domain are surveyed. The effectiveness of the proposed method is demonstrated for the optimization of the quad tilt-wing aircraft. The quad tilt-wing aircraft exhibits rotary-wing flight and fixed-wing flight modes by tilting its wings. As the characteristics of the dynamics of the quad tilt-wing aircraft demonstrate a significant nonlinear change depending on the tilt angle of the wing, we propose a method to optimize the structural parameters for an easy control of the aircraft. Simulation results show that the optimization scheme identifies the parameters that enable the aircraft to perform agile control to address a disturbance moment. Further, although the same controller is used in the original and optimized aircraft, the optimized aircraft can handle a disturbance in a shorter time when compared with the original aircraft.

Attitude stability control of micro-nano satellite orbit maneuver based on bias momentum

In this paper, an attitude stability control strategy based on cold air micro propulsion microsatellite orbital maneuver is designed. Firstly, the influence of environmental disturbance moment, uncertainty of rotational moment of inertia and thrust eccentricity moment on the attitude stability of the micro-nano-satellite is considered, and the attitude dynamics model of the micro-nano-satellite based on biased momentum wheel and magnetic moment device is established. Then, the disturbance moments such as environmental disturbance moments, rotational inertia uncertainty and thrust eccentricity moments are analyzed. In order to suppress the influence of various internal and external disturbance factors on the stability of the micro-nano-satellite during the deorbiting process, a robust adaptive sliding mode variable structure controller is designed. The designed robust adaptive sliding mode controller is able to compensate for various disturbances adaptively. The robust adaptive sliding-mode variable structure controller is designed with a reasonable distribution of torque considering the characteristics of bias momentum wheel control and magnetic control. Finally, numerical simulations are performed, and the simulation results show that the system has good robustness.

Flexible spacecraft attitude maneuver via adaptive sliding mode control and mixed component synthesis vibration suppression

<p indent=0mm>A mixed component synthesis vibration suppression method (MCSVS) is proposed to solve the problem of residual vibration of flexible attachments, which is difficult to control effectively. Theorems and inferences are provided, and their proofs are performed. Aiming at the problem that the attitude controllers cannot suppress the vibration of flexible attachments in spacecraft attitude maneuver, a strategy combining the MCSVS method with an attitude control method is proposed. Considering the existence of moment of inertia variation and external disturbance of spacecraft, an adaptive sliding mode variable structure controller is proposed. By introducing a sliding mode boundary layer and the update rate of the torque parameter, the disadvantages of torque chattering and parameter dependence are eliminated. Finally, the joint application of the MCSVS method and the adaptive variable structure controller is realized with the assistance of piezoelectric intelligent materials. Simulation results show that the control strategy without the MCSVS method cannot suppress the vibration of flexible attachments. After combining the MCSVS method with the attitude control method, the residual vibration is well controlled, and the attitude accuracy is improved.

Replacement of In-Orbit Extended Kalman Filter for Spacecraft Orbit Estimation via Neural Networks

Spacecraft orbit estimation on-board a spacecraft could be utilized in order to minimize measurement and process noise effects. This could be done through an estimation algorithm such as Kalman Filter (KF) or Extended Kalman Filter (EKF). EKF utilizes an orbital motion model of the spacecraft. The model is characterized by high degree of complexity, nonlinearity, and coupling between system states. This complexity increases the computational load of the EKF and may represent a serious problem for real-time application over the spacecraft on-board computer. This is due to limited spacecraft on-board computer computational resources. In order to overcome this problem, an algorithm based on Neural Networks is developed. The required training data set has been obtained via EKF. Various disturbance forces and moments are considered, such as earth’s oblatenss effect till (J4), aerodynamic drag, solar radiation pressure, gravity gradient moment, and magnetic disturbance moments. The developed neural networks algorithm is applied to a verified test case spacecraft, which utilizes a GPS receiver in order to obtain spacecraft position measurements. The developed neural networks algorithm has the same accuracy of the EKF with an average execution time equal to 82% of EKF. This indicates better applicability for real-time application.

Управляемый тензор инерции космического аппарата трансформируемой конструкции

A simplified model of a transformable spacecraft is considered, including a rod-type transformation mechanism with movable weights. The mechanism can be used to adapt the dynamic properties of the spacecraft to the environment or the operating conditions of on-board systems, for example, to counter the moments of external disturbances during attitude control and angular stabilization. By changing the position of the transformation mechanism, the spacecraft inertia tensor can be put in diagonal form, which makes it possible to exclude the force interconnections between the channels and to eliminate the constant component of the gravitational moment. For a simplified model of the transformation mechanism, we establish the analytical dependence of the components of the inertia tensor on the parameters determining the position of the transformation mechanism. It is shown that by adjusting the moving mass, which is 0.5% of the entire spacecraft mass, we obtain the spacecraft configuration that ensures the diagonality of the inertia tensor.

Iterative Sliding Mode and Increment Feedback Attitude Control for On-Orbit Capturing Process of Spacecraft

According to the characteristics of spacecraft capturing noncooperative targets in orbit, an increment feedback controller based on nonlinear iterative sliding mode is presented. Firstly, the attitude tracking error equation is established, and then, an increment feedback control law based on bounded iterative sliding modes is proposed, which does not need to estimate the uncertain moment of inertia and external disturbances. For comparing, an adaptive sliding mode controller has been designed in the paper. Some numerical simulations have been given in the presence of spacecraft on-orbit capturing noncooperative target, and the simulation results show that the increment feedback controller has strong robustness to the unknown parametric variations and external disturbances and has a smaller control input torque in control process.

Control of underactuated marine crafts with matched disturbances

ABSTRACT Stabilisation of marine craft in the presence of disturbances is important to many offshore activities. The process of stabilising a marine craft using the actuators is known as dynamic positioning, and is challenging for underactuated craft. In our work, we develop a robust dynamic positioning controller for an underactuated marine craft that ensures input-to-state-stability with respect to matched disturbances. Using the strict Lyapunov function approach of Malisoff and Mazenc [(2009). Constructions of strict Lyapunov functions. Springer-Verlag], we show that the proposed controller ensures uniform global asymptotic stability of the desired equilibrium when there are no disturbances. We also show that the closed-loop system is input-to-state stable with respect to matched environmental force and moment disturbances. Finally, we illustrate the performance of the proposed controller through simulations.

A Visual Grasping Strategy for Improving Assembly Efficiency Based on Deep Reinforcement Learning

The adjustment times of the attitude alignment are fluctuated due to the fluctuation of the contact force signal caused by the disturbing moments in the compliant peg‐in‐hole assembly. However, these fluctuations are difficult to accurately measure or definition as a result of many uncertain factors in the working environment. It is worth noting that gravitational disturbing moments and inertia moments significantly impact these fluctuations, in which the changes of the peg concerning the mass and the length have a crucial influence on them. In this paper, a visual grasping strategy based on deep reinforcement learning is proposed for peg‐in‐hole assembly. Firstly, the disturbing moments of assembly are analyzed to investigate the factors for the fluctuation of assembly time. Then, this research designs a visual grasping strategy, which establishes a mapping relationship between the grasping position and the assembly time to improve the assembly efficiency. Finally, a robotic system for the assembly was built in V‐REP to verify the effectiveness of the proposed method, and the robot can complete the training independently without human intervention and manual labeling in the grasping training process. The simulated results show that this method can improve assembly efficiency by 13.83%. And, when the mass and the length of the peg change, the proposed method is still effective for the improvement of assembly efficiency.

IMPACT OF METEOROLOGICAL STORMS ON THE E-REGION OF THE IONOSPHERE IN 2017–2018

The paper presents the results of observations of the sporadic Es layer during the period of meteorological disturbances in Kaliningrad in October 2017 and 2018 under quiet geomagnetic conditions. During the meteorological storms (October 29–30, 2017 and October 23–24, 2018), significant changes occurred in the dynamics of the Es-layer critical frequency. Observations of atmospheric and ionospheric disturbances in the Kaliningrad region show that the delay between the ionospheric response and the moment of maximum disturbances in atmospheric parameters is about 3 hours. These phenomena at the heights of the E-region might have been caused by propagation of acoustic-gravity waves generated by convective processes in the lower atmosphere during periods of a meteorological storm. Intensification of turbulent processes in the lower thermosphere leads to an increase in the atmospheric density and, accordingly, to higher recombination rates. This leads to a rapid decrease in the concentration of ions and, consequently, to a decrease in the critical frequency of the sporadic layer below the sensitivity threshold of ionosondes.

Влияние метеорологических штормов на область Е ионосферы в 2017–2018 гг

The paper presents the results of observations of the sporadic Es layer during the period of meteorological disturbances in Kaliningrad in October 2017 and 2018 under quiet geomagnetic conditions. During the meteorological storms (October 29–30, 2017 and October 23–24, 2018), significant changes occurred in the dynamics of the Es-layer critical frequency. Observations of atmospheric and ionospheric disturbances in the Kaliningrad region show that the delay between the ionospheric response and the moment of maximum disturbances in atmospheric parameters is about 3 hours. These phenomena at the heights of the E-region might have been caused by propagation of acoustic-gravity waves generated by convective processes in the lower atmosphere during periods of a meteorological storm. Intensification of turbulent processes in the lower thermosphere leads to an increase in the atmospheric density and, accordingly, to higher recombination rates. This leads to a rapid decrease in the concentration of ions and, consequently, to a decrease in the critical frequency of the sporadic layer below the sensitivity threshold of ionosondes.

Керування вектором тяги ракетного двигуна вдувом продуктів детонації в надзвукову частину сопла

For solving non-traditional problems of rocket flight control, in particular, for the conditions of impact of a nuclear explosion, non-traditional approaches to the organization of the thrust vector control of a rocket engine are required. Various schemes of gas-dynamic thrust vector control systems that counteract impact actions on the rocket were studied. It was found that the dynamic characteristics of traditional gas-dynamic thrust vector control systems do not allow one to solve the problem of counteracting impact actions on the rocket. Appropriate dynamic characteristics can provide a perturbation of the supersonic flow by injecting into the nozzle the detonation products with the main shock wave propagating in the supersonic flow. This way to perturb the supersonic flow in a rocket engine nozzle is investigated in this paper. In order to identify the principles of producing control forces and provide a perturbation of the supersonic flow by injecting into the nozzle the detonation products with the main shock wave propagating in the supersonic flow, a computer simulation of the nozzle flow was performed. The nozzle of the 11D25 engine developed by Yuzhnoye State Design Office and used in the third stage of the Cyclone-3 launch vehicle was taken as a basis. The thrust vector control scheme relies on the use of the main fuel component detonation. The evolution of the detonation wave in the supersonic flow of the combustion chamber nozzle was simulated numerically. According to the nature of the perturbation propagation in the nozzle, the lateral force from the perturbation has an alternating character with the perturbation stabilization in sign and magnitude when approaching the critical nozzle section. The value of the relative lateral force is sufficient for counteracting large disturbing moments of short duration. Thus, the force factors that can be used to control the rocket engine thrust vector are identified. Further research should focus on finding the optimal location of the detonation product injection in order to prevent mutual compensation of force factors.

HAPPINESS FACING TO THE PERFIDIOUS AND INVISIBLE CHALLENGE OF COVID-19

In this study we are dealing with a new aspect of the problem in discussion that is the pursuing of Happiness, supported by institutions and regulations in the domain, but in moments of disturbances, in moments of crisis. We need to have goals, actions to be accomplished, in order to achieve the desired state of satisfaction or Happiness that anyone can have. We are in the presence of a double determination: the first one is represented by the material, especially money background, influencing the life and activities of households and entities and, the second one is represented by the reverse action that is of Happiness affecting the management and the activities of individuals, households and firms/organizations. The survey of the literature in the field, data from the World Health Organization, from the national authorities, analyses of the specialists in healthcare and economics, reports of the people in difficult health and economic situations are used in order to be able to synthesize the situation at this moment and possible forecasts regarding medical healing and economic recovery of the countries. Nothing is hard to manage, if you have knowledge, required abilities/skills to anticipate challenges or to make fast and right decisions, altogether at Micro and Macro-levels, in the benefit of all parts involved in. The huge interest is to reestablish the economies, mental health of people, i.e. the elements of a functional economic infrastructure.

“Please call my daughter”: Ethical practice in dementia care as an art of dwelling

This article aims to extend the current understanding of ethical practice within a dementia context, in which people living with dementia are often taken for granted as mere beneficiaries of care, rather than as co-producers in day-to-day care practice. Building on a decade of voluntary work and a year of fieldwork (including six weeks’ intensive observation of nightlife) at a Jewish care home in London, I pay attention to the affective dimension of ethical practice at the moment of sleep disturbance of a resident with dementia. Inspired by Heidegger’s concept of dwelling, I understand the episode not as pathological, but as a process through which ethical subjects emerge in the making of ongoing, entangled ethical endeavors. I argue that ethical practice is neither predetermined nor random: rather, it is the way in which those involved continuously respond and attune to the ever-changing circumstances: what I call an ‘art of dwelling’.

An Archive of Violence

AbstractThis essay makes the case for sensationalism as an archive of violence. It traces the ways in which the Mexican filmmaker Felipe Cazals draws from the sensationalist tabloid Alarma! in the making of his film Las Poquianchis (1976), a film version of the story of human trafficking that led the tabloid to popularity. The visuality of sensationalism works mostly in the service of power: it keeps certain kinds of violence both out of sight and overexposed. Cazals and other artists and writers who draw materials from sensationalism complicate this visuality and counter it, but they do so by staying close to the kind of obscenity characteristic of sensationalism. The last segment of the essay revisits Elaine Scarry's seminal analysis of the relationship between language and pain. It offers a frame of interpretation for the most disturbing moments in sensationalism and in Cazals's film: moments defined by the screening of gruesome violence, traumatic bodily injury, violence by sexual means, and death.