Synchronous Velocity Research Articles

PIV experimental study on water-sediment two-phase flow in NACA0012 cascade

Abstract Sediment wear is one of the important reasons for the damage of hydraulic machinery components, and the motion characteristics of sediment are the key factors to determine the degree of wear damage. In order to reveal the mechanism of sediment wear of turbine guide vane, motion characteristics of sediment near the wall of NACA0012 cascade were studied by PIV test method. In this research, fluorescent and sediment particles were used as tracer particles respectively, and the particle images of solid and liquid phases were recorded by double-camera synchronous imaging method. Finally, the synchronous velocity field of solid and liquid phases was determined by correlation analysis of particle images. The experimental results show that the PIV test method can accurately determine the motion characteristics of the solid phase. There is velocity slip between the solid phase and the liquid phase, and the velocity deviation is related to the factors of particle characteristics and Reynolds number.

Synchronization of angular velocities of chaotic leader-follower satellites using a novel integral terminal sliding mode controller

Synchronization of satellite systems offers numerous advantages, including cost-effectiveness, flexibility, and extended area coverage. However, the presence of chaotic behavior in such systems poses substantial challenges. This paper investigates chaos in satellite systems and proposes a novel approach - the Novel Integral Terminal Sliding Mode (NITSM) controller - specifically designed for synchronizing the angular velocities of chaotic Leader-Follower satellite systems. The NITSM controller leverages limited-time features to eliminate chattering and exhibits remarkable robustness against external disturbances such as cosmic rays and solar storms. MATLAB simulations are conducted to validate the effectiveness of the proposed method, comparing the synchronization error of the NITSM controller with a common approach. The results demonstrate the superior performance of the Novel Integral Terminal Sliding Mode controller, showcasing reduced response time, robust behavior, and a substantial six-fold reduction in angular velocity synchronization error.

Assessing the impact of gait speed on gait stability using multi-scale entropy fused with plantar pressure signals.

Introduction: Walking speed can affect gait stability and increase the risk of falling. Methods: In this study, we design a device to measure the distribution of the plantar pressure to investigate the impact of the walking speed on the stability of the human gait and movements of the body. We fused the entropy acquired at multiple scales with signals of the plantar pressure to evaluate the effects of the walking speed on the stability of the human gait. We simultaneously collected data on the motion-induced pressure from eight plantar regions to obtain the fused regional pressure. To verify their accuracy, we obtained data on the plantar pressure during walking by using the force table of the Qualisys system. We then extracted the peak points and intervals of the human stride from pressure signals fused over three regions, and analyzed the mechanics of their regional fusion by using the regional amplitude-pressure ratio to obtain the distribution of the plantar pressure at an asynchronous walking speed. Furthermore, we introduced multi-scale entropy to quantify the complexity of the gait and evaluate its stability at different walking speeds. Results: The results of experiments showed that increasing the speed from 2 to 6km/h decreased the stability of the gait, with a 26.7% increase in the amplitude of pressure in the region of the forefoot. The hindfoot and forefoot regions were subjected to the minimal pressure at a speed of 2km/h, while the most consistent stress was observed in regions of the forefoot, midfoot, and hindfoot. Moreover, the curve of entropy at a speed of 2km/h exhibited a slow decline at a small scale and high stability at a large scale. Discussion: The multi-scale entropy increased the variation in the stability of the synchronous velocity of walking compared with the sample entropy and the analysis of regional fusion mechanics. Multi-scale entropy can thus be used to qualitatively assess the relationship between the speed and stability of the gait, and to identify the most stable gait speed that can ensure gait stability and posture control.

PDE-based distributed adaptive fault-tolerant attitude consensus of multiple flexible spacecraft

In this article, a distributed adaptive fault-tolerant control scheme is presented for the attitude consensus of multiple flexible spacecraft formulated by partial differential equations (PDEs). Each spacecraft is supposed to be actuated by a control torque on the rigid hub and a control force on the tip payload. First, a finite-time distributed observer is constructed to estimate the virtual leader's state for each follower spacecraft under local communication. Then, an individual controller is exploited for each follower spacecraft, which consists of an adaptive boundary control torque law to track the recovered attitude and velocity and an adaptive boundary control force law to eliminate the elastic deformation. Particularly, the parametric adaptation laws are incorporated to compensate the actuator faults and perturbations. The attitude synchronization errors, velocity synchronization errors, and elastic deformations can asymptotically stabilize to zero under the introduced controller. This work owns the following two major novelties. One is introducing a unified distributed control framework for the PDE-based attitude consensus of multiple flexible spacecraft. Another is developing a novel parametric adaptation strategy to accommodate the actuator faults. Lastly, comparative simulations verify and highlight the main results.

Fixed-Time Robust Networked Observers and Its Application to Attitude Synchronization of Spacecraft Systems.

This article studies fixed-time robust networked observers to estimate the information of a leader system containing unknown parameters. The construction of observers combines the internal model principle and the fixed-time control technique in a network with a directed topology. The observers are further applied to the fixed-time attitude synchronization problem for multiple spacecraft systems whose attitudes are represented by unit quaternion. Both rigorous analysis and numerical simulation demonstrate that the fixed-time synchronization of attitude and angular velocity between multiple spacecrafts and a specified leader system is achieved by the observer-based control design.

An Inexact-Penalty Method for GNE Seeking in Games With Dynamic Agents

We consider a network of autonomous agents whose outputs are actions in a game with coupled constraints. In such network scenarios, agents seek to minimize coupled cost functions using distributed information while satisfying the coupled constraints. Current methods consider the small class of multi-integrator agents using primal-dual methods. These methods can only ensure constraint satisfaction in steady-state. In contrast, we propose an inexact penalty method using a barrier function for nonlinear agents with equilibrium-independent passive dynamics. We show that these dynamics converge to an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon$</tex-math></inline-formula> -GNE while satisfying the constraints for all time, not only in steady-state. We develop these dynamics in both the full-information and partial-information settings. In the partial-information setting, dynamic estimates of the others' actions are used to make decisions and are updated through local communication. Applications to optical networks, velocity synchronization of flexible robots and wind farm optimization are provided.

Application of nonlinear stiffness mechanism on energy harvesting from vortex-induced vibrations

This study investigates the potential of vortex-induced vibration (VIV) as a renewable energy source, achieved when fluid flow interacts with a bluff body, inducing self-sustained oscillations through vortex shedding in the wake. While VIV research has traditionally focused on understanding its mechanisms and mitigating detrimental effects, interest in VIV energy harvesting has surged as a means to convert marine hydrokinetic (MHK) energy into usable electrical power. The nonlinear effects of two linear oblique springs on VIV energy harvesting are explored using the wake oscillator model, encompassing bistable and Duffing hardening stiffness. The study examines the response and energy harvesting performance while considering the impact of undeformed spring length, structural damping, and initial conditions on VIV energy conversion. Findings show that nonlinear stiffness application in the VIV system can broaden the synchronization bandwidth or reduce the VIV initiation flow speed. Bistable stiffness may broaden the synchronization velocity range, while Duffing hardening stiffness efficiently reduces the VIV initiation speed with small energy harvesting loss. Combining both stiffness types with appropriate control strategies presents a promising approach for achieving a broad synchronization VIV bandwidth and low initiation flow speed. Key parameters, such as the nondimensional parameter defining spring system obliquity and the ratio between undeformed spring length and cylinder diameter, significantly influence VIV response and energy harvesting. Moreover, optimal structural damping is vital to maximize energy harvesting efficiency, and understanding and controlling initial conditions are crucial for optimizing VIV synchronization bandwidth and energy harvesting efficiency for both bistable and Duffing hardening stiffness. This study provides valuable insights into VIV system dynamics and energy conversion potential with nonlinear springs, offering promising avenues for enhancing energy harvesting efficiency and inspiring further applications of nonlinear effects in VIV energy converters.

Joint Sequence Optimization-Based OFDM Waveform Design for Integrated Radar and Communication Systems

Orthogonal frequency division multiplexing (OFDM) is often used in integrated radar and communication (IRC) systems to improve the sharing of scarce spectrum resources and develop efficient solutions for intelligent vehicles. However, the communication symbols and pilot information carried by the integrated signal and the cyclic prefix of OFDM greatly limit the performance of the radar and communication. In this paper, we propose a joint sequence optimization-based OFDM waveform design method for IRC. First, the ambiguity function of the OFDM signal block and guard interval (GI) sequence are deduced in detail, and a new composite sequence with the cascading of Walsh code and m sequence is used to optimize the correlation of communication information, resulting in better ambiguity function characteristics. Then, a multivariate optimization model is explored, and the constrained particle swarm optimization algorithm based on weight allocation (WCPSO) is proposed to obtain the optimal GI sequence. It has lower sidelobe levels and higher information transmission efficiency. In addition, an improved received signal processing method is introduced to achieve stable communication synchronization and high-resolution distance and velocity estimation of multiple targets radar detection. Finally, numerical simulation results are presented to validate the effectiveness of the proposed method.

A Cooperative ADRC-Based Approach for Angular Velocity Synchronization and Load-Sharing in Servomechanisms

This paper is concerned with designing a dynamical synchronization (via a robust cooperative control) of an electromechanical system network (EMSN), consisting of nonidentical brushed DC motors, where only the motors’ angular velocity measurements are available. The challenge of the proposed approach is that the actuation provided by the motor needs to handle external disturbances to achieve the velocity tracking task and handle the interaction between both motors cooperatively to share the load and the disturbance rejection. The control’s basis involves differential flatness and an active disturbance rejection control (ADRC) framework augmented using ideas from the graph theory analysis and multi-agent networks. Experimental results verify the theoretical developments and show the effectiveness of the proposed control strategy despite unexpectedly changing load disturbance and parameters uncertainties. The proposed algorithm is suitable for embedded use due to its simplicity. It can be applied to a broad spectrum of mechatronic systems where dual-motor drive arrangements are necessary.

Synchronization of Four Axisymmetrically Distributed Eccentric Rotors in a Vibration System

This paper studies synchronization of a class of even pairs and symmetrically distributed eccentric rotors in a vibration system of a single mass body. A vibration system driven by four ERs with circular distribution structure and the same rotating direction is adopted as the dynamic model. The motion differential equations of the system are established based on Lagrange equation. The angular velocity and the phase of each rotor are perturbed by the average value of the synchronous velocity. The state equation of the system is obtained by applying the averaging method. According to the necessary condition of the steady-state motion, the synchronization condition and the dimensionless coupling torques of the system are deduced. The stability condition of the synchronous motion is derived by applying Lyapunov indirect method. The distribution law of the steady-state phase difference is discussed qualitatively by the numerical analysis of the theoretical results. Then combined with the numerical results, five sets of experiments are carried out on the experimental machine, which includes the sub-resonant state and the super-resonant state. The experimental results show that this vibration system has two super-resonant motion states and one sub-resonant motion state. The experiment proves the correctness of the theory, which can provide theoretical guidance for the design of this kind of vibration machine.

Development of a highly efficient rotary blanching machine for agricultural products

The article describes the operating conditions of a rotary blanching machine with synchronization of the angular velocity of the rotor with its metering device. Analytical equations describing the motion of a material particle during the transition from a paddle dispenser to a cassette container are derived. The basic requirement for the blanching machine design is justified, which consists in the fact that by the time the material weight detached from the dispenser blade to the cassette arrives, the lid of the latter must be fully open. This happens in the I-th, then in the II-th quadrant it closes and in the IV-th quadrant it opens.

Global Navigation Satellite System (GNSS) and other geospatial tools for various applications

Nowadays the Global Satellite Navigation Systems (GNSS) play a fundamental role in many areas as civil aviation, maritime and land navigation and geomatics, owing to the ability to provide worldwide, tridimensional, all-weather position, and velocity and time synchronization. The final product of the Global Navigation Satellite System exercise is the Three - Dimensional coordinates (3D) of the receiving station. These coordinates have been found reliable for most geospatial applications. However, some applications in data management required other information apart from geodetic coordinates. Hence; GNSS has been integrated with other methods of data acquisition to improve the quality of data for various applications. These have helped in solving a lot of problems where individual methods failed. This paper examines some satellite-based systems and reports the integration of GNSS with other data acquisition tools such as geodetic levelling, Remote Sensing, Geographic Information System (GIS), Inertial Navigation System (INS) and many others. In some cases, the synergy had resulted in other satellite or payload programs such as Gravity Recovery and Climate Experiment (GRACE), while it has improved the GNSS applications in so many areas. GNSS integration is therefore recommended for any application that requires the use of the location.

Beam–Wave Resynchronization Method of the Nonperiodic Meander Line and Folded-Waveguide SWS for TWTs

A beam-wave resynchronization (BWRS) method is proposed by changing the structural parameters of the nonperiodic (NP) slow wave structure (SWS) to reduce the phase velocity of the wave for traveling-wave tubes (TWT) application. The mathematical model and analysis for the BWRS method are introduced to investigate what condition the NP meander line SWS (ML-SWS) and the NP folded-waveguide SWS (FW-SWS) should satisfy so that the corresponding TWT can have a good output performance. As the applications, the NP zigzag ML-SWS and the concentric arc FW-SWS are designed according to the method, which is also compared with that designed according to the phase velocity synchronization (PVS). The simulated results show that, by using the BWRS method, the max output power (efficiency) of the zigzag ML-SWS TWT can be improved from 56.7 (18.9%) to 76.26 W (25.4%), and the bandwidth can be expanded from 6 to 10 GHz in the Ka-band. Furthermore, the max output power (efficiency) of the concentric arc FW-SWS TWT can be improved from 199 (27.6%) to 237 W (32.9%), and the bandwidth can be expanded more than twice in the W-band as before. These results indicate that the BWRS method is beneficial for the improvement of the output power and electron efficiency and may be beneficial for wider bandwidth.

Synchronization of the movement for multi-cylinder electrohydraulic servo driver

The article presents the problem of synchronization of piston rods velocity of the multi-cylinder electro-hydraulic servo drive. This task was presented on the example of a heavily loaded mobile caterpillar platform. For levelling the platform, a four-post electro-hydraulic support mechanism with a proportional valve control system was used. A linear external controller to synchronize the movement of the cylinders was used and a non-linear internal control system for each of the cylinders lifting the platform.

Investigation of High Interaction Efficiency of Sheet Beam TWT Based on All-Period Optimization and Beam Bunching Analysis

This article explores an extremely high beam&#x2013;wave interaction (BWI) efficiency technology of sheet beam traveling wave tubes (SBTWTs). An all-period phase velocity tapering optimization method is proposed to improve BWI efficiency of slow wave structure (SWS). The effects of the special electron bunching state and synchronous phase velocity change on the improvement of BWI efficiency generated by this method are analyzed. To solve the computational burden caused by dozens of parameters, self-developed 1-D nonlinear BWI code is used to calculate the BWI. For the best optimization effect, particle swarm optimization (PSO) algorithm selected from a variety of algorithms is utilized to search for the global optimal solution. The PIC simulation verification results show that by the all-period optimization method, the 80-period staggered double vane (SDV) SWS achieves a stable output power of 18 kW with 31 kV voltage 0.9-A current sheet beam at 30 GHz. The BWI efficiency of all-period phase velocity tapering SWS has reached 64.5&#x0025; at center frequency, the efficiency between 28 and 35 GHz exceeds 40&#x0025;.

Design Method of the Non-Periodic Meander Line and Folded-Waveguide SWS for TWTs Based on the Effective Phase Velocity Synchronization

A design method of the non-periodic meander line slow-wave structure (ML-SWS) and folded-waveguide slow-wave structure (FW-SWS) for traveling-wave tubes (TWTs) is proposed based on effective phase velocity synchronization. For the non-periodic ML-SWS and FW-SWS, the unified effective axial phase velocity seen by electrons, the dispersion equation, and the ideal beam-wave synchronization voltage are derived. The theoretical results demonstrate that the non-periodic ML-SWS and FW-SWS reported to date are consistent with the proposed method. Furthermore, two examples are presented as applications for the proposed method to the non-periodic SWS design, including the concentric arc FW-SWS and the zigzag ML-SWS. In addition, the simulated results of the two examples are in good agreement with the theoretical ones.

Sliding Mode Control with Sliding Perturbation Observer-Based Strategy for Reducing Scratch Formation in Hot Rolling Process

In a hot rolling process, excessive friction between rollers and steel plates may lead to the formation of scratches on the steel plate. To reduce scratch formation in the finishing mill of the hot rolling process, two techniques are proposed in this work: flying touch and velocity synchronization. The proposed flying touch method can reduce the impact of the generated force when the upper roller collides with the steel plate. In addition, the proposed velocity synchronization method can decrease the frictional force resulting from the velocity difference between the rollers and steel plate. The effectiveness of the proposed methods was demonstrated through simulations and experiments using a 1/40 downscaled hot rolling simulator. The simulations and experimental results demonstrate that the proposed methods can reduce the magnitudes of friction and impact forces that lead to scratch formation on the steel plates in the hot rolling process.

THE CONCEPT OF THE CLUTCH CONTROL LAW OF A CAR

Problem. The combination of comfortable automatic control of the car's transmission and at the same time preservation of high indicators of energy efficiency and cost of a design is possible by use of automatic mechanical transmission. The automatic clutch control system plays a significant role in providing comfort in such transmissions. The laws of controlling it are not perfect today. Goal. The aim of the work is to create a clear concept of the law of clutch control, which is easy to implement in a microcontroller and is well adapted to adapt to different driving conditions. Methodology. Graphically, the concept of the perspective law of clutch control is formed by two Bezier curves. One of the curves acts as a guide, and the other forms the surface of the law. Results. On the basis of the Bézier curves of the third degree the concept of the law is formed and the connection of the reference points of the Bézier curves with the physical parameters of the working process of vehicle movement is substantiated. Originality. The formation of the Bézier curve, which is decisive for the concept of the law, is formed on the basis of a typical working process of synchronization of the angular velocity of the clutch discs during the movement of the vehicle. In contrast to the laws of clutch control considered in the scientific literature, the proposed concept provides for clutch control outside the site of the synchronization process and ensures the avoidance of jerks during further acceleration. Practical value. The proposed algorithm provides full engagement of the clutch only after full synchronization of the clutch discs. The formation of a special form of the law in the form of a curve tangent to the abscissa axis reduces the jerks when closing the clutch discs.

Reinforcement Learning Based Multi-Agent Resilient Control: From Deep Neural Networks to an Adaptive Law

Recent advances in Multi-agent Reinforcement Learning (MARL) have made it possible to implement various tasks in cooperative as well as competitive scenarios through trial and error, and deep neural networks. These successes motivate us to bring the mechanism of MARL into the Multi-agent Resilient Consensus (MARC) problem that studies the consensus problem in a network of agents with faulty ones. Relying on the natural characteristics of the system goal, the key component in MARL, reward function, can thus be directly constructed via the relative distance among agents. Firstly, we apply Deep Deterministic Policy Gradient (DDPG) on each single agent to train and learn adjacent weights of neighboring agents in a distributed manner, that we call Distributed-DDPG (D-DDPG), so as to minimize the weights from suspicious agents and eliminate the corresponding influences. Secondly, to get rid of neural networks and their time-consuming training process, a Q-learning based algorithm, called Q-consensus, is further presented by building a proper reward function and a credibility function for each pair of neighboring agents so that the adjacent weights can update in an adaptive way. The experimental results indicate that both algorithms perform well with appearance of constant and/or random faulty agents, yet the Q-consensus algorithm outperforms the faulty ones running D-DDPG. Compared to the traditional resilient consensus strategies, e.g., Weighted-Mean-Subsequence-Reduced (W-MSR) or trustworthiness analysis, the proposed Q-consensus algorithm has greatly relaxed the topology requirements, as well as reduced the storage and computation loads. Finally, a smart-car hardware platform consisting of six vehicles is used to verify the effectiveness of the Q-consensus algorithm by achieving resilient velocity synchronization.

Combined control strategy for synchronization control in multi-motor-pendulum vibration system

Multi-motor-pendulum vibration systems have been applied to design shale shakers in petroleum drilling engineering. However, synchronization of the multi-motor-pendulum vibration system is instable on account of external load disturbance and systematic parameter restriction, which is a principal factor to decrease screening efficiency of shale shakers. In this work, to maintain stability synchronization of three eccentric rotors driven by three induction motors, a combined synchronous control strategy by tracking velocity and phase among the motors is proposed. First, the dynamic model of the system is deduced based on the Lagrange equation. Second, adjacent cross-coupled control combined with master–slave control is designed to control speed and synchronization between the motors in the multi-motor-pendulum vibration system. Third, to ensure the precision and robustness of the control system, the velocity error, phase error, and coupling error controllers are designed with reaching law algorithm and global sliding mode control; and stability of the controller system is validated by the Lyapunov theorem. Finally, the effectiveness of the control strategy is verified by numerical simulation and compared with previous findings. The results indicate that synchronous state and velocity overshoot of the motors can be controlled with the combined control strategy; and robustness of the control strategy is better than other methods.