Speed Reversal Research Articles

Investigation of naval submarine dynamic equilibrium, balancing and reverse speed considering control considerations

Investigation of naval submarine dynamic equilibrium, balancing and reverse speed considering control considerations

PERANCANGAN ROBOT BERODA DENGAN SISTEM KENDALI BERBASIS IOT DAN GUI MENGGUNAKAN SMARTPHONE ANDROID

A Wheeled Mobile Robot (WMR) is a robot that is often used for transporting a good in the industry. This study was conducted to integrate WMR with the Internet of Things (IoT) to control robots remotely, whereas wheeled robots with a DC motor driving power. Graphical User Interface (GUI) is applied for controlling this device via an Android smartphone. As a result; the robot can be driven via GUI commands with a forward speed = 0.535 m/s; reverse speed = 0.4 m/s; right-hand rotation speed = 25.2 rpm; left-hand rotation speed = 23.4 rpm. These robot performances are strongly influenced by the design, construction of the robot, the load received by the driving motor, and the capacity of the driving motor.

Dual stochastic descriptions of streamflow dynamics under model ambiguity through a Markovian embedding

Hamilton–Jacobi–Bellman equation (HJBE) and backward stochastic differential equation (BSDE) are the two faces of stochastic control. We explore their equivalence focusing on a system of self-exciting and affine stochastic differential equations (SDEs) arising in streamflow dynamics. Our SDE is a finite-dimensional Markovian embedding of an infinite-dimensional jump-driven process called the superposition of continuous-state branching processes (a supCBI process). We formulate new ergodic control problems to evaluate the worst-case streamflow discharge in the long run and derive their HJBEs and ergodic BSDEs. The constant ambiguity aversion classically used in assessing model ambiguity must be modified in our case so that the optimality equations become well-posed. With a suitable modification of the ambiguity-aversion coefficient depending on the distributed reversion speed, we demonstrate that the solutions to the optimality equations are equivalent to each other in the sense that they lead to the same result. Finally, we apply the proposed framework to the computation of realistic cases with an existing record of discharge through a numerical Markovian embedding.

A speed loop control method of a laser tracing measurement control system

In a laser tracking control system, a motor drives the load to achieve continuous forward and reverse rotation speed control, and the magnitude of the load changes periodically during the motor rotation to realize tracking. Based on these characteristics, we propose an integral-separated improved variable universe fuzzy proportional-integral (PI) control method with torque feedforward compensation method in this study. The proposed method achieves the control performances of fast response, high steady-state accuracy, and strong anti-interference. The conventional fuzzy PI control method achieves good performance only in the unidirectional acceleration of a motor; therefore, we have improved its fuzzy rules, and designed a novel universe contraction–expansion factor. Additionally, a load torque observer is introduced to observe and compensate for the external load and to further improve the anti-interference performance of the tracking control system. The experimental results demonstrate that the integral-separated improved variable-universe fuzzy PI control method achieves better performance in the forward and reverse speed regulation processes of the motor. The overshoot is 92% less than that of the conventional PI control when the target speed is set to ±500 rpm. The Luenberger observer is introduced to observe and compensate for the load torque. After the stabilizing the speed and applying an external load of 0.2 N m to the motor, the maximum speed reduction is observed to be 59% less than that obtained using the conventional PI control. The improved PI control method satisfies the speed loop control requirements of the laser tracking control system and can improve the steady-state tracking accuracy and robustness of the system.

Impact of jet velocity profile on the propulsive performance and vortex ring formation of pulsed jet propulsion

A squid-inspired jet propulsion system that indudes a deformable body and a nozzle exit attached to it is numerically studied. By prescribing the body deformation during a single discharge, we examine the impact of jet speed profiles on the vortex ring formation and propulsion performance of the system. Our results show that a secondary vortex ring following the leading vortex ring can be produced by the reverse cosine jet speed pattern at a given maximum stroke ratio, and for the other profiles (i.e., constant, cosine, reverse cosine, half cosine and rever half cosine styles) only distributed vortices are seen behind the leading vortex ring. The constant jet speed produces the largest time-averaged thrust due to jet momentum flux related thrust associated with its large jet speed. Except for the constant speed style, the largest mean thrust production and propulsion factor are obtained by the reverse cosine profile among the other four styles attributed to the formation of the secondary vortex ring. Nevertheless, this secondary vortex ring would not be produced at a small maximum stroke ratio for the reverse cosine speed fashion. We also find that the mean thrust production can reach a maximum under a specific maximum stroke ratio (Γm = 7.60) when two vortex rings are produced. This work may provide insight into the mechanical and control design of jet-based biomimetic propellers and robots.

A Fuzzy-Random Extension of Jamshidian’s Bond Option Pricing Model and Compatible One-Factor Term Structure Models

The primary objective of this paper is to expand Jamshidian’s bond option formula and compatible one-factor term structure models by incorporating the existence of uncertainty in the parameters governing interest-rate fluctuations. Specifically, we consider imprecision in the parameters related to the speed of reversion, equilibrium short-term interest rate, and volatility. To model this uncertainty, we utilize fuzzy numbers, which, in this context, are interpreted as epistemic fuzzy sets. The second objective of this study is to propose a methodology for estimating these parameters based on historical data. To do so, we use the possibility distribution functions capability to quantify imprecise probability distributions. Furthermore, this paper presents an application to the term structure of fixed-income bonds with the highest credit rating in the Euro area. This empirical application allows for evaluating the effectiveness of the fuzzy extension in fitting the dynamics of interest rates and assessing the suitability of the proposed extension.

A stochastic SIS epidemic infectious diseases model with double stochastic perturbations

In this paper, a stochastic SIS epidemic infectious diseases model with double stochastic perturbations is proposed. First, the existence and uniqueness of the positive global solution of the model are proved. Second, the controlling conditions for the extinction and persistence of the disease are obtained. Besides, the effects of the intensity of volatility [Formula: see text] and the speed of reversion [Formula: see text] on the dynamical behaviors of the model are discussed. Finally, some numerical examples are given to support the theoretical results. The results show that if the basic reproduction number [Formula: see text], the disease will be extinct, that is to say that we can control the threshold [Formula: see text] to suppress the disease outbreak.

Fuzzy Random Option Pricing in Continuous Time: A Systematic Review and an Extension of Vasicek’s Equilibrium Model of the Term Structure

Fuzzy random option pricing in continuous time (FROPCT) has emerged as an active research field over the past two decades; thus, there is a need for a comprehensive review that provides a broad perspective on the literature and identifies research gaps. In this regard, we conducted a structure review of the literature by using the WoS and SCOPUS databases while following the PRISMA criteria. With this review, we outline the primary research streams, publication outlets, and notable authors in this domain. Furthermore, the literature review revealed a lack of advancements for the equilibrium models of the yield curve. This finding serves as a primary motivation for the second contribution of this paper, which involves an extension of Vasicek’s yield curve equilibrium model. Specifically, we introduce the existence of fuzzy uncertainty in the parameters governing interest rate movements, including the speed of reversion, equilibrium short-term interest rate, and volatility. By incorporating fuzzy uncertainty, we enhance the model’s ability to capture the complexities of real-world interest rate dynamics. Moreover, this paper presents an empirical application of the proposed extension to the term structure of fixed-income public bonds in European Union. The empirical analysis suggests the suitability of the proposed extension of Vasicek’s model for practical applications.

Back EMF-Based Dynamic Position Estimation in the Whole Speed Range for Precision Sensorless Control of PMLSM

Back EMF-based sensorless control strategies for permanent magnet linear synchronous motor (PMLSM) have the potential to simplify the mechatronic system, reduce the cost and prolong the service life. However, the poor performance in the low-to-zero speed region limits their application range. In this paper, a novel back electromotive force (EMF)-based mover position estimator is proposed to achieve consistent good accuracy in the whole speed range including high speed, medium speed, low speeds, temporary standstill, and speed reversals. The three-phase flux linkages are obtained by directly calculating the integration of back EMF. To overcome the curve drift caused by the integrator, this paper proposes a jumping correction algorithm (JCA) and a uniform correction algorithm (UCA). The mover position is calculated from the corrected flux linkages. This paper also realizes a closed-loop sensorless trajectory tracking control system using the proposed position estimator. Experimental results on a PMLSM demonstrate that the proposed position estimator can guarantee stability and accuracy in the whole speed range. Compared with existing back EMF-based methods working only well in high-speed region and usually with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$mm$</tex-math></inline-formula> -level accuracy, the proposed method achieves an accuracy of sub-200 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu m$</tex-math></inline-formula> regardless of the reference trajectory, and has exciting prospect in industrial applications.

Online estimations for electrical and mechanical parameters of the induction motor by extended Kalman filter

In this study, a novel extended Kalman filter (EKF)-based observer is designed to increase the number of estimated states and parameters of the induction motor (IM). To perform the online estimations of stationary axis components of stator currents and rotor fluxes ([Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) as well as rotor mechanical speed ([Formula: see text]), which are required for direct vector control (DVC) systems along with the load torque ([Formula: see text]), rotor resistance ([Formula: see text]), magnetizing inductance ([Formula: see text]), and the reciprocal of the total inertia of the system ([Formula: see text]), the proposed EKF uses the measured phase currents and voltages together with the measured rotor speed. To estimate all of the five states ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) plus four parameters ([Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]), the proposed EKF-based observer does not include a switching operation nor a hybrid structure, which is a common approach in the literature for online state and parameter estimations of IMs and results in design complexity and computational load increase. In simulation studies, the estimation performance of the proposed EKF is tested and verified under the variations of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] in DVC systems that perform the speed and position controls of IM. The obtained results confirm the satisfying tracking performances and thus better control achievements of the speed and position controlled IM drives in this paper. Moreover, the proposed EKF and the EKF without [Formula: see text]-estimation are compared in the position control system to demonstrate the importance of the [Formula: see text] estimation. In the comparison, nearly 10 times less mean square error (MSE) is obtained in the estimations of [Formula: see text], [Formula: see text], [Formula: see text], and the magnitude of the rotor flux for the proposed EKF. Finally, the proposed EKF algorithm is tested and verified in real-time experiments with a challenging speed reversal scenario causing nonlinear variations in both [Formula: see text] and [Formula: see text].

Implementation of a new flux rotor based on model reference adaptive system for sensorless direct torque control modified for induction motor

Introduction. In order to realize an efficient speed control of induction motor, speed sensors, such as encoder, resolver or tachometer may be utilized. However, some problems appear such as, need of shaft extension, which decreases the mechanical robustness of the drive, reduce the reliability, and increase in cost. Purpose. In order to eliminate of speed sensors without losing. Several solutions to solve this problem have been suggested. Based on the motor fundamental excitation model, high frequency signal injection methods. The necessity of external hardware for signal injection and the adverse influence of injecting signal on the motor performance do not constitute an advantage for this technique. Fundamental model-based strategies method using instantaneous values of stator voltages and currents to estimate the rotor speed has been investigate. Several other methods have been proposed, such as model reference adaptive system, sliding mode observers, Luenberger observer and Kalman filter. The novelty of the proposed work consists in presenting a model reference adaptive system based speed estimator for sensorless direct torque control modified for induction motor drive. The model reference adaptive system is formed with flux rotor and the estimated stator current vector. Methods. The reference model utilizes measured current vector. On the other hand, the adjustable model uses the estimated stator current vector. The current is estimated through the solution of machine state equations. Practical value. The merits of the proposed estimator are demonstrated experimentally through a test-rig realized via the dSPACE DS1104 card in various operating conditions. The experimental results show the efficiency of the proposed speed estimation technique. Experimental results show the effectiveness of the proposed speed estimation method at nominal speed regions and speed reversal, and good results with respect to measurement speed estimation errors obtained.

Оценка геометрических параметров отпечатка и давления в зоне контакта рабочего инструмента с заготовкой при реверсивном поверхностном пластическом деформировании

The article presents the results of modeling and determining the influence of the parameters of reverse surface plastic deformation on the geometric characteristics of the plastic imprint and the pressure in the contact zone of the working tool under static and reverse impact. Using the software for 3D design SOLID WORKS-2019 and computational modeling in ANSYS-19.1, a finite element model of the contact zone was built to determine the geometric characteristics of the plastic indentation and the contact pressure between the working tool and the surface of the workpiece, depending on the geometry of the working tool, reversing frequency its rotation, the initial angle of installation and the amplitude of the angle of reverse rotation of the working tool. Based on the obtained results, to increase the pressure in the contact zone of the working tool with the workpiece, which affects the degree of hardening and smoothing of microroughnesses of the workpiece surface and the formation of compressive residual stresses, it is recommended to use the following parameters and hardening modes: working roller with a diameter of 20–30 mm, with a profile radius of 2 –2.5 mm, distance between tops of working roller profile 1.5–2 mm, initial installation angle of the working roller 90о, amplitude of the reverse rotation angle of the working roller ±6 – ±8о and reverse speed of the working roller 200–240 double strokes/min.

Normal and abnormal BCM rules realized in BaTiO3/Nb:SrTiO3 heterojunction

Recently, the ferroelectric memristors have attracted much attention for neuromorphic computing and artificial intelligence because of fast reversal speed, excellent fatigue, nondestructive readout. In this paper, the basic functions of biological synapses including paired-pulse facilitation/depression (PPF/PPD), spike-rate/amplitude-dependent plasticity (SRDP/SADP) have been successfully simulated in BaTiO3/Nb:SrTiO3 epitaxial heterojunction. Furthermore, normal and abnormal Bienenstock-Cooper-Munro (BCM) learning rules with sliding frequency threshold have been found from SRDP under positive and negative bias, respectively. This provides support for encoding and deep learning in the application of neuromorphic computing.

The SEV-SV Model—Applications in Portfolio Optimization

This paper introduces and studies a new family of diffusion models for stock prices with applications in portfolio optimization. The diffusion model combines (stochastic) elasticity of volatility (EV) and stochastic volatility (SV) to create the SEV-SV model. In particular, we focus on the SEV component, which is driven by an Ornstein–Uhlenbeck process via two separate functional choices, while the SV component features the state-of-the-art 4/2 model. We study an investment problem within expected utility theory (EUT) for incomplete markets, producing closed-form representations for the optimal strategy, value function, and optimal wealth process for two different cases of prices of risk on the stock. We find that when EV reverts to a GBM model, the volatility and speed of reversion of the EV have a strong impact on optimal allocations, and more aggressive (bull markets) or cautious (bear markets) strategies are hence recommended. For a model when EV reverts away from GBM, only the mean reverting level of the EV plays a role. Moreover, the presence of SV leads mainly to more conservative investment decisions for short horizons. Overall, the SEV plays a more significant role than SV in the optimal allocation.

Microstructure and high-frequency price discovery in the soybean complex

We develop a theoretical framework and propose a relevant empirical analysis of the soybean-complex prices’ cointegration relationships in a high-frequency setting. We allow for heterogeneous expectations among traders on the multi-asset price dynamics and characterize the resulting market behaviour. We demonstrate that the asset prices’ autoregressive matrix rank and the speed of reversion towards the long-term equilibrium are related to the market realized and potential liquidity, unlike the cointegrating vector. Our empirical application to the soybean complex, where we control for volatility, supports our theoretical results when the price idleness of the different assets is properly accounted for. Our analysis further suggests that the presence of cointegration among assets is related to the time of day and the contract maturities traded at a given time.

Numerical and Experimental Study on the Shutdown Transition Process of a Large Axial Flow Pump System Focusing on the Influence of Gate Control

Large axial flow pump systems (LAPS) are widely used in coastal pump stations. In the actual operation of a LAPS, various accidents often occur during shutdown due to the unreasonable control of stop flow measures such as the gate. In this paper, based on the secondary development of Flowmaster numerical software, a numerical simulation study was conducted on the shutdown process of a LAPS with different gate control laws. It was found that the MBV of the shutdown process was greater if the gate was closed more slowly after the unit was powered off. When a 30 s shutdown scheme was used, the MBV during shutdown was 1.63Qr. When a 60s long shutdown scheme was used, the MBV during shutdown was 1.67Qr, an increase of 2.45%. When the 150s long shutdown scheme was used, the MVV during the stopping process reached 1.68Qr, which is an increase of 3.07%. The shutdown method of closing the gate in advance can significantly improve the violent fluctuations of the KCPs of a LAPS during the shutdown transition and will effectively reduce the backflow and the reverse speed of the pump during the shutdown process. Taking the total gate closing time of 120 s as an example, when the 25% gate was closed in advance, the MBV and MRS during the shutdown process were reduced by 14.31% and 1.93%. When the shutdown scenario of preclosing 100% of the gates was adopted, the MBV and MRS during shutdown were reduced by 96.31% and 100%.

Stationary distribution and extinction of a stochastic HLIV model with viral production and Ornstein–Uhlenbeck process

In the past few decades, the human immunodeficiency virus (HIV), as a deadly pathogen, has imposed great harmful effects on human health. In addition, from the viewpoint of the microscopic, the interference of random factor exists in the process of virus replication. However, there are few works devoted to the theoretical studies of viral infection models with biologically reasonable stochastic effects yet. To study the effects of stochastic perturbations on the pathogenesis process of HIV/AIDS, in this paper, we develop and study a stochastic HLIV model with viral production and Ornstein–Uhlenbeck process, in which we assume that the conversion rate from an eclipse-phase cell to an infected cell satisfies the Ornstein–Uhlenbeck process. Firstly, by using the existence and uniqueness theory of solutions, we prove that there is a unique global solution to the stochastic model for any initial value. Then we use stochastic Lyapunov function methods and Fatou lemma to establish sufficient conditions for the existence of a stationary distribution of positive solutions to the stochastic system, which reflects the strong persistence of the disease. In addition, by adopting the comparison theorem of one-dimensional stochastic differential equation and the theory of ergodicity, we obtain sufficient conditions for complete eradication of the infected cells and free viruses. Our theoretical results show that the bigger speed of reversion or the smaller intensity of volatility is conducive to clearing infected cells and free viruses while the larger intensity of volatility or the smaller speed of reversion is not. We also find that this way of introducing stochastic perturbations is reasonable from the perspective of mathematics and biology. Finally, numerical simulations are carried out to demonstrate our main results. The modeling and methods can be applied to study other multigroup viral infection models or epidemic model with Ornstein–Uhlenbeck process, such as S-DI-A model, DS-I-A model, DS-DI-A model, SEI epidemic model, et al.

An Impact Inertial Piezoelectric Actuator Designed by Means of the Asymmetric Friction

With simple structure and control, impact inertial piezoelectric actuators are one promising type for precision positioning with large working stroke and high resolution. However, their applications still face some challenges, especially the incompatibility between speed and resolution as well as the motion instability due to the overturning moment. Therefore, innovative design of impact inertial actuators is urgently required. In this article, by designing an asymmetric compliant mechanism with a thick end and a thin end to generate asymmetric friction between the driving feet and U-groove, a novel impact inertial piezoelectric actuator was proposed. Its structure design, working principle, and output performances were addressed in detail. The results indicated that the thick end and thin end had quite different stepping characteristics, and the ideal stepping characteristic with quite small backward motion was achieved at the thick end. The displacement-time curves confirmed the motion stability of the actuator for bidirectional motions, and the small difference in forward and reverse speeds was explored. This actuator achieved the maximum speed of 7311 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m/s, the resolution of 221 nm, vertical and horizontal loading capacities being over 20 N and 1.4 N, respectively. Performance comparison with some previous impact inertial actuators further demonstrated the advancement.

Mechanical properties of hardened layer under reversible surface plastic deformation

The article presents the results of experimental studies to determine the influence of the parameters of reverse surface plastic deformation (RPD) on the mechanical properties of the surface layer of cylindrical parts made of carbon steel 45. To implement the proposed method of finishing and hardening processing, a device has been developed that provides reverse circular motion of the working tool. Using the HBRV-187.5 hardness tester, HMV-G21 microhardness tester and MET-2 microscope, the hardness of the surface layer, microhardness, grain structure and depth of the hardened layer of hardened parts were determined. Experimental studies have shown that after reverse SPD, the hardness of the surface layer increases by 9...15 % compared to the hardness of the original surface, and the microhardness increases by 1,6...1,8 times, which leads to a significant hardening of the surface layer. The depth of the hardened layer is 0.8...1.6 mm, and the degree of hardening is 55...80 %. According to the results of experimental studies and using the PyCharm computer program with the Python programming language, the optimal modes of hardening by reverse SPD were determined, providing both the maximum depth and the highest degree of hardening of the surface layer, which are formed under the following processing modes: longitudinal feed 0.08...0,10 mm/rev; workpiece rotation frequency 280...300 rpm; the value of the radial interference 0.28...0.30 mm; reverse speed RI 290...300 strokes/min; the initial installation angle of RI is 90° and the value of the angle of reverse rotation of RI is ±15°.

Prediction of the Stock Prices at Uganda Securities Exchange Using the Exponential Ornstein–Uhlenbeck Model

We use the exponential Ornstein–Uhlenbeck model to predict the stock price dynamics over some finite time horizon of interest. The predictions are the key to the investors in a financial market because they provide vital reference information for decision making. We estimated all the parameters of the model (mean reversion speed, long‐run mean, and the volatility) using the data from Stanbic Uganda Holdings Limited. We used the parameters to forecast the stock price and the associated mean absolute percentage error (MAPE). The predictions were compared against those by the ARMA‐GARCH model. We also found the 95% prediction intervals before and during the COVID‐19 pandemic. Results indicate that the exponential Ornstein–Uhlenbeck stochastic model gives very accurate and reliable predictions with a MAPE of 0.4941%. All the forecasted stock prices were within the prediction region established. This was not the case during the COVID‐19 pandemic; the predicted stock prices are higher than the actual prices, indicating the severe impact COVID‐19 inflicted on the stock market.