Speed Curve Research Articles

Isothermal extrusion speed curve design for porthole die of hollow aluminium profile based on PID algorithm and finite element simulations

The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional–integral–derivative (PID) control algorithm and finite element simulations. The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency. By taking the optimal solution temperature of the secondary phase as the target temperature, the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained. Results show that in the traditional constant extrusion speed process, the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement. As the extrusion speed increases, the temperature difference at the die exit of the profile along the extrusion direction increases. The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9 °C. Furthermore, the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container, porthole die and external environment.

Kayısıların Farklı Ortamlarda Kurutma Kinetiğinin İncelenmesi

In this study, Çöloğlu, Hacıhaliloğlu, Kabaaşı and Karacabey apricot species grown in Malatya province of Turkey were used. The effects of various drying environment on the drying kinetics of crude and pre-treated apricots have been investigated. The experiments were conducted in the sunlight and in the shade environment with SO2 treated and untreated apricot. While the drying speed curves of the dried apricots increased rapidly at the beginning, the drying speed curve started to decrease afterwards. The data was fitted to five different mathematical models. Midilli et al. model was determined as the best one to explain drying of apricots by comparing the coefficient of correlation determination (R2), mean absolute percentage error (MAPE) and root mean square error (RMSE) between the observed and expected moisture ratios.

Assessment of Sprint Parameters in Top Speed Interval in 100 m Sprint-A Pilot Study Under Field Conditions.

Improving performances in sprinting requires feedback on sprint parameters such as step length and step time. However, these parameters from the top speed interval (TSI) are difficult to collect in a competition setting. Recent advances in tracking technology allows to provide positional data with high spatio-temporal resolution. This pilot study, therefore, aims to automatically obtain general sprint parameters, parameters characterizing, and derived from TSI from raw speed. In addition, we propose a method for obtaining the intra-cyclic speed amplitude in TSI. We analyzed 32 100 m-sprints of 7 male and 9 female athletes (18.9 ± 2.8 years; 100 m PB 10.55–12.41 s, respectively, 12.18–13.31 s). Spatio-temporal data was collected with a radio-based position detection system (RedFIR, Fraunhofer Institute, Germany). A general velocity curve was fitted to the overall speed curve (vbase), TSI (upper quintile of vbase values) was determined and a cosine term was added to vbase within TSI (vcycle) to capture the cyclic nature of speed. This allowed to derive TSI parameters including TSI amplitude from the fitted parameters of the cosine term. Results showed good approximation for vbase (error: 5.0 ± 1.0%) and for vcycle (2.0 ± 1.0%). For validation we compared spatio-temporal TSI parameters to criterion values from laser measurement (speed) and optoelectric systems (step time and step length) showing acceptable RMSEs for mean speed (0.08 m/s), for step time (0.004 s), and for step length (0.03 m). Top speed interval amplitude showed a significant difference between males (mean: 1.41 m/s) and females (mean: 0.71 m/s) and correlations showed its independence from other sprint parameters. Gender comparisons for validation revealed the expected differences. This pilot study investigated the feasibility of estimating sprint parameters from high-quality tracking data. The proposed method is independent of the data source and allows to automatically obtain general sprint parameters and TSI parameters, including TSI amplitude assessed here for the first time in a competition-like setting.

Calculation of the Roadside Clear Zone Width along Highways Based on the Safe Slope

International crash data indicate that roadside characteristics contribute to more than half of all roadside accidents involving serious injury or death. Therefore, research on roadside safety is urgently needed. Based on the vehicle departure speed, pavement height (i.e., the difference between pavement elevation and ground elevation), slope gradient, and horizontal curve radius, this study uses PC-Crash simulation software to carry out tests of trucks and cars exiting a road. A chi-squared automatic interaction detection (CHAID) decision tree is used to explore the causative mechanism of vehicle rollover, and the concept of a “safe slope” to ensure that vehicles do not roll over is proposed. Aiming at straight and curved sections, discriminant functions of vehicle rollover and nonrollover are fitted through Bayesian discriminant analysis, and safe slope calculation models for trucks and cars are then constructed. Based on the obtained safe slope models, calculation methods for the safe slope and the roadside clear zone width involving different traffic compositions are proposed by calibrating the lateral distance from the final position of nonrollover vehicles to the road edge. The results show that the factors affecting vehicle rollover are, in descending order of importance, the slope gradient, pavement height, vehicle type, departure speed, and horizontal curve radius. For a section with a large proportion of cars, the slope gradient should not be steeper than 1:3.5. The horizontal curve radius should not be less than 600 m for a section with a large proportion of trucks and a slope gradient steeper than 1:3.5 or shallower than 1:2.5. Additionally, for a section with a pavement higher than 0.5 m and a slope gradient steeper than 1:2.5, the operating speed limit should be lower than 60 km/h. These research results have theoretical value and practical significance to improve the driving safety level and reducing the risk of roadside accidents.

Control of Unmanned Surface Vehicle Along the Desired Trajectory Using Improved Line of Sight and Estimated Sideslip Angle

Abstract In order to improve the accuracy and robustness of path following control for an Unmanned Surface Vehicle (USV) suffering from unknown and complex disturbances, a variable speed curve path following a control method based on an extended state observer was proposed. Firstly, the effect of the environmental disturbances on the USV is equivalent to an unknown and time-varying sideslip angle, and the sideslip angle is estimated by using the extended state observer (ESO) and compensated in the Line of Sight (LOS) guidance law. Secondly, based on the traditional LOS guidance law, the design of the surge velocity guidance law is added to enable the USV to self-adjust the surge velocity according to the curvature of the curve path, thus further improving the tracking accuracy. Finally, the heading and speed controller of the USV is designed by using a sliding mode control to track the desired heading and speed accurately, and then the path following control of the USV’s curve path is realised. Simulation results verify the effectiveness of the proposed method.

Controlling Film Thickness Distribution by Magnetron Sputtering with Rotation and Revolution

The laterally graded multilayer collimator is a vital part of a high-precision diffractometer. It is applied as condensing reflectors to convert divergent X-rays from laboratory X-ray sources into a parallel beam. The thickness of the multilayer film varies with the angle of incidence to guarantee every position on the mirror satisfies the Bragg reflection. In principle, the accuracy of the parameters of the sputtering conditions is essential for achieving a reliable result. In this paper, we proposed a precise method for the fabrication of the laterally graded multilayer based on a planetary motion magnetron sputtering system for film thickness control. This method uses the fast and slow particle model to obtain the particle transport process, and then combines it with the planetary motion magnetron sputtering system to establish the film thickness distribution model. Moreover, the parameters of the sputtering conditions in the model are derived from experimental inversion to improve accuracy. The revolution and rotation of the substrate holder during the final deposition process are achieved by the speed curve calculated according to the model. Measurement results from the X-ray reflection test (XRR) show that the thickness error of the laterally graded multilayer film, coated on a parabolic cylinder Si substrate, is less than 1%, demonstrating the effectiveness of the optimized method for obtaining accurate film thickness distribution.

A novel coupling strategy for automated vehicle’s longitudinal dynamic stability

The autonomous vehicle has been developed widely, and attracted much attention of global automotive industry. Wherein, longitudinal dynamics control is one of the most crucial issues of autonomous vehicles. The throttle-by-wire (TBW) control could implement the acceleration command through adjusting the throttle opening, thus control the driving torque of the fuel autonomous vehicle. However, an automated vehicle controlled by traditional TBW in low-friction road conditions could reach large slip ratio region, which could adversely cause the loss of vehicle longitudinal dynamic stability. To tackle the mentioned issues, this paper proposes an adaptive sliding-mode control (SMC) algorithm to optimize tire slip speed of the automated vehicle. When the intervention conditions of active acceleration are satisfied, the TBW can take over the throttle opening control instead of the driver. Firstly, the SMC can calculate an intervention of the effective torque input based on tire torque balance dynamics. Moreover, a traction control system (TCS) and TBW coupling strategy based on the logic threshold method is put forward to response the optimum slip speed curve. Thus, during the vehicle starting process, a three-layer control strategy consisting of TBW, torque control, and pressure control of TCS is involved. Finally, real-car snow and ice road tests are carried out, and experimental results demonstrate great performance of the proposed strategy in complicated low-friction road.

Geological monitoring networks for risk management close to large rock cliffs: the case history of Gallivaggio and Cataeggio in the italian Alps

Abstract. In areas located near large rock cliffs, risk reduction by early warning monitoring systems highligts potentiality but also critical issues and limits. The paper examines two rock slope failures that occurred in a short time from each other near inhabited areas in the Italian Alps. The viscous behavior of the rock mass was reconstructed through data processing from ground-based Synthetic Aperture Radar Interferometry (InSAR), and elaboration of acceleration and speed curves. Landslides types and underlying complexity associated with rock detachment mechanisms suggest the identification of precautionary alarm thresholds for collapse forecasting. The analysis of financial outlay, both for mitigation works and for monitoring activities, highlight the adequacy and the opportunity to combine passive systems, like embankments or rockfall drapery meshes, with a reliable monitoring network for early warning.

Viscous dark energy accretion activities : sonic speed, angular momentum and Mach number studies

In this present article, we study different accretion properties regarding viscous accretion of dark energy. Modified Chaplygin gas is chosen as the dark energy candidate. Viscosity is encountered with the help of Shakura–Sunyaev viscosity parameter. We study sonic speed vs radial distance curves. We compare between adiabatic and dark energy dominated cases and follow that sonic speed falls as we go nearer to the central gravitating object. As viscosity is imposed, a threshold drop in accretion sonic speed is followed. Average rate of fall in accretion sonic speed is increased with black hole’s spin. This is signifying that this kind of accretion is weakening the overall matter/energy infall. Specific angular momentum to Keplerian angular momentum ratio is found to fall as we go far from the black hole. Accretion Mach number turns high as we go towards the inner region and high wind Mach number is not allowed as we are going out. Combining, we conclude that the system weakens the feeding process of accretion.

Effect of car-body initial dynamic sway on overturning before high-speed trains negotiate wind speed variations

A new phenomenon has occurred during a full-scale test in which the maximum overturning coefficient did not appear at the maximum wind speed or the highest operating speed when a train negotiates wind speed variations along a section of railway. This study focused on this challenge, and conducted an experimental-numerical study of the relationship between the car-body initial dynamic sway and the operational safety during wind speed abrupt changes. The results revealed that the car-body initial dynamic-sway states (i.e., amplitude and speed) before a train passed through sections where the wind speed changed abruptly were the primary causes of this new phenomenon, and the effect of the car-body initial dynamic sway on the train’s overturning safety was greater than derailment safety. Furthermore, the probability of an increase in overturning risk was greater than the probability of a decrease in risk when the train negotiated the sections where wind speed changed abruptly with different initial dynamic-sway states of the car-body. As a result, we suggested a probability critical wind speed curve for the train’s ability to negotiate abrupt changes in wind speed, which provides a reference for developing a more reasonable train operation scheme in complex conditions.

Application of Multislice Spiral CT in Diagnosis of Ankle Joint Sports Injury

In recent years, with the continuous improvement of medical treatment at home and abroad, computerized tomography (CT) technology has developed rapidly. The market competition at home and abroad is becoming increasingly fierce. The manufacturing cost of CT machines is highly valued by manufacturers. Reducing the manufacturing costs of CT machines is of great significance to medical equipment companies. The CT host is composed of a fixed control system and a rotation control system. Based on the analysis of the existing CT host system structure, this paper designs and implements a set of low-cost asynchronous variable-frequency rotation control systems based on the unchanged control interface of the existing main rotation servo control system, improving the market competitiveness of the product. Based on the constant structure of the rotating machine of the CT machine, the simulation analysis of asynchronous variable frequency control is carried out. A set of asynchronous variable frequency control design schemes and multi-stage speed curve control methods compatible with the original system structure are obtained. The verification and analysis of the functions of acceleration and deceleration control, rotation positioning, fault protection, electromagnetic radiation and other functions at the highest speed meet the system’s main performance requirements, such as acceleration and deceleration time at the highest speed, positioning accuracy, and speed stability. Through internal system verification, testing and clinical verification, the control system designed in this paper meets the design requirements. According to experimental data, the system is fully compatible with a running accuracy of 0.3%. The main performance indicators such as acceleration time and positioning accuracy have been improved. The acceleration time from static acceleration to the maximum speed of 0.39 seconds per revolution increases from 21 seconds to 19.9 seconds, and the positioning accuracy was improved from 0.3° to 0.24°. Finally, this study explores the diagnostic value of multislice spiral CT (MSCT) in ankle trauma.

Application of Plane Homography for Vehicle Speed Calculations in Traffic Accident Investigations

The analysis of vehicle speeds at the moment of traffic accidents is becoming increasingly important. To solve difficult calculations arising from video analysis when the shooting direction of the camera is the same as the driving direction of the vehicles, an improved plane homography method is proposed. This method is based on detecting the frame rate of and extracting all of the key image frames from a surveillance video. Next, a normalizing approach for the control points is proposed to reduce the ill-conditions of matrix calculations when the perspective image is rectified to an orthographic image. The information in the rectified image is then measured and recorded by extracting the mark point information. Finally, the corresponding curve of time and speed for the examined vehicle is created, which can be used to analyze the average braking deceleration of the accident-causing vehicle. This method can directly determine the speed of a vehicle using videos of a traffic accident without any reference to the dimensions of the vehicle itself. Considering an actual traffic accident as an example, the driving trajectories and velocity curves for two vehicles are obtained using this method. The proposed method can effectively overcome the shortcomings of the commonly used speed recognition methods and it is easy to utilize.

Experimental Study of Self-starting Characteristics for H-Type Wind Turbine

In order to study self-starting characteristics for H-type wind turbine, firstly, the effect of low Reynolds number and large separated flow on aerodynamic characteristics of airfoil were analyzed in detail, then two H-type wind turbines with different aerodynamic configurations were tested in a low speed wind tunnel for collecting the static torques at different phase angles and time-rotating speed curves in starting process. Based on theoretical analysis and experimental data, the cause of self-stating problem of H-type wind turbine has been revealed. The aerodynamic profile parameters of the wind turbine are closely related to the dependency of starting on initial phase position, and the minimum static torque determines whether the wind turbine has potential to start from rest. The time-rotating speed curves exhibit two different starting behaviour features, determined by the minimum dynamic torque in driving force conversion stage. Unless both the minimum static torque and minimum dynamic torque in driving force conversion stage are greater than the friction torque, the self-starting of the wind turbine cannot be realized. The typical self-starting behavior characteristics is that the time-rotating speed curve includes four different stages of initial linear acceleration, plateau, rapid acceleration and stable equilibrium with the final tip speed ratio more than 1.

Optimization of Powertrain in EV

The method for preliminary powertrain design is presented in the paper. Performance of the EV is realized by motor torque–speed curve and gear ratio optimization. The typical two-zone mechanical characteristic of a PMSM traction motor is included in the optimization program. The longitudinal vehicle model is considered in the paper. Some examples try to show the calculation possibilities in application to existing vehicles: Tesla Model S and Mini Cooper SE.

Lactate Threshold Evaluation in Swimmers: The Importance of Age and Method.

The purpose of the study was to define the most appropriate method for the calculation of the speed corresponding to lactate threshold (sLT) in male swimmers. Eight boys and eight adolescents (age: 11.4±0.5 and 15.8±0.8 years) performed 7×200-m swimming front-crawl and after drawing the speed vs. lactate curve, the sLTs were calculated using five methods: i) the intersection of two linear regression lines, ii) visual inspection, iii) D-max, iv) D-max modified, v) intersection of combined linear and exponential regression lines. All methods were compared to the speed corresponding to maximal lactate steady state (sMLSS). Two to four 30-min efforts of continuous swimming at imposed constant pace were used for sMLSS calculation. In both groups, speed of D-max modified was similar to sMLSS (children, 1.061±0.073 vs. sMLSS: 1.071±0.072 m·s-1; p>0.05; effect size: ES=0.15, small; adolescents, 1.318±0.060 vs. sMLSS: 1.284±0.047 m·s-1; p>0.05; ES=0.64, medium). In adolescents, sLT calculated by intersection of two regression lines and by visual inspection presented medium ES (0.22-0.24) and were no different to sMLSS (1.296 ± 0.051, 1.295±0.053 m·s-1, p>0.05). When testing children, D-max modified is the most appropriate method to estimate sMLSS. The intersection of the linear regression lines and visual inspection are suggested for sMLSS determination in adolescents.

Evaluation of alternative turnout layout designs for an improved dynamic performance of a vehicle-turnout system

ABSTRACT The turnout is the key equipment for guiding trains to change lines in railway track, which can affect the vehicle running smoothness and limit the train speed drastically. This paper proposes an optimisation method for turnout layout of the diverging route by considering multiple curvatures or curvature changes through the vehicle-turnout dynamics, and the effect of train speed on dynamic response is studied. For the small numbered turnout, increasing the curve radius of a single circular curve type or using a double radii curves type with a larger front radius can effectively reduce the increase in wheel–rail forces and improve train running quality. For the large numbered turnout, the transition curve can be added to the diverging route to form a circular–transition curve or a transition–circular–transition curve type, thereby significantly reducing the dynamic response of the vehicle-turnout system. The wheel–rail dynamic response increases approximately linearly with the train speed in the circular curve of diverging route, but the increase rate decreases significantly with the train speed in the transition curve part, which is more conducive to the increase of the train speed passing through turnouts.

A scheduling and control integration optimization method for regenerative braking energy utilization

The utilization of regenerative braking energy is of great significance to the energy saving of subway. Therefore, this paper proposes an optimization method for scheduling and control integration, which not only adjusts the timetable but also optimizes the speed curves of trains. When there is a train braking, this method will try to find a train that accelerates to absorb the regenerative energy generated by the braking train. Firstly, this paper establishes the timetable energy saving optimization model, based on which the speed curves will be optimized. Furthermore, we design a scheduling optimization algorithm based on genetic algorithm, and optimizes speed curves of trains by binary search method to obtain a good solution. Finally, simulations are given using the real data of Beijing Metro Line 4 to evaluate the proposed method, and the results show that the integrated scheduling and control optimization method can reduce energy consumption by 15.18%. In the random disturbance simulations, the proposed method shows good robustness, which makes it possible to apply this method to the real subway operations.

Tooth bending stress analysis of high speed curve face gear of composite transmission

To promote the engineering application of composite transmission of high speed curve face gear, which consists of a cylindrical gear and a high speed curve face gear, the analysis of tooth bending stress should be taken into consideration. High speed curve face gear pair is a new type of curve face gear pair. Combined with the principle of high speed cam and curve face gear pair transmission, it can transfer the axial/rotation composite motion and power between two intersecting shafts. Based on the gear engagement principle, the gear meshing coordinate system was established and the fundamental of the high speed composite transmission was expounded. Combined with the tooth profile equation of generating gear, the tooth surface equation of high speed curve face gear was gained. Tooth force, contact ratio and normal load distribution were calculated. Then the tooth bending stress of high speed curve face gear during the transmission was calculated and analyzed in detail. Influence of basic parameters on tooth bending stress was discussed. Finally, the simulation and measurement experiment of tooth bending stress was carried out. By the comparison analysis of simulation, experiment and theory, the correctness of tooth bending stress calculation method was verified, which has important guiding significance for the further research of high speed curve face gear of composite transmission.

Unified multidisciplinary modeling and simulation analysis of internal power system

The internal combustion power equipment is a typical cyber-physical system (CPS). The traditional design method is to separate the information system from the physical system, and then to simulate and optimize separately every system. That can not achieve the best performance. Aiming at the internal combustion power equipment with multi-disciplinary deep integration, this paper establishes the multi-disciplinary model of the whole and key components based on Dymola software. There are mainly mechanical system, combustion system, cooling system, control system and other simulation models, including deceleration and fuel cut-off control unit modeling, start-stop control unit modeling and speed limit control unit modeling. The performance of each model is simulated and analyzed. The mathematical models of engine characteristic curve and fuel supply rate curve are established through experimental study. Finally, taking the simulation model of automobile power system as an example, the simulation calculation and experimental verification are carried out, and the relationship among fuel supply rate, torque, speed and valve of internal combustion engine is obtained, as well as the cooling capacity of the cooling system is studied. The experimental results show that the maximum error between the simulation speed curve and the actual speed curve is within ± 2 km/h. The research results of this paper can provide theoretical basis for multidisciplinary modeling and simulation of internal combustion power equipment, and also provide technical support for performance analysis of internal combustion engine.

Влияние плавного и ступенчатого регулирования ослабления возбуждения тяговых электродвигателей электровозов на скорость движения электроподвижного состава

ter reaching the maximum voltage at the 4th control zone of the rectifier-inverter converter of an AC electric locomotive, a further increase in speed is achieved by connecting the field attenuation system (FA) of traction electric motors (TEM). All domestic electric locomotives use the FA TEM system of the inductively active type with step switching. However, it has drawbacks, one of them is that step switching causes speed losses and slows down the acceleration of electric rolling stock (ERS). By 2025, the goal is to increase the speed of freight trains, which will increase freight turnover on the railway network [1]. One solution is to improve the ERS. In this regard, it is proposed to improve the standard FA TEM system of an electric locomotive by using IGBT transistors, which allow smooth regulation of the excitation current. In the article, using the graphical method of the RM, a curve of the train speed is constructed, which proves that the smooth control of the electric locomotive FA TEM allows you to quickly reach the maximum permissible speed of the electric locomotive on the section and to move at a higher speed in the ascent than with step-by-step regulation. The simulation of the 3ES5K series electric locomotive in the «Cortes» software complex on the Winter - Irkutsk-Sortirovochny section was also carried out, which proved that with the smooth regulation of the FA TEM, the technical speed of the ERS increases by at least 2,5 km/h.