Speed Curve Research Articles

Определение длины разгонного пути

The development of locomotive traffic safety systems has led to the fact that it is already possible to move freight trains at the yellow signal of the passing traffic light of most sections at the speed of more than 60 km/h due to the use of virtual coupling technology, in which the calculation of the permissible speed curve is carried out taking into account information about the movement of the train ahead transmitted between locomotives via radio channel. This means that it is possible to reduce the delimiting interval between trains on the stages without reducing the speed. Due to this, in areas with heavy traffic, it is possible to obtain the actual inter-train interval less than the one designed for three-digit auto-blocking, if a corresponding reduction in the interval of passing departure is ensured. The existing algorithms of station automation limit the possibilities of reducing the departure intervals, so there is a need to study the capabilities of stations to implement intervals smaller than was laid down when designing the site. To do this, the simulation of the departure of trains in virtual coupling was carried out. The conditions under which it is necessary to build the acceleration track are determined, and the method for determining its length is also presented.

Fuzzy model reference learning control in surgical robots

This paper proposes to apply the fuzzy model reference learning control method based on the guide control to the collaborative human-machine dragging process of the surgical robot. Variable damping coefficient adjustment parameter rules for fuzzy conductance controllers are trained by an offline learning mechanism in order to achieve the best human-machine interaction control effect. The surgical risk caused by the doctor's misoperation is lowered. Through the simulation experiment results, the speed curve tracking error is reduced by 70%. Trajectory curve tracking error is reduced by 57%. The both results prove that the strategy can reduce the error of the surgical robot and ensure the safety of robotic surgical operation.

Dynamical Stability Analysis of Rotating Composite Cutter Bar with Nanocarbon Materials

This paper studies the free vibration response of a spinning and variable cross-section composite cutter bar homogeneously enhanced with carbon nanomaterials. Based on the Rules of Mixture (ROM) and the Halpin–Tsai Model (HTM), we establish a motion model of the spinning and variable cross-section composite cutter bar by containing carbon nanomaterials, which combines the Euler–Bernoulli beam theory and Hamilton principle. In addition, the dynamic governing equations are solved by using the Galerkin method so as to obtain the characteristic equation. The curves of decay rate-rotating speed and natural frequency-rotating speed are obtained especially by numerical analysis, and the corresponding critical speed and instability threshold of the composite cutter bar are also calculated. By selecting different parameters such as length-to-diameter (or length-to-width-to-thickness) ratios and volume contents of carbon nanomaterials, cutter bar taper ratios, ply orientations, and stacking sequences, the relation between instability threshold and loss factor is obtained with respect to the composite cutter bar. The results obtained found that the cutter bar’s stiffness is increased by adding carbon nanomaterials into the carbon fiber-reinforced polymer composites. Its natural frequency and critical speed are increased, but the cutter bar’s damping decreases with the increasing content of carbon nanomaterials. The results of critical speed and fundamental natural frequency of composite cutter bar for high-speed machining are greatly meaningful.

Parameter Optimization of Large-Size High-Speed Cam-Linkage Mechanism for Kinematic Performance

The cam-linkage mechanism is a typical transmission mechanism in mechanical science and is widely used in various automated production equipment. However, conventional modeling methods mainly focus on the design and dimensional synthesis of the cam-linkage mechanism in the slow-speed scenario. The influence of component dimensions is not taken into consideration. As a result, the model accuracy dramatically falls when analyzing large-size cam-linkage mechanisms, especially in high-speed environments. The kinematic aspects of cam design have been investigated, but there are few studies discussing the motion characteristic and accuracy analysis models of the large-size cam-linkage mechanism under high-speed scenarios. To handle such issues, this paper proposes a parameter optimization methodology for the design analysis of the large-size high-speed cam-linkage mechanism considering kinematic performance. Firstly, the mathematical model of the cam five-bar mechanism is presented. The cam curve and motion parameters are solved forward with linkage length and output speed. Then, a particle swarm-based multi-objective optimization method is developed to find the optimal structure parameters and output speed curve to minimize cam pressure angle and roller acceleration and maximize linkage mechanism drive angle. A Monte Carlo-based framework is put forward for the reliability and sensitivity analysis of kinematic accuracy. Finally, a transverse device of a sanitary product production line is provided to demonstrate the applicability of the proposed method. With the parameter optimization, the productivity of the transverse device is doubled, from 600 pieces per minute (PPM) to 1200 PPM.

Lifetime prediction of turbine blades using global precipitation products from satellites

Abstract. The growing size of wind turbines leads to extremely high tip speeds when the blades are rotating. The blades are prone to leading edge erosion when raindrops hit the blades at such high speeds, and blade damage will eventually affect the power production until repair or replacement of the blade is performed. Since these actions come with a high cost, it is relevant to estimate the blade lifetime for a given wind farm site prior to wind farm construction. Modeling tools for blade lifetime prediction require input time series of rainfall intensities and wind speeds in addition to a turbine-specific tip speed curve. In this paper, we investigate the suitability of satellite-based precipitation data from the Global Precipitation Measurement (GPM) mission in the context of blade lifetime prediction. We first evaluate satellite-based rainfall intensities from the Integrated Multi-Satellite Retrievals for GPM (IMERG) final product against in situ observations at 18 weather stations located in Germany, Denmark, and Portugal. We then use the satellite and in situ rainfall intensities as input to a model for blade lifetime prediction, together with the wind speeds measured at the stations. We find that blade lifetimes estimated with rainfall intensities from satellites and in situ observations are in good agreement despite the very different nature of the observation methods and the fact that IMERG products have a 30 min temporal resolution, whereas in situ stations deliver 10 min accumulated rainfall intensities. Our results indicate that the wind speed has a large impact on the estimated blade lifetimes. Inland stations show significantly longer blade lifetimes than coastal stations, which are more exposed to high mean wind speeds. One station located in mountainous terrain shows large differences between rainfall intensities and blade lifetimes based on satellite and in situ observations. IMERG rainfall products are known to have a limited accuracy in mountainous terrain. Our analyses also confirm that IMERG overestimates light rainfall and underestimates heavy rainfall. Given that networks of in situ stations have large gaps over the oceans, there is a potential for utilizing rainfall products from satellites to estimate and map blade lifetimes. This is useful as more wind power is installed offshore including floating installations very far from the coast.

ПРАВО- И ЛЕВОСТОРОННЕЕ ДВИЖЕНИЕ НА ЖЕЛЕЗНЫХ ДОРОГАХ МИРА: ИСТОРИЯ И БУДУЩЕЕ

Starting with historical references on traffic direction choice and how railway transport has become the reason for the predomination of righthand traffic on transport other kinds, the authors dwelled on the examples of traffic directions on automotive and partially air and sea transport and then went to forecasting the future in the definition of motion directions on railway transport, technical limitations of the systems with floor traffic lights and approached to the analysis of signalless systems of traffic control with fixed block-plots and then with mobile ones. It was shown that modern solutions for high-speed lines should exclude fixed signals. The main domestic and foreign examples for the design and exploitation of such systems at the world railways and subways as well as advantages and disadvantages in terms of traffic capacity and safety were demonstrated. The comparison of domestic and foreign systems of interval regulation of train traffic was made in the article final part. The fundamental similarity of Russia signalless automatic blocking system “ALSO” with all-European system ETCS L2, preserving block-plot fixed lengths but excluding the use of checkpoint traffic lights, was demonstrated. In addition, the common principles for “ABTC-M” system, used on Russia railways, and ETCS L3 system with mobile block-plots, which rules out the use of traffic lights as well as the devices for track section vacancy control, are indicated. Both systems exclude fixed signals and fixed block sections. Then the example of the systems at railways and subways with mobile block-plots was demonstrated – the systems work on the difference in braking distances of trains, running in the same direction. These systems ensure the shortest headway thanks to data on speed and braking curve of a leading train. But such systems have a lot of limitations in terms of railway operation and safety.

PHANGS-JWST First Results: Spurring on Star Formation: JWST Reveals Localized Star Formation in a Spiral Arm Spur of NGC 628

We combine JWST observations with Atacama Large Millimeter/submillimeter Array CO and Very Large Telescope MUSE Hα data to examine off-spiral arm star formation in the face-on, grand-design spiral galaxy NGC 628. We focus on the northern spiral arm, around a galactocentric radius of 3–4 kpc, and study two spurs. These form an interesting contrast, as one is CO-rich and one CO-poor, and they have a maximum azimuthal offset in MIRI 21 μm and MUSE Hα of around 40° (CO-rich) and 55° (CO-poor) from the spiral arm. The star formation rate is higher in the regions of the spurs near spiral arms, but the star formation efficiency appears relatively constant. Given the spiral pattern speed and rotation curve of this galaxy and assuming material exiting the arms undergoes purely circular motion, these offsets would be reached in 100–150 Myr, significantly longer than the 21 μm and Hα star formation timescales (both < 10 Myr). The invariance of the star formation efficiency in the spurs versus the spiral arms indicates massive star formation is not only triggered in spiral arms, and cannot simply occur in the arms and then drift away from the wave pattern. These early JWST results show that in situ star formation likely occurs in the spurs, and that the observed young stars are not simply the “leftovers” of stellar birth in the spiral arms. The excellent physical resolution and sensitivity that JWST can attain in nearby galaxies will well resolve individual star-forming regions and help us to better understand the earliest phases of star formation.

Design and kinematics analysis of AGV with unilateral climbing rack in the roadway

To improve the speed of intelligent transformation of warehousing and logistics, a unilateral climbing shelf-type AGV in warehouse aisles is proposed. The modular design is adopted, and the crawling drive module, the cargo module, and the telescopic rotating arm are combined to form an AGV that can walk in all directions on the ground, climb, and traverse along the shelf track to complete the storage and retrieval operations. After the scheme is determined, 3D modeling is carried out through SliodWorks, performing static stress analysis on key stressed components. The kinematic model of the transition stage between ground and climbing is established by analytical method, and the kinematics simulation of the transition stage is completed in the SliodWorks Motion module. The results show that the movement speed curve of the cargo module is smooth, and there is no rigid impact. The Lagrangian dynamics equation is established for the transition process of AGV ground and climb, which provides a theoretical basis for control design. The overall structure of the AGV is reasonable, and the transition stage between the ground and the climb runs smoothly, meeting the design requirements.

Finite-Time Convergence ESO-Based Nonsingular Fast Terminal Sliding Mode Control for PMSM with Unknown Parameters and Time-Varying Load

In this paper, an extended state observer (ESO)-based nonsingular fast terminal sliding mode (NFTSM) control method is proposed for the speed tracking system of permanent magnet synchronous motor (PMSM) in the present of unknown parameters and time-varying load. Firstly, three finite time convergence ESO (FTCESO) are employed to estimate the lumped disturbances in one speed loop and two current loops, respectively, and the estimates are fed forward to controllers for compensation. Secondly, a NFTSM controller is designed, which can drive the speed of PMSM track in desired speed in finite time. The stability of resulting closed-loop system is proved by using Lyapunov theory. Finally, the simulation and experimental results are compared with the existing methods, and the results show that the proposed method has better performance in tracking different kind of desired speed curves, and also performs better in reducing the chattering phenomenon.

Vibration control of beams under moving loads using tuned mass inerter systems

Traditional tuned mass dampers (TMDs) have been proven efficient for the moving-load-induced vibration control of beams. However, a large tuned mass is required in TMDs to adjust the structural dynamic characteristics and achieve the demanded performance targets, which leads to additional dynamic effects and inconvenience of installation. The tuned mass inerter system (TMIS) is an ungrounded lightweight passive control device, which contains a suspended mass, a parallel-connected tuned spring and an inerter-based subsystem. In this study, the application and optimization of TMISs on vibration suppression of multi-span beam models under moving load series are investigated. Using the Bubnov-Galerkin integration method, the modal-superposition generalized system for specified modes of a beam with TMIS under successive moving load series is established. Then, a design strategy for TMISs is proposed to achieve the structural target performance demand by decreasing the moving load-induced resonant responses and attached tuned mass. In the optimization algorithm, the tuned mass ratio is taken as the optimal objective, and the limited dynamic response amplitude under different speed parameters is the constraint condition. A single-span simply supported beam with the TMIS under a moving load series is analyzed. The designed TMISs are tuned to the dominating mode with the maximum mass participate factor of the main structures. TMISs show good vibration mitigation compared to TMDs with equal tuned mass. Meanwhile, under the premise of identical structural performance demands, TMISs require less tuned mass than TMDs and achieve a lightweight control effect. The corresponding dynamic amplitude vs speed curves and time history response curves of beams with TMISs and TMDs are also depicted through comparative analyses. The vertical deflection and acceleration responses apparently decrease, and the resonance is mitigated due to the designed TMISs. The sensitivity analysis results indicate that TMISs attached to beams are insensitive to the perturbance of their parameters and the input moving load excitations; thus, TMIS proves to be a robust tuning system.

Adaptive window rotated second-order synchroextracting transform and its application in fault diagnosis of wind turbine gearbox

Time frequency (TF) analysis (TFA) based on vibration signals is a vital method for the health monitoring of wind turbine gearboxes. Based on classical synchrosqueezing transform and short-time Fourier transform (STFT), synchroextracting transform (SET) abstractly retains primary TF energy around the interested frequency components by reassigning the TF transformation coefficient. However, as the fixed window of these traditional TFA methods, they have poor matching effects on multi-component signals with fast-varying frequencies. To address this problem, this paper first optimizes the width of the short-term window based on STFT, and then proposes adaptive short-time Fourier transform (ASTFT). That is, the direction of the window function in the STFT is changed by automatically matching a series of rotation operators. Then, based on ASTFT and SET, the second-order partial derivatives of time and frequency are used to modify the formula of instantaneous frequency estimation. Therefore, adaptive window rotated second-order synchroextracting transform (AWRSSET) is put forward to obtain and sharpen TF representations of multi-component vibration signals of wind turbines in this paper. In order to accurately diagnose faults in wind turbines, this paper extracts the rotation speed curve from the TF plane, which is generated through AWRSSET, and then makes subsequent order-frequency analyses without a tachometer. AWRSSET can be applied to diagnosing faulty wind turbine gearboxes and gears with broken teeth under time-varying speed, both of which testify to the advantages of this method.

Scattering of kinks in the [formula omitted] model

In this study, based on the φ4 model, a new model (called the Bφ4 model) is introduced in which the potential form for the values of the field whose magnitudes are greater than 1 is multiplied by the positive number B. All features related to a single kink (antikink) solution remain unchanged and are independent of parameter B. However, when a kink interacts with an antikink in a collision, the results will significantly depend on parameter B. Hence, for kink–antikink collisions, many features such as the critical speed, output velocities for a fixed initial speed, two-bounce escape windows, extreme values, and fractal structure in terms of parameter B are considered in detail numerically. The role of parameter B in the emergence of a nearly soliton behavior in kink–antikink collisions at some initial speed intervals is clearly confirmed. The fractal structure in the diagrams of escape windows is seen for the regime B≤1. However, for the regime B>1, this behavior gradually becomes fuzzing and chaotic as it approaches B=3.3. The case B=3.3 is obtained again as the minimum of the critical speed curve as a function of B. For the regime 3.3<B≤10, the chaotic behavior gradually decreases. However, a fractal structure is never observed. Nevertheless, it is shown that despite the fuzzing and shuffling of the escape windows, they follow the rules of the resonant energy exchange theory.

Effective Throughput Analysis of Different Task Execution Strategies for Mid-Air Fitts' Tasks in Virtual Reality.

Fitts' law and throughput based on effective measures are two mathematical models frequently used to analyze human motor performance in a standardized pointing task, e.g., to compare the performance of input and output devices. Even though pointing has been deeply studied in 2D, it is not well understood how different task execution strategies affect throughput in pointing in 3D virtual environments. In this work, we examine the effective throughput measure, claimed to be invariant to task execution strategies, in Virtual Reality (VR) systems with three such strategies, "as fast, as precise, and as fast and as precise as possible" for ray casting and virtual hand interaction, by re-analyzing data from a 3D pointing ISO 9241-411 study. Results show that effective throughput is not invariant for different task execution strategies in VR, which also matches a more recent 2D result. Normalized speed vs. accuracy curves also did not fit the data. We thus suggest that practitioners, developers, and researchers who use MacKenzie's effective throughput formulation should consider our findings when analyzing 3D user pointing performance in VR systems.

Numerical Investigation and Experiment on Natural Circulation Resistance and Energy Characteristics in a Circulating Axial Pump

Abstract The influence of angle matching in rotor–stator interference (RSI) zone on natural circulation resistance (NCR) of circulating pump in natural circulation condition is illustrated by numerical method, and the analysis and optimization method of natural circulation based on loss coefficient curve are established through experiments. The mechanism and analysis formula of runaway speed are extracted, and the distribution diagram of Euler head density function (EHDF) is obtained to carry out image processing and analysis of secondary flow. Then, the optimal design interval of setting angle of impeller outlet under low flow resistance is acquired. As for the natural circulation loss of static parts, the optimal design interval of guide vane inlet angle and outlet angle with low flow resistance is obtained by analyzing the EHDF distribution diagram of the whole flow parts, which accounts for the position and reason of resistance. In this paper, the mechanism between runaway speed and loss coefficient curve is revealed and the resistance is optimized through the design and analysis of the RSI region, which provides theoretical methods for the analysis of the impeller performance of axial-flow circulating pump. Furthermore, it is a reference for the optimization design of natural circulation system.

The Estimation of Centrifugal Pump Flow Rate Based on the Power–Speed Curve Interpolation Method

During the global energy crisis, it is essential to improve the energy efficiency of pumps by adjusting the pump’s control strategy according to the operational states. However, monitoring the pump’s operational states with the help of external sensors brings both additional costs and risks of failure. This study proposed an interpolation method based on PN curves (power–speed curves) containing information regarding motor shaft power, speed, and flow rate to achieve high accuracy in predicting the pump’s flow rates without flow sensors. The impact factors on the accuracy of the estimation method were analyzed. Measurements were performed to validate the feasibility and robustness of the PN curve interpolation method and compared with the QP and back-propagation neural network (BPNN) methods. The results indicated that the PN curve interpolation method has lower errors than the other two prediction models. Moreover, the average absolute errors of the PN curve interpolation method in the project applications at 47.5 Hz, 42.5 Hz, 37.5 Hz, and 32.5 Hz are 0.1442 m3/h, 0.2047 m3/h, 0.2197 m3/h, and 0.1979 m3/h. Additionally, the average relative errors are 2.0816%, 3.2875%, 3.6981%, and 2.9419%. Hence, this method fully meets the needs of centrifugal pump monitoring and control.

Real-time Accelerometer-Based Event Detection Through KNN Classification Method

Real-time pattern and activity recognition techniques have experienced a recent surge in the use of advanced statistical techniques for analyzing data. More explicitly, Machine Learning classification methods have been used in a variety of applications and for different purposes, such as recognizing different types of events from accelerometer data (e.g. in smart watches, wearables, and vibration analysis). The objective of this work is to present a novel use of accelerometer-based pattern recognition techniques to detect the urban space infrastructure characteristics based on their effect on a vehicle’s body frame dynamics. For this study, we focus on detecting speed bumps, potholes and curves based on a real-time data streaming with the objective of rendering a street digitalization to automatically update an urban space Digital Twin. The present study has achieved real-time event detection for an urban trajectory with high accuracy which yields data that can be later fused with other sensors data. This approach is effectively contributing to the infrastructure layer of a multi-layered approach of digital modelling. Furthermore, the results contribute to expand the body of knowledge of real-time accelerometer event recognition techniques.

Vibration response analysis of dual-rotor system in aero-engines

In order to study dynamic characteristics of a dual-rotor aero-engine, a similar dual-rotor system dynamic model is established. The influence of the high- and low-pressure rotor rotation speed on the vibration response of the co-rotating or counterrotating dual-rotor system in aero-engine is analyzed combine with critical speed diagram, and the vibration characteristics are experimentally verified by dual-rotor test rig system. Both the simulation and experimental results reveal that in the critical speed diagram the total amplitude of the dual-rotor system increases, when the actual speed line gets closer to a level of critical speed curve. The rotor base frequency component corresponding to the critical speed increases, mean while the other rotor base frequency component changes little. The total amplitude of the dual-rotor system decreases when the actual speed line moves away from a level of critical speed curve. The rotor base frequency component corresponding to the critical speed decreases, mean while the other rotor base frequency component changes little. The total amplitude and both of the high- and low-pressure rotor base frequency component are substantially unchanged except the dual-rotor system crosses its critical speeds, when the entire actual speed line is away from the critical speed curve. In order to avoid the dual-rotor system failure caused by an out of range response, the actual speed line shouldn&apos;t approach the critical speed curves for a long time, when carrying out a dual-rotor system rotor dynamic experiment.

Evaluation of advanced curve speed warning system to prevent fire truck rollover crashes

Introduction: A disproportionately high number of deadly crash-incidents involve fire-tanker rollovers during emergency response driving. Most of these rollover incidents occur at dangerous horizontal curves (“curves”) due to unsafe speed. This study examined the effects of a curve speed warning system (CSWS) on fire tanker drivers’ emergency response behavior to develop system improvement suggestions. Method: Twenty-four firefighters participated in driving tests using a simulator. A fire tanker model, carrying a full tank of water, was used in emergency driving tests performed with and without CSWS. The CSWS was designed using the algorithm for passenger vehicles with a few initial modifications considering the unique requirements of heavy fire tanker and emergency driving. Results: The results indicated that the CSWS was effective in issuing preemptive warnings when the drivers were approaching curves with unsafe speed during emergency response. Warnings occurred more frequently at curves with smaller radius. Although the CSWS improved driving performance, it did not significantly reduce the number of rollover events. A detailed analysis of the rollover events provided suggestions for improvement of CSWS algorithms. Conclusions: To further improve the CSWS algorithm, the following may be considered: including increased safety speed margin below the rollover critical speed, moving the speed warning trigger from the curve apex to the curve entry point, extending the safe speed-control zone to cover the entire curve, and employing artificial intelligence to accommodate individual driving styles. Practical Applications: Fire tankers continue to be at increased risk of rollover during emergency response due to unsafe negotiation of dangerous curves. Development and use of advanced driver assist systems such as CSWS evaluated in this study may be an effective strategy to prevent deadly rollover crash-incidents. The knowledge generated by this study will be useful for system designers to improve the CSWS specifically designed for heavy emergency vehicles.

Screening and optimization method of defect points of G code in three axis NC machining

ABSTRACT G code is the input of the CNC system, and its quality affects the machining accuracy and efficiency. However, the G code generated by CAM has some defect points, which will seriously affect the processing quality and efficiency. To solve this problem, this paper proposes a method to screen and optimize the defect points of the G01 format G code of three-axis machining. First, a rough screening method based on the geometric characteristics of the trajectory is constructed. Second, a precise screening method through trend trajectories and box plot to screen out defect points is constructed. Finally, the NURBS curve is used to restore and discretize trajectories to obtain new points of G code. Two cases and experiments are used to verify the optimization effect. The experiments results show that after screening and optimization, the geometric characteristics of the two G codes, such as curvature and the difference between adjacent line segments, are obviously improved. The curves of setpoints speed and acceleration are smoother, the setpoints jerk is reduced, and the vibration is weakened. The processing time of the two G codes is shortened by 4.07% and 9.85% when the feed speed is 3000 mm/min and 2000 mm/min, respectively.

Research on Multi-objective Optimization of Freight Train Operation Process Based on Improved Bald Eagle Search Algorithm

&lt;p&gt;To study the optimization problem of freight train operation process under complex line conditions, this paper adopts the freight train multi-particle model to establish the multi-objective optimization model of the freight train. Aiming at the problem of difficult optimization caused by complex line conditions, a two-step method is used to find the optimal operation strategy of the freight train. Firstly, the greedy algorithm is used to select the optimal working condition sequence. Secondly, the multi-objective optimization algorithm is used to obtain the position of the ideal working condition transition point. By introducing the idea of non-dominated sorting, an improved multi-objective bald eagle search algorithm is proposed to optimize the operation process of freight trains. This algorithm adopts the evolution method of combining bald eagle population renewal with adaptive Gaussian mutation, and introduces preference information to increase the rationality of population evolution. The simulation results show that the optimal operation strategy of freight train selected by two-step method is in line with the actual operation situation, and the proposed multi-objective bald eagle search algorithm considers both convergence and distribution. The results can satisfy the preference of decision-makers, which can provide a reference target speed curve for railway workers.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;