Trapezoidal Profile Research Articles

Dizajn i razvoj sistema robotskih ruku za klasifikaciju i sortiranje primenom mašinskog vida

The main focus of this paper is to design and develop a system of two robot arms for classifying and sorting objects based on shape and size using machine vision. The system uses a low-cost and high-performance hierarchical control system including one master and two slaves. Each slave is a robot controller based on a microcontroller that receives commands from the master to control the robot arm independently. The master is an embedded computer used for image processing, kinematic calculations, and communication. A simple and efficient image processing algorithm is proposed that can be implemented in real-time, helping to shorten the time of the sorting process. The proposed method uses a series of algorithms including contour finding, border extraction, centroid algorithm, and shape threshold to recognize objects and eliminate noise. The 3D coordinates of objects are estimated just by solving a linear equation system. Movements of the robot's joints are planned to follow a trapezoidal profile with the acceleration/deceleration phase, thus helping the robots move smoothly and reduce vibration. Experimental evaluation reveals the effectiveness and accuracy of the robotic vision system in the sorting process. The system can be used in the industrial process to reduce the required time to achieve the task of the production line, leading to improve the performance of the production line.

ДОСЛІДЖЕННЯ МОЖЛИВОСТІ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ТЕПЛООБМІНУ В МОДИФІКОВАНИХ ТРАПЕЦІЄВИДНИМ ГВИНТОВИМ ПРОФІЛІМ ТРУБАХ МАЗУТОПІДІГРІВАЧА ПМ-40-15

Recently, a special direction in solving the problem of intensification of convection heat exchange, which is based on the idea of influencing the micro- and macrostructure of the flow of heat carriers by various swirls in the channels of their movement, has been widely developed in industrial heat engineering. Despite the huge number of publications on this topic, the issue of improving the effectiveness of heat exchangers remains far from its final solution. The research is aimed at studying the possibilities and limits of increasing the efficiency of heat transfer in the modified trapezoidal helical profile of the inner surface of the pipes of the fuel oil heater PM-40-15. To achieve this goal, the method of computer simulation using SolidWorks software was used. In this program, a geometric model of a fuel oil heater was created with both smooth standard pipes and modified pipes with trapezoidal profiles with a height of h = 2, 3 and 4 mm and relative steps of the screw profile S/D = 0.6, 0.8, 1.0, 1.2 and 1.5. The temperature of fuel oil M100 at the inlet of the fuel oil heater was taken to be 60°С, and the temperature of the walls of the pipes washed with superheated steam at a pressure of 1.0 MPa, 200°С. These parameters corresponded to the nominal mode of operation of the fuel oil heater PM-40-15. As a result of the research, it was found that the best efficiency indicators are achieved on pipes with a profile height h = 2 mm and a relative step S/D = 0.8.

Parametric study of trapezoidally corrugated web beam

In this paper, the behaviour of cold-formed steel beam having trapezoidal corrugation profile of web has been studied by finite element method using ANSYS APDL V12.0. In this investigation, the considered parameters are corrugation angle, and the thickness of web plate. The corrugation angle has been varied from 30˚, 33˚, 36˚ 39˚, 42˚ and 45˚. The thickness of the web is taken as 3 mm. From the study, it is concluded that a rise in corrugation angle leads to an increase in the strength capacity of beams. The average increase in strength capacity of a corrugated web beam is 22% over a plain web beam. The 45˚ angle of web corrugation is found to be excellent amongst all angles of web corrugation. The height to thickness (h/tw) ratio is the main variable responsible for the buckling of the beam. As the ultimate load behaviour of trapezoidal corrugated web beams with stiffeners was found to be better than beams without stiffeners, therefore its importance cannot be neglected in the analysis and design.

Molecular understanding of calorimetric protein unfolding experiments

Testing and predicting protein stability gained importance because proteins, including antibodies, became pharmacologically relevant in viral and cancer therapies. Isothermal scanning calorimetry is the principle method to study protein stability. Here, we use the excellent experimental heat capacity Cp(T) data from the literature for a critical inspection of protein unfolding as well as for the test of a new cooperative model. In the relevant literature, experimental temperature profiles of enthalpy, Hcal(T), entropy, Scal(T), and free energy, Gcal(T) are missing. First, we therefore calculate the experimental Hcal(T), Scal(T), and Gcal(T) from published Cp(T) thermograms. Considering only the unfolding transition proper, the heat capacity and all thermodynamic functions are zero in the region of the native protein. In particular, the free energy of the folded proteins is also zero and Gcal(T) displays a trapezoidal temperature profile when cold denaturation is included. Second, we simulate the DSC-measured thermodynamic properties with a new molecular model based on statistical-mechanical thermodynamics. The model quantifies the protein cooperativity and predicts the aggregate thermodynamic variables of the system with molecular parameters only. The new model provides a perfect simulation of all thermodynamic properties, including the observed trapezoidal Gcal(T) temperature profile. Importantly, the new cooperative model can be applied to a broad range of protein sizes, including antibodies. It predicts not only heat and cold denaturation but also provides estimates of the unfolding kinetics and allows a comparison with molecular dynamics calculations and quasielastic neutron scattering experiments.

Superlattice of spherical quantum dots with a trapezoidal potential profile with weak coupling of quasiparticles between layers of quantum dots

A theoretical study of the spectrum of quasiparticles in a superlattice of spherical quantum dots (QDs) with a trapezoidal potential profile with a weak coupling of quasiparticles between QD layers is carried out. The calculations were performed using the example of spherical QDs InGaAs embedded in GaAs in the form of a superlattice. The model of the trapezoidal QD profile with three variable parameters is especially suitable for considering such zero-dimensional structures when, due to the different lattice constants of the QD material and the matrix medium, the boundary between them is fuzzy and is modeled by a certain transition region. The dependences of the energies of the underlying bands on the geometric parameters of the superlattice are investigated, which can be used to determine the metric of zero-dimensional structures by comparing it with the experimental intraband absorption spectra. The sensitivity of the position of the bands to changes in the parameters of the potential profile is revealed, which makes it possible to efficiently analyze the tunneling passage of carriers between QDs, to study the processes of controlled relaxation of carriers in QDs, which is important for the operation of lasers based on zero-dimensional structures with mismatched lattice constants of the QD material and the matrix medium.

Principle of torque formation with reduced pulsation in switched reluctance motor with U-shaped poles

In the paper the types of motors for vehicles and highlights the switched reluctance motor type as one that has a simple design, high reliability and low cost. The principle of operation of switched reluctance motors (SRM) and their modifications are given. However, the widespread use of SRM in vehicles is constrained by the low specific torque and its high ripple. To increase the specific torque, a paired winding of windings on adjacent rods of U-shaped stator poles is proposed. The principle of formation of rotational force is shown and the estimation of efficiency of use of the electric power for its formation is offered. The COMSOL Multiphysics software environment analyzes the advantages and disadvantages of using U-shaped poles with a trapezoidal and rectangular profile, and selected the latter because of the greater torque at the same dimensions. It is shown that the width of the pole rods with a rectangular profile to ensure maximum torque should be about a third of the width of the base of the pole. A typical form of current of the pole winding, which minimizes the pulsation of the moment, is analyzed. The expediency of designing a specialized electric drive for the proposed topology of SRM and synthesis for it of the control law, which provides the required value of the moment with minimal ripple, is substantiated. As usual, to ensure the constant moment generated by the pole in a certain sector it is necessary to form a current of near trapezoidal shape in the pole winding. As a result of the research, conclusions were made about the possibility of reducing the cost of SRM technology when using a modular structure based on U-shaped poles with paired winding at the stator poles, in which the windings are wound on the rod of two adjacent poles, which allows them to be placed compactly the use of additional space and, accordingly, provides a greater density of the poles. Modeling the process of forming the torque of the motor in the COMSOL Multiphysics software environment showed the advantages of using poles with a rectangular profile compared to trapezoidal poles and confirmed the feasibility of using poles with a rod width of about a third of the pole base width.

Experimental measuring of printing speed in FDM

Fused Deposition Modeling (FDM) technology, based on material extrusion, helps additively manufacture, using cheap printers, stable mechanical parts in different materials. The dimensional deviations and staircase effect are the main drawbacks of this approach and limit its use to prototypes. The linear interpolation used to define the hot-end movements is responsible for continuous speed changes along the tool-path, contributing to dimensional and surface errors. In that sense, the study of the speed profile can help to improve the process. This work explains two printing speed estimation approaches an out-process measurement method, which estimates the average speed as a function of the interpolation segment length and direction, and an in-process method based on encoder measurements. We applied these solutions and an analytical approximation based on a trapezoidal speed profile to a printed 3D Archimedean spiral. All approaches detect abrupt speed changes, potential candidates to produce extrusion-movement synchronization problems, and, therefore, part errors.

Effects of internal dynamics on chemotactic aggregation of bacteria

The effects of internal adaptation dynamics on the self-organized aggregation of chemotactic bacteria are investigated by Monte Carlo (MC) simulations based on a two-stream kinetic transport equation coupled with a reaction–diffusion equation of the chemoattractant that bacteria produce. A remarkable finding is a nonmonotonic behavior of the peak aggregation density with respect to the adaptation time; more specifically, aggregation is the most enhanced when the adaptation time is comparable to or moderately larger than the mean run time of bacteria. Another curious observation is the formation of a trapezoidal aggregation profile occurring at a very large adaptation time, where the biased motion of individual cells is rather hindered at the plateau regimes due to the boundedness of the tumbling frequency modulation. Asymptotic analysis of the kinetic transport system is also carried out, and a novel asymptotic equation is obtained at the large adaptation-time regime while the Keller–Segel type equations are obtained when the adaptation time is moderate. Numerical comparison of the asymptotic equations with MC results clarifies that trapezoidal aggregation is well described by the novel asymptotic equation, and the nonmonotonic behavior of the peak aggregation density is interpreted as the transient of the asymptotic solutions between different adaptation time regimes.

Heat transfer analysis of longitudinal fins of trapezoidal and dovetail profile on an inclined surface

The trapezoidal and dovetail profiled longitudinal fin structures exposed to a convective-radiative environment and mounted on an inclined surface have been considered for the analysis. The fin structures have been assumed to be porous and fully wet in nature. The Darcy model has been implemented to simulate the fluid-solid interactions. Further, the convective and radiative heat transfer coefficients have been taken to be temperature-dependent. The resulting equation has been reduced by introducing the non-dimensional quantities and then solved by employing the Runge-Kutta Fehlberg 4th–5th order method along with the shooting technique. The effect of tip tapering, angle of inclination, fully wet nature, porosity, internal heat generation, and other pertinent parameters on the fin thermal profile and fin heat transfer rate has been presented graphically and discussed. It has been inferred that the dovetail fin profile achieves the highest heat transfer rate followed by rectangular and trapezoidal fin profiles provided the internal heat generation is minimal. The present work is significant for fin design purposes and also acts as a verification tool for future research.

VERTICAL STRESS DISTRIBUTION AT THE BASE OF SOIL DAMS WITH A TRAPEZOIDAL CROSS SECTION

Problem statement. The research materials outlined in this work make it possible to construct the design profile of dams from soil materials, taking into account the strong compressibility of the soil and check the strength of the foundation of soil dams in depth. In addition, the results obtained by us can be used to determine the lower boundary of the compressible thickness of the bases, to the upper boundary of which a distributed load of either a triangular or trapezoidal shape is applied. Methods. Theoretical studies of geomechanical processes using analytical and numerical mathematical methods. Analysis and generalization of the results of theoretical research. Results. In the course of writing this article, we obtained analytical dependences of stresses at the base of earth dams on the coordinates and applied to the upper boundary of the base of the trapezoidal external load and showed the methods of accounting. Scientific novelty. Analytical dependences of vertical normal at the base of a soil dam with a trapezoidal profile have been obtained. The profiles of the dam in the form of isosceles and non-isosceles trapezoids are considered. Practical significance. The research materials outlined in this work make it possible to construct the design profile of dams from soil materials, taking into account the strong compressibility of the soil and check the strength of the foundation of soil dams in depth. In addition, our results can be used to determine the lower boundary of the compressible strata of the bases, to the upper boundary of which a distributed load of either a triangular or trapezoidal shape is applied.

Design and analysis of broadband guided-mode resonant reflectors with coated triangular and trapezoidal profiles in TE polarization.

A low-refractive-index grating layer with symmetrical triangular/trapezoidal grooves covered with a high-refractive-index Si layer is used to design a broadband guided-mode resonant reflector. Software Rsoft is used to simulate the reflection and transmission spectra as well as the internal electric field distribution at the resonant wavelength. It is discovered that the interaction between resonant modes promotes the formation of a wideband spectrum. The reflector has been proven to provide wideband (Δλ > 450 nm) and high reflectivity (R > 98.4%) spectra over a wide range of base angles from 44° to 72°, and the maximum high reflectivity (R > 99%) spectral range in transverse electric polarization is 458 nm, spanning 1422 to 1880nm. The results not only demonstrate excellent tolerance to the base angle and grating depth but also provide more possibilities for the design of broadband reflectors.

Investigation of Lateral Confinement, Roller Aspect Ratio and Wear Condition on HPGR Performance Using DEM-MBD-PRM Simulations

It has been known that the performance of high-pressure grinding rolls (HPGR) varies as a function of the method used to laterally confine the rolls, their diameter/length (aspect) ratio as well as their condition, if new or worn. However, quantifying these effects through direct experimentation in machines with reasonably large dimensions is not straightforward, given the challenge, among others, of guaranteeing that the feed material remains unchanged. The present work couples the discrete element method (DEM) to multibody dynamics (MBD) and a novel particle replacement model (PRM) to simulate the performance of a pilot-scale HPGR grinding pellet feed. It shows that rotating side plates, in particular when fitted with studs, will result in more uniform forces along the bed, which also translates in a more constant product size along the rolls as well as higher throughput. It also shows that the edge effect is not affected by roll length, leading to substantially larger proportional edge regions for high-aspect ratio rolls. On the other hand, the product from the center region of such rolls was found to be finer when pressed at identical specific forces. Finally, rolls were found to have higher throughput, but generate a coarser product when worn following the commonly observed trapezoidal profile. The approach often used in industry to compensate for roller wear is to increase the specific force and roll speed. It has been demonstrated to be effective in maintaining product fineness and throughput, as long as the minimum safety gap is not reached.

Installation of Novel Suction Bucket Foundation with New Modular Geometry in a Large-scale Set-up

This paper investigates a modular bucket foundation design developed for large offshore wind turbines. Instead of the regular round shape, the modular bucket consists of trapezoidal profiles bolted together and additional stiffeners attached to the inside skirt. The design is more cost-effective and gives much higher buckling resistance during installation compared with the standard round bucket, which serves as a reference point in the research. The paper includes both jacking installation and suction installation tests performed on a large-scale set-up at Aalborg University. The installations took place in sand of varying relative density. Each test consists of measurements for the applied force or suction and the excess pore pressure around the bucket skirt with increasing penetration depth until full installation. Results indicate that regardless of the significant increase in soil penetration resistance of modular bucket measured during jacking installation, the required suction for installation in different sand conditions is very similar for both models. The data are compared with a cone penetration test (CPT)-based method for the calculation of soil penetration resistance. The method is adjusted according to the experimental results supported by finite-element method analysis.

Real - Time Trajectory and Velocity Planning for Autonomous Vehicles

Path planning algorithm integrated with a velocity profile generation-based navigation system is one of the most important aspects of an autonomous driving system. In this paper, a real-time path planning solution to obtain a feasible and collision-free trajectory is proposed for navigating an autonomous car on a virtual highway. This is achieved by designing the navigation algorithm to incorporate a path planner for finding the optimal path, and a velocity planning algorithm for ensuring a safe and comfortable motion along the obtained path. The navigation algorithm was validated on the Unity 3D Highway-Simulated Environment for practical driving while maintaining velocity and acceleration constraints. The autonomous vehicle drives at the maximum specified velocity until interrupted by vehicular traffic, whereas then, the path planner, based on the various constraints provided by the simulator using µWebSockets, decides to either decelerate the vehicle or shift to a more secure lane. Subsequently, a splinebased trajectory generation for this path results in continuous and smooth trajectories. The velocity planner employs an analytical method based on trapezoidal velocity profile to generate velocities for the vehicle traveling along the precomputed path. To provide smooth control, an s-like trapezoidal profile is considered that uses a cubic spline for generating velocities for the ramp-up and ramp-down portions of the curve. The acceleration and velocity constraints, which are derived from road limitations and physical systems, are explicitly considered. Depending upon these constraints and higher module requirements (e.g., maintaining velocity, and stopping), an appropriate segment of the velocity profile is deployed. The motion profiles for all the use-cases are generated and verified graphically.

The numerical parametric study of the stress-strain state of I-beams having versatile corrugated webs

Introduction. The numerical parametric study of the stress-strain state of I-beams, having versatile corrugated walls, was carried out in the ANSYS Mechanical APDL software package. Numerical results are obtained for displacements, equivalent stresses and stability coefficients depending on the change in the inclination angle of web corrugations for trapezoidal, wavy and triangular profiles. The obtained results can help to design and substantiate the design solutions applicable to bending elements.
 Materials and methods. The parametric study involved a series of numerical experiments conducted using the finite element method in the ANSYS Mechanical APDL software package. APDL parametric language was used to develop the software that was built into the software package. It allowed to perform a parametric reconstruction of the numerical model depending on varied parameters of the corrugated wall, and the reconstruction was followed by the numerical solution and post-processing of the calculation results. The calculations were made with the help of the model whose overall dimensions and material were identical to those of a standard I-beam having a solid wall exposed to a uniformly distributed transverse load.
 Results. The parametric study enabled the co-authors to identify the main features of the stress-strain state of the beams that had different types of corrugated walls. A parametric numerical model was compiled to determine maximum displacements, equivalent stresses and stability coefficients for various types of corrugated walls and various parameters of the corrugation angle. Isofields of equivalent stresses and buckling modes are provided for characteristic parameters and types of corrugations. The reliability of the obtained results was confirmed by the verification of the numerical model using the method of the strength of materials and corrugation inclination angle α = 0, which was the initial point of simulation for all types of corrugations.
 Conclusions. The results, obtained in the course of parametric studies, have identified the main features of the stress-strain state of beams having corrugated walls; they allow to substantiate their effectiveness as design solutions applied to bending elements.

FPGA-Based Hybrid Stepper Motor Drive System Design by Variable Structure Control

A stepper motor is usually operated in position open-loop control for simplicity. However, in order to improve the transient and steady-state performances of the stepper motor-based drive system, a high performance stepper motor drive system is usually designed to feed the encoder signal back to form a closed-loop system such as a general servo motor drive, and high-performance position and speed loop controller can then be used to overcome the nonlinear characteristics of the motor, such as the cogging force and impacts from external load. On the other hand, the existed cogging force of the hybrid stepper motor must be solved to increase the positioning precision. The variable structure control (VSC) is insensitive to the bounded uncertainty and load disturbance, and has been known as a high-performance controller. A predefined sliding surface is used to shape the system performances, and incorporate with switching control to achieve the robustness property. Thus, we applied the VSC to implement the stepper motor drive system about the position and speed control, and the switching control is used to overcome the cogging force. The field programmable gate array (FPGA) is a good alternative to be used to realize a motor drive system by considering its programmable ability and diverse designing environment. It is easily developed as an intellectual property (IP) for future use or combined as a part of a large control system. This paper showed the procedures to develop the hardware circuits for the variable structure controller, and applied it to stepper motor position and velocity control. Functions such as PI controllers, dq-axis transformation and two-phase space vector space vector modulation (SVPWM) designed for the stepper motor drives are also shown in the paper. The system simulation and hardware circuit realization are based on MATLAB/Simulink, and realized on Altera FPGA. Simulations on MATLAB/Simulink with trapezoidal velocity profile command, and experiments with and without the load added are shown to demonstrate the hardware performances and correctness.

Time to Collision for Emergency Obstacle Avoidance


 
 
 Time to collision is one of the indices to decide if a collision is avoidable. This paper presents the study on emergency obstacle avoidance from the viewpoint of time to collision. The times to collision at which the autonomous emergency steering has to be initiated to avoid a collision are derived for the five functions which are used for the generation of the emergency lane change paths. These functions are circular arcs, polynomial, ramp sinusoidal, sigmoid, and trapezoidal acceleration profiles. The times to collision at which the steering avoidance by using these functions has to be initiated are computed and compared. For a given lane change maneuver width of 3.5 m and coefficients of friction of 0.9, 0.5, 0.2, circular arcs give the shortest, and sigmoid gives the longest time to collision.
 
 

CFRP ropes for retrofitting heat-damaged concrete beams

The contribution of fiber reinforced polymer (CFRP) ropes for recovering mechanical performance of post-heated reinforced concrete beams is experimentally investigated. The ropes are implemented at variable profiles (parabolic, trapezoidal, and straight) within the side cover (NSM) or through the core of concrete beams (post-heated for 3 h to 400 and 500 °C). The mechanical response was evaluated under the effect of four-point loading with deflection and elongation measurements (in CFRP ropes) acquired versus loading up till failure. Meanwhile, load cracking formation and propagation until failure were observed and documented. Post-heating performance was also evaluated in terms of cracking severity and degradation in mechanical properties of concrete and reinforcing steel. The repaired beams recovered partially to fully their original load capacity while lost modest portion of their rotational ductility (at 17–37%). The best mechanical performance is attained when using the parabolic followed by the trapezoidal profiles. Higher damage extent had a more negative impact upon repair efficiency, evaluated by the different performance indicators of the study. Except that repaired with a straight profile, all beams showed sudden shear failure upon the rupture of the CFRP ropes near their anchorage ends. • It is advisable to strengthen concrete beams with SNSM CFRP ropes at variable profiles. • The best repair benefit was attained using a parabolic profile of SNSM CFRP ropes. • Anchorage of the CFRP ropes at their ends led to a significant improvement in repair efficiency. • Use of CFRP ropes at variable profiles altered the failure modes for the heat-damaged beams.

Roadbed Sedimentation on Folded Bases with Weak Soils

Purpose. The main purpose of the work is to construct accurate analytical dependences of the sedimentation of the roadbed base on its coordinates and the trapezoidal external load applied to the upper limit of the base. This will allow the foundation settlement profile to be calculated within and outside the embankment using the layer-by-layer stacking method. Methodology. Theoretical studies of geomechanical processes using analytical and numerical mathematical methods were applied to achieve the purpose, as well as analysis and generalization of the results of theoretical research. Findings. Analytical dependences of vertical and horizontal normal deformations on the half-plane coordinates to the upper limit of which the trapezoidal load is applied were obtained within the framework of the base model in the form of a linear elastic isotropic medium and the calculated scheme of planar deformation. On this basis, an algorithm for constructing a profile of a roadbed sedimentation made of soil materials has been developed. Originality. Analytical dependences of vertical normal deformations in the roadbed base with a trapezoidal profile on its coordinates are obtained. Practical value. The research materials presented in this work make it possible to construct the design profile of the roadbed of soil materials, taking into account the strong compressibility of the soil. In addition, the results obtained can be used to determine the lower limit of the compressible strata of the bases, to the upper limit of which a distributed load of either a triangular or a trapezoidal form is applied.

Energy consumption optimization for AC drives position control

PurposeThe main purpose of this paper is to evaluate the two energy saving position control strategies for AC drives valid for a wide range of boundary conditions including an analysis of their energy expenses.Design/methodology/approachFor energy demands analysis, the optimal energy control based on mechanical and electrical losses minimization is compared with the near-optimal one based on symmetrical trapezoidal speed profile. Both control strategies respect prescribed maneuver time and define acceleration profile for preplanned rest-to-rest maneuver.FindingsPresented simulations confirm lower total energy expenditures of energy optimal control if compared with near-optimal one, but the differences are only small due to the fact that two energy saving strategies are compared.Research limitations/implicationsDeveloped overall control system consisting of energy saving profile generator, pre-compensator and position control system respecting principles of field-oriented control is capable to track precomputed state variables precisely.Practical implicationsEnergy demands of both control strategies are verified and compared to simulations and preliminary experiments. The possibilities of energy savings were confirmed for both control strategies.Originality/valueExperimental verification of designed control structure is sufficiently promising and confirmed assumed energy savings.