Spring System Research Articles

Design criteria study and simulation for underactuated symmetric pinching mechanism of pinch roll machine in high-speed wire rod product line

Inspired by the underactuated robotic hand mechanism and its feature of shape adaptive and compliant envelop grasping, the paper presents an underactuated symmetric pinch mechanism to solve the problem of pinch rollers idle and slipped or pinched too tightly. Pinch roll machine is a key device in the high-speed wire rod product line. It is usually designed with actuated symmetric pinch mechanism. The paper considered the pinching and conveying condition of linear objects and discussed the possibility of the underactuated symmetric pinch mechanism to be applied in the pinch roll machine for the first time. Three kinds of underactuated symmetric pinch mechanism solutions are presented. A displacement can be generated at the underactuated joint when the symmetric synchronous pinch action is implemented. The spring system can buff the instantaneous clamping force to reduce the dynamic impact of clamping force. Suitable design criteria are deduced from statics and kinematics analysis. In the process of pinching and conveying wire rods, the contact force is required to be kept at a constant value when the size of wire rods changes. Thus, it can protect the rod from being damaged while pinching and conveying and it can avoid the fatigue damage caused by excessive pinching impact force. Then, the pinching and conveying conditions of four different kinds of variable diameter wire rods are analyzed through 3D modeling and motion simulation experiments. Simulation results show that the proposed underactuated pinching and conveying mechanism can satisfy shape adaptive pinching and conveying irregular long-shaped wire rods. The research method is novel and feasible. The design result will be beneficial to improve the service life of the pinch roll machine.

Asymptotically exact photonic approximations of chiral symmetric topological tight-binding models

Topological photonic edge states, protected by chiral symmetry, are attractive for guiding wave energy as they can allow for more robust guiding and greater control of light than alternatives; however, for photonics, chiral symmetry is often broken by long-range interactions. We look to overcome this difficulty by exploiting the topology of networks, consisting of voids and narrow connecting channels, formed by the spaces between closely spaced perfect conductors. In the limit of low frequencies and narrow channels, these void–channel systems have a direct mapping to analogous discrete mass–spring systems in an asymptotically rigorous manner and therefore only have short-range interactions. We demonstrate that topological tight-binding models that are protected by chiral symmetries, such as the SSH model and square-root semimetals, are reproduced for these void–channel networks with appropriate boundary conditions. We anticipate, moving forward, that this paper provides a basis from which to explore continuum photonic topological systems, in an asymptotically exact manner, through the lens of a simplified tight-binding model.

Failure properties of flexible composite under trouser-shaped tests

The failure properties of trouser-shaped tests on flexible composite called Uretek-3216LV were studied by experiment and theory. Based on the failure mechanical behavior of the trouser-type tests, theoretical model of the three stages (displacement, fiber stretching, and fiber breaking) were established. In the model, a spring system including the tail, tear del, and the fiber elongation is introduced to characterize the mechanical behavior of the displacement stage and the fiber stretching stages. Based on the strain wave model, the failure model of fiber breaking stage is established. Based on the trouser tearing tests and failure model, the trouser-shaped failure performance of flexible composites was analyzed in detail.

A discrete differential geometry-based numerical framework for extensible ribbons

As a typical mechanical structure, ribbons are characterized with three distinctly different dimensions, i.e., length ≫ width ≫ thickness, which leads to their exclusive behaviors different from the one-dimensional (1D) case of slender rods and the two-dimensional (2D) case of thin plates. In this paper, we report a discrete differential geometry (DDG)-based numerical method to simulate the geometrically nonlinear deformations of extensible ribbons. With a cross section-dependent regularized parameter introduced, the proposed 1D framework allows both in-plane stretching and out-of-plane bending in the ribbon mid-surface, aimed at bridging the gap between the linear Kirchhoff rod theory and the developable Sadowsky ribbon model. Instead of solving the ordinary differential equations (ODEs) directly with the associated boundary conditions, the mechanical object is discretized into a mass–spring system, and its equilibrium configuration is obtained through a dynamic relaxation method. The numerical framework is applied to seven typical occasions based on either experimental or published datasets in order to verify its performance. Quantitative agreements demonstrate the effectiveness and accuracy of the proposed discrete approach for extensible ribbons, which, as a computationally efficient numerical simulator, could provide a pivotal understanding of a batch of slender structures, and further inspire the simulation-guided design of man-made systems.

Derivation and Validation of Bandgap Equation Using Serpentine Resonator

Bandgap refers to a frequency band where free waves do not propagate. One of the characteristics of a bandgap is its ability to block the propagation of bending waves in a specific frequency band with a periodic structure. Additionally, it has been reported in previous studies that the vibration-reduction performance of a bandgap is superior to that of other reduction methods. A bandgap can be generated in various frequency bands through a simple parameter change in the unit structure. However, the bandgap for a desired frequency band can be determined accurately only with intensive simulations. To overcome this limitation, we have mathematically derived the bandgap using a serpentine spring as a unit structure. The bandgap equation is derived from the general mass–spring system and the final bandgap is derived by substituting the system into the serpentine resonator. The error map for the major design parameter is confirmed by comparing the derived bandgap with the simulation result. In addition, the theoretical bandgap is compared to the experiment value and the vibration-reduction performance of the serpentine resonator is also confirmed. Based on the theoretical and experimental result, the proposed serpentine resonator verifies that the bandgap can be derived mathematically without numerical analysis. Therefore, serpentine resonator is expected to have various applications since it dramatically reduces the time and cost for forming the bandgap of the desired frequency band.

A simple particle–spring method for capturing the continuous–discontinuous processes of brittle materials

Comparing to the continuum-based method such as the finite element method (FEM), particle–spring method can relatively easily simulate the cracking processes of brittle materials such as rocks by deactivating or adjusting springs/contacts. However, it is still challenging for building the equivalence between particle–spring system and the original continuous media, then capturing the whole continuous–discontinuous processes. In this work, a simple particle–spring system is proposed in which different types of springs are introduced including normal, tangential, pure shearing and Poisson’s springs. The stiffness of the springs are obtained by bridging the proposed model and triangular FEM element. Moreover, novel mixed type failure criteria for the breakage of the springs are also provided. By numerical studies the reliability and robustness of the model are proven which gives comparable results to the conventional FEM model. With the new model, progressive failure processes of rock-like material can be properly captured.

Distribution, sources and transport of polycyclic aromatic hydrocarbons (PAHs) in karst spring systems from Western Hubei, Central China

Karst groundwater is an important water resource but it is vulnerable to contaminants, due to the distinctive geological features of abundant transmissive fractures and conduits in the karst area which connect the surface to the underground systems. Anthropogenic activity-derived polycyclic aromatic hydrocarbons (PAHs) on the surface environment could enter groundwater easily and rapidly and threaten water security in karst areas. Samples in the multimedia environment from 10 specific karst spring systems from Western Hubei of Central China were collected to analyze 16 priority PAHs and to investigate their transport in these karst spring systems. The total concentrations of PAHs in the soil, river water, river sediments, spring water, and spring sediments ranged between 6.04 and 67.7 ng g−1, 4.56 and 11.4 ng L−1, 29.9 and 1041 ng g−1, 4.09 and 222 ng L−1, and 5.88 and 83.0 ng g−1, respectively. Levels of PAHs in this area were relatively low when compared to other karst areas. Proportions of low-molecular-weight (LMW)-PAHs in the water, sediments and soil (average 58.2–78.8%) were much higher than those of high-molecular-weight (HMW)-PAHs. The proportion of LMW-PAHs in the sediments (especially in river sediments) was higher than that in the soil. Characteristic ratio analysis and principal component analysis showed that PAHs were from high-temperature combustion of the mixture of coal and biomass, and vehicle emission, where coal and biomass combustion were the dominant sources. Significant correlations of PAH compositions in different media of karst spring systems were observed, especially in the Yuquangdong (YQD)-Migongquan (MGQ), Jiuzhenziquan (JZZQ), Xianyudong (XYD) and Fengdong (FD) karst spring systems, indicating the rapid PAH transport from the recharge area soil to the discharge area of spring water and sediments.

Co-deriving the Formulas for Centripetal Acceleration and Mass-Spring Period

There is a close connection between simple harmonic motion and uniform circular motion. This connection is widely taught and included in standard textbooks. Here, we exploit this connection to simultaneously derive two results from introductory mechanics: the period of a mass- spring system and the centripetal acceleration formula.Previously published derivations of the centripetal acceleration formula often rely on calculus, either via explicit computation or arguing geometrically about limits. One approach relies entirely on the kinematics of vectors, without invoking limits. Our approach likewise does not use limits, but is rooted in dynamics.

Characterization of Soft 3D Printed Actuators for Parallel Networks

Soft pneumatic actuators allow compliant force application and movement for a variety of tasks. While most soft actuators have compliance in directions perpendicular to their direction of force application, they are most often analyzed only in their direction of actuation. In this work, we show a characterization of a soft 3D printed bellows actuator that considers shear and axial deformations, modeling both active and passive degrees of freedom. We build a model based on actuator geometry and a parallel linear and torsional spring system which we fit to experimental data in order to obtain the model constants. We demonstrate this model on a soft delta mechanism and show how this single actuator model can be used to predict parallel structures of actuators with average positional errors of 4.0%. These results verify that the presented model and modeling approach can be used to speed up the design and simulation of more complex soft robot models by characterizing both active and passive forces of their one degree-of-freedom soft actuators.

CVGC-II: A New Version of a Compact Variable Gravity Compensator With a Wider Range of Variable Torque and Energy-Free Variable Mechanism

This article proposes a new version of a variable gravity compensation mechanism (CVGC-II) for mobile manipulation robots, such as mobile manipulators and exoskeletons. CVGC-II, which incorporated an energy-free variable mechanism in a smaller design space, exhibited improved performance with a wider range of variable torque values. These enhancements were achieved by adopting an optimal curved lever and hybrid spring system. First, the mechanism concept and specifications of the CVGC mechanism are described. Next, the contribution of the curved lever and hybrid spring system to the performance enhancement of CVGC-II is explained. Subsequently, the design methodologies for the main mechanical elements, including the lever, hybrid spring, and cam, are introduced. In the lever design, Hermite spline and B-spline curve model-based optimization is performed to generate the optimal curved shape of the lever. The hybrid spring system, consisting of compression coil springs and layered leaf springs, helps achieve a wider variable range by maximizing the storable energy in a limited design space. The experimental results showed that CVGC-II exhibited a 6.8 times wider variable range and energy-free variable mechanism under 1.5 and 1.3 times smaller size and weight, respectively.

Spatial and Temporal Evolution of Groundwater Chemistry of Baotu Karst Water System at Northern China

Karst water quality degradation has been a challenge for domestic and industrial water supplies worldwide. To reveal the possible factors response for karst water quality degradation, Baotu karst spring system is studied as an representative example. In this study, a hydrogeochemical investigation and mathematical, statistical, and geochemical modeling was conducted together to identify the major hydrochemical processes involved in the degradation process. It is found that the karst water is normally fresh, neutral-to-slightly alkaline, with calcium and magnesium as the predominant cations, and bicarbonate and sulfate as the predominant anions. The abnormally high chloride (95.05 mg/L) and nitrate concentrations (148.4 mg/L) give clues to the potential source of contamination in some karst water. The main hydrochemical facies of karst water are HCO3-Ca and HCO3 × SO4-Ca, accounting for 76% of water samples. The water hydrochemistry is controlled mainly by the dissolution of carbonate minerals (calcite, dolomite), followed by the dissolution of silicate and gypsum. The dissolution of calcite and dolomite mostly happens in the recharge area. In the discharge area, the karst water is basically in equilibrium with calcite. The negative SI value of gypsum represents that the water–gypsum interaction is dominated by dissolution along the whole flow path. Cation exchange is observed in the karst water in the indirect recharge area. Along the flow path, the contents of chloride, sulfate, nitrate, and TDS (Total dissolved solids, abbreviated TDS, indicates how many milligrams of dissolved solids are dissolved in one liter of water) vary significantly, which is mostly affected by pollution from human industrial and agricultural activities. The concentrations of major ions were maintained at a low level (<20 mg/L) in the 1960s in karst water. The fast elevation of the parameter values has occurred in the past two decades. The temporal elevation of some pollutants in karst water suggest that global changes (acid rain) and human activity (such as overusing fertilizer) are main factors resulting in the degradation of karst water quality in the study area. The results of this paper provide invaluable information for the management and protection of karst water resources in the urban and rural areas.

Toward Optimal False Data Injection Attack against Self‐Triggered Model Predictive Controllers

AbstractThis paper is aimed at exploring the optimal false data injection (FDI) attack against continuous time self‐triggered model predictive control (STMPC) systems with sample‐and‐hold input signals to address the potential security defects. First, the mathematical model of FDI attack against the considered STMPC system is established. Then, the difference between the states of the nominal system and the attacked system is explicitly calculated such that the impact of FDI attacks on the STMPC systems can be quantitatively analyzed. And finally, an efficient and effective algorithm to realize the desired FDI attack is proposed, and in order to maintain the flexibility of the attacker, the designed FDI attack algorithm is developed under different attacking scenarios, including attacking a single control node at each sampling time and attacking multiple control nodes each time. Finally, two simulation experiments are carried out based on a robot system and a cart–damper–spring system to verify the efficacy and optimality of the designed FDI attack strategy.

Perbaikan Sistem Pelacakan Panel Surya Menggunakan Penyesuaian Posisi Massa Tambahan

This study aims to obtain an effective solar panel tracking mechanism using energy-efficient electric actuators. Furthermore, we designed and implemented a semi-active solar tracking system. A tracking system is proposed to control solar panel orientation using a moving mass, a spring system, and an actuator. The weight of the moving mass and the spring constant are optimized to reduce actuator size. A stepper motor was used for this case. This electric drive is not the prime mover of the solar tracker; hence, it works against mass elements lighter than solar panel weight as used in the active solar tracker. Experimental results suggest that the average power required by the stepper motor is 0.21% of the energy generated by the solar tracking system. The results indicate that the proposed solar panel tracker works satisfactorily to control solar panel orientation.

Response analysis and optimization of the air spring with epistemic uncertainties

Abstract Traditional methods for the optimization design of the air spring are based on the deterministic assumption that the parameters are fixed. However, uncertainties widely exist during the manufacturing stage of the air spring. To model the uncertainties in air springs, evidence theory is introduced. For the response analysis of the air spring system under evidence theory, an evidence theory-based polynomial chaos method, called the sparse grid quadrature-based arbitrary orthogonal polynomial (SGQ-AOP) method, is proposed. In the SGQ-AOP method, the response of the air spring is approximated by AOP expansion, and the sparse grid quadrature is introduced to calculate the expansion coefficient. For optimization of the air spring, a reliability-based optimization model is established under evidence theory. To improve the efficiency of optimization, the SGQ-AOP method is used to establish the surrogate model for the response of the air spring. The proposed response analysis and the optimization method were employed to optimize an air spring with epistemic uncertainties, and its effectiveness has been demonstrated by comparing it with the traditional evidence theory-based AOP method.

Java script animation of generator rotors under different modes of oscillation in two area four machine system

Computer technology advancements aid in the creation of instructional plans that allow students to study in a variety of ways. Animations and digital maps make it easier to understand abstract concepts and ensure that learning is permanent. Animation is a technique of creating continuous motion and shape change illusion. Interconnected power system often seems to be an intractably intricate morass of equations and ad hoc rules of thumb. Lack in visibility impedes learning about the power system phenomena. Animation can help us to convey information that would otherwise require a thousand or more words. This work is all about the development of a visualization tool in order to understand oscillatory dynamics of generator rotor. The power vs phase angle curve gradient interacting with generator rotor inertia forms an equivalent mass spring system. So, by this very reason different modes of oscillation in mass spring system are animated. A two area four machine system is modelled in MATLAB/Simulink by using Kron reduction technique and different modes of oscillation are analyzed. Later the animation of generator rotors of two area system are created with the help of HTML, Cascading Style Sheets (CSS) and Java Script. Each animation is coupled to the results obtained in MATLAB/Simulink under different modes of oscillation.

Fluid–structure interaction approach with smoothed particle hydrodynamics and particle–spring systems

This paper presents a novel three-dimensional fluid–structure interaction (FSI) approach, where the meshless smoothed particle hydrodynamics (SPH) method is used to simulate the motion of incompressible fluid flows, whilst structures are represented by a simplified approach based on particle–spring systems. The proposed FSI technique allows to use independent spatial–temporal resolutions for the fluid and structural computational domains. The particle–spring elastic constants are calibrated and relationships with the mechanical material properties, Young’s modulus and Poisson’s ratio, are determined. Fluid and structure computational domains are separated by interfaces made of triangular elements whose position is updated during the simulation following the structural deformation. The coupling of the two media at the fluid–structure interfaces is handled by the introduction of solid and fluid boundary particles. This approach, automatically and without introducing further complexity, avoids the penetration of fluid particles into the solid domain. The efficiency and accuracy and the present method are validated with analytical/benchmark solutions from the literature.

A convolutional-iterative solver for nonlinear dynamical systems

In this paper, a new solver is developed to obtain the solution of nonlinear dynamical systems. The method is based on alternative field equations in which the convolution product appears in place of dot products. The technique is higher-order accurate in the sense that the accuracy is not lost by increasing the time-step, conserving constants of motion. Several examples, including bilinear hardening and softening mass–spring systems and a nonlinear elastic pendulum, are considered to show the validity of the new method.

Surface reconstruction and tissue recognition for robotic-based in situ bioprinting

In this study, an innovative approach for the surface reconstruction and mechanical evaluation of anatomical defects for robotic-based in situ bioprinting applications is presented. A touch probe was developed to be used as the end-effector of a 5 Degrees-of-Freedom robotic arm. The probe, based on the combination of a spring system and a light sensor, is able not only to reconstruct the surface but also to register the penetration depth for each contact point. The knowledge of this parameter allows the evaluation of the mechanical properties of the substrate and thus the recognition of the biological tissue. The probe was able to correctly identify the elastic moduli of silicone substrates with various shapes and stiffnesses (E = 4–23–160 kPa) and showed good agreement compared with standard uniaxial compression test. In situ bioprinting tests were performed onto meshes reconstructed with the probe using different path planning methods. Finally, the presented in situ bioprinting workflow was tested as a proof-of-concept onto an anthropomorphic phantom to completely regenerate a cranial defect. The complete knowledge of the geometry and the mechanical properties of the damaged site allows a more accurate path planning, enabling the deposition of different biomaterials for different target tissues and so the regeneration of heterogeneous anatomical defects.

Complex stiffness model of an air spring with auxiliary chamber considering inertial effects of gas in connecting pipeline

In this paper, an analytical complex stiffness model of an air spring system with auxiliary chamber is established considering inertial effects of gas in connecting pipeline. The established model can reflect the resonance phenomenon of the dynamic stiffness curve due to the gas inertia in connecting pipeline as well as the amplitude dependent characteristic of the dynamic stiffness. To obtain the key parameters of the model, a finite element model of the air spring system and a CFD model of the pipeline are developed respectively, then relative simulation analyses are operated. The complex stiffness of air spring system is calculated and investigated with the proposed model. The calculation results are compared with that of the experiments and the existing complex stiffness model. It shows that the calculation results of the proposed model agree well with the experimental results. The proposed model is especially suitable for air spring systems with large pipeline gas inertia and low pipeline damping. Moreover, it is deduced that when the inertial effect of gas in the pipeline decreases and the damping of the pipeline increases, the proposed model in this paper can be transformed into the existing model. Thus, this new complex stiffness model has a wide application range.

Chaotic Harris hawks optimization algorithm

Abstract Harris hawks optimization (HHO) is a population-based metaheuristic algorithm, inspired by the hunting strategy and cooperative behavior of Harris hawks. In this study, HHO is hybridized with 10 different chaotic maps to adjust its critical parameters. Hybridization is performed using four different methods. First, 15 test functions with unimodal and multimodal features are used for the analysis to determine the most successful chaotic map and the hybridization method. The results obtained reveal that chaotic maps increase the performance of HHO and show that the piecewise map method is the most effective one. Moreover, the proposed chaotic HHO is compared to four metaheuristic algorithms in the literature using the CEC2019 set. Next, the proposed chaotic HHO is applied to three mechanical design problems, including pressure vessel, tension/compression spring, and three-bar truss system as benchmarks. The performances and results are compared with other popular algorithms in the literature. They show that the proposed chaotic HHO algorithm can compete with HHO and other algorithms on solving the given engineering problems very successfully.