Counterweight Mass Research Articles

Statics and dynamics of a lunar anchored tethered system

Space tethered system has various attractive potential applications and now serves as promising lunar infrastructures hopefully. In this paper, statics and dynamics of a lunar anchored space tethered system in the restricted Earth-Moon three-body system will be studied to enable future potential applications. Nonlinear dynamics and potential applications of a space tether system extending from the lunar surface to the Earth’s side are investigated. The static equilibrium equations of the system with a distributed mass tether are established at the L1 side without considering small perturbations caused by eccentricity to analyze internal stress, detailed cross-sectional profiles, and counterweight mass. The elastic deformations are discretized using the assumed modes method, and the Lagrangian approach is used to derive the dynamical equations of the system with a viscoelastic tether considering the elastic elongation within the elliptical Earth-Moon restricted three-body system (EEMRTB). The oscillations of the tether as well as the distribution of stress and strain are addressed using numerical analysis considering both construction difficulty and power generation capacity, the ideal design parameter ranges are provided based on the nonlinear dynamic analysis. Additionally, a brief analysis of the accessible regions within the Earth-Moon system is also conducted. The validity, accuracy and advantage of the established dynamics are clarified.

Counterweight mass influences single-leg cycling biomechanics

Counterweight mass influences single-leg cycling biomechanics

Method for Calculating the Counterweight Mass of a Crank-and-Rod Mechanism

Method for Calculating the Counterweight Mass of a Crank-and-Rod Mechanism

Simulation and Experimental Research on Active Balancing Self-healing System of Motor Counterweight Mass for PLC Regulation

Simulation and Experimental Research on Active Balancing Self-healing System of Motor Counterweight Mass for PLC Regulation

Selecting the Counterweight Mass for a Crank Mechanism

Selecting the Counterweight Mass for a Crank Mechanism

A double variable-length pendulum with counterweight mass, kinematic excitation and electromagnetic forcing

This study introduces a novel double variable-length cable pendulum model and experimental setup featuring elastic suspension and counterweight mass. Our main goal is to investigate the complex dynamics resulting from variable length’s impact on vibration frequency and amplitude. Through numerical simulations and experiments, we explore the system’s response to different external forces. Utilizing methods like phase plots, bifurcation diagrams, and Lyapunov exponents, we delve into nonlinear dynamics. We also use vision-based techniques to assess friction damping-related vibrations and magnetic field interactions. The results reveal diverse behaviors, including chaotic and periodic oscillations, shedding light on control functions and parameter relationships. The developed cable system captures intricate nonlinear dynamics and attains stable vibration modes, as confirmed by vision-based measurements. This platform can analyze and control irregular dynamics in systems with elastically suspended weights driven by motors or mobile cranes. Its nature, encompassing kinematic excitation, electromagnetic interactions, and sliding friction, allows for exploring complex nonlinear dynamics. The system’s capacity to modulate vibration frequencies contributes to mitigating persistent vibrations.

A method for simulating forward falls and controlling impact velocity

Assessment of protective arm reactions associated with forward falls are typically performed by dropping research participants from a height onto a landing surface. The impact velocity is generally modulated by controlling the total height of the fall. This contrasts with an actual fall where the fall velocity is dependent on several factors in addition to fall height and not likely predictable at the onset of the fall. A counterweight and pulley system can be used to modulate the fall velocity in simulated forward falls in a manner that is not predictable to study participants, enhancing experimental validity. However, predicting the fall velocity based on participant height and weight and counterweight mass is not straightforward. In this article, the design of the FALL simulator For Injury prevention Training and assessment (FALL FIT) system is described. A dynamic model of the FALL FIT and counterweight system is developed and model parameters are fit using nonlinear optimization and experimental data. The fitted model enables prediction of fall velocity as a function of participant height and weight and counterweight load. The method can be used to provide controllable perturbations thereby elucidating the control strategy used when protecting the body from injury in a forward fall, how the control strategy changes because of aging or dysfunction or as a method for progressive protective arm reaction training.•Construction of device to simulate forward falls with controllable impact velocity using material that are commercially available is described•A dynamic model of the FALL FIT is developed to estimate the impact velocity of a simulated forward fall using participant height and counterweight load•The dynamic model is validated using data from 3 previous studies

The Dependency of the Dynamic Response of a Two Mast Bucket Wheel Excavator Superstructure on the Counterweight Mass and the Degree of Fourier Approximation of the Digging Resistance

The Dependency of the Dynamic Response of a Two Mast Bucket Wheel Excavator Superstructure on the Counterweight Mass and the Degree of Fourier Approximation of the Digging Resistance

A novel multimodal piezoelectric energy harvester with rotating-DOF for low-frequency vibration

This paper proposes a novel piezoelectric energy harvester with rotating-DOF to efficiently achieve multimodal vibration energy harvesting in low-frequency environments. The designing of the harvester based on the beam whose ends were connected to rotating shafts was accomplished firstly, and then the dynamic properties of the structure were numerically calculated by finite element analysis. Finally, experimental prototypes and test systems were designed to verify the correctness of the theory. This paper analyzed how that different key structural parameters and acceleration affect its output characteristics. Especially, the effect of double-rotating shafts on the energy harvesting performance was analyzed innovatively. The results acquired by experiments were in accord with those of simulation. Its first-order resonant frequency is down to 12.65 Hz, at which excellent output characteristics were obtained. The harvesting performance at the third-order resonant frequency was also remarkable, indicating the application prospect in the multimodal vibration circumstances. Moreover, the harvesting performance can be enhanced by the adjustable counterweight and proof mass, which improve environmental adaptability. Its maximum output is 35.73 V (12.65 Hz) and 24.69 V (43.64 Hz), and the output power is 2.13 mW and 1.02 mW under an acceleration of 1.96 m/s2. This paper provides a novel idea for low-frequency multimodal energy harvesting techniques.

Vibration analysis and parameter optimization of seedling pushing device of transplanting mechanism with planetary elliptic gears

ABSTRACT The vibration induced by the seedling pushing device in the transplanting mechanism gravely undermines the transplanting performance. In this study, the structure and working process of the transplanting mechanism were analyzed. Then, an orthogonal test design for optimizing the vibration performance of the transplanting mechanism was applied to determine the optimum operating speed, counterweight mass, and spring stiffness. The parameter optimization results were finally verified by planting quality simulation and bench test. The result shows that when the operating speed was 250.0 r/min, the counterweight mass was 0.9 kg, and the spring stiffness was 140.0 N/m, the mechanism’s working performance and planting effect were the best. According to the analysis of data collected by the sensor, the maximum stress value was 6.05 MPa (reduced by 18.8%), the perpendicularity was 93.58% (increased by 6.0%), and the coefficient of speed fluctuation was 3.16 (diminished by 28.7%), which effectively reduces the force of the transplanting mechanism on the seedlings and improves the quality of operation.

Methodology for calculating the counterweight mass of a crank-and-rod mechanism

A method for calculating the crank-and-rod mechanism for designing a piston drive or pump is proposed, providing a rational combination of mass, overall dimensions, values of wear and power loss in the bearing with maximum balancing. Calculations were carried out in the MathCAD program. The optimal ranges of the studied parameters are given. To calculate the mass of the counterweight, a criterion for the best balance of the crank mechanism was introduced. Determinations of displacements, velocities, accelerations and reaction forces are based on the d'Alembert principle with recording in vector form for each moment in time. Keywords crank-and-rod mechanism, internal combustion engine, balancing criterion, crankshaft, mass, counterweight, wear, power loss in the bearing

Extreme mechanical metamaterials with independently adjustable elastic modulus and mass density

The mechanical properties of artificially periodic structures are closely related to the geometric dimensions of the structures. In this letter, we derive analytical expressions for the equivalent elastic parameters of a hexagonal cellular structure with additional counterweight mass blocks, and the accuracy of these analytical expressions is verified by numerical results. By analyzing the analytical expressions, we rigorously demonstrate an approximate decoupling relationship between the elastic modulus and mass density. Finally, we creatively propose a structure that can simultaneously achieve perfect decoupling of elastic modulus and mass density as well as flexible adjustment of material parameters in an ultra-wide range.

The approximate calculation of the natural frequencies of a Stockbridge type vibration damper and analysis of natural frequencies' sensitivity to the structural parameters

Abstract. Vibration damper is widely used in overhead transmission lines to alleviate aeolian vibration. Its natural frequencies are important parameters for a vibration damper. In this paper, the approximate calculation formulas of natural frequencies of the one-side subsystem of a Stockbridge type vibration damper were derived and the design sensitivity analysis of the natural frequencies was studied using partial differential equations with respect to each concerned parameter including the length of the steel strand, the mass of the counterweight, the eccentric distance, and the radius of gyration of the counterweight. Through a case study that considered a variation of up to ±30 % in the values of the design parameters, the exact calculation and approximate calculation results of the natural frequencies were analysed, and the sensitivity of the vibration damper's natural frequencies to the design parameters was studied. The results show that, within the range of the parameters used in this study, the approximately calculated first-order frequency is lower than the exact values, whereas the approximately calculated second-order frequency is larger than the exact values. The sensitivity analysis indicates that the first-order frequency is highly sensitive to the steel strand's length, whereas it is moderately sensitive to the counterweight's mass and slightly sensitive to the eccentric distance and the gyration radius of the counterweight; the second-order frequency is highly sensitive to the steel strand's length and the gyration radius of the counterweight, moderately sensitive to the counterweight's mass, and slightly sensitive to the eccentric distance. It will provide theoretical guidance and approximate analysis method in engineering for the design of the vibration damper.

The Effect of Counterweight Mass and Line Stiffness on the Global Dynamic Performance of a Hanging-Mass Floating Offshore Wind Turbine

Abstract Innovative floating offshore wind turbine (FOWT) platforms that deviate from the conventional semi-submersible, spar, and tension leg platforms (TLP) have become increasingly common due to the need to tap into the high wind energy potential located in deeper waters. One example is the hanging-mass concept, in which a suspended counterweight stabilizes a positively buoyant floater. This work presents a two-dimensional, nonlinear, multi-body model used to assess the influence of the counterweight mass and the suspension line stiffness on the system’s global performance, using linear stability analysis and time-domain simulations to conduct a parametric study. For example, the counterweight mass has a strong influence on the amplitude of rotational degrees-of-freedom. Corresponding natural periods may occur within the linear wave energy range for suitable counterweight sizes due to this strong influence leading to undesirable motions. High-frequency multi-body modes are also dependent on both the line stiffness and counterweight mass, which may result in high relative motion amplitudes and slack lines in certain conditions. Finally, the parametric study results contribute to preliminary hanging-mass FOWT design recommendations.

Influence of the Mass and Line Stiffiness on the Dynamic Line Tension of a Floating Offshore Wind Turbine Stabilized by a Suspended Counterweight

As the offshore wind industry moves towards deeper waters, developers are adapting classical floating platform designs to optimize performance and cost. One such concept is a multi-body system consisting of a counterweight suspended from a buoyant hull using flexible cables. If the suspension lines remain in tension, the system may be assumed to behave as a rigid body. However, if a suspension line loses tension, relative motion between the bodies will occur which may destabilize the system. In this work, the hanging-mass floating offshore wind turbine is idealized as a forced spring pendulum. A parametric study is conducted by varying the line stiffness and counterweight mass to determine their effect on the dynamic line tension and global response of the system.

Stability of a mine excavator with a variable cab position

The publication deals with the problem of assessing the mining excavator stability with a variable cab position. It is determined that the efficiency of the excavator cycle operations largely depends on the position of the operator with respect to the boom and body, the glazing area of the cabin, the dimensions of the windows, the width and the number of jumpers. A technical solution is proposed to increase the visibility of mining excavators’ cabs. The design of the mechanism makes it possible to advance the efficiency of using quarry excavators by changing the position of the cabin both in the vertical plane and in the horizontal one. Counterweight mass, an assessment of the turntable equilibrium and the stability of a mining excavator with a variable cab position are performed using standard «MS Excel» tools.

Cutting of hard and brittle insulating materials using spark discharge-assisted diamond wire sawing

Hard and brittle insulating materials have good application prospects but are difficult to machine. This research focuses on the feasibility of cutting such materials using spark discharge-assisted diamond wire sawing. By the electrochemical discharge machining (ECDM) method, spark discharges are generated on the diamond wire. However, no spark discharge is produced when the thickness of workpiece is beyond 5.0mm, because of the difficulty in generating hydrogen gas film to electrically insulate the diamond wire from the electrolyte. To solve this problem, an oil film is online coated on the diamond wire to separate it from the electrolyte. Oil film may be absent at some micro areas where electrochemical reaction occurs and hydrogen gas is generated. Consequently, an electrically insulating film, which consists of oil and hydrogen gas, is formed on the diamond wire. Experimental results show that evenly distributed spark discharges are generated during the cutting of a 36.0mm thick workpiece. The combination of spark discharge and diamond wire sawing facilitates the spalling of hard and brittle insulating materials. The material removal rate (MRR) and surface roughness increase with the DC voltage, wire speed, and counterweight mass.

Research on electrochemical discharge-assisted diamond wire cutting of insulating ceramics

Insulating ceramics are difficult to cut because of their high hardness and brittleness properties. This research proposes an electrochemical discharge-assisted diamond wire method for cutting insulating ceramics. The high temperature generated from electrochemical discharge facilitates the spalling of ceramics by the moving diamond wire. Experimental results showed that the material removal rate (MRR) of the new cutting method increased compared with the conventional diamond wire cutting process. Besides, electrochemical discharge had limited influence on the surface roughness and the wear of diamond wire. Additionally, the influence of the process parameters (DC voltage, wire speed, and counterweight mass) on the MRR and surface roughness was analyzed through experiments. The results showed that the MRR and surface roughness initially increased and then decreased with the increasing DC voltage; however, the variation was little. The higher wire speed resulted in an increased MRR and had little influence on the surface roughness. The MRR and surface roughness increased with the increasing counterweight mass.

Basic parameters of the static stability, loads and strength of the vital parts of a bucket wheel excavator’s slewing superstructure

Determining a bucket wheel excavator (BWE)’s slewing superstructure weight and its center of gravity (COG) is of extreme importance not only in the design phase, but also after the completion of the erection process and during the operation of the machine. This paper presents a critical comparative analysis of the basic parameters of the static stability of a BWE 1600 superstructure, with the parameters being obtained by both analytical and experimental procedures. The analysis shows that a relatively small difference in superstructure mass, obtained by calculation, leads to a relatively large unfavorable shifting of its COG, necessitating a significant increase in counterweight mass for balancing. A procedure for superstructure 3D model mass correction is presented based on results obtained by weighing after the completion of the erection process. The developed model provides enough accuracy to determine the superstructure’s COG in the entire domain of the bucket wheel boom inclination angle, and enables accurate load analysis of the superstructure’s vital parts. The importance of this analysis is reinforced by the finding that the procedure prescribed by standard DIN 22261-2 gives results which are not on the side of safety, as shown by an example of strength analysis of a bucket wheel boom stays’ end eyes.

Thermodynamic and dynamic modeling of a single cylinder four stroke diesel engine

In this study the conjugate thermodynamic and dynamic modeling of a single cylinder four-stroke diesel engine was conducted. The gas pressure in cylinder was calculated with the first law of the thermodynamic and the general state equation of the perfect gases. The variation of the heat, given to the working fluid during the heating process of the thermodynamic cycle, was modeled with the Gaussian function. The dynamic model of the engine consists of the motion equations of piston, conrod and crankshaft. Conrod motion was modeled by 2 translational and 1 angular motion equations. In the derivation of the motion equations, the Newton method was used. Motion equations involve hydrodynamic and asperity frictions as well as gas forces. By preparing a heat release rate profile consistent with ones given in the literature, thermal efficiency, knocking, vibration, torque and emission characteristics of the engine were investigated. The counterweight mass and its radial distance were optimized. At full load, if the heat release period is initiated soon after the piston passed the top dead center, the pressure rise rate becomes critical from the knocking point of view however, a couple of degree of retarding of the heat release period avoids the knocking without causing significant loss in thermal efficiency. If the throttling is more than 70%, the temperature of the combustion gas is high enough for NOx formation. At full load the vibrational torque exerting on the crankshaft was determined as about 17 times the engine torque.