Gear Mechanism Research Articles

Sloppy gear mechanism for coupled stochastic transportation: From antiequilibrium flow to kinetic selectivity

Non-equilibrium transportation of particles through a restricted space (such as porous media or narrow channels) significantly differs from free space. With a simple model of two types of particles competing to transport via a passive single-lane channel connecting two chemical baths, we find two dynamical modes of transportation -- the dud mode and the ratchet mode. At the ratchet mode, the gradient flow of one type of particle forces the other into a transient anti-equilibrium flow against its gradient. At the dud mode, the two types of particles both flow according to their gradients. This counter-intuitive non-equilibrium effect can be explained by a sloppy gear mechanism. In addition to the anti-gradient flow observed in the ratchet mode, we find that the non-equilibrium sloppy gear mechanism suppresses the flow of one particle while allowing the flow for the other. This mechanism provides a general theoretical framework to explain and design the selective transportation of particles via passive channels.

Automation creation method for a double planet carrier gear train transplanting mechanism based on functional constraints

Abstract. In order to satisfy the design requirements of diversified seedling transplanting mechanisms, this paper carried out systematic research on the creation method of planetary gear train mechanisms for transplanting based on the graph theory and the structural and functional characteristics of the transplanting gear train so as to establish a complete configuration atlas of a transplanting gear train. The structure and transmission ratio constraints of the planetary gear train for transplanting are established on the basis of the displacement graph of the planetary gear train. Selection methods for the planetary gear train rack, input, and output components are also proposed. The classification of three types of planetary gear trains is introduced by analysing the motion characteristics of the seedling transplanting mechanism, which realizes the systematic screening and classification of the double planet carrier gear train (DPGT) configuration. A total of 528 DPGTs, which are suitable for transplanting, including 3 five-bar, 13 six-bar, 92 seven-bar, and 420 eight-bar DPGTs are obtained. The problem of the single planet carrier transplanting mechanism not satisfying the requirements of a diversified transplanting trajectory is solved.

A novel 500 kN axial eddy current damper using rack and gear mechanism: Design, testing, and evaluation

A novel 500 kN axial eddy current damper using rack and gear mechanism: Design, testing, and evaluation

Electromagnetic performance analysis of the umbrella shaping inner rotor coaxial magnetic gear with dual modulation rings

The coaxial magnetic gear is a new type of noncontact transmission mechanism, which avoids the inherent defects of the mechanical gearbox due to gear meshing transmission. To study a coaxial magnetic gear (CMG) with high torque density and low torque ripple to replace the mechanical gear in the semidirect drive wind turbine, a novel umbrella shaping inner rotor CMG (US-CMG) with an auxiliary modulation ring is proposed in this paper. The novel structure adopts a CMG with a dual modulated ring to increase the electromagnetic torque. In addition, the magnetic block of the poled inner rotor is divided into three pieces magnetized by Halbach arrays, and the middle piece is umbrella-shaped to reduce torque ripple. Based on the topology of the US-CMG and the principle of the magnetic field modulation, the operation mechanism of the US-CMG is analyzed. A contrastive analysis among the US-CMG, Halbach magnetized dual-modulator CMG (HM-CMG), and surface-mounted CMG (SM-CMG) is established to identify the performance of the US-CMG. Compared with the SM-CMG, the results show that the electromagnetic torque of the US-CMG has increased by 65.46%, and the torque ripple of the US-CMG is 57.6% of that of the SM-CMG.

Windage Loss Characteristics of Aviation Spiral Bevel Gear and Windage Reduction Mechanism of Shroud

With the increasing speed of aviation gear, windage loss has been the main component of power loss. Reducing windage is of great significance to improving the transmission efficiency of aviation spiral bevel gear. Firstly, the calculation model of enclosed spiral bevel gear was established, and the basic physical mechanism of windage power loss was illustrated by numerical simulation, so as to obtain the mechanical and energy characteristics of windage loss. Then, the influence of the geometry and clearance parameters of the shroud on the windage loss was studied by orthogonal test, variance analysis and optimization design. The mechanism of the shroud to reduce the windage loss under the multi-factors was also studied, and their interaction was obtained. The results show that the tooth surface clearance, heel clearance and meshing opening are significant factors, and the most significant factor is the heel clearance. The non-significant factor is the interaction of each factor. The least significant factor is the toe clearance. In other words, the windage power loss can be reduced to the greatest extent by simultaneously reducing the meshing opening of the shroud and the clearance value between shroud and the surface of the gear. Finally, based on the mechanism of reducing windage loss of shroud, the optimization design principle affecting the structural performance of shroud is put forward, which provides theoretical guidance for the practical application of shroud in windage reduction engineering.

Single Actuator with Versatile Controllability of 2-DOF Assistance for Exosuits via a Novel Moving-Gear Mechanism

Decreasing the system weight while maintaining the assistance performance can help reduce the metabolic penalty in exosuits. Various researchers have proposed a bi-directional cable-driven actuator that can provide two degrees of freedom (2-DOF) assistance by using a single motor. However, such systems face limitations associated with the controllability of the assistance force. This study proposes a novel cable-driven system, that is, a dual pulley drive, that can provide versatile controllability of 2-DOF cable actuation by using a single motor via a novel moving gear mechanism. The moving gear winds the cable by switching both the side pulleys, which are then used for 2-DOF cable actuation. The spiral springs embedded between the pulley and base shaft work to release the cable. Results of experiments demonstrate that the dual pulley drive provides a versatile range of motion. The proposed system can provide 34.1% of overlapping motion per cable round trip time and support the non-overlapping motion. The preliminary integration of the dual pulley drive to the exosuit confirms that the novel exosuit is considerably lighter than the state-of-the-art exosuit. The calculations indicate that the operating cable speed and force generated using the proposed design are higher than the existing exosuit.

Design and Research of Dragonfly Robot under the Background of Artificial Intelligence

Simulating the flight of dragonflies has always attracted scientists’ interest. This paper studies the theory and method of the transmission mechanism of dragonfly robot, establishes the relationship function model between wing swing angle and geometric parameters, and designs a kind of gear and rod mechanism transmission chain, including a pair of wing angle turnover mechanism, so that the wings swing smoothly, no jam phenomenon occurs, and improves the lift ratio. In this paper, the dynamic principle of Bionic Flapping Wing robot was analyzed, and the design scheme of driving mechanism is put forward; the project realizes the three-dimensional design of robot parts, the virtual digital prototype and simulation, and 3D printing of the prototype robot. During the design and manufacture, the lightweight design and processing of the fuselage and wings are carried out to reduce its weight. The drive circuit and algorithm are designed with 8051 chip as the CPU; the balance and attitude control methods are proposed.

A method for comprehensive performance optimization of four-leg landing gear based on the virtual equivalent parallel mechanism

Taking-off and landing on unstructured terrain can effectively expand the application of aircrafts. The terrain-adaptive taking-off and landing technology is achieved through adaptive landing gear. The performance of the adaptive landing gear determines the safety performance of the aircraft during taking-off and landing. This paper proposes a comprehensive performance optimization method for four-leg landing gears based on the virtual equivalent parallel mechanism (VEPM). This method associates the motion variables of the parallel mechanism with the terrain data, and combines the original mechanism to form a VEPM. By analyzing the comprehensive performance of the equivalent parallel mechanism, the particle swarm algorithm is used to optimize the dimensions of the landing gear mechanism. The new optimization method can enhance the comprehensive performance of the landing gear mechanism, which contributes to the structural design and optimal control of the terrain-adaptive landing gear.

Path tracking control of a tractor-trailer wheeled robot kinematics with a passive steering angle

In the present work, we propose a trajectory tracking control method for the tractor-trailer wheeled robot in that both the trailer and the tractor are able to precisely track an identical target trajectory curve at a low speed. To this end, two key innovations are presented as follows. Firstly, a passive steering angle and its gear steering mechanism are introduced for steering the trailer, so that it follows very well the trajectory of the tractor. Secondly, the motion laws of the tractor-trailer wheeled robot with a passive steering angle are established by analyzing the non-holonomic constraints. On this basis, a standard method is applied to establish its kinematics and dynamics models. The original motion task of the tractor-trailer wheeled robot is then transformed into a curvature tracking control issue of the tractor via a dynamic tracking target. Finally, the integral sliding mode control and the linear quadratic regulator are combined to design two proper torque controllers for implementing a prescribed motion task. Numerical simulation results show that both the tractor and the trailer can accurately move along the desired path simultaneously by adopting a dynamic tracking target and an appropriate passive steering angle, even though the tracking speed error of the tractor is large.

Исследование влияния цилиндрических самотормозящихся передач на работу привода в различных режимах

Many electromechanical drives require the fixation of the output link in a given position and the prevention of its spontaneous movement under load. To ensure this, the drive is usually equipped with a brake. However, in many cases it is possible to do without a special braking mechanism if a self-braking mechanism (gear) is included in the drive, which combines the functions of transferring motion and automatic braking the drive after the engine is turned off. This solution allows obtaining a simple and compact structure and reducing the cost of the drive by eliminating the brake. Dynamic models of an electromechanical drive with a power unit consisting of an electric motor and a gearbox, that is a cylindrical self-braking gear are considered. The equations of motion of the main system elements are given, which make it possible to assess the frequency and transient characteristics of the drive, the ability of its operation in various modes.

Non-circular gear transmission mechanism with variable-involute and variable-cycloid composite tooth profile

Non-circular gear transmission mechanism with variable-involute and variable-cycloid composite tooth profile

Effects of gear structural parameters on unsteady-state temperature field of large transmission ratio gear and tooth root thermal stress

A calculation method of tooth root stress for large transmission ratio gear and rack is proposed using a broken-line section model and thermal-mechanical coupling analysis. To describe the transient meshing dynamics between the gear and the rack, a contact deformation model between the gear and the rack is fitted by using the least square method, and the meshing temperature field is calculated using the Blok flash temperature theory. The method of the broken-line section is modified based on the fatigue crack growth path at the tooth root. A new broken-line section model to calculate the tooth root stress is established, and a stress permeability factor is introduced to identify the width of the broken line. Using the meshing temperature field of gear and rack, the calculation formulas of root bending stress and root compression stress are derived by the integral-iterative method under thermal-mechanical coupling, and the correctness of the maximum tooth root stress model is validated by the finite element method (FEM). Compared with other methods for analyzing the thermal strength of gear roots, the proposed novel broken-line section method has simpler calculations and higher accuracy, and it can systematically analyze the effect of structural parameters on the dynamic strength of gear transmission mechanisms under actual working conditions.

Residual stress evolution for tooth double-flank by gear form grinding

In gear form grinding, the complexity of tool-workpiece geometries affects the grinding force and heat distribution along the tooth profile, thus resulting in difficulties in the calculation of residual stress. Specifically, the stress and heat generated on the newly machined tooth flank were influenced by the former grinding passes. Unfortunately, this issue was ignored in the previous research. To fill this gap, this paper presents a thermal-mechanical coupling calculation model considering the differences in gear double-flank, and a new heat source optimization algorithm is proposed. Firstly, according to the kinematic analysis of gear form grinding, the Lagrange interpolation method is used to solve unevenly distributed moving heat sources on the curved surface. Secondly, based on the theory of plastic increment combined with the von Mises yield criterion considering work hardening, the relationship between the temperature and the grinding stress on the first grinding tooth flank and the second grinding tooth flank is obtained through load cyclic loading. Finally, the residual stress field in the final state of all tooth flanks is obtained through the release procedure. The gear grinding experiments were conducted to verify the model, and the comparison results showed good consistency. The influence of unevenness in gear form grinding is not only reflected in the stress distribution along the tooth profile, but also on the different flanks. Based on the correlation law between the processing parameters and the residual stress on the tooth flanks, the optimal machining parameter range is obtained. The study provides an important reference for the understanding of gear form grinding mechanisms and the optimization of the grinding process.

Development of a Dual-Input Magnetic Gear Train for the Transmission System of Small-Scale Wind Turbines

Magnetic gear mechanisms have advanced to have a promising future in transmission technology. Previous research indicates that magnetic gear mechanisms might replace mechanical gear mechanisms in some applications. Small-scale wind turbines (SWT) with counter-rotating rotors that were initially fitted by bevel gears are proposed to be replaced by a coaxial magnetic gear train (CMGT). The CMGT is intended for use as a speed multiplier in order to obtain maximum power at low wind speeds, due to its beneficial transmission of power without physical contact. The primary objective of this study is to build a dual-input CMGT that will be employed in the transmission system of small-scale counter-rotating wind turbines. A dual-input CMGT is built through the analytical modeling of an equivalent magnetic circuit (EMC), which aims to predict the magnetic flux density in the air-gaps of CMGT. Several models within design constraints were compared to obtain the optimum design parameters of the preliminary CMGT design resulting from an EMC analysis. The optimized critical design parameters were then selected and analyzed using finite-element analysis (FEA) to depict the performance of the proposed SWT design. According to the findings, the developed design can generate an inner air-gap flux density of 0.8314 T and an outer air-gap flux density of 1.0200 T. The model likewise produces promising simulation results with an output transmitted torque in the inner rotor (output link) of 8.7 Nm, 56.9 Nm in the outer rotor, and 48.0 Nm in the carrier with pole-pieces. Thus, this design can generate higher torque than a bevel-geared wind turbine. The speed characteristics are also compromised in order to raise the generator’s rotating speed to generate more power. Finally, this study demonstrates the performance and embodiment design of the proposed SWT using CMGT.

Modelling and experiment for grinding forces of gear form grinding considering complete tooth depth engagement

Grinding is an essential gear finishing method. Grinding force analysis and prediction are critical to understand grinding mechanisms. By using a geometry model for gear form grinding and surface grinding mechanisms, a theoretical model was established to calculate the gear form grinding force. By considering the complete tooth depth engagement between tooth grooves and wheel profiles during form grinding, three segments of the involute, transition arc and tooth bottom line, which were included in complete tooth groove profiles, were analysed using the model. Contact relations among the normal grinding depth, wheel equivalent radius, wheel linear velocity and wheel profile were obtained. In addition, grinding experiments were outperformed on the basis of the single tooth, and the unknown coefficients of the form grinding force calculation model were acquired. The effects of the grinding depth, feed speed and grinding speed on grinding force were analysed using the grinding force model. The comparison of the predicted values of the form grinding force model with the experimental results, indicated that the relative errors of tangential and normal grinding forces are within ±10% and ±12%, respectively. The results confirmed the accuracy of gear form grinding force calculation model. These findings play a key role in parameter optimisation during gear form grinding.

Analysis of retraction performance of aircraft landing gear in high and low temperature environment

Abstract In order to solve the problem that the internal mechanism parameters of the aircraft landing gear are difficult to measure and retractable, the retractable performance of the landing gear under high and low temperature environments is studied. This paper simplifies the retractable mechanism of the landing gear by analyzing the motion mechanism of the aircraft landing gear. The degree of freedom of the retractable mechanism is calculated to verify the accuracy of the simplified rear landing gear retraction mechanism. The simulation model of landing gear retraction mechanism under high and low temperature environment is constructed by Patran. The component deformation and shaft clearance of the retractable mechanism under low temperature (-55°C) and high temperature (74°C) environments are analyzed from the overall and detail dimensions. The quantitative effect of ambient temperature on the deformation of the retractable mechanism of the landing gear is studied. Then Adams is used to establish the kinematics simulation model of the retractable mechanism, and the friction coefficient of the kinematic pair under different ambient temperatures is incorporated. Based on the historical data of the high and low temperature environmental test of the landing gear, the correctness of the model is verified. The influence of the environmental temperature on the driving torque, movement angle and movement time of the retractable mechanism is quantified. The problem that the deformation parameters and motion characteristics of the retractable mechanism of the landing gear are difficult to measure is solved, and the research method of retractable performance of the landing gear mechanism under different ambient temperatures is formed.

Mechanical Variable Magnetic Gear Transmission: Concept and Preliminary Research

This letter presents a novel concept of a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">non-contact</i> variable transmission mechanism using a coaxial magnetic gear. Conventional variable transmissions have provided a function of a robust transmission shifting; However, their inherent <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">contact</i> -transmission manners such as traditional dog clutch, pulley, and load sensitive component-based mechanisms have increased their complexity, size, and weight, which restricts miniaturization and continuous operations of the system. The proposed coaxial magnetic gear-based variable transmission provides a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">non-contact</i> transmission ratio shifting mechanism by mechanically changing magnetic harmonics between coaxial components of the magnetic gear. Therefore, it may provide various features derived from the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">non-contact</i> power transmission such as uninterrupted and seamless transmission ratio shifting, backdrivable and transparent dynamics, series elastic actuation-like properties, and inherent over-load protection with an expanded operable output range. A design, mathematical model, and simulation using a finite element method magnetics of the proposed mechanism are presented. Lastly, the transmission ratio shifting is demonstrated with a prototype to verify the feasibility of the proposed mechanism.

Preclinical Assessment of a Rapid Anastomotic Device for HeartMate 3 Apical Cuff Implantation

<h3>Purpose</h3> The HeartMate3 (HM3) LVAD requires an apical cuff (AC) to left ventricle (LV) anastomosis. We developed an AC attachment device for the standard HM3 AC with 12 anchors and 4 compression plates. A Gen1 delivery tool requires a hand-held driver and sequential anchor delivery. A Gen2 delivery tool with a targeting system and improved anchors has a planetary gear mechanism that drives all anchors simultaneously. The study purpose was to assess functionality and hemostasis of HM3 AC anastomosis. <h3>Methods</h3> Standard HM3 ACs were implanted without cardiopulmonary bypass (CPB) in 8 calves (110 to 130 kg): left thoracotomy (n=2), median sternotomy (n=6). Implant time was from epicardial contact to complete anchor deployment. Blood pressure (BP) was measured by arterial line. After anchor deployment and AC attachment heparin was administered to ACT over 400 seconds. Fibrillation (n=2), rapid pacing (n=1) and vena cava inflow occlusion (n=5) were used for LV coring and custom AC plug insertion with resuscitation to baseline BP. Functionality and hemostasis were qualitatively assessed. Supraphysiologic testing (norepinephrine, 0.15 mcg/kg/min) was assessed in 4 cases (Gen1, n=3; Gen2, n=1). <h3>Results</h3> Implants were simple. Gen1 (n=6) implant time range was 63 to 94 seconds. Gen2 (n=2) times were 26 and 32 seconds. Prior to anticoagulation hemostasis was excellent. Five cases were assessed for post-plug hemostasis (2 fibrillated and 1 paced could not be resuscitated). After resuscitation there was minimal to no bleeding in 3 cases (2 Gen 1, 1 Gen 2). In 2 cases (1 Gen1, 1 Gen2) sutures were required at a single anchor site: 1 Gen1 had localized bleeding due to a single anchor failure (cap separation), 1 Gen2 had bleeding at a coronary artery perforation. Excellent hemostasis was maintained at supraphysiologic pressures (n=4, systolic BP range 211-248 mmHg). <h3>Conclusion</h3> Rapid HM3 apical cuff attachment is feasible. Hemostasis was excellent even at significant supraphysiologic blood pressure. Advantages are: 1) No HM3 AC manufacturing changes are required, 2) Implant time is greatly decreased, 3) Implant is easy without CPB, 4) Implant site targeting is precise, 5) The area of impacted myocardium is limited to the area under the AC sewing skirt, and 6) Low device profile permits use with mini-thoracotomy access. Suturing buttressing is feasible and may be necessary in case of coronary artery perforation.

Features of mathematical modeling transmission parameters of drilling rigs with planetary gears

The features of the approach to the mathematical modeling of power transmission parameters of drilling rigs (DR), which include gear planetary gear mechanisms in the kinematic structure, are considered. At the same time, the modeling features consist in the special properties of the kinematics and dynamics of planetary gears, as well as the presence of elements of complex relative motion in them. This circumstance requires a thorough analysis of the parameters at the design stage, which should be based on the use of available and promising methods of mathematical modeling with the possibility of using modern mathematical apparatus and numerical methods of calculations. In order to solve this problem, the authors proposed a method for mathematical modeling of mechanical processes in the transmissions of DR with planetary gears. This makes it possible, based on the results of theoretical studies, to predict the optimal parameters of the power transmission of DR.

Analysis of electromagnetic performance of differential multi-stage coaxial magnetic gears with large gear ratio and high torque density applied to high-power wind turbines

Magnetic gear is a non-contact transmission mechanism, which overcomes the drawback of mechanical gear transmission. Although the series multi-stage magnetic gear can provide a large gear ratio compared to the single-stage magnetic gear, the lower torque density of the series multi-stage magnetic gear limits its use in high-power wind turbines. According to the magnetic gear field modulation mechanism and the differential transmission method, a differential multi-stage coaxial magnetic gear transmission device is proposed, which can achieve transmission with a large gear ratio and large torque density. Based on the differential multi-stage coaxial magnetic gear structure and its working principle, the finite element method is used to simulate the electromagnetic performance of the multi-stage coaxial magnetic gear. Futhermore, the electromagnetic performance of the two stages of the proposed magnetic gear are compared. The results show that there is a significant difference between the the electromagnetic performance of the first stage and that of the second stage. The torque ripple of the first stage is more dramatic than that of the second stage. The torque ripple amplietude of the inner rotor of the first stage is 5.08‰ larger than that of the second stage. The torque ripple amplietude of the outer rotor of the first stage is 4.591‰ larger than that of the second stage.