High Gear Research Articles

Energy Efficiency Improvement of a Robotic Finger With Ultra High Molecular Weight Polyethylene Gear

Energy Efficiency Improvement of a Robotic Finger With Ultra High Molecular Weight Polyethylene Gear

An improved fractal model for tangential contact damping of high contact ratio gear considering friction effect

On the basis of the M-B fractal theory, a geometric model and contact mechanical model of the tooth surface contact mode were analyzed. According to the energy dissipation mechanism of tangential contact damping, a tangential contact damping model of tooth surface considering variable friction under dry friction condition was established by introducing the correction coefficient of tooth surface. First, obtained the load and tangential damping of a micro-convex body, and then the contact load and tangential contact damping of the tooth surface are obtained by integrating on the tooth surface. It was shown that the tangential contact damping of tooth surface is affected by various parameters including roughness amplitude, fractal dimension, curvature radius of tooth surface, normal contact load and tangential normal load ratio. The simulation results show that the tangential contact damping gradually increases when the normal contact load, friction coefficient, curvature radius of driving wheel and roughness amplitude increase. The tangential contact damping on the tooth surface increased with the increase in the tangential normal load ratio. When the tangential normal load ratio is 0.09, the tangential contact damping of the tooth surface reached a maximum, and then decreased with the increase of the tangential normal load ratio. The change in the tooth surface tangential contact damping with the fractal dimension is similar to the change in the tangential normal load ratio, which also increased and then decreased. When the fractal dimension is approximately 1.64, the tangential contact damping of the tooth surface reached the maximum. The tangential contact damping of tooth surface increases with the increase of modulus, transmission ratio and the number of teeth of the driving gear, and the number of teeth and modulus have a great influence on it, while the influence of transmission ratio is relatively weak.

Tool wear development in gear skiving process of quenched and tempered internal gears

Gear skiving is a highly productive machining process, especially for manufacturing of high strength internal gears as required for high performance electric drive trains. However, the complex process kinematics cause intense variations of the effective cutting parameters during tool engagement. Thus, particularly the tool must meet high requirements to achieve long tool life at required workpiece quality. These requirements are amplified even more when machining quenched and tempered materials from the massive blank.In the presented study, the influence of various key factors on the tool wear development in gear skiving process are quantified. In several tests, the cutting speed, workpiece tensile strength, cooling lubricant strategy, as well as the cutting strategy are varied in order to optimize tool life. Therefore, single-tooth tests on quenched and tempered internal gears from 31CrMoV9 (AISI 4340) steel are conducted and wear flank land width evolution of the tools is examined. In addition, the workpiece is evaluated with regard to surface quality. Results reveal that different factor level combinations can have various effects on tool wear characteristics and therefore on tool life. The correlations presented provide recommendations for practical application and contribute to deeper process understanding.

Development of an Agile Omnidirectional Mobile Robot With GRF Compensated Wheel-leg Mechanisms for Human Environments

Wheeled mobile robots have been receiving continuous attention in various fields because of their stability, efficiency, and simple mechanisms. However, most of them require significantly larger occupied space than humans and have limited maneuverability in the environment for humans, such as crowded corridors, floor thresholds, ramps, and elevators. This letter presents a new wheel-leg mobile robot that combines the legs for changeable support polygon and mecanum wheels for holonomic motion. The robot has a human-like slim shape with 4 wheel-leg mechanisms, each of which has one 2-DOF leg frame and one mecanum wheel. To allow 2-DOF leg motion while maintaining the orientation of the mecanum wheels, a unique parallel link mechanism was devised. In order to achieve agile motion and impact and vibration absorption capability, a back-drivable high payload compound planetary gear was developed. The ground reaction force (GRF) compensation mechanism in each leg reduces the required payload of the actuators. The letter describes the detailed mechanical design of the robot and the actuators. The effectiveness of the proposed robot was verified in various experiments, fast omnidirectional motion test, a climbing test of a single step, and a motion test in the elevator with people.

Surface integrity evolution of Nb-Ti microalloyed steels along the gear manufacturing chain

The increasing demand for high performance gears requires in-depth investigations of alternative materials to those commonly used. In this respect, microalloyed steels may appear as an alternative with technical and economic potential. Microalloyed steels may exhibit a more refined grain structure than conventional steels, which is commonly induced by the precipitation of highly stable and dispersed second-phase particles. This investigation aimed at understanding how the steel grain structure obtained by the addition of niobium (Nb) and titanium (Ti) as microalloying elements correlates to the material surface integrity promoted by a conventional gear manufacturing chain. The results indicated that the addition of microalloying elements leads to a refined and homogeneous grain structure. The residual stress state also proved to be both more compressive and homogeneous and the roughness exhibited greater stability. Such characteristics place the microalloyed steels in a prominent position regarding their application in the gear manufacturing, indicating the possibility of fatigue lifetime improvement.

Optimal design of high efficiency double helical gear based on dynamics model

A 16-degree-of-freedom dynamic model for the load contact analysis of a double helical gear considering sliding friction is established. The dynamic equation is solved by the Runge–Kutta method to obtain the vibration displacement. The method combines the friction coefficient model based on the elastohydrodynamic lubrication theory with the dynamic model, which provides a theoretical basis for the calculation of the power loss of the transmission system. Moreover, the sensitivity analysis of the parameters that affect the transmission efficiency is carried out, and an optimization method of meshing efficiency is proposed without reducing the bending strength of the gears. This method can directly guide the design of the double helical gear transmission system.

Drought Shocks and Gearing Impacts on the Profitability of Sheep Farming

The resilience and profitability of livestock production in many countries can be impacted by shocks, such as drought and market shifts, especially under high debt levels. For farmers to remain profitable through such uncertainty, there is a need to understand and predict a farming business’s ability to withstand and recover from such shocks. This research demonstrates the use of biophysical modelling linked with copula and Monte Carlo simulation techniques to predict the risks faced by a typical wool and meat lamb enterprise in South-Eastern Australia, given the financial impacts of different debt levels on a farming business’s profitability and growth in net wealth. The study tested five starting gearing scenarios, i.e., debt to equity (D:E) ratios to define a farm’s financial risk profiles, given weather and price variations over time. Farms with higher gearing are increasingly worse off, highlighting the implications of debt accumulating over time due to drought shocks. In addition to business risk, financial risk should be included in the analyses and planning of farm production to identify optimal management strategies better. The methods described in this paper enable the extension of production simulation to include the farmer’s management information to determine financial risk profiles and guide decision making for improved business resilience.

Multi-objective Optimization and Decision-making Method of High Speed Dry Gear Hobbing Processing Parameters

Multi-objective Optimization and Decision-making Method of High Speed Dry Gear Hobbing Processing Parameters

High Strength Corrosion Resistant Steel for Aircraft Landing Gears and Structures

<div class="section abstract"><div class="htmlview paragraph">High stressed aircraft landing gear and structural components are subjected to severe loading, corrosion and adverse environmental conditions. Materials such as high strength steels and high-strength titanium alloys are widely used for those critical components. The main criterions for choosing the materials are their strength and fatigue strength, toughness and ductility.</div><div class="htmlview paragraph">300M steel is widely used for high stress aircraft landing gears and structures; however, this steel is not corrosion-resistant and requires protective coatings.</div><div class="htmlview paragraph">Cobalt-free, quenched and tempered high strength corrosion resistant steel alloy (“HSCR steel”) provides the same strength, ductility, and toughness as the 300M steel and while it possesses corrosion resistance in salt spray test. HSCR steel has showed no rust after the standard salt spray test in accordance with ASTM B117 using a 5% NaCl concentration, natural pH, at 95°F, for 200 hours test duration.</div><div class="htmlview paragraph">Aircraft applications of the wrought HSCR steel include landing gear components, rotatable shafts, actuators, flap tracks, slat tracks, fasteners, and others.</div><div class="htmlview paragraph">Besides forging, the aircraft components can be manufactured from HSCR steel powders by:<ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Powder metallurgical-based hot isostatic pressing (PM HIP) to the near net shapes</div></li></ul></div><div class="htmlview paragraph">(NNS) followed by finish machining/surface finishing and heat treatment<ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Additive manufacturing (AM) followed by surface finishing and heat treatment.</div></li></ul></div><div class="htmlview paragraph">Modification of the HSCR steel is applicable for vacuum and investment casting of aircraft hydraulic fluid system, motion control and actuation system, cargo system, and flight safety components.</div><div class="htmlview paragraph">HSCR steel is a low cost alternative of Ti-6Al-4V alloy. The components made from Ti- 6Al-4V alloy can be substituted by the same weight components made from HSCR steel due to HSCR steel possesses slightly higher specific stiffness and specific strength (ratio of modulus elasticity and ultimate tensile strength to density) and slightly lower ductility and toughness compared to Ti-6Al-4V alloy.</div><div class="htmlview paragraph">Industrial production of HSCR steel is underway.</div></div>

Modelling and Experimental Study on Electrically Heating Garment to Enhance Personal Thermal Comfort

Electrically heating garment (EHG) is an effective protection for human in cold environment. In this study, we analysed the principal agents of heat transfer in EHG, and established a theoretical model including heat conduction, natural convection and radiation. To verify the model, the numerical simulations and experiments were compared, and showed a temperature discrepancy smaller than 0.3°C, which was acceptable in engineering design. Using numerical simulation, it is convenient to optimize the design parameters of EHG in different thermal conditions. For instance, to maintain the average temperature of skin within 32-34°C when people are in low metabolic activities, the power of heating elements should range from 73.1-110.7 W/m2 under high heating gear or 10.8-48.5 W/m2 under low heating gear. The more importance is that the calculation allows easy predesign of EHG. The effect of the arrangements of heating elements was studied, herein, the results of six arrangement patterns were presented. It is found that the most effective arrangement can raise the average temperature of skin under heating elements about 0.4-1.2°C than other cases.

Data-driven based optimization for high-speed dry cutting gear hobbing processing parameters

The formulation of gear hobbing processing parameters relies on extensive professional knowledge and artificial experience, and inappropriate processing parameters will lead to low machining precision and high manufacturing costs. In order to obtain suitable processing parameters in high speed dry hobbing gear process, Gradient boosting regression (GBR) and Generalized Regression Neural Network (GRNN) are adopted to establish a process parameter optimization model targeting gear machining accuracy and machining energy consumption. And then a method based on Differential Evolution (DE) algorithm, parameter adaptive multi-object differential evolution (AMDE), for hobbing processing parameter optimization is proposed. Machining experiment verification shows that the established gear hobbing accuracy prediction model and energy consumption estimation model have high prediction accuracy, and AMDE has strong optimization capabilities and robustness.

Sensor-Less and Control-Less Underactuated Grippers With Pull-In Mechanisms for Grasping Various Objects.

This paper proposes an underactuated grippers mechanism that grasps and pulls in different types of objects. These two movements are generated by only a single actuator while two independent actuators are used in conventional grippers. To demonstrate this principle, we have developed two kinds of gripper by different driving systems: one is driven by a DC motor with planetary gear reducers and another is driven by pneumatic actuators with branch tubes as a differential. Each pulling-in mechanism in the former one and the latter one is achieved by a belt-driven finger surface and a linear slider with an air cylinder, respectively. The motor-driven gripper with planetary gear reducers can pull-up the object after grasping. However, the object tends to fall when placing because it opens the finger before pushing out the object during the reversed movement. In addition, the closing speed and the picking-up speed of the fingers are slow due to the high reduction gear. To solve these drawbacks, a new pneumatic gripper by combining three valves, a speed control valve, a relief valve, and non-return valves, is proposed. The proposed pneumatic gripper is superior in the sense that it can perform pulling-up after grasping the object and opening the fingers after pushing-out the object. In the present paper, a design methodology of the different underactuated grippers that can not only grasp but also pull up objects is discussed. Then, to examine the performance of the grippers, experiments were conducted using various objects with different rigidity, shapes, size, and mass, which may be potentially available in real applications.

Robust control design for a planar humanoid robot arm with high strength composite gear and experimental validation

Aiming at uncertainties and variable loads of the robot arm, a nonlinear control algorithm is proposed. The design of the proposed control is based on the engineering practice of the planar humanoid robot arm with high strength composite gear. The proposed control, consisting of a PD control portion and a robust control portion, retains the dynamic characteristics of the system and realizes based on error. Theoretical analysis shows that the proposed control can guarantee the uniform boundedness and uniform ultimate boundedness. Based on the humanoid robot arm, the experimental validation with the proposed control is carried out and compared with the PID control. Numerical simulations and experimental results show that the proposed control can effectively deal with load changes and parameter uncertainties, and the trajectory tracking accuracy of the robot is improved significantly with the proposed control.

US FDA perspective: getting back into high gear – driving cell and gene therapy forward through 2022 and beyond

<div class="authors authors-lg"><div class="author"><div class="author-img"><img src="https://bioinsights.blob.core.windows.net/uploads/Peter Marks_3765 copy.jpg" data-image="1"></div><div class="author-det"> Peter Marks, MD, PhD, is the director of the Center for Biologics Evaluation and Research (CBER) at the Food and Drug Administration. The center is responsible for assuring the safety and effectiveness of biological products, including vaccines, allergenic products, blood and blood products, and cellular, tissue, and gene therapies. </div></div></div>

Experimental study of failing differential gears and introduction of a new condition indicator for ultra low speed applications

Detecting gear cracks in ultra low speed, high load planetary gears plays an important role in engineering praxis and in the development of differential gearboxes for vehicles. The analysis of the acceleration signals for condition monitoring purposes, which is widely used in the industry, cannot be applied for this use case. The aim of this paper and experimental study is to develop a new condition monitoring method, which makes it possible to detect cracks and follow the crack propagation in differential gears under realistic test conditions without any artificially seeded faults. The variation of the Locking Factor (LF) and its vibration spectrum over the complete testing time (14–81 h) is analysed with the new method. The successive change of the spectrum of the LF and the Condition Indicator (CI) is presented in this paper. Due to the complex structure of the test bed and the complex modulation phenomenon, a new approach was needed for detecting the cracks.

Dynamic behavior of a power re-circulating gear test rig including periodic variation of mesh stiffness and static transmission error

We characterized the dynamic behavior of a pair of high performance aeronautical gears which are part of a complex transmission system. The gear pair was tested using a mechanical recirculating power test rig designed to simulate the severe operating conditions of transmitted torque and angular speed. The test rig and the most important phenomena that influence its dynamic behavior are described. A (static) finite element model, developed to calculate the input parameters for the dynamic analysis of the tested gears, is also presented. Using the results of the FE model, we developed a lumped dynamical model with which it is possible to reproduce the most significant dynamic phenomena of the test rig. We characterized the behavior of the test rig focusing on the actual loads transmitted by the tested gears. The dynamic model was validated by comparing its results with the experimental outcomes in various test conditions. The comparison highlights the limitations of the design procedures based on common standards for assessing the dynamic overload experienced by heavy-duty gear transmission systems.

Tooth bending stress analysis of high speed curve face gear of composite transmission

To promote the engineering application of composite transmission of high speed curve face gear, which consists of a cylindrical gear and a high speed curve face gear, the analysis of tooth bending stress should be taken into consideration. High speed curve face gear pair is a new type of curve face gear pair. Combined with the principle of high speed cam and curve face gear pair transmission, it can transfer the axial/rotation composite motion and power between two intersecting shafts. Based on the gear engagement principle, the gear meshing coordinate system was established and the fundamental of the high speed composite transmission was expounded. Combined with the tooth profile equation of generating gear, the tooth surface equation of high speed curve face gear was gained. Tooth force, contact ratio and normal load distribution were calculated. Then the tooth bending stress of high speed curve face gear during the transmission was calculated and analyzed in detail. Influence of basic parameters on tooth bending stress was discussed. Finally, the simulation and measurement experiment of tooth bending stress was carried out. By the comparison analysis of simulation, experiment and theory, the correctness of tooth bending stress calculation method was verified, which has important guiding significance for the further research of high speed curve face gear of composite transmission.

Покращення тягового-швидкісних властивостей вдосконаленням методів вибору параметрів моторно-трансмісійної установки автомобіля

Aerodynamic characteristics have a major impact on the energy efficiency and traction and speed properties of the vehicle. In this article, based on previous studies of the aerodynamic characteristics of various car models, we propose an improved method for selecting engine and transmission parameters at the design stage. The aim of the study is to improve the dynamic properties of the car by improving the method of selecting the main parameters of the engine-transmission unit by refining the calculation of aerodynamic drag. To achieve it, the following tasks must be solved: to specify the method of selecting the maximum effective engine power; to specify a technique of definition of the maximum constructive speed of the car; to develop a technique for selecting gear ratios. The aerodynamic resistance to the movement of the vehicle is determined by the frontal coefficient of the specified resistance, the density of the air, the area of the frontal resistance and the speed of the vehicle. It is known from classical works on the aerodynamics of a car that in the range of vehicle speeds from 20 m / s to 80 m / s, taking the law of squares when assessing the force of air resistance, it is necessary to change the coefficient of frontal aerodynamic drag depending on the speed of the car. However, when carrying out calculations, this coefficient is taken constant, which leads to obtaining large values of the air resistance force at high speeds and lower at low speeds. There are two possible ways to improve the dynamic properties and energy efficiency of the car during its modernization (increasing the maximum design speed of the car by reducing the gear ratio in higher gear; reducing the maximum efficiency of the engine while maintaining the previous gear ratio in higher gear). As a result of the study, the method of selection (maximum effective engine power; maximum design speed of the car; gear ratios) at the design stage of the parameters of the motor-transmission unit of the car has been improved.

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Currently, the National Guard of Ukraine and other power structures of the state are actively working on the acquisition of subdivisions with modern weapons, including armored vehicles. For objective reasons, such work cannot be done in a short time, therefore, the BTR-70 armored troop-carrier, developed and adopted in the seventies of the last century, is still in operation in significant numbers. An analysis of the design of the armored troop-carrier indicates that its power plant has structural features that do not fully meet modern approaches to the design of such weapons and, moreover, the vehicles have practically exhausted their assigned resource. However, the experience of operating the BTR-70, including in the combat zone, testifies that the potential capabilities and maintainability inherent in its design make it possible to use the armored troop-carrier even after the end of its intended resource, although the aforementioned complicates and increases the cost of operation. One of the ways to solve this problem is the modernization of the power plant of the armored troop-carrier, in particular, the replacement of gasoline engines with modern diesel engines and the improvement of the transmission design. In the course of the study, traction and speed properties of the armored vehicle in the standard configuration and when equipped with two D245.30E2 engines and Deutz engines are calculated and estimated. As a change in the design of the transmission, the option of replacing the standard gearbox with a gearbox with an overdrive is considered. It was found that equipping an armored personnel carrier with modern diesel engines in both cases leads to a significant increase in traction properties and an improvement in the fuel efficiency of the vehicle. However, due to the fact that the crankshaft speed of diesel engines is approximately 25-30 % lower than the corresponding frequency of gasoline engines, the maximum speed of an armored personnel carrier with diesel engines is limited by the design of the transmission and is about 70 km / h. This does not meet modern requirements for machines of this type, therefore, as an option; it is proposed to install a step-up reducer (divider) at the inlet of the gearbox. In this case, it is possible to reduce the gear ratio of the transmission in higher gears and, accordingly, increase the maximum speed of the armored troop-carrier on paved roads.

High load capacity spur gears with conchoidal path of contact

The present study is devoted to investigation of spur gears with a conchoidal path of contact and a convex-convex contact between teeth. The load capacity and energy efficiency were evaluated using both theoretical and experimental approaches. The theoretical analysis showed that the conchoidal gear pairs are 5–21% stronger in terms of contact stress and have similar energy efficiency as compared to the involute gear pairs of the same configuration. Experiments were conducted on a gear test rig. Its energy efficiency was determined by measuring the active power of the motor driving the pinion shaft and controlling the torque at the gear shaft. The load capacity of the tested gear pair was estimated by analysing changes in the energy efficiency. It was found that the conchoidal gear pair has more than 20% higher load capacity and slightly higher energy efficiency, which agrees well with the mentioned theoretical results. Thereby, the study concludes a substantially higher load capacity of the conchoidal gears compared to the traditional involute ones.