Search results

The purpose of this paper is to present the design and implementation of a new manipulator with six joints driven by a single DC motor.

The manipulator consists of several modules, each of which has the twisting and pivoting degrees of freedom. Two clutches and one brake are mounted to control each joint. A clutch model based on PWM control is built to compute the average velocity of each clutch. Two parameters are involved in the model: PWM frequency and duty ratio. PWM frequency is limited by the natural frequencies of structure with all postures. The theoretical duty ratio should be adjusted according to the clutch model. Two experiments – line tracking and arc tracking – are carried out to verify the effectiveness of the control system.

The study has designed a manipulator with six joints driven by a single DC motor which powers all the modules through a main shaft and several clutches. In the manipulator, all the modules are supplied with a constant speed input and provide a bi‐directional variable output. Experimental results show the clutch model built for the manipulator can be applied to the joint control of all multi‐joint manipulators.

The paper describes a dexterous and light‐weight manipulator driven by a single motor and designed with bi‐directional joints.

Phosphating mild steel causes the surface to be etched into a network of microscopic channels 0.0004 to 0.0008 in. deep, the phosphate crystals being located on the intervening high spots. With this type of surface, running‐in is both rapid and safe and low friction conditions are soon established. The phosphate crystals do not act as a solid lubricant in the same sense as graphite or M0S2; initial friction is higher and final friction is much lower. Friction of MoS2, for example decreases with rubbing by a factor of 4, from 0.2 to 0.05, whereas the friction of phosphated steel decreased by a factor of 60, from 0.3 to 0.005. In addition, the final friction of the run‐in phosphated surface depended on temperature and pressure in a manner characteristic of ‘thin film’ fluid lubrication, not ‘boundary’ or ‘solid’ lubrication.

For high‐speed shaft scaling applications where axial space is at a premium, Flexibox Ltd., Nash Road, Trafford Park, Manchester 17, have developed a new mechanical seal—the type DD. This new seal can cope with peripheral speeds up to 15,000 ft./min. pressures up to 1,000 lb./sq. in. gauge and temperatures up to 500 deg. F.

The non-stationary operational wind loads vary in time and site and has remarkable effect on wind turbine drive train. The purpose of this paper is to determine the effects of wind class 3 and 7 on the life of wind turbine drive train. The two-wind class 3 and 7 are described by average wind speed and weight factor and effects of two variables on wind energy generation and wind turbine drive train studied.

The load distribution method is used to calculate stress range cycles for wind class 3 and 7. To determine the rise of force on wind turbine drive train, the load cycle method is proposed. The fatigue damage model is studied with respect to influence of different wind speeds and wind shear factor and then results analysed accordingly. Also sensitivity analysis has been carried out to assess the percentage of drop of energy generation and rise of tangential force for wind class 3 and 7. Linear fit method is used to determine the inclination of wind variation and wind shear of wind class 3 and 7. In this regard, two practical wind sites fall under the wind class 3 and 7 and 1.5 MW wind turbine have been taken in to account.

The results showed that the average rise of force on wind turbine drive train is 37.5% which can influence the drop in energy 34.7% for wind class 3. Similarly, the results of wind class 7 are showing that the average rise in force and drop in energy found to be 49.05% and 51.16%, respectively. The wind class 7 have higher tendency of wind fluctuations and weight factor that can cause a damage to wind turbine drive train components. The results showed that when wind speed increases to rated power 11.5 m/s the damages occurred and remain steady. Similarly, when weight factor increased from 0.18 to onwards the damage occurred. The increased wind loads increased the tangential loads on the wind turbine decreased life of the gearbox.

The results of study suggest that wind turbine should be design according to site specific wind environment for maximum energy generation and lowers the wind loads on the drive train component.

A simple economic analysis has revealed that in order for wind energy to be a viable alternative, wind-turbines (convertors of wind energy into electrical energy) must be able to operate for at least 20 years, with only regular maintenance. However, wind-turbines built nowadays do not generally possess this level of reliability and durability. Specifically, due to the malfunction and failure of drive-trains/gear-boxes, many wind-turbines require major repairs after only three to five years in service. The paper aims to discuss these issues.

The subject of the present work is the so-called white etch cracking, one of the key processes responsible for the premature failure of gear-box roller-bearings. To address this problem, a multi-physics computational methodology is developed and used to analyze the problem of wind-turbine gear-box roller-bearing premature-failure. The main components of the proposed methodology include the analyses of: first, hydrogen dissolution and the accompanying grain-boundary embrittlement phenomena; second, hydrogen diffusion from the crack-wake into the adjacent unfractured material; third, the inter-granular fracture processes; and fourth, the kinematic and structural response of the bearing under service-loading conditions.

The results obtained clearly revealed the operation of the white-etch cracking phenomenon in wind-turbine gear-box roller-bearings and its dependence on the attendant loading and environmental conditions.

The present work attempts to make a contribution to the resolution of an important problem related to premature-failure and inferior reliability of wind-turbine gearboxes.

Wind energy has become a distinguished field of energy among the alternative energy resources. Despite economical disadvantages, the production of wind energy is desired to fulfill the demand of the energy. Low reliability is a big issue in the development of wind energy technology that has affected wind farm operations. The purpose of the study is to find the reason for the low reliability and high downtime for wind turbines.

The systems engineering approach has a high success rate in handling complex systems such as wind farms. A failure finding model is presented based on the systems engineering, with the focus to analyze the failures at the interfaces. The required data have been collected by reviewing the literature.

Gear box interfaces are a vital reason for the higher downtime and frequent failures of wind turbines, and the bearing and the lubricant in the gear box are affected because of their inappropriate combination.

The reliability and the maintainability of the wind turbine is a topic of major importance. The study is an attempt to contribute to a more sophisticated solution to the reliability problem of the wind turbine. Moreover, it shows the importance of interfaces in designing the complex systems.

A series of articles dealing, in as simple a way as possible, with the basic facts of lubrication, lubricants, their selection and prescription, specification, application, and testing. This series is primarily intended for students, engineering personnel who may be unfamiliar with certain aspects and others who, one way or another, are interested in this important subject.

W. H. Marley & Co. Ltd., 105 High Road, London, N.11, have introduced this 3 in. indexing attachment to speed up certain operations which would otherwise call for a more elaborate dividing head. The index plate provides 24 divisions, and the full circle can thus be divided into the factors 2, 3, 4, 6, 8, 12, and 24. Alternative plates can be supplied. The headstock can be fitted with a centre as shown in FIG 1 or with a chuck. The bases of headstock and tailstock are arranged for mounting on the tables of milling, drilling or grinding machines, or wherever else required.

The purposes of this paper are optimization of high speed reducer in electric vehicles based on the analysis of lubrication and verification of simulation accuracy and optimization results.

The traditional CFD method presents poor applicability to complex geometric problems due to grid deformity. Therefore, moving particle semi-implicit (MPS) method is applied in this study to simulate lubrication of the reducer and analyze the influence of input speed and lubrication system design on the distribution. According to the results, the reducer is optimized. Meanwhile, the experiments for lubrication and churning power loss is carried out to verify the accuracy of simulation and optimization effects.

The flow field of lubricant inside the reducer is obtained. The lubrication system of reducer needs to be improved. Simulation and experiment show that the optimization is sufficient and efficient.

According to the simulation of lubrication, the reducer is optimized. The lubrication experimental setup is established. The conclusion of paper can provide the method and tool for reducer in electric vehicle.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0123/

Wear failure happens frequently in rubber seal of high-speed rotating shaft because of the dry friction. Some traditional lubrication methods are not effective because of the restrictions on the relative high speed, temperature and others. This paper aims to present a new method of lubrication with gas film for the rotation shaft seal based on the contact design.

To obtain the generation condition of gas film and good effect of lubrication in the contact gap between the shaft and its seal, a series of micro-spiral grooves are designed on the contact surface of rubber seal so as to obtain a continuous dynamic pressure difference.

The result is that the distribution of the gas film in the micro-gap is continuous under the design of the spiral grooves and the contact with eccentricity because of the deformation of rubber seal, which is verified through the simulation calculation and experiment test. It is confirmed that the lubrication method with gas film through designing micro-spiral grooves on the contact surface is effective, and can achieve self-adaptive air lubrication for the high-speed shaft under the premise of the reliable sealing.

The method of gas film lubrication is realized through designing a microstructure of spiral grooves on the rubber surface to change the contact status, which can form a mechanism of adaptive lubrication to reduce the dry friction automatically in the contact gap. For the cross-scale difference between the rubber seal and gas film, a new modeling method is presented by building the mapping relation for the split blocks and repairing technique with integrated computer engineering and manufacturing, to reduce the possibility of nonconvergence and improve the efficiency and accuracy of calculation.