Epicyclic Transmission Research Articles

Fuzzy Logic Controlled Two Speed Electromagnetic Gearbox for Electric Vehicle
 

Epicyclic transmission (ET), five-speed manual gearbox (5-SMT), automatic transmission (AT), and continuously variable transmission (CVT) are all possible transmission options for electric vehicles (EVs). The ET is so complex that motorists may be unaware that they are in gear. As the 5-SMT, AT, and CVT transistors are heavier, they consume more energy. Although a single-speed gearbox is lighter, it is not capable of developing enough torque for acceleration. Therefore, this study presents a fuzzy-logic-controlled electromagnetic two-speed gearbox (AEM-2SGB) model for EVs. The electromagnetic actuator is modelled in terms of electromagnet size, number of coil turns, supply current, and electromagnetic force needed to shift gears. The parametric analysis of AEM-2SGB is conducted using Matlab Simulink and a fuzzy simulation model. According to the results, the AEM-2SGB has a first-gear shift time of 110 ms at 300 Nm motor torque and a second-gear shift time of 116 ms at 110 km/h vehicle speed, with a maximum current supply of 16 A using a 24 V lithium ion battery. The AEM-2SGB reduces weight by 37%-66%, transmission losses by 40%–90%, and battery life by 5%.

Design and Dynamic Analysis of a Compact 10 MW Medium Speed Gearbox for Offshore Wind Turbines

Abstract This paper deals with the design of a compact gearbox for the DTU 10 MW reference offshore wind turbine. An innovative gearbox concept consisting of a fixed planetary stage and a differential compound epicyclic stage is proposed. Power splitting and compound epicyclic transmission technologies are employed, which can effectively reduce the gearbox size. The power transmission principle of the gearbox is described and power distribution ratios in two transfer paths are calculated via the geometrical and mechanical relationships among the gearbox components. The gearbox is designed based on the design loads and fatigue criteria by referring to relevant international standards. A high-fidelity drivetrain numerical model is established by means of a multi-body system (MBS) approach. Then, the power distribution ratios in two transfer paths are compared between the simulation results and the design values with a good agreement. Resonance analysis of the drivetrain model is conducted by means of the Campbell diagram and energy distribution of components, and the results show that no severe resonance phenomena appear in this drivetrain model. Additionally, the load-sharing behavior of the gearbox model is assessed under different environmental conditions, and the results indicate that the compact gearbox has a good load-sharing performance. Such a compact gearbox design, which fulfills all the design requirements for offshore applications, could be a good alternative for offshore wind turbines.

Synthesis of irregular motion mechanisms for production machine drives

Irregular motion of the working bodies is widely used in mixing equipment. It helps to achieve homogeneity of the mixtures, since the uniform motion may lead to the “dead” zones formation. The purpose of this work is to synthesize the mechanism for driving the mixer’s working shafts which includes an epicyclic transmission with a swing. This paper reports the studied pathways, velocities, and accelerations for different gear ratios at the final link, i.e. the swing. The research methods are analysis and synthesis of irregular motion mechanisms. It was found that in the mechanisms with the lowest pulsation, the amplitude of the angular acceleration change at the distance from the planet gear rotation axis to the pin equal to 14 mm is the smallest of the considered ones. The performance increases by 22 % with this coefficient of non-uniformity. As a result of the conducted research, we determined the main rational parameters for the synthesis of the considered mechanism.

Design of a compact 18-speed epicyclic transmission for a personal mobility vehicle

This paper describes the design and shifting dynamics of a novel and small-sized transmission which composed of three epicyclic gear modules and a hub shaft in conjunction with several clutches. The proposed epicyclic gear train can be used in a personal mobility vehicle such as an electric utility vehicle and small car, etc. And it is distinguished from others for its small size, light weight, high efficiency, and wide speed range up to 18 gear steps. In this paper, its dynamic behavior is dealt with in order to ensure the automatic and robust shifts according to the shift commands, focused on the shift mechanism design. First the overall structure and operating principles of the transmission are described in detail. Based on the CAD data of whole components, a detailed multibody dynamic model is built using ADAMS software which can analyze the dynamic behavior of a mechanical system. Then numerical simulations are performed during the shift and whole operating period. From the simulation and experiment results, the overall performance and operating principles of the 18 speed epicyclic transmission are discussed and the design of shift device is optimized to ensure the robust shift finally.

LOAD SHARING ANALYSIS OF PLANETARY GEAR BOX

One of the advantages of epicyclic transmissions is that the input torque is divided in a number of parallel paths. For n planet epicyclic system, each sun–planet–ring path is to transmit 1/n of the input torque. However, this is only true in the ideal case when there is equal load sharing between all the planets in the epicyclic system. Because of manufacturing errors, equal load sharing is not possible and the degree of inequality in load sharing has major role for gear system sizing, tolerancing schemes, and torque ratings. Therefore it is important to understand the fundamental cause of the unequal load sharing behavior in epicyclic gear sets. Load sharing behavior is associated with positional errors causing one or more planets to lead or lag the other planets. When the error is positive the planet with error lead the other planet while when the error is negative planet with error lags the other planet. Several manufacturing errors can introduce positional errors. Some of the common contributors are carrier pinhole position error, planet size variation, and run out of the gears. A set of precision planetary gear set is selected with the objectives of experimental and theoretical investigation of the load sharing behavior by introducing the position errors for the planets, the load shared by each planet is estimated by maximum stresses induced in each pin. The results of the experimentation are then validated with the FEM (Finite Element method) results.

Modelling and Analyzing Hybrid Electric Vehicles with Single and Dual Epicyclic Power Split Transmissions

The main aim of this paper is to investigate the performance of hybrid electrical vehicles (HEVs) using single and dual epicyclic power split transmissions (PST). The development of PST has been a crucial feature in the technological success of hybrid driveline vehicles. In this paper, single and twin epicyclic power split transmissions models are analyzed and the relationships of speed and torque of the engine, motor and generator are developed. The models are further extended to include all subsystems and a controller designer to be fitted in a typical hybrid electrical vehicle (HEV). Computer programmes for the analysis of epicyclic transmission based on a matrix method are developed and used. In addition, the performance and control strategy of the new system is presented. Three vehicle models are built-up; namely: traditional ICE vehicle, HEV with single epicyclic gearbox, and HEV with twin epicyclic gearbox. The vehicles are simulated over typical driving cycles. The results focus on fuel consumption comparisons but it is also shown how the single and twin epicyclic gearboxes use the engine and motor generator units differently. The simulations show that the twin epicyclic offers substantial improvements of reduction in energy consumption, though the benefits are sensitive to the driving cycle used.

Performance Analysis of Hybrid and Full Electrical Vehicles Equipped with Continuously Variable Transmissions

The main aim of this paper is to study the potential impacts in hybrid and full electrical vehicles performance by utilising continuously variable transmissions. This is achieved by two stages. First, for Electrical Vehicles (EVs), modelling and analysing the powertrain of a generic electric vehicle is developed using Matlab/Simulink-QSS Toolkit, with and without a transmission system of varying levels of complexity. Predicted results are compared for a typical electrical vehicle in three cases: without a gearbox, with a Continuously Variable Transmission (CVT), and with a conventional stepped gearbox. Second, for Hybrid Electrical Vehicles (HEVs), a twin epicyclic power split transmission model is used. Computer programmes for the analysis of epicyclic transmission based on a matrix method are developed and used. Two vehicle models are built-up; namely: traditional ICE vehicle, and HEV with a twin epicyclic gearbox. Predictions for both stages are made over the New European Driving Cycle (NEDC).The simulations show that the twin epicyclic offers substantial improvements of reduction in energy consumption in HEVs. The results also show that it is possible to improve overall performance and energy consumption levels using a continuously variable ratio gearbox in EVs.

Power Analysis of Epicyclic Transmissions Based on Constraints

Epicyclic gear transmissions have many applications. The internal power flow of epicyclic systems is highly related to the power loss of the system. A systematic method and generic formulas based on kinematic constraints are derived to conduct the power flow analysis, by means of Lagrange multipliers and newly introduced selection matrices. The method and formulas can be readily applied to complicated epicyclic systems. The graphic representation of the power flow of two examples verifies the balance of the power flow and virtual power flow. In the example of the Dual-E powertrain for hybrid electrical vehicles, an estimation of the total efficiency is derived. The pattern of contour maps of the total efficiency indicates the operational ranges of the powertrain with relatively low power losses.

Detection of a fatigue crack in a UH-60A planet gear carrier using vibration analysis

Two new methods of detecting a fatigue crack in a planet carrier of an epicyclic transmission are developed. These are tested using vibration data from a number of US Army UH-60A Black Hawk helicopter main transmissions. Vibration measurements of faulted and un-faulted transmissions over a range of torque levels in controlled test-cell and on-aircraft conditions are used. The results show that new methods are reliable under test-cell conditions, but less effective under low-torque on-aircraft conditions.

Selecting multi-freedom multi-loop kinematic chains to suit a given task

Developments of number synthesis and the means of enumerating kinematic chains have not lead to a significant flow of novel kinematic structures to successful mechanical designs. This paper addresses one of the difficulties, namely how to select a pertinent kinematic chain from the many that can be enumerated. To this end, a new and important concept called the variety of a kinematic chain is explained and discussed with particular attention to its relationship to the motion capabilities of mechanisms such as robot manipulators and gear trains. Many motion tasks have an inherent hierarchy of freedoms that closely relates to the variety of a kinematic chain, and hence variety can be used to select those candidate mechanisms best suited to an intended function. An epicyclic transmission is used to demonstrate this technique.

The Design of a Novel Mechanical Transmission for Speed Reduction

The design of a novel transmission for speed reduction is reported in this paper. The transmission is based on the layout of pure-rolling indexing cam mechanisms, for it is intended to eliminate backlash and friction, which are the main drawbacks of gear transmissions. The design relies on a unified methodology for indexing cam mechanisms, whereby the same procedure is used to design planar, spherical, and spatial mechanisms. Two versions of the speed reducer, that we term Speed-o-Cam, are described here, namely, planar, to couple shafts of parallel axes, and spherical, to couple shafts of intersecting axes. By means of a cascade of two planar versions of Speed-o-Cam, moreover, coaxial shafts can be coupled. Moreover, contrary to other alternatives to gear transmissions, such as harmonic drives or epicyclic transmissions, Speed-o-Cam caters to shafts with either parallel or intersecting axes; in the latter case, moreover, the angle at which the axes intersect can vary from 0° to 180° continuously. The design with shaft axes at 0° leads to an internal cam, i.e., one with its axis external to the axes of the follower and the roller in contact; for shaft axes at 180°, the design leads to an external cam, i.e., one with its axis lying between those of the follower and the roller in contact.

Reliability Analysis and Design of Epicyclic Gear Trains

The concepts of system reliability are applied for the structural reliability analysis and design of epicyclic gear trains. The reliability analysis is based on the representation of an epicyclic gear train as a series-parallel network. The power transmitted, the speed of the input shaft, the center distance between the gear pairs and the permissible stresses are assumed to be random variables following normal distribution. The layout of the gears and the speed ratios are assumed to be known. The face widths of the gears are taken as random design parameters. The design criterion is that the reliability of the gear train either in bending or surface wear failure mode at any of the output speeds must be equal to a specified value. The design of an epicyclic transmission system which gives four forward speeds and one reverse speed is considered for illustration. The results of the reliability-based design of the gear train are compared with those of the conventional deterministic design.