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In this investigation is presented a systematic approach for the mod-elling and analysis of power split transmissions which include an epicyclic gear train, in various configurations, as they are used in hybrid vehicles. Emphasis is placed on the efficiency of the epicyclic gear trains and the asso-ciated power-flow in the transmission. The approac...
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![Figure 1 Basic epicyclic gear train.[1]](profile/Essam-Esmail/publication/285578606/figure/fig1/AS:613945849167884@1523387505674/Basic-epicyclic-gear-train1_Q320.jpg)
Although the method presented in Pennestrí et al. work [1] is exactly similar to that presented in an earlier work by Pennestrí and Freudenstein [2]. Pennestrí and his coauthors [1] mention that a more extended table of mechanical efficiencies of one d.o.f. gear train kinematic inversions is embodied. Indeed, Pennestrí and his coauthors [1] have go...
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An investigation to symmetry in epicyclic gear trains (EGTs) is carried out in this research. As a consequence of the graph theoretic framework for EGTs, an EGT graph serves as an isomorphic substitute for its kinematic structure. In this work, Nauty & Traces software package is employed for an EGT graph for determining the automorphism group and o...
Citations
... At the very least, the allowed recirculation should not exceed a specified limit. The unfavorable effects of recirculation in differential gear trains and continuously variable transmission were also reported by Pennestrì et al. [1]. ...
... Not applicable. 1 ...
Recirculation is expected to be identified for its possibility to dramatically decrease the efficiency of planetary gear trains (PGTs). However, it exhibits an unexplained connection with the structure, making it challenging to identify without tedious computation through tooth and speed ratios, thus complicating the design process. This study employs a generic model utilizing the mechanical balance principle and reveals the fundamental laws of the previously unexplained connection for parallel-connected ring-sun-type PGTs. Two necessary and sufficient conditions, torque and structure, were proven for multi-stage and two-stage PGTs without recirculation, respectively. This shows that the structure, specifically whether the links are central gears or carriers, and the connections between them directly impact the recirculation of these PGTs. A geometric model representing the structure and kinematics was developed to visualize the power flow. Thus, the recirculation of parallel-connected ring-sun-type PGTs can be predicted without calculations. Our results provide the underlying insights to understanding recirculation from the structural connection viewpoint, thereby contributing to the conceptual design phase where the task is to select the kinematic structure and the gear size is unknown.
... The kinematic chain method [13][14][15][16] is used as the example shown in part 2 in this paper, the angular velocities of the body and each gear are shown in Table 1 by the motion analysis of a 2K-H multistage micro-planetary gear reducer. Table 2 is the transmission relations of a 2K-H multistage micro-planetary gear reducer shown in Fig. 3. ...
According to the principle of the gear overall size as small as possible, the structural analysis of multistage micro-planetary transmission is carried out. It is found that a 2K-H multistage micro-planetary gear reducer meets with the principle requirement. On this basis of the torque, power balance equations and force analysis of the basic members, the power distributions of a 2K-H multistage micro-planetary gear reducer are analyzed under considering power losses or not, the overall transmission efficiency calculation of a 2K-H multistage micro-planetary gear reducer is more intuitive and easy to operate. Meanwhile, it indicates a direction for further power losses analysis of multistage micro-planetary transmission.
... Most of the studies for computing the efficiency of PGTS are based on the fundamental circuit technique [1][2][3][4][5]16], on the concept of kinematic units [5,6], and on Graph-based techniques [7][8][9]12] A review of efficiency formulas for two-DOF PGTs are given in [10, 15, and 17]. New methodologies are proposed for computing the power flow and efficiency of PGTs in Refs [11][12][13][14]. ...
... Most of the studies for computing the efficiency of PGTS are based on the fundamental circuit technique [1][2][3][4][5]16], on the concept of kinematic units [5,6], and on Graph-based techniques [7][8][9]12] A review of efficiency formulas for two-DOF PGTs are given in [10, 15, and 17]. New methodologies are proposed for computing the power flow and efficiency of PGTs in Refs [11][12][13][14]. ...
The power developed within the elements of planetary gear train (PGT) may differ significantly from that being transmitted through it. This characteristic has a significant effect on the efficiency of split-power PGTs and requires a reliable, quick method to detect internal power circulation. By taking advantage of the usefulness of the graph-based approach, a simple preparatory power flow analysis, which provides a complete insight into the power flowing within the system elements without wasting time and effort in doing complicated mathematical computations, can be conducted. The graph-based approach is also useful in estimating the potential power which is related directly to the efficiency of PGTs. An analytical expression for the total efficiency of a PGR is derived using potential power analysis. Analysis of the power flowing through the PGR shows that there are internal power circulation and power amplification. The results are verified by an example. A brief comparison with existing efficiency formulas, which were applied to exactly the same system discussed here, is also given.
... The concept herein adopted for analysis is that to each circuit in a mechanism there corresponds a Basic Epicyclic Gear Train (BEGT). Therefore, with the help of gear train-graph correspondence introduced by Freudenstein [3,4], the topology of this powertrain, depicted in Figure 2, is initially decomposed into BEGTs whose kinematics is governed by the so-called Willis' equation [3][4][5][6]. ...
... The gear train-graphs correspondence is adopted to generate in a systematic way the set of equations whose solution provides the unknown angular speeds [3][4][5][6]. Since the gear train topology depends on activation of the clutches and brakes, the corresponding graphs are depicted for each driving mode. ...
... Regarding the efficiency calculation of the BEGT with two degrees-of-freedom, by means of the method of Pennestrì et al. [5,7,8], the mechanical efficiency is computed as a linear combination of angular speed ratios. Then it is necessary to assess if the Basic Epicyclic Gear Train (BEGT) works as DISO (dual input-single output) or SIDO (single input-dual output). ...
Efficiency in transportation of goods and people are crucial objectives for the sustainability of society and the protection of its environment. In the particular case of urban mobility, the current trend is toward the applications of hybrid propulsion, if not purely electric. The growing dimensions of urban areas suggest that a particular attention needs to be addressed to vehicles’ energy requirements, air quality and noise pollution. Hybrid technology satisfies the needs of small engines, with low emissions and high energy-efficiency. Therefore, for efficient power management of small internal combustion engines and electric sources, reduced costs and energy efficient gear transmission systems are required. A scheme of hybrid gear transmission, proposed by Sheu, with the aim of minimizing the emissions and fuel consumption, will be herein analysed to estimate the overall mechanical efficiency. In particular, we will discuss an application of a methodology based on graph theory for a systematic and unified analysis of the gear train mechanical efficiency, in all six driving modes. The phases of the proposed analysis are summarized in Table 1.Table 1
Phases of the proposed mechanical efficiency analysis procedure
... Thus, the technical literature presents various new concepts of wind turbines that meet the previous requirements, like the wind turbines of increased capacity that use several rotors [10], or several small rotors in different spatial disposal [16], or the counter-rotating wind turbines that use two coaxial rotors rotating in opposite directions [4]. Another direction consists in ensuring the optimal operation conditions of electric generators and, hence, a high efficiency of the mechanical energy conversion into electrical energy by maintaining a constant angular speed near its nominal value that can be achieved by: the integration of 2 degrees of freedom (DOF) planetary speed increasers into classical single rotor wind turbines where a servomotor [17] or a variable speed transmission [3, 12] is connected to one input, the use of electric generators with a mobile stator that allows the increase of the rotor speed versus the stator, and, thus, a higher efficiency [2]. 7th International Conference on Advanced Concepts in Mechanical Engineering IOP Publishing IOP Conf. ...
... The correlation of rotors' smaller speeds to the generators' higher speeds can be ensured by integrating speed increasers [4], which can have fixed axes for the lower kinematic ratios, or can be planetary transmissions working at higher speeds or included in counter-rotating wind turbines [14, 15]. The kinematics and statics, the efficiency and power flow modelling of complex planetary transmissions are presented and analysed in many scientific papers by using various methods: the graph theory applied in the kinematic analysis of planetary gear trains [9, 12]; the conjoint analysis and a general algorithm for the analysis of transmission ratios and efficiency for the 1DOF planetary transmissions with four, five and six constraints [13]; the graph and screws theory applied in efficiency computing [11]. A methodology for computing the power transmitted through complex gear mechanisms, including planetary gears and variable speed transmissions, is proposed in [8]. ...
Most of wind turbine applications for urban areas use electric generators with counter-rotating rotor and stator, able to ensure a better efficiency than the conventional turbines with one wind rotor and generator with fixed stator, and, hence, a higher production of electricity. These types of power systems have two independent wind rotors that require a complex control of the two independent input speeds to obtain the optimal output speed. This paper deals with the use of a 1DOF (Degree Of Freedom) compound planetary transmission with two inputs and two outputs and three sun gears, meant for the implementation in counterrotating wind turbines, which has the properties of summing the input torques and determined transmission of the independent speed. Firstly, the kinematic and static analysis of the proposed planetary transmission, assuming friction of gears, is performed. Afterwards, the mechanism efficiency model is established depending on the ratio of the two input torques. The transmission efficiency is simulated and analysed, with determination and representation of power flows, in the four distinct operating cases according to the k ratio values. The paper results allowed formulating recommendations on the design of these mechanical planetary transmissions used in wind turbines and broadening a database for the conceptual synthesis of wind systems.
... Published under licence by IOP Publishing Ltd 1 through the complex planetary transmissions consisting of planetary gears and a variable speed transmission, presenting the equation of power circulating through a branch by a kinematic approach. A method for establishing the efficiency of planetary gears based on the screw theory is described in [8], while [12] presents an approach on modelling the efficiencies of power transmissions used in hybrid vehicles based on graph theory. A combined analysis of efficiency and transmission ratio [13] allows identifying transmissions with high gear ratios and high efficiencies, a useful approach in the design of planetary gears. ...
The paper presents a study on the kinematic and static performances of a new type of 1DOF (Degree Of Freedom) planetary speed increaser to be implemented in wind turbines, a transmission with three operating cases: a) one input and one output, b) one input and two outputs, in which the speed of the secondary output is equal to the input speed, and c) with one input and two outputs, where the secondary output speed is higher than the input speed. The proposed speed increaser contains two sun gears and a double satellite, allowing operation with an output connected to the fixed stator of a classic generator (case I) or with two counterrotating outputs that drive a counter-rotating generator (with a mobile stator). A new variant of planetary transmission capable of providing the speed increase of the generator stator and, thus, the increase of the relative speed between the generator rotor and stator is obtained by the parallel connection of the speed increaser with a planetary gear. The three conceptual variants of planetary transmission are analytically modelled and comparatively analysed based on a set of kinematic and static parameters. The proposed transmission has higher performances compared to the same transmission with one input and one output, the increase of the kinematic amplification ratio and efficiency being achieved simultaneously.
... The hybrid vehicles use different power sources with various powertrain configurations, including the ICE, electric motors (EMs), electric generators and battery packs [6]. In this paper are studied the hybrid electric vehicles (HEVs) that are one of the solutions proposed to minimize problems associated with the energy crisis and global warming [3]. ...
Artigo Completo
The hybrid electric vehicle (HEV) became an alternative to reduce the fuel consumption. The HEV parallel configuration consists of two separated drive systems, such as the engine/powertrain system and an extra electric motors (EMs) system. The addition of an extra electrical power changes the engine operation point and consequently the fuel consumption. However, there are many ways to introduce this electrical power source as a secondary drive system. In this paper, two parallel HEV configurations are studied in a condition where the conventional engine/powertrain system, coupled to the vehicle front wheels, is the main power source and two different configurations of EMs drive system, coupled to the rear wheels, are auxiliary power sources. The first one consists of two in-wheel motors coupled directly to the vehicle rear wheels and the other one is an EM coupled to a differential system similar to the existent in the conventional vehicle powertrain. The aim of this paper is to simulate and compare the HEV behavior with the conventional vehicle behavior, both of them running in the Brazilian urban drive cycle NBR6601, evaluating differences in performance, fuel consumption and battery discharging when applicable.
... The power distribution from the electric motors throughout the powertrain also needs to be modelled. The kinematics and power flow of the PGT connecting the two motors in Configuration 1 and Configuration 2 can be determined using the procedure proposed by Pennestrí et al. (2012). A brief summary and adaptation to this particular case is now presented. ...
... InFigure 7(b), a block diagram describes the power flow among the different elements. In the procedure of Pennestrí et al. (2012), gears are represented by nodes, with power flowing to a basic epicycle gear train (BEGT). The interaction of the gears as part of the BEGT is represented by a block in this procedure. ...
Electric vehicles (EVs) offer the potential for energy-efficient transportation. To increase consumer acceptance, improved driving range and fault-tolerant traction represent two important challenges. This paper proposes a powertrain architecture that can provide fault-tolerant traction and increase the driving range for EV. In the proposed system, the traction power of two motors is combined through a planetary gear train (PGT). The propulsion system can operate with only one motor or with any combination of speeds in the two motors. The performance of the proposed powertrain architecture is analysed through simulations. Two different configurations are compared with conventional electric powertrain designs. The simulations account for different types of driving cycles and electric motor efficiency maps. Results indicate that the proposed powertrain architecture produces improvements in overall efficiency and driving range.
... shows a basic epicyclic gear train (BEGT).Figure 1 Basic epicyclic gear train.[1] For each basic epicyclic gear train , Willis's equation is written as follows í µí¼ í µí± − í µí±
í µí± í µí¼ í µí± + (í µí±
í µí± − 1)í µí¼ í µí± = 0 ...
... The gear ratio is defined as í µí±
= ± í µí± í µí± í µí± í µí± = ± í µí±í µí±¢í µí±í µí±í µí±í µí± í µí±í µí± í µí±¡í µí±í µí±í µí±¡ℎ í µí±í µí± í µí±¤ℎí µí±í µí±í µí± í µí± í µí±í µí±¢í µí±í µí±í µí±í µí± í µí±í µí± í µí±¡í µí±í µí±í µí±¡ℎ í µí±í µí± í µí±¤ℎí µí±í µí±í µí± í µí± [1] stated that the cases not considered by Merritt [40] are those with the gear ratio R within the range 0 < R < 1, but that is inexact. In particular, the formulae adopted for the estimation of efficiency in epicyclic inversions and two degree of freedom differential gearing are the same as those deduced by Merritt [3], Macmillan [4], Radzimovsky [5] and Pennestrí and Freudenstein [2]. ...
... The extended table of mechanical efficiencies of one d.o.f. gear train kinematic inversions obtained by [1] is probably due to the absence of a specific definition of the gear ratio R. By definition í µí±
= ± í µí± í µí± í µí± í µí± ⁄ , if we replaced i in place of j in the gear ratio Equation, then í µí±
ʹ = 1 í µí±
⁄ and some of the formulae tabulated in [1] are shown to be repeated. ...
Although the method presented in Pennestrí et al. work [1] is exactly similar to that presented in an earlier work by Pennestrí and Freudenstein [2]. Pennestrí and his coauthors [1] mention that a more extended table of mechanical efficiencies of one d.o.f. gear train kinematic inversions is embodied. Indeed, Pennestrí and his coauthors [1] have got confused in the gear ratio ranges due to an absence of a specific definition of the gear ratio R.
... In this system, the split power path is able to interconnect the mechanical and electrical power structures. Planetary gear is applied in this system to make a connection between the mechanical and electrical devices (Bayindir et al., 2011; Pennestrì et al., 2012). Since the electric motor is one of the important components in the HEV, the selection of electric motor type is seen to be compulsory. ...
This paper presents a detailed derivation of a permanent magnet synchronous motor, which may be used as the electric power train for the simulation of a hybrid electric vehicle. A torque tracking control of the permanent magnet synchronous motor is developed by using an adaptive proportional-integral-derivative controller. Several tests such as step function, saw tooth function, sine wave function and square wave function were used in order to examine the performance of the proposed control structure. The effectiveness of the proposed controller was verified and compared with the same system under a PID controller and the desired control. The result of the observations shows that the proposed control structure proves to be effective in tracking the desired torque with a good response. The findings of this study will be considered in the design, optimisation and experimentation of series hybrid electric vehicle.
