Compound Planetary Gear Research Articles

A helical drive in-pipe robot based on compound planetary gearing

The modern society is fuelled by very comprehensive grids of gas and liquid pipelines. In recent years, various in-pipe robots have been developed for inspection and maintenance tasks inside such pipes. In this paper, a novel in-pipe robot is proposed and developed for gas/oil well interventions at thousands of meters downhole. Due to the nature of such intervention, in-pipe robot design must be capable of carrying a very large payload, as large as 2500 N inside a pipe with diameter as small as 54 mm. The proposed design concept is based on a compound planetary gearing system. One of the major novelties of this design is the use of pipe wall as a ring gear for one stage of the compound planetary gear system; the other novelty is the generation of helical angle when the planetary gears are expanded to press on the pipe wall. The proposed concept is compact, efficient, and has never been reported before. In this paper, the helical angle, the velocity, and load capability of the proposed system will be analyzed. The load transportation capability of the proposed robot is also measured based on an experiment. Initial data have shown great potential in carrying large payloads.

Design of a six-speed transmission hub with an integrated brushless permanent-magnet motor used for electric bicycles

Purpose – The electric motor and multi-speed transmission hub are essential components for an electric bicycle. Traditionally, these two devices have been designed and manufactured independently. The purpose of this study is to propose a novel electromechanical device that artfully integrates an exterior-rotor brushless permanent-magnet (BLPM) motor into a transmission hub to become a compact structural assembly. Design/methodology/approach – A novel design that integrates a three-phase, 20-pole/18-slot exterior-rotor BLPM motor with a multi-speed transmission hub composed of a six-link, two-degrees-of-freedom (2-DOF) compound planetary gear train (PGT) is presented in this study to overcome inherent drawbacks of existing designs. An analytical approach, based on fundamental circuits, is developed to synthesize the clutching sequences and numbers of teeth of all gears of the PGT. Findings – The integrated device provides six forward speeds, including two underdrives, two direct drives, and two overdrives, as well as two drive modes: the motor-drive mode and the human-drive mode, for electric bicycles. The main feature of the proposed design is the spur gear teeth merged with the pole shoes of the stator to dramatically minimize the detent torque, which is an oscillatory torque that always induces vibration and acoustic noise of the BLPM motor. Originality/value – The gear teeth on the pole shoes of the stator provide functions not only for transmission, but also act as dummy slots for adjusting the magnetostatic field of the BLPM motor to effectively reduce the detent torque. The peak value of the detent torque of the integrated design is only 9 percent of the original BLPM motor with identical magnet properties and motor dimensions. Such a feature is contributive in suppressing the vibration and acoustic noise of the electric bicycle's BLPM motor. A BLPM motor rated at 310 W and 250 r/min for the integrated device is presented and analyzed by using the commercial finite-element package Ansoft/Maxwell 2D Field Simulator.

5-모드 하이브리드 동력전달 시스템의 정상상태 성능분석

Article history: The core of the automotive industry’s strategy to handle the climate change can be explained as the development and distribution of the vehicles with high fuel efficiencies and low emission. Clean Diesel, hydrogen fuel cell, electric, and especially hybrid power-train vehicles have been actively studied. This paper dynamically analyzes the performance of a hybrid system's five driving modes. The research subject consists of one engine, two electric motors, two simple planetary gears, and one compound planetary gears with five clutches. To define the steady state equation of the system, interaction formulas of five driving modes are introduced with motion variables and torque variables. These formulas are then used to analyze the speeds, torques, and power flows of each mode.

The Research on Natural Characteristic and Eigensensitivity of Ravingneaux Compound Planetary Gear Sets

The dynamic model of Ravingneaux compound planetary gear sets has been built. Then the Natural frequency and vibration model have been solved in the Ravingneaux compound planetary gear sets. The eigensensitivity to parameters have been researched based on the dynamical model. The varying trend of natural frequency according to the varying of parameters have been researched, which include gear mass (sun gear, ring gear , or planet gear), the moment of inertia of gears, the support stiffness , the torsional stiffness.

Torsional vibration and acoustic noise analysis of a compound planetary power-split hybrid electric vehicle

Theoretical and experimental analyses of torsional vibrations and acoustic noise for a deep hybrid electric vehicle driveline including an electric, continuously variable transmission are carried out. The dynamic and mathematical models with 16 degrees of freedom in a matrix form are developed for the torsional vibration characteristics of the hybrid driveline. On the other hand, the noise sources of the hybrid electric vehicle powertrain excited in the pure electric mode and the hybrid drive mode are tested and measured using acoustic and speed sensors. The noise orders and the frequency domain responses are constructed using signal treatment and torsional vibration analysis. The theoretical predictions for the natural frequencies and the corresponding vibration modes of the hybrid driveline are presented. The noise test results are also given in accordance with the torsional vibration modes of the hybrid driveline in the pure electric mode and the hybrid drive mode. The noise sources due to the self-excited and frequency-multiplied vibrations are found, focusing on the compound planetary gear set in the power-split electric, continuously variable transmission.

Graph-Based Models of Compound Planetary Gear Boxes

In the paper, graph-based models of planetary gears are presented. Especially, compound planetary gear boxes are analyzed. The rules of assignment of particular graphs are shortly described. Based upon these models, ratios for consecutive drives are calculated. Graph transformations are introduced aiming for presentation of every single drive separately. Kinematic equations are generated in algorithmic way based on the adequate subgraphs as well as their codes. Compatibility of results - obtained by means of different methods - was achieved. The presented method is simple and effective, moreover it can be used for other design tasks as e.g. optimization and further analyzes i.e. evaluation of effectiveness.

Inherent Characteristic Analysis for Torsional Vibration of a Planetary Transmission

A torsional vibration mechanical model of the transmission system of a certain cetarpillar vehicle is established using mass distribution method. The torsional vibration model, containing multi-stage simple and compound planetary gear transmissions, fixed-axis transmission and power split/converge system, is established based on Lagrange Equation. Matlab is used for presenting and writing the according program of the modal analysis of free torsional vibration. The study is focused on the torsional vibration characteristic of the system on one specific working condition and the similarity in the inherent characteristics of the system on different working conditions.

병렬형 하이브리드 자동차의 구동장치 설계 및 해석

This paper deals with the design and modal characteristics analysis of a drive-train for a paralleltype hybrid electric vehicle (HEV). The function of the drive-train system (DTS) in the HEV combines or divides the torque and velocity from the internal combustion engine along with the induction motor. The system consists of a compound planetary gear and unit’s electromagnetic clutch to provide the operation modes such as Engine Only (EO), Electric Vehicle (EV), and Hybrid Electric Vehicle (HEV) modes. In order to investigate the characteristics of the velocity and torque flow for the system, dynamic models of the HEV with DTS are derived from the prototype DTS. The performance of the derived dynamic models is evaluated by both computer simulations and experiments according to each mode.

Axial Thrust Force of Compound Planetary Spur Gear Set

Planetary gears are widely used in automotive and aerospace applications. Traditionally, automatic transmissions have four forward speeds, which can be achieved by using two planes of single pinion (sun-pinion-ring) planetary gear sets. Recently, there is a trend that transmissions have more than five forward speeds, which make compound planetary gear sets with two pinions (ring- or sun-pinion1-pinion2-ring) becoming common. Due to demands for higher power density and compactness, needle bearings are often used in these gear sets. There are significant axial thrust forces between the pinions and the carrier, which could lead to excessive wear of thrust faces and deterioration of bearing system performance. In this paper, we analyzed generation mechanism of axial thrust force in compound planetary spur gear set and calculated the axial thrust force. It was shown that axial thrust force always exists because of the torsional pendulum torque acting on the long planet. Experimental test for a compound planetary spur gear was taken to study axial thrust force and validate the theory calculation.

The Research on Nonlinear Vibration Characteristic of Ravingneaux Compound Planetary Gear Sets

The nonlinear dynamic model of Ravingneaux compound planetary gear sets has been built. The model includes time-varying mesh stiffness of gears, backlash as well as comprehensive mesh errors nonlinearities. By introducing relative displacements of components as the new generalized coordinates, uniform nonlinear differential equations of compound planetary gear sets are built. Then the nondimensional dynamic differential equations are derived. The nonlinear differential equations have been solved utilizing ariable step size Gill method. By changing system nondimensional excitation frequency, monocycle anharmonic response, multiply periodic subharmonic response, quasi-periodic response and chaotic response are obtained. By means of time histories, phase-plane diagram, Poincare maps and power spectrum, various responses are compared and analyzed in detail.

Analytical determination of mesh phase relations in general compound planetary gears

This paper systematically studies the mesh phase relations of general compound planetary gears. The mesh phase relations are described by the relative phases between mesh tooth variation functions of all gear meshes. The analysis allows for compound planetary gears having multiple mesh periods. A numbering method is proposed for accurate definition of the relative phases in a general compound planetary gear. By introducing the concepts of system-level, stage-level, and train-level relative phases, the relative phases between any two gear meshes in a compound planetary gear are calculated systematically. Important relations among these relative phases are derived. The results from this study are necessary for analytical or computational multibody studies on the static or dynamic response of general compound planetary gears.

Comprehensive Dynamic Model and Vibration Characteristics of Step-Type Compound Planetary Gear Sets

Step-type compound planetary gear sets are widely applied in vehicle systems. Comprehensive dynamic model of step-type compound planetary gear sets, which includes translational, rotational vibrations and static transmission errors, was established. Natural vibration characteristics of the system, such as natural frequencies and vibration modes, were analyzed. Belt shape distribution characteristics of its natural frequencies was researched. According to vibration characteristics of both central components and planets, natural vibration modes of the system are classified into three types: central components translational vibration and planets random vibration, central components rotational vibration and planets identical vibration, central components static and adjacent planets reverse vibration mode.

The Instantaneous Efficiency of Epicyclic Gears in Flight Control Systems

The instantaneous efficiency of an epicyclic gear rotary actuator is an important factor in sizing flight control systems where compound epicyclic gear trains are typically used. The efficiency variation can be smooth or fluctuating depending on the combination and timing of the teeth of ring, planet, and sun gears. In this paper, the instantaneous efficiency characteristics of synchronous and nonsynchronous actuators under forward-driving with opposing load and reverse-driving with aiding load are investigated. The emphasis will be on instantaneous, rather than average efficiency of gears. Several gear arrangements are considered: external and internal gears, simple planetary gears and compound planetary gears. Efficiency will be discussed considering not only the geometry of the mating gears, but also the relative phasing of the planet gears relative to the sun and ring gears. Synchronous compound epicyclic gears are shown to have large fluctuation in their instantaneous efficiency. When reverse-driving efficiency falls below 0%, the unit cannot be back-driven and will chatter. Nonsynchronous compound gears have a smaller variation in instantaneous efficiency. However, extra care must be taken in timing the compound planet gears, as well as clocking position of compound planet gears relative to ring gears and the sun gear.

Nonlinear Dynamic Characteristics of Compound Planetary Gear Train Sets Based on Harmonic Balance Method

A purely rotational model of Ravigneaux compound planetary gear train sets including time-varying mesh stiffness,synthetic mesh errors and gear backlashes is developed to show the nonlinear dynamic behavior of the system with the action of multi-clearances.The gap function is expressed as describing function and harmonic balance method(HBM) is used to convert the differential equations to nonlinear algebraic equations,which is solved iteratively by single rank inverse Broyden method.The steady state response of fundamental frequency is obtained.The influences of gear backlashes,time-varying mesh stiffness and synthetic mesh errors are analyzed by changing the value of the parameter.It is showed from the research that multiple value and amplitude jump discontinuities are presented on the dynamic curves,there the impact phenomenon is reflected.Meanwhile the nonlinearity degree of the system is increased by the coupling of stiffness fluctuation,mesh errors and backlashes.The HBM based on describing function can be used for more complicated model to obtain the steady state response of fundamental frequency,which provides a method for deeply researching the dynamic behavior of compound planetary gear train sets.

Influence of the Oil Churning, the Bearing and the Tooth Friction Losses on the Efficiency of Planetary Gears

The efficiency of a planetary gear depends on many factors: mainly on the tooth- and bearing friction losses, but beside them, in certain circumstances, also the oil churning losses have to be taken into consideration. This theoretical investigation was made to determine the oil churning, the bearing and the tooth friction losses of planetary gears and evaluate the influence of these types of friction losses on their efficiency. Optimization of the design of the planetary gear drives can result the best parameters leading to their highest efficiency even in the case of compound planetary gears.

Sensitivity of General Compound Planetary Gear Natural Frequencies and Vibration Modes to Model Parameters

Abstract This paper studies the sensitivity of general compound planetary gear natural frequencies and vibration modes to inertia and stiffness parameters. The model admits planetary gears having any combination of stepped-planet, meshed-planet, and multiple stage arrangements. Eigensensitivities in terms of eigenvalue and eigenvector derivatives are analytically derived for both tuned (i.e., cyclically symmetric) and mistuned systems. The results are expressed in compact closed-form formulas. The well-defined modal properties of general compound planetary gears simplify the expressions of eigenvalue sensitivities to ones that are proportional to modal strain/kinetic energies. Inspection of the modal strain/kinetic energy distribution plots provides an effective way to quantitatively and qualitatively determine the parameters that have the largest impact on a certain mode. For parameter perturbations that preserve the system symmetry, the structured modal properties imply that the modes of the same type are independent of the same group of system parameters. Parameter mistuning, with a few exceptions, splits a degenerate natural frequency of the unperturbed system into two frequencies; one frequency keeps its original value and retains its well-defined modal properties, while the other frequency changes and its associated mode lose its structured modal properties.

Purely rotational model and vibration modes of compound planetary gears

This study develops a rotational degree of freedom model of general compound planetary gears . The model clarifies the conflicting gear mesh deflection expressions in prior research. For systems with identical, equally spaced planet trains in each stage, all vibration modes are classified into one of two types: overall modes and planet modes. In overall modes, all planet trains in the same planet set move identically. In planet modes, only one planet set has motion, and the motion of each planet train in this planet set is a scalar multiple of that of the arbitrarily chosen first planet train in this set. These structured vibration properties are analytically proven in this study.

Dynamics analysis of the Minuteman cover drive

Recursive matrix relations in kinematics and dynamics analysis of a 1-DOF compound planetary gear train are established in the paper. The mechanism of the Minuteman cover drive is a system with four moving links and three gear pairs controlled by one electric motor. Knowing the rotation motion of the output link, the inverse dynamic problem is solved using an approach based on the principle of virtual work, but it has been verified the results in the framework of the Lagrange equations . Finally, some simulation graphs for the input and output angles of rotation , the torque and the power of the actuator are obtained.

Non-linear dynamic behaviour of compound planetary gear trains: Model formulation and semi-analytical solution

A discrete, non-linear, time-varying, torsional dynamic model of a multi-stage planetary train that is formed by any number of simple planetary stages is proposed in this study. Each planetary stage has a distinct fundamental mesh frequency and any number of planets spaced in any angular positions. The model allows the analysis of the gear train in all possible power flow configurations suitable for various gear drive ratios. It includes periodic variation of gear mesh stiffnesses as well as clearance (backlash) non-linearities that allow tooth separations. Equations of motion for the general case are formulated and solved semi-analytically using a hybrid harmonic balance method (HBM) in conjugate with inverse Fourier transform. Relative mesh displacements along lines of action of individual gear pairs were used as the continuation parameters to pass singular points and ill-conditioned equations in their proximity. At the end, a case study of a two-stage planetary train is used to demonstrate the effectiveness of the model and solution methods. The HBM solutions are compared to those obtained by a direct numerical integration method to assess their accuracy.

A new structure of combined gear trains with high transmission ratios

The aim of our research has been to perform the synthesis of a new structure of combined gear trains that would feature a very compact construction and a relatively inexpensive manufacturing process as well as very high transmission ratios and good efficiencies. After the analysis of existing structures, the new structure that represents the combination of a worm gearing and a compound planetary gear train connected in a specific way has been suggested. The synthesis procedure, the description and the characteristics of the suggested structure, the program for computer dimensioning, the verification through the three-dimensional model and the test of the physical model of the new worm-planetary gear train are presented in this paper.