Ligang Yao

Mathematical Modeling and Simulation of the External and Internal Double Circular-Arc Spiral Bevel Gears for the Nutation Drive

The purpose of this paper is to propose a pair of external and internal spiral bevel gears with double circular-arc in the nutation drive. Based on the movement of nutation, this paper develops equations of the tooth profiles for the gear set, leading to the mathematical modeling of the spiral bevel gear with a constant helical angle gear alignment curve, enabling the tooth surface to be generated, and permitting the theoretical contacting lines to be produced in light of the meshing function. Simulation and verification are carried out to prove the mathematical equations. Numerical control (NC) simulation of machining the external and internal double circular-arc spiral bevel gears is developed, and the spiral gears were manufactured on a NC milling machine. The prototype of the nutation drive is illustrated in the case study at the end of this paper.

Error Analysis and Compensation for Meshing Contact of Toroidal Drives

This paper investigates the meshing errors of the toroidal drive, reveals three typical latency errors and develops the error analysis in this typical type of gear drives. Having identified the latency errors, the error integrated coordinate transformation is implemented. This leads to the development of the error impinged meshing model. The model reveals for the first time the effect of the latency errors in gear meshing contact of a toroidal drive and characterizes the error effect on meshing contact. The effect of these errors on the gear coordinate frames is hence presented and on the contact paths of rollers is analyzed. The study leads to a new method for compensating the three latency errors by introducing a bearing with a changeable oil film. The method is then verified in a prototype and demonstrates to be effective.

Latency errors in the mathematical modelling and meshing characteristics of the toroidal drive

This paper reveals the latency errors in the manufacturing and assembly of the toroidal drive and integrates these errors in the coordinate systems and the mathematical models of the meshing equations for the conjugate surfaces between the planet worm-gear and the sun-worm and between the planet worm-gear and the stationary internal toroidal gear. The paper further develops the tooth profile model and the contact curves with the latency errors and examines the error effect on the helix model and the helix lead angle model. In addition, two kinds of limit curve model and the induced normal curvature models are further derived. This provides a comprehensive study of error effect on the meshing characteristics of the novel drive.

Design, analysis, and experimental validation of a novel seamless automatic transmission for electric vehicle

The transmission system has an important influence on the dynamic performance, endurance mileage, and energy saving in an all-electric vehicle. This article proposes an innovative two-speed seamless dry-friction automatic transmission system to improve the dynamic performance and endurance mileage of an all-electric vehicle with the existing battery technology. The proposed system consists of two-stage epicyclical gear sets without outer ring gears, a dry-friction clutch, and a brake band, realizes a seamless shifting between any two speeds in an electric vehicle. Based on the working principle and dynamic modeling of the proposed seamless dry-friction automatic transmission system, the ratio optimization was carried out to improve the dynamic performance and the power consumption at the same time, and the combination of the weight ratio method and the multi-island genetic algorithm method was introduced to solve the optimization problem. It is shown both theoretically and experimentally that the proposed seamless dry-friction automatic transmission method demonstrates a better dynamic performance and shifting comfort when compared to the automated manual transmission with same transmission ratio.

Design and Analysis on a Novel Electric Vehicle Powertrain

In order to obtain synthetically advantages from the independent multiple-motors-driven system and the centralized single-motor-driven system, a novel centralized dual-motor-coupling powertrain (DMCP) system with a single row double pinions gear train for electric vehicle (EV) is proposed. By means of changing the drive modes, the proposed powertrain can satisfy the demands of different running conditions with high energy utilization efficiency. In this paper, the analyses on the mechanism structure and operating principles of the proposed powertrain are carried out firstly. Then, for further improving the operating efficiency and providing the effective ways for optimal matching design of the novel DMCP, the parameters sensitivity analysis is studied under the certain tested driving cycle based on a systematic simulation model. The simulation result shows that the energy consumption is increased by 3% as compared to the result of automobile test with the single motor powertrain.

Generation of tooth profile for Roots rotor based on virtual linkage associated with Assur group

This article, for the first time, presents the generation of Roots rotor tooth profiles based on an Assur-group-associated virtual linkage method. Taking the original Roots rotor as an example, structure and geometry of the Roots rotor are introduced, and based on the principle of inversion, an equivalent virtual linkage is identified for generating dedendum tooth profile of the rotor. Using linkage decomposition associated with elemental Assur groups, algorithm for computing the tooth curve is constructed leading to the explicit expression of rotor profile and the corresponding numerical simulation, verifying the validity of the proposed approach. For demonstration purpose, the virtual linkage method is then extended to the generation of tooth profiles for the variants of Roots rotors with arc-cycloidal curves and arc-involute curves. Integrated with computer-aided design, computer-aided engineering and computer-aided manufacturing software platforms, as well as the three-dimensional printing technology, this article provides an efficient and intuitive approach for Roots rotor system design, analysis and development.

Dynamic modeling and characteristics analysis of the toroidal drive based on multibody of meshing rollers

This paper first develops a mathematical model for the dynamic characteristics analysis of a toroidal drive. This model allows the analysis of a toroidal transmission with any numbers of planet worm gears distributed around the sun worm and any numbers of spherical rollers distributed around the planet-worm gear. In the modeling process, distinguished with other kind of gear transmission modeling, the planet-worm gear tooth (spherical roller) is considered as independent components in the toroidal drive system, the vibration modes are classified into planet-worm gear, spherical roller and translational modes. Further, the characteristics of the vibration amplitude and the Eigen-value number of different modes are analytically investigated.

Geometric Modeling and Simulation on Toroidal Drive

This paper investigates the geometric characteristics of the sun-worm and the stationary internal toroidal gear in toroidal drive, explores the three dimensional modeling, carries out kinematical simulation and interference detection for this kind of drive. Further, the dynamical simulation is also developed. Finally, the NC manufacturing simulation is propose that solves cutter selection and undercutting elimination for the practical NC manufacturing of the stationary internal toroidal gear.