Yi Chang Wu

Conceptual Design of a 16-Speed Bicycle Drive Hub

This paper presents a design approach for the conceptual design of a novel 16-speed bicycle drive hub. First, a distributed-flow type planetary gear train, which consists of two parallel- connected transmission units and one differential unit, for the power transmission mechanism of a bicycle drive hub is proposed. Based on the kinematic analysis of the presented gear mechanism, a feasible clutching sequence is synthesized to provide 16 forward speeds. Then, the numbers of teeth of all gears are determined according to the desired velocity ratio of each speed. As a result, a schematic diagram of the embodiment of the proposed 16-speed drive hub is presented.

Kinematic Analysis of an 8-Speed Bicycle Transmission Hub

A transmission hub is a speed changing mechanism which is an important device in the transmission system of bicycles. This paper presents the kinematic analysis of an 8-speed bicycle transmission hub by using the fundamental circuit method. First, a distributed-flow type planetary gear mechanism, which consists of two parallel-connected transmission units and one differential unit, and the corresponding clutch sequence table of an 8-speed transmission hub are introduced. Based on the fundamental circuits, four kinematic equations of the transmission hub are derived. Then, the speed ratio of each speed is formulated, which is a function of gear ratios of external and internal gear pairs. By submitting the numbers of gear teeth into these formulas, the value of speed ratio at each speed can be calculated. Finally, the power-flow diagrams at related speeds are presented to illustrate the power-flow paths of the transmission hub.

Finite-Element Analysis of the Magnetostatic Field of a Coaxial Magnetic Gear Device

This paper presents the magnetostatic field analysis of a coaxial magnetic gear device proposed by Atallah and Howe. The structural configuration and speed reduction ratio of this magnetic gear device are introduced. The 2-dimensional finite-element analysis (2-D FEA), conducted by applying commercial FEA software Ansoft/Maxwell, is performed to evaluate the magnetostatic field distribution, especially for the magnetic flux densities within the outer air-gap. Once the number of steel pole-pieces equals the sum of the pole-pair numbers of the high-speed rotor and the low-speed rotor, the coaxial magnetic gear device possesses higher magnetic flux densities, thereby generating greater transmitted torque.

Design of 3-Speed Bicycle Transmission Hubs

This paper presents the embodiment designs of 3-speed transmission hubs which consist of basic planetary gear mechanisms and gear-shifting control mechanisms. Two feasible clutching sequence tables are synthesized by analyzing the kinematic structure of the gear mechanism. A mechanical control mechanism is used to control the engagement or disengagement of each clutch to guide the power flow from the rear sprocket via the gear mechanism to the hub shell. The power transmission path at each gear stage is further checked to verify the validity of the transmission hub. The embodiment designs of two 3-speed transmission hubs are presented.

Power-Flow Path Analysis of an Existing 8-Speed Bicycle Drive Hub

This paper presents kinematic analysis and power-flow analysis of an existing 8-speed bicycle drive hub by using the fundamental circuit method. First, a planetary gear mechanism, which consists of three basic planetary gear trains connected in series, and its clutching sequence table are introduced. Based on the fundamental circuits, six kinematic equations of the drive hub are derived. Then, the power-flow diagrams at related gears are illustrated based on the clutching sequence table, and the power-flow paths of the bicycle drive hub can be identified. The results of this study are beneficial to the development of multi-speed drive hubs for bicycles.

Thrust Study of a Novel PM Linear Synchronous Motor

This paper presents an analysis of a new type of permanent magnet excited transverse flux linear synchronous motor (PMTFLSM). This linear motor achieves a high thrust from its novel design and fabric. Its translator consists of cross-shaped core sets. Considering parameters such as magnet dimension, pole pitch, and tooth width of the translator, the effected thrust is analyzed and simulated with a 2D model of our PMTFLSM using the finite element method. Extensive simulations were conducted to investigate how the motor performs under a variety of parameter settings. Accordingly, motor characteristics are identified whereby an optimal combination of parameter values can be found. The new findings are then fed back to our motor design to validate performance improvement.

Mechanical Efficiency Analysis of a 16-Speed Bicycle Transmission Hub

This paper proposes an analytical method to evaluate the mechanical efficiency of the bicycle transmission hub. A 16-speed transmission hub, which consists of two transmission units and one differential unit, is presented first. By applying the concept of fundamental circuits, a step by step analysis process is then described to numerically calculate the angular speed, ideal torque and power flow, and actual torque and power flow by considering the gear-mesh loss of each link of the planetary gear train. Based on the power flow diagram, the mechanical efficiency at each speed of the transmission hub can be estimated.

Finite-Element Analysis of the Magnetic Field in a Magnetic Gear Mechanism

This paper presents finite-element analysis (FEA) of the magnetic field of a magnetic gear mechanism. An external type magnetic gear mechanism, which consists of two identical magnetic gears with sector-shaped permanent magnets, is introduced first. Then, the magnetostatic field distribution and transmitted torque of the magnetic gear mechanism are simulated by a commercial FEA package Ansoft/ Maxwell. Next, the effects of design parameters, including the air-gap length, the number of magnetic pole pairs, and the height of permanent magnets, on the maximum transmitted torque are discussed. The results of this work are beneficial to the design of magnetic gear mechanisms.

Conceptual Design of a Novel Three-Speed Geared Motor

The purpose of this paper is to develop a novel three-speed geared motor that integrates a basic epicyclic-type gear train with an exterior-rotor brushless DC (BLDC) motor to form a compact structural assembly. Unlike existing gear motors, the proposed device provides three speed ratios including an under drive, a direct drive, and an over drive, and is operated with a single clutch-to-clutch shaft. It provides a wider speed range than the traditional geared motor. Such an integrated design can be appropriately employed in high driving torque and low rotational speed applications or high rotational speed and low driving torque applications.

Magnetostatic Field Analysis of Disk-Type Permanent-Magnet Motors

The aim of this paper is to analyze the magnetostatic field of disk-type permanent-magnet motors by utilizing the 1-D equivalent magnetic circuit approach and the finite-element method. A 1-D equivalent magnetic circuit model, which is analogous to an electric circuit model, of the disk-type permanent-magnet motor is proposed. The accuracy of the analytical model is verified by a commercial 3-D finite-element analysis (FEA) package. The result shows that the air-gap flux density is in good agreement with an acceptable error of about 1.66%. The presented magnetic circuit approach is not only an accurate technique in predicting the magnetostatic field of disk-type permanent-magnet motors, but also effectively reduces the computing time. It is especially suitable for the preliminary design and optimization of permanent-magnet motors with axial-flux topologies.