Nan Yao

Magnetic field analysis of electromagnetic spherical actuators with multiple radial poles

This paper proposes a multiple degree-of-freedom (3-DOF) spherical actuator with novel three-dimensional (3D) pole patterns. Compared with conventional 2D pole patterns, the 3D pole patterns can significantly increase the magnetic flux density in winding areas, which in turn helps to improve the force/torque output performance of the system. A design concept of the spherical actuators with 3D pole configurations is introduced in this study. The magnetic field in the actuator is simulated with numerical method, and presented in 3D surfaces. The obtained results can validate the design concept and help the subsequent force analysis and sensing system design.

Flux Field Formulation and Back-Iron Analysis of Tubular Linear Machines

In electromagnetic machines, ferromagnetic material is one of the key components that affect the magnetic field and thus the output performance significantly. The objective of this paper is to study the influence of ferromagnetic material on magnetic field distribution of tubular electromagnetic linear machines. Generic magnetic field models are obtained for linear machines with various structure designs based on magnetic vector potential and Bessel functions. The magnetic field model is validated with numerical results from finite element calculations. The comparison between them shows that the flux model fits closely with the numerical computation. The obtained analytical model can be employed to study the flux density distribution of machine designs with single-sided, double-sided, and non back irons. It shows that the use of back iron, especially for the internal side, helps to greatly enhance the radial component of magnetic field. This component contributes to the axial force generation of tubular linear machines. The study could be useful for the design optimization of permanent-magnet linear machines.

Reliability of Wireless Sensor Network: Hotspot and critical challenges

Wireless Sensor Network (WSN) has attracted many concerns in different domains because of its special features. A WSN is a set of a large number of resource constrained sensor nodes which have abilities for information detection, data processing, and short-range radio communication. WSN can be used for both military applications and civil applications with the tasks such as detection and monitoring of significant events in different environments or large areas. How to improve the reliability of WSN is one of the essential challenges for WSN from theoretical research to actual application. Five hot research interests have been discussed respectively in this paper, and several relevant state-of-the-art technologies have been analyzed, then, future direction and critical technologies are proposed as well. In addition, a Generalized Stochastic Petri nets (GSPN) model is designed to evaluate the reliability of a parallel-redundant fault tolerant WSN. GSPN model is more observable, scalable and portable than Markov model.

Design and Analysis of Tubular Linear Machines with Dual Halbach Arrays

Linear machines are widely employed in robotics, transportation and manufacturing industries because complex rotation-to-translation conversion mechanism is no longer required. This paper proposed a novel tubular linear machine with dual permanent magnet (PM) Halbach arrays to achieve high force output performance. Based on Lorentz force law, the magnetic force output and force ripple for three-phase winding linear machine is formulated in analytical way. By taking advantage of the analytical models, the force output is simulated with respect to the motion of the mover. Numerical result is then obtained to validate the analytical force models. In addition, based on the technology of non-dimensionalization, the mathematical force models are employed to analyze the influence among the structure parameters on the force output and force ripple for design purpose of the tubular linear machines. The study in this paper could contribute to the design analysis and optimization of electromagnetic linear machines with similar poles patterns.

Magnetic Flux Distribution of Linear Machines with Novel Three-Dimensional Hybrid Magnet Arrays

The objective of this paper is to propose a novel tubular linear machine with hybrid permanent magnet arrays and multiple movers, which could be employed for either actuation or sensing technology. The hybrid magnet array produces flux distribution on both sides of windings, and thus helps to increase the signal strength in the windings. The multiple movers are important for airspace technology, because they can improve the system’s redundancy and reliability. The proposed design concept is presented, and the governing equations are obtained based on source free property and Maxwell equations. The magnetic field distribution in the linear machine is thus analytically formulated by using Bessel functions and harmonic expansion of magnetization vector. Numerical simulation is then conducted to validate the analytical solutions of the magnetic flux field. It is proved that the analytical model agrees with the numerical results well. Therefore, it can be utilized for the formulation of signal or force output subsequently, depending on its particular implementation.

A novel two degree-of-freedom ultrasonic planar motor driven by single stator

A novel two degree-of-freedom (DOF) ultrasonic planar motor based on traveling wave has been proposed in this paper. The stator is the key component of the planar motor. The proposed stator is in a bar type, consisting of three piezoelectric ceramic cylinders and a metal driving head. The effective elliptical motion of the driving head tip is formed by the second bending mode and the first longitude mode of the stator. The two working vibration modes are analyzed by FEM software, and the dimensions of the stator are optimized and determined via FEA. As a result of the optimization, frequencies of the two working modes are very close to 22 kHz. The major feature of the design is the multi-DOF motion achieved by a single stator.

Characteristics analysis of heat-fluid-solid coupling field for linear resonant testing platform

Efficient cooling method helps to improve the output performance of a motor, and liquid cooling is one of the best cooling methods. In this paper, a linear resonant testing platform is proposed to simulate the reciprocating motion of the linear oscillating motor, in which two check valves are adopted to achieve the cooling oil circulating. The thermal model is presented to calculate the thermal distribution of the testing platform in the condition with and without cooling oil for different current inputs. Shear stress model of the oil is built and mixing losses is systematically calculated to analyze the fluid damping characteristics. The relationship of the pressure, driving force, viscous, wall shear stress and mixing losses with the oil velocity is detailedly analyzed. The thermal analysis and fluid mixing losses formulation of the testing platform provide theoretical references for the design optimization and work efficiency improvement of the linear oscillating motor.

Force formulation of a three-phase tubular linear machine with dual Halbach array

A novel dual Halbach array is proposed in this paper to increase the output performance of tubular linear machines. The magnetic field distribution in three-dimensional (3D) space is formulated with Bessel functions analytically. Following that, the modeling of force output for linear machines with three-phase windings is carried out based on Lorentz force law. The formula component of force ripple is separated from the analytical expression of total force. It is found that for multi-phase tubular linear machines, the force output and force ripple are not only closely related to the instantaneous position of the mover, but also the starting position. Therefore, the force output of the linear machine is formulated for three typical starting positions as a function of mover positions. The derived models are simulated with respect to the movers motion. They are also validated with numerical results from finite element calculation. The study shows that an appropriate starting position of the mover helps to improve the output performance of the tubular linear machines. The proposed analytical force model can also be employed to analyze the influence of the structure parameters on the force output of linear machines with similar structures.