Lizhan Zeng

A Thrust Force Analysis Method for Permanent Magnet Linear Motor Using Schwarz–Christoffel Mapping and Considering Slotting Effect, End Effect, and Magnet Shape

A Schwarz-Christoffel (SC) mapping-based method is presented for accurately and efficiently predicting the thrust force of permanent magnet linear motors (PMLMs). It accounts for not only the slotting effect but also the end effect and the magnet shape. In this method, according to the magnet shape, the PMs are modeled as equivalent line currents on their surfaces. Through analyzing the invariant of the governing Poissonian field equation of line currents under a conformal mapping, the magnetic field boundary value problem in the air gap is mapped to a rectangle by the SC mapping, which is calculated with the SC Toolbox of MATLAB. Furthermore, the magnetic field solution is constructed with the line currents in a strip under the flux continuity condition. The cogging force due to the slotting effect and the end effect is obtained, respectively, by integrating the Maxwell stress tensor along the lines closely surrounding the slotted and finite-length iron core. The validity of the proposed method is examined by the finite-element method. The influences of the magnet shape on the thrust force pulsation characteristic are investigated for a PMLM equipped with rectangular PM and bread loaf PM.

A bioinspired touching sensor for amphibious mobile robots

An amphibious mobile robot relies on effective sensing ability to adapt itself in complicated amphibious environments. In this paper, we present a multifunctional whisker-like touching sensor with low energy consumption, inspired by amphibious animals. The sensor comprises a leverage system and a two-dimensional position tracing system, transforming the moving position of biowhisker to a changing laser spot coordinates. On land, the sensor driven by a motor is able to track the movement of biowhisker directly, telling the change of contact position, to sense nearby objects and explore their surface by touching. In underwater environment, the sensor can obtain in real-time external flow direction and velocity by passive impulsion. Testing results showed that our prototype can sense flow or drag force direction in 360° exactly, and tell flow velocity under 1 m/s, it can also recognize line or arc edges of obstacle correctly by touching.

Magnetic Field Analysis of Lorentz Motors Using a Novel Segmented Magnetic Equivalent Circuit Method

A simple and accurate method based on the magnetic equivalent circuit (MEC) model is proposed in this paper to predict magnetic flux density (MFD) distribution of the air-gap in a Lorentz motor (LM). In conventional MEC methods, the permanent magnet (PM) is treated as one common source and all branches of MEC are coupled together to become a MEC network. In our proposed method, every PM flux source is divided into three sub-sections (the outer, the middle and the inner). Thus, the MEC of LM is divided correspondingly into three independent sub-loops. As the size of the middle sub-MEC is small enough, it can be treated as an ideal MEC and solved accurately. Combining with decoupled analysis of outer and inner MECs, MFD distribution in the air-gap can be approximated by a quadratic curve, and the complex calculation of reluctances in MECs can be avoided. The segmented magnetic equivalent circuit (SMEC) method is used to analyze a LM, and its effectiveness is demonstrated by comparison with FEA, conventional MEC and experimental results.

Analysis and Optimization of a Novel 2-D Magnet Array with Gaps and Staggers for a Moving-Magnet Planar Motor

This paper presents a novel 2-D magnet array with gaps and staggers, which is especially suitable for magnetically levitated planar motor with moving magnets. The magnetic flux density distribution is derived by Fourier analysis and superposition. The influences of gaps and staggers on high-order harmonics and flux density were analyzed, and the optimized design is presented. Compared with the other improved structures based on traditional Halbach magnet arrays, the proposed design has the lowest high-order harmonics percentage, and the characteristics of flux density meet the demand of high acceleration in horizontal directions. It is also lightweight and easy to manufacture. The proposed magnet array was built, and the calculation results have been verified with experiment.

Cogging force computation for permanent magnet linear motor using numerical Schwarz-Christoffel mapping

We present an effective method based on Schwarz-Christoffel (SC) mapping for computing the cogging force of a permanent magnet linear motor (PMLM). The permanent magnets (PMs) are substituted by equivalent line currents at Gaussian integration points. Using numerical SC mapping, one pole-pair of the PMLM is mapped to a configuration where the magnetic field can be solved analytically. The cogging force due to the slotting effect is computed by the Maxwell stress tensor (MST) method. The results are verified with the finite element method (FEM).

Design of weighting filters with dynamic uncertainty for ultra precision positioning stage

In this paper, weighting filters are designed to characterize the performance demands and uncertainty specifications of an ultra precision positioning stage in IC manufacturing. To deal with dynamical uncertainty, the motion principles and structural properties of ultra-precision stage are discussed, and then dynamical parameters of the positioning stage are identified. A feedback controller is synthesis by using the weighting filters in H8 mathematical framework. Simulation results are presented to show the applicability of the proposed weighting filters.