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Über dieses Buch

A spherical actuator is a novel electric device that can achieve 2/3-DOF rotational motions in a single joint with electric power input. It has advantages such as compact structure, low mass/moment of inertia, fast response and non-singularities within the workspace. It has promising applications in robotics, automobile, manufacturing, medicine and aerospace industry.

This is the first monograph that introduces the research on spherical actuators systematically. It broadens the scope of actuators from conventional single-axis to multi-axis, which will help both beginners and researchers to enhance their knowledge on electromagnetic actuators. Generic analytic modeling methods for magnetic field and torque output are developed, which can be applied to the development of other electromagnetic actuators. A parametric design methodology that allows fast analysis and design of spherical actuators for various applications is proposed. A novel non-contact high-precision 3-DOF spherical motion sensing methodology is developed and evaluated with experiments, which shows that it can achieve one order of magnitude higher precision than conventional methods. The technologies of nondimensionalization and normalization are introduced into magnetic field analysis the first time, and a benchmark database is established for the reference of other researches on spherical actuators.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Over the past decades, spherical actuator has been a more and more popular research topic worldwide. Due to its advantages of compact size, high motion precision, fast response, direct driven, non-singularity in workspace and high efficiency, it has wide potential applications in robotics, manufacturing, automobile, precision assembling and medical surgery. The fundamental concepts and working principles of various spherical actuators are presented in the monograph. Systematic study approaches on the modeling, design, experimental investigation and orientation sensing technologies of permanent magnet (PM) spherical actuators are the focus of this book. In this chapter, the background and motivation of the development of multi-degree-of-freedom (multi-DOF) spherical actuator is introduced. Following that, the state of the art of the studies on spherical actuators is reviewed. Subsequently, the research objective and scope of a 3-DOF PM spherical actuator are presented. Finally, the outline of the monograph is proposed.
Liang Yan, I-Ming Chen, Chee Kian Lim, Guilin Yang, Kok-Meng Lee

Chapter 2. Magnetic Field Modeling

The magnetic field modeling of the PM-pole rotor is presented. According to the magnetic characteristics of the three regions of the rotor space, Laplace’s equations of magnetic scalar potential are derived. By using the boundary conditions in between neighboring regions as well as the spherical harmonic expansion of radial component of the residual magnetization vector, coefficients in the general solution of magnetic scalar potential are determined. The magnetic field flux density of the PM rotor is formulated analytically by taking the gradient of the scalar potential. The derived analytical magnetic field model can be used to formulate the torque output of the spherical actuator.
Liang Yan, I-Ming Chen, Chee Kian Lim, Guilin Yang, Kok-Meng Lee

Chapter 3. Torque Modeling

By utilizing the analytical magnetic field model, the actuator torque caused by the interaction between current carrying coils and the magnetic field of the PM-pole rotor is formulated based on Lorentz force law. This torque model relates the torque output of the spherical actuator to the current inputs of coils and the rotor orientation, which indicates that the torque output of the PM spherical actuator is orientation dependant. Nonsingularity is one of the important advantages of the PM spherical actuator. Based on the torque model, existence of inverse electromagnetics solution or nonsingularity workspace of the PM spherical actuator is verified through the condition numbers of the torque matrix. In addition, the minimum right-inverse electromagnetics solution is proposed to calculate the required current inputs for desired torque output. This solution can minimize the electric power consumption of the spherical actuator. The linear torque model can facilitate the real-time motion control of the actuator. It can also be used for the spherical actuator design to maximize the actuator torque output.
Liang Yan, I-Ming Chen, Chee Kian Lim, Guilin Yang, Kok-Meng Lee

Chapter 4. Prototype Development

Prototype development is an essential step to ensure the functionalities of the proposed 3-DOF PM spherical actuator. The research prototype can be used for conducting experimental works on magnetic field distribution as well as actuator torque output to verify the derived analytical models. This chapter discusses the prototype development of the PM spherical actuator with detail considerations in the design of the rotor poles and stator poles.
Liang Yan, I-Ming Chen, Chee Kian Lim, Guilin Yang, Kok-Meng Lee

Chapter 5. Experimental Investigation

In this chapter, the experimental investigation is conducted on the prototype of the PM spherical actuator to verify the analytical magnetic field model and torque model proposed in Chapter 2 and Chapter 3. The experimental investigation of the PM spherical actuator consists of two major tasks: measurement of magnetic field distribution and torque variation.
Liang Yan, I-Ming Chen, Chee Kian Lim, Guilin Yang, Kok-Meng Lee

Chapter 6. Three Degree-of-freedom Optical Orientation Measurement

Orientation measurement is an important topic for spherical actuators. The purpose of this study is to propose a high-precision non-contact displacement measurement method for 3-DOF rotational motions. The operating principle of the measurement method is based on the non-contact laser detection. It has several advantages compared with other orientation measurement methods. The non-contact property avoids friction and additional mass/inertia moment exerted on the moving part that may significantly reduce the system working efficiency. Compared with other non-contact measurement methods, it can achieve a high-precision measurement result, and its performance is not affected by environmental field. The algorithm for three rotation angles has been derived. Two experimental apparatus have been developed to conduct measurements, and to evaluate the proposed orientation measurement method.
Liang Yan, I-Ming Chen, Chee Kian Lim, Guilin Yang, Kok-Meng Lee

Chapter 7. Conclusions

This monograph has presented study on a permanent magnet spherical actuator with the following tasks: (1) formulation of the magnetic field produced by the PM-pole rotor; (2) torque modeling of the spherical actuator; (3) design and prototyping of the spherical actuator; (4) experimental investigation on the magnetic field distribution and torque variation; (5) investigation of a non-contact orientation measurement method base on laser detection. All these works are fundamental and critical to the position and velocity servo control of the PM spherical actuator. This chapter summaries the works that have been accomplished, and also recommends the future research topics.
Liang Yan, I-Ming Chen, Chee Kian Lim, Guilin Yang, Kok-Meng Lee

Backmatter

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