Electromagnetic Spherical Actuators Research Articles

3-DOF Outer Rotor Electromagnetic Spherical Actuator

Conventionally, many single-degree-of-freedom (single-DOF) actuators have been used to realize devices with multiple-degrees-of-freedom (multi-DOF). However, this makes their structures larger, heavier, and more complicated. In order to remove these drawbacks, the development of spherical actuators with multi-DOF is necessary. In this paper, we propose a new 3-DOF outer rotor electromagnetic spherical actuator with high torque density and wide rotation angles. The dynamic characteristics are computed employing 3-D FEM and its effectiveness is verified by carrying out measurements on a prototype. Then, in order to realize further high torque density, the electromagnetic pole arrangement is optimized using Genetic Algorithm (GA) and the effectiveness of the optimized stator poles arrangement is verified.

Magnetic field analysis of novel spherical actuators with three-dimensional pole arrays.

Spherical actuator is an electric device that can achieve multiple degree-of-freedom rotary motions in a single joint. Permanent magnet array is a key factor that influences the output performance of electromagnetic spherical actuators. In this paper, a novel three-dimensional (3D) pole array is proposed to improve the system flux density and thus the output performance. Analysis of magnetic field distribution is extremely important for spherical actuators with 3D magnet arrays. Thus, the investigation of magnetic field is conducted in analytical, numerical, and experimental ways. The general solution of magnetic scalar potential in 3D space is formulated analytically based on Laplace's equations and spherical harmonics, and then specific solutions of the magnetic scalar potential and magnetic flux density are obtained by using boundary conditions. Numerical computation is utilized to validate the analytical model and to facilitate the observation of the magnetic field variation. A research prototype and a testing platform of magnetic field have been developed for experimental study. The testing platform can move the probe to any position around the spherical actuator and measure the flux density automatically. Experiments are conducted to obtain the flux distribution. Both numerical and experimental results validate the analytical model well.

Characteristics verification of an independently controllable electromagnetic spherical motor.

We have been developing electromagnetic spherical actuators capable of three-degree-of-freedom rotation. However, these actuators require complex control to realize simultaneous triaxial drive, because rotation around one axis interferes with rotation around another. In this paper, we propose a new three-degree-of-freedom actuator where 3-axes rotation can be controlled easily. The basic structure and the operating principle of the actuator are described. Then the torque characteristics and the dynamic characteristics are computed by employing 3D-FEM and the effectiveness of this actuator is clarified. Finally, the experimental results using the prototype of the actuator are shown to verify the dynamic performance.

Dynamic Analysis of an Independently Controllable Electromagnetic Spherical Actuator

We have been developing electromagnetic spherical actuators capable of three-degree-of-freedom rotation. However, these actuators require complex control because rotation around one axis interferes with rotation around another. In this paper, we propose a new 3-DOF actuator where the 3-axes can be independently controlled, and the basic structure and the operating principle of the actuator are described. Then the dynamic performance under position feedback control is analyzed employing 3D-FEM and the effectiveness of this actuator is clarified.

Modeling and Iron-Effect Analysis on Magnetic Field and Torque Output of Electromagnetic Spherical Actuators With Iron Stator

This paper presents a three-degree-of-freedom permanent magnet (PM) spherical actuator with an iron stator. The major contribution of this paper is to study the effect of iron stator on the magnetic field and torque output of the electromagnetic spherical actuator quantitatively and qualitatively. It could be helpful for actuator design optimization. Based on the poles' arrangement and the iron boundary, the magnetic field of the PM-pole rotor and the actuator torque are formulated analytically. The effect of iron stator on the magnetic field and torque output is analyzed with respect to structural parameters. The result shows that the iron stator can increase the radial component of the flux density and thus the actuator torque output significantly.

Dynamic Analysis of 3 DOF Actuator Employing 3 D Finite Element Method

This paper describes the dynamic analysis method of a three degree-of-freedom electromagnetic spherical actuator considering the mutual effect among X-, Y- and Z-axis employing the 3-D finite element method, in which the magnetic field equation is fully combined with equations of electric circuit and motion. The validity of the analysis is confirmed by comparing with the measured results on a prototype.

Proposal of electromagnetic spherical actuator with 3‐DOF

PurposeThe purpose of this paper is to propose a new electromagnetic spherical actuator with three‐degree‐of‐freedom. Multi‐degree‐of‐freedom actuators which can be operated in arbitrary axis come to attract attention because of the solution for efficiency, weight, size, and so on. Particularly, spherical actuators are studied as the application to the joints and eyeballs for robots because they can be freely rotated in every axis direction.Design/methodology/approachThe paper proposes a new electromagnetic spherical actuator with three‐degree‐of‐freedom in rotation, and the torque characteristics of the actuator are computed by the 3D finite element method (FEM). The validity of the computation is confirmed through the measurement of a prototype.FindingsIt is found that this actuator realized the high torque of more than 1.0 Nm in every axis circumference.Originality/valueA new spherical three‐degree‐of‐freedom actuator is proposed. The torque characteristics of the improved model are calculated employing the 3D FEM. The validity of the analysis is verified through the comparison with the measured results of the prototype. Furthermore, the improved model is proposed to increase the torque, and the effectiveness of the model is confirmed.

三自由度球面アクチュエータの動作特性解析に関する研究

In this paper, coupled method for the dynamic characteristics of a 3-D electromagnetic spherical actuator under the open-loop control is proposed by the 3-D finite element method, in which the magnetic field equation is combined with equations of electric circuit and three-axes motions. The validity of the analysis is confirmed by comparing with the measured results of a prototype.