Permanent Magnet Spherical Actuator Research Articles

Finite Element Analysis and Structural Optimization of a Permanent Magnet Spherical Actuator

In order to derive the characteristics and adjust the electromagnetic system to the ultimate purpose of achieving better torque output and material usage reduction with constraints, this paper presents the finite element analysis and using improved niche genetic algorithm to the optimal design of a permanent magnet spherical actuator. The magnetic field distribution and torque calculation model based on finite element software are introduced and discussed. The proposed optimization algorithm surmounts effectively the local convergence problem of standard genetic algorithm. The sharing-between-population mechanism is proposed by means of using the better factor of population, saving best result strategy and enhancing global and partial searching ability for earlier achievement of optimal solution. The results show the output torque has been increased and the material has been effectively saved by comparison, which provides the references for related problems. Ill. 5, bibl. 15, tabl. 6 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.114.8.699

Design and Modeling of a Spherical Actuator with Three Dimensional Orientation Measurement System

This paper presents the design and modeling of a permanent magnet spherical actuator which consists of a rotor with eight cylindrical permanent magnet (PM) poles and a stator with twenty-four air-core coils. Torque and dynamic model of this PM spherical actuator are formulated analytically. An optimal design procedure is proposed to achieve a high torque output, and significant design parameters of the actuator are discussed. As there is no effective method for three dimensional orientation measurement of the spherical actuator currently, a novel orientation measurement system is proposed. Finally, experimental works are carried out, and the experiment results demonstrate the effectiveness of the proposed orientation measurement system.

Neural network identifier-based dynamic decoupling control of a novel permanent magnet spherical actuator

The real-time torque calculation and dynamic modelling have been the difficulties in the motion control of the permanent magnet spherical actuator. Based on the presented new configuration design, a simplified torque calculation model and a non-linear system dynamic model have been proposed. The perturbation of the system parameters, the model error and the external disturbance result in the actual system uncertainties, which have great effects on the control performance and caused the interferences on three degrees-of-freedom. Based on the modelling, this paper also presents the dynamic decoupling control scheme for the permanent magnet spherical actuator with neural network identifier. The feed forward neural network and adaptive learning algorithm are adopted to construct the neural network identifier for online identification of uncertainties and unmodelled dynamic parts in the motion process. The simulation and experiment results show the effectiveness of the proposed method by alleviating the inter-axis cross-coupling influences and offering high robustness to guarantee the static and dynamic performances.

Analysis of Pole Configurations of Permanent-Magnet Spherical Actuators

This paper presents a generic design concept of three degree-of-freedom (3-DOF) permanent-magnet (PM) spherical actuators. A ball-shaped rotor mounted with multiple layers of PM poles is concentrically housed in a spherical-shell-like stator with multiple layers of air-core coils. This design allows more rotor and stator poles to be incorporated to increase torque output and motion range of the actuator. The magnetic field and torque modeling methods are generalized to multiple layers of poles, which provides a convenient way to analyze field distribution and torque performance of spherical actuators with various pole configurations. The simulation results of flux distribution and torque variation of double-layer configuration are compared with those of single-layer one. It shows that the magnetic field distribution and torque variation for both configurations are coincident with PM-pole arrangement on the rotor surface. The tilting torque of double-layer design is larger than that of single layer, and the torque variation is more uniform. The spinning torque of single layer is relatively large. The proposed analyzing methods of field and torque could be employed for preliminary study of other PM spherical actuators.

Design and Analysis of a Permanent Magnet Spherical Actuator

This paper has proposed a 3-DOF spherical actuator consisting of a ball-shaped rotor with a full circle of permanent- magnet (PM) poles and a spherical-shell-like stator with two layers of circumferential air-core coils. One key feature of this design is the parametrization of PM and coil poles. Based on the torque model of the PM spherical actuator, the relationship between poles' parameters and torque output can be demonstrated. As a result, the actuator design aiming at achieving maximum torque output can be carried out from the relationships. Another advantage of this spherical actuator is its singularity-free workspace, which is verified with the actuator torque model and condition numbers.

Analytical and experimental investigation on the magnetic field and torque of a permanent magnet spherical actuator

This paper presents the torque model of a ball-joint-like three-degree-of-freedom (3-DOF) permanent magnet (PM) spherical actuator. This actuator features a ball-shaped rotor with multiple PM poles and a spherical stator with circumferential air-core coils. An analytical expression of the magnetic field of the rotor is obtained based on Laplace's equation. Based on this expression and properties of air-core stator coils, Lorentz force law is employed for the study of the relationship between the rotor torque and coil input currents. By using linear superposition, the expression of the actuator torque in terms of current input to the stator coils can be obtained in a matrix form. The linear expression of the actuator torque will facilitate real-time motion control of the actuator as a servo system. Experimental works are carried out to measure the actual magnetic field distribution of the PM rotor in three-dimensional (3-D) space as well as to measure the actual 3-D motor torque generated by the actuator coils. The measurement results were coincident with analytical study on the rotor magnetic field distribution and actuator torque expressions. The linearity and superposition of the actuator torque were also verified through the experiments.