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Background: The direct-drive linear motor system is usually a low-damping system, which will cause residual vibration and deteriorate the accuracy of the equipment especially in the high-speed start-stop motion. Purpose: By employing an eddy current damper (ECD), the residual vibration can be effectively reduced. However, the ECD secondary is normally made of a pure copper plate with low magnetic permeability, resulting in low airgap magnetic density and therefore small damping force. In this paper, a dual-sided hybrid excitation ECD which implements high-conductivity and high-permeability plate as the secondary is proposed to enhance the vibration suppression for the linear motor system. Methods: An analytical model is developed to quantitatively analyze the relationship between the damping force and the secondary thickness. Three dimensional finite element analysis (3D FEA) is employed to investigate the effects of different secondary materials and the secondary layer thicknesses on ECD performance. Results and Conclusion: Experiments are conducted to evaluate the damping force and the vibration suppression effect of the designed ECD. Compared with the pure copper secondary under the same secondary dimensions, the damping force is increased by 30.5% with the copper-steel-copper secondary, and the peak amplitude of the position error and the settling time of the system are reduced by 1.94 times and 1.80 times, respectively. [ABSTRACT FROM AUTHOR]

This article presents a new type of surface-mounted three-phase permanent magnet synchronous motor with the same number of poles and slots which has obvious advantages in cogging torque. Since the same-pole and same-slot three-phase permanent magnet motor has three or more slot types and the slots are not evenly distributed on the circumference, this article adopts an accurate subdomain model that considers the position and slot width of each slot separately to perform an analytical calculation of the magnetic field. The motor is divided into three subdomains and modeled by Maxwell’s equations, and the magnetic scalar vector equation satisfied by each subdomain is solved by the method of separation of variables. A 24-pole 24-slot three-phase permanent magnet motor consisting of 13-pole 12-slot and 11-pole 12-slot is used to verify the correctness of the proposed analytical computational model. Compared with the finite element analysis, the proposed analytical model shows high accuracy in the calculations of the magnetic flux density of the three subdomains. [ABSTRACT FROM AUTHOR]

A reaction sphere (RS) is a novel and promising actuator for microspacecraft attitude control systems (ACSs). However, the detection of the motor status, such as the rotating speed of the spherical rotor, is a difficult task. The equivalent circuit can be used to predict the motor status. This article presents an improved multi-layer transfer-matrix method for the equivalent circuit parameters’ calculation. Results compared with a finite element analysis (FEA) show that the proposed analytical model achieves an acceptable accuracy within the operating speed range. Meanwhile, its computation time is 0.072 s, on average, which is only 0.0003% of the FEA. [ABSTRACT FROM AUTHOR]

Compliant Parallel Mechanisms (CPMs) are widely used in micro/nano-positioning systems. In recent years, CPMs with a large travel range (≥1 mm) have been getting increasing attention. In this paper, a 3 Prismatic-Prismatic-Revolute (3PPR) planar CPM with a motion range of 5 mm × 5 mm × 5° is designed. The mechanical structure is characterized by the application of three joints based on a compliant four-bar mechanism, which guarantees the motions along/about the specific axes to improve motion accuracy. A double blade rotary pivot is served as a revolute joint to decrease the drift of pivot and produce a large rotation range without loss of compactness. The compliance matrix method is implemented to kinetostatic modeling, and the input coupling effect, which is always neglected or modeled complicatedly in 3-Degree-of-Freedom planar CPMs, is involved with the principle of superposition. The feasibility of the mechanical design and the accuracy of the developed kinetostatic model are validated by finite element analysis and experiments, respectively. The results indicate that the modeling method based on the compliance matrix method is concise, effective, and accurate, and can be extended to other more complicated CPMs. [ABSTRACT FROM AUTHOR]

The inductive reaction sphere (RS) brings the benefit of simple, economical, and miniaturized design, and it is capable of multi-DOF torque generation. Thus, it is a suitable choice for the angular momentum exchange actuator in attitude control of micro-spacecrafts. To synthesize symmetric distribution of eddy currents and improve the speed and stability of rotation, a novel 4-pole winding design is proposed. However, the developed simplified analytical model shows that reduced pole number degrades the torque generation. To enhance the output torque of 4-pole RS, its curved cores and electromagnets are redesigned to enable the side teeth to be functional. As the analytical torque model for the RS with the slotted cores is not available, a constrained optimization problem is formulated, and the optimized parameters are calculated based on the prediction model from supported vector machine and finite element analysis. The lab prototypes are developed to validate the proposed design and test the speed performance. The experimental results show that the 4-pole RS prototype obtains a stable rotation over 700 rpm about X, Y and Z axis respectively with the angular momentum of 0.08 kg·m 2 /s, being superior to the 6-pole counterpart. [ABSTRACT FROM AUTHOR]

Kinetostatic modeling is critical in the design of large range multi-degree-of-freedom compliant parallel mechanisms. However, geometric nonlinearities and coupling effects between kinematic chains create difficulties to the modeling. This paper presents a nonlinear method of kinetostatic modeling for these mechanisms. Geometric nonlinearities are considered by applying the beam constraint model, and load equilibrium conditions and geometric compatibility equations are combined to formulate the coupling effects between kinematic chains. Based on the proposed method, an iterative nonlinear kinetostatic model is developed for a 3-prismatic–prismatic–revolute large range compliant parallel mechanism. Approximate analytical models for three flexure joints are adopted to avoid the nested iteration algorithm, thereby increasing the computational efficiency. Compared with the linear kinetostatic model, the actuation forces are almost identical, and the open-loop position errors decrease by 68% to a value of 32.5 μm for a circular trajectory with a radius of 2.5 mm using finite element analyses. Furthermore, the computational efficiency increases significantly compared with the nested iterative model. In addition, the kinetostatic characteristics of the mechanism are analyzed, and the main reasons for geometric nonlinearities are investigated. Finally, experiments are conducted to validate the developed iterative nonlinear kinetostatic model. [ABSTRACT FROM AUTHOR]