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This article proposes a position detection method for a multi-to-one wireless power transmission (WPT) system for the first time and applies it to the position detection of a spherical motor. The traditional contact detection system has high friction resistance and poor rotor positioning accuracy. Although some noncontact measurement systems are not directly connected to the rotor, the structure or calculation of the measurement system is more complicated. To solve the abovementioned problems, this article proposes two structural topologies, which are evenly arranged on the upper part of the rotor and the receiving coil is placed on the rotor shaft. When the motor rotor rotates along with the three motion states of yaw, spin, and tilt, the receiving and multitransmitting coils will have an angular offset. The rotor position is obtained by a method of accurately estimating the mutual inductance. This method avoids complicated finite element calculations and saves a lot of time. Finally, the experiment verifies the above analysis and compares the data with the microelectromechanical system three-degree-of-freedom attitude detection method. This article provides insights into the position detection of spherical motors. This method simplifies the previous measurement system and obtains higher positioning accuracy. [ABSTRACT FROM AUTHOR]

This article proposes a rotor attitude estimation (RAE) method for spherical motors using the multiobject Kalman kernel correlation filter (MKKCF) algorithm in monocular vision. A permanent magnet spherical motor (PMSpM) is adopted as the research object, and a monocular area scan camera is equipped in the RAE system with a visual feature component mounted on top of the rotor output shaft. In the proposed MKKCF algorithm, the Kalman filter is used to enhance the robustness and accuracy of KCF tracker for each object. To simplify the proposed algorithm verification, a one-object tracking comparison is conducted among the KCF algorithm, the fast discriminative scale space tracking (FDSST) algorithm, and the Kalman KCF algorithm, and the results show that Kalman KCF tracker is more applicable for RAE. In addition, an RAE test bench is developed, and the MKKCF-based RAE method and the micro-electro-mechanical system (MEMS) (MPU9250) method are compared when estimating the rotor attitude. To set a benchmark, the contact rotor position measurement with encoders is used. The comparison results indicate that the MKKCF-based RAE method works with higher accuracy than the MEMS method. Finally, a closed-loop PMSpM control experiment is conducted by using the proposed MKKCF-based RAE method, and the practicability of the proposed method is proved. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive backstepping sliding mode control method based on a nonlinear disturbance observer (NDO) to solve the problem that the tracking performance of the motion system of a permanent magnet spherical motor (PMSpM) is degraded due to the influence of external nonlinear disturbance. First, the dynamic model of the PMSpM under the compound interference is established. Second, an NDO and an adaptive backstepping sliding mode controller are designed to compensate for the external disturbances and modeling uncertainties, and the stability of the closed-loop system using the proposed method is confirmed through the Lyapunov theorem. Then, compared with the results of proportion differentiation control and conventional sliding mode control, the simulation results show that the proposed method can significantly reduce input signal chattering and improve the trajectory tracking performance of the PMSpM. Finally, experimental results are provided to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a monolayer Halbach array based permanent magnet spherical motor (PMSpM) using cubic permanent magnets (PM). The research aims to provide a fast computing model to calculate the magnetic field for this PMSpM, which helps for future PMSpM optimization and control study. Three thickness equivalence principles are provided and compared for cubic PMs. The magnetic scalar potential is introduced, and the spherical harmonics expansion is implemented for rotor magnetic field analysis. Engineering revision is used to reduce the Legendre function deviation in polar angle direction. Torques and forces are deduced using the Lorentz force law, and relatively simple models of this PMSpM for both magnetic fields and torques are acquired. In addition, a prototype motor has been developed, and the analytic results of air-gap flux density and torque are compared with their finite element simulation and experimental results, which are proved consistent. It is concluded that the fundamental component of the spherical harmonics can be used to present the magnetic field model, which uses fewer integrals than the Biot-Savart law based solution, and the modeling results of the magnetic field flux density, forces and torques are in line with the expectations. The analytic models are proved correct. [ABSTRACT FROM AUTHOR]

Permanent magnet spherical motors (PMSMs) operate on the principle of the dc excitation of stator coils and three freedom of motion in the rotor. Each coil generates the torque in a specific direction, collectively they move the rotor to a direction of motion. Modeling and analysis of the output torque are of critical importance for precise position control applications. The control of these motors requires precise output torques by all coils at a specific rotor position, which is difficult to achieve in the three-dimension space. This article is the first to apply the Gaussian process to establish the relationship of the rotor position and the output torque for PMSMs. Traditional methods are difficult to resolve such a complex three-dimensional problem with a reasonable computational accuracy and time. This article utilizes a data-driven method using only input and output data validated by experiments. The multitask Gaussian process is developed to calculate the total torque produced by multiple coils at the full operational range. The training data and test data are obtained by the finite-element method. The effectiveness of the proposed method is validated and compared with existing data-driven approaches. The results exhibit superior performance of accuracy. [ABSTRACT FROM AUTHOR]

Non‐linear friction between the rotor and the rotor support mandrels would occur during the movement of the permanent‐magnet spherical motor (PMSpM). The friction which varies with the position causes PMSpM jitter or even stop it when running at low speeds, and the system operation accuracy is reduced. To solve these problems, this work proposes a parameter identification method of the Coulomb friction model. First, a dynamics model with the Coulomb friction of PMSpM is established by using generalised Euler angles and the Lagrangian energy method. Then, a parameter identification method of the Coulomb friction model based on COMSOL Multi physics coupled simulation and MEMS experiment is proposed to obtain the friction torque data of the PMSpM. Finally, the friction torque compensation in a closed‐loop control experiment is completed by using the friction data. The results show that the accuracy of trajectory tracking control is significant, and the error is reduced by 49.32%. Hence, the distribution of the friction torque field is accurate and effective. [ABSTRACT FROM AUTHOR]

Due to the complex spatial magnetic field distribution and the variable motion mode, the torque analysis of spherical motors is usually carried out by the finite-element method (FEM) with a large amount of calculation and time consumption. In order to improve analysis efficiency, this article proposes a spherical motor torque calculation method based on the permanent-magnet surface current model and Lorentz force, aiming to replace the finite-element calculation. First, the equivalent surface current analytical expression of the rectangular permanent-magnet magnetic field is derived. Then, this expression is used to establish the 3-D magnetic field analytical model of Halbach array permanent magnets in the rotor. Based on this magnetic field, the Lorentz force of the energized stator coil is calculated. Then, the electromagnetic torque generated by the rotor is analyzed. Finally, the analytical results of the magnetic field and the motor torque are compared with those by the FEM and experiments, verified that, under the premise of ensuring the calculation accuracy, the proposed method effectively shortens the calculation time and has higher stability. [ABSTRACT FROM AUTHOR]

The output torque is an important performance indicator of a motor. Due to the special structure of a permanent magnet spherical motor (PMSM), it is difficult to measure its torque. This paper proposes a novel method to measure the output torque of the PMSM. The proposed method uses the microelectromechanical system (MEMS) gyroscope to measure the rotor motion acceleration, which is then used to calculate the output torque based on the rotor dynamics equation. In this paper, we firstly simulate and analyze the output torque of the PMSM. Secondly, we design a torque-measuring device to measure the output torque. Thirdly, we compare and discuss the experimental and simulation results. The comparison results show that the proposed method is feasible. [ABSTRACT FROM AUTHOR]