Traditional multipoint hybrid maglev systems cannot realize the zero-power horizontal levitation state under eccentric load, which means the steady-state current is zero, and the air gap of each magnet is equal. This article proposes a new maglev system with two rotary magnets to solve this problem. The two magnets can move on an annular guideway to counteract the moment caused by the eccentric load. At first, we established the linear parameter varying model of this maglev system. Then, the control strategy is designed, which consists of a zero-power horizontal levitation controller and rotation controller. The levitation control is realized by introducing feedback of integral current and deviation of air gap in the proportional-derivative control system. The rotation controller employs a centroid observer and centroid Jacobian. It outputs the rotating angle at the demand of the zero-power and horizontal levitation. Experimental results demonstrate that the proposed maglev system has a better zero power and horizontal levitation performance than without rotary magnets. The direction of the air gap variation is opposite to that of the loading direction. The variation size of air gap length depends on the load weight, whereas rotation angle is related to the load weight and loading position.

In this paper, a novel three-degree-of-freedom piezoelectric-driven micro-positioning platform based on a lever combination compound bridge-type displacement amplification mechanism is proposed. The micro-positioning platform proposed in this paper aims to solve the current problem of the large size and small travel of the three-degree-of-freedom piezoelectric-driven micro-positioning platform. In this paper, a lever combination compound bridge-type displacement amplification mechanism combined with a new biaxial flexible hinge is proposed, the structural dimensions of the lever mechanism and the compound bridge mechanism are optimized, and the amplification multiplier is determined. The maximum output simulation analysis of the micro-positioning platform is carried out by using ANSYS, and the experimental test system is built for verification. The validation results show that the maximum errors between simulation and experiment in the z-direction, rotation direction around x, and rotation direction around y are 64 μm, 0.016°, and 0.038°, respectively, and the corresponding maximum relative errors are 5.6%, 2.4%, and 6.6%, respectively, which proves the feasibility of the theoretical design.

This article presents a three degrees of freedom (3-DOF) permanent maglev platform for a cleanroom conveyor system supported by four magnetic poles that utilize a variable flux path mechanism. Since the magnetic force of poles is generated and controlled entirely by the rotation of disk-type permanent magnets (PMs), the system exhibits a quasi-zero power consumption and anti-adsorption capability. First, the system mechanism is illustrated, and the magnetic force of the variable flux path pole is measured. Then the mathematical model and state-space of the maglev platform are established based on dynamic analysis. Afterward, a double closed-loop controller is designed for stable levitation and motion control, and the coordinate transformation matrix is used to decouple the control system. Finally, the simulations and experiments were implemented, and stable levitation and 3-DOF motion control were realized with a remarkable positioning precision. The results indicate that the controller and decoupling strategy are effective.

In this article, an electromagnetic actuator is proposed to improve the driving performance of magnetic levitation transportation applied to ultra-clean manufacturing. The electromagnetic actuator mainly includes the stator with the Halbach array and the mover with a symmetrical structure. First, the actuator principle and structure are illustrated. Afterward, in order to select a suitable secondary structure and analyze the characteristics of the actuator, the electromagnetic characteristics of actuators with different secondary structures are analyzed by the finite element method (FEM). Analysis results show that the actuator adopting the secondary structure with a Halbach array will increase the electromagnetic force and working stability. The secondary with the three-section Halbach array is selected for the electromagnetic actuator. Then, the influence of secondary permanent magnet (PM) thickness on the electromagnetic force is analyzed by FEM. The results indicate that the increase in PM thickness will lead to increased electromagnetic force and decreased utilization ratio of PM. Finally, a prototype of an electromagnetic actuator is built, and experiments are implemented. The correctness of the theoretical analysis and the effectiveness of the electromagnetic actuator are verified by experimental results.

Aiming to address the shortcomings of the single-point variable air gap permanent magnetic levitation system in terms of dynamic performance and anti-disturbance capabilities, an improved linear active disturbance rejection control (ILADRC) strategy is proposed. First, based on the system dynamics model, a conventional linear active disturbance rejection control (LADRC) controller is designed, with the total perturbation observed and compensated for in real time by a linear expanded state observer (LESO). Building upon this, the known part of the model is embedded into the LESO framework to enhance the accuracy of total perturbation observation, and the ILADRC controller is designed to further improve the system’s stability and perturbation resistance. The stability and tracking performance of the ILADRC are then verified through theoretical analysis. Finally, the ILADRC strategy is compared with proportional-integral-derivative (PID) control, traditional LADRC control, and auxiliary model-based linear active disturbance rejection control (AMLADRC) in both simulation and experimental settings. The results show that the ILADRC strategy outperforms the other three control strategies, significantly improving the system’s dynamic performance and disturbance resistance.

Aiming to realize levitation for a novel permanent magnetic levitation system, this paper proposes a double control strategy. The coupled dynamic model with two subsystems was established at first. According to the analysis of stable levitation, four joint control strategies of air gap length and rotation angle were designed. Then, the controller parameters tuning was implemented utilizing the improved PSO (particle swarm optimization) algorithm with non-linear inertia weight. At last, step response simulations and experiments were carried out to compare the performance of the proposed four control strategies. Results demonstrate the validity of PSO using for tuning proportional-integral-derivative (PID) parameters. In addition, the parallel double PD controller and cascade double PD controller both have better dynamic performance but more significant steady-state error. When using PID control for the air gap, the error could be eliminated. Compared with the parallel PID-PD control strategy, the cascade control is competitive in terms of 0.03 s rising time, 4.3 s settling time, and 24% peak overshoot.