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.

This study aims to develop a novel decoupling method for the independent control of the position and stiffness of a variable stiffness joint actuator (VSJA), which has been proven to be able to vary its stiffness in a larger range than other variable stiffness actuators. Using static analysis and the Jacobian matrix, we obtained the model of the stiffness of the robot joint actuator and dynamics. Based on the hybrid dynamic model of position and stiffness, it is possible to compensate for the torque of the variable stiffness joint actuator (VSJA) to enhance position control. Finally, after describing the actuator prototype, the established compliance control method is verified using simulation and experimental analysis.

High-static-low-dynamic-stiffness (HSLDS) vibration isolation systems, owing to their inherent nonlinearities, are prone to jump phenomena under high excitation amplitudes, leading to impaired low-frequency vibration isolation performance. To address this issue, this paper proposes a hybrid magnetic HSLDS isolator with an integrated electromagnetic shunt damper (EMSD), which is designed based on the principle of eddy current effects. This isolator can achieve superior low-frequency vibration isolation performance through active regulation of system stiffness and damping. First, the nonlinear magnetic force of the isolator and the electromagnetic coupling coefficient of the EMSD are derived. In addition, a negative resistance circuit based on an operational amplifier is designed to reduce the system impedance and enhance the damping force. Based on this, an electromechanically coupled, two-degree-of-freedom dynamic model of the isolator is developed to analyze its low-frequency vibration isolation performance. Experiments are performed to validate the effectiveness of the system in regulating both stiffness and damping. Additionally, an adaptive regulation strategy is proposed based on the experimental results; this strategy enables the system to adaptively adjust its stiffness and damping in response to variations in the vibration source frequency. Experimental results indicate that, compared to the passive state, the isolator employing the regulation strategy exhibits a 16.6% reduction in the initial isolation frequency and a 46.7% attenuation of the resonance peak. Optimal vibration suppression is achieved across the full frequency band.

An asymmetric stiffness structure, comprising a permanent magnet (PM) and an electromagnetic coil (EC), has been designed to create a vibration isolator with high-static-low-dynamic stiffness (HSLDS). The mathematical model of the system is established using the molecular current method and is compared with simulation results. Additionally, a nonlinear dynamic model of the single-degree-of-freedom vibration isolation system is developed. The influence of factors such as excitation and current on the displacement transmissibility of the system is analyzed using the incremental harmonic balance method (IHB). To validate the findings, an experimental test system is constructed. The results of the validation demonstrate that by adjusting the current in the EC, without altering the structural parameters of the system, the natural isolation frequency of the vibration isolation system can be reduced. This adjustment broadens the vibration isolation frequency band.

Variable-stiffness joints, with their inherent flexibility, enable highly secure human–robot interactions in unstructured environments. However, existing mechanisms are limited in terms of stiffness regulation flexibility and nonlinear centeracteristics. This paper proposes a compact variable-stiffness mechanism based on a nonlinear path surface coupled with a permanent magnetic nonlinear spring and a linear spring (LS), namely, permanent magnet-cam-variable stiffness actuators. This mechanism integrates the predictability of the LS, the rich magnetic-force nonlinearity of the permanent-magnet spring, and the nonlinear centeracteristics of the cam profile, thereby enabling arbitrary modulation of the stiffness curve. First, a mechanical model is established to examine how the cam-roller motion alters the LS deformation and the permanent-magnet air gap, thus revealing the mechanism of torque and stiffness modulation. Incorporating elastic deformation theory, the relationship between roller rotation angle, output torque, and equivalent stiffness is derived. Further simulation and experimental comparisons, performed by replacing different elastic elements, demonstrate that the proposed mechanism not only enables arbitrary adjustment of nonlinear stiffness but also exhibits superior torque range and response flexibility.