This article presents modeling and control strategies of a novel axial hybrid magnetic bearing (AHMB) for household flywheel energy storage system (FESS). The AHMB combines a passive permanent magnet (PM) magnetic bearing (MB) and an axial active MB in one unit, thus can offer benefits such as compactness of the structure, high load capacity, and low power consumption. A coupled magnetic field-circuit method is proposed for modeling this bearing. Compared with the regular equivalent magnetic-circuit (EMC) method, it introduces special concerns of the complex air-gap field, calculated from the conformal transformation of the air-gap geometry, to take into account the effect of flux fringing and leakage. A low-cost Hall sensor is used to replace the expensive Eddy-current position sensor to measure the changes in air gap flux density caused by the rotor axial displacement. Therefore, a novel flux density feedback control is adopted instead of the traditional position feedback control to directly stabilize the magnetically suspended flywheel. A prototype of this bearing is designed and fabricated, which is tested in a small-scale FESS. The simulation results and the experimental results demonstrate that the proposed model provides better accuracy than the traditional EMC and the flux-density feedback control strategy based on a low-cost Hall sensor can achieve a consistent performance with the traditional position feedback control strategy.

The operation and control of the cable-driven continuum robot (CDCR) is directly determined by the actuation of cables, and the relationship between the driving length and the tension as well as the morphology of the CDCR has not been deeply researched in previous literature. In this article, a novel methodology for perceiving the morphology, tension, and driving state of the robot is proposed, which can be calculated only by the dynamic driving length/speed of cables without using shape sensors and tension sensors. First, a model of the tension distribution along with the cable path is deduced, which takes into account the influence of the sliding friction. Second, a rigid-flexible coupling dynamic model considering the strain of the cable is established. Then, a nonlinear complementary model between the driving state and the tensions of cables is constructed based on the mechanism of cable actuation, and an efficient solution algorithm is presented. Experiments of a single arm driven by two cables and a three-tandem arm driven by multiple cables were conducted to validate the proposed method. The average errors of the perceiving morphology and tension are 1.85% and 7.26%, respectively, and the transaction between the slack and tensional state of the driving cable is accurately captured. In addition, the hysteresis behavior of the cable actuation is also perceived.

Active shape adjustment of a cable-mesh reflector is a significant procedure to compensate the effects of a complicated space environment in orbit. In this paper, the active shape adjustment of a large cable-mesh reflector with actuators is addressed, and the dynamic input voltage profiles of actuators are estimated using a novel fast model predictive control method. The electromechanical coupling dynamic model of the cable-mesh reflector with piezoceramic (PZT) actuators is first established by using piezoelectric constitutive equations and Hamilton’s principle. For a certain shape distortion, the dynamic control voltage profiles are then obtained via the novel fast model predictive control method in which the structural dynamics model is reformulated as a novel explicit repression form to avoid the computations of matrix exponential. Additionally, some fast computation strategies based on the Newmark-$\beta$ method are used to increase computational efficiency. Finally, a 30-meter diameter cable-mesh reflector is chosen as a numerical example, and the simulation results demonstrate that the proposed control algorithm provides a valid and efficient solution for the shape control of large cable-mesh reflectors.