Donghong Ning

1. Driven by the global surge of the ‘Blue Economy’ and the macro-level digital transformation of the ‘Smart Ocean,’ the intelligence level of marine equipment has emerged as a critical benchmark f...

Semi-active electromagnetic dampers are widely recognized for their capability to provide tunable mechanical characteristics and effectively enhance vibration control performance in electrified vehicle suspensions. However, precise damping force tracking remains challenging when the system is affected by mechanical friction, inertial disturbances, and circuit parameter uncertainties. To address these issues, this study proposes a hierarchical control architecture that integrates both mechanical and electrical dynamics for a semi-active DC-DC converter-based electromagnetic damper (DCEMD). The hierarchical control framework, consisting of an upper-layer and a lower-layer controller, is developed accordingly. In this system, the upper-layer H_∞ robust controller suppresses external mechanical disturbances through a disturbance force observer, while the lower-layer model-based adaptive backstepping sliding mode controller compensates for time-varying circuit parameters and ensures accurate damping force tracking. The DCEMD's broad and continuously controllable damping characteristics are experimentally validated, and its control performance is verified on a semi-active electromagnetic suspension experimental platform that incorporates realistic nonlinearities and disturbances. Experimental results demonstrate that the hierarchical control scheme and the designed DCEMD achieve superior vibration isolation and force-tracking precision compared with traditional semi-active systems and several benchmark control methods.

Inspired by the movements of sea turtle forelimbs, this study presents a bio-inspired underwater flapping wing with three degrees of freedom. This flapping wing mechanism can more accurately simulate the rotational motion of a sea turtle’s forelimbs to generate greater propulsive force. The highlight is the gear transmission mechanism arranged along the wingspan, enabling a preset increasing twist angle along the wingspan. Computational fluid dynamics simulations are conducted to evaluate the hydrodynamic performance of the proposed flapping wing system. The effects of different spanwise twist angles along the wingspan on thrust generation are quantitatively analyzed, as well as the influence of key kinematic parameters, including the longitudinal flapping angle, spanwise increasing twist angle, and elevation angle. The results indicate that, compared with a uniform twist angle, the spanwise increasing twist significantly increases the peak thrust during specific phases of the flapping cycle. It is further revealed by flow field analyses that the formation of vortices near the trailing edge enhances the propulsive force in the streamwise direction. To further validate the proposed concept, a prototype of the mechanism is fabricated and experimentally tested under low-frequency actuation, confirming the feasibility of the mechanical design. Overall, these results demonstrate the potential of the proposed approach for bio-inspired underwater propulsion and provide useful guidance for future flapping wing mechanisms and kinematic design.

Suspension performance control typically requires multiple system state inputs; however, many of these variables are difficult or impractical to measure directly. This article proposes a semiactive suspension control strategy designed for scenarios with missing state information, enabling effective control using only a single accelerometer input. To estimate suspension displacement and velocity, this article proposes an improved self-sensing approach for electromagnetic suspension systems. Suspension displacement is determined by integrating three-phase voltage signals generated by the permanent magnet synchronous motor (PMSM) with magnetic ring trigger signals embedded within the shock absorber. Suspension velocity is estimated using a fusion method that combines current-based and voltage-based approaches, leveraging rectified voltage and current measurements from the PMSM to improve robustness and accuracy. In addition, a reduced-order observer is designed to estimate vehicle body velocity using only the vertical acceleration signal. These estimated states, including suspension displacement, suspension velocity, and body velocity, are incorporated into a sliding mode control framework. The proposed method is validated through hardware-in-the-loop experiments, including both random excitation and bump tests. Results demonstrate that accurate state estimation and reliable control performance can be achieved using only a single accelerometer, even under sensor-constrained and load-varying conditions. Compared to passive suspension, the proposed control strategy significantly reduces body acceleration, suspension displacement, and tire dynamic load, thereby improving both ride comfort and vehicle handling.