Jinxiu Zhang

The detection of space-based gravitational waves is one of the most cutting-edge topics in contemporary physics. Among the critical components of detection instruments, the locking and release mechanism plays a pivotal role. After the satellite enters orbit, this mechanism must release the test mass into space with high positional accuracy and minimal residual velocity, allowing it to be subsequently captured by the electrode housing. To ensure precise release in a free-floating environment, piezoelectric stack actuator is employed as the actuation module in the crucial test mass release mechanism. However, the hysteresis behaviour inherent to piezoelectric materials introduces nonlinearities into the release process, which adversely affect the accuracy and stability of the system. To address this issue, we propose an Electro-Mechanical Bouc-Wen model, a novel hysteresis modelling framework that explicitly incorporates voltage rate dynamics and mechanical acceleration coupling. This enhancement enables more accurate characterization of asymmetric hysteresis under dynamic operating conditions, surpassing the limitations of classical Bouc-Wen model. Through dynamic modelling and experimental validation of the test mass release mechanism, and with model parameters optimized using a quantum particle swarm optimization algorithm, the proposed approach achieves high fitting accuracy. Furthermore, a hysteresis compensation strategy based on PID control is implemented and validated on the optimized model, demonstrating that the proposed method effectively mitigates the adverse impact of hysteresis on system performance.

Uncrewed Aerial–Aquatic Vehicles (UAAVs) have broad application potential in air–water missions, but efficient performance in two distinct media and stable transition remain challenging. This letter proposes a multirotor lifting-wing UAAV with dynamic morphing named Diving Hawk-4. The foldable rotor arms, designed with a parallelogram mechanism, can fold and unfold during motion. In the folded state, the vehicle reduces its envelope diameter by up to 63.8%, allowing it to traverse narrow spaces in aerial and underwater environments. The projected area decreases by 51.5%, which reduces the impact force during water entry. A two-stage morphing strategy enables the vehicle to exit the water within 0.7 s and then efficiently correct its attitude. The lifting wings reduce rotor thrust by 49.5% in simulation. Underwater, the folded state reduces drag by 38%, while the unfolded state increases turning rate by 91%. Aerodynamic and hydrodynamic evaluations, together with multi-domain tests, demonstrate the effectiveness of dynamic morphing.