Yating Yuan

Yating Yuan, Yu Liu

Continuous-time control of multiple quadrotors in constrained environments under signal temporal logic (STL) specifications is critical due to their nonlinear dynamics, safety constraints, and the requirement to ensure continuous-time satisfaction of the specifications. To ensure such control, a two-stage framework is proposed to address this challenge. First, based on geometric control, a Lyapunov-based analysis of the rotational tracking dynamics is performed to facilitate multidimensional gain design. In addition, tracking-error bounds for subsequent STL robustness analysis are derived. Second, using the tracking-error bounds, a mixed-integer convex programming (MICP)-based planning framework with a backward-recursive scheme is developed. The framework is used to generate reference trajectories that satisfy multi-agent STL tasks while meeting the trajectory requirements imposed by geometric control. Numerical simulations demonstrate that, compared with uniform gains, the optimized multidimensional gains yield less conservative time-varying bounds, mitigate oscillations, and improve transient performance, while the proposed framework ensures the satisfaction of multi-agent STL tasks in constrained environments with provable tracking guarantees.

Yu Liu, Shengbo Zhang, Yating Yuan

Modular multilevel converter (MMC) has been successfully applied in various power electronic systems owing to its high efficiency, scalability, and superior output performance. Although the half-bridge submodule (HBSM) is widely used in MMCs for its structural simplicity, it is incapable of handling direct-current (DC) short-circuit faults. The diode-clamp submodule (DCSM) addresses this limitation by providing DC fault ride-through capability. However, because its two identical capacitors are connected in series, the equivalent capacitance is halved. To overcome this drawback, an enhanced SM is proposed in this paper. For the same energy storage capacity, the proposed SM reduces the total required capacitance by 75% compared with the DCSM. In addition, the proposed SM requires one fewer diode than the DCSM, thereby lowering the overall MMC capital cost. The topology and the operating modes of the proposed SM are described in detail, and its functionality is experimentally validated. The results demonstrate that the proposed SM can suppress DC fault currents and restore normal operation without additional external protection devices.