Design of rules for in-flight non-parametric tuning of PID controllers for unmanned aerial vehicles

Designing high performance controllers for multirotors is a rigorous task that is often solved by trial and error approach. Trial and error tuning usually results in non-optimal controller parameters. Tuning controllers based on the existing quadrotor models would result in poor performance of quadrotors due to simplifications and inaccuracies in the underlying models. In this paper optimal tuning rules for quadrotor attitude dynamics are designed, which guarantees near-optimal performance and robustness. A single in-flight run of the Modified Relay Feedback Test that takes only few seconds with guaranteed stability is enough to have near-optimal tuning of the controller. The designed tuning rule is tested experimentally in-flight on a custom-built quadrotor. The results showed significant advantages in performance and robustness due to the proposed approach.     

回转支承多源性故障波致振动模型及其应用研究

讨论了回转支承中多源性故障的诊断。从点状激励下应力波的传播特性出发 ,通过对波形转换的分析 ,推导并证明了多源性故障的诊断模型和判别特征 ;经过对实际结构的测定和实例应用 ,说明本文提出的模型和结论正确有效     

Bifurcation of periodic motion of rigid rotor system supported by angular contact ball bearings

Rotor systems supported by angular contact ball bearings are complicated due to nonlinear Hertzian contact force. In this paper, nonlinear bearing forces of ball bearing under five-dimensional loads are given, and 5-DOF dynamic equations of a rigid rotor ball bearing system are established. Continuation-shooting algorithm for periodic solutions of the nonlinear non-autonomous dynamic system and Floquet multipliers of the system are used. Furthermore, the bifurcation and stability of the periodic motion of the system in different parametric domains are also studied. Results show that the bifurcation and stability of period-1 motion vary with structural parameters and operating parameters of the rigid rotor ball bearing system. Avoidance of unbalanced force and bending moment, appropriate initial contact angle, axial load and damping factor help enhance the unstable rotating speed of period-1 motion.     

无人机应用发展关键基础设施与低空公共航路网规划

当代无人机特点是数量众多、应用范围广、活跃频次高和用户众多。对于安全运行，高标准的无人机软硬件系统可靠性和鲁棒性至关重要。无人机运行高度依赖于新技术和外部高技术基础设施。其中，低空公共航路网（又称低空“天路”）是一种保障低空无人机安全和高效运行的关键新型基础设施。深入研究与推进低空“天路”为核心的无人机应用基础设施建设对于发展城市空中交通网、助力智慧交通发展非常有意义。文章在梳理无人机应用关键基础设施的基础上，进行了基于低空“天路”的新型基础设施建设的未来展望。