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.     

Knowledge spillovers through human mobility across national borders: Evidence from Zhongguancun Science Park in China

This paper investigates the impact of returnee entrepreneurs and their knowledge spillovers on innovation in high-tech firms in China. Using panel data for 1318 high-tech firms in Beijing Zhongguancun Science Park (ZSP) we find that returnee entrepreneurs create a significant spillover effect that promotes innovation in other local high-tech firms. The extent of this spillover effect is positively moderated by the non-returnee firm's absorptive capacity approximated by the skill level of employees. Multinational enterprises’ R&D activities positively affect the innovation intensity of non-returnee firms only when these local firms possess the sufficient level of absorptive capacity. Our findings have important implications for policy-makers and practitioners.