Trajectory tracking anti-disturbance control for unmanned aerial helicopter based on disturbance characterization index

This work studies the trajectory tracking control for unmanned aerial helicopter(UAH)system under both matched disturbance and mismatched ones.Initially,to tackle the strong coupling,an input-output feedback linearization method is utilized to simplify the nonlinear UAH system.Secondly,a set of finite-time disturbance observers(FTDOs)are proposed to estimate mismatched disturbances with their successive derivatives,which are utilized to design the feedforward controller via backstepping.Thirdly,as for matched disturbance,by defining the disturbance characterization index(DCI)to determine whether the disturbance is harmful or not for the UAH system,a feedback controller is proposed and a sufficient condition is established to ensure the convergence of the tracking error.Finally,some numerical simulations and comparisons illustrate the validity and advantages of our control scheme.

The Reference Genome of Tea Plant and Resequencing of 81 Diverse Accessions Provide Insights into Its Genome Evolution and Adaptation

Tea plant is an important economic crop,which is used to produce the world's oldest and most widely consumed tea beverages.Here,we present a high-quality reference genome assembly of the tea plant(Camellia sinensis var.sinensis)consisting of 15 pseudo-chromosomes.LTR retrotransposons(LTR-RTs)account for 70.38%of the genome,and we present evidence that LTR-RTS play critical roles in genome size expansion and the transcriptional diversification of tea plant genes through preferential insertion in promoter regions and introns.Genes,particularly those coding for terpene biosynthesis pro-teins,associated with tea aroma and stress resistance were significantly amplified through recent tandem duplications and exist as gene clusters in tea plant genome.Phylogenetic analysis of the sequences of 81 tea plant accessions with diverse origins revealed three well-differentiated tea plant populations,support-ing the proposition for the southwest origin of the Chinese cultivated tea plant and its later spread to western Asia through introduction.Domestication and modern breeding left significant signatures on hundreds of genes in the tea plant genome,particularly those associated with tea quality and stress resis-tance.The genomic sequences of the reported reference and resequenced tea plant accessions provide valuable resources for future functional genomics study and molecular breeding of improved cul-tivars of tea plants.