Singularity-free Aerial Deformation by Two-dimensional Multilinked Aerial Robot with 1-DoF Vectorable Propeller

Two-dimensional multilinked structures can benefit aerial robots in both maneuvering and manipulation because of their deformation ability. However, certain types of singular forms must be avoided during deformation. Hence, an additional 1 Degrees-of-Freedom (DoF) vectorable propeller is employed in this work to overcome singular forms by properly changing the thrust direction. In this paper, we first extend modeling and control methods from our previous works for an under-actuated model whose thrust forces are not unidirectional. We then propose a planning method for the vectoring angles to solve the singularity by maximizing the controllability under arbitrary robot forms. Finally, we demonstrate the feasibility of the proposed methods by experiments where a quad-type model is used to perform trajectory tracking under challenging forms, such as a line-shape form, and the deformation passing these challenging forms

Versatile Multilinked Aerial Robot with Tilting Propellers: Design, Modeling, Control and State Estimation for Autonomous Flight and Manipulation

Multilinked aerial robot is one of the state-of-the-art works in aerial robotics, which demonstrates the deformability benefiting both maneuvering and manipulation. However, the performance in outdoor physical world has not yet been evaluated because of the weakness in the controllability and the lack of the state estimation for autonomous flight. Thus we adopt tilting propellers to enhance the controllability. The related design, modeling and control method are developed in this work to enable the stable hovering and deformation. Furthermore, the state estimation which involves the time synchronization between sensors and the multilinked kinematics is also presented in this work to enable the fully autonomous flight in the outdoor environment. Various autonomous outdoor experiments, including the fast maneuvering for interception with target, object grasping for delivery, and blanket manipulation for firefighting are performed to evaluate the feasibility and versatility of the proposed robot platform. To the best of our knowledge, this is the first study for the multilinked aerial robot to achieve the fully autonomous flight and the manipulation task in outdoor environment. We also applied our platform in all challenges of the 2020 Mohammed Bin Zayed International Robotics Competition, and ranked third place in Challenge 1 and sixth place in Challenge 3 internationally, demonstrating the reliable flight performance in the fields

Comparative SNP and Haplotype Analysis Reveals a Higher Genetic Diversity and Rapider LD Decay in Tropical than Temperate Germplasm in Maize

Understanding of genetic diversity and linkage disequilibrium (LD) decay in diverse maize germplasm is fundamentally important for maize improvement. A total of 287 tropical and 160 temperate inbred lines were genotyped with 1943 single nucleotide polymorphism (SNP) markers of high quality and compared for genetic diversity and LD decay using the SNPs and their haplotypes developed from genic and intergenic regions. Intronic SNPs revealed a substantial higher variation than exonic SNPs. The big window size haplotypes (3-SNP slide-window covering 2160 kb on average) revealed much higher genetic diversity than the 10 kb-window and gene-window haplotypes. The polymorphic information content values revealed by the haplotypes (0.436–0.566) were generally much higher than individual SNPs (0.247–0.259). Cluster analysis classified the 447 maize lines into two major groups, corresponding to temperate and tropical types. The level of genetic diversity and subpopulation structure were associated with the germplasm origin and post-domestication selection. Compared to temperate lines, the tropical lines had a much higher level of genetic diversity with no significant subpopulation structure identified. Significant variation in LD decay distance (2–100 kb) was found across the genome, chromosomal regions and germplasm groups. The average of LD decay distance (10–100 kb) in the temperate germplasm was two to ten times larger than that in the tropical germplasm (5–10 kb). In conclusion, tropical maize not only host high genetic diversity that can be exploited for future plant breeding, but also show rapid LD decay that provides more opportunity for selection

Generalized Design, Modeling and Control Methodology for a Snake-like Aerial Robot

Snake-like robots have been developing in recent decades, and various bio-inspired ideas are deployed in both the mechanical and locomotion aspects. In recent years, several studies have proposed state-of-the-art snake-like aerial robots, which are beyond bio-inspiration. The achievement of snake-like aerial robots benefits both aerial maneuvering and manipulation, thereby having importance in various fields, such as industry surveillance and disaster rescue. In this work, we introduce our development of the modular aerial robot which can be considered a snake-like robot with high maneuverability in flight. To achieve such flight, we first proposed a unique thrust vectoring apparatus equipped with dual rotors to enable three-dimensional thrust force. Then, a generalized modeling method based on dynamics approximation is proposed to allocate the wrench in the center-of-gravity (CoG) frame to thrust forces and vectoring angles. We further developed a generalized control framework that can handle both under-actuated and fully actuated models. Finally, we show the experimental results with two different platforms to evaluate the flight stability of the proposed snake-like aerial robot. We believe that the proposed generalized methods can provide a solid foundation for the snake-like aerial robot and its applications regarding maneuvering and manipulation in midair

Identification of Maize <i>Rf4</i>-Restorer Lines and Development of a CAPS Marker for <i>Rf4</i>

Rf4 is one of the dominant restorer genes for maize C-type cytoplasmic male sterility (CMS-C), which has significant value in hybrid maize seed production. However, the highly complex fertility restoration mechanism of CMS-C makes it difficult to screen Rf4-restorer lines, and insufficient Rf4-restorer lines limit its use in current agricultural production. To search for Rf4-restorer lines, in this study, the genotypes of eighteen inbred maize lines at the Rf4 locus were analyzed based on the male fertility investigation of hybrid F1, the genetic analysis of F2 populations, molecular marker mapping, allelic tests, and Rf4 genomic sequence analysis. Our results indicated that of the eighteen maize inbred lines, ten were able to completely rescue CMS-C line CHuangzaosi (CHZS) male sterility. A genetic analysis showed that DAN598, PHT77, 78551S, and LH212Ht only contained one dominant restorer gene each, and the molecular-marker mapping indicated that their restorer genes were located at the short arm of chromosome 8. The allelic testing of the fertility of the restorer (Rf) demonstrated that the restorer gene of twelve inbred lines, including DAN598, PHT77, 78551S, and LH212Ht, was allelic to one restorer gene of A619. Furthermore, the genomic sequence alignment of Rf4 revealed that there were two different amino acids in the coding sequence between the A619 (Rf4Rf4) restorer lines and four CMS-C lines (rf4rf4). For the crucial S1596 site variation (TTT/TAC), DAN598, PHT77, 78551S, and LH212Ht shared the same bases (TTT) with A619 and encoded phenylalanine, while the four CMS-C sterile lines had the TAC and encoded tyrosine. Our results revealed that these tester lines, DAN598, PHT77, 78551S, and LH212Ht, were the Rf4-restorer lines. Additionally, derived from the sequence variants of Rf4, 39 possible Rf4-restorer lines from 129 inbred maize lines were detected. Furthermore, we developed a Cleaved Amplified Polymorphism Sequences (CAPS) marker based on the S1596 variations. The PCR amplification product of S1596 (TAC) was digested by the TatI endonuclease into two bands with sizes of ~260 bp and ~100 bp. In comparison, when S1596 was TTT, the PCR product could not be digested. In conclusion, in this study, we identified various Rf4-restorer lines for maize CMS-C and developed a molecular marker for Rf4. The reported results will contribute to the popularization and application of Rf4 in hybrid maize-seed production

Comparative transcriptome analysis of isonuclear-alloplasmic lines unmask key transcription factor genes and metabolic pathways involved in sterility of maize CMS-C

Although C-type cytoplasmic male sterility (CMS-C) is one of the most attractive tools for maize hybrid seed production, the detailed regulation network of the male sterility remains unclear. In order to identify the CMS-C sterility associated genes and/or pathways, the comparison of the transcriptomes between the CMS-C line C48-2 and its isonuclear-alloplasmic maintainer line N48-2 at pollen mother cell stage (PS), an early development stage of microspore, and mononuclear stage (MS), an abortive stage of microspore, were analyzed. 2,069 differentially expressed genes (DEGs) between the two stages were detected and thought to be essential for the spikelet development of N48-2. 453 of the 2,069 DEGs were differentially expressed at MS stage between the two lines and thought to be participated in the process or the causes of microspore abortion. Among the 453 DEGs, 385 (84.99%) genes were down-regulated and only 68 (15.01%) genes were up-regulated in C48-2 at MS stage. The dramatic decreased expression of the four DEGs encoding MYB transcription factors and the DEGs involved in “polyamine metabolic process”, “Cutin, suberine and wax biosynthesis”, “Fatty acid elongation”, “Biosynthesis of unsaturated fatty acids” and “Proline metabolism” might play an important role in the sterility of C48-2. This study will point out some directions for detailed molecular analysis and better understanding of sterility of CMS-C in maize

A preliminary identification of Rf*-A619, a novel restorer gene for CMS-C in maize (Zea mays L.)

C-type cytoplasmic male sterility (CMS-C) is widely utilized for hybrid maize seed production. However, genetic mechanisms underlying the fertility restoration are very complicated. At present, there is a divergence on the number of fertility restorer genes in maize inbred line A619 for CMS-C. To further elucidate the restoring mechanism of A619, we used genetic analysis and molecular markers to confirm the restorer genes of maize inbred line A619 for C-type male sterile line C48-2 in this study. Firstly, the fertility segregations of (C48-2 × A619)F2 populations were investigated under three environments during 2013–2015. The segregation ratio of fertile and sterile plants in the F2 population fit to 15:1 via chi-square test and this result suggested that there are two dominant restorer genes in A619 for CMS-C, i.e., Rf4 and a novel gene named Rf*-A619. Next, based on the sequence differences between Rf4 and its recessive allelic rf4, a novel dominant marker F2/R2 was developed and validated to genotyping Rf4 in the F2 population. Through genotypic analysis, we found that there were a certain amount of fertile individuals without Rf4 which accounted for 3/16 in the F2 population via chi-square test at the 0.05 level. These results provided another proof to sustain that the inbred line A619 contains one additional restorer gene for CMS-C fertility restoration except Rf4. At last, we used one SSR marker which is tightly linked with the dominant restorer gene Rf5 to analyze those fertile plants without Rf4 in the F2 population. The PCR amplification results showed that Rf*-A619 is not allelic to Rf5 but a novel restorer gene for CMS-C. These results not only provide a basis for the mapping and characterization of a novel restorer gene but also give a new insight into the mechanism of CMS-C fertility restoration

Měření a regulace výšky hladiny v krystalizační nádrži kontilití

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta elektrotechniky a informatiky. Katedra (455) měřící a řídící technik