No abstract

Summary In this paper, an output‐feedback trajectory tracking controller for quadrotors is presented by integrating a model‐assisted extended state observer (ESO) with dynamic surface control. The quadrotor dynamics are described by translational and rotational loops with lumped disturbances to promote the hierarchical control design. Then, by exploiting the structural property of the quadrotor, a model information–assisted high‐order ESO that relies only on position measurements is designed to estimate not only the unmeasurable states but also the lumped disturbances in the rotational loop. In addition, to account for the problem of “explosion of complexity” inherent in hierarchical control, the output feedback–based trajectory tracking and attitude stabilization laws are respectively synthesized by utilizing dynamic surface control and the corresponding estimated signals provided by the ESO. The stability analysis is given, showing that the output‐feedback trajectory tracking controller can ensure the ultimate boundedness of all signals in the closed‐loop system and make the tracking errors arbitrarily small. Finally, flight simulations with respect to an 8‐shaped trajectory command are performed to verify the effectiveness of the proposed scheme in obtaining the stable and accurate trajectory tracking using position measurements only.

The present study aimed to investigate the effect of tetramethylpyrazine (TMP) supplementation on growth performance, Campylobacter jejuni (C. jejuni) carriage and antimicrobial peptides in the epithelial tissue of caecum and skin in rabbits. Five treatments included control and C. jejuni challenge with the addition of TMP at 0, 50, 100 or 150 mg/kg of diet. The trial lasted for 35 days and C. jejuni challenge occurred on first day of feeding trial. The results showed that C. jejuni challenge worsened (P < 0.05) feed intake, body weight gain and feed efficiency, whereas TMP supplementation partially compensated (P < 0.05) growth performance. C. jejuni populations in the caecal content and on the skin were decreased (P < 0.05) in the treatments containing TMP. The mRNA levels of antimicrobial peptides, including defensin neutrophil peptide 4, macrophage cationic peptide 2, galectin 3 and cathelicidin were also decreased (P < 0.05) by C. jejuni challenge while they were increased (P < 0.05) with supplemental TMP. Linear and quadratic trends (P ≤ 0.012) of the three doses of TMP were found in growth performance, linear trends (P ≤ 0.049) in C. jejuni carriage, and linear and quadratic trends (P ≤ 0.012) in galectin 3. The results suggest that TMP can partially protect from C. jejuni infection by decreasing C. jejuni carriage and activating epithelial antimicrobial peptides.

No abstract

No abstract