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Conventional control strategies for holonomic Unmanned Aircraft Systems (UASs) require that, while executing a mission, the UAS attitude dynamics remains very close to zero in order to satisfy the assumption of small angles approximation. This requirement may be valid for hover flight, but not for translational flights or aggressive maneuvers. To overcome this issue, this paper presents the controllability analysis for a non-linear representation of a holonomic UAS. Under the proposed scheme, it is shown that it is possible to design control schemes for stabilizing the complete UAS state space without the necessity of separating the system in attitude and translation subsystems. A set of simulations are presented to evaluate the effectiveness of the proposed control laws. These results show that the proposed strategy enables the UAS to track a desired trajectory while keeping the attitude close to a desired value.

This paper deals with the problem of enabling a team of two Unmanned Aircraft Systems to perform an autonomous load transportation task. We propose a strategy whose main objective is to ensure a stable flight of the team of agents when cooperatively transporting the load. The strategy is based on the implementation of a neural network controller and a neural network estimator, using wavelet activation functions in combination with a cooperative multi-agent control approach. To show the effectiveness and applicability of the proposed framework, a real time experimental implementation is presented. Additionally, a comparison with respect to a classic control law is also provided, demonstrating the superior performance attained when adopting the proposed controller.

Background: Escherichia coli is the main bacterium associated with urinary tract infections (UTIs), including cystitis and pyelonephritis. Uropathogenic E. coli (UPEC) harbors numerous genes that encode diverse virulence factors contributing to its pathogenicity. The treatment of UTIs has become complicated due to the natural selection of E. coli strains that are multiresistant to several groups of antibiotics regularly used in clinical settings such as hospitals. Genomic reports of the global composition and distribution of the antibiotic resistance and virulence genes of these pathogenic strains are lacking in the Mexican population. Purpose and methods: The aim of this study was to globally characterize the genomes of a group of UPEC strains by massive parallel sequencing to determine the prevalence and distribution of virulence and antibiotic resistance genes associated with different serotypes and phylogenetic groups. Results: The strains exhibited 138-197 virulence genes and 29 antibiotic resistance genes related to antibiotics that are commonly used in clinical practice. Conclusions: These findings are relevant to the definition of new strategies for treating urinary tract infections in public hospitals and private practice. To further define the epidemiological distribution and composition of these virulence and antibiotic resistance genes, larger studies are needed.

There is evidence that the decreased precipitation attributed to climate change is the main cause of the low sugarcane ( Saccharum spp.) yields obtained in Mexico in recent years. The main objective of the present study was to establish whether temporal patterns in climate change affect sugarcane yields and irrigation requirements. In order to address these questions, we identified trends in climate parameters related to production in different agroecoregions where sugarcane is produced under different irrigation regimes. These regions were differentiated by means of geographic information systems and multivariate statistical analysis (principal components analysis), which were applied to data supplied by the 54 registered sugar mills in Mexico. Use of parametric models (linear regression) and non-parametric models (Mann–Kendall) enabled us to establish temporal trends in soil water availability and changes in productivity. Irrigation regime and production were related to climate patterns in the 7 agroecoregions identified. The temporal models revealed different trends in water availability, which affected crop yield. Decreased soil moisture was most evident in the agroecoregions where the crops were not irrigated or were managed with supplementary irrigation, and this affected the crop yields. The findings indicate the need to develop short and mid-term irrigation management policies for agroecoregions in Mexico.

Complex defects in the soft tissues of the foot and ankle caused by high-energy trauma, infection, cancer or diabetes require rapid and effective treatment which decreases the risk of infection, bone healing time, hospital stay and number total of surgical approaches. Authors report a clinical case of a 23-year-old female patient who suffers high-energy trauma due to a motorcycle accident which causes exposure of the distal third of the tibia, loss of the tibial joint face, and loss of tissue throughout the region of the malleolus medial of the right pelvic extremity. Tissue transfer to the pelvic limb is performed using left contralateral radial antebrachial free flap as donor area. This case report aims to emphasize the key aspects of the high energy trauma approach by using microvascular flaps, as well as the satisfactory evolution of the patient that directly affects the prognosis for life and function.

The stability analysis of a vision-based control strategy for a quad rotorcraft UAV is addressed. In the present application, the imaging sensing system provides the required states for performing autonomous navigation missions, however, it introduces latencies and time-delays from the time of capture to the time when measurements are available. To overcome this issue, a hierarchical controller is designed considering a time-scale separation between fast and slow dynamics. The dynamics of the fast-time system are stabilized using classical proportional derivative controllers. Additionally, delay frequency and time domain techniques are explored to design a controller for the slow-time system. Simulations and experimental results consisting on a vision-based road following task are presented.

An unmanned aerial vehicle (UAV) stabilization strategy based on computer vision and switching controllers is proposed. The main goal of this system is to perform tracking of a moving target on ground. The architecture implemented consists of a quadrotor equipped with an embedded camera which provides real-time video to a computer vision algorithm where images are processed. A vision-based estimator is proposed, which makes use of 2-dimensional images to compute the relative 3-dimensional position and translational velocity of the UAV with respect to the target. The proposed estimator provides the required states measurements to a micro-controller for stabilizing the vehicle during flight. The control strategy consists of switching controllers, which allows making decisions when the target is lost temporarily or when it is out of the camera's field of view. Real time experiments are presented to demonstrate the performance of the target-tracking system proposed.

This article proposes a methodology for enabling Unmanned Aircraft Systems (UASs) to avoid obstacles. The strategy, which makes use of a Robust Exact Differentiation (RED), relies on spiral trajectory tracking maneuvers, and is based on a backstepping controller with disturbance compensation. The RED strategy has been adopted since it enables the exact estimation of disturbances from the first moment, a characteristic that may be useful for real-time UAS operations in environments with obstacles. Our research concentrates in one of the main components of a Sense and Avoid (SSA) system, specifically, conflict resolution, leaving as future work the sensing aspect. To demonstrate the performance of the proposed solution, we present a set of simulation results as well as a real-time experiment where a holonomic UAS makes use of the estimation and control strategy while evolving in an environment with obstacles.

The incorporation of growth retardants (GR) such as ancymidol (ANC) or paclobutrazol (PBZ) in liquid culture media during multiplication stage of bananas decreases the excessive growth of stems and leaves. However, it is unknown if these chemicals have residual effect on further plant growth. To study the effect of ANC and PBZ on Grand Nain banana shoots, they were subcultured for five cycles in the multiplication stage and evaluated in elongation-rooting and acclimatization stages. Multiplication basal medium was Murashige and Skoog supplemented with 1.0 mg l−1 thiamine-HCl and 17.7 μM 6-benzylaminpurine (6-BAP), 9.75 μM ANC or 8.5 μM PBZ. Multiplied Grand Nain banana shoots were transferred to elongation-rooting stage and later on to ex-vitro conditions. The evaluation of GR residual effect and somaclonal variation on Grand Nain banana plants was determined through a comparative study of several morphological parameters in elongation-rooting and acclimatization stages. All morphological parameters evaluated in the elongation-rooting stage showed a similar performance with the exception of the pseudo-stem diameter of the vitroplants treated with both GR. There were significant differences for plant height in the acclimatization stage when shoots were multiplied in a medium containing ANC. The similarities of the parameters evaluated in both stages and the normal morphology recovery of vitroplants multiplied with PBZ suggest that there were no residual effects by adding PBZ to the culture media. The addition of ANC induced significant differences in plant height during the acclimatization stage.

International audience; The stability analysis of a vision-based control strategy for a quad rotorcraft UAV is addressed. In the present application, the imaging sensing system provides the required states for performing autonomous navigation missions, however, it introduces latencies and time-delays from the time of capture to the time when measurements are available. To overcome this issue, a hierarchical controller is designed considering a timescale separation between fast and slow dynamics. The dynamics of the fast-time system are stabilized using classical proportional derivative controllers. Additionally, delay frequency and time domain techniques are explored to design a controller for the slow-time system. Simulations and experimental results consisting on a vision-based road following task are presented, verifying the efficacy of the approach and showing the benefits of the stability analysis performed.

This paper reports current work on development and navigation control of an experimental prototype of a new tilt-rotor convertible aircraft (Quad-plane Mini Unmanned Aerial Vehicle). The goal of the work consists of estimating and tracking a road using a vision system, without any previous knowledge of the road, as well as developing an efficient controller for treat with situations when the road is not detected by the vision sensor. For dealing with this situation, we propose a switching control strategy applied in two operational regions: road detected and no road detected. The exponential stability is proved for the subsystem formed by the lateral position taking into account the switching boundaries between the operational regions. The control law is validated in the proposed platform, showing the expected behavior during autonomous navigation.

International audience; The problem of vision-based road following using a quad-rotor is addressed. The objective consists of estimating and tracking a road without a priori knowledge of such path. For thispurpose, two operational regions are defined: one for the case when the road is detected, and the other one for when it is not. A switching between imaging and inertial sensors measurements allows estimating the required vehicle's parameters in both regions. Also, for dealing with both aforementioned cases, a switching control strategy which stabilizes the vehicle's lateral position is proposed. The performance of the proposed switching methodologies is tested in real time experiments.

International audience; We propose a vision based position estimation algorithm to provide some level of autonomy for a quadrotor unmanned aerial vehicle (UAV). Our approach estimates the helicopter X-Y-Z position with respect to a ground landmark. This technique allows us to measure the position variables that are difficult to compute when using conventional navigation systems (for example, Global Positioning System, GPS) and inertial sensors in urban environment or indoor. Our method estimates the position and measures translational speed in a local frame. The control strategy is based on a full state feedback method. The effectiveness of the vision based control system is validated by experimental results.

International audience; This paper present the design of a novel embedded control system for improving attitude stabilization of a quad-rotor mini UAV. The control strategy uses low cost components and includes an extra control loop based on motor armature current feedback. This additional control loop significantly improves the performance of the quad-rotor attitude stability. This technique results in a controller that is robust with respect to external disturbances as has been observed experimentally.

Temporary immersion culture (TIS) offers several advantages over solid medium for banana shoot multiplication, e.g. TIS results in an increase in the multiplication rate and improves the quality of the plantlets. For a commercial application of this technique large vessels are required. When using 10-litre culture vessels an excessive growth of the shoots (leaves and pseudostem) was obtained, which limited the final number of shoots to be produced per flask and reduced the production capacity in the growth room. Labor costs also increased, since handling is more difficult when dividing and subculturing large shoots during the multiplication stage. The effect of growth retardants ancymidol (ANC), paclobutrazol (PBZ) and daminozide (DAM) in liquid shake cultures and TIS was investigated in order to reduce the size of the shoots and allow a better use of the space inside the culture vessel. In liquid shake cultures ANC and PBZ, independently of the tested concentrations, promoted bud cluster formation with reduced size and compact shape. Shoots multiplied with ANC or PBZ (2.5 mg l−1) after five subcultures, recovered their normal morphology after transfer to a hormone-free medium without growth retardants. However, during the acclimatization stage, plants multiplied in ANC (2.5 mg l−1) containing media showed reduced height in comparison with control plants and plants multiplied in PBZ and DAM containing medium. The application of PBZ and ANC in TIS (1-litre flasks) stimulated bud proliferation. Both compounds were also effective in controlling the excessive growth of the shoots and in inducing the formation of compact bud clusters. Shoots multiplied in TIS in presence of PBZ (2.5 mg l−1) were successfully transferred to semisolid or liquid rooting media in traditional culture vessels or TIS. The developed protocol was further scaled up in 10-litre TIS vessels.

This chapter explores the structural reforms that the Mexican sweetener industry has undergone. It discusses the implications these reforms have for the sweetener industries in Mexico and the USA. Problems in the production of sugarcane and sugar in Mexico are examined, and the prospects of the Mexican sugar industry is discussed in the context of the North American Free Trade Agreement.

International audience; The stability analysis of a vision-based control strategy for a quad rotorcraft UAV is addressed. In the present application, the imaging sensing system provides the required states for performing autonomous navigation missions, however, it introduces latencies and time-delays from the time of capture to the time when measurements are available. To overcome this issue, a hierarchical controller is designed considering a time-scale separation between fast and slow dynamics. The dynamics of the fast-time system are stabilized using classical proportional derivative controllers. Additionally, delay frequency and time domain techniques are explored to design a controller for the slow-time system. Simulations and experimental results consisting on a vision-based road following task are presented.