Transition control of a tail-sitter unmanned aerial vehicle with L1 neural network adaptive control

The main task of this work is to design a control system for a small tail-sitter Unmanned Aerial Vehicle(UAV)during the transition process.Although reasonable control performance can be obtained through a well-tuned single PID or cascade PID control architecture under nominal conditions,large or fast time-varying disturbances and a wide range of changes in the equilibrium point bring nonlinear characteristics to the transition control during the transition process,which leads to control precision degradation.Meanwhile,the PID controller’s tuning method relies on engineering experiences to a certain extent and the controller parameters need to be retuned under different working conditions,which limits the rapid deployment and preliminary validation.Based on the above issues,a novel control architecture of L1 neural network adaptive control associated with PID control is proposed to improve the compensation ability during the transition process and guarantee the security transition.The L1 neural network adaptive control is revised to solve the multi-input and multi-output problem of the tail-sitter UAV system in this study.Finally,the transition characteristics of the time setting difference between the desired transition speed and the desired transition pitch angle are analyzed.

Research Progress of hypersonic boundary layer transition control experiments

Hypersonic boundary layer transition is a hot yet challenging problem restricting the development and breakthrough of hypersonic aerodynamics.In recent years,despite great progress made by wind tunnel experiment,transition mechanism and transition prediction,only partial knowledge has been gained so far.In this paper,firstly,the specific scenarios of hypersonic boundary layer transition control are clarified.Secondly,the experimental research progress and mechanism of passive control and active control methods under different hypersonic transition control demands are summarized,with their advantages and disadvantages being analyzed separately.Plasma actuation is easy to produce controllable broadband aerodynamic actuation,which has potential in the field of boundary layer transition control.Hence,the following part of the paper focuses on plasma flow control.The feasibility of plasma actuation to control the hypersonic boundary layer transition is demonstrated and the research ideas are presented.Finally,hypersonic boundary layer transition control methods are summarized and the direction of future research is prospected.

Application of transitional care model in cancer pain management after discharge: a randomized controlled trial

Objective： We sought to determine any benefits of applying a transitional care model in the continuum of cancer pain management, especially after patients＇ discharge from the hospital. Methods： A total of 156 eligible participants were recruited and randomly assigned into intervention or control groups. The control group received standard care, while the intervention group received extra, specialized transitional care of pain management. Outcomes were measured at weeks 0 and 2-4 and included demographic data, the Brief Pain Inventory, Global Quality of Life Scale, and Satisfaction Degree of Nursing Service. Adequacy of analgesia and severity of pain were assessed with the Pain Management Index and interview findings. Results： After 2-4 weeks of intervention, there was a significant difference in the change in average pain score between intervention and control groups （P 〈 0.05）. Reductions in pain scores were significantly greater in the intervention group than in the control group （difference： 0.98, P 〈 0.05）. Regarding pain management outcomes, there was a significantly better condition in the intervention group compared with the control group; in the intervention group, 79% of patients had adequate opioids, whereas in the control group, only 63% of patients reported having adequate opioids. Furthermore, there was a signif- icant difference between the two groups in quality of life （QOL） scores （P 〈 0.05）; the intervention group had significantly higher quality of life than the control group （difference： 1.06）. Finally, there was a significant difference in the degree of satisfaction with the home nursing service; the intervention group had a significantly higher degree of satisfaction with the home nursing service in three aspects： quality, content, and attitude of service. Conclusions： The application of a transitional care model in cancer pain management after discharge could help patients to improve their cancer pain management knowledge and analgesics compliance. In addition, the continuum of care service will contribute to effective communication between health care providers and patients, which could further improve their relationship.

High-Resolution Rb Two-Photon Transition Spectroscopy by a Femtosecond Frequency Comb via Pulses Control

We experimentally observe the high resolution direct frequency comb spectroscopy using counter-propagating broadband femtosecond pulses on two-photon transitions in room-temperature ^87 Rb atoms. The Doppler broad- ened background is effectively eliminated with the pulse shaping method and the spectrum modulation technique. The combination of the pulse shaping method and the spectra modulation technique provides a potential approachto reduce background of at least 99%.

State and Mode Feedback Control for Discrete-time Markovian Jump Linear Systems With Controllable MTPM

In this note, the state and mode feedback control problems for a class of discrete-time Markovian jump linear systems(MJLSs) with controllable mode transition probability matrix(MTPM) are investigated. In most achievements, controller design of MJLSs pays more attention to state/output feedback control for stability, while the system cost in practice is out of consideration. In this paper, we propose a control mechanism consisting of two parts: finite-path-dependent state feedback controller design with which uniform stability of MJLSs can be ensured, and mode feedback control which aims to decrease system cost. Differing from the traditional state/output feedback controller design, the main novelty is that the proposed control mechanism not only guarantees system stability, but also decreases system cost effectively by adjusting the occurrence probability of system modes. The effectiveness of the proposed mechanism is illustrated via numerical examples.

A corridor-based flight mode transition strategy for agile ducted-fan tail-sitter UAV:Altitude-hold transition

As an attractive transition approach,the altitude-hold transition is a special type of super-maneuvering and the vertical/horizontal flight mode transition that an agile aircraft conducts at fixed altitude.However,it is still challenging to implement an autonomous control of the altitude-hold transition while the existing optimal transition planning methods cannot avoid an evident altitude change during the transition process.This paper proposes a corridor-based flight mode transition strategy and presents a successful flight demonstration of the altitude-hold transition on a small ducted-fan tail-sitter unmanned aerial vehicle.In the proposed corridor-based methodology,we model and analyze the transition corridor,concentrate on the dynamic characteristics of the altitude-hold transition,and emphasize that a valid transition trajectory should be governed by its transition corridor.The identified transition corridor reveals that for a given velocity trajectory,the solution for the corresponding trajectories of pitch angle and thrust is unique.Based on this,the transition trajectory generation problem is addressed simply on the velocity-acceleration plane.Furthermore,a proper flight control scheme is devised to track the generated transition trajectories.Finally,the effectiveness of the proposed method is verified through practical flight tests,in which the altitude change is less than 1.1 m during the entire transition course.

Gain self-scheduled H_∞ control for morphing aircraft in the wing transition process based on an LPV model

This article investigates gain self-scheduled H 1 robust control system design for a tailless fold- ing-wing morphing aircraft in the wing shape varying process. During the wing morphing phase, the aircraft＇s dynamic response will be governed by time-varying aerodynamic forces and moments. Nonlinear dynamic equations of the morphing aircraft are linearized by using Jacobian linearization approach, and a linear parameter varying （LPV） model of the morphing aircraft in wing folding is obtained. A multi-loop controller for the morphing aircraft is formulated to guarantee stability for the wing shape transition process. The proposed controller uses a set of inner-loop gains to provide stability using classical techniques, whereas a gain self-scheduled H 1 outer-loop controller is devised to guarantee a specific level of robust stability and performance for the time-varying dynamics. The closed-loop simulations show that speed and altitude vary slightly during the whole wing folding process, and they converge rapidly after the process ends. This proves that the gain self-scheduled H 1 robust controller can guarantee a satisfactory dynamic performance for the morphing aircraft during the whole wing shape transition process. Finally, the flight control system＇s robustness for the wing folding process is verified according to uncertainties of the aerodynamic parameters in the nonlinear model.

Effect of the coordinated reset stimulations on controlling absence seizure

Based on a macroscopic mean-field model associating with the thalamus and cerebral cortex, we investigate how the newly proposed coordinated reset stimulation(CRS) strategy controls the absence seizures as some key parameters are changed.Different from the previous stimulation processes, CRS represents the intermittent pulse current administered to different structures including cortex, specific relay nuclei(SRN) and thalamus reticular nucleus(TRN) at different time by using three different micro-electrodes. In particular, we first simulate a typical absence epilepsy activity under the combined effect of the coupling strength between inhibitory interneurons(IIN)-excitatory pyramidal neurons(EPN) and EPN-TRN pathway. And then we explore the control mechanism of different parameters of 3:2 ON-OFF CRS on spike and slow-wave discharges(SWDs)region. Through analyzing the corresponding two-dimensional bifurcation diagrams, we find CRS is effective on controlling absence seizures in proper ranges of stimulation parameters. Especially, the combination of frequency and positive input duration can inhibit the pathological area more effectively. The obtained results might be helpful to study the pathophysiology mechanism of epilepsy, although the CRS's feasibility still needs further exploration in clinical experiments.