Online Accurate Estimation of the Wheel-Rail Adhesion Coefficient and Optimal Adhesion Antiskid Control of Heavy-Haul Electric Locomotives Based on Asymmetric Barrier Lyapunov Function
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This paper proposes a new scheme of online accurate estimation of wheel-rail adhesion coefficient and optimal adhesion antiskid control of heavy-haul electric locomotives (HHEL) based on sliding mode and asymmetric barrier Lyapunov function (ABLF) theory. To achieve optimal adhesion control of the HHEL, it is necessary to precisely estimate the wheel-rail adhesion coefficient. However, the adhesion coefficient is difficult to be measured with a conventional physical sensor. The first novelty of this paper is to design a smart adhesion coefficient sensor based on sliding mode observer (SMO). The perception of the adhesion coefficient is transformed into the observation of load torque of the traction motors, and the wheel-rail adhesion coefficient is further calculated by using the load torque observed value. The HHEL achieves maximum traction from operating in the optimal adhesion point. However, wheel skidding is most likely to occur at this point. According to the changing trend of the adhesive coefficient characteristic curve, the operating state of a locomotive can be divided into two regions: the stable and skid regions. The second novelty of this paper is the adaptation of ABLF to guarantee that the HHEL operated at a stable region and the optimal adhesion antiskid control of HHEL is achieved. Finally, the simulation and experimental results verify the feasibility and effectiveness of the proposed method.Many authors agree that preliminary traction prior to closed or open reduction for congenital dislocation of the hip is helpful. Different ways of traction have been used and each of them has its own advantages and disadvantages. One of the problems in the very young child is the difficulty in maintaining a suitable traction that is biomechanically effective. We found that using a rocker bed made the traction more "user friendly" for the child, the parent and the doctors.
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A new sliding mode (SM) observer-based controller for single-phase induction motor is designed. The proposed control scheme is formulated using block control feedback linearization technique and high-order SM algorithms with measurements of the rotor speed and stator currents. The stability of the complete closed-loop system, including the rotor flux second-order SM observer, is analyzed in the presence of model uncertainty, namely, rotor resistance variation and bounded time-varying load torque.
Observer (physics)
Feedback linearization
Linearization
Wound rotor motor
Machine control
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Aims Good submucosal exposure is a key factor for success during ESD, and can be achieved by different traction devices. Nevertheless, they all provide a fixed amount of traction force that tends to decrease as the dissection progresses. In contrast, the A-TRACT device, tightenable, offers the possibility of increasing traction during the procedure to improve exposure.
Endoscopic submucosal dissection
Tractive force
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In this paper, based on the nonlinear disturbance observer, the model-following sliding mode controller is designed for the UAVs flight control system. First, the nonlinear disturbance observer is designed to observe the disturbance of the system, which converts the observed disturbance into the corresponding input. Then, the advantages of model following and sliding mode control are employed. Through Linear Quadratic Regulator method, the sliding surface is designed to make the sliding mode have good dynamic characteristics and to eliminate the steady state error. The simulations results demonstrate that the UAVs flight control system using the proposed method not only reduces the chattering, but also achieves satisfactory model following performance.
Mode (computer interface)
Observer (physics)
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To define the current application of preliminary traction for congenital dislocation of the hip (CDH), 335 members of the Pediatric Orthopaedic Society were surveyed, with an 87% response rate. Most respondents believe that traction reduces the incidence of avascular necrosis (AVN) and enables easier reduction. Only 5% of those surveyed do not use traction, but it is used more frequently in the Northeastern United States. Home traction, favored by 31% of the respondents, is used longer than hospital traction. Although traction is commonly used, a consensus to use preliminary traction has not been achieved. Practice patterns should not be used to determine effectiveness of a treatment.
Avascular Necrosis
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Multipolar traction is a recent advance in colorectal endoscopic submucosal dissection (ESD) to expose the submucosal field [1] particularly for challenging lesions like residual lesions [2]. Nevertheless, two limitations exist with four-point traction. First, traction tends to reduce as ESD progresses, although new devices that can be stretched during the procedure to increase traction seem promising [3] [4]. Second, systematically placing four traction points is expensive (four clips), time-consuming, and not needed for lesions < 4 cm. For small lesions, two-point adaptive traction seems sufficient, but additional focal traction on the difficult area could help the physician.
Endoscopic submucosal dissection
CLIPS
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Observer (physics)
Mode (computer interface)
Lyapunov stability
SIGNAL (programming language)
State variable
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A nonlinear predictive control (NPC) scheme in a cascaded structure for a permanent magnet synchronous motor drive is proposed. Taylor series expansion is used to predict the system response over a finite horizon. As NPC cannot remove completely the steady-state error in the presence of mismatched parameters and external perturbation, a disturbance observer is used to estimate the offset caused by parametric uncertainties and the load torque variation. In addition, input constraints (restrictions on the magnitude) are considered in the synthesis of the disturbance observer, resulting in an equivalent cascaded proportional integral action with an antiwindup compensator. The validity of the proposed controller was tested via simulation and experiment. Excellent results were obtained with respect to the speed trajectory tracking, stability, and disturbance rejection.
Model Predictive Control
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