This paper proposes two novel hybrid rotors permanent magnet (PM) machines for the high torque density in short duration condition operation. In order to enhance the torque performance, the flux concentrated structure of spoke-type PM is employed to increase the air-gap flux density. Meanwhile, the non-magnetic connector of the rotor is employed to eliminate the magnetic flux leakage. The rotors of the conventional machines and the proposed machines are optimized by the finite element analysis (FEA). Furthermore, based on the comparisons of electromagnetic performances for the optimized machines, including the open-circuit flux density, torque, PM eddy current loss, overload capability, the characteristics of the proposed machines are analyzed. The results indicate that the proposed machine can improve the torque at rated and overload operation with growth rate 14.3% and 13.1%, respectively. Finally, a 12-slots/10-pole PM machine is prototyped and FEA is to be validated.
This paper studies performance recovery problem of a class of uncertain nonaffine strict-feedback systems with mismatched uncertainties. First, the strict-feedback nonaffine system with mismatched system dynamics is transformed into an integrator-chain nonaffine system by a diffeomorphism. Second, the transformed system is converted to an affine one by constructing an auxiliary control input term, and dynamical uncertainties and external disturbances are viewed as total disturbance of the affine system. Then, a two-time-scale active disturbance rejection controller (ADRC) is designed for the transformed affine system. Under some mild assumptions, it can be proved that the proposed ADRC-based closed-loop system can achieve performance recovery and weak performance recovery in different cases of mismatched system dynamics, respectively. Experimental results on a magnetic levitation ball system demonstrate the effectiveness of the proposed control scheme.
Abstract：The study investigates the analytical sidewall stiffness and analytical elastic foundation modeling of a radial tire with a large section ratio for a heavy load vehicle.A proposed tire model with a flexible belt on an elastic analytical stiffness foundation is investigated.the analytical multi-stiffness function of a large section ratio sidewall is derived by combining the membrane feature caused by inflation pressure and the structural deformation caused by sidewall curvature.The experimental and theoretical results indicate the following: ① the bending characteristic of the belt within 0-180 Hz can be featured with the flexible belt on an elastic analytical stiffness foundation tire model.② the multi-stiffness function of the curved sidewall is related to the inflation pressure, structural curvature, and material properties.③ the inflation pressure effects the pre-tension force of the belt and the pre-tension membrane feature of the sidewall.Key words：heavy loaded radial tire；analytical elastic foundation；flexible belt on an elastic analytical stiffness foundation；uniform cross-section
The Large High Altitude Air Shower Observatory (LHAASO) has three sub-arrays, KM2A, WCDA and WFCTA. The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during the thunderstorm on 10 June 2021. The number of shower events that meet the trigger conditions increases significantly in atmospheric electric fields, with maximum fractional increase of 20%. The variations of trigger rates (increases or decreases) are found to be strongly dependent on the primary zenith angle. The flux of secondary particles increases significantly, following a similar trend with that of the shower events. To better understand the observed behavior, Monte Carlo simulations are performed with CORSIKA and G4KM2A (a code based on GEANT4). We find that the experimental data (in saturated negative fields) are in good agreement with simulations, assuming the presence of a uniform upward electric field of 700 V/cm with a thickness of 1500 m in the atmosphere above the observation level. Due to the acceleration/deceleration and deflection by the atmospheric electric field, the number of secondary particles with energy above the detector threshold is modified, resulting in the changes in shower detection rate.
This paper presents linear active disturbance rejection control (LADRC) for a two-degrees-of-freedom (2-DOF) manipulator system to achieve trajectory tracking. The system is widely used in engineering applications and exhibits the characteristics of high nonlinearity, strong coupling, and large uncertainty with two inputs and two outputs. First, the problem of dynamic coupling in the model of the 2-DOF manipulator is addressed by considering the dynamic coupling, model uncertainties, and external disturbances as total disturbances. Second, a linear extended state observer is designed to estimate the total disturbances, while a linear state error feedback control law is designed to compensate these disturbances. The main contribution is that the stability of the closed-loop system with two inputs and two outputs is analyzed, and the relationship between the performance of the closed-loop system and the controller parameters is established. The joint simulation of SolidWorks and Matlab/Simulink is conducted. The simulation and experimental results clearly indicate the superiority of LADRC over the PID for trajectory tracking and dynamic performance.
The vehicle transmission system is a power transmission device between the engine and the wheel load. As the connecting hub of the power system, the travel system and the braking system, it ensures the mobility and safety of special equipment in combat missions. From the four aspects of the transmission system structure composition characteristics, power transmission characteristics, energy flow characteristics and vehicle power characteristics, it is demonstrated that the transmission efficiency is an important technical indicator for evaluating the performance of the transmission system; based on the analysis of the relationship between power loss and transmission efficiency, a global model framework of the power loss of the transmission system is established from the perspective of the generation mechanism and structural characteristics, providing a theoretical basis for the performance characterization of the transmission system; from the three aspects of theoretical numerical research, simulation research and experimental demonstration research of transmission efficiency, the difficulties and key points of the research on the power loss of the vehicle transmission system are discussed, and it is pointed out that the multi-media and multi-parameter coupling simulation analysis and experimental research of large-scale mechanical equipment under complex operating conditions can provide guidance for the performance optimization and health management of vehicle transmission components, and the performance evaluation and matching design of the transmission system; it is expected that the comprehensive transmission efficiency analysis under multiple factors, as well as the coupling research of power loss characteristics, efficiency characteristics and performance degradation characteristics based on intelligent algorithms have practical engineering significance for the performance monitoring and evaluation of large-scale mechanical equipment.
Some gamma-ray bursts (GRBs) have a tera-electron volt (TeV) afterglow, but the early onset of this has not been observed. We report observations with the Large High Altitude Air Shower Observatory (LHAASO) of the bright GRB 221009A, which serendipitously occurred within the instrument's field of view. More than 64,000 photons >0.2 TeV were detected within the first 3000 seconds. The TeV flux began several minutes after the GRB trigger and then rose to a peak ~10 seconds later. This was followed by a decay phase, which became more rapid ~650 seconds after the peak. We interpret the emission using a model of a relativistic jet with half-opening angle of ~0.8°. This is consistent with the core of a structured jet and could explain the high isotropic energy of this GRB.
The paper presents a robust, proximate time-optimal controller for second-order systems. We simplify the ideal switching curve, and prove its stability and proximate time-optimality. To balance time and robustness. Bang-bang control and time-varying sliding mode control are combined and the time optimal control idea is incorporated into the time-varying sliding mode control design. The approach used here to derive the time-varying sliding surface is rarely used before. Simulation results demonstrate the effectiveness and practicality of the proposed controller with near time optimal performance.
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