Discrete Model Reference Adaptive Control for Gimbal Servosystem of Control Moment Gyro with Harmonic Drive

The double-gimbal control moment gyro (DGCMG) demands that the gimbal servosystem should have fast response and small overshoot. But due to the low and nonlinear torsional stiffness of harmonic drive, the gimbal servo-system has poor dynamic performance with large overshoot and low bandwidth. In order to improve the dynamic performance of gimbal servo-system, a model reference adaptive control (MRAC) law is introduced in this paper. The model of DGCMG gimbal servo-system with harmonic drive is established, and the adaptive control law based on POPOV super stable theory is designed. The MATLAB simulation results are provided to verify the effectiveness of the proposed control algorithm. The experimental results indicate that the MRAC could increase the bandwidth of gimbal servo-system to 3 Hz and improve the dynamic performance with small overshoot

A Comparative Study on the Hydrodynamic-Energy Loss Characteristics between a Ducted Turbine and a Shaftless Ducted Turbine

The shaftless ducted turbine (abbreviated as SDT), as an extraordinary innovation in tidal current power generation applications, has many advantages, and a wide application prospect. The structure of an SDT resembles a ducted turbine (abbreviated as DT), as both contain blades and a duct. However, there are some structural differences between a DT and a SDT, which can cause significant discrepancy in the hydrodynamic characteristics and flow features. The present work compares the detailed hydrodynamic-energy loss characteristics of a DT and a SDT by means of computational fluid dynamics (CFD), performed by solving the 3D steady incompressible Reynolds-averaged Navier-Stokes (RANS) equations in combination with the Menter’s Shear Stress Transport (SST k−ω) turbulence model and entropy production model. The results show the SDT features a higher power level at low tip speed ratio (TSR) and a potential reduction in potential flow resistance and disturbance with respect to the DT. Moreover, a detail entropy production analysis shows the energy loss is closely related to the flow separation and the reverse flow, and other negative flow factors. The entropy production of the SDT is lessened than that of the DT at different TSR. Unlike the DT, the SDT allows a large mass flow of water to leak through the open-center structure, which plays an important role in improving the wake structure and avoiding the negative flow along the central axis

Cloud-Based Fault Tolerant Control for a DC Motor System

The fault tolerant control problem for a DC motor system is investigated in a cloud environment. Packet dropout phenomenon introduced by the limited-capacity communication channel is considered. Actuator faults are taken into consideration and fault diagnosis and fault tolerant control methods towards actuator faults are proposed to enhance the reliability of the whole cloud-based DC motor system. The fault diagnosis unit is then established with purpose of obtaining fault information. When the actuator fault is detected by comparing the residual signal with a predefined threshold, a residual matching approach is utilized to locate the fault. The fault can be further estimated by a least-squares filter. Based on the fault estimation, a fault tolerant controller is designed to guarantee the stability as well as the control performance of the DC motor system. Simulation result on a DC motor system shows the efficiency of the fault tolerant control method proposed in this paper

Cloud-Based Fault Tolerant Control for a DC Motor System

The fault tolerant control problem for a DC motor system is investigated in a cloud environment. Packet dropout phenomenon introduced by the limited-capacity communication channel is considered. Actuator faults are taken into consideration and fault diagnosis and fault tolerant control methods towards actuator faults are proposed to enhance the reliability of the whole cloud-based DC motor system. The fault diagnosis unit is then established with purpose of obtaining fault information. When the actuator fault is detected by comparing the residual signal with a predefined threshold, a residual matching approach is utilized to locate the fault. The fault can be further estimated by a least-squares filter. Based on the fault estimation, a fault tolerant controller is designed to guarantee the stability as well as the control performance of the DC motor system. Simulation result on a DC motor system shows the efficiency of the fault tolerant control method proposed in this paper

Influence of Li3V2(PO4)(3) complexing on the performance of LiMnPO4 based materials utilized in lithium ion battery

LiMnPO4/C, LiMn0.8Fe0.2PO4/C, and corresponding composites with nominal formula of 0.8LiMnPO(4) center dot 0.2Li(3)V(2)(PO4)(3)/C and 0.8LiMn(0.8)-Fe0.2PO4 center dot 0.2Li(3)V(2)(PO4)(3)/C are synthesized via high temperature solid-state reaction. According to refinement results, the phase ratios of olivine and NASICON in 0.8LiMnPO(4) center dot 0.2Li(3)V(2)(PO4)(3)/C and 0.8LiMn(0.8)Fe(0.2)PO(4) center dot 0.2Li(3)V(2)(PO4)(3)/C are 84.2:15.8 and 81.2: 18.8, respectively. Complexing Li3V2(PO4)(3) plays negligible influence on discharge capacity when cycled between 2.5 and 4.4 V vs. Li+/Li. Instead, this strategy significant improves the rate capability of phosphate composites. The discharge capacities of composites at 2 C are 103.8 and 117.6 mA h g(-1) which are much higher than those of corresponding olivine counterparts, namely 35.3 and 91.1 mA h g(-1) (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved