Implicit fault-tolerant control: application to induction motors

In this paper we propose an innovative way of dealing with the design of fault-tolerant control systems. We show how the nonlinear output regulation theory can be successfully adopted in order to design a regulator able to offset the effect of all possible faults which can occur and, in doing so, also to detect and isolate the occurred fault. The regulator is designed by embedding the (possible nonlinear) internal model of the fault. This idea is applied to the design of a fault-tolerant controller for induction motors in presence of both rotor and stator mechanical faults.     

基于PLC的感应淬火数控系统设计

简要介绍了淬火机床的工作原理,利用PLC实现了感应淬火机床专用数控系统,并给出了系统的硬件设计,同时详细介绍了位置控制、手动操作、脉冲补偿、参数设置与显示、急停等程序设计.     

Predicting the effects of material properties gradient and residual stresses on the bending fatigue strength of induction hardened aeronautical gears

This paper proposes an experimental methodology to characterize complex parts presenting various gradients using aeronautical induction surface hardened spur gears. A 3D fatigue model taking into account residual stresses, microstructure variations, and surface roughness is then proposed for the prediction of the bending endurance limit. The model is based on the well-known Crossland criterion; calibrated with representative axial and torsion laboratory specimens. The results are compared with testing performed on a custom-made single tooth bending fatigue (STBF) rig. Fracture surface analysis using electronic microscopy is used to investigate the crack initiation sites. It is shown that residual stresses can have a significant impact on bending fatigue and that two induction treatments can present very different fatigue resistance even if the shape and depth of the hardened layer is identical in the root. The proposed methodology could be adapted to other geometries and surface treatments.     

电加热实现过盈配合的工艺改进

介绍一种投资少、简单实用、低耗清洁、适合多部位和不同部件使用的小型加热盘——电加热工艺法。解决了形状特异、大而重的金属件加热处理后,在热胀冷缩状态下,满足过盈配合的需要。通过工艺改进与传统方法对比、分析,阐述了在机械制造领域中的应用效果。     

Fuzzy logic speed controller optimization approach for induction motor drive using backtracking search algorithm

This paper presents an adaptive fuzzy logic controller (FLC) design technique for controlling an induction motor speed drive using backtracking search algorithm (BSA). This technique avoids the exhaustive traditional trial-and-error procedure for obtaining membership functions (MFs). The generated adaptive MFs are implemented in speed controller design for input and output based on the evaluation results of the fitness function formulated by the BSA. In this paper, the mean absolute error (MAE) of the rotor speed response for three phase induction motor (TIM) is used as a fitness function. An optimal BSA-based FLC (BSAF) fitness function is also employed to tune and minimize the MAE to improve the performance of the TIM in terms of changes in speed and torque. Moreover, the measurement of the real TIM parameters via three practical tests is used for simulation the TIM. Results obtained from the BSAF are compared with those obtained through gravitational search algorithm (GSA) and particle swarm optimization (PSO) to validate the developed controller. Design procedure and accuracy of the develop FLC are illustrated and investigated via simulation tests for TIM in a MATLAB/Simulink environment. Results show that the BSAF controller is better than the GSA and PSO controllers in all tested cases in terms of damping capability, and transient response under different mechanical loads and speeds.     

Inactivation kinetics for Salmonella Enteritidis in potato omelet using microwave heating treatments

The aim of this study was to model the inactivation of Salmonella enterica serovar Enteritidis in pasteurized omelet internally inoculated at different microwave heating treatments (300 W; 450 W, 600 W and 800 W). Results indicated a non significant change in Salmonella populations during the first 30 s treatment at 300 W and 450 W, being log reductions lower than 0.5 log CFU g⁻¹. However, after 40 s treatment, log reductions had risen to 4.8 log CFU g⁻¹ at 800 W. Inactivation rates were higher at 600 W and 800 W (0.67 and 0.63 s⁻¹) than at 300 W and 450 W (<0.34 s⁻¹). The temperature-dependent parameters of a Weibull model obtained by Mattick, Legan, Humphrey & Peleg (2001) were evaluated. It was concluded that combinations characterized by a temperature equal or above 70 °C ensured a minimum 4 log reduction of Salmonella population (i.e. 300 W-80 s; 450 W-60 s or 600 W/800 W-40 s). These results may be of value in food service establishments, as target treatments for microwavable potato omelet portions.     

Analytical study on optimal distribution of heating power in hyperthermia

In this paper we have investigated analytically optimal distribution of time dependent heating power Q₂(t)(W/m²) in a system, described by bio-heat equation in a multilayered tissue, consisting of skin, fat, muscle and tumor layers, so as to attain a beneficial desired temperature χ^? across the entire length of the tumor. The desired temperature of the tumor is achieved at the end of time of operation of the process when the surface cooling temperature is taken as constant. The spatial heating power per unit volume Q₁(x,t)(W/m³) is constructed according to the well known Beer's Law [1], given by, Q₁(x,t) = βe^− βxQ₂(t) when β is scattering coefficient.     

Closed loop torque SVM-DTC based on robust super twisting speed controller for induction motor drive with efficiency optimization

This paper presents a space vector modulation (SVM) based Direct Torque Control strategy (DTC) for induction motor (IM) in order to overcome the drawbacks of the classical DTC. SVM can reduce the high torque and flux ripples by preserving a fixed switching frequency. This technique is known by the closed loop torque SVM-DTC. Moreover, the control scheme performance is improved by inserting a second order sliding mode super twisting controller in the outer loop for speed regulation. This nonlinear technique ensures a good dynamic and high robustness against external disturbance. Furthermore, the IM energy optimization is treated in the second objective of this paper. A proposed model based loss minimization strategy is presented for efficiency optimization. This strategy chooses an optimal flux magnitude for each applied load torque. The proposed optimized SVM-DTC algorithm will be investigated by simulation and real time implementation using Matlab/Simulink with real time interface based on dSpace 1104 signal card.     

基于Ansoft12的感应电机参数化及其瞬态仿真

应用有限元分析软件Ansoft12,对感应电机进行了建模,并进行了参数化与动态仿真。结果显示可以为感应电机本体的理论研究及其控制系统的优化设计提供参考。     

Impact of compression,physical aging,and freezing rate on the crystallization characteristics of an amorphous sugar matrix

Amorphous matrices made up of sugar molecules, are frequently used in food and pharmaceutical industries. A drawback to their use is that they are susceptible to collapse, as a result of water uptake and an increase in temperature and subsequently crystallize. Herein, the crystallization characteristics of amorphous sugar (sucrose and α-lactose) preparations were analyzed, with the purpose of obtaining knowledge that could lead to the prediction of how long the amorphous state is retained under various conditions. The impact of compression, physical aging and freezing rate on the induction period (t_ind) for crystallization were examined. Freeze-dried sugar samples were compressed at 74 or 443 MPa (5 min) and then rehumidified at specified RHs. Some freeze-dried sucrose samples were physically aged, and alternatively freeze-drying was conducted under different conditions. The isothermal crystallization of the prepared samples at different temperatures (T), the glass transition and the crystallization temperature (T_cry) were measured, using differential scanning calorimetry. The compression markedly decreased the t_ind, while significantly lowered the hygroscopicity. Physical aging and slower-freezing also shortened the t_ind. The t_ind was found to be correlated exclusively with (T_cry–T), regardless of rehumidification, compression, sugar type, physical aging and freezing rate in the freeze-drying process.