Urgent Technical Problem Research Articles

Online monitoring device of disc cutter wear – Design and field test

The disc cutter is the main rock cutting tool of a tunnel boring machine (TBM), and its wear directly affects the cutter change decision. Therefore, real-time monitoring of disc cutter wear has become an urgent technical problem for boring machines. In this study, an online monitoring system based on an eddy current sensor is designed to monitor disc cutter wear in real time. The effects of three types of rock and muddy water mixture on the measurement data are compared. Results show that measuring the eddy current distance can solve the problem of inaccurate measurement after the disc cutter is covered by rocks. Besides, the error data of this method in measuring disc cutter wear are analyzed. A function test is performed for similar disc cutters on a multi-function disc cutter performance test bench, and a real-time continuous test is conducted for the wear of two disc cutters in a certain TBM project. With a comparison of monitored and measured results, it shows that the error is less than 1 mm, which indicates that the system exhibits stable transmission and high accuracy in measurement and meets engineering requirements.

Development of on-line rotational speed monitor system of TBM disc cutter

Disc cutter is the main rock breaking tool of TBM. It is angled worn frequently because of locked-rotor; as a result, monitoring relevant operating parameters of TBM disc cutter has become an urgent technical problem. This paper studies nondestructive and non-contact online detection disc cutter rotational speed method of based on eddy current sensor: applies eddy current sensor to detecting six 2mm-high metal bumps setting on the disc cutter, so as to detect the rotational speed of disc cutter. K60 MCU is applied as the main control core. The experimental results show that the on-line rotational speed monitor system of disc cutter features high anti-jamming ability and is reliable.

Eliminating Vertical Stripe Defects on Silicon Steel Surface by L1/2 Regularization

The vertical stripe defects on silicon steel surface seriously affect the appearance and electromagnetic properties of silicon steel products. Eliminating such defects is adifficult and urgent technical problem. This paper investigates the relationship between the defects and their influence factors by classification methods. However, when the common classification methods are used in the problem, we cannot obtain a classifier with high accuracy. Byanalysis of the data set, we find that it is imbalanced and inconsistent. Because the common classification methods are based on accuracy‐maximization criterion, they are not applicable to imbalanced and inconsistent data set. Thus, we propose asupport‐degree‐maximization criterion and anovel cost‐sensitive loss function and also establish an improved L1/2 regularization approach for solution of the problem. Moreover, by employing reweighted iteration gradient boosting algorithm, we obtain a linear classifier with a high support degree. Through analyzing the classifier, we formulate a rule under which the silicon steel vertical stripe defects do not occur in the existing production environment. By applying the proposed rule to 50TW600 silicon steel production, the vertical stripe defects of the silicon steel products have been greatly decreased.

Review of Coupled Vibration Problems in EMS Maglev Vehicles

(Received 14 April 2009; revised 28 January 2010; accepted 5 November 2009) The maglev train is a new type of guideway transportation for both long distance and urban applications in the 21 century. Recent progress in maglev technology indicates a probability of widespread commercial application of maglev systems in the near future. However, some economic and technical issues remain to be solved before the commercial application, and the vehicle-guideway coupled vibration problem is the most urgent technical problem that needs to be solved. In this article, the maglev vehicle-guideway coupled vibration problem, especially for the EMS system, is presented and divided into three main areas: the stationary vehicle-guideway, self-excited vibration; the moving vehicle-bridge coupled vibration; and the vehicle-guideway interaction caused by track irregularity. The available literature relevant to all the three coupled vibration problems is reviewed here, and the methodologies and main conclusions corresponding to each coupled vibration problem are compared and generalized as a reference for future work. The solutions proposed in the literature aiming to solve the coupled vibration problems are also enumerated, and their feasibility is discussed. Finally, work still required to solve the remaining problems is identified, and some suggestions for future research aimed at solving these remaining problems are provided.