Papers by Author: Zi Chen Chen

Abstract: Wireless sensors are increasingly adopted in mechanical systems to acquire and wirelessly transmit sensed information for machine condition monitoring. For wireless sensors on spindle, the reliability of the sensors system at high rotary speed is the key factor to guarantee the validity of monitoring. How to identify sensor failure accurately and timely is essential to enhance reliability of monitoring system. To address this issue, a novel method based on the BNs was presented to distinguish sensor failure from other transmission errors. The method described causal relationships of factors inducing sensor failure by graph theory and deduced sensor failure by Bayesian statistical techniques. Experiments carried on NC machining center prove the validity of this approach.

Abstract: To decrease the thermal error in the machining of high speed machine tools, a new design idea based on the cellular metal structures was proposed. With forced convection in cellular metals, the heat generated in machining will be dissipated and the machining precision can be guaranteed. The thermal property of machine slides using 2D rectangle cellular structures was studied with theoretical analyses and numerical simulation. The theoretical predictions are in good agreement with the finite element simulation results. The overall heat transfer coefficient and the thermal performance were acquired with the volume-averaging method and the relationships between the cellular porosity, cellular sizes and the thermal performance were discussed. The analyzed results show that the maximum thermal performance can be got when the cellular porosity equals about 0.85 and with the increase of cellular sizes, the thermal performance decreases.

Abstract: To describe the modular structure of numerical control (NC) system and deal with the problem of interference between modules in software reliability analysis, a module dependency graph (MDG) was presented and a scenario-based scheme was proposed. MDG describes reliability of module in different application environment, module dependency and structure of software with establishing maps among modules, execution scenarios and reliability. According to the information shown in MDG, an algorithm based on the idea of traversing directed graph in graph theory was proposed. The algorithm calculates the reliability of scenario with breadth-first principle. The reliability of system could be obtained from reliability and running frequency of scenario. The scheme eliminates the defects of the conventional methods which ignore module correlation. Case study proves the scheme could evaluate the reliability of NC software effectively.

Abstract: The proposed Axis-based Look-ahead NURBS Interpolator (ALANI) strictly confines the component acceleration and jerk at each axis during every interpolating period based on the mechanics of the machine tools, so that the acceleration and jerk at axes can not exceed the limit in order to avoid immoderate vibrations and shocks. Contour precision is also strictly guaranteed while interpolating. The interpolator can trace back and recalculate previous data if necessary after forwards calculation and verification. And the recalculation algorithm is able to choose optimized machining parameters to attain high efficiency. The introduction of ALANI and simulation experiment is present in this paper.