Applied Mechanics and Materials Vols. 16-19

Abstract: The standard of OSEK/VDX which used in the embedded operating system of car was analysized, and based on this, to select the open-source real-time operating system μC/OS-II as a operation system that will be loaded in the control chip. After that the kernel structure of the μC/OS-II was analysized, and modified the kernel of the system in accordance with OSEK/VDX standards, then translated the μC/OS-II system to the LPC2131 development board for the follow-up application development laid the foundation.

Abstract: This paper presents a method for drill wear state monitoring based on recognizing the cutting torque signals. It consists of two steps: firstly, decompose cutting torque components from the original signals by Wavelet Packet Decomposition (WPD); secondly, extracting wavelet coefficients of different wear states (i.e., slight, normal, or severe wear) with signal features adapting to Welch spectrum. The experiments on different tool wears of the multivariable features the results of Monitoring are significant and effective.

Abstract: Develops a finite element model to analyze the dynamic/static sensitivities of a certain white bodywork, i.e., the sensitivities of its bodywork’s natural frequency, torsional stiffness and flexural rigidity and mass to the thickness of sheet to make the bodywork, thus finding out the main parts affecting greatly the dynamic and static characteristics of bodywork to optimize its structure design. According to the sizes of contribution the body mass will make to the natural frequency and torsional stiffness and flexural rigidity, an optimal conceptual design is given. This method provides an important reference for improving the dynamic performance of bodywork, lightening its weight and optimizing its design.

Abstract: It is important to study system vibration characteristics for improving product quality and insuring safety operation of machine. In this paper, dynamics of rotor systems are studied in a large centrifugal compressor. The models of subsystems, such as coupling and bearing, are established by appropriate simplification. The finite element model of rotors is set up by taking interrelation of these subsystems into account. The unbalance responses and system stability are analyzed for overall unit and single cylinder. The results show that the critical speed and journal amplitude at working speed in the overall unit are greater than those of low pressure cylinder. The conclusion will provide guidance to compressor rotor system design.

Abstract: A bio-etching method using Thiobacillus ferrooxidans (T.f.) for processing micro-gear has been developed. The principle of bio-etching method is that certain microorganisms in nature consume some metal ions to be energy during their growth. The strain of Thiobacillus ferrooxidans consume elemental ferric and cooper ions as its energy source, so T.f. is selected as bio-etching tool, Leathen culture medium is selected as culture medium of T.f., and the thin copper sheet is used as the processed material. During the micro-gear is processed, firstly, thin copper sheet of 0.05mm is cleaned in the acid liquid and some materials such as dirt and grease are cleaned away, then, the anti-erode film is applied to the surface of thin copper sheet, then the surface of thin copper sheet is irradiated by ultraviolet under the condition that the surface is covered by mask film and developed, the anti-erode film that not covered by mask film will be dissolved and cleaned away, after that, thin copper sheet is put into the T.f. liquid and agitating, after the 3h, micro-gear is obtained. The result is showed that micro-gear can be processed by bio-etching method.

Abstract: The manufacturing template of whole impeller 5-axis machining based on UG was re-developed with NURBS interpolation principle and UG/knowledge fusion technology, and 5-axis NC machine and part model were established, each parts of machine were simulated in 3D motion with reading NC code. Human-computer interaction was processed fast with the template and guiding of digitized manufacturing, the cutting tracks of half-finishing machining and finishing machining for whole impeller were produced fast. The template involves 3-D modeling, craft flow programming of NC machining, program of NC machining and etc. and is tested on 5-axis NC machine, it is indicated that the scheme and program of NC machining for whole impeller is feasible.

Abstract: Contact-connection matrix is proposed to describe contact and connection relations between components. Extended interference matrix is given to settle non-orthogonal assembly problems effectively which other current methods are incapable of. Several rules that influence the efficiency of assembly are studied from the quantification point of view. The priorities of the rules can be customized to screen optimum components in every cyclic process to comprise an optimized sequence automatically, using the above matrices. The prototype system is developed on UG NX platform and a fixture with 30 parts containing tilt assembly directions is demonstrated as an example. The results indicate that the algorithm is efficient and flexible.

Abstract: The classical PID controller is based on the concrete model of the object and is only suitable for the design of linear control system. Step servo system is a typical nonlinear system, so the intelligent control strategies should be adopted. In this paper an approximate model of the step motor is presented, a compound fuzzy PI controller is designed to fulfill the control of the step motor, and is successfully applied to the automatic control the scanning device of eddy current nondestructive testing (ECNDT). The proposed controller is robust to load torques, cogging forces, and other disturbances. The fuzzy PI controller also guarantees asymptotic stabilization and possesses better dynamic performance compared with the traditional PID control algorithm. The simulation study and an experimental validation carried out on the automatic control system of the scanning device confirmed the suitability of the proposed approach.

Abstract: Although the traditional PID controller is widely used in many practical application fields, it’s unsuitable for the control of the complex plant. The powder metallurgy sintering process had such characteristics as nonlinearity and large delay, etc., and it’s difficult for the conventional PID controller to meet the control requirements. According to these traits, we used a parameter self-adjusting fuzzy controller to control the heating temperature of the vacuum sintering furnace. In practice it shows that every quality index and control effect of this scheme is better than that of traditional PID controller.

Abstract: Although the traditional PID controller is widely used in many fields, the system parameters varying and external disturbances existing in the DC servo system will cause large overshoot or poor stability. To improve the performance of the PID controller, a compound servo control system combining the conventional PID control and the fuzzy control is presented to meet the demand of a vehicular antenna servo system in this paper. Incorporating the fuzzy control and the conventional PID control, this paper presents a design method of the fuzzy PID controller that is based on the fuzzy tuning rules and formed by integrating two above control ideas. Simulation results are presented to show the efficiency of the proposed controller. The practical control effect shows that the control system that adopts the fuzzy PID controller has better performance than that of the traditional PID control system, and meets the performance requirements of the servo system.