Papers by Author: Xiao Fen Yu

Abstract: Location information is the most important for wireless sensor network (WSN). Due to the limitation of energy, cost and influence of environment, range-free localization schemes are more suitable for WSN despite of their low localization accuracy. Two methods, which are improved grids SCAN and multiple locating and averaging scheme, are presented to improve localization accuracy of range-free localization schemes and performed through performance evaluation based on ROCRSSI (Ring Overlapping based on Comparison of Received Signal Strength Indicator). By simulation it is concluded that ROCRSSI applying both methods can get better localization performances.

Abstract: A 6-DOF monolithic nanopositioning stage is developed for three coordinate measuring machines (CMM) with nanometer resolution. The stage consists of a monolithic flexure hinge mechanism, six piezoelectric actuators and six fiber-optic displacement sensors. A mathematical model of the constraint optimization problem is presented. Based on the solution of the optimization problem, the final design of the 6-DOF stage is also presented. The numerical analysis on static and dynamic behavior of the stage is done by using the finite element method. The experimental results of the performance of the 6-DOF stage are presented.

Abstract: The piezoelectric actuator demonstrates superior characteristics of high displacement resolution, miniature size, high-frequency response, strong power, no generate heat etc, So it is used in nano systems widely. But its inherent hysteresis, creep and non-linearity affect positioning accuracy seriously. In this paper, through the investigative experiment of a large travel piezoelectric actuator worktable’s creep characteristics, creep characteristic curve and the rules of the piezoelectric actuator creep were found. Based on the rules of the piezoelectric actuator creep characteristics, the piezoelectric actuator creep resistance driving method of two-level reversely applied voltage could remarkably reduce the creep error of system, namely, applying stepped voltage reversely according to two stages. The experiments show that the creep error of the system has been reduced from 3.80% to 0.26%, the period of creep tends to be stable, and also has been shortened within 10 seconds. This driving method make the quick and precise piezoelectric actuator positioning control with large displacement become possible. It also provides further scientific method to amend and reduce the creep effect of piezoelectric actuator, and improves the positioning accuracy of the system.

Abstract: So-called PV value can reflect the synthetic using performance of sliding bearings and the limit pressure of the lubricant. The newly developed multifunctional tester was introduced in this paper for investigating the PV limit values of bearings, in which the speed spectrum and load spectrum were first timely introduced to simulate the bearings' actual working conditions. In this test-bed, four samples, i.e., four friction couples can be dynamically and synchronously tested and measured. The developed measurement and control software based on object –oriented language has the functions of data collecting, processing, alarming and controlling etc. In the system, several measures have been taken to resist electromagnetism disturbances in both hardware and software parts. The disturbance signals have been effectively screened and restrained, so as to the stability and precision of the tested data have been greatly improved.

Abstract: The system bases on the theory of rolling-wheel to measure large diameter, by applying double counters to record the round grating’s signal and using the method of three rolling-wheels paralleling data acquisition, redundancy measurement and error amendment and so on, realizes the measurement of large axis workpieces’ diameter with high precision in on-line and dynamic condition. The experiment shows that the system can achieve the on-line dynamic measurement precision in m D µ 5 at the range of the diameter m m D 5 ~ 1 = complexly combining hardware and soft under the relevant control methods.

Abstract: This paper has developed the bimodal USM a novel actuation pattern, which can actuate the bimodal USM in nanometer magnitude with single actuation pattern instead of combination control of AC actuation pattern, pulse actuation pattern and DC actuation pattern. The novel actuation pattern utilizes a single chip micro-computer to produce a kind of wavelet actuation unit which contains several sine voltage waves with different amplitudes, each wavelet actuation unit is exerted on bimodal USM according to the instruction, by which the step control is obtained. Across the two electrodes of bimodal USM, the differential wavelet actuation voltages are applied to reduce the moving distance of each actuation step, thus the nanometer magnitude actuation sensitivity is achieved. The grating is used as position sensor and the subdivision formulae of mutual compensation functions are adopted to promote the real-time response. The experiment indicated that, with the novel wavelet differential actuation pattern, the actuation characteristic of bimodal USM was improved, the micro-nanometer positioning control was easy to be implemented and the important positioning control parameters under every different actuation conditions could be obtained through the study in the process of actuation.