Applied Mechanics and Materials Vols. 278-280

Abstract: Ultra-low frequency vibrations are ordinary physical phenomena, and absolute vibrant sensors are usually used to detect them. The author presents a method that using magnetoelectric speed sensor to detect ultra-low frequency vibrations. With cascade correcting circuit, the lowest frequency that can be measured will be less than 0.5Hz while the best damping is maintained. The author has systematically analyzed the correcting circuit, transfer function, theory of operation, and the difference between output characteristics before and after correcting to the ultra-low frequency sensor.

Abstract: In view of the difficulties caused by determining threshold for analog circuits test, a method based on principal component analysis (PCA) of node voltages was proposed to overcome these difficulties. At first, the principal component model of fault-free circuits was constructed. Then the circuits-under-test was compared with the principal component model to calculate the statistic for fault detection. The proposed method was used to test the output signal amplifying circuit, which is used in the ultrasonic liquid sensor. The testing results show that the PCA based method has a higher sensitivity than other test methods. And the proposed method can overcome the difficulties in determining threshold by the expert’s empirical knowledge. These make it a suitable candidate for analog circuits test.

Abstract: Radar sensors like ultra-wideband Doppler radar sensors may be utilized as a vibration sensing device in a restricted area for railroad monitoring. As long as something or someone enters the restricted area, the alert signals will be sent to the control center or train driver to stop the moving train and prevent accidents. Combining with visual monitor system, the radar sensors may compensate for the insufficient information under poor lighting, fogging, or raining environment. The simulations and experimental results supported its feasibility in a railroad system. The feasibility of further radar application is also discussed.

Abstract: A parameter monitoring and control system is designed in this paper. Hardware is composed of the on-site data acquisition model and remotely display and operating model, which communicated through wireless technology. It monitors the aquaculture parameters (including temperature, PH and dissolved oxygen (DO) concentration) on-line, and water pump or air blower are controlled depended on the value of the parameters. Software is designed respectively for each model, temperature compensation is used in the control system. Experiments show that monitoring and control system for aquaculture had excellent effect, it could reduce investment and human capital in aquaculture production.

Abstract: This paper describes a structure design of sensor bearing based on Hall element, the bearing by a Hall sensor and deep groove ball bearing, can measure speed of rotation, direction of rotation and acceleration signal etc. And with the Swedish SKF sensing bearing are compared, analyzes the bearing performance characteristics.

Abstract: A machine vision system was developed to investigate the detection of watermelon seeds exterior quality. The main characteristics of watermelon seeds appearance including area, perimeter, roughness and minimum enclosing rectangle were calculated by image analysis. Least square support vector machine optimized by genetic algorithm was applied for the classification of watermelon seeds exterior quality, and the broken seeds, normal seeds and high-quality seeds were distinguished finally. The surface irregularities defects of watermelon seeds were detected by machine vision grid laser. The experimental results show that the watermelon seeds exterior quality could be well detected and classified by machine vision based on least squares support vector machine.

Abstract: The objective of this work was to discuss a calculation method of dye concentration in mixed dye bath, to develop an optical fibre sensing system for in-situ monitoring of dye concentrations in a dye bath and control the rate of exhaustion to ensure that the dyeing process yields the desired product. A designed optical fibre sensing system was proved to be practicable to measure the single dye concentration accurately, it is important to chance right calculation method in measuring mixed dye bath concentration. The experiment prepared known concentration mixture with reactive red 2G and yellow 4G. Based on measured absorption spectra, dyes concentrations were calculated by derivative ratio method. The calculated results were compared with the prepared concentrations. The accuracy was discussed. The results show that calculated dyes concentration by derivative ratio method well matched the prepared value at the certain concentration range.

Abstract: Lumped and distributed dynamic/static models of constant temperature hot-wire probe are established according to heat balance principle. Dynamic and static characteristics of hot-wire probe are analyzed in terms of hot-wire probe sizes, control circuit parameters and flow velocity.Simulation results show that reliability and stability of the hot-wire probe depend on bias voltage.The dynamic and static characteristics of hot-wire probe refly on the ratio of length to diameter ratio crucially.Once the ratio exceeds 300, heat conduction terminal loss can be ignored. When over-heating ratio of hot- wire or flow velocity increases, heat conduction terminal loss can be omitted as well .Besides frequency response of hot-wire probe can be improved simultaneously.The above conclusions can provide guidance in the improved design for hot-wire probe and its control-circuits.

Abstract: In experiments of mechanical movement in outer space, maglev technology is used for simulating the weightless environment. Maglev rotor moves along a linear guide way. In the process of motion, eddy current sensors are needed for detecting the displacement between sensor and metal guide way. Because of the length requirement of guide way, splicing technique is used. This technique leads to the crack on detective surface and also the distortion of sensor signal. By the means of mathematical model analysis and finite element method, the rules of sensor signal are found out and verified by experiment. The results show that optimal crack width can weaken the distortion of sensor signal.

Abstract: In this paper, the real-time defects inspection was implemented via use of paralleled structure and high-speed operation of FPGA. The hardware circuit based on FPGA was established. According to signal characteristics of polymeric film defects, the preprocessing scheme of defect images based on FPGA was designed. The defect data were packed according to the defined format. Data processed were transferred to PC through USB2.0 real-timely to reconstruct defect microscopic images. The quantity of transferred data was decreased tremendously by this method. The inspecting speed was greatly improved.