ENGINEERING NEWS IN BRIEF

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                  ENGINEERING NEWS IN BRIEF
                        E-Mail Newsletter

                               No.56
             Issued by the Asian TOP Panel, August 2006

           The Chinese Mechanical Engineering Society (CMES)
           The Institution of Engineers, Indonesia (PII)
           The Japan Society of Mechanical Engineers (JSME)
           The Korean Society of Mechanical Engineers (KSME)

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    According to the agreement made in the 2nd Asian TOP Panel Meeting,
the ENGINEERING NEWS IN BRIEF (E-mail newsletter) has now been edited
by the CMES for the year 2006.

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[Contents]

(1) Control Strategy About Humanold Robot Stable Locomotion on Uneven
     Ground (Source: CMES)
(2) Multi-objective Decision-making of Materials Selection in Green Design
     (Source: CMES)
(3) Novel Flexible Eddy Current Array Sensor System for Proximity Sensing (Source:      CMES)
(4) Studies on methane hydrates near the sea bottom in the Okhotsk Sea (Source:      JSME)
(5) Development of Multifunctional Machine Tool for Micro-machining (Source: JSME)
(6) Locomotions of A Biped Robot: Static vs. Dynamic Gaits (Source : KSME)
(7) An Experimental Study on Shape Oscillation Mode of Pendant Droplet by an
     Acoustic Wave (Source : KSME)
(8) Development of Small Size Coriolis Mass Flowmeter (Source : KSME)

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(1) Control Strategy About Humanold Robot Stable Locomotion on Uneven Ground

     SHUAI Mei FU Chenglong Beihang University
     YANG Xiangdong CHEN Ken Tsinghua University

Since a humanoid robot tends to tip over easily while walking on uneven terrain, an online regulating control algorithm is proposed based on Kane collision theory, to prevent humanoid robot from tipping over while walking on uneven ground. This regulating algorithm can compute the dynamic model of the robot rapidly, and can estimate the values of the impacting force acting on leg by ground. These data of impacting force can be used to adjust the gait of legs and torso for a humanoid robot to pass over the scraggy obstacle successfully. By using this algorithm, walking simulations of online control on a 5-link humanoid model are performed in the MATLAB/Simulink environment and the effectiveness of the proposed algorithm is illustrated.

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(2) Multi-objective Decision-making of Materials Selection in Green Design

     HUANG Haihong LIU Guangfu LIU Zhifeng Hefei University of Technology

Cost and environmental impact are the two primary objectives for the material selection problem in green design. The quantitative analysis method is presented for the problem with the life cycle concept. The objectives and constraint conditions of the material selection problem are analyzed in green design, and the multi-objective decision-making model is established, which takes material lifecycle cost and lifecycle environmental impact (EI) as the two objective variables, and mechanical and physical properties, recyclability and other qualitative properties as the constraints. The material lifecycle cost is aggregated by the production cost, manufacturing cost and recycling cost. Eco-Indicator'99 is adopted to analyze the holistic lifecycle environmental impact of materials and processes, in order to quantify the decision objective EI. The possible solutions search algorithm (PSSA) is used to pre-select the materials to obtain the feasible solutions, and TOPSIS method is used to acquire the optimal solution. As shown in the reading lamp design case study presented for the materials selection of the reading lamp, the results of the multi-objective decision-making analysis can provide useful design guidelines.

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(3) Novel Flexible Eddy Current Array Sensor System for Proximity Sensing

     CHEN Xianglin DING Tianhuai HUANG Yiping Tsinghua University

Novel proximity eddy current sensor array and its testing system are developed to realize the real-time inspection of the small gaps between large curved surfaces. The flexible sensor probe, manufactured by the flexible printed circuit board (FPCB) process, is designed to consist of a forked coils array with a long flat cable by the investigations to the design, process and substrate materials for the eddy current array. The time division multiplexing (TDM) technology is introduced for the eddy current array to scan and sample all the sensor coils. Some reforms are implemented to the conventional oscillator to solve the problem of the coils having a low Q-factor and improve the performance of the sensor system. Experimental results show that the measurement accuracy of the sensor system can reach ±0.5% for a 2 mm full scale and the sensor system is suitable for online gap measurements.

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(4) Studies on methane hydrates near the sea bottom in the Okhotsk Sea

     Hitoshi SHOJI, Kitami Institute of Technology
     Hirotsugu MINAMI, Kitami Institute of Technology
     Akihiro HACHIKUBO, Kitami Institute of Technology

Gas hydrates are natural gas reservoirs in ice-like crystalline solids, and are stable in pore spaces of submarine sediments in water depths greater than about 500 m. They have been recovered both at larger sub-bottom depths and near the sea bottom. Gas hydrates near the sea bottom are related to the sites of enhanced fluid seepage such as cold seeps. Multidisciplinary field investigations were conducted to understand formation mechanisms of the near-bottom hydrates by scientists from Japan, Russia, Germany, Korea and Belgium offshore Sakhalin, Okhotsk Sea in 2003. Side scan sonar survey revealed seepage structures distributed at the sea bottom, circular in shape, with diameters up to 600 m. These structures are clearly connected with gas supply paths in sub-bottom sediments as revealed by high resolution seismic profiling. Gas hydrates were recovered within these seepage structures. Hydrates in the sediment cores formed layers or lenses in most cases, and small pieces or large aggregates to a lesser degree. Studies on near-bottom hydrates are required more for the potential energy resources and greenhouse effect gas considerations.

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(5) Development of Multifunctional Machine Tool for Micro-machining

     Masaru KATO, Akita Prefecture R&D Center
     Yoichi AKAGAMI, Akita Prefecture R&D Center

A high efficiency micro-machining equipment has been developed to fabricate micro molds for micro-structured parts such as DNA-chip and μTAS (micro total analysis system). These parts are expected as for the next generation of medical instruments. The developed equipment provides three machining functions : micro milling method, new polishing method using abrasives motion controlled under AC electric field, and nano-forming method using micro-structured diamond tools. We tested the equipment for machining performance. The micro milling method showed milling precision of micron order. Use of the new polishing method improved the surface roughness from Ra=0.043 to Ra=0.033. The nano-forming method was effective for giving a regular ruggedness of 1μm on the surface of injection mold for plastic DNA-chips.

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(6) Locomotions of a Biped Robot: Static vs. Dynamic Gaits

     Seungchul Lim, Inhwan Ko Myungji University

This study is concerned with computer simulations of a biped robot walking in static and dynamic gaits. To this end, a three-dimensional robot is considered possessing a torso and two identical legs of a typical design. For such limbs, a set of inverse kinematic solutions is analytically derived between the torso and the feet. Specific walking patterns are off-line generated meeting stability based on the VPCG or ZMP condition. Subsequently, to verify whether the robot can walk as planned in the presence of mass and ground effects, a multi-body dynamics CAE code has been applied to the resulting joint motions determined by inverse kinematics. As a result, the key parameters to successful gaits could be identified including inherent characteristics as well. Upon comparisons between the two types of gaits, dynamic gaits are concluded more desirable for larger humaniods.

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(7) An Experimental Study on Shape Oscillation Mode of Pendant Droplet by an Acoustic      Wave

     Byung Ha Kang, Jong Hoon Moon, Kookmin University
     Ho-Young Kim, Seoul National University

One of the fascinating prospects is the possibility of new hydrodynamics technology on micro-scale system since oscillations of micro-droplets are of practical and scientific importance. It has been widely conceived that the lowest oscillation mode of a pendant droplet is the longitudinal vibration, i.e. periodic elongation and contraction along the longitudinal direction. Nonlinear and forced oscillations of supported viscous droplet were focused in the present study. The droplet has a free contact line with solid plate and inviscid fluid. Natural frequencies of a pendant droplet have been investigated experimentally by imposing the acoustic wave while the frequency is being increased at a fixed amplitude. It is found that a pendant droplet shows the resonant behaviors at each mode similar to the theoretical analysis. The rotation of the droplet about the longitudinal axis is the oscillation mode of the lowest resonance frequency. This rotational mode can be invoked by periodic acoustic forcing and is analogous to the pendulum rotation. It is also found that the natural frequency of a pendant droplet is independent of the drop density and surface tension but inversely proportional to the square root of the droplet size.

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(8) Development of Small Size Coriolis Mass Flowmeter

     Ki Won Lim, Ji Jueng-Keun
     KRISS(Korea Research Institute of Standards and Science)

A Coriolis mass flowmeter(CMF), which has U-Shaped unique measuring tube was developed for direct mass flow measurement. In order to convert the time difference between two measuring tubes motion into mass flowrate and flow quantity, a signal processing circuit, as a part of CMF, was also developed. The CMF was designed as the 15 mm nominal diameter of pipe connection and the 8 mm stainless steel(sus 316) pipe was used for measuring tube. To maximize the flow signal(time difference) from the measuring tubes, the natural frequency of measuring tube was adjusted as 220 Hz, which is same as the frequency of exciter. The maximum displacement at the end of the measuring tube was measured as 0.05 mm, and the maximum time difference between two measuring tubes was observed as 20 , which was proper for discrimination and measuring range of CMF. The developed CMF was tested against the gravimetric flowmeter calibrator in the range of 3 kg/min and 30 kg/min . The results showed that the CMF has good linearity and repeatability in the tested flow range. Large size of CMF base on the current study experience will be developed.

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Editor : Tian Ruizhu
           The Dept. of Internationa Affairs
           Chinese Mechanical Engineering Society