Development of surface tension-driven microboats and microflotillas

Surface tension gradients may induce the motions of a floating solid fragment. This mechanism has been employed to drive miniaturized objects on a water surface. These objects could function, for example, as rotators. In the meanwhile, based on such a mechanism, we have recently developed microboats and microflotillas, and explored their movements on water surfaces. Isopropyl alcohol was adopted as the propellant. It had a surface tension much lower than water. Once the IPA exited the reservoir of a microboat or a microflotilla, the force induced by the difference between fore-and-aft surface tensions propelled the corresponding locomotive forwards. This article gives a simple review of the results that we have achieved to date, including exploration of SU-8 microboats, development of SU-8 microflotillas, and determination of driving mechanisms of these microboats and microflotillas. Two types of SU-8 microboats were developed, and their designs, fabrication and propulsion were explored. The first type of microboats did not have side rudders. They were capable of moving along their longitudinal directions. We considered the movements of this type of SU-8 boats in both horizontal and vertical planes. The second type of microboats had side rudders, which enabled these microboats to have radial motions. By varying the lengths of the side rudders, we were able to have a good control of the radial motions. To have more storage space, we further developed microflotillas, which each consisted of five SU-8 microboats that were linked with a Nylon rope. We explored design, fabrication and propulsion of these microflotillas, as well as their motions in both straight and circular channels. The developed boats and flotillas were capable of moving on water surfaces at speeds of order 0.1?m/s. Finally, we performed in situ observation of exchange processes of water and IPA inside the reservoir of a cm-scaled PDMS boat. Based on this observation, we interpreted driving mechanisms of the microboats and microflotillas. Existing approaches mainly use stationary devices for material supply and sensing detection. Compared with these devices, the developed boats and flotillas are mobile. This enables these miniaturized vehicles to actively deliver materials and sensors on demand for microfluidic applications.     

Fabrication and testing of a self-propelled, miniaturized PDMS flotilla

In this work, we developed a miniaturized PDMS flotilla, which was capable of moving on a water surface. The flotilla consisted of five mm-scaled PDMS boats that were linked together through μm-scaled PDMS bars. We explored its design, fabrication, propulsion, and motions in straight and circular channels. The flotilla was fabricated using a molding approach with two-layer SU-8 structures as the mold, and actuated by the difference between fore-and-aft surface tensions. It was tested in straight and circular channels at water levels of 2.0, 3.0, 6.0 and 9.0?mm, respectively. No collisions were observed between neighboring boats in all the tests. Travel distances ranged from 385 to 1,128?mm. Average speeds varied from 38.5 to 102.5?mm/s, and increased with the increase in water depth. Dramatic squat and trim phenomena were directly observed in the two types of tests conducted in the straight channel. They were mainly induced by the difference between surface tensions of water and flotilla propellant. Simple models were further developed to interpret driving mechanisms of the flotilla, and to extract its resistance coefficients in different motions. These coefficients ranged from 0.1 to 0.7 in the 2-, 3-, 6- and 9-mm tests performed in the straight channel. The two ends of the flotilla had direct contact with the outer sidewall of the circular channel during a circular motion. The supporting forces of the outer sidewall at these contact points provided the centripetal force needed for the circular motions. In the four tests conducted in either the straight or the circular channel, water resistances increased with the decrease in water depth. Furthermore, the flotilla suffered much larger resistances in the 2-mm test than in another three, implying that, to avoid the effect of shallow water, water is preferred to be deeper than 2?mm in the applications of the miniaturized flotilla. The results presented in this work indicate that the water flotilla was capable of traveling reasonably long distances in straight and circular channels at fast speeds. Due to its mobility on a liquid surface, such a miniaturized flotilla would have the capability of delivering different materials and sensors on demand in small-scale fluidic applications.     

基于机器艇与ZigBee的湖泊水质监测系统设计

湖泊是地表水资源的重要载体,为了全面、实时、高效地监测湖泊水环境,设计一种湖泊水质自动监测系统尤为重要;多艘机器艇搭载水温、pH值、溶解氧等传感器,在湖面上组成基于ZigBee的无线传感器网络进行数据采集;水质数据通过无线传感器网络传输到上位机进行分析显示;基于GPS和姿态传感器的运动控制算法实现了机器艇自主航行到指定监测点的功能;实验结果表明,系统实现了对湖泊水质的较大范围实时监测,能满足实际应用需求。     

Development of a self-propelled microflotilla

In this work, we initiated the effort of developing a so-called water microflotilla, which was capable of moving on a water surface. We explored its design, fabrication, propulsion, and motions in straight and circular channels. A water microflotilla comprised five microboats connected with a Nylon rope, and was fabricated using ultra-violet lithographic techniques. It was actuated by the difference between fore-and-aft surface tensions. The water microflotilla was tested in three straight and one circular channels at water levels of 3, 6 and 9?mm, respectively. In all the tests, the microflotilla moved like a rigid object, and no collisions were observed between neighboring microboats. Travel distances were above 0.44?m, and average speeds varied from 40.2 to 103.2?mm/s. Both the travel distances and the average speeds were found to increase with the increasing water depth and channel width. The two ends of the microflotilla had direct contact with the outer sidewall of the circular channel during a circular motion. The support forces of the outer sidewall at these contact points provided the centripetal force needed for the circular motion. Compared with a single microboat, such a microflotilla can be potentially employed to transport a large amount of supply in small-scale fluidic applications.     

Effect of reclining a seat on the discomfort from vibration and shock on fast boats

Passengers and crew on fast boats can experience high magnitudes of whole-body vibration and mechanical shocks that may present risks to health and cause discomfort. This study investigated the influence of reclining a seat on the discomfort caused by fast-boat motion and whether discomfort can be predicted by overall ride values according to current standards. Subjects judged the discomfort of simulations of a recorded fast boat motion in a seat reclined by 0°, 15°, 30°, 45°, or 60°. Reclining the seat caused no significant change in overall discomfort, suggesting that if a reclined seat can be shown to reduce risks of injury it may be acceptable in respect of comfort. The findings are inconsistent with the predictions of standards and show that revised frequency weightings are required to account for seat pan or seat back inclination.     

A dynamic geomonitoring system for Venetian coastal ecosystem: WATERS project

The main purpose of the WATERS project is to set up an innovative system for integrated monitoring of environmental parameters in the water body of the Venice lagoon, allowing—with limited investment and low operating costs—a sharp improvement in the environment survey and restoration practices. For this aim, 15 boats from AMAV's operating fleet, daily travelling over wide areas of the territory for normal refuse collection service, shall be equipped with special monitoring and data transmission devices. The research, co-financed by the European Union (EU) within LIFE Program 1997, to be carried out in tight cooperation with the appointed local authorities, shall be performed as follows: (1) testing and development of special monitoring equipment to be installed on the foreseen 15 AMAV's boats; (2) installation and testing, on the same boats, of GPS-NAVSTAR high-precision differential positioning system, integrated with available navigation instruments through a Kalman sequential filter; this system shall allow tagging of each sample with precise time and position reference marks; (3) set up of a data processing and transmission system, from AMAV's boats to a central control station; (4) development of a suitable geographical information system specific to the coastal environment, receiving the continuous flow of environment monitoring data, open to new software applications and created on the basis of existing historical and scientific documents; (5) design and development of a laboratory boat for supplementary hydrodynamic and physicochemical data, for taking samples of water, sediment and biomarkers, and for detailed in situ analysis of phenomena through the on-board equipment; and (6) validation of the correlations found among physico-chemical, biological and hydrodynamic environmental variables and determination of critical environment matrices. As a final result, the research will define a real management strategy for coastal environments, a widely applicable model derived from the strategy to be adopted for Venice, a very complex ecosystem affected by many phenomena and many sources of possible pollution (anthropogenic, agricultural, industrial, etc.), in the presence of particular tidal variations capable of producing significant impacts on the environment.     

A single-layer PDMS-on-silicon hybrid microactuator with multi-axis out-of-plane motion capabilities-part II: fabrication and characterization

This paper reports on fabrication and characterization of a new electrostatic microactuator that achieves out-of-plane multi-axis motion with a single silicon device layer. The multi-axis motion with the simple actuator design is possible by incorporating a three-dimensional (3-D) polydimethylsiloxane (PDMS) microstructure. This paper develops a new device processing method named "Soft-Lithographic Lift-Off and Grafting (SLLOG)" to fabricate the previously designed PDMS-on-silicon hybrid actuator structure. SLLOG is a low-temperature (less than 150/spl deg/C) process that allows replica molded PDMS microstructures to be integrated in silicon micromachined device patterns. The fabricated actuator is characterized using laser vibrometry. The experimental results demonstrate actuation motions achieved in three independent axes with fast dynamic response reaching a bandwidth of about 5 kHz. The fabricated PDMS-on-silicon actuator yields a vertical displacement up to 5 /spl mu/m and rotational motions with a 0.6-/spl deg/ tilting angle at a 40-V peak-to-peak ac actuation voltage.     

可印刷柔性应变传感器的制作及其对 人体运动行为监测研究

该文主要研究了导电浆料 PS@Ag/PDMS 的流变特性与印刷性,以聚苯乙烯微球表面镀 银(PS@Ag)的核壳结构粒子为导电填料,与聚二甲基硅氧烷(PDMS)预聚物及其固化剂复合配制 PS@Ag/PDMS 导电浆料,采用丝网印刷技术与旋涂工艺制备得到 PDMS-PS@Ag/PDMS-PDMS 三明治结构柔性应变传感器。柔性应变传感器在人体运动行为中的实时监测结果显示,该传感器在手肘关节与膝盖关节的弯曲——伸展循环运动中的相对电阻变化率分别高达约 0.75 0.50,展现出较高的可拉伸柔性、灵敏度及一致性,在人体运动行为监测中具有广阔的应用前景。     

All PDMS pneumatic microfinger with bidirectional motion and its application

This paper describes the experimental results on static and dynamic bending motions of all polydimethylsiloxane (PDMS) pneumatic microfinger. The proposed pneumatic microfinger consists of two PDMS diaphragms with different thicknesses or material properties. The microfinger is fabricated through PDMS molding process and the PDMS-to-PDMS bonding process. The out-of-plane motion of the microfinger is achieved by using the pulling force of the inflated actuator diaphragms while the square wave pneumatic force is supplied to the balloon actuators. In the case of the microfinger with different thickness of two diaphragms, the pressure-dependent dual-bending motion of the microfinger is available. The proposed working principle is confirmed from the steady-state bending angle measurement of the two types of the microfingers with different thicknesses of the bottom PDMS layers. While the pneumatic force is less than 20 kPa, the top diaphragm of Type A microfinger is fully inflated and the microfinger moves downward. Around 20 kPa, the bending direction of the microfinger starts to be changed from downward to upward. The microfinger with two types of PDMS films with different mixing ratio of base polymer and curing agent is also proposed for the improvement of the PDMS-to-PDMS bonding strength, the material property change, and the rapid manufacturing process. The microfinger moves only upward because the top PDMS diaphragm with excess of silicon hydride group is relatively stiffer than the bottom PDMS diaphragm with excess of vinyl group. The dynamic bending motion of the single microfinger and the object-lifting motion of the microfinger array are observed to evaluate their performance. The dynamic bending angle of the microfinger with golden air bone length is about 179/spl deg/ at 1 Hz, while the square wave input pressure of 250 kPa is supplied to finger structure.     

Assessment of human head pose in human-computer interaction

A system is described that estimates a user??s head position from a video image of it. The system includes three base algorithms: segmentation, detection of markers, and assessment of motion direction. The direction of head motion is determined by the dynamics of changing geometrical correlations between facial markers in the picture sequence. It is shown that the change in the angle formed by straight lines connecting the corners of the eyes and the tip of the nose have change dynamics similar to that of ??yawing.?? This system operates in real time (7 fps) and ensures high precision in assessing the direction of motions (p = 0.95).     

Application of the independent molecule model to the calculation of free energy and rigid-body motions of water hexamers

The stabilities of five water hexamers (cyclic, boat, book, prism and cage structure) in the gas phase were investigated with the independent molecule model. In this model, the position and orientation of each water molecule within the hexamer are characterized with a translational vector and Eulerian angles, and then each molecule can move freely as a rigid body with respect to the others. Force field energy minimization yielded structures for each hexamer. Normal mode analyses were done on the five hexamers. Hydrogen bond strength in the hexamer decreases in the order: boat, cyclic, book, cage and prism. Hydrogen bond lifetimes also decrease in this order. By estimating the internal energy and the vibrational entropy of rigid-body motions, we determined the temperature dependence of the free energy for each hexamer in the range 100–350 K. Free energy of the hexamers increases in the previously mentioned order also. The most stable hexamer is the boat, and the least stable is the prism. The stabilities of the boat and the cyclic are very similar. The more planar hexamers (cyclic and boat) are more stable than the three-dimensional hexamers (cage and prism). Although the experiments of Liu et al. [Nature 381 (1996) 501] were interpreted in terms of a cage cluster, our calculations indicate boat is more likely.     

时间最优的直升机对海攻击导引方法研究

就一架舰载直升机与多艘导弹艇的对抗攻击建模问题进行了研究,目的在于用最短的时间将舰载直升机导引到有多艘导弹艇的作战区域.文中在运用微分对策理论的同时结合了局部优化的思想,建立了攻击时间尽可能短的数学模型,进而推导出了对抗多方为达到各自作战目所应采取的最优控制策略,并给出了实现步骤与方法.最后,对一架舰载直升机与两艘导弹艇的对抗进行数值仿真,该直升机根据所建模型的要求在以尽可能短的时间击毁一艘导弹艇的同时与另一艘导弹艇保持最短距离,进而也能以最短时间迅速接近下一战区.仿真实例表明,文中的模型和方法可在一定程度上为实时作战指挥系统的研制、开发提供技术支持及理论依据.     

Humanoid robotics platforms developed in HRP

This paper presents humanoid robotics platform that consists of a humanoid robot and an open architecture software platform developed in METI’s Humanoid Robotics Project (HRP). The final version of the robot, called HRP-2, has 1540 mm height, 58 kg weight and 30 degrees of the freedom. The software platform includes a dynamics simulator and motion controllers of the robot for biped locomotion, falling and getting up motions. The platform has been used to develop various applications and is expected to initiate more humanoid robotics research.     

Self-calibration of environmental camera for mobile robot navigation

An environmental camera is a camera embedded in a working environment to provide vision guidance to a mobile robot. In the setup of such robot systems, the relative position and orientation between the mobile robot and the environmental camera are parameters that must unavoidably be calibrated. Traditionally, because the configuration of the robot system is task-driven, these kinds of external parameters of the camera are measured separately and should be measured each time a task is to be performed. In this paper, a method is proposed for the robot system in which calibration of the environmental camera is rendered by the robot system itself on the spot after a system is set up. Specific kinds of motion patterns of the mobile robot, which are called test motions, have been explored for calibration. The calibration approach is based upon executing certain selected test motions on the mobile robot and then using the camera to observe the robot. According to a comparison of odometry and sensing data, the external parameters of the camera can be calibrated. Furthermore, an evaluation index (virtual sensing error) has been developed for the selection and optimization of test motions to obtain good calibration performance. All the test motion patterns are computed offline in advance and saved in a database, which greatly shorten the calibration time. Simulations and experiments verified the effectiveness of the proposed method.     

用于程序循环控制的错误检测算法

为确保安全苛求系统中程序执行的正确性,针对程序循环控制中内存未更新、循环提前结束和循环滞后结束的问题,提出一种基于含签名和时间戳的算术(ANBD)码的循环控制错误检测算法。该算法通过ANBD码,将程序变量编码为含签名的码字。通过校验码字签名,检测循环控制错误。运用ANBD码中的时间标签,可检测内存未更新错误。另外,在ANBD码基础上,通过采用在线语句块签名分配算法、语句块签名函数和变量签名补偿函数,检测循环提前结束错误和循环滞后结束错误。该算法理论错误漏检概率为1/A,其中A为编码素数,选取97~10993的素数进行错误漏检概率测试,得到理论模型与测试结果的归一化均方误差(NMSE)约为-30 dB。测试结果表明,该算法可检测循环控制中出现的各类错误,且编码素数A接近2³²时,错误漏检概率可达10^-9,能够满足安全苛求系统的应用要求。     

Automatic evaluation of sports motion: A generic computation of spatial and temporal errors

In this paper, we propose an innovative automatic evaluation process for any sport motions. Based on a 2-level Dynamic Time Warping, the process allows the evaluation of both spatial and temporal errors of a novice motion based on an experts' motion database and without any prior knowledge on the sport. This new methodology is evaluated with regards to coaches' assessment on two different kinds of motions: tennis serves and karate tsuki.     

A General Framework for Assembly Planning: The Motion Space Approach

Assembly planning is the problem of finding a sequence of motions to assemble a product from its parts. We present a general framework for finding assembly motions based on the concept of motion space . Assembly motions are parameterized such that each point in motion space represents a mating motion that is independent of the moving part set. For each motion we derive blocking relations that explicitly state which parts collide with other parts; each subassembly (rigid subset of parts) that does not collide with the rest of the assembly can easily be derived from the blocking relations. Motion space is partitioned into an arrangement of cells such that the blocking relations are fixed within each cell. We apply the approach to assembly motions of several useful types, including one-step translations, multistep translations, and infinitesimal rigid motions. Several efficiency improvements are described, as well as methods to include additional assembly constraints into the framework. The resulting algorithms have been implemented and tested extensively on complex assemblies. We conclude by describing some remaining open problems. Received November 15, 1996; revised January 15, 1998.     

Design and development of an autonomous wave-powered boat with a wave devouring propulsion system

This paper describes the design, development, and experiments of an autonomous wave-powered boat with a wave devouring propulsion system (WDPS). The WDPS consists of two fins (hydrofoils) below the bow of the boat. They generate thrust force directly from wave power and reduce roll and pitch motion of the boat in the waves. As described herein, first we performed numerical analysis and a preliminary experiment to design the hull form and the WDPS. Based on the analysis and experimentally obtained results, we designed and developed a prototype autonomous wave-powered boat. We also developed electrically powered systems such as a navigation, control, and wireless communication system for the boat. Moreover, we experimentally tested the performance of the developed boat in a test tank and in a coastal sea area. The experimentally obtained results indicate that the developed wave-powered boat can be a useful tool for ocean observation.     

Motion recognition using local auto-correlation of space–time gradients

In this paper, we propose a motion recognition scheme based on a novel method of motion feature extraction. The feature extraction method utilizes auto-correlations of space–time gradients of three-dimensional motion shape in a video sequence. The method effectively exploits the local relationships of the gradients corresponding to the space–time geometric characteristics of the motion. For recognizing motions, we apply the framework of bag-of-frame-features, which, in contrast to the standard bag-of-features framework, enables the motion characteristics to be captured sufficiently and the motions to be quickly recognized. In experiments on various datasets for motion recognition, the proposed method exhibits favorable performances as compared to the other methods, and faster computational time even than real time.     

A study of density fronts and their effects on coastal pollutants

Density fronts represent regions of extremely high gradient or discontinuity in various parameters of physical interest, the most important being the water velocity and density fields. Such fronts strongly influence pollutant dispersion, by capturing oil slicks and other pollutants concentrated in surface films and drawing them down into the water column. Satellites, aircraft and boats were used to study the behavior of different types of fronts in Delaware Bay and their effect on pollutants in order to provide a basis for improving an oil drift and spreading model. LANDSAT satellites provided the most effective means of determining the location and extent of frontal systems over all portions of the tidal cycle. Satellite observations of flood-associated fronts on the New Jersey side of the Bay and ebb-associated fronts on the Delaware side agreed with boat measurements and model predictions.