Dummy Weight Research Articles

Effects of infant care posture and weight on static postural balance.

Studies investigating postural balance during various infant care postures have not been reported yet. The aim of this study was to measure static postural balance when holding an infant dummy in-arms and carrying an infant dummy on back according to different infant dummy weights. Sixteen healthy young subjects participated in a balance test. Infant dummies with weights of 4.6 kg (1-month) and 9.8 kg (12-month) were used in this study. All subjects were asked to naturally stand on a force platform in two infant care postures (holding an infant in-arms and carrying an infant on one's back). Center of pressure (COP) was measured from the force platform. Quantitative variables were derived from the COP. Two-way repeated measure analysis of variance (ANOVA) was performed to determine main effects of infant care postures, infant weight, and their interactions on COP variables. Back carrying a 12-month infant dummy had the greatest amplitude in all COP variables. Back carrying posture showed significantly greater mean distance and peak power, faster mean velocity, and wider COP area compared to holding posture (P< 0.05). There were significant weight effects of most COP variables mainly in AP direction (P< 0.01). Our results could contribute to the prevention of musculoskeletal diseases or prevention of fall due to various infant care activities by developing an assisting device to improve postural balance.

Sample-Efficient Policy Adaptation for Exoskeletons Under Variations in the Users and the Environment

Controlling lower-limb exoskeletons is extremely challenging due to their direct physical interaction with users wearing them which imposes additional safety concerns. Furthermore, the control policy needs to adapt for different users and surfaces the robot is traversing. Hence, it is crucial to design a control framework that can perform robustly in the presence of these variations. In this letter, we propose a sample-efficient method based on Bayesian Optimization (BO) to adapt a model-based walking controller for a lower-limb exoskeleton, XoMotion. In order to mitigate safety risks, we use a set of dummy weights with realistic inertial distributions in the experiments with the robot to find optimal policies. An extensive set of experimental results shows that the proposed controller can successfully adapt for different users and different terrains, in less than 15 real-world trials.

Analysis of maximum joint moment during infant lifting-up motion.

BACKGROUND: Infant care activities can induce musculoskeletal disease. However, little is known about the biomechanical joint load during lifting-up of an infant.OBJECTIVE: The aim of this study was to investigate normalized maximum moment during lifting-up of infant dummies weighing 4.6 kg, 7.6 kg, and 9.8 kg.METHODS: Six healthy young subjects participated in our study. All subjects performed lifting-up activities of dummies to shoulder height with their feet apart and natural postures in their comfortable speed. Three-dimensional reflective marker trajectories and ground reaction forces were used as input to calculate joint moments using a full body musculoskeletal model. Joint moments were normalized by each subject’s body mass. Friedman’s test was performed to compare mean differences of normalized joint moments for lifting up three dummy weights.RESULTS: Lumbar joint had the greatest normalized joint moment. Lumbar and hip extension moments were significantly increased with dummy weight ( 0.05). In contrast, knee extension and ankle plantarflexion moment were not significantly affected by dummy weight ( 0.05).CONCLUSIONS: These results indicate that the lumbar joint plays the most important role in infant lifting-up motion and that the load of lumbar and hip joint should be reduced when lifting a heavier infant. These results could contribute to the development of an effective lifting strategy and an assisting device for lifting an infant.

Binder-free 3D printing of covalent organic framework (COF) monoliths for CO2 adsorption

Covalent organic frameworks (COFs) present a large group of crystalline porous polymeric materials, which are formed with organic building blocks by strong covalent bonds. They have great potential in energy, environment, and biotechnology areas due to their high surface areas, tunable pore size distribution, and versatile functionality. However, they are largely synthesized in powder form only. The recent 3D printing technology requires the addition of binders. For the targeted applications in gas separation and adsorption, the existence of any binders not only increases the cost, but also reduces the surface area of the active materials and adds on dummy weight, which is especially harmful to functional porous materials where the retention of surface functionality and surface area is paramount. Herein, we report a binder-free, 3D printing process for COF materials (SNW-1 and ATFG-COF), capable of producing free-standing, crack-free 3D COF monoliths by the control of the solvent choices and their diffusion and evaporation among the different parts of the monoliths. Compared to SNW-1 with F127 binder added, the binder-free 3D monolith shows a larger surface area of 794 m2/g, which is similar to SNW-1 powder. The higher CO2 adsorption and CO2/N2 sorption selectivity compared to monoliths made with F127 binder further demonstrate the advantage of binder-free, 3D printing technology applied to COFs.

Design and Experimental Evaluation of a Fast Torque-Controlled Hydraulic Humanoid Robot

This paper reports the design and control of a fast torque-controlled hydraulic humanoid robot, TaeMu. The robot has 15 active joints that are all driven by hydraulic servocylinders with an external hydraulic power supply. The 1377-mm tall robot has a three-axis active torso used for static and dynamic balancing. It weighs 72.3 kg including a dummy weight stand for the arms. Its lightweight design with carbon-fiber-reinforced plastic allows the legs to have a similar mass distribution to that of human legs. We present the details of the hardware design including the hydraulic actuator selection, mechanism, and control systems, as well as the passivity-based controller design for joint torque control and whole-body motion control. We present experimentally obtained results, such as speed testing, basic torque control testing, full-body compliant balancing with attitude regulation/tracking, and balanced full-squat motions. The experimentally obtained results and estimated joint specification imply the high potential of the robot to perform human-like motions if the researchers can invent proper control algorithms.

Resonant frequency and hysteresis of a stack actuator made of single crystal (PMN-29PT) layers

In this study, we have presented the dynamic behavior of a piezoelectric stack actuator made of forty layers of single-crystal (PMN-29PT) with an area of 10 × 10 mm2 and thickness of 1 mm. To conduct a dynamic test of the actuator, we built a test apparatus with dummy weights that was placed over the top of the actuator to measure the actuation displacement. The resonant frequencies of the actuator with and without the dummy weight were determined as the excitation frequencies where a significant increase in the actuation displacement could be observed. We also proposed an analytical multi-degree-of-freedom (MDOF) model of the actuator to analytically predict the resonant frequency. Finite element analyses were conducted to validate the analytically predicted and measured resonant frequencies. With no dummy weight, the resonant frequency of the actuator was measured at 730.00 Hz, which was 0.70% higher than the one calculated by the MDOF model and 0.10% smaller than that of the finite element model. With a dummy weight, the measured resonant frequency was lower than 730.00 Hz and close enough to those computed by the MDOF model and the finite element model. The hysteresis curves of the actuator at various frequencies indicated that the actuator might incur a small energy loss.

자석바퀴기반 자기변형 에너지하베스터의 개념증명

This paper presents a proof-of-concept of a wheel-based magnetostrictive energy harvester (EH), which is a vibration-based EH. Coil-wound Galfenol cantilevers with two permanent magnets (PMs) act EH, while rotating wheels provide a forced vibration to EH. Four different cantilevers are designed and simulated for various end deflection. As expected from the simulation, the cantilever end deflection with triple cavity is the most. Three experiments are conducted to characterize the EH: the first with a magnetostrictive actuator, the second with a motor-driven wheel, and the third with the dummy weights. From the first experiment, the power reaches about 50 mV due to the relatively small displacement of the magnetostrictive actuator. From the second experiment, the power reaches about 120 mW. The power from the Galfenol cantilever is estimated to be about 60% of the total power from the wheel-based magnetostrictive EH.

Does overestimation of an object's mass during arm-raising modify postural adjustments?

By using a dummy weight during an arm-raising movement, we sought to determine whether (i) postural adjustments are modified and (ii) the required focal movement can be performed adequately. Standing on a force platform, 30 healthy young adults performed voluntary, arm-raising movements with cube-shaped boxes: a small 1kg box, a large 4kg box and a large 1kg box (i.e. the dummy weight, which looked as if it weighed 4kg). Postural adjustments were quantified in terms of the latency, intensity and duration of the positive phase of the vertical torque (Tz) and displacements of the center of pressure. Lifting the dummy and lifting the small 1kg box were associated with similar arm velocity curves. The characteristics of the positive Tz phase for the dummy box were intermediate between those observed for the small 1kg box and the large 4kg box. There were no differences between the three box-lifting conditions in terms of the latency and duration of Tz. We conclude that overestimation of the dummy's mass was rapidly corrected by a feedback mechanism. Postural control was modified online as soon as the dummy's true weight was perceived, which therefore enabled the maintenance of balance and adequate execution of the voluntary (focal) movement.

A07 月面ロボット用キャスティング作業システムに関する研究 : 多方向の引っ張りによる被投擲物の軟着地(M-OS13-2:テザーおよびマニピュレータ,M-OS13 宇宙機・宇宙ロボットのダイナミクスと制御,「海を越え,国を越え,世代を超えて!」)

We propose the method to control landing position and speed of an end-effecter in the air by multidirectional tension of wires. The end-effecter is connected with both dummy weights and reel system via the wires. After launching the end-effecter and dummy weights, its trajectory is changed by each tension of the wires when their motion is geometrically constrained. We develop the motion planner which makes the end-effecter reach the target at a suitable speed, and control algorithm for it. The proposed method is applied to the soft landing of the end-effecter. The effectiveness of the proposed method is verified through the experiment.

3207 鉄道車両の床下機器の高減衰弾性支持による車体弾性振動低減 : 新幹線相当車両における数値的検討と実車加振試験(OS1-2 振動の低減,OS1 交通・物流システムの高速化、利便性、快適性の向上,オーガナイズド・セッション(OS))

In this paper, we investigated the effect of reduction of flexural vibration in a railway vehicle carbody by supporting underfloor equipment using high-damping elastic mounts. At first, a numerical model for finite element method (FEM) simulation was built to check the reduction capability of flexural vibration by this method. Then, we developed underfloor equipment units with elastic mounts and dummy weight, so as to be able to easily change the layout and the mass of underfloor equipment. And excitation tests of a Shinkansen-type test vehicle with the underfloor equipment units were conducted, and good vibration reduction performance was observed in the tests.

2A2-C01 座圧分散クッションを使用した車椅子走行時の振動伝達特性と乗り心地評価(福祉ロボティクス・メカトロニクス(2))

In this study, we evaluated riding comfortableness of the attendant propelled wheelchair when using pressure redistributing cushions. Three types, a form type, a gel type and an air type cushions were respectively tested. The vibration propagating characteristics of these cushions were evaluated by measuring vibration of the dummy weight which was put on the pressure redistributing cushion during wheelchair running on tactile surface indicator road. In addition, a sensory test was conducted to compare the comfortableness of these cushions. Vibration wave form was analyzed by FFT, and sensory test was conducted by using questionnaire for subjects riding on the wheelchair with pressure redistributing cushion. As the result, the air type cushion indicated highest vibration damping performance, and the gel type was second, the form type cushion was third, respectively. The total result of the sensory test questionnaire correlated with the vibration damping performance. The cushion which has higher vibration damping performance provides better riding comfortableness to the occupant.

XY 선형 모션 스테이지 시스템의 반발력 보상 기구와 제어

본 논문에서는 별도의 외부 격리 구조물이나 추가 모터가 필요 없는 XY 선형 모션 스테이지를 위한 반발력 보상 시스템을 개발하였다. 개발된 시스템은 이동 가능한 마그넷 트랙, 스프링, 추가 질량을 포함한 자체 반발력 보상 구조를 가지고 있으며 이송용 모터 코일과 마그넷 트랙의 상대 위치를 검출할 수 있는 전용 센서를 개발하여 고정밀 추력 및 위치를 제어에 적용하였다. 먼저 반발력 보상 시스템을 모델링하고 모의 시험을 통해 이동 거리, 가속도, 하중, 허용 가능한 장비 크기와 같은 설계 요소를 최적화 하였다. 반발력 보상 시스템이 구비된 XY 모션 스테이지를 제작하였으며, 해당 시스템의 성능을 실험적으로 검증하였다. 실험결과 10m/s² 가감속 시에 85%의 반발력이 반발력 보상 시스템에 의해 흡수되었다.

Design and Construction of “ArtRo” Omnidirectional Walking Bipedal Robot using Hierarchical Reactive Behaviors Control Architecture

Bipedal robot locomotion has been a complicated and challenging matter over the time. This paper describes our work on building omnidirectional walking bipedal robot, included mechanical and electrical design aspect, and its behavior control as well. We adopted a technique introduced by Sven Behnke that enables omnidirectional walking on bipedal robot through the use hierarchical reactive behaviors control architecture. We called the robot “ArtRo”. Currently, ArtRo has successfully implemented a body consisting of two legs, lower abdomen, and a dummy weight representing the upper body load, with a total of 12 degrees-of-freedom (DOF). The mechanical system is designed optimally to facilitate the manufacturing process and the computation of robot parameters. The electrical system of ArtRo consists of main controller and actuator system. The main controller is an Atmel’s ATmega128-based microcontroller system. The actuator system implements a special method involving Time-Division Multiplexing (TDM) to control all ArtRo’s servo motors. The Sven Behnke’s technique has a low computational complexity. It is proven by its successful implementation on ArtRo’s main controller. Adaptation of the technique has been successfully implemented, ArtRo is capable to do omnidirectional walking, whether it is forward walking, side walking, or turning on the spot behavior.

Adjustment of submerged swimming to changes in buoyancy in cormorants

Waterbirds are buoyant because of volumes of air in their plumage and respiratory tract. When they are submerged, their buoyancy is reduced, owing to compression of these volumes of air with depth. We tested how the horizontal submerged swimming of cormorants (Phalacrocorax carbo sinensis (Blumelbach, 1798)) changed when their buoyancy was artificially reduced. Birds were filmed swimming under water once with lead weights (density 11 000 kg·m–3) and again with "dummy" weights (density 1100 kg·m–3) attached to their body. The dummy weights had negligible weight under water and served as control for the increased drag in the experiment. Cormorants swimming with weights tilted their bodies at an angle of 3°–7° below the swimming direction, whereas the body of birds in the control groups was tilted at 14°–16°. The tilt of the body affected the orientation and trajectory of the tail and feet during swimming. A hydrodynamic analysis showed that the lesser tilt of the body (while swimming with weights equivalent to 26% of body weight) resulted in a 55%–57% reduction of the vertical hydrodynamic forces (lift, drag, and thrust) generated by the birds to overcome buoyancy. When more weights were added and the birds became negatively buoyant, these vertical forces changed direction to prevent sinking. Thus, by adjusting the tilt of the body, the birds may dynamically control their buoyancy to maintain straight horizontal swimming despite changes in buoyancy.

トルクセンサを用いた介助型パワーアシスト車椅子の開発

This paper describes a power-assisted attendant-propelled wheelchair employing a model reference control algorithm based on velocity feedback control. The model equation encompasses two parameters, mass and viscous damping factor. The input of the control system is operator's force. Choosing the model mass less than the real value enables the operator to move the wheelchair with less effort. The goal is to realize functionality where the operator would always feel as though he/ she were propelling a lighter wheelchair on level ground.In order to measure the operator' s force we developed a propelling force sensing mechanism utilizing magnetostrictive torque sensors. The control circuit uses a16-bit single chip microcomputer and DC motor driver boards. The model parameters were chosen through experiments on surfaces indoors. Test drives with dummy weight(65kg)on surfaces indoors and slopes to buildings, and so on were conducted. Both young adults and elderly people took part in the tests. The results shown by the subjects indicate that they started the wheelchair with less than half of the force required when they operated a normal wheelchair. Adaptations of the parameters to the operator' s characteristics and to situations such as quick start or slow stop are to be solved.

Experimental and analytical studies on mechanical behavior of knife-edge-type metal-seal flange for fusion vacuum sealing

Mechanical behavior of a knife-edge-type metal-seal flange system was examined on the variations of the displacement between the flanges and reaction forces of the tightening bolts during load steps such as tightening the bolts, setting up a transverse weight load on the flange surface and 300 °C baking and cool down. These were compared with a thermo-elasto-plastic finite element method structural analysis. Good agreement was obtained for both the flange deformation and reaction forces of the bolts and copper gasket between experimental and analytical results. Effects of the transverse load by a dummy weight mounted at the flange surface on the changes of reaction force of the bolts and on gasket deformation were considered to be negligibly small in the view of vacuum seal characteristics. The application of Inconel Belleville spring washers between bolt heads and flange surface was confirmed to be quite effective for the suppression of the bolt force looseness and gasket relaxation due to cyclic heating and cooling of the knife-edge-type metal-seal flange system.

GLIM and normalising constant models in spatial and directional data analysis

A method is presented for evaluation of normalising constants in GLIM. Based on a weighted Poisson model and suitably chosen dummy weights a wide variety of normalising constant models can be fitted. Examples are given of an LR test for ‘von Misesness’ equivalent to Cox's (1975) score test, the estimation of κ for a Fisher distribution, and parameter estimation for a spatial Heterogeneous Poisson Process.

Geomagnetism and the Homeward Orientation of the Box Turtle, Terrapene Carolina

AbstractHoming in the box turtle, Terrapene Carolina, has been well documented, but the mechanisms involved are largely unknown. We used laboratory and field experiments to determine if the geomagnetic field may be used as an orientational cue. Turtles were trained in the laboratory to move along an east/west axis and were tested for directionality in a circular arena. Control turtles with dummy weights attached to the carapace oriented significantly to the training direction. Experimental turtles with magnets attached to the carapace were randomly oriented. In field tests, turtles were displaced from their home ranges to 4 release sites located symmetrically about the home site. Controls were displaced under normal magnetic field strength (Helmholtz coils off) and experimentals were displaced under increased field strength (15% increase over local geomagnetic field strength). The initial orientation of the control turtles clustered significantly in the homeward direction while the initial orientation of experimental turtles was not clustered in the homeward direction. Both control and experimental turtles showed compass orientation clustered in an eastward direction regardless of the directional relationship between the release site and home. This compass orientation appears to mask, to some degree, the homeward orientation of the turtles.

傾斜板法による粉体の壁面摩擦係数の測定 セル重量の影響の検討

To determine the wall friction coefficients of powders, the traditonal inclined plate method is simple, and its powder bed works actively in the test. However, in this method, the weight of the test cell must be negligibly small. In this report, we proposed a new method and a test apparatus which had two inclined plates with the same base angles. During measurement, the weight of the test cell could be cancelled by the dummy weight which was connected with the test cell by a string and placed on one of the plates. The wall friction coefficients of Sohma sand, wheat flour and corn starch, which were determined by the traditional method (the single-cell method) using heavier cells, decreased with the increasing weight of test cell. On the other hand, the wall friction coefficients of those powders determined by the new method (counter balance method) show the constant values for each powder.

Randomized Fractional Weighing Designs

Consider the problem of estimating unbiasedly a linear function, $\lambda?' \omega, \omega' = (\omega_1, \cdots, \omega_p)$, of $p$ weights $\omega_1, \cdots, \omega_p (0 < \omega_i < \infty$ for all $i = 1, \cdots, p)$ when the number of possible weighing operations, $n$, is smaller than $p$. Assume further that the weighing design is of the chemical type (each entry of the design matrix can assume one of the values $-1, 0, +1)$. A weighing design in which the number of weighing operations is smaller than the number of objects, $n < p$, will be called a fractional weighing design. A fractional weighing design is singular. As is well known, if a non-randomized weighing design is singular, one cannot estimate unbiasedly each of the $p$ weights. Some linear functions $\lambda?'\omega$ can be estimated, however, unbiasedly. For example, the sum of all $p$ weights can be estimated unbiasedly by a singular weighing design in which, at each weighing operation, all the objects are placed on one pan. Such a singular weighing design is in fact optimal. One can not attain the same precision in estimating the sum of all the $p$ weights by any non-singular design (see K. S. Banerjee [1]). Some linear functions of the weights can thus be estimated, with a sufficient degree of precision, on the basis of a number of weighing operations, $n$, smaller than the number of weights, $p$. A. M. Mood [4] has shown that if the design matrix of a non-singular weighing design is a Hadamard matrix (if it exists) then the design is optimal. We shall therefore study fractional weighing designs based on Hadamard matrices. If $p$ is such that no Hadamard matrix of order $p$ exists, we shall consider the smallest integer $p'$ larger than $p$, for which a Hadamard matrix exists and add $(p' - p)$ dummy weights. The linear functions $\lambda?'\omega$ can be extended in a way that assigns the dummy weights the coefficient zero. We shall then consider randomized fractional weighing designs which are constructed by choosing at random $n$ rows, independently and with replacement, from the given Hadamard matrix according to a probability vector $\xi$ of order $p$. Every such row specifies a weighing operation to be performed. Non-randomized fractional designs are special cases of the randomized designs under consideration. It is well known that if the weighing design is fractional $(n < p)$ then not all the linear functions $\lambda?'\omega$ are estimable under non-randomized designs. It is shown in the present paper that any linear function $\lambda?'\omega$ can be estimated unbiasedly under a proper randomization scheme. Optimal randomization procedures depend on the functional $\lambda?$. Complete class of unbiased estimation procedures is given for any linear function $\lambda?'\omega$. It is shown that every functional $\lambda?$ specifies a subset of, say $r (1 \leqq r \leqq p)$, admissible weighing operations (rows of the Hadamard matrix); in the sense that if other weighing operations are chosen then, either the estimation procedure is biased, or has a variance larger than the one that can be attained under the admissible weighing operations. It is also proven that if each of the $r$ admissible weighing operations $(1 \leqq r \leqq p)$ is chosen with probability equal to $1/r$, then the corresponding unbiased estimator has a uniformly (in $\omega$ and $\sigma^2$) minimum variance, relative to all the above specified randomization procedures. The formulae of the unbiased estimator of $\lambda?'\omega$ and its variance are extended in Section 4 to the case of random choice without replacement, of $n$ rows out of the $r$ admissible ones. This randomization procedure improves the results that can be obtained under the best randomization procedure with replacement. Finally, the relationship of the present study to the studies of S. Ehrenfeld and S. Zacks [2], [3] is discussed in Section 5.