Design of a powered ankle-foot prosthesis with an adjustable stiffness toe joint

ABSTRACT

This paper proposes a powered ankle-foot prosthesis called PANTOE II, which includes an ankle and a segmented foot with a toe joint. The ankle and toe joints are both driven by series elastic actuators, which can reduce the required velocity and energy consumption of the actuators. The mechanical design of the ankle and toe joints makes the prosthesis more compact. In addition, PANTOE II employs a more human-like foot, which includes the heel, the mid foot, and the toe. Both the heel and the toe are made of leaf springs, and the mid foot is used to install the transmission mechanisms. The finite state control strategy is used for controlling the prosthesis. To evaluate the basic performance of PANTOE II, experiments are conducted on a subject with a transtibial amputation. Wearing PANTOE II, the amputee feels more comfortable and presents more symmetrical walking gaits.     

Heuristic algorithm for a cutting stock problem in the steel bridge construction

A rectangular two-dimensional cutting stock problem in the steel bridge construction is discussed. It is the problem of cutting a set of rectangular items from plates with arbitrary sizes that lie in the supplier specified ranges, such that the necessary plate area is minimized. Several types of cutting patterns are used to compose the cutting plan. All of them are easy to generate and cut except the last one. The algorithm uses both recursive and dynamic programming techniques to generate patterns of the last type. The computational results of 22 practical instances indicate that the algorithm can produce solutions close to optimal, and the computation time is reasonable for practical use.     

Optimum design of steel frames using harmony search algorithm

In this article, harmony search algorithm was developed for optimum design of steel frames. Harmony search is a meta-heuristic search method that has been developed recently. It bases on the analogy between the performance process of natural music and searching for solutions to optimization problems. The objective of the design algorithm is to obtain minimum weight frames by selecting suitable sections from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange (W) shapes. Strength constraints of AISC load and resistance factor design specification and displacement constraints were imposed on frames. The effectiveness and robustness of harmony search algorithm, in comparison with genetic algorithm and ant colony optimization-based methods, were verified using three steel frames. The comparisons showed that the harmony search algorithm yielded lighter designs.     

钢铁企业集团订单分配模型研究

在集团统一销售的管理模式下,如何将订单在多个成员企业之间进行分配是钢铁企业集团需要研究的重要问题．为此,在对钢铁企业集团订单分配原则进行归纳总结的基础上,建立了以集团订单排产量最大和集团利润最大为目标的钢铁企业集团订单分配多目标优化模型;同时结合问题的特点,提出了模型求解的算法流程;最后,通过应用实例验证了模型和算法流程的可行性和有效性．     

钢管生产线质量保证系统

介绍了钢管生产线质量保证系统仪表配置、测量原理、系统构成以及安装使用中的注意事项。     

飞机座舱航向操纵脚蹬的操纵仿真

要使人体模型能在工程设计中代替人体对设计中的工效提出要求或做出评价 ,就必须将人体模型运动数据与真人实验数据进行比较 ,在两者误差满足工程需要的前提下才可使用。利用美军飞行员人体数据计算人体模型脚行程 ,并与实测值进行比较 ,对所建人体模型脚的可达行程进行了验证。在此基础上利用中国飞行员人体数据 ,得出中国人体模型的脚运动行程 ,在座舱设计中使用。     

Robust shape control in a sendzimir cold-rolling steel mill

The shape control problem for a Sendzimir 20-roll cold rolling steel mill is characterised by operation over a wide range of conditions arising from roll changes, changes in rolling schedules and changes in material gauge, width and hardness. Previous approaches to the problem suggest storing a large number of precompensator matrices to cater for the full range of operating conditions. This paper, on the other hand, attempts to synthesise a controller which is optimally robust to changes in the conditions associated with the rolling cluster, resulting in a reduced storage requirement for the controlling computer. The performance of the robust controller is evaluated via nonlinear simulation.     

钢铁企业在制品成本追溯模型研究*

针对钢铁企业在制品特点及成本管理的需求,将可追溯性的概念引入到在制品成本管理中,提出了钢铁企业在制品成本追溯方法,建立了在制品状态三维描述模型。该模型通过作业中心维、属性维和成本中心维对在制品进行描述,并采用巴科斯一诺尔范式对其进行数学规范,给出了在制品成本追溯规则和算法流程。通过在钢铁企业的应用实例,验证了在该模型的可行性,能够实现钢铁企业实际管理过程中对在制品的完整描述,提高了在制品成本核算的准确性。     

Numerical study of a steel sub-frame in fire

Steel-framed buildings are generally designed with “simple” shear-resisting connections, and lateral forces are resisted by vertical bracing and shear walls. When a beam is considered then the effects of the longitudinal restraints by the adjacent structure and the rotational restraint by the connections has to be taken into account. Because of structural interaction, the beam behaviour at elevated temperature is rather complex.This paper presents a numerical parametric study of a structural system consisting of an exposed steel beam restrained between a pair of fire protected steel columns. The structural sub-frame is modelled using 3D shell elements, thereby taking into account the effect of the local failure modes, and the realistic behaviour of the sub-frame exposed to natural fire. The numerical model accounts for the initial geometrical imperfections, nonlinear temperature gradient over the cross-section, geometrical and material nonlinearity and temperature dependent material properties.Results obtained using a general Finite Element software – LUSAS and a fire dedicated software – SAFIR, are compared. The influence of following variables: beam span/depth ratio, lateral restraint, gradient temperature within the cross-section and mechanical load level is presented in the paper. The failure modes, the development of the internal forces and displacements throughout the analysis are considered to exemplify the effects of the variables considered.     

Gray-box modeling for prediction and control of molten steel temperature in tundish

To realize stable production in the steel industry, it is important to control molten steel temperature in a continuous casting process. The present work aims to provide a general framework of gray-box modeling and to develop a gray-box model that predicts and controls molten steel temperature in a tundish (TD temp) with high accuracy. Since the adopted first-principle model (physical model) cannot accurately describe uncertainties such as degradation of ladles, their overall heat transfer coefficient, which is a parameter in the first-principle model, is optimized for each past batch separately, then the parameter is modeled as a function of process variables through a statistical modeling method, random forests. Such a model is termed as a serial gray-box model. Prediction errors of the first-principle model or the serial gray-box model can be compensated by using another statistical model; this approach derives a parallel gray-box model or a combined gray-box model. In addition, the developed gray-box models are used to determine the optimal molten steel temperature in the Ruhrstahl–Heraeus degassing process from the target TD temp, since the continuous casting process has no manipulated variable to directly control TD temp. The proposed modeling and control strategy is validated through its application to real operation data at a steel work. The results show that the combined gray-box model achieves the best performance in prediction and control of TD temp and satisfies the requirement for its industrial application.     

The energy cost and heart-rate response of trained and untrained subjects walking and running in shoes and boots

Abstract

To determine the difference in the energy cost of walking and running in a lightweight athletic shoe and a heavier boot, fourteen male subjects (six trained and eight untrained) has their oxygen uptake ([Vdot]O₂) measured while walking and running on a treadmill. They wore each type of footwear, athletic shoes of the subjects' choice (average weight per pair = 616 g) and leather military boots (average weight per pair = 1776g), at three walking speeds (4·0, 5·6 and 7·3 km hour^?1) and three running speeds (8·9, 10·5 and 12·1 km hour^?1). The trials for running were repeated at the same three speeds with the subjects wearing shoes and these shoes plus lead weights. The weight of the shoes plus the lead weights was equal to the weight of the subjects' boots. The [Vdot]O₂values with boots were significantly (p < 0·05) higher (5·9?10·2%) at all speeds, except the slowest walk, 4·0 km hour^?1Also, [Vdot]O₂with shoes plus lead weights were significantly (p<0·05) higher than shoes alone. Weight alone appeared to account for 48-70% of the added energy cost of wearing boots. The relative energy cost ([Vdot]O₂, ml kg^?1?) of trained and untrained subjects were the same at all speeds. These data indicate that energy expenditure is increased by wearing boots. A large portion of this increase may be attributed to weight of footwear. In addition, the increased energy cost of locomotion with boots appears to place a limiting stress on untrained subjects.     

Ergonomics of abrasive blasting: a comparison of high pressure water and steel shot

Abrasive blasting with silica sand has long been associated with silicosis. Alternatives to sand are being used increasingly. While NIOSH has done extensive investigations of the respiratory effects of the substitutes for sand, the ergonomic effects of the substitutes have not been examined. Too often, hazards are shifted, and technologies that might save workers' lungs could do so at the expense of their musculoskeletal systems. Hence, the objective of this study was to examine the ergonomic effects of alternatives to sand. Multiple methods, both qualitative and quantitative, were used to yield numerous kinds of data for the analysis of exposures to abrasive blasters. PATH, a method for quantifying ergonomic exposure in non-routine work, was combined with interviews with workers, biomechanical modeling and noise level readings to assess the ergonomics of two abrasive blasting operations: high-pressure water and steel shot. Advantages and disadvantages of each medium are discussed. High-pressure water was slightly less ergonomically stressful, environmentally cleaner, much quieter and less dusty that steel shot, and it was reported to be slower on those tasks where both media could be used.     

A multi-agent architecture for dynamic scheduling of steel hot rolling

Steel production is a complex process and finding coherent and effective schedules for the wide variety of production steps, in a dynamic environment, is a challenging task. In this paper, we propose a multi-agent architecture for integrated dynamic scheduling of the hot strip mill (HSM) and the continuous caster. The scheduling systems of these processes have very different objectives and constraints, and operate in an environment where there is a substantial quantity of real-time information concerning production failures and customer requests. Each process is assigned to an agent which independently, seeks an optimal dynamic schedule at a local level taking into account local objectives, real-time information and information received from other agents. Each agent can react to real-time events in order to fix any problems that occur. We focus here, particularly, on the HSM agent which uses a tabu search heuristic to create good predictive–reactive schedules quickly. The other agents simulate the production of the coil orders and the real-time events, which occur during the scheduling process. When real-time events occur on the HSM, the HSM agent might decide whether to repair the current schedule or reschedule from scratch. To address this problem, a range of schedule repair and complete rescheduling strategies are investigated and their performance is assessed with respect to measures of utility, stability and robustness, using an experimental simulation framework.     

Robust seismic design optimization of steel structures

Stochastic performance measures can be taken into account, in structural optimization, using two distinct formulations: robust design optimization (RDO) and reliability-based design optimization (RBDO). According to a RDO formulation, it is desired to obtain solutions insensitive to the uncontrollable parameter variation. In the present study, the solution of a structural robust design problem formulated as a two-objective optimization problem is addressed, where cross-sectional dimensions, material properties and earthquake loading are considered as random variables. Additionally, a two-objective deterministic-based optimization (DBO) problem is also considered. In particular, the DBO and RDO formulations are employed for assessing the Greek national seismic design code for steel structural buildings with respect to the behavioral factor considered. The limit-state-dependent cost is used as a measure of assessment. The stochastic finite element problem is solved using the Monte Carlo Simulation method, while a modified NSGA-II algorithm is employed for solving the two-objective optimization problem.     

高海拔地区电气外绝缘的补偿措施

指出了在高海拔地区因为空气稀薄、气压低,使电气设备外绝缘和空气间隙的放电电压降低。若采用传统的“加强绝缘”的方法,在实施时有很大困难;而采用“加强保护”来“加强绝缘”,这样高海拔地区的外绝缘强度即使有所下降,在某一高程下,仍然可以保证绝缘和过电压之间必要的配合。并已在实际工程中得到应用,可供类似工程借鉴、参考。     

A comparison of adaptive control strategies for hot steel strip rolling mills

Many modeling situations occur in which the plant has uncertain dynamics, nonlinearities, time varying characteristics and noise corrupted input and output measurements. These processes generally require a human operator whose function is to provide intelligent modeling and control. This exact situation occurs in the modeling and control of roll force in a hot steel rolling mill. It is the purpose of this paper to investigate and compare various adaptive control strategies for this problem.The first strategy uses a parameter identification technique to track the parameters in the roll force setup model from one steel run to the next. The next algorithm provides feedback control from run to run by an adaptive controller which uses a linear reinforcement learning scheme to adjust its parameters. The third method accounts for the above complexities by approaching the problem from a behavioral and structural point of view. The behavior of the model is assessed through a performance evaluator and the model is modified structurally and parametrically to improve the performance of the system as the process evolves. The derivation is based on correlation techniques and linear reinforcement learning theory, the latter of which provides memory and intelligence to the algorithm to model the decision process of the human operator. The results of this work serve to reinforce the opinion that the nonlinear mathematical structure of the model should be able to change from one steel run to the next in order to compensate for changes in mill characteristics and in the mill environment. Modeling results are presented from actual mill data and comparisons are made with time invariant models. In addition, the algorithms are general enough so that they may be easily applied to other processes that seem to defy traditional modeling techniques. They are not case dependent.     

Prediction of the response under impact of steel armours using a multilayer perceptron

This article puts forward the results obtained when using a neural network as an alternative to classical methods (simulation and experimental testing) in the prediction of the behaviour of steel armours against high-speed impacts. In a first phase, a number of impact cases are randomly generated, varying the values of the parameters which define the impact problem (radius, length and velocity of the projectile; thickness of the protection). After simulation of each case using a finite element code, the above-mentioned parameters and the results of the simulation (residual velocity and residual mass of the projectile) are used as input and output data to train and validate a neural network. In addition, the number of training cases needed to arrive at a given predictive error is studied. The results are satisfactory, this alternative providing a highly recommended option for armour design tasks, due to its simplicity of handling, low computational cost and efficiency.     

Management and control systems in the steel industry

Kimitsu Works, built during the period of Japan's rapid economic growth, was conceived and designed as a modern plant with emphasis on applying computers throughout its operation.Since the prototype of Kimitsu Integrated Information System (KIIS) was completed in 1970, KIIS has realized an integration of systems for processing information and data on steel plant operations from the receiving of orders to the shipping of products by assigning various functions of production control and operating control to a hierarchical structure of business computers, and process computers.After the oil crises, however, restructuring and modification of the existing systems became necessary to adopt to changes in the economy and plant-operating conditions, and to meet changes in manufacturing processes. Against such background, computer applications have been further expanded to fit the application of online systems to administrative areas in addition to the area of production control, and new computer systems have been developed to facilitate the control and analysis by staff departments.     

Multi-mode acid concentration prediction models of cold-rolled strip steel pickling process

In the steel strip pickling process, the control of the acid concentration is an important part for ensuring the strip surface quality. Now only X-ray method is used to detect the acid concentration online, but the price is very high and the maintenance is very hard. The acid concentration is not measured in most of the steel strip pickling lines online. In this paper, a soft measurement of acid concentration is developed. The pressure differential, conductivity and temperature are used to calculate the acid concentration including ferrous chloride (FeCl₂) and hydrogen chloride (HCl) concentration. The real pickling process is under a multi-mode condition. First, the spectral clustering based on geodesic distance is used to cluster the data into some groups. There are clearly linear relationship between the condition variables and the acid concentration. Then, orthogonal signal correction-iteratively reweighted least squares (OSC-IRLS) models based on the cluster data set are built to predict the acid concentration. The real field data set from cold-rolled strip steel pickling process is used to validate the model. The results demonstrate that the clustering method can improve the prediction result.     

Dynamic foot function and morphology in elite rugby league athletes of different ethnicity

It has long been assumed that foot function and morphology differ between ethnicities. However, quantitative research proving or disproving this relationship is sparse. As a starting point, the objective of this study was to investigate the plantar loading characteristics and foot geometry of athletes from three ethnicities, being Caucasian, Maori and Pacific Islanders. Four plantar pressure parameters were compared in 28 male elite rugby league players using an EMED-AT plantar pressure distribution platform [Novel GmbH, Munich, Germany] and the five-step method. Foot geometry measures were also taken, including arch index, coefficient of spreading, hallux angle and sub-arch angle. Five trials were collected per foot at a self-selected speed. It was found that Caucasian and Maori subjects had a relatively wider forefoot than the Pacific Island subjects; however the Pacific Islanders' foot was found to be wider than both these ethnicities in absolute terms. While Caucasian subjects loaded the toes to a much greater extent than the Maori and Pacific Island subjects, the latter demonstrated a greater loading of the mid and forefoot regions. Pacific Island subjects revealed a significantly more pronounced hallux valgus angle as compared to the Caucasian and Maori subjects. The results of this study may be relevant for/should be taken into consideration in footwear design issues, where allowances need to be made during the design process for anatomical differences between ethnicities. However these observations cannot be generalised to whole ethnic populations, and further research is required on non-athletes to build on the current research findings.