Key Postures Research Articles

A Muscle-based Feed-forward Controller of the Human Body

There is an increasing demand for human body motion data. Motion capture and physical animation have been used to generate such data. It is, however, apparent that such methods cannot automatically generate arbitrary human body motions. A human body is a redundant multi-linked body controlled by a number of muscles. For this reason, the muscles must work appropriately and cooperatively for controlling the whole body. It is well-known that the human body control system is composed of two parts: The open-loop feed-forward control system and the closed-loop feedback control system. Many researchers have investigated the characteristics of the latter by analyzing the response of a human body to various external perturbations. However, for the former, very few studies have been done. This paper proposes an open-loop feed-forward model of the lower extremities which includes postural control for accurate animation of a human body. Assumptions are made here that the feed-forward controller minimizes a certain objective value while keeping the balance of the body stable. The actual human motion data obtained using a motion capturing technique is compared with the trajectory calculated using our method for verification. The best criteria which is based on muscle dynamics is proposed. Using our method, dynamically correct human animation can be created by merely specifying a few key postures.

Video-Based Human Movement Analysis and Its Application to Surveillance Systems

This paper presents a novel posture classification system that analyzes human movements directly from video sequences. In the system, each sequence of movements is converted into a posture sequence. To better characterize a posture in a sequence, we triangulate it into triangular meshes, from which we extract two features: the skeleton feature and the centroid context feature. The first feature is used as a coarse representation of the subject, while the second is used to derive a finer description. We adopt a depth-first search (dfs) scheme to extract the skeletal features of a posture from the triangulation result. The proposed skeleton feature extraction scheme is more robust and efficient than conventional silhouette-based approaches. The skeletal features extracted in the first stage are used to extract the centroid context feature, which is a finer representation that can characterize the shape of a whole body or body parts. The two descriptors working together make human movement analysis a very efficient and accurate process because they generate a set of key postures from a movement sequence. The ordered key posture sequence is represented by a symbol string. Matching two arbitrary action sequences then becomes a symbol string matching problem. Our experiment results demonstrate that the proposed method is a robust, accurate, and powerful tool for human movement analysis.

China's Changing Japan Policy in the Late 1960s and Early 1970s and the Impact on Relations with the United States

For years, in studying postwar Sino-Japanese relations, particularly the normalization of bilateral relations, most scholars focused more on Japan's policy-making or the U.S. role than on Chinese diplomacy. Actually, in most of the Cold War period, China held a key posture in dealing with the Japan problem, whether its offensives succeeded or suffered setbacks, confronting the United States and later the Soviet Union and regaining China's central position in East Asia and even the world. As a rising great power, China exerted increasing influence on the postwar international order. And Japan policy constituted an indispensable part

Optimized motion simplification for crowd animation

AbstractSimulating a huge number of articulate figures in a real‐time application is one of the challenging research topics in character animation. Several researchers have tried to improve the performance of animation using the image‐based technique such as ‘impostor.’ This method improved the speed of the animation; however, the accuracy, memory, and interactivity problems related to motion remain to be resolved. In this regard, a ‘motion simplification’ framework for an articulate figure is proposed, which not only improves the speed of the animation but also conserves the features of the original motion. First, the motion sequence is analyzed using mean shift clustering for the purpose of extracting key postures and automatically generating the priority of joint reductions. These motion analysis results are directly utilized as the input of the proposed posture optimization. The least square method is applied in order to minimize the error between the original and the simplified posture. Finally, how to apply the proposed simplified motion in a real‐time application without decreasing the visual quality of the scene is shown. The experimental result shows that the proposed motion simplification can be successfully applied in a real‐time animation system. Copyright © 2006 John Wiley & Sons, Ltd.

Postural Influences on the Hormone Level in Healthy Subjects: I. The Cobra Posture and Steroid Hormones

Cortisol, testosterone, dehydroepiandrosterone (DHEA), and aldosterone were measured in the blood serum of healthy subjects who adopted the cobra posture (bhujangasana), a key posture of hatha yoga. The subjects were trained in yoga; blood samples were taken before and after the exercise at an interval of no more than 5 min. As revealed with a new confidence interval–evaluating method developed by A.I. Ivanov, cortisol decreased by 11% with a reliability of 0.99 in all subjects, while testosterone increased by 16% with a reliability of 0.95. Changes in DHEA and aldosterone varied. Proceeding from ideas about motor–visceral interactions, the authors hypothesize that, when the subjects adopted the cobra posture, the production of steroid hormones was controlled by neural mechanisms.

Development of computer-based environment for simulating the voluntary upper-limb movements of persons with disability.

Upper-limb orthotic systems have been designed for restoring the upper-limb functions of individuals with disabilities resulting from spinal cord injury (SCI), stroke and muscular dystrophy. These systems employ either functional electrical stimulation or external power. It is proposed that, instead of time-consuming and complicated monitoring using sensors and motion analysis, a software simulator with both angular displacement and acceleration parameters can facilitate the design of a control strategy for an orthosis. Reaching movements of three cervical SCI subjects are used to verify the simulator. A motion analysis system is used to measure the range of motion and joint angles during hand reaching. Results indicate that quaternion and spline curve techniques are suitable for interpolation of the hand reaching movements. The information needed for good simulation only compress the shoulder and elbow joint angles in a few key postures. Stimulated acceleration signals on the upper-arm segment have a high correlation coefficient (> 0.9) and a small root mean squared error (< 0.11 g) with a real bi-axial accelerometer.

A Muscle‐based Feed‐forward Controller of the Human Body

There is an increasing demand for human body motion data. Motion capture and physical animation have been used to generate such data. It is, however, apparent that such methods cannot automatically generate arbitrary human body motions. A human body is a redundant multi‐linked body controlled by a number of muscles. For this reason, the muscles must work appropriately and cooperatively for controlling the whole body. It is well‐known that the human body control system is composed of two parts: The open‐loop feed‐forward control system and the closed‐loop feedback control system. Many researchers have investigated the characteristics of the latter by analyzing the response of a human body to various external perturbations. However, for the former, very few studies have been done. This paper proposes an open‐loop feed‐forward model of the lower extremities which includes postural control for accurate animation of a human body. Assumptions are made here that the feed‐forward controller minimizes a certain objective value while keeping the balance of the body stable. The actual human motion data obtained using a motion capturing technique is compared with the trajectory calculated using our method for verification. The best criteria which is based on muscle dynamics is proposed. Using our method, dynamically correct human animation can be created by merely specifying a few key postures.

Modelling and simulation of the hand grasping using neural networks

In this paper we present preliminary results of a study on the use of artificial neural networks to model and simulate the hand grasping. Results of this study will provide a basic understanding of the co-ordination and control of multiple degrees of freedom upper limb prosthetic devices and robotic end effectors when interacting with the environment. We assumed the hand to be a black box with the inputs being the object and simulation time sequence, whilst the output is the grasping postures over time. We trained the network with samples of key postures of the hand grasping several object shapes and sizes. The back-propagation technique was used to update the weights of the network. We found that the neural network is able to reproduce the postures of the hand grasping objects of different shapes and sizes from a single set of neural network weights.

Realistic animation of human figures using artificial neural networks

We describe a new approach to the animation of human figures which can produce realistic animation and based on artificial neural networks (ANN). A fully connected ANN is trained with inputs and outputs of key frames obtained from image analysis and key postures and parameters of standing, walking and running. A behaviour index is introduced as an input to the ANN. Each index is unique to each behaviour. Other inputs include speed, cycle history and subsytem index. The subsystem index refers to the different subsytem of the human figure e.g. the right leg is a subsystem referred to by an index. The outputs are the joints displacements. The ANN is trained using the back propagation method. The ANN was able to generate realistic animations of walking and running and could merge three different behaviours; standing, walking and running. The proposed method should enable design evaluations, human factors analysis, task simulation and motion understanding easier for non-animation experts.

Some observations on mating behaviour of several cranes in captivity

Responding to the actions of the mate and taking somewhat fixed patterns,Grus japonensis, G. vipio, G. antigone, Anthropoides paradisea andBalearica regulorum pairs are finally led to copulation by a sequence of mating behaviours. There are slight differences in pre-copulatory behaviour patterns between the species and the female's ‘wing-spreading’, being the soliciting and key posture for copulation, differs between the genera; The female's wings are spread wide inGrus, fairly wide inAnthropoides, and are almost folded inBalearica. Post-copulatory behaviours, however, have definite species-specific characters. They usually consist of ‘head-down’ (bowing) or ‘warping’, ‘arching’, etc. immediately following the dismounting of the male inGrus. But a pair ofBalearica first keep their heads high, or gaze at each other for a while, and then show remarkable ‘ruffle-bowing’. These characteristic post-copulatory behaviours are obviously correlated with the threat displays, evolved under agonistic situations, typical to each species.

Physical Fitness in Military Personnel

To the Editor.— Twenty years ago, we examined the minimum muscular fitness of children here and abroad (Switzerland, Italy, Austria). The key posture muscles of our children proved considerably weaker and less flexible than their counterparts abroad, proving that our children are too sedentary. These findings were submitted to President Eisenhower at a White House luncheon conference and prompted him to establish the President's Council on Physical Fitness, then called Youth Fitness. Unfortunately, except for isolated programs, no national or even state efforts have been made except in the field of public relations. At this time, when the need for preventive medical care is of special interest, preventive programs should be started at once. We agree with Cooper that the time to keep the cardiovascular system in good working condition is before it starts to disintegrate, and would add exercise programs and training of exercise habits not at 18 years