Human Motion Analysis System Research Articles

Pendulum-based method for determining the temporal accuracy of digital video-based motion capture systems

Objective To develop a simple method to determine the temporal accuracy of motion analysis systems incorporating commercial digital video cameras. Methods A planar column pendulum with a natural frequency of 0.872 Hz was used to analyse five systems incorporating commercially available cameras and a single codec. Finding The frame rate for each camera was measured to be within 3% of the US National Television Systems Committee (NTSC) broadcasting digital video standard of 29.97 fps; however some cameras produced a frame duplication artefact. Least squares curve-fitting using a sinusoidal function revealed RMS differences between 3–5% for angular position and 5–15% for angular speed compared to the captured motion data. Conclusion A simple method of evaluating temporal accuracy of a digital-based motion capturing system is demonstrated and it is shown that some digital-video cameras and computer playback software contain data compression technology that may produce substantial temporal frame inaccuracies in recovered video sequences. The results indicate that temporal accuracy should be evaluated in digital-based human motion analysis systems prior to their use in experimentation.

Recent developments in human motion analysis

Visual analysis of human motion is currently one of the most active research topics in computer vision. This strong interest is driven by a wide spectrum of promising applications in many areas such as virtual reality, smart surveillance, perceptual interface, etc. Human motion analysis concerns the detection, tracking and recognition of people, and more generally, the understanding of human behaviors, from image sequences involving humans. This paper provides a comprehensive survey of research on computer-vision-based human motion analysis. The emphasis is on three major issues involved in a general human motion analysis system, namely human detection, tracking and activity understanding. Various methods for each issue are discussed in order to examine the state of the art. Finally, some research challenges and future directions are discussed.

Contribution to a marker-free system for human motion analysis

The <i>Journal of Electronic Imaging</i> (JEI), copublished bimonthly with the Society for Imaging Science and Technology, publishes peer-reviewed papers that cover research and applications in all areas of electronic imaging science and technology.

Dynamic Modeling of the Human Arm with Video-Based Experimental Analysis

The quantitative assessment of human joint torque capability has manyimportant applications. By means of a multibody approach, the authorsdescribed a formulation for 3D inverse dynamic analysis of a human armduring voluntary free movement. In particular, it is presented as a testcase where the kinematics of the arm is obtained by means of a video-based human motion analysis system.

The model-based human body motion analysis system

In this paper, we propose a model-based method to analyze the human walking motion. This system consists of three phases: the preprocessing phase, the model construction phase, and the motion analysis phase. In the experimental results, we show that our system not only analyzes the motion characteristics of the human body, but also recognizes the motion type of the input image sequences. Finally, the synthesized motion sequences are illustrated for verification. The major contributions of this research are: (1) developing a skeleton-based method to analyze the human motion; (2) using Hidden Markov Model (HMM) and posture patterns to describe the motion type.

Instrumentation considerations of a clinical and a computerized technique for the measurement of foot angles

Measurement of the foot angles either directly from the patient, from video images, or from radiographs is integral to podiatric clinical practice to confirm diagnoses and to plan, prescribe, and monitor treatment protocols. The reliability, precision, and accuracy involved in any measured value limits the validity and usefulness of the measurement to optimal patient management. Studies are described that ensured the accuracy and validity of the standard clinical tool, the universal goniometer (UG), by applying a calibration protocol. These same calibration angles were then measured by a computer-assisted human movement analysis system, the Ariel Performance Analysis System (APAS). The APAS was found to overestimate consistently the UG angular measures by less than 1 degree and this amount of error was considered clinically irrelevant. The angular results obtained by a clinician and a technician using the APAS on two separate days were tested and were found to be comparable and reliable to within 1 degree, and thus the analysis was deemed to be of excellent reliability and precision. The study found that clinicians could establish the accuracy and validity of their instruments by means of simple calibration, and that computer measures could be repeated on patients by a clinical or a technician. The simple calibration procedure described will assist the clinician to ensure that the measures obtained in the clinical setting have minimal measurement error and that the values can be confidently used to make decisions and draw clinical inferences.

Movement aftereffect of bi-vectorial transparent motion

Two moving random-pixel arrays (RPAs) were presented simultaneously in the same target field. These RPAs are perceived as two superimposed transparent moving sheets. Although two directions are perceived simultaneously during stimulus presentation, the movement aftereffect (MAE) is unidirectional. The visual system averages both motion signals in the MAE. For motion vectors of equal magnitude and perpendicular direction the MAE direction is the inverse of the sum of both vectors. In the first experiment we measured perceived direction of the MAE of transparent motion for a range of speed combinations. Results indicate that vector summation only predicts the correct MAE direction for combinations of equal speeds. It is suggested that the direction of the MAE of transparent motion is a resultant of the weighted summation of the component inducing vectors. The question then arises what determines the weighting factors. Directional sensitivity and MAE duration of the individual vectors under transparent conditions were measured and used to weigh the vectors and predict the MAE direction of transparent motion. Statistical analyses showed that MAE duration is a better basis to determine the weighting factors predicting the direction of the MAE of transparent motion than component sensitivity. The direction of the MAE of transparent motion thus seems to be determined by the amount of adaptation to the component vectors as reflected by MAE duration. The results suggest that this gain control cannot be located in the individual motion detectors and must be situated at or after some subsequent cooperation stage of the human motion analysis system.

Automated measurement systems for clinical motion analysis.

I present a computer-based data acquisition and processing system for human motion analysis. The Motion Analysis Laboratory, Children's Hospital at Stanford, exists to provide excellence in clinical evaluation, research, and teaching. The laboratory provides an objective base for assessment of locomotor dysfunction in four general areas--muscle function, energy expenditure, postural equilibrium, and motion data acquisition. Muscle function studies are used to determine the magnitude and timing of muscle activity patterns. An energy-cost index with heart rate as an estimate of energy expenditure is used to evaluate the energy demands of walking. A postural equilibrium measuring system is used to quantify the amount of body sway during stance. I describe a method for three-dimensional coordinate processing of human motion. Use of modern technology facilitates the rapid transfer of useful knowledge from the laboratory to the clinic team in an easily interpretable visual form.