Walking Direction Research Articles

Using inertial measurement units to identify medio-lateral ground reaction forces due to walking and swaying

Horizontal ground reaction forces (GRFs) due to human walking and swaying have been investigated (respectively) through direct measurements using a treadmill and a set of force plates. These GRFs have also been measured (or estimated) indirectly using acceleration data provided by inertial measurement units (IMUs).One motivation for this research has been the lack of published data on these two forms of loading that are generated by movements of the human body in the medio-lateral plane perpendicular to the direction of walking or the direction faced during swaying. The other motivation, following from successful developments in applying IMUs to in-situ vertical GRF measurements, has been to identify best practice for estimating medio-lateral GRFs outside the constraints of a laboratory.Examination of 852 treadmill measurements shows that medio-lateral GRFs at the first sub-harmonic of pacing rate can exceed 10% of body weight. Using a smaller and more recent set of measurements including motion capture, it has been shown that IMUs can be used to reconstruct these GRFs using a linear combination of body accelerations at each of the lower back and sternum positions. There are a number of potential applications for this capability yet to be explored, in particular relating to footbridge performance.A separate set of measurements using force plates has shown that harmonic components of medio-lateral dynamic load factors due to on the spot swaying can approach 50% of body weight. Such forces provide a capability to excite horizontal vibration modes of large civil structures with frequencies below 2 Hz that are problematic for mechanical excitation. As with walking, the ability to use IMUs to estimate medio-lateral swaying GRFs outside laboratory constraints has been demonstrated. As for walking a pair of IMUs is needed, but the best linear combination varies strongly between individuals, according to swaying style. In-situ application of indirect measurement has been successfully demonstrated through a very challenging application of system identification of a multi-storey building, including estimation of modal mass.

Natural locomotion based on a reduced set of inertial sensors: Decoupling body and head directions indoors.

Inertial sensors offer the potential for integration into wireless virtual reality systems that allow the users to walk freely through virtual environments. However, owing to drift errors, inertial sensors cannot accurately estimate head and body orientations in the long run, and when walking indoors, this error cannot be corrected by magnetometers, due to the magnetic field distortion created by ferromagnetic materials present in buildings. This paper proposes a technique, called EHBD (Equalization of Head and Body Directions), to address this problem using two head- and shoulder-located magnetometers. Due to their proximity, their distortions are assumed to be similar and the magnetometer measurements are used to detect when the user is looking straight forward. Then, the system corrects the discrepancies between the estimated directions of the head and the shoulder, which are provided by gyroscopes and consequently are affected by drift errors. An experiment is conducted to evaluate the performance of this technique in two tasks (navigation and navigation plus exploration) and using two different locomotion techniques: (1) gaze-directed mode (GD) in which the walking direction is forced to be the same as the head direction, and (2) decoupled direction mode (DD) in which the walking direction can be different from the viewing direction. The obtained results show that both locomotion modes show similar matching of the target path during the navigation task, while DD’s path matches the target path more closely than GD in the navigation plus exploration task. These results validate the EHBD technique especially when allowing different walking and viewing directions in the navigation plus exploration tasks, as expected. While the proposed method does not reach the accuracy of optical tracking (ideal case), it is an acceptable and satisfactory solution for users and is much more compact, portable and economical.

Detecting heel strikes for gait analysis through acceleration flow

In some forms of gait analysis, it is important to be able to capture when the heel strikes occur. In addition, in terms of video analysis of gait, it is important to be able to localise the heel where it strikes on the floor. In this study, a new motion descriptor, acceleration flow, is introduced for detecting heel strikes. The key frame of heel strike can be determined by the quantity of acceleration flow within the region of interest, and positions of the strike can be found from the centre of rotation caused by radial acceleration. Our approach has been tested on a number of databases which were recorded indoors and outdoors with multiple views and walking directions for evaluating the detection rate under various environments. Experiments show the ability of our approach for both temporal detection and spatial positioning. The immunity of this new approach to three anticipated types of noises in real CCTV footage is also evaluated in our experiments. The authors acceleration flow detector is shown to be less sensitive to Gaussian white noise, whilst being effective with images of low‐resolution and with incomplete body position information when compared with other techniques.

On the morphological variability of Ichniotherium tracks and evolution of locomotion in the sistergroup of amniotes.

Ichniotherium tracks with a relatively short pedal digit V (digit length ratio V/IV < 0.6) form the majority of yet described Late Carboniferous to Early Permian diadectomorph tracks and can be related to a certain diadectid clade with corresponding phalangeal reduction that includes Diadectes and its close relatives. Here we document the variation of digit proportions and trackway parameters in 25 trackways (69 step cycles) from nine localities and seven further specimens with incomplete step cycles from the type locality of Ichniotherium cottae (Gottlob quarry) in order to find out whether this type of Ichniotherium tracks represents a homogeneous group or an assemblage of distinct morphotypes and includes variability indicative for evolutionary change in trackmaker locomotion. According to our results, the largest sample of tracks from three Lower Permian sites of the Thuringian Forest, commonly referred to I. cottae, is not homogeneous but shows a clear distinction in pace length, pace angulation, apparent trunk length and toe proportions between tracks from Bromacker quarry and those from the stratigraphically older sites Birkheide and Gottlob quarry. Three Late Carboniferous trackways of Ichniotherium with relatively short pedal digit V from Haine’s Farm, Ohio, and Alveley near Birmingham, United Kingdom, that have been referred to the ichnotaxa “Baropus hainesi,” “Megabaropus hainesi” and “Ichniotherium willsi,” respectively, share a marked outward rotation of foot imprints with respect to walking direction. Apart from this feature they are in many aspects similar to the Birkheide and Gottlob records of I. cottae. With the possible exception of the Maroon Formation (Early Permian, Colorado) sample, Early Permian Ichniotherium trackways with a relatively short pedal digit V fall into the morphological spectrum of the three well defined “Hainesi–Willsi,” “Birkheide–Gottlob” and “Bromacker” morphotypes. With their more obtuse pace angulations and higher body-size-normalized pace and stride lengths the Bromacker type tracks imply higher walking speeds of their trackmakers compared to all other Ichniotherium tracks. More generally, a trend towards higher locomotion capability from the last common ancestor of all Ichniotherium producers to the last common ancestor of all “Ichniotherium with relatively short pedal digit V” and from the latter to the trackmakers of the mid-Early Permian Bromacker type can be deduced—with the reservation that overall sample size is relatively small, making this scenario a preliminary assessment. Whether the presumed advancements represent a more general pattern within diadectomorphs remains open until the non-European Ichniotherium trackway record improves. Ichnotaxonomic implications are discussed.

A typical social attention behaviors and its underlying neural mechanism in individuals with autism spectrum disorder

The ability to coordinate attention to events or objects between interactive social partners, referred to as social attention, is of great significance for adaptive social behaviors and nonverbal communications in our daily life, helping us to infer other person’s inner state (e.g., intentions, goals) and learn about where important events (e.g., food, danger) occur in the environment. In recent years, many studies have demonstrated that social cues (e.g., eye gaze, head orientation and walking direction of biological motion) can trigger reflexive attentional orienting effects using adapted central cueing paradigm originally designed by Posner. However, not all of us are equally adept at directing attention to where others are focusing on, and this ability is strongly impaired in individuals with autism spectrum disorder (ASD), a highly genetic neurodevelopmental disorder marked by striking social deficits and repetitive behaviors. Here we systematically reviewed recent work on abnormal social attention behaviors and its underlying neural mechanisms in ASD. We first expatiated a typical social attention behaviors indexed by covert and overt attention in ASD. It has been documented that ASD individuals tend to show reduced reflexive orienting effect manifesting itself in both covert attention and overt eye movement compared to typically developing individuals (TD). Yet some controversies concerning the malfunction of social attention in ASD remain to be resolved, based on some evidence demonstrating comparable orienting effect between ASD and TD group. Then we summarized the development course of social attention in ASD. Crucially, atypical orienting to eye gaze is more likely to be observed in younger children but not older children or adults with ASD. It is reasonable to postulate that ASD individuals may acquire this ability through overlearning the association between social cues and targets in everyday life as they grow older. Furthermore, we discussed the neural basis of abnormal social attention behaviors in ASD. Using a combination of psychophysical paradigms and neuroimaging techniques, researchers have reported atypical neural activities in superior temporal gyrus and prefrontal cortex under the supraliminal condition as well as abnormal activation in amygdala under the subliminal condition in the brain of ASD. Moreover, the ASD group showed much less difference in activation of frontoparietal attention networks between social and nonsocial attention task than the TD group, implying disruptive social attention in ASD. Finally, several perspectives on further investigations were put forward given the controversies and insufficient evidence concerning the malfunction of social attention in ASD. Future studies should employ multiple types of social cues (e.g., eye gaze and walking direction of biological motion) in conjunction with more ecological paradigms to investigate conscious and non-conscious social attention behaviors from a developmental approach. More importantly, more neuroimaging studies are needed to explore the functional connections among several key cortical regions and subcortical regions underlying atypical social attention behaviors in ASD. Such efforts will help to facilitate the early diagnosis and intervention of ASD.

몰입형 가상현실을 위한 다중 키넥트 기반 휴대용 전방향 네비게이션 시스템 개발 (Development of a Multiple Kinect Based Portable Omnidirectional Navigation System for Immersive Virtual Reality)

몰입형 가상현실을 위한 다중 키넥트 기반 휴대용 전방향 네비게이션 시스템 개발 (Development of a Multiple Kinect Based Portable Omnidirectional Navigation System for Immersive Virtual Reality)

Walking Direction Estimation for Gait Based Applications

Gait has become a popular trait for biometric person recognition/re-identification. This is due to its advantage of being captured without any subject cooperation. This made it suitable especially for video surveillance applications. However, the gait features obtained in such scenarios depends on the observed walking direction of the subject. In this paper, we deal with the problem related to walking direction estimation in unconstrained environments. Covariates factors (i.e. carrying different types of bag, clothing) affect considerably the accuracy of walking direction estimation problem. Therefore, we have proposed a solution which is suitable for both real time application and unconstrained environment where the user walking direction is different and affected by covariates factors. The discriminative power of this solution is verified through experiments. The performance of this method was evaluated on the CASIA-B database. Experimental results prove the effectiveness of our proposed walking direction estimation method.

A Theoretical Treatment of Crowd–Structure Interaction

A vertical crowd–structure interaction model including the interaction amongst pedestrians is developed to study the structural performances of the supporting structure with social force effect. This model can be used to analyze the vibration problem of footbridge under a large crowd excitation. The social force is firstly introduced to describe the dynamic interaction amongst the bipedal models with damping-spring legs modeling pedestrian movement on a three-dimensional plate structure. The social force determines the walking direction and velocity of pedestrian. Numerical studies show that the structural dynamic performances can be remarkably changed under the crowd action. The natural frequency of structure is decreased and is time-varying with an increase in the crowd density. However, the damping ratio of structure is increased. The proposed model could well describe the crowd–structure dynamic interaction.

DNA bipedal motor walking dynamics: an experimental and theoretical study of the dependency on step size.

We present a detailed coarse-grained computer simulation and single molecule fluorescence study of the walking dynamics and mechanism of a DNA bipedal motor striding on a DNA origami. In particular, we study the dependency of the walking efficiency and stepping kinetics on step size. The simulations accurately capture and explain three different experimental observations. These include a description of the maximum possible step size, a decrease in the walking efficiency over short distances and a dependency of the efficiency on the walking direction with respect to the origami track. The former two observations were not expected and are non-trivial. Based on this study, we suggest three design modifications to improve future DNA walkers. Our study demonstrates the ability of the oxDNA model to resolve the dynamics of complex DNA machines, and its usefulness as an engineering tool for the design of DNA machines that operate in the three spatial dimensions.

Walking Direction Estimation Based on Statistical Modeling of Human Gait Features With Handheld MIMU

Contrary to Global Navigation Satellite System or Wi-Fi based navigation, pedestrian dead reckoning (PDR) method with handheld inertial and magnetic sensors gives the opportunity to achieve indoor/outdoor ubiquitous pedestrian localization. A remaining PDR critical issue is the estimation of the walking direction. Existing methods are principally searching for the energy main axis, but they do not consider the variability of hand movements introducing robustness issues. A new method, based on statistical models and likelihood maximization adjusted to the person and his/her activity, is proposed in this paper. Performance is assessed with experiments in a motion capture room and a shopping mall. The new statistical approach gives globally better results than state of the art methods. A 1.4° to 15.3° error on the walking direction estimates is found over several “1-km walk” tests indoors.

Dead Reckoning in Structured Environments for Human Indoor Navigation

Provision for unrestricted movement by everybody, including disabled people, is among the basic aims of a Smart City. In this paper, we deal with human indoor navigation based on inertial sensors that are commonly found in devices, such as smartphones. The approach has gathered broad interest within the scientific community, since it does not require installation of external devices and allows the use of a smartphone both as measurement platform and user interface. Thus, it can be seen as an inclusive low-cost, low-energy human navigation aid. We focus this paper on the implementation of algorithms for estimating and tracking the heading direction of a user walking within a structured environment, e.g., a building. The main feature of the proposed method is that the estimation of direction is not referred to absolute headings based on the four cardinal directions, as usually done in the literature. To achieve sufficient reliability and, at the same time, preserve simplicity, our approach is based on detecting relative changes in the user direction with respect to a reference system obtained during an initial calibration phase. The fundamental direction, which exhibits the minimum distance with respect to the raw measured values, is then provided as output. Experimental results reported in this paper show that a user path can be traced with sufficient accuracy within four steps in the worst case.

Fractal analyses reveal independent complexity and predictability of gait.

Locomotion is a natural task that has been assessed for decades and used as a proxy to highlight impairments of various origins. So far, most studies adopted classical linear analyses of spatio-temporal gait parameters. Here, we use more advanced, yet not less practical, non-linear techniques to analyse gait time series of healthy subjects. We aimed at finding more sensitive indexes related to spatio-temporal gait parameters than those previously used, with the hope to better identify abnormal locomotion. We analysed large-scale stride interval time series and mean step width in 34 participants while altering walking direction (forward vs. backward walking) and with or without galvanic vestibular stimulation. The Hurst exponent α and the Minkowski fractal dimension D were computed and interpreted as indexes expressing predictability and complexity of stride interval time series, respectively. These holistic indexes can easily be interpreted in the framework of optimal movement complexity. We show that α and D accurately capture stride interval changes in function of the experimental condition. Walking forward exhibited maximal complexity (D) and hence, adaptability. In contrast, walking backward and/or stimulation of the vestibular system decreased D. Furthermore, walking backward increased predictability (α) through a more stereotyped pattern of the stride interval and galvanic vestibular stimulation reduced predictability. The present study demonstrates the complementary power of the Hurst exponent and the fractal dimension to improve walking classification. Our developments may have immediate applications in rehabilitation, diagnosis, and classification procedures.

A Novel Accelerometer-Based Technique for Robust Detection of Walking Direction.

Distance estimation in pedestrian dead reckoning is acquired using vector norm of accelerations, which results in positive values. However, anteroposterior acceleration is negative when a step is taken backward, which must be detected for accurate localization. This paper proposes a novel approach for the detection of walking direction, which uses a dominant trend duration. The approach evaluates anteroposterior acceleration out of a foot-worn accelerometer for temporal dominance of acceleration trends during swing phase of the walk. The approach is tested for forward and backward walks with speed variations on a straight path as well as for forward walk at normal speed on a turning path. To validate the detection accuracy, success rates per participant per walk trial are calculated and then overall success rate for all the trials are reported. Moreover, metrics precision, recall and F1 scores are calculated for detection reliability in both directions. Overall 98 ± 2% detection accuracy is achieved on linear path considering both directions and all speed variations, whereas 93 ± 7% on turning path including left and right turns. In comparison with the state-of-the-art bidirectional detection approach, the proposed approach delivers accurate detection with speed variations without requiring prior training and relies on a single sensory feature. Dominant trend duration is a novel and reliable feature to detect directional changes during communal walk with speed variation. The approach can be employed in different contexts, such as enabling pedestrian localization approaches to accommodate back stepping or any application that requires knowledge of changing directions while walking.

Dichotomy in Biological Motion Perception: Pigeons Use Feet Local Motion to Determine Direction

The study examines the visual processes underlying the detection of the motion of land animals, or biological motion. The ability to process the motion of other living beings has profound ecological implications in the wilderness and in our everyday life. Earlier models suggest that there are two distinct ways to process this information. One uses the shape of an entire figure and one uses the motion of one part of the body. In this experiment, we aim to study whether the local motion of the feet or the configuration of the body is used to determine the direction into which a figure is facing. We do this by training pigeons to discriminate facing direction of a stationary walking point‐light figure. Pigeons chose one of two walkers by pecking on a touch screen. Once the task was learned, catch trials of backwards walkers were introduced. This kind of display gives the pigeon opposing information about direction. While the shape of the walker tells them it is walking one way, the feet give the impression that it is moving in the other. Pigeons were successful in learning to discriminate directions and at the introduction of the catch trials, most birds used the local motion cue of the feet to determine direction. The results indicate that pigeons seem to being using the feet, rather than the shape of a figure, to process direction of movement. In conjunction with previous literature, this study suggests that there exists an innate “life detector” specialized for filtering the movement of the feet.

Single-Camera-Based Method for Step Length Symmetry Measurement in Unconstrained Elderly Home Monitoring.

single-camera-based gait monitoring is unobtrusive, inexpensive, and easy-to-use to monitor daily gait of seniors in their homes. However, most studies require subjects to walk perpendicularly to camera's optical axis or along some specified routes, which limits its application in elderly home monitoring. To build unconstrained monitoring environments, we propose a method to measure step length symmetry ratio (a useful gait parameter representing gait symmetry without significant relationship with age) from unconstrained straight walking using a single camera, without strict restrictions on walking directions or routes. according to projective geometry theory, we first develop a calculation formula of step length ratio for the case of unconstrained straight-line walking. Then, to adapt to general cases, we propose to modify noncollinear footprints, and accordingly provide general procedure for step length ratio extraction from unconstrained straight walking. Our method achieves a mean absolute percentage error (MAPE) of 1.9547% for 15 subjects' normal and abnormal side-view gaits, and also obtains satisfactory MAPEs for non-side-view gaits (2.4026% for 45°-view gaits and 3.9721% for 30°-view gaits). The performance is much better than a well-established monocular gait measurement system suitable only for side-view gaits with a MAPE of 3.5538%. Independently of walking directions, our method can accurately estimate step length ratios from unconstrained straight walking. This demonstrates our method is applicable for elders' daily gait monitoring to provide valuable information for elderly health care, such as abnormal gait recognition, fall risk assessment, etc. single-camera-based gait monitoring is unobtrusive, inexpensive, and easy-to-use to monitor daily gait of seniors in their homes. However, most studies require subjects to walk perpendicularly to camera's optical axis or along some specified routes, which limits its application in elderly home monitoring. To build unconstrained monitoring environments, we propose a method to measure step length symmetry ratio (a useful gait parameter representing gait symmetry without significant relationship with age) from unconstrained straight walking using a single camera, without strict restrictions on walking directions or routes. according to projective geometry theory, we first develop a calculation formula of step length ratio for the case of unconstrained straight-line walking. Then, to adapt to general cases, we propose to modify noncollinear footprints, and accordingly provide general procedure for step length ratio extraction from unconstrained straight walking. Our method achieves a mean absolute percentage error (MAPE) of 1.9547% for 15 subjects' normal and abnormal side-view gaits, and also obtains satisfactory MAPEs for non-side-view gaits (2.4026% for 45°-view gaits and 3.9721% for 30°-view gaits). The performance is much better than a well-established monocular gait measurement system suitable only for side-view gaits with a MAPE of 3.5538%. Independently of walking directions, our method can accurately estimate step length ratios from unconstrained straight walking. This demonstrates our method is applicable for elders' daily gait monitoring to provide valuable information for elderly health care, such as abnormal gait recognition, fall risk assessment, etc.

Kinesiology-inspired estimation of pedestrian walk direction for smart surveillance

The article proposes a novel approach for estimating the walk direction of a pedestrian conjointly exploiting the complementary nature of video-based and frame-based walk direction estimation methods. Video-based direction estimation classifies inter-frame features by HMM as underlying machine learning method. To exploit the intra-frame features for orientation estimation, kinesiology based study has been performed and lower body kinematics of sagittal plane is identified to be the most suitable choice for feature. This frame-based intra-frame feature is classified using Least Square Support Vector Machine (LS-SVM) for finding orientation per frame. The score-level fusion of estimated results from both the topologies using a rule based look-up table produces the ultimate estimate for walk direction. The proposed method is tested over three different databases and is found to perform better than state-of-the-art methods due to inheritance of both inter-frame and intra-frame feature.

Efficiencies for parts and wholes in biological-motion perception.

People can reliably infer the actions, intentions, and mental states of fellow humans from body movements (Blake & Shiffrar, 2007). Previous research on such biological-motion perception has suggested that the movements of the feet may play a particularly important role in making certain judgments about locomotion (Chang & Troje, 2009; Troje & Westhoff, 2006). One account of this effect is that the human visual system may have evolved specialized processes that are efficient for extracting information carried by the feet (Troje & Westhoff, 2006). Alternatively, the motion of the feet may simply be more discriminable than that of other parts of the body. To dissociate these two possibilities, we measured people's ability to discriminate the walking direction of stimuli in which individual body parts (feet, hands) were removed or shown in isolation. We then compared human performance to that of a statistically optimal observer (Gold, Tadin, Cook, & Blake, 2008), giving us a measure of humans' discriminative ability independent of the information available (a quantity known as efficiency). We found that efficiency was highest when the hands and the feet were shown in isolation. A series of follow-up experiments suggested that observers were relying on a form-based cue with the isolated hands (specifically, the orientation of their path through space) and a motion-based cue with the isolated feet to achieve such high efficiencies. We relate our findings to previous proposals of a distinction between form-based and motion-based mechanisms in biological-motion perception.

Heading estimation fusing inertial sensors and landmarks for indoor navigation using a smartphone in the pocket

Principal component analysis (PCA)-based approach for user heading estimation using a smartphone in the pocket suffers from an inaccurate estimation of device attitude, which plays a central role in both obtaining acceleration signals in the horizontal plane and the ultimate global walking direction extraction. To solve this problem, we propose a novel heading estimation approach based on two unscented Kalman filters (UKFs) fusing inertial sensors and landmarks. The first UKF is developed for the recalibration of device attitude estimation. We mathematically derive the measurement equation connecting observed user heading from landmarks with the quaternion vector representing device attitude. To decrease the nonlinearity of the measurement equation and make the filter more robust, we deploy the difference between user heading derived from the landmark and estimation result of PCA-based approach as the observation variable. The second UKF is developed for user heading estimation fusing estimation results of PCA-based approach and observed user headings from landmarks. Besides, we develop a robust landmark identification method by exploiting the acceleration and device pitch patterns, while noisy barometers are no longer required as previous methods. Experiments show that the proposed landmark-aided user heading estimation approach may improve accuracy performance significantly, which is very useful for continuous indoor navigation.

The influence of visual flow and perceptual load on locomotion speed

Visual flow is used to perceive and regulate movement speed during locomotion. We assessed the extent to which variation in flow from the ground plane, arising from static visual textures, influences locomotion speed under conditions of concurrent perceptual load. In two experiments, participants walked over a 12-m projected walkway that consisted of stripes that were oriented orthogonal to the walking direction. In the critical conditions, the frequency of the stripes increased or decreased. We observed small, but consistent effects on walking speed, so that participants were walking slower when the frequency increased compared to when the frequency decreased. This basic effect suggests that participants interpreted the change in visual flow in these conditions as at least partly due to a change in their own movement speed, and counteracted such a change by speeding up or slowing down. Critically, these effects were magnified under conditions of low perceptual load and a locus of attention near the ground plane. Our findings suggest that the contribution of vision in the control of ongoing locomotion is relatively fluid and dependent on ongoing perceptual (and perhaps more generally cognitive) task demands.

Control algorithm and evaluation of a powered wheeled walker for tracking a user

This study proposed a user-tracking control algorithm for a powered wheeled walker and examined how it improves the tracking performance of a user. Our newly developed powered wheeled walker based on the mechanism of infant walker and powered wheelchair has enhanced walking stability and needs less physical power to be moved. The walker is able to smoothly track user’s various movements (i.e. forward, backward translation, and rotation) using pelvis motion sensors determining walking direction and stereo cameras analyzing lower extremity motion. In particular, weighting factors of controllers using pelvis motion sensor and stereo cameras can be suitably adjustable online. The experimental testing was conducted to examine walker’s tracking performance, and the results from electromyography testing showed that the walker based on user-tracking control algorithm significantly decreased the magnitude of exerted muscle strength in both upper and lower extremity compared to conventional passive wheeled walker. Thus, we were able to successfully verify that the proposed walker can automatically track a user with gait impairment for safe walking without a helper.