Periodic Gait Research Articles

Collaborative Pedestrian Tracking and Data Fusion With Multiple Cameras

This work presents a framework of a collaborative multiple-camera tracking system for seamlessly object tracking across fixed cameras in overlapping and nonoverlapping fields of view (FOVs). The proposed system is constructed by two major elements: a client part responsible for single-camera object detection and tracking, and a server part responsible for multiple-camera collaborative tracking on the other hand. To improve object segmentation, this work proposes the concept of foreground edge extraction and compensation with an active edge image. For the single-camera tracking, the Kalman filter was applied. When the object was tracked, the system identified useful features for object matching. Color clustering was conducted using a K-mean clustering method, and the gait period was extracted. Furthermore, the homography technique was used to find the corresponding FOV lines in each camera view. Finally, this work used FOV lines for multiple-camera switching and then integrated various features for object matching. In addition, in order to provide a clear view for monitoring, we have implemented a visualization interface that will automatically show the continuous tracking result through a homography mapping. Simulation results indicate that the proposed system effectively addresses the seamless tracking problem in overlapping and nonoverlapping areas. This paper inspires a paradigm of human visual perception for multicamera object tracking, collaboration, and fusion through distributed cameras and computers.

Dual-ellipse fitting approach for robust gait periodicity detection

A new gait period detection algorithm, dual-ellipse fitting (DEF) approach, is proposed. DEF is that two regions of the whole silhouette divided by the centroid are fitted into two ellipses, respectively. We construct the gait fluctuation as a periodic function which depends on the eccentricities of two halves of the silhouette over time. Experimental results show that the proposed method is robust to scale, translation, direction of walking and carrying a bag.

Periodical gait asymmetry assessment using real-time wireless gyroscopes gait monitoring system

A real-time gait monitoring system that incorporates an immediate and periodical assessment of gait asymmetry is described. This system was designed for gait analysis and rehabilitation of patients with pathologic gait. It employs wireless gyroscopes to measure the angular rate of the thigh and shank in real time. Cross-correlation of the lower extremity (Ccnorm), and normalized Symmetry Index (SInorm) are implemented as new approaches to periodically determine the gait asymmetry in each gait cycle. Ccnorm evaluates the signal patterns measured by wireless gyroscopes in each gait cycle. SInorm determines the movement differences between the left and right limb. An experimental study was conducted to examine the viability of these methods. Artificial asymmetrical gait was simulated by placing a load on one side of the limbs. Results showed that there were significant differences between the normal gait and asymmetrical gait (p < 0.01). They also indicated that the system worked well in periodically assessing the gait asymmetry.

An upper-body can improve the stability and efficiency of passive dynamic walking

The compass-gait walker proposed by McGeer can walk down a shallow slope with a self-stabilizing gait that requires no actuation or control. However, as the slope goes to zero so does the walking speed, and dynamic gait stability is only possible over a very narrow range of slopes. Gomes and Ruina have results demonstrating that by adding a torso to the compass-gait walker, it can walk passively on level-ground with a non-infinitesimal constant average speed. However, the gait involves exaggerated joint movements, and for energetic reasons horizontal passive dynamic walking cannot be stable. We show in this research that in addition to collision-free walking, adding a torso improves stability and walking speed when walking downhill. Furthermore, adding arms to the torso results in a collision-free periodic gait with natural-looking torso and limb movements. Overall, in contrast to the suggestions that active control may be needed to balance an upper-body on legs, it turns out that the upper and lower bodies can be integrated to improve the stability, efficiency and speed of a passive dynamic walker.

Gait generation and control for biped robots with underactuation degree one

The paper develops a unified feedback control law for n degree-of-freedom biped robots with one degree of underactuation so as to generate periodic orbits on different slopes. The periodic orbits on different slopes are produced from an original periodic orbit, which is either a natural passive limit cycle on a specific slope or a stable periodic walking gait on level ground generated with active control. First, inspired by the controlled symmetries approach, a general result on gait generation on different slopes based on a periodic orbit on a specific slope is obtained. Second, the time-scaling control approach is integrated to reproduce geometrically same periodic orbits for biped robots with one degree of underactuation. The degree of underactuation is compensated by one degree-of-freedom in the temporal evolution that scales the original periodic orbit. Necessary and sufficient conditions are investigated for the existence and stability properties of periodic orbits on different slopes with the proposed control law. Finally, the proposed approach is illustrated by two kinds of underactuated biped robots: one has a passive gait on a specific ground slope and the other does not have a natural passive gait.

견형 4족 로봇의 위치 이동: 걷기 및 속보

본 논문은 다양한 지면에 적응 가능한 견형 4족 로봇의 위치 이동에 관한 것으로 정 보행과 동 보행의 구현 방법 및 특성을 주로 다루었다. 이를 위하여, 총 12 자유도의 로봇을 자체 제작하였으며, 몸통과 발의 운동궤적을 생체 모방 방식으로 생성한 후 역기구학에 의하여 그에 해당하는 각 다리의 관절각을 해석적으로 구하였다. 이러한 관절각 데이터를 상기 로봇의 ADAMS 모델에 적용하여 컴퓨터 시뮬레이션을 수행한 결과, 계획된 걷기 및 속보 걸음새가 동력학적으로 안정함을 확인하였다. 그러나 그 이전의 속보 패턴의 경우에는 시뮬레이션 결과와는 달리 실험 중 불안정한 거동을 보였다. 그에 따라 원인 분석을 하는 과정 중, 속보와 같은 동 보행의 경우 ZMP보다는 WSM의 개념을 적극적으로 활용하고 보행 주기를 최대한 단축시키는 것이 안정성 확보에 매우 중요함을 발견하였다. This paper is concerned with locomotion of dog-like quadruped robots that can adapt to various terrains, mainly dealing with implementation methods and characteristics of static and dynamic gaits. To this end, a 12-DOF robot is built in house, motional trajectories of its body and feet are generated mimicking biological life, and the corresponding leg joint angles are analytically obtained by inverse kinematics. Such joint angle data are then applied to the robot's ADAMS model for computer simulations so that the planned walk and trot gaits are both confirmed dynamically stable. However, contrary to the simulation results, previous trot patterns showed unstable behavior during experiments. This problem led us to analyze the reason, and in the course we discovered the importance of maximally utilizing the concept of WSM rather than ZMP and therefore reducing the gait period to secure the stability of dynamic gaits such as trot.

Stability analysis and time-varying walking control for an under-actuated planar biped robot

This paper presents two walking controllers for a planar biped robot with unactuated point feet. The control is based on the tracking of reference motions expressed as a function of time. First, the reference motions are adapted at each step in order to create a hybrid zero dynamic (HZD) system. Next, the stability of the walking gait under closed-loop control is evaluated with the linearization of the restricted Poincaré map of the HZD. When the controlled outputs are selected to be the actuated coordinates, most periodic walking gaits for this robot are unstable, that is, the eigenvalues of the linearized Poincaré map (ELPM) is larger than one. Therefore, two control strategies are explored to produce stable walking. The first strategy uses an event-based feedback controller to modify the ELPM and the second one is based on the choice of controlled outputs. The stability analysis show that, for the same robot and for the same reference trajectory, the stability of the walking (or ELPM) can be modified by some pertinent choices of controlled outputs. Moreover, by studying some walking characteristics of many stable cases, a necessary condition for stable walking is proposed. It is that the height of swing foot is nearly zero at the desired moment of impact. Based on this condition, the duration of the step is almost constant in presence of initial error, so a method for choosing controlled outputs for the second controller is given. By using this method, two stable domains for the controlled outputs selection are obtained.

Children's rearfoot and midfoot motion while walking in school shoes

navicular, 1 st and 5 th metatarsal heads and hallux. Rearfoot motion was measured with a wand marker cluster through a window in the shoe. A standing reference trial was used to embed segment axes and thence to calculate motion of the distal segment relative to the proximal segment. Data were normalised to the stance phase which was sub-divided from the anterior/posterior force data as: contact period (initial contact - maximum negative force); midstance (maximum negative force zero) and propulsion (positive force - toe-off). Results Five boys and seven girls participated in the study (mean age 9 years, range 5-13 years). During the contact period shoes decreased midfoot range of motion (ROM) in the frontal plane from 3.4° to 1.7° (p=0.002) and in the transverse plane from 22.0° to 11.6° (p<0.001). No significant difference in ROM occurred during midstance at either the rearfoot or midfoot. During propulsion shoes reduced rearfoot ROM in the frontal plane from 12.0° to 9.6° (p=0.026) and midfoot ROM in the sagittal plan from 19.6° to 10.8° (p<0.001) and in the transverse plan from 10.1° to 4.3° (p<0.001). Conclusions Traditional school shoes restrict children’s foot motion during walking particularly at the midfoot during the contact period and propulsion phases of gait. The medium and long-term impacts of these changes are the focus of further research. The impact of school shoes on foot motion should be considered when assessing the paediatric patient and evaluating the effect of shoe or in-shoe interventions.

BIPED HOPPING CONTROL BAzSED ON SPRING LOADED INVERTED PENDULUM MODEL

Human running can be stabilized in a wide range of speeds by automatically adjusting muscular properties of leg and torso. It is known that fast locomotion dynamics can be approximated by a spring loaded inverted pendulum (SLIP) system, in which leg is replaced by a single spring connecting body mass to ground. Taking advantage of the inherent stability of SLIP model, a hybrid control strategy is developed that guarantees a stable biped locomotion in sagittal plane. In the presented approach, nonlinear control methods are applied to synchronize the biped dynamics and the spring-mass dynamics. As the biped center of mass follows the mass of the mass-spring model, the whole biped performs a stable locomotion corresponding to SLIP model. Simulations are done to obtain a repeatable hopping for a three-link underactuated biped model. Results show that periodic hopping gaits can be stabilized, and the presented control strategy provides feasible gait trajectories for stance and swing phases.

Difference in force direction during propulsion between subjects with different push‐off locations

It could be hypothesized that when walking in a linear direction, the most efficient strategy would be to focus the force created by the push-off in the absolute opposite direction to the direction of propulsion. Forces in a medial or lateral direction could then be considered as loss of efficiency since these forces do not create movement in the intended direction. The aim of this study was to investigate if individual differences in push-off location of the forefoot resulted in difference in force direction. Three subjects with different push-off locations were identified through video gait analysis. The subjects were categorized as having either a lateral (subject 1), central (subject 2) or medial (subject 3) push of location. The subjects walked over a force plate (Kistler) where medial and lateral forces were registered. The results showed distinct differences in force direction between the subjects during the propulsive period of gait (70%-100%) (see figure ​figure11). Figure 1 Difference in force direction may lead to differences in propulsive efficiency. It could also be hypothesized that proximal segments need to compensate in order to keep a subject with medial or lateral force deviations walking in a linear direction of propulsion.

Dynamic Principles of Gait and Their Clinical Implications

A healthy gait pattern depends on an array of biomechanical features, orchestrated by the central nervous system for economy and stability. Injuries and other pathologies can alter these features and result in substantial gait deficits, often with detrimental consequences for energy expenditure and balance. An understanding of the role of biomechanics in the generation of healthy gait, therefore, can provide insight into these deficits. This article examines the basic principles of gait from the standpoint of dynamic walking, an approach that combines an inverted pendulum model of the stance leg with a pendulum model of the swing leg and its impact with the ground. The heel-strike at the end of each step has dynamic effects that can contribute to a periodic gait and its passive stability. Biomechanics, therefore, can account for much of the gait pattern, with additional motor inputs that are important for improving economy and stability. The dynamic walking approach can predict the consequences of disruptions to normal biomechanics, and the associated observations can help explain some aspects of impaired gait. This article reviews the basic principles of dynamic walking and the associated experimental evidence for healthy gait and then considers how the principles may be applied to clinical gait pathologies.

A simple model of a Slinky walking down stairs

The motion of a Slinky walking down a set of stairs is modeled by a simple dynamical system with two degrees of freedom undergoing inelastic collisions. Numerical integration of the model’s equations of motion shows that the model’s behavior is similar to observations of the motion of an actual Slinky. In particular, it is found that the model’s motion exhibits a periodic gait, although subject to more restrictive launch conditions than an actual Slinky.

Leg recirculation in horizontal plane locomotion

A protocol prescribing leg motion during the swing phase is developed for the planar lateral leg spring model of locomotion. Inspired by experimental observations regarding insect leg function when running over rough terrain, the protocol prescribes the angular velocity of the swing-leg relative to the body in a feedforward manner, yielding natural variations in the leg touch-down angle in response to perturbations away from a periodic orbit. Analysis of the reduced order model reveals that periodic gait stability and robustness to external perturbations depends strongly upon the angular velocity of the leg at touch-down. While the leg angular velocity at touch-down provides control over gait stability and can be chosen to stabilize unstable gaits, the resulting basin of stability is much smaller than that observed for the original lateral leg spring model with a fixed leg touch-down angle. Comparisons to experimental leg angular velocity data for running cockroaches reveal that while the proposed protocol is qualitatively correct, smaller leg angular accelerations occur during the second half of the swing phase. Modifications made to the recirculation protocol to better match experimental observations yield large improvements in the basin of stability.

Stability Analysis of Passive Dynamic Walking of Quadrupeds

We introduce a detailed numerical simulation and analysis framework to extend the principles of passive dynamic walking to quadrupedal locomotion. Non-linear limit cycle methods are used to identify possible gaits and to analyze the stability and efficiency of quadrupedal passive dynamic walking. In doing so, special attention is paid to issues that are inherent to quadrupedal locomotion, such as the occurrence of simultaneous contact collisions and the implications of the phase difference between front and back leg pairs. Limit cycles identified within this framework correspond to periodic gaits and can be placed into two categories: in-phase gaits in which front and back legs hit the ground at roughly the same time, and out-of-phase gaits with a ±90° phase shift between the back and front leg pairs. The latter are, in comparison, energetically more efficient but exhibit one unstable eigenvalue that leads to a phase divergence and results in a gait-transition to a less efficient in-phase gait. A detailed analysis examines the influence of various parameters on stability and locomotion speed, with the ultimate goal of determining a stable solution for the energy-efficient, out-of-phase gait. This was achieved through the use of a wobbling mass, i.e. an additional mass that is elastically attached to the main body of the quadruped. The methods, results, and gaits presented in this paper additionally provide a point of departure for the exploration of the considerably richer range of quadrupedal locomotion found in nature.

Age-related mechanical work expenditure during normal walking: The Baltimore Longitudinal Study of Aging

The aim of this cross-sectional study was to delineate age-associated kinematic and kinetic gait patterns of normal walking, and to test the hypothesis that older adults exhibit gait patterns that reduce generative mechanical work expenditures (MWEs). We studied 52 adult Baltimore Longitudinal Study of Aging participants (means age 72±9, from 60 to 92 years) who could walk 4 m unaided. Three-dimensional kinematic and kinetic parameters assessed during rotation-defined gait periods were used to estimate MWEs for the rotation of lower extremities about the medial–lateral (ML) and anterior–posterior (AP) axes of proximal joints, which represent MWEs in the AP and ML sides, respectively. Relationships between gait parameters and age were examined using regression analysis with adjustments for walking speed, sex, height, and weight. Older age was associated with slower self-selected walking speed ( p<0.001), shorter stride length ( p<0.001), and greater propensity of landing flat-footed ( p=0.003). With older age, hip generative MWE for thigh rotation was lower about the AP axis (hip abduction and adduction) during stance ( p=0.010) and higher about the ML axis (hip extension and flexion) during late stance ( p<0.001). Knee absorptive MWE for shank rotation about the AP axis (knee abduction and adduction) during early stance was also lower with older age ( p<0.003). These age-related gait patterns may represent a compensatory effort to maintain balance and may also reflect mobility limitations.

Dynamic stability and phase resetting during biped gait

Dynamic stability during periodic biped gait in humans and in a humanoid robot is considered. Here gait systems of human neuromusculoskeletal system and a humanoid are simply modeled while keeping their mechanical properties plausible. We prescribe periodic gait trajectories in terms of joint angles of the models as a function of time. The equations of motion of the models are then constrained by one of the prescribed gait trajectories to obtain types of periodically forced nonlinear dynamical systems. Simulated gait of the models may or may not fall down during gait, since the constraints are made only for joint angles of limbs but not for the motion of the body trunk. The equations of motion can exhibit a limit cycle solution (or an oscillatory solution that can be considered as a limit cycle practically) for each selected gait trajectory, if an initial condition is set appropriately. We analyze the stability of the limit cycle in terms of Poincaré maps and the basin of attraction of the limit cycle in order to examine how the stability depends on the prescribed trajectory. Moreover, the phase resetting of gait rhythm in response to external force perturbation is modeled. Since we always prescribe a gait trajectory in this study, reacting gait trajectories during the phase resetting are also prescribed. We show that an optimally prescribed reacting gait trajectory with an appropriate amount of the phase resetting can increase the gait stability. Neural mechanisms for generation and modulation of the gait trajectories are discussed.

Asymptotically Stable Walking of a Five-Link Underactuated 3-D Bipedal Robot

This paper presents three feedback controllers that achieve an asymptotically stable, periodic, and fast walking gait for a 3-D bipedal robot consisting of a torso, revolute knees, and passive (unactuated) point feet. The walking surface is assumed to be rigid and flat; the contact between the robot and the walking surface is assumed to inhibit yaw rotation. The studied robot has 8 DOF in the single support phase and six actuators. In addition to the reduced number of actuators, the interest of studying robots with point feet is that the feedback control solution must explicitly account for the robot's natural dynamics in order to achieve balance while walking. We use an extension of the method of virtual constraints and hybrid zero dynamics (HZD), a very successful method for planar bipeds, in order to simultaneously compute a periodic orbit and an autonomous feedback controller that realizes the orbit, for a 3-D (spatial) bipedal walking robot. This method allows the computations for the controller design and the periodic orbit to be carried out on a 2-DOF subsystem of the 8-DOF robot model. The stability of the walking gait under closed-loop control is evaluated with the linearization of the restricted Poincare map of the HZD. Most periodic walking gaits for this robot are unstable when the controlled outputs are selected to be the actuated coordinates. Three strategies are explored to produce stable walking. The first strategy consists of imposing a stability condition during the search of a periodic gait by optimization. The second strategy uses an event-based controller to modify the eigenvalues of the (linearized) Poincare map. In the third approach, the effect of output selection on the zero dynamics is discussed and a pertinent choice of outputs is proposed, leading to stabilization without the use of a supplemental event-based controller.

1002 歩行パターンにおける特徴抽出と健脚度解析(OS2-(1) ライフサポートにおける工学技術,オーガナイズドセッション)

In Recent developed nations, the Aging and falling birthrate is advancing rapidly. In Japan, the increasing burden rate of productive population becomes an important issue. Simultaneously, Administrative agency announced the concept of care prevention should be more introduced to prevent these problems. This study proposes self-health check system using human's gait pattern analysis as daily action. An integrated assessment index, Gait Period Assessment: GPA is proposed, which consists of Gait Period Variation Index: GPVI and Vertical Stroke Displacement Index: VSDI and Maximum Split Acceleration Index: MSAI. The age trend in Gait Pattern shows prominent more over 40's with this assessment.

Period-doubling gait and chaotic gait of biped walking model

Passive walking model can exhibit natural gait on a slope， depending only on the gravity. The gait changes with the changing of parameters. The fixed point of the periodical gait can be obtained by the combination of cell mapping method and Newton-Raphson iteration. By the aid of cell mapping method，periodical cells can be used as the initial value of iteration，and the basins of attraction can be obtained. Simulations of models with different parameters show that the increasing of moment of inertia will result in the appearance of period-doubling and chaotic gaits. The same effect can be obtained by the decreasing of foot radius or position of center of mass.

Improving horizontal plane locomotion via leg angle control

The lateral leg spring model has been shown to accurately represent horizontal plane locomotion characteristics of sprawled posture insects such as the cockroach Blaberus discoidalis. While passively stable periodic gaits result from employing a constant leg touch-down angle for this model, utilizing a similar protocol for a point mass model of locomotion in three dimensions produces only unstable periodic gaits. In this work, we return to the horizontal plane model and develop a simple control law that prescribes variations in the leg touch-down angle in response to external perturbations. The resulting control law applies control once per stance phase, at the instant of leg touch-down, and depends upon previous leg angles defined in the body reference frame. As a result, our control action is consistent with the neural activity evidenced by B. discoidalis during locomotion over flat and rough terrain, and utilizes variables easily sensed by insect mechanoreceptors. Application of control in the lateral leg spring model is shown to improve stability of periodic gaits, enable stabilization of previously unstable periodic gaits, and maintain or improve the basin of stability of periodic gaits. The magnitude of leg touch-down angle variations utilized during stabilization appear consistent with the natural variations evidenced by single legs during locomotion over flat terrain.