Dynamic Balancing and Walking for Real-Time 3D Characters

Kenwright, Ben; Davison, Richard; Morgan, Graham

doi:10.1007/978-3-642-25090-3_6

Cited by 16 publications

(7 citation statements)

References 39 publications

(47 reference statements)

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“…It was suggested that the VPP angle was related to the speed of walking: a larger positive VPP angle increased the average speed, while zero angle or a small negative VPP angle decreased the speed (Kenwright et al, 2011). Possibly, this parameter should be adapted online, for instance based on heuristics, in order to obtain an observer that could cope with speed changes.…”

Section: Sensitivitymentioning

confidence: 99%

Observing the State of Balance with a Single Upper-Body Sensor

2016

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The occurrence of falls is an urgent challenge in our aging society. For wearable devices that actively prevent falls or mitigate their consequences, a critical prerequisite is knowledge on the user's current state of balance. To keep such wearable systems practical and to achieve high acceptance, only very limited sensor instrumentation is possible, often restricted to inertial measurement units at waist level. We propose to augment this limited sensor information by combining it with additional knowledge on human gait, in the form of an observer concept. The observer contains a combination of validated concepts to model human gait: a spring-loaded inverted pendulum model with articulated upper body, where foot placement and stance leg are controlled via the extrapolated center of mass (XCoM) and the virtual pivot point (VPP), respectively. State estimation is performed via an Additive Unscented Kalman Filter (Additive UKF). We investigated sensitivity of the proposed concept to model uncertainties, and we evaluated observer performance with real data from human subjects walking on a treadmill. Data were collected from an Inertial Measurement Unit (IMU) placed near the subject's center of mass (CoM), and observer estimates were compared to the ground truth as obtained via infrared motion capture. We found that the root mean squared deviation did not exceed 13 cm on position, 22 cm/s on velocity (0.56-1.35 m/s), 1.2°on orientation, and 17°/s on angular velocity.Keywords: human gait and balance, wearable sensors, state estimation, virtual pivot point, extrapolated center of mass, capture point, additive unscented kalman filter, fall detection

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Section: Sensitivitymentioning

confidence: 99%

Observing the State of Balance with a Single Upper-Body Sensor

2016

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“…The VP can also be used to manoeuver, when the VP target is placed out of the trunk axis [ 12 , 21 ]. A simulation study proposes to shift the VP position horizontally as a mechanism to handle stairs and slopes [ 29 ]. The gait analyses provide insights into the responses of GRFs to changes in terrain.…”

Section: Introductionmentioning

confidence: 99%

Postural stability in human running with step-down perturbations: an experimental and numerical study

et al. 2020

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Postural stability is one of the most crucial elements in bipedal locomotion. Bipeds are dynamically unstable and need to maintain their trunk upright against the rotations induced by the ground reaction forces (GRFs), especially when running. Gait studies report that the GRF vectors focus around a virtual point above the centre of mass (VP A ), while the trunk moves forward in pitch axis during the stance phase of human running. However, a recent simulation study suggests that a virtual point below the centre of mass (VP B ) might be present in human running, because a VP A yields backward trunk rotation during the stance phase. In this work, we perform a gait analysis to investigate the existence and location of the VP in human running at 5 m s −1 , and support our findings numerically using the spring-loaded inverted pendulum model with a trunk. We extend our analysis to include perturbations in terrain height (visible and camouflaged), and investigate the response of the VP mechanism to step-down perturbations both experimentally and numerically. Our experimental results show that the human running gait displays a VP B of ≈−30 cm and a forward trunk motion during the stance phase. The camouflaged step-down perturbations affect the location of the VP B . Our simulation results suggest that the VP B is able to encounter the step-down perturbations and bring the system back to its initial equilibrium state.

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“…Next, we investigate how the VP control compensates for the additional energy caused by the ground level changes. Unlike Kenwright et al (2011) suggests offsetting the VP position horizontally, we found it sufficient to increase the damping coefficient to accommodate downhill grades. The time FIGURE 7 | Normalized vertical (A) and horizontal (C) impulses for downhill running with VP B control target at speeds of 2-5 ms −1 .…”

Section: Downhill Terrainmentioning

confidence: 50%

“…However, there is no formalism to describe how VP control can be used to accommodate varying terrain conditions. So far, a single study conceptually suggests to offset the VP position horizontally and proportional to the change in step size to traverse stairs and slopes (Kenwright et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Virtual Point Control for Step-Down Perturbations and Downhill Slopes in Bipedal Running

Drama

Badri-Spröwitz

2020

Front. Bioeng. Biotechnol.

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Bipedal running is a difficult task to realize in robots, since the trunk is underactuated and control is limited by intermittent ground contacts. Stabilizing the trunk becomes even more challenging if the terrain is uneven and causes perturbations. One bio-inspired method to achieve postural stability is the virtual point (VP) control, which is able to generate natural motion. However, so far it has only been studied for level running. In this work, we investigate whether the VP control method can accommodate single step-down perturbations and downhill terrains. We provide guidelines on the model and controller parameterizations for handling varying terrain conditions. Next, we show that the VP method is able to stabilize single step-down perturbations up to 40 cm, and downhill grades up to 20–40° corresponding to running speeds of 2–5 ms−1. Our results show that the VP approach leads to asymmetrically bounded ground reaction forces for downhill running, unlike the commonly-used symmetric friction cone constraints. Overall, VP control is a promising candidate for terrain-adaptive running control of bipedal robots.

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Dynamic Balancing and Walking for Real-Time 3D Characters

Cited by 16 publications

References 39 publications

Observing the State of Balance with a Single Upper-Body Sensor

Observing the State of Balance with a Single Upper-Body Sensor

Postural stability in human running with step-down perturbations: an experimental and numerical study

Virtual Point Control for Step-Down Perturbations and Downhill Slopes in Bipedal Running

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