Stability and Robustness of a 3D Slip Model for Walking Using Lateral Leg Placement Control

2012 ◽  
Author(s):  
Dominik Budday ◽  
Fabian Bauer ◽  
Justin Seipel
Keyword(s):  
Humanoid Robot ◽  
Performance Test ◽  
Control Mechanism ◽  
Sagittal Plane ◽  
Control Strategies ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Slip Model ◽  
The Stability

The SLIP model has shown a way to easily represent the center of mass dynamics of human walking and running. For 2D motions in the sagittal plane, the model shows self-stabilizing effects that can be very useful when designing a humanoid robot. However, this self-stability could not be found in three-dimensional running, but simple control strategies achieved stabilization of running in three dimensions. Yet, 3D walking with SLIP has not been analyzed to the same extent. In this paper we show that three-dimensional humanoid SLIP walking is also unstable, but can be stabilized using the same strategy that has been successful for running. It is shown that this approach leads to the desired periodic solutions. Furthermore, the influence of different parameters on stability and robustness is examined. Using a performance test to simulate the transition from an upright position to periodic walking we show that the stability is robust. With a comparison of common models for humanoid walking and running it is shown that the simple control mechanism is able to achieve stable solutions for all models, providing a very general approach to this problem. The derived results point out preferable parameters to increase robustness promising the possibility of successfully realizing a humanoid walking robot based on 3D SLIP.

scholarly journals Systematic stability analysis, evaluation and testing process, and platform for grid-connected power electronic equipment

2020 ◽  
Author(s):  
Ziqian Zhang ◽  
Robert Schürhuber ◽  
Lothar Fickert ◽  
Katrin Friedl ◽  
Guochu Chen ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Power System ◽  
Control Strategies ◽  
Three Dimensional ◽  
Electronic Equipment ◽  
Three Dimensions ◽  
Power Electronic ◽  
System Behavior ◽  
Linear Behaviour ◽  
The Stability

AbstractThe proportion of grid-connected power electronic equipment is already large enough to influence the dynamic characteristics of the modern power system. Ensuring the stability of grid-connected power electronic equipment in all relevant situations is one of the foundations for reliable power system operation. In contrast to conventional rotating machines, the stability of power electronic devices mostly depends on the applied control strategy, and a large diversity of different complex control strategies are in practical use. Also, the investigation of stability of such systems needs to take into account the non-linear behaviour of the power electronic equipment. These are the main reasons why the system behavior of grid-connected power electronic equipment cannot be reproduced satisfactorily when aplying a single method of stability analysis, evaluation and testing method. During the last years, faults which led to tripping of converters due to stability problems occurred frequently even though standardized fault compliance tests were performed on these converters. In this paper these stability issues are analyzed. Also, a three-dimensional stability analysis method is suggested in order to comprehensively cover system behavior. The three dimensions are the time/scale dimension, the equipment number dimension and the local or global range of the stability analysis dimension. Based on this three-dimensional framework, this paper proposes a stability evaluation as well as a test process applying a hardware-in-the-loop test concept. Through the verification and testing of the stability of the actual grid-connected power electronic equipment, the method proposed in this paper is verified for up-to-date equipment.

scholarly journals Evolution of a narrow-band spectrum of random surface gravity waves

2003 ◽  
Vol 478 ◽  
pp. 1-10 ◽  
Author(s):  
KRISTIAN B. DYSTHE ◽  
KARSTEN TRULSEN ◽  
HARALD E. KROGSTAD ◽  
HERVÉ SOCQUET-JUGLARD
Keyword(s):  
Three Dimensional ◽  
Low Frequency ◽  
Three Dimensions ◽  
Band Spectrum ◽  
Nls Equation ◽  
Random Surface ◽  
Narrow Bandwidth ◽  
Quasi Stationary State ◽  
The Stability ◽  
Three Dimensional Simulations

Numerical simulations of the evolution of gravity wave spectra of fairly narrow bandwidth have been performed both for two and three dimensions. Simulations using the nonlinear Schrödinger (NLS) equation approximately verify the stability criteria of Alber (1978) in the two-dimensional but not in the three-dimensional case. Using a modified NLS equation (Trulsen et al. 2000) the spectra ‘relax’ towards a quasi-stationary state on a timescale (ε2ω0)−1. In this state the low-frequency face is steepened and the spectral peak is downshifted. The three-dimensional simulations show a power-law behaviour ω−4 on the high-frequency side of the (angularly integrated) spectrum.

Towards Robustly Stable Musculo-Skeletal Simulation of Human Gait: Merging Lumped and Component-Based Modeling Approaches

2012 ◽  
Author(s):  
Justin Seipel
Keyword(s):  
Inverted Pendulum ◽  
Dynamic Models ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Human Model ◽  
Whole Body ◽  
Human Gait ◽  
Slip Model ◽  
Spring Loaded Inverted Pendulum ◽  
Low Dimensional

The objective of work presented in this paper is to increase the center-of-mass stability of human walking and running in musculo-skeletal simulation. The approach taken is to approximate the whole-body dynamics of the low-dimensional Spring-Loaded Inverted Pendulum (SLIP) model of locomotion in the OpenSim environment using existing OpenSim tools. To more directly relate low-dimensional dynamic models to human simulation, an existing OpenSim human model is first modified to more closely represent bilateral above-knee amputee locomotion with passive prostheses. To increase stability further beyond the energy-conserving SLIP model, an OpenSim model based upon the Clock-Torqued Spring-Loaded-Inverted-Pendulum (CT-SLIP) model of locomotion is also created. The result of this work is that a multi-body musculo-skeletal simulation in Open-Sim can approximate the whole-body sagittal-plane dynamics of the passive SLIP model. By adding a plugin controller to the OpenSim environment, the Clock-Torqued-SLIP dynamics can be approximated in OpenSim. To change between walking and running, only one parameter representing the preferred period of a stride is changed. The result is a robustly stable simulation of the center-of-mass locomotion for both walking and running that could serve as a first step toward increasingly anatomically accurate and robustly stable musculo-skeletal simulations.

scholarly journals Dynamics of gravity–capillary solitary waves in deep water

2012 ◽  
Vol 708 ◽  
pp. 480-501 ◽  
Author(s):  
Zhan Wang ◽  
Paul A. Milewski
Keyword(s):  
Solitary Waves ◽  
Water Waves ◽  
Periodic Structures ◽  
Time Integration ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Full Potential ◽  
Numerical Time Integration ◽  
The Stability ◽  
Nonlinear Focusing

AbstractThe dynamics of solitary gravity–capillary water waves propagating on the surface of a three-dimensional fluid domain is studied numerically. In order to accurately compute complex time-dependent solutions, we simplify the full potential flow problem by using surface variables and taking a particular cubic truncation possessing a Hamiltonian with desirable properties. This approximation agrees remarkably well with the full equations for the bifurcation curves, wave profiles and the dynamics of solitary waves for a two-dimensional fluid domain, and with higher-order truncations in three dimensions. Fully localized solitary waves are then computed in the three-dimensional problem and the stability and interaction of both line and localized solitary waves are investigated via numerical time integration of the equations. There are many solitary wave branches, indexed by their finite energy as their amplitude tends to zero. The dynamics of the solitary waves is complex, involving nonlinear focusing of wavepackets, quasi-elastic collisions, and the generation of propagating, spatially localized, time-periodic structures akin to breathers.

scholarly journals A Systematic Study of the Fracturing of Ronne - Filchner Ice Shelf, Antarctica, Using Multisource Satellite Data from 2001 to 2016

2017 ◽  
Author(s):  
Rongxing Li ◽  
Haifeng Xiao ◽  
Shijie Liu ◽  
Xiaohua Tong
Keyword(s):  
Satellite Data ◽  
Three Dimensional ◽  
Remote Sensing Data ◽  
Three Dimensions ◽  
Landsat 8 ◽  
Ice Shelf ◽  
Sar Imagery ◽  
The Stability ◽  
Fracture Mapping ◽  
New Framework

Abstract. We propose a new framework of systematic fracture mapping and major calving event prediction for the large ice shelves in Antarctica using multisource satellite data, including optical imagery, SAR imagery, altimetric data, and stereo mapping imagery. The new framework is implemented and applied for a comprehensive study of the fracturing of Ronne-Filchner Ice Shelf (RFIS), the second largest ice shelf in Antarctica, using a long time dataset dating back to 1957. New remote sensing data that have been made available in the past decade, including Landsat 8, WV-2, ZY-3 and others, greatly enhance our abilities to detect new fractures and monitor large rifts in three dimensions. Two large rifts, Rifts 1 and 2, were newly detected and are comparable to the Grand Chasm that caused a major calving event in the region in 1986. Three-dimensional rift models generated from quasi real-time stereo ZY-3 images revealed important topographic information about the large rifts that can be used to improve the reliability of ice shelf modeling and support enhanced analyses of ice shelf stability. Based on the results of the 2D and 3D fracture mapping, the spatial and temporal analyses of the overall fracture changes and large rift evolutions, i.e., the level of fracturing in RFIS, were slightly increased, particularly at the front of the ice sheet. The overall fracture observations do not seem to suggest immediate significant impacts on the stability of the shelf. However, the most active regional fracturing activities occurred at the front of Filchner Ice Shelf (FIS). A potential upcoming major calving event of FIS is estimated to occur in 2051. The stability of the ice shelf, particularly with regard to the developments of Rifts 1 and 2, should be closely monitored.

Stabilizing Passive Dynamic Walk Under Wide Range of Environments by Constraint Mechanism Fitted to Sole of Foot

2009 ◽  
Vol 21 (3) ◽  
pp. 403-411 ◽  
Author(s):  
Kazuyuki Hyodo ◽  
◽  
Takeshi Oshimura ◽  
Sadayoshi Mikami ◽  
Sho'ji Suzuki ◽  
...  
Keyword(s):  
Sagittal Plane ◽  
Three Dimensional ◽  
Sharp Edge ◽  
Shape Design ◽  
Geometrical Analysis ◽  
Forward Movement ◽  
Wide Range ◽  
Outdoor Environments ◽  
Lateral Plane ◽  
The Stability

This paper proposes a foot shape design to enhance the stability of passive dynamic walk by constraining fall down phenomenon in both sagittal and lateral planes. We focus on excessive side-to-side and forward leg swinging that causes a passive dynamic biped walker to fall over. Geometrical analysis showed that stability under a wide range of slope inclinations is achievable by limiting the swinging leg spatially to within a certain angle. Such a limit, or constraint, on swinging effectively prevents falling down on the lateral plane, while stable walking is maintained on the sagittal plane by constraining forward movement using a sharp edge at the head of a foot. We propose a foot prototype realizing these two constraints using a three-dimensional (3D) sole design and show that the proposed constraint is more effective for walking than an arctic foot shape. In verification experiments, the constraint stabilized the passive dynamic walker in a wide range of outdoor environments.

BIPED HOPPING CONTROL BAzSED ON SPRING LOADED INVERTED PENDULUM MODEL

2010 ◽  
Vol 07 (02) ◽  
pp. 263-280 ◽  
Author(s):  
SEYED HOSSEIN TAMADDONI ◽  
FARID JAFARI ◽  
ALI MEGHDARI ◽  
SAEED SOHRABPOUR
Keyword(s):  
Control Strategy ◽  
Inverted Pendulum ◽  
Hybrid Control ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Slip Model ◽  
Inverted Pendulum Model ◽  
Wide Range ◽  
Spring Loaded Inverted Pendulum ◽  
Mass Spring

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.

scholarly journals Route Identification Method for On-Ramp Traffic at Adjacent Intersections of Expressway Entrance

2019 ◽  
Vol 2019 ◽  
pp. 1-15
Author(s):  
Wenxuan Wang ◽  
Xiaodong Zhu ◽  
Yanli Wang ◽  
Bing Wu
Keyword(s):  
Traffic Flow ◽  
Feature Vector ◽  
Control Strategies ◽  
Three Dimensional ◽  
Simulation Models ◽  
Coordinated Control ◽  
Traffic Volume ◽  
Three Dimensions ◽  
Traffic Data ◽  
Identification Method

To determine the control strategy at intersections adjacent to the expressway on-ramp, a route identification method based on empirical mode decomposition (EMD) and dynamic time warping (DTW) is established. First, the de-noise function of EMD method is applied to eliminate disturbances and extract features and trends of traffic data. Then, DTW is used to measure the similarity of traffic volume time series between intersection approaches and expressway on-ramp. Next, a three-dimensional feature vector is built for every intersection approach traffic flow, including DTW distance, space distance between on-ramp and intersection approach, and intersection traffic volume. Fuzzy C-means clustering method is employed to cluster intersection approaches into classifications and identify critical routes carrying the most traffic to the on-ramp. The traffic data are collected by inductive loops at Xujiahui on-ramp of North and South Viaduct Expressway and surrounding intersections in Shanghai, China. The result shows that the proposed method can achieve route classification among intersections for different time periods in one day, and the clustering result is significantly influenced by three dimensions of traffic flow feature vector. As an illustrative example, micro-simulation models are built with different control strategies. The simulation shows that the coordinated control of critical routes identified by the proposed method has a better performance than coordinated control of arterial roads. Conclusions demonstrated that the proposed route identification method could provide a theoretical basis for the coordinated control of traffic signals among intersections and on-ramp.

Structural Failure Mechanisms of Common Flexor Tendon Repairs

Hand Surgery ◽  
2015 ◽  
Vol 20 (03) ◽  
pp. 369-379 ◽  
Author(s):  
Tim Sebastian Peltz ◽  
Roger Haddad ◽  
Peter James Scougall ◽  
Sean Nicklin ◽  
Mark Peter Gianoutsos ◽  
...  
Keyword(s):  
Failure Mechanisms ◽  
Biomechanical Testing ◽  
Tendon Repair ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Biomechanical Stability ◽  
Repair Method ◽  
Before And After ◽  
The Stability ◽  
Repair Techniques

Background: This study investigated the exact failure mechanisms of the most commonly used conventional tendon repair techniques. A new method, radiographing repair constructs in antero-posterior and lateral projections before and after tensioning was used. This allowed to precisely analyse failure mechanisms in regards to geometrical changes in all three dimensions. Additionally the biomechanical stability focusing on gapping was tested. Methods: Sheep fore limb deep flexor tendons were harvested and divided in eight groups of ten tendons. Three common variants of the Kessler repair method and four common 4-strand repair techniques were tested. Additionally a new modification of the Adelaide repair was tested. Results: Biomechanical testing showed no significant differences in gapping for the three tested 2-strand Kessler repair groups. Once a double Kessler or 4-strand Kessler repair was performed the stability of the repair improved significantly. Further significant improvements in biomechanical stability could be achieved by using cross locks in the repair like in the Adelaide repair method. Qualitative analysis using radiographs showed that all Kessler repair variants unfolded via rotations around the transverse suturing component, no matter which variant was used. Conclusions: Additional to the commonly described constriction of the repair construct, the rotating deformation is the main reason for repair site gapping in Kessler tendon repair methods. The term “locking” in a Kessler repair is misleading. The cruciate repairs tended to loose grip and drag (cheese-wire) through the tendon and therefore lead to gapping. The most stable repair constructs in all three dimensions were the Adelaide repair and its interlocking modification. This is due to the superior anchoring qualities of its cross locks and three dimensional stability.

scholarly journals Active attenuation of a trailing vortex inspired by a parabolized stability analysis

2018 ◽  
Vol 855 ◽  
Author(s):  
Adam M. Edstrand ◽  
Yiyang Sun ◽  
Peter J. Schmid ◽  
Kunihiko Taira ◽  
Louis N. Cattafesta
Keyword(s):  
Stability Analysis ◽  
Unstable Mode ◽  
Control Strategies ◽  
Three Dimensional ◽  
Suboptimal Control ◽  
Effective Control ◽  
Streamwise Vorticity ◽  
Control Scheme ◽  
Set Up ◽  
The Stability

Designing effective control for complex three-dimensional flow fields proves to be non-trivial. Often, intuitive control strategies lead to suboptimal control. To navigate the control space, we use a linear parabolized stability analysis to guide the design of a control scheme for a trailing vortex flow field aft of a NACA0012 half-wing at an angle of attack $\unicode[STIX]{x1D6FC}=5^{\circ }$ and a chord-based Reynolds number $Re=1000$ . The stability results show that the unstable mode with the smallest growth rate (fifth wake mode) provides a pathway to excite a vortex instability, whereas the principal unstable mode does not. Inspired by this finding, we perform direct numerical simulations that excite each mode with body forces matching the shape function from the stability analysis. Relative to the uncontrolled case, the controlled flows show increased attenuation of circulation and peak streamwise vorticity, with the fifth-mode-based control set-up outperforming the principal-mode-based set-up. From these results, we conclude that a rudimentary linear stability analysis can provide key insights into the underlying physics and help engineers design effective physics-based flow control strategies.

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