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start [2019/08/14 14:21]
Christian Schumacher [News]
start [2019/08/30 14:50] (current)
Maziar Sharbafi [Stance and Swing Detection Based on the Angular Velocity of Lower Limb Segments During Walking]
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-==== Stance ​and Swing Detection Based on the Angular Velocity ​of Lower Limb Segments During Walking  ​====+==== Parallel compliance design for increasing robustness ​and efficiency in legged locomotion-proof ​of concept ​====
-A new concept for stance ​and swing detection ​based on lower limb segments ​is introduced ​in a recently published paper by Grimmer et al. in //Frontiers in Neurorobotics// ​[[https://www.frontiersin.org/articles/10.3389/​fnbot.2019.00057/​full?&​utm_source=Email_to_authors_&utm_medium=Email&​utm_content=T1_11.5e1_author&​utm_campaign=Email_publication&​field=&​journalName=Frontiers_in_Neurorobotics&​id=459435|Stance and Swing Detection Based on the Angular Velocity of Lower Limb Segments During Walking]]. +A new concept for simultanous design ​and control of parallel compliance is introduced in this research. The analytical design approach is based on hybrid zero dynamics control method and the goal is increasing robustness in locomotion. This study is presented ​in a recently published paper by Sharbafi et al., in by Grimmer et al. in [[https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8716548|IEEE Transactions ​on Mechatronics]]. 
-{{ :stance_swing_concept.png?nolink&​500|}} +{{ :5link.png?205|}} 
-{{ :stance_and_swing2.png?nolink&​108|}}+{{ :acrobat.png?250|}}
 **Abstract:​** ​ **Abstract:​** ​
-Lower limb exoskeletons require the correct support magnitude and timing to achieve user assistance. This study evaluated whether the sign of the angular velocity of lower limb segments ​can be used to determine the timing of the stance and the swing phase during walking. We assumed that stance phase is characterized by positive, swing phase by a negative angular velocityThus, the transitions can be used to also identify heel-strike and toe-off. Thirteen subjects without gait impairments walked ​on a treadmill at speeds between 0.5 and 2.1 m/s on level ground and inclinations between −10 and +10°. Kinematic and kinetic data was measured simultaneously from an optical motion capture systemforce plates, and five inertial measurement units (IMUs). These recordings were used to compute the angular velocities ​of four lower limb segments: two biological (thigh, shank) and two virtual that were geometrical projections of the biological segments (virtual leg, virtual extended leg)We analyzed the reliability (two sign changes ​of the angular velocity per stride) and the accuracy (offset ​in timing between sign change and ground reaction force based timing) of the virtual ​and biological segments for detecting the gait phases stance and swing. The motion capture data revealed that virtual limb segments seem superior ​to the biological limb segments in the reliability of stance ​and swing detectionHowever, increased signal noise when using the IMUs required additional rule sets for reliable stance ​and swing detectionWith IMUs, the biological shank segment had the least variability in accuracy. The IMU-based heel-strike events of the shank and both virtual segment were slightly early (3.3–4.8% of the gait cyclecompared to the ground ​reaction force-based timing. Toe-off event timing showed more variability (9.0% too early to 7.3% too late) between ​the segments ​and changed with walking speed. The results show that the detection ​of the heel-strike,​ and thus stance phase, based on IMU angular velocity is possible for different segments when additional rule sets are includedFurther work is required ​to improve ​the timing accuracy for the toe-off detection (swing)+Benefiting from serial compliance in series elastic actuators ​can be considered as breakthrough in roboticsRecentlyapplying ​the parallel compliance in robot designs is growing based on its advantages such as reduction in consumed torquesIn this paperwe aim at employing parallel compliance ​to increase walking robustness ​of bipedal robots against model uncertaintiesUtilizing passive compliant elements instead ​of adapting ​the controller ​in order to cope with uncertainties makes the system more efficient ​and less sensitive ​to measurement issues such as delays ​and noiseWe introduce a methodology ​for designing both parallel compliance ​and controller using hybrid zero dynamics conceptThis study includes simulation results representing ​the design approach and preliminary experiments on parallel compliance effects on efficiency of a robot joint position control. The simulations comprise a compass gait (2-link) model and a 5-link model (see the figures). The ground ​slope and robot segment lengths are considered as uncertain parameters in the first and second models, respectively. The control target is met by the insertion ​of compliant structures parallel to the actuatorsIn order to employ ​the proposed method on a real robot, we suggest using pneumatic air muscles as parallel compliant elements. Pilot experiments on the knee joint of BioBiped3 robot support the feasibility of suggested method.
-For further publications of the autohr ​please check: [[https://​www.researchgate.net/​profile/​Martin_Grimmer3|ResearchGate]],​ [[https://​scholar.google.de/​citations?​hl=de&user=gDF_uHUAAAAJ&view_op=list_works&​sortby=pubdate|Google Scholar]], [[https://​orcid.org/​0000-0003-1921-1433|ORCID]] or [[https://​loop.frontiersin.org/​people/​390560/​overview|LOOP]]+ 
 +For further publications of the author ​please check: [[https://​www.researchgate.net/​profile/​Maziar_Ahmad_Sharbafi|ResearchGate]],​ [[https://​scholar.google.de/​citations?​user=MENjywMAAAAJ&hl=en|Google Scholar]], [[https://​orcid.org/​0000-0001-5727-7527|ORCID]] or [[https://​loop.frontiersin.org/​people/​254590/​overview|LOOP]]
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