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--- start [2020/01/08 13:05]
Martin Grimmer [Review of balance recovery in response to external perturbations during daily activities]
+++ start [2020/09/18 12:12]
Martin Grimmer [Lower limb joint biomechanics-based identification of gait transitions in between level walking and stair ambulation]
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 ===== Experiments =====
-Both in [[projects:projects|research projects]] and in [[:lauflabor_wiki|teaching courses]] at the Sports Science Institut at TU Darmstadt experimental studies are performed. Outcomes from student research and educational projects on biomechanics can be found in the awarded [[http://wiki.ifs-tud.de/|Teaching Wiki]] of our institute.
+Experimental studies are performed in both [[projects:projects|research projects]] and in [[:lauflabor_wiki|teaching courses]] at the Sports Science Institute at TU Darmstadt. Outcomes from student research and educational projects on biomechanics can be found in the awarded [[http://wiki.ifs-tud.de/|Teaching Wiki]] of our institute.
 <slider  ::model.jpg>
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 ====== News ======
+  * LEARN&ACT DAY of the Movement Academy [[http://wiki.ifs-tud.de/biomechanik/aktuelle_themen/bewak2019#mova_learn_act_days_ws1920|Motions and Emotions]] will be postponed due to the current situation
-  * {{::ansymb_logo_i.png?90 | Teaching course ANSYMB II}} **Running this winter term!** [[http://www.ansymb.tu-darmstadt.de/|   Analysis and Synthesis of Human Movements]]
 ====== Latest Publications ======
+==== Lower limb joint biomechanics-based identification of gait transitions in between level walking and stair ambulation  ====
-==== Review of balance recovery in response to external perturbations during daily activities  ====
+Gait transitions in between level walking and stair ambulation were investigated in one of our projects involving [[lab_members:lab_members_martingrimmer|Martin Grimmer]] and the Department of Electrical Engineering and Information Technology of [[https://www.etit.tu-darmstadt.de/fachbereich/professoren/aktuelle_professorinnen_und_professoren/index~1_34955.en.jsp|Ulrich Konigorski]]. A team of Postdocs, Phd candidates and students performed the one of the largest human gait studies ever, involving an instrumented staircase, in the Locomotion Laboratory. The work was recently published in the[[ https://doi.org/10.1371/journal.pone.0239148| PLOS ONE]].
-Balance related responses to perturbations were investigated in one of our latest studies by Dr. Dario Tokur, Dr. [[lab_members:lab_members_martingrimmer|Martin Grimmer]] and Prof. Andre Seyfarth. The work was recently published in [[https://doi.org/10.1016/j.humov.2019.102546|Human Movement Science]].
+{{ ::transition.jpg?400|}}
-{{ ::perturbation.png?300|}}
+**Abstract:**
+Lower limb exoskeletons and lower limb prostheses have the potential to reduce gait limitations during stair ambulation. To develop robotic assistance devices, the biomechanics of stair ambulation and the required transitions to level walking have to be understood. This study aimed to identify the timing of these transitions, to determine if transition phases exist and how long they last, and to investigate if there exists a joint-related order and timing for the start and end of the transitions. Therefore, this study analyzed the kinematics and kinetics of both transitions between level walking and stair ascent, and between level walking and stair descent (12 subjects, 25.4 yrs, 74.6 kg). We found that transitions primarily start within the stance phase and end within the swing phase. Transition phases exist for each limb, all joints (hip, knee, ankle), and types of transitions. They have a mean duration of half of one stride and they do not last longer than one stride. The duration of the transition phase for all joints of a single limb in aggregate is less than 35% of one stride in all but one case. The distal joints initialize stair ascent, while the proximal joints primarily initialize the stair descent transitions. In general, the distal joints complete the transitions first. We believe that energy- and balance-related processes are responsible for the joint-specific transition timing. Regarding the existence of a transition phase for all joints and transitions, we believe that lower limb exoskeleton or prosthetic control concepts should account for these transitions in order to improve the smoothness of the transition and to thus increase the user comfort, safety, and user experience. Our gait data and the identified transition timings can provide a reference for the design and the performance of stair ambulation- related control concepts.
+For further projects and publications of [[lab_members:lab_members_martingrimmer|M. Grimmer]] 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]]
+==== Doppler Radar for the Extraction of Biomechanical Parameters in Gait Analysis  ====
-**Abstract:**
+Doppler Radar for the extraction of biomechanical parameters during walking was investigated in one of our latest studies in cooperation with the Signal Processing Group of Prof. Zoubir. Ann-Kathrin Seifert and [[lab_members:lab_members_martingrimmer|Martin Grimmer]] performed a series of experiments in the Locomotion Laboratory. The work was recently published in the[[https://doi.org/10.1109/jbhi.2020.2994471| IEEE Journal of Biomedical and Health Informatics]].
-Balance is an essential capability to ensure upright standing and locomotion. Various external perturbations challenge our balance in daily life and increase the risk for falling and associated injury. Researchers try to identify the human mechanisms to maintain balance by intentional perturbations. The objectives of this work were to point out which areas of perturbation based research are well covered and not well covered and to extract which coping mechanisms humans use to respond to external perturbations. A literature review was performed to analyze mechanisms in response to external perturbations such as pushes to the body or ground level changes during standing, walking, running and hopping. To get a well-structured overview on the two dimensions, the perturbation type and the task, the Perturbation Matrix (PMA) was designed. We found that multiple studies exist for the tasks walking and standing, while hopping and running are covered less. However, all tasks still offer opportunities for both in-depth and fundamental research. Regarding the recovery mechanisms we found that humans can recover from various types of perturbations with versatile mechanisms using combinations of trunk, as well as upper and lower limb movements. The recovery movements will adapt depending on the perturbation intensity, direction and timing. Changes in joint kinetics, joint kinematics and muscle activity were identified on the joint level and leg stiffness and leg length on the global leg level. We believe that the insights from the extracted mechanisms may be applied to the hardware and control of robotic limbs or lower limb exoskeletons to improve the balance and robustness during standing or locomotion.
+{{ ::radar.jpg?400|}}
+**Abstract:**
+The applicability of Doppler radar for gait analysis is investigated by quantitatively comparing the measured biomechanical parameters to those obtained using motion capturing
+and ground reaction forces. Nineteen individuals walked on a treadmill at two different speeds, where a radar system was positioned in front of or behind the subject. The right knee angle was confined by an adjustable orthosis in five different degrees. Eleven gait parameters are extracted from radar micro-Doppler signatures. Here, new methods for obtaining the velocities of individual lower limb joints are proposed. Further, a new method to extract individual leg flight times from radar data is introduced. Based on radar data, five spatiotemporal parameters related to rhythm and pace could reliably be extracted. Further,
+for most of the considered conditions, three kinematic parameters could accurately be measured. The radar-based stance and flight time measurements rely on the correct detection of the time instant of maximal knee velocity during the gait cycle. This time instant is reliably detected when the radar has a back view, but is underestimated when the radar is positioned in front of the subject. The results validate the applicability of Doppler radar to accurately measure a variety of medically relevant gait parameters. Radar has the potential to unobtrusively diagnose changes in gait, e.g., to design training in prevention and rehabilitation. As contact-less and privacy-preserving sensor, radar presents aviable technology to supplement existing gait analysis tools for long-term in-home examinations.
 For further projects and publications of [[lab_members:lab_members_martingrimmer|M. Grimmer]] 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]]
-\\
-==== Biomechanical effects of passive hip springs during walking  ====
-The effects of passive springs at the hip were investigated in a collaboration project of Florian Haufe, Peter Wolf and Robert Riener from the [[https://sms.hest.ethz.ch/|Sensory-Motor Systems Lab]] from ETH Zurich and [[lab_members:lab_members_martingrimmer|Martin Grimmer]] from the Lauflabor. The work was recently published in the [[https://www.sciencedirect.com/science/article/abs/pii/S0021929019306797|Journal of Biomechanics]].
+==== A biarticular passive exosuit to support balance control can reduce metabolic cost of walking ====
-{{ ::passive_hip_spring.jpg?400|}}
+In this research the advantages of a biarticular thigh exosuit in supporting human walking is demonstrated. Find the details in our recently published paper (open access) by Barazesh, H and [[lab_members:lab_members_maziarahmadsharbafi|Sharbafi, M. A.]] in [[https://iopscience.iop.org/article/10.1088/1748-3190/ab70ed/pdf|Bioinspiration & Biomimetics]].
+{{ ::baexopassive.png?600|}}
 **Abstract:**
-Passive spring-like structures can store and return energy during cyclic movements and thereby reduce the energetic cost of locomotion. That makes them important components of the human body and wearable assistive devices alike. This study investigates how springs placed anteriorly across the hip joint affect leg joint angles and powers, and leg muscle activities during level walking at 0.5 to 2.1 m/s.
+Nowadays, the focus on the development of assistive devices just for people with mobility disorders has shifted towards enhancing physical abilities of able-bodied humans. As a result, the interest in the design of cheap and soft wearable exoskeletons (called exosuits) is distinctly growing. In this paper, a passive lower limb exosuit with two biarticular variable stiffness elements is introduced. These elements are in parallel to the hamstring muscles of the leg and controlled based on a new version of the FMCH (force modulated compliant hip) control framework in which the force feedback is replaced by the length feedback (called LMCH). The main insight to employ leg length feedback is to develop a passive exosuit. Fortunately, similar to FMCH, the LMCH method also predicts human-like balance control behaviours, such as the VPP (virtual pivot point) phenomenon, observed in human walking. Our simulation results, using a neuromuscular model of human walking, demonstrate that this method could reduce the metabolic cost of human walking by 10%. Furthermore, to validate the design and simulation results, a preliminary version of this exosuit comprised of springs with constant stiffness was built. An experiment with eight healthy subjects was performed. We made a comparison between the walking experiments while the exosuit is worn but the springs were slack and those when the appropriate springs were contributing. It shows that passive biarticular elasticity can result in a metabolic reduction of 14.7±4.27%. More importantly, compared to unassisted walking (when exosuit is not worn), such a passive device can reduce walking metabolic cost by 4.68±4.24%.
-We hypothesized that the anterior hip springs (I) load hip extension, (II) support hip flexion and (III) affect ankle muscle activity and dynamics during walking. Effects at the ankle were expected because hip and ankle redistribute segmental power in concert to achieve forward progression.
-We observed that the participants’ contribution to hip power did not increase during hip extension as the spring stored energy. Simultaneously, the activities of plantarflexor muscles that modulate energy storage in the Achilles tendon were reduced by 28% (gastrocnemius medialis) and 9% (soleus). As the spring returned energy with the onset of hip flexion, the participants’ contribution to hip power was reduced by as much as 23%. Soleus activity before push-off increased by up to 9%.
+For further publications of the author please check: [[https://www.researchgate.net/profile/Maziar_Ahmad_Sharbafi|ResearchGate]],
+[[ https://orcid.org/0000-0001-5727-7527|ORCID]] or [[https://loop.frontiersin.org/people/254590/overview|LOOP]]
-Instead of loading hip extension, anterior hip springs seem to store and return parts of the energy normally exchanged with the Achilles tendon. Thereby, the springs support hip flexion but may reduce elastic energy storage in and hence recoil from the Achilles tendon. This interaction should be considered during the design and simulation of wearable assistive devices as it might – depending on user characteristics – enhance or diminish their overall functionality.
+==== Bio-inspired neuromuscular reflex based hopping controller for a segmented robotic leg ====
-For further projects and publications of [[lab_members:lab_members_martingrimmer|M. Grimmer]] 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]]
+The bio-inspired neuromuscular reflex based controller can generate stable hopping motion in a real robot. Check out our recently published paper (open access) by Zhao et al. in [[https://iopscience.iop.org/article/10.1088/1748-3190/ab6ed8|Bioinspiration & Biomimetics]] for more details.
-\\
+{{ youtube>ACy2SbUh9U4?large|Bio-inspired neuromuscular reflex based hopping controller for a segmented robotic leg}}
-===== Biarticular muscles are most responsive to upper-body pitch perturbations in human standing =====
-Our latest publication features the results of [[http://lauflabor.ifs-tud.de/doku.php?id=lab_members:lab_members_christian_schumacher|Christian]]'s lab visit in the [[http://dbl.tudelft.nl/|Delft Biorobotics Lab]]. The study investigates important muscle groups to maintain an upright body posture when being perturbed. For this purpose, he used a novel type of balance perturbation, a control moment gyroscope (see Figure) that exerts a torque on the subject's upper body. Find more information in the published paper: [[https://www.nature.com/articles/s41598-019-50995-3|Link to Scientific Reports]].
-{{ :gyro.jpg?nolink&600|[[https://www.nature.com/articles/s41598-019-50995-3|Link to Scientific Reports]] }}
 **Abstract:**
-Balancing the upper body is pivotal for upright and efficient gait. While models have identified potentially useful characteristics of biarticular thigh muscles for postural control of the upper body, experimental evidence for their specific role is lacking. Based on theoretical findings, we hypothesised that biarticular muscle activity would increase strongly in response to upper-body perturbations. To test this hypothesis, we used a novel Angular Momentum Perturbator (AMP) that, in contrast to existing methods, perturbs the upper-body posture with only minimal effect on Centre of Mass (CoM) excursions. The impulse-like AMP torques applied to the trunk of subjects resulted in upper-body pitch deflections of up to 17° with only small CoM excursions below 2 cm. Biarticular thigh muscles (biceps femoris long head and rectus femoris) showed the strongest increase in muscular activity (mid- and long-latency reflexes, starting 100 ms after perturbation onset) of all eight measured leg muscles which highlights the importance of biarticular muscles for restoring upper-body balance. These insights could be used for improving technological aids like rehabilitation or assistive devices, and the effectiveness of physical training for fall prevention e.g. for elderly people.
+It has been shown that human-like hopping can be achieved by muscle reflex control in neuromechanical simulations. However, it is unclear if this concept is applicable and feasible for controlling a real robot. This paper presents a low-cost two-segmented robotic leg design and demonstrates the feasibility and the benefits of the bio-inspired neuromuscular reflex based control for hopping. Simulation models were developed to describe the dynamics of the real robot. Different neuromuscular reflex pathways were investigated with the simulation models. We found that stable hopping can be achieved with both positive muscle force and length feedback, and the hopping height can be controlled by modulating the muscle force feedback gains with the return maps. The force feedback neuromuscular reflex based controller is robust against body mass and ground impedance changes. Finally, we implemented the controller on the real robot to prove the feasibility of the proposed neuromuscular reflex based control idea. This paper demonstrates the neuromuscular reflex based control approach is feasible to implement and capable of achieving stable and robust hopping in a real robot. It provides a promising direction of controlling the legged robot to achieve robust dynamic motion in the future.
+For further publications of the author please check: [[https://www.researchgate.net/profile/Guoping_Zhao2|ResearchGate]],
+[[https://orcid.org/0000-0002-1908-5388|ORCID]] or [[https://loop.frontiersin.org/people/378544/overview|LOOP]]
+===== Biarticular muscles in light of template models, experiments and robotics: a review =====
+Read our recent review paper about biarticular muscles to learn about the scientific discoveries from simulation models, evidence from human experiments and beneficial design principles in robotic applications. Link to the published paper (open access): [[https://doi.org/10.1098/rsif.2018.0413|Link to Royal Society Interface]].
+{{ :props_muscles.jpg?nolink&200|[[https://doi.org/10.1098/rsif.2018.0413|Link to Royal Society Interface]] }}
+**Abstract:**
+Leg morphology is an important outcome of evolution. A remarkable morphological leg feature is the existence of biarticular muscles that span adjacent joints. Diverse studies from different fields of research suggest a less coherent understanding of the muscles’ functionality in cyclic, sagittal plane locomotion. We structured this review of biarticular muscle function by reflecting biomechanical template models, human experiments and robotic system designs. Within these approaches, we surveyed the contribution of biarticular muscles to the locomotor subfunctions (stance, balance and swing). While mono- and biarticular muscles do not show physiological differences, the reviewed studies provide evidence for complementary and locomotor subfunction-specific contributions of mono- and biarticular muscles. In stance, biarticular muscles coordinate joint movements, improve economy (e.g. by transferring energy) and secure the zig-zag configuration of the leg against joint overextension. These commonly known functions are extended by an explicit role of biarticular muscles in controlling the angular momentum for balance and swing. Human-like leg arrangement and intrinsic (compliant) properties of biarticular structures improve the controllability and energy efficiency of legged robots and assistive devices. Future interdisciplinary research on biarticular muscles should address their role for sensing and control as well as non-cyclic and/or non-sagittal motions, and non-static moment arms. \\
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