Martin Grimmer

Martin Grimmer
Technische Universität Darmstadt | TU · Institute of Sport Science

Phd, (rer. nat.)

About

65
Publications
47,921
Reads
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1,375
Citations
Introduction
MG received a diploma in sports science at FSU Jena (2008) and a Phd (2015) at TU Darmstadt, Germany. He was a guest researcher at the Arizona State University (2012) and Postdoc at Harvard (2015) and at the ETH Zurich (2016/17). Currently he is an Athene Young Investigator group leader at TU Darmstadt. His research interests include biomechanical analyses of human movements and the transfer of biological inspired mechanical principles to wearable robotics.
Additional affiliations
January 2018 - present
Technische Universität Darmstadt
Position
  • Athene Young Investigator
November 2016 - December 2017
ETH Zurich
Position
  • Researcher
October 2015 - October 2016
Technische Universität Darmstadt
Position
  • Lecturer
Education
October 2011 - February 2015
Technische Universität Darmstadt
Field of study
  • Biomechanics, Robotics, Prosthetics
September 2006 - September 2008
Friedrich Schiller University Jena
Field of study
  • Sports Science - Prevention & Rehabilitation - Certificate
August 2000 - September 2008
Friedrich Schiller University Jena
Field of study
  • Sports Science - Movement & Performance

Publications

Publications (65)
Preprint
To improve the control of wearable robotics for gait assistance, we present an approach for continuous locomotion mode recognition as well as gait phase and stair slope estimation based on artificial neural networks that include time history information. The input features consist exclusively of processed variables that can be measured with a singl...
Article
Passive prosthetic feet struggle to reproduce the human biological ankle range of motion and push-off. We propose the Hybrid-Hydraulic Ankle Prosthesis (H2AP), a prosthetic foot that provides a greater range of motion and push-off support compared to regular carbon feet. This novel prosthesis comprises a carbon foot and a hydraulic unit that includ...
Article
Full-text available
This study aims to improve our understanding of gait initiation mechanisms and the lower-limb joint mechanical energy contributions. Healthy subjects were instructed to initiate gait on an instrumented track to reach three self-selected target velocities: slow, normal and fast. Lower-limb joint kinematics and kinetics of the first five strides were...
Article
Full-text available
To minimize fatigue, sustain workloads, and reduce the risk of injuries, the exoskeleton Carry was developed. Carry combines a soft human–machine interface and soft pneumatic actuation to assist the elbow in load holding and carrying. We hypothesize that the assistance of Carry would decrease, muscle activity, net metabolic rate, and fatigue. With...
Conference Paper
Full-text available
Improving the quality of life for people with amputations through active prostheses requires appropriate knowledge of the locomotion task and gait phase of the user. A shank mounted Inertial Measurement Unit based estimation method for stair slope is presented in conjunction with an improved gait phase estimation. In contrast to prior work only one...
Article
Robotic limb design struggles to combine energy efficiency with human-like levels of movement versatility. High efficiency and a range of angles and torques are characteristics of human hopping at different frequencies. Humans use muscles in combination with tendons to achieve the required joint actuation. Therefore, we consider whether appropriate...
Article
Full-text available
This article presents a novel neuromechanical force-based control strategy called FMCA (force modulated compliant ankle), to control a powered prosthetic foot. FMCA modulates the torque, based on sensory feedback, similar to neuromuscular control approaches. Instead of using a muscle reflex-based approach, FMCA directly exploits the vertical ground...
Article
Full-text available
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 transi...
Conference Paper
Full-text available
This paper presents a novel approach for continuous gait phase estimation for human level walking, stair ascent and stair descent relying only on the kinematic variables of the shank, which are measurable by a single Inertial Measurement Unit (IMU) placed at the shank. We use data from an experiment with an instrumented stair to train Artificial Ne...
Conference Paper
Full-text available
Common active ankle joint prostheses comprise monoarticular actuators mimicking the function of the human soleus and tibialis anterior muscles, but lack the function of the biarticular human gastrocnemius muscle. Although these devices can mimic human ankle biomechanics in the sagittal plane, persons with transtibial amputation still show compensat...
Article
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 rig...
Preprint
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 rig...
Conference Paper
Full-text available
The knowledge of the gait phase can improve the support of an active prosthesis to increase the mobility of people with tran-stibial amputations. A Cross-Validation is used in this work to evaluate a novel approach for continuous gait phase estimation with Artificial Neural Networks. The estimation of the gait phase only uses kinematic variables of...
Article
Full-text available
The original article contains an error in Fig 3f whereby data is erroneously extrapolated beyond 80 years of age; this also affects statements made elsewhere in the article.
Article
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 whi...
Article
Full-text available
Daily human activity is characterized by a broad variety of movement tasks. This work summarizes the sagittal hip, knee, and ankle joint biomechanics for a broad range of daily movements, based on previously published literature, to identify requirements for robotic design. Maximum joint power, moment, angular velocity, and angular acceleration, as...
Chapter
Full-text available
The chapter focuses on three areas based on realization of neural control for gait assistance. The neural control could be identified by applying neuronal signals to control powered prostheses. For this, the first section summarizes the variety of possible control input signals for powered prostheses and exoskeletons with a focus on electromyograpy...
Article
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 mu...
Article
Full-text available
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 a positive, swing phase by a...
Conference Paper
Full-text available
In this paper, we present a novel template model- based control approach for control of ankle prosthesis. This method which is called FMCA (force modulated compliant ankle) employs ground reaction force to modulate ankle joint impedance. Inspired by our previous studies and also findings in human gaits, we know that leg force could play an importan...
Conference Paper
Full-text available
In this paper, we present a novel template model- based control approach for control of ankle prosthesis. This method which is called FMCA (force modulated compliant ankle) employs ground reaction force to modulate ankle joint impedance. Inspired by our previous studies and also findings in human gaits, we know that leg force could play an importan...
Article
Full-text available
Background: Physical and functional losses due to aging and diseases decrease human mobility, independence, and quality of life. This study is aimed at summarizing and quantifying these losses in order to motivate solutions to overcome them with a special focus on the possibilities by using lower limb exoskeletons. Methods: A narrative literature...
Article
Full-text available
Previous ankle exoskeleton assistance techniques that were able to demonstrate metabolic reductions can be categorized into those that delivered moment profiles similar to the biological ankle moment throughout the stance phase, and others that delivered positive power only during push off. Both assistance techniques and a powered-off condition wer...
Chapter
Great strides have been made over the last two decades to develop powered, active, ankle–foot orthoses and prostheses. Lightweight, powerful systems return gait movements and torques (kinematics and kinetics) to the user. An explosion of research in the areas of biomechanics, control, and mechanical design has allowed systems to assist and enhance...
Conference Paper
Perturbations are used to study and identify mechanisms of human motor control. This study introduces a concept for a movement manipulator prototype to explore human response and recovery strategies following temporary perturbations at the local joint level. We utilized a soft humanmachine interface in combination with a tethered actuation unit to...
Article
Full-text available
Muscle weakness—which can result from neurological injuries, genetic disorders, or typical aging—can affect a person's mobility and quality of life. For many people with muscle weakness, assistive devices provide the means to regain mobility and independence. These devices range from well-established technology, such as wheelchairs, to newer techno...
Conference Paper
Full-text available
Passive prosthetic feet are not able to provide non-amputee kinematics and kinetics for the ankle joint. Persons with amputations show reduced interlimb symmetry, slower walking speeds, and increased walking effort. To improve ankle range of motion and push off, various powered prosthetic feet were introduced. This feasibility study analyzed if pre...
Conference Paper
Full-text available
Active prosthetic knees have the capability to provide net positive work, which is required in daily activities like stair and ramp negotiation or sit-to-stand transfers. Adding this capability might help to increase user mobility, safety, and independence. This article summarizes the biomechanical knee requirements for different activities of dail...
Article
Full-text available
Background Different groups developed wearable robots for walking assistance, but there is still a need for methods to quickly tune actuation parameters for each robot and population or sometimes even for individual users. Protocols where parameters are held constant for multiple minutes have traditionally been used for evaluating responses to para...
Article
Full-text available
Active prosthetic knees have the capability to provide net positive work, which is required in daily activities like stair and ramp negotiation or sit-to-stand transfers. Adding this capability might help to increase user mobility, safety, and independence. This article summarizes the biomechanical knee requirements for different activities of dail...
Article
Full-text available
Zur Nachbildung des menschlichen Ganges werden in der Beinprothetik zunehmend biologische Wirkmechanismen nachempfunden. Bis zur Jahrtausendwende wurden vornehmlich passive Systeme entworfen, welche elastische, stützende oder auch dämpfende Eigenschaften abbilden können. Mit der Einführung von semi-aktiven Prothesenkomponenten wurde es zudem möglic...
Article
When defining requirements for any wearable robot for walking assistance, it is important to maximize the user’s metabolic benefit resulting from the exosuit assistance while limiting the metabolic penalty of carrying the system’s mass. Thus, the aim of this study was to isolate and characterize the relationship between assistance magnitude and the...
Article
Full-text available
This paper presents a review on design issues and solutions found in active lower limb prostheses. This review is based on a systematic literature search with a methodical search strategy. The search was carried out across four major technical databases and the retrieved records were screened for their relevance. A total of 21 different active pros...
Article
Full-text available
Background Current prosthetic ankle joints are designed either for walking or for running. In order to mimic the capabilities of an able-bodied, a powered prosthetic ankle for walking and running was designed. A powered system has the potential to reduce the limitations in range of motion and positive work output of passive walking and running feet...
Poster
Full-text available
Mobility can be limited due to age or impairments. Wearable lower limb robotics provide the chance to increase mobility and thus independence by reducing the metabolic cost of walking and thus effort. For studies that succeeded to reduce metabolics, two assisting strategies for plantarflexion support are used. A first strategy is designed to maximi...
Chapter
Mobility can be limited due to age or impairments. Wearable robotics provide the chance to increase mobility and thus independence. A powered soft exosuit was designed that assist with both ankle plantarflexion and hip flexion through a multi-articular suit architecture. So far, the best method to reduce metabolic cost of human walking with externa...
Conference Paper
Full-text available
Soft exosuits use structured functional textiles as a lightweight and conformal means to interface to the human body and deliver assistance in attempt to reduce the overall metabolic cost of walking. Here we present a soft exosuit that uses one actuator per leg to assist with both ankle plantarflexion and hip flexion thorough multi-articular suit a...
Conference Paper
Full-text available
Parameter sweeps allow for optimization of control parameters in assistive devices, but collecting data from a series of parameters at metabolic steady state is prohibitively time consuming. We implement a pair of continuous parameter sweeps, varying assistive force delivered by a soft exosuit in parallel with ankle plantarflexors and hip flexors f...
Poster
Full-text available
Parameter sweeps allow for optimization of control parameters in assistive devices, but collecting data from a series of parameters at metabolic steady state is prohibitively time consuming. We implement a pair of continuous parameter sweeps, varying assistive force delivered by a soft exosuit in parallel with ankle plantarflexors and hip flexors f...
Conference Paper
Full-text available
This paper introduces a novel measuring approach for detecting relative movement between stump and socket in lower limb prostheses. The application of the motion capturing based measuring approach is shown at a single male transtibial amputee using a Patella Tendon Bearing (PTB) socket. It further investigates and assesses the feasibility of measur...
Conference Paper
Full-text available
Conclusion: Initial testing of ROA shows a strong correlation with able-bodied kinematics and kinetics for both walking and running gaits. Future work will focus on clinical trials to fully understand how powered ankle systems affect amputees from a whole-body perspective and to identify the amputee groups that will benefit the most from the techno...
Conference Paper
Full-text available
The first measurements on the Walk-Run ankle could demonstrate that a powered ankle prosthesis enables one to perform walking, running, and standing using one prosthetic design. The running trial for the highest speed of 4 m/s highlighted the importance of an optimal spring stiffness to reduce the motor assistance. The human reference ankle angle w...
Thesis
Full-text available
Human upright locomotion emerged about 6 million years ago. It is achieved by a complex interaction of the biological infrastructure and the neural control. Bones, muscles, tendons, central nervous commands and reflex mechanisms interact to provide robust and efficient bipedal movement patterns like walking or running. Next to these locomotion task...
Conference Paper
Full-text available
Current active foot prostheses try to emulate the foot function by using a mono-articular series elastic actuator (SEA). In humans, a bi-articular actuation scheme is used to plantar-flex the foot through Soleus and Gastrocnemius muscles (in plantar-flexion the angle between foot and shank increases). In this study we investigated on using a bi-art...
Conference Paper
A powered ankle prosthesis that provides positive torque and power to the step can greatly improve amputee gait. This presentation will focus on the Ruggedized Odyssey Ankle, a powered ankle prosthesis that can support full powered running. Critical design and control methodologies are described and transtibial amputee participant data are discusse...
Conference Paper
Full-text available
The acceptance of artificial devices like prostheses or other wearable robots requires their integration into the body schemas of the users. Different factors induce, influence and support the integration and acceptance of the device that substitutes or augments a part of the body. Previous studies have shown that the inducing and maintaining facto...
Chapter
Full-text available
Human upright locomotion is a complex behavior depending on manifold requirements. Bones, muscles, cartilage and tendons provide mechanical infrastructure. Central nervous commands, reflex mechanisms from the spinal cord level or also preflexes defined by actuator properties provide input to create motion patterns like walking or running. Due to dy...
Article
Full-text available
A monoarticular series elastic actuator (SEA) reduces energetic and peak power requirements compared to a direct drive (DD) in active prosthetic ankle-foot design. Simulation studies have shown that similar advantages are possible for the knee joint. The aims of this paper were to investigate the advantages of a monoarticular SEA-driven hip joint a...
Conference Paper
Full-text available
In this paper we investigated on peak power (PP) and energy (ER) requirements for different active ankle actuation concepts that can have both elasticity and damping characteristics. A lower PP or ER requirement is an important issue because it will lead to a smaller motor or battery. In addition to spring, these actuation concepts are assumed to h...
Poster
Full-text available
PAKO is a Powered Ankle-Knee Orthoprosthesis being developed as a testbed for investigation on the muscular structure and control in human locomotion
Conference Paper
Full-text available
Peak power, peak torque and energy requirements are amongst the main issues for powered prosthetic ankles. Including series elastic actuators (SEA) can reduce peak power and energy requirements by reducing motor speed in comparison to a Direct Drive (DD). Parallel elastic actuation concept (PEA, the parallel spring can be compressed and elongated)...
Conference Paper
Full-text available
Elastic elements in prosthetic devices can help to reduce peak power (PP) and energy requirements (ER) for the actuators. Calculations showed that it is impossible with current commercial motor technology to mimic human ankle behavior in detail for higher walking and running speeds with single motor solutions using a Serial Elastic Actuator (SEA)....
Conference Paper
Full-text available
In ankle-foot prostheses a serial spring can assist the motor to reduce peak power (PP) and energy requirements (ER) during locomotion. Similar benefits can be expected for an active knee prosthesis. We compare the situation of a direct drive with a series elastic actuator optimized for minimal ER or for minimal PP. The simulations indicate that at...
Poster
Full-text available
In ankle-foot prostheses a serial spring can assist the motor to reduce peak power (P) and energy requirements (E) during locomotion [1,2]. Similar benefits can be expected for an active knee prosthesis. We compare the situation of a direct drive with a series elastic actuator optimized for minimal E or for minimal P.
Conference Paper
Full-text available
During walking and running, passive foot prostheses can only do positive work by releasing elastic energy stored in compliant structures. This limited ability to generate positive work can be improved in devices which actively support the push-off. Here, we estimate the peak power and energy requirements of a simulated serial elastic actuator (SEA)...