Roger Gassert

Last Name

Gassert

First Name

Roger

ORCID

0000-0002-6373-8518

Organisational unit

03827 - Gassert, Roger / Gassert, Roger

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Publications1 - 10 of 270

A Remotely Actuated Knee Perturbator for Human Knee Impedance Estimation
Tucker, Michael R.; Lambercy, Olivier; Gassert, Roger (2014)
Differentiable Biomechanics for Markerless Motion Capture in Upper Limb Stroke Rehabilitation: A Comparison With Optical Motion Capture
Unger, Tim; Moslehian, Arash Sal; Pfeiffer, J.D.; et al. (2025)
IEEE Transactions on Medical Robotics and Bionics
Marker-based Optical Motion Capture (OMC) paired with biomechanical modeling is currently considered the most precise and accurate method for measuring human movement kinematics. However, combining differentiable biomechanical modeling with Markerless Motion Capture (MMC) offers a promising approach to motion capture in clinical settings, requiring only minimal equipment, such as webcams, and minimal effort for data collection. This study compares key kinematic outcomes from biomechanically modeled MMC and OMC data in 15 individuals with stroke performing the drinking task, a functional task recommended for assessing upper limb movement quality. We observed a high level of agreement in kinematic trajectories between MMC and OMC, as indicated by high correlations (median r > 0.95 for the majority of kinematic trajectories) and median RMSE (root mean squared error) values ranging from 2∘-5∘ for joint angles, 0.04 m/s for end-effector velocity, and 6mm for trunk displacement. Trial-to-trial biases between OMC and MMC were consistent within participant sessions, with interquartile ranges of bias around 1-3∘ for joint angles, 0.01m/s in end-effector velocity, and approximately 3mm for trunk displacement. Our findings indicate that our MMC for arm tracking is approaching the accuracy of marker-based methods, supporting its potential for use in clinical settings. MMC could provide valuable insights into movement rehabilitation after stroke, potentially enhancing the effectiveness of rehabilitation strategies.
Development of an Assistive Dynamic Arm Support for a User With Spinal Muscular Atrophy
Gantenbein, Jessica; Weber, Micha; Gassert, Roger; et al. (2022)
ICCHP-AAATE 2022 Open Access Compendium "Assistive Technology, Accessibility and (e)Inclusion"
People affected by Spinal Muscular Atrophy typically suffer from decreased muscle strength in upper and lower limbs and face many challenges in accomplishing daily activities. This work presents the usercentered design, development, and long-term evaluation after two years of daily use of an assistive dynamic arm support for a specific user suffering from Spinal Muscular Atrophy. The personalized device provides active assistance to switch the user’s elbow between two functional positions and active or passive support of elbow flexion and extension sufficient to conduct activities of daily living such as eating, drinking, controlling the wheelchair or using computers or smartphones. The device was assessed at multiple time steps, whereas the device has shown to be robust with only minimal maintenance required. The user’s satisfaction, measured by the Quebec User Evaluation of Satisfaction with Assistive Technology 2.0 score, was perceived as high (average score between 3.6 and 4.3, possible range 0 to 5) and the Psychosocial Impact of Assistive Devices Scale indicated that the dynamic arm support positively affected the independence, well-being, and quality of life of the user (average score between 0.85 and 1.5, possible range -3 to +3). This work underlines the benefits of a user-centered design approach and longterm evaluations in terms of usability and, consequently, device adoption of assistive devices, as well as the need for adaptability to the individual needs of different users with muscular weakness.
Neuro-cognitive effects of degraded visibility on illusory body ownership
Pamplona, Gustavo S.P.; Giussani, Amedeo; Salzmann, Lena; et al. (2024)
NeuroImage
Based on visuo-tactile stimulation, the rubber hand illusion induces a sense of ownership for a dummy hand. Manipulating the visibility of the dummy hand during the stimulation influences cognitive aspects of the illusion, suggesting that the related brain activity may be influenced too. To test this, we analyzed brain activity (fMRI), subjective ratings, and skin conductance from 45 neurotypical participants undergoing a modified rubber hand illusion protocol where we manipulated the visibility (high, medium, and low) of a virtual hand, not the brush (virtual hand illusion; VHI). To further investigate the impact of visibility manipulations on VHI-related secondary effects (i.e. vicarious somatosensation), we recorded brain activity and skin conductance during a vicarious pain protocol (observation of painful stimulations of the virtual hand) that occurred after the VHI procedure. Results showed that, during both the VHI and vicarious pain periods, the activity of distinct visual, somatosensory, and motor brain regions was modulated by (i) visibility manipulations, (ii) coherence between visual and tactile stimulation, and (iii) time of visuo-tactile stimulation. Accordingly, embodiment-related subjective ratings of the perceived illusion were specifically influenced by visibility manipulations. These findings suggest that visibility modifications can impact the neural and cognitive effects of illusory body ownership, in that when visibility decreases the illusion is perceived as weaker and the brain activity in visual, motor, and somatosensory regions is overall lower. We interpret this evidence as a sign of the weight of vision on embodiment processes, in that the cortical and subjective aspects of illusory body ownership are weakened by a degradation of visual input during the induction of the illusion.
Reliability, validity and clinical usability of a robotic assessment of finger proprioception in persons with multiple sclerosis
Zbytniewska-Mégret, Monika; Kanzler, Christoph M.; Raats, Joke; et al. (2023)
Multiple Sclerosis and Related Disorders
Background: Multiple sclerosis often leads to proprioceptive impairments of the hand. However, it is challenging to objectively assess such deficits using clinical methods, thereby also impeding accurate tracking of disease progression and hence the application of personalized rehabilitation approaches. Objective: We aimed to evaluate test-retest reliability, validity, and clinical usability of a novel robotic assessment of hand proprioceptive impairments in persons with multiple sclerosis (pwMS). Methods: The assessment was implemented in an existing one-degree of freedom end-effector robot (ETH MIKE) acting on the index finger metacarpophalangeal joint. It was performed by 45 pwMS and 59 neurologically intact controls. Additionally, clinical assessments of somatosensation, somatosensory evoked potentials and usability scores were collected in a subset of pwMS. Results: The test-retest reliability of robotic task metrics in pwMS was good (ICC=0.69–0.87). The task could identify individuals with impaired proprioception, as indicated by the significant difference between pwMS and controls, as well as a high impairment classification agreement with a clinical measure of proprioception (85.00–86.67%). Proprioceptive impairments were not correlated with other modalities of somatosensation. The usability of the assessment system was satisfactory (System Usability Scale ≥73.10). Conclusion: The proposed assessment is a promising alternative to commonly used clinical methods and will likely contribute to a better understanding of proprioceptive impairments in pwMS.
A Method to Evaluate and Improve the Usability of a Robotic Hand Orthosis from the Caregiver Perspective
Meyer, Jan T.; Dittli, Jan; Stutz, Adrian; et al. (2020)
2020 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob)
Human-centered design of assistive technology aims to achieve high functional benefits while considering user opinions to increase device usability and promote acceptance. Considering the needs and opinions of all real-world user groups, including not only the target end-users with disabilities but also their caregivers (e.g. family members, friends, or paid helpers) can improve the design of assistive devices. In this study, the perspectives and performances of 15 participants (3 clinical, 12 non-clinical) placed in a caregiver role to prepare and don a wearable robotic hand orthosis on a wheelchairbound mock end-user were investigated. Through the use of eye tracking combined with a retrospective think-aloud protocol, usability issues of the orthosis were identified and addressed in a design iteration. These design changes positively influenced the device usability by means of fewer problems occurring during the unsupervised setup procedure, as well as a significantly lower total procedure time (p = 0.02) in a second evaluation round. The caregiver perspective proved useful to improve the robotic hand orthosis design and usability, paving the way for unsupervised administration and use of the assistive device.
Design and Compatibility of a High-Performance Actuation System for fMRI-Based Neuroscience Studies
Hara, Masayuki; Dueñas, Julio; Kober, Tobias; et al. (2010)
IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2010 : 18 - 22 Oct. 2010, Taipei, Taiwan
Monitoring Upper Limb Recovery after Cervical Spinal Cord Injury: Insights beyond Assessment Scores
Brogioli, Michael; Schneider, Sophie; Popp, Werner L.; et al. (2016)
Frontiers in Neurology
Background: Preclinical investigations in animal models demonstrate that enhanced upper limb (UL) activity during rehabilitation promotes motor recovery following spinal cord injury (SCI). Despite this, following SCI in humans, no commonly applied training protocols exist, and therefore, activity-based rehabilitative therapies (ABRT) vary in frequency, duration, and intensity. Quantification of UL recovery is limited to subjective questionnaires or scattered measures of muscle function and movement tasks. Objective: To objectively measure changes in UL activity during acute SCI rehabilitation and to assess the value of wearable sensors as novel measurement tools that are complimentary to standard clinical assessments tools. Methods: The overall amount of UL activity and kinematics of wheeling were measured longitudinally with wearable sensors in 12 thoracic and 19 cervical acute SCI patients (complete and incomplete). The measurements were performed for up to seven consecutive days, and simultaneously, SCI-specific assessments were made during rehabilitation sessions 1, 3, and 6 months after injury. Changes in UL activity and function over time were analyzed using linear mixed models. Results: During acute rehabilitation, the overall amount of UL activity and the active distance wheeled significantly increased in tetraplegic patients, but remained constant in paraplegic patients. The same tendency was shown in clinical scores with the exception of those for independence, which showed improvements at the beginning of the rehabilitation period, even in paraplegic subjects. In the later stages of acute rehabilitation, the quantity of UL activity in tetraplegic individuals matched that of their paraplegic counterparts, despite their greater motor impairments. Both subject groups showed higher UL activity during therapy time compared to the time outside of therapy time. Conclusion: Tracking day-to-day UL activity is necessary to gain insights into the real impact of a patient’s impairments on their UL movements during therapy and during their leisure time. In the future, this novel methodology may be used to reliably control and adjust ABRT and to evaluate the progress of UL rehabilitation in clinical trials.
An Environment Recognition and Parameterization System for Shared-Control of a Powered Lower-Limb Exoskeleton
Karacan, Kübra; Meyer, Jan T.; Bozma, H. Işil; et al. (2020)
2020 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob)
The daily use of advanced wearable robotic devices for the assistance of people with locomotor disabilities is still facing clear limitations in usability and acceptance (e.g. cost, complexity, and inability to maintain balance). In most devices, the correct selection and initiation of pre-defined functions and activities (e.g. walking and stair ascent-descent) rely on the user’s input and constant interpretation of the environment, which results in a substantial cognitive workload. In this study, a novel environment recognition and parameterization system that uses depth camera images is proposed as a potential assistant in the control of powered lower-limb exoskeletons. The feasibility of an online shared-control approach between the user and the system was assessed in two specific use-cases of lower-limb exoskeletons: Mode selection assistance and dynamic step adaptation. In a sequence of realistic daily life tasks, the assistance provided by the proposed system achieved an error below 10% with a loop frequency up to 400 Hz in terms of parameterizing the environment, and reduced the mean overall workload, measured with the Raw Task Load Index, by 19% in a group of seven neurologically intact subjects. In conclusion, an assistive environment recognition and parameterization system shows potential to reduce the cognitive workload on the user, and thereby positively influence device usability.
Investigation of a Cable Transmission for the Actuation of MR Compatible Haptic Interfaces
Chapuis, Dominique; Gassert, Roger; Gowrishankar, Ganesh; et al. (2006)
The First IEEE/RAS-EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob 2006)
This paper investigates a cable transmission to remotely actuate MR compatible robots over a distance of several meters. Such a transmission could be an interesting solution for haptic interfaces for neuroscience studies performing force feedback during functional magnetic resonance imaging (fMRI), as well as for robots for interventional MRI. MR compatible components, transmission length and bandwidth as well as cable properties are discussed. Experiments performed on an MR compatible test bench allowing variable transmission length up to 9 meters show a mechanical bandwidth of over 30 Hz. Transmission performances and flexibility are compared with those of a hydrostatic transmission

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