Effective Human-Machine Interaction (HMI) depends on accurately capturing and interpreting information from the human user. For systems relying on hand-based operation, understanding the limits of human cognitive-motor abilities is crucial to designing intuitive and efficient interfaces. This study presents an experimental setup involving four analog buttons with a minimally complex control, where human hand performance is assessed through simultaneous multi-finger Fitts' Law tasks. Initially, task difficulty was assumed to be computed by summing the individual indices of difficulty for each button, which resulted in peak throughput performance with two fingers. However, this approach did not align with Fitts' Law. By applying a weighted summation, with weights based on the variation of distances within a task, the difficulty measure better conformed to Fitts' Law, and the highest throughput was achieved with a single finger. These findings highlight the interdependence in multi-finger movement complexity and emphasize the importance of considering cognitive-motor limitations when designing HMI interfaces to optimize user performance.

Stroke survivors often exhibit motor impairments, which hinder activities of daily living. While grounded robotic perturbation devices can accurately quantify joint dynamics via system identification, their size and fixed positioning limit functional assessments under realistic conditions. To address this gap, we present the design and pilot evaluation of a novel, wearable perturbation device capable of delivering ungrounded force perturbations to the user’s forearm.

The device uses a linear solenoid actuator housed in a wrist brace to generate short, pulse-type forces, thereby inducing small angular deflections (approximately 1–3°) to the arm. An inertial measurement unit (IMU) placed on the brace tracks the resulting movement, while an accelerometer on the solenoid coil measures the perturbation force. Nine healthy participants performed three tasks—relax, resist, and move. Random pulse signals were used to prevent anticipation of the perturbations. The device successfully deflected the arm in all tasks. The largest deflections was recorded during the relax task and smaller, though still measurable, deflections in the resist and move tasks.

Estimated stiffness values in each task indicated that the device could distinguish different levels of joint rigidity, although comparisons with established literature showed some over- or underestimation. Factors such as non-rigid brace attachment and off-center actuator placement contributed to these discrepancies. Despite these limitations, the prototype demonstrates the feasibility of wearable, ungrounded force perturbations for assessing elbow dynamics. Future work will focus on improving the device’s rigidity, exploring multi-degree-of-freedom perturbations, and refining stiffness estimation algorithms to better capture realistic joint behaviors.

Field hockey sticks are interesting hand-held sports equipment, due to their duality in preferred stick behaviour. The stick is used for striking, where a high power is desired; but also for stopping, where good control is required. This report aims to identify the properties that influence stick performance and to design a field hockey stick with adaptable properties to improve stick performance; where performance is defined as the ability of the stick to develop a high velocity when hitting a ball, and to provide proper control when stopping the ball.
The stiffness, damping and mass of the stick are properties influencing the stick behaviour; these properties are present locally, at the impact location, as well as over the full length as deflective properties due to the moment originating from the ball impact.
The deflective stiffness and damping properties are identified by applying a disturbance force on the stick tip and measuring the displacement; this shows a range of stick stiffness from 1.4 to 3.0 kN/m and a stick damping from 0.5 to 2.7 Ns/m. Measurements are performed analysing the influence of stiffness, damping, mass and effective mass; this is done by a setup where a stick falls down towards a ball and the ball distance is measured. Additionally, a mathematical model is developed for the analysis of these stick properties. This consists of a collision model, including the coefficient of restitution reflecting the stiffness and damping properties. It can be concluded that the effective stick mass is most influential and the desired properties are opposite for striking and stopping.
A design of a mechanism that fits inside the stick is proposed, this mechanism reacts to the angular acceleration of the stick, and thereby changes its properties between striking and stopping a ball. It adapts the effective mass of the stick, by two weights moving towards the head of the stick when striking a ball. By this increase in effective stick mass, an increase of 7% (compared to the original effective mass) of the ball velocity after hitting the ball is expected.

The Shoulder Elbow Perturbator (SEP) is a robotic diagnostic device developed to assess multiple forms of motor impairment common in stroke patients. As an active medical device, the SEP would be bound to strict regulations if brought to market. By replacing its motor with a passive power source, this regulatory burden can be minimized, with the added advantage of greatly minimizing its cost. As a first step in developing this passive SEP, a prototype capable of reproducing one of the SEP’s basic tests was conceptualized. After evaluating multiple options for the passive energy source and associated components, a cost-effective design was developed using a spring, a variable radius winding drum to convert the spring’s force output to a constant torque, and a bicycle disc brake. A simulation of this design was then modeled and run through a variety of scenarios as a theoretical validation of the concept. The results of this process are promising, though testing with a physical prototype is needed for further validation.

Work-related musculoskeletal disorders (WRMSDs) are a leading cause of work leave in the construc tion industry. As Strukton experiences a shortage in workers for rail catenary construction, minimizing the occurance of WRMSDs is important. This is done by the implementation of new working methods or new worker aids, such as boom lifts and exoskeletons. Strukton has experienced that not all worker aids are, however, as helpful as expected. In order to find the right tools, a better understanding of the work and physical load is needed. This thesis aims to identify which parts of the catenary construction workarethemostdemandingbycombininganergonomicriskassessment(ERA)withthedevelopment of an in situ biomechanical analysis tool. The research consists of two major components. First, a qualitative ergonomic risk assessment was conducted to identify the most physically demanding tasks in rail catenary construction. Methods in cluded site visits to Strukton’s rail construction projects, unstructured and semi-structured interviews with workers and experts, and a questionnaire administered to 12 workers. These data were used to develop a Work Breakdown Structure (WBS), categorize tasks based on their physical demand, dura tion, and frequency, and identify prevalent ergonomic risks. Tasks such as wire tensioning, removing wires, and task related to the support portal were identified as high-risk activities. Back, shoulder, and ankle complaints are the most commonly reported by workers and might be related to these tasks. Fu ture research should expand the worker sample size, investigate the causes of WRMSDs further, and enhancethe reliability of task scoring. Recommendations for Strukton include adding sidewalks on site, redesigning boom lift platforms, introducing ergonomic tool bags, and using electric tools for tasks that require high force. The second component of the research involved designing and validating an in-situ biomechanical analysis tool. The tool leverages pose detection technology from widely available mobile devices and integrates it with musculoskeletal modeling software to capture and analyze joint kinematics and mo ments during construction tasks. This approach allows for task-specific quantification of physical loads experienced by workers, bridging the gap between qualitative insights and quantitative measurements. A pilot validation study demonstrated the feasibility of the tool in providing kinematic and joint moment data for biomechanical analysis, though further validation is needed to generalize its application. Poten tial uses of the tool include automating ERAs and validating conceptual worker aids. Future research should focus on deploying the tool in real-world working environments and refining the implementation of external force data in the modeling process. The findings of this thesis highlight the critical need for task-specific ergonomic interventions in the construction of rail catenaries. The combination of qualitative ERA and biomechanical analysis offers a comprehensive framework to identify risks and design targeted solutions. This work provides a foun dation for future research into ergonomic improvements in dynamic and physically intensive industries

In Upper Motor Neuron Lesion (UMNL) following stroke, patients can experience increased joint impedance, resisting joint rotation and hindering functional movement. This heightened impedance in UMNL is driven by both exaggerated reflexes and increased intrinsic muscle activation through co-contraction, hypertonus, or synergies. The simultaneous presence of these mechanisms complicates clinical distinction, especially given their theorised interplay, where increased intrinsic activation would further heighten reflex responses. Separate quantification of this intrinsic and reflexive impedance and their interaction, can aid in further investigation of the pathophysiology of post-stroke joint impairment and its treatment.

This work presents the investigation of an Open Loop System Identification (OL-SID) protocol, to perform this separate quantification of intrinsic and reflexive impedance for the elbow joint. Perturbation experiments were performed with 16 healthy subjects, using multisine positional perturbations and measuring the elbow torque response. An impedance model consisting of both intrinsic and reflexive parameters was fit to the estimated frequency response function (FRF), relating perturbation angle to joint torque. It was assessed how background muscle activation, as well as the frequency and velocity of the perturbation signal, influenced the modelled intrinsic stiffness, intrinsic damping, and reflex velocity-gain.

For this, three different biceps muscle activation levels were requested from the participants in different trials; 0%, 10%, and 30% of Maximum Voluntary Contraction (MVC), as confirmed by online EMG measurements. Participants were requested to not actively resist perturbations, but only to comply with the requested biceps activation level. Furthermore, three rotational multisine perturbations with a max. amplitude of 2 degrees were applied; Wide Bandwidth - High Velocity, Narrow Bandwidth - Low Velocity, and Wide Bandwidth - Low Velocity. Cross-combination of biceps activation levels and perturbation signal resulted in 9 impedance quantifications per participant.

Increased biceps activation resulted in a significant increase of intrinsic stiffness, intrinsic damping, and the reflex-gain. This confirmed the expected relationship between muscle activation and intrinsic impedance, as well as the theorised relation between intrinsic activation and the reflex response. Unexpectedly, differences in used perturbation bandwidth or velocity showed no clear influence on identified reflex gain. This contradicts findings of reflex suppression during high-bandwidth force perturbations in tasks that require resisting these perturbations, as well as during high-velocity binary or unidirectional joint stretches. This discrepancy shows that joint system identification results are highly dependent on perturbation type and subject task, emphasising the need to align the experimental design with the clinical question at hand.

Despite some shortcomings regarding low coherence of the estimated FRFs, and necessary further research on perturbation signal properties and their effect on the reflex response, the results of this study are promising. The observed trends in fitted parameters with increased activation levels in line with physiological expectations, indicate the ability of this technique to validly identify reflexive and intrinsic joint impedance. This distinction is highly valuable for advancing investigation of the pathophysiology and clinical presentation of UMNL post-stroke, in the pursuit of adequate treatment for different patients.

Work-related musculoskeletal disorders (WRMSDs) are prevalent among sonographers, particularly affecting the shoulder region due to repetitive and static movements. This study introduced an ergonomic posture and a mobile arm support (MAS) to reduce the load of muscles contributing to the stabilization of the shoulder. The experimental setup replicated a conventional cardiac ultrasound examination, using a phantom model and simulations to mimic cardiac ultrasound procedures. Professional cardiac sonographers were instructed to acquire three cardiac views (parasternal long-axis view (PLAX), apical four-chamber view (A4C), and subcostal window(SCW)) while surface EMG and joint angles of the shoulder, elbow, and back were measured. Additionally, subjects were tasked with completing a questionnaire to gather subjective outcomes of usability and satisfaction with the support and ergonomic posture. Muscular activity of the middle deltoid muscular activity (PLAX; F(3,12)10.15,p=.001,η2 p=.717, A4C; F(3,12)=5.75,p=.011,η2 p=.590) and superior trapezius (PLAX; F(3,12)=7.05,p=.005,η2 p=.638) decreased significantly during examinations with postural changes but increased significantly while only support was provided. The support was considered slightly useful (SUS=65.0±6.9, α=.585), but the ergonomic change was considered poor (SUS=43.0.0±14.4, α=.813). The increase in muscular activity was likely caused by incorrect placement of the MAS on the upper extremity and incorrect levels of support. Besides, sonographers reported a MAS would be useful when there is an additional functionality that applies contact force through the MAS. The addition of support to postural changes did not significantly reduce muscular load compared to examinations with only postural changes. Therefore, ergonomic postural change is a sufficient solution for mitigating WRMSDs development due to the only significant decrease in muscular activity.

Human intention detection with hand motion prediction is critical to drive the upper-extremity assistive robots. However, the traditional methods relying on physiological signal measurement are restrictive and often lack environmental context. We propose a novel approach that integrates gaze information, historical hand motion sequences, and environmental object data to predict future sequences of intended hand poses, adapting dynamically to the assistive needs of the patient without prior knowledge of the intended object for grasping. Specifically, we propose to use a vector-quantized variational autoencoder for robust hand pose encoding with an autoregressive generative transformer for effective hand motion sequence prediction. We demonstrate the usability of these novel techniques in a pilot study with healthy subjects. To train and evaluate the proposed method, we collect a dataset consisting of various types of grasp actions on different objects from multiple subjects. Through extensive experiments, we demonstrate that the proposed method can successfully predict sequential hand movement. Especially, the gaze information shows significant enhancements in prediction capabilities, particularly with fewer input frames, highlighting the potential of the proposed method for real-world applications.

This research investigates methodologies to reduce and implement negative inertia in robots for upper extremity diagnostics and rehabilitation. The robot’s responsiveness is enhanced by integrating accelerometers and Kalman filters into the control scheme, ensuring smoother physical human-robot interactions. A force gain that mimics negative inertia significantly improves system dynamics within the admittance control framework. Introducing dead zones for force and acceleration stabilizes responses at lower rendered inertia, crucial for handling spastic conditions. However, this research identifies a lack of standardized evaluation methods for negative inertia and highlights hardware constraints, such as bandwidth limitations, that restrict performance. Future research should focus on establishing evaluation standards and optimizing hardware to refine control precision. This work demonstrates the potential of advanced control strategies to optimize robotic rehabilitation, paving the way for more effective diagnostic and therapeutic interventions.

This paper aims to explore innovative fabrication methods for assistive gloves using origami design principles. The study addresses the limitations of current assistive gloves, such as bulkiness and lack of customisation, by developing a novel fabrication method that improves ergonomic design and manufacturing flexibility. The proposed method integrates 3D printing and welding techniques to create lightweight, customisable gloves that enhance rehabilitation for individuals with hand impairments, particularly stroke survivors. The paper details the design process, and testing methods, concluding with successfully creating a new fabrication approach for origami-based assistive gloves.

This thesis explores the application of origami-inspired inflatable structured sheets to enhance muscle function for individuals with muscle impairments, specifically focusing on the biceps brachii muscle. These sheets induce muscle contraction through pneumatic pressure, aimed at facilitating forearm flexion by strategically incorporating patterns that create air pockets. These sheets hold significant potential for assisting individuals with conditions such as muscular dystrophy, cerebral palsy, or spinal cord injuries. Compared to traditional solutions, they offer less bulkiness and greater adaptability, promoting natural movement and improving limb mobility. Furthermore, these sheets can be customized to fit various muscle contours and integrated with mechatronics for real-time adjustments, enhancing stability and resilience in muscle support applications. The study begins with the development of a comprehensive test setup that simulates muscle extension and flexion, integrating mechanical and electrical components. This setup includes a silicone muscle model of the biceps brachii muscle, essential for evaluating sheet performance. Subsequent chapters delve into the evaluation of materials and patterns for the sheets. Materials such as PVC-film, TPU-film, PET-film, and Nylon are assessed for biocompatibility, flexibility, temperature sensitivity, and adhesion characteristics. Here, TPU-film emerges as the most promising material due to its durability and adhesive properties under pressure. For the evaluation of the patterns, a preliminary study is conducted to determine optimal patterns that effectively respond to pneumatic pressure for inducing muscle contraction. This study reveals that combinations of parallel lines and zigzag structures show the most promising results among the tested patterns. Building on these findings, various structured sheets are tested around the muscle model to assess their ability to activate and contract muscles. An optimal structure is selected that conforms closely to the contours of the muscle model, ensuring optimal airflow and maximizing the potential for effective muscle contraction. However, challenges such as leakage affecting pressure retention and muscle activation are identified, underscoring the need for further optimization to achieve practical muscle activation and flexion. In conclusion, while this research provides valuable insights into the feasibility of origami-inspired structured sheets for muscle augmentation, ongoing refinement is crucial to address practical challenges and optimize performance.

Fear of pain is a psychological consequence that can hinder an athlete’s ability to resume their previous level of performance or even return to their sport. A desire exists to examine the influence of fear of pain on both mechanical and neural factors involved in postural control, particularly focusing on the lower extremities. Previous literature shows associations between jump tests and fear of pain, but existing methods cannot differentiate between neural and mechanical factors, necessitating a different approach. Given the absence of a method to measure lower extremity reflexes and intrinsic properties similar to those observed in the shoulder, the original Proprio setup was adapted for leg perturbation to investigate its impact on lower extremity postural control. The adapted setup consists of a platform for participants to stand on, with coupling provided by a stiff ankle brace. A group of seven participants performed a slack trial and multiple stiff trials in both angled and neutral positions. Metrics such as admittance, stiffness, and coherence were calculated for each trial. The suitability of the setup was evaluated based on the selectivity of results across different trials and positions. Additionally, coherence was assessed, indicating the linearity which is necessary for future parameter identification. Notable differences in admittance and stiffness were observed between different legs and trials. This demonstrates the ability of the new setup around the Proprio to differentiate between various conditions. Comparisons with previous studies on shoulder dynamics showed similar findings, suggesting accurate measurement of leg dynamics. High coherence values indicated linearity, supporting the potential for future estimation of intrinsic parameters and reflex gains in leg dynamics. Considering these factors, the adapted Proprio setup appears suitable for analyzing lower extremity postural control. The next steps include expanding the participant group for significance and parameter identification, which will enable the investigation of the impact of fear of pain on intrinsic and reflexive properties using this setup.

This study investigated the effects of lifting and carrying activities on ambulatory blood pressure (BP) responses in healthy adults. Participants performed simulated infant carrying tasks with different weight loads (0kg, 5kg and 10kg) using two lifting techniques (stoop and flat). Continuous BP was measured using the Finapres NOVA ambulatory BP monitor. The indicative results showed increases in peak systolic BP during lifting (5 kg: stoop +44.0 mmHg \& flat +41.1 mmHg) and average SBP during carrying phases (5 kg: stoop +12.96 mmHg \& flat +12.04 mmHg) compared to unloaded situations, with greater BP elevations observed for heavier loads (lifting 10 kg: stoop +56.9 mmHg \& flat +43.2 mmHg; carrying 10 kg: stoop +19.87 mmHg \& flat +14.11 mmHg). The lifting technique also impacted BP responses, as stoop lifting produced higher systolic BP peaks than flat lifting (+5.9 mmHg, +8.8 mmHg \& +19.6 mmHg for 0 kg, 5 kg \& 10 kg respectively). Detailed analyses were conducted by defining quantitative parameters such as baseline BP, peak BP during lifting, start BP after lifting, and end BP before lowering. The findings from this study have implications for developing guidelines on safe lifting and carrying practices for individuals with conditions like Marfan syndrome, which are prone to aortic complications from elevated BP.

Stroke causes severe tactile deficiencies, affecting motor control during object grasping and lifting. Understanding the fundamental neural disorders associated with tactile deficits is crucial for developing effective rehabilitation and treatment plans. Previous studies have investigated the dynamics between finger grasping behavior and arm muscle activation in stroke patients. However, the exact neuromuscular synergy between tactile perception and arm usage remains unexplored. In this study, we designed a comprehensive experimental platform and tested potential synergies in 12 healthy young adults, serving as a control group to establish a foundation for future studies on stroke patients. The experimental platform consists of a lever arm on which torques can be applied to the subject's arm. The end effector is equipped with a special ultrasonic friction modulation plate that can reduce apparent friction by up to 63%, simulating real-world grasping tasks in a controlled setting. The experiments were conducted under varying conditions of friction and arm usage. Results indicate significant effects of tactile stimulation on grasping force adaptation (p < 0.05 in 8 of 12 experimental conditions). In contrast, arm usage did not show significant synergy with tactile perception (p = 0.44 for grasping force adaptation amplitude, and p = 0.73 for reflex delay). These findings demonstrate that the experimental platform can provide insights into human tactile behaviors, which is critical for studying the synergy between tactile sensory and motor control. The results will lay the groundwork for future research on underlying pathologies and rehabilitation strategies for stroke patients.