This design project marks the collaborative efforts of Translas, a prominent welding company based in the Netherlands, and Skelex, a scale-up enterprise specializing in exoskeleton design. Translas developed the 8XE fume extractor torch. However, a common complaint of the new torch is its decreased usability and potential ergonomic risk. To address this problem, Skelex and Translas have united their expertise to develop an exoskeleton-lite solution, aimed at assisting welders in carrying the torch. The aim is to alleviate the physical strain of welding and enhance overall ergonomics. A literature review of welding, ergonomics, and exoskeletons reveal that musculoskeletal disorders form a significant societal problem with large financial losses, which provide opportunities for cutting-edge companies as Translas and Skelex, and form the groundwork for a problem definition, design goal, and drivers. Through a numerical model the specific ergonomic concerns of the 8XE torch are analysed, which is also used to assess the final design. It was found that generally static welding forces with the 8XE are within safe parameters as recommended by ergonomic experts. The bending stiffness of the 8XE cable contributes significantly to the wrist moment, being estimated to reach values of 0.5Nm in conventional welding, compared to the 0.7Nm contribution due to weight. Friction in the ball-and-socket joint, and inertia ore comparatively low, and do not significantly cause ergonomic concerns. An iterative prototyping phase diverges to explore various ways to offload the 8XE’s weight on the wrist to stronger body parts, converging to two good concepts. A simple strap off loading the weight on the wrist to the lower arm for a limited amount of welding positions, and an exoskeleton worn on the waist and shoulders carrying the full weight of the torch using a tool balancer. After three user tests, two of which with welders in industry, both concepts were combined which led to the creation of AeroGrip. AeroGrip is an exoskeleton-lite product that eases welding by changing the weight distribution on the upper extremities, improving ergonomics and helping welders ‘be their ultimate’; they can weld safely for longer, with more precision, whilst experiencing less strain. It is a system that attaches to the welding cable through a ladder strap and buckle. A hook attached to a Kevlar cable can be pulled out and attached to the special AeroGrip Gloves, which feature a leather tab with grommet. The Kevlar cable is attached to a power spring via a spool in the casing, which ultimately results in a Tension of ~12N. Two final user tests, and comparative numerical analysis show that AeroGrip eases welding, provides an ergonomic benefit, and is convenient to use. FEM analysis and friction analysis ensure feasibility, whilst an assembly plan and business case ensure viability.

The thumb finger is indispensable for an independent daily life. Implant replacement, which aims to restore joint mobility and functionality, is one of the surgical treatments for patients with osteoarthritis at the thumb-base. However, current designs and the biomechanical understanding of the thumb-base joint are inadequate. Small bone size, deep location, and high degree-of-freedom challenge the investigation on this exquisite joint. Taking advantage of 4D CT scanning, this dissertation examined bone shape, joint contact, and the active motion boundary of the thumb-base joint among participants without signs of joint degeneration. In detail, the analysis compared the joint movement between females and males for the etiology of thumb-base osteoarthritis. The deeper insights gained into the structure and mechanics of the asymptomatic thumb-base joints provide the baseline understanding of the thumb-base joints, which can help researchers and healthcare professionals improve and develop more effective treatments for patients with thumb-base osteoarthritis. Furthermore, the exploration of connecting information between the skeletal and skin systems opens up possibilities for future research perspectives. @en

Measuring the motions of human hand joints is often a challenge due to the high number of degrees-of-freedom. In this study, we proposed a hand tracking system utilizing action cameras and ArUco markers to continuously measure the rotation angles of hand joints during motion. Three methods were developed to estimate the joint rotation angles. The pos-based method transforms marker positions to a reference coordinate system and extracts a hand skeleton to identify the rotation angles. Similarly, the orient-x-based method calculates the rotation angles from the transformed x-orientations of the detected markers in the reference coordinate system. In contrast, the orient-mat-based method first identifies the rotation angles in each camera coordinate system using the detected orientations and then synthesizes the results regarding each joint. Experiment results indicated that the repeatability errors with one camera regarding different marker sizes were around 2.64–27.56 deg and 0.60–2.36 deg using the marker positions and orientations, respectively. With multiple cameras employed, the joint rotation angles measured by using the three methods were compared with that measured by a goniometer. Comparison results indicated that the results of using the orient-mat-based method are more stable and efficient and can describe more types of movements. The effectiveness of this method was further verified by capturing hand movements of several participants. Therefore, it is recommended for measuring joint rotation angles in practical setups.@en

This study measured the active range of motion (AROM) and functional range of motion (FROM) of finger joints and explored the relationships between them. The results revealed that the AROM cannot fully cover the FROM in some scenarios with force. @en

Measuring the motion of human hand joints is a challenging task due to the high number of DOFs. In this study, we proposed a low-cost hand tracking system built on action cameras and ArUco markers to measure finger joint rotation angles. The lens distortion of each camera was corrected first via intra-calibration and the videos of different cameras were aligned to the reference camera using a dynamic time warping based method. Two methods were proposed and implemented for extracting the rotation angles of finger joints: one is based on the 3D positions of the markers via inter-calibration between cameras, named pos-based method; the other one is based on the relative marker orientation information from individual cameras, named rot-based method. An experiment was conducted to evaluate the effectiveness of the proposed system. The right hand of a volunteer was included in this practical study, where the movement of the fingers was recorded and the finger rotation angles were calculated with the two proposed methods, respectively. The results indicated that although using the rot-based method may collect less data than using the pos-based method, it was more stable and reliable. Therefore, the rot-based method is recommended for measuring finger joint rotation in practical setups.

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Objective: To develop a steerable neuroendoscopic instrument (SNI) based on user requirements found by several means of user research, and to evaluate this instrument on usability and safety. Only 5% of the potential intraventricular neuroendoscopy (INE) cases are currently treated with endoscopy. For the other 95%, an endoscopic approach is impossible, due to the risk of damaging the surrounding tissue by movement of the endoscopic system, needed to reach the affected areas inside the ventricles. A hand-held SNI is theorised to overcome these problems. Methods: A human-centered design (HCD) approach was taken to come to engineering solutions. Expert interviews, surveys and secondary research were performed to acquire the design input. Intermediary prototypes were developed and tested. For the final experiment, 10 participants, of which one neurosurgeon, performed a task in a box trainer. The endoscope was equipped with markers, used to evaluate the movement of the endoscope during the test by means of video analysis, comparing a rigid instrument and the new prototype in a two-tailed paired T-test. Usability was measured through a questionnaire. The spans between digit 1-2, 2-5 and 1-5 of the dominant hand of the participants was measured. Results: A biopsy forceps with a shaft length of 290mm, with a laser-cut articulating portion of 14mm and maximum bending of 40° was developed. Handle dimensions were based on a grip between the distal phalanges and the thenar area of the palm of 10th percentile hand measurements to enforce a stable grip. Significantly less non-angular movement than in the old instrument(p=0.009) was observed. Angular movement reduction was significant in one direction (p=0.032) but not in both (p=0.063). The handle prototype is slightly too large. The forces on the controls were comfortable. No relationship was detected between the finger span measurements and the usability score per participant. Conclusion: The prototype consists of a handle design based on human factor guidelines and multiple user evaluations, and an articulate tip based on DEAM’s technology, now with dimensions optimised for INE biopsy and ETV. Safety is improved by significantly limiting movement in the system during use.

The human body, although seemingly symmetrical, can in fact be highly asymmetrical. Our bodies are predetermined by our DNA and co-shaped by our environment. This leads to most of the world's population having a discrepancy in leg length either from birth or developed during their life time. It is completely natural and goes unnoticed, as changes are incremental and people get used to it. On the contrary, when undergoing total hip replacement surgery and waking up with one leg longer than the other, the change is almost instantaneous and immediately noticeable. Current surgical solutions do not address this issue in a practical manner within the operating theatre, leading to surgical teams developing their own methods and procedures to evaluate the change in patient's leg length.
 
Introducing new workflows to medical professionals often entails neglecting the protocols they spent years practicing. This thesis identified this bottleneck and instead of introducing new methods and procedures, it was decided to build on existing ones. This was done by exploring common surgical workflows in respect to total hip replacement and determining an approach to enhance surgical team's capabilities in evaluating leg length discrepancy.. Important in achieving this goal it to make any given design solution effortless, reliable and undisruptive to various workflows

In order to do so, user research was performed by joining multiple surgical teams within the OR, thereby observing and evaluating their methods. One method in particular stood out, which is best described as the 'loaded assessment'. During this assessment the surgeon or circulating nurse will centre the patient's feet, apply pressure to the heels and try to evaluate the discrepancy. Although this method being seemingly simple, its execution is difficult to perform by a single person and varying pressure differences may confuse the assessment.

Following the initial research phase, co-creation sessions with technical experts were organised, after which various concepts were developed and tested on the basis of feasibility, desirability and viability. Finally, a functional prototype based on the loaded assessment principle was developed and tested for its functionality and conceptual expectation.

A high-fidelity digital representation of (part of) the human body is a key enabler for integrating humans in a digital twin. Among different parts of human body, building the model of the hand can be a challenging task due to the posture deviations among collected scans. In this article, we proposed a posture invariant statistical shape model (SSM) of the human hand based on 59 3D scans of human hands. First, the 3D scans were spatially aligned using a Möbius sphere-based algorithm. An articulated skeleton, which contains 20 bone segments and 16 joints, was embedded for each 3D scan. Then, all scans were aligned to the same posture using the skeleton and the linear blend skinning (LBS) algorithm. Three methods, i.e., principal component analysis (PCA), kernel-PCA (KPCA) with different kernel functions, and independent component analysis (ICA), were evaluated in the construction of the SSMs regarding the compactness, the generalization ability, and the specificity. The PCA-based SSM was selected, where 20 principal components were used as parameters for the model. Results of the leave-one-out validation indicate that the proposed model was able to fit a given 3D scan of the human hand at an accuracy of 1.21 ± 0.14 mm. Experiment results also indicated that the proposed SSM outperforms the SSM that was built on the scans without posture correction. It is concluded that the proposed posture correction approach can effectively improve the accuracy of the hand SSM and therefore enables its wide usage in human-integrated digital twin applications.

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