Energy dissipation plays a crucial role in mitigating noise and vibration in a wide range of applications. In the field of assistive devices, energy dissipation is used to improve the stability of joint motion and protect the musculoskeletal system from excessive loads. It is not surprising that considerable effort has gone into developing effective energy dissipation mechanisms for this application. However conventional devices are bulky, expensive, and rigid. They are known to cause discomfort, and skin trauma to the patients. With the advances in soft robotics, novel soft exoskeletons that demonstrate bio-mimetic functionality, increased comfort, and cost-effective designs are being developed. This work proposes a novel soft, passive damper, intended for operation as an energy dissipator in assistive devices. The study begins with an overview of the state of the art in assistive devices, and energy dissipation mechanisms. A comparison is made of the various modes of energy dissipation for the intended application, and the most suitable one is selected. A proof-of-concept passive flexible damper is designed. A prototype is assembled and its working is experimentally verified. The study concludes with the successful demonstration of a novel soft damper, comments on the current limitations, and suggests future research directions to improve on this approach. This work is a contribution to the development of a new class of soft energy dissipators. ... Read more

Background: The lack of access to electric powered wheelchairs for disabled people in low- and middle-income countries, that suit their rural environments, still remains an issue. Current available electric powered wheelchairs that do adapt to these rural environments are expensive and require complex control algorithms.
Objective: The aim of this research is to analyze the feasibility of an electric powered walking wheelchair with an one-degree-of-freedom closed-chain leg mechanism. The electric powered walking wheelchair should provide a solution for low-cost transportation for human adults with lower and upper extremity impairments in the poor road conditions of low- and middle-income countries. A scaled prototype will be designed, build and evaluated with the purpose that it lays the groundwork for future renditions in a true-scaled electric powered walking wheelchair.
Methods: Design requirements were formulated according to the ISO-7176 standards for wheelchairs and conceptual designs were generated, in which a final concept was selected according to the performance criteria. A final design was build and different tests were executed to evaluate the technical specifications and feasibility of the walking wheelchair.
Results: This resulted in the OctoWalker, an 1:3 scaled eight-legged walking wheelchair with a modified Trotbot leg mechanism, two DC motors, timing belt transmission, joystick control and electronic differential. The OctoWalker was able to walk on flat surfaces; steer to the left and right; climb over curb heights of 50 mm; and climb slopes up to 28° without the need of additional sensors and control features to maintain its stability.
Conclusion: The evaluation showed that a true-scaled OctoWalker would have a larger payload (135 kg), step length (675 mm) and speed (4.75 km/h) than currently existing leg-based electric powered wheelchairs. In future studies, improvements for a true-scaled OctoWalker are required in terms of travel range (2.5 km), wheelchair width (789 mm) and weight (140 kg), in order to achieve similar specifications as current stair-climbing and obstacle avoidance electric powered wheelchairs. Nonetheless, the OctoWalker opens up future opportunities for providing low-cost transportation for disabled people in low- and middle-income countries. ... Read more

According to the WHO, falls are responsible for over 38 million disability-adjusted life years lost each year, globally. Additionally, an estimated 684.000 individuals die of falling each year, making it the second leading cause of unintentional death. One of the most effective physical activity interventions to reduce the risk of falling, is targeted exercise that safely challenges balance. One tool, that is currently
being developed, which can aid physical therapists with these interventions is the GyBAR. A wearable device that uses gyroscopes to apply moments to the patient. This can be used to either provide balance assistance or challenge balance by applying perturbations. The goal of this research was to develop an interface for the GyBAR. The interface should contribute to the acceptance of the GyBAR. This can be achieved by an excellent perceived ease of use, which combined with perceived usefulness
are indicators for the Technology Acceptance Model (TAM). The interface inspired by a Voodoo-doll was developed by going through the following design process steps; the creation of a list of requirements; a brainstorm to generate ideas; the development of three concepts; and the selection and development of one concept into a prototype. The Voodoo Doll controls the GyBAR by a handheld model of the patient, which can be manipulated and translates the movements of the model to the actual patient. User tests were performed to validate the design. With a SUS-score of 82.81 (SD=7.48), which is within the 90-95 percentile, it can be concluded that the interface has an excellent perceived ease of use. Further development is encouraged are several recommendations for points of improvement are given.
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Rehabilitation robotics is a rapidly growing field in the engineering industry. Due to the high repeatability of motion, high therapy costs, and lack of proper quantitative assessment of patient status and progress, rehabilitation centers could benefit from the introduction of robotics. One such device already commercially available is the bodyweight supported treadmill device Lokomat (Hocoma, Switzerland). In this thesis, the kinematics analysis for a modified Lokomat orthosis has been made and validated. These kinematics calculate the Euler angles of the orthosis hip joint as a function of eight degrees of freedom, two degrees of freedom of actuators driving the thigh, and six degrees of freedom of the orthosis pelvis body. The kinematics were validated by using a low-cost HTC Vive VR tracker system, to capture the actual angle of the orthosis hip joint. The kinematics were tested in three experiments. Firstly, the kinematics were tested by moving the orthosis around by hand, tracing the range of motion of the linear actuators. Afterward, the kinematics were validated with a person wearing the device. The first dataset has the person suspended in the air, simulating walking, whilst the final dataset has the person dragging their feet over the ground, to simulate walking. The results from the first experiment indicate that the kinematics calculation tracks the measured angles with an RMSE of less than 6% of the total range of motion. Later experiments suffered from drift in the Vive trackers, mainly in the flexion angles, worsening performance. Compensating for this drift shows the kinematics to still be similarly accurate to the first experiment. ... Read more

The development of the Delft Cylinder Hand (DCH) demonstrated the design of a lightweight and functional hydraulic body-powered (BP) hand prostheses. The low friction losses of the hydraulics make it an attractive alternative to a classical mechanic transmission using rigid linkages and Bowden cables. There are benefits and trade-offs associated with BP and myoelectric prostheses. For example, improved sensory feedback is a benefit of BP prostheses. In this paper we set out to design a hybrid hydraulic actuation system for the body-powered DCH by extending the BP system with electro-hydraulic assistance, attempting to combine benefits of both BP and electrically actuated prostheses. We designed the hydraulic circuit, using a miniature external gear pump driven by a brushless DC (BLDC) motor in combination with solenoid valves to control the hydraulic flow. Furthermore, we designed a custom circuit board with a microcontroller, connected to pressure sensors and tactile sensors on the fingertips, to control the valves and the pump by a PD controller. Finally, we designed a 3D printed forearm structure, supporting the components, that connects to the hand through a wrist mechanism, allowing a pronation angle of 90°. We developed the hybrid prototype and verified its functioning by conducting several experiments. The prototype required an activation force of 53.5 N and 280 N mm of work done, at the input cylinder, to achieve a pinch force of 15 N, which is an improvement compared to commercial BP prostheses. Furthermore, the prototype was able to exert a pinch force of 22.5 N at an activation force of 100 N, at limited motor power, which is not as high as some commercial BP prostheses. Finally, the closing time of the prototype is 233 ms for a full close and 165 ms for the fingers to touch the thumb. The mass of the full prosthesis system is 901 g, including the battery pack, and could be reduced to an estimated 650 g. Future steps include optimization and miniaturization of hydraulic and electronic components, and mechanical structure of the prototype, reducing its mass to an acceptable level. Finally, extensive user testing is required to further validate the design direction. ... Read more

BACKGROUND - In a variety of patients with locomotive disorders gait efficiency is often assessed using mobile metabolic gas analysis during rehabilitative interventions. Conventionally, these measurements take 6 minutes per evaluated condition (e.g. with/without ankle-foot-orthosis; AFO). This duration is required since there is a dynamical delay between the instantaneous metabolic energy expenditure (ImEE), and the respiratory response measured at the mouth. Moreover, the breath-by-breath data is sparely sampled and noisy. Gait efficiency is therefore computed from an averaged (i.e. of 1-3 minutes) respiratory response during a steady-state metabolism (i.e. reached after 3-4 minutes). This is time consuming and can be exhausting for patients with severe gait impairments. In up-coming human-in-the-loop techniques, fast (2-3 minutes) predictions of the ImEE are made using an Instantaneous Cost Mapping (ICM) model. The ICM is based on a first-order response with a known time constant (τ) to a change in an external load (e.g. another walking speed). The τ is either identified on a subject-specific basis or set to a fixed average time constant already identified for healthy adults (42s; Selinger & Donelan, 2014). It is unknown whether this technique could be applied in patient populations with additional gait impairments. When applicable, the ICM model could speed-up the assessment of the gait efficiency and open ways to make human-in-the-loop protocols feasible device optimization (e.g. AFO tuning) in rehabilitation. AIM - This study investigates whether the subject-specific and/or general ICM model could reduce the required measurement duration in a variety of patients that cope with gait impairments as consequence of a neurology or neuromuscular disease. Secondarily, it explores whether there are differences in the identified subject-specific τ among the pathologies.METHODS - Post hoc metabolic data, recorded in the period of 2006 to 2019 within the Amsterdam University Medical Centers (UMC) was collected, containing walking trials of patients with Multiple Sclerosis, Cerebral Palsy, several neuromuscular disorders, healthy adults and typically developing children. The ICM model was tested for the subject-specific and general τ to estimate the ImEE. First, using full measurement durations and later the identified reduced measurement durations. The model outcome was assessed for individually correctness. RESULTS - Results show (n = 28) that the ICM model correctly estimates the ImEE using the total conventional measurement duration (subject-specific: 96%; general: 89% individually correctness). For the identified reduced measure duration (subject-specific: 2m33s; general: 3m:04s) reduced the individually correctness to 57%. No differences among the groups were found for the subject-specific τ and the average (τ = 41.7s ± 13.5s) was similar to the reported τ for healthy adults. CONCLUSIONS - Based on the results, it can be concluded that the ICM model show similar results to healthy adults from literature. This offers prospect for the clinical application of the model in rehabilitation depending on the purposes of use. Clinicians should consider the balance between the individually correctness and measurement duration of the predictions. Results should be treated with caution due to the small and heterogeneous sample size. Future research is needed to identify differences in subject-specific τ among pathologies. ... Read more

The subject of this thesis is to investigate whether the Cerebellar Model Articulation Controller (CMAC) can be used to anticipate controller corrections and increase performance by reducing delays in humanoid robots. This question can be divided into two subquestions. Firstly, whether the CMAC is a suitable architecture for the prediction of controller actions for a humanoid soccer robot. Using a 2D model of a robotic leg, the results of this thesis show that the CMAC can indeed learn to anticipate a corrective control signal 30 ms ahead. Secondly, whether the architecture of the aforementioned setup can increase the performance of adequately passing a ball by reducing delays. The experiments show that the use of a CMAC can increase the performance of the robotic setup. ... Read more

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine that can be treated by wearing a correctional rigid brace. The goal of brace treatment is prevention of curve progression, and in some cases the curve even decreases. The current problem concerning treatment of AIS lays in the design decisions made during manufacturing of the brace. Correctional forces are applied through static pressure pads added to the inside of the brace. Evaluation of the correct positioning and size of these forces is done through radiographic imaging which allows limited feedback intervals as cumulative exposure to ionizing radiation increases the risk of cancer development. The design of scoliotic braces is currently suboptimal as the manufacturing remains an inefficient process. Moreover, it was hypothesized that the corrective forces show decreasing time dependant behaviour due to viscoelastic properties of the human body adapting to the load.
The objectives of this study were therefore to increase the effectiveness of brace treatment, by determination of the time dependant behaviour and accurate positioning and sizing of correctional forces.
A dynamic brace was developed containing pressure regulated cuffs creating a three-point-bending system on the spine. A healthy (non-scoliotic) test subject wore the brace with the goal of creating a spinal curvature. The cuffs were tested on stress relaxation behaviour, which was needed to determine if possible changes in pressure were due to viscoelasticity of the cuffs or the body. The tests showed that pressure stayed constant over time, which excludes viscoelasticity of the cuffs. Moreover, compression tests were executed on a cuff to determine the relationship between external loads and internal pressures.
Ultrasound (US) imaging was used to evaluate the effect of the three-point-bending system on the spine. The images showed a curvature, but the results varied too much to draw conclusions from, as this imaging technique works best for large scoliotic curves. BoneMRI has higher imaging accuracy and adds an extra dimension, however supine positioning decreases the spinal curvature. The boneMRI results show a subtle curvature after applying pressure. The cuffs lengthened the spine and caused mechanical torsion. After one hour the lengthening remained equal but the mechanical torsion decreased to its starting value. Lengthening of the spine could be useful in brace treatment to create more space between vertebrae and facilitate vertebral realignment.
This research served as a proof of concept which can be further developed by testing on a scoliotic patient with a moderate spinal curvature. This could result in a dynamic brace used as a method to enhance the positioning and sizing of pressure pads for a static brace, or the dynamic brace design needs adjustment to use it as a daily worn brace which keeps correctional forces constant by adjusting pressures automatically.
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Tensegrity is a structural form that is defined as a set of rigid elements suspended in a net of continuous tension. This structure shows potential for compliance, impact tolerance and mechanical robustness. However, its non-linear coupled dynamics and often complex geometry require advanced control strategies. An actuator reference planning strategy to bring tensegrity robots closer to controlled full body movements was proposed by Guido Tournois \cite{GuidoThesis} in 2017. This strategy, called the Full Body Reference Planner (FBRP), finds a sequence of equilibrium configurations for a tensegrity structure, predominantly to follow a trajectory in space. However, the method is incapable of incorporating inequality constraints while obtaining said equilibrium configurations. This is a problem when dealing with certain restrictions, e.g., actuator limitations and stability of the structure.

In this thesis we implemented a robust way to account for inequality constraints while utilizing the FBRP. That was done by means of optimization, i.e., an implementation of a Sequential Quadratic Programming method to ensure inequality constraints were respected for each configuration. The approach was validated in scenarios related to practical applications where inequality constraints were enforced. The results showed advancements towards practical feasibility. Furthermore, the robustness, efficiency and accuracy of the method were validated. The extended implementation depicted robustness to parameter variations and good results in terms of accuracy. However, given the iterative nature of the method, it was more computationally expensive than its precursor. ... Read more

Currently the prevalence of general purpose mobile robots with manipulation capabilities is still low, despite various applications of such systems such as: disaster response, payload delivery, and assistive/service tasks. A suitable design for such a robot would be that of a torque-controllable quadrupedal manipulator. Its capability for legged locomotion enables high mobility, specifically on rough terrain, while its quadrupedal morphology provides a relatively large and stable base of support compared to bipedal robots. Torque-controlled joints allow for safer and more controllable interaction with the environment.

For such a system a challenge lies in the design of a controller that actually achieves the promising capabilities for locomotion and manipulation that the mechanical system offers. One of the currently most promising control frameworks for this purpose is that of hierarchical inverse dynamics. This real-time whole-body control framework allows for dynamic whole-body motions and compliant interaction with the environment while enforcing a strict priority between the desired control tasks. Although promising results have previously been attained with such controllers, it has not yet been applied for the control of a quadrupedal manipulator. The focus of this thesis is on the implementation of a hierarchical inverse dynamics controller for the control of a simulated quadrupedal manipulator, with a particular focus on the design of prioritized sets of control tasks which generate forms of stationary whole-body manipulation.

First a basic set of prioritized control tasks is presented, which is shown to satisfy the robot's most crucial control requirements. Subsequently three extended sets of control tasks are presented, which result in additional desirable emergent behavior of the robot. The first one of these depends on the inclusion of kinematic joint limit tasks to prevent kinematic singularities and self-collision, and to trigger whole-body reaching motion. Secondly a set of tasks is presented which is focused on utilizing motion of some of the torso's degrees of freedom to optimize the arm's posture according to a posture-related cost function. Thirdly a set of tasks is presented which enables contact force control at the end-effector for force-based manipulation. In addition to this final set of tasks, a higher-level controller is presented which detects external forces acting on the robot and computes a desired shift of the position of the robot's center of mass in order to mitigate the balance-disturbing effects of external forces. All of the presented sets of tasks do not exclude each other and allow to be implemented simultaneously in order to combine the individual benefits that they offer.

The results of this research project show that hierarchical inverse dynamics control can be successfully applied for the control of a simulated torque-controllable quadrupedal manipulator. Moreover, it is shown that well-designed sets of prioritized control tasks allow for emergent whole-body behaviors which exploit the advantages that both the robotic system and the control framework offer. Future work will need to investigate the transferability of these results to a physical robot. ... Read more

In this research the influence of the rower behavior and rigging setup on the boat performance is investigated in a data-driven model. There are different rowing styles and techniques between rowers. Making rowers row in synchrony, while important for the boat performance, is not easy. Rowers have their own signature rowing curve, of which only few aspects can be changed. The signature rowing curve can be based on the oar angle or the relative displacement of the rower. The latter is assumed to be constant for changes in the rigging setup and therefore preferred.
The data used in this study comes from a woman’s double, the rowers of which are members of the KNRB. In the boat measurements are done on the gate and foot forces, as well as the oar angles, the seat displacement and boat accelerations.
From the free body diagrams of the different parts of the system, a one-dimensional rowing model is derived. The model is driven with the measured forces on the rower and the oar angles. It can be validated with the measured boat accelerations. The distribution of the masses in the system are slightly changed. All drag force on the system is assumed to be viscous and is assumed to be proportional to the square of the boat velocity. The lateral forces on the blade and the oar deformation are neglected.
The relative motions of the rower are best predicted with the forces acting directly on the rower, after a compensation of the measured foot force. The best fit for the boat accelerations are found by combining the system acceleration with the relative accelerations of the rowers.
With the assumption that the rower can be modeled as a force constraint model, the rigging setup of the modeled boat is changed. The blade forces have a leading role on the resulting boat motions when changing the rigging parameters. However the blade forces might not be realistically modeled. Changing the lever ratio of the oar, by increasing the inboard length leads to a bigger covered oar angle and a higher boat velocity, but a lower work per stroke applied on the handle by the rower. Moving the footstretcher towards the bow of the boat shifts the oar angle and leads to a higher boat velocity and lower handle work per stroke as well. Changing individual rigging parameters did not result in big differences between the rowers.
No indications of improved synchronization between the rowers are found and the energy balance of the system is disrupted. The model simplifications of the blade forces may not be justified. After implementation of a more complex modeling of the blade forces indications of the synchronization might be found.
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