Gait rehabilitation attempts to alleviate gait and balance impairments caused by spinal cord injury. Conventional gait rehabilitation often includes unloading a portion of the user’s weight with a vertical force. This vertical force enables people to practice stepping but makes forward propulsion more difficult. Users will adopt a compensatory movement strategy during rehabilitation that may not completely transfer to unsupported walking. It is hypothesized that including a small forward force during vertical unloading makes gait rehabilitation more similar to unsupported locomotion. This thesis presents and investigates a novel patent of a device that passively generates a forward to propel the user forward. The forward force is generated using the vertical oscillations that naturally occur during gait. This thesis quantifies the forward force, simulates the impact on human gait and details the construction of a prototype. The prototype is then used to validate the simulations of the device. Analysis indicates that the ratio between the sprocket radius and the wheel radius is the key parameter for determining the amount of forward force. Simulations in which the device is coupled with the spring-loaded inverted pendulum model indicate that the device may generally deteriorate the walking velocity, step size and maximum height difference. Experiments with the prototype indicate that friction has a big effect on the functionality of the device, and that predictions from the simulation may be quantitatively off. The device may have a favorable interaction with the neurological control strategy of human gait, which was not modeled. Human trials will have to give a definite answer.

Spinal cord injuries (SCI) occur when damage to any part of the spinal cord is sustained. Depending on what vertebrae segment the injury occurs, the patient will develop paraplegia or tetraplegia and have a complete or incomplete spinal cord injury. After sustaining a spinal cord injury, the patient must undergo rehabilitation. For incomplete SCI patients, part of their rehabilitation is improving their mobility skills through gait training. To assess gait, the methods of the clinical eye and laboratory gait assessment are used. The starting goal of the project was to combine the quickness and easiness of conducting a gait assessment with the clinical eye with the objective data from a laboratory gait assessment into one system. This system consists of Xsens Awinda wireless motion trackers to collect the kinematic data and a user interface to view it. User research was conducted in the form of questionnaires and focus groups. The research aimed to learn more about how physiotherapists and physicians within Rijndam Revalidatie currently assess gait, what features and parameters they would like in the user interface, and how they would prefer the selected parameters to be visualized (in numbers, graphs, or animations). Three physiotherapists and physicians were also interviewed to better understand the process incomplete SCI patients go through in gait rehabilitation and who is involved in each step. From the results, a design direction and vision was created: “To develop an easy to use user interface that aids physicians and physiotherapists in selecting interventions for patients with incomplete spinal cord injuries in an objective and time efficient manner through intuitive data visualizations.” Using design methods and tools, ideas for the data visualizations and the interface layout were formed, selected, and then made into concepts. The layout and visualizations concepts were evaluated through concept test sessions with physiotherapists and physicians. In the sessions, the interface layout was assessed in terms of usability and functionality. The data visualizations were evaluated based on if the participants, who had minimal pre-existing knowledge on gait analysis, could understand them. From the evaluation results, the final design of Gait Vision was created. Gait Vision is an easy-to-use interface that allows physiotherapists and physicians to assess gait objectively and time-efficiently. It provides more accurate and objective information than can be obtained with the clinical eye, in a way that is more intuitive and comprehensible for clinicians with minimal gait assessment experience than laboratory gait assessment. An interactive prototype of the final design was developed using Adobe XD. The interface prototype and the visualization concepts were evaluated through conducting individual user tests with seven physicians and physiotherapists. The interface and visualizations were tested with regard to usability, functionality, intuitiveness, and aesthetics. Overall positive feedback was received regarding the interface and visualizations. Testing was also conducted to compare gait assessment with the clinical eye versus with the interface. The interface was found to more objective than the clinical eye. An implementation plan was developed to ensure Gait Vision survives in the long term. Future recommendations were also made to aid in the continuation of the development of Gait Vision.

Bio-inspired underwater vehicles are highly researched as a means for low-invasive monitoring. As a result, the performance of these vehicles has improved greatly. Research has thus far been directed towards the performances of the swimming motion. In order for the development of these bio-inspired underwater vehicles to continue, the increased reliability and durability should also be investigated. This research is aimed at long-term-autonomous bio-inspired underwater vehicles, specifically vehicles based on Median/Paired Fin swimming, which could provide continuous, unassisted monitoring of an area. The goal is to investigate existing options for the propulsive mechanism and find the most suitable solution. A suitable propulsive mechanism can cope with the pressure changes that the vehicle will face due to the varying depths while requiring no maintenance for extended periods of time. This expresses itself in a mechanism that has no dynamic contact between the internal mechanics of the vehicle and the external environment because the dynamic contact is prone to leakage. One actuator and two transmissions are proposed as propulsive mechanisms in this research. The actuator is a reluctance actuator and the transmissions are a flexure joint and a magnetic coupling. The transmissions will be used in combination with an electric motor that is located inside the hull. The reluctance actuator has been found to lack torque generation. The flexure joint will be fused with both the hull and the fin and will be actuated from within the vehicle. It has the ability to either follow the large deflections that are required without encountering fatigue or to resist pressure differences, but both are required. The magnetic coupling does possess the torque, the range of motion, and the rigidity to resist the pressure, and is therefore chosen to be used as the propulsive mechanism that will be investigated further. Existing designs of the magnetic coupling do not comply with the requirements of this swimming mode. Three types of designs are therefore proposed, the coaxial, the face-to-face, and the moment-arm design. To reduce the resultant noncontributing magnetic forces on the fin, the designs have been made symmetrical in the motion plane. To reduce the effect of unstable equilibriums that result from attractive forces on both sides, each type of design has a repulsive design as well as an attractive design. In addition, the designs have magnet orientations that are inspired by Halbach arrays to increase the magnetic field where desired and reduce it elsewhere. Simulations have been performed on the designs using the magnetic finite element method. These simulations indicated that the coaxial designs do not create enough coupling torque and the moment-arm designs create too much radial forces on the fin. The face-to-face coupling designs show promise, both in coupling torque and in resultant force directions. Simulations of the double-sided, face-to-face coupling with Halbach-inspired magnet orientation have been validated and the results indicate that this new magnetic coupling could serve as a solution to reduce maintenance and increase reliability and durability in bio-inspired underwater vehicles. The use of repulsive forces in this design transfers the noncontributing resultant forces from occurring in the unpredictable external environment of the fin to the controlled internal environment of the vehicle.

Falling is a significant problem for older adults. It can cause severe injury and even death. Furthermore, the fear of falling has a significant influence on the life of the elderly, and therefore they reduce their physical activity. Two new balance assistive devices are being developed to reduce the risk of falling. Both devices use a control moment gyroscope (CMG) to generate a moment to counter the falling motion. One device consists of a single CMG. The other device consists of two CMGs that are coupled such that the gimbals rotate in opposite direction. This is called a scissored pair CMG (SPCMG). The purpose of this study was to examine whether it is possible to design an (SP)CMG with a passive mechanism that exploits gyroscopic precession of gimbal(s) to emulate different types of impedances for balance assistance. To examine this, first, the equations of motion of a CMG and an SPCMG were derived. Next, the equations of motion were used to derive the impedance of the system. The impedance was optimized such that it would simulate the behaviour of a spring, a damper, a mass, a mass-spring-damper system, and a rotational PD controller which is proportional to the XCoM (PDXCoM), a measure of stability. The optimization used a gradient-based algorithm to find the minimum. Multiple optimizations with different random initial guesses were performed to increase the chance to find the global minimum. Two sets of optimizations were performed. One optimization with and one optimization without bounds on the optimization. The sets parameters that led to the best fit were used in a walking simulation to calculate the moments the device would generate during normal walking. It is shown that it is possible to simulate the dynamics of a spring, a damper, a mass, and a mass-springdamper system with a CMG and an SPCMG. However, it was not possible to replicate the dynamics of the PDXCoM with a CMG and an SPCMG. A walking simulation showed that the generated moments of the (SP)CMG were in the opposite direction of the angular velocity of the human. Therefore, using a passive mechanism to control an (SP)CMG could be used as balance assistance.

Trunk motor control is essential for the proper functioning of the upper extremities and is an important predictor of gait capacity in children with delayed development. Early diagnosis and intervention can potentially increase the trunk motor capabilities in later life. However, current tools used to assess the level of trunk motor control are largely observation-based and lack the sensitivity to change required to accurately monitor progress and effects of therapy in children below the age of 4. To the best of our knowledge, this is the first attempt to use trunk-attached inertial measurement units (IMUs) to differentiate different levels of trunk motor control in this population. We performed experiments with seven children to examine the applicability of the RMS of jerk as an outcome metric for the level of trunk motor control. This study showed that the root mean square (RMS) of jerk decreases for ages up to 24 months, is relatively independent of data segment and length, and shows results similar to a more established method: the centre of pressure (COP) velocity. These findings suggest that the RMS of jerk shows potential as a metric for the differentiation of different trunk motor control levels. However, due to the small sample size, a follow-up study is necessary to verify and validate these results.