Semi-active lower limb prostheses currently use variable damping to generate the gait cycle. This, however, only dissipates energy. Variable stiffness can store and release energy, making prostheses more efficient for walking. This study aims to design and evaluate a semi-active adjustable stiffness ankle-knee prosthesis that can change its stiffness during a single gait cycle. A Knee-ankle prosthesis that can change its stiffness from a high to low mode in a gait cycle was designed, tested and evaluated. The principle for stiffness change in this design is a leaf spring for which the force application point on the leaf spring moves. The design can move the application point quickly over a length since the rotation of the outer frame is converted into a linear motion of the application point. The stiffness, movement range, power usage and rate of stiffness change were evaluated with different tests. One test is for the stiffness and movement range, and one is for the power usage and stiffness rate of change. The ankle joint’s high and low stiffness modes were 1.4 N m/° and 0.6 N m/° respectively. The movement range for the ankle’s high and low stiffness mode was 0° - 15° and 0° - 20° respectively. The knee joint’s high and low stiffness modes were 2.4 N m/° and 0.2 N m/° respectively. The movement range for the knee’s high and low stiffness mode was 0° - 10° and 0° - 40° respectively. The stiffness is changeable from high to low mode in 0.4s, and the power usage is 9W. The prosthesis did not have a high enough stiffness for both joints. And the movement range of the low stiffness of the knee joint is too low. Nevertheless, the prosthesis has the novel ability to change the stiffness of both joints with only one motor. Furthermore, the linear movement of the force application point through a rotation has also not been done before, making the stiffness change fast. Still, more research and future designs are needed to make the prototype functional as an ankle-knee prosthesis. Nevertheless, the design is a promising first step to designing an efficient semi-active adjustable stiffness ankle-knee prosthesis.

Optimal settings and designs for prosthetic parameters, such as knee stiffness, are required to achieve effective and stable sit-to-stand (STS) movements for individuals with lower limb prostheses but remain inadequately defined. One possible solution is prosthetic modeling and predictive simulations. However, current literature primarily focuses on inverse kinematics, inverse dynamics, and most likely, gait. There remains a gap in optimizing the parameters during STS movement through predictive simulation. By utilizing SCONE (Simulated Controller OptimizatioN Environment for predictive simulating), this study aims to find the optimized prosthetic parameters and investigate the effect of varying transfemoral prosthetic knee joint stiffness on biomechanics and validate this approach. A modified musculoskeletal model with a prosthesis and neuromuscular controllers are combined for predictive sit-to-stand simulation. The control parameters for neuromuscular controllers and the prosthetic parameters are optimized by SCONE with predefined objective functions to obtain energy-oriented results. The simulation results were analyzed in terms of joint load, stability, kinematics, and energy cost. Lastly, the results were validated by comparison with an existing experimental dataset. The simulations indicated that prosthetic knee stiffness affects joint loads, stability, kinematics, and energy expenditure during STS movements. Higher knee stiffness generally leads to increased prosthetic side joint loads and contribution but requires higher damping ratios to ensure a successful STS movement, while extreme stiffness should be avoided. Optimal stiffness settings were identified near 70 Nm/rad with the damping ratio of 22 Nms/rad. Validation shows the feasibility of this approach as well as its limitations. This study demonstrates the potential and insights of predictive simulations in optimizing prosthetic knee parameters. However, the current approach is limited by the model, methodological, theoretical, and practical issues. Therefore, further validation and refinement are necessary. Future work may focus on building complex and customized models and exploring other movements.

Energy harvesting has gained lots of interest over the past few decades. This study explores the application of energy harvesting in lower limb prosthetic devices. The control system of a lower limb prosthesis includes sensors, wireless
systems and other active components which all require battery power. In order to save some of this battery power, reduce weight, and have the devices have a longer runtime, a form of energy regeneration is desired. Therefore the goal of
this study is to design and experimentally evaluate an energy harvesting system to power the control system of lower limb prostheses. The final prototype is designed following the process of setting up functional requirements, constraints and wishes. This leads to three derived concepts. After an evaluation against performance criteria and an in-depth evaluation concerning the power output, the compliant spring design is chosen to be worked out further and evaluated with a newly designed vibration shaker table. The relevant findings are laid out in the results. From these findings, interpretations and implications are discussed further, concerning advantages and limitations of the energy harvesters and the experiment. Results from the conducted experiment show a peak power output of 25.8 mW at an input amplitude of 12 mm and a frequency of 9 Hz. A power mass ratio of 0.21W/kg is achieved. The design meets the power demand requirements to power microprocessors and sensors of the control system of a lower limb prosthesis and extends runtime with 15.7%. However it is still important to investigate the power requirements for state of the art lower limb prostheses. Furthermore, it is recommended to improve overall efficiency in future studies, compare the results with state of the art energy harvesters based on vibrations, and execute a gait test for further design validation. The results from this study demonstrate comparable data and present the innovations possible in prosthesis design and the advancements in utilizing ambient power sources for energy harvesting. Enhancing the overall efficiency of this design, and promoting comparable results to other designs in the existing literature, could emphasize on the potential of energy harvesting applications.

Transfemoral prosthesis users typically perform the sit-to-stand motion unilaterally, placing minimal load on the prosthetic side. This increases the risk of injury and accelerates the degeneration of the intact limb. To address this, understanding compensation strategies is essential. Predictive neuromusculoskeletal modeling offers a method to investigate this. The aim of this study was to develop and validate a neuromusculoskeletal model with reflex-based muscle control to simulate the sit-tostand motion in non-amputees and transfemoral amputees with a passive prosthesis. We developed a three-dimensional sit-tostand musculoskeletal model of a non-amputee (20 degrees of freedom, 24 muscles) and a transfemoral amputee (20 degrees of freedom, 19 muscles), both incorporating a two-phase stand-up controller based on an existing two-dimensional reflex controller. We compared the simulation framework to measured kinematics, muscle activations, ground reaction forces, and existing literature on degrees of asymmetry and muscle forces. The developed framework was used to optimize prosthetic knee and ankle stiffness and damping for the sit-to-stand motion with a passive prosthesis. The simulated kinematics of the non-amputee matched measured kinematics. The prosthesis model indicated compensation strategies involving increased thoracic and lumbar extension, lumbar bending towards the non-amputated side,
increased pelvic tilt combined with decreased hip flexion, and heightened muscle activation and force. Optimization results suggested a knee stiffness of 0.1432 [Nm/deg] and damping of 0.0246 [Nm·s/deg], while the ankle required a stiffness of 0.1968 [Nm/deg] and damping of 0.1350 [Nm·s/deg]. These values are recommended for testing in future experiments.

Automation within an industrial sector has now for years been an obvious factor. Everywhere mechanical instruments and sensors are implemented for fast and precise processes. The agricultural sector is some steps behind in relation to other sectors. Reason being that there are many irregularities which in other sectors have been made into uniform variables. One of the problems that needs to be tackled within the agricultural sector is having the leaves of crops removed.
Rijk Zwaan has created a new variety of broccoli and to make this commercially viable, a harvest machine is required. One of the aspects of this harvesting process is removing the leaves. This has to be achieved in one continuous session, with at least a ground speed of 1 km/h, while the broccoli's are still in the field. With a focus on the best performance for the least destructive working principle. After listing all the requirements, ideas are structured in a morphological overview. A weighted criteria table will be used to select three ideas, which will be made into prototypes.
Results from the initial testing period will reveal the best concept, which will be optimised. This was the Metal Wire design, which exist of multiple stainless steel wires attached perpendicular to a rotating shaft. An important aspect that boosted the performance was the unravelled ends of these wires. These rotating shaft had the wires removing the leaves, while beating the leaves down from both sides.
After optimization, the current prototype could ensure a 60% of the top section and 80% of the middle section with 20% of the broccoli’s destroyed. Which was not enough to satisfy the goal, however the promising results could be improved with an upgraded machine. A clear trade-off was found between the performance and destruction. Significant improvements in results could be achieved by incorporating additional features such as a funnel and designing a more robust structure with fewer obstructions, controllable ground/rotational speed, and better alignment with the beds. Therefore at the current state the leaf removal machine operates substandard, but has potential to be developed into the desired product.