Many robotic applications require moving an end-effector through intricate closed-loop paths for object manipulation or locomotion. Conventionally, rotary-actuated rigid-link mechanisms perform this task successfully. However, several drawbacks, such as wear, play, and assembly difficulties, limit their performance. In high-speed applications, these rigid and often bulky links require high accelerations, leading to high power usage or the need for dynamic balancing, further complicating the mechanism. Rigid mechanisms are not the only ones that generate paths; compliant mechanisms are also widely used. However, compliant hinges cannot undergo complete rotations by definition, making cyclic actuation impossible. As a result, creating closed-loop paths typically requires multiple actuators—one per end-effector degree of freedom—adding to power demands and complexity. In contrast, closed-loop deformations can occur when dynamically actuating a soft body with a single actuator. We can create customizable soft bodies that leverage internal dynamics by structuring this soft body with a mechanical metamaterial made of tessellated compliant cells and designing its internal geometry. This research explores how these dynamics can be harnessed for path generation within mechanical metamaterials. Through multi-objective optimization, we embed reprogrammable control strategies within the metamaterial geometry, enabling adaptive responses to actuation frequency and amplitude for complex behaviors. We validate these designs with tabletop prototypes, building up to a self-propelled, walking prototype—a step toward autonomous robotic metamaterials.

Electric and hybrid vehicles are a common sight on the roads these days. The electric machine is known to be quiet, but sometimes high-frequency sounds are observed when driving. Over the years many different solutions have been developed to make the electric machine quieter, but almost no research looks into the possibility to generate sounds. This thesis looks into the possibility to produce nice sounds and reduce annoying sounds with electric machines. This is done by introducing harmonics into the current and creating additional excitations of the structure. To gain a complete understanding of this topic the electromagnetic domain and the structural domain have been analysed. A mathematical description of the forces has been created to be able to make predictions about the forces created by an injected current harmonic. Using the electromagnetic model the exact influence of current harmonics on the forces has been verified. The sound power level produced by the forces acting on the structure is calculated using the structural model. By properly selecting the current properties it is possible to create new temporal orders that produce sounds. For the analysed electric machine the sound power level of the desired sound is on average approximately 20dB lower than the sound power level of the fundamental current. Furthermore the sound power level is dominated by the excitation of the breathing modes. Using current injection existing sounds can be reduced. Using brute force optimisation the average radial forces were reduced. This reduces the sound power level during most of the run-up and reduces the influence of the breathing mode by up to 11dB. At some points during the run-up more sound is produced, because the tangential forces are increased, while the radial forces are decreased. In the end it is shown that the influence of the introduced current harmonics on the acoustics can be analysed using mathematics and the simulation results. New sounds can be produced, but the sound power level is limited by structural design of the electric machine.

Diamagnetic levitation presents a promising platform for realizing resonant sensors and energy harvesters. The technique offers mechanical isolation from the environment while operating with zero power consumption. This unique feature ensures exceptional sensitivity and accuracy in numerous applications. However, the presence of eddy currents in the levitating plate, induced by the alternating magnetic field, poses challenges, leading to increased damping and subsequently limiting the performance of levitating resonators. To address these issues, this study proposes a novel solution through the segmentation of diamagnetic plates. By dividing a pyrolytic graphite plate into smaller blocks, the flow of eddy currents is effectively restricted, resulting in reduced damping and significantly higher Q factors. By comparing the theoretical predictions using a FEM model from an earlier study with the measurements conducted the proposed technique is further validated. This comparative analysis demonstrates the effectiveness of the segmentation approach in mitigating damping due to eddy currents. Furthermore, the implementation of the proposed method led to remarkable results, with achieved Q factors exceeding 150 thousand.

Vibration attenuation in lightly damped blade-like systems such as cantilevers or end-effectors of robot manipulators can be dampened using Active Vibration Control (AVC). Piezoelectric patches in a collocated setup measure and control the bending modes of such a cantilever system using Positive Position Feedback (PPF). Tuning methods for PPF are based on optimisations for maximum disturbance rejection and disregard the presence of electronic noise. However, because electronic noise is amplified by controllers with high gains, it can become a significant error source in the system. In this paper, the effect of noise amplification is investigated for blade-like AVC systems. It is shown that there is a trade-off in the total dynamic error between vibration attenuation and noise amplification. An optimisation of this trade-off is proposed, which is performed on an industrial example of a blade-like system and validated experimentally. The optimisation shows clear improvement over traditional tuning methods that disregard the presence and effect of noise.

From the motion of electrons in an atom to the orbits of celestial bodies in the cosmos, governing equations are essential to the characterisation of dynamical systems. They facilitate an understanding of the physics of a system, which enables the development of useful techniques such as predictive control. An increasingly popular method to obtain these equations is Symbolic Regression, where governing laws are discovered from observations of the system. In this work, we extend the Deep Symbolic Regression package to the identification of dynamical systems. Preliminary tests revealed the limits of the method as applied to dynamical systems, and new methods of incorporating domain knowledge to constrain the expression space are added. We test the extended package on 3 strongly nonlinear ODEs that exhibit different dynamics as their parameterisation varies. Finally, we demonstrate the working of this method in practice by discovering the governing equation of a pendulum, from a video of its oscillation. This method achieved a 100% equation recovery rate on our tests, and was able to consistently retrieve the correct equation from datasets representing a diverse range of dynamics.

Vibration energy harvesting is a growing field of research. Harvesting energy from vibrations can be of use in devices in hard to reach places, such as sensors on a train track or a pacemaker. These devices makes use of batteries, which need to be replaced. Using energy harvesting this battery life could be improved.
The difficulty lies in harvesting low frequency vibrations. These vibrations are hard to harvest using a transducer such as a piezo. A solution could be using a frequency up converter, which can raise a vibrations frequency. This thesis shows the design of a Bi-stable Impact-driven Snap-through frequency up converter (BISup). Enhancing the behaviour of this bi-stable design could improve the energy harvesting capabilities. Different designs are made using ortho planar spring design, these designs are simulated and compared using ANSYS. These simulations are experimentally verified.

High-Speed Atomic Force Microscopy is widely used for investigating biological architectures and the semiconductor industry. The main limitation comes from parachuting or the Wile E. Coyote effect. Parachuting is the phenomenon where the cantilever taps on the sample towards a steep decrease in height, but does not get adjusted for this decrease fast enough, resulting in poor imaging quality at higher scan speeds. A proof-of-concept has been modeled for an adaptive raster scanning methodology on the X and Y piezo actuators. There will be investigated how a variable scan speed can decrease the effect of parachuting and thereby improve the spatial resolution. A detection algorithm is designed to measure the parachuting and uphill events at high scanning speed as accurately and precisely as possible during the forward scan. This has been done by defining a mixed signal that multiplies the first and second derivatives of the filtered deflection signal. A variable scan speed will be applied for the backward scan. The detection algorithm turned out to have a very high repeatability of 97.1% for the uphill events, and 93.6% for the parachuting events. Its accuracy turned out to have a maximum deviation of one signal period, which has been accounted for within the controller. Implementing this for the adaptive controller results in an improvement in both resolution and time efficiency. The adaptive controller is up to 9.5 times more accurate and time efficient compared to conventional methods.

Current service and installation activities to offshore wind turbines (OWTs) are mainly carried out by jack-up vessels. These vessels are less susceptive to disturbances caused by sea waves when they lift their hull from the water level by jacking down multiple legs to the seabed. An alternative is a crane mounted on a floating vessel, which has the benefits of being faster regarding sailing time, cheaper in operation, able to locate multiple times around the same offshore site and able to operate in deep waters. However floating crane vessels have a significant lower workability in comparison to jack-up vessels and are therefore not deployed in OWT activities yet.
Huisman initiated the three-dimensional (3D) motion compensated crane (MCC) project to improve the workability of crane vessels in offshore operations - thereby focusing on the performance of the equipped cranes - such that floating crane vessels will be able to install and service OWTs during an sufficiently large operational window. But to date MCCs have never been realized for offshore wind industry, which makes it difficult to estimate their performance beforehand and evaluate whether they are feasibile.
This thesis describes the development of a procedure to assess the feasibility of motion systems from a mechatronic design perspective and the motion compensation system of the Huisman 3D MCC is used as a case study. Several aspects of the MCC have been studied into more detail because these aspects are an determining factor regarding feasibility. These aspects are the influence of actuator type and crane boom flexibility and the performance during realistic offshore conditions. To investigate these aspects the system dynamics of the conceptual design are modelled, a controller is designed for the model and parameters are identified. Next the model is evaluated on its disturbance rejection capability because this is an important performance indicator for motion compensation, its robustness is examined and whether the OWT installation requirements are fulfilled.

Over the past decades the diamagnetic effect has been used for a variety of applications. This ranges from levitating a living frog to stabilizing a force sensor, designing an acceleration sensor and determin­ing the power of a laser. Diamagnetic levitation is the only method in which a passive stable levitation of an object can be achieved. Such a stable levitation has the benefits that the levitated object is iso­lated from its environment, thus eliminating mechanical damping and friction. Furthermore, no energy or control mechanisms are needed to sustain the levitation and to keep the object in its place. With the decrease in the damping, due to the elimination of the mechanical damping component, potential non­linearities in the movement of the plate can present themselves. Such nonlinearities can be exploited in, for example, energy harvesters. In such energy harvesters, the nonlinearities can be used to increase the range of frequencies at which energy can be harvested. As both diamagnetism and nonlineari­ties have their benefits, this study aims at investigating the nonlinear behaviour of a diamagnetically levitating plate in the vertical direction. An analytical model has been constructed which aimed at pre­dicting the (non)linear behaviour of a pyrolytic graphite plate, levitating over a 2x2 array of permanent magnets, which is actuated electrostatically. The model is verified numerically using COMSOL and has been used to predict both the static -­ and dynamic behaviour of the plate. Experiments have been conducted to assess the validity of the analytical predictions. It is found that the static behaviour and the linear dynamic behaviour of the plate can be predicted analytically within certain margins. The ana­lytical model indicates that all combinations of the magnetic force and electrostatic forces investigated have a softening effect on the levitating plate. A softening response is also observed in experiments. However, the analytical model cannot perfectly predict the experimental frequency response functions. A possible reasons for this discrepancy might be mode coupling. Overall, the study of the nonlinear dynamics for a diamagnetically levitating plate will help to gain more understanding on its fundamental mechanism and thus pave a way for its wider applications.

Any resonance based sensing method such as AFM or mass sensing using microfluidic cantilevers require high frequency stability. For mass measurement, a stable frequency allows for a lower mass resolution. One of the most commonly used methods to actuate these resonators is using piezoacoustics. A major downside of this method is the presence of spurious resonances, which corrugate the frequency response and can potentially degrade mass sensitivity. One way get rid of these spurious peaks is by
actuating photothermally (using laser light). This thesis is focused around designing and building a photothermal AFM to explore this. Additionally, some experiments are performed comparing piezoacoustic actuation to photothermal actuation in terms of the aforementioned frequency stability and
spurious peaks.

Vibration energy harvesting has proven to be a durable source of energy for a wide variety of applications, however not all of the positions these applications are placed at are suitable for conventional vibration energy harvesting. For some of these applications a frequency up-converted energy harvester could increase the power harvested. These systems are analysed in this thesis project, by first gaining insight in previously performed. After which a new method is designed and modelled. The design was then fabricated and a proof of concept was tested, of which the results are presented in this thesis project report.

It is relevant for various applications to seek a material that could be used for the active control of wave propagation. In this study, we explore tunablemetamaterials based on foldable origami sheets where the size of the bandgap can be tuned by the rigid folding along predefined crease lines. A combination of out-of-plane components and a crease results in the coupling and separation of bands in the band structure and eventually in a (modal) bandgap. The location, size, and vibration isolation performance are optimized and analyzed for a set of geometrical and material parameters, resulting in a potential design of aMiura-Ori structure. The methods used in this paper could be used for any kind of origami structure, which may lead to various new applications in the field of vibrations and acoustics.

With the incline of multidrug resistant bacteria due to the widespread use of antibiotics, there has been an ongoing search for a faster and more effective method to test the effect of antibiotics on bacteria. With current techniques for investigation of bacterial resistance requiring a minimum of 24 hours to complete, a new technique is essential to reduce the widespread misuse of antibiotics worldwide. In the last decade, new methods of this so-called Antibiotic Susceptibility Testing have been on the rise, with an emphasis on the use of nanomechanical oscillators as highly sensitive sensors. In this thesis, a novel method based on cavities in silicon substrates is introduced to detect the motion of a single motile bacterium and is compared to a highly sensitive sensor based on graphene membranes. A sensor with bacteria attached will exhibit random oscillations and these oscillations can be monitored with a laser. The rigid silicon substrates are intuitively not showing any oscillations. Nonetheless, the motility of a bacterium can still be observed by the changes in the laser path. By using an interferometric setup and monitoring the fluctuation in the voltage signal, coming from bacterial biophysical processes, the Signal-to-Noise-Ratio is determined. The amplitude increase in the fluctuation of the signal is evidently correlated with the motility of the bacteria and is demonstrated to show an increasing trend when presented with a deterministically known topographical location of the bacteria. Subsequently, the ability to detect motile cells enables the capabilities of Antibiotic Susceptibility Testing on these substrates, by monitoring the change in motion of the bacteria prior and post exposure to an effective antibiotic. The motion change, due to antibiotic exposure, is observed to show a significant difference even for a single bacterium, which opens up opportunities for an elementary non-invasive monitoring tool based on silicon.

2D flexure elements fulfil a pivotal role in the field of precision positioning systems as they do not suffer from backlash, friction or play and exhibit highly repeatable behaviour. However, planar building blocks are characterized by a limited design space as the majority of the flexure elements are flat and straight. In this thesis, it is proposed to investigate another type of flexure element that features spatial (3D) properties. More specifically, it considers the use of helical flexure geometries in motion stages. Insight into the linear kinematic behaviour of various helical surfaces with varying curvature is provided with the usage of parametric optimization, screw theory, unified stiffness method and a performance metric. The newly acquired insights served as a prerequisite for selecting a suitable topology capable of guiding a stage. For demonstration purposes, a motion stage prototype was fabricated consisting of three helical flexure elements. Additionally, an eigenfrequency analysis was performed and experimentally validated with a model vibration test. This has led to the successful realization of a helical based compliant motion stage.

Waves impacting on maritime structures can cause damage which endangers the environment around these structures. Due to high hydrodynamic loading, structures can enter the plastic regime, resulting possibly in structural failure. The understanding of the principles related to this structural failure due to waves is a key concept in this research. Due to a gap in existing literature, a simple approximation for the influence of plasticity on fluid-structure interaction is the first required step towards a better comprehension of structural failure of ship and offshore structures due to hydrodynamic loading. The choice is made to analyse a pendulum because of its ability to show clear and easy to interpret results, due to its few degrees of freedom. In an experiment, three different double pendulums are subjected to breaking waves created by dispersive focusing at three different locations in front of the pendulum. The top hinge of the pendulum is a normal hinge and the bottom hinge is a friction hinge that approximates plastic behaviour in a mechanical manner. The energy dissipated in the friction hinge, modelling plastic energy, and the energy transferred from the wave to the structure, called `total absorbed energy', decrease with increasing frictional torque. This means that when a structure allows for more plastic deformation, the energy that will be absorbed in total by the pendulum is larger. The energy transferred to the double pendulum shows more variability for the wave focused furthest away from the pendulum. A reduced-order model is constructed that can help explain the behaviour of the different pendulums.

The advent of machine learning and the availability of big data brought a novel approach for researchers to discover fundamental laws of motion. Computers allow to quickly find underlying physical laws from experimental data, without having in-depth knowledge of the system. Applications are widespread among numerous fields such as physics, chemistry, engineering, biology, climate science and finance. However, the problem is that often experimental data are polluted with noise. This causes symbolic regressors to capture the noise but not the underlying physics. In this work, we leverage the noise reduction properties of non-parametric machine learning, to improve symbolic regression methods. This combination allows for numerically robust differentiation and significantly increases the noise tolerance of common symbolic regressors. A new strategy is exemplified by combining Gaussian processes and the symbolic regression toolbox SINDy for finding governing equations from data. The method balances the quality of the fit and parsimony to avoid overfitting. The method is tested on well-known dynamical systems with varying properties. These will include the Duffing oscillator, as an example of a forced system, the Van der Pol oscillator, as an example of an autonomous system and the Lorenz attractor as an example of a chaotic system.

The demand for using thin-walled composite structures for instance, in aircraft and ships are rising in the industry. These structures contain material interfaces, and at these interfaces, the structure exhibits non-smooth field behavior which is known as weak discontinuity. It is essential to study the effects of such discontinuities on the performance of the structure. These structures are usually modeled with standard finite element method (FEM) with fitted or geometry conforming meshes to the discontinuities. Shear locking is a key hurdle to overcome in FEM when using first-order shear deformation theory (FSDT) for thin structures. Classical beam (Euler-Bernoulli) or plate (Kirchhoff-Love) theories do not face such issues but ignore shear deformation and set the requirement of shape functions that are C1 continuous. The popular mesh independent method, eXtended/Generalized finite element method (X/GFEM) has also been used to capture the kinematics of discontinuous thin structures that are also devoid of locking. The presented work introduces a high-order discontinuity-enriched finite element formulation for linear and nonlinear (large deformations) discontinuous FSDT beam and plate elements. High-order interpolations are used to mitigate shear locking. The high-order enrichment functions are constructed by using hierarchical shape functions of the p-version of FEM (p-FEM), where the linear enrichment function is obtained from the interface enriched generalized finite element method (IGFEM) is combined with hierarchical shape functions of p-FEM. Convergence study shows that the proposed method accurately captures the discontinuity kinematics leading to an exact solution when compared with the analytical solution. A high condition number of the stiffness matrix is observed in the stability study which leads to loss of stability. A Jacobi like diagonal preconditioner is used to reduce the condition number but does not work well for high-order interpolations.

Graphene is expected to open up a world of new possibilities in the field of micro and nano sensors, due to its outstanding properties. However, graphene membranes suffer from high damping which limit their performance. The physical mechanism behind this damping is still unknown. Therefore, in this work, it is investigated how coupling between eigenmodes due to nonlinear stiffness causes damping. Besides, a method to construct this nonlinear stiffness for reduced order models is improved. Using this, numerical simulations are compared to experimental results for validation.

In the past few decades, there has been a growing demand for low-cost disposable sensors to be utilized in hazardous and toxic environments such as high temperature and chemically aggressive environments, which can lead to irreversible damage to the sensor. Moreover, by cost reduction, they become more attractive for utilization in developing countries, where the research of new biomedical technologies has been restricted due to a decentralized healthcare system, lack of infrastructure and shortage of investment. This research focuses on developing a low-cost, disposable and easy to use mass sensor utilizing diamagnetic levitation. Diamagnetic levitation is the only stable form of levitation at room temperature and does not require external sources of energy, feedback loops or cooling for stable levitation. It is a low cost, easy to use, disposable sensor that makes it suitable for potential point-of-care applications. The sensor consists of a pyrolytic graphite plate that levitates above a checkerboard arrangement of permanent magnets with alternating magnetization. The system is actuated using electromagnetic excitation and the material properties of the sample are extracted by conducting a multi-modal analysis of the resonance frequencies and mode shapes; measured using a laser Doppler vibrometer (LDV). An opto-electronic phase lock loop utilizing the LDV is used to bring the levitating pyrolytic graphite into sustained mechanical oscillation controlled by a PID controller. The experimental mass sensitivity is measured by analysing the frequency shift associated with the placement of glass beads. The frequency stability is measured by computing the Allan deviation and the experimental precision of mass sensor is then computed. The results show that the precision of a diamagnetically levitated resonant mass sensors decreases with the decrease of the size of the levitating oscillator. The precision of a levitating oscillator of side length 2mm and thickness 0.08mm is found to be 14.4pg at a gate time of 0.1s for an instantaneous change in frequency.

This thesis presents the development of a contactless sensing system and the dynamic evaluation of an air-bearing based precision wafer positioning system. The contactless positioning stage is a response to the trend seen in the high-tech industry, with the substrates becoming thinner and larger to reduce the cost and increase the yield. With contactless handling, it is possible to avoid damage and contamination. The system works by floating the substrate on a thin film of air. A viscous traction force is applied on the substrate by steering the airflow. A cascaded control structure has been implemented to the contactless positioning system, where the Inner Loop Controller (ILC) controls the actuator which steers the airflow and the Outer Loop Controller (OLC) controls the position of the substrate by controlling the reference of the ILC. The dynamics of the ILC are evaluated and optimized for the performance of the positioning of the substrate. For the OLC a linear charge-coupled device (CCD) has been implemented as a contactless sensing system. The sensing concept is implemented in the contactless actuation system and the results are presented.