This paper introduces a fully compliant spherical joint with an optimized stiffness profile specifically for balancing a pendulum. The design builds on previous work that has successfully created a fully compliant spherical joint using tetrahedron-shaped elements connected in series. To efficiently compute and optimize the balancing behaviour of these compliant joints, a novel algorithm is developed and presented. Using this algorithm, optimizations are conducted to obtain simulated pendulum balancers under five different conditions. The performances of these results are analysed to assess the potential and limitations of the algorithm and these spherical joints. Based on one of the optimized results, a prototype is fabricated and expermentally validated, achieving a moment reduction of 90.5%. The deformation calculated by the TetraFEM tool closely matches the prototype’s deformation with an accuracy of 89.6%, demonstrating its potential for application in the development of shoulder exoskeletons.

In the semiconductor and photovoltaic industries, contactless positioning systems are increasingly employed to handle ultra-thin wafers, minimizing the risk of mechanical damage. A suitable and integrated sensor system would make this handling method more attractive in future applications. This Msc. thesis explores a novel concept in planar position measurement for flat, reflective objects using fiber optic sensors distributed across a measurement plane. This sensor configuration creates light profiles via transmitting fibers and utilizes the reflected light detected by receiving fibers to localize the object's position.
A Gaussian-distributed intensity pattern is first applied to the light profiles to validate this concept, establishing the theoretical relationship between brightness and planar positions. A prototype with a single set of fibers is then constructed to verify the proposed brightness model and determine the optimal, sparsest fiber spacing that maintains adequate resolution. In the next phase, algorithms are developed using simulated sensor arrays to calculate planar degrees of freedom based on the actual positions and brightness values from receiving fibers near the object's boundary. These algorithms are then implemented in a fabricated sensor array prototype, forming a complete distributed fiber optic sensor system.
The sensor's performance is evaluated using samples with varying center positions and orientations, resulting in an average error of less than 1 mm in the in-plane directions. In conclusion, the proposed sensor configuration limits planar position errors to sub-millimeter accuracy. The measurement range is significantly extended, and the sensor element no longer needs to be attached to the measured object. As a result, this system offers promising potential for contactless planar positioning of thin, fragile products with specular surfaces.

An earlier study introduced a formula for determining the holding force of a toroidal hydrostat gripper when gripping an object of constant radius, considering a linear stress/strain relationship. However, beyond the holding force, understanding the grasping disturbance force exerted on the object due to the rolling behavior during grip adjustment is crucial to ensure the objects are not damaged or displaced, and are successfully picked up. This study aims to extend the existing model by incorporating the disturbance force for objects with variable radii and using a non-linear stress/strain relationship for the membrane material.
A parametric model was developed to estimate these forces as a function of its geometric and material properties. The model was validated through experimental testing and refined using a tuning parameter obtained via optimization algorithms to address parameter uncertainties.
The model approximated the holding forces well, with a maximum deviation of 15\% at the maximum swallow distance. It overestimated the peak disturbance forces by a factor of 2.5. But when normalized, the force curves showed good resemblance.
Surprisingly, the obtained tuning parameter reached a high value of $1.45$. as the parameter uncertainties are thought to be less than 20%. This overestimation could be the result of an additional vacuum force, as evidenced by a clear difference in holding force and gripper behavior is observed in pulling tests for objects with smooth and rough surfaces.

Path generation mechanisms are those mechanisms that produce a predetermined path. Such mechanisms are prevalent in daily life, and many devices depend on path generation mechanisms or are derived from path generation mechanisms. One might think of examples such as vehicle suspension, film advance mechanisms or sewing machines. These are generally made with rigid body mechanics, such as linkages. However these rigid body mechanisms suffer from effects such as friction, play and wear. These problems are well known to be solved using compliant mechanisms. But, some path generation such as that necessary for a film advance mechanism can currently not be made using a fully compliant system. This is because full-cycle motion is necessary to produce the path that is generated by such mechanisms, and compliant mechanisms fundamentally are not able of producing full-cycle motion.
This thesis presents the synthesis of a compliant mechanism that is able to translate reversible reciprocating motion to a history dependent path that describes an area. This process is detailed in three separate texts. The first text is set up as a paper, and outlines the generated academic contribution. The second text is the design report, herein the full design and modelling process is described. The third text is the literature review in which the gap in research is detailed.

Dynamic balancing can offer significant benefits to applications where moving parts are present. It aims to reduce the reaction forces and moments due to inertia of the parts, thereby reducing vibrations. Dynamic balancing receives significant academic interest for planar and spatial applications, but limited attention for spherical mechanisms. This leads to the following goal of this thesis: Present novel force balanced spherical mechanisms design using inherent balancing planar pantograph theory for use in micro precision applications.

To achieve this goal, the thesis has been divided into three sub goals. First is defining the qualitative benefit of dynamic balancing for applications requiring micro-precision. This qualitative analysis looked into six different 'high speed precise' applications with motion and determined a potentially significant benefit exists for applications such as (space) telescopes, space manipulation, additive manufacturing, motions stages and beam steering. Engines and drives require new balancing methods to achieve significant benefit. However, the analysis also showed that many different aspects other then inertia also influence precision, thereby potentially reducing the gained benefit in precision. This is due to the addition of extra components or mass in most common dynamic balancing methods.

The second goal presents five new shaking force balanced spherical mechanisms using inherent balancing theory. Here the planar knowledge of inherently balanced shapes such as the pantograph as well as the use of projections are used to design three novel types of balanced spherical pantographs, namely the spherical pantograph, double spherical pantograph and the double S shaped mechanism with surrounding 4R four-bar linkage. Also, two additional variations of the spherical pantograph and the double spherical pantograph are presented, which leads to a total of five new designs. Each design has its required constraints and available design freedom described. Also, the balance conditions for the double spherical pantograph are presented.

The last goal shows ten novel force balanced remote center mechanisms, using the three types of inherently balanced spherical pantographs. These remote center mechanisms are either using a swivel joint or are a combination of spherical pantographs to form a parallel manipulator. This allows all end effectors to show spherical movement, around a fixed Center of Rotation. The pros and cons as well as feasible variations and constraints are also discussed.
To show the use case of a force balanced remote center mechanism, a realistic design has been made for a beam steering application, where a mirror can perform a tip/tilt movement around a shared center of rotation. The mechanism uses three scaled shifted double spherical pantographs as legs to form a parallel manipulator, with a mirrored surfaced attached to the end effector and positioned in the center of rotation.

Neutrally stable metamaterials can maintain differ- ent shapes without any energy input, making it a key innovation in the quest for more energy-efficient technologies. Despite this intriguing property, the research in this area is scarce. This study proposes a method for achieving neutral stability in metama- terials. This method is validated with a novel unit cell design that utilizing two identical beam elements that are mirrored. Each element displays a constant force characteristic. By pre- tensioning these elements, we align their constant force regions, thereby inducing a state of neutral stability. Through finite element method (FEM) simulations and geometrical optimisation, the beam of this design is optimised to achieve the optimal constant force response. A prototype is made and a test setup is constructed to validate the accuracy of the simulations and the feasibility of the method for achieving neutral stability. Results indicate that while perfect neutral stability was not fully achieved, this method can be applied on other constant force mechanisms to create neutrally stable metamaterials.

Drones are increasingly used nowadays, primarily for visual inspection tasks facilitated by onboard cameras. The field of aerial manipulation tries to expand the capabilities of drones by attaching a manipulator, enabling physical interaction. Unfortunately, the usability of aerial manipulators is hindered by disturbances resulting from the movements of the manipulator. These disturbances, including reaction forces and a shifting centre of mass, not only affect manipulation accuracy but also pose safety risks by potentially destabilizing the drone. In this thesis, a design is presented that addresses this challenge by leveraging the theory of dynamic balance.
A new design approach of making a manipulator fly, instead of the common approach of mounting a manipulator arm to a drone was used. This new approach avoids interference with the drone's components, allowing to focus on the design of the manipulator arm. Furthermore, it made it possible to create a manipulator which can manipulate above, to the side and underneath itself. This makes the presented manipulator arm more versatile than common aerial manipulators whose workspace is mostly located only above or below the drone. The kinematics, workspace and balance conditions of the manipulator arm are presented. Furthermore, the design's workspace is optimised while the mass of the manipulator is minimized in a bilevel optimisation. Finally, the design is validated both by simulation and measurements performed with the built prototype.
The design presented is the first inherently fully dynamically balanced manipulator with omnidirectional workspace which can be used for aerial manipulation.

Compliant mechanisms, particularly helicoidal shell joints, present intriguing possibilities in mechanical design with applications in medical devices, robotics, automotive, and aerospace engineering. This research focuses on the synthesis of nonlinear torque-angle profiles using a compliant helicoidal shell mechanism such as gravity-balancing profiles. This study required a thorough exploration of the mechanism’s diverse design variations through Finite Element Modeling (FEM) and more specifically, Isogeometric Analysis (IGA). Subsequently, a targeted optimization process is utilized, incorporating both global geometric parameter adjustments and localized modifications by using splines. The prominent challenge addressed is the synthesis of gravity balancing torque-angle profile, achieved by tailoring the output profile of a compliant shell mechanism through optimization. Considering the inherent sine function output of a pendulum during gravitational equilibrium, an algorithm is developed to optimize the mechanism’s behavior to align with a sine function, hence enabling gravity balancing. Additionally, experimental validation was undertaken through manufacturing prototypes and conducting measurements to provide a crucial link between simulations and real-world behavior. The results of this research, encompassing optimized geometry and experimental data, are presented, and comprehensively discussed. This research contributes a numerical methodology that utilizes isogeometric analysis and optimization algorithm within the framework of finite element analysis for achieving nonlinear torque-angle profiles in complaint helicoidal shell mechanisms, such as gravity balancing profiles, offering valuable insights for possible applications in various engineering domains.

Auxetic metamaterials offer various novel abilities, one of the abilities is to deform into a dome-shape under out-of-plane deformation. Contrary to a material with a positive Poisson's ratio, which deforms into a saddle-shape. A dome-shape is named synclastic deformation and a saddle-shape is named anticlastic deformation. Under out-of-plane deformation, the magnitude and sign of the Poisson's ratio influence the curvature of the material, and hence the final shape. Starting from a flat plane, manipulation of the Poisson's ratio can create various unusual shapes, such as an egg or a wave-shape. A desired shape might require a uniform Poisson's ratio or a varying Poisson's ratio distribution. Most of the current estimations on the relation between an auxetic material and the deformation shape are performed experimentally. This paper presents an analytical approach which shows the influence of a varying Poisson's ratio on the out-of-plane deformation of a material under pure bending conditions. Four Poisson's ratio distributions are applied which follow the formulas: S-curve, parabolic and cosine in one and two directions. The same model is build in the FEM software COMSOL which serves as the reference model. Comparison of the COMSOL model shows a Mean Absolute Percentage Error between 0.30% and 11.93% for the analytical model. Remarkably, the accuracy of the analytical model is high if a Poisson's ratio distribution varies in one direction, resulting in a Mean Absolute Percentage Error lower than one percent point. A limitation of the analytical model is that the Mean Absolute Percentage Error increases to 0.69% till 11.93% when the Poisson's ratio varies in two directions. The presented analytical approach provides a first step in determining a varying Poisson's ratio distribution that can deform into any desired shape. The resulting shapes are synclastic and combinations of synclastic and anticlastic.

This work aims to achieve a softening moment-angle response by utilizing compliant parts. The approach uses the principle of contact release, which involves initially prestressed torsional bars arranged in series, separated by rigid bodies. By stepwise activation of the torsional bars, a softening behavior is achieved. Mechanical stops are employed to maintain the initial prestress.
A Pseudo Rigid Body Model (PRBM) is developed to calculate the moment-angle behavior of the complete prototype. The optimization of the PRBM is performed using a cost function based on the least square error. The optimization parameters are the stiffness of the torsional bars and their initial prestress. Additionally, a Finite Element Analysis (FEA) is conducted to analyze the behavior of an individual I-profile torsional bar. Experimental validation of both the PRBM and the FEA models is carried out using a prototype. The prototype is constructed based on the results obtained from the PRBM optimization to follow the desired graph closely. The results from both FEA and PRBM align closely with the predicted curves, confirming the effectiveness of the proposed approach.

A growing energy demand has sparked interest into harvesting energy from the human body. Often, a rotational proof mass is used to harness energy for a wearable from kinetic motion of its user. The addition of a spring has the potential to significantly increase efficiency for these low-power rotational energy harvesters. In this research a system characterisation is performed from which a dimensionless ratio is formulated to determine optimal spring stiffness for maximisation of average power output as a function of harvester design parameters and excitation inputs. Creating a system that is optimized for the entirety of its operational range rather than for one specific excitation input. Implementation is investigated in the field of horology, where rotational energy harvesters are widely implemented. To increase harvesting efficiency of existing rotational energy harvesters without requiring significant design alterations a compliant design is proposed, prototyped and tested.

Compliant mechanisms are a popular alternative to conventional mechanisms because of their advantages on mass reduction, friction, backlash and lubrication. However, the major drawback in the use of compliant mechanisms is the stiffness is the desired direction of motion. The advantages of conventional and compliant mechanisms can be combined if the stiffness can be reduced or ideally removed, resulting in a zero-stiffness compliant mechanism. In current designs of zero-stiffness mechanisms, a preload is applied in the stiffest (compression) direction of a flexible beam. This working principle is based on Euler buckling. In this work, compliant mechanisms with zero-stiffness behaviour are obtained using lateral torsional buckling as their working principle. For this purpose, two compliant joints are modelled in a FEA, a translational and a rotational joint. The results of the FEA are verified by experiments. Also, a sensitivity analysis is performed on the cross-sectional dimensions of the flexible beams to optimize the range of zero-stiffness. Both types of joints showed zero-stiffness behaviour for the optimal preload and a good agreement is found between simulations and experiments. From the sensitivity analysis is found that a rectangular cross-section results in the largest range of zero-stiffness.

The use of origami-based mechanisms in the engineering field is growing as their advantages are better understood. Origami-based mechanisms have the advantage of being lightweight, compact, and their ability to transform from a flat sheet into complex three-dimensional structures makes them a source of inspiration to meet design challenges. A fold in paper is realized by a localized reduction in thickness, which reduces stiffness. Since most materials do not exhibit this property when folded, other techniques are used to facilitate this stiffness reduction. These include sandwiching a thinner material between rigid facets, or by thinning to create a groove joint (notch joint). The drawbacks of these techniques are that the first technique requires assembly, and the second technique requires complex material removal. Another technique has been proposed to reduce stiffness with simpler manufacturing methods, namely lamina emergent joints. These joints require cutting through the material, which can be done using well-established sheet manufacturing methods, such as laser cutting or stamping. However, the removal of material involves a trade-off between range of motion and stiffness in directions other than the desired bending motion. Initial research indicates that the groove joint is able to maintain the highest stiffness and range of motion, thus outperforming the lamina emergent joint. Therefore, the objective of this paper is to design an improved lamina emergent joint that approaches the performance of the groove joint. This is achieved by quantifying and evaluating the stiffness performance and range of motion of existing lamina emergent joints and then combining them on strong features. Improved designs are proposed that made an approach toward the groove joint and the best design was selected for optimization. The results showed that the selected design was not able to outperform the groove joint on both stiffness and range of motion. However, it was able to achieve similar in-plane shear stiffness and higher torsion stiffness than a groove joint with a lower thickness ratio. However, this also allowed more range of motion for the groove joint. So figuring out this trade-off between stiffness and range of motion is challenging and essential to design suitable joints in the future.

The exploration of compliant mechanisms, especially those providing linear motion, has become a central focus in recent engineering research. These mechanisms, characterized by their monolithic bodies and reduced component interactions, present an attractive alternative to traditional rigid mechanisms, having reduced friction, decreased energy losses, and cost efficiencies. Despite these advantages, designing and analyzing compliant mechanisms remain difficult tasks, with particular challenges arising when aiming for large-range linear motion with high support stiffness and minimal parasitic displacement. This study presents a unique design: the combination of a flexure-based linear guide with the features of a bistable compliant switch mechanism. Because a combination of these mechanisms has not been looked into while still offering a long stroke, high support stiffness and minimal parasitic motion. Through Finite Element Analysis (FEA) and subsequent iterations, an optimized model was conceived, prioritizing stiffness and minimizing undesired motions. This optimized design was turned into a 3D printed prototype. The experiments with the prototype confirmed the results of our computational insights, showcasing the parasitic motion of the prototype to be within 1mm, and its minimum stiffness at least being 10kN/m while still having a stroke of 70mm. A case study has been set up, of which the proof of concept works and is validated.

Vibrations have been studied in various engineering fields due to their detrimental and even destructive effects on structures. Suppressing low-frequency vibrations has been a research challenge for decades and is mostly achieved by implementing active vibration control techniques. In the last two decades, the emergence of locally resonant metamaterials has sparked the interest of several researchers to create passive vibration attenuation structures as an alternative to active vibration-suppressing techniques. This research focuses on developing a local resonator-based unit cell that is able to attenuate vibrations at a wide range of low frequencies. A literature research is performed on the state-of-the-art in the field of locally resonant metamaterials and their wave-suppressing properties. Several wave directions and types are considered,
while low-frequency vibration attenuating structures are actively discussed. A comparative study is done on current local resonator-based structures from which a novel compliant metamaterial is proposed that can suppress a wide range of low-frequency vibrations. The proposed novel compliant negative stiffness local resonator (NSLR) unit cell has the ability to attenuate low-frequency vibrations at a wide range of frequencies while exhibiting a large load-bearing capacity. This concept is based on compliant mechanisms and relies on the snap-through motion of buckled beams for its negative stiffness, whereas folded beams are used in the design as load-bearing positive stiffness components. The stiffness and load-bearing capacity of the unit cell is determined by analytical and FEM-based numerical models, while dispersion relations and transmissibility functions are used to identify the dynamic vibration attenuation behavior. A prototype is produced by FDM additive manufacturing and tested in an experimental setup to verify the load-bearing capacity. An analytical and numerical load-bearing capacity between 100 N and 102 N, and 111 N to 115 are established, respectively, with an effective vibration
attenuation displacement range of 2.5 mm. The FEM simulated band gap of a single unit cell ranges from 6.0 Hz to 64.8 Hz, while the analytical model shows a band gap from 9.6 Hz to 59.5 Hz. The manufactured NSLR prototype features parasitic resonator rotations, requiring additional stiffness constraints to test its vibration attenuation properties in practice. These analyses show the promising capabilities of the NSLR unit cell as a building block in metamaterials to protect
structures from low-frequency vibrations at a wide range.

Mechanical metamaterials are architected materials with unique properties derived from their internal structure, rather than the material they consist of. Introducing distinct stable states into the material architecture allows the creation of mechanical metamaterials with multiple effective properties that can be altered post-fabrication. So far these so-called reprogrammable mechanical metamaterials have only demonstrated responsive behaviour, where the state of the metamaterial is dictated by the external input, leading to complex actuation and limited functionality. This research introduces a transformative approach to overcome these limitations through state-dependent switching, enabling metamaterials to autonomously determine their state based on internal information. Leveraging internal instabilities in the form of bistable and slender buckling elements, a contactless and tessellatable 3D unit cell design that can switch between positive and negative Poisson's ratios upon a specified displacement threshold is introduced. State transition occurs based on internal state information, rather than the external input, enabling adaptive behaviour. Both, Finite Element Analysis (FEA) simulations and experimental validation demonstrate the ability of the unit cell to switch between positive and negative Poisson's ratio under the same repeated input. Preliminary FEA simulations further suggest that through the tessellation of this innovative unit cell, the adaptive behaviour can be exploited to create mechanical metamaterials capable of adaptive shape morphing and repeatable counting abilities.

In the semiconductor industry, integrated circuits with nanometre scale structures are manufactured on silicon wafers. Particle contamination on the topside of the wafer can result in the defectivity of the entire die. In the ever-increasing efforts to create smaller structures onto a wafer particle contamination becomes more restrictive to prevent the defectivity of the die. In order to reduce the risk of particle contamination the wafer is placed in a vacuum environment. But further risks exist, during the grasping and positioning of the wafer new particles are generated and are able to transport to critical surfaces. This study investigates what guidelines need to be followed for the design of a kinematic coupling for use in a vacuum, whilst keeping particle generation as low as possible. The guidelines can be used to determine an optimal kinematic coupling design for any arbitrary object shape, size and mass. First of all, it is determined that abrasive wear, adhesive wear, contact stresses and outgassing are the predominant factors that have an effect on particle generation and influence the design of a kinematic coupling. The first guideline optimizes the constraint method of the kinematic coupling. Here, the guideline states that each constraint needs to be able to translate parallel to the surface of the object, doing so minimizes abrasive and adhesive wear. This can be achieved by suspending the contact points by using, for example, (folded) leaf springs. The second guideline encompasses the contact point shape and size. To equally distribute contact stresses, a spherical indenter shape should be chosen. Here, the radius of the indenter is chosen to be as small as possible to prevent adhesive wear. The third and last guideline optimizes the position of the contact points placed on the object. These positions influence the positioning repeatability, an algorithm is introduced that can calculate the optimal position for the contact points to maximize this repeatability. Also, the stability of the grasp is determined in terms of maximum allowable external disturbance forces.

This research presents a measurement method for a compliant gripper finger, whereby the location of the contact with an object and the exerted grasp force are measured indirectly, instead of directly on the contacting surface. For this purpose, the deformation is measured using strain gauges at two locations on the inside structure of the finger, where high deformations occur. The finger is modeled using a Finite Element Analysis, whereby strain data at the two sensor locations is gathered for a set of different contact locations. Now, by matching the measured data to a modeled scenario, both the actual contact location in this scenario and the accompanying contact force can be determined. For the experimental validation, the compliant finger embedded with the two strain gauges is manufactured and an experimental setup has been built. The results show that the contact location can be inferred from strain measurement and contact force is determined accurately up to order of magnitude of 10^-1 newton. Comparing the force-deformation behavior of the original and the embedded finger, a maximum difference of 6% in actuation force was observed. Hence, the sensing method is useful to indirectly measure contact location and force for a compliant finger in contact with an object, while having a minor influence on the grasping performance of the original design.

This project presents a compliant slender mechanism with a low axial-bending stiffness ratio. This can be used in passive exoskeletons. Passive exoskeletons can assist people with their work by preventing injuries. Currently exoskeletons uses sliders to account for the extension of the spine when bending, but this could be uncomfortable. The proposed mechanism tries to solve this problem by having a low axial stiffness while maintaining its bending stiffness. It consist of vertical rigid bodies connected by horizontal flexures. The distance between the flexures is found to be a variable almost independent of the axial stiffness, thus able to easily influence the ratio. To help with future designs a PRBM-model is proposed that describes the proposed mechanism. This is then used in a dimensional optimization algorithm. The found design is then produced as a prototype and tested. The axial-bending stiffness ratio that has been found was 8.5 and the maximum error of the PRBM model 18%.