This research proposes and validates a novel grasping principle to be able to set caging grasps in cluttered environments. A prototype is designed making use of manoeuvering fingers which propagate along the object surface and are covered with everting belts to minimize slip and thus friction forces on the object and environment. Using several lab setups, it is shown that the designed gripper fingers closely follow spherical objects, and do so while exerting only negligible normal and friction forces on the object or surrounding clutter. Furthermore, the gripper is validated with a robotic system in a practical test case of grasping tomatoes from a dense cluttered pile. The gripper successfully grasped 100% of the objects without any control effort in terms of clutter avoidance and grasp pose control. This shows that this novel strategy for setting a caging grasp makes grasping difficult objects in cluttered environments robust and highly successful.

There is a constant drive to make the next generation machines in the semiconductor industry more precise and faster. For this machines with a high repeatability, good dynamics and long lifetime are needed. Compliant mechanisms are suitable candidates to be used in this kind of machines because they can be manufactured monolithically, don’t wear out over time and do not suffer from backlash which makes them ideal for precision mechanisms. However, in these machines parasitic motions and cross-axis couplings are present. These unwanted motions reduce the precision and increases the control complexity respectively. Strategies presented in literature to compensate for unwanted motions are summarized in the first part of this report. These strategies are evaluated and by combining two promising strategies a new compensation strategy is proposed. The second part of this report focusses on this new strategy. Using this new strategy a constant stiffness linear joint, a near zero parasitic motion translational guide with well constraint uncontrollable masses and a decoupled 2-DoF mechanism are synthesized. All these case studies needed to have a large range of motion because many effective strategies for small range of motion mechanisms are available in literature.

Introduction: When navigating through tight and delicate environments, steerable tools are highly desired. Follow-the-leader locomotion, as in the biological snake, is a solution that is obtained with shape memory control. The often used electric equipment to control the shape makes the current state-of-the-art of snake-like robots too complex. This thesis focused on a snake-like system using mechanical shape control to generate forward motion, to analyze the motion and comment on the expected behavior. Method: A 3D Simulink model was created with friction between the snake-like system and the surroundings as an important relation. A pre-defined sinus wave was passed through the snake-like system to analyze the motion. A low-cost, 3D printed, prototype was developed to validate the friction relation of the model. The prototype contains a belt feature with pre-defined path as shape control system and a snake-like system with four wheeled segments. Different configurations were assessed in the model by changing the wheel axis length, sinus amplitude and sinus frequency. Results: The prototype validated the realistic friction parameters in the model. Given the results of the model, the snake-like system creates forward motion by pushing against the surroundings when a sinus wave is pushed through the system. The wave parameters have a significant influence on displacement. When the configuration of the snake-like system creates more friction with the surroundings, the system is able to push itself further forward and generates more forward displacement. Conclusion:It is demonstrated that forward motion is possible when a snake-like system is connected to a mechanical shape control system. Now, the next step is to investigate random paths, to enable adaptable mechanical shape control being applied.

Current multi-DoF compliant manipulators are still rarely implemented in the industry because their range of motion (ROM) is limited as their designs are heavy and bulky or obtained by a serial set of multiple stacked flexure systems, which limits their compactness. The goal of this article is to overcome these limitations by considering them as an integrated multi-DoF compliant joint, either serial or parallel, and setting up a new method the Compliant Manipulator Design (COMAD)-method and investigate its performance. This method will combine the "Type synthesis of legs"-technique to include parallel kinematic solutions for the desired motion pattern whereafter the complete compliant solution space is obtained using the FACT-method. The method is applied for designing a 4-DoF-manipulator with a TTTR-motion pattern resulting in four new concepts composed of compactly aggregated wire flexures. After the concept selection, a demonstrator is manufactured which excellently possesses four decoupled motions with a relatively large ROM. This can be seen as a new milestone for designing multi-DoF compliant manipulators as it permits a larger ROM and better stiffness capabilities than those obtained from conventional methods because all compliant topologies are deflecting in series due to the parallel kinematic couplings within the multi-DoF flexure systems.

The moving parts in a mechanical device often rely on rolling or sliding contacts such as in ball bearings to gain motion. These suffice in many applications, but the friction inherent to their working principle limits their motion repeatability and thereby their precision. Flexure mechanisms are a popular alternative in the field of precision engineering because they gain motion by elastic deformation of slender segments such as thin spring steel plates, resulting in a highly repeatable motion due to the absence of friction and play. Furthermore, they are lubricant-free and do not generate particles, which makes them suitable for applications in space, astronomy, the semiconductor industry, and healthcare. A drawback of flexure mechanisms is their limited range of motion compared to their build volume, which results in voluminous designs and which limits their application field. Their range is limited by material stress but also because at large displacements the stiffness in their support directions decreases significantly, and their actuation effort increases at large deflections, resulting in high energy consumption and heat generation. Increasing the motion range would highly benefit the field of precision engineering and could also lead to innovations in healthcare or space. The motivation for this thesis is the observation that the vast majority of flexure mechanisms consist of initially straight and stress-free flexures. Recent developments in fabrication methods such as the additive manufacturing of steel are providing the possibility to create more complex shapes, which could improve the range of motion of flexure mechanisms. The objective of this thesis is to provide design strategies to increase the motion range of flexure mechanisms. The thesis consists of two parts, of which the first (chapters 2-4) focuses on a new method to design stressed and curved flexures. The second part (chapters 5 and 6) further develops a recent strategy to increase the range of motion using torsion reinforcement structures. @en

Singularity points are causing problems in motion converters. A solution is found and experimentally validated.

For more than 130 years there have been efforts to automate human services. One such automation is the use of computer-based solving methods to aid engineers in their search for their ideal goal, such as automated planar mechanism design. Contrary to creating mechanisms manually, automatic methods are able to create and evaluate mechanisms in quick succession. However, computers can often reach intricate designs which are not directly feasible in the physical domain. These programs do not focus on being able to manufacture the mechanisms, thus, the designs often have features that make it difficult or even impossible to create physically. Examples are inadequate spacing between joints or a mechanism consisting of many elements for which a good layer assignment is hard to find. To ensure these designs are physically feasible, a manufacturability check can be implemented. Sen et al. created a method to obtain manufacturable planar mechanisms for kinematic designs consisting of rigid bodies and revolute joints. This method identifies structural, kinematic or geometric infeasibilities for all layer assignments. When a mechanism is fully feasible, it can be manufactured. However, this method is still limited. It is only applicable for mechanisms consisting of rigid bodies and revolute joints. This restricts the application space of possible designs. Also, this method is not tested with physical examples. In this research, an extension of automatically created manufacturable mechanisms is developed. Firstly, it extends the method such that spring elements in a design can be checked for manufacturability and surrounding links can adapt their shape to accommodate for the springs, resulting in a wider field of applications. Secondly, a method is introduced to simplify the steps to manufacture the theoretical design. Four mechanism prototypes are built using the available methods and their manufacturability is evaluated. Lastly, this research can be used to find the layer assignment with the least amount of layers, resulting in thinner mechanisms for space-constrained applications.

The compliance (stiffness) of a human arm varies, depending on the task at hand. Some precise tasks require high stiffness, while others need a level of flexibility to deal with unknown disturbances. To describe this human behaviour a portable device is needed to give small force perturbations (input) while the resulting reaction of the arm (output) is measured. There are multiple state-of-the-art devices to choose from to provide such input. However, the majority of these devices either offer too little versatility or impede the free movement of the user. Implementation of a novel parallel mechanism allows for a lightweight (0.175kg) and compact device that can generate various signals in three degrees-of-freedom. Since the device is designed to be mounted around the wrist, it leaves your arm and hand unobstructed. A full-scale prototype is constructed and the concept is tested using a force sensor. Implementing powerful yet compact servo motors allows for controlled perturbations in the order of 4N, with bandwidths up to 12Hz.

This thesis presents a transformable metamaterial, inspired by origami. Generally, metamaterials are build up following the periodicity of Bravais lattices. This study aims to design a structure not following the Bravais lattices, but rather a different type of symmetry which tiles a sphere, in order to expand on current design studies. In this report the different types of spherical symmetries are discussed and the icosahedral symmetry group is used to design a theorical model. Then a prototype is designed and 3D-printed. Lastly the prototype is discussed and recommendations for further research are made.

Humans can compensate rapidly to unforeseen errors and circumstances while performing motor tasks. These tasks are exposed to sensory and motor noise and delays originated from the biological system characteristics, as well as to varying surrounding environments while performing movements. Therefore, uncertainty of the estimate of limb position arises. Error estimates during movement and displacements after a mechanical perturbation are compensated by relying on proprioceptive feedback from the body. Moreover, the motor system can rely on co-contraction as it increases the amplitude of the short latency stretch reflex, which plays an important role in minimizing the effects of disturbances. This study examines the influence of position, velocity, and pre-perturbation background muscle activity in the decision process of avoiding obstacles in the environment after a mechanical perturbation while performing a reaching task. After the perturbation, participants had to choose between two strategies: going in between or around the obstacles to reach an end target. Position of the hand, velocity, and EMG activity of four muscles in the shoulder and elbow were compared at different time epochs between both strategies. No significant differences were found in muscle activity pre-perturbation and lateral position before and up to 100ms after perturbation onset. Significant difference in lateral velocity was found 50ms after perturbation onset between the two strategies. Online corrections to avoid obstacles after a mechanical perturbation are modulated by the lateral velocity of the limb.

In this work, we present the ADAPT, a novel reconfigurable force-balanced parallel manipulator with pantograph legs for spatial motions applied underneath a drone. The reconfigurable aspect allows different motion-based 3-DoF operation modes like translational, rotational, mixed, planar without disassembly. For the purpose of this study, the manipulator is used in translation mode only. A kinematic model is developed and validated for the manipulator. The design and motion capabilities are also validated both by conducting dynamics simulations of a simplified model on MSC ADAMS, and experiments on the physical setup. The force-balanced nature of this novel design decouples the motion of the manipulator’s end-effector from the base, zeroing the reaction forces, making this design ideally suited for aerial manipulation in unmanned aerial vehicles (UAVs) applications, or generic floating-base applications.

In robotics, machine elements are accelerated in order for the machine to perform certain tasks, such as picking and placing objects. These accelerations result in inertia forces and inertia torques on the machine elements and on the base of the machine. These reaction forces and reaction torques on the base are called shaking forces and shaking moments. Shaking forces and shaking moments result in noise, vibration, wear and fatigue problems. Dynamic balancing eliminates shaking forces and shaking moments on the base, which results in low cycle times and high accuracy. However, the process of balancing a mechanism generally increases the masses, the moments of inertia, and the complexity of the mechanism. The method of inherent dynamic balance aims at minimizing these drawbacks by considering the balancing prior to the kinematic synthesis. With the method of principal vectors, a large number of inherently shaking force balanced mechanisms has been found. However, the options for shaking moment balanced mechanisms are still limited. In this thesis, an overview of current dynamic balancing methods is presented, along with a new method for the synthesis of inherently moment balanced mechanisms. This new method is used for the synthesis of inherently dynamically balanced 1-DoF pantographic linkages, where the desired motion of the end-effector is selected by the designer. This motion is defined as a set of precision positions. For this new method, the known method for RR chain synthesis from Burmester’s theory is combined with the shaking moment balancing condition. For the special case where the relationship between link angular velocities is linear, the shaking moment balancing condition is substituted into the RR chain design equation. For the general case where the relation between link angular velocities is non-linear, the equation of motion is numerically solved for a range of possible solutions in order to find the solution which reproduces the desired motion.

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.

As mechanisms become increasingly precise, so becomes the reduction of noise and vibration increasingly important. One method for eliminating vibrations in mechanisms is dynamic balancing. This method prevents vibrations from occurring by designing the mechanism such that the inertial forces and moments of all bodies in the mechanism cancel each other out kinematically. Generally, this is done by cleverly adding masses to existing mechanisms or by using symmetric mechanisms which move in opposite directions. Another method for the synthesis of mechanisms is topology optimization. This method can be used to design dynamically balanced mechanisms without the need for symmetry or redundant masses. An algorithm is developed, based on the 99-line code, to synthesize such dynamically balanced mechanisms. As a test case, an off-centered (thereby usually unbalanced) force-inverter is designed, and a significant reduction in the shaking forces and shaking moments is achieved. The resulting geometries are analyzed in COMSOL to verify the results of the algorithm and perform further analyses on the performance of the algorithm.

Bicycle simulator research has been the subject of considerable research, however, few of these attempts have integrated direct balance control and enough freedom of motion to deliver a real-world kinematic cycling experience. In this study, the B.I.K.E. (Bicycle Intrinsic Kinematics Emulator) system, a kinematic bicycle simulator, is developed with the purpose of letting its users experience realistic kinematic motion, which are: steer, roll, yaw and sway motions. This study validates the developed simulator by performing a kinematic comparison of bicycle motion among 15 participants of varying age and mass, and performs an initial subjective study to investigate effects common to indoor vehicle simulation. Manoeuvres performed by the participants are straight-line cycling, at low (5 km/h) to high (40 km/h) velocities, as well as performing a zig-zagging motion. The results show that users can successfully rely on existing bicycle skills to use the simulator. They also show that, in the kinematic sense, the simulator performs similarly to an outdoor bicycle, particularly at velocities below 35 km/h, but more work is needed in improving the vehicle model and control algorithm to accurately cover low to high-velocity cycling. Subjectively speaking, the simulator performs better than existing static solutions, but more work will be required to make the riding experience feel like real outdoor cycling.

Flapping-Wing Air Vehicles (FWAV) are autonomously flying vehicles that use their flapping wings to simultaneously stay aloft and enable controllable flight. FWAVs that are capable of controllable flight are reported in literature, though a theoretical background of the aerodynamic performance of different attitude control mechanisms is absent in literature and the robustness of attitude control mechanisms with respect to body motions is oftentimes omitted. The aim of this thesis is to develop a theoretical framework for the aerodynamic response of flapping wings that includes variation of attitude control parameters and motion of the vehicle body. This framework can be used to assist in research into new attitude control mechanisms for FWAVs that are not yet capable of attitude control, such as the compliant Atalanta FWAV. Analytical aerodynamic and kinematic descriptions are combined to analyze the aerodynamic performance of two suggested attitude control mechanisms: stroke amplitude variations and control of the angle of attack by means of pitching stiffness variations. It is shown in this research that both mechanisms have a significant influence on the lift production of a flapping wing, though this influence changes significantly when body motions are introduced. It is found that variations of the stroke amplitude provide the most predictable variations in lift for all cases of body motion that were considered, provided that the wing’s pitching hinge stiffness is high enough to ensure stable flapping kinematics under the influence of body motion.