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.

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.

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.

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.

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.

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.

The purpose of this project is to design and develop a set of force sensors to measure steering forces applied by an athlete down the ice track. Currently, there is not enough information about instrumentation in skeleton, and to maintain competitive advantages, most of the research remains private and unpublished. Athletes use their shoulders and knees to steer down the track. For this reason, four handmade piezoresistive tactile force sensors were built to measure the force applied by each joint. Each sensor has its own model to convert bits recorded into force. Results showed a difference between applied and calculated forces by each model. However, calculated results followed similar trends compared to the real values of the applied force. In addition, a graphical user interface was created to present the results to the athlete in a simple and easy way to read and understand. It is planned to use a shimmer (an inertial measurement unit) to collect information about accelerations developed on each run. Coupling both measurement systems have to be done during the processing stage. Further work has to be done regarding electronics size and testing the systems in a real run down the track.

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.

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

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.