A Curved Compliant Differential Mechanism With Neutral Stability

Differential mechanisms are remarkable mechanical elements that are widely utilized in various systems; nevertheless, conventional differential mechanisms are heavy and difficult to use in applications with limited design space. This paper presents a curved differential mechanism that utilizes a lightweight, compliant structure. This...

Lateral torsional buckling in translational and rotational compliant joints to obtain zero-stiffness behaviour

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...

Neutrally stable double-curved shells by inflection point propagation

Elastic structures that can deflect without springback, known as neutrally stable structures, form a remarkable group within their field, since they require the energetic state to remain unchanged during elastic deformation. Several examples in the literature obtain this state of neutral stability by the application of pre-stress, either as a...

Simulation for stability of a beam-mass based high-resolution MEMS gravimeter

In this paper, stability and mechanistic simulations for a four-beam-mass-based MEMS gravimeter were conducted, and guidelines for the gravimeter design were proposed. Based on a prototyped MEMS device, the nonlinear finite element model was validated first against the experimental results. Then, we demonstrated three different scenarios in...

A Curved Compliant Differential Mechanism with Neutral Stability: For the use in Exoskeleton Design

People in healthcare, warehousing, and the agriculture sector all have one thing in common. They require labour which can be demanding on the human body, this could lead to problems in the long term. A way to alleviate these problems is to use a passive exoskeleton. While passive exoskeletons can have a variety of different use cases and types...

Manufacturing method and experimental validation for a zero-stiffness compliant mechanism as a flexible head support

This paper presents a manufacturing method for a zero-stiffness compliant mechanism to be used as a flexible head support. The manufactured design consists of two curved, thin-walled U-beams made of high strength steel. The beams are prestressed in opposite directions to obtain zero torsional stiffness so that rotation of the head is allowed....

Three-step method to design the preload of geometries to create spatial large range of motion zero-stiffness compliant mechanisms

Stiffness compensation for piezoelectric energy harvesting: Improving the efficiency at low-frequency vibrations

In the field of vibration energy harvesting, vibration energy is tranduced to electrical energy to power small, low powered devices. Many energy harvesters are produced in the form of a resonator, where resonant amplification enables efficient operation of the energy harvester. At low frequencies below 10 hz, input motions quickly increase for a...

A stiffness compensated piezoelectric energy harvester for low-frequency excitation

In this work, a stiffness compensated piezoelectric vibration energy harvester is modelled and tested for low-frequency excitations and large input amplitudes. Attracting magnets are used to introduce a negative stiffness that counteracts the stiffness of the piezoelectric beam. This results into a nearly statically balanced condition and...

Neutrally stable transition of a curved-crease planar shell structure

Elastic neutral stability in compliant mechanisms is a remarkable appearance since it requires the energetic state of the structure to remain unchanged during a deformation mode. Several examples in literature require either plastic deformation or external constraints to be enforced to obtain a state of pre-stress and often require the use of...

Monolithic binary stiffness building blocks for mechanical digital machines

We introduce two essential building blocks with binary stiffness for mechanical digital machines. The large scale fully compliant mechanisms have rectilinear and rotational kinematics and use a new V-shaped negative stiffness structure to create two extreme states of stiffness by static balancing. The use of a mechanical bistable switch...

Towards Neutrally Stable Compliant Shells

Elastic neutral stability involves elastic deformation without stiffness or loads. It is a remarkable appearance, since the deformation of materials is normally associated with an increase of potential energy and a resulting opposing reaction force or moment. Neutrally stable mechanisms can be used to overcome unnecessary actuation which makes...

Zero stiffness composite shells using thermal prestress

Compliant shell mechanisms are thin walled structures that achieve their motion through deformation. Shell mechanisms are of recent interest for designing exoskeletons that are inconspicuous. One of the challenges in designing shell mechanisms is getting as much compliance as possible in certain directions while keeping the other directions...

Vibration energy harvesting: Optimal non-linear motion

An increased amount of work is done towards opti- mizing the mechanical design of vibrational energy harvesters in order to cope with varying ambient conditions. Here the performance of a piezoelectric energy harvester with varying non-linear spring characteristics is modelled and experimentally veri- fied, determining the optimal non-linear...

Statically Balanced Compliant Mechanisms: Theory and Synthesis

Design of a zero stiffness six degrees of freedom compliant precision stage

This paper presents the first zero stiffness six degrees of freedom (DoF) compliant precision stage. To deal with problems like backlash, friction and lubrication for performing ultra-precise positioning in a vacuum environment, a novel compliant structure is proposed. All six degrees of freedom are statically balanced (i.e. near zero stiffness)...

Linear Motion Systems. A Modular Approach for Improved Straightness Performance

This thesis deals with straight motion systems. A modular approach has been applied in order to find ways to improve the performance. The main performance parameters that are considered are position accuracy, repeatability and, to a lesser extent, cost. Because of the increasing requirements to positioning systems, concerning accuracy,...