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...

Design And Evaluation Of A Balanced Compliant Laparoscopic Grasper

In laparoscopic surgery, quality of haptic feedback is reduced compared to conventional surgery, leading to unintentional tissue damage during grasping. From the perspective of haptics, poor mechanical design of laparoscopic instrument joints induces friction and a nonlinear actuation-tip force relation. In this study, a novel laparoscopic...

Stiffness Compensation Through Matching Buckling Loads in a Compliant Four-Bar Mechanism

In this paper, a novel alternative method of stiffness compensation in buckled mechanisms is investigated. This method involves the use of critical load matching, i.e., matching the first two buckling loads of a mechanism. An analytical simply supported five-bar linkage model consisting of three rigid links, a prismatic slider joint, and four...

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...

Compliant Mechanisms That Use Static Balancing to Achieve Dramatically Different States of Stiffness

Stiffness in compliant mechanisms can be dramatically altered and even eliminated entirely by using static balancing. This requires elastic energy to be inserted before operation, which is most often done with an additional device or preloading assembly. Adding such devices contrasts starkly with primary motivations for using compliant...

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...

A method for tuning the stiffness of building blocks for statically balanced compliant ortho-planar mechanisms

In this paper a method is demonstrated for tuning the stiffness of building blocks for statically balanced compliant ortho-planar mechanisms. Three post-buckled mechanisms are proposed where the flexural rigidity can be manipulated over a part of their length in order to tune the ratio between the first two critical loads. A sensitivity...

Bennett Based Balanced Butterfly Linkage, Deployable Linkage with Inherent Balance

In this paper it is shown how a 2-DoF inherently force balanced spatial deployable Butterfly Linkage is found consisting of four entangled similar Bennett linkages moving synchronously and with the common center of mass in the central joint. This linkage is derived from the Grand 4R Four-Bar Based Inherently Balanced Linkage Architecture by...

Synthesis of mechanisms with prescribed elastic load-displacement characteristics

In this dissertation a collection of concepts to synthesise nonlinear springs is presented. Such springs can be useful in various application domains where, e.g., multi-stability or static balancing is desired. These behaviors are often sought to alleviate the effort required for actuation. The explored concepts are presented by showing the...

Static balancing of an inverted pendulum with prestressed torsion bars

This paper presents a method for the design of a statically balanced inverted pendulum. The non-linear moment-rotation characteristic of the pendulum's weight is approximated by a piecewise linear characteristic. Each transition is realized by engaging or disengaging one or more torsion bars, by means of mechanical stops. The whole set of...

Gravity balanced compliant shell mechanisms

The research on compliant shell mechanisms is a new and promising expansion of the well established compliant mechanisms research area. Benefits of compliant shell mechanisms include being spatial and slender, having organic shapes and their high tailorability of the load-displacement response. This work focusses on the design of a shell with...

A monolithic compliant large-range gravity balancer

A new monolithic fully compliant gravity balancer is designed with help of a design approach based on shape optimization. The balancer consists of one single clamped-clamped complex-shaped beam on which a weight is attached. The beam is modeled as a planar isogeometric Bernoulli beam. The goal function of the optimization consists of an...

Parameter analysis for the design of statically balanced serial linkages using a stiffness matrix approach with Cartesian coordinates

A statically balanced system is in equilibrium in every pose. In classical balancing solutions for serial linkages, each DOF is balanced by an independent element. Disadvantages are increased mass and inertia for counter-mass, and auxiliary links for spring solutions. Recent literature presents a method for balancing serial linkages without...

A monolithic compliant large-range gravity balancer

A new monolithic fully compliant gravity balancer is designed with help of a design approach based on shape optimization. The balancer consists of one single complex-shaped beam on which the weight is attached. The beam is modeled as a planar isogeometric Bernoulli beam. The goal function of the optimization consists of an energy based...

Statically Balanced Compliant Mechanisms: Theory and Synthesis

Principle and design of a mobile arm support for people with muscular weakness

This article describes the development of a mobile arm support for people with muscular diseases. The arm support is spring-balanced, with special attention on reduction of operating effort (high balancing quality and low friction), functionality (large range of motion), and aesthetics (inconspicuous design). The spring settings can be adjusted...

Energy-free systems: Theory, conception, and design of statically balanced spring mechanisms