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Symmetric Kinetostatic Behavior From Asymmetric Spatially Curved Beams

Amoozandeh, A. (author), Radaelli, G. (author), Herder, J.L. (author)

A cantilevered rod's endpoint has a symmetric stiffness profile throughout its range of motion. Generally, this is not the case for spatially curved compliant beams, particularly if they are asymmetric, i.e., their fixation is not in the symmetry plane of their endpoint operating field. This paper discusses a technique for obtaining symmetric...

journal article 2023

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Neutrally stable double-curved shells by inflection point propagation

Kok, Sjaak (author), Amoozandeh, A. (author), Radaelli, G. (author)

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...

journal article 2023

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Reversible shape morphing of a neutrally stable shell by untethered local activation of embedded Ni-Ti wires

van der Lans, Daan (author), Amoozandeh, A. (author), Radaelli, G. (author)

This paper presents a novel shape morphing concept, which exploits neutral stability to achieve reversible shape morphing. The concept is based on actively changing the material stiffness on a local level in order to perturb the neutral stability and thus induce the shell to deform. This concept is realized by embedding Ni-Ti wires in a...

journal article 2023

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A compliant Continuously Variable Transmission (CVT)

Amoozandeh, A. (author), Herder, J.L. (author), Radaelli, G. (author)

Continuously Variable Transmissions (CVT) can serve as subsystems for a variety of machineries and robotic systems. A compliant CVT mechanism based on the warping of twisting beams is presented here. The design works based on the demonstrated fact that the twist on one side of a beam can be transferred via sectional warping and propagate...

journal article 2023

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Characterization of spatially curved beams with anisotropically adaptive stiffness using sliding torsional stiffeners

Amoozandeh, A. (author), Radaelli, G. (author), van de Sande, W.W.P.J. (author), van Ostayen, R.A.J. (author), Herder, J.L. (author)

Compliant mechanisms (CM) with adaptive stiffness have been widely used in robotics and machine design applications. This paper proposes adapting the endpoint stiffness of a spatially curved compliant beam using a movable torsional stiffener and a new graphical characterization method for the resulting anisotropic stiffness of the endpoint...

journal article 2022

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A Curved Compliant Differential Mechanism With Neutral Stability

Mak, Robin (author), Amoozandeh, A. (author), Radaelli, G. (author), Herder, J.L. (author)

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. In this paper, a curved lightweight compliant type of differential mechanism is presented. This mechanism acquires...

conference paper 2022

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Neutrally stable transition of a curved-crease planar shell structure

Kok, Sjaak (author), Radaelli, G. (author), Amoozandeh Nobaveh, A. (author), Herder, J.L. (author)

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...

journal article 2021

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Asymmetric Spatial Beams with Symmetric Kinetostatic Behaviour

Amoozandeh, A. (author), Radaelli, G. (author), Herder, J.L. (author)

A method to achieve symmetric kinetostatic behaviour in an extensive working range at the endpoint of an asymmetric spatial beam, using cross-section optimization, is presented. The objective function of the optimization is defined as expanding the beam working range to the desired region, simultaneously maximizing symmetric behaviour in it....

book chapter 2021

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A Design Tool for Passive Wrist Support

Amoozandeh, A. (author), Radaelli, G. (author), Herder, J.L. (author)

A design tool for passive wrist support using compliant spatial beams as gravity balancer is presented. The aim of this assistive device is to reduce required effort for pronation-supination and flexion-extension by 70% to help patients with muscular weakness keeping their hand’s posture and doing daily tasks, while the forearm is rested. To...

conference paper 2021

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Passive autonomy: Hygromorphic rotational actuators

Joosten, Sebastiaan (author), Radaelli, G. (author), Vallery, H. (author)

Inspired by phenomena in the plant world, a meteoro-sensitive rotational actuator is developed. The design uses a hygro-active shell, whose water-based swelling is restricted at selective locations to form a helicoid structure. The influence of geometrical parameters on the performance is investigated using a numerical analysis of various...

journal article 2021

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Reverse-twisting of helicoidal shells to obtain neutrally stable linkage mechanisms

Radaelli, G. (author)

Mechanisms that consist of many elements and are potentially small sized, benefit from kinematic elementary units like revolute joints that are compliant and monolithic, and therefore could be produced without need for assembly. We present a novel concept of a compliant revolute joint that features low axis drift, high support stiffness and a...

journal article 2021

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The design of a compliant shape-preserving ring

Schreurs, K. W.A. (author), Radaelli, G. (author), Alijani, F. (author)

Compliant shape-preserving mechanisms fill a small niche within the established research field of compliant mechanisms. To date no report exists on a compliant shape-preserving ring, even though these mechanisms can give rise to a multitude of practical applications. They can essentially act as novel sealing mechanisms, compliant grippers or...

journal article 2020

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Study on the large-displacement behaviour of a spiral spring with variations of cross-section, orthotropy and prestress

Radaelli, G. (author), Herder, J.L. (author)

This work is dedicated to the study of the large-displacement behaviour of a spiral spring. Parameters that influence the local torsion stiffness of the beam that constitutes the spiral are varied and their effect is studied. Cross-sectional shape, orthotropic material orientation and prestress are the three classes of parameters that are...

journal article 2018

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Synthesis of mechanisms with prescribed elastic load-displacement characteristics

Radaelli, G. (author)

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...

doctoral thesis 2017

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Inspiration from folding patterns

Rommers, J. (author), Radaelli, G. (author), Herder, J.L. (author)

Origami is generally associated with decorative art, not the engineering<br/>world. For some time now, however, engineers have been using the gigantic<br/>database of origami folding patterns as inspiration for designing deployable<br/>mechanisms that can be fabricated efficiently from a flat sheet material.<br/>Most of these mechanisms do not...

journal article 2017

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Static balancing of an inverted pendulum with prestressed torsion bars

Radaelli, G. (author), Buskermolen, R. (author), Barents, R (author), Herder, J.L. (author)

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...

journal article 2017

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Gravity balanced compliant shell mechanisms

Radaelli, G. (author), Herder, J.L. (author)

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...

journal article 2017

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Design and optimization of a general planar zero free length spring

Delissen, A.A.T.M. (author), Radaelli, G. (author), Herder, J.L. (author)

A zero free length (ZFL) spring is a spring with special properties, which is commonly used in static balancing. Existing methods to create ZFL springs all have their specific drawbacks, which rises to the need of a new method to create such a spring. A method is proposed to design planar ZFL springs with specified stiffness (250–750 N/m)...

journal article 2017

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A monolithic compliant large-range gravity balancer

Radaelli, G. (author), Herder, J.L. (author)

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...

journal article 2016

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Shape optimization and sensitivity of compliant beams for prescribed load-displacement response

Radaelli, G. (author), Herder, J.L. (author)

This paper presents the shape optimization of a compliant beam for prescribed load-displacements response. The analysis of the design is based on the isogeometric analysis framework for an enhanced fidelity between designed and analysed shape. The sensitivities used for an improved optimization procedure are derived analytically, including...

journal article 2016