Lennart Rubbert

National Institute of Applied Science | INSA · Department of Mechatronics

Flexure mechanism design is an art, and this book provides the theoretical and practical foundation for scientists and engineers to express their creativity in this field. Flexure mechanisms, also known as compliant mechanisms, rely on the elasticity of matter to provide motion to mechanism linkages. Flexure mechanisms eliminate the disadvantages o...

Snake-like robots applications include surveillance and exploration of confined environments where human presence is incompatible. The attractiveness of this type of mechatronic structure is notably linked to the modular character and the hyper-redundancy of their architecture, which gives it both mechanical robustness and great manoeuvrability. Ho...

In this paper, the development of a method for the design of soft pneumatic actuators is described. The focus is given on the interest of using a deep learning model to explore the design space with a genetic algorithm. In particular, we propose to perform the automatic synthesis of the inner structure of pneumatic actuators using Bézier curves and...

Technological advances in additive manufacturing have made it possible to exploit composite materials, such as carbon-doped filaments, synthesised for specific function with tailored properties. The integration of carbon fibres, with good electrical and thermal conductivity, within an insulating polylactic acid (PLA) matrix produces a conductive fu...

The diagnosis and the treatment of gastrointestinal pathologies have experienced significant development in recent years with the invention of endoscopic capsules which facilitate the access to different sections of the gastrointestinal tract. At a research level, the concept of capsules has been used to perform several functions such as gastrointe...

In this paper, the use of the Kresling tower origami as a building block for compliant mechanism design is considered. Design tools to help building systems using this origami are introduced. First, a model which can describe the tower kinematics during its deployment is introduced. This model is exploited to link the origami pattern geometry to th...

In this paper, the use of the Kresling tower origami as a building block for compliant mechanism design is considered. Two contributions are introduced to develop a synthesis method of such a building block. First, models to link the origami pattern geometry to the Kresling tower kinematics are derived. The position of stable configurations, the le...

Manipulation at the sub-micron scale often requires force-sensing capabilities of milli- to nanonewton forces. This article presents a novel design of a compliant load cell with mechanically adjustable stiffness. The system enables adapting force sensitivity to the requirements of a specific application. The principle of the stiffness adjustment is...

Compliant Wren mechanisms (CWM) constitute specific compliant structures of particular interest. Derived from Wren mechanisms, they can exhibit a large variety of motions, from quasi translation to quasi rotation. In this paper, the development of models for the analysis and synthesis of CWM is considered. A kinematic model is introduced first to a...

In this paper, we introduce the design of a variable-diameter wheel for mobile robots. The goal is to improve maneuverability and crossing capacity of such robots by actively controlling the diameter of wheels. Origami patterns have been recently considered in robotics for the design of compliant and deployable structures. In our context, complianc...

In this paper, we present an experimental evaluation of tactile feedback for remote needle insertion in soft tissues. A needle with tip force sensing is used to detect changes of tissues and puncture events during insertion. This information is provided to the user during teleoperation by means of a tactile display. Evaluation is conducted by repro...

Bistable mechanisms can be used for performing specific functions such as locking or negative stiffness generation. These compliant structures are then of interest at different scales, with different corresponding manufacturing technologies. One of them is additive manufacturing, which is interesting for the integration of such structures. Although...

Remote manipulation in robotized percutaneous procedures can offer increased safety to radiologists as well as patients. Providing feedback to the radiologist on needle-tissue interactions is however mandatory in addition to the medical images. A tactile feedback strategy is developed in this paper. Two types of information are considered: tissue p...

The use of mechanical bistable structures in the design of microrobots and mesorobots has many advantages especially for flexible robotic structures. However, depending on the used fabrication technology, the adequacy of theoretical and experimental mechanical behaviors can vary widely. In this paper, we present the manufacturing results of bistabl...

Microbiota analysis is a fundamental element for a better understanding of microbiota role, its relationship with the human body and its impact on different pathologies. There is today no non-invasive tool for easy collection of the microbiota in the small intestine. In this paper, we describe the development of such a device that opens the way to...

Classical mechanical watch plain bearing pivots have frictional losses limiting the quality factor of the hairspring-balance wheel oscillator. Replacement by flexure pivots leads to a drastic reduction in friction and an order of magnitude increase in quality factor. However, flexure pivots have drawbacks including gravity sensitivity, nonlinearity...

Robot design in contexts such as computer-assisted medical interventions remains challenging. Compact, dexterous mechanisms with particular mobilities are needed, the synthesis of which requires a systematic evaluation of workspace and singular positions. The evaluation of singular positions and their classification are still difficult to perform i...

In previous work, we showed that two degree of freedom oscillators can be advantageously applied to horological time bases since they can be used to eliminate the escapement mechanism. We subsequently examined planar two degree of freedom oscillators based on parallel flexure stages. We noted that these oscillators are strongly affected by the orie...

Compliant mechanisms are of great interest in precision engineering. In this paper, we propose a higher-order continuation method to help their rigid-body kinematic design. The method helps to investigate the choice of a mechanism configuration through the whole exploration of the workspace, and eases the kinematic analysis to avoid, or take advant...

Classical pivots have frictional losses leading to the limited quality factor of oscillators used as time bases in mechanical watches. Flexure pivots address these issues by greatly reducing friction. However, they have drawbacks such as gravity sensitivity and limited angular stroke. This paper analyses these problems for the cross-spring flexure...

An original exploration strategy for the analysis of parallel mechanisms based on a generic higher-order continuation method is proposed for accurate calculation of the numerical solutions. The method requires the closed-loop kinematic equations only, which makes it easy to implement. As an illustration, the paper discusses the kinematic analysis o...

We define isotropic springs to be central springs having the same restoring force in all directions. In previous work, we showed that isotropic springs can be advantageously applied to horological time bases since they can be used to eliminate the escapement mechanism. This paper presents our designs based on planar serial 2–DOF linear isotropic sp...

The mechanical isotropic harmonic oscillator comprises at least a two degrees of freedom linkage supporting an orbiting mass with respect to a fixed base with springs having isotropic and linear restoring force properties wherein the mass has a tilting motion. The oscillator may be used in a timekeeper, such as a watch.

The mechanical isotropic harmonic oscillator comprises at least a two degrees of freedom linkage supporting an orbiting mass with respect to a fixed base with springs having isotropic and linear restoring force properties wherein the mass has a tilting motion. The oscillator may be used in a timekeeper, such as a watch.

The mechanical isotropic harmonic oscillator comprises at least a two degrees of freedom linkage supporting an orbiting mass with respect to a fixed base with springs having isotropic and linear restoring force properties. The oscillator may be used in a timekeeper, such as a watch.

Résumé Depuis son introduction en 1675, le balancier-spiral est la base de temps exclusive de la montre mécanique. Or cet oscillateur présente deux difficultés limitatives qui n'ont jusqu'à présent pas été contournées : un facteur de qualité limité (en particulier par des phénomènes tribologiques), ainsi que la nécessité d'un échappement, mécanisme...

The rigid-body replacement method is often used when designing a compliant mechanism. The stiffness of the compliant mechanism, one of its main properties, is then highly dependent on the initial choice of a rigid-body architecture. In this paper, we propose to enhance the efficiency of the synthesis method by focusing on the architecture selection...

In this paper we present the design of a compact active cardiac stabilizer based on planar compliant mechanisms and piezoelectric actuators. Considering an assembly of planar manufactured structures helps to simplify the manufacturing process and may increase the compactness. Parallel architectures constitute interesting solutions for their intrins...

Surgical robotics helps to increase the surgeon's accuracy and limits the invasiveness of the surgery. The complexity of an operation room implies to design surgical devices that are as compact as possible and that can be easily sterilized. One interesting design approach is to combine compliant mechanisms, which have a monolithic structure, and pi...

This paper presents a design method dedicated to compliant mechanisms, with emphasis on the use of ant colony optimization to determine the optimal geometry of a mechanism. Ant colony optimization is of particular interest because it does not need any fine tuning of its internal parameters. This robustness and the efficiency of the design method ar...

Giving assistance to surgeons during beating heart procedures is currently a great challenge in medical robotics: a high level of safety is required while the beating heart yields high forces and dynamics. In this article, we investigate the design of an active cardiac stabilizer that will provide a motionless area of interest during the surgery. A...

A new design method for parallel compliant mechanisms based on the singularity analysis of parallel mechanisms is presented in this paper. Here a 3-US parallel mechanism is introduced and its singular configurations are analyzed with Grassmann–Cayley algebra for the design of a compliant mechanism with RRP mobilities. A novel architecture of compli...

In this paper, three aspects of the use of compliant mechanisms for a new surgical tool, an active cardiac stabilizer, are outlined. First, the interest of compliant mechanisms in the design of the stabilizer is demonstrated with in vivo experimental evaluation of the efficiency of a prototype. We then show that the specific surgical constraints le...