Experimental Characterization of a Binary Actuated Parallel Manipulator

This paper describes the BAPAMAN (Binary Actuated Parallel MANipulator) series of parallel manipulators that has been conceived at LARM. Basic common characteristics of BAPAMAN series are described. In particular, it is outlined the use of a reduced number of active degrees of freedom, the use of design solutions with flexural joints and Shape Memory Alloy (SMA) actuators for achieving miniaturization, cost reduction and easy operation features. Given the peculiarities of BAPAMAN architecture, specific experimental tests have been proposed and carried out with the aim to validate the proposed design and to evaluate the practical operation performance and the characteristics of a built prototype, in particular, in terms of operation and workspace characteristics

An anthropomorphic soft skeleton hand exploiting conditional models for piano playing.

The development of robotic manipulators and hands that show dexterity, adaptability, and subtle behavior comparable to human hands is an unsolved research challenge. In this article, we considered the passive dynamics of mechanically complex systems, such as a skeleton hand, as an approach to improving adaptability, dexterity, and richness of behavioral diversity of such robotic manipulators. With the use of state-of-the-art multimaterial three-dimensional printing technologies, it is possible to design and construct complex passive structures, namely, a complex anthropomorphic skeleton hand that shows anisotropic mechanical stiffness. We introduce a concept, termed the "conditional model," that exploits the anisotropic stiffness of complex soft-rigid hybrid systems. In this approach, the physical configuration, environment conditions, and conditional actuation (applied actuation) resulted in an observable conditional model, allowing joint actuation through passivity-based dynamic interactions. The conditional model approach allowed the physical configuration and actuation to be altered, enabling a single skeleton hand to perform three different phrases of piano music with varying styles and forms and facilitating improved dynamic behaviors and interactions with the piano over those achievable with a rigid end effector

Enhanced stiffness modeling of manipulators with passive joints

The paper presents a methodology to enhance the stiffness analysis of serial and parallel manipulators with passive joints. It directly takes into account the loading influence on the manipulator configuration and, consequently, on its Jacobians and Hessians. The main contributions of this paper are the introduction of a non-linear stiffness model for the manipulators with passive joints, a relevant numerical technique for its linearization and computing of the Cartesian stiffness matrix which allows rank-deficiency. Within the developed technique, the manipulator elements are presented as pseudo-rigid bodies separated by multidimensional virtual springs and perfect passive joints. Simulation examples are presented that deal with parallel manipulators of the Ortholide family and demonstrate the ability of the developed methodology to describe non-linear behavior of the manipulator structure such as a sudden change of the elastic instability properties (buckling)

Desktop microforming and welding system powered by a flextensional Terfenol-D transducer

Magnetostrictive Terfenol-D was examined as a prime-mover for bulk motion in a microforming system. Careful design and analysis led to the creation of a Terfenol-D transducer capable of 3.8 kN of blocked force and 212 µm of displacement. A linear model of the Terfenol-D transducer to simulate its output as a function of displacement under saturation magnetic field was created that matched both force and displacement within 10%. Thermal drift occurred at a rate of 2 µm/ºC. A flextensional lever system was designed to amplify the displacement of the Terfenol-D transducer to levels sufficient for microforming. Sub-micron displacement resolution was observed, with no perceivable effects from friction or backlash. The full system provided 365 N of blocked force and 1.6 mm of displacement. A linear model of the full system was also created that used the linear model of the transducer\u27s output which matched experimental results for displacement with a 2% error and force with an 11% error, which was found to be useful for selection of design parameters. In ultrasonic-assisted punching, a circular punch of 3.2 mm diameter that vibrates transversely at 9.6 kHz was used to punch samples of 1100-O at several punching speeds and vibration intensities. Higher speed punching tests showed up to a 30% reduction in punching force accompanied by an apparent elimination of adiabatic strain rate effects. Lower speed punching showed a smaller degree of softening, but an increased burnished-to-fractured area ratio. A study on the effects of vibration waveform on a polymer vibration welding process on 0.25 and 0.5 mm ABS sheet was conducted using sine, square, and triangle waves at differing penetration depths. A preliminary study was first used to determine control levels of basic welding parameters that compared the effects of clamping load and penetration depth on the two sheet thicknesses. It was found that square waves provided slightly higher penetration rates than sine waves, and triangle waves significantly lower penetration rates than sine waves. Penetration rates and achievable penetration depths varied with sheet thickness. A minimum penetration rate threshold was found below which it was not possible to achieve adequate penetration; beyond this lower penetration rates generally resulted in higher strength

Design and modeling of a compliant mechanism

Compliant mechanisms are widely used in high precision systems, because they provide high resolution, frictionless, smooth and continuous motion. These kinds of mechanisms are also cheaper than the other types of high precision mechanisms. The main idea of this kind of mechanism is that no additional joints are used for creating the motion, the deflection of the flexible elements are used to create the desired motion. In this thesis, a planar parallel compliant mechanism is designed. The mechanism is actuated from three ends by using piezo mike micromotors to create motion in XY plane. The mathematical model of the mechanism is derived by using Euler Bernoulli dynamic equation for the three beams on the mechanism. The separation of variables technique is used to solve the dynamic equations. Necessary transformations are calculated for defining the center position of the stage in terms of the deflections of the beam. The mathematical model is represented in state space form and it is simulated in MATLAB Simulink. The position results are compared with another simulation called COMET. The mathematical model is reduced to two input and two output system in order to make the XY position control of the mechanism by using PID control. Finally, the mechanism is manufactured by using laser cutting and water jet cutting techniques, open loop experiments of the mechanism are verified by actuating the piezo motors manually and by giving voltage signal

A novel approach to micro-telemanipulation with soft slave robots: integrated design of a non-overshooting series elastic actuator

Micro mechanical devices are becoming ubiquitous as they find increas- ing uses in applications such as micro-fabrication, micro-surgery and micro- probing. Use of micro-electromechanical systems not only offer compactness and precision, but also increases the efficiency of processes. Whenever me- chanical devices are used to interact with the environment, accurate control of the forces arising at the interaction surfaces arise as an important chal- lenge. In this work, we propose using a series elastic actuation (SEA) for micro- manipulation. Since an SEA is an integrated mechatronic device, the me- chanical design and controller synthesis are handled in parallel to achieve the best overall performance. The mechanical design of the μSEA is handled in two steps: type selection and dimensional synthesis. In the type selection step, a compliant, half pantograph mechanism is chosen as the underlying kinematic structure of the coupling element. For optimal dimensioning, the bandwidth of the system, the disturbance response and the force resolution are considered to achieve good control performance with high reliability. These objectives are achieved by optimizing the manipulability and the stiffness of the mechanism along with a robustness constraint. In parallel with the mechanical design, a force controller is synthesized. The controller has a cascaded structure: an inner loop for position control and an outer loop for force control. Since excess force application can be detrimental during manipulation of fragile objects; the position controller of the inner loop is designed to be a non-overshooting controller which guar- antees the force response of the system always stay lower than the reference value. This self-standing μSEA system is embedded into a 3-channel scaled tele- operation architecture so that an operator can perform micro-telemanipulation. Constant scaling between the master and the slave is implemented and the teleoperator controllers preserve the non-overshooting nature of the μSEA. Finally, the designed μSEA based micro-telemanipulation system is im- plemented and characterized

Workshop on "Robotic assembly of 3D MEMS".

Proceedings of a workshop proposed in IEEE IROS'2007.The increase of MEMS' functionalities often requires the integration of various technologies used for mechanical, optical and electronic subsystems in order to achieve a unique system. These different technologies have usually process incompatibilities and the whole microsystem can not be obtained monolithically and then requires microassembly steps. Microassembly of MEMS based on micrometric components is one of the most promising approaches to achieve high-performance MEMS. Moreover, microassembly also permits to develop suitable MEMS packaging as well as 3D components although microfabrication technologies are usually able to create 2D and "2.5D" components. The study of microassembly methods is consequently a high stake for MEMS technologies growth. Two approaches are currently developped for microassembly: self-assembly and robotic microassembly. In the first one, the assembly is highly parallel but the efficiency and the flexibility still stay low. The robotic approach has the potential to reach precise and reliable assembly with high flexibility. The proposed workshop focuses on this second approach and will take a bearing of the corresponding microrobotic issues. Beyond the microfabrication technologies, performing MEMS microassembly requires, micromanipulation strategies, microworld dynamics and attachment technologies. The design and the fabrication of the microrobot end-effectors as well as the assembled micro-parts require the use of microfabrication technologies. Moreover new micromanipulation strategies are necessary to handle and position micro-parts with sufficiently high accuracy during assembly. The dynamic behaviour of micrometric objects has also to be studied and controlled. Finally, after positioning the micro-part, attachment technologies are necessary

Dynamics and Controls of Fluidic Pressure-Fed Mechanism (FPFM) of Nanopositioning System

Flexure or compliant mechanisms are employed in many precisions engineered devices due to their compactness, linearity, resolution, etc. Yet, critical issues remain in motion errors, thermal instability, limited bandwidth, and vibration of dynamic systems. Those issues cannot be negligible to maintain high precision and accuracy for precision engineering applications. In this thesis, a novel fluidic pressure-fed mechanism (FPFM) is proposed and investigated. The proposed method is designing internal fluidic channels inside the spring structure of the flexure mechanism using the additive manufacturing (AM) process to overcome addressed challenges. By applying pneumatic/hydraulic pressure and filling media into fluidic channels, dynamic characteristics of each spring structure of the flexure mechanism can be altered or adjusted to correct motion errors, increase operating speed, and suppress vibration. Additionally, FPFM can enhance thermal stability by flowing fluids without affecting the motion quality of the dynamic system. Lastly, the motion of the nanopositioning system driven by FPFM can provide sub-nanometer resolution motion, and this enables the nanopositioning system to have two linear motion in a monolithic structure. The main objective of this thesis is to propose and validate the feasibility of FPFM that can ultimately be used for a monolithic FPFM dual-mode stage for providing high positioning performance without motion errors while reducing vibration and increasing thermal stability and bandwidth

Int.rnational Conkrsnca on Robotlu h AutDmatlon New Orbans. IA- Aprll2W4 Analysis and Design of Parallel Mechanisms with Flexure Joints

Abstract-Flexure joints are frequently used in precision mo-tion stages and micro-robotic mechanisms due lo their monolithic construction. The joint compliance, howeyer, can affect the static and dynamic performance of the overall mechanism. In this paper, we consider the analysis and design of general platform type parallel mechanisms containing flexure joints. We consider static performance measures such as task space stiffness and manipulability, while subject to constraints such as joint stress, mechanism size, workspace volume, and dynamic characteristics Based on these performance measures and constraints, we adopt the multi-ohjedive optimization approach. We first obtain the Pareto frontier, which can lhen he used to select the desired design parameters based on secondary criteria such as performance sensitivity. To simplify presentation, we consider only lumped ap-proximation of flexure joints in the pseudo-rigid-body approach. A planar mechanism is included to illustrate the analysis and design techniques. Tools presented in this paper cm also he applied to a broader class of compliant mechanisms, including robots with inherent joint flexibility as well as complianl robots for contact tasks. I