98 research outputs found
A Compliant PKM Mesomanipulator: Kinematic and Dynamic Analyses.
The kinematic and dynamic analyses of a PKM mesomanipulator are addressed in this paper: the proposed robot architecture allows only pure translations for the mobile platform, while the presence of flexure hinges introduces compliance into the structure. The analytical solutions to direct and inverse kinematic problems are evaluated after a brief introduction of the basic adopted nomenclature, the manipulator workspace and the robot singularity configurations are then described, and the analytical solution to the inverse dynamic problem is presented. Thereafter, an overview on some of the simulations results obtained through a software implementation of the described algorithms is addressed, and the most salient aspects of this topic are summarized in the final conclusions
Large deflection of a non-linear, elastic, asymmetric Ludwick cantilever beam subjected to horizontal force, vertical force and bending torque at the free end
The investigated cantilever beam is characterized by a constant rectangular cross-section and is subjected to a concentrated constant vertical load, to a concentrated constant horizontal load and to a concentrated constant bending torque at the free end. The same beam is made by an elastic non-linear asymmetric Ludwick type material with different behavior in tension and compression. Namely the constitutive law of the proposed material is characterized by two different elastic moduli and two different strain exponential coefficients. The aim of this study is to describe the deformation of the beam neutral surface and particularly the horizontal and vertical displacements of the free end cross-section. The analysis of large deflection is based on the Euler-Bernoulli bending beam theory, for which cross-sections, after the deformation, remain plain and perpendicular to the neutral surface; furthermore their shape and area do not change. On the stress viewpoint, the shear stress effect and the axial force effect are considered negligible in comparison with the bending effect. The mechanical model deduced from the identified hypotheses includes two kind of non-linearity: the first due to the material and the latter due to large deformations. The mathematical problem associated with the mechanical model, i.e. to compute the bending deformations, consists in solving a non-linear algebraic system and a non-liner second order ordinary differential equation. Thus a numerical algorithm is developed and some examples of specific results are shown in this paper. © Springer Science+Business Media Dordrecht 2014
Innovative modular SMA actuator
A modular design for a shape memory actuator is proposed. The actuator is able to perform linear movements, while the modularity allows force and/or stroke improvements. Experimental results show how the behavior of the proposed implementation is sufficient for a wide class of problems and can be improved with proper developments
Robotics rehabilitation of the elbow based on surface electromyography signals
Physical rehabilitation based on robotic systems has the potential to cover the patient’s need of improvement of upper extremity functionalities. In this article, the state of the art of resistant and assistive upper limb exoskeleton robots and their control are thoroughly investigated. Afterward, a single-degree-of-freedom exoskeleton matching the elbow–forearm has been advanced to grant a valid rehabilitation therapy for persons with physical disability of upper limb motion. The authors have focused on the control system based on the use of electromyography signals as an input to drive the joint movement and manage the robotics arm. The correlation analysis between surface electromyography signal and the force exerted by the subject was studied in objects’ grasping tests with the purpose of validating the methodology. The authors developed an innovative surface electromyography force–based active control that adjusts the force exerted by the device during rehabilitation. The control was validated by an experimental campaign on healthy subjects simulating disease on an arm, with positive results that confirm the proposed solution and that open the way to future researches
Automatic Procedures as Help for Optimal Cam Design
ABSTRACT
In this work we suggest a synthesis of recent results
obtained on the application of soft-computing techniques to
solve typical automatic machines design problems. Particularly,
here we show an optimization method based on the application
of a specialized algorithms ruled by a generalized software
procedures, which appears able to help the mechanical designer
in the first part of the design process, when he has to choose
among different wide classes of solutions. In this frame, among
the different problems studied, we refer here about the choice
of the best class of motion profiles, to be imposed to a cam
follower, which must satisfy prefixed design specifications. A
realistic behaviour of the system is considered and the
parameter model identification is set up by a soft computing
procedure. The design, based on theoretical knowledge,
sometimes is not sufficient to fulfil desired dynamical
performances, in this situation, a residual optimization is
achieved with the help of another optimizing method.
The problem of a cam-follower design is presented. A class
of motion profiles and the best theoretical motion profile is
selected by an evolutionary algorithm. A realistic model is
considered and its parameter identification is achieved by a
genetic algorithm. The residual optimization is achieved by a
servomotor optimized by another genetic algorithm.
Evolutionary approach is used during all the design process
and, as was shown, it allows really interesting performance in
terms of simplicity of the design process and in terms of
performance of the product
Machine tools thermostabilization using passive control strategies
The aim of this study is to investigate passive control strategies using Phase Change Materials in Machine Tools (MTs) thermostabilization. By considering the main issues related to the thermal stability, authors presented the application of novel multifunctional materials to Machine Tools structures. A set of advanced materials are considered: aluminium foams, corrugate-core sandwich panels and polymeric concrete beds. The adopted solutions have been infiltrated by phase change materials (PCMs) in order to maintain the thermal stability of MTs when the environmental temperature is perturbed. The paper shows the results of simulative and experimental tests
Precision point design of a cam indexing mechanism
This work regards on the design of a cylindrical cam indexing mechanism with a motion law that passes through a positional precision point. A numerical algorithm is proposed to solve this problem and, particularly, a genetic algorithm. The algorithm and the encoding of the problem are described
PKM mechatronic clamping adaptive device
This study proposes a novel adaptive fixturing device based on active clamping systems for smart micropositioning of thin-walled precision parts. The modular architecture and the structure flexibility make the system suitable for various industrial applications. The proposed device is realized as a Parallel Kinematic Machine (PKM), opportunely sensorized and controlled, able to perform automatic error-free workpiece clamping procedures, drastically reducing the overall fixturing set-up time. The paper describes the kinematics and dynamics of this mechatronic system. A first campaign of experimental trails has been carried out on the prototype, obtaining promising results
Design of an innovative olive picking machine
This work describes the complete design of an olive picking machine especially conceived for secular olive plants with the purpose of increasing the mechanization level of the harvest operation and permitting the production of high quality oil; the design is made considering all the mechanical, agronomical and economical aspects involved in this issue. Once defined the picking technique, the first step consists in the design of the shacking device used for the separation of the olives from the plant, the next step is the design of the support structure, including the arms and the frame; finally there is a description of the hydraulic plant that drives the moving parts of the machine; in order to increase the flexibility of the machine, it is adapted also for other works, like pruning, that can be performed outside the harvest season. Starting from the principal characteristics of the cultivations the design of the machine and its implementation is realized considering all functional features, including verifications of resistance according to the current standards; finally the economic aspects are hinted to confirm the marketing appeal of the machine
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