1,721,005 research outputs found
Development of a mechatronic system for the mirror therapy
Full text linkThis paper fits into the field of research concerning robotic systems for rehabilitation. Robotic systems are going to be increasingly used to assist fragile persons and to perform rehabilitation tasks for persons affected by motion injuries. Among the recovery therapies, the mirror therapy was shown to be effective for the functional recovery of an arm after stroke. In this paper we present a master/slave robotic device based on the mirror therapy paradigm for wrist rehabilitation. The device is designed to orient the affected wrist in real time according to the imposed motion of the healthy wrist. The paper shows the kinematic analysis of the system, the numerical simulations, an experimental mechatronic set-up, and a built 3D-printed prototype
On the Kinematics of the gait with jumping stilts
No full textThis work deals with the kinematic analysis of the gait cycle of a subject fitted with jumping stilts. A motion capture analysis was conducted by recording the trajectory of the subject’s free-flying hoof during a complete gait cycle. A six-degrees of freedom serial chain was used to simulate the subject’s legs kinematic on the sagittal plane. The positions and velocities of the subject’s free-flying hoof obtained from the photo-frames of the video and from the kinematic model was used to validate the model
A mechanism for converting revolute motion into harmonic rotating motion
No full textIn this paper, we describe the design and construction of a cam mechanism to convert a revolute motion into a symmetrical oscillating harmonic movement. The mechanism consists of a harmonic cam driven by a revolute electric motor joined to a follower by a desmodromic constraint. The linear reciprocating motion of the follower was then transmitted, by a rack-pinion mechanism, to a final device that oscillates symmetrically. The entire mechanism was designed to be used as the propeller of a boat model. The final device, indeed, will be connected to a tail that propels the boat. On account of the peculiar application for which the device is intended, the need for symmetrical motion of the tail - either in a cycle, from side to side and return, or in a semi-cycle, from side to side - becomes evident. The analysis of the kinematics and the analytic model of its dynamics are presented throughout the paper. A numerical model, able to capture the mechanism performance when the friction effects were taken into account and to predict its behavior when the motion conditions were varied, was developed as well. During construction of the mechanism, efforts were made to reduce friction, weight, and the overall dimensions. Several laboratory tests were carried out in order to clarify the mechanism's performance. Particular care was dedicated to measure the coefficient of friction between the materials of the desmodromic constraint and to the kinematics parameters for validating the design requirements. The dedicated test benches arranged and the data collected from the tests are presented in the paper
Kineto-Elasto-Static Synthesis of a 3-CRU Spherical Wrist for Miniaturized Assembly Tasks
No full textA novel method for the solution of the forward displacement problem of spherical parallel manipulators
No full textRobotic-Like Formulation of the Approximated Body-Guidance Problem
Full text linkA classical problem in the mechanics of mechanisms is the body-guidance synthesis. As first formulated by Burmester, the problem consists of finding the dimensions of a planar four-bar linkage whose coupler link attains a prescribed set of finitely separated poses. The problem is solved either in exact, up to five prescribed poses, or in approximate forms by several methods. Many of them rely on the algebraic geometry to find center- and circle-point loci of the RR dyads composing the mechanism. The method was also used to find the circle-point locus of the PR dyad. In this paper a different approach was followed. We propose a formulation of the problem by using the vector loop equations, usually employed in robotics for kinematic analysis, to obtain the set of nonlinear synthesis equations then solved by advanced and stabilized algorithms. The method allows us to achieve the approximate solution of the body-guidance problem either with RR or PR dyads with high accuracy also including prescribed timing
A benchmark problem with singularities for multibody system dynamics formulations with constraints
Full text linkWhen performing the numerical integration of multibody systems (MBS) dynamics, it is possible to choose from a wide variety of methods and implementations. Selecting the most appropriate option for a particular application is not a straightforward task; as a consequence, several benchmark examples have been formulated by the MBS research community with the intent to assess the accuracy and performance of different solution methods when applied to certain kinds of mechanical problems. This paper introduces a variation of the slider-crank mechanism, already employed as a benchmark problem in the MBS literature, intended to evaluate the performance of formulations that feature kinematic constraints. Three cases, featuring singular configurations and external actions, were defined. The example is used to illustrate some necessary elements in the definition of a benchmark problem and in the process of comparing different solution methods, as well as difficulties that can arise during this task. The use of the proposed example was demonstrated in the evaluation of the behaviour of different solution methods, which employed both fixed- and variable-step integration formulas
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