1,721,241 research outputs found
Gregorio R. de Yurre, Etica
No full textDecerf Paul. Gregorio R. de Yurre, Etica. In: Revue Philosophique de Louvain. Troisième série, tome 62, n°75, 1964. pp. 527-528
Gregorio R. de Yurre, Etica
No full textDecerf Paul. Gregorio R. de Yurre, Etica. In: Revue Philosophique de Louvain. Troisième série, tome 62, n°75, 1964. pp. 527-528
Gregorio R. de Yurre, Totalitarismo y egolatria
No full textDecerf Paul. Gregorio R. de Yurre, Totalitarismo y egolatria. In: Revue Philosophique de Louvain. Troisième série, tome 62, n°75, 1964. pp. 532-533
Meccanismo parallelo traslazionale
No full textTranslational parallel manipulators (TPMs) with DELTA-like architectures are the most known and affirmed ones, even though many other TPM architectures have been proposed and studied in the literature. In the patent application, this author has presented a TPM with three equal limbs of Universal-Revolute-Universal (URU) type, with only one actuated joint per limb, which has overall size and characteristics similar to DELTA robots. The presented translational 3-URU architecture is different from other 3-URUs, proposed in the literature, since it has the actuators on the frame (base) even though the actuated joints are not on the base, and it features a particular geometry. Choosing the geometry and the actuated joints highly affects 3-URU’s behavior. Moreover, putting the actuators on the base allows a substantial reduction of the mobile masses, thus promising good dynamic performances, and makes the remaining part of the limb a simple chain constituted by only passive R-pairs.
https://www.mdpi.com/2218-6581/9/3/6
Kinematic analysis of multi-DOF planar mechanisms via velocity-coefficient vectors and acceleration-coefficient Jacobians
No full textIn the literature, velocity coefficients (VCs) and acceleration coefficients (ACs) were substantially proposed for single-degree-of-freedom (single-DOF) planar mechanisms. Their effectiveness in solving the kinematic analysis of these mechanisms is due to the fact that they only depend on the mechanism configuration. Such property also holds when they are defined for spatial single-DOF scleronomic and holonomic mechanisms, but was not exploited; moreover, some extensions of the VC and AC concepts to multi-DOF planar (or spatial scleronomic and holonomic) mechanisms are possible, but have not proved their practical usefulness. Here, first, the velocity-coefficient vectors (VCVs) together with their Jacobians (acceleration-coefficient Jacobians (ACJs) are proposed as an extension of the concepts of VC and AC to multi-DOF scleronomic and holonomic mechanisms. Then, a general algorithm, based on VCVs and ACJs and on a notation, previously presented by the author, which uses the complex-number method, is proposed for solving the kinematic-analysis problems of multi-DOF planar mechanisms and to find their links’ dead-center positions. The effectiveness of the proposed algorithm is also illustrated by applying it to a case study. The proposed algorithm is efficient enough for constituting the kinematic block of any dynamic model of these mechanisms, and simple enough for being presented in graduate courses
A geometric and analytic technique for studying multi-DOF planar mechanisms’ dynamics
No full textMost approaches of analytical mechanics (e.g., D'Alembert principle) build dynamic models of mechanisms that are difficult to relate with clear geometric interpretations. This feature is a drawback that confines their use to the implementation of algorithms in multi-body-dynamics software, whose results must be interpreted by using the designer intuition when the mechanism must be modified to match particular design requirements. Here, starting from D'Alembert principle, the dynamic model of any multi-degrees-of-freedom (multi-DOF) planar mechanism (PM) is obtained by suitably combining the dynamic models of all the single-DOF PMs generated by locking all the actuated joints, but one. The dynamic models of the so-generated single-DOF PMs are written by using an approach, presented in a previous paper, which admits a geometric interpretation through diagrams, named “active-load diagrams”, and fully discloses the role of instant centers (ICs) in the dynamic behavior of single-DOF PMs. Accordingly, the resulting dynamic model of the generating multi-DOF PM admits a geometric interpretation that reveals the role of ICs in multi-DOF PMs’ dynamic behavior. Such geometric interpretation is so effective that, formally, the model could be written starting from it without any analytic consideration the same way as the equilibrium equations can be written from free-body diagrams in the Newton-Euler formulation. The presented model is general and, as far as this author is aware, is novel. The proposed model and the associated algorithms for solving dynamic problems are also illustrated through a case study. The obtained results are of interest in mechanism analysis and design
The Role of Instant Centers in Kinematics and Dynamics of Planar Mechanisms: Review of LaMaViP’s Contributions
No full textTheoretical kinematics and dynamics is one of the research fields where LaMaViP (Laboratory of Mechatronics and Virtual Prototyping) operates, which is the lab leaded by the author at the University of Ferrara. In the last two decades, this research activity at LaMaViP has produced, among others, many novel results that highlight how instant centers’ (ICs) locations condition the kinetostatic and dynamic behaviors of planar mechanisms, and that provide tools suitable for design purposes. This paper reviews/summarizes the tools devised at LaMaViP for PM analysis and synthesis through ICs, and shows that they are a complete set of tools, which make the full description of PMs’ kinematics and dynamics possible, and that the new IC features, identified while setting up these tools, are relevant in machine design
Metrics proposed for measuring the distance between two rigid-body poses: review, comparison, and combination
No full textThe concept of distance between two rigid-body poses is important in path planning, positioning precision, mechanism synthesis, and in many other applications. In the definition of such a distance, two approaches mainly prevail, which lead to a number of formulas devised to match the needs of motion tasks. Despite the different approaches and formulas, some important theoretical results, which drive toward distance-metrics definitions useful for design and application purposes, have been stated. This paper summarizes the two different approaches together with a critical review of the literature on the distance metrics they generated, and, then, it illustrates a technique, previously proposed by the author, for combining different metrics to obtain novel distance-metric definitions that are tailored to specific applications
Dimensional Synthesis of a Novel 3-URU Translational Manipulator Implemented through a Novel Method
No full textA dimensional synthesis of parallel manipulators (PMs) consists of determining the values of the geometric parameters that affect the platform motion so that a useful workspace with assigned sizes can be suitably located in a free-from-singularity region of its operational space. The main goal of this preliminary dimensioning is to keep the PM far enough from singularities to avoid high internal loads in the links and guarantee a good positioning precision (i.e., for getting good kinematic performances). This paper presents a novel method for the dimensional synthesis of translational PMs (TPMs) and applies it to a TPM previously proposed by the author. The proposed method, which is based on Jacobians’ properties, exploits the fact that TPM parallel Jacobians are block diagonal matrices to overcome typical drawbacks of indices based on Jacobian properties. The proposed method can be also applied to all the lower-mobility PMs with block diagonal Jacobians that separate platform rotations from platform translations (e.g., parallel wrists)
A Novel 3-URU Architecture with Actuators on the Base: Kinematics and Singularity Analysis
No full textTranslational parallel manipulators (TPMs) with DELTA-like architectures are the most known and affirmed ones, even though many other TPM architectures have been proposed and studied in the literature. In a recent patent application, this author has presented a TPM with three equal limbs of Universal-Revolute-Universal (URU) type, with only one actuated joint per limb, which has overall size and characteristics similar to DELTA robots. The presented translational 3-URU architecture is different from other 3-URUs, proposed in the literature, since it has the actuators on the frame (base) even though the actuated joints are not on the base, and it features a particular geometry. Choosing the geometry and the actuated joints highly affects 3-URU’s behavior. Moreover, putting the actuators on the base allows a substantial reduction of the mobile masses, thus promising good dynamic performances, and makes the remaining part of the limb a simple chain constituted by only passive R-pairs. The paper addresses the kinematics and the singularity analysis of this novel TPM and proves the effectiveness of the new design choices. The results presented here form the technical basis for the above-mentioned patent application
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