The Design of Looped-Synchronous Mechanism With Duplicated Spatial Assur-Groups

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Xu Wang ◽  
Weizhong Guo
Keyword(s):  
Optimization Method ◽  
Degree Of Freedom ◽  
Transmission Ratio ◽  
Main Body ◽  
Prime Mover ◽  
Dynamic Simulations ◽  
Closed Chain ◽  
Stator Blade ◽  
Assur Group ◽  
Aero Engines

The looped-synchronous mechanism (LSM) is a special one degree-of-freedom (DOF) closed chain of transmission with a large number of duplicated units that synchronizes the motion of many output links. This kind of mechanism can be found in many applications such as stator blade adjusting mechanisms for various aero-engines. The LSMs are composed of a large number of links and joints and must be designed by specific means. Spatial Assur-group, which is a concept extended from traditional Assur-group(in planar scope), and usually with a little number of parts and joints, is used in this work to design LSM. First, based on the formula of DOF of spatial Assur-group, all possible combinations are listed and two feasible combinations are chosen as the main body of each unit of LSM, combining with a prime mover to meet the requirement to be inexpandable and adjustable. Second, the condition for transmission ratio of the used Assur-group to be 1 is distilled for being synchronous and looped under the situation that all units of LSM have the same topology. To meet the condition, the needed dimensional conditions are researched and mathematical deduction is used to figure out the possibilities. Third, after confirming that it is impossible to meet the condition strictly, an optimization method in the environment of Simulink is used to approach the condition as close as possible. Finally, numerical and dynamic simulations are carried out to verify the effectiveness of the mentioned methods.

Design and Analysis of a Sixteen-Legged Vehicle With Reconfigurable Close-Chain Leg Mechanisms

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Jianxu Wu ◽  
Yan-an Yao ◽  
Yibin Li ◽  
Sen Wang ◽  
Qiang Ruan
Keyword(s):  
Sensitivity Analysis ◽  
Kinematic Analysis ◽  
Walking Speed ◽  
Gluteus Maximus ◽  
Degree Of Freedom ◽  
Probability Analysis ◽  
Dynamic Simulations ◽  
Closed Chain ◽  
Legged Vehicle ◽  
Leg Mechanisms

In order to exert the advantages of simplified control and integral rigidity, a novel 16-legged walking vehicle is proposed as a carrying platform based on closed-chain mechanisms. Considering the demand for mobility of one degree-of-freedom leg mechanism, we adopt the reconfigurable approach for trajectory flexibility. Serving as a walking module, the whole close-chain leg mechanism is designed to construct the walking vehicle. On the basis of kinematic analysis and sensitivity analysis, the reconfigurable leg with “gluteus maximus” is presented for increasing the obstacle-surmounting ability. In terms of the whole vehicle, the reconfiguration assignments and strategies are analyzed to satisfy the different climbing requirements. The obstacle-climbing capabilities of the legged units are evaluated through the probability analysis. In slope-climbing process, the supporting and the propelling regions for reconfiguration are discussed and obtained with two decision conditions. A series of dynamic simulations and experiments are performed to testify the walking stability, the walking speed, the steering performance, the terrain adaptability, and the obstacle-surmounting capability.

Kinematic and Workspace Modelling of a 6-PUS Parallel Mechanism

2018 ◽  
Author(s):  
Jérôme Landuré ◽  
Clément Gosselin
Keyword(s):  
Kinematic Analysis ◽  
Parallel Mechanism ◽  
Inverse Kinematic ◽  
Degree Of Freedom ◽  
Accurate Description ◽  
Transmission Ratio ◽  
Inverse Kinematic Problem ◽  
Jacobian Matrices ◽  
Six Degree Of Freedom

This article presents the kinematic analysis of a six-degree-of-freedom six-legged parallel mechanism of the 6-PUS architecture. The inverse kinematic problem is recalled and the Jacobian matrices are derived. Then, an algorithm for the geometric determination of the workspace is presented, which yields a very fast and accurate description of the workspace of the mechanism. Singular boundaries and a transmission ratio index are then introduced and studied for a set of architectural parameters. The proposed analysis yields conceptual architectures whose properties can be adjusted to fit given applications.

scholarly journals Framework for estimation of nacelle drag on isolated aero-engines with separate jets

2020 ◽  
Vol 234 (14) ◽  
pp. 2025-2040
Author(s):  
Santiago Ramirez-Rubio ◽  
David G MacManus
Keyword(s):  
Mach Number ◽  
Near Field ◽  
Angle Of Attack ◽  
Field Method ◽  
Main Body ◽  
Reduced Order Models ◽  
Reduced Order ◽  
Flow Capture ◽  
Aero Engines ◽  
Engine Size

Typically, the evaluation of nacelle drag in preliminary design is required to find an overall optimum engine cycle and flight trajectory. This work focuses on the drag characteristics of aero-engine nacelles with separate jet exhausts. The main body of analysis comes from 3D numerical simulations. A new near-field method to compute the post-exit force of a nacelle is presented and evaluated. The effects of the engine size, Mach number, mass flow capture ratio and angle of attack are assessed. The results obtained from the numerical assessments were used to evaluate conventional reduced-order models for the estimation of nacelle drag. Within this context, the effect of the engine size is typically estimated by the scaling ratio between the maximum areas and Reynolds numbers. The effect of the angle of attack on nacelle drag is mostly a function of the nacelle geometry and angle of attack. In general, typical low-order models based on skin friction and form factor can underestimate the friction drag by up to 15% at cruise operating point. Similarly, reduced-order models based solely on Reynolds number, and Mach number can underestimate the overall nacelle drag by up to 74% for free stream Mach number larger than the drag rise Mach number.

PREDICTING THE TRANSMISSIBILITY OF A GLOVE MATERIAL TO THE PALM USING A SIMPLE LUMPED PARAMETER MODEL OF THE HAND AND THE GLOVE

2016 ◽  
Vol 78 (6-10) ◽  
Author(s):  
K.A.M. Rezali ◽  
A. As’arry ◽  
Z.A. Zulkefli ◽  
R. Samin ◽  
N.A.A. Jalil
Keyword(s):  
Degree Of Freedom ◽  
Lumped Parameter Model ◽  
Main Body ◽  
Body Segments ◽  
Lumped Parameter ◽  
Translational Spring ◽  
Reasonable Prediction ◽  
Three Degree Of Freedom

Assessing a glove for its ability to reduce vibration transmitted to the hand can be improved if the transmissibility of the glove to the hand can be predicted. This study proposes a simple lumped parameter model of the hand and the glove for predicting the transmissibility of a glove to the hand. The model of the hand consists of three main body segments: the palm, the fingers, and the palm tissues, connected via translational and rotational springs and dampers. The glove material was represented by translational spring and damper. The results showed that the glove transmissibility predicted using the model overestimated the glove transmissibility measured experimentally at frequencies greater than 62 Hz, implying that a simple three degree-of-freedom model of the hand and the glove may not be able to provide a reasonable prediction of glove transmissibility.

scholarly journals Variable Stiffness Mechanism for the Reduction of Cutting Forces in Robotic Deburring

2021 ◽  
Vol 11 (6) ◽  
pp. 2883
Author(s):  
Matteo Bottin ◽  
Silvio Cocuzza ◽  
Matteo Massaro
Keyword(s):  
Conceptual Design ◽  
Cutting Forces ◽  
Variable Stiffness ◽  
Optimization Method ◽  
The Other ◽  
Design Parameters ◽  
Test Cases ◽  
Dynamic Simulations ◽  
Main Design ◽  
The One

One of the main issues related to robotic deburring is that the tool can get damaged or stopped when the burr thickness exceeds a certain threshold. The aim of this work is to devise a mechanism that can reduce cutting forces automatically, in the event that the burr is too high, and is able to return to the baseline configuration when the burr thickness is acceptable again. On the one hand, in normal cutting conditions, the mechanism should have high stiffness to ensure high cutting precision. On the other hand, when the burr is too high the mechanism should exploit its compliance to reduce the cutting forces and, as a consequence, a second cutting cycle will be necessary to completely remove the burr. After the conceptual design of the mechanism and the specification of the desired stiffness curve, the main design parameters of the system are derived thanks to an optimization method. The effectiveness of the proposed mechanism is verified by means of dynamic simulations using selected test cases. A reduction up to 60% of the cutting forces is obtained, considering a steel burr up to 6 mm high.

Optimizing Cutting Planes for Advanced Joining and Additive Manufacturing

2016 ◽  
Author(s):  
Brandon Massoni ◽  
Matthew I. Campbell
Keyword(s):  
Additive Manufacturing ◽  
Cutting Planes ◽  
Three Dimensional ◽  
Optimization Method ◽  
Main Body ◽  
Optimal Separation ◽  
Complex Shapes ◽  
Definition Of ◽  
The Individual ◽  
Manufacturing Alternatives

While additive manufacturing allows more complex shapes than conventional manufacturing processes, there is a clear benefit in leveraging both new and old processes in the definition of new parts. For example, one could create complex part shapes where the main “body” is defined by extrusion and machining, while small protruding features are defined by additive manufacturing. This paper looks at how optimization and geometric reasoning can be combined to identify optimal separation planes within a complex three-dimensional shapes. These separations indicate the joining processes in reverse. The optimization method presents possible manufacturing alternatives to an engineering designer where optimality is defined as a minimization of cost. The process identifies the cutting planes as well as the combination of processes required to join the individual parts together. The paper presents several examples of complex shapes and describes how the optimization finds the optimal results.

Transonic Turbine Stage Heat Transfer Investigation in Presence of Strong Shocks

2007 ◽  
Author(s):  
A. de la Loma ◽  
G. Paniagua ◽  
D. Verrastro ◽  
P. Adami
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Turbine Stage ◽  
Test Rig ◽  
Unsteady Heat Transfer ◽  
Tube Test ◽  
Stator Blade ◽  
Transonic Turbine ◽  
Aero Engines ◽  
Layered Thin Film

This paper reports the external convective heat transfer distribution of a modern single-stage transonic turbine together with the physical interpretation of the different shock interaction mechanisms. The measurements have been performed in the compression tube test rig of the von Karman Institute using single and double-layered thin film gauges. The three pressure ratios tested are representative of those encountered in actual aero-engines, with M2, is ranging from 1.07 to 1.25 and a Reynolds number of about 106. Three different rotor blade heights (15%, 50% and 85%) and the stator blade at mid-span have been investigated. The measurements highlight the destabilizing effect of the vane left running shock on the rotor boundary layer. The stator unsteady heat transfer is dominated by the fluctuating right running vane trailing edge shock at the blade passing frequency.

Design of Planar Multi-Degree-of-Freedom Morphing Mechanisms

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Lawrence W. Funke ◽  
James P. Schmiedeler ◽  
Kai Zhao
Keyword(s):  
Shape Matching ◽  
Design Space ◽  
Degree Of Freedom ◽  
Limiting Factor ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Extrusion Dies ◽  
Assur Group ◽  
Synthesis Procedure ◽  
Block Approach

This paper seeks to advance the design of planar multiloop shape-changing mechanisms used in a variety of applications, such as morphing extrusion dies and airfoils. The presence of defects is a limiting factor in finding suitable single-degree-of-freedom (DOF) morphing mechanisms, particularly when the number of shapes to achieve is large and/or the changes among those shapes are significant. This paper presents methods of designing multi-DOF mechanisms to expand the design space in which to find suitable defect-free solutions. The primary method uses a building block approach with Assur group of class II chains, similar to the current 1-DOF synthesis procedure. It is compared to both the 1-DOF procedure and an alternative multi-DOF procedure that generates mechanisms with single-DOF subchains. In all cases, a genetic algorithm is employed to search the design space. Two example problems involving four prescribed shapes demonstrate that mechanisms exhibiting superior shape matching are achieved with the primary multi-DOF procedure, as compared to the other two procedures.

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