scholarly journals Vibration Modelling and the Difference Between Different Vibration Models for a Fewer-DOF Parallel Robot

2020 ◽  
Author(s):  
Shuai Fan ◽  
Shouwen Fan ◽  
Xin Zhang ◽  
Guangkui Song ◽  
Weibin Lan
Keyword(s):  
Design Process ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Parallel Robot ◽  
Machining Accuracy ◽  
Object A ◽  
Vibration Model ◽  
Kane’S Equation ◽  
Joint Clearances ◽  
Vibration Performance

Abstract The accuracy of the vibration model used in the design process directly affects the vibration performance of a parallel robot in practice, which determines the machining accuracy and the surface finish of the manufactured products. Considering a drilling parallel robot with a passive branch and few degrees of freedom as the implementation object, a vibration modelling method is proposed in which Kane’s equation is utilized, and various commonly ignored factors, such as the passive branch, the joint clearances and gravity, are considered. To explore the effects of the passive branch, which was considered ideal in previous studies, two dynamic models are derived in which the passive branch is rigid or flexible. To explore the effects of the joint clearances, which were ignored in previous studies, two stiffness models of branches are derived, in which the joint clearances are considered or ignored. Finally, numerical examples are presented for analysing the effects of these commonly ignored factors on the vibration performance of the drilling parallel robot. Regarding to the effects of these commonly ignored factors, the findings of this paper can serve as a reference for designers in simplifying the vibration model in the design process of parallel robot.

Inverse Dynamics of a 3-P[2(US)] Translational Parallel Robot

Robotica ◽  
2018 ◽  
Vol 37 (4) ◽  
pp. 708-728 ◽  
Author(s):  
Mahmood Mazare ◽  
Mostafa Taghizadeh ◽  
M. Rasool Najafi
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Inverse Dynamics ◽  
Virtual Work ◽  
Equations Of Motion ◽  
Parallel Robot ◽  
Qualitative Behavior ◽  
Work Model ◽  
Forward Kinematic ◽  
Good Agreement

SummaryIn this paper, a type of parallel robot with three translational degrees of freedom is studied. Inverse and forward kinematic equations are extracted for position and velocity analyses. The dynamic model is derived by Lagrange’s approach and the principle of virtual work and related computational algorithms implementing inverse and forward dynamics are presented. Furthermore, some numerical simulations are performed using the kinematic and dynamic models in which the results show good agreement with expected qualitative behavior of the mechanism. Comparisons with the results of work-energy and impulse-momentum methods quantitatively verify the validity of the derived equations of motion. Also, a relative computational effectiveness is observed in implementation of virtual work model via the simulations.

Clearance-Induced Position Uncertainty of Planar Linkages and Parallel Manipulators

2017 ◽  
Vol 9 (6) ◽  
Author(s):  
Kwun-Lon Ting ◽  
Kuan-Lun Hsu ◽  
Jun Wang
Keyword(s):  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Target Position ◽  
Parallel Manipulators ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Joint Clearance ◽  
Position Uncertainty ◽  
Kinematic Effect ◽  
Joint Clearances

The paper presents a simple and effective kinematic model and methodology to assess and evaluate the extent of the position uncertainty caused by joint clearances for multiple-loop linkage and manipulators connected with revolute or prismatic pairs. The model is derived and explained with geometric rigor based on Ting's rotatability laws. The significant contributions include (1) the clearance link model for a P-joint that catches the translation and oscillation characteristics of the slider within the clearance and separates the geometric effect of clearances from the input error, (2) the generality of the method, which is effective for multiloop linkages and parallel manipulators, and (3) settling the dispute on the position uncertainty effect to parallel and serial robots due to joint clearance. The discussion is illustrated and carried out through symmetrically configured planar 8 bar parallel robots. It is found that at a target position, the uncertainty region of a three degrees-of-freedom (DOF) three-leg parallel robot is enclosed by a hexagon with curve edges, while that of its serial counterpart is enclosed by a circle included in the hexagon. A numerical example is presented. The finding and proof, though only based on three-leg planar 8 bar parallel robots, may have a wider implication suggesting that based on the kinematic effect of joint clearance, parallel robots tends to inherit more position uncertainty than their serial counterparts. The use of more loops in not only parallel robots but also single-DOF linkages cannot fully offset the adverse effect on position uncertainty caused by the use of more joints.

Research on the vibration model and vibration performance of cold orbital forging machines

2021 ◽  
pp. 095440542110450
Author(s):  
Lin Hua ◽  
Mingzhang Chen ◽  
Xinghui Han ◽  
Xuancheng Zhang ◽  
Fangyan Zheng ◽  
...  
Keyword(s):  
Dynamic Models ◽  
Vertical Vibration ◽  
Absolute Difference ◽  
Equivalent Stiffness ◽  
External Excitation ◽  
Horizontal Vibration ◽  
Equivalent Damping ◽  
Vibration Model ◽  
Vibration Performance ◽  
Orbital Forging

The vibration of cold orbital forging (COF) machines is a major issue for the quality of forging parts. It is therefore necessary to investigate the vibration of COF machines and provide some effective methods for reducing the vibration. In this paper, horizontal and vertical dynamic models of COF machines are established. These dynamic models are then effectively verified by conducting experiments. By using dynamic models of the COF machine, the vibration performance of the COF machine is investigated. To investigate methods for reducing the vibration of the COF machine, the effects of some key parameters on the vibration of the COF machine are studied, which include the eccentricities and rotation angular speeds of the inner eccentricity ring and the outer eccentricity ring, the amplitude and frequency of external excitation, and the equivalent stiffness and equivalent damping between swing shaft and bearing. Investigative conclusions can be drawn: During the COF process, vertical vibration is more drastic than horizontal vibration. A larger absolute difference between the eccentricities of the inner eccentricity ring and the outer eccentricity ring contributes to reducing the horizontal vibration of the COF machine. A larger equivalent stiffness and a larger equivalent damping between the swing shaft and bearing, a smaller amplitude and a smaller frequency of the external excitation contribute to reducing the vertical vibration of the COF machine.

Analysis and Optimization of a New Differentially Driven Cable Parallel Robot

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Hamed Khakpour ◽  
Lionel Birglen ◽  
Souheil-Antoine Tahan
Keyword(s):  
Kinematic Analysis ◽  
Design Methodology ◽  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Cable Robot ◽  
Proper Design ◽  
Two Indices ◽  
Three Degrees Of Freedom ◽  
Cable Robots

In this paper, a new three degrees of freedom (DOF) differentially actuated cable parallel robot is proposed. This mechanism is driven by a prismatic actuator and three cable differentials. Through this design, the idea of using differentials in the structure of a spatial cable robot is investigated. Considering their particular properties, the kinematic analysis of the robot is presented. Then, two indices are defined to evaluate the workspaces of the robot. Using these indices, the robot is subsequently optimized. Finally, the performance of the optimized differentially driven robot is compared with fully actuated mechanisms. The results show that through a proper design methodology, the robot can have a larger workspace and better performance using differentials than the fully driven cable robots using the same number of actuators.

Footbridges as an important part of a system: the context as an experience

2021 ◽  
Author(s):  
Toon Maas ◽  
Mohamad Tuffaha ◽  
Laurent Ney
Keyword(s):  
Design Process ◽  
Degrees Of Freedom ◽  
The Other ◽  
Infrastructure Projects ◽  
Good Design ◽  
Cultural Processes ◽  
The Relationship

<p>“A bridge has to be designed”. Every bridge is the exploration of all degrees of a freedom of a project: the context, cultural processes, technology, engineering and industrial skills. A successful bridge aims to dialogue with these degrees of freedom to achieve a delicate equilibrium, one that invites the participation of its users and emotes new perceptions for its viewers. In short, a good design “makes the bridge talk.”</p><p>Too often, the bridge, as an object, is reduced to its functionality. Matters of perceptions and experiences of the users are often not considered in the design process; they are relegated to levels of chance or treated as simple decorative matter. The longevity of infrastructure projects, in general, and bridges, in particular, highlights the deficiencies of such an approach. The framework to design bridges must include historical, cultural, and experiential dimensions. Technology and engineering are of paramount importance but cannot be considered as “an end in themselves but a means to an end”. This paper proposes to discuss three projects by Ney &amp; Partners that illustrate such a comprehensive exploration approach to footbridge design: the Poissy and Albi crossings and the Tintagel footbridge.</p><p>The footbridges of Poissy and Albi dialogue most clearly with their historical contexts, reconfiguring the relationship between old and new in the materiality and typology use. In Tintagel, legend replaces history. Becoming a metaphor for the void it crosses, the Tintagel footbridge illustrates the delicate dialogue of technology and engineering on one side and imagination and experience on the other.</p>

A Parallely Actuated Work Support Module for Reconfigurable Machining Systems

1998 ◽  
Author(s):  
Venkat Gopalakrishnan ◽  
Sridhar Kota
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Degrees Of Freedom ◽  
Mechanical Design ◽  
Performance Criteria ◽  
Machining Accuracy ◽  
Parallel Mechanisms ◽  
Element Analysis ◽  
Work Support ◽  
Reconfigurable Machining

Abstract In order to respond quickly to changes in market demands and the resulting product design changes, machine tool manufacturers must reduce the machine tool design lead time and machine set-up time. Reconfigurable Machine Tools (RMTs), assembled from machine modules such as spindles, slides and worktables are designed to be easily reconfigured to accommodate new machining requirements. The essential characteristics of RMTs are modularity, flexibility, convertibility and cost effectiveness. The goal of Reconfigurable Machining Systems (RMSs), composed of RMTs and other types of machines, is to provide exactly the capacity and functionality, exactly when needed. The scope of RMSs design includes mechanical hardware, control systems, process planning and tooling. One of the key challenges in the mechanical design of reconfigurable machine tools is to achieve the desired machining accuracy in all intended machine configurations. To meet this challenge we propose (a) to distribute the total number of degrees of freedom between the work-support and the tool and (b) employ parallely-actuated mechanisms for stiffness and ease of reconfigurability. In this paper we present a novel parallely-actuated work-support module as a part of an RMT. Following a brief summary of a few parallel mechanisms used in machine tool applications, this paper presents a three-degree-of-freedom work-support module designed to meet the machining requirements of specific features on a family of automotive cylinder heads. Inverse kinematics, dynamic and finite element analysis are performed to verify the performance criteria such as workspace envelope and rigidity. A prototype of the proposed module is also presented.

The Machining Parameters Online Monitoring Method for Stability Prediction

2011 ◽  
Vol 141 ◽  
pp. 559-563
Author(s):  
Yong Xiang Jiang ◽  
San Peng Deng ◽  
Yu Ming Qi ◽  
Bing Du
Keyword(s):  
Dynamic Models ◽  
Grinding Wheel ◽  
Machining Accuracy ◽  
Machining Parameters ◽  
Regenerative Chatter ◽  
Monitoring Method ◽  
Good Surface ◽  
Prediction And Control ◽  
The Stability ◽  
Online Detecting

Unstable grinding due to the regenerative chatter is one of the most critical errors and a serious limitation to achieve good surface quality. The machining accuracy of CNC is greatly depending on online detecting, prediction and control ability of abnormal phenomena in machining such as chatter. Based on the mechanism of regenerative chatter, the dynamic models of cylindrical plunging are established by considering both the rotate speed of workpiece and grinding wheel. The traverse grinding can be assumed as the sum of several stepwise plunging grinding with respect to the grinding contact area. The stability caused by online detecting indexes of grinding parameters was analyzed. Grinding experiments of online chatter detecting were carried out and agreed well with the theoretical results that show good application future for online chatter detecting.

Development of a reduced dynamic model for comfort evaluation of rail vehicle systems

2016 ◽  
Vol 230 (4) ◽  
pp. 489-504 ◽  
Author(s):  
Mortadha Graa ◽  
Mohamed Nejlaoui ◽  
Ajmi Houidi ◽  
Zouhaier Affi ◽  
Lotfi Romdhane
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Railway Vehicle ◽  
Passenger Comfort ◽  
Rail Vehicle ◽  
Vehicle System ◽  
Comfort Evaluation ◽  
Complex Models ◽  
Reduced Dynamic

In this paper, an analytical reduced dynamic model of a rail vehicle system is developed. This model considers only 38 degrees of freedom of the rail vehicle system. This reduced model can predict the dynamic behaviour of the rail vehicle while being simpler than existing dynamic models. The developed model is validated using experimental results found in the bibliography and its results are compared with existing more complex models from the literature. The developed model is used for the passenger comfort evaluation, which is based on the value of the weighted root mean square acceleration according to the ISO 2631 standard. Several parameters of the system, i.e., passenger position, loading of the railway vehicle and its speed, and their effect on the passenger comfort are investigated. It was shown that the level of comfort is mostly affected by the speed of the railway vehicle and the position of the seat. The load, however, did not have a significant effect on the level of comfort of the passenger.

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