Computer-aided curvature analyses of planar four-bar linkage mechanism

2005 ◽  
Vol 168 (2) ◽  
pp. 1175-1188 ◽  
Author(s):  
Tzong-Mou Wu ◽  
Cha’o-Kuang Chen
Keyword(s):  
Linkage Mechanism ◽  
Computer Aided ◽  
Four Bar Linkage

Automatic Selection of Mechanism Designs from a Three-Dimensional Design Map

1992 ◽  
Vol 114 (3) ◽  
pp. 359-367 ◽  
Author(s):  
S. Kota
Keyword(s):  
Selection Process ◽  
Three Dimensional ◽  
Quantitative Comparison ◽  
Linkage Mechanism ◽  
Computer Aided ◽  
Definite Pattern ◽  
Design Selection ◽  
Four Bar Linkage ◽  
Synthesis Approach ◽  
Selection Of

Often a simple (four-bar linkage) mechanism to trace a desired path is sought. Dimensions of linkages to trace a specified coupler curve exactly are difficult to determine. Precision point techniques do not guarantee that the desired path will be generated. The methodology presented in this paper is based on indirect synthesis approach to select four-bar linkages that trace a given desired path. A practical, computer-aided three-dimensional design chart for the selection of four-bar linkage candidate designs that trace symmetrical paths is presented. It is based on hypothesis that any arbitrary path can be approximated by a symmetrical path at least for the purpose of choosing an initial design. Four-bar linkages that generate symmetrical paths are easier to design and exhibit a definite pattern of changes in their shape as the linkage parameters are varied. General design categories and the corresponding solution subspaces in the 3-D design map are identified to aid in the selection of candidate designs. The automation of the design-selection process requires a satisfactory means to quantitatively compare the “desired” and the “known” coupler curves. This paper addresses the issues involved in quantitative comparison of two arbitrary curves using parameterization and shape evaluation. A design example of automated selection of mechanism designs is also presented.

Optimal Control of a Flexible Mechanism Using a Combined Feedforward-Feedback Strategy: Simulation and Experiment

1999 ◽  
Author(s):  
Hubertus v. Stein ◽  
Heinz Ulbrich
Keyword(s):  
Optimal Control ◽  
Control Strategy ◽  
System Performance ◽  
High Speed ◽  
Time Varying ◽  
Linkage Mechanism ◽  
Additional Degree ◽  
Control Approach ◽  
Feedback Optimal Control ◽  
Four Bar Linkage

Abstract Due to the elasticity of the links in modern high speed mechanisms, increasing operating speeds often lead to undesirable vibrations, which may render a required accuracy unattainable or, even worse, lead to a failure of the whole process. The dynamic effects e.g. may lead to intolerable deviations from the reference path or even to the instability of the system. Instead of suppressing the vibration by a stiffer design, active control methods may greatly improve the system performance and lead the way to a reduction of the mechanism’s weight. We investigate a four-bar-linkage mechanism and show that by introducing an additional degree of freedom for a controlled actuator and providing a suitable control strategy, the dynamically induced inaccuracies can be substantially reduced. The modelling of the four-bar-linkage mechanism as a hybrid multi body system and the modelling of the complete system (including the actuator) is briefly explained. From the combined feedforward-feedback optimal control approach presented in (v. Stein, Ulbrich, 1998) a time-varying output control law is derived that leads to a very good system performance for this linear discrete time-varying system. The experimental results show the effectiveness of the applied control strategy.

scholarly journals Feeding mechanics and bite force modelling of the skull of Dunkleosteus terrelli , an ancient apex predator

2006 ◽  
Vol 3 (1) ◽  
pp. 77-80 ◽  
Author(s):  
Philip S.L Anderson ◽  
Mark W Westneat
Keyword(s):  
High Speed ◽  
Prey Capture ◽  
Mouth Opening ◽  
Biomechanical Model ◽  
Bite Force ◽  
Rapid Expansion ◽  
Large Individual ◽  
Linkage Mechanism ◽  
Feeding Mechanics ◽  
Four Bar Linkage

Placoderms are a diverse group of armoured fishes that dominated the aquatic ecosystems of the Devonian Period, 415–360 million years ago. The bladed jaws of predators such as Dunkleosteus suggest that these animals were the first vertebrates to use rapid mouth opening and a powerful bite to capture and fragment evasive prey items prior to ingestion. Here, we develop a biomechanical model of force and motion during feeding in Dunkleosteus terrelli that reveals a highly kinetic skull driven by a unique four-bar linkage mechanism. The linkage system has a high-speed transmission for jaw opening, producing a rapid expansion phase similar to modern fishes that use suction during prey capture. Jaw closing muscles power an extraordinarily strong bite, with an estimated maximal bite force of over 4400 N at the jaw tip and more than 5300 N at the rear dental plates, for a large individual (6 m in total length). This bite force capability is the greatest of all living or fossil fishes and is among the most powerful bites in animals.

A New Method for Determining the Effects of Structural Flexibility on the Dynamic Behavior of High Speed Mechanisms

1999 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
Dynamic Behavior ◽  
High Speed ◽  
New Method ◽  
Structural Flexibility ◽  
Structural Elements ◽  
Dynamics Modeling ◽  
Linkage Mechanism ◽  
Active Materials ◽  
Response Characteristics ◽  
Four Bar Linkage

Abstract A new method for the analysis of the effects of structural flexibility on the dynamic behavior of mechanical systems is presented. The developed method is in most part based on “tracing” the “propagation” of the effects of the high frequency motion requirements on the dynamic response characteristics of machines with structural flexibilities, particularly those with closed-loop kinematic structures. The method considers the “filtering” action of structural elements with flexibility. Such filtering of higher frequency motions is shown to have a predictable effect on the steady state motion of such mechanical system. The main advantage of the developed method is that the effects of such flexibilities can be determined without the need to perform the usual dynamics modeling and computer simulations. The method is shown to be very simple and readily implementable. The method is applied to a four-bar linkage mechanism with a longitudinally flexible coupler link. The obtained results are shown to be highly accurate as compared to those obtained by computer simulation. The application of the method to systematic design of machines with structural flexibility for high speed and precision operation, optimal integration of smart (active) materials into the structure of such machines, and some related issues are discussed.

KINETOSTATIC ANALYSIS FOR FOUR-BAR LINKAGE MECHANISM OF PROSTHETIC KNEE JOINT

2019 ◽  
Vol 19 (04) ◽  
pp. 1950018 ◽  
Author(s):  
XUHUI LIU ◽  
TIANTIAN GUO ◽  
JIAHAO ZHANG ◽  
GUANG YANG ◽  
LUCHAN SUN ◽  
...  
Keyword(s):  
Knee Joint ◽  
Group Method ◽  
Linkage Mechanism ◽  
Analysis Software ◽  
Prosthetic Knee ◽  
Damping Effect ◽  
D’Alembert Principle ◽  
Prosthetic Knee Joint ◽  
Four Bar Linkage ◽  
The Relationship

In this paper, a mathematical model of four-bar linkage mechanism is built to investigate the prosthetic knee joint, by means of the bar group method, and the motion of the prosthetic knee joint is simulated by motion analysis software. In the state of motion of the four linkage mechanism, to the moving component of the mechanism, the relationship between the moving displacement, velocity and acceleration are obtained. On the basis of the above investigation, dynamic statics analysis for the moving component of four-bar linkage mechanism are completed by the ‘D’Alembert principle. The research results show that, with the change of the rotating angle of the active part, the counter-force of rotating pair and the balance torque on active component are all changeable, which will provide a theoretical basis for the design of prosthetic knee joint mechanism with longer life and better damping effect.

Active Vibration Control for the Closed Loop Flexible Mechanisms Combined the Feedback and Feed-Forward Strategy: Part 2 — Control Design and Simulation

2000 ◽  
Author(s):  
Zhang Xianmin ◽  
Chao Changjian
Keyword(s):  
Equations Of Motion ◽  
Active Vibration Control ◽  
Elastic Vibration ◽  
Linkage Mechanism ◽  
Control Laws ◽  
Feed Forward ◽  
Feed Forward Control ◽  
Active Vibration ◽  
Four Bar Linkage ◽  
Flexible Mechanisms

Abstract On the basis of the complex mode theory and the equations of motion of the flexible mechanisms developed in part 1, a hybrid independent modal controller is presented, which is composed of state feedback and disturbance feed-forward control laws. As an illustrative example, the strategy is used to control the elastic vibration response of a four-bar linkage mechanism. The imitative computational result shows that the vibration is efficiently suppressed.

Over-Constrained Mechanisms Derived From RPRP Loops

2018 ◽  
Author(s):  
Kwun-Lon Ting ◽  
Kuan-Lun Hsu
Keyword(s):  
Computer Aided Design ◽  
Random Search ◽  
Modular Approach ◽  
Input Output ◽  
Assembly Strategy ◽  
Revolute Joints ◽  
Computer Aided ◽  
Prismatic Joints ◽  
Aided Design ◽  
Four Bar Linkage

This paper addresses the assembly strategy capable of deriving a family of over-constrained mechanisms systematically. The modular approach is proposed. It treats the topological synthesis of over-constrained mechanisms as a systematical derivation rather than a random search. The result indicates that a family of over-constrained mechanisms can be constructed by combining legitimate modules. A spatial four-bar linkage containing two revolute joints (R) and two prismatic joints (P) is selected as the source-module for the purpose of demonstration. All mechanisms discovered in this paper were modeled and animated with computer aided design (CAD) software and their mobility were validated with input-output equations as well as computer simulations. The assembly strategy can serve as a self-contained library of over-constrained mechanisms.

scholarly journals An investigation of various actuation mechanisms in robot arm

2019 ◽  
Vol 52 (9-10) ◽  
pp. 1299-1307 ◽  
Author(s):  
J Prakash ◽  
M Ilangkumaran
Keyword(s):  
Analytical Approach ◽  
Robot Arm ◽  
Force Analysis ◽  
Linkage Mechanism ◽  
Actuation Mechanism ◽  
Research Activities ◽  
Grasping Force ◽  
Object Shapes ◽  
End Effectors ◽  
Four Bar Linkage

Many research activities have been carried out to develop a simple mechanism for grasping irregular object shapes using two- or three-fingered robot end effectors. The idea behind this work is to develop three-fingered intelligent grippers that are capable of sensing different factors like weight, effort required, compactness, robustness, and stability of the object held during the manipulations. In this paper, five different actuation mechanisms, namely, edge-cam-operated actuation mechanism, toggle-linkage-based actuation mechanism, wedge-cam-operated gripper, sliding slotted pin–ball joint arrangement, and rack-and-pinion-operated four-bar linkage mechanism, are introduced. The actuation and grasping force of the gripper are to be determined using the analytical approach (static force analysis). Finally, the effective intelligent gripper mechanism is identified based on grasping force for grasping 1 kg weight of a prespecified object.

Four-Bar Linkage Mechanism for Insectlike Flapping Wings in Hover: Concept and an Outline of Its Realization

2005 ◽  
Vol 127 (4) ◽  
pp. 817-824 ◽  
Author(s):  
Rafał Z˙bikowski ◽  
Cezary Galin´ski ◽  
Christopher B. Pedersen
Keyword(s):  
Insect Flight ◽  
Micro Air Vehicles ◽  
Flapping Wing ◽  
Flapping Wings ◽  
Test Bed ◽  
Linkage Mechanism ◽  
Actual Design ◽  
Straight Line Mechanism ◽  
Four Bar Linkage ◽  
Air Vehicles

This paper describes the concept of a four-bar linkage mechanism for flapping wing micro air vehicles and outlines its design, implementation, and testing. Micro air vehicles (MAVs) are defined as flying vehicles ca. 150 mm in size (handheld), weighing 50–100 g, and are developed to reconnoiter in confined spaces (inside buildings, tunnels, etc.). For this application, insectlike flapping wings are an attractive solution and, hence, the need to realize the functionality of insect flight by engineering means. Insects fly by oscillating (plunging) and rotating (pitching) their wings through large angles, while sweeping them forward and backward. During this motion, the wing tip approximately traces a figure eight and the wing changes the angle of attack (pitching) significantly. The aim of the work described here was to design and build an insectlike flapping mechanism on a 150 mm scale. The main purpose was not only to construct a test bed for aeromechanical research on hover in this mode of flight, but also to provide a precursor design for a future flapping-wing MAV. The mechanical realization was to be based on a four-bar linkage combined with a spatial articulation. Two instances of idealized figure eights were considered: (i) Bernoulli’s lemniscate and (ii) Watt’s sextic. The former was found theoretically attractive, but impractical, while the latter was both theoretically and practically feasible. This led to a combination of Watt’s straight-line mechanism with a drive train utilizing a Geneva wheel and a spatial articulation. The actual design, implementation, and testing of this concept are briefly described at the end of the paper.

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