The Design of Three Jointed Two-Degree-of-Freedom Robot Fingers

1987 ◽  
Author(s):  
S. O. Leaver ◽  
J. M. McCarthy
Keyword(s):  
Mechanical Model ◽  
Degrees Of Freedom ◽  
Two Degrees Of Freedom ◽  
Mechanical Hand ◽  
Planar Manipulators ◽  
Payload Capacity ◽  
Human Finger ◽  
Finger Tip ◽  
Fully Coupled ◽  
Two Degree Of Freedom

Abstract The design of modern mechanical hands requires a choice for the kinematic structure of the finger. The typical finger is a planar manipulator with one, two, or three independently controllable joints. Each controllable joint requires a motor and sensor system which increases the weight of the hand. There is a desire to minimize the number of degrees of freedom in a mechanical hand because the payload capacity of a manipulator is limited. Two degrees of freedom provides the required positioning capability of a finger tip (though not the ability to control contact angle). Three joints are required to provide the ability to enclose grasped objects. This paper considers the design of fingers which are planar manipulators with three joints but only two degrees of freedom. In addition to the fully coupled design, twelve classes of finger designs with varying degrees of de-coupling are presented. It happens that one of these classes includes the human finger, a mechanical model of which is presented in detail.

scholarly journals Turning characteristics of biomimetic robotic fish driven by two degrees of freedom of pectoral fins and flexible body/caudal fin

2018 ◽  
Vol 15 (1) ◽  
pp. 172988141774995 ◽  
Author(s):  
Zonggang Li ◽  
Liming Ge ◽  
Weiqiang Xu ◽  
Yajiang Du
Keyword(s):  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Robotic Fish ◽  
Flexible Body ◽  
Caudal Fin ◽  
Two Degrees Of Freedom ◽  
Pectoral Fins ◽  
Turn On ◽  
Biomimetic Robotic Fish ◽  
Two Degree Of Freedom

This article considers the turning characteristics of robotic fish with two-degree-of-freedom pectoral fins and flexible body/caudal fin. The hydrodynamics are first established for three cases propelled by both sides of pectoral fins, flexible body/caudal fin, and composite of them. Then, the turning characteristics of such three cases are analyzed by numerical simulations and experiments. The results show that if robotic fish is cooperatively propelled by pectoral fins and flexible body, it can obtain the fast turning speed and the average turning speed is up to 0.6 rad s−1. The smallest turning speed is achieved as robotic fish is only propelled by pectoral fins; however, it can turn on the spot in this case. The presented results provide the more abundant ways of turning, the better maneuverability, and the higher turning speed for the proposed robotic fish.

A 7R-Based, Two Degrees of Freedom Robomech

2000 ◽  
Author(s):  
Ahmad A. Smaili
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Architecture ◽  
Degree Of Freedom ◽  
Robot Arm ◽  
End Effector ◽  
Kinematic Constraints ◽  
Two Degrees Of Freedom ◽  
Synthesis Procedure ◽  
Two Degree Of Freedom

Abstract A robomech is a crossbreed of a mechanism and a robot arm. It has a parallel architecture equipped with more than one end effector to accomplish tasks that require the coordination of many functions. Robomechs with multi degrees of freedom that are based on the 4R and 5R chains have found their way into the literature. This article presents a new, two-degree of freedom robomech whose architecture is based on the 7R chain. The robomech is capable of performing two-function tasks. The features, kinematic constraints, and synthesis procedure of the robomech are outlined and an application example is given.

Two-Degree-of-Freedom Decoupled Nonredundant Cable-Loop-Driven Parallel Mechanism

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Hanwei Liu ◽  
Clément Gosselin ◽  
Thierry Laliberté
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
The Other ◽  
End Effector ◽  
Two Degrees Of Freedom ◽  
Actuation Redundancy ◽  
Rigid Link ◽  
Force Closure ◽  
Two Degree Of Freedom

A novel two-degree-of-freedom (DOF) cable-loop slider-driven parallel mechanism is introduced in this paper. The novelty of the mechanism lies in the fact that no passive rigid-link mechanism or springs are needed to support the end-effector (only cables are connected to the end-effector) while at the same time there is no actuation redundancy in the mechanism. Sliders located on the edges of the workspace are used and actuation redundancy is eliminated while providing force closure everywhere in the workspace. It is shown that the two degrees of freedom of the mechanism are decoupled and only two actuators are needed to control the motion. There are two cable loops for each direction of motion: one acts as the actuating loop while the other is the constraint loop. Due to the simple geometric design, the kinematic and static equations of the mechanism are very compact. The stiffness of the mechanism is also analyzed in the paper. It can be observed that the mechanism's stiffness is much higher than the stiffness of the cables. The proposed mechanism's workspace is essentially equal to its footprint and there are no singularities.

scholarly journals On Nonconservative Stability Problems of Elastic Systems With Slight Damping

1966 ◽  
Vol 33 (1) ◽  
pp. 125-133 ◽  
Author(s):  
G. Herrmann ◽  
I. C. Jong
Keyword(s):  
Degrees Of Freedom ◽  
Compressive Load ◽  
Viscous Damping ◽  
Two Degrees Of Freedom ◽  
Stability Problems ◽  
Damping Coefficients ◽  
Stability And Instability ◽  
Elastic Systems ◽  
Nonconservative Loading ◽  
Two Degree Of Freedom

A linear two-degree-of-freedom system with slight viscous damping and subjected to nonconservative loading is analyzed with the aim of studying the effects of damping on stability of equilibrium. It is found that, in such systems, multiple ranges of stability and instability may exist in a richer variety than in corresponding systems without damping. Further, for certain systems, instability either by divergence (static buckling) or by flutter may occur first as the compressive load increases, depending upon the ratio of the damping coefficients in the two degrees of freedom. It is shown finally that systems exist for which the destabilizing effect of slight viscous damping cannot be removed completely whatever the ratio of the (positive) damping coefficients.

Period-1 Motions in a Two-Degree-of-Freedom Nonlinear Oscillator With Periodic Excitation

2015 ◽  
Author(s):  
Albert C. J. Luo ◽  
Bo Yu
Keyword(s):  
Analytical Solutions ◽  
Nonlinear Oscillator ◽  
Degrees Of Freedom ◽  
Harmonic Amplitude ◽  
Periodic Excitation ◽  
Periodic Motions ◽  
Two Degrees Of Freedom ◽  
Approximate Analytical Solutions ◽  
The Stability ◽  
Two Degree Of Freedom

In this paper, analytical solutions for period-1 motions in a periodically forced, two-degrees-of-freedom system with a nonlinear spring are developed. The stability and bifurcation of the periodic motions are completed by the eigenvalue analysis. Both symmetric and asymmetric periodic motions are found in the system. Analytical solutions of both stable and unstable period-1 are presented. Finally, numerical simulations of stable and unstable motions in the two degrees of freedom systems are presented. The harmonic amplitude spectrums show the harmonic effects on periodic motions, and the corresponding accuracy of approximate analytical solutions can be observed.

A meshing principle for generating a cylindrical gear using an Archimedes hob with two degrees of freedom

2009 ◽  
Vol 224 (1) ◽  
pp. 169-181 ◽  
Author(s):  
Y Zhao ◽  
D Su ◽  
W Wei ◽  
X Dong
Keyword(s):  
Numerical Simulations ◽  
Industrial Application ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
Verification And Validation ◽  
Cylindrical Gear ◽  
Two Degrees Of Freedom ◽  
Numerical Examples ◽  
Two Degree Of Freedom

Thorough and systematic investigations are performed into the meshing principium of generating a cylindrical gear by an Archimedes hob based on the two-degree-of-freedom theory of gearing geometry. The numerical examples show the verification and validation of the formulated principium and the developed model. Conclusions suitable for industrial application are reached by means of numerical simulations.

Vibration of Cams Having Two Degrees of Freedom

1964 ◽  
Vol 86 (4) ◽  
pp. 343-349 ◽  
Author(s):  
N. S. Eiss
Keyword(s):  
Analytical Solutions ◽  
Vibration Analysis ◽  
Vibration Amplitude ◽  
Degrees Of Freedom ◽  
Degree Of Freedom ◽  
The Other ◽  
Tabular Form ◽  
Two Degrees Of Freedom ◽  
Cam Follower ◽  
Two Degree Of Freedom

The vibration analysis of cam-follower systems is extended to models having two degrees of freedom. Two models are considered, one in which the cam support is rigid and the follower has two degrees of freedom, and the other, in which the cam support and follower each have one degree of freedom. Analytical solutions to six acceleration pulses are listed in tabular form. An example shows how tabulated solutions are added to give the displacement of a follower to a modified trapezoidal acceleration function. In another example, it is demonstrated how the parameters of a two-degree-of-freedom model are selected to give the minimum vibration amplitude.

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