Reconfiguration Manipulability Analyses for Redundant Robots

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Tongxiao Zhang ◽  
Mamoru Minami ◽  
Osami Yasukura ◽  
Wei Song
Keyword(s):  
Sufficient Conditions ◽  
End Effector ◽  
Redundant Robots

This paper is concerned with a concept of reconfiguration manipulability inspired from manipulability. The reconfiguration manipulability represents a shape-changeability of each intermediate link when a prior end-effector task is given. Through analyses of reconfiguration matrices, we propose a method to judge whether the plural shape-changing subtasks can be executed simultaneously or not. Then the sufficient conditions guaranteeing sustainability of reconfiguration manipulability space are presented, which are the conditions for keeping the reconfiguration manipulability as high as possible under the prior end-effector task. Further, we confirm the proposed analyses can be useful practically for evaluating the realistic manipulator's configurations and structures.

A Statically Balanced Gough/Stewart-Type Platform: Conception, Design, and Simulation

2009 ◽  
Vol 1 (3) ◽  
Author(s):  
Marco Carricato ◽  
Clément Gosselin
Keyword(s):  
Sufficient Conditions ◽  
Parallel Manipulators ◽  
Point Of View ◽  
Theoretical Point ◽  
Constant Force ◽  
Parallel Mechanisms ◽  
End Effector ◽  
Neutral Equilibrium ◽  
The Difference ◽  
Elastic Elements

Gravity compensation of spatial parallel manipulators is a relatively recent topic of investigation. Perfect balancing has been accomplished, so far, only for parallel mechanisms in which the weight of the moving platform is sustained by legs comprising purely rotational joints. Indeed, balancing of parallel mechanisms with translational actuators, which are among the most common ones, has been traditionally thought possible only by resorting to additional legs containing no prismatic joints between the base and the end-effector. This paper presents the conceptual and mechanical designs of a balanced Gough/Stewart-type manipulator, in which the weight of the platform is entirely sustained by the legs comprising the extensible jacks. By the integrated action of both elastic elements and counterweights, each leg is statically balanced and it generates, at its tip, a constant force contributing to maintaining the end-effector in equilibrium in any admissible configuration. If no elastic elements are used, the resulting manipulator is balanced with respect to the shaking force too. The performance of a study prototype is simulated via a model in both static and dynamic conditions, in order to prove the feasibility of the proposed design. The effects of imperfect balancing, due to the difference between the payload inertial characteristics and the theoretical/nominal ones, are investigated. Under a theoretical point of view, formal and novel derivations are provided of the necessary and sufficient conditions allowing (i) a body arbitrarily rotating in space to rest in neutral equilibrium under the action of general constant-force generators, (ii) a body pivoting about a universal joint and acted upon by a number of zero-free-length springs to exhibit constant potential energy, and (iii) a leg of a Gough/Stewart-type manipulator to operate as a constant-force generator.

A New Approach to Type Synthesis of Spatial Robotic Mechanisms

1992 ◽  
Author(s):  
Akhtar N. Malik ◽  
D. R. Kerr
Keyword(s):  
Robot Manipulators ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Type Synthesis ◽  
End Effector ◽  
New Approach ◽  
Parallel Platform ◽  
Necessary And Sufficient

Abstract This paper presents a new approach for carrying out the type synthesis of spatial parallel platform-type mechanisms, used as robot manipulators. It takes into account the total mobility of the system and the partial mobility of its sub-mechanisms. The paper also provides the necessary and sufficient conditions for the mechanisms to function with specified end-effector freedoms, which are described in two theorems. The total number of possible mechanisms with given mobility and structure are tabulated. The work is based on a modified Grübler mobility criterion and also on the consideration of kinematic restraints.

On the Problem of Constrained Path Following For Manipulators

1988 ◽  
Vol 110 (4) ◽  
pp. 443-448
Author(s):  
A. Sankaranarayanan ◽  
M. Vidyasagar
Keyword(s):  
Collision Avoidance ◽  
Force Control ◽  
Robot Manipulator ◽  
Sufficient Conditions ◽  
Path Following ◽  
Necessary And Sufficient Conditions ◽  
End Effector ◽  
Circular Contour ◽  
Necessary And Sufficient

Force Control involves moving the end-effector of a robot manipulator on the surface of an object while ensuring that no other part of the manipulator collides with the object. Suppose C is a given contour to be followed. If the end-effector can move between two points a and b on C while meeting the collision avoidance requirement, we can say that a path exists between a and b. We begin by considering a planar manipulator and a circular contour and derive the necessary and sufficient conditions for a path to exist between a pair of points. By extending these ideas, sufficient conditions are derived for a noncircular contour. The advantages of a (kinematically redundant) 3-link planar manipulator over a 2-link manipulator are pointed out. Finally, we consider spatial manipulators and derive the necessary and sufficient conditions for the case where the contour lies on the surface of a sphere.

scholarly journals Redundancy Resolution Using Tractrix: Simulations and Experiments

2009 ◽  
Author(s):  
V. C. Ravi ◽  
Subrata Rakshit ◽  
Ashitava Ghosal
Keyword(s):  
Degrees Of Freedom ◽  
Redundancy Resolution ◽  
Redundant Manipulator ◽  
End Effector ◽  
Redundant Robots ◽  
Natural Motion ◽  
Fixed Base ◽  
Effective Use ◽  
Actuated Joints ◽  
Present Simulation

Hyper-redundant robots are characterized by the presence of a large number of actuated joints, many more than the number required to perform a given task. These robots have been proposed and used for many application involving avoiding obstacles or, in general, to provide enhanced dexterity in performing tasks. Making effective use of the extra degrees of freedom or resolution of redundancy have been an extensive topic of research and several methods have been proposed in literature. In this paper, we compare three known methods and show that an algorithm based on a classical curve called the tractrix leads to a more ‘natural’ motion of the hyper-redundant robot with the displacements diminishing from the end-effector to the fixed base. In addition, since the actuators at the base ‘see’ the inertia of all links, smaller motion of the actuators nearer to the base results in a smoother motion of the end-effector as compared to other two approaches. We present simulation and experimental results performed on a prototype eight link planar hyper-redundant manipulator.

Optimal Continuous Path Planning for Seven-Degrees-of-Freedom Robots

1986 ◽  
Vol 108 (3) ◽  
pp. 213-218 ◽  
Author(s):  
B. Benhabib ◽  
A. A. Goldenberg ◽  
R. G. Fenton
Keyword(s):  
Path Planning ◽  
Trajectory Planning ◽  
Degrees Of Freedom ◽  
Polynomial Interpolation ◽  
Continuous Path ◽  
End Effector ◽  
Joint Level ◽  
Redundant Robots ◽  
Planning And Control ◽  
Optimization Search

The paper addresses the problem of end effector trajectory planning and control of seven degrees of freedom (DOF) kinematically redundant robots. An off-line optimal continuous path planning method is developed for on-line control at joint level. The specified end effector path is approximated by a set of location nodes selected on the desired path. The motion control of the robot is provided by cubic polynomial interpolation at joint level. The proposed approach to trajectory planning of kinematically redundant robots consists of obtaining an optimal set of nodes which guarantees minimum deviation from the desired Cartesian path. The redundant DOF of the robot is used as a constrained variable in the optimization search. The method is illustrated in an example.

Application of redundant robots to constrained-motion tasks

Robotica ◽  
1992 ◽  
Vol 10 (5) ◽  
pp. 397-407 ◽  
Author(s):  
Veljko Potkonjak
Keyword(s):  
Free Motion ◽  
Constrained Motion ◽  
End Effector ◽  
Redundant Robot ◽  
Redundant Robots ◽  
Passive Compliance ◽  
Two Phases ◽  
The Impact

SUMMARYThe problem of the constrained motion of robot end-effector is discussed. The redundant robot is considered, redundancy being added in order to improve robot working characteristics. In the phase of free motion towards the constraint the errors of basic non-redundant configuration are corrected by means of redundancy. During the constrained motion redundancy plays the role either of active or passive compliance. Between these two phases, the collision with the constraint occurs, and the impact can be absorbed by using redundancy.

Force Compensating Trajectories for Redundant Robots: Experimental Results

2009 ◽  
Vol 21 (1) ◽  
pp. 104-112
Author(s):  
Daniela Vassileva ◽  
◽  
George Boiadjiev ◽  
Haruhisa Kawasaki ◽  
Tetsuya Mouri ◽  
...  
Keyword(s):  
Configuration Space ◽  
Null Space ◽  
End Effector ◽  
New Approach ◽  
Working Zone ◽  
Redundant Robots ◽  
Control Schemes ◽  
Position And Orientation ◽  
Pseudo Inverse ◽  
Eigenvectors And Eigenvalues

We proposed a new approach for redundant robots trajectories planning, based on the Null space (or Kernel) features. The Null space (Kernel) exists only in the case of redundant robots and it describes these joints motion which do not affect the robot end-effector motion in the sense of both position and orientation. Based on this “hidden motion” realized in the configuration space, which does not affect the motion in the working zone, we can control independently the robot end-effector position and orientation motions, or just maintain its state while some external force is applied to it. The proposed control strategy is simple, no additional penalty functions are used to restraint the end-effector motion as in the case of the conventional methods. No pseudo inverse kinematics calculations are required; the desired trajectories are generated directly in the configuration space. No complicated control schemes are introduced, the proposed method is based on solving algebraic systems of equations and finding eigenvectors and eigenvalues. In the paper the results from simulations and experiments based on the proposed method are presented and discussed.

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