scholarly journals Trajectory planning of kinematically redundant parallel manipulators by using multiple working modes

2016 ◽  
Vol 98 ◽  
pp. 216-230 ◽  
Author(s):  
Daniel Reveles R. ◽  
J. Alfonso Pamanes G. ◽  
Philippe Wenger
Keyword(s):  
Trajectory Planning ◽  
Parallel Manipulators

Stiffness of Cable-based Parallel Manipulators With Application to Stability Analysis

2005 ◽  
Vol 128 (1) ◽  
pp. 303-310 ◽  
Author(s):  
Saeed Behzadipour ◽  
Amir Khajepour
Keyword(s):  
Stability Analysis ◽  
Trajectory Planning ◽  
Stiffness Matrix ◽  
Sufficient Conditions ◽  
Parallel Manipulators ◽  
Rotational Stiffness ◽  
New Approach ◽  
Cable Forces

The stiffness of cable-based robots is studied in this paper. Since antagonistic forces are essential for the operation of cable-based manipulators, their effects on the stiffness should be considered in the design, control, and trajectory planning of these manipulators. This paper studies this issue and derives the conditions under which a cable-based manipulator may become unstable because of the antagonistic forces. For this purpose, a new approach is introduced to calculate the total stiffness matrix. This approach shows that, for a cable-based manipulator with all cables in tension, the root of instability is a rotational stiffness caused by the internal cable forces. A set of sufficient conditions are derived to ensure the manipulator is stabilizable meaning that it never becomes unstable upon increasing the antagonistic forces. Stabilizability of a planar cable-based manipulator is studied as an example to illustrate this approach.

An algorithm for smooth trajectory planning optimization of isotropic translational parallel manipulators

2015 ◽  
Vol 230 (12) ◽  
pp. 1987-2002 ◽  
Author(s):  
Mahmood Reza Azizi ◽  
Rahmatolah Khani
Keyword(s):  
Trajectory Planning ◽  
Parallel Manipulators ◽  
Geometric Constraints ◽  
Nsga Ii ◽  
End Effector ◽  
B Splines ◽  
Planning Optimization ◽  
Need To Evaluate ◽  
Significant Performance ◽  
Fifth Order

This paper presents a new algorithm for smooth trajectory planning optimization of isotropic translational parallel manipulators (ITPM) that their Jacobian matrices are constant and diagonal over the whole robot workspace. The basic motivation of this work is to formulate the robot kinematic and geometric constraints in terms of optimization variables to reduce the mathematical complexity and running time of the resulting algorithm which are important issues in trajectory planning optimization. To achieve this aim, the end-effector trajectory of ITPMs in Cartesian space is defined using fifth-order B-Splines, and as a main contribution, all of the actuators limitations and robot constraints are formulated in terms of B-Spline parameters with no need of any information about the workspace geometry. Then the total required energy, total time of motion, and maximum absolute value of actuators’ jerk are defined as objective functions and non-dominated sorting genetic algorithm-II (NSGA-II) is used to solve the resulting nonlinear constrained multi-objective optimization problem. Finally, the proposed algorithm is implemented in MATLAB software for Cartesian parallel manipulator (CPM) as a case study, and the results are demonstrated and discussed. The obtained results show the significant performance of the proposed algorithm with no need to evaluate the robot’s constraints and boundaries of its workspace in each point of the end-effector trajectory.

Trajectory Planning and Impact Reduction in Wire-Actuated Parallel Manipulators With Elastic Wires

2010 ◽  
Author(s):  
Maryam Agahi ◽  
Leila Notash
Keyword(s):  
Trajectory Planning ◽  
Parallel Manipulator ◽  
Optimal Trajectory ◽  
Parallel Manipulators ◽  
Mobile Platform ◽  
Kinematics And Dynamics ◽  
Redundancy Resolution ◽  
Impact Reduction ◽  
Optimization Routine ◽  
Optimal Trajectory Planning

In the work presented, the optimal trajectory planning in wire-actuated parallel manipulators in the presence of an obstacle is investigated. The kinematics and dynamics of a wire-actuated parallel manipulator considering the elasticity and damping effects of wires are described. The redundancy resolution of planar wire-actuated parallel manipulators is investigated at the torque level in order to perform desirable tasks to minimize the effect of impact, while maintaining positive tension in each wire. A local optimization routine is used in the simulation to minimize the tension in the wires while modifying the trajectory of the mobile platform and maintaining positive wire tensions. During collision, the tension in the wires is optimized to reduce the effect of impact, and after collision, the trajectory is modified and the wire tensions are minimized in order to avoid collision for the remainder of the trajectory. The effectiveness of the presented approach is studied through a simulation of an example planar wire-actuated manipulator.

Singularity-free trajectory planning of platform-type parallel manipulators for minimum actuating effort and reactions

Robotica ◽  
2008 ◽  
Vol 26 (3) ◽  
pp. 371-384 ◽  
Author(s):  
Chun-Ta Chen ◽  
Hua-Wei Chi
Keyword(s):  
Trajectory Planning ◽  
Particle Swarm Optimization Algorithm ◽  
Numerical Technique ◽  
Parallel Manipulators ◽  
Singular Points ◽  
Planning Problem ◽  
Control Points ◽  
Swarm Optimization ◽  
Trajectory Representation

SUMMARYDue to the existence of singular configurations within the workspace for a platform- type parallel manipulator (PPM), the actuating force demands increase drastically as the PPM approaches or crosses singular points. Therefore, in this report, a numerical technique is presented to plan a singularity-free trajectory of the PPM for minimum actuating effort and reactions. By using the parametric trajectory representation, the singularity-free trajectory planning problem can be cast to the determination of undetermined control points, after which a particle swarm optimization algorithm is employed to find the optimal control points. This algorithm ensures that the obtained trajectories can avoid singular points within the workspace and that the PPM has the minimum actuating effort and reactions. Simulations and discussions are presented to demonstrate the effectiveness of the algorithm.

Synthesis of Two-Degree-of-Freedom Rotational Decoupled Manipulators of a 2R-Type Branch

2013 ◽  
Vol 284-287 ◽  
pp. 1929-1935
Author(s):  
Da Xing Zeng ◽  
Wen Juan Lu ◽  
Li Jie Zhang ◽  
Yi Tong Zhang
Keyword(s):  
Trajectory Planning ◽  
Screw Theory ◽  
Parallel Manipulators ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Precision Control ◽  
Kinematic Chains ◽  
Parallel Kinematic ◽  
Branch Type ◽  
Two Degree Of Freedom

Strong coupling is one of the prominent features of the general parallel mechanisms(Par. Mec.), which has led to difficulty in the trajectory planning and precision control. To solve this problem, the designing of motion decoupled parallel mechanisms(Dec. Par. Mec.) has become a hot topic. This paper, based on the work achieved in our pre-papers, is to make an improvement on the criterion for a branch type synthesis of the rotational decoupled parallel mechanisms(Rot. Dec. Par. Mec.), which ensures the decoupling of the rotations in each limb. This paper focuses on a type synthesis of the decoupled parallel mechanisms with two degree of freedoms (DOFs). Decoupled parallel manipulators with two parallel kinematic chains, one of which is of type 2R(R represents rotation), are taken into consideration in this paper. A large number of novel decoupled architectures are already obtained, some of which have got an application for a China Patent. What has been done in this paper is carried out by means of the screw theory, which has effectively avoided complex equations by synthesis.

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