Parameter optimum design of spherical 2-DOF parallel manipulator with actuation redundancy

Author(s):  
Li-Jie Zhang ◽  
Yong-Quan Li ◽  
Wen-Ya Shi
2014 ◽  
Vol 28 (1) ◽  
pp. 20-28 ◽  
Author(s):  
Zhufeng Shao ◽  
Xiaoqiang Tang ◽  
Liping Wang ◽  
Dengfeng Sun

2005 ◽  
Vol 127 (4) ◽  
pp. 550-563 ◽  
Author(s):  
C. K. Kevin Jui ◽  
Qiao Sun

Parallel manipulators are uncontrollable at force singularities due to the infeasibly high actuator forces required. Existing remedies include the application of actuation redundancy and motion planning for singularity avoidance. While actuation redundancy increases cost and design complexity, singularity avoidance reduces the effective workspace of a parallel manipulator. This article presents a path tracking type of approach to operate parallel manipulators when passing through force singularities. We study motion feasibility in the neighborhood of singularity and conclude that a parallel manipulator may track a path through singular poses if its velocity and acceleration are properly constrained. Techniques for path verification and tracking are presented, and an inverse dynamics algorithm that takes actuator bounds into account is examined. Simulation results for a planar parallel manipulator are given to demonstrate the details of this approach.


Robotica ◽  
2011 ◽  
Vol 30 (3) ◽  
pp. 379-388 ◽  
Author(s):  
Roger Boudreau ◽  
Xu Mao ◽  
Ron Podhorodeski

SUMMARYIn this work, accuracy enhancement through backlash elimination is considered. When a nonredundantly actuated parallel manipulator is subjected to a wrench while following a trajectory, required actuator torque switching (going from positive to negative or vice versa) may occur. If backlash is present in the actuation hardware for a manipulator, torque switching compromises accuracy. When in-branch redundant actuation is added, a pseudoinverse torque solution requires smaller joint torques, but torque switching may still occur. A method is presented where concepts of exploiting a nullspace basis of the joint torques are used to ensure that single sense joint torques can be achieved for the actuated joints. The same sense torque solutions are obtained using nonlinear optimization. The methodology is applied to several examples simulating parallel manipulators in machining applications.


2014 ◽  
Vol 687-691 ◽  
pp. 616-622
Author(s):  
Liang Liang Zhang ◽  
Yao Jiang ◽  
Tie Min Li

A time-optimal control of a 4RRR parallel manipulator with actuation redundancy is reported. A method using both redundant actuation and velocity planning is carried out to achieve the shortest moving time of the platform travelling through an assigned path without reducing precision caused by the backlashes in the actuators. The problem is simplified and an adaptive method of time-optimal control is designed based on the characteristics such as pre-coupling of time segments and decoupling of the redundant torques and time segments of this problem. The result demonstrates that this method can solve this problem with high speed. It serves as an example of both time-optimal control in robotics and multi-parameter optimization.


Sign in / Sign up

Export Citation Format

Share Document