Robotics and Mechanisms Laboratory

Actuation Redundancy

Parallel manipulators are increasingly being used nowadays due to the advantages over their serial counterparts such as their higher load carrying capacity. From a design perspective, it is important to find out the maximum load which can be applied or sustained by a particular parallel manipulator. Force-moment capability plots are used for this purpose. Additionally, actuation redundancy, which translates into more actuation options than required to perform a particular task, is a very important factor for the completion of the task without failure. Recently a new analytical method has been proposed for determining the force-moment capabilities of redundant planar parallel manipulators. In this proposed research, the main task is to extend the new analytical method of finding the force-moment capabilities of planar parallel manipulators to a redundant 6-DOF spatial parallel 3-RRRS manipulator. This new method ensures that the greatest number of actuators are working at their maximum limits so that greater output wrenches can be obtained. Successful application will lead to a design tool for the analysis of force-moment capabilities of spatial parallel manipulators.

 

 

From a design perspective, it is important to find the maximum load which can be applied or sustained by a particular parallel manipulator. Force-moment capability analysis is necessary for this purpose. Recently, two new methods namely, a numerical scaling factor method and an analytical explicit method, have been proposed for determining the force-moment capabilities of redundant planar parallel manipulators. In this work, these methods are extended to redundant 6-DOF (degree-of-freedom) spatial manipulators. The methods are applied to the 3-RRRS device. Comparison between the two methods is made. The results show that the explicit method determines higher maximum force-moment capabilities than the scaling factor method. The results for four different cases studied under the explicit method are also presented.