Planning of Graspless Manipulation

Graspless manipulation aims to manipulate an object with a small load by using the surrounding environment. When a robot must act dexterously in complex environments like construction sites,@home, etc, graspless manipulation is very effective(Fig.1). But, on the other hand, contact with the environment brings the danger of excessive force occurring between the object and the environment or between the object and the manipulator, when a trivial position error is taking place. And, during graspless manipulation, an object may fall down because it is not grasped rigidly by a manipulator. Thus we must make a motion plan which enables the task to be completed safely and reliably. Our motion plan is made in such a way as shown below.

(1) Motion Planning Using Feasible Manipulation Region:

We define gStabilityh as the index, which express the reliability of the manipulation. Considering the stability and the geometrical factor, we calculate the feasible manipulation region within the object configuration space. Find the optimal pass in the feasible manipulation region, we get the optimal fingers position and optimal finger force. (Fig.2)

(2) Object Compliance:

We design the object compliance considering positions and compliance of fingers in order to prevent the danger of excessive force and the interruption of the work.

In this study, we aim to make the flexible motion planning which can cope with the variation of tasks, shapes, and physical feature of an object.

Keywords: Graspless Manipulation, Dexterous Control, Compliance, Motion Planning

Reference

1) Y.Maeda,Y.Aiyama,T.Arai,T.Ozawa:gAnalysis of Object-Stability and Internal Force in Robotic Contact Tasksh, Proc. 1996 IEEE/RSJ IROSf96, Vol.2, pp.751-756, Osaka(Japan), Nov, 1996.

2) K.Kimura: gAnalysis and design for Object Compliance in Graspless ManipulationhMaster thesis, faculty of Engineering, The University of Tokyo, 1998.

Fig. 1 Picking a book from a shelf

Fig. 2 Force needed for object motion