Evaluation of 3D grasps with physical interpretations using object wrench space

Abstract

SUMMARYIn this paper we propose an intuitive and practical grasp quality measure for grasping 3D objects with a multi-fingered robot hand. The proposed measure takes into account the object geometries through the concept of object wrench space. Physically, the positive measure value has a meaning of the minimum single disturbance that grasp cannot resist, while the negative measure value implies the minimum necessary helping force that restores a non-force-closure grasp into a force-closure one. We show that the measure value is invariant between similar grasps and also between different torque origins. We verify the validity of the proposed measure via simulations by using computer models of a three-fingered robot hand and polygonal objects.

Partial convex hull algorithms for efficient grasp quality evaluation

“…This metric however has enjoyed limited use because it is costly to compute and the authors provide a method only slightly better than a brute force approach. A similar method was proposed in [19]. Li and Sastry defined the concept of task wrench space (TWS), i.e., the set of wrenches that can be generated while executing a specific task [20].…”

In-hand rolling motion planning using independent contact region (ICR) with guaranteed grasp quality margin

“…In our previous work [17], a physically meaningful grasp measure was proposed as the scale of the convex hull of OWS with respect to the convex hull of GWS. This is to find the maximum scale factor, a, such that…”

“…In this paper, we use this measure to define the grasp quality. Refer to [17] for the details of this method.…”

“…In the planning, we find acceptable contact positions of fingers using the ICRs considering a priori known object geometry. For the required grasp quality measure, we utilize the distance metric between the absolute grasp wrench space (GWS) and the object wrench space (OWS) borrowed from the authors' former work [17].…”

Searching force-closure optimal grasps of articulated 2D objects with n links

“…In addition to the above mentioned quality criteria, there are other criteria that have been proposed to evaluate grasps and fixtures of 2D and 3D objects, one of these criteria determines optimum gripping points by minimizing the average value of the normal forces applied on the object in order to balance any external perturbation (Mangialardi et al, 1996); on the other hand a fixturing can be evaluated using two indexes, one that minimizes the sum of all normal contact forces and the other minimizes the maximum normal contact force (Xiong et al, 2002); other proposals for assessing the quality of a grasp is the distance between the wrench origin and two sets of generalized wrenches (the union or the Minkowski sum of primitive contact wrenches) (Zheng and Qian, 2009) and the distance between the convex hulls of the absolute grasp wrench space and the object wrench space (Jeong and Cheong, 2010). Although different approaches have been proposed using different quality criteria for evaluating a grasp or fixture, these are focussed on a single object, either 2D or 3D.…”