Finger design automation for industrial robot grippers: A review <s> General Metrics: <s> The authors address the problem of planning optimal grasps. Two general optimality criteria that consider the total finger force and the maximum finger force are introduced and discussed. Their formalization using various metrics on a space of generalized forces is detailed. The geometric interpretation of the two criteria leads to an efficient planning algorithm. An example of its use in a robotic environment equipped with two-jaw and three-jaw is described. > <s> BIB001 </s> Finger design automation for industrial robot grippers: A review <s> General Metrics: <s> We consider the problem of finding optimum force closure grasps of two and three-dimensional objects. Our focus is on grasps which are useful in practice, namely grasps with a small number of fingers, with friction at the contacts. Assuming frictional contact and rounded finger tips-very mild assumptions in practice-we give new upper (and lower) bounds on the number of fingers necessary to achieve force closure grasps of 2-D and 3-D objects. We develop an optimality criterion based on the notion of decoupled wrenches, and use this criterion to derive optimum two and three finger grasps of 2-D objects, and optimum three finger grasps for 2-D objects. We present a simple O(n) algorithm for computing these optimum grasps for convex polygons, a O(n log n) algorithm for nonconvex polygons, and an O(n/sup 3/) algorithm for polyhedra. In studying these optimum grasps, we derive several interesting theoretical results concerning grasp geometry. > <s> BIB002 </s> Finger design automation for industrial robot grippers: A review <s> General Metrics: <s> The convex hull of a set of points is the smallest convex set that contains the points. This article presents a practical convex hull algorithm that combines the two-dimensional Quickhull algorithm with the general-dimension Beneath-Beyond Algorithm. It is similar to the randomized, incremental algorithms for convex hull and delaunay triangulation. We provide empirical evidence that the algorithm runs faster when the input contains nonextreme points and that it used less memory. computational geometry algorithms have traditionally assumed that input sets are well behaved. When an algorithm is implemented with floating-point arithmetic, this assumption can lead to serous errors. We briefly describe a solution to this problem when computing the convex hull in two, three, or four dimensions. The output is a set of “thick” facets that contain all possible exact convex hulls of the input. A variation is effective in five or more dimensions. <s> BIB003 </s> Finger design automation for industrial robot grippers: A review <s> General Metrics: <s> A scheme for learning to grasp objects using visual information is presented. The learning problem is divided into two separate subproblems: choosing grasping points and predicting the quality of a given grasp. For each grasp we store location parameters that code the locations of the grasping points, quality parameters that are relevant features for the assessment of grasp quality, and the associated grade. The location parameters, using a special coding which is not object specific, are used to locate grasping points on new target objects. A function from the quality parameters to the grade is learned from examples. Grasp quality for novel situations can be generalized and estimated using the learned function. An experimental setup using an AdeptOne manipulator was developed to test this scheme. The system had demonstrated an ability to grasp a relatively wide variety of objects, and its performance had significantly improved with practice following a small number of trials. The knowledge learned for a set of objects was successfully generalized to new objects. <s> BIB004 </s> Finger design automation for industrial robot grippers: A review <s> General Metrics: <s> This article addresses the problem of computing stable grasps of three-dimensional polyhedral objects. We consider the case of a hand equipped with four hard fingers and assume point contact with friction. We prove new necessary and sufficient conditions for equilibrium and force closure, and present a geometric characterization of all possible types of four-finger equilibrium grasps. We then focus on concurrent grasps, for which the lines of action of the four contact forces all intersect in a point. In this case, the equilibrium conditions are linear in the unknown grasp parameters, which reduces the problem of computing the stable grasp regions in configuration space to the problem of constructing the eight-dimensional projec tion of an ll-dimensinnal polytope. We present two projection methods: the first one uses a simple Gaussian elimination ap proach, while the second one relies on a novel output-sensitive contour-tracking algorithm. Finally, we use linear optimization within the valid configuration... <s> BIB005 </s> Finger design automation for industrial robot grippers: A review <s> General Metrics: <s> This paper presents and analyses ten criteria that assess the quality of a set of three-finger grips suitable for dextrous manipulation on real 2D parts. The set of candidate hand configurations is the result of a previous process of grasp generation from the object image. The proposed criteria include six that depend on the actual finger configuration of the gripper. The kinematics of the Barrett hand has been used. The criteria are merged to give a global quality value that can be used to select the best grip to execute. Experimental results include tests on stability and the effect of parameter variation. <s> BIB006 </s> Finger design automation for industrial robot grippers: A review <s> General Metrics: <s> We present Partial Quick Hull (PQH), an algorithm to efficiently compute one of the most commonly used grasp quality metrics. The metric relies on the computation of the convex hull of a set of points in a six dimensional space. Built on top of widely used QuickHull algorithm, PQH exploits the relationship between the convex hull and the grasp quality metric to avoid computing the whole convex hull. PQH determines at run time when the computation can be ended because the grasp quality metric can be already determined from a partially computed convex hull - hence the name of the algorithm. This improvement greatly accelerates grasp quality evaluation for force closure grasps. When the grasp is not force closure, the partial computation does not apply and PQH then behaves exactly like QuickHull. A large set of experimental tests show how PQH largely outperforms QuickHull and better scales with the size of the input. <s> BIB007
General metrics are the quality measures that do not take the (assembly) task into account. As these metrics provide a general information regarding stability of the grasp, they are more suitable for simple pick and place tasks. BIB001 introduce the most popular methods for measuring grasp quality. They propose using the largest disturbance wrench that can be resisted in all directions by the contacts as a grasp quality metric. From a geometrical perspective, this resembles the radius of the largest ball centered at the origin, which is inscribed in the convex hull of the unit contact wrench (see Fig. 7 ). To determine this metric, computation of a convex hull in six dimensions is required. The freely available QuickHull BIB003 implementation (Qhull, 2015) is widely used to solve this problem. Computing the convex hull for every set of grasp is computationally expensive. BIB007 have shown that for the force-closure grasps most of the computation of the convex hull is unnecessary based on the definition of the quality metric presents by BIB001 . Thus, BIB007 propose the Partial Quick Hull (PQH) algorithm to efficiently compute the metric. PQH determines, on the fly, when the computation can be ended as the quality metric can be already computed before completely determining the convex hull. This method noticeably reduces computation time when using this metric. Zheng (2013) presents a different algorithm for the grasp quality measure proposed by BIB001 . Zheng's method iteratively grows a polytope containing the origin in the grasp wrench space (GWS) as though the minimum distance between the origin and the facets of the polytope quickly converges to the quality metric value. This method is more efficient than others in the way that it does not require computation of the Quickhull algorithm. Besides, there is no need for approximating the friction cone hence it provides more accurate results. Another widely used quality measure that is similar to BIB001 is presented by BIB002 . They propose a method that first collects the grasp sets with the best resistance to disturbance forces and from these selects those which resist external torques better. While the studies reviewed so far are considering contact wrenches, some researchers focused on introducing quality metrics based on the geometric properties of the workpiece. BIB006 propose a metric based on the area of the grasp polygon formed by the contact points on the workpiece. Chinellato et al. propose that maximizing the area of the triangle formed by three contact points on the workpiece increases the stability of the grasp. Minimizing the effects of internal and gravitational forces is another essential factor in obtaining a stable grasp. Thus, the distance between the center of mass of the object and the centroid of the polyhedron formed by the contact points has been proposed as grasp quality metric (Jean BIB005 BIB004 ). On one hand, the geometric based metrics are computationally cheap and simple to implement. On the other hand, they all suffer from a bold assumption that an unlimited amount of force can be applied by the fingers. In other words, the fingers may have to exert extremely large forces for resisting small disturbances, which is not realistic.