Orienting parts by inside-out pulling

Abstract

A common task in automated manufacturing processes is that of orienting (or feeding) parts prior to assembly. In this paper, we propose a new type of feeder. We consider sensorless orientation of polygonal parts with elevated edges by pull actions with an overhead finger. We show that any asymmetric convex polygonal part can be oriented by a sequence of pull operations. We give an Ç´Ò ¿ µ algorithm to compute the shortest sequence of pull operations to orient a convex polygonal part with Ò vertices, if such a sequence exists. We also show that there exist non-convex parts that cannot be fed by a sequence of pull operations.

Exact Bounds on the Contact Driven Motion of a Sliding Object, With Applications to Robotic Pulling

“…The stable equilibrium that occurs when pulling along a straight line was recognized, without proof, by Mason [10], Lynch and Mason [8], and Berretty et al [2]. For completeness, we provide a proof in Subsection IV-A.…”

“…For completeness, we provide a proof in Subsection IV-A. To the best of our knowledge, Berretty et al is the only work, apart from ours, to explicitly take advantage of this stability [2]. However, the method of Berretty et al is limited to orienting asymmetrical convex polygons.…”

“…The existence of the stable equilibrium was observed, without proof, in Mason [10], Lynch and Mason [8], and Berretty et al [2]. The robotic pulling trajectories generated in Subsection V-C automatically use the stable equilibrium to reduce pose uncertainty.…”

“…Naturally, smaller objects or tighter bounds are required for smaller tables. Figure 4 shows the experimental setup that we used to test the robotic pulling trajectories generated by the planning algorithm in Subsection V-C. 2 Note that this distance is independent of the pulling velocity, see Equation (??). Experimental data was collected using an ABB 140 manipulator equipped with a conical finger.…”

Capturing a concave polygon with two disc-shaped fingers

“…Ability to capture an object clearly contributes to the robustness and success of grasping tasks as we can guarantee a successful grasp of an object when it cannot escape from the surrounding fingers during the entire grasping execution. 1 A comprehensive review on grasping works can be found in [2].…”