Optimal Curved Fences for Part Alignment on a Belt

Abstract

In automated packing or assembly it is often necessary to bring randomly oriented parts into uniform alignment. Mechanical methods such as vibratory bowl feeders are often used for this purpose, although there is no theory for the systematic design of such feeders. A slanted “fence” attached to the stationary sides of a conveyor belt is also capable of orienting a stream of parts and a sequence of such fences has been shown [17] to function as a systematically designable linear parts feeder. A limitation of fence alignment is that once a part has left contact with a fence, its final orientation is confined to a narrow range of angles but is not unique. Here we consider the design of a single fence, consisting of a straight slanted section followed by an optimal curved tail. The straight section selectivity aligns certain edges of the part, while the curved tail preserves this alignment precisely as the part leaves contact with the fence. We have found the shortest tail which guarantees alignment. Optimal curved fences may be used individually for alignment of parts on a conveyor belt. They also lend themselves to systematic design of multi-fence linear parts feeders [8], [17].

Optimal Shape and Motion Planning for Dynamic Planar Manipulation

“…Caine [3] develops a framework and set of computational tools for designing the shapes of features in a vibratory bowl feeder. Similarly, Brokowski et al [2] optimize the shape of a curved fence used to reorient parts traveling along a conveyer belt. Rodriguez and Mason [20,21,19] build a framework for computing end effector shapes for 1 DOF actuators and desired contact interactions based on sets of contact normals.…”

A Near-Quadratic Algorithm for Fence Design

“…In order to avoid any uncertainty in the orientation of the part as it leaves a fence, we add a carefully curved tail, as in [4]. This ensures that when the part leaves the fence, the aligned edge is parallel to and facing the wall from which the fence emanates.…”

“…They discretize the set of allowable fences, so their solution is not complete, in the sense that when their algorithm fails to design a feeder, there may still exist a solution that requires an angle not in their set. Later, Brokowski et al [4] constrained the part to one of Ǵѵ orientations by adding a curved tail to each fence. This led to the complete algorithm of Wiegley et al [15], which allows for all possible fence angles and is guaranteed to find a sequence of fences to orient a part if one exists.…”

Trap design for vibratory bowl feeders

“…The input is a description of the part shape and the output is a sequence of open-loop actions that moves a part from an unknown initial orientation into a unique final orientation. Among the sensorless part feeders considered in literature are the parallel-jaw gripper [17,21], the single pushing jaw [2,27,28,32], the conveyor belt with a sequence of (stationary) fences placed along its sides [10,14,33,36], the conveyor belt with a single rotational fence [1], the tilting tray [20,31], vibratory plates and programmable vector fields [11].…”