Patent attributes
Randomly presented physical items can be temporarily stored in a grid-based material handling system, e.g., before they are handled by a robot. The grid-based material handling system arranges the randomly presented physical items within the grid, so that they exit the grid in an ordered sequence, e.g., for pickup by the robot. Programmable modules execute sequencing logic to move the items to target locations within the grid. The modules move interfering items out of the way of other items that are in transit to their target locations, as needed. The programmable modules allow the items to exit the grid when the requirements of a departure policy are met.