Controller and method for transporting devices

A storage system comprising:

• a first set of parallel rails or tracks extending in an X-direction, and a second set of parallel rails or tracks extending in a Y-direction transverse to the first set in a substantially horizontal plane to form a grid pattern comprising a plurality of grid spaces;
• a plurality of stacks of containers located beneath the rails, and arranged such that each stack is located within a footprint of a single grid space;
• a plurality of transporting devices each arranged to selectively move in the X and/or Y directions, above the stacks on the rails and arranged to transport a container;
• a robotic arm for picking items from containers stored beneath the rails;
• and
• a controller configured and arranged to control movement of a plurality of transporting devices.

A method for controlling movement of a plurality of transporting devices, the method comprising the steps of:

• determining a plurality of routes from one location on a grid-like structure to another location on the grid-like structure for a first transporting device, the grid-like structure comprising a plurality of rails and a robotic arm for picking items from containers stored beneath the rails;
• generating at least one leg for each of the plurality of routes determined by the determining step;
• calculating a shunt path for the robotic arm so as to shunt the robotic arm, wherein the shunt path is calculated at a predetermined time before which the robotic arm must commence movement to permit the uninterrupted passage of the first transporting device;
• and
• providing clearance for the first transporting device to traverse a leg of a determined route.