Abstract
The invention relates to an automated storage and retrieval system comprising a plurality of container handling vehicles on a rail system operable to handle storage containers, each container handling vehicle comprises a positioning node. The system comprises a positioning system having reference positioning nodes spaced in fixed positions on and/or proximate the rail system to determine the position of each of the container handling vehicles. The control system communicates each container handling vehicle and the positioning system, and instructs a first container handling vehicle to move to a target position, repeatedly receives position data from the positioning system of a position of the first container handling vehicle and repeatedly receive position data from the positioning system of a position of a second container handling vehicle, and instructs the second container handling vehicle to move with the first container handling vehicle at a predetermined separation from the first container handling vehicle