System and method of operating an automated storage and retrieval system

A system for use in an automated storage and retrieval system, the system comprising:

• a plurality of container handling vehicles operable to handle storage containers, each container handling vehicle comprising:
• a positioning node, and
• a local controller adapted to control movements of the each container handling vehicle;
• a positioning system comprising at least three reference positioning nodes configured to be spaced in fixed positions, the positioning system being adapted to determine a position for each container handling vehicle among the plurality of container handling vehicles based on signal measurements between the positioning node of the each container handling vehicle and the at least three reference positioning nodes;
• and
• a control system adapted to communicate with the local controller in each container handling vehicle and the positioning system, the control system being adapted to:
• instruct a first container handling vehicle of the plurality of container handling vehicles to move to a target position,
• receive first position data from the positioning system of a first position of the first container handling vehicle and receive second position data from the positioning system of a second position of a second container handling vehicle of the plurality of container handling vehicles, and
• instruct the second container handling vehicle to move with and follow the first container handling vehicle within a predetermined separation from the first container handling vehicle based on the first position data and the second position data of the first position and second position of the first and second container handling vehicles.

A method of controlling movement of a plurality of container handling vehicles in a system comprising a plurality of container handling vehicles operable to handle storage containers, each container handling vehicle comprising a positioning node, and a local controller adapted to control movements of the each container handling vehicle;

• a positioning system comprising at least three reference positioning nodes configured to be spaced in fixed positions, the positioning system being adapted to determine a position for each container handling vehicle among the plurality of container handling vehicles based on signal measurements between the positioning node of the each container handling vehicle and the at least three reference positioning nodes;
• and a control system adapted to communicate with the local controller in each container handling vehicle and the positioning system;
• wherein the method comprises, at the control system:
• instructing a first container handling vehicle to move to a target position,
• receiving first position data from the positioning system of a first position of the first container handling vehicle and receiving second position data from the positioning system of a second position of a second container handling vehicle, and
• instructing the second container handling vehicle to move with and follow the first container handling vehicle within a predetermined separation from the first container handling vehicle based on the first position data and the second position data of the first position and second position of the first and second container handling vehicles.