A storage system for storing and transporting a plurality of storage bins to and from an upper location and a lower location of a three dimensional storage grid constructed by columns interconnected by top rails, the storage system comprising the three dimensional storage grid , characterized in further comprising: - a movable continuous chain running from the upper location to the lower location of said storage grid , said chain comprises compartments fitted for holding the bins ; - robot vehicles , running on the top of the storage grid , and comprising a hoisting gear for picking up, carrying, and placing bins that is located on the side of the main body of the vehicle or is integrated in the main body of the robot vehicle for loading and unloading bins to and from the compartments in the continuous chain ; - a sensor for detecting the position of the compartments of the movable chain relative to the upper location on the storage grid where bins are loaded or unloaded; - a control system for controlling the loading and unloading of the bins from the compartments in the chain , the control system comprises a master controller connected to a first and second control system, said first control system controlling the movements and actions of each robot vehicle , and said second control system controlling the movable chain , and where the master controller is connected to said sensor for detecting the position of the compartments relative to the upper location on the storage grid, and is adapted for controlling the speed of the movable chain relative to the positions of the robot vehicles , based on information about the location and speed of each mobile vehicle as well as the movements of the chain with compartments , for adjusting the speed of the continuous chain according to current speeds and locations of robot vehicles picking up or delivering bins 4 to and from compartments of the chain for providing optimal speed of loading/unloading and utilization of each compartment in the movable chain. - a movable continuous chain running from the upper location to the lower location of said storage grid , said chain comprises compartments fitted for holding the bins ; - robot vehicles , running on the top of the storage grid , and comprising a hoisting gear for picking up, carrying, and placing bins that is located on the side of the main body of the vehicle or is integrated in the main body of the robot vehicle for loading and unloading bins to and from the compartments in the continuous chain ; - a sensor for detecting the position of the compartments of the movable chain relative to the upper location on the storage grid where bins are loaded or unloaded; - a control system for controlling the loading and unloading of the bins from the compartments in the chain , the control system comprises a master controller connected to a first and second control system, said first control system controlling the movements and actions of each robot vehicle , and said second control system controlling the movable chain , and where the master controller is connected to said sensor for detecting the position of the compartments relative to the upper location on the storage grid, and is adapted for controlling the speed of the movable chain relative to the positions of the robot vehicles , based on information about the location and speed of each mobile vehicle as well as the movements of the chain with compartments , for adjusting the speed of the continuous chain according to current speeds and locations of robot vehicles picking up or delivering bins 4 to and from compartments of the chain for providing optimal speed of loading/unloading and utilization of each compartment in the movable chain. <EOS>