Stacker crane control system

1. A stacker crane control system for controlling a stacker crane,

the stacker crane comprising:

a travel carriage configured to travel along a travel route;

a mast supported on the travel carriage in an orientation along a vertical direction;

a lift configured to move up and down within a predetermined lifting range along the mast;

a lifting apparatus configured to raise and lower the lift; and

a transfer apparatus supported by the lift and comprising a holding unit configured to hold an article,

wherein the stacker crane is configured to perform a transfer operation of transferring the article between the holding unit and a transfer destination, and

wherein the travel carriage is controlled so as to be stopped at reference stop positions that are preset at a plurality of locations along the travel route; and

the stacker crane control system comprising:

a sway detection unit configured to detect a reference swaying amount that is a swaying amount of the mast at a detection height, with the detection height set greater than or equal to the height of a lowermost part of the transfer apparatus when the lift is located at an upper limit of the lifting range;

a lifting height acquiring unit configured to acquire lifting height information that indicates a lifting height, which is the height of the lift, at a plurality of points in time;

a transfer control unit configured to control the transfer apparatus; and

a storage unit in which information regarding a mast reference position measured when the travel carriage is stopped at each of the plurality of reference stop positions is stored, and the mast reference position is a position of the mast at the detection height when the travel carriage is stopped at the reference stop position and the mast is standing still,

wherein the transfer control unit converts the reference swaying amount detected by the sway detection unit into a lifting height swaying amount that is a swaying amount of the mast at the lifting height indicated by the lifting height information, and starts the transfer operation of the transfer apparatus if the lifting height swaying amount is stably smaller than or equal to a predetermined determination threshold,

wherein the sway detection unit comprises:

a position detection sensor configured to dynamically detect the position of the mast at the detection height in a direction along the travel route; and

a stop position acquiring unit configured to acquire stop position information that indicates at which of the plurality of reference stop positions the travel carriage is stopped, and

wherein the sway detection unit acquires from the storage unit the mast reference position associated with the reference stop position indicated by the stop position information, and detects, as the reference swaying amount, a difference between the mast reference position and a result of the detection by the position detection sensor.

2. The stacker crane control system according to claim 1 , wherein:

the reference swaying amount is an amplitude of swaying of the mast at the detection height,

the lifting height swaying amount is an amplitude of swaying of the mast at the lifting height, and

the transfer control unit calculates, as the lifting height swaying amount, X 2 defined by the following expression (1)

X 2= X 1( H 2/ H 1) 3   (1)

where H 1 is the detection height, H 2 is the height of the lift, and X 1 is the reference swaying amount.

3. The stacker crane control system according to claim 1 , wherein:

the stop position acquiring unit comprises a stop-position detection sensor configured to detect an actual stop position, which is a position at which the travel carriage is actually stopped, and

the sway detection unit determines a corrected mast reference position by correcting the mast reference position based on a difference between the actual stop position and the reference stop position that corresponds to the actual stop position, and detects, as the reference swaying amount, a difference between the corrected mast reference position and the detection result of the detection by the position detection sensor.