Transport system, transport method, and non-transitory storage medium

1. A transport system comprising a transport robot configured to transport an item picked up from a shelving unit or to be stored into the shelving unit, wherein:

the transport robot includes:

a placing table on which the item is to be placed,

a sensor, and

a lifting mechanism configured to lift and lower the placing table;

the placing table includes an engaging portion configured to engage with the shelving unit;

the shelving unit includes:

a first protrusion protruding inward from a side board of the shelving unit, or

a first recess formed in the side board of the shelving unit;

the placing table includes:

a second recess that engages with the first protrusion protruding inward from the side board of the shelving unit, or

a second protrusion that engages with the first recess formed in the side board of the shelving unit;

the shelving unit includes a plate-shaped member extending in a vertical direction, the plate-shaped member being the first protrusion;

the placing table includes a cutout that engages with the plate-shaped member, the cutout being the second recess;

the plate-shaped member has a plurality of holes arranged at different heights; and

the sensor is configured to detect each of the holes in the plate-shaped member is located inward of the cutout.

2. The transport system according to claim 1 , wherein the engaging portion is configured to restrict horizontal movement of the placing table.

3. The transport system according to claim 1 , wherein the transport robot is further configured to

pick up the item from the shelving unit and place the item on the placing table, and

store the item placed on the placing table into the shelving unit.

4. The transport system according to claim 1 , wherein:

a sliding material or a roller is provided in the cutout of the placing table; and

the placing table is configured to slide while being engaged with the plate-shaped member.