US Patent 10472172 Robotic inventory handling

An inventory handling system (20, 150) includes multiple shelving units (22) for mounting over a horizontal floor (24). Each shelving unit contains a vertical array of shelves (28) on which containers (30) are placed. One or more floor robots (36) travel among the shelving units along first paths on the floor. One or more lift robots (32, 80, 120, 152) move independently of the floor robots along second paths in a vertical plane over vertical faces of the shelving units, and transfer the containers between the shelves and the floor robots.