“…1), and it is possible to distinguish a subset of those that rely on the reproduction of a pre-programmed route, such as where a map that has been pre-designed and uploaded, or a route that is mapped by markers or lines [1][2][3]. A distinction can be drawn between those that rely on reference points, such as magnetic lines [4], RFID [5,6], QRCode [7,8], and others, and those that employ image recognition [9] and artificial intelligence techniques [10][11][12][13]. Another group uses sound (ultrasonic) waves [14,15] or electromagnetic waves, such as laser [16][17][18], infrared [19] technologies, and radio waves [20][21][22], such as Bluetooth [23] or UWB [24,25] technologies.…”