A control system comprising: one or more processors ; and a computer-readable storage medium storing instructions that, when executed by the one or more processors , cause the control system to perform functions comprising: storing data indicating an association between a first optical identifier and a first robot ; sending, to the first robot , data encoding the first optical identifier for display by the first robot ; and after sending the data encoding the first optical identifier , sending, to a second robot , the data indicating the association between the first optical identifier and the first robot ; wherein the functions further comprise: determining that a predetermined amount of time passed since (i) storing the data indicating the association between the first optical identifier and the first robot or (ii) sending the data encoding the first optical identifier to the first robot ; in response to determining that the predetermined amount of time passed, sending, to the first robot , data encoding a second optical identifier of the first robot for display by the first robot ; and storing data indicating an association between the second optical identifier and the first robot . one or more processors ; and a computer-readable storage medium storing instructions that, when executed by the one or more processors , cause the control system to perform functions comprising: storing data indicating an association between a first optical identifier and a first robot ; sending, to the first robot , data encoding the first optical identifier for display by the first robot ; and after sending the data encoding the first optical identifier , sending, to a second robot , the data indicating the association between the first optical identifier and the first robot ; storing data indicating an association between a first optical identifier and a first robot ; sending, to the first robot , data encoding the first optical identifier for display by the first robot ; and after sending the data encoding the first optical identifier , sending, to a second robot , the data indicating the association between the first optical identifier and the first robot ; wherein the functions further comprise: determining that a predetermined amount of time passed since (i) storing the data indicating the association between the first optical identifier and the first robot or (ii) sending the data encoding the first optical identifier to the first robot ; in response to determining that the predetermined amount of time passed, sending, to the first robot , data encoding a second optical identifier of the first robot for display by the first robot ; and storing data indicating an association between the second optical identifier and the first robot . determining that a predetermined amount of time passed since (i) storing the data indicating the association between the first optical identifier and the first robot or (ii) sending the data encoding the first optical identifier to the first robot ; in response to determining that the predetermined amount of time passed, sending, to the first robot , data encoding a second optical identifier of the first robot for display by the first robot ; and storing data indicating an association between the second optical identifier and the first robot . <EOS>