System and method for coordinating movement of mobile drive units

A system for transporting inventory items, comprising:

• a plurality of mobile drive units;
• a plurality of inventory holders;
• and
• a management module operable to:
• receive, from a first mobile drive unit, a reservation request requesting use of a first path segment to move in a first direction;
• determine that a second mobile drive unit is currently located on the first path segment;
• determine whether the second mobile drive unit is moving in the first direction;
• in response to determining that the second mobile drive unit is not moving in the first direction, transmit a reservation response indicating that the reservation request is denied;
• and
• in response to determining that the second mobile drive unit is moving in the first direction, transmit a reservation response indicating that the reservation request is granted;
• wherein the first mobile drive unit is operable to:
• receive the reservation response;
• in response to receiving the reservation response, determine whether the reservation request was granted;
• in response to determining that the reservation request was granted, move across the first path segment in the first direction;
• in response to determining that the reservation request was denied:
• wait a predetermined amount of time;
• and
• after waiting the predetermined amount of time, transmit a second reservation request requesting use of the first path segment to move in the first direction.

A system for transporting inventory items, comprising:

• a plurality of mobile drive units;
• a plurality of inventory holders;
• and
• a management module operable to:
• receive, from a first mobile drive unit, a reservation request requesting use of a first path segment to move in a first direction;
• determine that a second mobile drive unit is currently located on the first path segment;
• determine whether the second mobile drive unit is moving in the first direction;
• in response to determining that the second mobile drive unit is not moving in the first direction, transmit a reservation response indicating that the reservation request is denied;
• and
• in response to determining that the second mobile drive unit is moving in the first direction, transmit a reservation response indicating that the reservation request is granted;
• wherein the management module is operable to transmit the reservation response indicating that the reservation request is granted by:
• determining whether the first path segment extends farther from the first mobile drive unit than a second path segment currently reserved by the second mobile drive unit;
• in response to determining that the first path segment does not extend farther from the first mobile drive unit than the second path segment, transmitting a reservation response indicating that the reservation request is granted;
• and
• in response to determining that the first path segment extends farther from the first mobile drive unit than the second path segment, transmitting a reservation response indicating that a reservation has been granted on a portion of the first path segment, wherein the portion is less than an entirety of the first path segment.

A system for transporting inventory items, comprising:

• a plurality of inventory holders;
• and
• a plurality of mobile drive units, wherein at least a first mobile drive unit is operable to:
• transmit a request to a management module for use of a path segment;
• receive a reservation response and a command to move in a first direction;
• initiate movement in the first direction along the path segment;
• detect, using a sensor, an object located on the path segment in the first direction from the first mobile drive unit;
• determine whether the object comprises a second mobile drive unit moving in the first direction;
• in response to determining that the object detected by the sensor comprises a second mobile drive unit moving in the first direction, continue movement in the first direction;
• and
• in response to determining that the object does not comprise a second mobile drive unit moving in the first direction, terminate movement in the first direction.

A system for transporting inventory items, comprising:

• a plurality of inventory holders;
• and
• a plurality of mobile drive units, wherein at least a first mobile drive unit is operable to:
• receive a command to move in a first direction;
• initiate movement in a first direction along a path segment;
• detect an object located on the path segment in the first direction from the first mobile drive unit;
• determine whether the object comprises a second mobile drive unit moving in the first direction;
• in response to determining that the object comprises a second mobile drive unit moving in the first direction, continue movement in the first direction;
• in response to determining that the object does not comprise a second mobile drive unit moving in the first direction, terminate movement in the first direction;
• and
• wherein the first mobile drive unit is operable to determine that the object comprises a second mobile drive unit moving in the first direction by determining whether the first mobile drive unit detects a drive identification signal transmitted by a second mobile drive unit, the drive identification signal indicating that the second mobile drive unit is a mobile drive unit moving in the first direction.

An apparatus for transporting inventory items, operable to:

• transmit a request to a management module for use of a path segment;
• receive a reservation response and a command to move in a first direction
• initiate movement in the first direction along the path segment;
• detect, using a sensor, an object located on the path segment in the first direction from the first mobile drive unit;
• determine whether the object comprises a second mobile drive unit moving in the first direction;
• in response to determining that the object detected by the sensor comprises a second mobile drive unit moving in the first direction, continue movement in the first direction;
• and
• in response to determining that the object does not comprise a second mobile drive unit moving in the first direction, terminate movement in the first direction.