Optimizing truck loading of pallets

1. A method for loading pallets on a vehicle, the method comprising:

receiving pallet information for a shipment, the pallet information describing pallets to be included in the shipment, each pallet being associated with one or more pallet characteristics;

for each pallet to be included in the shipment, assigning the pallet to a respective pallet characteristic group based on its pallet characteristics, each pallet characteristic group including pallets having substantially similar characteristics, wherein an assigned slot for each pallet of a given pallet characteristic group is swappable with assigned slots of other pallets of the given pallet characteristic group when loading pallets on the vehicle according to a loading solution, wherein a number of pallet characteristic groups is more than one and fewer than a number of pallets to be included in the shipment;

receiving vehicle constraint information for the vehicle, the vehicle constraint information describing rules for loading pallets on the vehicle;

determining, by a warehouse management system, candidate loading solutions for loading the pallets on the vehicle, the candidate loading solutions being a subset of all possible loading solutions for loading the pallets on the vehicle, each candidate loading solution (i) satisfying the rules for loading pallets on the vehicle, and (ii) assigning, for each pallet to be included in the shipment, a respective slot for the pallet on the vehicle;

evaluating, by the warehouse management system, at least some of the candidate loading solutions;

based on the evaluating, selecting one of the candidate loading solutions; and

loading the vehicle, wherein loading the vehicle comprises:

retrieving, by an automated storage and retrieval system, (i) a first pallet to be loaded on the vehicle in a first slot, according to the selected candidate loading solution, and (ii) a second pallet to be loaded on the vehicle in a second, different slot, according to the selected candidate loading solution;

receiving data from a pallet identification device that indicates that the second pallet has arrived at the vehicle;

determining, based on the data from the pallet identification device and based on the selected candidate loading solution, that the second pallet has arrived at the vehicle out of sequence, according to the selected candidate loading solution;

determining that the second pallet is assigned to a same pallet characteristic group as the first pallet; and

loading the second pallet on the vehicle in the first slot, in place of the first pallet.

2. The method of claim 1 , wherein the one or more pallet characteristics include a pallet weight and a pallet size.

3. The method of claim 1 , wherein the rules for loading pallets on the vehicle include a rule that specifies a total weight of pallets to be loaded on the vehicle.

4. The method of claim 1 , wherein the rules for loading pallets on the vehicle include a rule that specifies a maximum height of pallets to be loaded on the vehicle.

5. The method of claim 1 , wherein the rules for loading pallets on the vehicle include a rule that specifies that a total weight of pallets to be loaded on a left side of the vehicle is to be substantially similar to a total weight of pallets to be loaded on a right side of the vehicle.

6. The method of claim 1 , wherein the rules for loading pallets on the vehicle include a rule that specifies two or more zones for the vehicle, with at least two of the zones being associated with different total weights of pallets to be loaded in the respective zone.

7. The method of claim 1 , wherein the rules for loading pallets on the vehicle include a rule that specifies that adjacent pallets to be loaded on the vehicle are to have substantially similar heights.

8. The method of claim 1 , wherein evaluating at least some of the candidate loading solutions includes determining, for each of the at least some of the candidate loading solutions, a respective solution cost, the solution cost representing an efficiency of a candidate loading solution with respect to loading the vehicle, wherein the selected candidate loading solution is selected based on its solution cost.

9. The method of claim 8 , wherein determining a solution cost for a candidate loading solution includes:

(i) for each pallet to be included in the shipment, determining a pallet cost for loading the pallet on the vehicle according to a position and orientation of its assigned slot as defined in the candidate solution; and

(ii) aggregating the pallet costs.

10. The method of claim 1 , wherein loading the second pallet on the vehicle is performed by a pallet mover that receives the second pallet from the automated storage and retrieval system.

11. A computer system comprising:

one or more data processing apparatuses including one or more processors, memory, and storage devices storing instructions that, when executed, cause the one or more processors to perform operations for loading pallets on a vehicle, comprising:

receiving pallet information for a shipment, the pallet information describing pallets to be included in the shipment, each pallet being associated with one or more pallet characteristics;

for each pallet to be included in the shipment, assigning the pallet to a respective pallet characteristic group based on its pallet characteristics, each pallet characteristic group including pallets having substantially similar characteristics, wherein an assigned slot for each pallet of a given pallet characteristic group is swappable with assigned slots of other pallets of the given pallet characteristic group when loading pallets on the vehicle according to a loading solution, wherein a number of pallet characteristic groups is more than one and fewer than a number of pallets to be included in the shipment;

receiving vehicle constraint information for the vehicle, the vehicle constraint information describing rules for loading pallets on the vehicle;

determining, by a warehouse management system, candidate loading solutions for loading the pallets on the vehicle, the candidate loading solutions being a subset of all possible loading solutions for loading the pallets on the vehicle, each candidate loading solution (i) satisfying the rules for loading pallets on the vehicle, and (ii) assigning, for each pallet to be included in the shipment, a respective slot for the pallet on the vehicle;

evaluating, by the warehouse management system, at least some of the candidate loading solutions;

based on the evaluating, selecting one of the candidate loading solutions; and

loading the vehicle, wherein loading the vehicle comprises:

retrieving, by an automated storage and retrieval system, (i) a first pallet to be loaded on the vehicle in a first slot, according to the selected candidate loading solution, and (ii) a second pallet to be loaded on the vehicle in a second, different slot, according to the selected candidate loading solution;

receiving data from a pallet identification device that indicates that the second pallet has arrived at the vehicle;

determining, based on the data from the pallet identification device and based on the selected candidate loading solution, that the second pallet has arrived at the vehicle out of sequence, according to the selected candidate loading solution;

determining that the second pallet is assigned to a same pallet characteristic group as the first pallet; and

loading the second pallet on the vehicle in the first slot, in place of the first pallet.

12. The system of claim 11 , wherein the one or more pallet characteristics include a pallet weight and a pallet size.

13. The system of claim 11 , wherein the rules for loading pallets on the vehicle include a rule that specifies a total weight of pallets to be loaded on the vehicle.

14. The system of claim 11 , wherein the rules for loading pallets on the vehicle include a rule that specifies a maximum height of pallets to be loaded on the vehicle.

15. The system of claim 11 , wherein the rules for loading pallets on the vehicle include a rule that specifies that a total weight of pallets to be loaded on a left side of the vehicle is to be substantially similar to a total weight of pallets to be loaded on a right side of the vehicle.

16. The system of claim 11 , wherein the rules for loading pallets on the vehicle include a rule that specifies two or more zones for the vehicle, with at least two of the zones being associated with different total weights of pallets to be loaded in the respective zone.

17. The system of claim 11 , wherein the rules for loading pallets on the vehicle include a rule that specifies that adjacent pallets to be loaded on the vehicle are to have substantially similar heights.

18. The system of claim 11 , wherein evaluating at least some of the candidate loading solutions includes determining, for each of the at least some of the candidate loading solutions, a respective solution cost, the solution cost representing an efficiency of a candidate loading solution with respect to loading the vehicle, wherein the selected candidate loading solution is selected based on its solution cost.

19. The system of claim 18 , wherein determining a solution cost for a candidate loading solution includes:

(i) for each pallet to be included in the shipment, determining a pallet cost for loading the pallet on the vehicle according to a position and orientation of its assigned slot as defined in the candidate solution; and

(ii) aggregating the pallet costs.

20. The system of claim 11 , wherein loading the second pallet on the vehicle is performed by a pallet mover that receives the second pallet from the automated storage and retrieval system.