Lift and tilt platform

1. A system, comprising:

an inventory holder comprising a plurality of compartments configured to hold a plurality of items;

a mobile drive unit configured for movement within a facility, the mobile drive unit comprising a docking head assembly attached to a frame of the mobile drive unit, the docking head assembly comprising:

a docking platform;

a tilting mechanism disposed below the docking platform and comprising a first actuator configured to cause tilting of the docking platform with respect to a horizontal axis of the mobile drive unit; and

a lifting mechanism disposed below the tilting mechanism, the lifting mechanism comprising:

a lower frame connected to the mobile drive unit;

an upper frame pivotably connected to the tilting mechanism; and

a second actuator configured to cause vertical lifting of the docking platform with respect the horizontal axis of the mobile drive unit; and

a management device in communication with the mobile drive unit and configured to:

cause the lifting mechanism to lift the inventory holder into a first orientation by raising the docking platform into engagement with the inventory holder and further raising the inventory holder until the inventory holder is lifted;

access ramp information identifying properties of an inclined ramp extending between a first floor of the facility and a second floor of the facility;

determine a tilt angle for tilting the docking platform based at least in part on the ramp information; and

after the lifting mechanism has lifted the inventory holder into the first orientation, cause the tilting mechanism to tilt the docking platform in accordance with the tilt angle to cause the inventory holder to tilt into a second orientation so that the mobile drive unit is positioned to transport the inventory holder along the inclined ramp.

2. The system of claim 1 , wherein the management device is further configured to cause the mobile drive unit to transport the inventory holder along the inclined ramp when the inventory holder is in the second orientation.

3. The system of claim 2 , wherein the management device is further configured to:

cause the mobile drive unit to transport the inventory holder along the inclined ramp from a first location on the first floor to a second location on the second floor;

cause the tilting mechanism to return the docking platform to the first orientation;

cause the lifting mechanism to disengage the docking platform from the inventory holder by lowering the docking platform; and

cause the mobile drive unit to move from the second location on the second floor to a third location on the second floor while disengaged from the inventory holder.

4. The system of claim 1 , wherein the management device is further configured such that causing the tilting mechanism to tilt the docking platform to cause the inventory holder to tilt into the second orientation further comprises causing the lifting mechanism to lower the docking platform at or about the same time as the tilting mechanism tilts the docking platform into the second orientation, the docking platform remaining in engagement with the inventory holder when in the second orientation.

5. A computer-implemented method, comprising:

determining a tilt angle for a tilting mechanism of a mobile drive unit based at least in part on path data, the path data associated with a path extending between a first surface and a second surface, the second surface being higher than the first surface;

causing a lifting mechanism of the mobile drive unit to lift a holder structure with respect to a horizontal axis of the mobile drive unit, the lifting mechanism comprising a lower frame connected to the mobile drive unit and an upper frame pivotably connected to the tilting mechanism;

causing the tilting mechanism to tilt the holder structure in accordance with the tilt angle and with respect to the horizontal axis; and

causing the mobile drive unit to transport the holder structure on the path, with the holder structure tilted in accordance with the tilt angle.

6. The computer-implemented method of claim 5 , further comprising receiving sensor data from a sensor of the mobile drive unit, the sensor data descriptive of a sensed angle of the mobile drive unit with respect to a reference surface.

7. The computer-implemented method of claim 6 , wherein:

the path data is stored in association with a facility map that includes the path; and

the method further comprises updating the path data based at least in part on the sensor data.

8. The computer-implemented method of claim 6 , wherein:

the sensor is a gyro sensor; and

the method further comprises:

determining an updated tilt angle based at least in part on the sensor data; and

causing the tilting mechanism to tilt the holder structure in accordance with the updated tilt angle at least while the mobile drive unit is located on the path.

9. The computer-implemented method of claim 5 , further comprising, after a leading portion of the mobile drive unit is on the path, causing the lifting mechanism to lower the holder structure at or about the same time as the tilting mechanism tilts the holder structure in accordance with the tilt angle.

10. The computer-implemented method of claim 9 , further comprising, prior to causing the lifting mechanism to lower the holder structure:

receiving sensor data representative of a position of the mobile drive unit with respect to the path; and

determining that the leading portion of the mobile drive unit is on the path is based at least in part on the sensor data.

11. The computer-implemented method of claim 5 , wherein the tilt angle is equal to a path angle measured between a horizontal plane of the first surface and a non-horizontal plane of the path.

12. The computer-implemented method of claim 5 , wherein the tilting mechanism is configured to tilt the holder structure at an angular velocity that corresponds to a velocity of the mobile drive unit.

13. The computer-implemented method of claim 5 , wherein:

the mobile drive unit is a ramp mobile drive unit; and

the method further comprises causing a floor mobile drive unit to transport the holder structure to a first position on the first surface proximate to the path prior to causing the lifting mechanism of the mobile drive unit to lift the holder structure.

14. A mobile drive unit, comprising:

a frame;

a drive unit attached to the frame and configured to move the mobile drive unit; and

a docking head assembly attached to the frame, the docking head assembly comprising:

a docking platform configured to engage with a holder structure;

a tilting mechanism disposed below the docking platform and comprising a first actuator coupled to the docking platform and configured to cause tilting of the docking platform with respect to a horizontal axis of the mobile drive unit; and

a lifting mechanism disposed below the tilting mechanism, the lifting mechanism comprising:

a lower frame connected to the mobile drive unit;

an upper frame pivotably connected to the tilting mechanism; and

a second actuator configured to cause vertical lifting of the docking platform with respect the horizontal axis of the mobile drive unit.

15. The mobile drive unit of claim 14 , further comprising a management device configured to:

determine a tilt angle for the tilting mechanism based at least in part on path data, the path data associated with a path extending between a first floor and a second floor of a facility;

cause the lifting mechanism to lift the holder structure with respect to the horizontal axis after the mobile drive unit is disposed below the holder structure;

cause the tilting mechanism to tilt the holder structure in accordance with the tilt angle and with respect to the horizontal axis; and

cause the mobile drive unit to transport the holder structure on the path, with the holder structure tilted in accordance with the tilt angle.

16. The mobile drive unit of claim 14 , wherein:

the lifting mechanism further comprises:

a first scissor link coupled to each of the upper frame and the lower frame;

a second scissor link coupled to each of the upper frame and the lower frame; and

a connecting member extending between a first middle joint of the first scissor link and a second middle joint of the second scissor link; and

the second actuator is coupled to the lifting mechanism via the connecting member.

17. The mobile drive unit of claim 14 , wherein:

the lifting mechanism is configured to couple and decouple with the holder structure by vertically moving the docking platform between:

a first vertical position in which the docking platform is disposed below the holder structure without physically contacting the holder structure, the holder structure resting on a support surface when the docking platform is in the first vertical position; and

a second vertical position in which the docking platform physically contacts the holder structure and supports the holder structure, the holder structure held above the support surface when the docking platform is in the second vertical position; and

the tilting mechanism is configured to tilt the docking platform between:

a level orientation in which the docking platform is level with respect to the horizontal axis, the holder structure held in the level orientation when the docking platform is in the second vertical position and the level orientation; and

a tilted orientation in which the docking platform is tilted with respect to the horizontal axis, the holder structure held in the tilted orientation when the docking platform is in the second vertical position and the tilted orientation.

18. The mobile drive unit of claim 14 , wherein the mobile drive unit is configured to detachably couple with the holder structure and transport the holder structure between floors of a facility.

19. The mobile drive unit of claim 14 , wherein the upper frame is pivotably connected to the tilting mechanism at a pivot point, and wherein the tilting mechanism is configured to tilt the holder structure about the pivot point.

20. The mobile drive unit of claim 14 , wherein the tilting mechanism is configured to tilt the holder structure independent of the lifting mechanism lifting the holder structure.

21. A computer-implemented method, comprising:

determining a tilt angle for a tilting mechanism of a mobile drive unit based at least in part on path data, the path data associated with a path extending between a first surface and a second surface, the second surface being higher than the first surface;

causing a lifting mechanism of the mobile drive unit to lift a holder structure with respect to a horizontal axis of the mobile drive unit;

causing the tilting mechanism to tilt the holder structure in accordance with the tilt angle and with respect to the horizontal axis, wherein the tilting mechanism is configured to tilt the holder structure at an angular velocity that corresponds to a velocity of the mobile drive unit; and

causing the mobile drive unit to transport the holder structure on the path, with the holder structure tilted in accordance with the tilt angle.