Bot having high speed stability

1. A method for transporting items in a storage and retrieval system with an autonomous transport vehicle, the method comprising:

independently driving at least two drive wheels of the autonomous transport vehicle;

disposing a drive wheel encoder adjacent each drive wheel; and

identifying, with a controller in communication with the encoders, a kinematic state of the autonomous transport vehicle within the storage and retrieval system based only on incremental data received by the controller from the drive wheel encoders, independent of drive wheel slippage.

2. The method of claim 1 , further comprising determining, with the controller, command logic for operating the autonomous transport vehicle based on the kinematic state.

3. The method of claim 1 , further comprising disposing one or more of a wheel encoder for each drive wheel, an inertial sensor, at least one storage shelf location sensor and at least one line following sensor on the autonomous transport vehicle, and

receiving data, with the controller, from the one or more of the wheel encoder for each drive wheel, the inertial sensor, the at least one storage shelf location sensor and the at least one line following sensor for identifying the kinematic state.

4. The method of claim 1 , further comprising determining, with the controller, a position of the autonomous transport vehicle within the storage and retrieval system independent of drive wheel slippage.

5. The method of claim 4 , further comprising determining, with the controller, the position of the autonomous transport vehicle based on a drive wheel having a lowest velocity of the at least two drive wheels when a positive torque is applied by the at least two drive wheels.

6. The method of claim 4 , further comprising determining, with the controller, the position of the autonomous transport vehicle based on a drive wheel having a highest velocity of the at least two drive wheels when a negative torque is applied by the at least two drive wheels.

7. The method of claim 4 , further comprising filtering spurious data from each of the encoders with an extended Kalman filter of the controller.

8. The method of claim 4 , further comprising sensing guide lines on a surface of the storage and retrieval system with at least one line following sensor of the autonomous transport vehicle, and

weighting data, with the controller, from each of the encoders based on a guide line deviation signals provided by the at least one line following sensor.

9. The method of claim 4 , verifying, with the controller, a position of the autonomous transport vehicle by detecting one or more datum lines on a surface of the storage and retrieval system.

10. The method of claim 1 , further comprising disposing at least one releasably lockable caster wheel on the autonomous transport vehicle.

11. The method of claim 1 , further comprising determining, with the controller, a position of the autonomous transport vehicle within a storage aisle of the storage and retrieval system independent of drive wheel slippage.

12. The method of claim 1 , further comprising determining, with the controller, a position of the autonomous transport vehicle on a transfer deck of the storage and retrieval system independent of drive wheel slippage.

13. The method of claim 1 , further comprising determining, with the controller, a position of the autonomous transport vehicle with respect to a storage shelf of the storage and retrieval system independent of drive wheel slippage, and

effecting placement position of a payload carried by the autonomous transport vehicle on the storage shelf from the determined position of the autonomous transport vehicle.