Systems and methods for materials handling vehicle odometry calibration

Patent metadata

Field	Value
Publication number	US-10458799-B2
Application number	US-201815889481-A
Country	US
Kind code	B2
Filing date	Feb 6, 2018
Priority date	May 26, 2015
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

Systems and methods for calibrating odometry of a materials handling vehicle. One embodiment of a method includes determining a current location of the materials handling vehicle, determining an odometry distance from the current location to a destination based on a calculation of a determined number of rotations of a wheel and a circumference of the wheel, and determining a positioning system distance from the current location to the destination. Some embodiments include comparing the odometry distance with data from the positioning system distance to calculate a scaling factor, applying the scaling factor to a fast alpha filter to achieve a fast filter result, and applying the scaling factor to a slow alpha filter to achieve a slow filter result. Similarly, some embodiments include applying the fast alpha filter to the scaling factor to smooth noise, calculating an updated odometry distance utilizing the scaling factor, and utilizing the updated odometry distance.

First claim

What is claimed is:

1. A materials handling vehicle comprising materials handling hardware, a wheel, an odometer, a positioning system, and a vehicle computing device, wherein the vehicle computing device stores logic that when executed by a processor, causes the materials handling vehicle to perform at least the following:
determine a current location of the materials handling vehicle within a warehouse;
determine, via the odometer, an odometry distance from the current location to a destination based on a calculation of a determined number of rotations of the wheel and a circumference of the wheel;
determine, via the positioning system, a positioning system distance from the current location of the materials handling vehicle to the destination;
compare the odometry distance with the positioning system distance to determine a difference and to calculate a scaling factor based on the odometry distance and the positioning system distance;
utilize an exponential moving average filter to determine a value from a filter output;
adjust the scaling factor to the value when the difference exceeds a threshold;
calculate an updated odometry distance utilizing the updated scaling factor; and
utilize the updated odometry distance to operate the positioning system.

2. The materials handling vehicle of claim 1 , wherein the logic further causes the materials handling vehicle to log a raw scaling factor measurement on the materials handling vehicle.

3. The materials handling vehicle of claim 1 , wherein the logic further causes the materials handling vehicle to determine whether a change in the scaling factor is a result of at least one of the following: wheel wear and wheel change.

4. The materials handling vehicle of claim 1 , wherein the current location of the materials handling vehicle is received from at least one of the following: a user input and triggering of a sensor.

5. The materials handling vehicle of claim 1 , further comprising an image capture device that is coupled to the vehicle computing device, wherein the image capture device captures images for identifying the positioning system distance.

6. The materials handling vehicle of claim 1 , wherein the logic causes the materials handling vehicle to traverse a predetermined route to reach the destination.

7. The materials handling vehicle of claim 1 , wherein calculating the scaling factor comprises dividing the positioning system distance by the odometry distance.

8. The materials handling vehicle of claim 1 , wherein the logic causes the materials handling vehicle to define a travel distance that is dependent on the difference between the odometry distance and the positioning system distance.

9. The materials handling vehicle of claim 1 , wherein the vehicle computing device is configured to receive data related to a vehicle position from a remote computing device.

10. The materials handling vehicle of claim 1 , wherein the logic further causes the materials handling vehicle to:
utilize the scaling factor to determine a slow change value to the odometry distance, based on wear of the wheel;
utilize the scaling factor to determine a fast change value to the odometry distance, based on changing of the wheel;
compare the slow change value with the fast change value;
in response to determining that a difference between the slow change and the fast change value is within a predetermined tolerance, update the scaling factor by setting the scaling factor to be about equal to the slow change value to smooth noise; and
in response to determining that a difference between the slow change value and the fast change value is not within the predetermined tolerance, update the scaling factor by setting the scaling factor to be about equal to the fast change value to smooth noise.

11. The materials handling vehicle of claim 10 , wherein utilizing the scaling factor to determine a slow change value includes calculating FV 1 =FV 0 (α)+MV (1−α), where FV 1 is a new value, FV 0 is a prior value, MV is a measured value, and α is equal to about 0.99.

12. The materials handling vehicle of claim 10 , wherein utilizing the scaling factor to determine a fast change value includes calculating FV 1 =FV 0 (α)+MV (1−α), where FV 1 is a new value, FV 0 is a prior value, MV is a measured value, and α is equal to about 0.9.

13. The materials handling vehicle of claim 10 , wherein the predetermined tolerance is equal to about 0.075.

14. The materials handling vehicle of claim 10 , wherein utilizing the scaling factor to determine a slow change value includes calculating FV 1 =FV 0 (α)+MV (1−α), where FV 1 is a new value, FV 0 is a prior value, MV is a measured value, and α is an alpha value.

15. The materials handling vehicle of claim 10 , wherein utilizing the scaling factor to determine a fast change value includes calculating FV 1 =FV 0 (α)+MV (1−α), where FV 1 is a new value, FV 0 is a prior value, MV is a measured value, and α is an alpha value.

16. A materials handling vehicle comprising a wheel and a vehicle computing device, wherein the vehicle computing device stores logic that when executed by a processor, causes the materials handling vehicle to perform at least the following:
determine a current location of the materials handling vehicle;
determine an odometry distance from the current location to a destination based on a calculation of a determined number of rotations of the wheel and a circumference of the wheel;
determine a positioning system distance from the current location to the destination;
compare the odometry distance with the positioning system distance to calculate a scaling factor;
utilize the scaling factor to determine a fast change value representing a fast change to the odometry distance, based on changing of the wheel;
update the scaling factor by setting the scaling factor to be about equal to the fast change value to smooth noise;
calculate an updated odometry distance utilizing the updated scaling factor; and
utilize the updated odometry distance to operate a positioning system.

17. The materials handling vehicle of claim 16 , wherein:
calculating the scaling factor comprises dividing the positioning system distance by the odometry distance, and
the logic further causes the materials handling vehicle to utilize the scaling factor to determine a slow change value representing a slow change to the odometry distance, based on wear of the wheel.

18. A method for calibrating odometry of a materials handling vehicle comprising:
determining a current location of the materials handling vehicle;
determining an odometry distance from the current location to a destination based on a calculation of a determined number of rotations of a wheel and a circumference of the wheel;
determining a positioning system distance from the current location to the destination;
comparing the odometry distance with data from the positioning system distance to calculate a scaling factor, wherein calculating the scaling factor comprises dividing the positioning system distance by the odometry distance;
utilizing the scaling factor to determine a slow change value representing a slow change to the odometry distance, based on wear of the wheel;
updating the scaling factor by setting the scaling factor to be about equal to the slow change value to smooth noise;
calculating an updated odometry distance utilizing the updated scaling factor; and
utilizing the updated odometry distance to operate a positioning system.

19. The method of claim 18 , further comprising utilizing

Assignees

• Crown Equip Corp

Inventors

• Fanselow Timothy William
• Thode Justin Forbes
• Estep Ryan Michaels

Classifications

• G01C25/00 Primary

  Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass (testing, calibrating or compensating compasses G01C17/38) · CPC title

• G01C21/206 Primary

  specially adapted for indoor navigation · CPC title

• G01C22/02 Primary

  by conversion into electric waveforms and subsequent integration, e.g. using tachometer generator {(G01C22/002, G01C22/004, G01C22/006 take precedence)} · CPC title

• G05D1/021

  specially adapted to land vehicles · CPC title

• G05D1/243

  Means capturing signals occurring naturally from the environment, e.g. ambient optical, acoustic, gravitational or magnetic signals (using passive navigation aids external to the vehicle G05D1/244; using signals from positioning sensors located off-board the vehicle G05D1/249) · CPC title