ESTIMATING MOTION OF WHEELED CARTS

• US 20180178822A1
• Filed: 08/09/2017
• Published: 06/28/2018
• Est. Priority Date: 09/04/2015
• Status: Active Grant

• Current Assignee: Gatekeeper Systems, Inc.
• Original Assignee: Gatekeeper Systems, Inc.
• Inventors: Carter, Scott J., Hannah, Stephen E., James, Jesse M., Ramanathan, Narayanan V.
• Granted Patent: US 10,546,502 B2
• Time in Patent Office: Days
• CPC Class Codes: B60T 7/12 for automatic initiation; for initiation not subject to will of driver or passenger limiting speed of vehicles other than rail vehicles B60K31/00
• CPC Class Codes: B60T 7/18 operated by wayside apparatus
• CPC Class Codes: B62B 3/14 characterised by provisions for nesting or stacking, e.g. shopping trolleys collapsible shopping trolleys B62B3/027
• CPC Class Codes: B62B 3/1404 Means for facilitating stowing or transporting of the trolleys; Antitheft arrangements B62B5/0423 takes precedence
• CPC Class Codes: B62B 3/1416 mounted on the handle
• CPC Class Codes: B62B 5/00 Accessories or details specially adapted for hand carts B62B3/1404 , B62B9/00 take precedence; wheels, axles, or axle bearings for vehicles B60B; castors for vehicles, castors in general B60B33/00
• CPC Class Codes: B62B 5/0096 Identification of the cart or merchandise, e.g. by barcodes or radio frequency identification [RFID]
• CPC Class Codes: B62B 5/0423 braking or blocking when leaving a particular area
• CPC Class Codes: G01C 17/00 Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes using gyroscopic effect G01C19/00
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01P 3/02 Devices characterised by the use of mechanical means
• CPC Class Codes: G01P 3/48 by measuring frequency of generated current or voltage in general G01R23/00
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: G01S 5/014 Identifying transitions between environments
• CPC Class Codes: G01S 5/02685 involving dead reckoning based on radio wave measurements
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G05D 1/028 using a RF signal
• CPC Class Codes: G06Q 10/00 : Administration; Management
• CPC Class Codes: G06Q 10/06 : Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
• CPC Class Codes: G08B 13/1427 : with transmitter-receiver for distance detection
• CPC Class Codes: G08B 13/1436 : with motion detection
• CPC Class Codes: G08B 21/0261 : System arrangements wherein the object is to detect trespassing over a fixed physical boundary, e.g. the end of a garden
• CPC Class Codes: G08B 29/24 : Self-calibration, e.g. compensating for environmental drift or ageing of components
• CPC Class Codes: G08G 1/00 : Traffic control systems for road vehicles arrangement of road signs or traffic signals E01F9/00 ; automatic vehicle control B62D
• CPC Class Codes: G08G 1/207 : with respect to certain areas, e.g. forbidden or allowed areas with possible alerting when inside or outside boundaries

Abstract

Examples of systems and methods for locating movable objects such as carts (e.g., shopping carts) are disclosed. Such systems and methods can use dead reckoning techniques to estimate the current position of the movable object. Various techniques for improving accuracy of position estimates are disclosed, including compensation for various error sources involving the use of magnetometer and accelerometer, and using vibration analysis to derive wheel rotation rates. Also disclosed are various techniques to utilize characteristics of the operating environment in conjunction with or in lieu of dead reckoning techniques, including characteristic of environment such as ground texture, availability of signals from radio frequency (RF) transmitters including precision fix sources. Such systems and methods can be applied in both indoor and outdoor settings and in retail or warehouse settings.

Claims

1. (canceled)

2. A navigation method for a human-propelled wheeled cart, the method comprising:

determining a position of the human-propelled cart with a dead reckoning navigation system that is in an active navigation mode;

measuring, with a vibration sensor disposed on the human-propelled cart, vibration data representative of vibrations experienced by the human-propelled cart as the human-propelled cart travels over a surface;

analyzing the vibration data to detect an entrance event associated with the human-propelled cart crossing through an entrance to a building; and

in response to the detection of the entrance event, transitioning the dead reckoning navigation system to an inactive navigation mode in which position of the human-propelled cart is not determined by the dead reckoning navigation system.

3. The navigation method of claim 2, wherein determining the position of the human-propelled cart comprises:

measuring, with a magnetometer, a magnetic heading of the human-propelled cart;

analyzing the vibration data to determine a spectrum of vibrations of the human-propelled cart;

estimating, from the spectrum of vibrations, a rotation rate of a wheel of the human-propelled cart; and

estimating the position of the human-propelled cart based at least partly on the estimated rotation rate of the wheel and the measured magnetic heading of the human-propelled cart.

4. The navigation method of claim 3, wherein estimating the rotation rate of the wheel comprises:

determining a peak in the spectrum of vibrations associated with forward or rearward movement of the human-propelled cart.

5. The navigation method of claim 2, wherein analyzing the vibration data to detect an entrance event associated with the human-propelled cart crossing through an entrance to a building comprises:

detecting a change in a signal from the vibration sensor.

6. The navigation method of claim 5, wherein detecting a change in the signal from the vibration sensor comprises:

detecting a change in vibration power in the vibration data;

or

detecting a change in magnitude of the signal from the vibration sensor.

7. The navigation method of claim 6, wherein detecting a change in vibration power comprises analyzing a vibration power spectrum.

8. The navigation method of claim 5, wherein detecting a change in the signal from the vibration sensor comprises:

detecting vibrations associated with a rough, outdoor surface; and

subsequently detecting vibrations associated with smooth indoor flooring.

9. The navigation method of claim 8, wherein:

the rough, outdoor surface comprises asphalt or concrete; and

the smooth, indoor surface comprises linoleum or tile.

10. The navigation method of claim 2, further comprising:

analyzing the vibration data to detect an exit event associated with the human-propelled cart crossing through an exit to a building; and

in response to detecting the exit event, transitioning the dead reckoning navigation system back to the active navigation mode in which position of the human-propelled cart is determined by the dead reckoning navigation system.

11. The navigation method of claim 10, further comprising resetting the position of the human-propelled cart used by the dead reckoning navigation system based at least in part on detecting the exit event.

12. The navigation method of claim 11, wherein resetting the position of the human-propelled cart comprises receiving a reference position signal from an external reference source.

13. The navigation method of claim 12, wherein the external reference source comprises one or more of:

a radio frequency (RF) beacon, an ultrasound beacon, a magnetic marker, an electronic article surveillance (EAS) transmitter, a very low frequency (VLF) source, or a global navigation satellite system (GNSS) satellite.

14. The navigation method of claim 12, further comprising correlating a change in strength of the reference position signal with the detected exit event.

15. The navigation method of claim 10, wherein a wheel of the human-propelled cart comprises a brake configured to inhibit movement of the cart, the method further comprising:

determining, with the dead reckoning navigation system, whether the human-propelled cart has crossed a containment boundary; and

in response to determining the cart has crossed the containment boundary, communicating a braking signal to actuate the brake.

16. The navigation method of claim 15, further comprising:

analyzing the vibration data to determine that the human-propelled cart is being pushed or dragged over the surface;

determining the human-propelled cart has been pushed or dragged back across the containment boundary; and

communicating an unlocking signal to deactuate the brake.

17. The navigation method of claim 2, further comprising:

analyzing the vibration data to detect a vibration signature associated with the surface; and

updating a navigation parameter of the dead reckoning navigation system based at least partly on the detected vibration signature.

18. The navigation method of claim 17, wherein the navigation parameter comprises one or more of:

a surface roughness, a coordinate of a boundary associated with the surface, or a spacing or a width associated with expansion joints or tile joints.

19. The navigation method of claim 17, further comprising updating a ground plan or a site configuration file with the navigation parameter.

20. The method of claim 2, wherein the building comprises a retail store and the human-propelled cart comprises a shopping cart.