SENSOR SYSTEM AND METHOD FOR USE WITH AN AUTOMATED GUIDED VEHICLE (AGV)

• US 20120197477A1
• Filed: 08/02/2011
• Published: 08/02/2012
• Est. Priority Date: 08/03/2010
• Status: Active Grant

• Current Assignee: Fori Automation Incorporated (Lincoln Electric Holdings Incorporated)
• Original Assignee: Fori Automation Incorporated (Lincoln Electric Holdings Incorporated)
• Inventors: Colwell, Dean
• Granted Patent: US 8,751,147 B2
• Time in Patent Office: Days
• US Class Current: 701/25
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G05D 1/0212 with means for defining a desired trajectory involving a plurality of land vehicles G05D1/0287

Abstract

A sensor system for use with an automated guided vehicle (AGV) includes a plurality of sensor units electronically coupled to a sensor control module via parallel communications. Each sensor unit may include a sensor array having a plurality of sensor elements, a conditioning circuit having one or more filter/amplifiers, and a conversion circuit. The sensor control module may be configured to communicate with other AGV components via serial communications. The sensor system is capable of obtaining and storing sensor readings with or without associated offset values and can use the sensor readings to determine the center of a magnetic field using methods that require relatively little processing power. A method of calibrating the sensor system may include determining and storing offset values for a plurality of sensor elements and may be performed with the sensor system installed or uninstalled to the AGV.

Claims

1. A sensor system for use with an automated guided vehicle (AGV), comprising:

a sensor housing being attached to the AGV; and

a sensor board being at least partially located within the sensor housing and including a plurality of sensor units electronically coupled to a sensor control module, wherein each of the sensor units interacts with an indicating system that follows a pre-determined path along the ground and each of the sensor units includes;

a sensor array having a plurality of sensor elements, the sensor elements take sensor readings regarding the position of the AGV with respect to the indicating system;

a conditioning circuit being electronically coupled to the sensor array and having a plurality of filter/amplifiers, the filter/amplifiers process the sensor readings from the sensor array; and

a conversion circuit being electronically coupled to the conditioning circuit, the conversion circuit converts the sensor readings from the conditioning circuit for transmission to the sensor control module.

2. The sensor system of claim 1, further comprising:

one or more additional sensor board(s) having a plurality of sensor elements, each of the sensor boards is electronically coupled to the sensor control module and is distinguished from the other sensor boards through the use of dipswitches.

3. The sensor system of claim 2, wherein the sensor boards include a snap-in connector located at one or more end(s) of the sensor board so that multiple sensor boards can be connected end-to-end.

4. The sensor system of claim 2, wherein the sensor boards extend in a generally parallel orientation across at least a portion of the width of the AGV and the sensor boards help the AGV navigate in a forward direction along the pre-determined path.

5. The sensor system of claim 2, wherein one or more of the sensor boards extends across at least a portion of the width of the AGV and helps the AGV navigate in a forward direction along the pre-determined path, and one or more of the sensor boards extends along at least a portion of the length of the AGV and helps the AGV navigate in a sideways direction from the pre-determined path.

6. The sensor system of claim 1, wherein the plurality of sensor elements include magnetic field sensing elements that are able to evaluate both the strength and the direction of a magnetic field produced by a magnetic indicating system located along the ground.

7. The sensor system of claim 1, wherein the sensor control module is electronically coupled to the plurality of sensor units via a parallel communications and is electronically coupled with an AGV supervisory device via a serial communications.

8. The sensor system of claim 1, wherein the sensor housing is pivotally attached to an underside of the AGV so that the sensor housing can pivot out of the way when the AGV encounters an obstacle in the pre-determined path.

9. A method for operating a sensor system for an automated guide vehicle (AGV), comprising the steps of:

(a) providing a sensor system having a plurality of magnetic sensor elements that interact with a magnetic indicating system that is laid out on the ground and follows a pre-determined path;

(b) obtaining sensor readings from the magnetic sensor elements;

(c) storing the sensor readings from the magnetic sensor elements at a memory device; and

(d) using the stored sensor readings to determine a center of field value that represents the center or centroid of a corresponding magnetic field produced by the magnetic indicating system.

10. The method of claim 9, wherein step (d) further comprises using the stored sensor readings and the following equation to determine the center of field value:

11. The method of claim 10, wherein the center of field value equation only uses sensor readings (m_n) that are greater than a threshold value so that the number of sensor elements included in the calculation (N) is less than the total number of sensor elements of the sensor system.

12. The method of claim 9, wherein steps (b)-(d) are part of a periodic process, and the method further comprises the steps of:

interrupting the periodic process to perform one or more of the following functions;

a calibration function, a read sensor function, or an analyze readings function; and

resuming the periodic process following completion of the one or more functions.

13. The method of claim 12, wherein the step of interrupting the periodic process includes performing the analyze readings function, and the analyze readings function includes one or more of the following:

determining the presence or absence of a magnetic field, determining the width of a magnetic field, determining minimum and/or maximum strengths of a magnetic field, determining the direction of a magnetic field, determining the presence or absence of a location marker, or determining the number of maxima and/or minima strengths of a magnetic field.

14. The method of claim 12, wherein the step of interrupting the periodic process includes performing the read sensor function, and the read sensor function uses one or more of the following:

identification of a sensor board;

identification of a sensor sweep direction;

identification of a magnetic field polarity;

identification of a sensor reading threshold value;

or identification of a minimum magnetic field width threshold value.

15. The method of claim 9, further comprising the step of:

establishing a sensor reading threshold value, wherein only sensor readings that are above the threshold value are used in the center of field value equation.

16. The method of claim 15, further comprising the steps of:

providing the sensor system so that the sensor elements are spaced along at least a portion of the lateral width of the AGV from a leftmost sensor element to a rightmost sensor element; and

consecutively obtaining sensor readings for each of the sensor elements in a sensor sweep direction that is either from the leftmost sensor element to the rightmost sensor element or from the rightmost sensor element to the leftmost sensor element.

17. The method of claim 16, further comprising the steps of:

defining a first edge of the corresponding magnetic field at the location of the first sensor element in the sensor sweep direction that has a sensor reading above the sensor reading threshold value; and

defining a last edge of the corresponding magnetic field at the location of the last sensor element in the sensor sweep direction that has a sensor reading above the sensor reading threshold value.

18. A method for calibrating a sensor system for an automated guided vehicle (AGV), comprising the steps of:

(a) initializing a sensor system having a plurality of sensor elements;

(b) obtaining and averaging a plurality of sensor readings for each of the sensor elements;

(c) using the averaged sensor readings for each of the sensor elements to generate a corresponding offset value for each of the sensor elements; and

(d) electronically storing the offset values for each of the sensor elements in the sensor system.

19. The method of claim 18, wherein steps (a) through (d) are performed while the sensor system is attached to the AGV and is an environment that is generally free from any significant magnetic fields produced by a magnetic indicating system located on the ground.

20. The method of claim 18, wherein steps (a) through (d) are performed while the sensor system is removed from the AGV and is an environment that is generally free from any significant magnetic fields produced by a magnetic indicating system located on the ground.

21. The method of claim 19, wherein step (a) is performed in response to a command that is sent to the sensor system from an AGV supervisory device or an external device.