Vehicle detection two-wire magnetic field sensing probe with communication capability

• US 8,937,560 B2
• Filed: 02/26/2013
• Issued: 01/20/2015
• Est. Priority Date: 02/26/2013
• Status: Active Grant

• Current Assignee: Diablo Controls Incorporated
• Original Assignee: Diablo Controls Incorporated
• Inventors: Seabury, Thomas W.
• Primary Examiner(s): HOFSASS, JEFFERY A
• Application Number:
  US13/777,135
• Publication Number:
  US 20140239945A1
• Time in Patent Office: 693 Days
• Field of Search: 340/933, 340/941, 340/942, 340/943, 701/1
• US Class Current: 340/933
• CPC Class Codes: G08G 1/042 using inductive or magnetic detectors

Abstract

A system of communicating vehicle detection is provided. The system may include a probe having at least a probe controller and a magnetic sensor for detecting the Earth'"'"'s magnetic fields, and a control system having a main controller, an output port and a two-wire interface for communicating with the probe. The probe controller may be configured to quantify detected magnetic fields into a sensor output value per iteration at a predefined frequency, and initiate an interrupt per iteration the sensor output value is determined to exceed a predefined sensor value. The main controller of the control system may be configured to communicate a supply signal to the probe over a first line of the two-wire interface, monitor a return signal from the probe over a second line of the two-wire interface for interrupts, and generate a call signal on the output port indicative of confirmed vehicle detection if the number of consecutive interrupts in the return signal exceed a predefined interrupt limit.

Claims

1. A system of communicating vehicle detection, comprising:

a probe having at least a probe controller and a magnetic sensor for detecting the Earth'"'"'s magnetic fields, the probe controller being configured to quantify detected magnetic fields into a sensor output value per iteration at a predefined frequency, and initiate an interrupt per iteration the sensor output value is determined to exceed a predefined sensor value; and

a control system having a main controller, an output port and a two-wire interface for communicating with the probe, the main controller being configured to communicate a supply signal to the probe over a first line of the two-wire interface, monitor a return signal from the probe over a second line of the two-wire interface for interrupts, and generate a call signal on the output port indicative of confirmed vehicle detection if the number of consecutive interrupts in the return signal exceed a predefined interrupt limit.

2. The system of claim 1, wherein the magnetic sensor is a multi-axis magnetic sensor configured to quantify the Earth'"'"'s magnetic fields in terms of direction and magnitude per axis thereof.

3. The system of claim 1, wherein the magnetic sensor is a three-axis magnetometer configured to quantify the Earth'"'"'s magnetic fields in terms of direction and magnitude as detected by each axis thereof, each axis being perpendicular to one another.

4. The system of claim 1, wherein the probe controller, in an initialization mode of operation, is configured to:

determine an initial sensor reading of the magnetic fields as measured by each axis of the magnetic sensor upon initial install or reset, and

define a base reference value corresponding to the initial sensor readings to be retrievably stored in a memory accessible to the probe controller.

5. The system of claim 4, wherein the probe controller, in a detection mode of operation, is configured to:

determine an absolute difference between the initial sensor reading and an immediate sensor reading per axis of the magnetic sensor, and

define the sensor output value as a sum of the absolute differences to be compared with the base reference value.

6. The system of claim 4, wherein the predefined sensor value is comprised of the base reference value and a preset sensitivity value, the preset sensitivity value corresponding to a desired degree of sensor sensitivity to changes in the magnetic fields.

7. The system of claim 4, wherein the probe further includes nonvolatile memory within which the base reference value is retrievably stored.

8. The system of claim 1, wherein the control system further includes a user interface providing one or more of a manual reset button, a failsafe/security switch, and a sensitivity switch.

9. The system of claim 1, wherein the control system is configured to communicate with a plurality of probes disposed in series relative to one another.

10. A system of communicating vehicle detection, comprising:

at least one multi-axis magnetic sensor for detecting the Earth'"'"'s magnetic fields; and

a control system having a controller, an output port and a two-wire interface for communicating with the magnetic sensor, the controller being configured to quantify changes in the magnetic fields as detected by each axis of the magnetic sensor into a sensor output value per iteration at a predefined frequency, initiate an interrupt per iteration the sensor output value exceeds a predefined sensor limit, communicate a supply signal to the magnetic sensor over a first line of the two-wire interface, monitor a return signal from the magnetic sensor over a second line of the two-wire interface for interrupts, and generate a call signal indicative of confirmed vehicle detection if the number of consecutive interrupts in the return signal exceed a predefined interrupt limit.

11. The system of claim 10, wherein the controller is further configured to adjust the predefined sensor limit by initiating one or more interrupts on the supply signal over the first line of the two-wire interface, the number of interrupts corresponding to different sensitivity settings.

12. The system of claim 10, wherein the controller, in an initialization mode of operation, is further configured to:

determine an initial sensor reading of the magnetic fields as measured by each axis of the magnetic sensor upon initial install or reset,

define a base reference value corresponding to the initial sensor readings to be retrievably stored in a memory accessible to the controller,

determine an absolute difference between the initial sensor reading and an immediate sensor reading for each axis of the magnetic sensor, and

define the sensor output value as a sum of the absolute differences for all axes of the magnetic sensor to be compared with the base reference value.

13. The system of claim 12, wherein the controller determines the predefined sensor limit based on the base reference value and a preset sensitivity value, the preset sensitivity value corresponding to a desired degree of sensor sensitivity to changes in the magnetic fields.

14. The system of claim 12, wherein the controller is configured to initialize the magnetic sensor upon any one or more of an installation of the magnetic sensor, a manual reset and an automated reset.

15. The system of claim 10, wherein the control system is in electrical communication with a plurality of multi-axis magnetic sensors connected in series relative to one another, the control system maintaining communication with each of the plurality of multi-axis magnetic sensors through a single two-wire interface.

16. A method of communicating vehicle detection over a two-wire interface, the method comprising the steps of:

quantifying changes in the Earth'"'"'s magnetic fields as detected by each axis of a multi-axis magnetic sensor into a sensor output value per iteration at a predefined frequency;

initiating an interrupt per iteration the sensor output value exceeds a predefined sensor limit;

communicating a supply signal to the magnetic sensor over a first line of the two-wire interface;

monitoring a return signal from the magnetic sensor over a second line of the two-wire interface for interrupts; and

generating a call signal indicative of confirmed vehicle detection if the number of consecutive interrupts exceed a predefined interrupt limit.

17. The method of claim 16, wherein the predefined sensor limit is adjusted by initiating one or more interrupts on the supply signal over the first line of the two-wire interface, the number of interrupts corresponding to different sensitivity settings.

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

determining an initial sensor reading of the magnetic fields as measured by each axis of the magnetic sensor upon initial install or reset;

defining a base reference value corresponding to the initial sensor readings to be retrievably stored in a memory;

determining an absolute difference between the initial sensor reading and an immediate sensor reading for each axis of the magnetic sensor; and

defining the sensor output value as a sum of the absolute differences for all axes of the magnetic sensor to be compared with the base reference value.

19. The method of claim 18, wherein the predefined sensor limit is determined based on the base reference value and a preset sensitivity value, the preset sensitivity value corresponding to a desired degree of sensor sensitivity to changes in the magnetic fields.

20. The method of claim 18, wherein the initialization steps are performed upon any one or more of an installation of the magnetic sensor, a manual reset and an automated reset.