Sensor diagnostic apparatus and method thereof

• US 8,620,613 B2
• Filed: 12/18/2008
• Issued: 12/31/2013
• Est. Priority Date: 12/25/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Segawa, Eigo, Shiohara, Morito
• Primary Examiner(s): BHAT, ADITYA S
• Application Number:
  US12/338,282
• Publication Number:
  US 20090164164A1
• Time in Patent Office: 1,839 Days
• Field of Search: 702/116, 702/128
• US Class Current: 702/128
• CPC Class Codes: G07C 3/08 Registering or indicating the production of the machine either with or without registering working or idle time
• CPC Class Codes: G08G 1/017 identifying vehicles G08G1/015, G08G1/054 take precedence

Abstract

A sensor diagnostic apparatus for diagnosing a sensor includes a moving object counter, a reference value storage, and a comparator. The moving object counter counts, in accordance with identification data acquired by a plurality of sensors in a predefined time period, a local number of moving objects moving between a sensing area of a first sensor and a sensing area of a second sensor near the first sensor. The reference value storage stores a preset reference value for the first sensor and the second sensor. The comparator compares a value derived from the local number of moving objects counted by the moving object counter with the preset reference value stored in the reference value storage to determine the first sensor to be in trouble when a difference between the value derived from the local number of moving objects and the preset reference value exceeds a predefined threshold value.

Claims

1. A sensor diagnostic apparatus for diagnosing a sensor among a plurality of sensors, each of said plurality of sensors identifying an object and outputting acquired identification data of the identified object, said sensor diagnostic apparatus comprising:

a moving object counter counting, in accordance with identification data acquired by the plurality of sensors in a predefined time period,

a first local number of moving objects of which the identification data are acquired by a first sensor and a second sensor near the first sensor, and

a second local number of moving objects of which the identification data are acquired by the first sensor and a third sensor near the first sensor, the first, second and third sensors being stationary;

a reference value storage storing

a first preset reference value for the first sensor and the second sensor; and

a second preset reference value for the first sensor and the third sensor; and

a comparator comparing

a first value derived from the first local number to the first preset reference value, and

a second value derived from the second local number to the second preset reference value,

to determine that the first sensor is in error when

a first difference between the first value and the first preset reference value exceeds a first predefined threshold value, and

a second difference between the second value and the second preset reference value exceeds a second predefined threshold value.

2. The sensor diagnostic apparatus of claim 1, wherein

each of said plurality of sensors outputs, as well as the identification data, data of an acquired time of the identification data, and

said moving object counter counts the first local number of moving objects of which the identification data were acquired by the first sensor and the second sensor and the acquired times of the identification data indicate times within the predefined time period.

3. The sensor diagnostic apparatus of claim 2, wherein

said comparator compares the first local number of moving objects, a to the first preset reference value.

4. The sensor diagnostic apparatus of claim 2, wherein

said comparator compares a ratio to the first preset reference value, wherein said ratio is the ratio of the first local number of moving objects to the total number of moving objects identified by the first sensor.

5. The sensor diagnostic apparatus of claim 1, wherein

said reference value storage stores a plurality of first preset reference values corresponding to different environmental conditions, and

said comparator compares the first value derived from the first local number of moving objects to a first preset reference value selected, in accordance with a current environmental condition, from among the plurality of first preset reference values stored in the reference value storage.

6. The sensor diagnostic apparatus of claim 1, wherein

said comparator determines the first sensor to be normal when the first difference is less than or equal to the first predefined threshold value,

said sensor diagnostic apparatus further comprises:

an updater updating the first preset reference value in accordance with the first local number of moving objects when the comparator has determined the first sensor to be normal.

7. A sensor diagnostic method executed by a sensor diagnostic apparatus for diagnosing a sensor among a plurality of sensors, each of said plurality of sensors identifying an object and outputting acquired identification data, said sensor diagnostic method comprising:

counting, in accordance with identification data acquired by the plurality of sensors in a predefined time period,

a first local number of moving objects of which the identification data are acquired by a first sensor and a second sensor near the first sensor, and

a second local number of moving objects of which the identification data are acquired by the first sensor and a third sensor near the first sensor, the first, second and third sensors being stationary;

storing a first preset reference value for the first sensor and the second sensor;

storing a second preset reference value for the first sensor and the third sensor; and

comparing, by the sensor diagnostic apparatus,

a first value derived from the first local number to the first preset reference value, and

a second value derived from the second local number to the second preset reference value

determining that the first sensor is in error when

a first difference between the first value and the first preset reference value exceeds a first predefined threshold value, and

a second difference between the second value and the second preset reference value exceeds a second predefined threshold value.

8. The sensor diagnostic method of claim 7, wherein

each of said plurality of sensors outputs, as well as the identification data, data of an acquired time of the identification data, and

the sensor diagnostic apparatus counts, in said operation of counting the first local number of moving objects, the first local number of moving objects of which the identification data were acquired by the first sensor and the second sensor and the acquired times of the identification data indicate times within the predefined time period.

9. The sensor diagnostic method of claim 8, wherein

the sensor diagnostic apparatus compares the first local number of moving objects to the first preset reference value in said operation of comparing a first value derived from the first local number of moving objects to the first preset reference value.

10. The sensor diagnostic method of claim 8, wherein

the sensor diagnostic apparatus compares a ratio to the first preset reference value in said operation of comparing a first value derived from the first local number of moving objects to the first preset reference value, wherein said ratio is the ratio of the first local number of moving objects to the total number of moving objects identified by the first sensor.

11. The sensor diagnostic method of claim 7, wherein

the sensor diagnostic apparatus stores a plurality of first preset reference values corresponding to different environmental conditions in said operation of storing a first preset reference value, and

the sensor diagnostic apparatus compares the first value derived from the first local number of moving objects to a first preset reference value selected, in accordance with a current environmental condition, from among the plurality of first preset reference values in said operation of comparing a first value derived from the first local number of moving objects to the first preset reference value.

12. The sensor diagnostic method of claim 7, wherein

the sensor diagnostic apparatus determines the first sensor to be normal when the first difference is less than or equal to the first predefined threshold value in said operation of comparing a first value derived from the first local number of moving objects to the first preset reference value,

said sensor diagnostic method further comprising:

updating the first preset reference value in accordance with the first local number of moving objects when the sensor diagnostic apparatus has determined the first sensor to be normal in said operation of comparing a first value derived from the first local number of moving objects to the first preset reference value.