SENSOR DIAGNOSTIC APPARATUS AND METHOD THEREOF

• US 20090164164A1
• Filed: 12/18/2008
• Published: 06/25/2009
• Est. Priority Date: 12/25/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Shiohara, Morito, Segawa, Eigo
• Granted Patent: US 8,620,613 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• 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, said sensor diagnostic apparatus comprising:

a moving object counter for counting, in accordance with identification data acquired by the 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;

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

a comparator for comparing 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.

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 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

a dimension of said preset reference value is identical to a dimension of the local number of moving objects, and

said comparator compares the local number of moving objects, as the value derived from the local number of moving objects, with the preset reference value.

4. The sensor diagnostic apparatus of claim 2, wherein

a dimension of said preset reference value is identical to a dimension of a ratio of the local number of moving objects against a whole number of moving objects identified by the first sensor, and

said comparator compares the ratio of the local number of moving objects against the whole number of moving objects identified by the first sensor, as the value derived from the local number of moving objects, with the preset reference value.

5. The sensor diagnostic apparatus of claim 1, wherein

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

said comparator compares the value derived from the local number of moving objects with a preset reference value selected, in accordance with a current environmental condition, from among the plurality of 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 difference between the value derived from the local number of moving objects and the preset reference value is less than or equals to the predefined threshold value,

said sensor diagnostic apparatus further comprising:

an updater for updating the preset reference value for the first sensor and the second sensor in accordance with the 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 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;

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

comparing a value derived from the local number of moving objects counted in the operation of counting a local number of moving objects with the preset reference value 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.

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 local number of moving objects, the 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

a dimension of said preset reference value is identical to a dimension of the local number of moving objects, and

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

10. The sensor diagnostic method of claim 8, wherein

a dimension of said preset reference value is identical to a dimension of a ratio of the local number of moving objects against a whole number of moving objects identified by the first sensor, and

the sensor diagnostic apparatus compares the ratio of the local number of moving objects against the whole number of moving objects identified by the first sensor, as the value derived from the local number of moving objects, with the preset reference value in said operation of comparing a value derived from the local number of moving objects with the preset reference value.

11. The sensor diagnostic method of claim 7, wherein

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

the sensor diagnostic apparatus compares the value derived from the local number of moving objects with a preset reference value selected, in accordance with a current environmental condition, from among the plurality of preset reference values in said operation of comparing a value derived from the local number of moving objects with the 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 difference between the value derived from the local number of moving objects and the preset reference value is less than or equals to the predefined threshold value in said operation of comparing a value derived from the local number of moving objects with the preset reference value,

said sensor diagnostic method further comprising:

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