Moving direction detection method, moving direction detection apparatus, and program code

• US 6,820,002 B2
• Filed: 04/04/2003
• Issued: 11/16/2004
• Est. Priority Date: 04/08/2002
• Status: Expired due to Term

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Terada, Toshihito
• Primary Examiner(s): ARTHUR JEANGLAUDE, GERTRUDE
• Application Number:
  US10/407,045
• Publication Number:
  US 20030191582A1
• Time in Patent Office: 592 Days
• Field of Search: 701/23, 701/79, 701/110, 701/200, 701/201, 701/207, 701/210, 701/213, 701/214, 701/300, 342/357.01, 342/357.03, 342/357.08
• US Class Current: 701/207
• CPC Class Codes: G01C 21/185 for gravity
• 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

Abstract

A walking direction detection apparatus has an azimuth detection unit and acceleration detection unit. After a vertical direction with respect to the ground of an apparatus is corrected based on the detection direction of a gravitational acceleration component, a periodic up/down pattern of the absolute value of acceleration is detected. A value where the acceleration component in the horizontal direction becomes maximal or minimal is detected at a predetermined timing at which the acceleration component in the vertical direction transits from a maximal value to minimal value. The direction of the apparatus is corrected based on the direction of the acceleration component in the horizontal direction of that value. Based on these correction results, the walking direction of the movable body is detected.

Claims

1. A moving direction detection method for detecting a moving direction of a movable body, comprising:

an acceleration component acquisition step of acquiring information of an acceleration component in a vertical direction, and an acceleration component in a horizontal direction in association with an acceleration of the movable body, which is produced upon motion of the movable body;

a vertical acceleration extreme detection step of detecting a maximal value where a change over time in absolute value of the acceleration component in the vertical direction, acquired in the acceleration component acquisition step, turns from up to down, and a minimal value where a change over time in absolute value of the acceleration component in the vertical direction turns from down to up;

a horizontal acceleration extreme detection step of detecting a maximal value where a change in absolute value of the acceleration component in the horizontal direction turns from up to down within a time period between detection times of the maximal and minimal values of the absolute value of the acceleration component in the vertical direction in the vertical direction extreme detection step;

a horizontal acceleration direction detection step of detecting a direction of the acceleration component in the horizontal direction at a detection time of the maximal value of the absolute value of the acceleration component detected in the horizontal direction in the horizontal acceleration extreme detection step; and

a moving direction detection step of detecting a moving direction of the movable body based on the direction of the acceleration component in the horizontal direction detected in the horizontal acceleration direction detection step.

2. A method according to claim 1, wherein the horizontal acceleration extreme detection step includes a step of detecting the maximal value of the absolute value of the acceleration component in the horizontal direction in a time interval between a detection time of the maximal value of the absolute value of the acceleration component in the vertical direction detected in the vertical acceleration extreme detection step, and a time of the minimal value of the absolute value of the acceleration component in the vertical direction as a time after the detection time of the maximal value, and

the moving direction detection step includes a step of detecting the moving direction of the movable body based on a direction which is opposite to the direction of the acceleration component in the horizontal direction, which is detected in the horizontal acceleration direction detection step.

3. A method according to claim 2, wherein the horizontal acceleration extreme detection step includes a step of detecting the maximal value of the absolute value of the acceleration component in the horizontal direction in a time interval between a predetermined time after the detection time of the maximal portion of the absolute value of the acceleration component in the vertical direction detected in the vertical acceleration extreme detection step, and the time of the minimal portion of the absolute value of the acceleration component in the vertical direction.

4. A method according to claim 1, wherein the horizontal acceleration extreme detection step includes a step of detecting the maximal value of the absolute value of the acceleration component in the horizontal direction in a time interval between a time of the maximal value of the absolute value of the acceleration component in the vertical direction detected in the vertical acceleration extreme detection step, and a time of the minimal value of the absolute value of the acceleration component in the vertical direction as a time before the detection time of the maximal value, and

the moving direction detection step includes a step of detecting the moving direction of the movable body based on the direction of the acceleration component in the horizontal direction, which is detected in the horizontal acceleration direction detection step.

5. A method according to claim 4, wherein the horizontal acceleration extreme detection step includes a step of detecting the maximal value of the absolute value of the acceleration component in the horizontal direction in a time interval between a predetermined time before the detection time of the maximal portion of the absolute value of the acceleration component in the vertical direction detected in the vertical acceleration extreme detection step, and the time of the minimal portion of the absolute value of the acceleration component in the vertical direction.

6. A method according to claim 1, wherein the vertical acceleration extreme detection step includes a step of detecting the maximal and minimal values in accordance with a smoothing differential method, and

the horizontal acceleration extreme detection step includes a step of detecting the maximal value in accordance with the smoothing differential method.

7. A method according to claim 1, wherein the moving direction detection step includes steps of:

detecting the direction of the acceleration component in the horizontal direction detected in the horizontal acceleration direction detection step a plurality of number of times in accordance with a predetermined time intervals; and

detecting the moving direction of the movable body based on the plurality of directions detected in the moving direction detection step.

8. A method according to claim 1, wherein the horizontal acceleration extreme detection step includes a step of detecting a first maximal value of the acceleration component in the horizontal direction in a time interval between a time of the maximal value of the absolute value of the acceleration component in the vertical direction, detected in the vertical acceleration extreme detection step, and a time of the minimal value of the absolute value of the acceleration component in the vertical direction as a time before the detection time of the maximal value, and a second maximal value of the acceleration component in the horizontal direction in the time interval between the time of the maximal value of the absolute value of the acceleration component in the vertical direction, detected in the vertical acceleration extreme detection step, and a time of the minimal value of the absolute value of the acceleration component in the vertical direction as a time after the detection time of the maximal value,

the method further comprises a comparison step of comparing absolute values of the first and second maximal values of the acceleration component in the horizontal direction detected in the horizontal acceleration extreme detection step, and wherein

the moving direction detection step includes the step of detecting, when it is determined in the comparison step that the absolute value of the first maximal value is larger than the absolute value of the second maximal value, the moving direction of the movable body based on the direction of the acceleration component in the horizontal direction detected in the horizontal acceleration direction detection step, and of detecting, when it is determined in the comparison step that the absolute value of the second maximal value is larger than the absolute value of the first maximal value, the moving direction of the movable body based on a direction exactly opposite to the direction of the acceleration component in the horizontal direction detected in the horizontal acceleration direction detection step.

9. A method according to claim 1, wherein the moving direction detection step includes a step of detecting a direction based on a meridian, and detecting the moving direction of the movable body based on detected direction, and the direction of the acceleration component in the horizontal direction, detected in the horizontal acceleration direction detection step.

10. A moving direction detection apparatus which can be carried by a movable body, and comprises:

an acceleration detection unit which detects a acceleration component of the moving direction detection apparatus;

a first correction unit which corrects a carrying direction of the moving direction detection apparatus with respect to the vertical direction based on the direction of the acceleration component detected by the acceleration detection unit;

a second correction unit which corrects the carrying direction of the moving direction detection apparatus with respect to the horizontal direction based on a periodic up/down pattern of an acceleration component of the moving direction detection apparatus which is detected by the acceleration detection unit; and

a moving direction detection unit which detects a moving direction of the movable body in accordance with correction results of the first and second correction units.

11. An apparatus according to claim 10, wherein the second correction unit detects a maximal value where a change over time in absolute value of the acceleration component in the horizontal direction,

detects a direction of the acceleration component in the horizontal direction at a detection time of the maximal value, and

corrects the carrying direction of the moving direction detection apparatus with respect to the horizontal direction of the apparatus with reference to the detected direction.

12. An apparatus according to claim 11, wherein the second correction unit detects the maximal value of the absolute value of the acceleration component in the horizontal direction at a specific timing on the periodic up/down pattern of the absolute value of the acceleration component in the vertical direction in association with the acceleration of the movable body.

13. An apparatus according to claim 12, wherein the acceleration detection unit acquires acceleration components in the vertical direction of the movable body at a predetermined time intervals,

the apparatus further comprises a storage unit which stores data of times corresponding to the predetermined time intervals, and data of acceleration components in the vertical direction corresponding to the data of times, and

the second correction unit stores the data of acceleration components acquired by the acceleration detection unit in correspondence with the data of times corresponding to the predetermined time intervals, which are stored in the storage unit, and detects the maximal value of the acceleration component in the vertical direction by comparing an absolute value of an acceleration component in the horizontal direction, which is stored in the storage unit in correspondence with a predetermined time, with an absolute value of an acceleration component in the vertical direction, which is stored in correspondence with a time before or after the predetermined time.

14. An apparatus according to claim 10, further comprising:

an apparatus direction detection unit for detecting the direction of the apparatus with reference to a meridian, and

wherein the moving direction detection unit detects, as the moving direction of the movable body, a direction obtained by correcting the direction detected by the apparatus direction detection unit using the first and second correction units.

15. A medium having program code and data code which is readable by a computer, including:

program code of acquiring an acceleration component in a vertical direction, and an acceleration component in a horizontal direction perpendicular to the vertical direction, in association with an acceleration produced upon motion of a movable body;

program code of detecting a maximal value where a change over time in acceleration component in the vertical direction turns from up to down, and a minimal value where the change over time in acceleration component in the vertical direction turns from down to up;

program code of detecting a maximal value where a change over time in acceleration component in the horizontal direction turns from up to down in a time interval between detection times of the maximal and minimal values of the acceleration component in the vertical direction;

program code of detecting a direction of the acceleration component in the horizontal direction at a detection time of the maximal value of the acceleration component in the horizontal direction; and

program code of determining a direction specified in correspondence with the direction of the acceleration component in the horizontal direction as a detection result of a moving direction of the movable body.