Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1999-09-07
2001-11-13
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S253000, C700S258000, C318S568100, C318S568110, C318S568120, C901S001000, C901S009000, C701S023000
Reexamination Certificate
active
06317652
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a legged mobile robot which is capable of recognizing the positional relationship between its legs and an obstacle to its walking from image data captured through a vision sensor.
2. Description of the Related Art
Autonomous legged mobile robots have a vision sensor such as a CCD (Charge-Coupled Device) camera, for example. An autonomous legged mobile robot equipped with such a CCD camera recognizes the position of an obstacle present in the course of robot walking from image data obtained by the CCD camera, and walks in a manner to negotiate the recognized obstacle. In order to achieve a wider range of vision, the CCD camera is generally mounted on an upper end, e.g., a head, of the body of the legged mobile robot.
Legged mobile robots are expected to act in a three-dimensional space containing obstacles such as a staircase, etc., in which other types of robots such as wheeled robots cannot easily move. For a legged mobile robot to freely move in a three-dimensional space, it is necessary to accurately calculate the positional relationship between a leg of the robot, particularly, a foot to be landed on the floor and an obstacle present in the course of robot walking. However, since the legged mobile robot has a number of joints between the foot of the leg and the head thereof, it is difficult to accurately calculate the positional relationship between the foot and the obstacle.
In view of the above drawback, there has been proposed a legged mobile robot having a camera mounted on the foot of a leg thereof, as disclosed in Japanese laid-open utility model publication No. 5-93778. When the position of an obstacle to the legged mobile robot is recognized by the camera on the foot of the leg, the legged mobile robot can accurately calculate the positional relationship between the foot and the obstacle because the calculations are free of positioning errors of the joints of the robot.
However, the camera installed on the foot of the leg is disadvantageous in that the camera tends to be easily damaged or smeared by the environment in which the robot walks, and results in an increase in the weight of the leg that is apt to impair the walking performance of the robot.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a legged mobile robot comprising a base body, a plurality of legs operatively connected to the base body, a vision sensor mounted on the base body, image input means for capturing image data via the vision sensor, and positional relationship calculating means for calculating the positional relationship between of an obstacle present in the course of robot walking and one of the legs from the image data captured by the image input means, so that the legged mobile robot can walk while recognizing the positional relationship between the obstacle and the leg as calculated by the positional relationship calculating means.
The position (attitude) of the leg of the legged mobile robot is recognized by the legged mobile robot itself. Therefore, when the position of the obstacle is recognized from the image data of the obstacle captured by the vision sensor, the positional relationship between the leg and the obstacle can basically be calculated. However, if the vision sensor is mounted on the base body of the legged mobile robot, then when the positional relationship between the foot and the obstacle is calculated, the position of the vision sensor with respect to the foot suffers a variation because positioning errors of a number of joints present between the foot and the visual sensor are added. As a result, the position of the obstacle calculated from the image data of the obstacle captured by the vision sensor also suffers a variation with respect to the position of the foot, and hence the positional relationship between the foot and the obstacle cannot accurately be calculated.
In view of the above difficulty, the positional relationship calculating means calculates the positional relationship between the obstacle and the leg from image data containing both images of a portion of the leg and the obstacle as captured by the image input means. Since the relative positional relationship between the obstacle and the leg is calculated directly from the image data containing the images of the portion of the leg and the obstacle, the positional relationship between the obstacle and the leg can accurately be calculated regardless of the positioning errors of the joints.
In order for the vision sensor to capture the image data containing the images of the portion of the leg and the obstacle, the vision sensor has to capture image data when both the portion of the leg and the obstacle can enter the visual field of the vision sensor. Depending on the attitude of the leg, however, both the portion of the leg and the obstacle may not enter the visual field of the vision sensor.
For example, when the vision sensor is to capture image data containing both images of the tip end of a foot, which is a portion of the leg, and an obstacle, if the visual field of the vision sensor is obstructed by the knee of the leg, then the foot does not enter the visual field of the vision sensor. When the vision sensor is to capture image data containing both images of the knee of a foot, which is a portion of the leg, and an obstacle, if the leg is positioned behind the base body, then the knee does not enter the visual field of the vision sensor. In order for both the portion of the leg and the obstacle to enter the visual field of the vision sensor, it is necessary to provide a space, in which the obstacle can be present, around the portion of the leg that has entered the visual field of the vision sensor.
If the portion of the leg does not enter the visual field of the vision sensor or there is no space, in which the obstacle could be present, around the portion of the leg that has entered the visual field of the vision sensor, then image data that is captured by the image input means does not contain both the image of the portion of the leg and the image of the obstacle, or contains only one of those images. Even when the positional relationship calculating means processes the image data which does not contain both the image of the portion of the leg and the image of the obstacle for the purpose of calculating the positional relationship between the leg and the obstacle, the processing is simply a waste of processing time.
According to the present invention, the legged mobile robot further comprises positional relationship recognizing means for recognizing the positional relationship between a visual field of the vision sensor and the leg
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, the image input means comprising means for capturing the image data via the vision sensor when both the portion of the leg and the obstacle can enter the visual field of the vision sensor as determined by the positional relationship recognizing means.
With the above arrangement, the positional relationship calculating means processes only image data which possibly contains both an image of a portion of the leg and an image of an obstacle for calculating the positional relationship between the leg and the obstacle. Therefore, wasteful processing is prevented from being performed.
The legged mobile robot further comprises walking operation modifying means for modifying details of subsequent walking operation of the legged mobile robot depending on the positional relationship between the leg and the obstacle as calculated by the positional relationship calculating means.
For example, when the legged mobile robot walks up a staircase, the legged mobile robot may basically walks with a constant leg stroke depending on the width of steps of the staircase. However, the landed position of a leg on the staircase may be displaced toward the edge of a step or a leg may face the staircase at a varied angle due to slippage of the leg when it is landed on the staircase. If the legged mobile robot continues to walk with the constant leg stroke, then the leg may
Arent Fox Kinter Plotkin & Kahn
Cuchlinski Jr. William A.
Honda Giken Kogyo Kabushiki Kaisha
Marc McDieunel
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