Abstract:
A robot having a leg mechanism having high rigidity, so as to enable moving on wheels, on the leveled ground, and also moving on the bipedalism, on the unleveled ground, and also enabling to execute exchanging between the wheel running and the bipedalism in a short time, comprising: a body; and left and right leg portions in lower portion of the body, wherein each leg portion has a wheel, which can be drive, at a tip thereof, and a supporting portion, which is movable in roll and pitch directions, the each leg portion has three (3) degrees of freedom, roll, pitch and pitch from the body side, and the supporting portion has at least two (2) of contact points to be in contact with a ground, and makes up a stable region by a contact point of the wheel and the contact point of the supporting body, and thereby oscillating the left and right leg portions, alternately, so as to make bipedalism, and further operating the supporting body, so as to run on the wheels.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a robot equipped with a mobile apparatus, in particular, a mobile capacity, for automatically conducting an operation or work to be a target. 
         [0002]    In relation to a robot having a mobile mechanism for enabling to move on a level ground or an unleveled ground, a humanoid robot is disclosed in the following Patent Document 1. In this Patent Document 1 is disclosed the humanoid robot, equipped with a driving wheels at portion corresponding to the soles of feet, so that it can run on the level ground, by means of the wheels through conducting an inverted pendulum control, while on the unleveled ground, with using the side surfaces of the feet as the soles, by turning roll shafts of ankles by 90 degrees, thereby conducting bipedalism. 
         [0003]    [Patent Document 1] Japanese Patent Laying-Open No. 2005-288561 (2005). 
       BRIEF SUMMARY OF THE INVENTION 
       [0004]    However, with such the method as was mentioned above, because of much degrees of freedom to be passed through, from the wheels up to a trunk, there is a possibility of shortage of stiffness or rigidity at the toes when running on the wheels. Also, when switching between the running on the wheels and the bipedalism, it is necessary to change the condition of the wheels to touch on the ground, and therefore the time necessary for transition thereof comes to be long. 
         [0005]    An object, according to the present invention, is to provide a robot, for achieving a leg mechanism having high rigidity, so as to enable moving on the wheels, on the leveled ground, and also moving on the bipedalism, on the unleveled ground, and further that mechanism can be switched between the on-wheel running and the bipedalism. 
         [0006]    For accomplishing the object mentioned above, according to the present invention, there is provided a robot, comprising: a body; and left and right leg portions in lower portion of said body, wherein each leg portion has a wheel, which can be drive, at a tip thereof, and a supporting portion, which is movable in roll and pitch directions. 
         [0007]    Also, for accomplishing the object mentioned above, according to the present invention, within the robot described in the above, said each leg portion has three (3) degrees of freedom, roll, pitch and pitch from said body side. 
         [0008]    Also, for accomplishing the object mentioned above, according to the present invention, within the robot described in the above, said supporting portion has at least two (2) of contact points to be in contact with a ground, and makes up a stable region by a contact point of said wheel and the contact point of said supporting body, and thereby oscillating said left and right leg portions, alternately, so as to make bipedalism, and further operating said supporting body, so as to run on said wheels. 
         [0009]    And also, for accomplishing the object mentioned above, according to the present invention, within the robot described in the above, a distance of a roll rotation shaft of said supporting body from a ground is so determined that the roll rotation shaft of said supporting body comes to be in parallel with said ground when at least two (2) points, including, are in contact with the ground, and also said roll rotation shaft of said supporting body and a center of cross-section circle of said roll rotation shaft are constructed to be coincident with, and a pitch rotation shaft of said supporting body and a rotation shaft of said wheel are constructed to be coincident with each other. 
         [0010]    According to the present invention mentioned above, it is possible to provide a leg mechanism having high rigidity, so as to enable moving on the wheels, on the leveled ground, and also moving on the bipedalism, on the unleveled ground, and further this mechanism provides a robot enabling to execute exchanging between the wheel running and the bipedalism in a short time. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0011]    Those and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings wherein: 
           [0012]      FIG. 1  is an entire structural view of a robot, according to an embodiment of the present invention; 
           [0013]      FIG. 2  is a view for explaining the degree freedom of leg portions of the robot, according to the embodiment of the present invention; 
           [0014]      FIG. 3  is a perspective view for explaining the structures of the leg portions of the robot, according to the embodiment of the present invention; 
           [0015]      FIG. 4  is a perspective view for explaining the structures of the leg portions of the robot under the inverted condition thereof, according to the embodiment of the present invention; 
           [0016]      FIG. 5  is a perspective view for explaining the operations of a supporting body of the robot, according to the present invention; 
           [0017]      FIG. 6  is a plane vide for showing  FIG. 4  in the X-axis direction; 
           [0018]      FIG. 7  is a plane vide for showing  FIG. 4  in the Y-axis direction; 
           [0019]      FIGS. 8A to 8D  are views for explaining about the grounding condition when driving the supporting body into a roll direction; and 
           [0020]      FIGS. 9A to 9D  are views for explaining about the grounding condition when driving the supporting body into a pitch direction. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Hereinafter, an embodiment according to the present invention will be fully explained by referring to  FIGS. 1 to 9  attached herewith. 
         [0022]      FIG. 1  is an entire structural view of a robot, according to an embodiment of the present invention. 
         [0023]    In  FIG. 1 , a robot  1  according to the present invention has two (2) pieces of leg portions, i.e., a left foot  6  and a right foot  7 , and a body  3  above them. On both sides of the body  3 , it has two (2) pieces of arm portions, i.e., a left arm  4  and the right arm  5 . Also, above the body  3  is provided a head portion  2 . For example, the left foot  6  and the right foot are used for movement of the robot  1 , and the left arm  4  and the right arm  5  are used in workings or operations, such as, holding or grasping a matter, etc. The body  3  comprises a controller apparatus for controlling the operation of each portion, and sensors for detecting an inclination angle of the body to the direction of gravity and an angular velocity. 
         [0024]      FIG. 2  is a view for explaining the degree freedom of leg portions of the robot, according to the embodiment of the present invention. 
         [0025]    In  FIG. 2 , the robot  1  has five (5) pieces of joints and one (1) piece of wheel, for each of the left and right leg portions, i.e., the left foot  6  or the right foot  7 . In the figure, a roll shaft means a shaft of rotating around the X-axis, and a pitch shaft means a shaft of rotating around the Y-axis. The left foot  6  and the right foot  7  have first roll joints  101 L and  101 R, first pitch joints  102 L and  102 R, second pitch joints  103 L and  103 R, respectively, from the body  100  side, and at the tips thereof, they comprise wheel joints  106 L and  106 R, support pitch joints  104 L and  104 R, and support roll joints  105 L and  105 R, in parallel. 
         [0026]    Each of the joints has a power source (i.e., a motor), a reduction gear and an angle detector (i.e., a rotary encoder or a potentiometer) built therein, and they drive parts connected therewith. The left foot  6  and the right foot  7  are equal to, in the constituent elements thereof, and the structures thereof are symmetric with an X-Z plane passing through the body  3 , therefore in  FIG. 3 , explanation will be given only on the left foot  6 . 
         [0027]      FIG. 3  is a perspective view for explaining about the structures of leg portion, according to the present embodiment. 
         [0028]    In  FIG. 3 , a first leg link  8  is connected with the body  3  at the upper end thereof, and at the lower end of the Z-axis is connected with a first leg actuator  9 , having a driving axis rotating around the X-axis. The first leg actuator  9  is connected with a second leg link  10 , and it oscillates or rocks the second leg link  10  by a predetermined angle around the X-axis. The second leg link  10  is connected with a second leg actuator  11 , having a driving shaft rotating around the Y-axis, at the lower end thereof, and the second leg actuator  11  oscillates or rocks a third leg link  12  by a predetermined angle around the Y-axis. A third leg actuator  13  is attached at an end of a longitudinal side of the Z-axis, with respect to the connection between the second leg actuator  11  and the third leg link  12 , and it oscillates or rocks a fourth leg link  14  by a predetermined angle around the Y-axis. 
         [0029]    A wheel  16  is attached at a reverse end in the longitudinal direction of the Z-axis with respect to the connection of the third leg actuator  13  and the fourth leg link  14 , to be freely rotatable in the Y-axis direction. A wheel driving actuator  15  can rotate infinitely, and is attached on the fourth leg link  14 , thereby driving the wheel  16  through a belt, a shaft or a gear, etc., for example. A pitch shaft driving actuator  17  of the supporting body is attached on the fourth leg link  14 , in coaxial with the wheel  16 , and oscillates or rocks a support connection link  18  by a predetermined angle around the Y-axis. A roll shaft driving actuator  19  of the supporting body is attached on a support connection link  18 , and oscillates or rocks the supporting body  20  by a predetermined angle around the X-axis. The wheel  16  is in a torus body having a circular cross-section, and is so formed that it is in contact with the ground, not on a line, but at a point. 
         [0030]    In many cases, movement by the legs is conducted by controlling an attitude of the robot, in accordance with ZMP (Zero Moment Point), and thereby conducting walking. The ZMP is a center of reaction at the contacting point on the ground, and is a point on a floor surface where the moment due to the reaction comes to be zero (0). When the robot walks, there is necessity of conducting a walking control by taking an inertial force due to the movement of the robot itself, the gravity on the robot, the reaction force receiving from the floor, etc., into the consideration thereof. If production of a walking pattern in such a manner, that the ZMP installs itself within a supporting convex polygon by a foot sole of the robot, it is possible to make the robot walk without falling down. Thus, when conducting the bipedalism, it is preferable to form the supporting convex polygon as large as possible, by taking the stability into the consideration thereof. 
         [0031]    The supporting body  20  is formed in the configuration extending in the X-axis direction and the Y-axis direction, and in an example shown in  FIG. 3 , the supporting convex polygon is so shaped by changing the attitude that it is in contact with the ground at least two (2) points or more than that, together with the wheels, and therefore this contributes to an increase of the stability when conducting the bipedalism. 
         [0032]      FIG. 4  is a perspective view for showing the leg portion under the inverted condition of the robot, according to the present embodiment. 
         [0033]    In this  FIG. 4 , this leg portion is in the attitude when the robot moves on the wheels on a flatland, while conducting the inverted two (2) wheels control. As shown in  FIG. 4 , the pitch shaft driving actuator  17  of the supporting body is driven by a predetermined angle, so as to take the attitude of connecting only the wheels  16  on the ground, and the robot moves on the wheels  16  through the inverted two (2) wheels control. In this instance, with the conventional robot, a backrush for each joint and positional error due to spring property are accumulated as large as the number of the joints passing through from the wheels  16  to the body  3 . For this reason, there is a drawback that the rigidity of the system becomes low, and therefore it is difficult to execute the inverted two (2) wheels control with stability (for example, with the example shown in the Japanese Patent Laying-Open No. 2005-288561 (2005), it passes through five (5) degrees of freedom from the wheels to the body trunk). 
         [0034]    According to the embodiment of the present invention, since the joints are three (3) to be passed through, i.e., the first leg actuator  9 , the second leg actuator  11  and the third leg actuator  13 , therefore it is possible to achieve the inverted two (2) wheels control of high rigidity. 
         [0035]      FIG. 5  is a perspective view for explaining the operation of the supporting body of the robot, according to the present embodiment. 
         [0036]      FIG. 6  is a plane view for showing  FIG. 4  seeing in the X-axis direction. 
         [0037]      FIG. 7  is a plane view for showing  FIG. 4  seeing in the Y-axis direction. 
         [0038]    In  FIG. 5 , without executing the inverted two (2) wheels control, both the supporting body  20  and the wheel  16  are in the attitude of being in contact with the ground with driving the pitch shaft driving actuator  17  of the supporting body by a predetermined angle. As is shown in  FIG. 5 , the supporting body  20  of the robot  1 , according to the present embodiment, is in contact with the ground at the two (2) points, i.e., a first supporting body contacting point  202  and a second supporting body contacting point  203 . Since the supporting body  20  has two (2) degrees of freedom, i.e., a roll rotation shaft  21  of the supporting body and a pitch rotation shaft  22  of the supporting body, then it can be controlled so that the wheel  16 , the first supporting body contacting point  202  and the second supporting body contacting point  203  are in contact with the ground  200 , with certainty, if there is unevenness on the ground a little bit. 
         [0039]    Also, in this instance, the supporting convex polygon, being defined by three (3) points, i.e., the contacting point  201  of the wheel on the ground, the first supporting body contacting point  202  and the second supporting body contacting point  203 , is called “grounding triangle” in the explanation, which will be given below. 
         [0040]    Hereinafter, explanation will be given about the condition that the grounding triangle defined by the contacting point  201  of the wheel on the ground, the first supporting body contacting point  202  and the second supporting body contacting point  203 , does not change even if the roll rotation shaft  21  of the supporting body and the pitch rotation shaft  22  take any attitude. Herein, an advantage or merit of that the grounding triangle does not change lies in that, since the stability of ZMP does not change to disturbances if the supporting body takes any attitude, the robot can always maintain a certain or constant stability. 
         [0041]      FIGS. 8A to 8D  are views for explaining the grounding condition, in particular, when driving the supporting body in the roll direction. 
         [0042]    In  FIGS. 8A to 8D , a relationship between the position of the roll rotation shaft  21  of the supporting body and a center  24  of the wheel cross-section of the wheel  16  and the size of a radius  25  of the cross-section circle of the wheel, so as not to change the configuration of the grounding triangle  204 , which is defined by the contacting point  201  of the wheel on the ground, the first supporting body contacting point  202  and the second supporting body contacting point  203 , is as below. 
         [0043]    Namely,  FIGS. 8A to 8D  are views for showing the grounding condition of the wheel  16  and the supporting body  20  of the robot  1 , seeing in the X-axis direction. Among those,  FIGS. 8A and 8B  are views for showing the constructing, in which the roll rotation shaft  21  of the supporting body and the center  24  of the cross-section circle of the wheel are not coincident with, while  FIGS. 8C and 8D  are views for showing the constructing, in which the roll rotation shaft  21  of the supporting body and the center  24  of the cross-section circle of the wheel are coincident with each other. Also, in this instance, a distance  26  of the roll rotation shaft of the supporting body from the ground is determined in such a manner that the roll rotation shaft  21  of the supporting body is always in parallel with the X-axis when the three (3) points, i.e., the contacting point  201  of the wheel on the ground, the first supporting body contacting point  202  and the second supporting body contacting point  203  are in contact with the ground  200 . 
         [0044]      FIG. 8A  shows an attitude, in which the fourth leg link  14  is in parallel with the Z-axis. In this instance, the grounding triangle  204  is defined by the three (3) points; i.e., the contacting point  201  of the wheel on the ground, the first supporting body contacting point  202  and the second supporting body contacting point  203 .  FIG. 8B  shows the condition where the roll shaft driving actuator  19  of the supporting body is driven by a predetermined angle from the condition shown in  FIG. 8A , so as to incline the rotation shaft  23  of the wheel to the ground  200 . As apparent from those figures, an apex of the grounding triangle  204  moves, and thereby defines a grounding triangle  205  having a new configuration. Such change of the configuration of the grounding triangle results into a cause of reason of loosing the stability. 
         [0045]      FIG. 8C  also shows the attitude, in which the fourth leg link  14  is in parallel with the Z-axis, as shown in  FIG. 8A . However, they are so constructed that the roll rotation shaft  21  of the supporting body and the center  24  of the cross-section circle of the wheel are coincident with each other.  FIG. 8D  shows the condition where the roll shaft driving actuator  19  of the supporting body is driven by a predetermined angle from the condition shown in  FIG. 8C , so as to incline the rotation shaft  23  of the wheel to the ground  200 . In this instance, the grounding triangle  204  does not change the configuration thereof, and therefore no change of the stability between  FIG. 8C  and  FIG. 8D . 
         [0046]    Although  FIGS. 8A to 8D  show an example of the case where the roll rotation shaft  21  of the supporting body and the center  24  of the cross-section circle of the wheel are shifted in the Z-axis direction, but it is apparent that, also in case where they are shifted in the Y-axis direction, the grounding triangle  204  changes the configuration thereof when driving the roll rotation shaft  21  of the supporting body, and therefore the explanation thereof was omitted herein. 
         [0047]      FIGS. 9A to 9D  are views for explaining about the grounding condition, in particular, when driving the supporting body in the pitch direction. 
         [0048]      FIGS. 9A to 9D  are views for showing the grounding condition of the wheel  16  and the supporting body  20  of the robot  1 , seeing in the Y-axis direction. Among those,  FIGS. 9A and 9B  are views for showing the constructing, in which the pitch rotation shaft  22  of the supporting body and the rotation shaft  23  of the wheel are not coincident with, while  FIGS. 9C and 9D  are views for showing the constructing, in which the pitch rotation shaft  22  of the supporting body and the rotation shaft  23  of the wheel are coincident with each other. 
         [0049]      FIG. 9A  shows an attitude, in which the fourth leg link  14  is in parallel with the Z-axis. In this instance, the grounding triangle  206  is defined by the three (3) points; i.e., the contacting point  201  of the wheel on the ground, the second supporting body contacting point  203  and the first supporting body contacting point  202  laying in the positive direction of the Y-axis in the figures.  FIG. 9B  shows the condition where the pitch shaft driving actuator  17  of the supporting body is driven by a predetermined angle from the condition shown in  FIG. 9A , so as to incline the fourth leg link  14  to the ground  200 . As apparent from those figures, apexes of the grounding triangle  206  move, and thereby define a grounding triangle  207  having a new configuration. Such change of the configuration of the grounding triangle results into a cause of reason of loosing the stability. 
         [0050]      FIG. 9C  also shows the attitude, in which the fourth leg link  14  is in parallel with the Z-axis, as shown in  FIG. 9A . However, they are so constructed that the pitch rotation shaft  22  of the supporting body and the rotation shaft  23  of the wheel are coincident with each other.  FIG. 9D  shows the condition where the pitch shaft driving actuator  17  of the supporting body is driven by a predetermined angle from the condition shown in  FIG. 8C , so as to incline the fourth leg link  14  to the ground  200 . In this instance, the grounding triangle  204  does not change the configuration thereof, and therefore no change of the stability between  FIG. 9C  and  FIG. 9D . 
         [0051]    As was mentioned above, according to the present invention, the grounding triangle, being defined by the three (3) points, i.e., the contacting point  201  of the wheel on the ground, the first supporting body contacting point  202  and the second supporting body contacting point  203 , does not change, even if the driving the roll rotation shaft  21  of the supporting body and the pitch rotation shaft  22  of the supporting body take any attitude. 
         [0052]    This condition of no change is because the distance  26  of the roll rotation shaft of the supporting body is determined in such a manner that the roll rotation shaft  21  comes to be always in parallel with the X-axis, when the three (3) points, i.e., the contacting point  201  of the wheel on the ground, the first supporting body contacting point  202  and the second supporting body contacting point  203  are in contact with the ground  200 . 
         [0053]    Further, it is because the roll rotation shaft  21  of the supporting body and the center  24  of the wheel are constructed to be coincident with, and moreover because the pitch rotation shaft  22  of the supporting body and the rotation shaft  23  of the wheel are constructed to be coincident with each other. 
         [0054]    In this manner, if satisfying the condition mentioned above, the supporting convex polygon comes to be constant irrespective of the attitude of the supporting body, and the stability to the disturbance does not change, therefore it is possible to achieve a mechanism having high stability. 
         [0055]    While we have shown and described several embodiments in accordance with our invention, it should be understood that disclosed embodiments are susceptible of changes and modifications without departing from the scope of the invention. Therefore, we do not intend to be bound by the details shown and described herein but intend to cover all such changes and modifications that fall within the ambit of the appended claims.