Abstract:
A quadruped walking robot, comprising a body part having a horizontal swing part, a horizontal swing drive part, an upper side upper leg part pivotally supported on the horizontal swing part, a lower side upper leg part disposed parallel with the lower part of the upper side upper leg part, an upper leg rotatingly driving part rotatingly driving the upper side upper leg part, a lower leg part having an upper end part to which the tip part of the upper side upper leg part and the tip part of the lower side upper leg part are pivotally connected on the upper and lower sides, and ground-contact part disposed at the lower end part of the lower leg part, and an elastic extensible part disposed at the middle part of the lower side upper leg part and elastically extending/retracting in the longitudinal direction.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a quadruped (four-legged) walking robot having four leg sections and is self-moving by actuating the respective leg sections. 
     BACKGROUND OF THE INVENTION 
     Conventionally, various self-moving robots have been developed, some of which have wheels, others of which have caterpillars, and still others of which have leg sections. As a walking robot having leg sections, multi-legged walking robots such as a biped or two-legged robot, a three-legged robot, a quadruped or four-legged robot, a six-legged robot, etc., have been developed. In particular, various types of quadruped walking robots have recently been developed in view of high stability in walking motions, and by a reason that these robots are manufactured mimicking a four-legged animal such as, for example, a dog, a cat, etc. 
     A walking motion of the quadruped walking robot is carried out in such a manner that, for example, in a state where the tip ends of the three legged sections are grounded to support the weight of a main body portion, etc., the remaining one leg is grounded after being moved to another point of the ground using the leg as a free or idle leg, and walking and movement are executed with the weight of a robot supported, by changing over such grounding legs and an idle leg at the respective leg sections by turns. 
     As such a quadruped walking robot, Patent Document 1 refers to a multi-legged walking robot in which a plurality of legs or leg sections are provided for the sides of the main body portion, and describes a construction in which the respective legs are provided with the first turning axis, the second turning axis and the third turning axis. A leg of the quadruped walking robot according to Patent Document 1 is composed of a first unit disposed at the side of the main body portion, a second unit attached to the first unit via a first joint portion, and a third unit attached to the second unit via a second joint portion, wherein the first joint portion is composed of a first turning axis having its axial direction in the direction parallel to the side of the main body portion, and a second turning axis having its axial direction in the perpendicular direction to the side of the main body portion, and the second joint portion is composed of a third turning axis parallel to the second turning axis. 
     Patent Document 1: Japanese Published Unexamined Patent Application No. 2002-11679 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the above-described conventional multi-legged walking robot has the following problems.
     (1) Since the first, the second and the third turning axes are turned in a multi-legged walking robot according to Patent Document 1, it is necessary to provide a driving portion such as a motor to drive the respective turning axes, wherein twelve driving portions are totally required in a case of four legs. Therefore, there is a problem that the number of driving portions is increased, the production costs thereof are remarkably raised, and the weight is incidentally increased.   (2) Also, only by reducing the number of turning axes in order to decrease the number of driving portions, the degree of freedom of the legs is reduced, wherein since it becomes impossible to move the tips of the legs to optional positions, stabilized walking control cannot be carried out, and in particular where ZMP control is executed to carry out stabilized walking, the tips of the ground legs cannot be moved to optional positions. Therefore, there are other problems that the balance of the robot is worsened, the tips of the legs slip on the ground during walking, and the walking is not stabilized.   

     The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a quadruped walking robot capable of achieving a decrease in production costs and lightening the weight thereof by reducing the number of driving portions and capable of carrying out stabilized walking motions even if the degree of freedom in the leg sections is lowered. 
     Means for Solving the Problems 
     In order to solve the above-described problems, a quadruped walking robot according to the present invention includes the following construction. 
     A quadruped walking robot according to a first aspect of the present invention has four leg sections at the sides of a main body portion, wherein the leg section includes a horizontal swivel portion disposed so as to freely swivel in the horizontal direction in the main body portion; a horizontal swivel driving portion disposed in the main body portion, which drives and turns the horizontal swivel portion in the horizontal direction; an upper side upper leg portion rotatably axially attached to the horizontal swivel portion so as to freely turn in the vertical direction; a lower side upper leg portion disposed roughly parallel to the lower part of the upper side upper leg portion, which is rotatably axially attached to the horizontal swivel portion so as to freely turn in the vertical direction; an upper leg driving and turning portion disposed in the horizontal swivel portion, which drives and turns the upper side upper leg portion in the vertical direction; a lower leg portion in which the distal end part of the upper side upper leg portion and the distal end part of the lower side upper leg portion are axially supported vertically at the upper end portion; and a grounding portion disposed at the lower end portion of the lower leg portion; wherein the lower side upper leg portion is provided with a resilient extension and contraction portion that is disposed at an intermediate part thereof and is resiliently extended and contracted in the lengthwise direction. 
     With such a construction, the following actions can be brought about.
     (1) Since the upper side upper leg portion is driven and turned in the upward direction or the downward direction by driving the upper leg driving and turning portion of the leg portion, it is possible to make the lower leg portion into an idle leg by moving the same in the upward direction and to ground it by moving the same in the downward direction. Also, by driving the horizontal swivel driving portion and moving the horizontal swivel portion in the right direction or the left direction when the leg portion is an idle leg, it is possible to swivel the leg portion in the forward direction or the backward direction.   (2) By carrying out a crawl-walking motion in which a motion of making the lower leg portion of the leg portion into an idle leg by moving it upward, swiveling the leg portion in the forward direction and grounding the same is executed one after another in the respective leg portions, it is possible to cause the quadruped walking robot to advance, retract and turn. At this time, the posture of the main body portion is controlled by a control unit, with the main body portion supported by three leg portions other than the leg portion which is made into an idle leg, so that the ZMP (Zero Moment Point) which is a point on the ground on which the total sum of the gravities of the respective parts of the quadruped walking robot and the moments based on inertia forces are made into zero is positioned inside a triangle for which the grounding points of the grounding legs are made into vertices thereof, a so called supporting polygon. Accordingly, stabilized walking motions can be carried out.   (3) By resiliently extending and contracting the resilient extension and contraction portion, it is possible to vary the inclination of the lower leg portion with respect to the upper side upper leg portion, wherein the posture of the leg portions can be varied in association with movement of the main body portion and the posture thereof at the time. Accordingly, even a dual-driving system that has two driving portions per leg portion can bring about stabilized walking motions without the grounding portion slipping on the ground.   (4) Since the leg portion is composed of the dual-driving system that has two driving portions per leg portion, it is possible to reduce the number of driving portions in comparison with a triple-driving system, wherein the production costs can be lowered, and at the same time, the weight can be lightened.   (5) Although the leg portion is a dual-driving system including two driving portions, it is possible to achieve a walking motion close to a normal triple-driving system and three degrees of freedom since the lower side upper leg portion includes a resilient extension and contraction portion.   

     Herein, the quadruped walking robot is provided with four leg portions, each of which is located at both sides of the front part and the rear part of the main body portion thereof. In a state where the grounding portions of the three leg portions thereof are grounded and support the weight of the main body portion, the remaining one leg portion is made into an idle leg and is moved to another point of the ground. After that, the leg portion is grounded there. That is, it is possible to execute a crawl walking motion in which walking is carried out by alternately changing over the grounding leg portions and the idle leg for all leg portions, and a trot walking motion in which walking is carried out by making one pair of diagonal leg portions of the four leg portions, for example, the leg portion at the right side portion of the front part and the leg portion at the left side portion of the rear part into idle legs, and making the remaining two legs into grounding legs, and alternately changing over the idle leg portions and the grounding leg portions. In addition, where a trot walking motion is carried out by providing a locking mechanism portion so that the sliding portion of the resilient extension and contraction portion is locked at the tubular portion so as not to be extended and contracted, it is preferable that the resilient extension and contraction portion is locked by operating the locking mechanism portion. 
     A resilient extension and contraction portion that is provided with a tubular portion disposed in the lengthwise direction of the lower side upper leg portion, and a sliding portion slidably inserted into the tubular portion, and a spring member fitted inside the tubular portion may be used. 
     A motor such as a geared motor may be used as the horizontal swivel driving portion and the upper leg driving and turning portion. Also, turning axes fixed at the horizontal swivel portion and the upper side upper leg portion are turned via one through a plurality of gears, whereby it is possible to drive and turn the horizontal swivel portion and the upper side upper leg portion. 
     A quadruped walking robot according to Claim  2  of the present invention has a construction in the invention of Claim  1 , in which the resilient extension and contraction portion includes a tubular portion disposed in the lengthwise direction of the lower side upper leg portion, a sliding portion slidably inserted into the tubular portion, and a spring member fitted inside the tubular portion and pressing the sliding portion in the extension and contraction direction. 
     With the construction, the following actions can be brought about in addition to those of Claim  1 .
     (1) Since the sliding portion inserted into the tubular portion slides along the inner wall of the tubular portion, and at the same time, is pressed by a spring member fitted in the tubular portion, the resilient extension and contraction portion is resiliently extended and contracted, wherein it is possible to vary the posture of the leg portions corresponding to movement of the main body portion and the posture thereof at the time. Therefore stabilized walking can be carried out.   

     A quadruped walking robot according to Claim  3  of the present invention has a construction in the invention of Claim  1  or Claim  2 , in which a locking mechanism portion, disposed in the resilient extension and contraction portion of the respective leg portions, for locking and unlocking the resilient extension and contraction portion is provided. 
     With the construction, the following actions can be brought about in addition to those of Claim  1  or Claim  2 .
     (1) Since the resilient extension and contraction portion can be locked or unlocked so as not to extend and contract by the locking mechanism portion, the resilient extension and contraction portion is resiliently extended and contracted by unlocking the same where the quadruped walking robot carries out crawl walking, and a stabilized walking motion can be carried out. For example, where a trot walking motion is carried out, the resilient extension and contraction portion is locked to cause the lower leg portion not to be inclined toward the main body portion due to movement of the main body portion, etc., wherein a stabilized trot walking motion can be carried out.   

     Herein, there are some locking mechanism portions, one of which is provided with a locking hole drilled in the tubular portion and an insertion pin inserted into the locking hole, wherein locking is carried out by inserting the insertion pin into the locking hole, and the other of which is provided with a solenoid, an insertion pin fixed at the movable portion of the solenoid, and a locking hole or a locking groove formed in the resilient extension and contraction portion, into which the insertion pin is inserted, wherein locking is carried out by the insertion pin being inserted into the locking hole or the locking groove by supplying electricity to the solenoid. 
     A quadruped walking robot according to a fourth aspect of the present invention has a construction in the invention of the third aspect, in which the locking mechanism portion is provided with a locking hole drilled in the tubular portion and an insertion pin inserted into the locking hole. 
     With the construction, the following actions can be brought about in addition to those of Claim  3 .
     (1) By inserting the insertion pin into the locking hole, it is possible to prevent the sliding portion from sliding inside the tubular portion, and by pulling out the insertion pin from the locking hole, it is possible to unlock the sliding portion.   

     EFFECTS OF THE INVENTION 
     As described above, with the quadruped walking robot according to the present invention, the following advantageous effects can be brought about. 
     According to the invention of Claim  1 ,
     (1) As for the leg portion, since a dual-driving system having two driving portions per leg portion is employed, it is possible to provide a leg walking robot capable of reducing the number of driving portions in comparison with a triple-driving system, reducing the production costs and lightening the weight.   (2) Since, by resiliently extending and contracting the resilient extension and contraction portion, the inclination of the lower leg portion can be varied for the upper side upper leg portion, and the posture of the leg portions can be varied, corresponding to movement of the main body portion and the posture thereof at the time, a quadruped walking robot can be provided, which is excellent in stability and can carry out stabilized walking motions without the grounding portion sliding on the ground even in the case of a dual-driving system including two driving portions per leg portion.   (3) Since the lower side upper leg portion includes a resilient extension and contraction portion although the leg portion is based on a dual-driving system having two driving portions, it is possible to achieve a walking motion close to a normal triple-driving system of three degrees of freedom. Therefore, it is possible to provide a quadruped walking robot, which has excellent stability in walking motions, capable of smoothly walking.   

     According to the invention of Claim  2 , in addition to the effect of Claim  1 ,
     (1) Since the sliding portion inserted into the tubular portion slides along the inner wall of the tubular portion, and at the same time, is pressed by a spring member fitted in the tubular portion, the resilient extension and contraction portion is resiliently extended and contracted, wherein it is possible to vary the posture of the leg portions corresponding to movement of the main body portion and the posture thereof at the time. Therefore, it is possible to provide a quadruped walking robot that is able to carry out stabilized walking and is excellent in stability.   

     According to the invention of Claim  3 , in addition to the effects of Claim  1  or Claim  2 ,
     (1) Since it is possible to lock the resilient extension and contraction portion by the locking mechanism portion so as not to extend and contract and to unlock the same, the resilient extension and contraction portion is resiliently extended and contracted by unlocking the same and stabilized walking motions can be carried out where the quadruped walking robot carries out a crawl walking motion, and, for example, where a trot walking motion is carried out, a stabilized trot walking motion can be executed by locking the resilient extension and contraction portion so that the lower leg portions are not inclined toward the main body portion due to movement of the main body portion. That is, various types of walking movements are possible only by actuating or unlocking the locking mechanism portion, wherein it is possible to provide a quadruped walking robot that is excellent in diversity of walking motions.   

     According to the invention of Claim  4 , in addition to the effects of Claim  3 ,
     (1) It is possible to prevent the sliding portion from sliding inside the tubular portion by inserting the insertion pin into the locking hole, and it is possible to unlock the sliding portion by pulling out the insertion pin from the locking hole. Accordingly, it is possible to provide a quadruped walking robot in which switching of walking motions can be simply carried out.   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view depicting the major parts of the leg portion of the front part of a quadruped walking robot according to a first Embodiment; 
         FIG. 2  is a rear side view of a leg portion of the quadruped walking robot according to the first Embodiment; 
         FIG. 3A  is a schematic view describing a crawl walking motion of a quadruped walking robot according to the first Embodiment; 
         FIG. 3B  is a schematic view describing a crawl walking motion of a quadruped walking robot according to the first Embodiment; 
         FIG. 3C  is a schematic view describing a crawl walking motion of a quadruped walking robot according to the first Embodiment; 
         FIG. 3D  is a schematic view describing a crawl walking motion of a quadruped walking robot according to the first Embodiment; and 
         FIG. 3E  is a schematic view describing a crawl walking motion of a quadruped walking robot according to the first Embodiment; 
         FIG. 4A  is a schematic view describing ZMP control when a quadruped walking robot according to the first Embodiment makes a crawl walking motion; and 
         FIG. 4B  is a schematic view describing ZMP control when a quadruped walking robot according to the first Embodiment makes a crawl walking motion; 
         FIG. 5A  is a schematic view describing a motion of a resilient extension and contraction portion of a quadruped walking robot according to the first Embodiment; and 
         FIG. 5B  is a schematic view describing a motion of a resilient extension and contraction portion of a quadruped walking robot according to the first Embodiment; 
         FIG. 6  is a partially sectional side view of the major parts of a locking mechanism portion; and 
         FIG. 7  is a partially sectional side view of the major parts depicting another example of the locking mechanism portion. 
     
    
    
     DESCRIPTION OF THE SYMBOLS 
     
         
         
           
               1  Quadruped walking robot 
               2  Main body portion 
               2   a  Upper side main body plate 
               2   b  Lower side main body plate 
               2   c  Fixing hole 
               2   d  Widened portion 
               20   a , 3   b , 3   c  Leg portions 
               4  Horizontal swivel portion 
               4   a  Upper side swivel plate 
               4   b  Lower side swivel plate 
               4   c , 4   d  Side part swivel plates 
               4   e  Fixing hole 
               5  Horizontal swivel driving portion 
               5   a  Horizontal driving axis 
               6  Horizontal driving side gear 
               7  Horizontal driven side gear 
               8  Horizontal swivel axis 
               9  Upper side upper leg portion 
               9   a  Upper side upper leg portion turning axis 
               9   b  Upper leg driven side gear 
               10  Upper leg driving and turning portion 
               10   a  Upper leg driving axis 
               10   b  Upper leg driving side gear 
               11  Lower side upper leg portion 
               11   a  Lower side upper leg turning axis 
               11   b  Lower leg portion side member 
               11   c  Horizontal swivel portion side member 
               12  Resilient extension and contraction portion 
               12   a  Tubular portion 
               12   b  Sliding portion 
               12   c  Spring member 
               13  Lower leg portion 
               13   a ,  13   b  Lower leg plates 
               14  Upper side lower leg axis 
               15  Lower side lower leg axis 
               16  Shock-absorbing portion 
               17 , 17   a , 17   b , 17   c  Grounding portions 
               18   a , 18   b  Supporting polygons 
               19   a , 19   b  ZMPs 
               20   a , 20   b  Setting ZMPs 
               21  Locking mechanism portion 
               22  Casing portion 
               23  Solenoid portion 
               24 , 28  Insertion pins 
               25 , 27  Locking holes 
               26  Locking groove 
           
         
       
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, a description is given of one embodiment of the present invention with reference to  FIG. 1  through  FIG. 7 . 
     First Embodiment 
       FIG. 1  is a perspective view depicting the major parts of the leg portion of the front part of a quadruped walking robot according to the first Embodiment, and  FIG. 2  is a rear side view of a leg portion of the quadruped walking robot according to the first Embodiment. Also, although a description is given of only one leg portion of the front part of the quadruped walking robot, the respective leg portions have the same construction, and a description of the other leg portions is omitted. 
     In the drawing, reference numeral  1  denotes a quadruped walking robot according to the first Embodiment, and reference numeral  2  denotes a main body portion composed of an upper side main body plate  2   a  and a lower side main body plate  2   b  vertically disposed parallel to each other and having widened portions  2   d  at the front end portion thereof and the rear end portion thereof. Reference numeral  20   a  denotes left and right leg portions at the front part of the quadruped walking robot  1 . Reference numeral  4  denotes a horizontal swivel portion provided at the side of the widened portion  2   d  of the main body portion  2  so as to freely swivel in the horizontal direction. Reference numeral  5  denotes a horizontal swivel driving portion, which is fitted and fixed in a rectangular fixing hole  2   c  drilled at the upper side main body plate  2   a  of the main body portion  2 , for driving and swiveling the horizontal swivel portion  4 . Reference numeral  6  denotes a horizontal driving side gear fixed at the horizontal driving axis  5   a  (Refer to  FIG. 2 ) of the horizontal swivel driving portion  5 . Reference numeral  7  denotes a horizontal driven side gear engaged with the horizontal driving side gear  6 , and reference numeral  8  denotes a horizontal swivel axis fixed at the horizontal driven side gear  7 . The horizontal swivel portion  4  is composed of an upper swivel plate  4   a  on the upper side, a lower side swivel plate  4   b  on the lower side, and side swivel plates  4   c  and  4   d  at both side portions. The horizontal swivel axis  8  has the upper end portion and the lower end portion fixed at the upper side swivel plate  4   a  and the lower side swivel plate  4   b , which are rotatably axially supported at the upper side main body plate  2   a  of the main body portion  2  and the lower side main body plate  2   b  thereof. 
     Reference numeral  9  denotes an upper side upper leg portion rotatably axially supported at the horizontal swivel portion  4  in the vertical direction at one end part thereof. Reference numeral  9   a  denotes an upper side upper leg portion turning axis fixed at one end portion of the upper side upper leg portion  9  and rotatably axially supported at the side portion swivel plates  4   c  and  4   d . Reference numeral  10  denotes an upper leg turning and driving portion, which is fitted and fixed in a rectangular fixing hole  4   e  drilled in the side portion swivel plate  4   c , for driving and turning the upper side upper leg portion  9 . Reference numeral  11  denotes a lower side upper leg portion disposed roughly parallel to the lower part of the upper side upper leg portion  9  and rotatably axially supported at the horizontal swivel portion  4  at one end part thereof. Reference numeral  11   a  denotes a lower side upper leg turning axis fixed at one end portion of the lower side upper leg portion  11  and rotatably axially supported at the side portion swivel plates  4   c  and  4   d . Reference numeral  12  denotes a resilient extension and contraction portion disposed at an intermediate portion of the lower side upper leg portion  11 . Reference numeral  12   a  denotes a tubular portion disposed along the lengthwise direction of the lower side upper leg portion  11  and fixed at the lower leg portion side member  11   b , and  12   b  denotes a sliding portion fixed at the horizontal swivel portion side member  11   c  of the lower side upper leg portion  11  and slidably inserted into the tubular portion  12   a . Reference numeral  13  denotes a lower leg portion whose upper part is axially supported at the upper side upper leg portion  9  and at the other end portion of the lower side upper leg portion  11 . Reference numerals  13   a  and  13   b  denote a front side lower leg plate and a rear side lower leg plate of the lower leg portion  13 , respectively. Reference numeral  14  denotes an upper side lower leg axis fixed at the other end portion of the upper side upper leg portion  9  and axially supported at the upper end portion of the lower leg portion  13 . Reference numeral  15  denotes a lower side lower leg axis fixed at the other end portion of the lower side upper leg portion  11  and axially supported at the lower part of the upper side lower leg axis  14  of the lower leg portion  13 . Reference numeral  16  denotes a shock-absorbing portion composed of a plurality of supporting pins provided at the lower end portion of the lower leg portion  13  along the lengthwise direction and spring members fitted to the respective supporting pins. Reference numeral  17  denotes a grounding portion disposed at the lower part of the shock-absorbing portion  16 , the lower part of which is formed to be curvature-shaped. 
     In  FIG. 2 , reference numeral  5   a  denotes a driving axis of the horizontal swivel driving portion  5 , which is a horizontal driving axis having a horizontal driving gear  6  fixed thereon, and  9   b  denotes an upper leg driven side gear fixed on the upper side upper leg turning axis  9   a . Reference numeral  10   a  is an upper leg driving axis that is a driving axis of the upper leg turning and driving portion  10 , and  10   b  denotes an upper leg driving side gear fixed at the upper leg driving axis  10   a  and engaged with the upper leg driven side gear  9   b . Reference numeral  12   c  denotes a spring member fitted inside the tubular portion  12   b , one end of which is fixed at the bottom portion of the tubular portion  12   a  and the other end of which is fixed at the distal end of the sliding portion  12   b.    
     Herein, a geared motor may be used as the horizontal swivel driving portion  5  and the upper leg driving and turning portion  10 . 
     With respect to the quadruped walking robot  1  according to the first Embodiment constructed as described above, a description is given below of the walking motions thereof with reference to  FIGS. 1 and 2 . 
     First, a description is given of basic motions of a leg portion, in which the leg portion  3  is made into an idle leg from a grounded state, is swiveled in the horizontal direction, and thereafter is grounded. 
     As depicted in  FIGS. 1 and 2 , in order to raise the lower leg portion  12  upward from a state where the grounding portion  17  is grounded on the ground and to make the leg portion  3  into an idle leg, the upper leg driving and turning portion  10  is driven to turn the upper leg driving side gear  10   b  in the direction of the arrow y in  FIG. 2 , and the upper leg driven side gear  9   b  engaged with the upper leg driving side gear  10   b  is turned rightward of the arrow, wherein the upper side upper leg portion  9  is turned upward. In line therewith, the lower leg portion  13  moves upward. Also, since the lower side upper leg portion  11  is turned upward in line with upward turning of the upper side upper leg portion  9 , the grounding portion  17  of the lower leg portion  13  is able to keep a downward-faced posture. 
     In order to swivel the leg portion  3  in the horizontal direction in a state where the leg portion  3  is made into an idle leg, the horizontal driving side gear  6  is turned in the direction of the arrow β by driving the horizontal swivel driving portion  5 , and the horizontal driven side gear  7  engaged with the horizontal driving side gear  6  is turned rightward when observed from upward. Then, the horizontal swivel portion  4  is turned rightward. Accordingly, the leg portion  3  is swiveled forward. 
     When the leg portion  3  is swiveled to a predetermined position, the upper leg turning and driving portion  10  is driven to turn the upper leg driving side gear  10   b  rightward (in the direction of the arrow x) in  FIG. 2 , and the upper leg driven side gear  9   b  is turned leftward to turn the upper side upper leg portion  9  downward, wherein the leg portion  13  is moved downward to ground the grounding portion  17 . 
     In addition, in order to carryout a smooth walking motion, the movement of the lower leg portion  13  in the vertical direction and the swivel motion of the leg portion  3  in the horizontal direction can be simultaneously carried out. At this time, the grounding portion  17  depicts a roughly arc-shaped locus. 
     Next, a description is given of a crawl walking motion based on repeated execution of the basic motions of the leg portion, which has been described above, with respect to the respective leg portions sequentially, with reference to  FIG. 3 . 
       FIG. 3A through 3E  are schematic views describing a crawl walking motion of a quadruped walking robot according to Embodiment 1. 
     In  FIG. 3 , reference numeral  1  denotes a quadruped walking robot,  FIG. 2  denotes a main body portion, and  FIG. 3 ,  3 A,  3 B, and  3 C denote leg portions. Reference numerals  17 ,  17   a ,  17   b , and  17   c  denote grounding portions of the tips of the respective leg portions  3 ,  3   a ,  3   b , and  3   c.    
     As depicted in  FIG. 3A , the grounding portions  17 ,  17   a ,  17   b , and  17   c  are grounded on the ground in a state where the quadruped walking robot is stopped. 
     As depicted in  FIG. 3B , the lower leg portion  13  of the leg portion  3  is moved upward, and simultaneously the leg portion  3  is swiveled in the forward direction. At this time, the leg portion  3  is an idle leg, and the grounding portion  17  thereof is off the ground. Further, the leg portions  3   a ,  3   b  and  3   c  are grounding legs, and the grounding portions  17   a ,  17   b  and  17   c  thereof are grounded, wherein the main body portion  2  is supported at three points. After the leg portion  3  is swiveled in the forward direction, the lower leg portion  13  is moved downward to ground the grounding portion  17 . 
     Subsequently, as depicted in  FIG. 3C through 3E , the other leg portions  3   a ,  3   b  and  3   c  are made into idle legs as in the above-described leg portion  3 , in the order of the leg portion  3   c  ( FIG. 3C ), the leg portion  3   a  ( FIG. 3D ) and the leg portion  3   b  ( FIG. 3E ). At this time, the other remaining three leg portions are made into grounding legs and support the main body portion  2 . The leg portions  3   a ,  3   b  and  3   c  that are made into idle legs are swiveled forward, and are stepped forward in the advancing direction by turns and grounded, whereby the quadruped walking robot  1  carries out a crawl walking motion. 
     In addition, in  FIG. 3 , a description is given of walking in the forward direction of the quadruped walking robot  1 . However, by adequately controlling the horizontal swivel direction of the leg portions  3 ,  3   a ,  3   b  and  3   c  and sequence by which the leg portions are made into idle legs, the quadruped walking robot  1  can move rearward, turn, and stamp its feet, etc. 
     Next, a description is given of ZMP control in crawl walking, with reference to  FIG. 4 . 
       FIGS. 4A and 4B  are schematic views describing the ZMP control for a crawl walking motion of a quadruped walking robot according to the first Embodiment. 
     In  FIG. 4 , reference numeral  18   a  denotes a supporting polygon which is a triangle in which the grounding portions  17   a ,  17   b  and  17   c  on the ground are the vertices. Reference numeral  18   b  denotes a supporting polygon which is a triangle in which the grounding portions  17 ,  17   a  and  17   b  are the vertices. Reference numerals  19   a  and  19   b  denote ZMPs (Zero Moment Points) that are the points on the ground where the total sum of the gravities of the respective parts of the quadruped walking robot  1  and the moments due to inertia becomes zero. Reference numerals  20   a  and  20   b  denote setting ZMPs preset so that the ZMPs are located inside the supporting polygons  18   a  and  18   b . The setting ZMPs  20   a  and  20   b  are established inside the supporting polygons  18   a  and  18   b , and at the same time are set at such a position where smooth walking can be carried out, for example, a position where a gravity does not greatly change in the crawl walking motion. 
     As depicted in  FIG. 4A , the leg portion  3  is an idle leg, and the leg portions  3   a ,  3   b  and  3   c  are the grounding legs. The grounding portions  17   a ,  17   b  and  17   c  are grounded and support the main body portion  2  at three points. Since the ZMP  19   a  in the state supported by the three points is made coincident with the setting ZMP  20   a  set in advance, the quadruped walking robot  1  does not fall down. 
     As depicted in  FIG. 4B , the leg portion  3  that was an idle leg is grounded. Continuously, when the leg portion  3   c  is made into an idle leg, the control unit (not shown) first calculates the ZMP  19   b  when the main body portion is supported by the grounding portions  17 ,  17   a  and  17   b  of the leg portions  3 ,  3   a  and  3   b  at three points. Herein, the ZMP  19   a  is calculated by a ZMP equation on the basis of the position and posture of the main body portion  2 . 
     Next, the control unit drives the horizontal swivel driving portion  5  and the upper leg driving and turning portion  10  of the respective leg portions  3 ,  3   a  and  3   b  as the grounding legs, and controls the position and posture of the main body portion  2 . That is, the horizontal swivel driving portion  5  of the respective leg portions  3 ,  3   a  and  3   b  is driven, and the respective leg portions  3 ,  3   a  and  3   b  are swiveled backward. At this time, since the grounding portions  17 ,  17   a  and  17   b  of the respective leg portions  3 ,  3   a  and  3   b  are grounded on the ground, the main body portion  2  moves to the position of a roughly forward position of the main body portion  2 ′ toward the forward direction by backward swivel of the respective leg portions  3 ,  3   a  and  3   b , and the leg portions  3 ,  3   a  and  3   b  move to the positions of the leg portions  3 ′,  3   a ′ and  3   b ′. Further, it is possible to incline the posture of the main body portion  2  by driving the upper leg turning and driving portion  10  of the leg portions  3 ,  3   a  and  3   b.    
     As described above, the quadruped walking robot  1  carries out crawl walking and moves forward while the control unit is controlling the posture of the main body portion  2  so that the ZMP  19   b  of the quadruped walking robot  1  is made coincident with the setting ZMP  20   b  set inside the supporting polygon  18   b.    
     Also, as depicted in  FIG. 4B , where the main body portion  2  moves roughly forward in a state where the grounding portions  17 ,  17   a  and  17   b  of the leg portions  3 ,  3   a  and  3   b  are grounded, the main body portion  2  is caused to smoothly move by the resilient extension and contraction portion  12  secured at the respective leg portions  3 ,  3   a  and  3   b . Hereinafter, a description is given of motions of the resilient extension and contraction portion. 
       FIG. 5A  and  FIG. 5B  are schematic views describing motions of the resilient extension and contraction portion of a quadruped walking robot according to the first Embodiment. Also, in the drawings, reference symbol “A” and “B” are plan views and side views, respectively. 
     In  FIG. 5 , reference symbol L 1  denotes a distance between the side portion of the main body portion  2  and the grounding portion  17 , and L 2  denotes a swivel radius of the leg portion  3  in the horizontal direction. 
     As depicted in  FIG. 5A , the grounding portion  17  of the leg portion  3  is grounded diagonally forward left of the main body portion  2 . In this state, when the main body portion  2  moves in the forward direction as described in  FIG. 4B , the leg portion  3 ′ becomes roughly orthogonal to the side portion of the main body portion  2 ′ on the plane as depicted in  FIG. 5B . Since the distance L 1  between the side portion of the main body portion  2 ′ and the grounding portion  17  is roughly the same as the distance in the before-forwarding state depicted in  FIG. 5A , the distance L 1  is smaller than the swivel radius L 2  of the leg portion  3 . Therefore, the resilient extension and contraction portion  12  provided at the lower side upper leg portion  11  is caused to contract, wherein the grounding portion  17  side of the lower leg portion  13  is entered into an inclined state toward the side portion of the main body portion  2 ′. 
     Herein, the quadruped walking robot  1  according to the first Embodiment has two degrees of freedom because it is of a dual-driving system having two driving portions  5  and  10  for one leg portion  3 . Therefore, although it is not possible to set the posture of the leg portion  3  in a grounded state to an optional posture, it is possible to vary the posture of the lower leg portion  13  of the leg portion  3 ′, corresponding to movement of the main body portion  2 ′, by extending and contracting the resilient extension and contraction portion  12  as described above, wherein the quadruped walking robot  1  can carry out stable walking without the grounding portion  17  slipping on the ground. 
     Further, differing from the crawl walking motion, it is possible to carry out a trot walking motion, in which a pair of leg portions on a diagonal line of the leg portions  3 ,  3   a ,  3   b , and  3   c , for example, the leg portions  3  and  3   c  are made into a set, and the one set of leg portions is made into idle legs while the other set of leg portions  3   a  and  3   b  are made into grounding legs, and sets of the idle legs and the grounding legs are alternately changed over. The ZMP control for carrying out a trot walking motion is the same as the crawl walking motion, excepting that a rectilinear band-like area connecting a set of grounded leg portions on a diagonal line together, for example, the grounding portions  17  of the leg portions  3  and  3   c , is made into a supporting polygon, the setting ZMP is established inside the corresponding supporting polygon, and the position and posture of the main body portion  2  is controlled so that a ZMP is set to accord with the setting ZMP. 
     In addition, where a trot walking motion is carried out, in order to carry out a stabilized walking motion, it is possible to fix extension and contraction of the resilient extension and contraction portion  12  so that the grounding portion  17  side of the lower leg portion  13  is not inclined toward the side portion of the main body portion  2 ′ due to extension and contraction of the resilient extension and contraction portion  12  by the locking mechanism portion. Hereinafter, a description is given of the locking mechanism portion with reference to  FIG. 6 . 
       FIG. 6  is a partially sectional side view depicting the major parts of the locking mechanism portion. 
     In  FIG. 6 , reference numeral  11  denotes a lower side upper leg portion,  12  denotes a resilient extension and contraction portion,  12   a  denotes a tubular portion,  12   b  denotes a sliding portion,  12   c  denotes a spring member,  21  denotes a locking mechanism portion,  22  denotes a casing portion disposed on the outer wall of the tubular portion  12   a ,  23  denotes a solenoid portion disposed inside the casing portion  22 ,  24  denotes an insertion pin fixed at the movable part of the solenoid portion  23 ,  25  denotes a locking hole drilled in the tubular portion  12   a , and  26  denotes a locking groove provided at a position communicating with the locking hole  25  with a predetermined extension and contraction length of the sliding portion  12   b.    
     As depicted in  FIG. 6 , at the locking mechanism portion  21 , the solenoid portion  23  causes the insertion pin  24  to be inserted into the locking hole  25  and the locking groove  26  by supplying electricity, or causes the inserted pin  24  to be pulled out. By the insertion pin  24  being inserted into the locking hole  25  and the locking groove  26 , the sliding portion  12   b  is fixed with respect to the tubular portion  12   a , where the resilient extension and contraction portion  12  can be fixed so as not to extend and contract. 
     Therefore, since the resilient extension and contraction portion  12  secured at the lower side upper leg portion  11  is not extended and contracted, there is no case where the lower leg portion  13  is inclined toward the main body portion  2  due to movement of the main body portion  2 . Since, in the ZMP control for a trot walking motion, the position and posture of the main body portion  2  are controlled in a state where the main body portion  2  is supported at two points by leg portions on a diagonal line, it is sufficient that one leg portion has two degrees of freedom, wherein no such trouble occurs as the grounding portion  17  slips in a crawl walking motion. Therefore, since the lower leg portion  13  can hold a roughly vertical posture without inclining by fixing the resilient extension and contraction portion  12  so as not to extend and contract, stabilized trot walking can be carried out without swaying of the main body portion  2 . Additionally, by pulling out the insertion pin  24  from the locking hole  25  and the locking groove  26 , the resilient extension and contraction portion  12  can be resiliently extended and contracted by the spring member  12   c . Therefore, the control unit (not shown) controls the electric current flowing in the solenoid portion  23  of the locking mechanism portion  21  and unlocks the resilient extension and contraction portion  12  so as not to extend and contract, and it is possible to carry out stabilized crawl walking as described above. Thus, when selecting crawl walking or trot walking, it is possible to determine whether or not the resilient extension and contraction portion  12  is extended and contracted in response to the walking motion. 
     Next, a description is given of another example of the locking mechanism portion with reference to  FIG. 7 . 
       FIG. 7  is a partially sectional side view depicting the major parts of another example of the locking mechanism portion. 
     In  FIG. 7 , reference numeral  21 ′ denotes a locking mechanism portion,  27  denotes a locking hole drilled in the tubular wall of the tubular portion  12   a , and  28  denotes an insertion pin inserted into the locking hole  27 . 
     As depicted in  FIG. 7 , since the resilient extension and contraction portion  12  can be manually locked and unlocked so as not to extend and contract by inserting the insertion pin  28  into the locking hole  27  or pulling out the same therefrom, the insertion pin  28  is pulled out from the locking hole  27  where crawl walking is carried out, and the insertion pin  28  is inserted into the locking hole  27  where trot walking is carried out, wherein it is possible to carry out stabilized walking when causing the quadruped walking robot  1  to perform either walking. 
     Since the quadruped walking robot  1  according to the first Embodiment is constructed as described above, it has the following actions.
     (1) By driving the upper leg driving and turning portion  10  of the leg portion  3 , the upper leg driving side gear  10   b  is turned, and the upper leg driven side gear  9   b  engaged with the upper leg driving side gear  9   a  is turned, wherein the upper side upper leg portion  9  is turned and moved in the upward direction or in the downward direction, and the lower leg portion  13  can be made into an idle leg by moving it in the upward direction, and can be grounded by moving the same in the downward direction. In addition, by driving the horizontal swivel driving portion  5  when the leg portion  3  is made into an idle leg, the horizontal driving side gear  6  is turned, and the horizontal driven side gear  7  engaged with the horizontal driving side gear  6  is turned, wherein the horizontal swivel portion  4  is turned and moved in the right direction or in the left direction, and it is possible to swivel the leg portion  3  in the forward direction or in the backward direction.   (2) It is possible to carry out a crawl walking motion in which motions of making the lower leg portion  13  of the leg portion  3  into an idle leg by moving the same upward, swiveling the leg portion  3  in the forward direction and grounding the same are executed in sequence with respect to the leg portions  3 ,  3   a ,  3   b  and  3   c , and it is possible to move the quadruped walking robot  1  forward, backward and swivel the same. At this time, since the control unit controls the posture of the main body portion  2  so that the center of gravity of the quadruped walking robot  1  is located inside a triangle the vertices of which are the grounding portions of the grounding legs while supporting the main body portion  2  by means of the remaining three leg portions other than the leg portion which is an idle leg, stabilized walking motions can be carried out.   (3) As the resilient extension and contraction portion  12  is caused to resiliently extend and contract by the sliding portion  12   b  inserted into the tubular portion  12   a  sliding along the inner wall of the tubular portion  12   a , at the same time the sliding portion  12   b  is pressed by the spring member  12   c  fitted in the tubular portion  12   a . When carrying out crawl walking, it is possible to vary the inclination of the lower leg portion  13  in connection to the upper side upper leg portion  9  by extending and contracting the resilient extension and contraction portion  12 , and it is possible to vary the posture of the leg portion  3 , corresponding to the posture of the main body portion  2 . Therefore, stabilized walking can be carried out without the grounding portion  17  slipping on the ground.   (4) The locking mechanism portion  21  locks the sliding portion  12   b  with respect to the tubular portion  12   a  by the insertion pin  24  being inserted into the locking hole  25  and the locking groove  26  by supplying electricity of the solenoid portion  23  and locks the resilient extension and contraction portion  12  so as not to extend and contract. Since the lower leg portion  13  is not inclined toward the main body portion  2  due to movement of the main body portion  2 , it is possible to carry out stabilized trot walking without swaying even in a two-point supported state. Further, the control unit can lock and unlock the resilient extension and contraction portion  12  so as not to extend and contract by controlling the electric current flowing in the solenoid portion  23 , wherein when trot walking is carried out, the resilient extension and contraction portion  12  is locked, and when crawl walking is carried out, the resilient extension and contraction portion  12  is unlocked. That is, the resilient extension and contraction portion  12  can be switched in response to the mode of walking motions.   

     INDUSTRIAL APPLICABILITY 
     As described above, the present invention relates to a quadruped walking robot having four leg portions and self-moving by actuating the respective leg portions. In particular, according to the present invention, it is possible to provide a quadruped walking robot the production costs and weight of which can be reduced by reducing the number of driving portions, and which is capable of carrying out stabilized walking motions even with the degree of freedom reduced in the leg portions.