Patent Publication Number: US-2011054681-A1

Title: Robot

Description:
This application relates to and claims priority from Japanese Patent Application No. 2009-197570 filed on Aug. 28, 2009, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a robot, and in particular, it relates to a suspension of a foot thereof. 
     As a technology for absorbing concave/convex on a surface of a traveling road, thereby for traveling with stability, those are already known in the following Patent Documents 1 and 2, for example. 
     With the method disclosed in the Patent Document 1, with driving a suspension member by an actuator, in such that a reaction is generated against an input from the road surface, thereby the input having a high frequency, such as, the concave/convex on the road surface, for example, is reduced to be applied thereon. 
     Also, in the Patent Document 2, for the purpose of controlling a position of gravity with respect to a centrifugal force during the time when it corners, there is disclosed an inverted pendium mechanism having a magnetic floating slider on a truck equipped with a driving mechanism thereon. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Brief Summary of the Invention 
     [Patent Document 1] Japanese Patent Laying-Open No. H07-276955 (1995). 
     [Patent Document 2] Japanese Patent Laying-Open No. 2005-075070 (2005). 
     For a robot carrying out an inverted pendium movement with appropriately controlling wheels attached at tips of leg portion, which are provided by two (2) pieces at the left-hand and right-hand sides on a lower portion of a body thereof, it is important to absorb the concave/convex on a surface of road, thereby to run with stability. 
     For this, there can be considered a means of loading suspensions on the leg portions, but for carrying out the inverted pendium movement, it is necessary to bring the gravity center thereof to be high, and further, to set a spring constant to be small for absorbing the concave/convex on the surface of road. 
     Also, for making a footprint thereof small, it is necessary to set width between the wheels separating on both sides. For this reason, due to disturbances, such as, a centrifugal force during the time when cornering, the concave/convex on the road surface, and an inclination of the road surface, etc., the left-hand side and the right-hand side are unbalanced in an amount of sinking of the suspension, therefore a swing is generated in a rolling direction (see  FIG. 10 ); i.e., there is a drawback that a possibility of turnover thereof becomes high, and then a stability is lost. 
     With the method disclosed in the Patent Document 1, since suspension member are driven by actuators in such a manner that a reaction of an input from the road surface can be generated, then it is possible to deal with an input having high frequency, such as, the concave/convex on the road surface, for example, but it is impossible to deal with a n input having a low frequency, such as, an inclination of the road surface. 
     Also, in the Patent Document 2 is disclosed a inverted pendium movement mechanism having a magnetically floated slider on a truck having the driving mechanism thereon, for controlling a position of the gravity center thereof, with respect to the centrifugal force during the time when cornering; however, it is not enough for an input having high frequency, such as, the concave/convex on the road surface, for example. 
     An object of the present invention is to provide a leg portion suspension for a robot, having two (2) sets of leg portions on both sides, in a lower portion of a body, and enabling to run on the wheels, with stability, on the concave/convex on the road surface, with controlling the wheels, which are provided at tips of those leg portions. 
     The object mentioned above is accomplished by a robot, having left and right leg portions on a lower portion of a body, each of the legs comprising: a wheel attached at a tip of said leg portion, to be drivable; a suspension having a spring and a dumper, being attached in parallel, between said wheel and said body; and an actuator, being attached between said suspension and said body, wherein said suspension and said actuator are connected in series, and an inclination detecting means mounted on said body detects an inclination angle and an angular velocity of said robot with respect to a direction of gravity, and a control instruction value outputting means controls said actuator upon basis of information thereof, so that said robot travels along a target angle and a target angular velocity thereof. 
     Also, the object mentioned above is accomplished by the robot, as described in the above, wherein said spring is connected with an actuator expanding and constructing up and down, in series, and said dumper is provided in parallel with said spring and said actuator. 
     Also, the object mentioned above is accomplished by the robot, as described in the above, further comprising: an actuator for use of said wheel, a lower frame being connected with said actuator, a slide rail being connected with said lower frame, and an upper frame being connected with said slide rail, wherein said actuator is connected with said upper frame, and being constructed with a first arm, being attached at an upper end of said lower frame to be rotatable only around an X-axis upon assumption that a traveling direction of said robot is said X-axis, and at an opposite end in a longitudinal direction thereof being connected with a second arm to be rotatable around said X-axis, said second arm, being connected with said first arm at one end to be rotatable around said X-axis, an opposite end in the longitudinal direction thereof being connected with said spring upper frame to be rotatable around said X-axis, and being connected with said spring at an end portion thereof extending by a predetermined angle, said spring being connected with said second arm at one end thereof, and being connected with said actuator lever at an opposite end in the longitudinal direction thereof, and said actuator lever being connected with said spring at an end thereof and being connected with an output axis of said actuator at an opposite end in the longitudinal direction thereof. 
     According to the present invention, since it is possible to suppress a rolling on both sides of an upper portion, being generated due to the unbalance on both sides in the amount of sinking of the suspension, because of the disturbances, such as, the centrifugal force during the time when cornering, the concave/convex on the road surface, and the inclination of the road surface, etc., and therefore, it is possible to provide the suspensions for the leg portion of the robot for enabling a stable running thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       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: 
         FIG. 1  is a view for showing the entire structures of a robot, according to an embodiment 1 of the present invention; 
         FIG. 2  is a view for showing the structures of leg portions of the robot, according to the embodiment 1 of the present invention; 
         FIG. 3  is a control block diagram of the robot, according to the embodiment 1 of the present invention; 
         FIG. 4  is a flowchart for showing a control, according to the present invention; 
         FIG. 5  is a view for showing an actual implementation of the leg portion of the robot, according to the embodiment 1 of the present invention; 
         FIG. 6  is a view for showing the structures of the leg portion of the robot, according to an embodiment 2 of the present invention; 
         FIGS. 7A and 7B  are views for showing an actual implementation of the leg portion of the robot, according to an embodiment 3 of the present invention; 
         FIGS. 8A and 8B  are views for showing operations of actuators, in the actual implementation of the leg portion of the robot, according to an embodiment 3 of the present invention; 
         FIG. 9  is a view for showing a relationship of sizes of the robot, according to an embodiment 3 of the present invention; and 
         FIG. 10  is a view for showing rolling on the conventional robot. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments according to the present invention will be fully explained by referring to the attached drawings. 
     Embodiment 1 
       FIG. 1  shows the entire structures of a robot, according to an embodiment of the present invention. 
     In  FIG. 1 , a robot  1  according to the present invention has two (2) pieces of leg portions; i.e., a left thigh (a part above the knee)  6  and a left shank (a part below the knee)  8 , and a right thigh (a part above the knee)  7  and a right shank (a part below the knee)  9 , and a body  3  above those. On both left and right sides are provided two (2) pieces of arm portions; i.e., a left arm  4  and a right arm  5 . Also, on an upper part of the body  3  is provided a head portion  2 . 
     For example, the two (2) pieces of leg portions; i.e., the left thigh  6  and the left shank  8  and the right thigh  7  and the right shank  9  are used for movement of the robot  1 , and the left arm  4  and the right arm  5  are used for a job, such as, holding of an article, etc. The body  3  comprises therein a controller apparatus for controlling an operation of each part, and sensors for detecting an inclination angle and/or an angular velocity of the body with respect to the direction of gravity. 
       FIG. 2  is a block diagram for showing the left shank  8  and the right shank  9  of the robot  1 . 
     In this  FIG. 2 , the robot  1  is provided with leg suspensions  101 L and  101 R in each of the leg portions on both left and right sides, respectively, as is shown in  FIG. 2 . The leg suspensions  101 L and  101 R are equal to each other, in the constituent elements thereof, and the structures thereof are symmetric with each other, on an X-Z plane passing through a gravity center  100  of the robot. Accordingly, hereinafter, explanation will be given only the leg suspension  101 L. 
     The leg suspension  101 L has a wheel  204 L, as is shown in the figure, and on an upper portion thereof is connected a spring  203 L and a dumper  202 L, in parallel with, and further on an upper portion of thereof is provided an actuator  201 L. Herein, the actuator  201 L is attached in such a direction that it outputs force in the Z-axis direction. 
       FIG. 3  is a control block diagram according to the present invention. 
     When the robot shown in  FIG. 2  runs on the road surface having concave/convex thereon or on an inclined road surface, or when it receives a centrifugal force during when it corners, vibrations in up/down direction of the robot are absorbed by the springs  203 L and  203 R and the dumpers  202 L and  202 R. However, when the left and the right springs  203 L and  203 R differ in an amount of sinking thereof, an upper body of the robot inclines to a side having the larger sinking, and due to a returning force thereof is generated the rolling or swinging on the left and right sides. 
     Then, according to the present embodiment, as is shown in  FIG. 3 , an inclination sensor  205  is mounted on the body  3 , so as to detect the inclination angle and the angular velocity of the body  3 , with respect to the direction of gravity, with an aid of this inclination sensor  205 , while the controller apparatus  206  controls the actuators  201 L and  201 R, appropriately, upon basis of information detected by the inclination sensor  205 , so that the inclination and the angular velocity are coincide with target values thereof. 
     Each of the actuators  201 L and  201 R builds stores a source of power or movement (for example, a motor) and a reduction mechanism, and an angular detector (for example, a rotary encoder or a potentiometer) or a position detector (for example, a linear encoder), and it drives the part(s), with which it is connected. 
       FIG. 4  is a view for showing a controlling flowchart of the robot, according to the present invention. 
     In  FIG. 4 , this calculating process is executed at a predetermined sampling time, every ΔT. After starting, firstly an angle θ in direction of left and right sides of the body (herein after, “body left/right angle”) and an angular velocity ω in direction of left and right sides of the body (herein after, “body left/right angular velocity”) from the inclination sensor  301  are read therein, in a step S 210 . Next, in a step S 211 , addition is made on a product, obtained by multiplying a predetermined control gain K P  on a difference between a body left/right target angle θ ref     —     c  which is given in advance, and the body left/right angle θ, and a product, obtained by multiplying a predetermined control gain K D  on a difference between a body left/right target angular velocity ω ref     —     c  which is given in advance, and the body left/right angular velocity ω, thereby calculating a controlling force F. Next, shifting into a step S 212 , by adding or subtracting a maintenance force F n  for supporting a weight of the robot and the controlling force F with each other, a left-leg controlling force F 1  and a right-leg controlling force F r  are calculated, and in a step S 213 , the left-leg controlling force F 1  and the right-leg controlling force F r  are outputted to the actuators  201 L and  201 R shown in  FIG. 3 , respectively. 
       FIG. 5  is a view for showing an actual implementation condition of the left shank  8  of the robot  1 , according to the embodiment 1. 
     In this  FIG. 5 , the left shank  8  shown in  FIG. 1  comprises an actuator  11 , which is connected in such a manner that a longitudinal direction of an upper frame  10  of spring and an axis of direction of generating a force are almost in parallel with, a spring/dumper  12 , which is connected in such a disposition that it is coincide with an output axis of the actuator  11 , a lower frame  13  of spring, which is attached in such manner that it has a degree of freedom of sliding only in the longitudinal direction of the upper frame  10  of spring, a wheel actuator  15  for rotating in a direction of pitch axis in the figure at a lower end in the longitudinal direction of this lower frame  13  of spring, and a wheel  14 , which is attached on an output axis of this wheel actuator  15 . Herein, at the lower end of the spring/dumper  12  is connected the lower frame  13  of spring. 
     As was mentioned in the above, according to the present invention, the inclination detecting means mounted on an upper portion detects the inclination angle and the angular velocity thereof with respect to the direction of gravity, with inputting an addition of the force for maintaining a predetermined neutrality and a predetermined control amount, which can be obtained from the inclination and the angular velocity of the upper body, into the actuator provided on the side where the upper body sinks, while inputting a subtraction of the force for maintaining the predetermined neutrality and the predetermined control amount mentioned above, into the actuator provided on the side where the upper body extends, it is possible to lighten the rolling of the upper body, thereby enabling running or traveling with stability. Also, with the rolling of high frequency exceeding a response capacity of the actuator, it is absorbed by the spring and the dumber, to be stabilized. 
     Embodiment 2 
     Next, explanation will be made on a leg suspension of the robot, according to an embodiment 2. 
     Although the actuator  201 L and the dumper  202 L are connected in series in the embodiment 1, however in the embodiment 2, the actuator  201 L and the dumper  202 L are connected in parallel. With the parallel connection of the actuator  201 L and the dumper  202 L, it is possible to control an oscillation of a servo system of the actuator  201 L, and thereby enabling to provide a more stable control. 
     Also, the control is executed in the similar manner to that of the embodiment 1, along the flowchart shown in  FIG. 4 . 
       FIG. 6  is a diagram for showing the left shank (the part below the knee)  8  and the right shank (the part below the knee)  9  of a robot having the structures different from those of the robot shown in the embodiment 1. However, it is assumed that the robot  1  comprises the leg suspensions  101 L and  101 R on the respective leg portions on the left and the right sides thereof, as is shown in  FIG. 5 . 
     In  FIG. 6 , since the leg suspensions  101 L and  101 R are equal to each other in the constituent elements thereof and also the structures are symmetric with respect to the X-Z plane passing through the gravity center  100  of the robot, therefore explanation will be given only about the leg suspension  101 L, hereinafter. 
     The leg suspension  101 L, as is shown in the figure, has the wheel  204 L, and above thereof is connected the spring  203 L and the actuator  201 L in series, and wherein the dumper  202 L is connected with the spring  203 L and the actuator  202 L in parallel. Herein, the actuator  201 L is attached in such direction that it outputs a force in the Z-axis direction, and operates in the similar manner to that described in the embodiment 1. 
     Embodiment 3 
     Next, explanation will be given on the leg suspension of a robot, according to an embodiment 3. 
       FIGS. 7A and 7B  are views for showing an actual implementation condition of the leg suspension  101 L of the robot  1 , according to the embodiment 2. 
     For the purpose of increasing a capacity of absorption of the concave/convex on the road surface, it is necessary to lengthen the stroke of suspension; however in general, the spring comes to be large, there are many cases where it cannot be installed within a narrow space, such as, the leg portion of the robot. However, installing each of the elements in such construction as will be shown below, it is possible to install them even within the narrow space, such as, the leg portion of the robot. 
     The leg suspension  101 L shown in  FIG. 2  is attached on an upper end of a spring lower frame  22  to be rotatable only around the X-axis, together with the wheel  20 , the wheel actuator  21  for driving this wheel, the spring lower frame  22  connected with the wheel actuator  21 , a spring upper frame  26  connected through a slide rail  24  for allowing the degree of freedom only in the Z-axis direction between the spring lower frame  22 , and an actuator  29  enabling to oscillate or swing an actuator lever  28  in the X-axis direction only by a predetermined angle, and being connected with the spring upper frame  26 . Further, it is constructed with a first arm  23 , which is connected to be rotatable around the X-axis with a second arm  25  at an opposite end in the longitudinal direction, the second arm  25 , being connected at an end thereof to be rotatable around the X-axis together with the first arm  23 , an opposite end thereof in the longitudinal direction being connected with the spring upper frame  26  to be rotatable around the X-axis, and being connected with a spring  27  at an end portion thereof extending by a predetermined angle, the spring  27  being connected with the second arm  25  at an end and connected with the actuator lever  28  at an opposite end in the longitudinal direction thereof, the actuator lever  28 , being connected with the spring  27  at an end, and connected with an output shaft of the actuator  29  at an opposite end in the longitudinal direction thereof, and a dumper for connecting between the spring lower frame  22  and the spring upper frame  26 , though not shown in the figure. 
     Herein,  FIG. 7A  shows a condition when the robot runs on the road surface, normally, and  FIG. 7B  is a view for showing a condition when the wheel receives a force from the road surface because of the convex portion on the road surface. 
     When the wheel  20  receives the force from the road surface in the Z-axis direction, the wheel  20 , the wheel actuator  21  and the spring lower  22  moves, as a unit, in the Z-axis direction along the slide rail  24  as an unit. Accompanying this, the first arm turns around a center, a point  22 P, and further at a point  23 P, the second arm connected with the first arm  23  turns about a center, a point  25 P, in the clockwise direction, thereby operating to pull up the spring  27 , which is connected with the second arm  25  at a point  25 S. 
     Herein, the spring  27  corresponds to the spring  203 L shown in  FIG. 5 , and although the spring  203 L is a compression spring within the construction shown in  FIG. 5 , but in  FIG. 6 , the force from the road surface is transferred to the spring  27  after converting it from a compression into a tension. 
       FIGS. 8A and 8B  are views for explaining operations of the actuator  29 , and in particular,  FIG. 8A  shows a condition where an angle defined by the actuator lever and the Y-axis is θa.  FIG. 8B  shows a condition where the angel defined by the actuator lever and the Y-axis is θb by turning the actuator lever around in the clockwise direction. Accordingly, the spring  27  is pulled up in a negative direction of Y-axis, and accompanying with that, the first arm  23  and the second arm  25  are rotated round, thereby generating a force for suppressing the wheel  20  onto the road surface. 
     Herein, the actuator lever  28  and the actuator  29  correspond to the actuator  201 L shown in  FIG. 5 , and within the construction shown in  FIG. 5 , the actuator  201 L has an output of expanding and constructing up and down. However, in  FIG. 6 , the actuator lever  28  is turned by the actuator  29 , thereby control the distance between the point  25 S and the point  28 S, so as to input an operation force to the spring  17 . 
       FIG. 9  is a view for explaining about the relationship of sizes, according to the present invention. 
     In  FIG. 9 , when the wheel  20  moves only by distance d from a neutral position, the spring lower frame  22  moves from an initial point B to a point B′ along the slide rail  24  (not shown in the present figure), and accompanying with that, the first arm  23  and the second arm  25  turn up to the position shown by a dotted line, wherein the point  25 S, at which the spring  27  of the second arm  25  is attached, moves by “e”. Herein, “e” can be expressed by an equation shown below, (Equation 1): 
     
       
         
           
             
               
                 
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     Therefore, displacement of extension of spring/wheel can be expressed by the following equation. 
     
       
         
           
             
               
                 
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     Stroke of the wheel  20  is determined by the maximum extension of the spring  27  from a natural length thereof, however if trying to keep the spring expansion to be large, there is a necessity of a long spring. Then, if determining “h” to be about “4”, for example, the extension of the spring  27  comes to “T/4 mm” when the wheel  20  strokes by “T mm”; therefore, it is enough that the spring  27  is short in the length thereof, and thereby enabling a compact installation. 
     Upon basis of such calculation mentioned above, it is possible to determine the springs and value of sizes thereof, which can be installed in the space of the leg, being narrow in a room of installation, and thereby achieving the compact suspension. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential feature or characteristics thereof. The present embodiment(s) is/are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forgoing description and range of equivalency of the claims are therefore to be embraces therein.