Abstract:
The present invention provides a mobile object capable of stable movement and jumping. The mobile object includes two moving means attached to left and right sides under a body; a sensor to detect attitude of the body; a controller to receive information from the sensor and perform calculation; two telescopic actuators attached between the body and the two moving means and configured to generate vertical forces; a rotary actuator provided at the center of the two telescopic actuators and configured to rotate around a moving direction of the body; a roll link connected with an output part of the rotary actuator; two suspensions connecting left and right ends of the roll link and the moving means; and foot frames attached between the suspensions and the moving means, wherein the controller controls the rotary actuator so that the sensor detects a target tilt angle and a target angular velocity of the body.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a mobile object including a body and a set of moving means on the left and the right as seen in the moving direction under the body, and further having a mechanism allowing jumping mounted thereon. 
       BACKGROUND ART 
       [0002]    A technology disclosed in PTL 1 provided below is known as an example of mobile objects capable of jumping in related art. 
         [0003]    According to a method disclosed in PTL 1, a moving mechanism including swing arms on the left and the right of a mobile object is provided to allow jumping by releasing springs compressed by driving the swing arms. 
       CITATION LIST 
     Patent Literature 
       [0004]    PTL 1: JP 2009-35157 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    In the related art in PTL 1, only release of elastic energy stored in the spring is used as jumping means. Thus, an unexpected disturbance such as a step on a road surface or a change in the friction of the mechanism may cause variation in the expanding speed of the left and right springs depending on the balance of loads on the body, which may results in imbalance between left and right in jumping. 
         [0006]    In other words, the mobile object may become out of balance at the body during jumping and fall when landing. 
         [0007]    An object of the present invention is to provide a mobile object capable of suppressing imbalance between left and right of a body during moving or jumping caused by a disturbance such as an unexpected step or a slope on a road surface, which allows stable movement and jumping. 
       Solution to Problem 
       [0008]    To achieve the object, the present invention is directed to a mobile object including: two moving means attached to left and right sides under a body; a sensor configured to detect attitude of the body; a controller configured to receive information from the sensor and perform calculation; two telescopic actuators attached between the body and the two moving means and configured to generate vertical forces; a rotary actuator provided at the center of the two telescopic actuators and configured to rotate around a moving direction of the body; a roll link connected with an output part of the rotary actuator; two suspensions connecting left and right ends of the roll link and the moving means; and foot frames attached between the suspensions and the moving means, wherein the controller controls the rotary actuator so that the sensor detects a target tilt angle and a target angular velocity of the body. 
         [0009]    To achieve the object, in the present invention, the moving means preferably each include a motor provided in the foot frame and a wheel driven by the motor. 
         [0010]    To achieve the object, in the present invention, the telescopic actuators preferably each include a position detector. 
         [0011]    To achieve the object, in the present invention, the sensor preferably detects a lateral tilt angle and an angular velocity of the body with respect to the direction of gravity. 
         [0012]    To achieve the object, in the present invention, the controller preferably calculates a sum of a product of a difference between the lateral tilt angle and a lateral tilt angle target value and a predetermined positional gain and a product of a difference between the angular velocity and an angular velocity target value and a predetermined velocity gain, the sum being used as a control command value. 
         [0013]    To achieve the object, in the present invention, the controller preferably outputs the control command value to the rotary actuator. 
       Advantageous Effects of Invention 
       [0014]    According to the present invention, a mobile object capable of suppressing imbalance between left and right of a body during moving or jumping caused by a disturbance such as an unexpected step or a slope on a road surface, which allows stable movement and jumping can be provided. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1  is an overall configuration diagram of a mobile object according to the present invention. 
           [0016]      FIG. 2  is a control block diagram of the mobile object according to the present invention. 
           [0017]      FIG. 3  is a flowchart illustrating control of the mobile object according to the present invention. 
           [0018]      FIGS. 4(   a ) to  4 ( d ) are diagrams illustrating operation of the mobile object according to the present invention. 
           [0019]      FIGS. 5(   a ) and  5 ( b ) are diagrams illustrating operation of the mobile object according to the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0020]    Embodiments of the present invention will be described below with reference to the drawings. 
       First Embodiment 
       [0021]    A configuration of a mobile object  1  according to the present embodiment will be described with reference to  FIG. 1 . 
         [0022]      FIG. 1  is a view of the mobile object  1  seen from the upper-left rear with respect to the moving direction. 
         [0023]    In  FIG. 1 , the moving direction of a robot  1  is represented by an X axis, the direction around the X axis is referred to as a roll direction, an axis perpendicular to the X axis and parallel to the horizontal plane in the moving direction is referred to as a Y axis, the direction around the Y axis is referred to as a pitch direction, an axis perpendicular to the X axis and the Y axis is referred to as Z axis, and the direction around the Z axis is referred to as a yaw direction, which are hereinafter used unless other special expressions are stated. 
         [0024]    In  FIG. 1 , the mobile object  1  of the present embodiment includes a body  2  having a shape that is symmetric in the Y-axis direction, and telescopic actuators  10 L and  10 R that extend and compress in the Z direction and that are connected to left and right ends of the body  2 , respectively. The other ends in the longitudinal direction of the telescopic actuators  10 L and  10 R are connected with foot frames  12 L and  12 R, respectively. The body  2  has attitude measuring means such as a gyroscope configured to measure the attitude of the mobile object and a controller configured to control respective parts of the mobile object on the basis of its attitude, which are mounted therein. 
         [0025]    The telescopic actuators  10 L and  10 R are actuators capable of extending and retracting output ends in the extending direction or in the compressing direction, having a degree of freedom extending and compressing only in the Z direction, each including a power source (such as a hydraulic, pneumatic, or linear motor) and a position detector (such as a linear encoder), and configured no drive parts connected to the output ends. Furthermore, a rotary actuator  3  capable of swinging around the X axis is provided at the center of the body  2 , and a roll link  4  having a shape with the longitudinal direction along the lateral direction of the rotary actuator  3  is connected with an output shaft of the rotary actuator  3 . 
         [0026]    The rotary actuator  3  is rotatable around the X axis, includes a power source (such as a motor), a speed reducer, and an angle detector (such as a rotary encoder or a potentiometer), and drives a part connected with the output shaft. The roll link  4  is connected at the center in the longitudinal direction with the output shaft of the rotary actuator  3 , and is connected at both ends in the longitudinal direction with suspensions  11 L and  11 R with ball joints therebetween. The suspensions  11 L and  11 R are connected at ends opposite in the longitudinal direction to the ends connected with the roll link  4  with the foot frames  12 L and  12 R, respectively, with ball joints therebetween. 
         [0027]    The spring constants of the suspensions  11 L and  11 R are determined so that loads applied on the telescopic actuators  10 L and  10 R become close to 0 at predetermined positions, and a small amount of energy is used to drive the telescopic actuators  10 L and  10 R during normal movement. 
         [0028]    For ensuring roll stiffness, the suspensions  11 L and  11 R may be set so that a reaction force equal to or larger than the weight of the body  1  is generated and that the springs of the suspensions  11 L and  11 R are compressed only when excessive loads are input. 
         [0029]    The foot frames  12 L and  12 R have wheels  13 L and  13 R, respectively, rotatable around the Y axis. The controller reads a value from the attitude measuring means provided in the body  2  and drives actuators for movement provided in the foot frames  12 L and  12 R, so that the wheels  13 L and  13 R are controlled. to maintain an inverted attitude. 
         [0030]    Although moving means are constituted by the actuators for movement and the wheels  13 L and  13 R provided in the foot frames  12 L and  12 R herein, the moving means are not limited to those including wheels as long as the moving means allow movement on a road surface. Furthermore, although the telescopic actuators  10 L and  10 R are described as extending and compressing in the Z direction that is the driving direction of a hydraulic, pneumatic, or linear motor, or the like herein, the telescopic actuators  10 L and  10 R may generate a force in the Z direction with swing arms constituted by two-joint links, or may generate a force in the Z direction by releasing elastic energy by using springs provided therein, for example. 
         [0031]      FIG. 2  is a control block diagram of the mobile object  1  according to the present invention. 
         [0032]    In  FIG. 2 , when the mobile object  1  of  FIG. 1  moves on an irregular road surface or a sloped road surface or receives a centrifugal force during cornering, vertical vibration of the mobile object  1  is reduced by the frictional resistances in the suspensions  11 L and  11 R and the telescopic actuators  10 L and  10 R. If the amounts of sinking of the left and right suspensions  11 L and  11 R are different, the upper body of the mobile object  1  tilts toward the side with the larger amount of sinking. If it is attempted to make the mobile object  1  recover from the tilt by using the telescopic actuators  10 L and  10 R, lateral rolling (rotational vibration around the X axis) is caused because the actuators  10 L and  10 R have relatively rough positional accuracy characteristics like air cylinders. 
         [0033]    A tilt sensor  201  is mounted on the body  2  to detect a tilt angle and an angular velocity of the body  2  with respect to the direction of gravity, and the controller  202  properly controls the rotary actuator  203  so that the tilt and the angular velocity of the body  2  become equal to target values on the basis of detection information from the tilt sensor  201 . 
         [0034]    Next, operation of the mobile object  1  according to the present invention will be described with reference to  FIGS. 3 and 4(   a ) to  4 ( d ). 
         [0035]      FIG. 3  is a flowchart illustrating control of the mobile object  1  according to the present invention. 
         [0036]    Step 1: Detect the lateral tilt angle θ and the angular velocity ω of the body  2  with respect to the direction of gravity by the tilt sensor  201  mounted on the body  2  (S 100 ). 
         [0037]    Step 2: Calculate a sum of a product of a difference between the lateral tilt angle θ obtained in S 100  and a lateral tilt angle target value θ ref     —     c  and a predetermined positional gain K p  and a product of a difference between the angular velocity ω obtained in S 100  and an angular velocity target value ω ref     —     c  and a predetermined velocity gain K d , which is used as a control command value F (S 101 ). 
         [0038]    Step 3: Output the control command value F calculated in S 101  to the rotary actuator  3  (S 102 ). 
         [0039]    The steps 1 to 3 are performed at every predetermined sampling time ΔT. 
         [0040]    Next, operation of the mobile object  1  going over a step will be described with reference to  FIGS. 4(   a ) to  4 ( d ). 
         [0041]      FIG. 4(   a ) is a schematic diagram illustrating a state in which the mobile object  1  according to the present invention moves normally on a flat road surface. Herein, the mobile object  1  is moving from the back toward the front in the drawing. During the movement, the roll link  4  is subjected to loads from the suspensions  11 L and  11 R connected with the left and right ends, bus the driving force from she rotary actuator  3  for driving the roll link  4  is small because the left and right loads are balanced. 
         [0042]      FIG. 4(   b ) is a diagram illustrating the mobile object  1  at a moment one wheel (the left wheel herein) of the mobile object  1  runs on a step. The impact force from the step is input to the wheel  13 L, and then transmitted through the foot frame  12 L, which is not illustrated here, to the telescopic actuator  10 L and the suspension  11 L in parallel. The telescopic actuator  10 L and the suspension  11 L are compressed to predetermined lengths to absorb the impact force from the road surface. 
         [0043]      FIG. 4(   c ) is a diagram illustrating the mobile object  1  tilted after a lapse of certain time after one wheel ran on the step. The suspension  11 L that has absorbed the impact from the step starts to extend again and tilts rightward. 
         [0044]      FIG. 4(   d ) is a diagram illustrating the mobile object  1  having recovered from the tilt. When the mobile object  1  is tilted as in  FIG. 4(   c ), the rotary actuator  3  is controlled to offset the tilt of the mobile object I as in the flowchart of  FIG. 3 . Specifically, the roll link  4  is rotated in the counterclockwise direction in the drawing so as to reduce the load on the suspension  11 L and apply a load on the suspension  11 R. In this manner, the mobile object recovers from the tilt and can move stably. 
         [0045]      FIGS. 5(   a ) and  5 ( b ) are diagrams for explaining jumping operation of the mobile object  1 . 
         [0046]      FIG. 5(   a ) illustrates a state of normal movement on a flat road surface.  FIG. 5(   b ) is a diagram illustrating the mobile object  1  at a moment of jumping. 
         [0047]    The mobile object  1  jumps by quickly extending the left and right telescopic actuators  11 L and  11 R. If the attitude of the mobile object  1  is off the target at the moment of jumping owing to the irregularity and the slope of the road surface, the rotary actuator  3  is controlled according to the control flowchart illustrated in  FIG. 3  so that the attitude will recover. 
         [0048]    As a result of using separate actuators for jumping and for maintaining the attitude in the roll direction in this manner, the mobile object  1  according to the present invention can use an actuator with relatively rough accuracy, placing priority on the speed, for the actuator used for jumping and an actuator with relatively lower speed, placing priority on the positional accuracy, for the actuator used for maintaining the attitude in the roll direction. 
         [0049]    According to the present invention, as illustrated in  FIG. 4(   d ), since the impact force from the step when the mobile object  1  comes to the step is transmitted to the telescopic actuator  10 L and the suspension  11 L in parallel, the telescopic actuator  10 L and the suspension  11 L can absorb the impact force from the road surface by being compressed to predetermined lengths. 
         [0050]    Thus, according to the present invention, the mobile object can jump sideways by using the operation illustrated in  FIG. 4(   d ) to lose the load balance on a flat surface without any step by itself and performing jumping operation as in  FIG. 5(   b ) from this state. In other words, the mobile object can run up steps of stairs or the like by jumping sideways, for example. In this case, the mobile object is assumed to be capable of running up if the mobile object can jump to a maximum height of 240 mm taking typical heights of stairsteps into account. 
         [0051]    As described above, according to the present invention, a mobile object capable of not only realizing stable movement and jumping but also running up stairsteps where appropriate can be provided. 
       REFERENCE SIGNS LIST 
       [0052]      1  mobile object 
         [0053]      2  body 
         [0054]      3  rotary actuator 
         [0055]      4  roll link 
         [0056]      5  mobile object 
         [0057]      10 L,  10 R telescopic actuator 
         [0058]      11 L,  11 R suspension 
         [0059]      12 L,  12 R foot frame 
         [0060]      13 L,  13 R wheel 
         [0061]      201  tilt sensor 
         [0062]      202  controller 
         [0063]      203  rotary actuator