Patent Publication Number: US-2010126787-A1

Title: Moving object

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2008-302315 filed on Nov. 27, 2008 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a moving object, and more particularly, to a moving object that moves through inverted wheel control. 
     2. Description of the Related Art 
     In general, an inverted wheel-type moving object such as an inverted two-wheel vehicle or the like is controlled as to move while the position of a center of gravity of the moving object is modified to maintain the stability thereof by driving the right and left driving wheels. In addition, a construction for driving an inertial body provided above the wheels to stabilize an inverted state is described in, for example, Japanese Patent Application Publication No. 2006-205839 (JP-A-2006-205839). In the inverted wheel-type moving object, the inertial body slides when the inverted wheel-type moving object is in motion. Thus, the center of gravity of the moving object swiftly moves on a vertical line of an axle. 
     Therefore, the inverted state of the moving object can be stabilized. Further, a carriage body is mounted with a battery for driving a motor. In this inverted wheel-type moving object, the wheels are controlled to hold the moving object inverted in accordance with, for example, an output from a gyro sensor. That is, the wheels need to be controlled such that the center of gravity of the entire moving object is located above the axle in the longitudinal direction of the moving object. 
     As an example of an inverted wheel-type moving object, there is also developed a moving object provided with a passenger seat (hereinafter “passenger-type moving object”) in which a passenger sits. In the passenger-type moving object, the wheels are driven to stabilize an inverted state of the moving object when a passenger occupies the passenger seat. Further, from a practical point of view, it is preferable to allow the moving object to move even when the passenger does not sit therein. 
     The position of the center of gravity of the moving object greatly changes depending on whether or not a passenger occupies the moving object. That is, a great gap is created in the longitudinal direction of the moving object between the position of the center of gravity of the moving object when occupied by the passenger and the position of the center of gravity when the moving object is unoccupied. In this case, the angle of inclination at which the moving object may be held inverted when occupied by a passenger is greatly different from the angle of inclination at which the moving object may be held inverted with the passenger not sitting therein. In this case, inversion control needs to be changed. 
     Alternatively, the height of the moving object from the ground is limited. That is, the dimensional margin of the moving object needs to be increased to prevent a region other than the wheels from coming into contact with the ground. For example, a case where a step panel is provided on the lower side in front of the passenger seat will be taken into account. In this case, when the angle of inclination for holding the moving object inverted greatly changes, the tip of the step panel comes into contact with the ground. In other words, the moving object needs to be designed such that the region other than the wheels does not come into contact with the ground regardless of whether or not the passenger sits in the moving object. Thus, there is a restriction on the design of the moving object, and the size of the step panel or the like is limited. As described hitherto, the inverted wheel-type moving object for passenger use cannot stably move with ease regardless of whether or not a passenger is seated thereon. Further, when the moving object is provided with a slide mechanism as described in Japanese Patent Application Publication No. 2006-205839 (JP-A-2006-205839), the construction of the moving object is complicated. 
     SUMMARY OF THE INVENTION 
     The invention provides a moving object having a simple construction may move stably regardless of whether the moving object is occupied. 
     A moving object according to one aspect of the invention is a moving object that moves through inverted pendulum control, and is equipped with a passenger seat in which a passenger sits; a chassis disposed below the passenger seat; a wheel rotatably mounted on the chassis; a drive portion that rotationally drives the wheel; and a weight unit that is provided at least partially in front of an axle of the wheel. Thus, the angle of inclination of the moving object in an inverted state can be restrained from changing depending on whether or not the passenger sits therein. Accordingly, the moving object can maintain its balance in the longitudinal direction thereof, and may move stably with a simple construction regardless of whether or not the passenger sits therein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and/or further features and advantages of the invention will become more apparent from the following description of an example embodiment with reference to the accompanying drawings, in which like numerals are used to represent like elements and wherein: 
         FIG. 1  is a perspective view showing a construction of a moving object according to the embodiment of the invention; 
         FIG. 2  is a view showing the construction of the moving object according to the embodiment of the invention; 
         FIG. 3  is a perspective view showing the moving object when occupied by a passenger; and 
         FIG. 4  is a block diagram showing a configuration of a control system of the moving object according to the embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
     A moving object according to this embodiment of the invention is an inverted wheel-type moving object that moves through inverted pendulum control. The moving object moves to a predetermined position through the driving of wheels on the ground. Furthermore, the moving object may be held inverted by driving the wheels in accordance with an output from a gyro sensor or the like. Further, the moving object moves in accordance with an amount of an operation performed by an operator while being held inverted. 
     The construction of a moving object  100  according to this embodiment of the invention will be described using  FIGS. 1 to 3 .  FIG. 1  is perspective view schematically showing the construction of the moving object  100 .  FIG. 2  is a view schematically showing the construction of the moving object  100 , consisting of a lateral view on the left side and a front view on the right side.  FIG. 3  shows a situation in which an occupant is seated in the moving object  100 . It should be noted, as shown in  FIGS. 1 and 2 , that a forward direction with respect to the moving object  100 , a leftward direction with respect to the moving object  100 , and an upward direction with respect to the moving object  100  are referred to as a +X direction, a +Y direction, and a +Z direction respectively. Further, in  FIGS. 1 and 2 , the construction of the moving object  100  is partially shown as a through-view for the sake of intelligible explanation. 
     The moving object  100  is an inverted wheel-type moving object (a mobile object). As shown in  FIG. 2 , the moving object  100  is equipped with a right driving wheel  18  and a left driving wheel  20  that are disposed coaxially with each other. It is assumed herein that a rotational shaft for the right driving wheel  18  and the left driving wheel  20  is referred to as an axle C 1 . The moving object  100  includes a passenger seat  11  to seat a passenger. Accordingly, the moving object  100  is a sitting posture-type mobility robot that can move with a person seated thereupon. Further, the moving object  100  may also move w when unoccupied. For example, when a user wishing to get on the moving object  100  performs a remote operation, the moving object  100  moves to the position of the user. For example, when the user presses a calling button or the like, the moving object  100  moves toward the user. Then, after the moving object stops in front of the user wishing to move, the user gets on the moving object. 
     The moving object  100  is provided with a frame  10  that serves as a skeleton thereof. The frame  10  is constructed of a light aluminum pipe or the like. In addition, the moving object  100  is provided with a cover  13  for covering the frame  10 . The cover  13  covers a later-described chassis  12  and the like. The moving object  100  is provided with a chair-shaped passenger seat  11 . The passenger seat  11  is fixed to the cover  13  and the frame  10 . The frame  10  and the cover  13  are bent along the shape of the passenger seat  11 . 
     The passenger seat  11  has a seat  11   a  and a seatback  11   b.  The seat  11   a  serves as a sitting surface on which a passenger  80  sits, and hence is disposed substantially horizontally. When the passenger  80  sits on the seat  11   a,  the moving object  100  can thereby move with the passenger  80  seated thereon as shown in  FIG. 3 . The seatback  11   b  extends from the rear of the seat  11   a  diagonally backward and upward, and serves as a seatback portion for supporting the back of the passenger  80 . Accordingly, the moving object  100  moves with the passenger  80  leaning against the seatback  11 . 
     The chassis  12  is disposed directly below the passenger seat  11 . The chassis  12  includes the right driving wheel  18  and the left driving wheel  20 . The chassis  12  rotatably supports the right driving wheel  18  and the left driving wheel  20 . The right driving wheel  18  and the left driving wheel  20  are used to move the moving object  100 . The right driving wheel  18  and the left driving wheel  20  rotate around the axle Cl. That is, the right driving wheel  18  and the left driving wheel  20  are disposed coaxially with each other. The chassis  12  is mounted on the frame  10 . 
     A motor (not shown) for driving the right driving wheel  18  and the left driving wheel  20  is mounted on the chassis  12 . Further, because the moving object  100  is an inverted wheel-type moving object, a vehicle body  22  (an upper body portion) including the passenger seat and the like tilts around the axle Cl. That is, the vehicle body  22  including the passenger seat  11  and the like is rotatably supported. The vehicle body  22  serves as an upper body portion that rotates around the axle Cl. In other words, the vehicle body  22  is that region which tilts around the axle C 1 . This vehicle body  22  includes the frame  10 , the cover  13 , the passenger seat  11 , and the like. Furthermore, the chassis  12  may be partially or entirely included by the vehicle body  22 . In an inverted state, the angle of inclination of the vehicle body  22  changes through the driving of the right driving wheel  18  and the left driving wheel  20 . The vehicle body  22  is provided with a gyro sensor for measuring the angle of inclination, and the like. As shown in  FIG. 1 , a midpoint between the right driving wheel  18  and the left driving wheel  20  is defined as a coordinate center O. That is, the coordinate center O, which is an origin of a coordinate system, exists on the axle C 1 . The traveling direction of the moving object  100  is perpendicular to the axle C 1  on a horizontal plane. 
     A step panel  17  is provided at the front of the chassis  12 . The passenger  80  gets on the step panel  17  and then sits in the passenger seat  11 . The step panel  17  is mounted to a lower side of the passenger seat  11 . Further, the step panel  17  extends forward of the passenger seat  11 . As shown in  FIG. 3 , both feet of the passenger  80  are laid on the step panel  17 . The step panel  17  is mounted to the chassis  12 . 
     Further, the step panel  17  is provided at a midway portion thereof with a front bar  14  for preventing the moving object  100  from tipping forward. Further, a rear bar  15  for preventing the moving object  100  from tipping rearward. That is, the front bar  14  disposed in front of the axle C 1  and the rear bar  15  disposed behind the axle C 1  can prevent the moving object  100  from being tipped in the longitudinal direction. The front bar  14  protrudes forward of the chassis  12 , and the rear bar  15  protrudes backward of the chassis  12 . Accordingly, a tip of the front bar  14  comes into contact with the ground when the moving object  100  tilts excessively forward, and a tip of the rear bar  15  comes into contact with the ground when the moving object  100  tilts excessively backward. 
     The front bar  14  and the rear bar  15  can be rotationally driven. Rotational shafts of the front bar  14  and the rear bar  15  are disposed below (on a −Z side with respect to) the axle C 1  for the right driving wheel  18  and the left driving wheel  20 . Further, auxiliary wheels are provided at the tips of the front bar  14  and the rear bar  15 , respectively. In the inverted state, the auxiliary wheel provided on the front bar  14  and rear bar  15  are not in contact with the ground. In contrast, when a passenger  80  is getting on or off the moving object  100  the auxiliary wheels come into contact with the ground. 
     The passenger seat  11  is provided on both sides thereof with arm rests  16 . The arm rests  16  are fixed to the frame  10  and the cover  13 . The arm rests  16  extend forward from positions slightly below the elbows of the passenger  80  respectively. The arm rests  16  are disposed higher than the seat  11   a.  Further, the arm rests  16  are substantially parallel to the seat  11   a.  The arm rests  16  are disposed on the right and left sides of the passenger seat  11  respectively. Thus, the passenger  80  can lay both his/her arms on the respective arm rests  16 . The arm rests  16  are mounted to an intermediate stage of the seatback  11   b.  As shown in  FIG. 3 , the passenger  80  sits with both his/her hands laid on the respective arm rests  16 . 
     Furthermore, the arm rests  16  are provided with an operation module  21 . 
     It should be noted herein that the operation module  21  is mounted on the right arm rest  16 . Further, the operation module  21  is mounted near the tip of the arm rest  16 . Thus, the operation module  21  is disposed at a position of the right hand of the passenger  80  and hence allows an improvement in operability. The operation module  21  is provided with an operation lever (not shown) and a brake lever (not shown). The operation lever is an operation member for helping the passenger adjust the speed of the moving object  100  and the direction of the moving object  100 . The passenger can adjust the speed of the moving object  100  by adjusting the operation amount of the operation lever. Further, the passenger may designate the moving direction of the moving object  100  by adjusting the operation direction of the operation lever. In accordance with the type of operation exerted on the operation lever, the moving object  100  may advance, stop, retreat, make a left turn, make a right turn, pivot leftward, or pivot rightward. The passenger may brake the moving object  100  by tumbling the brake lever. As a matter of course, the operation module  21  may be mounted on the left arm rest  16 . It is also appropriate to mount operation modules  21  on both the arm rests  16  respectively. Furthermore, the operation module  21  may be mounted on a member other than the arm rests  16 . 
     Two batteries  31  and a control box  32  are mounted on the chassis  12 . The longitudinal positions of the batteries  31  and the control box  32  with respect to the axle C 1  change in accordance with the angle of inclination of the vehicle body  22 . The chassis  12  is provided with a base plate on which the batteries  31  and the control box  32  are laid. Accordingly, the batteries  31  and the control box  32  are disposed directly below the seat  11   a.  In this case, the two batteries  31  are disposed in front of the control box  32 . The two batteries  31  are arranged along the Y direction. The batteries  31  are rechargeable secondary batteries. The charge/discharge of the batteries  31  is controlled by the control box  32 . 
     The control box  32  includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a communication interface, and the like, and controls various movements of the moving object  100 . The control box  32  executes various controls according to a control program stored in, for example, the ROM. The control box  32  controls the motor and the like through a conventional feedback control such as robust control, state feedback control, PID control, or the like to hold the moving object  100  inverted. Thus, the moving object  100  travels while accelerating/decelerating in accordance with the operation of the operation module  21 . 
     Further, the batteries  31  and the control box  32  are installed above the axle C 1 . The batteries  31  are located in front of (on the +X side with respect to) the axle C 1 , and the control box  32  is disposed behind (on the −X side with respect to) the axle C 1 . In this case, the control box  32  is disposed apart from the batteries  31 . That is, the control box  32  is disposed opposite and apart from the batteries  31  by a certain distance directly above the axle C 1 . By disposing the batteries  31  in front of the axle C 1 , the center of gravity of the vehicle body  22  may be located directly above the axle C 1 . The center of gravity of the vehicle body  22  is located substantially directly above the axle C 1  when the angle of inclination of the vehicle body  22  remains unchanged, regardless of whether or not a passenger  80  is in the moving object  100 . This will be described below. 
     First, the position of the center of gravity of the moving object  100  will be described. In the inverted wheel-type moving object  100 , with a view to holding the moving object  100  inverted, the vehicle body  12  is disposed such that the center of gravity thereof is located directly above the axle C 1 . Further, the center of gravity of the vehicle body  12  needs to be located on a vertical line extending past the axle C 1  regardless of whether a passenger  80  is seated on the moving object  100 . It should be noted that the empty weight of the moving object  100  (the weight of the moving object  100  with no passenger sitting therein) is lighter than the weight of the entire moving object  100  including the passenger  80 . Further, the body of the moving object  100  is about the same as or lighter than that of the passenger  80 . In particular, it is preferable to reduce the weight of the moving object  100  from the standpoint of size reduction of the motor and the like. For example, the moving object  100  weighs about 67 kg and is approximately as heavy as or lighter than the passenger  80 . 
     The sitting posture-type moving object  100  is designed in consideration of riding comfort of the passenger  80 . Therefore, the position of the center of gravity of the moving object  100  with the passenger  80  sitting therein is important. Accordingly, the moving object  100  is designed such that the center of gravity of the moving object  100  and the passenger  80  with a standard body type is located near a position directly above the axle C 1 . In this manner, the angle of inclination of the vehicle body during the movement of the moving object  100  in the inversed state may be reduced. That is, since the center of gravity of the moving object  100  is located directly above the axle C 1  during the movement of the moving object  100  in the inversed state, the angle of inclination of the vehicle body  22  is small. The seat  11   a  of the passenger seat  11  is horizontal, and the riding comfort is improved. Thus, the position of the passenger seat  11  in the longitudinal direction of the moving object  100  (in the X direction) is designed such that the center of gravity of the passenger  80  is located close to the axle C 1 . That is, the longitudinal position of the passenger seat  11  with respect to the chassis  12  is determined in consideration of the center of gravity of the passenger  80 . 
     When the moving object  100  is not occupied, the center of gravity of the vehicle body  22  including the passenger  80  is deviant. The passenger  80  is approximately as heavy as or heavier than the moving object  100 . Therefore, the center of gravity of the vehicle body  22  greatly changes depending on whether or not the passenger  80  is in the moving object  100 . To hold the moving object  100  inverted when it is not occupied, the vehicle body  22  is more inclined than in the case where the passenger  80  is in the moving object  100 . In other words, because the passenger  80  is heavier than the moving object  100 , and therefore, the center of gravity of the vehicle body  22  is close to the position directly above the axle C 1  when the passenger is seated on the moving object  100 , even if the center of gravity of the vehicle body  22  is located behind the axle C 1  when the passenger is not in the moving object  100 . Accordingly, the angle of inclination of the vehicle body  22  changes depending on whether or not a passenger  80  is in the moving object  100 . Especially in the case where the moving object  100  is provided with the step panel  17 , the front bar  14 , and the rear bar  15 , these components come into contact with the ground when the angle of inclination of the vehicle body  22  increases. Thus, the moving object  100  cannot stably run with ease. 
     Owing to the design of the moving object  100 , the center of gravity of the vehicle body  22  is located behind (on the −X side with respect to) the axle C 1  when the moving object  100  is unoccupied. Accordingly, if the center of gravity of the vehicle body  22  is located directly above the axle when the passenger is in the moving object  100 , the center of gravity of the vehicle body  22  is located behind the axle C 1  when the passenger is not in the moving object  100 . Thus, in this embodiment of the invention, the batteries  31  are installed in front of the axle C 1 . That is, the batteries  31  are disposed on the +X side with respect to the axle C 1 . 
     In general, the batteries  31  are the heaviest electric unit components mounted on the moving object  100 . For example, it is assumed that the total weight of the entire electric unit is about 10 kg, and that the weight of each of the batteries  31  is about 3.5 kg. In this case, because the moving object  100  is provided with the two batteries  31 , the total weight of the batteries  31  is about 7 kg. Thus, the ratio of the weight of the batteries  31  to the total weight of the electric unit is about 70%. In particular, when the passenger  80  is not in the moving object  100 , the moving object  100  is not so heavy, and hence the disposition of the batteries  31  is important. That is, the center of gravity of the vehicle body  22  may be located above the axle C 1  in accordance with the disposition of the batteries  31 . On the other hand, the total weight is heavier when the passenger  80  is in the moving object  100 . Thus, the change in the position of the center of gravity of the vehicle body  22  is small even when the center of gravity shifts to a position in front the batteries  31 . Thus, the center of gravity of the vehicle body  22  can be located directly above the axle C 1  even when the passenger is in the moving object  100 . 
     As described above, the very heavy components in the electric unit, namely, the batteries  31  are disposed in front of the axle C 1 . Thus, the position of the center of gravity of the vehicle body  22  can be restrained from changing depending on whether or not the passenger  80  is in the moving object  100 . Accordingly, the change in the angle of inclination of the vehicle body  22  is small, and the moving object  100  can stably travel in any state. Further, the change in the angle of inclination of the vehicle body  22  is small. Therefore, the step panel  17 , the front bar  14 , the rear bar  15 , and the like can be distanced from the ground. That is, the dimensional margin of the moving object  100  with respect to the ground can be reduced, and the degree of freedom in designing the moving object  100  is thereby enhanced. Therefore, the moving object  100  can obtain a space saving structure, and a contribution to the size reduction of the moving object  100  can be made. 
     Further, the passenger seat  11  is provided with the seatback  11   b,  and hence the center of gravity of the entire moving object including the passenger  80  tends to be located on the rear side. In the construction in which the passenger seat  11  is provided with the seatback  11   b,  the rear side of the moving object  100  is heavy. When the passenger  80  leans against the seatback  11   b,  the center of gravity of the moving object  100  tends to be located on the rear side. That is, when the passenger  80  leans against the seatback, the center of gravity of the entire moving object including the passenger  80  shifts to a position behind the axle C 1 . In this case as well, because the batteries  31  are disposed toward the front, the moving object  100  can move stably. 
     Furthermore, the batteries  31  are disposed toward the front, and the control box  32 , which is lighter than the batteries  31 , is disposed toward the rear. That is, the control box  32  is disposed behind the axle C 1 . Thus, the unnecessary space directly below the seat  11   a  may be reduced. Accordingly, the space for the moving object  100  can be saved, and a contribution to the size reduction of the moving object  100  can be made. 
     For example, if the batteries  31  are disposed behind the axle C 1  and a coordinate (x, y, z) of the center of gravity of the vehicle body  22  is (−23, 2, 159) when a passenger is seated on the moving object  100 , and the center of gravity of the vehicle body  22  is located behind the axle C 1  by 23 mm. In this case, the vehicle body  22  needs to be inclined forward by 8.2° to hold the unoccupied moving object  100  inverted. On the other hand, when the batteries  31  are disposed in front of the axle C 1 , the coordinate (x, y, z) of the center of gravity of the vehicle body  22  is (1, 2, 159). That is, the center of gravity of the vehicle body  22  deviates from the axle C 1  only by 1 mm In this case, even when the moving object  100  is unoccupied, the moving object  100  may be held inverted by inclining the vehicle body  22  backward only by 0.36°. In these examples, the center of gravity of the vehicle body  22  is located substantially directly above the axle C 1  when the passenger is seated in the moving object  100 . In this manner, by disposing the batteries  31  on the front side, the angle of inclination of the vehicle body  22  is restrained from changing depending on whether the passenger  80  is seated in the moving object  100 . Accordingly, the moving object  100  can move stably. 
     Further, the weight balance of the moving object  100  is adjusted by adjusting the disposition of the existing batteries  31 . Therefore, there is no need to lay any additional weight on the moving object  100 . As a result, the weight of the moving object  100  is not increased. Further, there is no need to separately provide a slide mechanism for shifting the center of gravity of the vehicle body  22  or the like. Mechanical simplification and cost reduction can be achieved. 
     Next, the configuration of a control system of the moving object  100  will be described using  FIG. 4 .  FIG. 4  is a block diagram showing the configuration of the control system including the control box  32 . 
     The signal from a gyro sensor  33  provided on the vehicle body  22  is input to the control box  32 . That is, an angle of inclination detected by the gyro sensor  33  is input to the control box  32 . The gyro sensor  33  is installed on, for example, the vehicle body  22 . 
     More specifically, the gyro sensor  33  is fixed to the chassis  12  near a coordinate center  0 . Further, an operation amount of the operation module  21  is input to the control box  32 . For example, a translational speed of the moving object  100  in the longitudinal direction thereof, a right or left pivoting speed of the moving object  100 , or the like is input from the operation module  21  as an operation amount. Rotational speeds of motors  34  and  36  are input to the control box  32  from encoders  38  and  39  respectively. 
     Based on these input values, the control box  32  outputs command torques to the motors  34  and  36 , which drive the right driving wheel  18  and the left driving wheel  20  respectively. That is, the motor  34  rotationally drives the right driving wheel  18  in accordance with the command torque, and the motor  36  rotationally drives the left driving wheel  20  in accordance with the command torque. It should be noted that motive powers from the motors  34  and  36  are transmitted to the right driving wheel  18  and the left driving wheel  20  via pulleys or the like respectively. 
     The control box  32  performs inverted control calculation based on an operation amount from the operation module  21  and a detection signal from the gyro sensor  33 , and calculates a control target value. In addition, the control box  32  calculates the current rotational speeds of the motors and a difference in target rotational speed corresponding to the control target value. The control box  32  then multiplies this difference by a predetermined feedback gain to perform feedback control. The control box  32  outputs command values to the motors  34  and  36  that correspond to the driving torques respectively via an amplifier or the like. Thus, the moving object  100  moves at a speed corresponding to the operation amount and in a direction corresponding to the operation amount. 
     It should be noted that the batteries  31  supply electric power to the respective electric components of the control box  32 , the operation module  21 , the gyro sensor  33 , the motors  34  and  36 , the encoders  38  and  39 , and the like. That is, the electric power supply voltage supplied from the batteries  31  serves to operate all, some, or one of the electric components mounted on the moving object  100 . 
     Although the two-wheeled moving object has been described in the foregoing example, the invention is not limited thereto. That is, the invention is also applicable to an inverted wheel-type moving object having one wheel or an inverted wheel-type moving object having three or more wheels. 
     While the invention has been described with reference to the example embodiment thereof, it should be understood that the invention is not limited to the described embodiment or construction. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the example embodiment are shown in various combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.