Patent Publication Number: US-2023150359-A1

Title: Self-balancing two-wheeled vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/948,519 filed Sep. 22, 2020, which is a continuation of U.S. application Ser. No. 16/278,538, filed Feb. 18, 2019, which is now granted as U.S. Pat. No. 10,780,780, which is a continuation of U.S. application Ser. No. 16/023,498, filed June 29, 2018, which is now granted as U.S. Pat. No. 10,245,952 and which claims priority to and the benefit of U.S. Provisional Patent Application No. 62/614,474, filed Jan. 7, 2018, the contents of all of which are incorporated herein in their entirety. 
    
    
     FIELD 
     The specification relates generally to two-wheeled vehicles. In particular, the following relates to a self-balancing two-wheeled vehicle. 
     BACKGROUND OF THE DISCLOSURE 
     Toy vehicles are constructed to entertain both young and old children. The toy vehicles are intended to simulate the motion of actual real-world vehicles, such as cars, motorcycles, etc. In the case of traditionally two-wheeled vehicles, such as motorcycles, however, additional “training” wheels are generally provided to enable the two-wheeled vehicles to maintain their balance in an upright position. In some cases, these toy vehicles are remotely controlled via either a remote controller or an application executing on a mobile device that communicates with the toy vehicle either tethered or wirelessly to enable a person to modify the behavior of the toy vehicle. While such toy vehicles simulate basic movements of their real world counterparts, the expectations of users have been heightened as a result of the effects in modern movies and simulation games, such as auto racing games. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect, there is provided a self-balancing two-wheeled vehicle, comprising a body, a first wheel rotatably coupled to the body, a second wheel rotatably coupled to the body, the second wheel having at least one lateral roller rotatable about an axis that is one of oblique and orthogonal to a rotation axis of the second wheel, the self-balancing two-wheeled vehicle further comprising at least one motor coupled to the second wheel to control rotation of the second wheel and the at least one lateral roller, at least one sensor coupled to the body to generate orientation data therefor, and a control module coupled to the at least one sensor and the at least one motor to control operation thereof at least partially based on the orientation data generated by the at least one sensor. 
     The second wheel can have a first drive interface and a second drive interface to which the at least one motor is coupled, and the first drive interface can be rotatable independent of the second drive interface. A first of the at least one motor can be coupled to the first drive interface and a second of the at least one motor can be coupled to the second drive interface. The second wheel can have a plurality of lateral rollers. Rotation of the lateral rollers can be at least partially based on a difference in angular velocity of the first drive interface and the second drive interface. Each lateral roller can be rotated by a transmission translation member engaged by at least one gear, each of the at least one gear being rotated via one of the first drive interface and the second drive interface. A first of the at least one gear can be rotated via the first drive interface and a second of the at least one gear can be rotated via the second drive interface. 
     The first drive interface can fully control rotation of the rear wheel about a rear axle. 
     The at least one sensor can include an accelerometer that generates acceleration data, and the control module can control operation of the at least one motor at least partially based on the accelerometer data received from the accelerometer. 
     The self-balancing two-wheeled vehicle can further comprise a receiver coupled to the control module to communicate operational commands received from a remote control unit to the control module, the remote control unit having a set of user controls and communicating the operational commands generated by actuation of the user controls, the control module controlling the at least one motor at least partially based on the operational commands. The control module can at least partially control the at least one motor to maintain a center-of-gravity of the self-balancing two-wheeled vehicle over an area of contact of the first wheel and the second wheel with a travel surface. The first wheel can be pivotable relative to the body, and pivoting of the first wheel can be controlled by the control module at least partially based on the operational commands received from the remote control unit. Pivoting of the first wheel can be at least partially controlled by the control module to maintain the center-of-gravity of the self-balancing two-wheeled vehicle over the area of contact of the first wheel and the second wheel with the travel surface. 
     The operational commands can include a wheelie command, and the remote control unit, upon receiving the wheelie command from the remote control unit, can control the second wheel to accelerate in a first direction away from the first wheel and immediately subsequently accelerate in a second direction towards the front wheel to reorient the self-balancing two-wheeled vehicle so that the center-of-gravity of the self-balancing two-wheeled vehicle is over the area of contact of the second wheel with the travel surface, wherein the control module controls the at least one motor at least partially to maintain the center-of-gravity of the self-balancing two-wheeled vehicle is over the area of contact of the second wheel with the travel surface. 
     In another aspect, there is provided a self-balancing two-wheeled vehicle, comprising a body, a first wheel rotatably coupled to the body, a second wheel rotatably coupled to the body, the second wheel having at least one lateral roller rotatable about a roller axis that is one of oblique and orthogonal to a rotation axis of the second wheel, at least one motor coupled to the second wheel to control rotation of the second wheel and the at least one lateral roller, at least one sensor coupled to the body to generate orientation data therefor, a control module coupled to the at least one sensor and the at least one motor to control operation thereof at least partially based on the orientation data generated by the at least one sensor, and a receiver coupled to the control module to communicate operational commands received from a remote control unit to the control module, the remote control unit having a set of user controls and communicating the operational commands generated by actuation of the user controls, wherein the control module at least partially controls the at least one motor at least partially based on the operational commands to urge the self-balancing two-wheeled vehicle towards a position in which the center-of-gravity of the self-balancing two-wheeled vehicle is over the area of contact of the second wheel with the travel surface, and wherein the operational commands comprise a wheelie command, and wherein the control module, upon receiving the wheelie command from the remote control unit, controls the second wheel to accelerate in a first direction away from the first wheel and immediately subsequently accelerate in a second direction towards the front wheel to urge the self-balancing two-wheeled vehicle towards the position in which the center-of-gravity of the self-balancing two-wheeled vehicle is over the area of contact of the second wheel with the travel surface. 
     The at least one motor can include at least two motors, and a first of the at least two motors can be coupled to the first drive interface and a second of the at least two motors can be coupled to the second drive interface. 
     The second wheel can have a plurality of lateral rollers, and rotation of the lateral rollers can be at least partially based on a difference in angular velocity of the first drive interface and the second drive interface. 
     Each lateral roller can be rotated by a transmission translation member engaged by at least one gear, each of the at least one gear being rotated via one of the first drive interface and the second drive interface. 
     The at least one sensor can include an accelerometer that generates acceleration data, and the control module can control operation of the at least one motor at least partially based on the accelerometer data received from the accelerometer. 
     The self-balancing two-wheeled vehicle can further include a receiver coupled to the control module to communicate operational commands received from a remote control unit to the control module, the remote control unit having a set of user controls and communicating the operational commands generated by actuation of the user controls, wherein the control module controls the at least one motor at least partially based on the operational commands. 
     The control module can at least partially control the at least one motor, and wherein the first wheel is pivotable relative to the body, and pivoting of the first wheel can be controlled by the control module at least partially based on the operational commands received from the remote control unit. 
     Pivoting of the first wheel can be at least partially controlled by the control module to urge the self-balancing two-wheeled vehicle towards the position in which the center-of-gravity of the self-balancing two-wheeled vehicle is over the area of contact of the first wheel and the second wheel with the travel surface. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       For a better understanding of the various embodiments described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: 
         FIG.  1    shows a toy motorcycle having a composite wheel in accordance with one embodiment thereof; 
         FIG.  2    is a partially disassembled view of a rear portion of the toy motorcycle of  FIG.  1   ; 
         FIG.  3    is a perspective view of the partially disassembled composite wheel shown in  FIG.  1   ; 
         FIG.  4    shows a drive assembly coupled to gears driving a plurality of peripheral translation assemblies of the composite wheel of  FIG.  3   ; 
         FIG.  5    is a rear section view of the rear portion of the toy motorcycle of  FIG.  2    illustrating various components of the composite wheel; 
         FIG.  6    is a top section view of the rear portion of the toy motorcycle of  FIG.  2    illustrating various components of the composite wheel; 
         FIG.  7    shows the toy motorcycle on a travel surface; 
         FIG.  8    is a schematic diagram showing various electronic components of the toy motorcycle of  FIGS.  1  to  7   ; 
         FIG.  9    shows a steering assembly of the toy motorcycle of  FIGS.  1  to  7   ; 
         FIG.  10    shows the joystick of the remote control unit of  FIG.  8    and directional regions to which the joystick can be moved; 
         FIGS.  11 A to  11 D  are rear views of the rear wheel of the toy motorcycle of  FIGS.  1  to  7    showing operation of the rear wheel when the joystick is moved to the different directional regions shown in  FIG.  10   ; 
         FIG.  12    shows a winding travel path of the toy motorcycle of  FIGS.  1  to  7   ; 
         FIG.  13    shows a rotational travel path of the toy motorcycle of  FIGS.  1  to  7   ; 
         FIG.  14    shows the toy motorcycle of  FIGS.  1  to  7    in a drifting driving orientation; 
         FIG.  15    shows the toy motorcycle of  FIGS.  1  to  7    being operated to balance on the rear wheel; 
         FIG.  16    is a top sectional view of a rear wheel of a toy motorcycle in accordance with another embodiment; and 
         FIG.  17    is a top sectional view of the rear wheel and rear wheel support of the toy motorcycle of  FIG.  16    showing the drive arrangements driving the rear wheel. 
     
    
    
     DETAILED DESCRIPTION 
     For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein. 
     Various terms used throughout the present description may be read and understood as follows, unless the context indicates otherwise: “or” as used throughout is inclusive, as though written “and/or”; singular articles and pronouns as used throughout include their plural forms, and vice versa; similarly, gendered pronouns include their counterpart pronouns so that pronouns should not be understood as limiting anything described herein to use, implementation, performance, etc. by a single gender; “exemplary” should be understood as “illustrative” or “exemplifying” and not necessarily as “preferred” over other embodiments. Further definitions for terms may be set out herein; these may apply to prior and subsequent instances of those terms, as will be understood from a reading of the present description. 
     Any module, unit, component, server, computer, terminal, engine or device exemplified herein that executes instructions may include or otherwise have access to computer readable media such as storage media, computer storage media, or data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape. Computer storage media may include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Examples of computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by an application, module, or both. Any such computer storage media may be part of the device or accessible or connectable thereto. Further, unless the context clearly indicates otherwise, any processor or controller set out herein may be implemented as a singular processor or as a plurality of processors. The plurality of processors may be arrayed or distributed, and any processing function referred to herein may be carried out by one or by a plurality of processors, even though a single processor may be exemplified. Any method, application or module herein described may be implemented using computer readable/executable instructions that may be stored or otherwise held by such computer readable media and executed by the one or more processors. 
     A self-balancing two-wheeled vehicle is provided. A two-wheeled vehicle is any type of vehicle having two wheels as its only means of ground contact during normal operation for travel over and resting on a travel surface, such as, for example, a floor, a road, a dirt path, etc. The two wheels are at least sometimes “in line”; that is, they often share a common plane. Examples of two-wheeled vehicles include bicycles and motorcycles whose front wheels, when oriented for travel in a straight line, share a common plane with their rear wheels. 
     The two-wheeled vehicle has a body, and first and second wheels rotatably coupled to the body. The second wheel has at least one lateral roller rotatable about an axis that is one of oblique and orthogonal to a rotation axis of the second wheel. At least one motor is coupled to the second wheel to control rotation of the second wheel and the at least one lateral roller. At least one sensor is coupled to the control module and generates orientation data. A control module is coupled to the at least one motor to control operation thereof at least partially based on the orientation data generated by the at least one sensor. 
     By controlling rotation of the second wheel and the at least one lateral roller at least partially based on the orientation data generated by the at least one sensor, the upright orientation of the two-wheeled vehicle can be maintained where a two-wheeled vehicle would otherwise normally be unable to maintain its balance in an upright position (that is, with only its two wheels contacting a travel surface). 
     Further, various maneuvers can be carried out by the two-wheeled vehicle. For example, the two-wheeled vehicle can simulate a “drifting” motion, wherein the rear wheel can appear to be travelling along a path that is not normal to the rotation axis thereof. Still further, the two-wheeled vehicle can be configured to perform a “wheelie”, wherein the two-wheeled vehicle is reoriented so that the two-wheeled vehicle balances itself on its rear wheel. 
       FIG.  1    shows a self-balancing two-wheeled vehicle in accordance with an embodiment. The self-balancing two-wheeled vehicle is a toy motorcycle  20  that has a front wheel  28  that is coupled to the body  24  via a front wheel support in the form of a set of forks  32 . The front wheel  28  freely rotates about an axle  36  that is held between the forks  32 . The forks  32  are secured in a fixed position and orientation to the body  24  of the toy motorcycle  20 . A rear wheel  40  is rotatably coupled to a rear wheel support  44  that extends from the body  24 . A rider figurine  48  is positioned atop of the body  24  in a riding position, clutching at the handlebars that are connected to the forks  32  as if to steer the toy motorcycle  20 . 
       FIG.  2    shows a drive arrangement  52  within the rear wheel support  44  after removal of a rear wheel support cover  46 . The drive arrangement  52  includes a first rear wheel control motor  56   a  (which may, for simplicity, be referred to as a first motor  56   a ), which has a drive gear  60  that engages a first of four intermediate drive gears  64   a  to  64   d  that are coupled together to transmit torque from the first motor  56   a  to a first (left) side of the rear wheel  40 . The fourth intermediate drive gear  64   d  is rotatably mounted on a rear axle  68 . The drive arrangement  52  also includes a second rear wheel control motor  56   b  (which may, for simplicity, be referred to as a second motor  56   b ), which drives another set of intermediate drive gears coupled together to transmit torque from the second motor  56   b  to a second (right) side of the rear wheel  40 . The first and second motors  56   a ,  56   b  are battery-powered electric motors as will be described below. While, in the illustrated embodiment, each side employs four intermediate drive gears, other drive arrangements with other numbers of drive gears can be employed in alternative embodiments. In a further embodiment, the motors can be coupled directly to the sides of the rear wheel. 
     The construction of the rear wheel  40  and its operation in conjunction with the drive arrangement  52  will now be described in relation to  FIGS.  2  to  6   . The rear wheel  40  is a composite wheel as at least some components thereof do not simply rotate about a rotation axis RA of the rear wheel  40 , but move in other manners, as will be described. The fourth intermediate drive gear  64   d  has a wheel-engaging projection  66  with a rectangular profile that extends towards the rear wheel  40 . The wheel-engaging projection  66  is received within a similarly profiled recess  72  of a drive interface in the form of a projection bracket  76  extending outwardly from a first (left) gear disk  80   a  that is also rotatably mounted on the rear axle  68 . The wheel-engaging projection  66  engages the interior sides of the recess  72  of the projection bracket  76  such that rotation of the fourth intermediate drive gear  64   d  causes the first gear disk  80   a  to rotate. Any other suitable configurations for transferring torque from the drive arrangements to the first gear disk  80   a  can be employed. The first gear disk  80   a  acts as a gear and has a toothed gear face  84   a  extending inwardly along a circular periphery thereof. 
     A second gear disk  80   b  has a drive interface in the form of a projection bracket  76  that is similarly engaged by the wheel-engaging projection  66  of a fourth intermediate drive gear  64   h  of a second set of intermediate drive gears  64   e  to  64   h . Both the second gear disk  80   b  and the fourth intermediate drive gear  64   h  are rotatably mounted on the rear axle  68 . The second gear disk  80   b  acts as a gear and has a toothed gear face  84   b  extending inwardly along a circular periphery thereof similar to the gear face  84   a  of the first gear disk  80   a.    
     The drive interfaces enable the motors  56   a ,  56   b  to control operation of the rear wheel  40 . In this particular embodiment, the drive interfaces enable the motors  56   a ,  56   b  to control operation of the gear disks  80   a ,  80   b  which control operation of the rear wheel  40  as is described herein. While, in the illustrated and described embodiments here, the drive interfaces are non-round drive recesses, any other suitable feature(s) for enabling the motors  56   a ,  56   b  to control operation of the rear wheel  40  can be employed, such as a set of one or more projections, a set of two or more recesses, or a combination of recesses and projections. 
     In an alternative embodiment, a single motor can be employed and use a variable transmission to provide different torque to each of the gear disks  80   a ,  80   b  in place of the two motors. 
     Positioned intermediate the first gear disk  80   a  and the second gear disk  80   b  is a support frame made from a first support frame portion  88   a  and a second support frame portion  88   b . The support frame is freely rotatably mounted on the rear axle  68 . The support frame portions  88   a ,  88   b  define eight recesses. A transmission translation member  96  is freely rotatably mounted within each of the recesses of the support frame. Each transmission translation member  96  has a frustoconical gear  100  that is dimensioned to fit between and engage the gear faces  84   a ,  84   b  of the first and second gear disks  80   a ,  80   b . A roller control element in the form of a peripheral gear face  104  is coupled to the frustoconical gear  100  via a neck  108  that is freely rotatably secured between the support frame portions  88   a ,  88   b . The transmission translation members  96  are mounted within the recesses of the support frame so that they rotate around axes that are perpendicular to the rotation axis RA of the rear wheel  40 , but do not intersect it. In some alternative embodiments, the transmission translation members  96  can be mounted so that they rotate about axes that are radial relative to the rotation axis RA of the rear wheel  40 . In some alternative embodiments, the transmission translation members  96  can be mounted on axles of a support frame that are perpendicular to the rotation axis RA of the rear wheel  40 . 
     Two wheel shell portions  116  are secured to the support frame portions  88   a ,  88   b  and are freely rotatably mounted on the cylindrical exterior of the projection brackets  76  of the gear disks  80   a ,  80   b . The two wheel shell portions  116  mate together to form a wheel shell. The wheel shell portions  116  have a structure therein to rotatably support eight axles  124  that are aligned with corresponding apertures in the shell formed by the shell portions  116 . A roller hub  125  is mounted on each axle  124 . Each roller hub  125  has a roller gear face  140  that meshes with the peripheral gear face  104  of a corresponding transmission translation member  96 . Rotation of the transmission translation members  96  is translated into rotation of the roller hub  125  via engagement of the peripheral gear face  104  with the roller gear face  140 . Two roller supports  128  are mounted on the roller hubs  125  and a lateral roller  132  is positioned over each of the roller supports  128 . The lateral rollers  132  rotate about a central axis RRA of the axles  124  that is orthogonal to the rotational axis RA of the gear disks  80   a ,  80   b . In alternative embodiments, the lateral rollers can be designed to rotate about axes that are oblique to the rotational axis RA of the gear disks. The lateral rollers  132  have an exterior surface  136  with an arcuate profile, and are preferably made from a soft, grippy material, such as rubber or polyurethane. The arrangement of the lateral rollers  132  protruding through the shell apertures  126  and the arcuate profile of the exterior surfaces  136  are such that the arcuate profiles define a generally circular outer profile of the rear wheel  40 . 
     A side cover plate  144  covers an open side of each wheel shell portion  116 . 
     Operation of the rear wheel  40  is controlled by the motors  56   a ,  56   b , which act to drive rotation of the first and second gear disks  80   a ,  80   b  independent of one another. The motor  56   a  transfers torque to the first gear disk  80   a  via the intermediate drive gears  64   a  to  64   d , thus controlling its rotation relative to the body  24  of the toy motorcycle  20 . Similarly, the motor  56   b  transfers torque to the second gear disk  80   a  via the intermediate drive gears  64   e  to  64   h , thus controlling its rotation relative to the body  24 . The gear disks  80   a ,  80   b  are rotated about the rear axle  68  and thus the rotation axis RA that is coaxial to the rear axle  68 . As each gear disk  80   a ,  80   b  rotates, its respective gear face  84   a ,  84   b  urges the teeth of the frustoconical gears  100  of the transmission translation members  96  to move in the same angular direction. 
     In order to cause the rear wheel  40  to act as a conventional wheel, the motors  56   a ,  56   b  are operated to rotate the first gear disk  80   a  and the second disk gear  80   b  at the same angular velocity (that is, with the same angular speed and direction) about the rear axle  68 . As the gear faces  84   a ,  84   b  of the gear disks  80   a ,  80   b  are simultaneously rotated at the same angular velocity, they engage the teeth of the frustoconical gears  100  of the transmission translation members  96 , trapping the frustoconical gears  100  between them. The transmission translation members  96  freely rotate within the recesses between the support frame portions  88   a ,  88   b , which is freely rotatable about the rear axle  68 . The trapped frustoconical gears  100  of the transmission translation members  96  are thus rotated with the gear disks  80   a ,  80   b  as they rotate. The exterior surfaces  136  of the lateral rollers  132  provide a somewhat continuous surface that simulates the travel surface of a conventional motorcycle tire. In this mode, the motors  56   a ,  56   b  can be operated to rotate the gear disks  80   a ,  80   b  at the same angular speed in either a first angular (forward rotational) direction, causing the rear wheel  40  to rotate to drive the toy motorcycle  20  forward, or in a second angular (backward rotational) direction, causing the rear wheel  40  to rotate to drive the toy motorcycle  20  backward. 
     The motors  56   a ,  56   b  can also be operated to rotate the first gear disk  80   a  at a different angular velocity than the second gear disk  80   b  about the rear axle  68 . That is, at least one of the angular speed and the angular direction of rotation of the first gear disk  80   a  differs from that of the second gear disk  80   b . The difference in angular velocity between the gear disks  80   a ,  80   b  causes the gear faces  84   a ,  84   b  of the gear disks  80   a ,  80   b  to rotate relative to one another. As the gear disks  80   a ,  80   b  rotate relative to one another, the gear faces  84   a ,  84   b  simultaneously rotate all of the frustoconical gears  100  of the transmission translation members  96 . The transmission translation members  96  rotate about their rotation axes at a rate that is proportional to the difference in the angular velocities of the gear disks  80   a ,  80   b.    
     The transmission translation members  96  and the lateral rollers  132  act as peripheral translation assemblies to transfer torque applied by the gear disks  80   a ,  80   b  to the lateral rollers  132  to cause rotation of the lateral rollers  132 . As the transmission translation members  96  rotate, engagement of the edge of the rotating peripheral gear faces  104  with the circumferential recess patterns  140  on the lateral rollers  32  causes the lateral rollers  132  to rotate according to the rotational direction and speed of the transmission translation members  96 , thereby translating the torque of the transmission translation members  96  about their rotation axes transmitted to the lateral rollers  132 . Further, the support frame portions  88   a ,  88   b  and the transmission translation members  96  positioned therebetween rotate about the rear axle  68  at an angular velocity that is the average of the angular velocities of the gear disks  80   a ,  80   b.    
       FIG.  7    shows the toy motorcycle  20  positioned on a travel surface  224 . The rear wheel  40  of the toy motorcycle  20  can be operated to drive the rear wheel  40  relative to the travel surface  224  in a forward direction RF or a backward direction RB, and, simultaneously, in a left direction RL or a right direction RR, as will be discussed below. 
       FIG.  8    shows various physical and/or logical components of the toy motorcycle  20  that act to control its movement. A control module  228  is coupled to a battery unit  232 , to the left rear wheel control motor  56   a  controlling rotation of the first gear disk  80   a , to the right rear wheel control motor  56   b  controlling rotation of the second gear disk  80   b , and to a front wheel steering motor  242 . The left rear wheel control motor  56   a  and the right rear wheel control motor  56   b  may, for simplicity, be referred to simply as the left motor  56   a  and the right motor  56   b  respectively. The front wheel steering motor  242  controls pivoting of the forks  32  and, thus, the front wheel  28 . A set of sensors  248  are coupled to the control module  228 . The sensors  248  include orientation sensors for determining the orientation of the toy motorcycle  20  and an inertial measurement unit (“IMU”) for determining its acceleration. The battery unit  232  includes one or more batteries for powering the left motor  56   a  and the right motor  56   b , as well as the control module  228  and the sensors  248 . The control module  228  controls the direction of rotation of each motor  56   a ,  56   b , as well as its speed of rotation. In doing so, the control module  228  controls the power supplied by the battery unit  232 . An RF receiver  252  is coupled to the control module  228  for receiving operation commands via radio frequency signals sent by a remote control unit  256 . 
     As shown, the remote control unit  256  has a set of user controls, including a steering wheel  260 , a joystick  264 , and a wheelie button  268 . In response to user interaction with the controls, the remote control unit  256  generates operation commands, such as “turn left x units”, “drive forward with y speed units and drive left with z speed units” (where the units are interpreted by the control module  228 ), and “perform a wheelie”. While the remote control unit  256  in this embodiment communicates operational commands via radio frequency, the remote control unit  256  may communicate with the toy motorcycle  20  via wired communications, Bluetooth, or any other suitable means in other embodiments. 
       FIG.  9    shows a steering assembly  272  of the toy motorcycle  20 . The steering assembly  272  includes the front wheel steering motor  242  that is controlled by operation commands in the form of steering commands generated by the remote control unit  256  ( FIG.  8   ) as a result of turning the steering wheel  260 . Two rigid steering rods  280  ( FIG.  9   ) are pivotally coupled to laterally opposite ends of a motor output member  284  that is driven by the front wheel steering motor  242 . The steering rods  280  are pivotally coupled to opposite sides of the head assembly  32 , so that pivoting of the motor output member  284  by the front wheel steering motor  242  in a first or second direction pivots the head assembly  32  (in the first or second direction) and thus the front wheel  28  ( FIG.  7   ). A centering spring  287  is optionally provided so that when the steering wheel  260  ( FIG.  8   ) is released by the user, the front wheel steering motor  242  may be de-powered, and the centering spring  287  ( FIG.  9   ) returns the head assembly  32  back to a home position in which the front wheel  28  ( FIG.  7   ) is pointed directly forward. 
     Now with reference to  FIGS.  7 ,  8 , and  10   , the joystick  264  is biased to return to a center position C when not urged in another direction. The joystick  264  has two degrees of movement. When the joystick  264  is pivoted away from the center position C, the remote control unit  256  transmits operation commands in the form of drive commands to the toy motorcycle  20  to control operation of the motors of the toy motorcycle  20  (not shown, but similar in design and operation to the motors  56   a ,  56   b  of the toy motorcycle  20  of  FIG.  1   ) coupled to the two gear disks  80   a ,  80   b . Pivoting of the joystick  264  in a forward direction  288  or a backward direction  290  controls the average rotation speed of the gear disks  80   a . Similarly, pivoting of the joystick  264  in a left direction  292  or a right direction  294  controls the difference in rotation speed of the gear disks  80   a . The joystick  264  can move away from center both in the forward direction  288  or the backward direction  290  and in the left direction  292  or the right direction  294  simultaneously to drive the rear wheel  40  simultaneously forward or backward, and left or right. Pivoting of the joystick  264  in the forward direction  288  or the backward direction  290  away from the center position C is resisted less than movement of the joystick  264  in the left direction  292  or the right direction  294  away from center in order to require a conscious effort of the user to cause lateral movement and to avoid accidental lateral movement. 
       FIG.  10    shows the mappings between positions of the joystick  264  and the rotation directions of the gear disks  80   a ,  80   b  as shown in  FIGS.  11 A to  11 D . 
       FIGS.  11 A to  11 D  are rear views of the rear wheel  40  illustrating its operation, wherein both gear disks  80   a  rotate in a forward rotational direction (i.e., the rotational direction of the rear wheel  40  to drive the rear wheel  40  forward across a surface), both rotate in a backward rotational direction (i.e., the direction of rotation of a wheel to move a vehicle backward), the first gear disk  80   a  rotates in a forward rotational direction and the second gear disk  80   b  rotates in a backward rotational direction, and the first gear disk  80   a  rotates in a backward rotational direction and the second gear disk  80   b  rotates in a forward rotational direction. 
     The angular velocity of the rear peripheries of the first gear disk  80   a  and the second gear disk  80   b  are illustrated as v 1  and v 2  respectively. Movement of the rear wheel  40  in the forward direction RF or the backward direction RB is determined by the average angular velocity of the gear disks  80   a ,  80   b , as the lateral rollers  132  that contact the travel surface  224  to provide the ground contact surface of the rear wheel  40  rotate about the rear axle  68  at the average angular velocity of the gear disks  80   a ,  80   b . If the average angular velocity (that is, the average of v 1  and v 2 ) represents rotation of the rear wheel  40  in a forward rotational direction (that is, the rotational direction of the rear wheel  40  to drive the rear wheel  40  forward across a surface), then the rear wheel  40  moves at least partially in a forward direction RF. Alternatively, if the average angular velocity represents rotation of the rear wheel  40  in a backward rotation direction (that is, the rotational direction of the rear wheel  40  to drive the rear wheel  40  backward across a surface), then the rear wheel  40  moves at least partially in a backward direction RB. The speed at which the rear wheel  40  moves in a forward direction RF or a backward direction RB is proportional to the speed component of the average angular velocity of the gear disks  80   a ,  80   b . If the average angular velocity is zero, then the toy motorcycle  20  is neither driven forward or backward by the rear wheel  40 . 
     Similarly, movement of the rear wheel  40  in the left direction RL or the right direction RR is determined by the difference in the angular velocities v 1  and v 2  of the gear disks  80   a ,  80   b . If the angular velocities v 1  and v 2  are equal, then the rear wheel  40  is not driven laterally. If, instead, the angular velocities v 1  and v 2  are not equal, then the lateral rollers  132  also rotate about axes that are orthogonal to the rotational axis RA of the rear wheel  40  to also drive the rear wheel  40  laterally. In particular, if v 1  is greater in the forward rotational direction than v 2 , then the lateral rollers  132  rotate to translate the rear wheel  40  in the left direction RL at a speed relative to the difference between v 1  and v 2 . Conversely, if v 1  is less than v 2  in a forward rotational direction, then the lateral rollers  132  rotate to translate the rear wheel  40  in the right direction RR at a speed relative to the difference between v 1  and v 2 . 
     Generally, the driving force of the rear wheel  40  across the travel surface  224  is a combination of the driving force along the forward direction RF or backward direction RB as a result of the average angular velocity of the gear disks  80   a ,  80   b , and the driving force along the left direction RL or the right direction RR as a result of the difference in the angular velocity of the gear disks  80   a ,  80   b . Thus, the rear wheel  40  can drive in the forward or backward direction RF that is orthogonal to the rotation axis RA of the rear wheel  40 , in a right direction RR or a left direction RL that is parallel to the rotation axis RA of the rear wheel  40 , and in another direction that is a combination of the forward direction RF or the backward direction RB, and the right direction RR or the left direction RL and, thus, oblique to the rotation axis RA of the rear wheel  40 . 
       FIG.  11 A  shows the rear peripheries of the two gear disks  80   a  rotating in a forward rotational direction at angular velocities v 1  and v 2  respectively. As the average angular velocity will be in the forward rotational direction, the rear wheel  40  will drive in the forward direction RF across the travel surface  224 . The rear wheel  40  may also simultaneously drive laterally, depending upon the difference between v 1  and v 2 . 
       FIG.  11 B  shows the rear peripheries of the two gear disks  80   a  rotating in a backward rotational direction at angular velocities v 1  and v 2  respectively. As the average angular velocity will be in the backward rotational direction, the rear wheel  40  will drive in the backward direction RB across the travel surface  224 . The rear wheel  40  may also simultaneously drive laterally, depending upon the difference between v 1  and v 2 . 
       FIG.  11 C  shows the rear periphery of the first gear disk  80   a  rotating in a forward rotational direction at angular velocity v 1  and the rear periphery of the second gear disk  80   b  rotating in a backward rotational direction at angular velocity v 2 . If the average angular velocity (that is, the average of v 1  and v 2 ) represents rotation of the rear wheel  40  in a forward rotational direction, then the rear wheel  40  drives in a forward direction RF. Alternatively, if the average angular velocity represents rotation of the rear wheel  40  in a backward rotation direction, then the rear wheel  40  drives in a backward direction RB. The speed at which the rear wheel  40  drives in a forward direction RF or a backward direction RB is proportional to the speed component of the average angular velocity of the gear disks  80   a ,  80   b . Additionally, the rear wheel  40  also simultaneously drives laterally in a direction determined by the difference between v 1  and v 2  at a speed proportional to the difference between v 1  and v 2 . 
       FIG.  11 D  shows the rear periphery of the first gear disk  80   a  rotating in a backward rotational direction at angular velocity v 1  and the second gear disk  80   b  rotating in a forward rotational direction at angular velocity v 2 . If the average angular velocity represents rotation of the rear wheel  40  in a forward rotational direction, then the rear wheel  40  drives in a forward direction RF. Alternatively, if the average angular velocity represents rotation of the rear wheel  40  in a backward rotation direction, then the rear wheel  40  drives in a backward direction RB. The speed at which the rear wheel  40  drives in a forward direction RF or a backward direction RB is proportional to the speed component of the average angular velocity of the gear disks  80   a ,  80   b . Additionally, the rear wheel  40  also simultaneously drives laterally in a direction determined by the difference between v 1  and v 2  at a speed proportional to the difference between v 1  and v 2 . 
     Referring now to  FIGS.  7  to  11 D , using the remote control unit  256 , a user can direct the toy motorcycle  20 , when turned on and in an upright position atop of a travel surface, to perform various maneuvers, such as travelling forwards or backwards in a straight line by pivoting the joystick  264  in the forward direction  288  or the backward direction  290 . 
     The toy motorcycle  20  is self-balancing in an upright orientation via control of the rear wheel control motors  56   a ,  56   b  and the front wheel steering motor  242  by the control module  228 . The control module  228  receives orientation and acceleration data from the sensors  248 , as well as the drive commands received from the remote control unit  256 , and determines how to control operation of the composite rear wheel  40  and the front wheel steering motor  242  controlling pivoting of the front wheel  28  to maintain the toy motorcycle  20  upright. The composite rear wheel  40  can be controlled to drive backwards or forwards, and simultaneously left or right by independent operation of the gear disks  80   a ,  80   b , and the front wheel  28  can be operated to pivot to maintain the center-of-gravity generally over the area of contact between the front wheel  28 , the rear wheel  40 , and the travel surface  224 . 
     When the toy motorcycle  20  is turned on, allowed to calibrate, and placed upright atop of a travel surface, the control module  228  receives orientation and acceleration data from the sensors  248  and, in response, determines how to modify control of the left motor  56   a , the right motor  56   b , and the front wheel steering motor  242  to maintain the center-of-gravity of the toy motorcycle  20  over the area of contact of the wheels  28 ,  40  with the travel surface  224 . This can include modifying or ignoring the operational commands received from the remote control unit  256 . 
       FIG.  12    shows operation of the toy motorcycle  20  so that the toy motorcycle  20  appears to be making a series of alternating turns in an s-shaped pattern. The toy motorcycle  20  can travel forwards or backwards along an s-shaped path by steering the front wheel  28  via the steering wheel  260  of the remote control unit  256  while pivoting the joystick  264  in the forward direction  288  or the backward direction  290  respectively. 
     This general maneuver can also be achieved by maintaining the front wheel straight (by not turning the steering wheel  260  on the remote control unit  256 ) and by alternating the joystick  264  between left and right of center C while the joystick  264  is urged in the forward direction  288  or the backward direction  290 . This causes the rear wheel  40  to swing around alternatingly. Thus, as the rear wheel  40  is capable of lateral movement, front wheel steering can be mimicked. 
       FIG.  13    shows the toy motorcycle  20  rotating about the front wheel  28  by operation of the rear wheel  40  in such a manner that the average angular velocity of the gear disks  80   a ,  80   b  is zero, but the left gear disk  80   a  is rotated in a forward rotational direction and the right gear disk  80   b  is rotated in a backward rotational direction, as shown in  FIG.  11 C . 
       FIG.  14    shows the toy motorcycle  20  being operated to simulate “drifting” or controlled oversteer by steering the front wheel  28  in one direction MF (i.e., left or right) and causing the rear wheel  40  to move both forward and in the same direction in which the front wheel  28  is being steered using the joystick  264 . As a result, the rear wheel  40  is moved in a direction DD that is oblique to the rotation axis RA of the rear wheel  40 . 
       FIG.  15    illustrates the toy motorcycle  20  performing a “wheelie”, wherein the toy motorcycle  20  is reoriented to travel upon the rear wheel  40  only. This is achieved by actuating the wheelie button  268  of the remote control unit  256 . Upon actuation of the wheelie button  264 , the control module, upon receiving an operational command in the form of a wheelie command generated by the remote control unit  256 , controls the motors  56   a ,  56   b  to cause the toy motorcycle  20  to accelerate straight backwards for a set time or until a minimum speed is reached, and then accelerate quickly forwards. The inertia of the upper portion of the toy motorcycle  20  resists the forward acceleration and the toy motorcycle  20  is reoriented so that the toy motorcycle  20  is balancing on the rear wheel  40  only (i.e., performs a wheelie). The control module  228  determines how to control the motors  56   a ,  56   b  to maintain the center-of-gravity of the toy motorcycle  20  over the area of contact of the front wheel  28  and the rear wheel  40  with the travel surface  224 . As there is no contact of the front wheel  28  with the travel surface  224  in this orientation, the control module  228  maintains the center-of-gravity of the toy motorcycle  20  over the area of contact of the rear wheel  40  with the travel surface  224 . The rear wheel  40  can move in a forward direction RF or a backward direction RB, and in a left direction RL or a right direction RR, or any combination of a forward direction RF or a backward direction RB, and in a left direction RL or a right direction RR in order to maintain the center-of-gravity over the area of contact of the rear wheel  40  with the travel surface  224 . 
     Alternatively, a user could employ the joystick  264  to perform the same sequence of actions without actuating the wheelie button  268 . Still further, the toy motorcycle  20  could be placed on a surface such that the toy motorcycle  20  is generally in a wheelie orientation (that is, with its center-of-gravity positioned over the area of contact of its rear wheel  40  with the travel surface  224 ), and the control module  228  can recognize its orientation and control the motors  56   a ,  56   b  and the front wheel steering motor  242  to maintain this orientation. In this case, the control module  228  may recognize the wheelie orientation (that is, the orientation of the toy motorcycle  20  when the center-of-gravity is above the area of contact of the rear wheel  40  with the travel surface) and control the rear wheel  40  (and the pivoting of the front wheel, in some cases) to maintain the center-of-gravity over the area of contact of the rear wheel  40  with the travel surface. 
     Referring now to  FIGS.  7  to  15   , during the performance of all of these maneuvers, the control module  228  continually processes the orientation and acceleration information from the sensors  248  and determines how to maintain the center-of-gravity over the area of contact of the wheels  28 ,  40  with the travel surface  224  by adjusting the operation of the left and right motors  56   a ,  56   b  controlling the composite rear wheel  40 , and operation of the front wheel steering motor  242  controlling the pivoting of the front wheel  28 . As a result, the two-wheeled toy motorcycle  20  is able to maintain itself upright where the toy motorcycle  20  would otherwise tip over. 
       FIGS.  16  and  17    show a composite rear wheel  300  of a toy motorcycle in accordance with another embodiment. The composite rear wheel  300  has an exterior shell  304  similar to the shell of the rear wheel  40  formed by the shell portions  116  of the toy motorcycle  20  of  FIGS.  1  to  6   , with a few exceptions. The exterior shell  304  is driven via a drive interface in the form of a non-round drive recess  308  on a first side, and has a hub  312  with a fixed orientation therein. The hub  312  has a plurality of radial axles  316  atop of which are freely rotatably mounted a set of transmission translation members  320 . Secured to the inside the exterior shell  304  are positioning rings  324  that have a set of apertures in which necks  328  of the transmission translation members  320  are secured. Each of the transmission translation members  320  has a peripheral gear face  332  that turns a lateral roller  336  on a roller axle  338  in a similar manner as in the embodiment illustrated in  FIGS.  1  to  7   . The lateral rollers  336  are at fixed positions relative to the exterior shell  304 . 
     A gear disk  340  is freely rotatably positioned within the exterior shell  304 , and has a projection bracket  344  that extends through a round aperture in a second side of the exterior shell  304 . The projection bracket  344  has a drive interface in the form of a non-round drive recess  348  for driving the gear disk  340 . The gear disk  340  has a toothed gear face  352  that engages a frustoconical gear  356  of the transmission translation member  320 . 
     The hub  312  and the gear disk  340  are freely rotatably mounted on a rear axle  360  that is secured to a rear wheel support  364 . A first drive arrangement  368   a  includes a motor (hidden) and is coupled to the gear disk  340  to drive the gear disk  340 . A second drive arrangement  368   b  includes a motor  372  and is coupled to the exterior shell  304  to drive the exterior shell  304 . The second drive arrangement  368   b  drives rotation of the rear wheel  300  and thus the set of lateral rollers  336  about the rotation axis RA of the rear wheel  300 . 
     If the gear disk  340  is rotated with the same angular velocity as the exterior shell  304 , then the toothed gear face  352  does not move relative to the frustoconical gears  356  of the transmission translation members  320 . As a result, the lateral rollers  336  do not rotate about the roller axles  338  to drive the rear wheel  300  laterally. If, instead, the gear disk  340  is rotated at a different angular velocity than is the exterior shell  304 , then the toothed gear face  352  rotates relative to the frustoconical gears  356  of the transmission translation members  320 , causing them to rotate about the roller axles  338  to drive the rear wheel laterally. Thus, from a drive arrangement perspective, the rear wheel  300  is driven in generally the same manner as is the rear wheel  40  of the toy motorcycle  20  of  FIGS.  1  to  6    and the rear wheel  40  of the toy motorcycle  20  of  FIG.  7   , with the exception that greater forward angular velocity applied by the first drive arrangement  368   a  to the gear disk  340  relative to the angular velocity of the second drive arrangement  368   b  to the exterior shell  304  results in lateral movement in a right direction RR. 
     In an alternative embodiment, a toy motorcycle similar to the toy motorcycle  20  of  FIGS.  1  to  15    may be provided that does not have a steering mechanism to control of the orientation of the front wheel, like the toy motorcycle of  FIGS.  1  to  15   . That is, the front wheel of the toy motorcycle in this alternative embodiment is in a fixed orientation relative to the body thereof. The toy motorcycle without front wheel orientation control can maintain its center-of-gravity positioned over the area of contact between the front and rear wheels and a travel surface solely through control of its motors (similar to motors  56   a ,  56   b  of the toy motorcycle  20  of  FIGS.  1  to  15   ) that operate its composite rear wheel. The toy motorcycle in this alternative embodiment is capable of performing all of the same maneuvers as the toy motorcycle  20  of  FIGS.  1  to  15   , but may not possess the stability of the toy motorcycle  20  while simulating a drifting maneuver as its front wheel is in a fixed orientation. 
     In some embodiments, the sensors of the self-balancing two-wheeled vehicle can only determine orientation and the control module can determine how to control the motors driving the rear wheel and the front wheel steering motor only using orientation data. 
     The front wheel may also be constructed and controlled like the rear wheel. 
     A single continuous lateral roller that is rotatable can be used in place of multiple lateral rollers. In this case, the axis about which the single continuous lateral roller rotates is a curved axis that is generally at each point orthogonal to a rotation axis of the second wheel. 
     While it has been shown that the rear wheel includes one or more lateral rollers and is controlled by at least one rear wheel control motor, and that the front wheel is optionally steerable via a front wheel steering motor, it is alternatively possible for the self-balancing vehicle to have a different structure, wherein the rear wheel is pivotable and is controlled by a rear wheel steering motor and for the front wheel to include the lateral rollers which are driven by at least one front wheel control motor. Thus, the wheel that steers via pivoting need not be the front wheel, and may be referred to as a first wheel, and the other wheel, which includes lateral rollers, may be referred to as a second wheel. Similarly the front wheel steering motor may be referred to as a first wheel steering motor, and similarly the at least one rear wheel control motor (e.g. the first and second rear wheel control motors) may be referred to as at least one second wheel control motor or at least one motor coupled to the second wheel. 
     Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the above examples are only illustrations of one or more implementations. The scope, therefore, is only to be limited by the claims appended hereto.