Abstract:
A usage detection system for a self-balancing powered unicycle is disclosed. The usage detection system is adapted to detect an indication of intended usage from a user and to provide an indication of intended usage. The indication of intended usage comprises manipulation of the overall unicycle device resulting from preparatory action taken by the user prior to the onset of the intended usage. Operation of the powered unicycle may thus be controlled based on an indication of intended usage from the usage detection system.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to powered single-wheeled devices and more particularly to powered unicycles with self-balancing functionality. 
       BACKGROUND TO THE INVENTION 
       [0002]    Powered self-balancing vehicles for use while standing are known. Such vehicles include two-wheeled vehicles and single-wheeled vehicles (i.e. unicycles). 
         [0003]    In a powered self-balancing unicycle, an electronic or mechanical system that controls the wheel in the appropriate direction is typically used to achieve fore-and-aft balance. This type of automatic fore-and-aft balance technology is well known and described, for example, in U.S. Pat. No. 6,302,230. A sensor and electronic equipment are typically provided. Information detected by the sensor and the electronics is relayed to a motor. The motor drives the wheel in the appropriate direction and at sufficient speed to maintain fore-and-aft balance. 
         [0004]    Known embodiments of a powered self-balancing unicycle do not include a handle bar supported by a shaft. For example, U.S. patent application Ser. No. 12/281,101 presents a single wheel, coupled to a frame to which two platforms (one on each side of the wheel) are attached. 
       SUMMARY OF THE INVENTION 
       [0005]    According to a first aspect of the invention, there is provided a self-balancing powered unicycle device comprising: a single wheel; a drive arrangement adapted to drive the wheel; a balance control system adapted to maintain fore-aft balance of the unicycle device; at least one foot platform for supporting a user of the unicycle device; a usage detection system adapted to detect an indication of intended usage from a user and to provide an indication of intended usage; and a control system adapted to control operation of the unicycle based on the indication of intended usage from the usage detection system wherein the indication of intended usage comprises manipulation of the overall unicycle device resulting from preparatory action taken by the user prior to the onset of the intended usage. 
         [0006]    There is proposed a self-balancing powered unicycle comprising usage detection system that is arranged to detect an indication of intended usage provided by a user manipulating the overall unicycle device as a result of preparatory action prior to the intended usage. Based on a detected indication of intended usage, the operation of the unicycle may be controlled. In other words, the unicycle may be adapted to alter or change a mode of operation depending on whether or not a user intends to use the unicycle. For example, operation of a drive arrangement of the unicycle may be permitted (e.g. powered) when a user lifts the unicycle and lowers it towards the ground. By way of further example, operation of a drive arrangement may be disabled when a user alights from the unicycle and lifts it from the ground. Thus, embodiments may be adapted to control, change, alter or modify one or more operations, processes or procedures of a self-balancing powered unicycle, and this can be based on a detected indication of intended usage provided by a user manipulating the overall unicycle device. 
         [0007]    Thus, embodiments may provide a self-balancing powered unicycle that is devoid of any user input interfaces (such as buttons, switches, levers, touch-sensitive screens, etc.) which a user would otherwise be required to operate or manipulate in order to indicate their intended use of the unicycle. For example, unlike conventional self-balancing powered unicycles, embodiments may not have an on/off switch/button for turning the unicycle on or off. Instead, embodiments may detect, from user manipulation of the overall unicycle device, that a user&#39;s intends to use the device and then turn on the drive arrangement and/or balance control system for example. 
         [0008]    Embodiments may therefore be adapted to infer a user&#39;s intended usage of a self-balancing powered unicycle from manipulation of the overall unicycle device (resulting from preparatory action taken by the user prior to the onset of the intended usage). Examples of manipulation of the overall unicycle device resulting from preparatory action taken by the user prior to the onset of the intended usage may include: the unicycle being picked up or lifted by the user; the unicycle being shaken at a predetermined frequency; the unicycle being orientated to a predetermined orientation (such as vertical for example); and/or the unicycle being manipulated in accordance with a predetermined sequence of actions (such as opening the casing, and subsequently unfolding/deploying the foot platform(s), for example). 
         [0009]    The usage detection system may, for example, provide an indication that a user is present on the unicycle and wishes to use the unicycle device. 
         [0010]    Embodiments may therefore allow for rapid deployment by being adapted to automatically activate a drive arrangement and/or the balance control system of the unicycle when a user stands on the unicycle. Similarly, embodiments may enable rapid disablement by being adapted to automatically de-activate a drive arrangement and/or the balance control system of the unicycle when a user dismounts from the unicycle. Such automatic activation/de-activation may provide power savings, and may also improve device safety by altering operation (e.g. stopping the motor from turning the wheel) when a user alights the unicycle (intentionally or accidentally). 
         [0011]    A usage detection system of a proposed embodiment may provide an indication or signal which is used by a control system to alter operation of the unicycle upon occurrence of one or more predetermined conditions indicating a use&#39;s intended usage of the unicycle. Such embodiments may therefore enable quick and easy deployment from an off configuration (wherein the rotation of the wheel is disabled, for example) to an on configuration (wherein rotation of the wheel is enabled, for example). This deployment may require little or no input from the user, but instead may be automatically achieved when the user is in close proximity with, or contacts) one or more predetermined parts of the unicycle, or when the user manipulates the overall unicycle in a predetermined manner for example. 
         [0012]    Embodiments may enable the powered unicycle to automatically disable if the user alights or dismounts from the unicycle (e.g. by intentionally stepping off the foot platform(s) or by falling off). The usage detection system may therefore facilitate multiple functions, including the provision of an automatic power saving mode, the provision of quick start-up/deployment, and the provision of an automatic-shutdown safety feature. The usage detection system may thus provide not only for improved user interaction, but also for improved safety and to protect the unicycle. 
         [0013]    The usage detection system may comprise one or more proximity sensors adapted to detect the existence of an entity in close proximity with the proximity sensor. Further, at least one of the one or more proximity sensors may employ at least one of: infrared reflection; ultrasonic sensing; microwave sensing; pressure sensing; temperature sensing; capacitive sensing; and light detection to detect the existence of an entity in close proximity with the proximity sensor. 
         [0014]    An embodiment may further comprise a handle for lifting the unicycle. Such a handle may be used to hold the unicycle above the ground, for example to enable a user to lift, carry, convey or place the unicycle. The handle (or a portion of the unicycle close to the handle) may also comprise part of the usage detection system so that the manipulation of the unicycle via the handle may be used to provide an indication of intended usage and thus control operation of the powered unicycle. For example, the handle may comprise a proximity sensor and/or accelerometers. 
         [0015]    An embodiment may further comprise a casing adapted to cover at least a portion of the outer rim of the wheel, and the casing may comprise a proximity sensor. 
         [0016]    According to another embodiment, the entity presence detection system may comprise a load sensing system adapted to determine a loading applied to at least one part of the powered unicycle. Further, the load sensing system may be adapted to determine at least one of: a deflection of the wheel axel; a compressive force applied to the wheel axel; a force applied to a handle or lifting portion of the unicycle device; a deflection of the at least one foot platform; a tensile force applied to the at least one foot platform; and a compressive force applied to the at least one foot platform, so as determine a loading applied to at least part of the powered unicycle. In such embodiments, operation of the unicycle may be based on a value of the loading applied to one or more of its parts. For example, for a heavier user exerting a greater load on the unicycle, the drive arrangement may be adapted to provide extra power for rotating the wheel. Conversely, for a small/lightweight user exerting a lower load on the unicycle, the drive arrangement may be adapted provide reduced power so as to ensure the wheel rotates within a desired speed range (and not too quickly for example) and/or to conserve power/energy. 
         [0017]    In some embodiments, the usage detection system may comprise a processing unit adapted to process signals in accordance with an algorithm to determine a user&#39;s intended usage of the unicycle device. By way of example, such an algorithm may be adapted to determine if the signals from the drive arrangement, the at least one foot platform, the usage detection system and/or the balance control system exhibit a predetermined characteristic indicating a user&#39;s intended usage of the unicycle device. 
         [0018]    The signals from the drive arrangement and/or the balance control system may comprise information relating to at least one of: casing orientation; inclination or angle of a part of the unicycle; value of compressive force applied to at least part of a foot platform; accelerometer data; gyroscope data; motor torque; speed of wheel rotation; current; motor temperature, distance travelled, time of journey; battery parameters; and a motor drive voltage. 
         [0019]    According to yet another embodiment, the entity presence detection system may comprise a vibration sensor adapted to detect a frequency of vibration of at least one part of the powered unicycle. The entity presence detection system may be adapted to determine an intended usage of the unicycle device if a detected frequency of vibration of at least one part of the powered unicycle is within a predetermined range. For example, an embodiment may be adapted to turn-on if it detected that the user is shaking the unicycle device at a predetermined frequency. Such embodiments may be thought of as providing a ‘shake to activate’ functionality. 
         [0020]    In embodiments, the usage detection system may be adapted to detect the indication of intended usage based on if the user manipulates the overall unicycle device in accordance with a predetermined pattern of movement. For example, the usage detection system may determine that the user intends to use the unicycle device by detecting that user is holding the unicycle in an upright configuration and alternately spinning/rotating the unicycle left and right (e.g. alternatively rotating the unicycle clockwise and anti-clockwise when viewed from directly above). Such embodiments may thus enable a user to control operation of the unicycle by performing one or more gestures and/or movements with the unicycle. 
         [0021]    Thus, there is proposed the concept of a self-balancing powered unicycle is devoid of a switch, button or input interface adapted to receive an indication of usage from the user. Instead of requiring a user to operate one or more input interfaces, embodiments can appear to be absent or free of any user input interfaces that are specifically adapted to receive input commands via a physically manipulated portion or surface of the unicycle device. In other words, embodiments may be adapted to infer an intended usage from a user&#39;s manipulation of the overall device which results from action taken by the user as part of preparing for the intended usage. The onset of a predetermined manipulation of the overall unicycle device may indicate a certain intended usage, and then cessation or removal of the predetermined manipulation may indicate a different intended usage (such as the ending the previously intended usage). 
         [0022]    According to another aspect of the invention, there is provided a usage detection system for a self-balancing powered unicycle wherein the usage detection system is adapted to detect an indication of intended usage from a user and to provide an indication of intended usage, and wherein the indication of intended usage comprises manipulation of the overall unicycle device resulting from preparatory action taken by the user prior to the onset of the intended usage. 
         [0023]    Embodiments may comprise one or more proximity sensors adapted to detect the existence of an entity in close proximity with the proximity sensor. 
         [0024]    Embodiments may be further adapted to be integrated into a handle of a self-balancing powered unicycle. 
         [0025]    An embodiment may comprise a load sensing system adapted to determine a loading applied to at least one part of a self-balancing powered unicycle. 
         [0026]    Some embodiments may comprise a processing unit adapted to process signals in accordance with an algorithm to determine a user&#39;s intended usage of the self-balancing powered unicycle. 
         [0027]    In an embodiment, the entity presence detection system may comprise a vibration sensor adapted to detect a frequency and/or amplitude of vibration of at least one part of a self-balancing powered unicycle. 
         [0028]    For the avoidance of doubt, reference to a single wheel should be taken to mean the generally circular unit that is positioned between the legs of a user and adapted to rotate about an axis to propel the unicycle in a direction during use. The single wheel may therefore be formed from one or more tyres and/or hubs that are coupled together (via a differential, for example). For example, an embodiment may comprise a single hubless wheel having a single hubless rim with a plurality of separate tyres fitted thereon. Alternatively, an embodiment may comprise a single hubless wheel formed from a plurality of hubless rims (each having a respective tyre fitted thereon), wherein the plurality of hubless rims are coupled together via a differential bearing arrangement. 
         [0029]    Embodiments may provide a self-balancing powered unicycle that can alter its operation depending on a detected intended usage of the unicycle. For example, the drive arrangement and/or balance control system may be automatically enabled or disabled to facilitate rapid and simple operation of the unicycle. Detection of an intended usage may be based on a user&#39;s manipulation of the overall device, therefore removing the need for a user to operate button, switches or the like. A ‘button-less’ self-balancing powered unicycle device may therefore be provided which has the appearance of being ‘smart’ or ‘intelligent’ because it can deduce a user&#39;s intended use of the device from their actions which manipulate the overall unicycle device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    An example of the invention will now be described with reference to the accompanying diagrams, in which: 
           [0031]      FIG. 1  is an isometric view of an embodiment of a powered unicycle device in a closed configuration; 
           [0032]      FIG. 2  is an exploded diagram of components internal to the casing of  FIG. 1 , 
           [0033]      FIGS. 3A &amp; 3B  are side and front elevations, respectively, of the embodiment of  FIG. 1 , wherein the casing is moving between a closed and open configuration; 
           [0034]      FIGS. 4A &amp; 4B  are side and front elevations, respectively, of the embodiment of  FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in a stowed configuration; 
           [0035]      FIG. 5  is an isometric view of the embodiment of  FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in a stowed configuration; 
           [0036]      FIGS. 6A &amp; 6B  are side and front elevations, respectively, of the embodiment of  FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in an active configuration; 
           [0037]      FIG. 7  is an isometric view of the embodiment of  FIG. 1 , wherein the casing is in an open configuration and the foot platforms are in an active configuration; 
           [0038]      FIG. 8  is simplified isometric view of another embodiment of a self-balancing powered unicycle device; 
           [0039]      FIG. 9  is simplified isometric view of a modified version of the embodiment of  FIG. 8 ; 
           [0040]      FIG. 10  is simplified isometric view of a modified version of the embodiment of  FIG. 8 ; 
           [0041]      FIGS. 11A &amp; 11B  are side and front elevations, respectively, of the of an embodiment of a powered unicycle device, wherein the casing is moving between a closed and open configuration; 
           [0042]      FIGS. 12A &amp; 12B  are side and front elevations, respectively, of the embodiment of  FIG. 11 , wherein the casing is in an open configuration and the foot platforms are in an active configuration; 
           [0043]      FIGS. 13A &amp; 13B  are side and front elevations, respectively, of a drive arrangement according to an embodiment; 
           [0044]      FIG. 14  is a cross sectional view of the drive arrangement of  FIG. 13  taken along the line C-C; and 
           [0045]      FIG. 15  is a side elevation of the drive arrangement of  FIG. 13  wherein internal components are depicted by dashed lines. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]      FIGS. 1-5  show one embodiment of a powered unicycle device  100 .  FIG. 1  shows the powered unicycle device  100  with a casing  110  in a closed configuration so that it encases a single wheel  120 . Here, the casing  110  is formed from a first, upper portion  110 A that covers the top (uppermost) half of the wheel  120 , and a second, lower portion  110 B that covers the bottom (lowermost) half of the wheel  120 .  FIG. 2  illustrates an exploded view of components internal to the casing  110 , namely a wheel  120  and drive arrangement  135 . 
         [0047]    Referring back to  FIG. 1 , the wheel  120  spins about a central axis  125 . The first, upper portion  110 A of the casing is retained in a fixed position relative to the central axis  125 , whereas the second, lower portion  1106  of the casing is adapted to rotate about the central axis  125 . Rotation of the second lower portion  1106  about the central axis  125  moves the casing between closed and open configurations (as illustrated by  FIGS. 3-4 ). In the closed configuration (shown in  FIG. 1 ), the casing  110  encloses the wheel  120  so that the outer rim  130  of the wheel  120  is not exposed. In the open configuration (shown in  FIG. 5 ), the outer rim  130  of the wheel  120  is exposed so that it can contact a ground surface. 
         [0048]    Referring now to  FIG. 2 , rotation of the single wheel  120  is driven by a drive arrangement  135  according to an embodiment. The drive arrangement  135  includes guide wheels  140  attached to an outwardly facing side of respective batteries  145 . In this embodiment, there are two pairs of angled guide wheels  140 , wherein the two guide wheels in each pair share are tapered or conical such that they have a sloped surface which is not perpendicular to the radial plane of the single wheel  120 . Put another way, the contact surface of each guide wheel is inclined with respect to the radial plane of the single wheel  120 . The guide wheels  140  of each pair are also positioned spaced apart to provide a gap between the two guide wheels of a pair. 
         [0049]    A rib  150  is provided around the inner rim of the wheel  120  and fits into the gap between the two guide wheels  140  in each pair. The guide wheels  140  are therefore adapted to contact with the inner rim of wheel  120  where they spin along with wheel  120  and hold wheel  120  in place by way of the rib  150 . Of course, it will be appreciated that other arrangements, including those with only one guide wheel per battery  145 , are possible. 
         [0050]    The batteries  145  are mounted on a motor  155  which drives a pair of drive wheels  160  positioned at the lowermost point along the inner rim of the wheel  120 . The batteries  145  supply power to motor  155  and, this embodiment, there are two batteries in order to create a balanced distribution of volume and weight. However, it is not necessary to employ two batteries  145 . Also, alternative energy storage arrangements may be used, such as a flywheel, capacitors, and other known power storage devices, for example. 
         [0051]    The drive arrangement  135  is adapted to be fitted inside the wheel. In other words, the drive arrangement is sized and shaped so that it can be positioned in the void define by the inner rim of the wheel  120 . Further, the drive arrangement  135  is movable between a locked configuration and an unlocked configuration. 
         [0052]    In the locked configuration, when fitted inside the wheel  120 , the drive arrangement  135  engages with the rim of the wheel  120  to prevent its removal from the wheel. Here, in the embodiment shown, the guide wheels  140  contact the inner rim of wheel  120  and hold wheel  120  in place by way of the rib  150  when the drive arrangement is in the locked configuration. 
         [0053]    In the unlocked configuration, when fitted inside the wheel  120 , the drive arrangement  135  disengages with the rim of the wheel  120  to permit its removal from the wheel. Here, in the embodiment shown, the drive arrangement contracts in size when moved from the locked configuration to the unlocked configuration so that the guide wheels  140  no longer contact the inner rim of wheel  120  and no longer hold the wheel  120  in place by way of the rib  150 . Such reduced size (e.g. diameter) of the drive arrangement  135  when in the unlocked configuration thus enables the drive arrangement  135  to be removed from the wheel  120 . 
         [0054]    It will therefore be understood that the drive arrangement  135  of the illustrated embodiment can be quickly and easily connected or removed to/from the wheel  120  for repair or replacement, for example. Arranging the drive arrangement  135  in the unlocked configuration permits its removal or fitting from/to the wheel  120  (because, for example, its dimensions when in the unlocked configuration permit its fitting inside the wheel). When fitted inside the wheel  120 , the drive arrangement can be arranged in the locked configuration so that it engages with the rim of the wheel  120  to prevent its removal (because, for example, its dimensions when in the locked configuration prevent the drive arrangement from being removed from the wheel). 
         [0055]    When the drive arrangement  135  is fitted inside the wheel and in the locked configuration, a pair of drive wheels (not visible in  FIG. 2 ) is adapted to contact the inner rim of the wheel  120 . Here, the pair of drive wheels comprises first and second rollers that are inclined with respect to the radial plane of the wheel. By way of contact with the inner rim of the wheel  120 , the drive wheels transmit torque from the motor  155  to the wheel  120 . It will be understood that this drive system operates by friction and it may be preferable to avoid slippage between the drive wheels and the inner rim of wheel  120 . Positioning the drive wheels at the lowermost point enables the weight of a user to provide a force which presses the drive wheels against the inner rim of the wheel  120 , thereby helping to reduce or avoid slippage. 
         [0056]    Referring to  FIGS. 5-7 , two foot platforms  165  are coupled to the second, lower portion  110 B of the casing  110 , with one on each side of wheel  120 . In the open configuration, the foot platforms  165  are movable between a stowed configuration, wherein the foot platforms are substantially parallel with the plane of the wheel (as shown in  FIG. 5 ), and an active configuration, wherein the foot platforms are substantially perpendicular to the plane of the wheel (as shown in  FIGS. 6-7 ) so as to support a user&#39;s weight. Thus, in this embodiment, the foot platforms  165  are movable between: (i) a stowed configuration wherein they are flat against the side of the wheel and can be rotated (with the second, lower portion  110 B of the casing) about the central axis  125  so as to be positioned inside (and covered by) the first, upper portion  110 A of the casing; and (ii) an active configuration, wherein they project outwardly from the side of the wheel to provide a support surface for the feet of a user. Accordingly, the foot platforms  165  are upwardly foldable into a stowed configuration that narrows the profile of the unicycle  100  to aid in storage and carrying. In use, the foot platforms are moved to the active configuration, and the user stands with one foot on each platform  165 . 
         [0057]    The drive arrangement  135  includes a gyroscope or accelerometer system  170  which senses forward and backward tilt of the device in relation to the ground surface and regulates the motor  155  accordingly to keep the device upright. In this way, the user is provided a way of controlling the acceleration and deceleration of the unicycle by varying the pressure applied to various areas of the foot platforms  165 . It also enables the unicycle to self-regulate its balance in the fore-and-aft plane. 
         [0058]    When not in use, the foot platforms  165  are moved to the stowed configuration and then rotated (with the second, lower portion  1106  of the casing) about the central axis  125  so as to move the casing to the closed configuration. Thus, in the closed configuration, the foot platforms  165  are stored inside the casing (covered by the first, upper portion  110 A of the casing). 
         [0059]    The embodiment of  FIGS. 1-7  also comprises a lifting handle  180  coupled to the drive arrangement  135  via a plurality of rods  185 . The lifting handle  180  is positioned at the top of the casing  110 , above the wheel  120 , and may be used to hold the unicycle  100  above the ground, for example to enable a user to lift, carry, convey or place the unicycle  100 . 
         [0060]    A retractable carrying strap  190  is also provided and attached to the top of the casing  100 . The carrying strap  190  may be used to carry the unicycle  100 , for example over the shoulder of user. A hook may be provided on the bottom of the case to create rucksack-like belts from the carrying strap  190 . 
         [0061]    The embodiment of  FIGS. 1-7  also comprises an entity presence detection system  200  adapted to detect the presence of a user. More specifically, in this embodiment, the entity presence detection system  200  comprise a proximity sensor  200  situated on each side of the first, upper portion  110 A of the casing above the central axis  125 . Each proximity sensor  200  is adapted to detect the existence of a user&#39;s leg in close proximity with the proximity sensor  200 . In order to do this, the proximity sensors  200  may, for example, employ infrared reflection, ultrasonic sensing, and/or and light detection principles to detect if/when a user&#39;s leg is positioned in close proximity with the proximity sensor (e.g. contacting the first, upper portion  110 A of the casing). 
         [0062]    The proximity sensors  200  provide a signal indicating whether or not a user&#39;s presence it detected. This signal is provided to a control system (not shown) which is to control operation of the powered unicycle, by controlling the drive arrangement  135  for example. Based on an indication of detected user presence provided by the signal(s) from the proximity sensors  200 , the control system controls operation of the powered unicycle. 
         [0063]    Here, the entity presence detection system  200  is also adapted to trigger an activating system which moves the casing between the closed and open configurations. More specifically, the entity presence detection system  200  further comprises proximity sensors  210  incorporated into the handle  180  which are adapted to detect when a user&#39;s hand contacts the upper surface of the handle (e.g. when a user grips the handle  180 ). When one of the proximity sensors  210  incorporated into the handle  180  detects a user&#39;s hand contacting the upper surface of the handle  180 , it provides an activation signal which triggers the activating system which, in turn, causes the second, lower portion  110 B of the casing to rotate about the central axis to move from the closed configuration to the open configuration. This process of rotating the second, lower portion  110 B of the casing from the closed configuration to the open configuration is depicted by  FIGS. 3-4 . 
         [0064]    It will therefore be understood that, in this embodiment, the proximity sensors  210  in the lifting handle  180  may be used to initiate the activating system and move the casing from the closed configuration to the open configuration. Thus, when a user holds the unicycle  100  by the handle, the proximity sensors  210  triggers the activating system. In response to this trigger, the activating system moves the casing to the open configuration (depicted in  FIGS. 4 &amp; 5 ) so that the lowermost portion of the wheel is exposed and can be brought into contact with a ground surface. In other words, when lifted by the lifting handle  180 , the unicycle may be arranged in an open configuration ready for deployment (e.g. placement on a ground surface). 
         [0065]    Further, when placed on the ground and the balance control system is activated, release of the handle causes the foot platforms to move from the stowed configuration (shown in  FIGS. 4 &amp; 5 ) to the active configuration (shown in  FIGS. 6 &amp; 7 ). 
         [0066]    When the user no longer desires to use the unicycle, the user grips the lifting handle to lift the unicycle from the ground. This results in the proximity sensors  210  triggering the activating system once again which then causes the foot platforms to move from the active configuration (shown in  FIGS. 6 &amp; 7 ) to the stowed configuration (shown in  FIGS. 4 &amp; 5 ), and then subsequently causes the activating system to move the casing from the open configuration (depicted in  FIGS. 4 &amp; 5 ) to the closed configuration (depicted in  FIG. 1 ). 
         [0067]    Turning now to  FIG. 8 , there is depicted a self-balancing powered unicycle  300  according to an embodiment of the invention. 
         [0068]    The self-balancing powered unicycle  300  comprises: a single wheel  310 ; a drive arrangement (not visible) adapted to drive the wheel  310 ; a balance control system (not visible) adapted to maintain fore-aft balance of the unicycle  310 ; a casing  320  adapted to cover a portion of the outer rim of the wheel  310 ; a foot platform  330  projecting horizontally outwardly from each side of the casing  320  for supporting a user of the unicycle; a handle  340  for lifting the unicycle  300 ; a user presence detection system  350  adapted to detect the presence of a user on or at the handle  340 ; and a control system (not visible) adapted to control operation of the powered unicycle based on an signal from the user presence detection system  350 . 
         [0069]    Here, the user presence detection system comprises a proximity sensor  350  integrated into the upwardly facing surface of the  340 . The proximity sensor  350  comprises a light sensitive detector that is adapted to detect the existence of an entity in close proximity with the proximity sensor  350  based on the amount (e.g. intensity or luminosity) of light incident on the light sensitive detector. 
         [0070]    When a user holds the handle  340  (with at least one of their hands), the light sensitive detector detects the associated drop/decrease in the amount of light incident on the light sensitive detector (caused by the user&#39;s hand covering a portion of the light sensitive detector). As a result, the proximity sensor  350 , provide an indication that the user is present at the handle  340  of the unicycle. Based on this indication, the control system is adapted to control operation of the powered unicycle. More specifically, in this example, the control system disables the drive arrangement so that the rotation of the wheel is prevented. Such disabling of the drive arrangement is arranged on the premise/assumption that when the user is holding the handle  340 , the user is either lifting/carrying the unicycle  300  or wishes to stop the unicycle  300 . 
         [0071]    The embodiment of  FIG. 8  may therefore enable rapid disablement of the unicycle  300  by being adapted to automatically de-activate a drive arrangement when a user dismounts from, or carries, the unicycle  300 . Such automatic activation/de-activation may provide power savings, and may also improve device safety by altering operation (e.g. stopping the motor from turning the wheel) when a user picks up the unicycle  300 . 
         [0072]    Referring to  FIG. 9 , there is depicted a modification to the embodiment of  FIG. 8 . More specifically, the self-balancing powered unicycle  400  of  FIG. 9  is similar to that of  FIG. 8 , except for the difference that the handle  340  does not comprise a proximity sensor integrated therein. Instead, the user presence detection system comprises a proximity sensor  410  integrated into each side of the casing  320 . More specifically, each proximity sensor  410  is arranged in a vertically-extending direction above a respective foot platform  330  and employs infrared reflection to detect the existence of an entity in close proximity with it. It will therefore be understood, that each proximity sensor  410  is adapted to detect the presence of a user&#39;s lower leg (e.g. foot, ankle and/or calf) next to, adjacent, or contacting the proximity sensor. 
         [0073]    When a user stands on the foot platforms  330  (e.g. with each foot supported by a respective foot platform  330 ), the proximity sensors  410  detect the associated increase in infrared light reflected back to the proximity sensors  410 . As a result, the proximity sensors  410 , provide an indication that the user is present on the foot platforms  330  of the unicycle  400 . Based on this indication, the control system is adapted to control operation of the powered unicycle. More specifically, in this example, the control system enables the drive arrangement so that the rotation of the wheel is permitted. Such enabling of the drive arrangement is arranged on the premise/assumption that when the user is present on the foot platforms  330 , the user wishes to operate the unicycle  400 . 
         [0074]    Conversely, when a user stands user alights or dismounts from the unicycle  400  (e.g. by intentionally stepping off the foot platform(s)  330  or by falling off), the proximity sensors  410  detect the associated decrease in reflected infrared light reflected. As a result, the proximity sensors  410 , provide an indication that the user is not present on the foot platforms  330  of the unicycle  400 . Based on this indication, the control system is adapted to disable the drive arrangement so that the rotation of the wheel is not permitted. Such disabling of the drive arrangement is arranged on the premise/assumption that when the user is not present on the foot platforms  330 , the user has fallen or stepped away the unicycle  400  and wishes to stop the unicycle  400 . 
         [0075]    The embodiment of  FIG. 9  may therefore enable rapid disablement of the unicycle  400  by being adapted to automatically de-activate a drive arrangement when a user dismounts or falls from the unicycle  400 . Such automatic activation/de-activation may provide for improved device safety. 
         [0076]    Referring to  FIG. 10 , there is depicted a modified version of the embodiments of  FIGS. 8 and 9 . More specifically, the self-balancing powered unicycle  500  of  FIG. 10  is similar to that of  FIGS. 8 and 9 , except for the difference that the entity presence detection system does not comprise a proximity sensor integrated either in the handle  340  or the casing  320 . Instead, the entity presence detection system comprises a signal processing system housed within the casing  320 . The signal processing system (such as a processing unit for example) is adapted to process signals from one or more parts of the unicycle  500  in accordance with an algorithm to determine if an entity is present on, at or near a part of the powered unicycle  500 . 
         [0077]    More specifically, in the embodiment of  FIG. 10 , the entity presence detection system comprises a processing unit (not visible) that is adapted to process signals from the drive arrangement and/or the balance control system in accordance with a predetermined algorithm. The algorithm is adapted to determine if the signals from the drive arrangement and/or the balance control system exhibit a predetermined characteristic indicating the presence or non-presence of an entity on, at or near a part of the powered unicycle. 
         [0078]    By way of example, the signals from the drive arrangement and/or the balance control system comprise information relating to at least one of: accelerometer data; gyroscope data; motor torque; speed of wheel rotation; and a motor drive voltage. Using such information, the processing unit is adapted to determine the presence or non-presence of an entity on, at or near a part of, the unicycle  500 , by determining if values and/or relationships between values are within a predetermined range for example. 
         [0079]    It will be appreciated that variations on the user presence detection systems described above may employ other concepts for determining the presence of a user. For example, in another embodiment, the user presence detection system may comprise a load sensing system adapted to determine a loading applied to at least one part of the powered unicycle (such as a foot platform for example). Such a load sensing system may be adapted to determine at least one of: a deflection of the at least one foot platform; a tensile force applied to the at least one foot platform; and a compressive force applied to the at least one foot platform of the unicycle so as determine a loading applied to the at least one foot platform. If the loading is above a predetermined threshold, it may be determined that a user is supported (e.g. standing on) the at least one foot platform and therefore present on the unicycle for example. 
         [0080]    In another example, the entity presence detection system may comprise a vibration sensor adapted to detect a frequency of vibration of at least one part of the powered unicycle. Such a user presence detection system may, for example, be adapted to determine the presence or non-presence of a user by determining if a detected frequency of vibration of at least one part of the powered unicycle is within a predetermined range. 
         [0081]    In yet another example, the entity presence detection system may comprise a proximity sensor adapted to detect the proximity of the ground in relation to a part (such as the foot platform(s) or the base of the casing) of the unicycle. The determined proximity may be used to indicate if the unicycle has left the ground (i.e. is no longer in contact with the ground) due to being lifted or jumping for example. Such a determination may then be used to control the drive arrangement so as to enable, disable or adjust rotation of the wheel for example. 
         [0082]    Embodiments may be provided separately from a self-balancing powered unicycle and therefore adapted to be fitted to (or integrated with) an existing self-balancing powered unicycle. In others, embodiments may be provided as a standalone entity presence detection system which can be retro-fitted to a conventional self-balancing powered unicycle. Such a system may also be adapted to be employed or installed in a self-balancing powered unicycle at time of manufacture. 
         [0083]    Thus, there is provided a self-balancing powered unicycle comprising: a single wheel; a drive arrangement adapted to drive the wheel; a balance control system adapted to maintain fore-aft balance of the unicycle device; at least one foot platform for supporting a user of the unicycle device; an entity presence detection system adapted to detect the presence of an entity on, at or near a part of the powered unicycle and provide an indication of detected entity presence; and a control system adapted to control operation of the powered unicycle based on the indication of detected entity presence from the entity presence detection system. 
         [0084]    There is proposed a self-balancing powered unicycle comprising an entity presence detection system that is arranged to detect the presence of an entity on, at or near the powered unicycle. Based on a detected presence or non-presence of an entity (such as a user for example), the operation of the unicycle may be controlled. In other words, the unicycle may be adapted to alter its operation depending on whether or not an entity is present on the unicycle. For example, operation of a drive arrangement of the unicycle may be prevented when no user is present on the unicycle. By way of further example, operation of a drive arrangement may be altered to provide an improved or desired response based on characteristics or properties a detected presence. 
         [0085]    The entity presence detection system may, for example, provide an indication that a user is present on the unicycle and wishes to use the unicycle device. Embodiments may therefore allow for rapid deployment by being adapted to automatically activate a drive arrangement and/or the balance control system of the unicycle when a user stands on the unicycle. Similarly, embodiments may enable rapid disablement by being adapted to automatically de-activate a drive arrangement and/or the balance control system of the unicycle when a user dismounts from the unicycle. Such automatic activation/de-activation may provide power savings, and may also improve device safety by altering operation (e.g. stopping the motor from turning the wheel) when a user alights the unicycle (intentionally or accidentally). 
         [0086]    An entity presence detection system of a proposed embodiment may provide an indication or signal which is used by a control system to alter operation of the unicycle upon occurrence of one or more predetermined conditions indicating an entity is present or not-present on the unicycle. Such embodiments may therefore enable quick and easy deployment from an off configuration (wherein the rotation of the wheel is disabled, for example) to an on configuration (wherein rotation of the wheel is enabled, for example). This deployment may require little or no input from the user, but instead may be automatically achieved when the user is in close proximity with, or contacts) one or more predetermined parts of the unicycle. 
         [0087]    Embodiments may enable the powered unicycle to automatically disable if the user alights or dismounts from the unicycle (e.g. by intentionally stepping off the foot platform(s) or by falling off). The entity presence detection system may therefore facilitate multiple functions, including the provision of an automatic power saving mode, the provision of quick start-up/deployment, and the provision of an automatic-shutdown safety feature. The entity presence detection system may thus provide not only for improved user interaction, but also for improved safety and to protect the unicycle. 
         [0088]    The entity presence detection system may comprise one or more proximity sensors adapted to detect the existence of an entity in close proximity with the proximity sensor. Further, at least one of the one or more proximity sensors may employ at least one of: infrared reflection; ultrasonic sensing; microwave sensing; pressure sensing; temperature sensing; and light detection to detect the existence of an entity in close proximity with the proximity sensor. 
         [0089]    An embodiment may further comprise a handle for lifting the unicycle. Such a handle may be used to hold the unicycle above the ground, for example to enable a user to lift, carry, convey or place the unicycle. The handle may also comprise part of the entity presence detection system so that the handle (or a part thereof) may be used to provide an indication of detected user presence and thus control operation of the powered unicycle. For example, the handle may comprise a proximity sensor. 
         [0090]    An embodiment may further comprise a casing adapted to cover at least a portion of the outer rim of the wheel, and the casing may comprise a proximity sensor. 
         [0091]    According to another embodiment, the entity presence detection system may comprise a load sensing system adapted to determine a loading applied to at least one part of the powered unicycle. Further, the load sensing system may be adapted to determine at least one of: a deflection of the wheel axel; a compressive force applied to the wheel axel; a deflection of the at least one foot platform; a tensile force applied to the at least one foot platform; and a compressive force applied to the at least one foot platform, so as determine a loading applied to the at least one foot platform of the powered unicycle. In such embodiments, operation of the unicycle may be based on a value of the loading applied to one or more of its parts. For example, for a heavier user exerting a greater load on the unicycle, the drive arrangement may be adapted to provide extra power for rotating the wheel. Conversely, for a small/lightweight user exerting a lower load on the unicycle, the drive arrangement may be adapted provide reduced power so as to ensure the wheel rotates within a desired speed range (and not too quickly for example) and/or to conserve power/energy. 
         [0092]    In some embodiments, the entity presence detection system may comprise a processing unit adapted to process signals in accordance with an algorithm to determine if an entity is present on, at or near a part of the powered unicycle. By way of example, such an algorithm may be adapted to determine if the signals from the drive arrangement and/or the balance control system exhibit a predetermined characteristic indicating the presence or non-presence of a user on the powered unicycle. 
         [0093]    The signals from the drive arrangement and/or the balance control system may comprise information relating to at least one of: casing orientation; inclination or angle of a part of the unicycle; value of compressive force applied to at least part of a foot platform; accelerometer data; gyroscope data; motor torque; speed of wheel rotation; and a motor drive voltage. 
         [0094]    Embodiments may process signals from the unicycle in accordance with one or more algorithm to identify discrepancies between user control input the unicycle&#39;s drive arrangement and/or balance control system, for example. In this way, it may be determined if a user is actively controlling the unicycle or the unicycle is not operating as expected (e.g. as may occur in a ‘runaway’ situation). 
         [0095]    In yet another embodiment, the entity presence detection system may comprise a vibration sensor adapted to detect a frequency of vibration of at least one part of the powered unicycle. The entity presence detection system may be adapted to determine the presence or non-presence of a user based on if a detected frequency of vibration of at least one part of the powered unicycle is within a predetermined range. 
         [0096]    Thus, there is proposed an entity presence detection system for a self-balancing powered unicycle, wherein the entity presence detection system is adapted to detect the presence of an entity on, at or near a part of the powered unicycle and provide an indication of detected entity presence. 
         [0097]    Embodiments may comprise one or more proximity sensors adapted to detect the existence of an entity in close proximity with the proximity sensor. 
         [0098]    Embodiments may be further adapted to be integrated into a handle of a self-balancing powered unicycle. 
         [0099]    An embodiment may comprise a load sensing system adapted to determine a loading applied to at least one part of a self-balancing powered unicycle. 
         [0100]    Some embodiments may comprise a processing unit adapted to process signals in accordance with an algorithm to determine if an entity is present on, at, or near a part of a self-balancing powered unicycle. 
         [0101]    In an embodiment, the entity presence detection system may comprise a vibration sensor adapted to detect a frequency and/or amplitude of vibration of at least one part of a self-balancing powered unicycle. 
         [0102]    Embodiments may provide a self-balancing powered unicycle that can alter its operation depending on the presence of an entity on, at or near a part of the unicycle. For example, the drive arrangement may be automatically enabled or disabled to facilitate rapid and simple operation of the unicycle. 
         [0103]    Referring to  FIGS. 11-12 , there is depicted a modification to the embodiment of  FIGS. 1-5 . The powered unicycle device of  FIGS. 11-12  is similar to that of  FIG. 1-5  except that is does not include the entity presence detection system  200  adapted to detect the presence of a user. More specifically, the embodiment of  FIGS. 11-12  does not comprise a proximity sensor  200  situated on each side of the first, upper portion  110 A of the casing above the central axis  125 . Instead, in the embodiment of  FIGS. 11-12 , the handle  180  is also adapted to trigger an activating system which moves the casing between the closed and open configurations. More specifically, movement of the handle relative to the casing  110  in an outward direction (away from the centre of the wheel  120 ) as depicted by an arrow labeled “A”, triggers the activating system which in turn causes the second, lower portion  110 B of the casing to rotate about the central axis to move from the closed configuration to the open configuration. This process of rotating the second, lower portion  110 B of the casing from the closed configuration to the open configuration is depicted by  FIG. 11 . 
         [0104]    It will therefore be understood that, in this embodiment, the lifting handle  180  may be used to initiate the activating system and move the casing from the closed configuration to the open configuration. Thus, when a user holds the unicycle  100  by the handle above the ground, the force of the unicycle pulling downwards under the influence of gravity causes upward movement of the lifting handle  180  relative to the casing  110  (as depicted by an arrow labeled “A”) which triggers the activating system. In response to this trigger, the activating system moves the casing to the open configuration so that the lowermost portion of the wheel is exposed and can be brought into contact with a ground surface. In other words, when lifted by the lifting handle  180 , the unicycle may be arranged in an open configuration ready for deployment (e.g. placement on a ground surface). 
         [0105]    Further, when placed on the ground, the depression of the handle in a downward/inward direction (towards the centre of the wheel  120 ) as depicted by an arrow labeled “B” moves the rods  185  and cause the foot platforms to move from the stowed configuration to the active configuration (shown in  FIG. 12 ). Here, downward movement of the rods causes the foot platforms  165  to rotate about an axis and the rods then hold the foot platforms  165  in place to support the feet of user. 
         [0106]    When the user no longer desires to use the unicycle, the user pulls on the lifting handle to lift the unicycle from the ground. This results in upward movement of the lifting handle  180  and the associated rods  185  relative to the casing  110  (as depicted by an arrow labeled “A”) which then causes the foot platforms to move from the active configuration (shown in  FIG. 12 ) to the stowed configuration. 
         [0107]    Thus, there is proposed a powered unicycle with self-balancing functionality that may be carried by a user when not in use, wherein a casing encloses the wheel and protects the wheel from coming into contact with external objects or the user for example. The wheel may therefore be protected from damage during transit. Also, when carrying the unicycle, the casing may protect a user or external object from coming into contact with dirt, fluid and/or dust present on the wheel. 
         [0108]    Embodiments may allow for rapid deployment by being movable from a closed (e.g. stowed) configuration, wherein the wheel is encased by the casing, to an open (e.g. activated) configuration, wherein part of the outer rim of the wheel is exposed for contacting a ground support surface. 
         [0109]    Embodiments may employ an activating system adapted to move the casing from the closed configuration to the open configuration. Such an activating system may be used to expose part of the outer rim of the wheel upon occurrence of one or more predetermined conditions indicating the user desires to use the unicycle. Such embodiments may therefore enable quick and easy deployment from a closed configuration (wherein the wheel is covered for protection) to an open configuration (wherein the wheel is readied for contact with the ground). This deployment may require little or no input from the user, but instead may be automatically achieved when the user and/or unicycle performs one or more predetermined actions or movements with the unicycle. 
         [0110]    Embodiments may comprise one or more handles. Such a handle may be used to hold the unicycle above the ground, for example to enable a user to lift, carry, convey or place the unicycle. The handle may also form part of the activating system so that the handle (or a part thereof) may be used to initiate the activating system and move the casing from the closed configuration to the open configuration for example. In other embodiments, the handle may form part of a control system so that it may be used to control or initiate operation of the unicycle device. 
         [0111]    The activating system and/or drive arrangement of the unicycle device may be adapted to be responsive to an indication that the user intends to use the unicycle device. Such an indication may be provided from: an accelerometer system which detects movement of the unicycle device; movement of a part of the activating system relative to the casing; a load detection system which detects loading on at least part of the unicycle device; or any combination thereof. 
         [0112]    The at least one foot platform may be movable between a stowed position and an active position in response to the user lifting the unicycle device by the handle. For example, the handle may be designed such that when it is pulled or pushed from/to the casing it causes the activating system to move the unicycle from the closed configuration to the open configuration. 
         [0113]    Turning now to  FIGS. 13-15 , there is depicted a drive arrangement  1200  according to an embodiment of the invention. Such a drive arrangement  1200  is adapted to fit inside the wheel of a hubless unicycle so that it may be used to drive (e.g. rotate) the wheel. 
         [0114]    The drive arrangement  1200  is adapted to be movable between a locked (or expanded) configuration, in which when fitted inside a hubless wheel the drive arrangement engages with the rim of the of the wheel to prevent its removal from the wheel, and an unlocked (or contracted) configuration, in which when fitted inside the hubless wheel the drive arrangement  1200  disengages with the rim of the wheel to permit its removal from the wheel. The drive arrangement  1200  may therefore be quickly and easily connected to (or removed from) the hubless wheel for repair or replacement. 
         [0115]    The drive arrangement  1200  comprises a motor  1210  adapted to drive a hubless wheel by applying a force to the inner rim of the hubless wheel. Here, the drive arrangement  1200  comprises a drive wheel  1220  which is driven by the motor  1210  and adapted to contact the inner rim of the wheel (when the drive arrangement is fitted inside the wheel and in a locked configuration). 
         [0116]    The drive arrangement  1200  also comprises guide wheels  1230  attached to an outwardly facing side of respective batteries  1240 . Here, there are two pairs of guide wheels  1230 , wherein the two guide wheels in each pair share the same axis of rotation (e.g. by sharing the same axle) and are positioned spaced apart to provide a gap between the two guide wheels. 
         [0117]    When the drive arrangement is fitted inside the wheel and in a locked configuration, a rib provided around the inner rim of the wheel fits into the gap between the two guide wheels  1140  in each pair. The guide wheels  1140  are therefore adapted to contact with the inner rim of wheel where they spin along with wheel and prevent its removal in the locked configuration. 
         [0118]    The batteries  1240  are mounted on the motor  1210 . The batteries  1240  supply power to motor  1210 . Alternative energy storage arrangements may of course be used, such as a flywheel, capacitors, and other known power storage devices, for example. 
         [0119]    Also mounted on the motor  1210 , and provided in-between the batteries  1240  is a balance control system  1250 . The balance control system  1250  is adapted to maintain fore-aft balance of the unicycle device by controlling the motor. 
         [0120]    Within the balance control system  1250 , there is provided a locking system which is adapted to move the drive arrangement  1200  from the unlocked configuration to the locked configuration when activated. Here, the locking system comprises a rotatably mounted locking bar  1270  (visible in  FIG. 15 ) that can be rotated (using an exposed portion  1280 ) through an angle of ninety degrees (90°) between a locked and unlocked position. In the locked position (depicted in  FIG. 15 ), the locking bar  1270  extends into the batteries  1240  to exert an outwardly extending pressing force on the batteries which tends to move the batteries in an outward direction (i.e. a direction extending radially outward from the center of the drive arrangement  1200 ). This pushes the batteries outwardly so as to increase the diametrical extent of the drive arrangement  1200 . In other words, moving (e.g. rotating) the locking bar  1270  to the locked position expands the size of the drive arrangement  1200  by moving the batteries outwards (from the centre of the drive arrangement  1200 ). Conversely, when the locking bar  1270  is moved to the unlocked position, the pressing force is removed from the batteries  1240  and they move in an inward direction (i.e. a direction extending radially inward towards the center of the drive arrangement  1200 ), due to a biasing force from a spring for example. This moves the batteries inwardly so as to decrease the diametrical extent of the drive arrangement  1200 . Put another way, moving (e.g. rotating) the locking bar  1270  to the unlocked position contacts the size of the drive arrangement  1200  by moving the batteries inwards (towards the centre of the drive arrangement  1200 ). 
         [0121]    The locking bar  1270  of this embodiment is adapted to be turned manually by a user. However, in alternative embodiments, the locking bar  1270  may be turned using a motor arrangement which is activated in response to a signal provided by the user for example. It will therefore be appreciated that the locking system may comprise an electrical or mechanical locking arrangement (or a combination thereof) which moves the drive arrangement  1200  between the locked and unlocked configuration. 
         [0122]    Here, the locking bar  1270  is formed from an electrically conductive material (such as metal) so that it forms an electrical connection between the batteries  1240  and the balance control system  1250  and the motor  1210  when in the locked position. Thus, when in the unlocked position, the balance control system  1250 , the motor  1210  and the batteries  1240  may be electrically isolated from each other, thereby preventing operation of the drive arrangement  1200 . This may therefore provide a safety feature which prevents the motor  1210  or control system  1250  from operating, for example, when the drive arrangement  1200  is place into the unlocked configuration (for removal, replacement or repair, for example). 
         [0123]    Embodiments may therefore provide a self-balancing powered unicycle that is modular in nature. The drive arrangement may be easily engaged and disengaged to/from the wheel to facilitate rapid and simple repair or replacement. 
         [0124]    For example, the locking system may comprise a mechanical linkage, such as a reverse motion linkage, a parallel motion linkage, a crank and slider linkage, a bell crank linkage, or any combination thereof, for example. These mechanical linkages are well known in the art, and any such suitable mechanical linkage may be used to translate movement of a trigger, switch or lever to movement of a locking element so as to move the drive arrangement between the locked and unlocked configuration. 
         [0125]    It will be appreciated that a variation on the hubless drive arrangement described above is one based on gear transmission instead of friction. The drive wheel may be replaced by a gear, and accordingly the inner rim of the wheel may have alternating protruding and indented segments (i.e. “teeth”). 
         [0126]    Although an embodiment has been described which uses a pivoted rod which moves the drive arrangement between a locked and unlocked configuration, other concepts may be used to alter the configuration of the drive arrangement. For example, an electronic locking system may be used which is responsive to one or more signals indicating that the user wishes to repair, inspect, replace, or simply remove the drive arrangement from the wheel. Such signals may be provided from a user input interface (such as a button, switch or a touchscreen for example) and/or a movement detection system (employing accelerometers for example). Alternatively, a mechanical arrangement may be used which moves the drive arrangement between the locked and unlocked configurations when a mechanical trigger, lock or release is moved. A combination of both mechanical and electronic systems may also be employed for moving the drive arrangement between the locked and unlocked configurations. 
         [0127]    According to an embodiment, there is provided a drive arrangement for a self-balancing powered unicycle having a single hubless wheel, the drive arrangement comprising: a motor adapted to drive the wheel by applying a force to the rim of the wheel, wherein the drive arrangement is adapted to be fitted inside the wheel, and wherein the drive arrangement is adapted to be movable between a locked configuration, in which when fitted inside the wheel the drive arrangement engages with the rim of the of the wheel to prevent its removal from the wheel, and an unlocked configuration, in which when fitted inside the wheel the drive arrangement disengages with the rim of the wheel to permit its removal from the wheel. 
         [0128]    There is proposed a drive arrangement for a self-balancing powered unicycle that can be quickly and easily connected or removed to/from the unicycle wheel for repair or replacement, for example. Also, by being fitted inside the wheel, embodiments may help to reduce the overall size or profile of the unicycle, thereby improving its portability. 
         [0129]    Embodiments may allow for easy maintenance by being movable from a locked configuration, wherein the drive arrangement is engaged with the wheel to enable driving of the wheel, to an unlocked configuration, wherein the drive arrangement disengages from the wheel so that it may be removed from the wheel (for servicing, repair, fault diagnosis or replacement, for example). 
         [0130]    Embodiments may further comprise a balance control system adapted to maintain fore-aft balance of the unicycle device by controlling the motor. 
         [0131]    In embodiments, the drive arrangement may further comprise a locking system to move the drive arrangement from the unlocked configuration to the locked configuration when activated. Such a locking system may comprise a mechanical linkage, such as a reverse motion linkage, a parallel motion linkage, a crank and slider linkage, a bell crank linkage, or any combination thereof, for example. Accordingly, in embodiments, a locking system may be provided which disengages the drive arrangement from the wheel upon occurrence of one or more predetermined conditions indicating the user desires to remove the drive arrangement from the wheel. Such an indication may be provided, for example, by movement of the overall unicycle device in accordance with a predetermined pattern of movement. Embodiments may therefore enable quick and easy removal of the drive with little or no input from the user. 
         [0132]    Embodiments may further comprise an energy storage device, such as one or more battery cells or capacitors for example. Further, such embodiments may comprise a locking system which is adapted to form at least part of an electrical connection between the electrical energy storage and the motor. 
         [0133]    The drive arrangement may comprise a drive wheel adapted to be driven by the motor and to contact the rim of the wheel. 
         [0134]    An embodiment may therefore provide a self-balancing powered unicycle comprising: a single hubless wheel; and a drive arrangement according to an embodiment. 
         [0135]    Embodiments may therefore provide a self-balancing powered unicycle that is modular in nature. The drive arrangement may be easily engaged and disengaged to/from the wheel to facilitate rapid and simple repair or replacement. 
         [0136]    While specific embodiments have been described herein for purposes of illustration, various modifications will be apparent to a person skilled in the art and may be made without departing from the scope of the invention. 
         [0137]    For example, although embodiments have been described as employing single concepts or components for detecting an indication of intended usage from a user, it should be understood that embodiment may employ one or more combinations of such concepts or components. A proximity sensor may therefore be employed in conjunction with a vibration sensor, and the signal provided by these sensors may be used in isolation (for altering unicycle operation in different ways for example), or may be used together (for confirming a signal from one of the sensors for example).