Patent Description:
Mobility vehicles are mostly based on wheels for their simplicity of operation and low maintenance costs. One of paramount properties of a wheel is their drivability necessary to go beyond obstacles and provide smooth motion to the vehicle and passengers. It is common knowledge that bigger the wheel diameter, bigger the drivability and off-road performance. Some heavy-duty vehicles like tractors have wheels that are sometimes almost as high as the vehicle itself for guaranteeing traction in wet soil, dirt, swamps, stairs slopes or the like. So, the bigger the wheel, the better the wheel. However, bigger is the wheel, less comfortable it is for example for entering a parking, for driver visibility or for entering the vehicle).

At the end of <NUM>th century one variant of a motorcycle was invented with only one wheel of more than <NUM> meters of diameter and a driver was positioned within the wheel. But it was not comfortable because of limited visibility for driver. Therefore, size of the wheels we see on existing vehicles do correspond to a compromise between a wish to have larger diameter and numerous constraints of comfort, cost, maintenance, etc..

For example, document <CIT> describes a conventional mobility vehicle.

There is therefore a need for a new type of wheel that could provide both the comfort of a law diameter wheel and the drivability of a high diameter wheel.

With this invention, we discovered a solution that allows to have comparatively big effective wheel radius (up to several meters) for personal mobility vehicle. At the same time, this radius does not alter the comfort of mobility vehicle use. Also, our invention allows to have a variable wheel radius which is very suitable for turning, climbing stairs at certain speed and going beyond obstacles.

Current invention corresponds to a mobility vehicle that draws its properties from a special kind of a track that can change its rigidity. It can become rigid with fixed form and curvature corresponding to a wheel shape with large diameter on lower side of the track or totally flexible as usual track on upper side to not create problems with its practical use.

In a normal wheel only lower part is actually "used" during its operation. This part is in contact with the ground at each moment of time and corresponds to <NUM>% of its circumference. The remaining <NUM>% of the wheel is a "price to pay" and, in a sense, not used during motion.

The suggested track adapts to this situation by changing the rigidity of the track so as be in a rigid mode in its lower part and in a flexible mode in its upper part. When rigid, the track correspond to circular wheel and thus plays a role of a wheel in contact with the ground. The upper part of the track is changed to flexible mode and allows to use space above the track for practical reasons (motor, platform passenger space). Changing from flexible to rigid state of the track and back is mechanically similar to respectively zipping and unzipping thus inspiring the name of the vehicle.

More particularly, the invention relates to a mobile system including variable flexibility track and at least two rollers around which the tariable flexibility track is wrapped, wherein the rollers are adapted to change the rigidity and the curvature of the track to adapt its shape to different functionalities as being a wheel or having a part of circular wheel with different curvature or being foldable. The said variable flexibility track being composed of:.

The whole system playing a role of propulsion system, but also to play a role of amortisseurs and compact.

The general view of a Personal mobility vehicle <NUM> is presented on <FIG> in one of its general embodiments. The vehicle relies on a Standing platform <NUM>, a Guiding device <NUM>, Optional seat <NUM> and Motor or pedals <NUM>. Its main part is composed of Variable flexibility tracks <NUM> in contact with the ground.

Controlling rollers <NUM> can change the track's rigidity from flexible to rigid and back. They can also change the track's curvature. Mobile vehicle lean on the tracks with Controlling rollers <NUM>. The radius of a "wheel part" of the track curvature can be varied by the Controlling rollers <NUM> for example by the distance between those rollers. Most of the functionality is provided by those tracks and rollers.

The Standing platform <NUM> and the Variable flexibility tracks <NUM> are presented more in detail in <FIG> that illustrates the principle of the invention. The Direction of motion <NUM> indicates the possible direction in which the vehicle advances. The Variable flexibility track <NUM> has four consecutive states of operation. The first state is a Locking mechanism <NUM> is where the track is switched from a flexible to a rigid state and remains in the rigid state. The operation of switching is performed by the Controlling roller <NUM> in locking mode (when rotating clockwise). The track remains rigid during the second state which is a Rigid state <NUM> where it plays a role of a wheel and is essential to the operation of the vehicle. Afterwards, the track enters into the third state which is an Unlocking state <NUM> where the operation of switching is done by Controlling roller <NUM> in unlocking mode where the track is switched back from a rigid state to a flexible state and continues in the fourth an last state which is the Flexible state <NUM>, and so on. In reverse motion the roles of rollers is inversed.

The principle of the forces that operates on the vehicle with tracks is reflected on <FIG>. When a Weight <NUM> is present on the platform, this weight is distributed across the platform's Elasticity <NUM>. Then, the weight is transmitted down through a Pressure <NUM> on supports of the rollers to rollers axes and then to rollers outer surface by Rolling pressure <NUM> similarly to a skateboard. The force thus goes from the rollers to the tracks and is transmitted by the Rolling pressure <NUM>. Then the force is transmitted by a Rigid track elasticity <NUM> and then by a Pressure <NUM> to the ground. Summarizing up, the tracks are in contact with the platform at two points of the rollers. As if a skateboard was rolling inside a big wheel with a Radius of effective wheel <NUM> formed by a track.

Some interesting properties of the invention derive from a combination of multiple new features. The first one is a track locking mechanism that can be realized in various embodiments which will be shown in detail below. The second is a roller that plays both the locking and the unlocking role, the contact role, the guiding role and the traction role.

The goal of variable flexibility tracks is three-fold. First, it can provide a big wheel radius allowing going beyond obstacles in a smooth manner. Second, it provides comfort to use upper part of a vehicle without constraints. Third, it serves as a shock absorber. Indeed, the flexible curve based on limited flexibility of metal and joints between the track pieces produce a cumulated effect of a spring absorbing shocks. Among other benefits one can mention easier folding of a vehicle, easier maintenance and reduced weight due to the fact that variable flexibility track plays several roles and thus reduced the vehicle weight.

The central point of the track is its ability to change from a rigid to a flexible state. This change operates on the level of track pieces which can be "locked" in certain range of positions by pairs or multiple locking mechanisms and form a rigid system.

On <FIG> the general principle of the locking mechanism is presented (a side view is used across figure). In <FIG> a track is in the flexible state where multiple Track elements <NUM> are connected by multiple Track hinges <NUM>. <FIG> shows a detailed view of two Track elements <NUM> that are not locked and can move in a Positive folding direction <NUM> and/or a Negative folding direction <NUM> to achieve Maximum positive folding <NUM> and a Maximum negative folding <NUM> limited by the Track hinge <NUM> only. The angle between the positive and the negative folding corresponds to an Unlocked flexibility angle range <NUM>.

<FIG> shows a view off two Track elements <NUM> which are linked and blocked by a Locking mechanism <NUM> that limits the rotation of two Track elements <NUM> with respect to each other. The locking mechanism blocks the position of a Track element <NUM> at a certain Locked angle <NUM>. The Locking mechanism <NUM> can have multiple steps of locking, thereby leading to various Locked angles <NUM>. If the locking mechanisms between the multiple track elements are locked, the track will represent a semi-rigid structure of circular form with a certain curvature radius. In practice, the Locked angle <NUM> will not be fixed and will vary due to inherent flexibility of material from which elements are made, to the drift of the Track hinge <NUM> and the drift of the Locking mechanism <NUM> and the elasticity of the materials. Combined, those effects lead to a Locked flexibility angle range <NUM>. This range will not exceed few degrees in general. <FIG> is a general view of several Track element <NUM> that are locked between them. The semi-rigid structure is characterized by an Effective wheel curve <NUM> and an Effective wheel radius <NUM>. Therefore, this semi-rigid structure can play a role of a wheel with a radius and rigidity that is controlled by the Locking mechanisms <NUM>. Both properties are key to the invention which targets to obtain a foldable wheel with large radius and whose elasticity plays a role of a shock absorber. This curvature and radius vary because of the Locked flexibility angle range <NUM> and by locking the track its curvature varies in a certain range. It should be noted that locking could be positive to obtain circular curvature, but it could be also negative if it is necessary to keep track in inverted position.

Various configurations of Locking mechanism <NUM> embodiments are presented in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>. For simplicity of illustration on this and other figures we use three columns with representing a Side view <NUM> a Top view <NUM> and Front view <NUM>. All solutions above summarize the possibility to have a principle of the "big wheel" realized with tracks.

Three configurations of locking mechanism of a sliding type are presented on <FIG>. A configuration on <FIG> is where every Track element <NUM> bears a Locking element <NUM> that can move along a Guiding rail <NUM>, have a form that completes a Fixed hook <NUM> and can enter into a rigid configuration of Locked position <NUM> with a Fixed hook <NUM> on another Track element <NUM>. When the Locking element <NUM> is in a central Locked position <NUM> it hooks to a Fixed hook <NUM> and makes two Track element <NUM> locked to each other. When the Locking element <NUM> is moved aside to an Unlocked position <NUM>, the two Track element <NUM> are not locked any more and can move freely around the Track hinge <NUM> thus putting the track in its usual foldable state. The Locking element <NUM> also prevents that Track element <NUM> moves in the direction of Negative folding direction <NUM>.

A configuration on <FIG> is similar to the previous solution. The difference resides in the fact that three Track element <NUM> are locked together.

In configuration on <FIG> one Track element <NUM> bears a Fixed element with holes <NUM> that is firmly fixed to the Track element <NUM> and has one or several Multiple locking hole <NUM>. The second track element bears a Sliding element with rod <NUM> that moves along a Guiding rail <NUM> and has a Rod <NUM>. At different angles between the two track elements, the Sliding element with rod <NUM> can move along the Guiding rail <NUM> and lock the two track elements by positioning the Rod <NUM> in one Multiple locking hole <NUM>. The selected hole defines the angle between the two track elements. In an unlocked state, the Sliding element with rod <NUM> is in an Unlocked position <NUM> and the Track element <NUM> can move in the positive and the negative folding directions. When the Sliding element with rod <NUM> is in the Locked position <NUM>, a hole of the Fixed element with holes <NUM> and the rod of the Sliding element with rod <NUM> are aligned and the Rod <NUM> goes into the Multiple locking hole <NUM>. The Multiple locking hole <NUM> allow various angles of the locking mechanism.

On <FIG> embodiments based on rotating locking mechanisms are presented. With first configuration shown on <FIG> every track element bears a Rotating hook <NUM> that rotates around an Axis <NUM> within a Rotating range <NUM> and whose position is conditioned by a Positioning spring <NUM>. The Rotating hook <NUM> is made in such a form that by folding two track elements, the corresponding Rotating hooks <NUM> slide along each other due to their form and rotate around the Axis <NUM>. At some point due to the effect of the Positioning spring <NUM> they lock in a position preventing the two track elements to move beyond certain angle. It should be noted that when the Rotating hook <NUM> of a previous track element is being fixed, the one of the next track element can still rotate.

<FIG> shows a configuration where the track elements bear clutches of two types. Both of them have a Cogwheel type surface <NUM>. The first type of Big radius clutch <NUM> rotates around a Rotation hinge <NUM> that is positioned more towards the edge of the track element and has a bigger lever radius. A Small radius clutch <NUM> rotates around the Rotation hinge <NUM> that is positioned more towards the center of the track element and has a smaller lever radius. The two clutches can rotate around their hinges without disturbing each other passing from the Locked position <NUM> to the Unlocked position <NUM> ( indicated with a dotted line). In this position the track elements are in unlocked position allowing free motion. When the Big radius clutch <NUM> and the Small radius clutch <NUM> are in the Locked position <NUM>, their Cogwheel type surface <NUM> coincide and several track elements are in a locked position.

<FIG> shows a configuration where one track element bears a Fixed hook <NUM> and a second track element bears a Locking hook <NUM> that have a Rotating latch <NUM> that has one or more holes. When the Rotating latch <NUM> is in the Unlocked position <NUM>, the two track elements can move freely. When Rotating latch <NUM> is in the Locked position <NUM> the Rotating latch <NUM> rotates until its hole coincides with the Fixed hook <NUM> and the two track elements are in the locked position with respect to each other.

On <FIG> embodiments based on double-chain approach are presented. <FIG> shows an embodiment where a Track element <NUM> rotates around Track hinge <NUM> and can be locked by a second chain also composed of an Element of second chain <NUM> with an Opening <NUM> rotating around a Hinge of second chain <NUM>. The first main chain bears Forward pointing hook <NUM> and Backward pointing hook <NUM>. To reach a locking position, two elements of the first chain are folded so that tips of the two hooks of adjacent elements align and can be passed into the Opening <NUM> of the Element of second chain <NUM> by lowering the second chain on the first. Then by unfolding the two elements of the track tips of the two hooks are locked in the Opening <NUM> due to their form and are set in a locked position. If the Opening <NUM> thas several separated holes, locking is possible at various angles and at negative folding as well (e.g. necessary to keep the track having a specific form on it upper side with respect to rollers).

<FIG> shows an embodiment where the track elements contains the same Forward pointing hook <NUM> and Backward pointing hook <NUM>. The second upper chain contains a locking element being a Dovetail hook <NUM> to keep the track elements in a locked position. It operates in a similar way as the previous solution. The two elements of the track need to be folded to align two hooks and let them enter into the Dovetail hook <NUM> of the second chain by lowering it. Once done, the track elements unfolds and lock themselves reaching the situation shown on the figure where two hooks of the first main chain are locked in the Dovetail hook <NUM> of the second chain. The form of Dovetail hook <NUM> also prevents negative folding.

On <FIG> two other embodiments are presented. With embodiment on <FIG> a locking mechanism is placed inside a hinge linking two Track elements <NUM> that have each half of a Cylindrical part of hinge <NUM>. The cylindrical parts rotate around an Axis with tips <NUM> that rotates in an Axis space <NUM> and can also shift in the direction of its axis of rotation. The Axis with tips <NUM> contains a First tip on axis <NUM> that is positioned in a First locking hole <NUM> of the first cylindrical part of the first track element and can only shift in axis direction but not rotate. Therefore the Axis with tips <NUM> and first that track element can not rotate with respect to each other. The axis also contains a Second tip on axis <NUM> that can freely move in a Corridor of rotation <NUM> which represent a wider space over <NUM> degrees around the axis. The Corridor of rotation <NUM> allows the cylindrical part of the second hinge to rotate around the axis.

When the second track element is positioned at a certain angle with respect to the first track element, a Second tip on axis <NUM> is aligned with a Second locking hole <NUM> that is present in the Axis space <NUM> at certain angle only (as First tip on axis <NUM>). The Axis with tips <NUM> can then be shifted to a position where the First locking hole <NUM> coincides with the Second locking hole <NUM>. The Axis with tips <NUM> is then locked with respect to both cylindrical parts of the hinge. The two track elements and the axis become a rigid system where elements stay at a defined angle with respect to each other. Multiple Second locking holes <NUM> can provide multiple locking angles of the track elements. Shifting of the Axis with tips <NUM> can be reached by mechanically shifting as in clutch, or using contactless force (f. In the latter case axis is more protected from dust.

In embodiment shown on <FIG> the first track element contains a Cogwheel <NUM> and the second track element contains a Cog <NUM>. When two track elements are folded, the Cog <NUM> advances and rotates the Cogwheel <NUM> around an Axis <NUM>. A Spring for clutch <NUM> is in contact with Cogwheel <NUM> and allows its rotation in one direction only. A Locking clutch <NUM> prevents the Cog <NUM> to advance beyond certain limit and locks the two track elements at specific angle because the Spring for clutch <NUM> prevents the Cogwheel <NUM> from backward rotation. To unlock the system and return to flexible folding of the track elements, the Spring for clutch <NUM> should be moved aside.

Various embodiments of tracks assemblies are illustrated on <FIG>. In the most prominent embodiment shown on <FIG> the number of tracks is four and they provide four Contact point with the ground <NUM> as in a normal four-wheel car or a motorcycle. Four-point contact provides maximum stability for necessary maneuvers that will be performed. Each track is guided by two rollers resulting eight rollers. A second embodiment shown on <FIG> illustrates a combination of two tracks, but involves still eight rollers and still deliver four points of contact. Third embodiment is shown on <FIG> where three tracks are involved and three Contact point with the ground <NUM> are achieved. This configuration is less stable that four point of contact. Fourth embodiment shown on <FIG> features two tracks with two Contact point with the ground <NUM> are used. The equilibrium of the vehicle will also be reached with mechanisms maintaining stability with gyroscopes for example. Finally, an embodiment shown on <FIG> can be used like a skateboard. This solution will benefit from a larger Contact point with the ground <NUM> and a special turning mechanism.

On <FIG> a locking process is illustrated for the locking mechanism of type shown on <FIG>) where a locking chain is used to lock the track.

The vehicle leans on a Lean roller for track <NUM> that rolls on track in already locked state. Therefore, the vehicle weight is transmitted to those rollers which transmit this weight to rigid track which in turn with its inherent flexibility lean on the ground. Bigger the lean rollers, smother the motion but track folding radius is a constraint.

To convert a track to a rigid state other elements are required. An Encoding roller for track <NUM> positions adjacent track elements at specified angle with respect to each other and a specified position with respect to a locking chain. An Encoding roller for chain <NUM> positions the chain so that an Element of second chain <NUM> position and angle allows that a Forward pointing hook <NUM> and a Backward pointing hook <NUM> can enter into an Opening <NUM> of the locking chain coinciding with track hooks. The locking occurs by lowering the chain on the track to overlay opening on the hooks and further unfolding of the track with a Lean roller for track <NUM> and a Guiding roller for chain <NUM>. The correct locking occurs at specific position of two rollers.

A top view of the rollers positions is explained on <FIG>. A platform leans on Lean roller for track <NUM>. The Encoding roller for track <NUM> and the Encoding roller for chain <NUM> are positioned so that to achieve locking effect. Track elements and their Forward pointing hook <NUM> and Backward pointing hook <NUM> are positioned with respect to the Element of second chain <NUM> so that they can enter into the Opening <NUM> at a specific time. Then, the Guiding roller for chain <NUM> unfold the locking chain and when the Lean roller for track <NUM> is in contact with rigidly locked track elements, it's already a rigid system.

Various functionalities of a track derive from its ability to change curvature and are explained on <FIG>. A Roller <NUM> (or system of rollers as explained above) can set the angle of locking mechanism for every pair of track elements from a Locking mechanism position one <NUM> to a Locking mechanism position two <NUM> (and vice versa depending on the direction of motion). The combined effect of angles between individual track elements is the change of a curvature of the track from a Larger radius <NUM> to a Smaller radius <NUM>.

A change of curvature occurs in various embodiments adapted for each locking mechanism. For locking mechanism as shown on <FIG> and <FIG> a first embodiment is that track does not change and bears a Forward pointing hook <NUM> and a Backward pointing hook <NUM> but angle at which they are blocked is controlled by the Opening <NUM> of locking chain. The Element of second chain <NUM> could have openings of several sizes that would block hooks of the track at different angles. Size of such openings are controlled for example by sliding elements reducing the opening or that opening has various gradations of gaps and by positioning the locking chain hooks are locked at desired angles. Another embodiment is where opening remains the same, but hooks have several steps at different heights which with same opening of locking chain would correspond to different angles of locking between track elements. The advantage of the second embodiment is a difference in lever allowing to lock track elements at more open angles with bigger lever (where more force is needed) and at higher curvatures (where less force is needed) the lever is smaller.

The effect of curvature change is explained on <FIG> where the Standing platform <NUM> of the vehicle moves in the Direction of motion <NUM>. A curvature increase transition with side view of the platform is shown on <FIG>.

The original track form is a High curvature with small radius <NUM> and track is locked at its Big radius of low curvature <NUM>. This configuration provides that position is Platform height at low curvature <NUM> above the ground.

The result of the operation is a Low curvature with big radius <NUM> where track is locked at its Small radius of high curvature <NUM> and Platform height at high curvature <NUM> above the ground. Thus, the platform changes its height above the ground by a Height difference <NUM> between two states of high and low track curvature. Changing height of the platform or one of the tracks provides very useful functionality in various drivability scenarios.

A transitions between a Low curvature with big radius <NUM> and a High curvature with small radius <NUM> occurs across one half-cycle of track rotation around rollers. When curvature change is required, a Controlling roller <NUM> starts to change the curvature of the track. Intermediate states of the track are shown on <FIG> and Figure 11c. In each of those states the track has one part of low curvature and one part of high curvature separated by a Joint point <NUM>.

To avoid an "angle" between two curvature areas at the Joint point <NUM> and thus a "bump" effect in motion, a Tangent bigger curvature <NUM> and a Tangent smaller curvature <NUM> have to be equal in the Joint point <NUM>. This can be reached by intermediate locking angle between two track elements that provides equal tangents of two circular segments of the track have and thus a smooth junction.

A curvature decrease effect shown on <FIG> has a reverse effect. Let's assume that motion occurs in the same direction. The track goes from a High curvature with small radius <NUM> to a Low curvature with big radius <NUM> and the radius goes from a Small radius of high curvature <NUM> to a Big radius of low curvature <NUM>. Subsequently platform (or track alone) goes from bigger height to lower height.

The operation of change goes through intermediate states: Intermediate track state four <NUM>, Intermediate track state five <NUM>. A forward roller first changes the curvature of the Joint point <NUM> with given angle between track elements and continues to do so at High curvature with small radius <NUM>. Here, achieving smoothness between two circular parts of the track with different radiuses is unlikely and a Tangent bigger curvature <NUM> and a Tangent smaller curvature <NUM> can not be equal because of negative angle. Further, the track gradually passes from a Intermediate track state four <NUM> to an Intermediate track state five <NUM> and at the end to a Low curvature with big radius <NUM>.

The <FIG> explains three various turning options for a vehicle where three turning methods are present. For each method a Position before turning <NUM> and a Position after turning <NUM> are shown as well as a Rotating trajectory <NUM>.

A first turning method shown in <FIG> implies configuration of four tracks or two tracks one after another as shown in the Position before turning <NUM>. The forward pair of tracks or First pair of track rotates <NUM> turns to follow the Rotating trajectory <NUM> as a normal four-wheel car would do. A second turning method shown in shown in <FIG> implies that at the Position before turning <NUM> the Speed of outer track <NUM> becomes higher respectively to Speed of inner track <NUM>. Therefore, Position after turning <NUM> follows the Rotating trajectory <NUM> similar to tanks. A third turning method shown in shown in <FIG> implies that at the Position before turning <NUM> the two tracks deform in the direction Rotating trajectory <NUM> to reach Deformed curved state <NUM>. This can be achieved with Additional hinges <NUM> between the track elements.

For all three turning methods, to take turns at rather high speed with comfort for a user, inclination of the platform is possible by having an additional effect of one track changing its curvature and thus lifting one side of the platform leading to inclination of standing or sitting passenger as shown in Platform inclination <NUM>.

The Figure 13a-e explain the use of track curvature change to overcome boardwalk steps in a city. At a time moment shown on Figure 13a the four track configuration (seen from the side) moves in Direction of motion <NUM> where it approaches a Sidewalk step <NUM>. View is fixed on the tracks meaning that ground moves leftwards. At a moment shown on Figure 13b both tracks change their curvature to heighten the position of the platform before touching Sidewalk step <NUM>. At a moment shown on the Figure 13c where first track touches the Sidewalk step <NUM> the first track starts to change its curvature to normal. At a moment shown on Figure 13d the first track is now present on the Sidewalk step <NUM> level with normal curvature and the second track is at lower level with its higher curvature. At a moment shown on Figure 13e the second track follows the same behavior as the first one and ends on Sidewalk step <NUM> with the lower curvature.

The <FIG> explains the way a platform of four tracks can optionally move on stairs. There are several embodiments where tracks can change curvature and lift rear part of the platform to maintain the driver at best possible horizontal orientation with respect to stairs inclination. The most comfortable solution seems, however, to be achieved with a mode illustrated on the figure where a platform splits into a section First section <NUM> and a Second section <NUM>. At the moment of reaching a stairs the two tracks (on one side) achieve four Contact point with staircase <NUM>. At the same time the Lifting step of first section <NUM> raises as well as the Lifting step of second section <NUM>. To avoid injuries, the Extending floor <NUM> bridges the space between two sections at the same way as escalator. The platform remains horizontal and composed of two sections.

To increase adherence with stairs the track elements can have a Low grip <NUM> and High grip <NUM> making Contact gripping point <NUM> much more stable (shown on lower part of the figure).

The <FIG> show some optional comfort elements of the invention. In the Motor version of the vehicle <NUM> the platform remains flat for the driver and the luggage. The Motor <NUM> is beneath the platform. In case of electric motor an option is to have the Battery <NUM> located directly below the platform near the motor or in the track elements. This would make the weight supported by tracks and rollers lower.

In Bicycle version of the vehicle <NUM>, the Pedals <NUM> remain in front and can be connected to front roller with changing speeds. In both versions the Guiding pad <NUM> allows controlling direction of the vehicle, changing gears, a reverse motion, making the vehicle rotate around its vertical axis, etc. An Umbrella <NUM> or holder for normal umbrella would protect from rain and can be attached to the same vertical stand as the control pad or be more towards rear of the vehicle (and be foldable). For comfort, the Seat <NUM> can be foldable and allow luggage beneath. Additional elements like Barrier <NUM> to lean upon can be provided.

Claim 1:
A mobile system including at least one variable flexibility track (<NUM>) and at least two rollers (<NUM>, <NUM>, <NUM>) around which the variable flexibility track is wrapped, wherein the rollers are adapted to change the rigidity and the curvature of the Variable Flexibility track to modify its shape so as to be a wheel or to have a part corresponding to a circular wheel with different curvature or to be foldable, said variable flexibility track being composed of:
- a plurality of track elements (<NUM>) and hinges (<NUM>) linking said plurality of track elements so as to allow rotation of the track elements with respect to each other around the hinges, and
- a locking mechanism (<NUM>) on each track elements that allows locking a position of the track elements with respect to the adjacent ones at various angles; and said rollers being in contact with the variable flexibility track and comprising at least one of
- a mechanism that interacts with locking mechanism (<NUM>) of each track element (<NUM>) to change the rigidity of the variable flexibility track (<NUM>) that can be present within the variable flexibility track within rollers,
- a mechanism for changing a curvature or a relative position of the tracks to allow navigation on stairs and cross other obstacles,
- a mechanism for steering the mobile system by applying different speed and/or curvature to the tracks.