GUIDING AND SUPPLY OF MINIATURE VEHICLES

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to track sets for miniature vehicles and, more specifically, to the construction of miniature vehicles and of the types of tracks on which one or several vehicles can run.

2. Discussion of the Related Art

Track sets for miniature cars are generally formed of sections placed end-to-end and following the desired course with curves, bends, bridges, etc. Miniature cars are placed on the track and comprise two current pick-up shoes intended to contact two conductive strips of a supply rail made in the tracks. Most often, a pin protruding from the bottom of the car is engaged in a groove of the rail between the two conductive strips and is used as guiding means. The user manipulates a control handle setting the voltage between the conductive strips, which conditions the power supply voltage of the car motor and, thereby, its speed.

A problem of current track sets is the wearing or the deformation of the shoes intended to contact the strip conductors. Indeed, such shoes are relatively fragile and, when the scale model car is manipulated by the user, there are risks of deformation which then adversely affect the operation. Further, oxidation phenomena, both at the level of the supply rails and of the shoes, disturb the voltage level applied to the vehicle motor.

Further, such contacts limit the degree of lateral freedom of the car on the track, since the car must always follow a given rail, which alters the natural behavior of the vehicle and limits the interactions between the different pilots. Further, when the car leaves the rail, a manual intervention is necessary even if the car is always on the track. Finally, there are specific constraints as to the track set layout so that the different lanes are equitable, for example, a simple oval results in an outer lane longer than the inner lane.

There also exist circuits enabling the cars to change lanes by multiplying the supply rails across the circuit width. However, such circuits always require contacts.

Another alternative is the driving of fully autonomous radio controlled vehicles on tracks represented by a simple drawing on an adequate support, or passive structures. This type of structure however has the well known defects of requiring some experience from the pilot to avoid going off track, and a periodic recharge of the power source used aboard the vehicle.

SUMMARY OF THE INVENTION

The present invention aims at overcoming all or part of the disadvantages of known track sets for miniature vehicles. More specifically, the present invention aims at solving the problem of the use of conductive contacts with the circuit.

Another object of an embodiment of the present invention is to improve the users' experience.

Another object is to improve the driving assistance provided to a user, especially in bends and other track areas where there is a risk of going off track.

To achieve all or part of these objects as well as others, the present invention provides a miniature vehicle and associated track set system comprising:

a track formed of sections placed end-to-end, each section comprising, across its thickness, at least one conductor taking part in the generation of a magnetic field;

at least one first power supply circuit generating A.C. electric signals for exciting the conductors; and

at least one miniature vehicle comprising:

a first winding and a second winding having different orientations, likely to detect a magnetic field generated by the track; and

at least one second electronic circuit receiving the respective amplitudes measured across the windings, programmed to determine the lateral position of the vehicle on the track.

According to an embodiment of the present invention, the first and second windings are respectively horizontal and vertical.

According to an embodiment of the present invention, the vehicle comprises a third transversal winding enabling the second electronic circuit to detect an angular position of the vehicle with respect to the axis of the magnetic field.

According to an embodiment of the present invention, each track section comprises an arrangement of conductors taking part in the forming of several parallel magnetic fields across the track width.

According to an embodiment of the present invention, the second electronic circuit comprises a microcontroller programmed to have the position of the vehicle on the track servo-controlled by the controlling of a motor-driven steering system equipping the vehicle.

According to an embodiment of the present invention, the vehicle comprises means for extracting the power necessary to its operation from the magnetic field radiated by the track.

According to an embodiment of the present invention, the vehicle comprises means of radio frequency communication with a control handle.

According to an embodiment of the present invention, the vehicle comprises means for detecting data transmitted by the first electronic circuit, via the magnetic field, said first circuit communicating with a control handle.

The present invention also provides a miniature vehicle of such a system.

The present invention also provides a track section of such a system.

The foregoing objects, features, and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified top view of a track set for miniature vehicles;

FIG. 2 is a simplified cross-section view along line II-II of FIG. 1 illustrating the track set operation;

FIG. 3 shows an embodiment of a track section;

FIG. 4 very schematically shows an example of distribution of inductive windings in a miniaturized vehicle according to an embodiment of the present invention;

FIGS. 5A and 5B illustrate the amplitude and phases of the A.C. signals across inductive windings of a vehicle according to its position on the track of FIG. 2;

FIG. 6 illustrates, in the form of blocks, an embodiment of a method for determining the lateral position of a vehicle;

FIGS. 7, 7A, and 7B respectively show an alternative track section and the amplitudes and phases of the A.C. signals across inductive windings of a vehicle according to its position on the track; and

FIG. 8 is a simplified electric diagram of an embodiment of an electronic circuit equipping a miniature vehicle.

DETAILED DESCRIPTION

The same elements have been designated with the same reference numerals in the different drawings. For clarity, only those elements and steps which are useful to the understanding of the present invention have been shown and will be described. In particular, the construction of the miniature vehicles will only be described as concerns the electronic control and interpretation circuits specific to the present invention, the rest of the vehicle (body, drive motors, guide wheel mechanism, etc.) is already used in current miniature vehicles, in particular radio controlled vehicles. The tracks intended to generate the magnetic field necessary to the operation of the type of vehicle forming the subject matter of the present invention may be made and powered in different manners. Only the position of conductors inside of these tracks, and thus the shape of the magnetic lines of this field, will be described.

The present invention will be described in relation with a miniature car. It more generally applies whatever the miniature vehicle (motorcycle, truck, bicycle, etc.).

FIG. 1 is a simplified top view of an embodiment of a track set for miniature vehicles. Currently, the track set comprises a track 1 formed of several models of sections 11, 12, 13, 14, and 15 placed end-to-end and which differ from one another by their length or their shape (straight or rounded). Currently still, one or several miniature vehicles 2 are placed on track 1.

A power supply block 3, intended to be connected by a plug 31 to the power line distribution system or to be powered by a battery, not shown, is connected by a connection 32 to a connector 161 of a section 16 of the track set. Connector 161 powers conductive elements 5 of section 16, which is electrically connected to its neighboring sections, and so on to power the different track sections as will be seen hereafter. Block 3 may also communicate with a cabled remote control handle 4 or, as shown, by a radio system schematically shown by an antenna 34 on the side of block 3 and by an antenna 44 on the side of handle 4. Handle 4 comprises control elements (schematized by a handle 41) intended to transmit acceleration and braking, or even steering orders to car 2. These orders are either directly sent by handle 4 to car 2 which is then provided with radio transmit-receive means, or conveyed by an electric signal generated by control and power supply block 3 and resulting in a modulation of the characteristics of the generated magnetic field.

A specificity of the described system is that the track conductors take part in the generation of a magnetic field likely to be detected by windings contained in vehicle 2 and exploited by electronic circuits thereof to determine the lateral position of the car on the track.

Preferably, the windings present in the vehicle and used by it to detect the magnetic field generated by the track are also used to extract the power supply necessary to its operation (electric operation of the control circuit) and to that of the drive motors. As a variation, all or part of the power may originate from a battery, which is preferably rechargeable.

As an example, a first set of windings is used to measure the position and a second set of windings is used for the power supply. This enables to optimize the size of the windings according to their function.

FIG. 2 is a transverse cross-section view along line II-II of FIG. 1 schematically showing the magnetic field generated by the track set. The track comprises, across its thickness, longitudinal conductors taking part in the generation of the magnetic field. The current therein is alternating, and flows in opposite directions at a given time. The example of FIG. 2 assumes the presence of three parallel conductors 51, 52, and 53 approximately close to the edges of the track and at the center. Each conductor may actually be formed of several juxtaposed wires. In the example of FIGS. 1 and 2, the assembly of track sections connect conductors 51, 52, and 53 in series (for example, via male-female connectors, not shown) to form a winding 5 having its two ends connected to connector 161 to be powered by block 3. For example, the connections between spirals are performed at the level of section 16 as schematically shown in FIG. 1 so that the three conductors conduct the same current in series.

As compared with usual track sets, the track surface comprises neither rail nor apparent conductor. This improves the circuit experience. The track surface may be planar or bumpy according to the desired experience. Similarly, it may simulate different types of coatings (road, dust track, etc.). Car 2 is only in contact with track 1 by its wheels 23. Further, this contact is only mechanical and not electric.

As illustrated in FIG. 2, an electric power supply (A.C. voltage) of windings 51, 52, and 53 generates a magnetic field in a vertical plane (perpendicular to the longitudinal direction of the track) and symmetrical with respect to the middle of the two conductors, this middle preferably corresponding to the center of the track. An example of instantaneous current flow direction in these conductors has been schematically shown. The magnetic field is detected at least by two vertical and horizontal windings 21v and 21h integrated in car 2.

FIG. 4 is a simplified perspective view in which the envelope of car 2 has been shown in dotted lines to illustrate an example of arrangement of horizontal and vertical conductive windings 21h and 21v used to determine the lateral position of the vehicle on the track. In the example of FIG. 4, a third transversal winding 21t used according to an embodiment which will be subsequently described has also been shown.

The respective ends of windings 21 of vehicle 2 are connected to one or several electronic circuits 25 of voltage measurement, interpretation of these measurements, and control. A capacitive element may take part in the magnetic coupling.

FIGS. 5A and 5B show examples of amplitude and phase Uh and Uv respectively present across windings 21h and 21v according to the lateral position of car 2 on track 1. The phase is represented by the respective signs of signals Uh and Uv on the drawings: if the signs are opposite, then the signals across windings 21h and 21v are in phase opposition. If not, they are in phase.

As illustrated in FIG. 5A, the phase of signal Uh across winding 21h inverts at the center of the track, which corresponds to the middle of excitation winding 5. As for vertical winding 21v, the amplitude thereacross increases from the track edges, to cross a zero value straight above the conductors of winding 5. Between the two conductors of winding 5, amplitude Uv increases across the width of the track to reach a maximum at its center. The interpretation of amplitudes Uh and Uv enables to determine the position of the car on the track. In simplified fashion, the phase of voltage Uh across the horizontal winding determines the right-hand or left-hand position of the vehicle with respect to the track center while the amplitude of voltage Uv across the vertical winding enables to evaluate its position between the track edges and the center. When the car is at the center of the track, the position may be refined by the vertical winding, the right-hand or left-hand position with respect to the center remaining given by the horizontal winding.

FIG. 6 is a block diagram illustrating steps implemented, on the side of car 2, to determine its lateral position on the track.

The tracks of circuit 1 (FIG. 1) are assumed to be powered and to generate a magnetic field surrounding car 2.

The succession of steps which will be described in relation with FIG. 6 is performed in a loop, in order to know as accurately as possible the vehicle position and to enable an automatic adjustment of its course, as will be seen hereafter.

A first step (block 61) comprises measuring and converting into digital signals the respective values of voltages Uh and Uv across windings 21v and 21h of the vehicle. This measurement and conversion uses usual circuits for measuring an A.C. voltage between two terminals and an analog-to-digital conversion. These voltages are representative of the amplitude of the field detected by the horizontal and vertical coils. The measurements are then compared by a microcontroller. For example, the respective absolute values of these amplitudes are compared (block 62, |Uh|>|Uv|?). This comparison is preferably performed based on normalized values, that is, values divided by the maximum possible amplitude of the considered signal. As a variation, other tools usual in signal processing are used to avoid taking into account oscillations linked to the power supply voltage or saturation phenomena. If the field measured by the horizontal coil is greater than that measured by the vertical coil, and thus if voltage Uh is in absolute value greater than voltage Uv, this means that the vehicle is away from the track center (left-hand or right-hand portion in FIG. 5A). Conversely, if the vertical field component is the largest, this means that the vehicle is close to the track center.

In the case of a lateral position (output Y of block 62), the phase of the measured voltage is then tested (block 63, Uh>0 ?) to determine whether the car is located to the right (block 64, R—output N of block 63) or to the left (block 65, L—output Y of block 63). This phase is preferably obtained by the sign of the measured voltages in case of a synchronous digitalization, but any other usual phase determination principle (analog mixer, correlator, etc.) may also be used. If voltage Uv is, in module, greater than voltage Uh (output N of block 62), the vehicle is considered to be in a median position (block 66, M) on the track.

In practice, the different measured signals may be linearized and compensated according to the rectified voltage to refine the measurement. It is also possible to have a servo-control of the sampling time so that it corresponds to the signal maximum, or to any other value capable of providing a value which is steady and/or the least sensitive to the magnetic disturbances caused by the variations of the vehicle consumption. For example, the magnetic field of the track may be periodically decreased at the frequency of the measurements to avoid saturation phenomena due to the rectification to power the vehicle. This enables to exploit a simultaneous measurement on both windings, which improves the accuracy. Another solution to avoid saturated signals is to use windings dedicated to the measurement.

Once the current position (block 67, CURRENT POS) has been obtained, it is used by the microcontroller (block 68, CONTROL) to correct the course of the vehicle if need be.

In parallel, a next position acquisition is carried out by the system (return to block 61).

According to an alternative embodiment, the position is determined by comparing voltages Uh and Uv with determined thresholds during the system manufacturing or in a calibration phase.

The control of the vehicle position may take different forms. It is based on the variation of the lateral position (and thus of signals Uh and Uv) along time.

For example, a motor for controlling the wheels (for example, the front wheels) of car 2 is controlled according to the variation of the vehicle position with respect to a recorded reference position. The user does not act upon the steering, but only upon the acceleration-braking The car is guided on an imaginary rail corresponding to a recorded lateral position. This position is not necessarily always on the same side of the track, and the lateral position profile may vary over the circuit.

According to another example, the servo-control only aims at avoiding for the vehicle to go off track by centering back its position when it gets too far towards the edges. For this purpose, the comparisons of the vertical and horizontal signals are refined in order to check whether the vertical signal decreases or increases (block 69, FIG. 6) or whether its phase inverts, once the vehicle has been detected as being to the right or to the left of the track.

According to still another example, the user has a steering wheel on control handle 4, which enables him to select a lateral reference position on the track. The servo-control then forces the car to follow the corresponding imaginary rail, thus enabling the user to optimize the car course in bends, or to overtake or, on the contrary, get in the way of other cars on the track. This operating mode provides a great freedom of maneuver and of selection of courses, while avoiding the issues of the guiding of a radio-controlled car with no track following aid. This also suppresses the notion of inner and outer track of a track set with conventional rails where the tracks do not cross, and the lack of equity thereof.

The exploitation of the measurements may take many forms according to the application and to the type of desired servo-control. Once these criteria have been established, the microcontroller just has to be programmed in adapted fashion.

FIGS. 7, 7A, and 7B illustrate an alternative embodiment according to which an additional conductor 54 is added in the track. With an alternation of the flow direction in the conductors such as schematically shown in FIG. 7, field lines such that they create two “magnetic tunnels” are then obtained. As illustrated in FIGS. 7A and 7B, the possible amplitudes of signals Uh and Uv follow patterns which repeat twice on the track.

A better lateral positioning accuracy can thus be obtained and the track width can be increased without decreasing the power transmitted to the vehicle at the cost of a slightly more complicated processing of the signals. By keeping the position determination algorithm described hereabove, this structure may also be used to restrict the area accessible to a vehicle since it can then not exit its magnetic tunnel. This then resembles an operation on rails while avoiding the disadvantages of electric contacts between the vehicles and the track.

FIG. 8 is an example of a simplified electric diagram of circuit 25 contained in a miniature vehicle of the described system.

As indicated previously, this circuit is based on the use of a microcontroller 8 (μC) comprising, in addition to digital processing means, all the necessary storage elements as well as, in this example, the elements of communication with the control handle (4, FIG. 1) symbolized by an antenna 80. A direct radio frequency transmission is assumed between car 2 and handle 4, enabling the car to receive the orders provided by the user in terms of acceleration, braking, and possibly steering. As a variation, these communications transit through the track and are conveyed by the magnetic field, for example, by modulating it in amplitude or frequency, or by superposing an additional signal to the current in the conductors, to transmit orders from handle 4 to the vehicles. Microcontroller 8 and circuit 25 of the vehicle then comprise the means necessary to process this information.

In the example of FIG. 8, the miniature car is assumed to draw the power necessary to the operation of the circuits that it comprises (voltages Vcc and Vdd) from the magnetic field radiated by the track. For this purpose, respective terminals 212 and 214 of horizontal winding 21h are connected to the A.C. input of a first diode bridge 811 (for example, fullwave) of a circuit 81 for generating a D.C. power supply voltage Vcc. Similarly, terminals 216 and 218 of vertical winding 21v are connected to the A.C. inputs of a rectifying diode bridge 813. The rectified outputs of bridges 811 and 813 are sent, after being filtered by a capacitor 812 across which a D.C. power supply voltage Vdd is present, on a linear regulator 814 (REG). The output of regulator 814 provides regulated voltage Vcc. For example, data relative to the output voltage are sampled from the midpoint of a resistive dividing bridge 816 and 818 associated with a stabilization capacitor 815. Output voltage Vcc is provided to a storage capacitor 817. As a variation, circuit 81 for generating the power supply voltage internal to the vehicle comprises composite or auto-synchronous bridges. It is also possible to add capacitors in parallel on windings 21 to form a resonant circuit improving the power efficiency and decreasing the necessary number of spirals. The parallel capacitors can be switchable, for example by being serially connected with a switch (for example formed of two head-to-tail NMOS transistors with a common source). It is then possible not to connect the capacitors during the periods of measurement of the vehicle position on the track, which avoids a perturbation of the measurement. These capacitors can also be used outside of these measurement periods, by switching the switch for inducing a high frequency current in the winding. This excitation can then be detected by magnetic coupling during the passing of the vehicle above a determined track section. This can also implement a tachometer counter function. The distinction between different vehicles can originate from an identifier coded in the high frequency excitation or from the time difference between the transmission time of this current and the end of the track excitation. The transmission preferably occurs when the excitation level is low. It is also possible not to connect these capacitors for longer periods so as to limit or control the supply voltage Vdd.

As a variation, windings 21 may be series-connected, thus decreasing the number of rectification branches: three rectification branches (instead of four) are then sufficient, without decreasing the recovered power due to the current source behavior of these windings.

On the magnetic field detection side, respective end terminals 212, 214 and 216, 218 of the horizontal and vertical windings are grounded by resistive dividing bridges (formed of pairs of resistors 821 and 822; 823 and 824; 825 and 826; 827 and 828). The respective midpoints of these bridges are connected to analog measurement inputs of microcontroller 8. To stabilize the voltages, capacitors 820 and 829 connect the respective midpoints of the resistive bridges assigned to a same winding. Further, two other inputs of microcontroller 8 are connected, via resistors 831 and 833, to respective terminals 212 and 218 of the horizontal and vertical windings. This additional connection enables the microcontroller to synchronize the digitizations of the horizontal and vertical signals with interrupts of its program, thus making it easier to the render the phase of these signals. Other digitization methods also enable to render this information, while avoiding the use of interrupts. To avoid too high a voltage across the microcontroller, diodes 832 and 834 limit it to power supply voltage Vcc.

Microcontroller 8 exploits the voltages measured across the windings to detect the vehicle position, for example, as illustrated in relation with FIG. 6.

Then, the microcontroller controls the car position on the track and manages the power supply of motor 851 for accelerating and braking the vehicle.

According to a first example of servo-control, the microcontroller controls a motor 841 (M) for driving a motor-driven steering system of the car. For example, this control is performed via an H bridge formed of four transistors 842, 843, 844, 845 in series by pairs between power supply terminal Vcc and the ground. The selection of regulated voltage Vcc rather than voltage Vdd reserved to the vehicle drive motor enables to provide a motion at constant speed of the guide wheels, and thus a more stable and accurate servo-control. Preferably, an inductive element 848 having the function of avoiding voltage dips on the power supply in transitions of the H bridge is interposed between high transistors 842 and 843 of the bridge and power supply voltage Vcc. The respective gates of transistors 842 and 844 receive a common control signal from microcontroller 8 and are grounded by a resistor 846. Similarly, the gates of transistors 843 and 845 are grounded by a resistor 847 and connected to an output of the microcontroller. As usual for an electric steering control, the pair of transistors 842, 844 or 843, 845 which has been made conductive conditions the rotation direction.

The steering control may also be performed by the user by means of handle 4, for example, to cause a change of lane or lateral position. Preferably, in an operation where the steering wheel of handle 4 is at rest, the microcontroller controls the lateral position of the car on its lane or on a determined pattern.

Wheels 23 of the vehicle are driven by at least one motor 851 of a pulse-width modulation (PWM) controlled circuit 85. Motor 851 drives the rear and/or front wheels. In the shown example, circuit 85 comprises two transistors 852 and 853 in series between voltage Vdd and the ground, motor 851 being connected between power supply Vdd and the junction point of transistors 852 and 853. Transistor 853 is used to cause an acceleration of the vehicle by being controlled by microcontroller 8, and its gate (in the arbitrary case of a MOS transistor) is grounded by a resistor 854. Transistor 852 is used to control a possible braking of the vehicle if this function is desired. In the shown example, the gate of transistor 852 is connected on the one hand to the terminal for providing voltage Vdd by a resistor 855 and on the other hand to microcontroller 8 via a bipolar level-shifting transistor 856. The base of bipolar transistor 856 is connected by a resistor 857 to an output of the microcontroller and its emitter is grounded.

According to a preferred embodiment illustrated in FIGS. 4 and 8, the vehicle comprises an auxiliary winding 21t used to detect a possible askew position of the vehicle. Winding 21t has its respective terminals 211 and 219 connected on the one hand to the midpoint of a resistive dividing bridge 861 and 862 between voltage Vcc and the ground and on the other hand to an input of microcontroller 8 via a resistor 863. Terminal 211 is further directly connected to the microcontroller.

The voltage obtained across winding 21t enables, with an adapted programming that can be deduced from the vertical and horizontal windings, to detect the angular position of the car with respect to the axis of the magnetic field. This for example enables to detect a tendency of the car to be askew, for example, in a bend, which cannot be detected by the horizontal and vertical windings. This may be used to cause a counter-steering by means of the vehicle wheels. It is also used to detect the angle taken by the vehicle in the case of a lane change.

In usual manner for radio controlled vehicles, the vehicle may comprise other inputs (not shown). For example, inputs may be used to detect the angular position of the guide wheels of the vehicle.

It should be noted that the circulation direction is not detected by the microcontroller and is thus free for the user. It is for example possible to have vehicles simultaneously circulating in opposite directions. However, once the vehicle has been launched on the track, a turn-around thereof can be detected due to auxiliary winding 21t.

Other embodiments than that illustrated in FIG. 8 are possible, be it for the switch type (bipolar, MOS, relay, etc.), the number of motors, the signal adaptation, etc. The implementation of a magnetic position detection and of a servo-control may further use components and elements existing on usual vehicles.

An advantage of the described embodiments is that they avoid any electric contact between the track and the vehicle. The friction is thus decreased and the disadvantages of a possible contact defect are avoided. Another advantage is the feeling of freedom given to the circuit user.

It should be noted that the described embodiments are also compatible with the rendering of a lane effect on the circuit as in a rail circuit, while allowing lane changes.

Various embodiments have been described, various alterations and modifications will readily occur to those skilled in the art. In particular, although the present invention has been described in relation with the integration of several conductors in the track, a single conductor is sufficient for the generation of a magnetic field enabling a position servo-control. The use of several conductors is especially intended to facilitate the power recovery by the vehicle for its power supply. Further, the circuit power supply has not been described and may have many different implementations.

Further, the practical implementation of the present invention based on the functional indications given hereabove is within the abilities of those skilled in the art using available electronic circuits.

Moreover, the programming of the microcontroller to have it exploit the signals of the horizontal and vertical windings is within the abilities of those skilled in the art to give the miniature vehicle circuit the desired function(s) (for example, position servo-control only, possibility of changing lanes, etc.).

Finally, although the present invention has been described in relation with an example according to which the vehicle windings are horizontal, vertical in the longitudinal direction, with a possible additional transverse winding, it may be provided for these windings to have other orientations (oblique, for example), provided to accordingly adapt the signal processings.

Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited only as defined in the following claims and the equivalents thereto.

GUIDING AND SUPPLY OF MINIATURE VEHICLES

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CPC

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