REMOTE CONTROL VEHICLE

Abstract

A remote-control vehicle is disclosed. The vehicle comprises a first wheel and a second wheel offset along the longitudinal axis of the vehicle. The vehicle further comprises a device adapted to apply a torque to the first wheel, a sensor configured to monitor the pitch angle of the vehicle, and a control module. The control module is configured to control the torque applied by the device to the first wheel in accordance with the monitored vehicle pitch angle so as to accelerate the vehicle while maintaining the vehicle pitch angle within a range of acute angles. Also disclosed is a second remote-control vehicle, comprising: a first wheel and a second wheel offset along the longitudinal axis of the vehicle, a steering system adapted to steer the first wheel, a sensor configured to monitor the roll angle of the vehicle, and a control module configured to control the steering of the first wheel in accordance with the monitored vehicle roll angle while the vehicle is travelling so as to maintain the vehicle roll angle within a range of acute angles. A third remote-control vehicle is also disclosed and comprises: a first wheel and a second wheel, a device adapted to apply a torque to the first wheel, a sensor configured to monitor the pitch angle of the vehicle, and a control module configured to control the torque applied by the device to the first wheel in accordance with the monitored vehicle pitch angle when the vehicle is in free fall so as to maintain the vehicle pitch angle within a specified range of angles.

Claims

1. A remote-control vehicle comprising: a first wheel and a second wheel offset along the longitudinal axis of the vehicle, a device adapted to apply a torque to the first wheel, a sensor configured to monitor the pitch angle of the vehicle, and a control module configured to control the torque applied by the device to the first wheel in accordance with the monitored vehicle pitch angle so as to accelerate the vehicle while maintaining the vehicle pitch angle within a range of acute angles.

2. A remote-control vehicle according to claim 1, wherein the control module is configured to adjust the torque applied to the first wheel so as to stabilise the vehicle pitch angle while causing the vehicle to accelerate.

3. A remote-control vehicle according to claim 1, wherein the control module is configured to control the applied torque so as to raise the second wheel and thereafter to maintain an acute vehicle pitch angle while accelerating the vehicle.

4. A remote-control vehicle according to claim 3, wherein the control module is configured to raise the second wheel by controlling the applied torque to be sufficient to overcome the gravitational torque exerted on the first wheel by the vehicle so that the load borne by the second wheel is reduced such that the acceleration of the vehicle causes the second wheel to be raised.

5. A remote-control vehicle according to claim 3, wherein the control module is configured to maintain an acute vehicle pitch angle by adjusting the applied torque so as to counteract variations in the monitored pitch angle.

6. A remote-control vehicle according to claim 1, wherein the control module is configured to maintain the vehicle pitch angle within a range of acute angles such that the centre of mass of the vehicle is maintained within a range of positions horizontally offset from the rotational axis of the first wheel.

7. A remote-control vehicle according to claim 1, wherein the first wheel is a forward wheel and the second wheel is a rear wheel, and wherein the device comprises a brake adapted to apply a braking torque to the forward wheel so as to accelerate the vehicle in the opposite direction to the direction of travel.

8. A remote-control vehicle according to claim 1, wherein the first wheel is a rear wheel and the second wheel is a forward wheel, and wherein the device comprises a motor adapted to apply a driving torque to the rear wheel so as to accelerate the vehicle in the same direction as the direction of travel.

9. A remote-control vehicle according to claim 1, further comprising a device adapted to apply a torque to the second wheel, wherein the control module is configured to control the torque applied by the device to the second wheel in accordance with the monitored vehicle pitch angle so as to accelerate the vehicle while maintaining the vehicle pitch angle within a range of acute angles.

10. A remote-control vehicle according to claim 1, wherein the vehicle further comprises a third wheel.

11. A remote-control vehicle according to claim 10, wherein the vehicle is configured to apply a torque to the third wheel accordingly when a torque is applied to the first wheel.

12. A remote-control vehicle according to claim 10, wherein the vehicle further comprises a fourth wheel.

13. A remote-control vehicle according to claim 1, wherein the sensor comprises an orientation sensor and a rotation sensor.

14. A remote-control vehicle according to claim 13, wherein the orientation sensor comprises an accelerometer configured to monitor the orientation of the vehicle with respect to the direction of acceleration due to gravity.

15. A remote-control vehicle according to claim 13, wherein the rotation sensor comprises a gyroscopic sensor.

16. (canceled)

17. A remote-control vehicle according to claim 1, wherein the range of acute angles is 30-70.

18. (canceled)

19. A remote-control vehicle according to claim 1, wherein the control module is configured to maintain the vehicle pitch angle at a substantially constant acute angle while accelerating the vehicle.

20. (canceled)

21. A remote-control vehicle according to claim 1, adapted to allow the vehicle to be steered while the vehicle pitch angle is maintained within a range of acute angles.

22. A computer readable storage medium configured to store computer executable code that when executed by a computer configures the computer to: receive data comprising a monitored pitch angle of a remote-control vehicle; and send a control signal to a device of the remote-control vehicle to control the torque applied by the device to a first wheel of the remote-control vehicle in accordance with the monitored vehicle pitch angle so as to accelerate the vehicle while maintaining the vehicle pitch angle within a range of acute angles.

23. A computer-implemented method comprising: receiving data comprising a monitored pitch angle of a remote-control vehicle; and sending a control signal to a device of the remote-control vehicle to control the torque applied by the device to a first wheel of the remote-control vehicle in accordance with the monitored vehicle pitch angle so as to accelerate the vehicle while maintaining the vehicle pitch angle within a range of acute angles.

24.-56. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Examples for the present invention will now be described, with reference to the accompanying drawings, wherein like reference numerals indicate like features, and in which:

[0084] FIG. 1 is a perspective view of a first example remote-control vehicle according to the invention;

[0085] FIG. 2 shows a side view of the first example remote-control vehicle at various stages of a first example travelling mode;

[0086] FIG. 3 shows a side view of a second example remote-control vehicle according to the invention at different stages of a second example travelling mode;

[0087] FIG. 4 is a partial section top view of a third example remote-control vehicle according to the invention;

[0088] FIG. 5 shows a front view of the third example remote-control vehicle in three different variations of a third example travelling mode;

[0089] FIG. 6 is a top view of the third example remote-control vehicle at various stages along a path travelled in the third example travelling mode;

[0090] FIG. 7 shows a side view of a fourth example remote-control vehicle according to the invention at different stages during a ramp jump in a fourth example travelling mode below a side view of the fourth example remote-control vehicle at the same stages during an equivalent ramp jump without the fourth example travelling mode engaged;

[0091] FIG. 8 shows a side view of the fourth example remote-control vehicle at multiple stages during a second ramp jump both with and without the fourth example travelling mode engaged; and

[0092] FIG. 9 is a schematic diagram showing an example receiver and control board interface of a remote-control vehicle according to the invention.

DESCRIPTION OF EMBODIMENTS

[0093] Referring to FIGS. 1 and 2, a first example remote-control vehicle according to the invention is now described. The vehicle 101 is illustrated travelling in a wheelie mode. Three spatial axes, X, Y, and Z are indicated, with the vehicle 101 travelling forwards along the ground in a direction parallel to the X axis. The vehicle 101 has the form of a model truck comprising an outer body 115 that substantially covers driving, steering, suspension, and control systems (not shown). The present example is powered by a battery (not shown). However, the vehicle, and any other vehicle according to the present disclosure may alternatively or additionally be powered by nitromethane, petrol, and oil-based systems.

[0094] The vehicle comprises four wheels 103, 105, 107, 109. The four wheels are arranged in a rectangular configuration such that first and second wheels 103 and 105 are aligned on the right side of the vehicle, and third 107, and fourth 109 wheels are aligned on the left side of the vehicle. The present example vehicle has driven rear wheels and front steering. Thus, first 103 and third 107 wheels are driven by an electric motor (not shown), and thus have a torque applied to them in order to accelerate the vehicle forwards. The vehicle may, as an alternative, be driven by an internal combustion motor. Steering is performed by the second 105 and fourth 109 wheels, which are configured to rotate or pivot about axes parallel to yaw axis of the vehicle.

[0095] The vehicle 101 is controllable with command signals received via a radio-frequency link. An antenna 117 (which may be external, as shown, or may be integrated into the receiver of the vehicle) receives signals relating to throttle, braking, and steering actions to be performed by the vehicle. It is also envisaged that vehicles according to the invention may receive remote-control commands via a wired connection or via microwave or infrared frequency communication. The signal is decoded, and commands from the decoded signal are sent to an electronic speed controller, by way of conventional remote-control vehicle components that are well-known in the art.

[0096] In addition to the electronic components commonly employed in remote-control cars according to the prior art, the vehicle 101 further comprises a control module 111 that controls the actions of the vehicle in accordance with readings from a sensor 113 as well as in accordance with control signals issued by a user and received via the antenna 117. The control module 111 is in the form of a microelectronic controller, typically referred to as a control board, that has integral sensors 113 including gyroscopic sensors and accelerometers. In particular, the sensors 113 include a three-axis gyroscopic sensor capable of monitoring changes to the relative attitude of the sensor and therefore of the vehicle 101 itself, within which the control board 111 is mounted. The controller board 111 further includes a three-axis accelerometer that can monitor acceleration of the board in three orthogonal axes and thus can monitor acceleration of the board 111 and vehicle 101 owing to the application of external forces, and can also monitor the absolute orientation of the vehicle 101 with respect to the direction of acceleration due to gravity (i.e. relative to the downward direction).

[0097] In the present example, the control board has the specific form of an aerial positioning wheel controller (APWC). The APWC stabiliser unit is a small computer consisting of a circuit board with PWM input/output connections, a high-speed processor, and attitude sensors that detect orientation and attitude. The APWC is an interface that combines and corrects user input commands, whilst simultaneously reading all of the sensor data relating to the attitude of the vehicle on three axes, and calculates the optimal commands to send to the control components of the vehicle, in particular the servo and ESC.

[0098] The APWC of the present example comprises a 32-bit MPU6000 STM processor, which is able to rapidly process and calculate information from its six-degree-of-freedom (6DOF) sensors. In the present example it is necessary to use several sensors, rather than a single sensor, in controlling the vehicle. 6DOF refers to the inbuilt inertial sensorsthe accelerometer measures acceleration forces, and the gyro measures rotational forces on each axis. These are the six degrees of freedom.

[0099] The APWC is connected between the RX and control components via standard PWM connectors. It is therefore able both to correct driver input and to counteract outside factors such as gradients, bumps, etc., with high speed and precision, offering seamless attitude stabilisation on three axes.

[0100] Like all computers, the APWC needs software to operate. The present example runs firmware that combines the measurements from all of the sensors and applies complex Kalman filtering alongside a wide array of custom parameters.

[0101] The basis of the code is built around a PID loop technique, which involves the following:

P reaction depends on the present error
I on the accumulation of past errors
D is a prediction of future errors, based on current rate of change

[0102] A PID controller is a control loop feedback mechanism widely used in control systems. The PID controller takes data from sensors and compares it against expected values. The difference is called the error, and accordingly the APWC alters the speed of the motor or angle of the servo in order to reduce the error. Thus by tuning the PID settings and utilising high-speed, high-accuracy components, the vehicle can be stabilized in various stunt modes.

[0103] The vehicle 101 is shown driving at an elevated attitude so as to perform a wheelie. The pitch angle at which the vehicle is oriented is shown as being formed between the direction in which the vehicle is travelling, namely forwards, indicated by arrow A and parallel with the X axis, and the longitudinal axis of the vehicle 101 indicated by arrow B. The particular longitudinal axis that extends through the centre of the vehicle 101 is indicated by arrow L. This can be seen to be parallel with arrow B, since both denote the longitudinal direction of the vehicle, namely the axis extending along the vehicle from the back to the front, for example from the first wheel 103 at the rear to the second, forward wheel, 105.

[0104] It can be seen that pitch angle is an acute angle. In the illustrated mode, this is achieved by the control module 111 receiving data from the sensors 113 including the current monitored pitch angle , as measured by the accelerometer sensors, and controlling the electric motor (not shown) of the vehicle so as to moderate the driving torque applied to the first 103 and third 107 wheels in order to maintain an acute pitch angle.

[0105] In this way, the amount of power supplied to the rear wheels 103, 107 is kept at the appropriate level to maintain the vehicle 101 in a rotated state about the transverse or pitch axis indicated by arrows P and L by balancing the torques acting upon the vehicle 101 about the pitch axis once the desired pitch angle has been achieved. For instance, should, while the vehicle is travelling forwards, the torque exerted by the combination of the normal contact force asserted upon the rear wheels 103, 107 by the ground or surface upon which the vehicle is travelling and the gravitational force effectively pulling the centre of mass of the vehicle downwards exceed the torque exerted upon the vehicle as a result on the motor (not shown) applying a forward drive to the rear wheels 103, 107, the net torque will result in the pitch angle being reduced, thus bringing the longitudinal axis L of the vehicle closer towards alignment with the direction of travel A. In the illustrated mode, this decrease in pitch angle is detected by the gyroscopic sensors 113, and in response to receiving data indicating the monitored pitch angle, the control module 111 controls the motor (not shown) such that the power, or amount of drive, applied to the rear wheels 103, 107 is increased. By applying such drive increases in response to detected pitch angle decreases, and, conversely, decreasing the power applied to the rear wheels when the pitch angle increases or exceeds a desired threshold, and by moderating the magnitudes and rates of change in these applied torques in accordance with the magnitudes and rates of change of monitored vehicle pitch angle changes, the vehicle can effectively sustain a prolonged wheelie mode indefinitely, or as long as desired or commanded by a controlling user.

[0106] The user may desire to maintain a particular pitch angle in this wheelie mode, or it may simply be desired to maintain the vehicle at a pitch angle that is within a given range of acute angles. The control module may be configured to adjust the torque applied by the motor in response to any detected deviation from the desired pitch angle in the first scenario, which may be preconfigured or which may be configurable or changeable by way of user commands. The controller 111 may also be configured to simply maintain any acute angle, or an acute angle within a specific configured range of angles, when the vehicle is travelling in wheelie mode, and it will be understood that this scenario requires less frequent micro-adjustment of the driving torque in response to monitored changes than would be required by the first scenario.

[0107] The centre of mass of the vehicle 101 is indicated at point C. As can be seen, when the vehicle pitch angle is acute, or at any angle greater than 0 and less than 90, the centre of mass will be laterally offset from, namely in front of in the direction of travel, the axes running between the rear wheels 103, 107. Therefore, even in absence of any corrections for variation in the pitch angle during wheelie mode, a forward driving torque should be applied to the rear wheels in order to balance the rotational torque resulting from the centre of mass not being vertically above the axis between the points where the vehicle (and in particular rear wheels 103, 107) are in contact with the ground. In other words, in order to maintain a vehicle 101 in a prolonged state of controlled overbalancing, with the centre of mass offset from the rear wheel access, the vehicle is accelerated forwards. The wheelie mode may also be thought of as the control module 111 controlling the drive applied to the rear wheels 103, 107 so as to continually accelerate the rear wheels 103, 107 under the centre of mass C of the vehicle at such a rate that the rear wheels are perpetually unable to catch up with the centre of mass, and the degree of vehicle rotation about the transverse axis is substantially unchanged.

[0108] Several stages of the wheelie mode are depicted for the first example vehicle at FIG. 2. At each of the stages A-F, vehicle 101 is shown at a position along a straight path, as viewed from the right of the vehicle, together with an indication of the vehicle pitch angle . The six views shown, A-F, represent the vehicle 101 accelerating in the wheelie mode and indicate the position and orientation of the vehicle at equal time intervals, with time increasing in the progression A-F.

[0109] At A, the vehicle is stationary, has a pitch angle of 0 (that is the wheelbase is horizontal and all four wheels, of which two 103, 105, are shown, are in contact with the ground 119), and the motor (not shown) is inactive, that is not applying any torque to the wheels. The centre of mass is indicated by the cross labelled C in the first view. The centre of mass is a distance X.sub.C ahead of the rear wheels 103 and a height Z.sub.C above the surface 119.

[0110] A throttle command is requested by the user via the radio control link to the vehicle to increase torque and thus increase speed. In response to the throttle command, the motor begins to apply a driving torque to the rear wheels between views A and B. Hence in view B the front wheels 105 have just come out of contact with the surface, as the vehicle 101 has rotated a small amount, as indicated by the small pitch angle of around 10, with very little angular acceleration. The driving torque applied to the rear wheels means that the contact force exerted upon the rear wheels by the surface may be resolved into a normal component and a frictional component F.sub.X, as indicated by the respective arrows in view B.

[0111] The wheelie mode rotation giving rise to the elevated pitch angle of the vehicle may be understood by considering the rotation and torques acting about the axis containing the centre of mass indicated by the cross C an anticlockwise torque acting upon the vehicle about this axis results from the friction exerting a positive torque Z.sub.CX.sub.F and the normal force exerting a negative torque X.sub.CN. Neglecting angular acceleration, since the magnitude of this may be assumed to be negligible, then the positive and negative torques should sum to zero, and thus Z.sub.CF.sub.X=X.sub.CN. Since the rotation of the vehicle is not rapid, the centre of mass C does not accelerate upwards quickly, and so the vertical forces sum to zero. Neglecting any aerodynamic effects that may exert forces upwards or downwards upon the vehicle body, can force N exerted by the horizontal surface is equal to the weight of the vehicle MG. Therefore, F.sub.X=MGX.sub.C/Z.sub.C. Therefore, in order to begin the wheelie mode and move the vehicle 101 from stage A to stage B, the minimum force required to be applied by the driven rear wheels is MGX.sub.C/Z.sub.C. In most car-shaped remote-control vehicles, such as that of the present illustrated example, X.sub.C is greater than Z.sub.C, at this stage thus giving rise to a greater threshold force requirement. However, in alternative vehicles to the present example, such as remote-control motorcycles, Z.sub.C may be greater than X.sub.C, thus reducing the force requirement. Generally, and in the present example, the ratio of these distances is of the order of unity, and therefore the horizontal force exerted by the wheels must be of the same order as the weight of the vehicle. Since torque on a wheel with radius R, as indicated in view B, is given by =rF.sub.x, and so =rmgX.sub.c/Z.sub.c. The forward acceleration of the vehicle in the direction of travel, depicted as the left to right direction in the present figure, is equal to F.sub.X/M (where M is the mass of the vehicle), since it is the directional force exerted upon the wheel by the surface that provides the forward acceleration. The vehicle therefore enters into a wheelie when the vehicle accelerates forwards at a rate of gX.sub.c/Z.sub.c. The acceleration is indicated by the incremental distance covered by the vehicle increasing with each successive time increment indicated by the views descending down the figure. The acceleration is continued through the views B-C, C-D, and D-E, and accordingly the pitch angle increases to around 45. In the present example, the control module is configured to maintain a vehicle pitch angle between 35 and 45. For this reason, after the throttle has been applied, that is the motor has provided a driving torque, to the wheels throughout stages B-E, when the control board sensor detects that a pitch angle of 45 has been reached, as illustrated at E, the control module controls the motor to stop applying a driving torque to the rear wheels so as to prevent any further increase of the pitch angle beyond the desired range. It is also envisaged that the control module may be configured or configurable to have this desired range be alterable in accordance with commands received from a user via the remote-control communication system and that it may be configurable in this way or preconfigured to set the range to a desired specific value on-the-fly, or simply set to maintain a controlled wheelie at any acute pitch angle by moderating the applied torque to keep the front wheels elevated but in front of the rear wheels.

[0112] The reduction of the applied throttle between stages E and F is applied by the control module in such a way as to override any throttle, that is acceleration, commands received from a user controlling the vehicle. In this way, the user simply applies the throttle on the control interface (not shown), and in response to the received command the vehicle accelerates accordingly, while moderating the actual degree of drive applied to the rear wheels in order to stay within the desired pitch angle range. It is also envisaged that the wheelie mode may be switched on or off, for example in accordance with a toggle wheelie on or off command received from a controlling user so that the vehicle may selectively accelerate in response to a throttle of command without performing a wheelie as illustrated at FIG. 2, or with the control module continually moderating the applied drive to keep the vehicle in a wheelie.

[0113] When the vehicle is in wheelie mode, the control module may also override the received remote control throttle command in order to meet the conditions to put the vehicle into a wheelie orientation, as described with reference to views A and B above, in cases where the degree of acceleration commanded by a remote-controlling user is insufficient to begin or maintain a wheelie.

[0114] At stage F, the vehicle pitch angle of 40 is within the configured range of acute angles, and so the control module maintains the level of driving torque at its current rate in order to maintain this angle. The control module continues to do this until a deviation in monitored pitch angle is detected by the sensor that will bring the vehicle pitch angle outside of the desired range. The vehicle will therefore control the vehicle to accelerate, while in wheelie mode, for as long as the motor can supply the requisite power to maintain the wheelie attitude.

[0115] It can be seen that the ratio X.sub.C/Z.sub.C decreases as the vehicle pitch angle increases. For example, at stage F this ratio will have a value of approximately three. With reference to the wheelie condition described above, it will be understood that the accelerating force exerted between the wheels and the ground that is required to maintain a wheelie in the pitch angle shown at stage F is approximately three times less than the force required to be applied by the wheels to the ground in order to maintain the 10 degree pitch angle shown at stage B. Therefore, at a given speed of travel, less power is required to maintain a steeper vehicle pitch angle than a shallower one. It will also be understood, however, that the duration for which the vehicle can maintain a wheelie will be limited by the driving power the motor is capable of supplying. Since this power is proportional to the velocity of the vehicle, as the vehicle continues to accelerate, as is necessary for maintaining an acute pitch angle, the requisite power will increase, and at some point will exceed the maximum power output of the motor of the vehicle. In view of the power-to-weight ratios of remote-control vehicles that are currently available, it is envisaged that the upper limit imposed on maximum wheelie duration by vehicle power limitations will be far greater than the duration for which even a skilled remote-control vehicle user could maintain a wheelie attitude using manual adjustments to the throttle control.

[0116] The vehicle 101 may also perform a wheelie as illustrated throughout stages A-F of FIG. 2 after the vehicle is already in motion. Thus in such cases Figure A may represent the vehicle travelling forwards at a constant speed, or accelerating at a rate insufficient to lift the front wheels 105 from the surface 119 when a wheelie command is received, which then causes the acceleration provided by the driven wheels 103 to be controlled by the control module to exceed the wheelie threshold discussed above.

[0117] FIG. 3 shows a second example vehicle 201 according to the invention at various stages in executing a stoppie, front wheelie, or endo. The remote vehicle 201 differs from the first example vehicle in that it has the form of a two-wheeled motorcycle. Aside from the different appearance of the vehicle body 215, and the difference that the vehicle 201 comprises only a first, front wheel 203 and a second, rear wheel 205, the vehicle 201 has motor, braking, steering, and electronic transmission receiving and control functions to those of the first example vehicle 101.

[0118] FIG. 3 is also analogous to FIG. 2 in that it depicts the vehicle at various stages separated by equal time intervals during an exemplary stoppie mode motion.

[0119] At stage A the vehicle is travelling in a forward direction indicated by the arrow X left to right as shown. Between views A and B, the motorcycle 201 enters stoppie mode, either in response to a specific stoppie remote control command, or in response to a braking command that is acted upon the control module (not shown) either by default or when the degree of applied braking commanded by the user exceeds a predetermined threshold.

[0120] The stoppie manoeuvre is begun by the application of the brake to the front wheel 203. This causes a retarding torque to be asserted upon the front wheel, resulting in the rate of forward rotation of this wheel being reduced and consequently, owing to friction between the surface 219 and the front wheel 203, the speed of travel of the vehicle in the X direction being reduced. It will be understood that this condition is analogous to the driving torque applied to the rear wheel in the previous example and the frictional force between the rear wheels and the surface 119 in that example which resulted in acceleration in the forward direction, rather than the backward direction as in the present case. An upper bound to the friction force F.sub.X, indicated for view B is imposed by limiting friction. With a coefficient of static friction between the wheel 203 and the surface 219 represented by a .sub.s, the frictional force satisfies the condition F.sub.X less than or equal to .sub.sN=.sub.smg, where the normal force N, indicated for view B, equals the weight of the motorcycle MG, as in the previous example. Therefore, the condition to perform the stoppie is mgL/H less than or equal to .sub.smg. Therefore, the coefficient of static friction between the tyre of the wheel 203 and the surface 219 must be greater than or equal to the ratio of the horizontal and vertical measurements of the centre of mass of the vehicle as defined in the same way as for the previous example, indicated by the arrows. In other words, the weighting of the vehicle and the friction between the front wheel and the surface must be such that X.sub.C/Z.sub.C less than or equal to .sub.s. In the present example, the coefficient of friction is just greater than one, while the ratio of centre of mass C horizontal wheel offsets height is approximately one, and so a stoppie may be performed. Similar geometrical constraints apply analogously to the friction and weighting of the first example vehicle illustrated at FIGS. 1 and 2.

[0121] The controlled braking applied by the brakes to the forward wheel 203 cause the motorcycle 201 to rotate about the pitch axis of the vehicle such that the centre of mass C continues to travel in the X direction faster than the slowed forward wheel 203, resulting in the elevated pitch angle of approximately equal to 10. It will be understood that, for the purpose of simplicity in the present figure, this angle corresponds to the magnitude of the deviation from 0, or from a flat attitude with front and rear wheels contacting the ground, in both wheelie and stoppie modes, thus the pitch angle of the vehicle is ascribed a positive value in each of the first and second example travelling modes so far described. The respective pitch angles indicated in each of FIGS. 2 and 3 would therefore take negative values when measured from the reference system of the other figure, and so the meaning of acute vehicle pitch angle will be understood to mean a range of angles between and not including either 0 and 90 or 0 and 90, depending on the reference system used.

[0122] Through stages B-D, the forward wheel brake remains applied by the control module which continues to monitor the vehicle pitch angle. Consequently the vehicle continues to decelerate, as indicated by the progressively smaller distances travelled in each equal time increment shown up to stage D. The braking torque also serves to increase the vehicle pitch angle during these stages. In the particular case illustrated, the range of acute angles at which the control module is configured to maintain the vehicle is 30-70. Therefore, when the increase in vehicle pitch angle between stages C and D is detected by the control board sensors, the control module assesses that a vehicle pitch angle, 35, approximately, as shown at stage D, has been reached and the braking is reduced. This results in a smaller degree of deceleration being applied to the vehicle between stages D and E, and also in the vehicle pitch angle being substantially maintained at the same value between these two stages. At all stages during the stoppie while the centre of mass C is displaced along the X axis from the forward wheel, some degree of deceleration is needed to maintain the stoppie attitude. The control module continues to moderate the degree of braking torque applied to the forward wheel so as to keep the vehicle pitch angle within the configured range, until the deceleration has reduced the speed of travel of the vehicle 201 to zero, that is until the vehicle is stationary.

[0123] With reference to FIGS. 4-6, a third example vehicle according to the invention is now described. The vehicle 301 is a four wheeled remote-control car, shown in plan view in FIG. 4. The vehicle comprises components similar to those present in the first example vehicle, including a remote-control receiving antenna 317, first, second, third, and fourth wheels 303, 305, 307, 309, car-shaped body 315 covering the internal components, and a steering system 321 shown by way of partial cutaway of the outer body 315. The vehicle 301 also comprises a control module including orientation sensors (not shown) which may be similar to that of each of the first and second example vehicles. In the present example, the orientation sensors are mounted within the vehicle 301 in such a way as to monitor the absolute value of, and changes to the relative value of, the vehicle roll angle, i.e. rotational displacement about the longitudinal axis labelled L.

[0124] As with most conventional four wheeled vehicles, including remote-control vehicles, the steering arrangement 321 is adapted to turn the front wheels 305, 309 through a steering angle S. Alternatively, other envisaged examples may employ four-wheel steering or rear-wheel steering. The steering system 321 comprises a conventional steering linkage to alter the direction of travel of the vehicle by turning both front wheels in accordance with steering remote-control commands received via the antenna 317. The linkage may conform to a variation of any steering geometry, such as Ackermann geometry, to account for the respective turning radii of the wheels 305, 309 when steering the vehicle through a curved path. The control module is configured to monitor the roll angle of the vehicle and adjust the steering angle applied to at least one of the front wheels 305, 309 in order to maintain an acute vehicle roll angle so as to perform a skiing manoeuvre. The third example vehicle is shown in front view at three stages of performing a skiing manoeuvre in FIG. 5. These three stages, labelled A, B, and C are shown in plan view in FIG. 6 with the vehicle 301 being depicted at various points, in each of the three stages A, B, and C, along a path of travel.

[0125] The vehicle 301 can enter skiing mode starting from a position with all four wheels in contact with the surface or ground 319, via driving over a ramp such that the third and fourth wheels 307, 309 are raised upwards by the incline of the ramp, with the first and second wheels 303, 305 on the other side of the vehicle 301 remaining either off the ramp or lower than the third and fourth wheels 307, 309 owing to the incline of the ramp. The vehicle may also be started in skiing mode beginning from a standstill, by positioning the stationary vehicle 301 on an inclined surface such that the vehicle is tilted about its longitudinal axis, and subsequently controlling the vehicle to drive forwards off of the surface, with the vehicle then maintaining the inclined roll angle after driving off of the tilted surface.

[0126] As a further alternative, the vehicle 301 may enter a skiing position starting from a non-tilted state by way of steering alone. This would involve steering being applied, either through manually input remote-control commands, or by the control module in response to a remote-control command to enter skiing mode, to such a degree that the central vehicle force felt by the vehicle in the reference frame of the turning vehicle is sufficient to move the centre of mass of the vehicle in the radial direction of the turn through which the vehicle is steered, thus causing the third and fourth wheels 307, 309 to be lifted off of the surface 319 so that the vehicle 301 is in a tilted position, as shown at stage A of FIG. 5 for example.

[0127] When travelling in the skiing mode, the control module of the vehicle 301 receives data from the gyroscopic and acceleration sensors so as to monitor the roll angle of the vehicle as shown in FIG. 5. The control module is configured such that, when the vehicle is travelling along a straight path, the centre of mass indicated by the cross labelled C in FIG. 5, is kept vertically above the line between the points of contact between the front 305 and rear 303 wheels and the surface 319. It will be appreciated that, for a given vehicle, there will be a particular angle at which the vehicle centre of mass lies in the same vertical plane as the points or centroids of contact area between the wheels and the road. The control module of the vehicle 301 is configured to maintain this particular roll angle, or a range of roll angles centered around or merely including this characteristic roll angle by automatically applying corrective steering. For instance, when travelling along a straight path as indicated at the portions of the route depicted in FIG. 6 marked with an A, the control module detects any changes in the monitor roll angle that correspond to the deviation from the angle at which the centre of mass C is above the wheels 303, 305, and in response applies a corrective steering adjustment, applying a steering angle directed towards the side of the vehicle towards which the centre of mass has deviated with respect to the line of the wheels 303, 305. In other words, when increases such that the centre of mass, starting from the state shown in view A, moves to the right of the vehicle (that is towards the left hand side of the figure) the control module adjusts the steering angle of the front wheel 305 so that the wheel, and the portion of the vehicle below the centre of mass, moves correspondingly under the centre of mass, thus reducing (p to the value depicted at view A. The same applies correspondingly when a decrease in roll angle is detected, with the control module steering the vehicle to the left, starting from view A, so as to again keep the vehicle balanced with the centre of mass above the wheels that are rolling on the surface. The adjustments made to the steering in order to maintain this balance may be configured to be proportional or otherwise positively related to the deviation in roll angle detected by the on board sensors. Thus a small over-balancing to the right of the vehicle (the left of the figure) would be automatically corrected by a correspondingly small steering angle to the left as viewed when facing towards the direction of travel. A greater or more rapid angular deviation from this balanced position, on the other hand, which may for example be caused by undulations in an uneven driving surface or wind or other aerodynamic effects will require a larger corrective adjustment to the steering angle in order to bring the centre of mass back into its balanced position.

[0128] When the vehicle is travelling along paths that are not straight, such as those shown at portions B and C of FIG. 6, the vehicle 301 must be maintained at a different roll angle from that depicted at Figure A in order to remain in a balanced skiing orientation. This may be understood in view of the sections of the path marked B and C in FIG. 6, which represent, for the sake of simplicity, arcs of circles with different radii. The radius of curvature of the path at section B is greater than that of the path at section C. In the present example, the vehicle is envisaged as traversing this path with unchanging scalar speed, with the velocity changing only as a result of the direction of travel being changed as the car is steered along the path. These changes in the direction of travel, and thus in the vehicle velocity, require a centripetal acceleration towards the centre of each notional circle defined by the arc-shaped path section at each of B and C. This acceleration is indicated by the arrow A for the vehicle 301 at each of these stages shown.

[0129] The shape of the path shown in FIG. 6 is arbitrary, and a user controlling the vehicle via remote-control may steer the vehicle along any route as chosen by the user, as is possible with conventional remote-control vehicles. The vehicle 301 is able to maintain a skiing orientation by adjusting the roll angle at which the control module is configured to maintain the vehicle by way of corrective steering adjustments in accordance with the path taken by the vehicle as controlled by a user, taking into account the centripetal acceleration and the changes thereto that this may require. For example, the balanced roll angle is approximately 45 as shown in view A, when the vehicle is travelling in a straight line as shown in FIG. 6. The horizontal offset perpendicular to the direction of travel between the centre of mass and the line between the points of contact between the surface 319 and the wheels 305, 303, Y.sub.C is equal to zero.

[0130] In view B of FIG. 5, however, the user is applying a left hand steer to the vehicle via remote-control, and so the vehicle is accelerating centripetally to the left of the direction of travel. More specifically, the wheels in contact with the ground are accelerated in the direction indicated by arrow a. Considering torques acting upon the vehicle about the centre of mass, this results in a torque about the longitudinal axis of the vehicle being exerted in the anticlockwise direction as viewed in FIG. 5. Therefore, unless a balancing torque is applied, the vehicle will continue to roll in the anticlockwise direction, thus increasing (p beyond its desired value or range of values, and potentially rolling the vehicle onto its roof. In order to provide this balancing torque, therefore, the control module detects the turn being commanded by the user, either by way of interpreting the steering commands themselves, monitoring the steering angle of the front wheels themselves, or monitoring the centripetal acceleration using the control board. Using this data, the control module adjusts the balancing roll angle, which for the present example vehicle corresponds to 45 when the vehicle is travelling in a straight line, so that the centre of mass is retained with a horizontal offset perpendicular to the direction of travel Y.sub.C to the left of the wheels 305, 303. The control module automatically selects an optimum or balancing roll angle, as shown in Figure B, wherein this offset Y.sub.C means that a gravitational torque is exerted about the axis between the wheel contact points, or rather a normal force torque is exerted by the surface 319 upon the wheels 305, 303 resulting in a clockwise (as shown in FIG. 5) torque about the centre of mass with the same magnitude of the torque due to the centripetal acceleration a. In this way, the control module shifts the centre of mass offset so as to balance the centrifugal force felt by the car in its own accelerating reference frame when the car is steered around a curve by the user. In this way, a user can steer the vehicle 301 along any arbitrary route, and the control module will supplement the manually controlled steering with automatic, small scale, rapidly applied micro-adjustments to the steering in order to maintain the skiing orientation at all times when the skiing mode is active.

[0131] As shown in view C in FIG. 5 and at section C of the path shown in FIG. 6, the vehicle is steered more sharply, that is around a circular arc having a smaller radius than that of B, and the centripetal acceleration of the wheels is directed towards the right of the vehicle. Correspondingly, the control module detects this and shifts the balancing roll angle so that the centre of mass is offset to the right of the wheel line by a distance Y.sub.C in order to keep the vehicle 301 balanced on two wheels 305, 303. Thus the roll angle maintained at stage C is consequently larger than the balancing roll angle required for straight paths shown in view A.

[0132] With reference to FIGS. 7 and 8, a fourth example vehicle, configured for a fourth example travelling mode is now described. FIG. 7 shows two views, A and B, each showing the fourth example vehicle 401 at several stages of a ramp jump. View A depicts the motion of the vehicle 401 jumping off of a ramp 423 in an unaltered travelling mode, whereas view B depicts the same jump performed with the fourth, self-stabilising jumping mode activated.

[0133] The incline profile of the ramp 423 is such that, when the vehicle 401 drives up the ramp at speed, the vehicle is brought quickly into a steeply inclined position by its traversal of sharply curved section 423a. The vehicle then comes to an elongated section of the ramp that is straight, meaning its incline in the vertical plane in which the vehicle body is travelling is constant along this section. By traversing this section, the vehicle body is imparted with no or negligible angular momentum before the vehicle leaves the ramp and begins the jump. In absence of any angular momentum, the vehicle body does not rotate about its pitch axis during the effective free fall of the jump, and remains in the sharply inclined orientation indicated by pitch angle throughout its substantially parabolic trajectory towards the ground 419. It can be seen that, in this case, the vehicle 401 will land, at the end of its trajectory, upon only its rear wheels 403, and thus a damaging impact may be suffered by the vehicle.

[0134] In order to mitigate this effect, the control module (not shown) of the vehicle 401 may be brought into a self-stabilising jump mode, wherein the orientation of the vehicle 401 during the jump is automatically adjusted so that the landing involves all four wheels 403, 405 making simultaneous contact with the ground. In this mode, as illustrated at view B, immediately after the rear wheel 403 (and its corresponding other rear wheel, not shown) comes out of contact with the ramp 423, the vehicle 401 is effectively in free fall. In practice, this will not be a state of perfect free fall since some external forces such as aerodynamic effects will be exerted upon the vehicle. However, these effects should be negligible, and so the state of free fall will be readily detectable by the accelerometer integrated with the control module (not shown).

[0135] When the control board detects that this effective free fall state has been entered, by monitoring that the contact force exerted by the surface 419 or the ramp 423 upon the vehicle 401 has ceased, the control module uses the monitored pitch angle as measured by the on-board sensors, and begins a corrective adjustment accordingly. In the present case, the angular momentum about the pitch axis of the vehicle body 415 is zero or negligible.

[0136] The wheels 403, 405 will likely still be spinning, even if not being actively driven, having been rolling immediately before the vehicle left the ramp 423. In the case that the wheels do remain spinning at the beginning of the jump, the total angular momentum of the vehicle I.sub.1 will be directed anticlockwise as shown by the arrow, by virtue of the angular momentum of the spinning wheels alone. Upon detecting that the vehicle pitch angle .sub.1 is inclined away from the desired pitch angle, that is an acute angle close to 0, having a value of approximately 60, the control module applies a torque in the reverse rolling direction upon the wheels 403, 405. This angular acceleration .sub.1 is in the clockwise direction as viewed in FIG. 7. In the case that the wheels 403, 405 are spinning at this stage, the angular acceleration .sub.1 may be applied simply by applying a braking torque, namely activating the brakes on the spinning wheels, so as to retard the forward motion. The effect of this is that the angular momentum of the wheels is reduced. However, since the angular momentum of the vehicle 401 as a whole must be conserved, the angular momentum, and in particularly the angular velocity of the vehicle body itself is increased, to a non-zero value, in the anticlockwise direction as viewed in FIG. 7. In other words, braking the spinning wheels in mid-jump causes the vehicle body 415 to begin rotating forwards, thereby reducing the vehicle pitch angle .

[0137] The control module is configured to apply the clockwise torque to the wheels, and in the present example vehicle, which is a four-wheel drive remote-control car, to all four wheels, to such a degree that the desired orientation of a substantially 0 degree pitch angle is achieved during the jump. Thus, when the vehicle leaves the ramp, with wheels spinning at an angular velocity and having a moment of inertia I.sub.w, the angular momentum of the entire vehicle is equal to that of the wheels, so that I.sub.1=I.sub.w.sub.w.

[0138] The angular acceleration applied to the wheels is calculated by the control module in accordance with the known moment of inertia of the vehicle body I.sub.B and the monitored vehicle pitch angle .sub.1 and angular velocity of the body .sub.B. Should the angular acceleration .sub.1 be sufficient to bring the angular velocity of the wheels .sub.w to zero, that is sufficient to stop the wheels spinning, but insufficient to bring the vehicle body to a 0 degree pitch angle during the duration of a typical ramp jump, then the control module may additionally apply an additional reverse, or clockwise torque to the wheels by engaging the motor in a reverse gear so as to provide further clockwise angular acceleration to the wheels. As can be seen in view B of FIG. 7, the result of the corrective torque being controllably applied by the control module to the wheels is that the vehicle body is rotated forward, owing to its now non-zero angular momentum.

[0139] In the indicated portion of the jump, the angular momentum of the entire vehicle I.sub.2, which is the same, owing to conservation of angular momentum as the starting angular momentum I.sub.1, is equal to the angular momentum in the forward, anticlockwise direction of the vehicle body minus the angular momentum in the reverse, clockwise direction of the wheels. Depending on the initial angular velocity of the wheels and the angular acceleration .sub.1 applied to them, this value may be positive, negative, or zero. The control module selects the appropriate value, in accordance with the known moment of inertia I.sub.w of the wheels to provide the vehicle body with sufficient angular velocity .sub.B to bring the vehicle 401 to the desired attitude during the jump.

[0140] At the antepenultimate stage of the jump depicted in view B, the angular momentum .sub.B of the body in the anticlockwise direction as viewed has resulted in the pitch angle of the vehicle changing to a small negative value, approximately 10, having rotated past a level attitude. In response to the detection by the control board sensors that the pitch angle has exceeded the configured range of acute angles, which in this case is any angle with an absolute value greater than 0 and less than or equal to 5, or in some configurable modes, in response to the earlier detection that the initially imparted rotation has brought the pitch angle within this desired range, a further angular acceleration .sub.2 is applied to the wheels, by the motor. Thus, in order to slow, and if necessary reverse, the rotation .sub.B of the body so that the orientation of the vehicle is within the desired range, the motor applies a torque to the wheels so as to increase their angular velocity in the forward rolling direction, that is anticlockwise as viewed in B. As can be seen, in the penultimate stage depicted in view B, the rotation of the vehicle has been reversed by the angular acceleration of the body resulting from the wheels being accelerated by .sub.2, so that the vehicle pitch angle is brought back to a value of approximately 5.

[0141] Between the penultimate stage and the final stage illustrated in B, very little rotation has occurred to the body 405. This is because the control module calculates and applies an appropriate degree of acceleration .sub.2 so as to make only slight, corrective adjustments, since the pitch angle of the vehicle is close to the desired range at this point during the jump. This relatively subtle degree of rotation, in comparison with that seen between the first four stages of the jump shown may also be seen between the antepenultimate and penultimate stages of the jump. This is a result of the control module moderating the degree of torque applied so as to optimally stabilise the vehicle attitude as quickly and efficiently as possible.

[0142] In this way, at the final stage of the jump depicted in B, the pitch angle of the vehicle is zero. Once this has been achieved, the control module monitors the pitch angle as well as the angular velocity about the pitch axis of the vehicle. Upon determining that the pitch angle is within the desired range and that the angular velocity .sub.B in the clockwise direction, although small, should be brought to zero in order to keep the vehicle at this pitch angle, a small corrective torque is applied to the wheels in the clockwise direction, accelerating the wheels by .sub.3, the magnitude of which is calculated by the control module to bring the body of the vehicle 415 to a non-rotating state. Since, in the present case the vehicle body 415 had no angular momentum upon leaving the ramp at the beginning of the jump, conservation of angular momentum will mean that the angular velocity, that is the rotation rate, of the wheels .sub.w is the same at the point where the vehicle lands as it was when the vehicle left the ramp 423.

[0143] In some examples, the vehicle 401 may have the capability to receive or be configured with user-defined, or automatically detected target landing vehicle pitch angles. This capability would be useful, for example, in cases wherein the surface 419 upon which the vehicle would land at the end of a jump is inclined about the traverse axis of the vehicle. It is envisaged that a user may send a pitch angle parameter to the vehicle via remote-control, corresponding to the inclination of the landing surface 419, or possibly that additional sensors such as optical sensors on the vehicle may detect the inclination of the landing surface and adjust the target pitch angle or target range of pitch angles accordingly.

[0144] The fourth example vehicle is shown executing the self-stabilised jump mode in a different form of ramp jump in FIG. 8. View A in this figure depicts the vehicle 401 at multiple stages of the jump with the self-stabilising jump function switched off. The ramp 823 from which the vehicle performs the jump by being launched into a jumping trajectory differs from that of the previous figure in that the portion of the ramp 823a leading to the launching edge is curved upwards. As a result, when the vehicle 401 drives off of this ramp, it is imparted with an initial non-zero amount of angular momentum in the clockwise direction as viewed. It can be seen that, without the aid of self-stabilisation by the control module, the vehicle rotates throughout the duration of the jump shown at view A, and this continued rotation leads the vehicle 401 to land in a potentially damaging manner, without any wheels in contact with the ground. In each of the cases shown at A and B, the initial total angular momentum of the vehicle 401, I.sub.1 is non-zero and in the anticlockwise direction, and is equal to the angular momentum of the body I.sub.B.sub.B plus any angular momentum of the wheels, which will probably be in the anticlockwise direction also, I.sub.W.sub.W. Upon detecting that the vehicle 401 is mid-jump, that is in effective free fall, the control module detects both the angular rotation rate .sub.B of the body, since the control board is mounted within the body, and the pitch angle of the body, which is approximately 70. In response, the control module calculates the appropriate torque to apply so as to accelerate the wheels by .sub.1 backwards. Considering rotation in the anticlockwise direction as having a positive value, this acceleration .sub.1 causes .sub.W to be reduced, and since the angular momentum I.sub.1 of the vehicle cannot change when the vehicle is in mid-air, the angular momentum of the body, and therefore the angular velocity B of the body, as the moments of inertia I are fixed, must increase in the anticlockwise direction.

[0145] As can be seen in view B this results in the clockwise rotation of the body 405 being slowed, and eventually reversed, so that the body is rotated towards the desired level attitude wherein the vehicle pitch angle has an absolute value less than or equal to 5. Although the control module may be programmed to achieve this in a number of variations upon the corrective stabilisation mode, in the present case the acceleration applied to the wheels initially .sub.1 is relatively great so as to quickly reverse the undesired rotation and impart rotation towards the desired vehicle pitch angle.

[0146] As indicated by the progressively smaller changes in vehicle pitch angle between the equal time increments of the stages illustrated, the control module, throughout the subsequent part of the jump following the initial application of .sub.1, applies a torque accelerating the wheels by .sub.2 in the forward direction, with .sub.2 having a relatively small value compared with that of .sub.1. This causes the forward rotation initiated by the application of .sub.1 to be slowed. Once the desired vehicle pitch angle of 0 has been reached, as shown at the penultimate illustrated stage, a final, smaller still torque is applied to the wheels to accelerate them .sub.3 slightly in the forward rolling direction, that is anticlockwise as viewed, so as to halt the rotation of the vehicle body 415.

[0147] In contrast to the example jump shown in FIG. 7, in the present figure the anticlockwise angular frequency of the wheels will be less than at the final stage of the jump than at the beginning of the jump. Indeed, depending on the rotational rates involved, the wheels may be rotating backwards, that is clockwise as shown, at the end of the stabilisation process. This is because angular momentum has been removed from the initially rotating vehicle body and imparted into the wheels by the time the vehicle lands upon the surface 419.

[0148] In addition to the four examples described above, other example remote-control vehicles are envisaged that are similar to the preceding examples but differ in the number of wheels they comprise. For instance, a two-wheeled model motorcycle or a tricycle may readily be configured with a control module according to the fourth example vehicle 401 so as to perform a self-stabilising jump.

[0149] Likewise, a motorcycle or tricycle may be configured in accordance with the first described example vehicle 101 in order to perform a controlled wheelie travelling mode. Equally, three or four wheeled vehicles may be configured to perform the second example travelling mode described above. Indeed, the number and arrangement of wheels is arbitrary as long as the configuration of the vehicle as a whole lies within the geometrical constraints required for performing the aforementioned described example travelling modes.

[0150] It is also envisaged that any one vehicle may be configured with one or more control modules programmed to enable the vehicle to perform any of the first, second, third, and fourth described travelling modes, or any combination thereof, since the presence of one of these capabilities in a vehicle does not necessarily preclude the presence of any of the others.

[0151] An example arrangement of a receiver-control board interface which may be comprised by any of the examples described herein is shown schematically in the connection diagram of FIG. 9. A user operating a transmitter 959 to control a vehicle causes a radio signal 961 to be transmitted by the transmitter. The signal 959 is received by the receiver 951 of the vehicle. The receiver 951 is connected via wired connections 955 to the control board 911. The control board is connected to the other vehicle components via wired outputs 963. However, it is also possible in some examples, wherein the control board is separate from the remote-control vehicle, for the control board to be in wireless communication with the receiver and the other outputs via which the vehicle is controlled.

[0152] The control signal that is received by the receiver 951 is passed through the control board 911, whereupon the signal is altered, if necessary, in accordance with data received from sensors in the vehicle, in order for the vehicle to travel in a controlled mode as described above. The control signal is then passed via the outputs 963 to the electronic speed control, in order to control the torque applied by the brake or motor to the vehicle wheels, or to the steering system.

[0153] The control board may be configured with external programming containing computer-executable instructions for performing the wheelie, stoppie, skiing, controlled jump and flip manoeuvres described above. The introduction of such programming is illustrated in the present example as being performed via a USB interface 957 with the control board 911. However, it is envisaged that the control board may be programmed or configured by way of any sort of interface, including a wireless connection.