EP3717085B1

EP3717085B1 - Remote control vehicle

Info

Publication number: EP3717085B1
Application number: EP18811615.6A
Authority: EP
Inventors: Nicholas Moss
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-11-30
Filing date: 2018-11-21
Publication date: 2024-02-28
Anticipated expiration: 2038-11-21
Also published as: JP7272674B2; JP2021504090A; GB2568912B; CN111655346A; US20200368629A1; GB2568912A; GB201719934D0; CN111655346B; WO2019106339A1; EP3717085A1

Description

Remote-control vehicles, such as model radio control cars, trucks, and motorcycles have been in existence for many years. They are generally powered either by internal combustion engines or electric motors. The vehicles are typically controlled by an operator using radio control equipment, which chiefly comprises left and right steering controls, and speed controls, conventionally including throttle and brake controls. Some electric powered cars, and to a lesser extent, internal combustion powered cars, also have reverse operation, meaning that they can be driven backwards as well as forwards by the engine or motor.
As remote-control vehicles have developed, and their engines and motors have become more powerful, it has become possible for some vehicles to provide enough power to lift the front end of the vehicle off the ground so that it performs a "wheelie". With full sized vehicles, the performing of wheelies is generally restricted to two-wheeled vehicles such as bicycles and motorcycles, owing to the power-to-weight ratio required to perform this manoeuvre. Riders of bicycles and motorcycles are also at a further advantage over drivers of cars, for instance, with respect to performing wheelies, because it is possible for the rider of a motorcycle or bicycle to shift their weight with respect to the centre of mass of the cycle so as to assist in tipping it.
Full sized motorcycles and bicycles are also capable of performing "front wheelies", a manoeuvre commonly known as an "endo" or a "stoppie". This trick is performed by lifting the rear wheel of the cycle by way of careful application of brake pressure to the front wheel. With full sized vehicles, a driver progressively applying the front brake in combination with leaning forward to shift their centre of mass closer to the front wheel can lift and maintain the rear wheel in an elevated position. With full sized vehicles, stoppies, like wheelies, are generally restricted to bicycles and motorcycles rather than cars.
As the power-to-weight ratio of the model vehicles that are available has improved, and as there has been a general tendency for the centre of mass of model vehicles to be higher, it is possible in many cases to operate such vehicles so as to lift the front of the vehicle off the ground for extended periods. Such stunts take advantage of the high level of torque available from modern engines and motors. However, it remains extremely difficult if not impossible for an operator to maintain the vehicle in a wheelie attitude without some form of mechanical stabilisation. Most often, this stabilisation takes the form of a "wheelie bar", comprising a support structure mounted on or around the rear of the vehicle and having one or more small wheels that contact and roll along the ground when the vehicle reaches the wheelie attitude. A wheelie bar thereby prevents the vehicle from lifting its forward end any further. Thus, as long as sufficient driving power is maintained, conventional remote-control vehicles may hold a wheelie attitude by effectively running on one or more rear main wheels and the one or more small wheels of a wheelie bar.
Front wheelies on remote-control vehicles are generally less controlled, since front-mounted support structures equivalent to rear-mounted wheelie bars are generally not used. Therefore, operators attempting to perform a front wheelie or stoppie with a remote-control vehicle commonly have difficulty applying the correct amount of brake pressure to the front wheel so as to cause the rear wheel or wheels to lift without the vehicle over-rotating and performing a full forward somersault. Likewise, the power-to-weight ratios of some remote-control vehicles is so great that an operator can cause a remote-control vehicle lacking a wheelie bar to execute a complete somersault by opening the throttle.
There is therefore a need to provide a remote-control vehicle capable of performing these manoeuvres in a controlled manner.
WO 2016/073896 A1 discloses a self-righting model vehicle adapted to perform a self-righting manoeuvre when it is inverted, using a righting mechanism to rock the inverted model vehicle and tumble it upright.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided 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. The vehicle is thus capable of reaching and maintaining a wheelie attitude while moving, without requiring a wheelie bar. The vehicle may achieve this by using a stabilisation system that can include a gyro stabilisation system combined with one or more accelerometers to automatically control the amount of power provided by the engine or motor of the vehicle so as to perform a controlled wheelie. Thus by implementing a stabilisation system used on the pitch axis of the vehicle, the torque applied to the wheels by the engine, motor, or brakes may be controlled in a way programmed so that the car may perform a wheelie or stoppie, wherein the braking or driving power is automatically adjusted so as to hold the vehicle in either a wheelie or a stoppie attitude for as long as commanded by the operator via a remote-control system, such as a radio control system, or an optical or infrared system.
In performing a wheelie or a stoppie, the attitude of the vehicle need not be maintained necessarily by balancing the weight of the vehicle, that is by shifting the centre of mass of the vehicle to be vertically over the first wheel. When fullsize motorcycles ridden by human drivers perform wheelies or stoppies, for example, the rider may move their body so as to change their riding position and thereby shift their weight in order to balance the vehicle at a tilted orientation or otherwise to assist in achieving or maintaining the wheelie or stoppie. Conversely, the present invention may facilitate performing a wheelie where the remote-control vehicle substantially comprises parts that may not be moved in order to provide an assistive weight shift. Rather, the acceleration caused by the traction or friction between at least the first wheel and the surface upon which the vehicle is travelling may allow the vehicle to be kept at an acute angle. In other words, the vehicle may be kept at a tilted pitch angle, with the second wheel raised, by way of applying a controlled acceleration to the vehicle through the first wheel.
Maintaining the vehicle pitch angle within a range of acute angles may comprise the control module correcting the pitch angle of the vehicle at a given time or for a given period towards a specified value. It may also comprise, rather than maintaining a single acute angle, permitting some variation of vehicle pitch angle during acceleration, with the control module configuring the braking and/or throttle applied by the vehicle so as to prevent the vehicle pitch angle reaching a value outside a specified range of acute angles.
Acceleration as recited above may refer to a change to the speed of the vehicle in the direction of travel, and thus may include both speeding up and slowing down.
The longitudinal axis of the vehicle may be understood as the line running fore and aft through the vehicle, aligned in the same vertical plane as the direction of travel. Thus the axis may be pictured as extending directly from the front to the back of the vehicle. The term longitudinal axis is used, when defining the offset between the first and second wheels as recited above, to refer to the direction in which the axis is oriented, rather than any particular translational position of the axis within the vehicle. That is, the first and second wheel need not necessarily be aligned in the same longitudinally aligned plane in all embodiments. The relative positions of the first and second wheels in the yaw axis and the pitch or lateral axis of the vehicle may be different in different embodiments, or may be the same, depending in part upon the arrangement of the wheels.
The vehicle pitch axis may be understood as being the lateral or transverse axis of the vehicle, in accordance with the generally accepted definitions of vehicle principle axes. The pitch angle therefore may refer to the orientation about the pitch axis, that is about a horizontal axis that is perpendicular to the direction of vehicle travel, or to the longitudinal axis of the vehicle. The vehicle pitch angle, in other words, may be understood as the angle between the direction of travel, which is typically substantially the same as the slope of the ground or surface on which the vehicle is travelling in the same vertical plane as the vehicle longitudinal axis, and the longitudinal axis of the vehicle. It may also be understood as the angular displacement between the longitudinal axis of the vehicle and the horizontal plane, that is the plane perpendicular to acceleration due to gravity. An acute angle may be understood as any angle that is greater than but not including 0°, and is less than but not including 90°. An acute vehicle pitch angle thus may represent an attitude wherein the second wheel is raised, and offset from the first wheel in the direction of travel. That is, wherein the vehicle pitch angle is greater than 0°, where 0° represents an attitude at which the second wheel is in contact with the ground or surface and is not raised, and an angle less than 90°, and wherein 90° represents vertical attitude, or an attitude at which the second wheel is vertically above the first wheel.
Advantageously, the control module of the vehicle may be configured to adjust the torque applied to the first wheel so as to stabilise the vehicle pitch angle while causing the vehicle to accelerate. Thus the control module may be programmed to implement a feedback system wherein it controls the forces acting upon the wheels by either the brake or the engine or motor so as to reactively reverse any changes to the vehicle pitch axis as monitored by the sensor. The control module may therefore be configured to increase the applied torque in response to a decrease in the monitored pitch angle, for example, and conversely to decrease the applied torque in response to an increase in the monitored pitch angle. In this way, the vehicle may sustain an acute vehicle pitch angle during a period of acceleration, or while the vehicle is accelerated. In this condition, the vehicle pitch angle may be acute while the vehicle accelerates, owing to the stabilisation provided by the control module. In other words, the control module may cause the vehicle pitch angle to be acute such that the second wheel is raised, while causing the vehicle to accelerate.
Typically, the adopting of an acute vehicle pitch angle involves the second wheel, and in some embodiments further wheels, being held at a raised position, or at a position where those wheels are not in contact with the ground. To accomplish this, the control module may be 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. The second wheel being raised may be understood as the second wheel being elevated or raised up above the surface, or from the surface, that is removed from contact with the surface on which the vehicle is travelling. Thus, to enter a wheelie attitude, the vehicle may be configured to momentarily, or for a predetermined or configurable period, to increase the torque applied to the first wheel to such a degree that the traction or friction between the first wheel and the ground or surface combined with this increased torque causes the first wheel to change speed in the direction of travel at a different rate to the resulting change in speed of the vehicle as a whole, or as the geometric centroid or centre of mass of the vehicle. In other words, the increased torque may speed up or slow down the first wheel so as to accelerate it, relative to the vehicle as a whole, in the direction of travel towards the second wheel and causing the vehicle to rotate. This rotation is about the transverse or pitch axis, and can result in the second wheel being lifted off the ground.
In this way, the control module may be 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.
Once the wheelie or stoppie mode has been initiated by the control module bringing the vehicle pitch angle to an acute angle, the control module may be programmed to maintain the achieved acute pitch angle, or maintain a different acute pitch angle, or indeed a range of acute angles by way of corrective torque adjustments. Thus the control module may be configured to maintain an acute vehicle pitch angle by adjusting the applied torque so as to counteract variations in the monitored pitch angle.
Typically, 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. In this way, the pitch angle of the vehicle is controlled so as to not reach or exceed the angle at which the vehicle centre of mass is above the first wheel, or above the rotational axis of the first wheel, or above the axle between the first wheel and a parallel wheel. That is, the control module is typically configured to perform the wheelie or stoppie manoeuvre while accelerating the vehicle in or against the vehicle travel direction, thus not balancing the vehicle over the first wheel, but rather adjusting the torque applied to the first wheel so as to maintain an equilibrium. This equilibrium is reached, or maintained, between, on one hand, the gravitational torque exerted on the vehicle about the first wheel as a result of the vehicle centre of mass being horizontally offset from the first wheel, and, on the other hand, the reaction torque exerted on the vehicle about the first wheel as a result of the torque exerted by the device upon the first wheel. To maintain this equilibrium, the vehicle is typically accelerated in a single direction, parallel or antiparallel to the direction of travel, as a result of the torque applied by the device to the first wheel, assuming sufficient traction or friction between the surface of travel and the first wheel.
In some embodiments, the first wheel is a forward wheel and the second wheel is a rear wheel, and 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. In this way, in order to control the vehicle to perform a stoppie, the control module can cause the brake to be applied to the first wheel so as to lift the rear wheel while decreasing the speed of the vehicle, thus achieving an acute vehicle pitch angle. The control module may be programmed to maintain thereafter the vehicle at an acute pitch angle while accelerating the vehicle against the direction of travel. This may continue until the vehicle has come to a halt, or it may be terminated while the vehicle is still travelling. The stabilisation system of the vehicle may therefore have the capacity to reduce the brake applied to the first wheel, or indeed increase it as appropriate, so that the remote-control car, motorcycle, or other form of vehicle does not flip forwards under heavy braking but rather performs a controlled stoppie or endo.
In some embodiments, the first wheel is a rear wheel and the second wheel is a forward wheel, and 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. Therefore, rear wheel-driven remote-control motorcycles, cars, and other types of vehicles may perform wheelies by the control module moderating the drive applied to one or more of, or each of, the rear wheels.
In some embodiments, the vehicle is adapted to be able to perform both wheelies and stoppies. In such embodiments the device may further comprise a device adapted to apply a torque to the second wheel, and the control module may be 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 with an a range of acute angles. The device for applying the torque to each of the first and second wheels may be different respective devices, or the vehicle may be configured such that one device, or connected devices, apply the required torque to each of the first and second wheels. The number of wheels on the vehicle may differ between different embodiments, such that the vehicle may take the form of a bicycle, tricycle, car, or truck, for instance. Each of these examples may be adapted to be able to perform one or both of the wheelie and stoppie modes. For example, for remote-control motorcycles, the first and second wheel may be in a linear arrangement aligned with the longitudinal axis of the vehicle. In fourwheeled vehicles, the device may be adapted to apply torque to either or both of the pair of forward wheels and the pair of rear wheels.
For two-wheeled, motorcycle-like arrangements, the torque applying device may be adapted to rotationally accelerate or decelerate either or both of the forward and rear wheels.
In some embodiments, the vehicle comprises a third wheel. In some of these embodiments, the vehicle is configured to apply a torque to the third wheel accordingly when a torque is applied to the first wheel. Thus, in tricycle-like three-wheeled arrangements, both rear wheels may be adapted to comprise a device for driving them so as to perform a wheelie and/or the single forward wheel may comprise a brake adapted to apply a slowing torque moderated to perform a stoppie.
In some three-wheeled embodiments, the vehicle may include a second device for applying the torque to the third wheel, or the same device as adapted to apply a torque to the first wheel may apply a torque to both the first and third wheels.
In some embodiments, the vehicle further comprises a fourth wheel. Thus the first wheel may be one of a pair of wheels, namely left- and right-side wheels, connected to the first axle, and the device may be adapted to apply a torque to the axle itself or to both of the pair of wheels, typically to an equal or a substantially equal degree.
Additionally or alternatively, the second wheel may be one of a pair of wheels, and may be connected to an axle together.
In other words, the vehicle may comprise two wheel sets offset from one another along the transverse, that is the lateral or pitch, axis of the four or more wheeled vehicle, such as a car. Each of these sets may comprise a first and second wheel. The four wheels may be in a regular quadrilateral arrangement, for example with the distance between the first wheels of each set being the same as the distance between the second wheels of each set, or these distances may be different, for example the distance between the rear wheels may be greater than that between the forward wheels.
Typically, the sensor comprises an orientation sensor and a rotation sensor. More preferably, the orientation sensor comprises an accelerometer configured to monitor an orientation of the vehicle with respect to the direction of acceleration due to gravity. Thus the absolute orientation, that is the orientation of the vehicle relative to the vertical axis, may be monitored. In particular, the sensor may monitor the vehicle pitch angle with respect to the vertical direction.
Typically, the rotation sensor comprises a gyroscopic sensor. For some years, miniature gyroscopes have been used in conventional remote-control vehicles on the steering axis, so as to provide stabilisation to cars and make them easier to drive. In some cases, these may be configured to make "drift" car driving possible for non-expert operators. Gyros have also been used to stabilise model bicycles and motorbikes so that these vehicles remain upright when travelling and fall over less frequently. Such sensors may monitor the variation in their relative orientation. It is preferable that, rather than including a gyroscopic sensor alone, the vehicle includes both an accelerometer and a gyroscopic sensor. This is advantageous because gyroscopic sensors are reactive to changes in orientation, and thus are suitable for stabilising a system. However, combining monitored data from both gyroscopic and accelerometer sensors allow the detected changes in orientation to be referenced against the vertical direction or the horizontal plane. Thus the gyroscopic sensor and the accelerometer may have their readings combined so as to monitor changes in absolute orientation, thereby allowing the vehicle pitch angle and changes thereto to be calculated.
Typically, the control module is configured to control the torque so as to accelerate the vehicle while maintaining the vehicle pitch angle within a range of acute angles upon receiving a remote-control command to accelerate the vehicle. In such embodiments, a user operating the remote-control vehicle may transmit a remote-control command to either apply the brake or the throttle of the vehicle, so as to slow it down or speed it up respectively. In response to receiving these commands, the control module may moderate the actual braking or motor acceleration applied by the vehicle so as to perform a stoppie or a wheelie automatically. In some embodiments, wheelie and stoppie commands are received and interpreted by the control module as commands that are distinct from or separate from braking and acceleration commands, and so an operating user may cause the vehicle to perform a wheelie or a stoppie independently of issuing braking or accelerating commands.
The control module may be programmed to bring the vehicle within a particular predetermined range of angles. In some embodiments, the range of acute angles within which the control module is configured to maintain the vehicle is 30° to 70°. In some embodiments, the range of acute angles is 40° to 60°.
In some embodiments, the control module is configured to maintain the vehicle pitch angle at a substantially constant acute angle while accelerating the vehicle. Although some variation in pitch angle is expected during the performing of a wheelie or stoppie, the control module may be programmed to stabilise the vehicle so that the vehicle pitch angle is corrected towards a constant acute angle.
In some embodiments, the vehicle is adapted to receive a remote-control command including a pitch angle parameter, wherein the control module is configured to maintain the vehicle pitch angle at an acute angle corresponding to the pitch angle parameter. In such embodiments, the pitch angle parameter could be preconfigured, either as part of the programming of the vehicle or control module, or it may be received via a remote-control command received by the vehicle while it is in use. The parameter could be transmitted to the vehicle so as to set or adjust the maintained acute vehicle pitch angle while the vehicle is travelling. In some embodiments, the pitch angle parameter is representative of a desired range of acute angles in which the control module is configured to maintain the vehicle during the performance of a wheelie or stoppie.
Although the geometry discussed thus far refers chiefly to wheelie and stoppie modes being performed on surfaces that are substantially level, that is perpendicular to the vertical axis, the vehicle may also be capable of performing these modes upon surfaces that are inclined. In such cases, when the vehicle is travelling uphill or downhill on a surface that has a component of inclination about the pitch axis of the vehicle, the control module may be configured to adjust the range of acute angles at which it is configured to maintain the vehicle pitch angle so that in either case the vehicle performs a wheelie or stoppie, with the second wheel raised above the ground, in accordance with the direction of vehicle travel having some angular displacement from the horizontal plane.
Although the vehicle will typically be controlled so as to be accelerated along a straight path so as perform a wheelie, it is also envisaged that an operator may issue steering commands to the vehicle while this stunt is being performed, thereby directing the vehicle along a path that is not straight and comprises curves. Thus in some embodiments the vehicle is adapted to allow the vehicle to be steered while the vehicle pitch angle is maintained within a range of acute angles. This may be achieved by way of differential motors or braking adapted to apply different degrees of torque to each of the left and right driven wheels in a car, for example. The vehicle may, in such embodiments, be configured to combine steering commands with the pitch angle-maintaining output of the control module, in order to keep the vehicle at a wheelie attitude while it is steered by a user.
In accordance with the invention there is also provided a computer readable storage medium configured to store a 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. Therefore, a remote-control vehicle comprising suitable components may be configured with such instructions so as to be able to perform a wheelie or stoppie in the manner described in connection with the aforementioned vehicles.
In accordance with the invention there is also provided 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. Therefore, a control module, which may be part of the remote-control vehicle or may be separate from and in communication with it, can execute the method so as to cause the vehicle to perform a wheelie or stoppie in the manner described above.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

Figure 1 is a perspective view of a first example remote-control vehicle according to the invention;
Figure 2 shows a side view of the first example remote-control vehicle at various stages of a first example travelling mode;
Figure 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;
Figure 4 is a schematic diagram showing an example receiver and control board interface of a remote-control vehicle according to the invention.

DESCRIPTION OF EMBODIMENTS

Referring to Figures 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.
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.
The vehicle 101 is controllable with command signals received via a radiofrequency 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.
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).
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.
The APWC of the present example comprises a 32-bit MPU6000 STM processor, which is able to rapidly process and calculate information from its sixdegree-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 sensors - the accelerometer measures acceleration forces, and the gyro measures rotational forces on each axis. These are the six degrees of freedom.
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.
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. 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

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.
The vehicle 101 is shown driving at an elevated attitude so as to perform a wheelie. The pitch angle θ 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.
It can be seen that pitch angle θ 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 θ, 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.
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 θ 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.
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.
The centre of mass of the vehicle 101 is indicated at point C. As can be seen, when the vehicle pitch angle θ 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 θ 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.
Several stages of the wheelie mode are depicted for the first example vehicle at Figure 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 θ. 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.
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_C ahead of the rear wheels 103 and a height Z_C above the surface 119.
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 Fx, as indicated by the respective arrows in view B.
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_CX_F and the normal force exerting a negative torque -XcN. 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 ZcFx = XcN. 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, Fx = MGXc/Zc. 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 MGXc/Zc. In most car-shaped remote-control vehicles, such as that of the present illustrated example, X_C is greater than Z_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, Zc may be greater than X_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 τ = rF_x, and so τ = rmgX_c/Z_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_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_c/Z_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 θ 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.
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 Figure 2, or with the control module continually moderating the applied drive to keep the vehicle in a wheelie.
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 remotecontrolling user is insufficient to begin or maintain a wheelie.
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.
It can be seen that the ratio Xc/Zc decreases as the vehicle pitch angle θ 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.
The vehicle 101 may also perform a wheelie as illustrated throughout stages A-F of Figure 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.
Figure 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.
Figure 3 is also analogous to Figure 2 in that it depicts the vehicle at various stages separated by equal time intervals during an exemplary stoppie mode motion.
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.
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 Fx, 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 µ_s, the frictional force satisfies the condition F_X less than or equal to µ_sN = µ_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 µ_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 Xc/Zc less than or equal to µ_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 Figures 1 and 2.
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 θ 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 θ 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 Figures 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.
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.
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 Figure 4. 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.
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.
The control board may be configured with external programming containing computer-executable instructions for performing the wheelie and stoppie 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.
Methods are also provided, in accordance with the invention, to provide steps of operating a remote control vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a first example remote-control vehicle according to the invention;
Figure 2 shows a side view of the first example remote-control vehicle at various stages of a first example travelling mode;
Figure 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;
Figure 4 is a partial section top view of a third example remote-control vehicle according to the invention;
Figure 5 shows a front view of the third example remote-control vehicle in three different variations of a third example travelling mode;
Figure 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;
Figure 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;
Figure 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
Figure 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

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.
The vehicle 101 is shown driving at an elevated attitude so as to perform a wheelie. The pitch angle θ 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.
It can be seen that pitch angle θ 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 θ, 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.
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 θ 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.
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.
The centre of mass of the vehicle 101 is indicated at point C. As can be seen, when the vehicle pitch angle θ 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 θ 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.
Several stages of the wheelie mode are depicted for the first example vehicle at Figure 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 θ. 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.
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_C ahead of the rear wheels 103 and a height Z_C above the surface 119.
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_X, as indicated by the respective arrows in view B.
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_CX_F and the normal force exerting a negative torque -X_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_CF_X = X_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_X = MGX_C/Z_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_C/Z_C. In most car-shaped remote-control vehicles, such as that of the present illustrated example, X_C is greater than Z_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_C may be greater than X_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 τ = rF_x, and so τ = rmgX_c/Z_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_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_c/Z_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 θ 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.
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 Figure 2, or with the control module continually moderating the applied drive to keep the vehicle in a wheelie.
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 remotecontrolling user is insufficient to begin or maintain a wheelie.
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.
It can be seen that the ratio X_C/Z_C decreases as the vehicle pitch angle θ 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.
The vehicle 101 may also perform a wheelie as illustrated throughout stages A-F of Figure 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.
Figure 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.
Figure 3 is also analogous to Figure 2 in that it depicts the vehicle at various stages separated by equal time intervals during an exemplary stoppie mode motion.
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.
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_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 µ_s, the frictional force satisfies the condition F_X less than or equal to µ_sN = µ_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 µ_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_C/Z_C less than or equal to µ_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 Figures 1 and 2.
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 θ 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 θ 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 Figures 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.
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.
With reference to Figures 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 Figure 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.
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 Figure 5. These three stages, labelled A, B, and C are shown in plan view in Figure 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.
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.
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 Figure 5 for example.
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 ϕ as shown in Figure 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 Figure 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 Figure 6 marked with an A, the control module detects any changes in the monitor roll angle ϕ 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 ϕ 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 ϕ 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.
When the vehicle is travelling along paths that are not straight, such as those shown at portions B and C of Figure 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 Figure 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.
The shape of the path shown in Figure 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 ϕ 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 Figure 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_C is equal to zero.
In view B of Figure 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 Figure 5. Therefore, unless a balancing torque is applied, the vehicle will continue to roll in the anticlockwise direction, thus increasing ϕ 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_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_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 Figure 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.
As shown in view C in Figure 5 and at section C of the path shown in Figure 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_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.
With reference to Figures 7 and 8, a fourth example vehicle, configured for a fourth example travelling mode is now described. Figure 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.
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 θ 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.
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).
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 θ 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.
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 Iω₁ 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 θ₁ 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 α₁ is in the clockwise direction as viewed in Figure 7. In the case that the wheels 403, 405 are spinning at this stage, the angular acceleration α₁ 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 ω of the vehicle body itself is increased, to a non-zero value, in the anticlockwise direction as viewed in Figure 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 θ.
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 ω_w and having a moment of inertia I_w, the angular momentum of the entire vehicle is equal to that of the wheels, so that Iω₁ = I_wω_w.
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_B and the monitored vehicle pitch angle θ₁ and angular velocity of the body ω_B. Should the angular acceleration α₁ be sufficient to bring the angular velocity of the wheels ω_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 Figure 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.
In the indicated portion of the jump, the angular momentum of the entire vehicle Iω₂, which is the same, owing to conservation of angular momentum as the starting angular momentum Iω₁, 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 α₁ 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_w of the wheels to provide the vehicle body with sufficient angular velocity ω_B to bring the vehicle 401 to the desired attitude during the jump.
At the antepenultimate stage of the jump depicted in view B, the angular momentum ω_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 α₂ is applied to the wheels, by the motor. Thus, in order to slow, and if necessary reverse, the rotation ω_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 α₂, so that the vehicle pitch angle is brought back to a value of approximately -5°.
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 α₂ 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.
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 ω_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 α₃, 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 ω_w is the same at the point where the vehicle lands as it was when the vehicle left the ramp 423.
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.
The fourth example vehicle is shown executing the self-stabilised jump mode in a different form of ramp jump in Figure 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, Iω₁ is non-zero and in the anticlockwise direction, and is equal to the angular momentum of the body I_Bω_B plus any angular momentum of the wheels, which will probably be in the anticlockwise direction also, I_Wω_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 ω_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 α₁ backwards. Considering rotation in the anticlockwise direction as having a positive value, this acceleration α₁ causes ω_W to be reduced, and since the angular momentum Iω₁ of the vehicle cannot change when the vehicle is in mid-air, the angular momentum of the body, and therefore the angular velocity ω_B of the body, as the moments of inertia I are fixed, must increase in the anticlockwise direction.
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 α₁ is relatively great so as to quickly reverse the undesired rotation and impart rotation towards the desired vehicle pitch angle.
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 α₁, applies a torque accelerating the wheels by α₂ in the forward direction, with α₂ having a relatively small value compared with that of α₁. This causes the forward rotation initiated by the application of α₁ 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 α₃ slightly in the forward rolling direction, that is anticlockwise as viewed, so as to halt the rotation of the vehicle body 415.
In contrast to the example jump shown in Figure 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.
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.
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.
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.
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 Figure 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.
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.
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.

Claims

A remote-control vehicle (101, 201) comprising:
a first wheel (105, 203) and a second wheel (103, 205) offset along the longitudinal axis of the vehicle,

a device adapted to apply a torque to the first wheel, (105, 203)

a sensor (113) configured to monitor the pitch angle of the vehicle, and

a control module (111) configured to control the torque applied by the device to the first wheel (105, 203) in accordance with the monitored vehicle pitch angle so as to accelerate the vehicle by changing the speed of the vehicle in the direction of travel, while maintaining the vehicle pitch angle within a range of acute angles at which the second wheel is raised.
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.
A remote-control vehicle according to claim 1 or claim 2, 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, 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.
A remote-control vehicle according 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.
A remote-control vehicle according to any of the preceding claims, 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.
A remote-control vehicle according to any of the preceding claims, 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, or
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.
A remote-control vehicle according to any of the preceding claims, 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.
A remote-control vehicle according to any of the preceding claims, wherein the vehicle further comprises a third wheel, wherein the vehicle is configured to apply a torque to the third wheel accordingly when a torque is applied to the first wheel, wherein the vehicle further comprises a fourth wheel.
A remote-control vehicle according to any of the preceding claims, wherein the sensor comprises an orientation sensor and a rotation sensor, and 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, and
wherein the rotation sensor comprises an accelerometer or gyroscopic sensor.
A remote-control vehicle according to any of the preceding claims, wherein the control module is configured to control the torque so as to accelerate the vehicle while maintaining the vehicle pitch angle within a range of acute angles upon receiving a remote-control command to accelerate the vehicle.
A remote-control vehicle according to any of the preceding claims, wherein the range of acute angles is 30°-70° or 40°-60°, or wherein the control module is configured to maintain the vehicle pitch angle at a substantially constant acute angle while accelerating the vehicle.
A remote-control vehicle according to any of the preceding claims, adapted to receive a remote-control command including a pitch angle parameter, wherein the control module is configured to maintain the vehicle pitch angle at an acute angle corresponding to the pitch angle parameter.
A remote-control vehicle according to any of the preceding claims, adapted to allow the vehicle to be steered while the vehicle pitch angle is maintained within a range of acute angles.
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 by changing the speed of the vehicle in the direction of travel, while maintaining the vehicle pitch angle within a range of acute angles at which a second wheel of the remote-control vehicle is raised.
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 by changing the speed of the vehicle in the direction of travel, while maintaining the vehicle pitch angle within a range of acute angles at which a second wheel of the remote-control vehicle is raised.