Method for Anti-wheelie control of a saddle-ride vehicle, and vehicle comprising said control

Abstract

The method entails determining, during the vehicle travel, a maximum admissible driving torque which, on the basis of a mathematical model of the motorcycle and on travel parameters, generates a vertical limit contact force between the front wheel of the vehicle and the ground. The method furthermore entails comparing, during the vehicle travel, a driving torque required by the driver of the vehicle with the maximum admissible driving torque. The method entails controlling the engine so that: (i) when the driving torque required by the driver is equal to or lower than the maximum admissible driving torque, the driving torque delivered to the rear drive wheel corresponds to the driving torque required by the driver; and (ii) when the driving torque required by the driver is greater than the maximum admissible driving torque, the driving torque delivered to the rear drive wheel corresponds to an effective driving torque which is lower than the driving torque requested by the driver.

Description

METHOD FOR ANTI-WHEELIE CONTROL OF A SADDLE-RIDE VEHICLE, ANDVEHICLE COMPRISING SAID CONTROLDESCRIPTIONTECHNICAL FIELD

[0001] The present invention concerns improvements to saddle-ride vehicles, in partic- ular to motorcycles. In particular, the present invention concerns a system for wheelie control and suppression in motorcycles.B ACKROUND ART

[0002] Saddle-ride vehicles, in particular two-wheel motorcycles, can be subject to wheeling when the driver requires a sudden increase in the torque delivered during an acceleration phase. During the wheelie the front wheel of the motorcycle lifts off the ground with the consequent risk of loss of control of the vehicle. If not controlled, the wheelie entails the risks of loss of control of the vehicle and overturning.

[0003] In order to improve driver comfort and safety, and reduce the risks arising from loss of contact between the front steered wheel and the ground, systems have been studied for suppressing or controlling motorcycle wheelying. These systems are based essentially on signals of sensors on board the vehicle, which are adapted to detect the occurrence of a wheelie condition, namely detachment of the front steered wheel from the ground, and to implement measures for controlling the torque delivered by the engine, in order to re- set the motorcycle to the correct driving position, with the front wheel adhering to the ground.

[0004] Typically, anti-wheelie control systems are based on detection of the angular velocity or angular acceleration of the front steered wheel and the rear drive wheel of a motorcycle. When the motorcycle does a wheelie, the front wheel loses its grip and there- fore its angular velocity decreases with respect to the angular velocity of the rear drive wheel. The occurrence of this situation triggers a torque control of the motorcycle, which tends to reduce the torque delivered by the engine to the rear drive wheel. The drop in the torque delivered entails the more or less abrupt return of the vehicle to the conditions of correct contact with the ground.

[0005] The consequent cessation of the wheelie conditions causes cessation of the torque control effect with consequent renewed tendency of the vehicle to lift off the ground again, if the driver does not release the accelerator control. This situation entails a pitch oscillation of the vehicle, which makes driving uncomfortable and can be risky for the road-holding of the vehicle.

[0006] A system of this type is disclosed in EP2985213.SUMMARY

[0007] According to one aspect, a control method and system are proposed, in addition to a vehicle that comprises said control system, aimed at reducing or eliminating the draw- backs of the known systems and methods for wheelie control of saddle-ride vehicles, in particular motorcycles.

[0008] Essentially, the invention is based to the fact that the known wheelie suppression systems are based on the detection of a parameter indicating that the vehicle is in wheelie conditions, namely that the front wheel loses its grip on the ground. The wheelie suppres- sion system intervenes when the phenomenon to be avoided or suppressed has already been triggered. This causes the drawbacks described above, in particular due to the delay in intervention of the wheelie suppression or control.

[0009] To alleviate or eliminate the drawbacks of the known art, the present invention is based on the fact of determining an incipient wheelie condition based on a dynamic model of the vehicle, without the need for one or more sensors to have actually detected the occurrence of the wheelie. This allows the control system to intervene in advance, namely to prevent onset of the phenomenon to be suppressed or controlled, namely de- tachment of the front wheel from the ground.

[0010] According to one aspect, a method is described for the anti-wheelie control of a saddle-ride vehicle comprising a frame, a front steered wheel, a rear drive wheel, and an engine connected to the rear drive wheel and adapted to deliver a driving torque to the rear drive wheel. The method comprises determining, during travel of the vehicle, a max- imum admissible driving torque which, based on a mathematical model of the vehicle and on travel parameters, generates a vertical limit contact force (namely a reaction force in a vertical direction) between the front wheel of the vehicle and the ground. In a furtherstep, the method comprises comparing, during travel of the vehicle, a driving torque re- quired by a driver of the vehicle with the maximum admissible driving torque. The method then comprises controlling the engine so that: (i) when the driving torque required by the driver is equal to or lower than the maximum admissible driving torque, the driving torque delivered to the rear drive wheel corresponds to the driving torque required by the driver; and (ii) when the driving torque required by the driver is greater than the maximum admissible driving torque, the driving torque delivered to the rear drive wheel corre- sponds to an effective driving torque which is lower than the driving torque required by the driver. Essentially, each driving torque is associated, according to the typical param- eters of the vehicle and the instantaneous travel parameters, with a given apparent weight, namely a vertical force, of the front wheel. The more the vehicle tends to wheely, the more the front wheel is perceived by the driver as light, because the driving torque gen- erates a vertical force that counters the force of gravity, or the real weight, of the front axle of the vehicle. The maximum admissible driving torque is a torque that generates a vertical contact force considered to be a limit force, namely beyond which the wheel is too near detachment from the ground or, in an extreme case, corresponds to detachment from the ground. By correlating the driving torque with the vertical limit contact force between front wheel and ground, it is possible to adjust the driving torque, and therefore the torque on the rear wheel, before the front wheel detaches from the ground.

[0011] In some embodiments, to determine (during travel) the maximum admissible driving torque, a vehicle model and travel speed data can be used. For example, the max- imum admissible torque, below also indicated as limit torque (or equivalently the limit force or maximum admissible force in a direction parallel to the ground exchanged be- tween rear drive wheel and ground) can be determined as a function of parameters defin- ing the vehicle, namely defining a model of the vehicle, and some travel parameters, de- ducible from sensors on board the vehicle. In particular, according to some embodiments the limit force (or maximum admissible force) and consequently the limit torque (or max- imum admissible torque) are determined on the basis of physical parameters of the vehi- cle, its speed of travel, the roll angle and the first derivative in time of the roll angle. The physical parameters of the vehicle can be relative to the position of the centre of gravity, weight and aerodynamic characteristics.

[0012] Further advantageous embodiments of the method described here are defined inthe attached claims and described below with reference to the attached drawings.

[0013] According to a further aspect, a controller that performs a method as defined above, and a saddle-ride vehicle comprising said controller, are described here.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention will be better understood by following the description and the at- tached drawings, which show an illustrative non-limiting embodiment of the invention. More in particular:Fig.l shows a schematic lateral view of a motorcycle with indication of the forces applied during travel;Fig.2 shows a diagram that illustrates the trend of the quantities at play in the wheelie control;Fig.3 shows a functional block diagram illustrating the control system;Fig. 4 shows a schematic lateral view of a motorcycle with indication of the forces applied during travel in an operating condition in which the wheelie is not incipient;Fig. 5 shows a schematic lateral view of a motorcycle with indication of the forces applied during travel in an operating condition in which the wheelie is incipient; andFig. 6 shows a schematic lateral view of a motorcycle with indication of the forces applied during travel in an operating condition in which the wheelie has occurred.DETAILED DESCRIPTION

[0015] Fig.l shows an illustrative lateral view of a saddle-ride motor vehicle, in partic- ular in the example a motorcycle 1, to which the wheelie control system described here can be applied. In Fig. l some physical quantities are indicated which are relevant for understanding what is described below and which will be referred to further on.

[0016] In Fig.l the motorcycle 1 comprises a frame 3, a saddle 4, a front steered wheel 5, a rear drive wheel 7, and an engine 9 connected to the rear drive wheel 7 and adapted to deliver a driving torque to the latter.

[0017] In short, the method and the system described here are based on the principle of calculating, based on a mathematical model characteristic of the motorcycle and on travel parameters, a torque to the rear drive wheel which, in the conditions of the motorcycle at that moment, is such as to generate a vertical reaction force Fzf on the front wheel 5 equalto a given value. In some embodiments, and / or in some travel conditions, the predeter- mined value is equal to zero. Said vertical reaction force Fzf on the front wheel 5, also called vertical contact force between the front wheel of the vehicle 1 and the ground T, is equal and opposed to the weight force which the front end exerts on the ground T. In practice, the vertical reaction Fzf on the front wheel 5 is the apparent weight of the front wheel perceived by the driver.

[0018] The torque thus calculated during the vehicle travel is indicated here as “limit torque” or “maximum admissible driving torque”.

[0019] The limit torque thus calculated is compared in a continuous manner with the torque which the pilot requires the engine to deliver via the accelerator control. This torque is indicated below as “required torque” or “driving torque required by the driver”.

[0020] In the following description, frequent reference will be made to the longitudinal force Fxr applied to the rear wheel, namely the force in the direction of travel (direction x) transmitted between rear drive wheel 7 and the ground T on which the motorcycle 1 travels. This force is proportional, through the radius Rrof the rear drive wheel 7, to the driving torque applied to the axle of said rear drive wheel, the driving torque applied to the rear drive wheel being Fxr*Rr. The two quantities (torque and force) are therefore perfectly interchangeable.

[0021] In short, to avoid or control wheeling of the motorcycle 1, a control unit provided on the motorcycle controls the engine 9 so that it delivers the required torque if it is lower than the limit torque, and the limit torque (or a torque which is a function of the limit torque) if the torque required is greater than the limit torque.

[0022] In the present context reference will be made to the limit torque which corre- sponds to a vertical reaction force Fzf on the front wheel equal to zero. However, this is not strictly necessary, since the control could be set so that the limit torque, or maximum admissible driving torque, is determined as a function of a value of Fzf greater than zero. The vertical limit contact force can correspond to the vertical reaction force Fzf beyond which the wheel detaches from the ground T, namely Fzf equal to zero, or to such a small vertical reaction force Fzf namely substantially equal to or close to zero, as to represent an incipient wheelie.

[0023] To determine the limit torque, a motor vehicle model can be used that takes ac- count of the mass distribution and aerodynamic characteristics of the vehicle, in addition to a limited number of parameters relative to the travel conditions, as clarified further on.

[0024] A simplified method of determining the limit torque (and therefore the limit value of Fxr) is described below with reference to Fig.1 in simplified travel conditions of the vehicle 1 in the absence of inclination, i.e., with null roll angle.

[0025] With reference to Fig.1, mg is the resulting weight force, applied to the centre of mass G of the motorcycle 1. Fa, Fi indicate respectively the horizontal aerodynamic force and the vertical aerodynamic force applied to the motorcycle and Mp is the aerodynamic torque. The aerodynamic forces and torque, generated by the resistance to travel of the motorcycle in the air are given by:where CD, CL e cp are the respective aerodynamic coefficients and vxis the speed of travel.

[0026] On the basis of the equations of equilibrium of the forces and moments, we have:whereIyy is the inertia around the pitch axis of the vehicle is the angular acceleration of the vehicle around the pitch axis and where, following the notations shown in Fig.1 :Fzf is the vertical reaction force on the front wheel 5Fzr is the vertical reaction force on the rear drive wheel 7Fxr is the horizontal reaction force on the rear drive wheel 7If is the distance between the projection onto the ground T of the centre of mass G and the point of contact between ground and front steered wheel lris the distance between the projection onto the ground T of the centre of mass G and the point of contact between ground and rear drive wheel 7A is the distance of the centre of mass G from the ground T.

[0027] Assuming null acceleration of the vehicle in all directions and absence of pitch, based on the equations of equilibrium, the reaction force in the vertical direction Fzf ap- plied on the front wheel is given bywhere wb = lr + If

[0028] By setting a null reaction force in the vertical direction on the front wheel 5, namely by setting Fzf= 0, the equations (3) and (4) can provide the longitudinal force Fxr(and therefore the driving torque Rr*FxF) to be applied to the rear drive wheel 7 to obtain the condition of null weight on the front wheel 5:

[0029] The wheely control and reduction method described here essentially entails cal- culating Fxr(and therefore the corresponding driving torque Rr*FxF) at each instant of travel of the motorcycle 1 and comparing this value with the driving torque value (and consequent horizontal reaction force on the rear drive wheel) required by the driver. Wheeling of the vehicle 1 is avoided or controlled by ensuring that a control unit of the engine delivers the torque required by the driver if it is lower than the limit torque calcu- lated on the basis of the vehicle model (and proportional, through the radius of the rear drive wheel 7, to the force Fxr). If, on the other hand, the torque required by the driver is greater than the limit torque, calculated on the basis of the model and corresponding to the force Fxr calculated on the basis of the equation (5), the control unit will oblige the engine to deliver the limit torque or in any case a torque lower than the required torque and a function of the limit torque. If Fzf # 0, the vertical reaction force Fzf on the front wheel 5 is a function of the horizontal reaction force Fxr on the rear drive wheel 7 and therefore of the driving torque Rr*Fxr.

[0030] Various driving conditions are illustrated in Figs. 4-6. Fxr indicates the limit value of the horizontal reaction force on the rear wheel as defined above and calculated according to formula (5), corresponding to the limit driving torque. As indicated above, formula (5) allows calculation of the limit value of the force Fxr and thus of the driving torque corresponding to a zero vertical reaction force on the front wheel. Using the same approach, a limit value of the force Fxr and thus a limit value of the torque correspondingto a vertical reaction force on the front wheel greater than zero can be calculated.

[0031] Returning to Figs. 4-6, FR denotes the horizontal reaction force on the rear wheel corresponding to the torque required by the rider during acceleration. In Fig. 4, the force FR is less than the limit value of Fxr . In Fig.5 FR is similar but still less than Fxr. In Fig.6 the torque required by the rider corresponds to a force FR greater than the limit value of Fxr. In this case, the front wheel 5 lifts slightly off the ground T bringing the vertical reaction force to zero.

[0032] The operating condition in Fig.6 is prevented by the method and controller de- scribed here, which act by limiting the torque delivered before actual lift-off of the mo- torcycle front wheel from the ground occurs. In essence, the condition in Fig.6 does not occur because the torque delivered by the engine to the rear drive wheel is limited before actual lift-off of the front wheel from the ground occurs. In the case where the torque required by the rider corresponds to a force FR greater than the limit value of Fxr, the torque actually delivered by the engine will be limited to that corresponding to the limit value of Fxr.

[0033] It should be understood that the required torque and the limit torque referred to above refer to the rear drive wheel 7. These torque values are correlated with correspond- ing torque values on the drive axle, through the parameters that define the transmission between engine 9 and rear drive wheel 7, including the gear engaged.

[0034] In the preceding discussion, an analytical model has been used, valid in the case of rectilinear travel of the motorcycle 1, with null roll angle and null acceleration. This condition simplifies the calculation, but does not correspond to the real travel conditions. In an embodiment closer to reality, the dynamic effects of the rolling movement of the motorcycle can also be taken into account. In this case it is simpler to write the equilib- rium equations of the forces and moments in matrix form obtaining:whereare the forces on the wheels and the subscripts x, y, z indicate the directions parallel to the direction of travel, parallel to the ground and orthogonal to the direction of travel, and orthogonal to the ground, respectively; the subscripts r and f indicate the rear wheel (r) and the front wheel (f); furthermore:the plane orthogonal to the ground.

[0035] The equation (7) is given byAlso in this case, by setting the force Fzf to zero, the limit torque is calculated (or equiv- alently the limit force Fxr) that corresponds to a condition of incipient wheelie, namely the value that sets to zero the reaction in a vertical direction of the ground T on the front steered wheel (force Fzf in Fig.1). The following is obtained:(ID

[0036] Note that the limit force (Fxr) and therefore the corresponding limit torque is a function of the following quantities: longitudinal speed (speed in direction x), roll angle (0), roll rate (namely the first derivative in time of the roll angle: cj>), and the physical parameters of the motorcycle, which appear in m, lr, MP, h. The limit force Fxr can be expressed as:where cAis an equivalent aerodynamic coefficient.

[0037] In this way, the simple mathematical model used is adapted to take account of the rolling kinematics and not only of the longitudinal and vertical dynamics.

[0038] Note also that the travel speed (longitudinal speed vxin direction x) of the mo- torcycle 1 can be calculated from the speed of the engine (once the gear engaged is known), from the speed of the front wheel 5, or from the speed of the rear drive wheel 7. Therefore, the analytical formula of the equation (12) can be expressed to a different de- gree of precision on the basis of the availability of on-board sensors.

[0039] Once the limit force Fxrhas been calculated, or equivalently the limit torque RrFxr, it must be compared with the force required by the driver, which corresponds to the torque required and is expressed bywhere T is the driving torque required by the driver, calculated on the basis of the map of the engine, p is the efficiency of the transmission between engine 9 and rear drive wheel 7, kcis the gear engaged and Rris the radius of the rear drive wheel 7.

[0040] Regardless of the model used to represent the motorcycle 1, the method gener- ally entails calculating the limit force Fxr(or the limit torque FxrRr^ solely on the basis of geometrical quantities of the vehicle and the travel conditions (speed vxand roll angle ([>). To control wheeling of the motorcycle, or more precisely to limit the lifting (pitch) movement of the motorcycle in the event of wheeling, the control method provides that the torque delivered by the engine is equal to the torque required by the driver if Fxr> FRand, on the other hand, is a function of the limit torque calculated on the basis of the model if Fxr< FR.

[0041] Compared to the prior art methods, this control method allows prompter inter- vention to reduce the torque delivered, since it is not based on the detection of a wheelie condition, namely it does not wait to intervene until the front wheel of the motorcycle has already lifted off the ground, but intervenes prior to the occurrence of this condition.

[0042] Once the control system has identified a condition in which Fxr< FR, the func- tion of a pre-wheelie controller is activated. This controller acts prior to occurrence of the wheelie, namely prior to lifting of the front wheel 5 from the ground T (and consequent reduction of the angular velocity of the front steered wheel with respect to the angular velocity of the rear drive wheel), since it is activated by the condition Fxr< FRidentified as described above, and not by a signal of a wheelie detection sensor, for example a sensor that determines the occurrence of a difference in rotation speed (or a difference in accel- eration) of the front and rear wheels. The object of the pre-wheelie controller is to max- imize vehicle performance but at the same time prevent it from assuming an excessive pitch angle.

[0043] The output signal of the pre-wheelie controller is a control signal of the torque delivered by the engine. In the embodiment described here, the controller provides a torque control signal defined by:where at each instant or step k'. uk= uk-1+ K1dk+ K2ek(15) where ukis a feedback signal defined in a recursive manner and calculated at each itera- tive step (k) by the controller. The feedback signal takes account of the pitch dynamics, andKi, K2 are two gain constants defined experimentally,0kis the first derivative with respect to the pitch angle time, 0kis the second derivative with respect to the pitch angle time.

[0044] In short, the pre-wheelie controller is activated when the condition Fxr< FRoccurs and has the function of generating a control command of the torque delivered (eq.14) which replaces the signal of torque required by the driver and is a function of the limit force Fxr, namely of the limit torque RrFxr.

[0045] Since the pre-wheelie controller is activated before the motorcycle 1 actually wheelies, namely before the front wheel 5 detaches from the ground, the anti-wheelie control is more efficient and prompter than when obtained with the systems of the known art.

[0046] In some embodiments, the control method also entails verifying whether, despite the intervention of the pre-wheelie controller, the vehicle tends to wheelie with conse- quent increase in the pitch angle beyond a limit value. For said purpose, the method com- prises a wheelie control step based on the traditional technique of verifying the condition of lifting from the ground of the front steered wheel 5, for example based on the signals of angular velocity or angular acceleration of the front steered wheel 5 and rear drive wheel 7. When the front steered wheel 5 detaches from the ground, it begins to decelerate angularly, or in any case to have an angular velocity or acceleration different from the rear drive wheel 7. Signals provided by sensors normally present on the motorcycle 1 allow verification of this situation.

[0047] If the vehicle tends to wheelie despite the pre-wheelie control provided on the basis of eq. (14), the control signal of the delivered torque is corrected with a factor which is a function of the pitch angle. The control signal becomes:where0k is the instant pitch angle (measured or calculated)0 is a reference pitch angle0Ois the pitch angle at the moment of detachment of the front wheel 5 from the ground K3is a gain coefficient

[0048] The pitch angle and its derivatives can be obtained by means of appropriate sen- sors, for example through an inertial platform provided on the motorcycle. Inertial plat- forms generally provide the angular accelerations and velocities on three Cartesian axes, from which the angular pitch acceleration, pitch rate and pitch angle can be obtained. In some embodiments, inertial platforms can be used which are already configured to pro- vide in output the data relative to the pitch angle and its first and second derivatives in time.

[0049] The coefficient K3can be in turn a function of the pitch rate, namely of the first derivative in time of the pitch angle, namelyK3= f(0).

[0050] The diagram of Fig.2 illustrates some curves which are significant for under- standing the method described above. The curve Cl shows the torque required by the driver. The curve C2 shows the limit torque FxrRr calculated on the basis of themotorcycle model, as described above. C3 is the control signal of the torque provided to the engine. The curve C4 is the acceleration signal.

[0051] As can be seen in Fig.2, the curve C3 coincides with the torque required by the driver (curve Cl) until triggering of the pre-wheelie control, at time to. This is the time at which the limit torque FxrRr calculated is equal to the required torque and beyond which the torque required by the driver is greater than the limit torque.

[0052] The curve C7 is the angular velocity of the rear drive wheel 7 and the curve C5 is the angular velocity of the front steered wheel 5. It can be seen that at time ti the accel- eration of the front steered wheel 5 becomes lower than the acceleration of the rear drive wheel 7. At this time, therefore, detachment of the front steered wheel 5 from the ground T occurs. This triggers the anti-wheelie control according to eq. (19). Consequently, the torque delivered by the engine is modulated in a manner such as to limit the pitch angle, bringing the front steered wheel 5 back towards the ground T. The resulting oscillation of the angular velocity (see curve C5 after time ti) is the result of this control which contin- uously re-positions the front steered wheel towards the point of contact with the ground T.

[0053] The curve C6 indicates the extension of the front suspension. Note that this has very limited dynamics, indicating the efficiency of the anti-wheelie control obtained with the method described above.

[0054] Fig. 3 illustrates a functional block diagram that summarises the operation of the anti -wheelie system based on the method described so far. The number 100 indicates a plurality of sensors or transducers provided on the motorcycle 1. These sensors can com- prise in particular a revolution counter 101 adapted to detect the rotation speed of the engine, a sensor 102 that detects an acceleration command, for example the command sent by the driver to the actuator of the throttle body that controls the flow rate of com- bustion air supplied to the engine. The number 103 indicates a sensor that provides infor- mation on the gear engaged. The data of these sensors, together with the mathematical model of the motorcycle (cf. Fig.1), allow the control unit to calculate the torque FR*RT and the force FR or the torque required by the driver.

[0055] The numbers 104 and 105 indicate speed and / or acceleration sensors of the front steered wheel 5 and rear drive wheel 7. The numbers 106 and 107 indicate sensors of theroll angle c[) and of the derivative in time of the roll angle (roll rate cj)). The numbers 108 and 109 indicate sensors, optional, that detect the range of the front and rear suspen- sions, for example potentiometers.

[0056] Based on the signals of the sensors 101 to 107, a control unit 120 calculates the limit torque FxrRr, or the limit force Fxrdefined above.

[0057] The numbers 110 and 111 indicate pitch rate and angular acceleration rate sen- sors, namely the first derivative in time (0) and the second derivative in time (0) of the pitch angle.

[0058] One or more of the sensors mentioned can be integrated in, or consist of, an inertial platform with which the motorcycle 1 is equipped.

[0059] The control unit 120 comprises a block indicated overall by the number 121, which determines the onset of a pre-wheelie condition, namely it determines when the condition Fxr< FRoccurs, via the data of the sensors from 101 to 109. The block 121 comprises: a block 122 for calculation of the force FR (or torque FR RT) required by the driver; a block 123 for calculating the limit force Fxr(or limit torque FxrRr) and a com- parison block 124. If the block 124 shows that Fxr< FR, the pre-wheelie control function is activated, represented by a block 125 of the control unit 120.

[0060] The control block 125 comprises a block 126 that performs the function of feed- back controller on the pitch rate and the output of which is added to the output of the block 123 (see equation (14) and equation (16)). The number 128 indicates the torque control signal, at the output of the control unit 120 (signal uk, eq. (14) and eq. (16)). The signal 12 controlling the torque delivered by the engine 9 replaces the signal of the torque required by the driver from the moment when the condition Fxr< FRoccurs. The signal of the torque required by the driver goes back to controlling the torque delivered when the required torque goes back to being equal to or lower than the “limit torque” or “max- imum admissible driving torque” FxrRr.

[0061] The control method and system described above can be upgraded for implemen- tation of the control described here on commercial vehicles, which can be driven by per- sons with different physical characteristics (build, height, weight, which also affect the aerodynamic coefficients of the vehicle, in addition to its overall weight during travel)and different driving styles. Furthermore, it is useful to take account of other factors that can affect the efficiency of the control such as, for example, the type of tyres, their state of wear and inflation pressure.

[0062] To take account of these factors and optimize the wheelie control, an adaptive strategy can be provided that modifies one or more of the coefficients that come into play in calculation of the torque control signal when the anti-wheelie control is activated.

[0063] The modification of the adaptive parameters or coefficients can be carried out based on the result of a number n of the most recent interventions of the anti-wheelie control.

[0064] According to one aspect, considering that beyond a certain roll angle (namely beyond a certain degree of inclination when cornering), it is desirable for the front steered wheel 5 not to lose its grip on the ground T and to remain firmly in contact with it, one of the control coefficients can be modified so that, beyond a safety roll angle (c[>max)> the limit force Fxris lower than the one providing a reaction force Fzf equal to zero. For said purpose, for example, for a roll angle c[) > (c[>max) the equation (12) can be modified towhere ki is comprised between 0 and 1. Using in the denominator of the expression de- fining the limit force Fxr(and therefore the limit torque FxrRk) a reduction factor of the roll angle c[) , the value of the limit force Fxrfor which the anti -wheelie control is triggered is lower, therefore essentially anticipating the moment of activation of control of the torque delivered to the drive wheel, namely its reduction with respect to the torque re- quired by the driver, preventing detachment of the front steered wheel 5 from the ground. This reduced value of the force Fxris used by the control system only when the roll angle exceeds the safety value (pmax. Essentially, the modification intervenes on the feedfor- ward component of the wheelie control by adapting it to the roll angle. The factor ki can be modified, for example, if for an n number of interventions of the driving torque limi- tation control, the motorcycle has detached from the ground in the presence of roll angle values greater than the safety limit value [c[) > (c[>max)]-

[0065] According to some embodiments, the control can be adapted to obtain a more gradual (slower) lifting of the nose of the motorcycle 1 simultaneously with a suddenacceleration, to increase driving comfort. For example, the value attributed to the coeffi- cients used for calculating the torque signal uk(eq.14) may be such that the motorcycle 1 has an excessively rapid pitch movement, in particular in the acceleration phase. This can occur, for example, if the driver has a particularly slim build with respect to the av- erage, according to which the coefficients used in the above equations are calculated.

[0066] The adaptive system can intervene to adapt the control, for example if for a high percentage of interventions of the anti-wheelie control an excessive wheelie speed has occurred, greater than a limit value.

[0067] In this case it is possible to intervene by modifying the coefficient CA in the equa- tion (12) or an offset value Foffset can be added in said equation, obtaining

[0068] In both cases the control can be auto-adaptive and can intervene on one or the other or both the above-mentioned coefficients of the equation 12 or 12’ if 0 > 0maxoccurs, where 0maxis a maximum admissible value of the pitch rate for a high percentage of interventions of the anti -wheelie control.

[0069] In some conditions the motorcycle may never detach from the ground or may lift off excessively (pitch angle too high). These conditions can occur, for example, if the driver has a body mass greater or lower than the one considered in setting the coefficients of the calculation formulas referred to above. This situation can be corrected by interven- ing on the coefficient Ks or on the coefficient 0 in the equation (16).

[0070] As indicated above, when the anti-wheelie control intervenes, the torque deliv- ered is controlled so that the front steered wheel 5 of the motorcycle 1 detaches from the ground within a limit compatible with the needs of the driver. Typically, the control is set (eq.16) so that during intervention of the anti -wheelie control the motorcycle lifts by ap- proximately 1-2° with respect to the condition of detachment from the ground. This con- dition of detachment from the ground must last for a limited period of time to increase the perceived driving comfort. If the control is such as to maintain the front steered wheel 5 detached from the ground for a time greater than a value tmax, it is possible to intervene on the coefficients used in order to reduce the detachment time from the ground. For said purpose it is possible to intervene again on the coefficients CA and Foffset in the equations(12) and (12’). The coefficients m, lr, h and CA in the equations (12) and (12’) and / or the coefficient K3 in the equation (16) can also be modified.

[0071] Analogously, the coefficients m, lr, h and CA in the equations (12) and (12’) can be modified inversely to the preceding manner, if the control is too incisive and prevents any detachment from the ground during the acceleration phases.

[0072] The return of the vehicle to its position with the front steered wheel 5 resting on the ground after a controlled wheelie must be, if possible, smooth and not abrupt, to in- crease driving comfort. The greater or lesser graduality of the lowering translates into lesser or greater diving of the front suspensions when the front steered wheel 1 returns to contact with the ground T. By providing the motorcycle 1 with sensors at least on the front suspension, it is possible to verify that the return to resting on the ground is suffi- ciently smooth, based on the diving extent (and / or diving speed) of the front suspensions. If the lowering is too great or too rapid, the control can be corrected by acting on the coefficient K3 in eq. (16).

[0073] All the above-mentioned adaptive interventions can be bidirectional, according to the type of adaptation required, and the adaptations can be non-symmetrical, for exam- ple to prioritize driving safety over performance.

Claims

CLAIMS1. A method for anti-wheelie control of a saddle-ride vehicle comprising a frame, a front steered wheel, a rear drive wheel, and an engine connected to the rear drive wheel adapted to supply a driving torque to the rear drive wheel; wherein the method comprises the following steps: determining, during travel of the vehicle, a maximum admissible driving torque that, based on a mathematical model of the motorcycle and on driving parameters, generates a corresponding vertical limit contact force between the front wheel of the vehicle and the ground; comparing, during travel of the vehicle, a driving torque required by a driver of the vehicle with the maximum admissible driving torque; controlling the engine so that: when the driving torque required by the driver is equal to or lower than the maximum admissible driving torque, the driving torque supplied to the rear drive wheel corresponds to the driving torque required by the driver; and when the driving torque required by the driver is greater than the maximum admissible driving torque, the driving torque supplied to the rear drive wheel corresponds to an effective driving torque that is lower than the driving torque required by the driver.

2. The method of claim 1, wherein when the driving torque required by the driver is greater than the maximum admissible driving torque, the effective driving torque is a function of the maximum admissible driving torque.

3. The method of claim 2, wherein the effective driving torque is equal to the maximum admissible driving torque added to a feedback value calculated as a function of the dynamics of the pitch angle.

4. The method of claim 3, wherein the feedback value is a function of the first derivative and of the second derivative in time of the pitch angle.

5. The method of one or more of the preceding claims, wherein when the driv- ing torque required by the driver is greater than the maximum admissible driving torque, the driving torque supplied to the rear drive wheel is equal to the maximum admissible driving torque.

6. The method of one or more of the preceding claims, wherein the vertical limit contact force is equal or close to zero.

7. The method of any one of the preceding claims, wherein the maximum ad- missible driving torque is a function of geometric parameters of the vehicle, of the speed of the vehicle, of the roll angle and of the first derivative in time of the roll angle.

8. The method of any one of the preceding claims, comprising at least one of the following features: the effective driving torque is modifiable as a function of the roll angle, so as to reduce the effective driving torque when the roll angle exceeds a maximum safety value; the effective driving torque is modifiable in an adaptive manner to limit the lifting speed of the front wheel of the vehicle; the effective driving torque is modifiable in an adaptive manner to limit the max- imum pitch angle; the effective driving torque is modifiable in an adaptive manner to limit a dwell time of the vehicle in conditions of detachment of the front steered wheel from the ground; the effective driving torque signal is modifiable in an adaptive manner to reduce suspension diving of the front steered wheel at the end of a wheelie.

9. A controller for anti-wheelie control of a saddle-ride vehicle comprising a front steered wheel, a rear drive wheel and an engine connected to the rear drive wheel adapted to supply a driving torque to the rear drive wheel; wherein the controller is con- figured to:determine, during travel of the vehicle a maximum admissible driving torque that, based on a mathematical model of the motorcycle and on driving parameters, generates a corresponding vertical limit contact force between the front wheel of the vehicle and the ground; compare, during travel of the vehicle, a driving torque required by a driver of the ve- hicle with the maximum admissible driving torque; control the engine so that: when the driving torque required by the driver is equal to or lower than the maximum admissible driving torque, the driving torque supplied to the rear drive wheel corresponds to the driving torque required by the driver; and when the driving torque required by the driver is greater than the maximum admissible driving torque, the driving torque supplied to the rear drive wheel corresponds to an effective driving torque that is lower than the driving torque required by the driver.

10. The controller of claim 9, configured so that when the driving torque re- quired by the driver is greater than the maximum admissible driving torque, the effective driving torque is a function of the maximum admissible driving torque.

11. The controller of claim 10, configured so that the effective driving torque is equal to the maximum admissible driving torque added to a feedback value calculated as a function of the dynamics of the pitch angle.

12. The controller of claim 11, configured so that the feedback value is a func- tion of the first derivative and of the second derivative in time of the pitch angle.

13. The controller of any one of claims 9 to 12, configured so that when the driving torque required by the driver is greater than the maximum admissible driving torque, the driving torque supplied to the rear drive wheel is equal to the maximum ad- missible driving torque.

14. The controller of any one of claims 9 to 13, configured so that the vertical limit contact force is equal or close to zero.

15. The controller of any one of claims 9 to 14, configured so that the maximum admissible driving torque is a function of geometric parameters of the vehicle, of the speed of the vehicle, of the roll angle and of the first derivative in time of the roll angle.

16. The controller of any one of claims 9 to 15, configured so as to carry out at least one of the following functions: modify the effective driving torque as a function of the roll angle, so as to reduce the effective driving torque when the roll angle exceeds a maximum safety value; modify the effective driving torque in an adaptive manner to limit the lifting speed of the front wheel of the vehicle; modify the effective driving torque in an adaptive manner to limit a maximum pitch angle; modify the effective driving torque in an adaptive manner to limit the dwell time of the vehicle in conditions of detachment of the front steered wheel from the ground; modify the effective driving torque signal in an adaptive manner to reduce sus- pension diving of the front steered wheel at the end of a wheelie.

17. A saddle-ride vehicle comprising a frame, a front steered wheel, a rear drive wheel, an engine connected to the rear drive wheel; and a controller according to one or more of claims 9 to 16.

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