Method and system for controlling the slip of the rear wheel of a motorcycle

Abstract

A method and a system for controlling the slip of a rear wheel of a motorcycle, the latter comprising a chassis with which there is associated said rear wheel, a front wheel and carrying a vehicle engine controlled by an electronic control unit (80), and a gear assembly for transferring the motion from the engine to the rear wheel. There is provided for indirectly controlling the slip of the rear wheel, without detecting the rotation velocity of the front wheel, by using data provided members associated with the engine and in particular with a secondary shaft of the gear assembly of the vehicle, such data being analysed by a control unit (10) which dialogues with the electronic control unit (80) which acts on the torque generated by the engine, limiting it, when said data show a slip of the rear wheel.

Description

[0001] METHOD AND SYSTEM FOR CONTROLLING THE SLIP OF THE REAR WHEEL OF A MOTORCYCLE

[0002] The present invention relates to a method and a system for controlling and limiting the unwanted slip of the rear drive wheel of a motorcycle, according to the preamble of the corresponding independent claim.

[0003] As known, the riding of a rear traction motorcycle (or however of a motor vehicle comprising only one rear drive wheel, a vehicle which should be considered to fall within the definition of "motorcycle") may be difficult in a low grip conditions like the ones encountered in an off-road use of the vehicle; in these conditions, unless this is requested by the driver / rider to obtain determined and desired behaviours, the rear drive wheel may slip deteriorating the controllability of the vehicle.

[0004] In order to counteract the slip (and control the traction) of the drive wheel of the motorcycle there are known control systems which help the rider or user to drive / ride the vehicle under low grip conditions. Such systems limit the slip of the wheel during the acceleration steps and control the traction of such wheels.

[0005] The traction control systems optimise the force applied to the rear drive wheel upon variation of the conditions of the ground, therefore managing the dynamics of the slip of the rear wheel.

[0006] In prior art traction control systems, in order to control the slip of the rear drive wheel, there is controlled the difference between the longitudinal velocity of the vehicle and the tangential rotation velocity of the rear wheel (it should be observed that such velocities may be different causing the wheel to slip), normalised to the longitudinal velocity of the vehicle. This according to thefollowing formula

[0007] Λ= (Vrear−Vx) / Vx

[0008] wherein

[0009] A= longitudinal slip of the drive wheel;

[0010] Vrear= tangential velocity of the drive wheel;

[0011] Vx= longitudinal velocity of the vehicle.

[0012] However, in order to implement a direct control on the slip of the wheel, there arises the need for such slip to be detected and calculated in real time; however, this requires the instantaneous knowledge of the velocity of the rear wheel and of the longitudinal velocity of the vehicle. This entails that there be provided for on the motorcycle at least two velocity sensor members, a first velocity member or sensor associated with the rear wheel and a second velocity sensor associated with the non-drive wheel; by detecting and measuring such sensors, one can estimate the longitudinal velocity of the vehicle. However, this measurement requires suitable basic assumptions and subsequent processing of the data obtained by the sensor member associated with the nondrive wheel; this results in possibility of obtaining a longitudinal velocity value of the vehicle that is not very precise, a value that can result in an error in evaluating the slip of the drive wheel with resulting erroneous action mode for counteracting such slip by splitting the torque transferred by the engine to the drive wheel.

[0013] The prior art solutions which engage said sensor members arranged on the front and rear wheels of the motorcycle may reveal problems also related to the connection with a traction control unit arranged on the vehicle, costs for such sensor members and for the connections.

[0014] In addition, the use of a velocity sensor arranged on the front wheel entails that such sensor is subject to atmospheric and environmental agents, agents which canresult in malfunctions or failures to the sensor.

[0015] Lastly, in some competitions, regulatory restrictions of some races prohibit the use of a sensor on the front wheel of the vehicle.

[0016] US2024 / 034287 discloses a method for monitoring the traction of a motor vehicle. The velocity of the vehicle and the circumferential velocity of at least one drive wheel are detected through suitable sensors arranged on the motor vehicle. In the text in question, it is indicated that the essential component of a traction control system is the slip controller. This allows to control the slip of the rear wheel by adapting the torque of the engine and therefore the drive torque of a drive wheel. The input variables of the slip adjuster are the actual slip and the reference slip (setpoint) of at least one drive wheel. In this case, the actual slip is calculated based on the velocity of the vehicle and on the peripheral velocity of at least one drive wheel. The difference between the set-point slip and the actual slip determines the control deviation.

[0017] The control deviation is entered into a PID traction controller. The slip acceleration is determined depending on the difference between the acceleration of the drive wheel and the acceleration of the vehicle determined starting from the detected velocity of the vehicle and the circumferential velocity of the drive wheel. Using the PID traction controller, the drive torque of the drive wheel is determined by the sum of a component P, a component I and a component D of the PID traction controller. The drive torque is returned to the driven wheel (motorcycle rear wheel).

[0018] Therefore, this prior art document uses at least one velocity sensor associated with the drive wheel, a sensor which should therefore be arranged in proximity of such wheel. This entails that a such sensor is arranged in a position whichcan be subjected to impacts by objects near which the motorcycle moves, especially should the vehicle be used offroad. In this case, the rear wheel of the motorcycle could come into contact with shrubs or with stones which are raised by the front wheel and which could impact against the sensor damaging it.

[0019] Besides this, a such sensor is exposed to atmospheric agents, same case applying to soil or mud on which the motorcycle moves, which could further prevent the correct operation of the sensor associated with the drive wheel.

[0020] As a result, the reliability of a such sensor may be decreased with resulting impossibility to have a real and effective traction control based on the data detected by the sensor.

[0021] Besides this, the prior art methodology operates based on a fixed set-point so as to evaluate the sliding of the drive wheel. However, especially in the off-road field, imposing a limitation to the rotation of the rear drive wheel in a motorcycle could result in the impossibility by the rider to control the motorcycle during a jump and while the vehicle is in the air: the rider should have the possibility to still manage the drive torque delivered to the rear wheel to control or direct the trim of the vehicle in the air. In the absence of such control, stemming from a limitation of the velocity imposed to the drive wheel, there may arise problems in riding the motorcycle especially when it touches the ground after a jump.

[0022] FR2980150 discloses a method for determining whether the drive wheels of a four-wheeled vehicle (or however having two drive wheels) connected to axes connected to a differential are subject to loss of grip. The limitation of the output torque from a powertrain acts if there is detected the loss of grip of the drive wheels, so as to limit therotation velocity upstream of a differential of a transmission. The loss of grip is determined by measuring the input rotation velocity to the differential, determining the derived rotation velocity and comparing the derivative of the rotation velocity with a stored value.

[0023] This prior art document describes the traction control in a vehicle having at least two drive wheels arranged on axes connected through a differential, a solution which does not apply to the field of two-wheeled motorcycles and in particular to off-road motorcycles. Also in this case, there is measured the rotation velocity at the input of the differential by using a sensor necessarily arranged in a position (differential input) in which such sensor may be subject to impacts and it has elements which could damage it (such as water) preventing the correct operation thereof with resulting erroneous measurement of the input rotation velocity to the differential.

[0024] Furthermore, the prior art solution discloses the comparison of the datum detected (rotation velocity) with a fixed reference value. And this, if applied to the field of an off-road motorcycle, could result in the impossibility having a correct control of the vehicle during a jump, as indicated above also in relation to the United States prior art document.

[0025] DE102014225447 relates to a method and a device for detecting the slip of the wheels of a motor vehicle during an acceleration process due to a torque applied unintentionally. According to the prior art document, there is provided for the comparison of the measured angular accelerations of the wheels, with an angular acceleration of the wheels calculated based on the longitudinal acceleration of the vehicle, so as to allow to detect an unwanted acceleration with loss of traction of the wheels.The accelerations are measured by means of a sensor.

[0026] Furthermore, by applying the motion equation, one can determine whether the loss of traction of the wheel of the wheels is intentional or unintentional, so as to start, if necessary, the stop of the actuation as a safety function. The invention also relates to device for detecting the slip of the wheels of a motor vehicle during an acceleration process, wherein the device comprises at least one means for detecting the slip of a wheel and switch off means for stopping the transmission, wherein the detection means is configured so that the slip of a wheel is detected when the measured angular acceleration of the wheel is greater than the a admissible maximum presumed angular acceleration of the wheel determined based on the translational longitudinal acceleration of the vehicle, and the switch off means for stopping the transmission is configured so that the switching off of the transmission is started upon the detection of a wheel which slips during an acceleration process.

[0027] This prior art document basically discloses a safety system which may stop the acceleration of the rear drive wheel. This through a comparison of a datum detected as a predefined datum. This solution may be hazardous should it be applied to an off-road motorcycle, where the rider should have the possibility to change the torque delivered to the drive wheel during the jump so as to be allow to direct the motorcycle while in flight and guide a correct landing thereof on the ground, as indicated above. This prior art solution may prevent such control of the torque while the vehicle is in flight and therefore the use thereof could result in problems during the landing of the motorcycle on the ground.

[0028] JPH0370638 discloses an apparatus for the traction control to prevent the slip of the drive wheels when a control force applied to the drive wheels becomes excessivein a vehicle equipped with a manual transmission. This with the aim of preventing the stop of the engine.

[0029] According to the prior art document, this is done by carrying out a control so as to respectively adjust the braking force of a drive wheel and output of an engine based on the detection of a slip condition of the drive wheel and a connection condition of a clutch.

[0030] There are provided for slip detection means, and clutch connection condition detection means, an engine velocity detection means and a drive wheel velocity detection means. Based on the results obtained by such means, the braking force of a drive wheel is adjusted by a means for adjusting the braking force of the drive wheel, while the power of an engine is adjusted by a means for adjusting the torque delivered to the drive wheel.

[0031] WO2016058843 discloses a traction control system for a motor vehicle which consists of a controller configured to start a traction control action on one or more wheels of the vehicle. The controller is configured to hinder the traction control action as a function of the low load condition on one or more wheels. The low load condition of the wheel is identified depending on at least one of a signal indicating the pitch of the vehicle and a signal indicating the lifting of the vehicle.

[0032] Also in this case, the prior art system intervenes with a mode that can result in the impossibility for the rider who uses a motorcycle in off-road mode, during a jump and while in flight, to control the vehicle by acting on the throttle of the motorcycle. As mentioned above, this could then lead to hazardous effects when the motorcycle is landing on the ground.

[0033] An object of the present invention is to provide a method and a system for controlling the traction of the rear drivewheel of a motorcycle and therefore adapted to limit the slip on low-grip surfaces of such wheel, that are improved with respect to similar prior art methods and systems.

[0034] In particular, an object of the present invention is to provide a method and a system of the type mentioned above which can be implemented and obtained also using sensor and control members possibly already provided on a motorcycle so as to exploit the connections already provided between them.

[0035] Another object of the present invention is to provide a method and a system of the type mentioned above which ensure an action in real time on the drive wheel so as to limit and avoid the slip thereof.

[0036] These and other objects which shall be apparent to the person skilled in the art are attained by a method and a system according to the attached claims.

[0037] For a better understanding of the present invention hereto attached below purely by way of example are the drawings, wherein:

[0038] figure 1 shows a block flow diagram of a system according to the present invention;

[0039] figure 2 shows a block flow diagram of a part of the system according to the invention;

[0040] figure 3 shows a block flow diagram of a portion of the part of the system of figure 2; and

[0041] figure 4 shows a state machine diagram which discloses a part of a method according to which the system according to the invention operates.

[0042] For the traction control of the drive wheel, the present invention exploits sensor members (or simply "sensors") different from specific sensors applied to the wheels, rear drive and front driven, of the vehicle. Such sensors are: A) a sensor or triaxial accelerometer through which there is determined, in particular, the longitudinal acceleration ofthe motorcycle and the rule of the accelerations to which the motorcycle is subjected. The spatial axes X, Y, Z on which such accelerometer operates do not necessarily correspond with those of the vehicle.

[0043] B) a rotation velocity sensor of the secondary shaft of the gearbox of the vehicle connected through the transmission member of the rear wheel of the motorcycle. This sensor allows to determine the velocity of the rear wheel, drive wheel, of the vehicle;

[0044] C) an engine revolutions sensor (RPM sensor);

[0045] D) a sensor for detecting the angular position of the valve of the throttle-equipped body (or TPS) usually used to manage, through a special control unit, a combustion engine. This sensor and the RPM sensor allow to determine the torque generated by the engine;

[0046] E) a position transducer of the drum of the gearbox from which there is obtained the signal of the engaged gear.

[0047] With an "indirect" measurement, these sensors allow to carry out an action for controlling the slip, of the rear wheel. This without using sensors specifically designed for the direct measurement of the velocity of both wheels.

[0048] However, the method provides for the possibility of maintaining the traction control or the slip of the rear drive wheel of the motorcycle even should the user or rider engage the usual clutch of the vehicle, travelling on uneven altimetric profiles and in the event of jumps, like when using the vehicle off-road. Such control is also maintained and carried out progressively as a function of the action of the rider on the clutch.

[0049] Therefore, the system (and the method) provides for the logic level 1, connected to a control level 2 of a control unit 3, in which there is present a first operative part 4 for detecting a jump. The logic level 1 of the control unit3 also comprises a second operative part 5 adapted to detect the activation of the clutch and a third operative part 6 adapted to detect the engaged gear. There is also present an operative part 7 which may estimate the velocity of the vehicle, said part not being used to calculate the control action by a proportional and integral controller (PI) 10 on the acceleration error of the wheel. Such controller is shown in figure 3; it will be described below. Alternatively, it may also be a proportional integral derivative controller.

[0050] Returning to the logic level 1, its various parts 4-7 operate based on the data obtained through the sensors mentioned above. In particular:

[0051] i) the signal aimuwhich represents the acceleration on the three axes of the motorcycle reach the operative part. The identification of a jump stage of the vehicle, which subsequently comprises a stop of the control carried out by the controller 10 (which is, therefore, disengaged even progressively as a function of the actuation of the clutch by the rider), occurs through a triaxial accelerometer by calculating the rule of the acceleration signals on three axes (ax, ay, az) and according to a suitable validation logic (as indicated below). Such logic allows to discriminate various types of jumps which require specific methods for re-introducing the controller PI 10 to the conclusion of each jump.

[0052] More particularly, the identification of a jump is based on the rule of the acceleration signals detected by the triaxial sensor on three spatial axes. This allows to generate a signal according to the following formula:

[0053] |anorm| =2√(ax2+ ay2+ az2)

[0054]

[0055] Such signal is compared with various threshold values and the comparison can allow to identify jumps of differenttypes. A low threshold value S1 allows to detect jumps with long free-falling stages, following which there is imposed a controller deactivation time 10 of a predefined duration. A threshold value S2, greater than the first, as well as a validation time in the order of tenths of a second, allows to detect jumps that do not have a long and clear flight phase and which may be described as "jolts" or "discharges with partial detachments from the ground". Regarding these, the step for deactivating the controller 10 following the landing has a duration proportional to the duration of the jump stage.

[0056] Figure 4 shows a state machine diagram which describes the identification of the jumps.

[0057] In figure 4, the jump is identified starting from an initial condition 40. In such initial condition it is evaluated whether the vehicle is moving without jumps (subblock 41) or whether to evaluate the existence of a such jump (block 42) given that the rule of the accelerations is lower than a threshold value S2.

[0058] From each of such sub-blocks 41 and 42 one can directly switch to a condition in which the type of the jump (block 43) is validated and evaluated.

[0059] In particular:

[0060] a) if the rule is lower than the value SI, the jump validation path switches from block 40 to block 43. Therefore, it is completed with a "masking" time in the deactivation of the control defined by block 44 and then followed by return to block 40 and in particular to sub-block 41.

[0061] b) In the event of jolts, that is if the rule is below S2, one switches from sub-block 41, through sub-block 42 and therefore to block 43, completing the whole with the masking time in deactivation (block 43). Therefore, there follows a return to block 40 and in particular to sub-block 41.It should be observed that the threshold values are S1< S2 and that the duration of the counters is in the order of hundreds of milliseconds (that is several tenths of a second).

[0062] ii) the operative part 5 of the logic level 1 of the control unit 3 is adapted to detect the actuation of the clutch. The status of the transmission (that is if motion is transferred to the rear drive wheel) is determined through two velocity measurements of transmission members: a first measurement is obtained by the RPM sensor of the engine (signal ωENGin figure 1), upstream of the usual clutch of the vehicle; the second measurement is obtained downstream of the clutch of the velocity sensor by the gearbox (signal ωwin figure 1). iii) the operative part 6 detects the engaged gear and receives a signal nGEARfrom a sensor which detects such selected gear. Obviously, the engaged gear may also be detected in any other known manner, for example through the usual control unit of the running engine, in such detection, based on a comparison with tabled data.

[0063] The indication of the engaged or disengaged gear which is obtained from the control level 2 of the control unit 3 allows, for example, to identify certain riding stages during which the traction control automatically adapts to the engaged gear.

[0064] As a matter of fact, it is known that the traction control parameters always automatically adapt (they update or shift), during the standard use of the vehicle, depending on the engaged gear. Having the gear sensor (that is the position transducer of the drum of the gearbox) available allows to identify some specific riding phases - which are the gear shift and the neutral gear - wherein the traction control system must be disabled.

[0065] The traction control action is calculated by thecontroller PI 10. It is shown in figure 3 where, through a block flow diagram, its main components are shown. Such controller 10 comprises (see figure 3) a first component 12 which receives signals relating to the longitudinal acceleration axof the vehicle by the triaxial accelerometer and, through comparison with a reference longitudinal slip datum Λref, it defines the reference longitudinal acceleration datum to which the traction control is connected based on the error between such reference longitudinal acceleration and the acceleration of the rear wheel.

[0066] The output data from the first component 12 of the PID controller 10 reaches a component 13 which applies saturation to the received signal in a known manner. Such component limits the value to the plausible values only and regarding which there is required an action of the control unit 3 by saturating the received signal. Such component 13 sets a range of values within which the output data from the component 12 should remain.

[0067] Such component 12, generates, as an output signal, an acceleration value of the reference drive wheel arearrefwhich passes through a component (summing node) 15 where it is algebraically summed to a signal relating to the acceleration of the rear wheel obtained through the velocity sensor arranged on the secondary shaft of the gearbox. From the component 15 there is output an acceleration error signal eaccwhich represents the error between the measured acceleration of the rear wheel and the calculated reference acceleration. Such signal is therefore treated in a known manner by a component 16 which carries out the saturated proportional and integral control action.

[0068] Such component 16 receives a first datum (Trider), a second datum (eacc) and produces an output signal (Tact).

[0069] More particularly, the first Trider datum represents thedrive torque requested by the rider from the vehicle engine detected on the drive shaft, while the output datum Tactis the torque value which is requested by the control unit 3. The datum Trideris estimated starting from the data obtained in particular from the control of the number of engine revolutions and the opening of the accelerator by the rider. The datum Trider may obviously refer to a value detected on the output shaft of the transmission or on the rear wheel. Such estimate is obtained through the operation maps of the engine.

[0070] Usually, Tact is lower than Trider and it is a percentage of the latter datum. As a matter of fact, in the event of low grip of the wheel on the ground and the rider "opens" the throttle, the torque could not be transmitted from the wheel to the ground; therefore, such torque, that is Tact, is adjusted by the control unit 3 to a value such not to generate the slip.

[0071] To summarise, the component 16, carries out the following functions:

[0072] 1. calculates the acceleration error following a proportional and integral strategy.

[0073] 2. limits the drive torque between a minimum value (zero) and a maximum value equal to the torque Trider which is the one requested by the rider using the throttle knob. This serves to prevent the motorcycle from "accelerating" more than requested by the rider.

[0074] This is carried out through the input signal eacc(used to calculate the control action) and the signal Trider for maximum saturation; as a function thereof, the component 16 produces in output Tactwhich corresponds to the drive torque demand made by the traction control system sent to the engine control unit or of the engine.

[0075] The generated torque can reach a limit value which canbe delivered by the engine as a function of the specific condition of use of the vehicle on the particular ground in which it moves, a deliverable value which limits the slip, preferably without however avoiding it entirely so as to ensure an appropriate riding of the motorcycle especially when used in off-road mode.

[0076] The output Tact of the component 16 defines the output of the controller PI 10; as a function of the presence or absence of a slip of the drive wheel and the extent of said slip, the output signal Tact, which reaches the usual engine control unit (not shown), modifies the torque delivered by the engine so as to limit and reduce such slip. This will be indicated subsequently.

[0077] The control action of the control unit 3 is applied solely under certain conditions under which the slip of the rear drive wheel of the motorcycle may manifest itself. Such conditions for example are those in which: the drive torque requested by the rider is greater than a threshold value; the velocity of the rear wheel is higher than a pre-set threshold value; the clutch is not engaged; a jump has not been detected; a gear shift has not been detected.

[0078] All this in the absence of validated errors for the sensors connected to the control unit 3.

[0079] Therefore, the control level 2 provides for (see figure 1) an activation logic component 25 which enables or disables the controller PI 10 to operate to generate the signal indicating the need to intervene on the torque generated by the engine to limit and counteract the slip of the drive wheel.

[0080] Such activation logic component 25 receives data from the operative parts 4, 5 and 6 of the logic level 1 and data relating to the torque (Trider) requested by the user and to the velocity of the drive wheel Vrear; based on such data,the activation logic component 25 may enable or not enable the controller PI 10 to intervene, the controller 10 which also receives such values Triderand Vrear. The knowledge of the torque requested by the rider is required to superiorly limit the torque demand of the traction control system to that of the rider, so as to avoid accelerations greater than the desired ones. This is an essential functionality that cannot be overlooked.

[0081] In an embodiment, the controller 10 calculates the percentage of reduction and sends it to the engine control unit. In other solutions (that is with other engine control units), it may send the torque demand directly to the engine control unit.

[0082] As mentioned, from the control level 2 of the control unit 3 there is emitted a signal adapted to modify, when needed, the value of the torque generated by the engine of the motorcycle. The control logic level 2 is also shown in figure 2 where parts corresponding to those already described relating to figures 1 and 3 are indicated using the same reference numerals. In figure 2 there are indicated: the triaxial accelerometer 30 with its members, per se known, to define the accelerations on the axes X, Y and Z of the vehicle (blocks 30A, 30B, 30C); a block 31 defining the rotation velocity sensor of the secondary shaft of the gearbox (connected through a transmission member to the rear wheel) from which there is indirectly obtained the rotation velocity of the rear wheel ωr(and from which there is also obtained the acceleration of the rear wheel entered into the controller PI 10); and the blocks 32, 33, 34 defining, respectively, the RPM sensor (which detects the rotation velocity of the engine ωe), the position transducer of then drum of the gearbox (which generates a signal τg) and the angular position sensor a of the valve of the throttle-equipped body. For the sake of simplicity, such sensors are arranged in a block defining the engine control unit, herein indicated with 80.

[0083] Figure 2 shows that the controller PI 10 generates a control signal Tc (block 35 of figure 2 and output datum from the block 10 of figure 1) relating to the torque requested by the traction control to limit the slip of the rear drive wheel of the motorcycle.

[0084] The control signal Tc calculated by the controller 10 is applied to the current engine point calculating a reduction factor of the delivered torque should there be detected a slip of the drive wheel. This value is used to calculate the control variables of the combustion engine, in particular the injection of fuel into the engine and the variation of the ignition timing.

[0085] Parallel to the calculation of the control signal there is also estimated the torque requested from the engine by the rider (Trider) and the torque requested from the engine by the controller 10, instant by instant. This estimate is made through a model depending on the TPS value and the number of revolutions of the engine. The control signal and the estimate of the torque requested by the rider are summed obtaining a desired torque value to be delivered to the rear drive wheel. There is then calculated the factor for reducing the torque to be delivered to limit the slip, which is the percentage difference between the torque requested by the control 10 and the torque requested by the rider through the action of a usual acceleration control member of the motorcycle. All this is carried out by the control unit 3 that is by its controller 10. The engine control unit receives the torque reduction percentage to be implemented and applies such value generating the corresponding torque.

[0086] The reduction factor is mapped by the engine controlunit with further two quantities in the management of the combustion engine. Such quantities are the variation of the timing angle or the ignition timing and the variation of the injection as a function of the reduction percentage of the torque requested by the rider. In the event of absence of an RBW control. In the presence of an RBW control, there is also considered the change in the opening of the throttle-equipped body as a function of the reduction percentage of the torque requested by the rider.

[0087] The first quantity of those indicated above is the variation of the ignition timing which moving from the optimal ignition point allows to reduce the delivered torque considering the same air flow in the intake ducts. Depending on the quantities indicated above, there is considered the presence / absence of the fuel injection during the engine cycle. The absolute values of these quantities depend on the work point of the engine, defined by the TPS value and by the engine revolutions.

[0088] Therefore, in a combustion engine not provided with the ride-by-wire (RBW) system, these are not the only variables on which one acts. In the event of a combustion engine provided with a ride-by-wire system, there are three quantities on which one can act to obtain the torque decrease. The possibility of changing the opening of the throttle-equipped body, therefore modifying the airflow in the intake ducts, is to be added to the quantities mentioned above. In this sense, the variation of the ignition timing and the variation of the opening of the throttle-equipped body may be used to obtain the same effects in terms of torque delivery, but with different dynamic and stress characteristics of the engine.

[0089] Such procedure allows to modify the torque delivered by the engine so as to control the slip of the rear drive wheelof the motorcycle after such slip has been detected.

[0090] Having the inventive characteristics reported in the claims below (which also comprise solutions and devices equivalent to those described in the present document), the proposed solution allows to quickly limit the slip of the drive wheel and also by using components already present on the vehicle for controlling the operation of the engine and of the transmission, that is without requiring further additional devices specifically designed to detect the rotation velocity of the front wheel of the motorcycle and without the sensors conventionally used for a direct measurement of the slip of the rear wheel of the vehicle.

[0091] In other words, the slip of the drive wheel is calculated indirectly by controlling the quantities which are physically strictly connected to such slip, without using velocity sensors arranged at the drive wheel and possibly at the front one adapted to measure the rotation velocity. This may allow to limit and reduce the torque generated by the drive wheel only when this is required so as to avoid jeopardising the management of the motorcycle by the rider for example when the motorcycle carries out a jump on an off-road path.

[0092] As a matter of fact, thanks to the invention, during a jump the rider may still act on the throttle of the vehicle to accelerate the drive wheel so as to manage the configuration during the flight and control the landing on the ground to prevent the motorcycle from falling thereon.

[0093] The identification of the rule of the acceleration signals described above and the comparison thereof with the various threshold signals as indicated above allows to disable the traction control described above (which would inevitably intervene during a jump) and it allows the rider to fully manage the power, allowing the rider to manage theconfiguration of the vehicle during the jump.

[0094] Lastly, with respect to the prior art solutions, the detection of the wheel velocity not directly carried out on the wheel, but upstream, on the transmission, allows to obtain a correct estimate of such velocity without being affected by the problems that the direct detection of such velocity of the wheel would involve, as indicated above (for example exposure of the velocity sensor to impacts or damage of such sensor in off-road conditions). Such detection on the transmission enables to have a more robust technical solution with respect to the prior art solutions in terms of protection of the sensor (incorporated in the engine and therefore protected from external damage). The solution of the invention also allows not to quickly lose the recognition and the control of the slip of the rear drive wheel of the motorcycle.

Claims

CLAIMS1. Method for controlling the slip and the traction of a rear drive wheel of a motorcycle associated with a motorcycle associated with a chassis of the vehicle, said motorcycle having at least one front wheel, said chassis carrying an engine controlled by an electronic control unit (80) and a gear and transmission assembly comprising a clutch, said control providing for detection of the slip of the rear drive wheel through a detection of the acceleration (arear) of such rear drive wheel and through a detection of the longitudinal acceleration (ax) of the motorcycle, said acceleration of the drive wheel (arear) and said longitudinal acceleration (ax) of the motorcycle being used so as to generate a control signal (Tc) of a torque generated by the engine applied to the rear drive wheel so as to limit its slip, the control of the slip being carried out without using velocity detectors specifically capable of detecting the rotation velocity of the front wheel and therefore detect the longitudinal velocity of the vehicle, characterised in that the acceleration of the rear drive wheel (arear) is indirectly determined by detecting the rotation velocity of a secondary shaft of the gear assembly of the vehicle, the longitudinal acceleration (ax) of the motorcycle being obtained through triaxial accelerometer.

2. Method according to claim 1, characterised in that there is provides for detection of the number of revolutions of the engine and the angular position (α) of the valve of a throttle-equipped body of the engine for controlling the torque delivered by the engine.

3. Method according to claim 1, characterised in that there is provides for detection of the number of revolutions of the engine and / or the position of a drum of the gearbox so as to determine whether the clutch is actuated and thatis whether the gear is engaged to verify the possibility of having to disable the traction control.

4. Method according to claim 1, characterised in that said control signal (Tc) is emitted by a controller (10) which receives the data of the longitudinal acceleration of the vehicle (ax), of the acceleration of the rear drive wheel (arear), the number of revolutions of the engine and the angular position of the throttle-equipped body (α).

5. Method according to claim 4, characterised in that the control signal (Tc) is sent to the electronic control unit (80) for controlling the engine, said electronic control unit (80) estimating at the same time, instant by instant, the torque delivered by the engine, such data relating to the control signal (Tc) and to the estimate of the torque being compared to define a torque value to be delivered to the rear drive wheel, therefore there being calculated a factor for reducing the torque to be delivered to limit the slip, said reduction factor being equal to a value of the percentage difference between the torque delivered and a torque requested by a rider of the vehicle.

6. Method according to claim 5, characterised in that, depending on the calculated reduction factor, the electronic control unit (80 ) for controlling the engine acts on the injection of fuel into the engine and on the ignition timing of the engine and / or on the opening of the throttle-equipped body to change the airflow in an engine intake duct.

7. Method according to claim 1, characterised in that it is detected whether the vehicle is carrying out jumps, the control of the slip and of the traction of the rear drive wheel being suspended during such jumps carried out by the motorcycle.

8. Method according to claim 7, characterised in that each jump of the motorcycle is identified through a detectionof the accelerations of the vehicle on three spatial axes, said accelerations defining a vehicle acceleration rule which is compared with threshold values adapted to allow the identification of the type of jump and the deactivation time of the slip and traction control.

9. Method according to claim 4, characterised in that the action of the controller (10) is subordinated to an operating enabling generated by an activation logic component (25) as a function of the existence of specific operating situations.

10. Method according to claim 9, characterised in that the action of the controller (10) is deactivated in specific operating situations including the gear shift and the neutral gear engagement time.

11. System for controlling the slip and the traction of a rear drive wheel of a motorcycle associated with the chassis, said motorcycle having at least one front wheel, said chassis carrying an engine controlled, in its operation, by an electronic control unit (80), and a gear and transmission assembly comprising a clutch, said system operating according to the control method of claim 1, the slip della of the rear drive wheel being detected based on the control of the acceleration of the rear drive wheel and of the longitudinal acceleration of the vehicle, characterised in that there is provided for a rotation velocity sensor of the secondary shaft of the gear of the motorcycle through which there is indirectly detected the acceleration (arear) of the rear drive wheel, there being provided for a triaxial accelerometer for determining the longitudinal acceleration (ax) of the vehicle, the system being provided with sensor devices specifically capable of detecting a velocity of the front wheel and therefore the longitudinal velocity of the motorcycle.

12. System according to claim 11, characterised in that it comprises a controller (10) adapted to define a control signal relating to the torque to be applied to the engine to limit the slip of the rear drive wheel, said controller (10) receiving the acceleration data of the rear drive wheel and the longitudinal acceleration of the vehicle, there being provided for an angular position sensor of a valve of a throttle-equipped body of the engine connected to said controller and adapted to send to the latter signals relating to the position (α) of such vehicle.

13. System according to claim 11, characterised in that said controller (10) is a proportional and integral controller or, alternatively, a proportional integral derivative controller connected to the electronic control unit of the engine, the control signal (Tc) being sent by such electronic control unit.

14. System according to claim 11, characterised in that the controller (10) is a part of a control unit (3) comprising a first logic level (1) and a control level (2) to which the controller belongs, said first logic level having a first operative part (4) adapted to detect whether the vehicle is carrying out a jump, a second operative part (5) adapted to detect the activation of a clutch of the vehicle, and a third operative part (6) adapted to detect the engaged gear.

15. System according to claim 11, characterised in that the controller (10) is connected to an activation logic component (25) which enables or disables the controller (10) to generate the control signal (Tc).

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