METHOD FOR CONTROLLING AN ELECTRIC OR HYBRID POWERTRAIN, CONTROL UNIT, POWERTRAIN AND VEHICLE

Description

[0001] The present invention relates to a method for controlling a powertrain ("GMP") of an electric or hybrid thermal-electric vehicle. It applies more particularly in the field of engine control, which brings together all the techniques for managing an engine based on the information provided by its sensors.

[0002] The present invention solves a problem that occurs when an electric or hybrid vehicle is parked on a slope. Indeed, as explained in more detail later in this application, when the parking brake is deactivated on a slope, the powertrain can start to oscillate on its suspensions, generating mechanical shocks that can be strongly felt by the occupants of the vehicle.

[0003] The state of the art, in particular patent application US2009 / 0043465A1, suggests preventively blocking the powertrain. A major drawback of this preventive solution is of a safety nature, because it generates a risk of unexpected movement of the vehicle when the parking brake is deactivated on the flat: if a slope has been detected by mistake, then the powertrain is blocked for nothing and it is its release that causes the unexpected movement of the vehicle. This is a problem that the present invention proposes to solve.

[0004] Patent application US2015 / 027798A1 discloses a method for controlling a GMP having the same drawbacks as the method according to US2009 / 0043465A1.

[0005] The invention therefore aims to remedy the aforementioned drawbacks, in particular to reduce the oscillations of an electric or hybrid GMP when the parking brake is deactivated, without the risk of unexpected movement, by a curative and not a preventive correction method. To this end, the present invention relates to a method according to claim 1.

[0006] The present invention also relates to a device according to claim 4.

[0007] The present invention also relates to a powertrain comprising such a device, as well as an electric or hybrid vehicle comprising such a powertrain.

[0008] Other characteristics and advantages of the invention will appear with the aid of the following description given with reference to the appended figures: 1, 2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d and 4 which illustrate the problem posed by the state of the art; 5, 6, 7, 8, 9 and 10 which illustrate a non-limiting example of embodiment of the invention, resolving this problem.

[0009] As illustrated in the figure 1 , all the control laws of an electric motor 10 of a vehicle 1, accompanied by their parameters, are implemented in software form in a computer 12 commonly called ECU (Electronic Control Unit). The role of the engine control is to translate the will of a driver, known from the information received from accelerator and brake pedal sensors 13, into a positive or negative engine torque setpoint. This torque setpoint is then transmitted to a power electronics module 14, which notably includes an inverter and a chopper, which translates this torque setpoint into voltage and intensity setpoints of a current supplied by a battery 15. The motor 10 receives these voltage and intensity values, thus converting electrical power into engine torque. Finally, this torque is transmitted to wheels 16 of the vehicle via a reducer 17.The assembly consisting of the engine 10 and the reducer 17 forms the GMP of the vehicle 1.

[0010] The GMP is supported by the body 19 of the vehicle 1 by means of a suspension system 18, the role of which is to limit the propagation of vibrations generated by the engine 10. Depending on the engine torque transmitted to the wheels 16, and within the limit of their deformation capacities, these suspensions 18 allow the GMP to move around the axis of the wheels 16. These movements are similar to pivoting of the GMP around the axis of the driving wheels 16. The direction of pivoting of the engine 10 is a function of the sign of the torque produced by the GMP.

[0011] Thus, as illustrated by the figure 2a , when it delivers zero torque, the GMP remains in an equilibrium or rest position.

[0012] With a positive torque corresponding to a forward motor mode or a reverse generator mode, as illustrated by the figure 2b , the GMP pivots backwards in the opposite direction to the engine torque.

[0013] With negative torque corresponding to a reverse motor mode or a forward generator mode, as illustrated by the figure 2c , the GMP pivots forward in the opposite direction to the engine torque.

[0014] To ensure that vehicle 1 is immobilized when engine 10 is stopped, a parking function called "Park" makes it possible to mechanically lock the powertrain so as to prevent any pivoting. As illustrated by the figure 2d , the GMP rotation lock is ensured by a parking finger 101 engaging in a toothed crown 102 fixed at the output of the motor 10 or the reducer 17. The actuation of the finger 101 is either mechanical via a lever, or electrically controlled via a button, both being manipulated by the driver.

[0015] A problem occurs when the vehicle 1 is parked on a slope. Indeed, when the vehicle 1 is parked on a slope, a force is exerted on the finger 101: this force is a function of the mass of the vehicle 1 and the angle of the slope. The rotor of the motor 10 being mechanically secured to the stator, the force causes the pivoting of the motor 10 and the powertrain as a whole. The pivoting of the motor 10 is therefore also a function of the mass and the angle of the slope. The direction of the pivoting depends on the direction of the slope (upward or downward) or the orientation of the vehicle relative to the slope (facing or back to the slope).

[0016] THE figures 3a, 3b, 3c et 3d illustrate this problem in the case of a vehicle facing a slope of value x. The figure 3b illustrates the engagement phase of finger 101: as long as the finger is not engaged, the motor rotates negatively, until finger 101 finds an inter-tooth space, then takes up the inter-tooth play. The figure 3c illustrates the pivoting of the GMP after this engagement phase. The mass of the vehicle exerts a force on the finger 101, resulting in the pivoting of the GMP. This pivoting is not seen by the motor 10, because its stator and rotor are linked by the finger 101. The vehicle 1 is then immobilized in a stable state, until the driver deactivates the Park function. figure 3d illustrates the disengagement of the finger 101: when the finger 101 is disengaged, the suspensions 18 “freely” return the GMP to its rest position. This release phase is not controlled and generates oscillations of the GMP around its equilibrium position, i.e. an alternation of pivoting in the positive direction then in the negative direction. The number and amplitude of the oscillations are functions of the force exerted on the finger 101 before its disengagement, the characteristics of the suspensions 18 (elasticity, damping, stiffness, etc.) and the mass of the GMP. For example, the figure 4 graphically illustrates, as a function of time expressed in seconds on the abscissa, the evolution of the position in degrees of the rotor noted Wxx_sens_emot_psn and the rotation speed in revolutions per minute of the motor noted Vxx_emot_n during disengagement of the finger 101 at an instant t=8.25 on a slope of 26%. These oscillations, which last almost 2 seconds until an instant t=10, are strongly felt by the occupants of the vehicle 1 and are accompanied by mechanical shock noises. They therefore generate discomfort for the occupants of the vehicle 1. This is a problem that the present invention aims to solve.

[0017] To solve this problem, the patent application cited above suggests applying a torque preventively before the finger is disengaged, so as to keep the powertrain stationary after the brake is released. A major drawback of this solution is safety-related, because it is very complicated with this solution to guarantee that there is no risk of unexpected movement of the vehicle when the finger is disengaged, particularly when the brake is released (the driver being able to intervene during the disengagement), simply because the slope information may be erroneous. There is then a risk of applying a force on a flat surface or a force of the opposite sign, briefly causing the vehicle to move unexpectedly for the driver.

[0018] An aim of the invention is to solve the aforementioned problems and drawbacks in the disengagement of the parking finger, by dynamically correcting the engine speed: this involves detecting rapid variations in the engine speed and damping them by applying an engine torque opposite to these variations. According to the invention, the correction must be strictly positive in negative slope and strictly negative in positive slope, in opposition to the derivative of the engine speed, modulated in amplitude according to the slope, so that the correction is brief but very damped.

[0019] In a preferred embodiment because it is simple to implement, illustrated by the functional diagram figure 5 , a method 4 according to the invention taking the engine speed as input may for example comprise a derivation step 41, in order to take into account only the variations in the engine speed, followed by a phase advance filtering step 42, in order to ensure sufficient sensitivity to the variations in the speed, followed by an amplification step 43, in order to modulate the amplitude of the correction torque, followed by a saturation step 44, in order to adapt the direction of the correction to the direction of the slope as well as to the possibilities of the engine. The method provides a corrective torque value as output. This same embodiment is illustrated by the architecture diagram of the figure 10 , where a corrector 2 according to the invention may for example comprise the following modules: a bypass module 21 implementing the bypass step 41; a filtering module 22 implementing the phase advance filtering step 42; an amplification module 23 implementing the amplification step 43; a saturation module 24 implementing the saturation step 44, allowing in particular, depending on the sign of the slope x determined by a module 31, only negative torque via a module 24a or only positive torque via a module 24b, a switch 24c making it possible to exclusively select either the output of the module 24a or the output of the module 24b, depending on the sign of the slope x received from the module 31.

[0020] The corrector 2 receives the engine speed 10 as input from the derivation module 21, it receives the absolute value |x| of the slope (in %) determined by a module 32 as input from the amplification module 23 and it receives the sign of the slope x as input from the saturation module 24. The corrector 2 provides a correction torque value as output from the saturation module 24.

[0021] A module 24 allows, upon exiting the Park position, to activate the correction over a predefined period of time ζ, of the order of 0.5 seconds for example, counted from the detection of the oscillations. A module 35 allows the correction torque to be taken into account only during this period of time ζ, the torque requested by the driver being taken into account after expiry of this period of time ζ.

[0022] The adjustment parameters of the corrector 2 are therefore the coefficient of the phase advance filter (noted a), the time constant of the phase advance filter (noted T), the data of the gain G applied by the amplification module 23 as a function of the slope x, as well as the Min and Max limit values ​​of the saturation coefficient applied by the saturation module 24 as a function of the motor used and the sign of the slope.

[0023] During the first stage 41 illustrated by the graph of the figure 6 , which represents the evolution over time of the engine speed in revolutions per minute without correction (curve 61 plotted in light showing the variations of greatest amplitude) as well as its derivative in revolutions per minute per second (curve 62 plotted in darker showing the variations of lowest amplitude), the derivation module 21 makes it possible to estimate the variation in the rotation speed of the engine 10, that is to say its acceleration. The correction torque which will be applied to the engine to attenuate its oscillations will be proportional to this acceleration. For example, it can be calculated by applying the formula for the derivative in the Laplace domain, the transfer function of the derivator 21 being noted p.

[0024] During the second stage 42 illustrated by the graph of the figure 7 , which represents the evolution over time of the derivative of the engine speed without correction in revolutions per minute per second (curve 71 plotted in light showing the variations of lower amplitude) as well as this same derivative once corrected by the phase advance filtering module 22 (curve 72 plotted in darker showing the variations of greater amplitude), the latter making it possible to detect the slightest variation in the speed and therefore to have no correction delay. This filter is defined by the following transfer function FT: FT = 1 + a . Tp / 1 + Tp Or : T is the filter time constant defined as a function of the resonance frequency f of the system to be corrected (the motor in this case, of the order of 5 Hz), with T=1 / f; a is an adjustment coefficient to be adjusted as a function of the desired phase advance, with a value always greater than or equal to 1, of the order of 3 in this embodiment. After the filtering module 22, the response is shifted in time in order to obtain a better response time of the corrector.

[0025] During the third stage 43 illustrated by the graph of the figure 8 , which represents the evolution over time of the engine torque correction setpoint in Newton-meters (curve 81 plotted in dark showing the variations of smaller amplitude) as well as the derivative of the engine speed corrected by phase advance (curve 82 plotted in lighter showing the variations of larger amplitude), the amplification module 23 applies a negative gain in order to invert the sign of the calculated torque, so that the latter is in phase opposition with the acceleration of the engine, this in order to brake it. On the other hand, the gain is used to modulate the amplitude of the torque. In order to obtain a robust and effective correction whatever the level of slope on which the vehicle is located, the gain can be defined according to the vehicle's inclination information, this inclination being able for example to be provided by an automatic trajectory correction device, of the "ESP" type.Thus, the output torque of the amplification module 23 is of opposite sign and modulated according to the limits of the motor. In the present embodiment, the gain value has been chosen in the interval [-1; -0.4], with an increase (or a decrease in absolute value) proportional to the increase in the slope.

[0026] During the fourth stage 44 illustrated by the graph of the figure 9, which represents the evolution over time of the engine torque correction setpoint in Newton-meters (curve 91 plotted in light showing alternately positive and negative variations) as well as this same setpoint saturated by the saturation module 24 (curve 92 plotted in darker showing only negative variations), the latter allowing, depending on the limits of the engine used, to limit the maximum torque demand, so as not to ask the engine to provide a corrective torque which is beyond its possibilities. It also allows the torque to be saturated negatively or positively respectively on a positive or negative slope, in order to limit the effect of the delay linked to the achievement of the torque. This saturation is therefore also defined according to the sign of the slope, obtained for example using an automatic trajectory correction device.

[0027] In addition to preventing any unexpected movement of the vehicle, the main advantage of the present invention is that it offers excellent sensitivity to variations in engine speed, i.e. responsiveness. Of course, with the correction according to the invention, the first shock is not eliminated, but it is drastically reduced. On the other hand, if the oscillation is zero, for example if the vehicle is parked on the flat, then the correction is necessarily zero as well, and therefore there is no longer any risk of unexpected movement of the vehicle.

Claims

1. Method (4) for controlling the power train of a vehicle (1), the power train being mounted on the vehicle by means of suspension elements (18) and including an electric motor (10) capable of transmitting torque to wheels (16) of the vehicle, the power train including a locking pin (101), the pin being moveable: - from an engagement configuration in which the rotor (102) of the motor is rigidly connected to the stator of the motor, thereby immobilizing the vehicle; - to a disengagement configuration in which the rotor (102) is released from the stator, thereby enabling the vehicle to move; the method being characterized in that it includes a step of dynamically correcting the speed of the motor which, when the locking pin moves from the engagement configuration to the disengagement configuration when the vehicle is immobilized on a slope, modulates the correction as a function of the value of the slope (x) as well as its upward or downward direction relative to the vehicle, said dynamic correction step including a saturation step (44), in order to orient the correction as a function of the upward or downward direction of the slope relative to the vehicle and to limit its amplitude as a function of the capabilities of the motor, the correction being strictly positive on negative slopes and strictly negative on positive slopes, opposing the derivative of the motor speed, which is modulated in amplitude as a function of the slope, thereby damping the oscillations of the power train on the suspension elements around the axle of the wheels.

2. Method according to Claim 1, the dynamic correction step including, before the saturation step (44): - a step of measuring the speed of the motor; - a step (41) of calculating the derivative of the motor speed, in order to estimate the variations in the rotational speed of the motor; - a phase-advance filtering step (42), in order to increase the sensitivity of the correction to these variations; - an amplification step (43), in order to modulate the amplitude of the correction as a function of the value of the slope (x) on which the vehicle is immobilized.

3. Method according to the preceding claim, characterized in that the amplification step includes applying to the correction a gain value (G) which is an increasing function of the slope value (x).

4. Device for controlling the power train of a vehicle (1), the power train being mounted on the vehicle by means of suspension elements (18) and including an electric motor (10) capable of transmitting torque to wheels (16) of the vehicle, the power train including a locking pin (101), the pin being moveable: - from an engagement configuration in which the rotor (102) of the motor is rigidly connected to the stator of the motor, thereby immobilizing the vehicle; - to a disengagement configuration in which the rotor (102) is released from the stator, thereby enabling the vehicle to move; the device being characterized in that it includes a module (2) for dynamically correcting the speed of the motor including: - a module for measuring the speed of the motor; - a module (21) for calculating the derivative of the motor speed, in order to estimate the variations in the rotational speed of the motor; - a phase-advance filtering module (22), in order to increase the sensitivity of the correction to these variations; - an amplification module (23), in order to modulate the amplitude of the correction as a function of the value of a slope (x) on which the vehicle is immobilized, the correction being strictly positive on negative slopes and strictly negative on positive slopes, opposing the derivative of the motor speed, which is modulated in amplitude as a function of the slope; - a saturation module (24), in order to orient the correction as a function of the upward or downward direction of the slope relative to the vehicle and to limit its amplitude as a function of the capabilities of the motor in such a way that, when the locking pin is moved from the engagement configuration to the disengagement configuration, when the vehicle is immobilized on the slope, the oscillations of the power train on the suspension elements about the wheel axis are damped.

5. Power train including a device according to Claim 4.

6. Electric or hybrid vehicle (1) including a power train according to Claim 5.