KR102267583B1 - A method of controlling the torque transmitted to the wheels of an electric vehicle or a hybrid vehicle according to an allowable regenerative torque - Google Patents

Abstract

A method of controlling the torque transmitted to the wheels of a vehicle comprising an electric machine is based on an interpretation of the position of an accelerator pedal moved by a driver between a fully depressed position and a released position over a pressing stroke, wherein the pressing stroke comprises an upper region and It consists of a lower region, wherein the position of the pedal in the upper region determines the negative torque set point, the lower region along the upper region in the direction of depression, wherein the position of the pedal in the lower region determines the positive torque set point; , a transition point between the two regions is a neutral point corresponding to a torque set point of zero, and the position of the neutral point moves according to the regenerative torque allowed by the vehicle.

Description

A method of controlling the torque transmitted to the wheels of an electric vehicle or a hybrid vehicle according to an allowable regenerative torque

The present invention relates to a method of controlling the torque of a wheel in an electric vehicle or a hybrid vehicle.

More particularly, the present invention relates to a method for controlling torque transmitted to the wheels of a vehicle comprising an electric machine, said control method comprising: a release position and a release position over a depression stroke comprising an upper region and a lower region; based on the interpretation of the position of the accelerator pedal moved by the driver between the full depression positions, wherein the pedal position in the upper region determines a negative torque setpoint, the lower region after the upper region in the direction of depression The pedal position in the region determines the positive torque setpoint. The transition position between the two regions is the neutral point corresponding to the torque setpoint of zero.

The vehicle in question may be a fully electric vehicle or a hybrid vehicle, which in this case comprises at least one internal combustion engine and one electric machine.

In hybrid or electric vehicles, only a torque actuator, an internal combustion engine and an electric machine can be used to achieve a high level of deceleration. The advantage of an electromechanical braking action is energy recovery during deceleration when the driver releases the pedal. The greater the value of the deceleration, the greater the amount of energy recovered. Nevertheless, it is not always good to have a vehicle that brakes too heavily when the accelerator pedal is released. It is also advantageous to be able to modulate the deceleration with the accelerator pedal. The maximum deceleration can vary over time. To ensure good drivability, it is useful to successfully manage the interpretation of the accelerator pedal according to the level of regeneration, regardless of the maximum regeneration value.

In the overall evaluation of modern vehicles, drivability is a very important factor. Therefore, one of the main purposes of an automobile control system is to make the response of the powertrain pleasant.

In a hybrid vehicle, there are at least two actuators capable of supplying torque to the wheels. The driver's request is met by the sum of the torques supplied by the electric machine and the internal combustion engine. By distributing the driver's torque request from 100% electric to 100% conventional, the overall consumption of the hybrid powertrain can be optimized.

Due to the electrical machine, it is also possible to recover energy during deceleration. This is because the electric machine is reversible and has two modes of operation: as a motor and as a generator. When the driver releases the pedal, the vehicle benefits from the friction of the internal combustion engine and the accumulated deceleration generated by the regeneration of the electrical machine.

The entire stroke of the accelerator pedal of an electric or hybrid vehicle is divided as a whole into two areas. The first depressing zone, starting first from the upper position, manages the negative torque to the zero force setpoint. The second region after the first in the direction of depression transmits a positive torque to the wheel. The physical position of the depressed pedal corresponding to the transition between these two regions corresponds to a torque setpoint of zero: this is the neutral point of the pedal.

The greater the regenerative torque generated by the electric machine, the stronger the feeling of deceleration, and the greater the energy recovery in the battery. The lower the regenerative torque, the less limited the vehicle and less energy is recovered to the vehicle battery.

In figure 1 a distinction is made between a negative torque at the wheel during deceleration in a first part of the stroke and a positive torque at the wheel during acceleration in a second part of the stroke. The closer the neutral point is to full depression of the pedal (depression value 1), the more the pedal positioning can be used to fine-tune the negative torque and less it can be used to fine-tune the positive torque.

The maximum regenerative torque or allowable regenerative torque may vary for several reasons:

- Battery charging: If the battery is fully charged, it simply cannot reproduce the deceleration torque.

- If the electrical machine is damaged, its ability to generate regenerative torque is reduced.

The value of the regenerative torque may be made to change over time:

- Interpretation of pedal strokes can be differentiated, for example, to distinguish between "typical driving modes", such as between "eco mode" and "sport mode" Yes: it should be possible to adjust the handling of the vehicle in harmony with the mode employed, especially in the regeneration phase.

- Some vehicles are provided with a specific driving, or "brake" mode, which can be activated by the driver and indicates the driver's desire for a very high regenerative torque.

- Finally, in order to avoid "free" movement at the start of the accelerator pedal stroke, the regenerative torque is always zero when stopped.

Finally, for a given position of the neutral point in the stroke of the pedal, the greater the minimum value of allowable regenerative torque, the less the driver can modulate with the accelerator pedal. If the regeneration torque is high, its capacity for modulation is very useful in certain circumstances, for example when approaching roundabout.

The driver's ability to use the accelerator pedal to modulate the regenerative force of the powertrain is important for drivability and brake safety, especially when such force varies according to different parameters (battery charge, vehicle speed, driving mode, etc.). raises important issues. The above problem becomes more and more important as the amplitude of the change of the regenerative torque over time increases.

It is an object of the present invention to regulate the regenerative torque at the accelerator pedal with different levels of regenerative torque without free movement in a comfortable manner.

For this purpose, the invention proposes that the position of the neutral point is moved according to the regenerative torque permitted by the vehicle.

Preferably, the negative torque set point is the torque set point supplied by the electric machine of the hybrid vehicle in regeneration mode.

Due to these measures, the operation of the powertrain when the electric machine is in generator mode is finely controlled when the driver releases the accelerator pedal. This allows the driver to obtain different types of handling from the vehicle, from the smallest limit to the most limiting, depending on the performance of the electric machine.

Other features and advantages of the present invention will become apparent from the following description of non-limiting embodiments with reference to the accompanying drawings.
1 shows the transmission of torque according to the pressing of the pedal.
2 shows for example the difference in allowable regenerative torque between two driving modes.
3 highlights the effect of changing the mode on the pedal stroke.
4 shows the strategy of the proposed neutral point movement.

A non-limiting embodiment of the invention is shown in the drawings and relates in particular to the case of control of the torque transmitted to the wheels of a fully electric vehicle or a hybrid vehicle comprising at least one internal combustion engine and one electric machine. This control is based on the interpretation of the position of the accelerator pedal. The accelerator pedal is moved between a released position and a fully depressed position by the driver. It moves over a depression stroke consisting of an upper region and a lower region after the upper region in the direction of depression, in which the pedal position determines the negative torque setpoint and in the lower region the pedal The position determines the positive torque setpoint. The transition position between these two regions is the neutral point corresponding to the torque setpoint of zero.

In the case of a hybrid vehicle, the negative torque set point is in principle the torque set point supplied by the electric machine in regenerative mode, as in a fully electric vehicle. The regenerative torque setpoint is thus limited by the energy storage capacity of the vehicle battery.

The neutral point is advantageously movable in response to a change in the driving mode of the vehicle. The non-limiting example described below relates to the transition from a “nominal” or “normal” driving mode to a “brake” driving mode (where sustained regenerative braking is achieved). This conversion is illustrated in FIG. 2 . Overall, the present invention proposes that the neutral point moves up in the stroke of the pedal after the transition from the standard driving mode to a mode programmed to allow a higher level of regenerative torque than the standard mode.

During the transition, the regeneration torque increases. In order to maintain the driver's ability to fine-tune this, the present invention provides that the position of the neutral point is moved in accordance with an acceptable regenerative torque. In this example, the neutral point moves from 10% to 20% of the pedal press.

A change in the position or "value" of the neutral point has consequences for the driver's desired interpretation. Referring to Figure 3, if the driver depresses the pedal 50% when the neutral point moves from 10% to 20%, the "calibration" of the pedal (reflecting the percentage of available traction torque requested from the powertrain) "corrected depression" is reduced. In this example, the driver approaches 40% of the vehicle's maximum performance in "Normal" mode, and only approaches 30% in "Brake" mode. Movement of the neutral point results in a loss of power to the wheels: if this movement occurs in the transition from the "normal" mode to the "brake" mode, there is no movement to the wheels of the vehicle unless the driver simultaneously adjusts the pedal position. lose power

However, the transition from the "normal" mode to the "brake" mode is not intended to impact the handling of the vehicle if the driver does not release the pedal. Therefore, it is desirable to offset the movement time of the neutral position for the mode change. In this regard, the present invention proposes the strategy shown in FIG. 4 , according to which an abrupt change in the neutral point can occur before the driver requests that the vehicle be braked by releasing the accelerator pedal. none.

In general, when the vehicle is accelerated or the driver wishes that the vehicle speed is maintained (region A), it is desirable that none of the mode transitions impact the vehicle handling. Thus, movement of the neutral point of the pedal is delayed for changes in the allowable regenerative torque. In the example described above, the movement of the neutral position is delayed in time with respect to the adoption of the “break” mode.

A mode change is considered to move the neutral position only when the driver wishes to decelerate, and in particular the mode change is considered only when the driver expresses his intention by releasing the pedal. The neutral position can then be adjusted (zone B). Finally, it is advantageous to filter the transition so that the driver does not feel unpleasant.

Claims (10)

A method of controlling a torque transmitted to wheels of a vehicle comprising an electric machine, the method of controlling torque by a driver between a release position and a full depression position over a depression stroke comprising an upper region and a lower region. is made based on an analysis of the position of the moving accelerator pedal, the pedal position in the upper region determines a negative torque setpoint, and the pedal position in the lower region after the upper region in the direction of depression is a positive torque setting determine a positive torque setpoint, the position of the transition between the two regions being the neutral point corresponding to the torque setpoint of zero, the position of the neutral point being the regenerative torque of the electric machine permitted by the vehicle ), characterized in that it moves according to the torque control method. Method according to claim 1, characterized in that the negative torque setpoint is a torque setpoint supplied by the electric machine of the hybrid vehicle in a regenerative mode. Method according to claim 1 or 2, characterized in that the neutral point moves after a change in the driving mode of the vehicle. 3. Torque control according to claim 2, characterized in that the neutral point moves upward upon the stroke of the pedal after transition from the standard driving mode to a driving mode programmed to allow a higher level of regenerative torque than the standard driving mode. Way. 3. Method according to claim 2, characterized in that the regenerative torque set point is limited by the energy storage capacity of the vehicle battery. Method according to claim 1 or 2, characterized in that the movement of the neutral point of the pedal is delayed for a change in the permissible regenerative torque. 4. Method according to claim 3, characterized in that the movement of the neutral point is delayed in time with respect to the mode change. Method according to claim 6, characterized in that the movement of the neutral point occurs when the driver indicates an intention to decelerate by releasing the pedal. Method according to claim 1 or 2, characterized in that the vehicle is a fully electric vehicle. Method according to claim 1 or 2, characterized in that the vehicle is a hybrid vehicle comprising at least one internal combustion engine and one electric machine.

Images