METHOD FOR COMPENSATING FOR THE INTERRUPTION OF TRACK FORCE DURING A SHIFTING OPERATION IN SHOOTING MODE

Description

[0001] The present invention relates to the control of the torque of an electric traction machine during gear change in braking, in an electric or hybrid architecture which does not allow for the coupling to the wheel of a regenerative torque electric source during gear changes in pure electric mode.

[0002] More specifically, it is intended to provide a method for compensating for torque loss at the wheel in the event of a gear change during braking, on a vehicle equipped with an electric traction machine connected to the vehicle's wheels by a gearbox capable of transmitting the braking torque of the electric machine to the wheels during deceleration in at least two gear ratios, and a mechanical braking system acting on the wheels independently of the electric machine.

[0003] Publication FR 2 973 299 describes a hybrid architecture with two pure electrical ratios, between which changes are made by moving a sliding gear. After being disengaged, the sliding gear passes through an intermediate neutral position, where no torque from the electric traction machine is transmitted to the wheel, before being engaged on the opposite side.

[0004] This type of transmission implies that during a braking phase provided by an electric motor, an electric gear change is observed in ZEV mode (for Zéro Emission Vehicle ), a torque interruption at the wheel. The braking torque of the electric motor is then no longer transmitted to the wheels. Furthermore, in order to allow disengagement during the initial phase of the gear change, it is necessary to cancel the torque supplied by the electric motor in order to reduce the torque exerted at the dog clutch. This torque cancellation directly impacts the braking torque at the wheel, which is very poorly received by the user. Documents WO 2009 / 080901 A1 and US 6 126 251 A disclose methods for gear changes during braking. According to these documents, at least part of the regenerative torque of an electric machine, diminished during the opening phases of the drivetrain, is compensated by the hydraulic braking control.

[0005] The present invention aims to compensate for the lack of braking torque at the wheel, both during the torque cancellation phase when preparing for disengagement, but also during gear change using the vehicle's braking system.

[0006] To this end, it proposes a method for compensating for torque interruption according to claim 1, and therefore for defining a mechanical braking torque setpoint at the wheels, which is a function of the type of control of the electric machine, and of the date of the request for a downshift to the gearbox.

[0007] This invention finds a preferred, but not limiting, application on any vehicle whose gearbox does not allow for the coupling to the wheel of an electrical source of regenerative torque, during gear changes in electric mode.

[0008] The present invention will be better understood upon reading the following description of a non-limiting embodiment thereof, with reference to the accompanying drawings, in which: there figure 1 is a simplified diagram of the gearbox in question, and the figure 2 , illustrates the application of the invention.

[0009] On the figure 1 , we have represented in summary the architecture of a four-speed hybrid transmission 1 comprising two concentric primary shafts 2, 3, connected respectively to a thermal engine 4 and an electric traction machine 5. The secondary shaft 6 carries two idler gears 7, 8, allowing the establishment of two first electrical ratios according to the position of the sliding gear 9, when the thermal engine is not connected to the transmission.

[0010] During gear changes in "pure" electric mode between gears 1 and 2, torque transmission to the wheels is interrupted. This occurs during traction, but also during "regenerative" braking, where the electric motor transmits braking torque to the wheel. When shifting between these two gears in "regenerative" braking mode, the braking torque is interrupted when the sliding gear 8 passes through its intermediate neutral position. The disengagement of the clutch is not immediate, but its preparation begins instantly.

[0011] If we consider a control system for the electrical machine during these transition phases, its main inputs are as follows: ME_Tq_sp : torque setpoint of the main electrical machine in Nm, ME_Tq_esti : estimation of the torque produced by the main electrical machine in Nm DLS_tgt : gearbox ratio requested; at the moment of a request to change gears up (or down) T0, the requested gearbox report signal DLS_tgt For example, it changes from the value 2 to the value 1, or from 1 to 2. The moment the gear change is complete is Tf, SCM_Ctrl_typ : type of gearbox control: for example no control, torque control, or speed control.

[0012] To compensate for the failure of the braking torque of the electric machine 5, the invention aims to impose on the main braking system of the vehicle a mechanical braking torque setpoint, denoted BRK_Tq_sp. This instruction is expressed in Nm. Its value, imposed on the main braking system by the proposed method, is the output data.

[0013] The torque setpoint of the electric machine 5 (called the main machine if the transmission can also receive energy input from secondary electric machines) is noted ME_Tq_sp(t). The torque setting referred to the wheel, ME_Tq_sp_whl, is linked to the torque setting of the electrical machine ME_Tq_sp(t) by the transmission ratio

[0014] ME_ratio_whl (t) between the machine and the wheel, according to the relationship: ME _ Tq _ sp _ whl t = ME _ Tq _ sp t * ME _ ratio _ whl t .

[0015] The estimate of the torque produced by the main electric machine referred to the wheel ME_Tq_esti_whl can be defined analogously from the estimation of the torque produced by the electric machine, as the product of an estimation of the torque produced by the electric machine ME_Tq_esti(t) by the same reduction ratio up to the wheels ME_ratio_whl : ME _ Tq _ esti _ whl t = ME _ Tq _ esti t * ME _ ratio _ whl t .

[0016] To account for a delay of 0 < t_delay <= 1s between sending a torque command from the main electrical machine referred to the wheel and its actual application, a delayed torque command referred to the wheel is defined. ME_Tq_sp_whl_delay, such as ME_Tq_sp_whl _ delay(t) = ME_Tq_sp_whl(t - t_delay) with 0 < t_delay <= 1 second. Then, we define a delay coefficient α, such that: α t = ME _ Tq _ sp _ whl t − ME _ Tq _ sp _ whl _ delay t / t _ delay

[0017] Thanks to the coefficient α, we can define a torque setpoint for the main electric machine referred to the anticipated wheel. ME_Tq_sp_whl_ant such as : ME _ Tq _ sp _ whl _ ant t = Int α T 0 , Or Int is a discrete integral initialized at the moment T0, with the initial condition ME_Tq_sp_whl ( T0 ). The torque setpoint of the electric machine referred to the anticipated wheel ( ME_Tq_sp_whl_ant), is thus defined from the torque setpoint referred to the wheel ( ME_Tq_sp_whl ) based on the delay coefficient α representing the difference between sending a torque command from the electric machine referred to the wheel and its actual application.

[0018] According to the invention, a mechanical braking torque setpoint for the wheels is first defined at time t: BRK_Tq_sp_raw(t). This instruction is a raw, unsaturated mechanical braking torque instruction, dependent on the type of control of the electrical machine. SCM_Ctrl_typ and the end date of the upward or downward ratio change T f to the gearbox. Depending on the type of piloting, BRK_Tq_sp_raw(t) is defined as follows.

[0019] If there is no piloting [ SCM_Ctrl_ typ (t) = pas de pilotage ], then the unsaturated mechanical braking setpoint is zero: BRK_Tq_sp_raw(t) = 0

[0020] If the electric machine is driven by torque [ SCM_Ctrl_typ(t) = pilotage en couple], and as long as the date tis prior to the end of the ascending or descending passage [ t < Tf ], the unsaturated mechanical braking torque setpoint BRK_Tq_sp_raw(t) is equal to the difference between the anticipated date of torque demand on the electric machine and the estimated torque on the wheel at time t: BRK_Tq_sp_raw(t) = ME_Tq_sp_whl_ant(t) - ME_Tq_esti_whl (t) .

[0021] If the electric machine is driven by torque [ SCM_Ctrl_typ(t) = pilotage en couple ], and as soon as date t is later than or equal to the end of the ascending or descending passage [ t > = Tf ] , the instruction is zero ( BRK_Tq_sp_raw(t) = 0).

[0022] If the electric machine is speed-controlled [ SCM_Ctrl_typ(t) = pilotage en vitesse ], and as long as date t is prior to the end date of the upward or downward transition [ t < Tf ] , The unsaturated mechanical braking setpoint is equal to the anticipated torque setpoint referred to the wheel: BRK _ Tq _ sp _ raw t = ME _ Tq _ sp _ whl _ ant t

[0023] If the electric machine is speed-controlled [ SCM_Ctrl_typ(t) = pilotage en vitesse As soon as the date t is later than or equal to the end of the ascending or descending passage [t >= Tf], the unsaturated mechanical braking setpoint is zero: BRK_Tq_sp_raw(t) = 0.

[0024] In other words, the mechanical braking instruction BRK_Tq_sp_raw(t) is zero when the electric machine is not driven, before the upshift or downshift request T0 and after the end of the upshift or downshift. T f Before the end of the ascending or descending passage, it is equal to: the difference between the anticipated torque demand at the electric machine and the estimated anticipated torque at the wheel BRK_Tq_sp_raw(t) = ME_Tq_sp_whl _ ant(t) ME_Tq_esti_whl(t), if the electric machine is driven by torque, and with the anticipated torque setpoint referred to the wheel ME_Tq_sp_whl_ant(t), if the electric machine is speed-controlled.

[0025] We move from the unsaturated mechanical braking torque setting BRK_Tq_sp_raw(t) to the mechanical braking torque setting BRK_Tq_sp(t), through the following relationships: if BRK _ Tq _ sp _ raw t > 0 , BRK _ Tq _ sp t = 0 if BRK _ Tq _ sp _ raw t < = 0 , BRK _ Tq _ sp t = BRK _ Tq _ sp _ raw t .

[0026] If the torque estimate of the electric machine ME_Tq_esti is not available at time t; the invention plans to rely on the torque setpoint returned to the retarded wheel, ME_Tq_sp_whl_delay to calculate the estimated torque at the wheel ME_Tq_esti_whl. It becomes: ME _ Tq _ esti _ whl t = ME _ Tq _ sp _ whl _ delay t , with a delay limited, for example, to 0.05 seconds: 0 < t _ delay < = 0 , 05 s .

[0027] There figure 2The simulation demonstrates the advantage of the proposed solution, which compensates for the vehicle's lack of deceleration during a gear change. In this example, the vehicle's acceleration before the gear change is -1.2 m / s². Without the invention (dashed line curve), the braking torque of the electric motor decreases without compensation from the moment an upshift or downshift is requested. T0. The vehicle's acceleration simultaneously leaves its initial value, rising to zero before descending more gently back to zero. With the invention (solid line curve), the vehicle's acceleration remains at -1.2 m / s² during the gear change.

Claims

1. Method for compensating for torque loss at the wheels in the event of a gear change during braking on a vehicle equipped with an electric traction motor (5) connected to the vehicle's wheels by a gearbox (1) capable of transmitting the braking torque of the electric motor (5) to the wheels during deceleration in at least two gear ratios, and a mechanical braking system acting on the wheels independently of the electric motor, characterised in that a mechanical braking torque setpoint is defined for the wheels at time (t) (BRK_Tq_sp_raw(t)) as a function of the type of control of the electric motor, and the end time of the downshift (Tf), and that, if the electric motor is controlled by torque, this setpoint is equal to the difference, before the end time of the downshift (Tf), between an anticipated torque demand on the electric machine (ME_Tq_sp_whl_ant(t)) and the estimated torque at the wheel (ME_Tq_esti_whl(t)), and in that the mechanical braking setpoint at time (t) BRK_Tq_sp_raw(t) is equal to an anticipated torque setpoint reduced to the wheel (ME_Tq_sp_whl_ant(t)), before the gear shift down end time (Tf), if the electric machine is speed-controlled.

2. Method for compensating for torque breakage according to claim 1, characterised in that the mechanical braking setpoint (BRK_Tq_sp_raw(t)) is zero when the electric machine is not being controlled.

3. Method for compensating for torque breakage according to claim 1 or 2, characterised in that the mechanical braking torque setpoint (BRK_Tq_sp_raw(t)) is zero after the end of the downshift.

4. Method for compensating for torque interruption, according to one of the preceding claims, characterised in that the estimate of the torque of the electric machine reduced to the wheel (ME_Tq_esti_whl(t)) is the product of an estimate of the torque produced by the electric machine (ME_Tq_esti(t)) by the reduction ratio to the wheels (ME_ratio_whl).

5. Method for compensating for torque breakage according to the previous claim, characterised in that if an estimate of the torque of the electric machine (ME_Tq_esti) is not available at time (t), the estimation of the torque at the wheel (ME_Tq_esti_whl) is based on a delayed torque setpoint (ME_Tq_sp_whl_delay(t)).

6. Torque break compensation method according to the previous claim, characterised in that the delay (t_delay) is less than 0.05s.

7. Method for compensating for torque breakage according to one of the preceding claims, characterised in that the mechanical braking torque setpoint (BRK_Tq_sp_raw(t)) is an unsaturated raw setpoint.

8. Method for compensating for torque breakage according to one of the preceding claims, characterised in that the torque setpoint (BRK_Tq_sp(t)) is linked to the unsaturated mechanical braking torque setpoint BRK_Tq_sp_raw(t) by the following relationships: - if BRK_Tq_sp_raw t > 0 , BRK_Tq_sp t = 0 , and - if BRK_Tq_sp_raw t < = 0 , BRK_Tq_sp t = BRK_Tq_sp_raw t .