FR3015411A1 - TORQUE SETTING CALCULATION METHOD FOR AN ELECTRIC MACHINE COUPLED TO A THERMAL MOTOR OF A HYBRID VEHICLE - Google Patents

Abstract

A torque setpoint calculation method for an electric machine (12) connected to a traction motor (2) of a hybrid vehicle, which recharges a high voltage battery (16) supplying energy to an electric traction machine (20). ), which supplies a converter (18) for charging a low-voltage battery of the on-board network (10), characterized in that it defines four charge levels of the high-voltage battery (16) comprising a high range where it is largely charged, an average range, a minimum low range for the onboard network, and a critical low range with a risk of damage to this battery or failure of the onboard network.

Description

The present invention relates to a torque setpoint calculation method of a secondary electric machine coupled to a traction engine of a vehicle. hybrid comprising a main electric machine directly driving the wheels, and a hybrid vehicle implementing such a method.

A known type of hybrid vehicle, presented in particular by the document FR-A1-2955532, comprises a traction engine driving the wheels of the front axle, which is permanently coupled to a secondary front electric machine that can operate as a motor, particularly for starting this heat engine, and a generator for recharging by an inverter an energy storage device comprising a high voltage battery. The high voltage battery powers a main rear electric machine driving the wheels of the rear axle, which can operate as a motor to deliver a torque on these wheels, or as a generator to recover the kinetic energy of the vehicle by recharging the battery. It is thus possible to achieve different modes of operation, including a mode without emission of polluting gases with only the electric motor, called electric mode or "ZEV" mode, a hybrid mode and a sport mode combining the two engines to promote respectively the consumption and the performance of the vehicle, and a mode with four-wheel drive to improve safety and handling. The document cited furthermore presents a method for distributing the electrical power delivered by the secondary electrical machine, preserving this power when the high voltage battery has a sufficiently low level of energy, to supply the main electrical back machine in order to ensure in particular a traction of the vehicle with the four driving wheels. However, it may happen in some cases that these strategies are not sufficient to ensure a minimum energy level in the high voltage battery, which may have the consequence of damaging the battery, or no longer supplying a converter with this battery. which recharges the battery of the low-voltage on-board network, with the risk of stopping the computers connected to this network, which can lead to breakdowns. The present invention is intended to avoid these disadvantages of the prior art. It proposes for this purpose a torque setpoint calculation method for a first electrical machine connected to a traction motor of a hybrid vehicle, which receives a torque setpoint for a charging current of a high voltage battery delivering a energy to an electric traction machine, and a torque setpoint for a current delivered to a load converter of a low-voltage battery of the on-board network, characterized in that it defines four charge levels of the high-voltage battery comprising a high range of the maximum load at a first maximum target load threshold, an average range of this first threshold at a second minimum target load threshold for the converter, a low range of this second threshold at a third intermediate threshold, and a low critical range of this third threshold at the minimum load level, this range involving a risk of damage to the battery or failure of the battery. bucket edge and then apply the following torque instructions: - high range zero torque setpoint; - In average range a battery charge torque setpoint to maintain its current load level, with a zero torque load shedding of this allowed setpoint; - In low range a non-zero torque setpoint comprising at least a minimum converter power supply, with an allowable load shedding of the battery charge torque setpoint; and - in critical low range at maximum possible torque converter power supply. These charging ranges optimize the safety of the vehicle each time, while allowing, if possible, a response to the driver's demands for torque on the driving wheels. The torque setpoint calculation method according to the invention may further include one or more of the following features, which may be combined with each other. Advantageously, the first threshold between high and medium range and the second between medium range and low range, include a hysteresis that varies this threshold depending on whether the actual load level crosses up or down. In particular, the method can establish the battery charge torque instruction with a calculation of the difference between the target battery charge and its current load, the result being delivered to a second power calculation for the battery charge, using other information such as the vehicle speed, the slope or the altitude, then by a third calculation which divides the load power by the speed of the electric machine before filtered to give the gross load reference torque, and it finally imposes for a regime minimum rotation of the first electric machine, a limit by the battery charge maximum recovery torque.

In particular, the method can establish the converter torque setpoint with a calculation of the difference between the target load for the converter and its current load, the result being delivered to a second power calculation for this converter, using other information. like the speed of the vehicle, the slope or the altitude, then by a third calculation which divides this power by the speed of the electric machine before filtered to give the torque of the converter raw setpoint, and it imposes finally for a minimum revolutions of the first electric machine, a limit by the maximum recovery converter torque. The invention also relates to a hybrid vehicle having a first secondary electrical machine coupled to a traction engine, which recharges a high voltage battery delivering energy to an electric traction machine, and to a low voltage battery of the network. by a converter, this vehicle comprising means implementing a torque setpoint calculation of the secondary electrical machine comprising any of the preceding characteristics.

The invention will be better understood and other features and advantages will appear more clearly on reading the following description given by way of example and in a nonlimiting manner, with reference to the appended drawings, in which: FIG. a diagram of a hybrid vehicle implementing a torque setpoint calculation method according to the invention; - Figure 2 is a diagram showing the main control functions of the engine of this vehicle; FIGS. 3 and 4 show for this method the calculation of the torque setpoint for the charge of the battery and the supply of the on-board network, respectively; and FIG. 5 is a graph showing, as a function of time, an example of operation of the method, showing the charge level of the battery as well as the set pairs. FIG. 1 shows a hybrid vehicle comprising a thermal engine 2 which may be of the gasoline or diesel type, driving the front wheels 6 by a transmission 4. The heat engine 2 has an electric starter 8 powered by a low battery voltage 10 of the onboard network, comprising a voltage which is generally 12V. A rear main electrical machine 20 is coupled directly to the rear wheels 22 of the vehicle, and a front secondary electric machine 12 is permanently coupled to the heat engine 2 to assist in its operation. The two electrical machines 12, 20 are connected to an inverter 14 itself connected to a high voltage battery 16, which may be of the order of 220V, to receive a charge current from the battery coming from these machines working as a generator. , or deliver them energy from this battery giving operation of the engine machines. In particular, the front electric machine 12 can be used as a starter to quietly start the heat engine 2 to 10 after stopping, giving an operation of the type "Stop and Sart". The low-voltage battery of the on-board network 10 is recharged by a DC-DC converter 18 which takes the energy from the high-voltage battery 16, with an adaptation of the voltage of the current produced by this converter. In general, the high voltage battery 16 may comprise electrochemical cells comprising all types of technologies, or capacitors, grouped into one or more modules, and connected together in series or in parallel. For some vehicles the high voltage battery 20 16 can also be recharged on a power distribution network, after a connection to this network during a stop of the vehicle. The hybrid vehicle can thus operate with different modes of running, including an electric mode using the rear electric machine 20, the engine 2 being stopped and the transmission 4 25 in neutral, a hybrid mode using all the engines, and a mode four-wheel drive with both engines, also called "E-AWD" mode, to improve the motor skills and handling of the vehicle, or to give a sporty driving. FIG. 2 shows an interface function of the driver's will 34, receiving various information on the operation of the vehicle, including in particular the torque demand of the driver 301 5 4 1 1 6 pressing the accelerator pedal, which transmits data to a conductive will translation function 36, as well as an organic limiting function 30 calculating the torque limit that each member can deliver. A function for distributing the torque setpoint 38 between the different motorizations receives a global torque request from the conductive will translation function 36, as well as the organic limits of each motorization defined by the organic limitation function 30, so that to distribute this demand on each engine, The distribution function of the torque setpoint 38 distributes the will of the driver 36 between a torque setpoint on the front axle and a setpoint on the rear axle, by issuing torque instructions for the engine thermal 2, the front electric machine 12 and the rear electric machine 20.

The front electric machine 12 works as a generator by taking a moderate torque from the heat engine 2, in order to supply a small electrical power, which is generally delivered continuously, to the DC-DC converter 18 in order to maintain a minimum voltage in the onboard network. necessary for its operation.

The front electric machine 12 also works by generating a larger torque, in order to provide a high electrical power, delivered to the high voltage battery 16 to recharge it to maintain a sufficient level of charge, allowing the machine 20 rear electric powered by this battery to provide at all times a motor torque. The engine torque coming from the rear electric machine 20 can meet in particular the performance requirements requested by the driver, this torque being added to that delivered by the heat engine 2, for motricity needs with the four-wheel drive mode E -AWD, or on-demand security needs including ABS or ESP driver assistance systems.

The torque supplied by the heat engine 2 is then decomposed into a torque delivered on the front wheels 6, and a torque delivered on the front electric machine 12 which serves to supply on the one hand the small electrical power to the current converter DCDC 18, and on the other hand the electric charging power of the high voltage battery 16 which may be larger. The method according to the invention is implemented at the level of the distribution function of the torque setpoint 38. FIGS. 3 and 4 show a similar calculation implemented by the torque setpoint calculation method, establishing for the machine electrical before 12 respectively the torque setpoint for charging the high-voltage battery CSOC, which is not a priority, and the torque setpoint for the converter CDCDC for the on-board network, which has priority. If auxiliaries using the high voltage are arranged in the vehicle, for example an air conditioning unit comprising an electric drive, they may also have priority. The CSOC battery charge torque setpoint is determined from a PSOC setpoint power, which is itself determined by the difference between the target load and the current load of the high voltage battery 20 16. The torque converter setpoint CDCDC is determined from the electrical power consumed by the onboard network. With the known strategies, it happens in certain life situations that they are not sufficient to maintain a SOC 25 energy level in the high voltage battery 16, which can lead to damage to this battery, or stop on-board computers by insufficient power supply of the low-voltage battery 10, which can put the vehicle down. In particular, these life situations can be the following: - in the event of a strong acceleration of the vehicle requested by the driver and thus of the DCDC converter being offloaded, following a poor estimation of the power taken by this converter to supply the on-board network it is possible to maintain insufficient SOC battery charge and use it in a charging range which damages it; a poor consideration of electrical efficiencies when calculating the conversion of the mechanical power to the electrical power; or - losses in the rear electric machine 20 important and poorly estimated. Note that when the rear electric machine 20 is not used 10 remaining coupled to the rear wheels 22, it is advantageously controlled to give it the driving torque to not brake the vehicle, which generates significant electrical losses , which may be greater than 1 kW. It is therefore necessary, under these conditions, to make the instructions of the machines robust in order to provide additional energy to the high-voltage battery 16. This need is greater when the energy taken by the front electric machine 12 is saturated with mechanical stresses such as the limitations of the link with the heat engine that drives it, or internal stresses. The method according to the invention proposes to optimize the production of the CSOC battery charge and CDCDC converter setpoint instructions, in order to secure the control of the front electric machine 12 in order to avoid an excessive discharge of the high voltage battery 16, or losses of the onboard network. In particular, it is desired to ensure a level of high voltage battery charge SOC which is always constant when the torque setpoint of the front electric machine is intended solely for the on-board network, with CMEL = CDCDC. In this way, the different losses of the conversion of the mechanical energy into electrical energy for the on-board network, including in particular the losses of the low voltage network, the DCDC converter and the machine, are taken into account. front electric. As a result, it is not possible to rely on the power estimated and sampled by the DCDC converter, so a new specific target battery charge threshold for the SOC_DCDC converter is introduced, for which the strategy used for the load torque reference is duplicated. CSOC battery, similarly comprising a hysteresis. FIG. 5 shows a high range PH that ranges from the maximum load 100% to a first maximum target load threshold 70 for the SOC battery CSOC, comprising a high level SOC_CSOC-H crossed in the rising direction and a low level SOC_CSOC -B crossed in the direction of the descent to obtain a hysteresis. A mean range PM goes from the first SOC_CSOC target battery charge threshold 70 to a second minimum target current load threshold 72 intended for the SOC_CDCDC converter, comprising a high SOC level CDCDC-H crossed in the rising direction and a level bottom SOC _CDCDC-B crossed in the direction of the descent to obtain a hysteresis. A low range PB goes from the second target battery charge threshold SOC_CDCDC to a third intermediate threshold 74.

A critical low range PBC from the third intermediate threshold 74 to the minimum level of 0% load, which involves a risk of damage to the high voltage battery 16 or network failure. When the charge of the high voltage battery SOC is close to its SOC-CSOC target load, the CSOC battery charge torque setpoint becomes low. But the yields of an electric machine are even lower than the torque setpoint will be reduced. In order to improve the overall recharge efficiency given by the front electric machine 12, the hysteresis is introduced for the first 70 and the second threshold 72 which varies this threshold depending on whether the actual SOC load level passes it uphill or downwards. downhill. In this situation it is preferable to undergo the losses of charge and discharge of the high voltage battery 16, rather than those of the front electric machine 12. In general, the method of calculating the torque setpoint implements the principle next.

In high range PH (SOC> SOC_CSOC), one does not have torque control (CSOC = 0 and CDCDC = 0). In average PM range (SOC_CSOC> SOC> SOC_CDCDC), there is a torque setpoint to maintain the current SOC load level, with zero torque shedding allowed if necessary to meet a request of the torque driver on the wheels elevated motor (CSOC> 1 = 0 and CDCDC = 0). In the low range PB (SOC_CDCDC> SOC), there is a non-zero torque setpoint, without shedding, comprising at least a minimum supply torque of the low voltage battery of the onboard network (CSOC> / = 15 0 and CDCDC> 0). In low critical range PBC (SOC_CDCDC »SOC), a maximum torque converter CDCDC is imposed corresponding to the limits of the possibilities of the engine, the electric machine and the connection between them, without load shedding possible, in order to obtain a recovery of the level SOC battery charge as fast as possible. FIG. 3 presents a first calculation 40 of the difference between the target battery charge SOC_CSOC and its current charge SOC, the result being delivered to a second calculation 42 of charge power PSOC, using other information 44 such as, for example, the speed vehicle, slope 25 or altitude. A third calculation 46 divides the load power PSOC by the speed of the filtered front electric machine N-MEL-AV-F, obtained by filtering the speed of the front electric machine 50, by a first-order filter for example, for give the set load torque CSOC_brut. A limit 52 is then imposed by the maximum recovery torque for the CSOC-Recup-Max load, in order to avoid an infinite setpoint torque when the speed of the machine is low, particularly with a speed of the thermal engine 2 close idle, to get the CSOC battery charge torque. Alternatively to set a maximum recovery torque for the load, it can impose by calibration a minimum speed of the machine, which will give this maximum torque recovery. Depending on the sign convention, the CSOC battery charge and CDCDC converter pairs may be positive or negative. In all cases, these couples make it possible to take energy from the heat engine, in order to ensure a positive energy supply to the high voltage circuit and to the battery of the onboard network 10. FIG. similar, a first calculation 60 of the difference between the target power supply of the SOC converter _CDCDC and the current battery charge SOC, the result being delivered to a second power supply calculation PDCDC 62, using the other information 44 as the speed vehicle, slope or altitude. A third calculation 66 divides the PDCDC power supply by the speed of the filtered front electric machine N-MEL-AV-F, to give the gross target torque converter CDCDC_brut.

A limit 68 is then imposed by the maximum recovery torque for the CDCDC-Recup-Max converter, in order to avoid an infinite setpoint torque when the speed of the machine is almost zero, in order to obtain the torque converter CDCDC. Alternatively to set a maximum recovery torque for the converter, one can impose by calibration a minimum speed of the machine, which will give this maximum torque recovery. FIG. 5 shows, as a function of the time t, the upper part of the charge level of the high voltage battery SOC between 0 and 100%, and in the lower part the instructions of the CSOC battery charge and the CDCDC converter, as well as the sum of these two instructions which is the final torque-total setpoint delivered to the electric machine before 12.

The final torque-total setpoint therefore corresponds to an overall supply of energy to the high-voltage network, which will be consumed in priority by the DCDC converter 18 to recharge the battery of the on-board network 10, then by the other hybrid auxiliaries, then by the rear electric machine 20, and finally by the high voltage battery 16 which makes a buffer for the remaining load current available. The high voltage battery 16 stores the surplus energy, or provides the difference in energy consumed by the DCDC converter 18, the hybrid auxiliaries and the rear electric machine 20.

In general, the CSOC battery charge is not a priority vis-à-vis the traction of the vehicle. If the heat engine is at its maximum torque, we first give the converter torque CDCDC which has priority, even if it does not satisfy the will of the driver, then reduces if necessary the battery charge torque CSOC to obtain more torque available on the drive wheels. Before time t1 is in the average PM range with the SOC battery charge rising, the CSOC battery charge torque setpoint decreases at the same time. The torque setpoint converter CDCDC is zero.

At time t1 the SOC battery charge reaches the target high charge level for the SOC_CSOC-H battery, the torque setpoint for this CSOC load is canceled. Between times t1 and t2 we are in the high range PH, the two sets of torque CSOC and CDCDC are zero, the battery charge SOC goes down.

At time t2 the SOC battery charge which has gone down, reaches the low level of target charge for the SOC_CSOC-B battery, the CSOC battery charge torque setpoint goes back up. Between times t2 and t3 we cross the average range PM. At time t3 the SOC battery charge reaches the target low level of charge for the SOC_CDCDC-B converter, it enters the low range PB and then the critical low range PBC. The CDCDC converter torque setpoint goes up, the CSOC battery charge torque setpoint is maintained. Between the times t3 and t4, we obtain a total torque-total torque comprising the sum of these two couples, which is maximum. The SOC battery charge level is rising.

At time t4 the SOC battery charge which has risen, reaches the target high charge level for the SOC_CDCDC-H converter, it leaves the low range PB, the torque setpoint converter CDCDC is canceled. Between times t4 and t5 the SOC battery charge level rises and goes through the average PM range, the CSOC battery charge torque setpoint gradually decreases. In general, the method for calculating the torque according to the invention makes it possible to ensure the operational safety of the on-board network, to optimize fuel consumption, in particular by conserving a possibility of energy recovery when braking stored in the vehicle. the high-voltage battery, while maintaining as much as possible a potential for performance and safety thanks to the torque on the rear axle that can be brought.

Claims (5)

CLAIMS1 - Torque setpoint calculation method for a first electric machine (12) connected to a traction motor (2) of a hybrid vehicle, which receives a torque setpoint (CSOC) for a load current of a high voltage battery (16) delivering energy to an electric traction machine (20), and a torque setpoint (CDCDC) for a current delivered to a converter (18) for charging a low voltage battery (10) of the network characterized in that it defines four charge levels of the high voltage battery (16) comprising a high range (PH) of the maximum charge (100%) at a first threshold (70) of maximum target charge (SOC CSOC), a mean range (PM) of this first threshold at a second target minimum target load threshold (72) for the converter (SOC CDCDC), a low range (PB) of this second threshold at a third intermediate threshold (74) , and a critical low range (PBC) of this third threshold at the min level load imum (0%), this range with a risk of battery damage or failure of the onboard system, then applies the following torque setpoints (CSOC, CDCDC): - in high range (PH) a setpoint zero torque; - in medium range (PM) a battery charge torque setpoint (CSOC) to maintain its current load level, with a zero torque load shedding of this allowed setpoint; in the low range (PB) a non-zero torque setpoint comprising at least a minimum converter supply torque (CDCDC), with an authorized shedding of the battery charge torque setpoint (CSOC); and - in the critical low range (PBC) the maximum possible converter power supply setpoint (CDCDC). 2 - Method of calculating torque setpoint according to claim 1, characterized in that the first threshold (70) between high range (PH) and average range (PM) and the second (72) between medium range (PM) and rangebasse (PB), have a hysteresis that varies this threshold depending on whether the actual charge level (SOC) crosses it up or down. 3 - torque setpoint calculation method according to claim 1 or 2, characterized in that it establishes the battery charge torque instruction (CSOC) with a calculation (40) of the difference between the target battery charge (SOC CSOC ) and its current load (SOC), the result being delivered to a second power calculation (42) for the battery charge (PSOC), using other information (44) such as vehicle speed, slope or altitude then by a third calculation (46) which divides the load power (PSOC) by the speed of the filtered front electric machine (N-MEL-AV-F) to give the gross load reference torque (CSOC_brut), and it finally imposes for a minimum rotation speed of the first electrical machine (12), a limit (52) by the maximum battery recovery battery torque (CSOC-Recup-Max). 4 - Torque setpoint calculation method according to any one of the preceding claims, characterized in that it establishes the converter torque setpoint (CDCDC) with a calculation (60) of the difference between the target load for the converter (SOC_CDCDC) and its current load (SOC), the result being delivered to a second power calculation (62) for this converter (PDCDC), using other information (44) such as vehicle speed, slope, or altitude, and then by a third calculation (66) which divides this power (PDCDC) by the speed of the filtered before electric machine (N-MEL-AV-F) to give the torque of raw converter (CDCDC_brut), and imposes finally for a minimum rotation speed of the first electrical machine (12), a limit (68) by the maximum recovery converter torque (CDCDC-Recup-Max). 5 - Hybrid vehicle having a first electric machine (12) coupled to a traction engine (2), which recharges a high voltage battery (16) delivering energy to an electric traction machine (20), and a low-voltage battery (10) of the on-board network by a converter (18), characterized in that it comprises means implementing a torque setpoint calculation of the secondary electric machine (12) produced according to any one of the claims preceding.