FR3001684A1 - Method for managing recuperation of energy for hybrid car, involves calculating final set point torques, which give decreasing and increasing accelerations when forward movement and downward movement of vehicle are high - Google Patents

Abstract

The method involves estimating slope (11) of a road (10) for a braking request by a speed regulation or limitation system by using estimation function receiving information on speed of a vehicle (12) and torque delivered by a power unit (14). Final set point torque (30) for supporting acceleration reduction is calculated when forward movement of vehicle is high. Another final set point torque for supporting acceleration increase is calculated when downward movement of the vehicle is high. The estimation is transmitted to calculation function of minimum authorized vehicle acceleration (16). An independent claim is also included for a hybrid car.

Description

The present invention relates to a method for managing the energy recovery for a hybrid vehicle comprising a system for regulating or limiting the speed of a vehicle. speed, and a motor vehicle implementing such a management method. Hybrid-engined motor vehicles generally comprise, in addition to the combustion engine, an auxiliary engine that can work as a generator and as a motor, which, during braking, enables the vehicle to recover kinetic energy for storage in energy storage means. , and use this energy at other times, especially to revive the speed of this vehicle.

In particular, hybrid electric type vehicles include an electric machine that can brake the vehicle by operating as a generator, and recharge storage batteries with the recovered energy. In addition, certain vehicles include a system for regulating or automatically limiting the speed of this vehicle.

The speed control system is in relation with the control computer of the engines, to request these engines based on driving conditions, an adjustment of the power delivered to obtain the desired speed. The speed limitation system also applies, depending on the driving conditions, a limitation of the power delivered by the engines, so as not to exceed the set speed. To comply with the set speed, a known method, presented in particular by the document FR-B1-2912978, automatically controls the wheel braking system if the engine brake is not sufficient, when a braking requirement of this vehicle so as not to exceed this speed.

However, in the case of a hybrid vehicle, it is possible to use the auxiliary drive in a known manner in order to brake the vehicle, in order to respect the speed setpoint of the regulation or speed limitation system. However, the braking power available with the auxiliary power unit depends on the possibility of storage in the energy storage means, in particular in batteries for a hybrid electric vehicle. One can then obtain various operations on the same rolling cycle, with different braking depending on the state of charge of the energy storage means, including in particular a lack of braking by the auxiliary motorization in the case of a a sufficiently filled storage system that can no longer receive energy. The present invention is intended to avoid these disadvantages of the prior art. It proposes for this purpose a power recovery management method for a hybrid vehicle comprising a heat engine, and an auxiliary motor that recharges energy storage means by energy recovery by braking the vehicle, the vehicle comprising a speed regulation or speed limitation system which in some cases requires braking of the vehicle in order to respect a set speed, characterized in that for a braking demand by the regulation or limitation system, it estimates the slope of the road, then in the case of a climb it calculates a final setpoint torque which gives a decreasing acceleration when this rise is stronger, and in the case of a descent it calculates a final setpoint torque which gives an acceleration increasing when this descent is stronger. An advantage of the management method according to the invention is that it is possible to obtain in a simple and economical way, with only additional software, a better regularity in the level of braking brought by the auxiliary motorization, by limiting the recovered energy. by this braking has a sufficiently low value due to the braking level which decreases if the rise is less strong, and which vanishes in the case of a descent, to limit the energy level in the storage means. This means not being saturated, it can operate more repetitively on similar rolling cycles. The energy recovery management method according to the invention may further comprise one or more of the following features, which may be combined with each other. Advantageously, the method estimates the slope of the road with a function of estimating this slope, which receives information on the speed of the vehicle and on the torque delivered by the powertrain.

Advantageously, the estimate of the slope is transmitted to a calculation function of the minimum authorized vehicle acceleration, which establishes from mappings the minimum acceleration allowed for the vehicle as a function of this estimated slope. In particular the cartography can authorize the following minimum accelerations, for the descents a stabilization of the speed for a slope of -1%, and a slight acceleration of the vehicle which is bigger and bigger when the descent is stronger, for a road flat a slight braking of the vehicle with a value of about -0.5m / s2, and for the climbs a slight braking of the vehicle which is bigger and bigger when the rise is stronger, with a ceiling from a threshold which is about -1m / s2. Advantageously, the minimum allowed acceleration is transmitted to a calculation function of the minimum authorized powertrain, which also receives an estimate of the resistant forces applying to the vehicle, to deduce a minimum authorized powertrain, which gives the acceleration of the vehicle corresponding to this authorized minimum. Advantageously, the minimum authorized powertrain torque is delivered to a calculation function of the minimum authorized powertrain torque, furthermore receiving an indication of the minimum torque that can be delivered by the heat engine, in order to deduce therefrom a minimum safe powertrain torque that can be obtained by the system for regulating or limiting the speed of the vehicle, which corresponds to the smallest value between the minimum authorized powertrain and the minimum torque that can be delivered by the heat engine. Advantageously, the minimum safe powertrain torque is delivered to a function for calculating the torque setpoint for the speed regulation or speed limitation system, which also receives a torque setpoint requested by this system, to limit this setpoint by minimum powertrain torque, in order to obtain the final setpoint torque demanded by the system which corresponds to the highest value between the torque setpoint requested by the system and the minimum authorized safe powertrain. The invention also relates to a hybrid motor vehicle having a heat engine, and an auxiliary motor that recharges energy storage means by energy recovery by braking the vehicle, the vehicle having a system of regulation or limitation of its speed which in some cases requires braking of the vehicle in order to respect a set speed, this vehicle comprising means implementing an energy recovery management method comprising any one 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 graph showing the operation of a method of managing energy recovery according to the prior art, during a repetitive rolling cycle; FIG. 2 is a graph showing the operation of this method during a decrement of the vehicle speed reference; FIG. 3 is a graph showing the operation of a method for managing energy recovery according to the invention during the same repetitive rolling cycle; FIG. 4 is a graph showing the operation of this method during the same decrement of the vehicle speed reference; and - Figure 5 is a diagram showing the operation of this method. FIG. 1 shows for a hybrid vehicle comprising a thermal engine, and an electric machine connected to batteries as an auxiliary motor, as a function of the time t expressed in seconds on the horizontal axis, in its upper part the speed of the vehicle Vveh expressed in km / h, in its central part the slope of the road P expressed in%, which is positive when the road goes up, and in its lower part the load level of these SOC batteries expressed in%. The vehicle travels in a loop for a time of about 400s the same cycle comprising a succession of climbs and descents, the highest climb can reach a slope of + 6%, and the strongest descent can reach a slope of - 7.5%. The vehicle has a Vveh speed control system, giving a constant target speed of 90km. The vehicle comprises a method of managing the energy recovery which during descents systematically activates the electric machine, to obtain a braking of the vehicle to respect the set speed, while recovering as much electrical power as possible which is stored in batteries. Initially at time t = 0, the batteries have a charge level of 83%, and the slope of the road is 0%. It can be seen that for the first driving cycle C1, the speed of the vehicle Vveh is maintained at 90km / h, but the charge level of the SOC battery rises at the end of the cycle to 97%, after having passed nearly 100% at the end of the cycle. the descent including the steepest slope, a little before the end of the cycle. For the second C2 taxiing cycle starting at 400s, the SOC battery charge level remains high, down to 93% during heavy rises, and reaching twice the saturation level of 100% during the most downhill descents. strong. During these saturations, it can be noted that since the batteries can no longer store electrical energy, the electric machine no longer produces braking torque, and that the speed of the vehicle rises for the first time to 93km / h, then a second time to 113km. / h during the strongest descent. During the following two cycles C3, C4 shown in this graph, the SOC battery level and the Vveh vehicle speed remain similar to those of the second cycle C2, with the same 10 times the set speed. With this method of energy recovery management, it quickly arrives at a saturation of the batteries because of the high energy systematically recovered during the first descents. A vehicle operation is obtained that is not repetitive for passages on similar taxiing cycles, this vehicle respecting the speed setpoint in some cases, and does not respect thereafter, which may surprise the driver and disrupt it, and in some cases be dangerous. FIG. 2 shows for the same hybrid vehicle, as a function of the time t expressed in seconds on the horizontal axis, in the upper part, the vehicle speed Vveh expressed in km / h, in the central part the battery charge level. SOC expressed in%, and in the lower part the longitudinal acceleration of the vehicle Acc expressed in m / s2. Initially between t0 and t1, from the stop the vehicle receives a setpoint of the speed control system which is 120 km / h. The vehicle takes 20s to reach this set speed, using the electric machine to deliver additional mechanical power with fuel savings, by taking energy from the batteries that have a SOC energy level of 98.5 to 94.5%. In parallel, there is a sharp acceleration of the vehicle Acc 30 during this first time.

In a second time between t1 and t2 = 100s, the speed of the vehicle Vveh is stabilized according to the set speed of 120km / h, the charge level of SOC batteries decreases steadily to reach 91%, batteries delivering a small power to power the vehicle's on-board network. At time t2, the vehicle speed reference suddenly rises to 40 km / h. During a third time between t2 and t3 = 120s, the energy recovery management method will use the electric machine to deliver a significant braking on the drive wheels in order to meet this new set speed as soon as possible, producing a strong electric power that is stored in the batteries. We note that we have a strong negative acceleration, including a peak that exceeds 1m / s2, with during this third time a sharp decrease in the speed of the vehicle Vveh which falls below 80km / h, and a rise very fast SOC battery level, which reaches almost 100% at time t3. During a fourth time between t3 and t4 = 175s, the negative acceleration of the vehicle is substantially constant with a low level of the order of 0.2m / s2, which allows a slow decay of the vehicle speed Vveh following a constant slope. . This low level of braking is due to batteries that with a saturated charge level can no longer receive electrical energy, the electric machine is then disabled. At time t4, the vehicle's target speed of 40 km / h is reached, the acceleration of this vehicle Acc becomes zero again, and the charge level of the SOC batteries begins to decrease slowly, these batteries delivering a small power for the power supply. This type of energy recovery management method gives a strong variation of the braking of the vehicle by the electric machine, with absolute values varying between more than 1 and 0.2m / s2. during all the braking, which is uncomfortable.

FIGS. 3 and 4 show the same operating cases for a method of managing the energy recovery according to the invention, which will maintain a sufficient energy level in the batteries to allow the delivery of a current to the machine to provide a motive power, and also try to limit this load to a target level, to allow a limited additional electric recharge from a braking by the electric machine that generates power. To maintain the load at the target level, the method will in particular discharge the batteries when the level is above this target, by delivering a current to supply the network for example, without consuming fuel. The method will further limit the braking of the vehicle by the electric machine to reduce the additional recharge of the batteries. A first type of taxiing concerns flat or uphill roads For this first type of rolling, in the case of a regulation or a limitation around a setpoint speed which varies little, the braking needs of the vehicle are low. they are made without using the energy recovery system. The speed setpoint is always respected, without recharging the batteries.

In the case of a requested deceleration with a sharp decrease in the set speed, the method can achieve limited braking with the electric machine to reach this new setpoint more quickly. In particular, there are decreases in the set speed of this kind, when the speed limit on the road drops from 130 to 110 or 90km / h, or from 90 to 50km / h. The level of energy recovery allowed to improve the delivery of compliance with the set speed must then be limited to ensure maximum reproducibility during successive similar cycles. The authorized deceleration of the vehicle is established by maps 30 depending on the slope of the road. In practice, it is sought to obtain a quantity of recovered electrical energy that is substantially constant regardless of the slope. In particular this amount may be equal to the difference between the maximum charge level and the target charge level. The braking of the vehicle will then be higher in the case of a higher climb, is lower in the case of a lower climb.

A second type of taxiing involves downhill routes. For this second type of rolling, in the case of a request for braking by the regulation system or speed limit of the vehicle, the electric machine is never used to not generate electrical energy that would recharge the batteries, to obtain operation that remains constant for subsequent similar cycles. Only the engine brake of the engine is used, even if the vehicle can not then respect the set speed. FIG. 3 shows the same running cycle as that presented in FIG. 1, with the energy recovery method according to the invention.

Initially at time t = 0, the batteries have a charge level of 83%. It can be seen that for the first Cl cycle, the vehicle speed Vveh first reaches twice 95 km / h during descents including a slope of -5%, then 110 km / h for the highest descent of - 7.5%.

During this first cycle, the operation of the electric machine is similar to that shown in FIG. 1, for descents including a slight slope not exceeding -2 or -3%, with the same recharging of the batteries, and for climbs with a discharge. batteries that allows the electric machine to deliver a motor torque. But for more pronounced descents, this braking is very limited with a low battery recharge. At the end of this first running cycle Cl, the charge level of the SOC batteries increases slightly by about 5% to reach the value of 88%.

For the second cycle C2 running has a vehicle speed identical to that of the first cycle Cl, and the battery charge level also increases slightly by about 4% to reach the value of 92%. The batteries are not saturated, and can continue to receive electrical energy produced during braking by the electric machine. It is the same for the two cycles of running following C3, C4 with a small increase in the level of charge of the batteries, which reaches 96% at the end of this third cycle and 97% at the end of this fourth cycle. It will be noted that during the most pronounced descent of the fourth C4 taxiing cycle, the batteries are just reaching saturation with a 100% load level, the Vveh vehicle speed reaching 112km / h, being slightly higher than before. . Thus, during these 4 successive cycles of rolling, a good repeatability of the vehicle speed is automatically controlled by the control system or limitation, which reassures the driver and improves safety.

FIG. 4 shows the same vehicle speed reference deviation as that presented in FIG. 2, which abruptly goes from 120 to 40km / h at time t2, with the energy recovery method according to the invention. The method then limits the braking of the vehicle to a maximum value of -0.5m / s2 by using the electric machine, in order to obtain a low electrical power for recharging the batteries. The complete charge of SOC batteries to reach the level of 100%, then requires a time of about 20s, between time t2 and time t5 which is 140s. The speed of the vehicle Vveh then reached the value of about 60 km / h. Then during the time between t5 and t6 = 170s, the batteries being saturated, the braking of the vehicle is substantially constant with a low level of the order of 0.2m / s2, which gives a slow decrease of the speed of the vehicle Vveh following a constant slope. At time t6, the vehicle's target speed of 40 km / h is reached, the acceleration of this vehicle Acc becomes zero again, and the charge level of the SOC batteries begins to decrease slowly.

It is found that the acceleration differences of the vehicle are low, with gradual variations, which gives a good level of comfort. FIG. 5 shows, at the top of the diagram, a function for estimating the slope of the road 10, which receives information on the speed of the vehicle 12 and on the torque delivered by the powertrain 14, in order to deduce from it the estimate 11. The torque of the powertrain comes from different engines, including the engine and the electric machine. Alternatively the hybrid vehicle could include another type of auxiliary motor, for example using a hydraulic power. The estimation of the slope 11 is transmitted to a calculation function of the minimum authorized vehicle acceleration 16, which establishes from mappings the minimum acceleration allowed by the method for the vehicle 17 as a function of this estimated slope.

An example of possible mapping comprises the following pairs of values, comprising first the value of the slope in%, then the value of the minimum allowed acceleration of the vehicle in m / s2: Slope: -5 -3 -2 -1 0 2 5 10 Acc. Veh: 0.5 0.4 0.3 0 -0.5 -0.8 -1 -1 For descents a minimum acceleration is allowed giving a stabilization of the speed for a slope of -1%, and a slight increase of this speed which is bigger and bigger when the descent is stronger. For a flat road, it allows a minimum acceleration giving a slight braking of the vehicle, with a value of -0.5m / s2. For the climbs a minimum acceleration is allowed, giving a slight brake of the vehicle, which is bigger and bigger when the climb is stronger, with a ceiling from 5% which is -1m / s2. The minimum allowed acceleration 17 is transmitted to a calculation function of the minimum authorized powertrain 18, which also receives an estimate of the resistant forces applying to the vehicle 20, to deduce the torque that should deliver the powertrain, or torque authorized minimum power train 19, so that the acceleration of the vehicle corresponds to this authorized minimum. The resistant forces include aerodynamic forces, efforts due to the slope of the road, and rolling forces. The minimum authorized powertrain 19 is delivered to a calculation function of the minimum authorized powertrain 22, which also receives an indication of the minimum torque which the engine 24 can deliver, by its braking torque given by the engine brake, so as to to deduce a minimum powertrain torque 23 that can be achieved by the vehicle speed control system or limitation. This minimum powertrain power pair 23 corresponds to the smallest value between the minimum authorized powertrain 19 for the regulation or speed limitation system, and the minimum torque 15 delivered by the heat engine 24. If the minimum torque delivered by the thermal engine 24 is lower than the minimum authorized powertrain 19, the regulation or speed limitation system can request that minimum torque of the engine, which is the engine brake. If the minimum torque delivered by the thermal engine 24 is greater than the minimum authorized powertrain 19, this system will be able to use energy recovery within the limit of this minimum powertrain torque. The minimum safe powertrain pair 23 is delivered to a function for calculating the torque setpoint for the regulation or speed limitation system 26, which also receives a torque setpoint requested by this system 28, to limit this setpoint. by the minimum powertrain pair 23, to obtain the final target torque 30 actually requested by the control system or limitation. The torque setpoint requested by the system 28 evolves according to the driver's request and the driving conditions, in order to tend to best respect the speed setpoint of the vehicle, in order to ensure a good level of delivery of the system. regulation or limitation. The final setpoint torque 30 corresponds to the highest value between the torque setpoint requested by the system 28, and the minimum authorized safe drive torque 23. If the system needs a positive torque to accelerate or maintain the speed of the vehicle, the torque setpoint requested by the system 28 will be applied to the powertrain. If the system needs a negative torque to brake the speed of the vehicle, the torque setpoint requested by the system 28 will decrease and pass under the minimum authorized powertrain 23, this torque will be requested to the powertrain that can implement the electric machine to perform energy recovery. Thus, with only additional software implemented by the existing computers, without adding equipment on this vehicle as complementary braking means, a compromise between the service provided to the driver by the regulation or speed limitation systems , and the reproducibility of this benefit.

Claims (4)

CLAIMS1 - A method for managing energy recovery, for a hybrid vehicle comprising a heat engine and an auxiliary engine that recharges energy storage means by energy recovery by braking the vehicle, the vehicle having a system of regulating or limiting its speed which in certain cases requires braking of the vehicle in order to respect a set speed, characterized in that for a braking demand by the regulation or limitation system, it estimates the slope of the road ( 11), then in the case of a climb it calculates a final setpoint torque (30) which gives a decreasing acceleration when this rise is stronger, and in the case of a descent it calculates a final setpoint torque which gives increasing acceleration when this descent is stronger. 2 - A method of managing the energy recovery according to claim 1, characterized in that it estimates the slope of the road (11) with a function of estimating this slope (10), which receives information on the vehicle speed (12) and the torque delivered by the power train (14). 3 - A method of managing the energy recovery according to claim 1 or 2, characterized in that the estimate of the slope (11) is transmitted to a calculation function of the minimum authorized vehicle acceleration (16), which establishes from mappings the minimum acceleration allowed for the vehicle (17) according to this estimated slope. 4 - A method of managing the energy recovery according to claim 3, characterized in that the mapping authorizes the following minimum accelerations, for descents stabilization of the speed for a slope of -1%, and a slight acceleration of the vehicle which is bigger and bigger when the descent is stronger, for a flat road a slight braking of the vehicle with a value of about -0.5m / s2, and for the climbs a slight braking of the vehicle which is more and more large when the amount is stronger, with a cap from a threshold that is about -1m / s2. - A method of managing the energy recovery according to claim 3 or 4, characterized in that the minimum allowed acceleration (17) is transmitted to a calculation function of the minimum authorized powertrain (18), which also receives a estimating the resistant forces applying to the vehicle (20), to deduce a minimum authorized powertrain (19) which gives the acceleration of the vehicle corresponding to this authorized minimum. 6 - A method for managing energy recovery according to claim 5, characterized in that the minimum authorized powertrain (19) is delivered to a calculation function of the minimum authorized safe powertrain (22), receiving further an indication the minimum torque that can be delivered by the heat engine (24), so as to deduce a minimum safe powertrain (23) that can be obtained by the vehicle speed regulation or limitation system, which corresponds to the smallest value between the minimum authorized powertrain (19) and the minimum torque that can be delivered by the heat engine (24). 7 - A method of managing the energy recovery according to claim 6, characterized in that the minimum powertrain torque (23) is delivered to a function of calculating the torque setpoint for the control system or limitation of the speed (26), which further receives a torque setpoint requested by this system (28), to limit this setpoint by the minimum safe powertrain (23), in order to obtain the final setpoint torque (30) requested by the system which corresponds to the highest value between the torque setpoint requested by the system (28) and the minimum authorized safe powertrain (23). 8 - Hybrid motor vehicle having a heat engine, and an auxiliary motor that recharges energy storage means by energy recovery by braking the vehicle, the vehicle including a system for regulating or limiting its speed which in some cases requires a braking of the vehicle to meet a set speed, characterized in that it comprises means implementing a method of managing the energy recovery made according to any one of the preceding claims.