Method and device for controlling an energy equivalence factor in a hybrid motor propulsion plant

Abstract

A method of determining an equivalence energy factor representing weighting applied between an infeed of energy of thermal origin and an infeed of energy of electrical origin, to minimize on an operating point overall energy consumption of a hybrid motor propulsion plant for an automotive vehicle including a heat engine and at least one electric motor powered by a battery. This factor is controlled in a discrete manner as a function of an instantaneous state of energy of the battery, and of an energy target, and as a function of the vehicle running conditions.

Claims

1. A method for controlling a distribution of power between a heat engine and an electric machine powered by a battery in a hybrid motor propulsion plant for a motor vehicle, the method comprising: determining an initial energy equivalence factor representing weighting applied between an infeed of energy of thermal origin from the heat engine and an infeed of energy of electrical origin from the electric machine to minimize at an operating point overall energy consumption of the hybrid motor propulsion plant for a motor vehicle based on an energy equivalence hypothesis which considers an instantaneous state of energy of the battery, a target energy, and predicted running conditions of the vehicle; controlling a distribution of power between the heat engine and the electric machine based on the initial energy equivalence factor; correcting, a posteriori, the energy equivalence hypothesis based on encountered running conditions to provide a corrected energy equivalence factor; and controlling a distribution of power between the heat engine and the electric machine based on the corrected energy equivalence factor.

2. The method of claim 1, wherein the target energy is dependent on predictions regarding the running conditions.

3. The method of claim 1, further comprising determining an integrated term of an estimation of a state of energy of the battery.

4. The method of claim 3, wherein the integrated term is dependent on the difference between the target energy and the instantaneous state of energy of the battery.

5. The method of claim 4, wherein calculation of the integrated term is looped by an integral proportional calculation regarding a state of charge of the battery.

6. The method of claim 3, wherein the integrated term is looped by an anti-windup factor.

7. The method of claim 1, being pre-compensated by a term dependent on a conversion yield of the electrical energy into mechanical energy.

8. The method of claim 1, further comprising providing a saturator defining a minimum saturation limit and a maximum saturation limit at which forced recharge and discharge modes occur respectively.

Description

(1) The present invention proposes a control method and device ensuring optimized control of the equivalence factor with a view to coming as close as possible to the optimal solution, taking into account all the influencing factors.

(2) The present invention with this objective proposes controlling the equivalence factor in a discrete manner on the basis of the instantaneous state of energy of the battery, and a target energy depending on the vehicle running conditions and/or predictions regarding the running conditions.

(3) The proposed device in particular comprises an integrator of a term representative of the difference between the instantaneous state of energy of the battery and the target energy state.

(4) Further features and advantages of the present invention will become clear upon reading the following description of a non-limiting embodiment thereof, given with reference to the accompanying drawing, of which the sole FIGURE schematically shows the implemented device.

(5) In this device a first comparator C1 receives, in input values, the state of energy soe.sub.k of the battery at the moment k, and target state of energy value soe.sub.target. The difference (soe.sub.target−soe.sub.k) is multiplied by a correction gain K.sub.p. A second comparator C2 sums the result [K.sub.p(soe.sub.target−soe.sub.k)] and a correction term of the integral type, which assures a correction of the equivalence factor on the basis of the encountered running conditions. This sum is saturated by the saturator S, which assures that the equivalence factor will remain within the controlled limits. The minimum saturation (sat.sub.min−1/η) and maximum saturation (sat.sub.max−1/η) limits assure that forced recharge and discharge modes are controlled.

(6) The maximum saturation sat.sub.max is the maximum equivalence value assuring a control of the motor propulsion group such that the energy of the battery is recharged to the maximum. The saturation sat.sub.min is the minimum equivalence factor assuring a control of the motor propulsion group such that the battery is discharged to the maximum. The integrator I integrates the difference between the output of the saturator S and its own integration multiplied by a correction gain K.sub.i with the aid of the comparator C3. By integrating this difference, the integrator cannot run out of control when the system is saturated. This method is known by the name “anti-windup” or anti-racing or desaturator. The output of the saturator is added with a term 1/η of the “feedforward” or pre-positioning term type with the aid of the comparator C4. This “feedforward” or pre-positioning term makes it possible to directly adapt the equivalence factor on the basis of an encountered and/or predicted running situation.

(7) To summarize, the proposed device comprises a loop integrator of a term representative of the difference between the instantaneous state of the energy of the battery and the target energy state of the battery combined with an anti-windup device. It also comprises a proportional compensation term.

(8) The control implemented with this device also has a feedforward term. The equivalence factor is controlled in a discrete manner in accordance with the following equation:
S.sub.k+1=1/η.sub.c+Kp(soe.sub.target−soe.sub.k+1)+KpKi(soe.sub.target−soe.sub.k)

(9) In this equation soe.sub.target is the target energy state to be reached and soe.sub.k is the energy state of the battery at the moment k. K.sub.p and K.sub.i are, respectively, the proportional and integral correction gains; ηc is the mean yield of conversion of the electrical energy into thermal energy. The mean yield of conversion ηc may thus be calculated in order to adapt permanently to the circumstances on the basis of the knowledge a priori of foreseeable running conditions or on the basis of analysis of the previous running conditions. The integral correction provides a correction a posteriori of energy equivalence hypotheses.

(10) If, for example, a type of running “in congestion” is identified, it is possible to provide the conversion yield η.sub.c with a value suitable for situations of congestion and to obtain an equivalence factor substantially different from the equivalence factor on a motorway.

(11) In addition, the desired target energy soe.sub.target can be defined on the basis of the running conditions. If the vehicle has a navigation system, it is then possible to utilize the information provided thereby in order to optimize the target.

(12) Lastly, when the equivalence is saturated, i.e. the equivalence factor s reaches limit values, imposing a recharge or a discharge of the battery at all costs, the equivalence factor s does not exceed acceptable limits (lower and upper) because the anti-windup avoids any untimely runaway of the integral term.

(13) In conclusion, the invention makes it possible: to use the energy contained in the battery more suitably and to draw all possible benefits therefrom to reduce consumption, to take into account the environment and the driver, to take into account the altitude profile in the event that information is provided via the navigation system, and to manage energy fluxes based more on an “energy state” of the battery than on the state of charge thereof, which is more advantageous in terms of consumption.