Propulsion system control with MPC

• US 9,963,150 B2
• Filed: 02/07/2017
• Issued: 05/08/2018
• Est. Priority Date: 06/16/2016
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Livshiz, Michael, Whitney, Christopher E, Wong, Kevin C, Bernardini, Daniele, Bemporad, Alberto
• Primary Examiner(s): Wright, Dirk
• Application Number:
  US15/426,306
• Publication Number:
  US 20170361842A1
• Time in Patent Office: 455 Days
• Field of Search: None
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 10/16 Axle differentials, e.g. for dividing torque between left and right wheels
• CPC Class Codes: B60W 2510/0619 Air-fuel ratio
• CPC Class Codes: B60W 2510/0623 Fuel flow rate
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 2710/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2710/105 Output torque
• CPC Class Codes: B60W 30/188 Controlling power parameters of the driveline, e.g. determining the required power
• CPC Class Codes: B60W 30/1882 characterised by the working point of the engine, e.g. by using engine output chart
• CPC Class Codes: F16H 59/14 Inputs being a function of torque or torque demand
• CPC Class Codes: Y02T 10/84 Data processing systems or methods, management, administration

Abstract

A propulsion system, control system, and method are provided for optimizing fuel economy, which use model predictive control systems to generate first and second predicted actual axle torques and first and second predicted actual fuel consumption rates based on first and second sets of possible command values, respectively. The sets of possible command values include commanded engine output torques and commanded transmission ratios. First and second costs are determined for the first and second sets of possible command values, respectively, based on a first predetermined weighting value, a second predetermined weighting value, the first and second predicted actual axle torques, respectively, the first and second predicted actual fuel consumption rates, respectively, an axle torque requested, an engine output torque requested, a transmission ratio requested, and a fuel consumption rate requested. One of the first and second sets of possible command values is selected and set based on the lower cost.

Claims

1. A method for controlling a propulsion system of a motor vehicle, the method comprising:

generating a first predicted actual axle torque and a first predicted actual fuel consumption rate based on a first set of possible command values, the first set of possible command values including a first commanded engine output torque and a first commanded transmission ratio;

generating a second predicted actual axle torque and a second predicted actual fuel consumption rate based on a second set of possible command values, the second set of possible command values including a second commanded engine output torque and a second commanded transmission ratio;

determining a first cost for the first set of possible command values based on a first predetermined weighting value, a second predetermined weighting value, the first predicted actual axle torque, the first predicted actual fuel consumption rate, an axle torque requested, an engine output torque requested, a transmission ratio requested, and a fuel consumption rate requested;

determining a second cost for the second set of possible command values based on the first predetermined weighting value, the second predetermined weighting value, the second predicted actual axle torque, the second predicted actual fuel consumption rate, the axle torque requested, the engine output torque requested, the transmission ratio requested, and the fuel consumption rate requested;

selecting one of the first and second sets of possible command values based on the lower of the first and second costs;

setting desired command values based on the possible command values of the selected one of the first and second sets; and

controlling a vehicle parameter based on at least one of the desired command values.

2. The method of claim 1, further comprising determining the first and second costs with the following cost equation:

3. The method of claim 2, further comprising applying the cost equation iteratively to arrive at the lowest cost for a plurality of sets of possible command values, the plurality of sets of possible command values including the first and second sets of possible command values, the method further comprising selecting the set of possible command values of the plurality of command values having the lowest cost, wherein the set of possible command values having the lowest cost is defined as one of the first and second sets of possible command values.

4. The method of claim 3, further comprising:

determining an accelerator pedal position (PP);

determining an engine speed (RPM);

determining a vehicle speed (V);

determining an air-fuel ratio (AF);

determining the axle torque requested (Ta_r) based on the accelerator pedal position (PP) and the vehicle speed (V);

determining the fuel consumption rate requested (FR_r) based on the axle torque requested (Ta_r), the vehicle speed (V), the engine speed (RPM), and the air-fuel ratio (AF);

determining the transmission ratio requested (Rat_r) based on the axle torque requested (Ta_r) and the vehicle speed (V); and

determining the engine output torque requested (Te_r) based on the axle torque requested (Ta_r), the transmission ratio requested (Rat_r), and a final drive ratio (FD).

5. The method of claim 4, further comprising determining the first and second predicted actual axle torques and the first and second predicted actual fuel consumption rates with the following set of equations:

6. The method of claim 1, further comprising determining the first and second costs with the following cost equation:

Cost=λ

_a*(Ta_a_k−

Ta_r)²+λ

_a*(Ta_a_k+1−

Ta_r)²+λ

_a*(Ta_a_k+2−

Ta_r)²+λ

_f*(FR_a_k−

FR_r)²+λ

_f*(FR_a_k+1−

FR_r)²+λ

_f*(FR_a_k+2−

FR_r)²+λ

_e*(Te_c_k−

Te_r)²+λ

_e*(Te_c_k+1−

Te_r)²+λ

_r*(Rat_c_k−

Rat_r)²+λ

_r*(Rat_c_k+1−

Rat_r)²+λ

<sub>Δ

r</sub>*(Δ

Rat_c_k)²+λ

<sub>Δ

r</sub>*(Δ

Rat_c_k+1)²λ

<sub>Δ

e</sub>*(Δ

Te_c_k)²+λ

<sub>Δ

e</sub>*(Δ

Te_c_k+1)²

where

λ

_a=the first predetermined weighting value;

Ta_a_k=predicted actual axle torque at a prediction step k;

Ta_r=axle torque requested;

Ta_a_k+1=predicted actual axle torque at a prediction step k+1;

Ta_a_k+2=predicted actual axle torque at a prediction step k+2;

λ

_f=the second predetermined weighting value;

FR_a_k=predicted actual fuel consumption rate at the prediction step k;

FR_r=fuel consumption rate requested;

FR_a_k+1=predicted actual fuel consumption rate at the prediction step k+1;

FR_a_k+2=predicted actual fuel consumption rate at the prediction step k+2;

λ

_e=a third predetermined weighting value;

Te_c_k=engine output torque commanded at the prediction step k;

Te_r=engine output torque requested;

Te_c_k+1=engine output torque commanded at the prediction step k+1;

λ

_r=a fourth predetermined weighting value;

Rat_c_k=transmission ratio commanded at the prediction step k;

Rat_r=transmission ratio requested;

Rat_c_k+1=transmission ratio commanded at the prediction step k+1;

λ

<sub>Δ

r</sub>=a fifth predetermined weighting value;

Δ

Rat_c_k=change in transmission ratio commanded at the prediction step k;

Δ

Rat_c_k+1=change in transmission ratio commanded at the prediction step k+1;

λ

<sub>Δ

e</sub>=a sixth predetermined weighting value;

Δ

Te_c_k=change in engine output torque commanded at the prediction step k; and

Δ

Te_c_k+1=change in engine output torque commanded at the prediction step k+1,

wherein Ta_a_k+1 and FR_a_k+1 are equal to the first predicted actual axle torque and the first predicted actual fuel consumption rate, respectively, when generated based on the first set of possible command values for Te_c_k and Rat_c_k, and Ta_a_k+1 and FR_a_k+1 are equal to the second predicted actual axle torque and the second predicted actual fuel consumption rate, respectively, when generated based on the second set of possible command values for Te_c_k and Rat_c_k.

7. The method of claim 6, further comprising determining the first and second predicted actual axle torques and the first and second predicted actual fuel consumption rates with the following set of equations:

8. A motor vehicle propulsion control system for a motor vehicle having a transmission and an engine, the motor vehicle propulsion control system comprising:

a prediction module configured to generate a first predicted actual axle torque and a first predicted actual fuel consumption rate based on a first set of possible command values, the first set of possible command values including a first commanded engine output torque and a first commanded transmission ratio, the prediction module being further configured to generate a second predicted actual axle torque and a second predicted actual fuel consumption rate based on a second set of possible command values, the second set of possible command values including a second commanded engine output torque and a second commanded transmission ratio;

a cost module configured to;

determine a first cost for the first set of possible command values based on a first predetermined weighting value, a second predetermined weighting value, the first predicted actual axle torque, the first predicted actual fuel consumption rate, an axle torque requested, an engine output torque requested, a transmission ratio requested, and a fuel consumption rate requested; and

determine a second cost for the second set of possible command values based on the first predetermined weighting value, the second predetermined weighting value, the second predicted actual axle torque, the second predicted actual fuel consumption rate, the axle torque requested, the engine output torque requested, the transmission ratio requested, and the fuel consumption rate requested; and

a selection module configured to select one of the first and second sets of possible command values based on the lower of the first and second costs and set desired command values based on the possible command values of the selected one of the first and second sets.

9. The motor vehicle propulsion control system of claim 8, further comprising an actuation module configured to control a vehicle parameter based on at least one of the desired command values.

10. The motor vehicle propulsion control system of claim 9, wherein the cost module is configured to determine the first and second costs with the following cost equation:

11. The motor vehicle propulsion control system of claim 10, further comprising a steady state optimizer module configured to:

determine an accelerator pedal position (PP);

determine an engine speed (RPM);

determine a vehicle speed (V);

determine an air-fuel ratio (AF);

determine the axle torque requested (Ta_r) based on the accelerator pedal position (PP) and the vehicle speed (V);

determine the fuel consumption rate requested (FR_r) based on the axle torque requested (Ta_r), the vehicle speed (V), the engine speed (RPM), and the air-fuel ratio (AF);

determine the transmission ratio requested (Rat_r) based on the axle torque requested (Ta_r) and the vehicle speed (V); and

determine the engine output torque requested (Te_r) based on the axle torque requested (Ta_r), the transmission ratio requested (Rat_r), and a final drive ratio (FD).

12. The motor vehicle propulsion control system of claim 11, wherein the prediction module is further configured to determine the first and second predicted actual axle torques and the first and second predicted actual fuel consumption rates with the following set of equations:

13. The motor vehicle propulsion control system of claim 8, wherein the cost module is further configured to determine the first and second costs with the following cost equation:

Cost=λ

_a*(Ta_a_k−

Ta_r)²+λ

_a*(Ta_a_k+1−

Ta_r)²+λ

_a*(Ta_a_k+2−

Ta_r)²+λ

_f*(FR_a_k−

FR_r)²+λ

_f*(FR_a_k+1−

FR_r)²+λ

_f*(FR_a_k+2−

FR_r)²+λ

_e*(Te_c_k−

Te_r)²+λ

_e*(Te_c_k+1−

Te_r)²+λ

_r*(Rat_c_k−

Rat_r)²+λ

_r*(Rat_c_k+1−

Rat_r)²+λ

<sub>Δ

r</sub>*(Δ

Rat_c_k)²+λ

<sub>Δ

r</sub>*(Δ

Rat_c_k+1)²λ

<sub>Δ

e</sub>*(Δ

Te_c_k)²+λ

<sub>Δ

e</sub>*(Δ

Te_c_k+1)²

where

λ

_a=the first predetermined weighting value;

Ta_a_k=predicted actual axle torque at a prediction step k;

Ta_r=axle torque requested;

Ta_a_k+1=predicted actual axle torque at a prediction step k+1;

Ta_a_k+2=predicted actual axle torque at a prediction step k+2;

λ

_f=the second predetermined weighting value;

FR_a_k=predicted actual fuel consumption rate at the prediction step k;

FR_r=fuel consumption rate requested;

FR_a_k+1=predicted actual fuel consumption rate at the prediction step k+1;

FR_a_k+2=predicted actual fuel consumption rate at the prediction step k+2;

λ

_e=a third predetermined weighting value;

Te_c_k=engine output torque commanded at the prediction step k;

Te_r=engine output torque requested;

Te_c_k+1=engine output torque commanded at the prediction step k+1;

λ

_r=a fourth predetermined weighting value;

Rat_c_k=transmission ratio commanded at the prediction step k;

Rat_r=transmission ratio requested;

Rat_c_k+1=transmission ratio commanded at the prediction step k+1;

λ

<sub>Δ

r</sub>=a fifth predetermined weighting value;

Δ

Rat_c_k=change in transmission ratio commanded at the prediction step k;

Δ

Rat_c_k+1=change in transmission ratio commanded at the prediction step k+1;

λ

<sub>Δ

e</sub>=a sixth predetermined weighting value;

Δ

Te_c_k=change in engine output torque commanded at the prediction step k; and

Δ

Te_c_k+1=change in engine output torque commanded at the prediction step k+1,

wherein Ta_a_k+1 and FR_a_k+1 are equal to the first predicted actual axle torque and the first predicted actual fuel consumption rate, respectively, when generated based on the first set of possible command values for Te_c_k and Rat_c_k, and Ta_a_k+1 and FR_a_k+1 are equal to the second predicted actual axle torque and the second predicted actual fuel consumption rate, respectively, when generated based on the second set of possible command values for Te_c_k and Rat_c_k.

14. The motor vehicle propulsion control system of claim 13, wherein the prediction module is further configured to determine the first and second predicted actual axle torques and the first and second predicted actual fuel consumption rates with the following set of equations:

15. The motor vehicle propulsion control system of claim 14, wherein:

Te_min<

Te_c_k<

Te_max;

Te_min<

Te_c_k+1<

Te_max;

Rat_min<

Rat_c_k<

Rat_max;

Rat_min<

Rat_c_k+1<

Rat_max;

Δ

Te_c_k<

Δ

Te_c_max;

Δ

Te_c_k+1<

Δ

Te_c_max;

Δ

Rat_c_k<

Δ

Rat_c_max; and

Δ

Rat_c_k+1<

Δ

Rat_c_max,

where

Te_min=a minimum possible engine output torque;

Te_max=a maximum possible engine output torque;

Rat_min=a minimum possible transmission ratio;

Rat_max=a maximum possible transmission ratio;

Δ

Te_c_max=a maximum possible change in engine output torque; and

Δ

Rat_c_max=a maximum possible change in transmission ratio.

16. A propulsion system for a motor vehicle, comprising:

an engine operable to power the motor vehicle, the engine having an engine output shaft configured to transfer engine output torque;

a continuously variable transmission having a variator assembly including a first pulley and a second pulley, the first and second pulleys being rotatably coupled by a rotatable member, at least one of the first and second pulleys including a movable sheave translatable along an axis to selectively change a gear ratio between the engine output shaft and a transmission output shaft;

a drive axle configured to be driven via the transmission output shaft, the drive axle being configured to output axle torque to a set of wheels; and

a control system comprising;

a prediction module configured to generate a first predicted actual axle torque and a first predicted actual fuel consumption rate based on a first set of possible command values, the first set of possible command values including a first commanded engine output torque and a first commanded transmission ratio, the prediction module being further configured to generate a second predicted actual axle torque and a second predicted actual fuel consumption rate based on a second set of possible command values, the second set of possible command values including a second commanded engine output torque and a second commanded transmission ratio;

a cost module configured to;

determine a first cost for the first set of possible command values based on a first predetermined weighting value, a second predetermined weighting value, the first predicted actual axle torque, the first predicted actual fuel consumption rate, an axle torque requested, an engine output torque requested, a transmission ratio requested, and a fuel consumption rate requested; and

determine a second cost for the second set of possible command values based on the first predetermined weighting value, the second predetermined weighting value, the second predicted actual axle torque, the second predicted actual fuel consumption rate, the axle torque requested, the engine output torque requested, the transmission ratio requested, and the fuel consumption rate requested; and

a selection module configured to select one of the first and second sets of possible command values based on the lower of the first and second costs and set desired command values based on the possible command values of the selected one of the first and second sets.

17. The propulsion system of claim 16, wherein the prediction module is further configured to determine the first and second predicted actual axle torques and the first and second predicted actual fuel consumption rates with the following set of equations:

18. The propulsion system of claim 17, wherein the cost module is configured to determine the first and second costs with the following cost equation:

19. The propulsion system of claim 17, wherein the cost module is further configured to determine the first and second costs with the following cost equation:

Cost=λ

_a*(Ta_a_k−

Ta_r)²+λ

_a*(Ta_a_k+1−

Ta_r)²+λ

_a*(Ta_a_k+2−

Ta_r)²+λ

_f*(FR_a_k−

FR_r)²+λ

_f*(FR_a_k+1−

FR_r)²+λ

_f*(FR_a_k+2−

FR_r)²+λ

_e*(Te_c_k−

Te_r)²+λ

_e*(Te_c_k+1−

Te_r)²+λ

_r*(Rat_c_k−

Rat_r)²+λ

_r*(Rat_c_k+1−

Rat_r)²+λ

<sub>Δ

r</sub>*(Δ

Rat_c_k)²+λ

<sub>Δ

r</sub>*(Δ

Rat_c_k+1)²λ

<sub>Δ

e</sub>*(Δ

Te_c_k)²+λ

<sub>Δ

e</sub>*(Δ

Te_c_k+1)²

where

λ

_a=the first predetermined weighting value;

Ta_r=axle torque requested;

Ta_a_k+2=predicted actual axle torque at a prediction step k+2;

λ

_f=the second predetermined weighting value;

FR_r=fuel consumption rate requested;

FR_a_k+2=predicted actual fuel consumption rate at the prediction step k+2;

λ

_e=a third predetermined weighting value;

Te_r=engine output torque requested;

Te_c_k+1=engine output torque commanded at the prediction step k+1;

λ

_r=a fourth predetermined weighting value;

Rat_r=transmission ratio requested;

Rat_c_k+1=transmission ratio commanded at the prediction step k+1;

λ

<sub>Δ

r</sub>=a fifth predetermined weighting value;

Δ

Rat_c_k=change in transmission ratio commanded at the prediction step k;

Δ

Rat_c_k+1=change in transmission ratio commanded at the prediction step k+1;

λ

<sub>Δ

e</sub>=a sixth predetermined weighting value;

Δ

Te_c_k=change in engine output torque commanded at the prediction step k; and

Δ

Te_c_k+1=change in engine output torque commanded at the prediction step k+1.

20. The propulsion system of claim 19, the control system further comprising a steady state optimizer module configured to:

determine an accelerator pedal position (PP);

determine an engine speed (RPM);

determine a vehicle speed (V);

determine an air-fuel ratio (AF);

determine the axle torque requested (Ta_r) based on the accelerator pedal position (PP) and the vehicle speed (V);

determine the fuel consumption rate requested (FR_r) based on the axle torque requested (Ta_r), the vehicle speed (V), the engine speed (RPM), and the air-fuel ratio (AF);

determine the transmission ratio requested (Rat_r) based on the axle torque requested (Ta_r) and the vehicle speed (V); and

determine the engine output torque requested (Te_r) based on the axle torque requested (Ta_r), the transmission ratio requested (Rat_r), and a final drive ratio (FD).