METHOD AND CONTROLLER FOR CONTROLLING OUTPUT TORQUE OF A PROPULSION UNIT

• US 20120101705A1
• Filed: 07/05/2010
• Published: 04/26/2012
• Est. Priority Date: 07/07/2009
• Status: Active Grant

• Current Assignee: Volvo Lastvagnar AB (Volvo AB)
• Original Assignee: Volvo Lastvagnar AB (Volvo AB)
• Inventors: Templin, Peter
• Granted Patent: US 8,447,491 B2
• Time in Patent Office: Days
• US Class Current: 701/99
• CPC Class Codes: B60W 30/20 Reducing vibrations in the driveline

Abstract

Method for controlling output torque (T_eng) of a propulsion unit in a vehicle powertrain including driven wheels drivingly connected to the propulsion unit via a mechanical transmission with a drive shaft, wherein the method including the steps of registering driver torque demand (T_d) for vehicle propulsion, registering propulsion unit rotational speed (ω_e), and controlling the output torque (T_eng) of the propulsion unit to asymptotically follow the driver torque demand (T_d) using a closed-loop linear-quadratic regulator (LQR) based controller (9) having the driver torque demand (T_d) and the propulsion unit rotational speed (ω_e) as input data, in order to minimize driveline oscillations.

Claims

1. Method for controlling output torque (T_eng) of a propulsion unit in a vehicle powertrain comprising driven wheels drivingly connected to said propulsion unit via a mechanical transmission with a drive shaft, characterized in that, said method comprising the steps of:

registering driver torque demand (T_d) for vehicle propulsion;

registering propulsion unit rotational speed (ω

_e);

controlling said output torque (T_eng) of said propulsion unit to asymptotically follow said driver torque demand (T_d) using a closed-loop linear-quadratic regulator (LQR) based controller (9) having said driver torque demand (T_d) and said propulsion unit rotational speed (ω

_e) as input data, in order to minimize driveline oscillations.

2. Method according to claim 1, wherein said controller (9):

receives a full state vector information ({circumflex over (x)}) from a state observer (12) based on at least said propulsion unit rotational speed (ω

_e);

generates a controller torque demand (T_f) used for controlling output torque (T_eng) of said propulsion unit based on said driver torque demand (T_d) and said full state vector information ({circumflex over (x)}).

3. Method according to claim 2, wherein said state observer (12) is based on Loop Transfer Recovery (LTR) design, and said state observer (12) is adapted to generate said full state vector information ({circumflex over (x)}) based on at least said propulsion unit rotational speed (ω

_e) and controller torque demand (T_f).

4. Method according to any of claim 2 or 3, wherein said full state vector information ({circumflex over (x)}) includes as state variable at least drive shaft torsion angle (θ

_s), and preferable also propulsion unit rotational speed (ω

_e), and vehicle speed (ω

_v).

5. Method according to any of claims 2 to 4, wherein said controlling of said output torque (T_eng) of said propulsion unit is realized by regulating at least the following three performance index components of said controller (9) to zero:

a time derivative of a drive shaft torque ({dot over (T)}_shaft) of said drive shaft;

an integrated difference (x_u) between said driver torque demand (T_d) and said controller torque demand (T_f); and

a current difference between said driver torque demand (T_d) and said controller torque demand (T_f).

6. Method according to any of claims 2 to 5, wherein said step of registering driver torque demand (T_d) for vehicle propulsion comprises the steps of:

translating an accelerator pedal position into said driver torque demand (T_d);

deriving a torque reference set point (T_r) from said driver torque demand (T_d) by comparing said driver torque demand (T_d) with at least one active torque limitations (8), and setting said torque reference set point (T_r) to the minimum torque value out of said torque values of said comparison;

supplying said torque reference set point (T_r) to said controller (9) as said driver torque demand (T_d).

7. Method according to any of claims 2 to 6, wherein said step of generating an controller torque demand (T_f) used for controlling output torque (T_eng) of said propulsion unit comprises the steps of:

generating a compensated torque (T_c) by said controller (9);

comparing said compensated torque (T_c) with at least one active torque limitations (8), and;

setting said controller torque demand (T_f) to the minimum torque value out of said torque values of said comparison.

8. Method according to any of the preceding claims, wherein also driveline backlash is taken into account in said method for controlling output torque (T_eng) of a propulsion unit by the following step:

in case the backlash will be traversed, providing an intermediate torque hold value (U_rhold) that a requested torque (T_d, T_r) may not exceed until a driveline contact-mode (1, 2) is reached, in order to limit acceleration shocks following the traversing of the backlash.

9. Method according to claim 8, wherein said step is realized by:

including backlash angle (θ

_b) as state variable in said full state vector information ({circumflex over (x)});

determining if the driveline is in negative side contact mode (1), positive side contact mode (2), or non-contact mode (3), based on driveline state mode transition conditions;

determining if backlash will be traversed;

determining said intermediate torque hold value (U_rhold);

controlling said output torque (T_eng) of said propulsion unit by means of optimal control law of the controller (9) in driveline contact mode (1, 2), and controlling said output torque (T_eng) of said propulsion unit by means of open-loop control during driveline non-contact mode (1).

10. Method according to any of claim 8 or 9, wherein said intermediate torque hold value (U_rhold) is determined by numerical optimization based on at least an estimate of a time derivative of the backlash angle ({dot over (θ

)}_b) at the time instance when the opposing side of the backlash is reached.

11. Method according to claim 9, wherein said driveline state mode transition conditions are based on backlash angle (θ

_b), the time derivative of said backlash angle ({dot over (θ

)}_b), and drive shaft torque (T_shaft).

12. Method according to claim 11, wherein said driveline state mode transition condition for determining when said driveline goes from:

negative side contact mode (1) to non-contact mode (3) is drive shaft torque (T_shaft)>

0;

positive side contact mode (2) to non-contact mode (3) is drive shaft torque (T_shaft)<

0;

non-contact mode (3) to negative side contact mode (1) are backlash angle (θ

_b)=−

α and

time derivative of said backlash angle ({dot over (θ

)}_b)<

0; and

non-contact mode (3) to positive side contact mode (2) are backlash angle (θ

_b)=α and

time derivative of said backlash angle ({dot over (θ

)}_b)>

0,

wherein said backlash angle (θ

_b) is limited by −

α

≦

θ

_b≦

α

.

13. Propulsion unit torque controller (9) for controlling output torque (T_eng) of a propulsion unit in a vehicle powertrain comprising driven wheels drivingly connected to said propulsion unit via a mechanical transmission with a drive shaft, characterized in that said controller (9) is a closed-loop linear-quadratic regulator (LQR) based controller (9), and in that said controller (9) is arranged to control said output torque (T_eng) of said propulsion unit by the following steps:

registering driver torque demand (T_d) for vehicle propulsion;

registering propulsion unit rotational speed (ω

_e);

controlling said output torque (T_eng) of said propulsion unit to asymptotically follow said driver torque demand (T_d) having said driver torque demand (T_d) and said propulsion unit rotational speed (ω

_e) as input data, in order to minimize driveline oscillations.

14. The controller (9) according to claim 13, wherein said controller (9) is arranged to:

receive a full state vector information ({circumflex over (x)}) from a state observer (12) based on at least said propulsion unit rotational speed (ω

_e);

generate a controller torque demand (T_f) used for controlling output torque (T_eng) of said propulsion unit based on said driver torque demand (T_d) and said full state vector information ({circumflex over (x)}).

15. The controller (9) according to claim 14, wherein said controller (9) is arranged to control said output torque (T_eng) of said propulsion unit by regulating the following three performance index components of the controller (9) to zero:

a time derivative of a drive shaft torque ({dot over (T)}_shaft) of said drive shaft;

an integrated difference (x_u) between said driver torque demand (T_d) and said controller torque demand (T_f); and

a current difference between said driver torque demand (T_d) and said controller torque demand (T_f).

16. The controller (9) according to any of claims 13 to 15, wherein also driveline backlash is taken into account when controlling output torque (T_eng) of a propulsion unit by the following step:

in case the backlash will be traversed, providing an intermediate torque hold value (U_rhold) that a requested torque (T_d, T_r) may not exceed until a driveline contact-mode (1, 2) is reached, in order to limit acceleration shocks following the traversing of the backlash.

17. The controller (9) according to claim 16, wherein said step is realized by:

including backlash angle (θ

_b) as state variable in said full state vector information ({circumflex over (x)});

determining if the driveline is in negative side contact mode (1), positive side contact mode (2), or non-contact mode (3), based on driveline state mode transition conditions;

determining if backlash will be traversed;

determining said intermediate torque hold value (U_rhold);

controlling said output torque (T_eng) of said propulsion unit by means of optimal control law of the controller (9) in driveline contact mode (1, 2), and controlling said output torque (T_eng) of said propulsion unit by means of open-loop control during driveline non-contact mode (1).