Method and control unit for electric control of an actuator of an injection valve

1. A control unit for electric activation of an actuator of an injection valve in an injection system for an internal combustion engine, comprising:

a) A pilot control which sets a controlled variable of the actuator in accordance with a predetermined target value in accordance with a pilot control characteristic, with the pilot control characteristic being defined by an axis section and a characteristic gradient, and

b) A regulator which determines a control deviation of the controlled variable and readjusts the pilot control characteristic as a function of the control deviation,

c) wherein the regulator, within the framework of the readjustment, sets the axis section of the pilot control characteristic.

2. The control unit according to claim 1 , wherein

a) The regulator readjusts at least one of the axis section and the characteristic gradient of the pilot control characteristic for a target value jump,

b) The regulator determines a dynamic control deviation for the target value jump which occurs temporarily immediately after the target value jump before the regulating out, and

c) The regulator sets the pilot control characteristic as a function of the dynamic control deviation.

3. The control unit according to claim 2 , wherein

the regulator calculates the adapted axis section of the pilot control characteristic from the following variables:

a) Target value of the controlled variable before the target value jump,

b) Target value of the controlled variable after the target value jump,

c) Actual value of the controlled variable immediately after the target value jump before the control deviation is regulated out,

d) Controlled variable before the target value jump,

e) Controlled variable immediately after the target value jump before the control deviation is regulated out.

4. The control unit as claimed in claim 3 ,

characterized in that

the regulator calculates the adapted axis section of the pilot control characteristic in accordance with the following formula:

OffsReal

=

OffsCal

+

E

⁢

⁢

1

TGT

·

Δ

⁢

⁢

E

·

(

PMW

⁢

⁢

2

-

PMW

⁢

⁢

1

)

(

E

⁢

⁢

2

TGT

-

E

⁢

⁢

1

TGT

)

·

(

E

⁢

⁢

2

TGT

-

E

⁢

⁢

1

TGT

+

Δ

⁢

⁢

E

)

with

OffsReal: Adapted axis section of the pilot control characteristic after the readjustment,

OffsCal: Non-adapted axis section of the pilot control characteristic before the readjustment,

E 1 TGT : Target value of the controlled variable before the target value jump,

E 2 TGT : Target value of the controlled variable after the target value jump,

E 2 ACT : Actual value of the controlled variable directly after the target value jump before the control deviation is regulated out,

ΔE: =E 2 ACT −E 2 TGT , control deviation of the controlled variable immediately after the target value jump before the control deviation is regulated out,

PWM 1 : Control variable before the target value jump, and/or

PWM 2 : Control variable immediately after the target value jump before the control deviation is regulated out.

5. The control unit according to claim 1 , wherein

the regulator, within the framework of the readjustment, in addition to the axis section of the pilot control characteristic, also sets the gradient of the pilot control characteristic.

6. The control unit according to claim 5 , wherein

the regulator calculates the adapted characteristic gradient of the pilot control characteristic as a function of at least one of the following variables:

a) Control variable before the target value jump,

b) Axis section of the pilot control characteristic before the target value jump,

c) Adapted axis section of the pilot control characteristic after the target value jump, and

d) Target value before the target value jump.

7. The control unit according to claim 6 , wherein

the controller calculates the adapted characteristic gradient of the pilot control characteristic in accordance with the following formula:

K

=

PWM

⁢

⁢

1

-

OffsReal

E

⁢

⁢

1

TGT

with

K: Adapted characteristic gradient of the pilot control characteristic after the readjustment

PWM 1 : Controlled variable before the target value jump,

OffsReal: Adapted axis section of the pilot control characteristic after the readjustment,

E 1 TGT : Target value of the controlled variable before the target value jump.

8. The control unit according to claim 1 , wherein

a) The control unit determines for a target value jump the dynamic control deviation which occurs temporarily immediately after the target value jump before the regulating out,

b) The control unit compares the dynamic control deviation with a predetermined maximum value,

c) The control unit readjusts the axis section of the pilot control characteristic only when the amount of dynamic control deviation exceeds the maximum value.

9. A motor vehicle with a control unit according to claim 1 .

10. A method for electric activation of an actuator of an injection valve in a fuel injection system for an internal combustion engine, comprising:

a) Predetermining a target value for a controlled variable of the actuator,

b) Pilot control of the controlled variable in accordance with a pilot control characteristic which is predetermined by an axis section and a characteristic gradient with, within the framework of the pilot control, in accordance with the predetermined target value in accordance with the pilot control characteristic a controlled variable being determined for electrical activation of the actuator,

c) Readjustment of the pilot control characteristic with, within the framework of the readjustment a control deviation being determined and the pilot control characteristic being adapted as a function of the control deviation,

d) wherein within the framework of the readjustment of the axis section the pilot control characteristic is set.

11. The method according to claim 10 , wherein

a) the readjustment is undertaken for a target value jump,

b) for the target value jump the dynamic control deviation is determined which occurs temporarily immediately after the target value jump before the regulating out, and

c) the pilot control characteristic is set as a function of the dynamic control deviation.

12. The method according to claim 11 , wherein

the adapted axis section of the pilot control characteristic is calculated from the following variables:

a) Target value of the controlled variable before the target value jump,

b) Target value of the controlled variable after the target value jump,

c) Actual value of the controlled variable immediately after the target value jump before the control deviation is regulated out,

d) Control variable before the target value jump

Control variable immediately after the target value jump before the control deviation is regulated out.

13. The method according to claim 12 , wherein

the adapted axis section of the pilot control characteristic is calculated in accordance with the following formula:

OffsReal

=

OffsCal

+

E

⁢

⁢

1

TGT

·

Δ

⁢

⁢

E

·

(

PMW

⁢

⁢

2

-

PMW

⁢

⁢

1

)

(

E

⁢

⁢

2

TGT

-

E

⁢

⁢

1

TGT

)

·

(

E

⁢

⁢

2

TGT

-

E

⁢

⁢

1

TGT

+

Δ

⁢

⁢

E

)

with

OffsReal: Adapted axis section of the pilot control characteristic after the readjustment,

OffsCal: Non-adapted axis section of the pilot control characteristic before the readjustment,

E 1 TGT : Target value of the controlled variable before the target value jump,

E 2 TGT : Target value of the controlled variable after the target value jump,

E 2 ACT : Actual value of the controlled variable immediately after the target value jump before the control deviation is regulated out,

ΔE: =E 2 ACT −E 2 TGT , control deviation of the controlled variable immediately after the target value jump before the control deviation is regulated out,

PWM 1 : Control variable before the target value jump, and/or

PWM 2 : Control variable immediately after the target value jump before the control deviation is regulated out.

14. The method according to claim 10 , wherein,

within the framework of the readjustment, in addition to the axis section of the pilot control characteristic, the characteristic gradient of the pilot control characteristic is also set.

15. The method according to claim 14 , wherein

the adapted characteristic gradient of the pilot control characteristic is calculated as a function of at least one of the following variables:

a) Control variable before the target value jump,

b) Axis section of the pilot control characteristic before the target value jump,

c) Adapted axis section of the pilot control characteristic after the target value jump, and

d) Target value before the target value jump.

16. The method according to claim 15 , wherein

the adapted characteristic gradient of the pilot control characteristic is calculated in accordance with the following formula:

K

REAL

=

PWM

⁢

⁢

1

-

OffsReal

E

⁢

⁢

1

TGT

with

K REAL : Adapted characteristic gradient of the pilot control characteristic after the readjustment

PWM 1 : Control variable before the target value jump,

OffsReal: Adapted axis section of the pilot control characteristic after the readjustment,

E 1 TGT : Target value of the controlled variable before the target value jump.

17. The method according to claim 10 , comprising:

Pulse with modulated activation of the actuator by a final stage with a variable pulse duty ratio, with the pilot controlled and regulated controlled variable being the pulse duty ratio of the final stage.

18. The method according to claim 10 , wherein

the actuator is a piezoactuator.

19. The method according to claim 10 , wherein

the controlled variable of the actuator is the electrical energy stored in the actuator.

20. The method according to claim 10 , wherein

the pilot control characteristic is readjusted during operation of the injection system only temporarily and/or individually.

21. The method according to claim 10 , wherein

a) for a target value jump the dynamic control deviation is determined which occurs temporarily immediately after the target value jump before the regulating out,

b) the dynamic control deviation is compared with a predetermined maximum value

the pilot control characteristic is only readjusted in the dynamic control deviation exceeds the maximum value.

22. The method according to claim 21 , wherein

at least one of the following ambient conditions are checked to see whether they have changed:

a) Temperature, especially ambient temperature, coolant temperature or oil temperature,

b) State of ageing of at least one of the internal combustion engine, of the injection system and of the actuator, and

c) Electrical capacitance of the actuator.

23. The method according to claim 10 , wherein

a) In normal operation of the injection system ambient conditions are checked to see whether they have changed,

b) The pilot control characteristic is only readjusted if the ambient conditions have changed.