Method for operating an internal combustion engine for a motor vehicle, and a system for an internal combustion engine

1. A method for operating an internal combustion engine for a motor vehicle, comprising:

receiving measurement signals of a cylinder pressure sensor which are representative of a pressure in a cylinder of the internal combustion engine,

determining cylinder pressure fluctuations in the cylinder of the internal combustion engine as a function of the received measurement signals of the cylinder pressure sensor,

increasing an exhaust gas recirculation rate of the internal combustion engine as a function of the determined cylinder pressure fluctuations until a predefined limiting value of the cylinder pressure fluctuations is reached,

determining an actual value of the exhaust gas recirculation rate if the predefined limiting value of the cylinder pressure fluctuations is reached, and storing the determined actual value as a setpoint value for the exhaust gas recirculation rate of the internal combustion engine,

determining a center of combustion as a function of the received measurement signals of the cylinder pressure sensor, and

adapting the setpoint value of the exhaust gas recirculation rate as a function of the determined center of combustion.

2. The method as claimed in claim 1 , further comprising:

receiving measurement signals of the cylinder pressure sensor which are representative of an intake pressure in an intake manifold of the internal combustion engine,

determining an air mass, sucked in in the intake manifold, as a function of the received measurement signals of the cylinder pressure sensor that are representative of the intake pressure in the intake manifold, and

controlling the exhaust gas recirculation rate of the internal combustion engine as a function of the determined air mass.

3. The method as claimed in claim 2 , further comprising:

determining a knocking intensity as a function of the received measurement signals of the cylinder pressure sensor or as a function of measurement signals of a knocking sensor,

adapting an ignition angle of a crankshaft of the internal combustion engine which is coupled to a piston in the cylinder, as a function of the determined knocking intensity, and

adapting the setpoint value of the exhaust gas recirculation rate as a function of the adaptation of the ignition angle.

4. The method as claimed in claim 1 , further comprising:

determining a combustion period as a function of the received measurement signals of the cylinder pressure sensor, and

adapting the setpoint value of the exhaust gas recirculation rate as a function of the determined combustion period.

5. The method as claimed in claim 1 , further comprising

adapting the setpoint value of the exhaust gas recirculation rate by controlling an ignition angle of a crankshaft of the internal combustion engine which is coupled to a piston in the cylinder.

6. The method as claimed in claim 1 , further comprising:

receiving measurement signals of a knocking sensor which are representative of a knocking intensity of a respective cylinder, and

adapting the setpoint value of the exhaust gas recirculation rate as a function of the received measurement signals of the knocking sensor.

7. The method as claimed in claim 1 , further comprising:

determining a knocking intensity as a function of the received measurement signals of the cylinder pressure sensor or as a function of measurement signals of a knocking sensor,

adapting an ignition angle of a crankshaft of the internal combustion engine which is coupled to a piston in the cylinder, as a function of the determined knocking intensity, and

adapting the setpoint value of the exhaust gas recirculation rate as a function of the adaptation of the ignition angle.

8. The method of claim 1 , wherein increasing the exhaust gas recirculation rate of the internal combustion engine comprises increasing the exhaust gas recirculation rate until the center of combustion occurs.

9. A system for an internal combustion engine having a cylinder, comprising:

a cylinder pressure sensor which is arranged in the internal combustion engine of the motor vehicle and whose measurement signals are representative of a pressure in the cylinder of the internal combustion engine; and

a device and memory coupled thereto, the device being configured to:

receive measurement signals of the cylinder pressure sensor which are representative of a pressure in a cylinder of the internal combustion engine,

determining cylinder pressure fluctuations in the cylinder of the internal combustion engine as a function of the received measurement signals of the cylinder pressure sensor,

increasing an exhaust gas recirculation rate of the internal combustion engine as a function of the determined cylinder pressure fluctuations until a predefined limiting value of the cylinder pressure fluctuations is reached,

determining an actual value of the exhaust gas recirculation rate if the predefined limiting value of the cylinder pressure fluctuations is reached, and storing the determined actual value in the memory as a setpoint value for the exhaust gas recirculation rate of the internal combustion engine,

determine a center of combustion as a function of the received measurement signals of the cylinder pressure sensor, and

adapt the setpoint value of the exhaust gas recirculation rate as a function of the determined center of combustion.

10. The system as claimed in claim 9 , wherein the device is further configured to:

receive measurement signals of the cylinder pressure sensor which are representative of an intake pressure in an intake manifold of the internal combustion engine,

determine an air mass, sucked in in the intake manifold, as a function of the received measurement signals of the cylinder pressure sensor that are representative of the intake pressure in the intake manifold, and

control the exhaust gas recirculation rate of the internal combustion engine as a function of the determined air mass.

11. The system as claimed in claim 9 , wherein the device is further configured to

determine a knocking intensity as a function of the received measurement signals of the cylinder pressure sensor or as a function of measurement signals of a knocking sensor,

adapt an ignition angle of a crankshaft of the internal combustion engine which is coupled to a piston in the cylinder, as a function of the determined knocking intensity, and

adapt the setpoint value of the exhaust gas recirculation rate as a function of the adaptation of the ignition angle.

12. The system as claimed in claim 9 , wherein the device is further configured to

determine a combustion period as a function of the received measurement signals of the cylinder pressure sensor, and

adapt the setpoint value of the exhaust gas recirculation rate as a function of the determined combustion period.

13. The system as claimed in claim 9 , wherein the device is further configured to adapt the setpoint value of the exhaust gas recirculation rate by controlling an ignition angle of a crankshaft of the internal combustion engine which is coupled to a piston in the cylinder.

14. The system as claimed in claim 9 , wherein the device is further configured to

receive measurement signals of a knocking sensor which are representative of a knocking intensity of a respective cylinder, and

adapt the setpoint value of the exhaust gas recirculation rate as a function of the received measurement signals of the knocking sensor.