Method for determining a model upstream pressure by means of a mathematical model in an electronically regulated motor vehicle brake system

A method for determining a model upstream pressure (PTMC—mod) by means of a mathematical model in an electronically regulated motor vehicle brake system, in which regulation of an electrically controllable hydraulic valve causing a build-up of brake pressure on at least one wheel brake is carried out using the model upstream pressure (PTMC—mod) as at least one parameter, and the brake system having wheel sensors for providing a vehicle speed signal indicating the speed of the vehicle and having a brake pedal that can be operated, comprising the steps of:

• from the vehicle speed signal (vref) generating at least a first low pass filtered vehicle speed signal by means of at least a first low pass filter with a first limit frequency (fg1), from whose time profile a first point in time (t1) of a significant decrease in speed is detected, which decrease is used as a starting criterion for determining a time duration (Timer) starting with a deceleration of the vehicle initiated by a braking process, which time duration (Timer) ends at a second point in time (t2) at an onset of electronic regulation of the braking process,
• comparing the time duration (Timer) with at least one of a first or a second threshold time value (SW1, SW2) for determining a class of an actuation speed of the brake pedal, and
• depending on the result of the comparing step, determining the model upstream pressure (PTMC—mod) by means of the mathematical model.