Method for providing the clamping force generated by a parking brake

1. A method for providing a clamping force generated by a parking brake in a vehicle, the method comprising:

determining the clamping force, which is at least partially generated by an electromechanical braking device which includes an electric brake motor which applies a brake piston against a brake disk, as a function of a motor constant of the brake motor, the motor constants being ascertained from instantaneous measured values of motor currents, which are measured during an activation of the brake motor;

wherein for determining the motor constant, a no-load voltage and a no-load current are measured on the brake motor during a no-load phase, and the motor current is ascertained during a dynamic current change phase.

2. The method of claim 1 , wherein the measured values are ascertained during a clamping operation of the brake motor for generating the clamping force.

3. The method of claim 2 , wherein the motor current is ascertained after the brake motor is switched on during an initial phase of the current and the no-load current is ascertained during a subsequent phase.

4. The method of claim 1 , wherein multiple measured values of the motor current are ascertained in the dynamic current change phase and used as a basis for the calculation of the motor constants.

5. The method of claim 1 , wherein the motor constant is calculated in a recursive algorithm.

6. The method of claim 1 , wherein the motor constant is calculated according to the equation

R

ges

=

U

s

⁢

⁢

0

ⅇ

γ

1

+

I

0

K

M

=

γ

2

·

R

ges

·

J

ges

T

A

where

R ges denotes the total resistance of the brake motor and line resistances

U s0 denotes the no-load voltage on the brake motor

I 0 denotes the no-load current of the brake motor

J ges denotes the mass moment of inertia of the brake motor including a downstream gear unit

T A denotes a scanning time

and γ 1 , γ 2 are variables that are calculated recursively according to the equations

y ( n )=γ 1 +γ 2 ·n

y ( n )=1 n ( I A ( n )− I 0 ),

 where

n denotes an integer control variable for consecutive, discrete points in time,

I A denotes the motor current during a dynamic current change phase.

7. The method of claim 6 , wherein the variables γ 1 , γ 2 are calculated in a recursive algorithm.

8. The method of claim 6 , wherein the variables γ 1 , γ 2 are calculated in a recursive algorithm according to a least error squares method.

9. A regulating/control unit for providing a clamping force generated by a parking brake in a vehicle, comprising:

a determining arrangement to determine the clamping force, which is at least partially generated by an electromechanical braking device which includes an electric brake motor which applies a brake piston against a brake disk, as a function of a motor constant of the brake motor, the motor constants being ascertained from instantaneous measured values of motor currents, which are measured during an activation of the brake motor;

wherein for determining the motor constant, a no-load voltage and a no-load current are measured on the brake motor during a no-load phase, and the motor current is ascertained during a dynamic current change phase.

10. A parking brake in a vehicle, comprising:

a regulating/control for providing a clamping force generated by a parking brake in a vehicle, including:

a determining arrangement to determine the clamping force, which is at least partially generated by an electromechanical braking device which includes an electric brake motor which applies a brake piston against a brake disk, as a function of a motor constant of the brake motor, the motor constants being ascertained from instantaneous measured values of motor currents, which are measured during an activation of the brake motor;

wherein for determining the motor constant, a no-load voltage and a no-load current are measured on the brake motor during a no-load phase, and the motor current is ascertained during a dynamic current change phase.