Method for electrically actuated braking of a motor vehicle and electrically actuated brake system
First Claim
1. A method of operating an electrically actuated braking system of a motor vehicle, which comprises the following steps:
- measuring wheel speeds of individual wheels of a motor vehicle with wheel sensors;
individually controlling electrical, continuously acting wheel brake actuators such that an independent brake pressure is applied to each wheel of the motor vehicle;
carrying out the following calculation and control procedures in a control unit;
calculating a wheel slip and a wheel acceleration for each wheel;
storing a respective actual value of the brake pressure in case of an upward transgression of a predefined first threshold value for one of the wheel slip and the wheel acceleration;
forming a quotient of the stored actual value and a pressure value that is characteristic of the motor vehicle at a coefficient of friction μ
=1 for the respective wheel, and estimating a first coefficient of friction;
carrying out a brake-pressure closed-loop control operation to prevent locking at the individual wheels with reference to the estimated coefficient of friction in accordance with a predefined algorithm;
clearing the first coefficient of friction in case of a downward transgression of a second threshold value for one of the wheel slip and the wheel acceleration, and replacing the first coefficient of friction with a new estimated coefficient of friction that can be increased up to a value for a dry underlying surface; and
using the stored brake pressure as a setpoint value for a brake-pressure closed-loop control operation to prevent locking.
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Accused Products
Abstract
Electrical, continuously acting wheel brake actuators are individually controlled. The following calculation and control procedures are carried out in a control unit: the wheel slip and the wheel acceleration are calculated for each wheel; if the wheel slip or the wheel acceleration exceed a predefined first threshold value, then the respective actual value of the brake pressure is stored; the quotient of the stored actual value and a pressure value which is characteristic of the vehicle is formed for the respective wheel, and the coefficient of friction μ is thus estimated; and an ABS brake-pressure closed-loop control operation is carried out at the individual wheels using the value.
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Citations
8 Claims
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1. A method of operating an electrically actuated braking system of a motor vehicle, which comprises the following steps:
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measuring wheel speeds of individual wheels of a motor vehicle with wheel sensors; individually controlling electrical, continuously acting wheel brake actuators such that an independent brake pressure is applied to each wheel of the motor vehicle; carrying out the following calculation and control procedures in a control unit; calculating a wheel slip and a wheel acceleration for each wheel; storing a respective actual value of the brake pressure in case of an upward transgression of a predefined first threshold value for one of the wheel slip and the wheel acceleration; forming a quotient of the stored actual value and a pressure value that is characteristic of the motor vehicle at a coefficient of friction μ
=1 for the respective wheel, and estimating a first coefficient of friction;carrying out a brake-pressure closed-loop control operation to prevent locking at the individual wheels with reference to the estimated coefficient of friction in accordance with a predefined algorithm; clearing the first coefficient of friction in case of a downward transgression of a second threshold value for one of the wheel slip and the wheel acceleration, and replacing the first coefficient of friction with a new estimated coefficient of friction that can be increased up to a value for a dry underlying surface; and using the stored brake pressure as a setpoint value for a brake-pressure closed-loop control operation to prevent locking. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A brake system for a motor vehicle, comprising:
- wheel speed sensors disposed at at least some wheels of a motor vehicle;
electrically actuated, continuously acting wheel brake actuators individually controlled for applying independent brake pressures to respective wheels or each group of wheels; an electronic control unit connected to said wheel speed sensors and to said wheel brake actuators, said electronic control unit being programmed to; calculate a wheel slip and a wheel acceleration for each wheel; store a respective actual value of the brake pressure if a predefined first threshold value for one of the wheel slip and the wheel acceleration is exceeded; form a quotient of the stored actual value and a pressure value that is characteristic of the vehicle at a coefficient of friction μ
=1 for the respective wheel and to estimate a first coefficient of friction;carry out a brake-pressure closed-loop control operation to prevent locking at the individual wheels with reference to the estimated coefficient of friction and in accordance with a predefined algorithm; clear the first estimated coefficient of friction if one of the wheel slip and the wheel acceleration falls below a second threshold value, and replacing the first estimated coefficient of friction by a respective new estimated coefficient of friction that can be increased up to a value corresponding to a dry underlying surface; and said electronic control unit controlling said wheel brake actuators with the stored brake pressure as a setpoint value for a brake-pressure closed-loop control operation to prevent locking.
- wheel speed sensors disposed at at least some wheels of a motor vehicle;
Specification