Process for determining the coefficient of friction m.mu.
AssigneeRobert Bosch GmbH
InventorGunther Schmidt
Life of this patent
Estimating the term…
Abstract
A method for determining the coefficient of friction .mu. between the wheel and the road is described. Assuming a moving vehicle, the brake pressure on a non-driven wheel (measuring wheel) is increased until a tendency to lock occurs. At the same time, the driving torque is increased so that the braking force of the measuring wheel and the increased driving force of the driving wheel on the same vehicle side equal each other. Additionally, an increased driving force of the second driving wheel must be removed by braking.
Claims18
A method for determining a coefficient of friction .mu. between a tread of a tire of a vehicle, having at least two driven and at least two non-driven wheels, and a road surface, using pressure control devices for application of respective brake pressure at wheel brakes, and using control circuit, which receives signals corresponding to wheel speeds, for controlling the pressure control devices and for varying engine torque, wherein
- in the case where the vehicle is not being braked and is not significantly accelerated, the control circuit continuously increases, in response to a trigger signal at a start time, and by means of the pressure control devices, a brake pressure which produces a braking force on a measuring wheel which is not driven;
- simultaneously, the control circuit increases engine output to increase a driving force on a first driven wheel on the same side of the vehicle as the measuring wheel such that the braking force of the measuring wheel and the driving force of the first driven wheel approximately compensate each other;
- a second driven wheel is braked such that it remains approximately at a given speed;
- and
- a measuring time period required for increasing the brake pressure to produce locking of the measuring wheel is determined and used as a measure for the coefficient of friction.
A method for determining a coefficient of friction (.mu.) between a tread of a tire of a vehicle, having at least two driven and at least two non-driven wheels, and a road surface, in the case where the vehicle is not being braked and not significantly accelerated, using pressure control devices for application of brake pressure at respective wheel brakes, and using a control circuit, which receives signals corresponding to wheel speeds, for controlling the pressure control devices and for varying engine torque, the method comprising the steps of:
- generating a trigger signal at a start time;
- causing, in response to the trigger signal, a continuous increase in a brake pressure which produces a braking force on a measuring wheel which is a first non-driven wheel, and causing a simultaneous increase in the engine torque to increase a driving force on a first driven wheel on the same side of the vehicle as the measuring wheel such that the braking force of the measuring wheel and the driving force of the first driven wheel approximately compensate each other;
- braking a second driven wheel such that it remains approximately at a given speed;
- determining a measuring time period required for increasing the brake pressure to produce locking of the measuring wheel;
- and
- calculating the coefficient of friction based on the measuring time period.
Dependencies are inferred from the claim text.