Mercedes-benz Aktiengesellschaft

Daimler-benz Ag

Daimler Chrysler Ag

Armin Muller

Richard Zimmer

Rainer Freitag

Andreas Faulhaber

Manfred H Burckhardt

Gerhard Kurz

Martin Klarer

Harry Troster

Eberhard Pfeifle

Wolfgang Hinrichs

Thomas Ruhl

Reinhold Schob

Thomas Rohrig-Gericke

Hartmut Cordt

Wolfgang Gautsch

In a method for braking a motor vehicle at low speeds in order to avoid a collision with an obstacle in its immediate vicinity, the distance and the relative speed between the vehicle and the obstacle are determined by sensor and are based on the calculation of a necessary braking pressure or a deceleration. The brake pressure is generated at least partially independently of the driver. In order to minimize the reaction time in the case of slow approach to an obstacle in the case where the relative speed falls below a threshold value and the distance falls below a proximity limit, the braking torque is set to a smaller value than the engine torque. In the case where the distance falls below a stop limit, which is smaller than the proximity limit, the braking torque and the engine torque are adjusted in such a way that the braking torque exceeds the engine torque.

Method and appliance for braking a motor vehicle in the immediate vicinity of an obstacle

An apparatus and method adapts response slip threshold values for a drive slip and/or a brake slip control system to the tires fitted to a motor vehicle. The drive torque provided at the driven vehicle wheels is determined from measured operating data such as fuel supply and/or combustion air supply, engine speed and total transmission ratio of the drive train of the vehicle. From this determination, the adhesion coefficient .mu..sub.a utilized is determined with a predetermined or measured axle load at the driven vehicle wheels. From the correlation of these adhesion coefficients .mu..sub.a with measured values of the drive slip .lambda..sub.a, the .mu. slip characteristic of the tires is determined and, corresponding thereto, the response slip thresholds .lambda..sub.A and .lambda..sub.B for the drive slip and the antiblocking control are set. A sliding averaging over the quotient .mu..sub.a /.lambda..sub.a of continuously determined .mu.a, .lambda..sub.a value pairs is utilized for recognizing the tire characteristic of summer/winter tires.

Method and apparatus for adapting motor vehicle drive slip threshold

A vehicle is equipped both with an anti-lock system working on the return-flow principle and with a drive-slip control device working on the differential brake principle, in which the return pump is utilized as an auxiliary pressure source for loading the driven vehicle wheels with brake pressure. In an operational situation requiring drive-slip control, a pump working at a low pressure level is actuated, even before the control responds, and conveys brake fluid both into the brake circuit of the driven vehicle wheel and into the brake circuit of the non-driven vehicle wheels, which are shut off from the brake unit of the brake system by, on one hand, an ASR-function control valve and, on the other hand, by an isolating valve. The pre-charge pump of the return pump of the brake circuits of the driven vehicle wheels is used as a low-pressure pump. This pressurization of the brake circuits with a moderate brake pressure causes a compensation of the lifting play and is utilized both for the drive-slip control and for normal braking.

Road vehicle hydraulic service-brake system and activation process

A process for compensating systematic errors of an acceleration sensor. The result of a sliding average of the output of the accelerometer, determined when acceleration in the primary measurement direction is zero, is subtracted from the output of the accelerometer thus producing a signal representative of acceleration only in the primary direction. A functional check of the accelerometer is provided by aligning the accelerometer in a second direction and comparing the acceleration measured in this second direction to the acceleration measured in the primary direction by a second device for determining acceleration and indicating a malfunction when the two measured accelerations are different and it is determined that acceleration only in the primary direction is present.

Process for compensating acceleration sensor errors

A process for anti-lock control on a racing vehicle having an aerodynamic design which results, at high speeds, in a clear increase both of the front-axle load and the rear-axle load of the vehicle. On a wheel requiring control, the response of the anti-lock control is triggered in the direction of a brake-pressure reduction when an axle-related reference quantity K.sub.h or K.sub.v, formed as a sum of weighted amounts of the wheel-circumference deceleration Z and of the brake slip of the respective vehicle wheel related to a reference speed, exceeds a threshold value. At least during the formation of the reference quantity critical for the front axle, the reciprocal value of the locking limit, determined with inclusion of negative lift forces and air resistance, of the vehicle wheels, plus a safety value .DELTA.Z.sub.o, is taken as a weighting factor X.sub.v. Within the framework of an anti-lock system suitable for carrying out the process, a brake unit switchable to different values of the brake-force distribution under the control of its electronic control unit is provided.

Process and system for anti-lock control

In a drive-slip control system (ASR) for a motor vehicle with rear-axle drive, operating on the principle of retarding again a driven vehicle wheel having a tendency to spin by activating its wheel brake, the rear-axle differential is provided with a locking device which, as the difference in the propulsive torques which can be transmitted via the driven vehicle wheels, between the latter and the roadway increases, develops an increasing degree of locking. The locking device is constructed using multi-plate clutches, which provide a frictional, limited-slip coupling between the driving ring gears and the cage of the differential on which the differential bevel gears of the differential are also mounted. In addition, the multi-plate clutches can be applied hydraulically, controlled being exercised via a solenoid valve.

Drive-slip control system

In an antilock braking system (ABS) operating on the recirculating principle with a static brake circuit and a tandem master cylinder as the brake booster, a control stage is provided in order to lessen the intensity of reaction shocks noticeable at the brake pedal when the antilock control commences. From the onset of a pressure reduction signal, the control stage generates, for at least one brake-pressure control valve of the ABS, an operating voltage for the drive motor of the recirculating pump unit which rises with increasing duration of this signal. After a predetermined rising time, the voltage can reach a maximum value, correlated with maximum speed of the motor, and then is held at this value at least until dying-out, or otherwise rises to that value which is reached within the pressure-reduction signal duration. At the dropping of the pressure reduction signal, the control stage effects a constant or stepwise reduction in the operating voltage of the motor until the motor is at a standstill, such that the time integral of the operating voltage over its reduction is greater than the time integral over the rising time of the operating voltage of the drive motor of the recirculating pump unit.

Control stage for actuation of recirculating pump unit drive motor of an

A method for correcting the rotational speeds of vehicle wheels determined by wheel sensors, a measurement of wheel speeds of the wheels of a vehicle being carried out, with specific driving conditions being that the vehicle is being neither accelerated nor braked and has no transverse acceleration. In a first part of the method, a matching of the measured wheel speeds is carried out under the specific driving conditions when the condition that the vehicle speed is below a first threshold value is satisfied. The matching of the measured wheel speeds is carried out by determining a matching factor for each of the two vehicle sides, so that, for example for the left vehicle side, matched wheel speeds are obtained from the measured wheel speeds. One of the matched wheel speeds of the left vehicle side is made equal to the associated measured wheel speed and the other of the two matched wheel speeds of the left vehicle side is obtained from the associated measured wheel by multiplying by the matchine factor of the left vehicle side, in such a way that the two matched wheel speeds of the left vehicle side assume the same value. In a second part of the method, the measured wheel speeds are balanced under the specific driving conditions when the condition that the vehicle speed is above a threshold value is satisfied. The balancing is carried out by determining a balancing factor for each wheel in relation to a reference wheel, in such a way that the balance wheel speed and the wheel speed of the reference wheel coincide with one another, and the measured wheel speeds are multiplied by the balancing factors determined in the second part of the method.

Process for correcting the rotational speeds of vehicle wheels

Method of and apparatus for determining slip thresholds for a propulsion slip control system of a motor vehicle, whereby the instantaneously effective coefficient of friction between vehicle and road is determined from the measured values of vehicle speed and of the vehicle longitudinal acceleration and a slip value is associated therewith as a threshold value for the propulsion slip control system.

Method and apparatus for determining slip thresholds for a propulsion

Method of and apparatus for adapting slip threshold values for a propulsion slip and/or braking slip control system to the existing tires of a motor vehicle. Here, the instantaneously effective coefficient of friction between vehicle and road is determined from the measured values of the vehicle speed and vehicle longitudinal acceleration from a graph, and with the predetermined value or the predetermined function for the slip thresholds being substituted or corrected by the slip values measured at the driven wheels by use of an operational state defined by a measurement window of a performance graph.

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Backnang, Germany

Armin Muller