DE102010053540A1 - Method for controlling clutch in drivetrain of motor vehicle, involves using reference value for setting coupling torque during start-up process, where reference value considers angular acceleration of engine and actual coupling torque - Google Patents

Abstract

The method involves using a reference value for setting a coupling torque during a start-up process, where the reference value considers an angular acceleration of an engine and an actual coupling torque. The angular acceleration of the engine is determined from temporal derivative of an engine speed characteristic using a sensor. The reference value is calculated from summation of a product of an engine sided torque of inertia and the angular acceleration of the engine and the actual coupling torque.

Description

The invention relates to a method for controlling a clutch in the drive train of a motor vehicle, in which at least one reference variable is used for setting a clutch torque, in particular during a starting operation.

For engine speed control during a starting process of a motor vehicle, a suitable nominal clutch torque is usually set on the clutch in such a way that a specific change over time of the engine rotational speed and thus a certain engine rotational speed profile are achieved. To determine a suitable clutch desired torque u. a. motor-side reference variables used. Since such leaders are model-based, i. H. based on current sensor signals and long-term adapted parameters, these are subject to errors. As a result, it is possible to set a faulty clutch desired torque on the clutch with respect to the engine torque actually generated by the engine and as a result disturbances. In particular, in the initial phase of a start-up, this can lead to an uncomfortable drop in engine speed up to stalling of the engine. Another problem arises from the fact that for adjusting a certain engine speed, it is necessary to compensate for the time varying occurring errors on a feedback control, whereby the cost increases and the dynamics of the clutch control can be affected.

Out WO / 03006842 a method for controlling a clutch is known, in which, in particular for carrying out a starting operation of a motor vehicle with an automated manual transmission or with an automated clutch, a stored in the engine control starting characteristic for setting a desired clutch torque is used. In this case, a corresponding clutch torque is set on the clutch as a function of the engine speed on the starting characteristic. Since the startup characteristic is determined model-based, it is subject to errors. As a result, this embodiment is also subject to the above-mentioned disadvantages. In addition, an adaptation of the starting characteristic by additional measures is required in this approach to control certain driving situations when starting and to consider the driver's request.

It is therefore an object of the invention to provide a simplified method for controlling a clutch of the aforementioned type, in which, especially during a start-up, the reliability is increased and comfort impairments are avoided. This object is solved by the features of claim 1.

Since according to the invention at least one reference variable is used for adjusting the clutch torque, which at the same time takes into account the angular acceleration of the engine and the clutch torque transmitted to the drive train, both possible errors in the determination of the actual clutch torque and any errors in the determination a desired clutch torque from the reference variable automatically compensated by this. The consideration of the current angular acceleration of the engine acts in this case similar to a correction variable, which at least approximately integrates the actual torque difference between the generated engine torque and the actual clutch torque. In this way, a suitable target clutch torque for setting a desired engine speed curve can be determined largely error-free, in particular for small torque differences. An undesirable, the ride comfort impairing falling or increasing the engine speed, especially at the beginning of a startup is so safely avoided. In this case, a certain speed targeted, without one, a control deviation compensating, feedback can be adjusted.

Preferably, the angular acceleration of the engine is sensor-based determined from the time derivative of the engine speed curve, which is usually detected in a motor vehicle, for example, for controlling an automated transmission or an automated clutch continuously. Since only the sensor-based detected engine speed curve and its time derivative are included in the calculation, so the angular acceleration of the engine can be determined largely error-free. The actual clutch torque may be calculated based on a particular clutch torque model based on, for example, detecting the disengagement position of the clutch and considering one or more long-time-adapted parameters.

wobei

ω_Eng(t):

Motorwinkelgeschwindigkeit, die Motordrehzahl n_Eng(t) = ω_Eng(t)/2π

J_Eng:

motorseitiges Trägheitsmoment,

T_Eng(t):

Motormoment,

T_Cl(t):

Ist-Kupplungsmoment und

t:

Zeit ist.

Preferably, to set the clutch torque is a reference variable T * / Eng (t) which is calculated from the sum of, on the one hand, the product of the engine-side moment of inertia and the current angular acceleration of the engine and, on the other hand, the actual clutch torque currently transmitted to the driveline on the clutch:

in which

ω _Eng (t):

Motor angular velocity, the engine speed n _Eng (t) = ω _Eng (t) / 2π

J _Eng :

motor-side moment of inertia,

T _Eng (t):

Engine torque,

T _Cl (t):

Actual clutch torque and

t:

Time is.

korrigierten näherungsweise berechneten Motormoment T * / Eng(t). Da die Winkelbeschleunigung des Motors

weitgehend fehlerfrei sensorbasiert berechnet werden kann und das Ist-Kupplungsmoment T_Cl(t) selbst in die Berechnung der Führungsgröße T * / Eng(t) eingeht, werden bei einer modellbasierten Bestimmung des Soll-Kupplungsmoments aus der Führungsgröße T * / Eng(t) und bei einer modellbasierten Bestimmung des Ist-Kupplungsmoments T_Cl(t) die dabei durch das Kupplungsmomentenmodell verursachten Fehler durch die Führungsgröße T * / Eng(t) selbst von vornherein kompensiert. Auf diese Weise ist es möglich, durch die Verwendung der Führungsgröße T * / Eng(t) ein geeignetes Soll-Kupplungsmoment zum Einregeln eines gewünschten Motordrehzahlverlaufs weitgehend fehlerfrei zu berechnen.This is based on the experience that in the slip phase of the clutch, the angular acceleration of the engine is approximately proportional to the torque difference between engine torque and clutch torque and inversely proportional to the engine-side moment of inertia of the clutch behaves. The reference variable T * / Eng (t) corresponds to a function of the angular acceleration of the engine

corrected approximately calculated engine torque T * / Eng (t). Because the angular acceleration of the engine

can be calculated sensor-based largely error-free and the actual clutch torque T _Cl (t) itself in the calculation of the reference variable T * / Eng (t) is received, are in a model-based determination of the desired clutch torque from the reference variable T * / Eng (t) and in a model-based determination of the actual clutch torque T _Cl (t) the error caused by the clutch torque model by the reference variable T * / Eng (t) even compensated from the outset. In this way it is possible by using the reference variable T * / Eng (t) to calculate a suitable desired clutch torque for adjusting a desired engine speed curve largely error-free.

einstellt. Soll beispielsweise die Motordrehzahl konstant gehalten werden, so wird eine Momentendifferenz von Null zwischen der berechneten Führungsgröße T * / Eng(t) und dem Kupplungssollmoment T ^_Cl(t) eingestellt:

Here, for example, a desired clutch torque T ^ _Cl (t) can be specified so that due to the difference between the reference variable T * / Eng (t) and target clutch torque T ^ _Cl (t) a certain angular acceleration of the engine

established. For example, if the engine speed is to be kept constant, then a torque difference of zero between the calculated command value T * / Eng (t) and set the clutch target torque T ^ _Cl (t):

If, in contrast increase the engine speed, a torque difference of greater than zero between the clutch torque T ^ _Cl (t) and the engine torque T * / Eng (t) set:

Accordingly, to reduce the engine speed, a torque difference of less than zero between the clutch target torque T ^ _Cl (t) and the engine torque T * / Eng (t) set:

The invention can also be used in particular for controlling clutches in dual-clutch transmissions and can also be used as part of other engine speed control strategies in the slip phase of the clutch, such as, for example, B. in switching operations or in a continuous slip control.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 03006842 [0003]

Claims (3)

Method for controlling a clutch in the drive train of a motor vehicle, in which at least one reference variable is used for setting a clutch torque, in particular during a starting process, characterized in that the reference variable takes into account both the angular acceleration of the engine and the actual clutch torque. A method according to claim 1, characterized in that the angular acceleration of the engine is sensor-based determined from the time derivative of the engine speed curve. A method according to claim 1 or 2, characterized in that the command variable is calculated from the sum of on the one hand the product of the engine-side moment of inertia and the angular acceleration of the engine and on the other hand the actual clutch torque.