GB2398396A

GB2398396A - Method of control means for controlling a drive unit.

Info

Publication number: GB2398396A
Application number: GB0401871A
Authority: GB
Inventors: Volker Pitzal; Schwertfuehrer Gerit Von
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-01-31
Filing date: 2004-01-28
Publication date: 2004-08-18
Anticipated expiration: 2024-01-28
Also published as: GB0401871D0; FR2850612A1; GB2398396B; FR2850612B1; DE10304113A1

Abstract

A method of controlling a drive unit (1), particularly a vehicle engine, allows recognition of torque-increasing errors arising outside a drive control device (20) of the drive unit. The drive unit (1) is controlled by at least one control magnitude (25). An actual torque value, which is ascertained (60) from at least one operating magnitude of the drive unit differing from the at least one drive control magnitude, of the drive unit is checked (40) for plausibility with a torque value (90) characteristic for the at least one drive control magnitude. The control magnitude could be: a fuel injection, an ignition angle or an air feed. The operating magnitude could be: engine rotational speed, engine temperature or induction duct pressure.

Description

METHOD OF AND CONTROL MEANS FOR CONTROLLING A DRIVE UNIT

The present invention relates to a method of and control means for controlling a drive unit, especially of a vehicle.

Methods for control of a drive unit are known, in which the drive unit is controlled in drive by at least one control magnitude. The control magnitude can in that case refer to, for example, fuel feed, ignition angle or air feed. The two last-mentioned magnitudes, however, are usually only for diesel engines.

According to the first aspect of the present invention there is provided a method of controlling a drive unit, which is controlled by at least one control magnitude, comprising the steps of ascertaining an actual torque value from at least one operating magnitude of the drive unit different from the at least one control magnitude and checking the ascertained actual torque value for plausibility by reference to a reference torque value characteristic for the at least one control magnitude.

According to a second aspect of the invention there is provided control means for controlling a drive unit, comprising a control device for controlling the drive unit by at least one control magnitude and means for ascertaining an actual torque value of the drive unit from at least one operating magnitude of the drive unit different from the at least one control magnitude and checking the ascertained actual torque value for plausibility by reference to a reference torque value characteristic for the at least one control magnitude.

A method exemplifying and control means embodying the invention may have the advantage that through checking the actual torque value, which is ascertained from the at least one operating magnitude of the drive unit different from the at least one drive control magnitude, for plausibility with the reference torque value characteristic for the at least one control magnitude it becomes possible to recognise torque-increasing errors arising outside the control system or outside a control apparatus, for example errors attributable to combustion of foreign matter.

It is particularly advantageous if a second actual torque derived from the at least one control magnitude of the drive unit is selected as the torque value characteristic for the at least one control magnitude. In this manner the plausibility check can be realised in particularly reliable manner by comparison of the second actual torque value, which is formed from the at least one control magnitude, with the actually existing first actual torque derived from the at least one operating magnitude. Although the actual torque formed from the at least one control magnitude does not detect a torque-increasing error lying outside the drive control, such an error is detected by the first actual torque derived from the at least one operating magnitude.

A further advantage results if a target torque of the drive unit is selected as torque value characteristic for the at least one control magnitude. In this way, tolerances of a torque model for determination of the at least one control magnitude from the target torque, as well as tolerances in the computation back of the second actual torque from the at least one control magnitude, do not enter the plausibility check and the check can be more accurate.

Preferably, the second actual torque is monitored in that it is compared with a permissible torque. In this manner, a continuous torque monitoring can be realised.

Preferably, also, the first actual torque is determined in dependence on a rotational speed value of the drive unit. Consequently, the first actual torque can be determined in particularly simple manner and without an additional sensor. Determination of the first actual torque can be realised in this way for all combustion engines with a rotational speed sensor. In the case of present-day engines, this is normally the case.

A further advantage results if, for a case in which the first actual torque deviates from the characteristic torque value by more than a predetermined value, the plausibility check is recognised as subject to error and an error reaction is initiated. In this manner it can be ensured that torque-increasing errors outside the drive control do not have the consequence of faulty functions of the drive unit and faulty torque monitoring.

Examples of the method and embodiments of the control means of the present invention will now be more particularly described with reference to the accompanying drawings, in which: Fig. 1 is a block circuit diagram of an engine control means in which methods exemplifying the present invention can be performed; Fig. 2 is a function diagram of a first method exemplifying and first control means embodying the invention; Fig. 3 is a function diagram of a second method exemplifying and second control means embodying the invention; and Fig. 4 is a function diagram of a third method exemplifying and third control means embodying the invention.

Referring now to the drawings there is shown in Fig. 1 a control device 20 for controlling a drive unit 1, which is illustrated in Figs. 2 to 4. The drive unit 1 drives, for example, a motor vehicle and is, for example, an engine. The engine can be constructed as inter alla a combustion engine, an electric motor or a motor based on an alternative drive concept.

In the following, it is assumed by way of example that the motor is a combustion engine, such as an Otto engine or a diesel engine. The device 20 then has the form of an engine control. According to Fig. 1 a driverdesired torque is supplied by an accelerator pedal 45 of the vehicle to the engine control 20. In addition, as illustrated in Fig. 1 one or more external torque demands 50 can be supplied to the engine control 20, such demands being produced by external vehicle functions such as a brake antilocking system, a traction control system, a cruise control or the like and passed on to the engine control 20.

In the engine control 20 there is then carried out, in known manner, a torque co-ordination of the supplied torque demands 50 and the driverdesired torque, whereby a resultant target torque to be translated by the drive unit 1 is determined. The determination of the target torque is carried out in a first plane 85 of the control 20 of Fig. 3, i.e. a socalled functional plane, which serves for realization of the totality of the functions necessary for operation of the engine. According to Fig. 3, determination of a target torque is carried out in a target torque determining unit 35. The formed target torque is subsequently supplied to a torque model 30 and there transformed in dependence on operating magnitudes 55, which according to Fig. 1 are similarly fed to the engine control 20, in known manner into a drive control duration and/or a drive control start for at least one drive control magnitude.

The operating magnitudes 55 can be, for example, engine rotational speed, engine temperature, induction duct pressure, etc. A fuel injection 5, an ignition angle 10 or an air feed 15 can be selected as the at least one control magnitude. In the case of a diesel engine, usually only the fuel injection 5 is selected, whereas in the case of an Otto engine one or more of the control magnitudes can be selected for translation of the target torque.

With the fuel injection 5 there results from the drive control duration and the drive control start a fuel mass which is introduced into a combustion chamber of the engine and which is required for translation of the target torque. With the ignition angle 10 there results from the drive control start an ignition angle for ignition of the air/fuel mixture which is in the combustion chamber and required for translation of the target torque. With the air feed 15 there results from the drive control duration and the drive control start of, for example, a throttle flap a fresh air charge in the combustion chamber necessary for translation of the target torque. Formation of the drive control duration and the drive control start of the at least one control magnitude is carried out in a block 25 in the first plane 85 of the control in dependence on the torque model 30, which is similarly arranged in the first plane 85.

The predetermined target torque is translated by the drive unit 1 in a known manner by means of the at least one control magnitude represented by the block 25.

In the following, initially the first example of the method and first embodiment of the control means are described on the basis of Fig. 2. Merely the block 25 for the at least one control magnitude is illustrated in the first plane 85. This magnitude can be set, as described for the second example according to Fig. 3, from a predetermined target torque with the help of the torque model 30, or, however, in any other known manner, with respect to drive control duration and/or drive control start. Torque monitoring is carried out in a second plane 90 of the control 20. On the basis of the drive control duration and/or drive control start, which is or are calculated in the first plane 85, of the at least one control magnitude an actually present first actual torque of the engine or drive unit 1 sets in. A second actual torque is now determined in a computing-back unit 65 with the help of the inverse of the torque model 30 in the second plane 90 of the control 20 on the basis of the at least one control magnitude from the first plane 85. This second actual torque of the engine is compared in a torque comparison unit 70 with a permissible torque. The permissible torque is formed in the second plane 90 in a determining unit 75 in dependence on a redundant signal detection 80. The permissible torque can be ascertained in a known manner in dependence on driver wish indicated at the accelerator pedal 45. The redundant signal detection 80 can then detect the setting of the accelerator pedal 45 in redundant manner with the help of, for example, two sensors. If the second actual torque exceeds the permissible torque, an error reaction is triggered. The described method ensures that errors internal to the control 20, which lead to a falsifying increase in the at least one control magnitude and thus of the second actual torque, are securely recognized. Due to the small tolerance between the determination of the drive control duration and/or the drive control start of the at least one control magnitude from, for example, the torque model 30 on the one hand and the determination of the second actual torque from the drive control duration and/or the drive control start of the at least one control magnitude with the help of, for example, the inverse of the torque model 30 on the other hand, the torque comparison in the torque comparison unit 70 can be designed with a small error tolerance so that an error reaction can take place rapidly.

In addition, in the second plane 90 the reaction of the engine to the translation of the target torque or to the control of the drive unit 1 by the at least one drive control magnitude, for example in the form of the engine rotational speed course which results, is prepared. The course of the engine rotational speed can be detected in a known manner by, for example, a rotational speed sensor (not illustrated) and passed on to the control 20 as one of the operating magnitudes 55. This preparation can be carried out, for example, in the form of computation of the first actual torque from the engine rotational speed signal supplied by the rotational speed sensor. An example for computation of the first actual torque from the engine rotational speed course is known from MTZ 12/2002, issue 63, pages 1020 to 1027. Determination of the first actual torque is carried out according to Fig. 2 in a rotational speed preparation unit 60 in the second plane 90. The first actual torque is compared in a plausibility checking unit 40 of the second plane 90 with the second actual torque from the unit 65. If the second actual torque deviates from the first actual torque by more than a predetermined value, the plausibility check is recognised as subject to error and an error reaction is initiated. The predetermined value can, for example, be applied to a check state in such a manner that on the one hand small tolerances between the first actual torque and the second actual torque are still permitted as measuring error tolerances, but greater deviations between the first actual torque and the second actual torque due to torque-increasing errors, which lie outside the range of action of the control 20, are recognised as errors. Torque-increasing errors outside the control 20, for example due to combustion of foreign substances, are therefore reliably recognised and lead to an error reaction.

In the second example of Fig. 3 the same reference numerals characterize the same elements as in the first example of Fig. 2. Determination of the drive control duration and/or the drive control start of the at least one control magnitude from the torque model and the target torque in the first plane 85 has already been described. The torque monitoring in the second plane 90 in the second example corresponds with that of the first example. By contrast to the first example, in the case of the second example the first actual torque of the rotational speed preparation unit 60 is compared in the plausibility checking unit 40 with the target torque from the target torque determining unit 35. If the first actual torque deviates from the target torque by more than the predetermined value the plausibility check is recognised as subject to error and an error reaction initiated. The advantage in the case of plausibility checking of the first actual torque with the target torque is that the tolerances of the torque model 30 as well as the inverses of the torque model 30 do not enter into the plausibility check. In this manner the plausibility check is more accurate, so that the predetermined value is lower and torque-increasing errors outside the range of action of the engine control 20 are recognised even more quickly.

According to the third example of Fig. 4, in which the same reference numerals characterize the same elements as in the previous figures, the rotational speed preparation unit 60 is arranged in the first plane 85 of the control 20. This has the advantage that less storage and running time requirement for determination of the hrst actual torque in the rotational speed preparation unit 60 is necessary than in the second plane 90, i.e. the monitoring plane. As illustrated in Fig. 4 by dashed-line arrows, the plausibility check of the hrst actual torque in the plausibility checking unit 40 can be carried out either with the second actual torque according to the first example or with the target torque according to the second example. The torque monitoring is carried out in the third example as described for the previous examples in the second plane 90, which realises the functional monitoring of the drive unit 1.

The computation of the hrst actual torque that arises was described by way of example with the help of the engine rotational signal. The first actual torque that arises can, however, also be determined from one or more operating magnitudes of the drive unit 1, for example from an air/fuel mixture ratio measured in an exhaust gas tract of the engine, which operating magnitudes are different from the at least one drive control magnitude. In this manner it is ensured that a torque-increasing error lying outside the range of action of the control 20 can be recognised in the plausibility check with the target torque or with the second actual torque.

Further possibilities for computation of the hrst actual torque result from, for example, evaluation of a pressure signal of a cylinder internal pressure sensor or through evaluation of a knock sensor system, in which an ignition frequency component can be extrapolated from the vibration behaviour of the engine block, in dependence on which the first actual torque can be determined.

The method exemplifying and control means embodying the invention can, as indicated, be used not only for Otto engines, but also for diesel engines. The at least one control magnitude has to be appropriately selected in each instance.

The second actual torque and the target torque each represent a torque value which is characteristic for the at least one control magnitude and by which the first actual torque is checked for plausibility.

As an error reaction it can ultimately be provided that the drive unit 1 is switched off, for example by cutting out the fuel feed. In the case of a plausibility check subject to error the torque monitoring can, in addition, be switched off.

Claims

1. A method of controlling a drive unit, which is controlled by at least one control magnitude, comprising the steps of ascertaining an actual torque value from at least one operating magnitude of the drive unit different from the at least one control magnitude and checking the ascertained actual torque value for plausibility by reference to a reference torque value characteristic for the at least one control magnitude.

2. A method as claimed in claim 1, wherein the reference torque value is a further actual torque value derived from the at least one control magnitude of the drive unit.

3. A method as claimed in claim 1, wherein the reference torque value is a target torque value of the drive unit.

4. A method as claimed in claim 2, comprising the step of monitoring the further actual torque value by comparing it with a permissible torque value.

5. A method as claimed in any one of the preceding claims, wherein the first- mentioned actual torque value is ascertained in dependence on a rotational speed of the drive unit.

6. A method as claimed in any one of claims 2 to 4, comprising the step of determining the further actual torque value in dependence on at least one of a control duration and a control beginning of the at least one control magnitude.

7. A method as claimed in any one of the preceding claims, wherein the at least one control magnitude refers to fuel injection, ignition angle or setting of air feed control means.

8. A method as claimed in any one of the preceding claims, wherein the step of checking comprises recognition of error and initiation of a reaction thereto if the first- mentioned actual torque value differs from the reference torque value by more than a predetermined amount.

9. A method as claimed in any one of the preceding claims, wherein the drive unit is a motor vehicle engine.

10. Control means for controlling a drive unit, comprising a control device for controlling the drive unit by at least one control magnitude and means for ascertaining an actual torque value of the drive unit from at least one operating magnitude of the drive unit different from the at least one control magnitude and checking the ascertained actual torque value for plausibility by reference to a reference torque value characteristic for the at least one control magnitude.

11. Control means as claimed in claim 10, wherein the drive unit is a motor vehicle engine.