DE102011075143B4 - Method and device for checking the plausibility and / or limiting a requested drive torque - Google Patents

Abstract

Method for providing a maximum permissible drive torque (MZ) for plausibility checking and / or for limiting a requested drive torque (MA_E1) in a drive system (1) with an engine control unit (4) and a drive motor (2), with the following steps: - Determining a first permissible relative drive torque (MZ1_rel) depending on an operating point specification, in particular a speed (s) of the drive motor, and a drive torque specification, in particular an accelerator pedal position of an accelerator pedal (FP_E1), with the aid of a predetermined function, in particular with the aid of a characteristic map (23); - Specifying a maximum drive torque (MMax) of the drive motor (2); - Determination of the maximum permissible drive torque (MZ) based on the specified maximum drive torque (MMax) and on a permissible relative drive torque (MZ_rel), the permissible relative drive torque (MZ_rel) being determined as a function of a fifth permissible relative drive torque (MZ5_rel), which depends on the first permissible relative drive torque (MZ1_rel); wherein a gradient of the fifth permissible relative drive torque (MZ5_rel) is flattened by forming a ramp in order to obtain the permissible relative drive torque (MZ_rel).

Description

Technical area

The invention relates generally to drive systems having a drive motor that is driven by an engine control unit to provide a drive torque. Furthermore, the present invention relates to measures for monitoring the requested by the engine control unit drive torque.

State of the art

Drive systems for motor vehicles generally have, in addition to the drive motor, an engine control unit which converts a driver input, for example a driver desired torque, into a drive torque to be provided by the drive motor. Since the use of drive systems in motor vehicles is safety-critical, it is necessary to check any malfunction of the engine control unit by additional plausibility functions and, if necessary, to limit the requested drive torque.

From the publication DE19536038 A1 a method and a device for controlling the drive unit of a motor vehicle is known in which the maximum permissible torque or the maximum permissible power is determined and when exceeding this limit by a calculated actual torque or power value at least one fault reaction is initiated.

From the DE 197 39 565 A1 For example, a method and a device for controlling a torque of a drive device of a motor vehicle are known. The desired or actual torque of the drive unit is related to a predetermined maximum allowable torque, and the torque is limited or reduced when the desired or actual torque exceeds the maximum allowable torque.

From the DE 10 2006 004 280 A1 a method for torque monitoring of a hybrid drive is known. In this case, a permissible total torque is compared with the sum of an actual torque of an electric motor and the actual torque of an internal combustion engine.

From the DE 10 2010 028 546 A1 a method for reducing the engine torque in a motor vehicle is known. The motor torque is limited to a maximum permissible value, which is below a maximum possible value.

Disclosure of the invention

According to the invention, a method is provided for providing a maximum permissible drive torque for plausibility checking and / or for limiting a requested drive torque according to claim 1 and a device, a drive system and a computer program product according to the independent claims.

Further advantageous embodiments of the present invention are specified in the dependent claims.

• – Ermitteln eines ersten zulässigen relativen Antriebsmoments abhängig von einer Betriebspunktangabe, insbesondere einer Drehzahl des Antriebsmotors, und einer Antriebsmomentvorgabe, insbesondere einer Fahrpedalstellung eines Fahrpedals, mithilfe einer vorgegebenen Funktion, insbesondere mithilfe eines Kennfelds;
• – Vorgeben eines maximalen Antriebsmoments des Antriebsmotors;
• – Ermitteln des maximal zulässigen Antriebsmoments basierend auf dem vorgegebenen maximalen Antriebsmoment und auf dem ersten zulässigen relativen Antriebsmoment.

According to a first aspect, a method for providing a maximum permissible drive torque for checking the plausibility and / or for limiting a requested drive torque in a drive system with an engine control unit and a drive motor is provided. The method comprises the following steps:

• Determining a first permissible relative drive torque depending on an operating point specification, in particular a rotational speed of the drive motor, and a drive torque input, in particular an accelerator pedal position of an accelerator pedal, using a predetermined function, in particular by means of a map;
• - Specifying a maximum drive torque of the drive motor;
• Determining the maximum permissible drive torque based on the predetermined maximum drive torque and on the first permissible relative drive torque.

According to a multi-level concept, the determination of the requested drive torque is generally carried out in a first plane, while essentially a separate function is implemented in a second plane, which outputs a maximum permissible drive torque to be requested at each point in time. By permanently monitoring the drive torque requested by the first level by means of the maximum permissible drive torque determined in the second level, the drive torque requested by the first level can be made plausible. The maximum permissible drive torque determined in the second level is generally determined by modeling the function of the first level in the second level.

When adapting the engine control unit to the particular type of drive system, a variety of parameters must be set. Due to the replication of the functions of the first level in the second level necessary for the plausibility of the required drive torque, there are therefore many dependency dependencies for the individual parameters, so that the outlay for the Application of the individual parameters for the commissioning of a drive system is considerable.

An idea of the above method is to provide a function that converts the drive torque setting and the current operating point of the drive motor, in particular in the form of a speed specification, into a first allowable relative drive torque that is used to determine a maximum allowable requested drive torque. For different drive motors thus a fixed function can be used, for. Example, as a map that is suitable for drive motors with different maximum deployable drive torques, as it specifies the maximum requestable drive torque as a relative indication that indicates the maximum requestable drive torque relative to the maximum selectable by the selected drive motor drive torque. The provision of a function which provides such a relative indication has the advantage that, when the drive motor controlled by the engine control unit is changed and a change in the parameter application associated therewith, no re-processing of the first level is necessary. The effort for applying the parameters for the plausibility functions of the second level can thus be significantly reduced.

Furthermore, the requested drive torque can be limited by the maximum permissible drive torque.

The requested drive torque can be made plausible by the maximum permissible drive torque, wherein in particular an error signal is generated when the requested drive torque exceeds the maximum permissible drive torque.

According to one embodiment, the requested drive torque in a first software level and the first allowable relative drive torque in a second software level can be determined.

It can be provided that an allowable drive torque is determined from the first permissible relative drive torque by multiplying it by the maximum drive torque.

Furthermore, a relative drive torque requested by ancillaries can be applied in addition in order to obtain the permissible relative drive torque, wherein a portion of the first permissible relative drive torque is acted upon additively below a predefined drive torque threshold instead of the relative drive torque requested by the ancillaries.

According to one embodiment, a decrease in the maximum permissible drive torque can be limited in terms of amount to a predetermined gradient.

Furthermore, it can be provided that a relative speed control torque requested by a speed control is applied additively in order to obtain the permissible relative drive torque, wherein the speed control torque is determined as a function of a difference between an instantaneous speed and a set speed.

• – eine Einrichtung zum Ermitteln eines ersten zulässigen relativen Antriebsmoments abhängig von einer Betriebspunktangabe, insbesondere einer Drehzahl des Antriebsmotors, und einer Antriebsmomentvorgabe, insbesondere einer Fahrpedalstellung eines Fahrpedals, mithilfe einer vorgegebenen Funktion, insbesondere mithilfe eines Kennfelds;
• – eine Einrichtung zum Ermitteln des maximal zulässigen Antriebsmoments basierend auf einem vorgegebenen maximalen Antriebsmoment und auf dem ersten zulässigen relativen Antriebsmoment.

According to a further aspect, an apparatus for providing a maximum permissible drive torque for checking the plausibility and / or for limiting a requested drive torque in a drive system with an engine control unit and a drive motor is provided. The device comprises:

• - A device for determining a first permissible relative drive torque depending on an operating point, in particular a speed of the drive motor, and a drive torque input, in particular an accelerator pedal position of an accelerator pedal, using a predetermined function, in particular using a map;
• - Means for determining the maximum permissible drive torque based on a predetermined maximum drive torque and on the first permissible relative drive torque.

In another aspect, a drive system is provided with a drive motor and the above apparatus.

In another aspect, a computer program product is provided that includes program code that, when executed on a computing device, performs the above method.

Brief description of the drawings

Preferred embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. Show it:

1 a schematic representation of an engine system for operating a drive unit; and

2 a schematic functional representation of a function for plausibility of a requested drive torque.

Description of embodiments

1 shows a schematic representation of a drive system 1 with a drive motor 2 , which may be formed, for example, as an internal combustion engine or electric motor.

The drive motor 2 can be via a driver unit three from an engine control unit 4 be driven to provide a drive torque. The driver unit three sets a specification of a requesting drive torque M _A in a corresponding control of the drive motor 2 around. In the case of an electric motor as a drive motor 2 can the driver unit three comprise a power unit, for example, by suitable commutation and by selecting a duty cycle of pulse width modulation corresponding power switch drives, such as IGBTs, IGCTs, MOSFETs and the like to provide the requested drive torque M _A corresponding power to the electric motor, so that the drive torque is provided , In the case of a gasoline engine as a drive motor 2 The requested drive torque M _A can correspond to the specification of an air charge to be set in cylinders of the internal combustion engine, wherein the air charge of the gasoline engine determines the drive torque to be provided. The driver unit three then serves to set a throttle actuator according to a desired air charge. In the case of a diesel engine as a drive motor 2 For example, the drive torque M _{A to} be requested can indicate the fuel quantity to be injected, which is decisive for the provided drive torque in a diesel engine. The requested drive torque M _A is in this case by the driver unit three converted into corresponding opening periods of injection valves and it will be generated corresponding control variables for the injectors.

drive motor 2 and driver unit three thus form a unit which is an indication of a requested drive torque M _{A is} provided, wherein the requested drive torque M _{A is} implemented in a suitable manner.

The requested drive torque M _A is from the engine control unit 4 determined by specifications. In particular, an accelerator pedal position of an accelerator pedal 5 to represent such a requirement. A driver of the motor vehicle gives about the position of the accelerator pedal 5 an indication of a driver's desired torque to the engine control unit 4 before, from which the engine control unit 4 In a manner known per se, a drive torque M _{A to} be requested is determined.

Furthermore, the engine control unit 4 with a brake pedal 6 be coupled to interpret a braking request of the driver of the motor vehicle as an immediate reduction of the driver's desired torque to zero or a minimum value.

The engine control unit 4 determined from the requirements, in particular the accelerator pedal position, the brake pedal position and the like, the requested drive torque M _A and provides this the driver unit three to disposal. The function for determining the drive torque M _{A to be} requested is in a first software level E 1 of the engine control unit 4 executed. That is, in the engine control unit 4 implemented microcontroller (not explicitly shown) performs the functions of the first level E1 in a similar manner.

In addition receives the engine control unit 4 when commissioning with a specific drive motor, a parameter set to the engine control unit 4 to the selected drive motor 2 adapt. The adjustment is made so that the engine control unit 4 based on the parameters of the selected drive motor 2 the control of the drive motor 2 can make so that the requested drive torque M _A by the drive motor 2 provided.

In addition to the first software level E1, a second software level E2 is also provided. The second level E2 corresponds to a separate environment for performing functions. The functions of the second level E2 may also be in the microcontroller of the engine control unit 4 or be implemented in a separate microcontroller. It is essential that the functions of the first and second levels E1, E2 can not be influenced in their execution, however, to improve the accuracy at all significant points, a minimum selection is made with values of the software level E1.

The functions of the second level E2 essentially simulate the functions of the first level E1 and as a result have a maximum permissible drive torque M _Z. The maximum permissible drive torque M _Z can serve to limit and / or make plausible the drive torque M _A to be requested, which is determined in the first plane E 1. An error can be signaled if the requested drive torque M _{A of} the first plane E 1 exceeds or is limited by the maximum permissible drive torque M _{Z of} the second plane E 2.

In 2 a functional diagram is shown showing the redundant simulation of the permitted drive torque in the second software level E2. This replica has at all torque generating points a minimum selection with the value of the first software level E1, so that in the Result only the actual errors in the presence of excessive drive torque impact.

The functional _diagram represents the plausibility check of the drive torque M _{A_E1} to be requested determined in the first level E1. This plausibility check is made by the first minimum block 21 made, to which the to be requested in the first software level E1 requested drive torque M _{A_E1} and a determined in the second software level E2, maximum allowable drive torque M _{Z are} supplied. As a result, the smaller of the two drive torque data is obtained as the drive torque M _{A to be} requested. At the same time, an error signal FS can be generated if the requested drive torque M _{A_E1} ascertained in the first software level E1 _exceeds the maximum permissible drive torque M _Z.

The maximum permissible drive torque M _Z is determined from the relative permissible drive torque M _{Z_rel} , which in a first multiplier 22 by multiplying by the maximum deliverable drive torque M _{max of} the drive motor 2 can be determined. The maximum drive torque M _max is an applicable parameter and is selected according to the selected drive motor 2 fixed. The maximum drive torque M _max corresponds to a drive torque which can be maximally provided by the drive motor.

• – eine vorgegebene, gemäß den Funktionen der ersten Ebene E1 überprüfte Fahrpedalstellungsangabe F_{P_E1};
• – eine Fahrpedalstellungsangabe, die von einem ersten Fahrpedalsensor F_P1 erfasst wird;
• – eine Fahrpedalstellungsangabe, die von einem zweiten Fahrpedalsensor F_P2 erfasst wird; und
• – eine Angabe, die einer Schaltstellung eines Idle-Schalters F_IDLE zugeordnet ist und bei einer erkannten unbetätigten Stellung des Fahrpedals 5 einen vorgegebenen prozentualen Stellungswert, wie beispielsweise von 0,1, und bei einer erkannten betätigten Stellung des Fahrpedals einen Wert von 1 als Fahrpedalstellungsangabe an den zweiten Minimumblock 24 ausgibt.

To provide the relative allowable drive torque M _{Z_rel} is a map 23 provided that an operating point information in the form of an engine speed n and the smallest possible accelerator pedal position information are supplied as the drive torque input. The in the map 23 used accelerator pedal position indication is corresponding to a relative displacement of the accelerator pedal 5 indicated, where 0 no deflection and 1 a complete (maximum possible) deflection of the accelerator pedal 5 equivalent. The smallest possible accelerator pedal position is in a second minimum block 24 by selecting the smallest value from the following information:

• A predetermined accelerator pedal position _indication F _{P_E1} checked in accordance with the functions of the first plane E1;
• An accelerator pedal position indication detected by a first accelerator pedal sensor F _P1 ;
• An accelerator pedal position indication detected by a second accelerator pedal sensor F _P2 ; and
• - An indication that is assigned to a switching position of an idle switch F _IDLE and a detected unactuated position of the accelerator pedal 5 a predetermined percentage position value, such as from 0.1, and at a detected actuated position of the accelerator pedal, a value of 1 as accelerator pedal position indication to the second minimum block 24 outputs.

The smallest value of the accelerator pedal position information is the map 23 supplied and a relative first permissible drive torque M _{Z1_rel} is determined therefrom in conjunction with the rotational speed n.

The thus determined relative first permissible drive torque M _{Z1_rel} can optionally z. B. limited in another (not shown) minimum block by a provided from the first software level E1 more accurate current relative drive torque _value M _{ACCPED_E1} to get no tolerance _{widening of} the monitoring at this point, as long as the first software level E1 at this position is not incorrectly large value calculated.

Furthermore, in a first maximum block 25 a maximum _selection between the first permissible relative drive torque M _{Z1_rel} and a relative cruise _{control torque} M _{R_rel} determined. The relative _vehicle speed _{control torque} M _{R_rel} corresponds to an indication of a cruise control and is provided with respect to the predetermined maximum drive torque M _max . The result of the first maximum block 25 during active cruise control corresponds to the relative cruise _{control torque} M _{R_rel} as long as the brake pedal 6 not operated. Will the brake pedal 6 actuated, this is signaled in accordance with a brake pedal signal L _B and a switch 26 switched accordingly, so that instead of the _vehicle speed _{control torque} M _{R_rel} the limited first relative allowable drive torque M _{Z1_rel is passed} as a second relative allowable drive torque M _{Z2_rel} .

Next, for the determination of the relative permissible drive torque M _{Z_rel} the torque _absorption of ancillaries such. As an air conditioner, a generator and the like are taken into account. For this purpose, from the functions of the first software level E1, the additional (required) drive torque M _ASC requested by the auxiliary units, such as the air conditioning system and the like, becomes the applied maximum drive torque M _{max of} the selected drive motor 2 in order to obtain a relative drive torque M _{ASC_rel} required for the operation of the _accessories . This will be in a first division block 27 carried out.

To ensure that in a coasting operation no compensation of the requested by the ancillary drive torque is made, is now for a given drive torque _range M _range , which is specified as a relative size with respect to a maximum deployable drive torque, such. Example, a range of 0 to 20%, a linear course of provided for the accessory compensation drive torque to accept. The drive torque _range M _range indicates the maximum torque value up to which only a partial compensation of the drive torque received by the ancillaries is carried out. Furthermore, a slope value S is specified, which indicates the slope of this linear course. In detail, the second relative allowable drive torque M _{Z2_rel} and an indication of the drive torque _range M _{range become} a third minimum block 28 whose output is connected to a second multiplication block 29 connected is. The multiplication block 29 multiplies the given slope S and the result of the minimum selection of the third minimum block 29 and takes the product to a fourth minimum block 30 to, which also receives the relative requested by the ancillaries drive torque M _{ASC_rel} .

The relative requested by the ancillary components drive torque M _{ASC_rel} essentially corresponds to the current active relative _{accessory compensation of} the software level E1 and allows an increase in the permitted drive torque exactly to this legitimate value, as long as the _{accessory compensation} in the software level E1 is not incorrectly excessive.

The result of the minimum selection of the fourth minimum block 30 is in a first summation block 31 is added to the second relative allowable drive torque M _{Z2_rel} . As a result, a third relative allowable drive torque M _{Z3_rel is obtained} . This value becomes a second maximum block 32 fed to the also received via CAN torque request M _{CAN is} supplied. The CAN torque requests represent torque requests from vehicle dynamics _{interventions} , such as traction control, engine _drag torque control, an automatic brake system, and the like. If the CAN torque _{request requests} a higher torque than the third relative allowable drive torque M _{Z3_rel} , then this is considered the fourth relative permissible drive torque M _{Z4_rel} passed.

If the software level E1 limits the CAN torque request to smaller values, then it can be provided that these smaller values are then also used as a release, in order to avoid tolerance widening, as long as there is no error in the software level E1 at this point. Whether there is an error in the software level E1 is already established in the software level E1.

In active speed controllers, such as in an idle area or an area close to idle, is in the second summation 33 the fourth relative permissible M _{Z4_rel added} a speed control torque M _D. The speed controller moment M _T resulting from a predetermined target rotational speed n _set, wherein a difference from the current speed n and the predetermined target rotational speed n _set in a first subtractor 34 is determined and in a third maximum block 35 is supplied, together with the size of zero to n only a positive rotational speed difference between the actual speed and the predetermined target rotational speed n _set to allow.

The speed difference dn becomes a fifth multiplication block 36 multiplied by an applicable factor F. The resulting product becomes a fifth minimum block 37 supplied, which is the minimum of the value 1 and the product of the fifth multiplication block 36 determined and this in a third subtraction block 38 subtracted from the value 1.

The result corresponds to a relative speed control torque M _D which is in the second summation block 33 the fourth relative permissible drive torque M _{Z4_rel is} added. The result corresponds to the fifth relative permissible drive torque M _{Z5_rel} , which is a fourth maximum _block 39 is supplied.

Optionally, the relative speed control torque M _{D can} still be limited with a relative speed controller control variable obtained from the software level E1.

The fourth maximum block 39 forms together with a fourth multiplication block 40 and a third subtraction block 41 a ramp function, which _forms a flattening of the slope by forming a ramp at a rapid drop of the fifth relative allowable drive torque M _{Z5_rel} . This is the output of the fourth maximum block 39 with the fourth multiplication block 40 connected, which also a waste factor AF is supplied. The product of the fourth multiplication block 40 becomes a subtraction block 41 which subtracts a ramp-down value RA from the product and the result subtracts an input of the fourth maximum-block 39 provides. The loop thus formed is executed cyclically, so that the result of the fourth maximum block 39 corresponds to the relative permissible drive torque M _{Z_rel} and _Z is provided at a rapid decrease of the fifth relative allowable drive torque M _{Z5_rel} with an _absolute reduced gradient.

An idea on which the above method is based is that steps are provided in the software level E2, each of which has a specific tolerance with regard to the torque request of the software level E1, eg, B. of about 20%, allow. In the event of an incorrectly large torque request in the software level E1, z. B. because of data, malfunction or error of the microcontroller, in only one place, the torque request of the software level E1 can be limited accordingly without the monitoring are impaired in other stages. This is done by using the value limited in the case of an error as the basis for calculating the limit values of the subsequent stages.

Claims (11)

Method for providing a maximum permissible drive torque (M _Z ) for plausibility _checking and / or for limiting a requested drive torque (M _{A_E1} ) in a drive system ( 1 ) with an engine control unit ( 4 ) and a drive motor ( 2 ), with the following steps: determining a first permissible relative drive torque (M _{Z1_rel} ) depending on an operating point specification, in particular a rotational speed (n) of the drive motor, and a drive torque specification, in particular an accelerator pedal position of an accelerator pedal (F _{P_E1} ), by means of a predetermined function, especially using a map ( 23 ); - Specifying a maximum drive torque (M _Max ) of the drive motor ( 2 ); - Determining the maximum permissible drive torque (M _Z ) based on the predetermined maximum drive torque (M _Max ) and on an allowable relative drive torque (M _{Z_rel} ), wherein the permissible relative drive torque (M _{Z_rel} ) depends on a fifth allowable relative drive torque (M _{Z5_rel} ) which depends on the first allowable relative drive torque (M _{Z1_rel} ); wherein a slope of the fifth allowable relative drive torque (M _{Z5_rel} ) is flattened by forming a ramp to obtain the allowable relative drive torque (M _{Z_rel} ). The method of claim 1, wherein the requested drive torque (M _A ) is limited by the maximum allowable drive torque (M _Z ). Method according to Claim 1 or 2, in which the requested drive torque (M _{A_E1} ) is made _plausible by the maximum permissible drive torque (M _Z ), wherein in particular an error signal is generated when the requested drive torque (M _{A_E1} ) _exceeds the maximum permissible drive torque (M _Z ). exceeds. Method according to one of claims 1 to 3, wherein the requested drive torque (M _{A_E1} ) in a first software level (E1) and the first permissible relative drive torque (M _{Z_rel} ) in a second software level (E2) is determined. Method according to one of claims 1 to 4, wherein from the first permissible relative drive torque (M _{Z_rel} ) by multiplying the maximum drive torque (M _Max ) an allowable drive torque (M _Z ) is determined. Method according to one of claims 1 to 5, wherein a relative requested by ancillaries drive torque (M _ASC ) is applied additive to obtain the allowable relative drive torque, wherein below a drive torque threshold instead of the relative requested by the ancillary drive torque (M _ASC ) a share of the first permissible relative drive torque (M _{Z1_rel} ) is applied additively. Method according to one of claims 1 to 6, wherein a decrease in the maximum permissible drive torque is limited in amount to a predetermined gradient. Method according to one of claims 1 to 7, wherein a relative demanded by a speed control speed control torque (M _D ) is applied additive to obtain the permissible relative drive torque, the speed control torque (M _D ) depending on a difference of a current speed (n) and a target speed (n _soll ) is determined. Device for providing a maximum permissible drive torque (M _Z ) for plausibility _checking and / or for limiting a requested drive torque (M _{A_E1} ) in a drive system ( 1 ) with an engine control unit ( 4 ) and a drive motor ( 2 ), comprising: - a facility ( 23 ) for determining a first permissible relative drive torque depending on an operating point specification, in particular a rotational speed (n) of the drive motor ( 2 ), and a drive torque specification, in particular an accelerator pedal position of an accelerator pedal ( 5 ), using a given function, in particular using a map; - An institution ( 21 ) for determining the maximum permissible drive torque (M _Z ) based on a predefined maximum drive torque (M _Max ) and on an admissible relative drive torque (M _{Z_rel} ), wherein the device ( 21 ) is configured to determine the allowable relative drive torque (M _{Z_rel} ) in _response to a fifth allowable relative drive torque (M _{Z5_rel} ) that depends on the first allowable relative drive torque (M _{Z1_rel} ); and to flatten a slope of the fifth allowable relative drive torque (M _{Z5_rel} ) by forming a ramp to obtain the allowable relative drive torque (M _{Z_rel} ). Drive system with a drive motor and a device according to claim 9. Computer program product containing a program code which, when placed on a computer Data processing unit is carried out, the method according to one of claims 1 to 8 performs.

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