EP2035672B1 - Control unit for operating a vehicle drive - Google Patents

Abstract

The invention relates to a control unit for operating a vehicle drive and to a method for operating the control unit. The problem addressed by the invention is to provide a control unit for a vehicle drive with improved fault detection sensitivity. According to the invention, the final target moment (Msoll) output by the control unit is limited from above with a limiting moment (MGrenz), dependent on the measured/set values of the accelerator pedal indicator, when the detected vehicle speed (v) lies below a starting speed limit (x).

Description

The invention relates to a control unit for operating a vehicle drive and the application of the control unit for operating an internal combustion engine or an electrical machine in a motor vehicle and a method for operating the device.

The monitoring of drive control devices is generally designed as a three-level monitoring concept. Such a surveillance concept is from the document DE 44 38 714 A1 known. It describes a method and a device for controlling the drive power of a vehicle with a microcomputer having at least two mutually independent planes, wherein a first level performs the control functions and a second level performs the monitoring functions. A third level is a control level which controls the surveillance level and thus the microcomputer.

The object of the invention is to provide a control unit for a vehicle drive with improved fault detection sensitivity.

This object is achieved by the features of claim 1.

For this purpose, the control unit according to the invention has a first limiting device, in which a preliminary setpoint torque can be limited upward with a maximum limit torque to a final target torque when a detected vehicle speed is greater than or equal to a starting limit speed. In the limiting device, this provisional setpoint torque can be limited upward to a final setpoint torque with a limit torque dependent on the measured / manipulated variables of the accelerator pedal value encoder if the detected vehicle speed is below a starting limit speed.

The approach limit speed defines a limit to the vehicle speed. From and above this approach limit speed, the vehicle is in normal driving. In this area, the setpoint torque is limited by a maximum limit torque upwards. This prevents the drive from attempting to generate an undesirably high torque in the event of a fault.

Speeds below the approach limit speed are added to the starting range of the vehicle. In this case, the setpoint torque is limited upwards with a limit torque dependent on the measured / manipulated variables of the accelerator pedal value encoder. This has the advantage that the limit torque can be selected lower than the maximum torque limit. As a result, the error detection sensitivity of the device is increased in the starting range.

In one embodiment of the invention, a limiting device is provided, by means of which the limiting torque, which is dependent on the measuring / manipulated variables of the accelerator pedal value encoder, can be limited downwards with a definable minimum limiting torque. In internal combustion engines, it is necessary, for example because of compliance with emission regulations, to set a lower operating limit, which at standstill or in the Starting operation should not fall below. The minimum limit torque represents this lower operating limit and ensures proper operation of the vehicle drive.

Further advantages and embodiments will become apparent from the dependent claims and the descriptions. The schematic representation of an embodiment of the control unit shown in the figure will be described in more detail below.

The figure shows a control unit of a vehicle drive, typically an internal combustion engine. The illustrated control unit is also suitable for other drives, such as electromechanical drives, hybrid drives or fuel cells.

The control unit has inter alia a process level 1 for the calculation of drive control and diagnostic functions, which is referred to below as a function computer 1, and an associated process monitoring level 2 for monitoring torque-relevant drive control functions of the function computer 1, hereinafter referred to as monitoring computer 2 becomes. The function computer 1 receives via external connections 3a to 3d information from measuring or position encoders on the operating state of the motor vehicle and / or the internal combustion engine. For this measurement / manipulated variables are forwarded to the function computer 1. For example, the functional computer 1 receives information about a pedal value transmitter of an accelerator pedal via an external connection 3a, information about the setting of a vehicle speed limiter via a connection 3b, and a torque specification Md of an electronic stability program or the like via a connection 3c.

A processing device 4 of the function computer 1 processes the incoming information and calculates a provisional setpoint torque Mvsoll from the different incoming measurement / manipulated variables and possibly the additional information assigned to them. In addition, the processing device 4 controls the starting torque. Furthermore, the device 4 adapts the driving behavior of the motor vehicle to the pedal value requested by the pedal value transmitter of the gas pedal.

An allocation device 5 of the function computer 1 assigns a maximum speed Nmax to a preliminary setpoint value Mvsoll supplied to it by the processing device 4.

In a device 6, the value of Nmax is compared with a current actual speed Nist. In the illustrated embodiment, Nmax subtracts the value for the current actual speed Nist. This may be the speed of a vehicle wheel or vehicle drive (e.g., an internal combustion engine). The device 6 supplies the result of this operation to a device 7.

The device 7 is typically designed as a speed controller, which reduces the actual speed Nist, if this is greater than Nmax. The device 7 assigns the maximum speed Nmax an accelerator pedal-dependent torque limit value MGrenz and supplies this torque limit value MGrenz to a selector 8.

In an alternative embodiment, this accelerator pedal value-dependent torque limit value MGrenz is already determined in the processing device 4 or the allocation device 5 from Mvsoll.

The selector 8 is also fed a value for a minimum limit torque MGmin. This minimum limit torque MGmin results from the requirements of the vehicle drive for proper operation. For example, these are the legal requirements for the exhaust emissions of an internal combustion engine.

The selector 8 is designed, for example, as a comparator. The comparator 8 determines the larger of the values of the two moments MGmin and MGrenz as maximum torque and supplies this maximum torque to an input of a switching device 9.

In this case, the resulting maximum torque usually corresponds to the torque limit value MGrenz. Only when the torque limit value MGrenz is smaller than MGmin, the device 8 outputs MGmin as the output value to the switching device 9.

The switching device 9 has a further input to which a maximum limit torque Mmax is supplied. This may be a maximum limit torque of the drive means, e.g. an internal combustion engine or act at a maximum torque limit of a vehicle wheel.

The switching device 9 is connected to a device 10. This device 10 controls the switching position of the switching device. 9

For this purpose, the device 10 connects the input of the switching device 9, the maximum limit torque applied to the Mmax, with the output of the switching device 9 when the vehicle speed does not fall below the limit value x.

In this case, Mmax is output from the switching device 9 to the device 11.

The device 10 connects the input of the switching device 9 connected to the device 8 to the output of the switching device 9 when the vehicle speed falls below a limit value x. In this case, the output value of the device 8 (MGrenz or MGmin) is output from the switching device 9 to a limiting device 11. For this purpose, device 10 typically sends a control signal to the switching device 9.

The limiting device 11 receives from the processing device 4 the provisional setpoint torque Mvsoll. This provisional setpoint torque Mvsoll is limited in the limiting device 11 to a final setpoint torque Msetpoint.

In the illustrated embodiment, the device 11 also receives from the monitoring unit 2 a value for a final allowable moment Mzul.

The limiting device 11 determines from the different supplied moments Mvsoll, Mmax or MGrenz or MGmin and Mzul a final value Msoll. For this purpose, the provisional setpoint torque Mvsoll with the limit value Mmax or MGrenz or MGmin and the final permissible torque Mzul is limited to the final setpoint torque Msetpoint. The resulting final setpoint torque Msetpoint is output for conversion by the function computer 1 of the control unit.

The monitoring computer 2 of the control unit receives information about the external connections 3a to 3d Operating state of the motor vehicle and the vehicle drive. In the illustrated embodiment, this information is forwarded to the monitoring computer 2 via the function computer 1.

These are, for example, information about a pedal value sensor of an accelerator pedal, information about the setting of a vehicle speed limiter and a torque input Md of an electronic stability program.

A device 12 of the monitoring computer 2 processes the incoming information and calculates a provisional permissible torque Mvzul from the different incoming torque requests and possibly the additional information assigned to them. In addition, this processing device 12 controls the starting torque. Furthermore, the device 12 adapts the driving behavior of the motor vehicle to the pedal value requested by the pedal value transmitter of the gas pedal.

An allocation device 13 of the monitoring computer 2 assigns a maximum speed Nmax to a provisional permissible torque Mvzul supplied to it by the processing device 12. For this purpose, a characteristic field or a conversion function is stored in the allocation device 13, for example.

In a device 14, the value of Nmax is compared with a current actual speed Nist. In the illustrated embodiment, Nmax subtracts the value for the current actual speed Nist. This may be the speed of a vehicle wheel or a vehicle drive (eg an internal combustion engine). The device 14 supplies the result of this operation to a device 15.

The device 15 is typically implemented as a comparator. If Nmax - Nist> = 0, then no signal (or the value 0) is forwarded from device 15 to device 16. If Nmax - Nist <0, then a signal (or the value 1) is forwarded from device 15 to device 16.

The device 16 is also still connected to means 17. This device 17 outputs a signal (or a value 1) to the device 16 when the vehicle speed v falls below a limit value x.

The device 16 is typically implemented as a logical "AND". It outputs a control signal to a switching device 19 when a signal is present at both inputs of the device 16 (or device 17 and device 15 both send a value 1 to the device 16). Between the device 16 and a device 19, a device 18 is provided in the illustrated embodiment.

The device 18 delays the signals. Thus, time differences between functional level and monitoring level, e.g. compensated by the reaction time of the speed controller 7, and the data flow synchronized. Alternatively or additionally, it is intended to send a signal from device 18 to device 19 only when the conditions Nist> = Nmax and v <x have existed for a defined period of time.

The switching device 19 has an input to which the maximum torque Mmax a vehicle wheel or the vehicle drive is supplied.

The switching device 19 has a further input to which a value for the minimum limit torque MGmin is supplied.

The switching device 19 is connected to the device 16. If the device 16 sends no control signal, the input of the switching device 19 is connected to the output of the switching device 19, to which the maximum limit torque Mmax is applied. In this case, the maximum limit torque Mmax is passed from the switching device 19 to a device 21.

If the device 16 sends a control signal, the input of the switching device 19 is connected to the output of the switching device 19, to which the minimum limiting torque MGmin is applied. In this case, the minimum limit torque MGmin is passed from the switching device 19 to a limiting device 21.

In the illustrated embodiment, between the switching device 19 and the device 21 to a device 20 is provided. This device 20 receives from the switching device 19 a value for the minimum limit torque MGmin or a value for the maximum limit torque Mmax. If the new incoming value deviates from the previous old value, then device 20 adjusts its output value via a transient function, e.g. a ramp, steadily to the newly received value. The device 20 outputs its output value to a device 21.

The device 21 is also supplied by the device 12, the provisional allowable torque Mvzul. From the different supplied torque Mmax or MGmin and Mvzul the device 21 determines a value for a final allowable torque Mzul.
In this case, Mvzul is limited by the maximum limit torque Mmax to Mzul if the driving speed v does not fall below the limit value x and / or there is no excessively high rotational speed Nist (> = Nmax). As, as a rule, the preliminary admissible moment should not exceed the maximum admissible moment, the final admissible moment Mzul will most often correspond to the preliminary admissible moment Mvzul.

If the conditions for an excessively high speed Nact (> = Nmax) are present in the starting range (v <x), then the provisional permissible torque Mvzul is increased by the, usually very low, minimum limiting torque MGmin to the final permissible torque Mzul limited. In this case, there is a very low final allowable torque Mzul.

The determined value for the final permissible torque Mzul is forwarded to the function computer 1 for the purpose of limiting Msoll. In addition, the monitoring computer 2 outputs the final permissible torque Mzul for implementing a speed-dependent torque comparison and, if appropriate, for triggering fault reactions to other, not shown, functional areas of the monitoring computer 2.

In the function computer 1, a provisional desired torque Mvsoll is determined in the device 4 from many different torque requests.

In normal driving mode, from a vehicle speed limit x up, this target torque Mvsoll is limited by a maximum torque Mmax. In addition, the monitoring computer 2, as already shown, forms as another Limit a value for a final allowable moment Mzul. Since v <x is not satisfied, the switching device 19 remains in the illustrated basic position and forwards the moment Mmax on. Accordingly, this value Mmax or a transition value for Mmax formed in device 20 in device 21 is compared with Mvzul. The smaller of these two values is output as the current value for Mzul.

In the starting region, below a vehicle speed limit x, the switching device 9 switches over and forwards the values output by the device 8. As a rule, the accelerator pedal-dependent limit torque MGrenz is forwarded. Only if the value of MGrenz falls below the value of MGmin does the device 8 forward MGmin. In the monitoring computer 2, the value Mzul is formed as a further limitation. If the vehicle speed lies below the limit value x and the actual rotational speed Nist does not exceed the limit value Nmax, then, as in normal operation, Mmax or a transition value for Mmax formed in device 20 in device 21 is compared with Mvzul. The smaller of the two values is output as the current value for Mzul.
In this case, the provisional setpoint torque Mvsoll in the device 11 is generally limited by MGrenz and Mmax to a final setpoint torque Msetpoint upwards.
However, if MGrenz assumes a value smaller than MGmin in the starting range, then the function computer 1 limits the provisional setpoint torque Mvsetpoint with MGmin. Since MGmin is a very low value, this usually means that a final target torque Msetpoint limited to MGmin is formed in device 11.

If the monitoring level 2 in the starting range detects that the rotational speed Nist exceeds the maximum rotational speed Nmax, then means 16 sends a signal to the switching device 19. Now, the minimum limit torque MGmin is passed from the switching device 19 or a transition value formed in the device 20 to the device 21. Thus, in the limiting device 21, the final permissible torque Mzul is limited to MGmin upwards. This moment Mzul is passed on to the device 11 of the function computer 1. There, the provisional setpoint torque Mvsoll is now limited by Mzul to the value of MGmin and this value is output as the desired torque Msoll to be controlled.

Claims (12)

1. Control unit for operating a vehicle drive, with a function computer (1) and a monitoring computer (2), such that

   - The function computer (1) is connected via a data connection (3a, 3b, 3c, 3d) to an accelerator pedal signal emitter and to a further measurement value or regulating value emitter, and

   - a provisional nominal torque (Mvsoll) can be formed in a processing device (4) for measurement/regulating values of the measurement or regulating value emitter,

   characterised in that
   a first limiting device (11) is provided, in which this provisional nominal torque (Mvsoll)

   - can be limited upwards by a maximum limit torque (Mmax) to a final nominal torque (Msoll), if a measured vehicle speed (v) is higher than or equal to an initial limit speed (x),

   - can be limited upwards by a limit torque (MGrenz) that depends on the measurement/regulating values received from the accelerator pedal signal emitter to a final nominal torque (Msoll), if the measured vehicle speed (v) is lower than an initial limit speed (x).
2. Control unit according to Claim 1,
   characterised in that
   a second limiting device (8) is provided, in which the limit torque (MGrenz) can be limited downwards with a determinable minimum limit torque (MGmin).
3. Control unit according to Claim 2,
   characterised in that
   in the first limiting device (11) the final nominal torque (Msoll) can be limited upwards by a variable limit value (Mzul) formed in the monitoring computer (2).
4. Control unit according to Claim 2,
   characterised in that
   an assigning device (5) and a rotation speed regulator (7) are provided, such that

   - a maximum speed (Nmax) can be assigned to the provisional nominal torque (Mvsoll) by means of the assigning device (5), and

   - a measured speed (Nist) can be reduced by the speed regulator (7) if the said measured speed (Nist) is higher than the maximum speed (Nmax).
5. Control unit according to any of Claims 1 to 3,
   characterised in that

   - the measurement/regulating values input into the function computer (1) are also input into a monitoring computer (2) associated with the function computer (1),

   - a provisional allowable torque (Mvzul) can be formed in the monitoring computer (2) from the incoming measurement/regulation values.
6. Control unit according to Claim 5,
   characterised in that
   the monitoring computer (2) comprises a limiting device (21) in which the provisional allowable torque (Mvzul) can be limited upwards by the maximum torque (Mmax) to a final allowable torque (Mzul), if the measured drive rotation speed (Nist) is lower than or equal to the maximum speed (Nmax) assigned to it and/or if the vehicle's speed (v) is higher than or equal to the limit value (x) assigned to it.
7. Control unit according to Claim 5,
   characterised in that
   the monitoring computer (2) comprises a limiting device (21) in which the provisional allowable torque (Mvzul) can be limited upwards by the minimum allowable limit torque (MGmin) to a final allowable torque (Mzul), if the measured drive rotation speed (Nist) is higher than the maximum speed (Nmax) assigned to it and if the vehicle's speed (v) is lower than the limit value (x) assigned to it.
8. Control unit according to Claim 7,
   characterised in that
   the monitoring computer (2) can detect that the rotation speed (Nist) of the vehicle's drive is higher than or equal to the maximum speed (Nmax) and the vehicle's speed (v) is higher than the limit value (x) assigned to it, only when these conditions are fulfilled together over a time period (dt) that can be set variably.
9. Control unit according to either of Claims 7 or 8,
   characterised in that
   in a device (20) of the monitoring computer (2)a transition function for a steady transition from a previously valid limit value (Mmax; MGmin) to a newly entered limit value (MGmin; Mmax) can be formed and input into the limiting device (21).
10. Control unit according to Claims 8 or 9,
    characterised in that
    in the monitoring computer (2) an error signal can be generated and emitted when it is detected that the measured rotation speed (Nist) of the vehicle's drive is higher than a maximum speed (Nmax).
11. Use of the control unit according to any of Claims 1 to 10 for operating an internal combustion engine or an electric machine in a motor vehicle.
12. Method for operating the control unit according to any of Claims 1 to 10.

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