DRIVE DEVICE FOR A VEHICLE

Description

[0001] The invention relates to a drive device for a particularly electrically operated vehicle according to the preamble of claim 1.

[0002] Such a drive device has an accelerator pedal that has a signal connection to a drive controller. The drive controller generates a desired torque based on a raw accelerator pedal value initiated by the driver. A pulse-controlled inverter converts this desired torque in conjunction with an electric motor. The electric motor is mentioned here merely as an example. Alternatively, any other actuator can generally be used.

[0003] When the accelerator pedal is depressed accordingly, the drive torque generated by the drive system exceeds a vehicle-specific destabilization threshold, above which a static friction limit between the vehicle wheels and the road surface is exceeded during driving, resulting in vehicle destabilization. A distinction is made between a high static friction limit for dry road surfaces, a medium static friction limit for wet road surfaces, and a low static friction limit for icy road surfaces. Especially in vehicles with high-performance drive systems, the electric motor can generate drive torques that even exceed the destabilization threshold corresponding to the high static friction limit.

[0004] With regard to vehicle safety, the functional safety of the accelerator pedal, the drive control and the pulse-controlled inverter must meet very high safety requirements in order to prevent the incorrect generation of excessive drive torque in the signal processing path between the accelerator pedal and the pulse-controlled inverter, which exceeds the destabilization threshold.

[0005] A generic drive device for a vehicle is known from FR 3 102 964 A1.

[0006] The object of the invention is to provide a drive device with a reliable signal processing path between the accelerator pedal and the drive unit, which is structurally simple compared to the prior art and in particular the path of the drive control allows a higher fault tolerance.

[0007] The object is solved by the features of claim 1. Preferred developments of the invention are disclosed in the subclaims.

[0008] The invention is based on a drive device for a vehicle in which an accelerator pedal is signal-connected to a drive controller. The drive controller requests a torque from the actuator control unit based on a raw accelerator pedal value from the driver. The torque requested or generated by the drive controller is used to control an actuator control unit, namely a pulse-controlled inverter, of an actuator, namely an electric motor. According to the characterizing part of claim 1, the actuator control unit has an enabling device by means of which an error in the torque requested by the drive controller can be determined.

[0009] According to the invention, a signal processing path is provided between the accelerator pedal and the actuator (e.g., the electric motor), in which the release device is installed directly in the actuator control unit. The drive torque required by the drive control is therefore not checked in the drive control itself, but rather downstream in the actuator control unit. Using the release device according to the invention, a potentially dangerous, destabilizing torque is only released when the customer explicitly requests it. This request is expressed by depressing the accelerator pedal.

[0010] The routine in the activation device is executed based on the raw accelerator pedal value, the predefined vehicle-specific destabilization threshold, and the torque requested by the drive control system. Against this background, the signal processing in the accelerator pedal and the signal processing in the actuator control unit must be designed with a higher level of safety integrity than the signal processing in the drive control system. For example, the functional safety of the accelerator pedal and the functional safety of the actuator control unit can meet high safety requirements according to ISO 26262 (for example, ASIL D), while the drive control system can meet lower safety requirements (for example, ASIL C). In this case, the drive control system can be simpler and thus more cost-effective than a drive control system designed for higher safety requirements (for example, ASIL D).Alternatively, the accelerator pedal and actuator control unit can be designed according to ISO 26262 to ASIL C, while the drive control can be designed with lower safety requirements according to ASIL B. However, this depends on the destabilization potential of the installed drive units.

[0011] If a fault-free torque is determined, the release device can release the torque requested by the drive control to the drive unit without limitation. In this case, the actuator control unit controls the drive unit based on the torque requested by the drive control. In contrast, if a faulty torque is determined, the release device can block the torque to the drive unit. Instead, the release device can release a minimum torque to the drive unit, thus limiting the torque of the drive control.

[0012] The aforementioned minimum torque is preferably smaller than a vehicle-specific destabilization threshold. Upon reaching such a destabilization threshold, a static friction limit (on dry, wet, or icy road surfaces) between the vehicle wheels and the road surface is exceeded during driving, resulting in vehicle destabilization.

[0013] In a technical implementation, the routine can be designed so that the fault determination occurs at least when the torque requested by the drive control is greater than the vehicle-specific destabilization threshold. In contrast, the release device can remain deactivated if the torque requested by the drive control is less than the vehicle-specific destabilization threshold.

[0014] It is preferred if the activation device can be implemented with minimal software effort and can operate with minimal computational effort. Against this background, the activation device can be constructed as follows: The activation device can have a comparator module in which the raw accelerator pedal value generated by the accelerator pedal is comparable to a threshold value. The threshold value can preferably be formed from a raw accelerator pedal value that correlates with the vehicle-specific destabilization threshold.

[0015] If the raw accelerator pedal value generated by the accelerator pedal is greater than the limit value, the comparator module can generate an enable signal. Using the enable signal, a connected enable module in the signal processing path can release the requested torque from the drive control system toward the drive unit. Conversely, if the raw accelerator pedal value generated by the accelerator pedal is less than the limit value, the comparator module can generate a blocking signal. Using the blocking signal, the enable module connected in the signal processing path can block the requested torque from the drive control system toward the drive unit. Instead, the enable module can release the minimum torque toward the drive unit.

[0016] The release device also features a minimum selection module. This module has a signal connection to the enable module. The minimum selection module selects between a predefined torque limit, which is smaller than the destabilization threshold, and the torque requested by the drive control. The minimum selection module selects the smaller of these two parameters, which is defined as the minimum torque.

[0017] In this way, it is ensured that the release device only releases the torque requested by the drive control towards the drive unit if it is guaranteed that the torque is less than the destabilization threshold, or if it is guaranteed that, on the one hand, the torque is greater than the destabilization threshold and, on the other hand, the raw accelerator pedal value generated by the accelerator pedal is greater than the limit value defined above.

[0018] An embodiment of the invention is described below with reference to the attached figure, in which a drive device for an electrically powered vehicle is shown in a schematic block diagram.

[0019] In the figure, the drive device has an accelerator pedal FP that is signal-connected to a drive controller ASG. The drive controller ASG requests a torque M ASG based on a raw accelerator pedal value R FP initiated by the driver. The torque M ASG is used to control a pulse-controlled inverter PWR of an electric machine EM during driving. In the drive controller ASG, the torque M ASG is generated, among other things, on the basis of a characteristic curve in which the torque M ASG is plotted as a function of the accelerator pedal travel, i.e., the raw accelerator pedal value R FP. In addition, there are various other influencing factors that determine the torque, such as the Drive Select preselection.

[0020] In the further signal processing path, the torque M ASG requested by the drive controller ASG is applied to the signal input of an enable module 1. The enable module 1 is part of an enabling device 3 installed in the pulse-controlled inverter PWR, which is used to determine the error of the torque M ASG requested by the drive controller ASG. If the enabling device 3 determines a fault-free torque M ASG, the enable module 1 releases the torque M ASG as a drive torque MA toward the electric motor EM. In this case, the pulse-controlled inverter PWR controls the electric motor EM based on the torque M ASG requested by the drive controller ASG.

[0021] If the release device 3 determines a faulty torque M ASG, the enable module 1 blocks the torque M ASG in the direction of the electric motor EM. Instead, the enable module 1 releases a minimum torque M min in the direction of the electric motor EM.

[0022] As can be seen from the figure, the enabling device 3 has a comparator module 5 which is in signal connection with the enable module 1. In the comparator module 5, the raw accelerator pedal value R FP generated by the accelerator pedal FP is compared with a limit value RD. The limit value RD is read into the comparator module 5 from an applicable characteristic curve stored in a database 7. The characteristic curve plots the torque M ASG requested by the drive control ASG as a function of the raw accelerator pedal value (i.e. accelerator pedal travel). A vehicle-specific destabilization threshold MD is entered in the characteristic curve, above which a static friction limit between the vehicle wheels and the road surface is exceeded during driving, resulting in vehicle destabilization.In addition, the accelerator pedal raw value RD, which correlates with the vehicle-specific destabilization threshold MD, is entered in the characteristic curve and forms the limit value for the comparator module 5.

[0023] If the accelerator pedal raw value R FP generated by the accelerator pedal FP is greater than the limit value RD, an enable signal SF is generated in comparator block 5. If the enable signal SF is present at the signal input of enable block 1, enable block 1 releases the torque M ASG requested by the drive control ASG toward the electric motor EM.

[0024] If, on the other hand, the raw accelerator pedal value R FP generated by the accelerator pedal FP in comparator block 5 is smaller than the limit value RD , comparator block 5 generates a blocking signal Ss. If the blocking signal Ss is present at the signal input of enable block 1, this blocks the torque M ASG generated by the drive control ASG and instead releases the minimum torque M min in the direction of the electric machine EM. The enable block 1 therefore limits the torque M ASG requested by the drive control ASG to the minimum torque M min and releases this in the direction of the electric machine EM. A fault in the drive control ASG would therefore not affect the torque generated by the electric machine EM, but would be limited to a less critical - controllable - value.

[0025] The release device 3 also has a minimum selection module 9, which is also signal-connected to the release module 1. In the figure, a torque limit DML is read into the minimum selection module 9 from the characteristic curve stored in the database 7. The torque limit DML is dimensioned to be smaller by a safety factor ΔM than the destabilization threshold MD.

[0026] Minimum selection block 9 selects the smaller value between the torque limit DML and the torque M ASG requested by the drive controller ASG and sets this value as the minimum torque M min. The minimum torque M min, together with the torque M ASG, is applied to the signal input of enable block 1.

[0027] The functioning of the enable device 3 is explained below using a first example in which the accelerator pedal FP is depressed to 80%, so that the accelerator pedal raw value R FP is 80%. In fault-free normal operation, the drive control ASG (based on the stored characteristic curve) determines a requested torque M ASG of 3500 Nm from the accelerator pedal raw value R FP of 80%. The destabilization threshold MD is, for example, 4000 Nm, while the torque limit DML is 3900 Nm lower by a safety margin of 100 Nm. The accelerator pedal raw value RD which correlates with the destabilization threshold MD is 90%. Since the accelerator pedal raw value R FP generated by the accelerator pedal FP is less than the limit value RD , a blocking signal Ss is generated in the comparator module 5, which is applied to the enable module 1.

[0028] In addition, the torque MASG and the torque limit DML are present at the signal input of minimum selection block 9. Since the torque MASG (3500 Nm) is less than the torque limit (3900 Nm), the torque MASG is set as the minimum torque M min in minimum selection block 9. Accordingly, enable block 1 releases the minimum torque M min as the drive torque MA toward the electric motor EM.

[0029] In a second example, faulty signal processing occurs in the drive control ASG with otherwise identical output parameters as in the first example. Accordingly, instead of a faulty torque M ASG of 3500 Nm, an erroneous, excessively high torque of 6000 Nm is generated in the drive control ASG. In this case, the erroneously requested torque M ASG lies above the destabilization threshold MD (4000 Nm). If such an excessively high torque M ASG were implemented at the electric motor EM, vehicle destabilization would therefore occur. Vehicle destabilization would only occur if the driver were traveling with a certain lateral acceleration (cornering). Statistically speaking, this situation is very likely.

[0030] In the second example above, the incorrectly requested torque M ASG (6000 Nm) is significantly greater than the torque limit (3900 Nm). Accordingly, the minimum selection block 9 sets the torque limit of 3900 Nm as the minimum torque M min . In the further signal flow, the enable block 1, to which the blocking signal Ss is applied, therefore releases the minimum torque M min (corresponding to the torque limit DML) as the drive torque MA toward the electric motor EM. This reliably prevents the electric motor EM from being driven with the excessively high, incorrect torque M ASG of 6000 Nm.

[0031] A third example concerns the same constellation as above, but with a raw accelerator pedal value R FP generated by the accelerator pedal FP of, for example, 95% instead of 80%. This results in the following situation: Since the raw accelerator pedal value R FP generated by the accelerator pedal FP is now greater than the limit value RD , an enable signal SF is generated in comparator block 5, which is applied to the signal input of enable block 1. In this case, the accelerator pedal FP is depressed so far by the driver that a potentially destabilizing torque has been authorized by the driver during certain driving maneuvers. Therefore, enable block 1 releases the torque M ASG as drive torque MA toward the electric motor EM. LIST OF REFERENCE SYMBOLS:

[0032] 1Enable module 3Enable device 5Comparator module 7Database 9Minimal selection module FPAccelerator pedal ASGDrive control PWRActuator control unit R FP The accelerator pedal raw value generated by the accelerator pedal M ASG The torque requested by the drive control DMLTorque limit MD Destabilization threshold M min Minimum torque MA ,Drive torque RD Limit value SF Enable signal S s Lock signal EMElectric machine

Claims

1. Drive device for a vehicle, with an accelerator pedal (FP) in signal communication with a drive controller (ASG), which based on an accelerator pedal raw value (RFP) requests a torque (MASG), which can be used to control a pulse inverter (PWR) of an electric motor (EM) in driving mode, wherein a potentially dangerous, destabilizing torque (MASG) is only released by means of the release apparatus when a driver of the vehicle explicitly requests this, which is done by means of depressing the accelerator pedal (FP), characterized in that, the pulse inverter (PWR) has a release apparatus (3), by means of which an error determination of the torque (MASG) requested by the drive controller (ASG) can be performed.

2. Drive device according to claim 1, characterized in that, when an error-free torque (MASG) is determined, the release apparatus (3) releases the torque (MASG) in the direction of the electric motor (EM), so that the pulse inverter (PWR) controls the electric motor (EM) on the basis of the torque (MASG) requested by the drive controller (ASG), and / or in that when an error torque (MASG) is determined, the release apparatus (3) blocks the torque (MASG) in the direction of the electric motor (EM) and instead releases a minimum torque (Mmin) in the direction of the electric motor (EM).

3. Drive device according to claim 2, characterized in that the minimum torque (Mmin) is smaller than a vehicle-specific destabilization threshold (MD) above which, in drive mode, a static friction value limit between the vehicle wheels and the road surface is exceeded, resulting in vehicle destabilization.

4. Drive device according to claim 3, characterized in that the fault determination is carried out at least when the torque (MASG) requested by the drive controller (ASG) is greater than the vehicle-specific destabilization threshold (MD).

5. Drive device according to any one of claims 3 or 4, characterized in that the release apparatus (3) has a comparator module (5) in which the accelerator pedal raw value (RFP) generated by the accelerator pedal (FP) is comparable with a limit value (RD), and in particular in that the limit value (RD) is formed from an accelerator pedal raw value correlating with the vehicle-specific destabilization threshold (MD).

6. Drive device according to claim 5, characterized in that, when an accelerator pedal raw value (RFP) generated by the accelerator pedal (FP) is greater than the limit value (RD), the comparator module (5) generates a release signal (SF) by means of which a release module (1) releases the torque (MASG) in the direction of the electric motor (EM), or in that, when an accelerator pedal raw value (RFP) generated by the driving pedal (FP) is lower than the limit value (RD), the comparator module (5) generates a blocking signal (SS) by means of which the release module (1) blocks the torque (MASG) in the direction of the electric motor (EM) and instead releases the minimum torque (Mmin) in the direction of the electric motor (EM).

7. Drive device according to claim 6, characterized in that the release apparatus (3) has a minimum selection module (9), which is in signal communication with the release module (1), and in that the minimum selection module (9) from a torque limit (DML) which is smaller than the destabilization threshold (MD) and from the torque (MASG) requested by the drive controller (ASG) selects the smaller value and sets the minimum torque (Mmin).