Control system for a motor vehicle

Abstract

The present invention relates to a control system (1) for a motor vehicle, the control system comprising at least a first control unit (8), in particular a central control unit, a second control unit (6), in particular a brake control unit, and a third control unit (7), in particular an actuator control unit, wherein the second control unit (6) is designed to determine a driving request, in particular from a driver and / or a driving motion controller of the motor vehicle, and to transmit the driving request to the third control unit (7), which is designed to receive the determined driving request and to control an actuator (3), in particular of a braking system (2), according to the driving request. According to the invention, the second control unit (6) is designed to also transmit the determined driving request to the first control unit (8), and the first control unit (8) is designed to process the determined driving request and to transmit the same as a modified driving request to the third control unit (7), and, upstream of the third control unit (7), there is a decision device (9) by which either the driving request from the second control unit (6) or the modified driving request from the first control unit (8) is fed to the third control unit (7).

Description

[0001] R. 414856

[0002] - 1 -

[0003] Description

[0004] title

[0005] The present invention relates to a control system for a motor vehicle comprising at least a first control unit, in particular a central control unit, a second control unit, in particular a brake control unit, and a third control unit, in particular an actuator control unit, wherein the second control unit is configured to determine a driving request, in particular from a driver and / or a vehicle motion controller, and to send it to the third control unit, which is configured to receive the determined driving request and, depending on the driving request, to control an actuator, in particular from a brake system.

[0006] The invention further relates to a method for operating a control system for a motor vehicle, comprising at least one first control unit, in particular a central control unit, a second control unit, in particular a brake control unit, and a third control unit, in particular an actuator control unit, wherein the second control unit determines a driving request, in particular from a driver of the motor vehicle, and sends it to the third control unit, wherein the third control unit receives the determined driving request and, depending on the received driving request, controls an actuator of the motor vehicle.

[0007] State of the art

[0008] Control systems are known from the state of the art. With the increasing centralization of control units and control unit functions, the entire control architecture in motor vehicles is changing. Force, torque, speed, and slip requirements are increasingly being centrally recorded (R. 414856).

[0009] - 2 - and evaluated, which are currently acquired and evaluated locally and partially implemented locally. The arbitration and coordination necessary for decision-making regarding control is implemented in existing control systems across different control units, function-specifically, without a global or central focus. Because the friction brake is preferred as the actuator in today's control architecture for, for example, wheel-stabilizing control interventions, distributed arbitration is possible. However, if vehicle dynamics control interventions are also to be provided by means of electric actuators, this requires an extension of the arbitration concept. Therefore, despite the electric actuators remaining the same, a target architecture with centralized arbitration and coordination can expand the application range of an electric drive.Arbitration, as a central element, makes it possible to shift various functions to different control units.

[0010] Disclosure of the invention

[0011] The control system according to the invention, with the features of claim 1, has the advantage that reliable communication between the control units is ensured, which allows the control system to continue operating even if one of the control units fails. The control system according to the invention also enables particularly fast communication.

[0012] According to the invention, the second control unit is configured to send the determined driving request to the first control unit, and the first control unit is configured to process the determined driving request and send it as a modified driving request to the third control unit. A decision-making device is connected upstream of the third control unit, through which either the driving request from the second control unit or the modified driving request from the first control unit is supplied to the third control unit. The control system thus provides that the decision-making device supplies only one of the two control signals from the first or second control unit to the third control unit. If the first or the second control unit fails, the R. 414856

[0013] - 3 -

[0014] The decision unit prioritizes the only available control signal and forwards it to the third control unit. If both the determined and the modified driving request are present and receivable by the third control unit, the decision unit decides which of the two signals to use. This decision is made primarily based on the signal waveforms and / or the signal strength of the two incoming control signals, in order to make an advantageous choice that specifically balances precise versus rapid actuator control.

[0015] Preferably, the decision-making device includes an offset module configured to apply an offset value to the driving request sent from the second control unit to the third control unit. This offset value affects or influences the control signal in such a way that a comparison of the control signals sent from the first and second control units to the third control unit is made possible, particularly taking into account the time differences resulting from the respective signal paths. By applying an offset value for the shorter signal path from the second control unit to the third control unit, the faster control signal is effectively slowed down to enable a quick and reliable comparison of the two control signals.

[0016] Furthermore, it is preferably provided that the decision-making device includes a comparison module downstream of the offset module, configured to select the smaller of the two driving requests and supply it to the third control unit. The comparison module thus ensures that the smaller of the two driving requests is always supplied to the control unit. This prevents an overreaction in the third control unit or in the actuator controlled by the control unit on the shorter emergency signal path directly from the second control unit to the third control unit. In particular, this ensures that the determined driving request is only used in an emergency situation, and otherwise the modified driving request is used as the basis for controlling the actuator. R. 414856

[0017] - 4 -

[0018] Furthermore, it is preferably provided that the offset value of the offset module is selected as a function of the signal propagation time of a control signal from the second control unit via the first control unit to the third control unit. The signal propagation time takes into account the latency of the modified driving request compared to that of the determined driving request, thus ensuring an advantageous comparison of the signals.

[0019] Preferably, the decision-making device is configured to select the offset value of the offset module depending on the gradient of the determined driving requirement. By taking the gradient into account, for example, an emergency situation is recognized, and the faster, i.e., direct, signal path is thereby preferred over the slower signal path to enable a rapid response in emergency situations.

[0020] The method according to the invention, with the features of claim 7, is characterized in that the second control unit also sends the determined driving request to the first control unit, that the first control unit (8) processes the determined driving request depending on predefinable, in particular customer-specific, parameters and sends it as a modified driving request to the third control unit, wherein a decision-making device is connected upstream of the third control unit, which supplies the third control unit with either the driving request from the second control unit or the modified driving request from the first control unit. This results in the advantages already mentioned above. In particular, the control system according to the invention is configured to execute the method according to the invention.

[0021] Preferably, the determined or modified driving requirement is selected by the decision-making device depending on a gradient of the driving requirement.

[0022] Preferably, the offset value is specified depending on the presence of the modified driving request. If the modified request is not present, for example due to a failure of the central control unit, the offset value is preferably not specified or is set to R. 414856.

[0023] - 5 -

[0024] Set to zero so that the determined driver requirement is not affected by the offset value.

[0025] Further advantages, preferred features, and combinations of features will become particularly apparent from the foregoing and from the claims. The invention will now be explained in more detail with reference to the drawing. To this end, we show...

[0026] Figure 1 shows an advantageous control system for a braking system of a motor vehicle.

[0027] Figure 2 shows a decision-making device of the control system.

[0028] Figure 3 shows a first application example of the control system,

[0029] Figure 4 shows a second application example of the control system, and

[0030] Figure 5 shows a third application example of the control system.

[0031] Figure 1 shows a simplified representation of an advantageous control system 1 for a braking system 2 of a motor vehicle. The braking system 2 has at least one controllable actuator 3 for actuating a wheel brake 4. The wheel brake 4 is to be actuated depending on a driver request, which the driver specifies, for example, by pressing a brake pedal 5. The control system 1 detects this driver request and, depending on the driver request and, if applicable, other information, controls the brake actuator 3.

[0032] The control system 1 includes a first control unit 6, which is connected in particular to a sensor assigned to the brake pedal 5 for detecting the brake pedal actuation. The sensor can detect, for example, the travel distance and / or the speed of movement of the brake pedal and / or any actuation force acting on the brake pedal. The control unit 6 thus directly determines the driving request made by the driver, in this case a braking request. R. 414856

[0033] - 6 -

[0034] The control unit 6 is connected to another control unit 7, which is designed to control the actuator 3 of the brake system 2 depending on the driving requirement in order to implement the determined driving requirement.

[0035] The control system 1 also includes a control unit 8, which in this case is configured as the central control unit of the braking system or the motor vehicle, specifically as a central brake control unit. The control unit 8 is connected to the two control units 6 and 7 in order to receive the driving request determined by control unit 6 and to supply control unit 7 with a modified driving request based on the determined driving request. In particular, the control unit 8 serves to implement the driving request in a customer-specific manner, for example, to achieve a sportier or smoother braking behavior of the braking system. The application of the braking behavior can thus be carried out on the central control unit 8, in particular by the vehicle manufacturer itself.Furthermore, when modifying the driving requirement, the control unit 8 can also take into account other boundary conditions, such as the current traffic or driving situation, for example a current driving speed or current weather conditions, in order to meet external influences through the modified driving requirement.

[0036] There are thus two signal paths available leading from the brake pedal 5 to the actuator 3. The first signal path, S1, is the direct and short signal path between control units 6 and 7. The second signal path, S2, runs from control unit 6 through control unit 8 to control unit 7. Due to the detour via the central control unit 8, the second signal path, S2, is longer than the first, resulting in a latency in the signals reaching the third control unit, 7. However, the existence of two signal paths, S1 and S2, ensures that, for example, a brake request can be implemented even if the central control unit 8 fails. In this respect, signal path S1 can also be considered an emergency signal path. Signal path S2 represents the normal signal path, while signal path S1 is an emergency signal path. R. 414856

[0037] - 7 -

[0038] A decision unit 9 is connected upstream of the control unit 7, which decides which signal or from which of the signal paths S1 , S2 the control signal is actually taken into account by the control unit 7 as a driving request.

[0039] Figure 2 shows a simplified representation of the decision unit 9. The decision unit 9 comprises a comparison module 10 and an offset module 11. The offset module 11 is solely assigned to signal path S1 and is located upstream of the comparison module 10 in signal path S1. The control unit 8 is directly connected to the comparison module 10 via signal path S2. The comparison module 10 is designed as a min-block, which selects the smaller of the two detected driving requests from signal paths S1 and S2 and feeds it to the third control unit 7.

[0040] Offset module 11 is configured to apply an offset to the control signal from signal path S1. The offset value is freely selectable and can be adjusted according to customer requirements and the planned takeover time and / or gradient of signal path 1. The offset value can be used as a fixed parameter value, a parameter curve, or a logic-based offset value. Offset module 11 is preferably configured to implement the following formula for calculating the offset value:

[0041] Offset value [Nm] = tRound-Trip-Time [s] x Takeover gradient [Nm / s]

[0042] The following example calculation illustrates this using a driver braking request. Communication via the network of control system 1 is assumed to take 20 ms. It therefore takes 40 ms, the so-called round-trip time, for the driving request to arrive at the arbitration at the axle level or at the control unit 7 via signal path S2. If the emergency signal path S2 is to be selected from a desired takeover gradient of, for example, 20,000 Nm / s, this results in a required offset value of 800 Nm Newton meters, which is added to the control signal coming from the emergency signal path S2. Due to the lower latency on this signal path S2, it is preferred during rapid braking, even if the exact R. 414856

[0043] - 8 -

[0044] The signal value is not reached due to the offset. During slow deceleration, signal path S1, which corresponds to the exact value of the driving request, is used.

[0045] This results in two information streams: a fast signal path with low latency but a different target value (emergency signal path S1) and a second signal path with a precise target value but increased latency (normal signal path S1). These can be processed via the offset-based min-arbitration of the decision device 9. Crucially, the emergency signal path S2 requires direct activation. The inaccuracy of the driving request can be hidden in the actuator dynamics and compensated for by confirming the target value via normal signal path S1.

[0046] Figure 3 shows an example of slow deceleration with a gradient of 5000 Nm / s. The torque Md is plotted against time t. The first line FA represents the driving request detected by the sensor. Following the detected driving request is the control signal from control unit 6 to the central control unit 8, containing the determined driving request, as shown by line 6-8 in Figure 3. Due to latency, this is followed by the modified driving request in signal path S2 from control unit 8 to control unit 7, shown as line 8-7. The control signal of the emergency signal path S1 is shown with a dashed line 6-7, which, due to the offset, reacts significantly later than the normal signal path. Because, according to the present embodiment, the deceleration is slow and the gradient of the driving request is lower than the specified takeover gradient of 20.If the value is 000 Nm / s, the decision device 9 selects the modified driving request according to line 8-7 for the control of the actuator 3 by the control unit 7. In this respect, the resulting control signal AS corresponds to the modified driving request.

[0047] Figure 4 shows the diagram from Figure 3 in another application, where rapid deceleration with a gradient of 50,000 Nm / s takes place. Here, too, an offset value of 800 newton meters is added to the emergency signal path S2 by the offset module 11. In this case, the deceleration is faster than the desired takeover gradient. R. 414856

[0048] - 9 -

[0049] Therefore, the emergency signal path S1 is selected by the decision-making device 9 using the offset module 11 and the comparison module 10. This allows the maximum braking request, in this embodiment of -10,000 Newton meters, to be reached and maintained after only 0.2 seconds, as shown in Figure 4. It can be seen that the request from the emergency signal path S1 does not correspond exactly to the driver's request of -10,000 Newton meters, as the offset of 800 Newton meters has been added. The driving request from the normal signal path S1, on the other hand, corresponds exactly to the driver's request, but only arrives at the decision-making device 9 with a latency of 40 ms. As soon as the control signal of the normal signal path S2 is lower than the driving request with the offset, the control signal of the normal signal path S2 is selected by the decision-making device 9 and passed on to the control unit 7 to control the actuator 3, in this case after approximately 0.22 seconds.

[0050] Figure 5 shows another embodiment, in which, however, the braking process accelerates exponentially. Here, too, an offset value of 800 Nm is added to the emergency signal path. Initially, the braking is slower than the desired takeover gradient; therefore, the normal signal path S2 is initially selected in the decision unit 9 for transmission to the control unit 7 and the actuator 3. As the braking accelerates, after approximately 0.09 seconds the braking gradient matches the selected takeover gradient. From this point on, the decision unit 9 transmits the now dominant emergency signal path S1 to the control unit 7, because this now corresponds to the minimum of both applied driving requirements. However, this only remains the case until the maximum braking demand is reached and remains constant.As soon as the control signal of the normal signal path S2 is lower than the control signal of the offset emergency signal path S1, in this case after approximately 0.4 seconds, the control signal of the normal signal path S2 is passed on to the control unit 7 by the decision device 9. Due to the selected synchronization logic of the decision device 9, seamless switching between the two signal paths S1 and S2 is possible, depending on the desired takeover gradient and the latency of the signal paths. R. 414856.

[0051] - 10 -

[0052] When the normal signal path is selected, communication can still be maintained via the emergency signal path S1. As soon as it is detected that the normal signal path S2 is no longer available, the offset value or offset module 11 is preferably deactivated so that the control signal from

[0053] Signal path S1 corresponds to the original control signal of the emergency signal path S1, i.e., the determined driving requirement.

Claims

R. 414856 - 11 - Claims 1. Control system (1) for a motor vehicle comprising at least a first control unit (8), in particular a central control unit, a second control unit (6), in particular a brake control unit, and a third control unit (7), in particular an actuator control unit, wherein the second control unit (6) is configured to determine a driving request, in particular from a driver and / or a vehicle motion controller, and to send it to the third control unit (7), which is configured to receive the determined driving request and, depending on the driving request, to control an actuator (3), in particular from a brake system (2), characterized in that the second control unit (6) is configured to also send the determined driving request to the first control unit (8), and that the first control unit (8) is configured to process the determined driving request and send it as a modified driving request to the third control unit (7), wherein a decision-making device (9) is connected upstream of the third control unit (7), by which either the driving request of the second control unit (6) or the modified driving request of the first control unit (8) is supplied to the third control unit (7).

2. Control system according to claim 1, characterized in that the decision unit (9) has an offset module (11) which is configured to transfer the signal from the second control unit (6) to the third control unit (7) to apply an offset value to the sent travel request.

3. Control system according to one of the preceding claims, characterized in that the decision-making device (9) has a comparison module (10) which is connected downstream of the offset module (11) and is configured to select the smaller of the two driving requirements and supply it to the third control unit (7). R. 414856 - 12 - 4. Control system according to one of claims 2 and 3, characterized in that the offset value of the offset module (11) is selected as a function of a signal propagation time of a control signal from the second control unit (6) via the first control unit (8) to the third control unit (7).

5. Control system according to one of the preceding claims, characterized in that the decision device (9) is configured to select the offset value depending on a gradient of the determined driving requirement.

6. Method for operating a control system (1) for a motor vehicle comprising at least one first control unit (8), in particular a central control unit, a second control unit (6), in particular a brake control unit, and a third control unit (7), in particular an actuator control unit, wherein the second control unit (6) determines a driving request, in particular from a driver of the motor vehicle, and sends it to the third control unit (7), wherein the third control unit (7) receives the determined driving request and, depending on the received driving request, controls an actuator (3), in particular of a brake system (2), characterized in that the second control unit (6) also sends the determined driving request to the first control unit (8), and that the first control unit (8) processes the determined driving request depending on predefinable parameters and sends it as a modified driving request to the third control unit (7).wherein a decision-making device (9) is connected upstream of the third control unit (7), which supplies the third control unit (7) with either the driving request of the second control unit (6) or the modified driving request of the first control unit (8).

7. Method according to claim 7, characterized in that the determined or modified driving requirement is selected depending on a gradient of the driving requirement. R. 414856 - 13 - 8. Method according to one of claims 7 and 8, characterized in that the determined driving requirement is subjected to an offset value.

9. Method according to one of claims 7 to 9, characterized in that the offset value is specified depending on the presence of the modified driving requirement.

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