Method for controlling the longitudinal dynamics of a vehicle

Abstract

A method for controlling the longitudinal dynamics of a vehicle, where the vehicle has a friction brake system brakes, a drive system with an electromotive drive acting on at least one wheel, and a battery for supplying power to the electromotive drive determines state information which describes the state of the vehicle and/or the state of the brake system and/or of the drive system. Route information is determined which describes the route profile of the vehicle. An action plan for implementing a future braking request by the friction brakes and/or the electromotive drive on the basis of the state information and the route information is determined. The action plan specifies, for future times and/or areas on the route, whether a braking request of the vehicle is to be implemented by means of the friction brake and/or the drive system and implements a braking request accordingly.

Claims

1. A method for controlling the longitudinal dynamics of a vehicle, wherein the vehicle has a brake system with friction brakes, and a drive system with a plurality of electromotive drive which each act on at least one wheel of the vehicle different from one another and a battery for supplying power to the electromotive drive comprising: determining state information which describes the state of at least one of the vehicle, the brake system, and the drive system; determining route information which describes the route profile of a future route of the vehicle; determining an action plan for implementing a future braking request by at least one of the friction brakes and the plurality of electromotive drives on the basis of the state information and the route information, wherein the action plan specifies, for at least one of future times and areas on the route, whether a braking request of the vehicle is to be implemented by one of: the brake system, the drive system and both the friction system and drive system determining for the action plan at least for the one of future times and areas on the route that one of: a first electromotive drive of the plurality of electromotive drives is to generate a drive torque for the at least one wheel and a second electromotive drive of the plurality of electromotive drives is to recuperate energy from the associated at least one different wheel; the first electromotive drive is to generate a drive torque for the at least one wheel and the second electromotive drive is to be actively energized to decelerate the associated at least one different wheel; and the first electromotive drive is to be actively energized to decelerate the at least one wheel and the second electromotive drive is to recuperate energy from the associated at least one different wheel; and implementing a braking request, triggered in the vehicle, in accordance with the action plan.

2. The method as claimed in claim 1, wherein the state information comprises at least one of the following variables: the state of charge of the battery, the temperature of the battery, the temperature of the electromotive drive, the temperature of the friction brakes.

3. The method as claimed in claim 1, wherein in the case of implementation of the braking request by the drive system the action plan specifies whether the drive system is to be actively energized in order to decelerate the vehicle or energy is to be recuperated into the battery via the drive system.

4. The method as claimed in claim 1, wherein the determination of the action plan further comprises predicting which braking processes will be necessary for defined areas of the future route owing to the route profile.

5. The method as claimed in claim 1, wherein the route information further comprises at least one of a bend profile of the future route and an altitude profile of the future route.

6. The method as claimed in claim 1, wherein the route information further comprises a traffic situation on the future route.

7. The method as claimed in claim 1, wherein the route information further comprises information which has been received indirectly or directly from other vehicles on the future route of the vehicle.

8. The method as claimed in claim 1, wherein the determination of the state information further comprises the determination of a braking performance currently implemented by the friction brakes.

9. The method as claimed in claim 1, wherein the determination of the state information further comprises evaluating operating parameters of the brake system and/or of the drive system during preceding braking processes.

10. The method as claimed in claim 1, further comprising extrapolating the state information while taking into account the action plan and the route information, wherein the action plan is defined for at least one of the future times and areas on the route on the basis of the extrapolated state information.

11. The method as claimed in claim 1, wherein the action plan specifies, for the at least one future time and area on the route, whether an acceleration request of the vehicle is to be implemented by the electromotive drive or a combustion drive of the vehicle, and further comprises implementing an acceleration request, triggered in the vehicle, in accordance with the action plan.

12. The method as claimed in claim 1, wherein the action plan specifies, for the at least one future time and area on the route that electrical consumers of the vehicle are activated in order to discharge the battery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

(2) FIG. 1 shows a flowchart of an exemplary method sequence,

(3) FIG. 2 shows a schematic illustration of an exemplary sequence of the data processing, and

(4) FIG. 3 shows an exemplary system architecture for the implementation of the method.

(5) In the text which follows, features that are similar or identical are denoted by the same reference signs.

(6) FIG. 1 shows a flowchart of an exemplary method sequence. In this context, in a first step 100, state information which describes the state of the vehicle, of the brake system and/or of the drive system is firstly determined. With respect to the state of the vehicle, this information can comprise, for example, a speed of the vehicle, an acceleration of the vehicle, a wheel speed, an inclination of the vehicle relative to the horizontal, or further information which characterizes activation of the brake system. For example output signals of a pedal travel sensor, an applied brake pressure or the duration of a braking process can be used for this.

(7) With respect to the state of the brake system, in particular information which permits a conclusion to be drawn about the vehicle state which is relevant for braking is relevant here. For example, the temperature of the friction brake can be used for this purpose, said temperature providing information on the extent to which a friction brake is loaded and the extent to which it can be further loaded. The temperature of the friction brake can be determined, for example, directly here by means of a corresponding temperature sensor, or can be calculated from a temperature model which, for example, accesses preceding braking maneuvers and evaluates the brake pressures and braking durations occurring in the process. The state of the drive system can be determined by temperature sensors in the electromotive drive, the cooling system of the drive or an inverter connected upstream of the drive. In addition, the sensor system of a battery system can also be triggered in this context, for example in order to determine the state of charge of the battery of the electromotive drive.

(8) In a second step 102, route information which describes the route profile of a future route of the vehicle is subsequently determined. For this purpose, recourse can be made, for example, to the information of a global positioning system (GPS), from which, for example, the bend profile present on the future route or an altitude profile of the future route can be determined. The information relating to the future route can be further refined here by also taking into account a traffic load factor of the future route. For this purpose, recourse can be made, for example, to sources such as a radio data system (RDS), traffic message channel (TMC) or else to the GSM (global system for mobile telecommunications) mobile radio network. In this context, corresponding information can be acquired both from other vehicles as well as from a central source, for example a server for providing traffic information.

(9) After the state information and the route information has been determined, subsequently this data is used in step 104 to determine an action plan which describes how implementation of a future braking request is to be carried out by means of the friction brakes and/or the electromotive drive for future times and/or areas on the route. In this context, the determination of the action plan can also be implemented as an interactive process in which on the basis of a determined action plan it is extrapolated how the state information of the vehicle will change along the route. The action plan can then be refined further on the basis of this extrapolated state information. The objective of the action plan here is to use the existing infrastructure, that is to say the brake system and the drive system, as efficiently as possible during subsequent braking requests and acceleration requests. Particular emphasis is placed here on avoiding excessive use of the friction brake and simultaneously avoiding overloading of the individual components, that is to say, for example, the battery, the electromotive drive or the friction brake.

(10) An exemplary scenario for defining the action plan is described here below. It is determined from the state information here, for example, that the battery is fully charged, and recuperation and consequently recuperative braking is accordingly not possible. In addition, the electromotive drive is not critical in respect of its temperature loading and consequently is fully deployable. However, the friction brake is at a raised temperature, but can still be fully used for emergency braking. In this context, it has been determined for a defined route section, from the travel information, that a high braking performance is necessary, for example, owing to a negative gradient.

(11) In this case, the action plan may provide that in order to implement a braking request the electromotive drive is actively energized, with the result that a deceleration torque is generated. In this way, overheating of the friction brakes is prevented and the battery is at least partially discharged. The friction brake accordingly also continues to be available and is not overloaded.

(12) If an acceleration request or a braking request is subsequently present in step 106, it is firstly checked at what point in the action plan, that is say at what point in time or area of the route, the vehicle is currently located. Taking this as a basis, it is then determined from the action plan how the braking request or acceleration request is to be implemented, after which corresponding implementation of the request is carried out.

(13) FIG. 2 shows a schematic illustration of an exemplary sequence of the data processing within the scope of the method described above.

(14) In this context, the state information and route information are first determined as input signals. In the illustrated variant of the data processing, these are divided into vehicle information 202 which describes the vehicle and its components per se, that is to say for example the vehicle speed and acceleration 204, the inclination of the vehicle 206, or current activation parameters of the brake system 208. In addition, the input signals also contain drive information or braking information 210 which describes the state of the drive system and of the brake system. This includes temperature information of the friction brake 212, temperature information of the drive system 214, that is to say of the electromotive drive, of an inverter and of the cooling system of the drive, as well as information from the sensor system of the battery system 216, which indicate, for example, the state of charge of the battery or its temperature. The vehicle information 202 and the drive information and/or braking information 210 form in combination the state information of the vehicle here.

(15) Finally, the input signals also include the route information 218, which is composed, for example, from data from a GPS system 220, an RDS system or TMC 222 and information from the mobile radio network (GSM) 224. For the data processing, information relating to a currently implemented braking performance of the friction brake 226, along with a possible history of preceding braking maneuvers 228, is derived here, for example, from the vehicle information 202. During the determination of the history of preceding braking maneuvers 228 it is also possible here to have recourse, e.g. to the route information 218.

(16) A temperature model for the friction brake 230 is then generated from the combination of the current braking performance 226 and the history of preceding braking maneuvers 228. This temperature model for the friction brake 230 is then input, together with the drive information and/or braking information 210, into a function block in which a braking-relevant vehicle state 232 is determined from the input signals. The term “braking-relevant vehicle state” is to be understood here as meaning any information which directly provides conclusive information as to the extent to which the friction brakes or the components of the drive system for implementing a braking request or acceleration request can be loaded, and will be able to be loaded in future. For this purpose, a current temperature of the friction brake 234, a thermal load capacity of the electromotive drive 236 and the temperature and/or charging capacity of the battery 238 are determined.

(17) In parallel with the determination of the braking-relevant vehicle state 232, an upcoming route 240 is also determined from the route information 218. In this context, an altitude profile 242 of the upcoming route, as well as a traffic situation 244 on the upcoming route, are also determined. A prediction of the number and type of braking maneuvers 246 to be expected in the future is then produced on the basis of the information relating to the upcoming route 242. The action plan 248 is then determined from the combination of the braking-relevant vehicle states 232 and the braking maneuvers 246 to be expected in the future. The action plan specifies here how a future braking request or acceleration request is to be implemented by the drive system and/or the brake system.

(18) In this context, this action plan 248 can also directly influence driving functions such as an ACC system 250 so that the information obtained from the action plan 248 can also be taken into account when controlling this system.

(19) If a braking request or acceleration request is then triggered 252, the action plan is then used to determine how this request is to be implemented. Accordingly, an optimized braking strategy or acceleration strategy 254 is then used, said strategy specifying, for example, whether the request is to be implemented by recuperative braking 256, by activating the friction brake 258, by active energization of the drive system in order to decelerate the vehicle 260, or by acceleration by means of the electromotive drive 262. The braking and acceleration strategy can also include here the fact that electrical consumers are selectively activated 264 in order to discharge the battery to such an extent that sufficient battery capacity is available for subsequent deceleration of the vehicle by means of recuperative braking.

(20) By analogy to the data processing sequence described above, FIG. 3 finally represents an exemplary system architecture which is suitable for implementing the method. In order to determine the input signals described above, the system architecture has corresponding sensors 300 here. The output signals of the sensors 300 are then provided to a central control unit 302, which determines the action plan 248 from the received signals. In addition, the central control unit 302 is designed to obtain a braking request and/or acceleration request 252. On the basis of the corresponding implementation of the requests according to the action plan 248, the control unit 302 is connected here to further control units of the friction brake 306, of the battery system 308, of the electromotive drive for recuperative deceleration 310 and of the electromotive drive 312, in such a way that it actuates the corresponding control units according to the action plan 248.

(21) In this context, the control unit 302 also communicates with automated driving functions 250, with the result that information derived from the action plan can also be provided to these driving functions. In addition, the control unit 302 also communicates with other vehicles or central servers for data processing 304 using communication interfaces, so that further information can be acquired via these interfaces and in turn input into the determination of the action plan.

(22) The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the scope of the following claims.