Patent Application
20230119982
The present disclosure claims the benefit of priority of co-pending European Patent Application No. 21 202 930.0, filed on Oct. 15, 2021, and entitled “METHOD FOR PERFORMING BRAKE DISC CLEANING OF A VEHICLE,” the contents of which are incorporated in full by reference herein.
The present disclosure relates to a method for performing brake disc cleaning of an at least partially electrically driven vehicle, a computer program element configured to carry out the method and an at least partially electrically driven electric vehicle including a control unit configured to carry out the method.
BEV (Battery Electric Vehicle) and PHEV (Plug-in Hybrid Electric Vehicle) cars with sizable electric machines see very little use of friction brakes since regenerative braking is prioritized and will cover most braking needs. When the requested deceleration reaches a certain level, part of the braking will be carried out by the friction brake.
Since hard braking is relatively seldom in the everyday driving, the friction brake is thus not sufficiently used, which results in rust at cold and damp brake discs.
Rust on brake discs will lead to significantly lower brake performance and thus unwanted longer brake distance. Another side effect is unpleasant noise at very low speeds (such as parking maneuvers), where friction brakes are still used, and even when brakes are not engaged.
Disc clean function is adopted in many EVs (Electric Vehicles) today by applying only friction brakes so that the cumulative sum of each brake event temperature rise is reached at the desired level, e.g. 100 degrees C. In this way, the brake disc rust problem can be mitigated. However, in this case, no/less recuperation is possible.
Today, there is no specific selection of brake events when it comes to disc cleaning. The nominal way is to use friction brakes at regular intervals, even if some of these include low brake energy and are of little use. All brake events will be subject to friction brake application as soon as the disc clean function is activated. This strategy is very energy ineffective, specifically when considering the sharp demand of longer range in BEVs.
There may, therefore, be a need to provide an improved method for performing brake disc cleaning of an at least partially electrically driven vehicle.
The problem is at least partially solved or alleviated by the subject matter of the present disclosure.
According to a first aspect, there is provided a method for performing brake disc cleaning of an at least partially electrically driven vehicle (ego-vehicle, host vehicle, own vehicle) including a brake system with at least one friction brake. A surface of the friction brake can be brought into contact with a corresponding brake disc. The method includes, not necessarily in this order:
Hence, there is provided a smarter, e.g. more energy efficient, method for brake disc cleaning.
In an example, the vehicle-ahead information may include at least one of a number of conditions such as a time gap between the vehicle and the vehicle ahead, a predicted deceleration needed of the vehicle and a brake energy anticipated of the vehicle, etc., which is used for assessing braking conditions of the vehicle, i.e. for predicting a needed deceleration level of the vehicle. Therefore, vehicle-ahead information can be gathered by using several units of the vehicle used for observation of the environment, e.g. cameras, radar sensors, sensors for determining acceleration etc.
In an example, further information may be combined with the vehicle-ahead information for determining an upcoming brake event of the at least partially electrically driven vehicle (in the following ego-vehicle). This further information includes at least one of an adaptive regenerative braking force of the ego-vehicle and driver behavior information of the ego-vehicle such as actual pedal position. An adaptive regenerative braking function can be used as information source in order to indicate a potential level (force) of braking needed.
If the needed deceleration level of the ego-vehicle can be predicted to be above a certain value in an upcoming brake event of the ego-vehicle, thus gaining high brake energy, the brake disc cleaning can be carried out only at this type of brake event so that an unnecessary use of friction brakes can be minimized.
Further, in an example, the prediction of the needed deceleration level of the ego-vehicle may be carried out by determining a safety distance to the vehicle ahead, and/or calculating a corresponding regeneration brake force of the ego-vehicle, and/or determining a required braking force of the ego-vehicle based on the vehicle mass and/or an estimated road load, and/or determining a required brake energy and/or brake power of the ego-vehicle.
Determining a safety distance d to the vehicle ahead can be done by multiplying the time gap tgapbetween the ego-vehicle and the vehicle ahead with the actual velocity vego of the ego-vehicle:
d=tgap*vego
For calculating an adaptive regeneration brake force of the ego-vehicle, the acceleration as needed to get zero relative velocity between the ego-vehicle and the vehicle ahead within a safety distance d when approaching the vehicle ahead is calculated by:
where:
Hence, the acceleration apred is the acceleration needed for activating brake disc cleaning.
Determining a required braking force Fbrake. of the ego-vehicle based on the vehicle mass mass and an estimated road load Froadload, which is only estimated by a vehicle motion sensor such as an acceleration sensor etc., can be done by calculating:
F
brake=mass*a+Froadload
The roadload can be calculated using a set of constants that are multiplied with the vehicle speed v both linear and squared: F_rl=c1+c2*v+c3* v{circumflex over ( )}2.
The needed brake energy Ebrake of the ego-vehicle depends on the brake disc temperature model readily available for each vehicle and can be determined by:
where:
The needed brake power Pbrake of the ego-vehicle is calculated by:
Pbrake=Fbrake*rW*ωwheel>Preq [kW]
where:
Further, in an example, a brake event of the ego-vehicle may be triggered when at least one, some or all of the following conditions are fulfilled:
In case a one pedal drive is applicable for the ego-vehicle, at least one of the following conditions may also need to be fulfilled:
In another example, a computer program element is suggested, being configured to carry out a method as described above, when executed by a processor.
In another example, an at least partially electrically driven electric vehicle is suggested, including one or more units configured to acquire vehicle-ahead information, one or more units configured to acquire ego-vehicle information, and at least one control unit configured to carry out the method as described above.
The ego-vehicle information may at least include a pedal status and/or brake information and/or a regeneration brake force of the ego-vehicle.
Exemplary examples of the disclosure will be described in the following with reference to the following drawings.
The figures are merely schematic representations and serve only to illustrate examples of the disclosure. Identical or equivalent elements are in principle provided with the same reference signs.
As can be seen, information is collected in a central module 10, which can process the information and also instruct the braking system 200, 201. The braking system 200, 201 is indicated as brake control module 200 for friction brakes, of which the brake discs need to be cleaned e.g. from rust, and an electric motor unit 201, which is responsible for regeneration braking. In order for the central module 10 to instruct the braking module 200, 201, information from units 100 for environmental observation such as cameras, radar and other sensors, as well as driver behavior information from unit 101 and needed brake energy from the brake disc model 102 of the vehicle are necessary.
Driver behavior information is mainly the status of the acceleration and brake pedals or from the single pedal, being adapted for accelerating and braking in case of a one pedal drive.
When all necessary information is available, the central module 10 calculates the predicted brake force (in N) and converts it into energy (in J). This energy is compared with needed brake energy (in J) for the upcoming brake event. Then, a level for friction brake torque as well as for regeneration brake torque is calculated.
As soon as the accelerator pedal is released or the brake pedal is pressed (in one pedal configuration only as soon as the pedal is released in a predetermined position), the request for applying the respective torques is sent to the modules 200 and 201 for acting accordingly, thus activating brake disc cleaning.
In one example, the following conditions need to be fulfilled to send the request:
In
With the suggested method, it is possible to minimize the activation of disc cleaning application, by predicting the use of friction brake at upcoming brake events. Only in case a needed deceleration level of the vehicle is predicted as high enough (exceeding a predefined value) and thus high brake energy is expected in an upcoming brake event, the brake disc cleaning is carried out. Hence, the unnecessary use of friction brakes can be minimized.
Other variations to the disclosed examples can be understood and effected by those skilled in the art in practicing the claimed invention, from the study of the drawings, the disclosure, and the appended claims. In the claims the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items or steps recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable non-transitory computer-readable medium such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, including a processor and a memory, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21 202 930.0 | Oct 2021 | EP | regional |
