METHOD FOR FREEING AT LEAST ONE LOCKED WHEEL OF A VEHICLE AND PROPULSION SYSTEM FOR A VEHICLE

Abstract

The disclosure relates to a method for freeing at least one locked wheel of a vehicle. One step of the method relates to identifying a locking scenario comprising the identification of the at least one locked wheel. A further method step is selecting a wheel freeing strategy being suitable for the identified locking scenario. Another step is directed to applying the selected wheel freeing strategy. Furthermore, the disclosure is directed to a propulsion system for a vehicle having at least one wheel. The propulsion system comprises at least one propulsion actuator. Moreover, at least one wheel speed sensor is provided, the wheel speed sensor being configured for detecting the rotational speed of the at least one wheel. Additionally, the propulsion system has at least one brake unit being configured for braking the at least one wheel and a control unit being configured for performing the above method.

Claims

1. A method for freeing at least one locked wheel of a vehicle, the method comprising: identifying a locking scenario comprising the identification of the at least one locked wheel, selecting a wheel freeing strategy being suitable for the identified locking scenario, and applying the selected wheel freeing strategy.

2. The method according to claim 1, wherein the identifying the locking scenario comprises evaluating whether the vehicle is moving.

3. The method according to claim 1, wherein the identifying the locking scenario comprises detecting of one or more wheels rotating in place.

4. The method according to claim 1, wherein the identifying the locking scenario comprises identifying a propulsion actuator being coupled to the locked wheel.

5. The method according to claim 1, wherein the identifying the at least one locked wheel comprises detecting a wheel speed of each of the vehicle's wheels and detecting or estimating a motion of the vehicle, wherein the respective wheel speeds of each of the vehicle's wheels are compared to the motion of the vehicle or the estimation of the motion of the vehicle.

6. The method according to claim 1, wherein the identifying the at least one locked wheel comprises detecting a yaw motion of the vehicle and comparing the detected yaw motion to an estimated yaw motion of the vehicle.

7. The method according to claim 1, wherein the selecting a wheel freeing strategy or the wheel freeing strategy comprises detecting obstacles in the surroundings of the vehicle.

8. The method according to claim 1, wherein the wheel freeing strategy comprises at least one of: increasing the level of requested torque for the vehicle or for the at least one locked wheel only, requesting torque in alternating directions for the vehicle or for the at least one locked wheel only, or requesting intermittent torque for the vehicle or for the at least one locked wheel only.

9. The method according to claim 1, wherein the wheel freeing strategy comprises allowing the at least one locked wheel to be dragged by at least one remaining wheel.

10. The method according to claim 1, wherein the wheel freeing strategy comprises stopping the vehicle or displaying a message to a user of the vehicle or sending a message to a user remote from the vehicle.

11. The method according to claim 1, wherein the wheel freeing strategy comprises the request for a braking action to be applied to at least one of the non-locked wheels.

12. The method according to claim 1, further comprising verifying whether the at least one locked wheel has been unlocked.

13. The method according to claim 1, further comprising verifying whether the identified locking scenario is still valid.

14. A propulsion system for a vehicle having at least one wheel, the propulsion system comprising: at least one propulsion actuator being drivingly connectable to the at least one wheel, at least one wheel speed sensor being configured for detecting the rotational speed of the at least one wheel, at least one brake unit being configured for braking the at least one wheel, and a control unit being connected to the at least one propulsion actuator, the at least one wheel speed sensor and the at least one brake unit, the control unit being configured to perform the method for freeing at least one locked wheel of a vehicle, the method comprising: identifying a locking scenario comprising the identification of the at least one locked wheel, selecting a wheel freeing strategy being suitable for the identified locking scenario, and applying the selected wheel freeing strategy.

15. The propulsion system according to claim 14, further comprising a detection unit to detect obstacles in the surroundings of the vehicle.

Description

[0044] Examples of the invention will be described in the following with reference to the following drawings.

[0045] FIG. 1 shows a vehicle comprising a propulsion system according to the present disclosure and

[0046] FIG. 2 shows a method according to the present disclosure.

[0047] 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.

[0048] FIG. 1 shows a vehicle 10 having four wheels 12 and a propulsion system 14.

[0049] The wheels 12 are coupled with the propulsion system 14.

[0050] In more detail, the exemplary propulsion system 14 comprises a total of four propulsion actuators 16, wherein each of the propulsion actuators 16 is drivingly connected to one of the wheels 12. The vehicle of the present example is thus a four-wheel-drive vehicle. Moreover, each of the wheels 12 can be actuated individually. The propulsion actuators 16 are for example electric propulsion actuators each comprising an electric motor.

[0051] Moreover, a wheel speed sensor 18 is attributed to each of the wheels 12. Each of the wheel speed sensors 18 is configured for detecting the rotational speed of the corresponding wheel 12.

[0052] Furthermore, the propulsion system 14 comprises a total of four brake units 20. Each of the brake units 20 is coupled with one of the wheels 12 such that each of the brake units 20 is configured for braking the corresponding wheel 12 individually.

[0053] The propulsion system 14 also has a detection unit 22 for detecting obstacles in the surroundings of the vehicle 10.

[0054] In the present example, the detection unit 22 comprises a front detection unit 24 and a rear detection unit 26.

[0055] Moreover, a control unit 28 is provided as a part of the propulsion system 14.

[0056] The control unit 28 is connected to each of the propulsion actuators 16, to each of the wheel speed sensors 18, and to each of the brake units 20.

[0057] Furthermore, the control unit 28 is connected to the front detection unit 24 and the rear detection unit 26.

[0058] Additionally, an inertial measurement unit 30 forms part of the propulsion system 14 and is connected to the control unit 28.

[0059] Beyond that a display unit 33 is provided which is connected to the control unit 28.

[0060] Also a vehicle model 32, i.e. an information model of the vehicle 10, is connected to the control unit 28.

[0061] Each of the connections of the control unit 28 is configured for transmitting communicative signals, especially request and data.

[0062] The control unit 28 is configured for performing a method for freeing a locked wheel which will be explained in the following with further reference to FIG. 2.

[0063] The method comprises essentially three steps, wherein in a first step 34 a locking scenario is identified. This comprises the identification of at least one locked wheel 12.

[0064] In the present example, the at least one locked wheel 12 is identified in that a wheel speed of each of the wheels 12 is detected by the corresponding wheel speed sensors 18.

[0065] Additionally, a longitudinal motion of the vehicle 10 is detected by the inertial measurement unit 30. In other words, the method evaluates if the vehicle is moving.

[0066] Subsequently, the respective wheel speeds of each of the wheels 12 can be compared to the longitudinal motion of the vehicle 10.

[0067] For the pure purpose of explanation, it is assumed that in a first illustrative example a longitudinal motion of the vehicle is detected. Furthermore, a wheel speed of the wheel 12 represented in the lower right corner of the propulsion system 14 is detected to be zero while the wheel speeds of the remaining wheels are different from zero.

[0068] Consequently, it is possible to detect that the wheel 12 represented in the lower right corner is locked and that it is dragged by the remaining wheels 12.

[0069] These detection results can be summarized as the identified locking scenario.

[0070] In a second illustrative example it is assumed that no longitudinal motion of the vehicle 10 is detected. Additionally, the wheel speed of the wheel 12 being represented in the lower right corner is detected to be different from zero, wherein the wheel speed of the remaining wheels is detected to be zero. Thus, one can conclude that the wheel 12 being represented in the lower right corner is rotating in place. Consequently, the locked wheel 12 has to be amongst the remaining wheels.

[0071] Additionally or alternatively, the at least one locked wheel, here for example the wheel 12 represented in the lower right corner, can also be identified in that a yaw motion of the vehicle 10 is detected and compared to an estimated yaw motion of the vehicle 10. The yaw motion can be detected by the inertial measurement unit 30. The estimated yaw motion can be calculated using the vehicle model 32.

[0072] Since each of the wheels 12 produces a characteristic deviation between the actual yaw motion and the estimated yaw motion when being locked, a locked wheel 12 can be identified by comparing these two yaw motion parameters.

[0073] Strictly speaking, no wheel speed sensors 18 are necessary if the locked wheel is to be detected via the yaw motion. However, assessing the yaw motion and the wheel speed at the same time enhances the reliability of the detection result.

[0074] The identification of the locking scenario may make further use of the vehicle model 32 in that the propulsion actuator 16 being coupled to the locked wheel 12 is identified. Thus, the vehicle model 32 contains information about the relations between the propulsion actuators 16 and the wheels 12. In the example shown in FIG. 1, there is a 1:1 relationship between each propulsion actuator 16 and the corresponding wheel 12. However, it is also imaginable that only one propulsion actuator 18 is used per axle or that only the wheels of one axle are driven wheels, i.e. coupled to a propulsion actuator 18. This also forms part of the locking scenario.

[0075] Once the locking scenario has been identified, a wheel freeing strategy being suitable for the identified locking scenario is selected. This is a second step 36 of the method. Thereafter, in a third step 38, the selected wheel freeing strategy is applied.

[0076] Considering again the first illustrative example, having the wheel 12 represented in the lower right corner locked, an appropriate freeing strategy may be to increase the level of requested torque for the locked wheel 12 only. Another strategy that can be applied alternatively or additionally is to request torque in alternating directions for the locked wheel 12. Furthermore, intermittent torque for the locked wheel 12 can be requested. This can be done as an alternative to the freeing strategies mentioned before or in addition thereto.

[0077] A further freeing strategy consists in allowing the locked wheel 12 to be dragged by the remaining wheels. However, this strategy is less advantageous for the first illustrative example.

[0078] Beyond that, in the first illustrative example, the vehicle 10 is stopped and a braking action is requested for all non-locked wheels 12. Thus, the vehicle stands still during the application of the freeing strategy. Additionally, a message is displayed to a user of the vehicle via display unit 33, informing the user that a wheel freeing method is performed.

[0079] The selection of the wheel freeing strategy can also comprise the detection of obstacles in the surroundings of the vehicle. To this end the detection unit 22 is used. In the first illustrative example, the decision to stop the vehicle 10 and request a braking action for all non-locked wheels is for example due to obstacles detected in the surroundings of the vehicle 10. Thus, the risk of collision with these obstacles is remedied.

[0080] Also during the application of the freeing strategy the detection unit 22 may be used in order to monitor the surroundings and detect a potential shortening of a distance between the vehicle 10 and an obstacle in its surroundings.

[0081] The method periodically verifies whether the identified locking scenario is still valid. This is illustrated by an arrow 40. If a locking scenario has been found to be invalid, the method jumps back to the first step 34 and an updated locking scenario is identified.

[0082] Additionally, the method periodically verifies whether the locked wheel 12 has been unlocked. If so, the method can be abandoned. This is illustrated by an arrow 42.

[0083] 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 medium such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, 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.

LIST OF REFERENCE SIGNS

[0084] 10 vehicle [0085] 12 wheel [0086] 14 propulsion system [0087] 16 propulsion actuator [0088] 18 wheel speed sensor [0089] 20 brake unit [0090] 22 detection unit [0091] 24 front detection unit [0092] 26 rear detection unit [0093] 28 control unit [0094] 30 inertial measurement unit [0095] 32 vehicle model [0096] 33 display unit [0097] 34 first step [0098] 36 second step [0099] 38 third step [0100] 40 arrow [0101] 42 arrow