Abstract:
A method for operating an automobile includes the steps of a) detecting an object in an environment of the automobile with an environmental detection device; b) evaluating a collision risk of the automobile with the object; and c) depending on the evaluation, adjusting the steering angle of the automobile with a steering angle actuating device. The steering wheel is decoupled with the decoupling device depending on the adjustment performed in step c), so that the rotation of the steering wheel caused by the adjustment of the steering angle is smaller than if the same adjustment were made when the steering wheel is not decoupled.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of German Patent Application, Serial No. 10 2010 053 156.1, filed Dec. 1, 2010, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a method for operating an automobile with an environmental detection device, a steering angle actuating device, which is configured to adjust a steering angle independent of an operator, a steering wheel for manual adjustment of a steering angle of the automobile by an operator, and a decoupling device for at least partially decoupling a rotation of the steering wheel from an adjustment of the steering angle of the automobile caused by the steering angle actuating device, with the steps: a) detecting an object in the environment of the automobile with the environmental detection device; b) evaluating a collision risk of the automobile with the object; and c) depending on the evaluation, adjusting the steering angle of the automobile with the steering angle actuating device. The invention also relates to an automobile with an environmental detection device. 
         [0003]    The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention. 
         [0004]    Various driver assistance systems for assisting a vehicle operator with operating an automobile are known. For example, driver assist systems are known which assume transverse guidance tasks by applying additional steering torque on the steering system of the automobile. With this additional steering torque, the vehicle should be steered on a specified path commensurate with predetermined parameters. One example is the so-called heading control: this driver assistance system has the objective to control the vehicle so as to move along the center of the lane. A camera system with a connected image processing system measures the necessary environmental data. In addition, sensor data from the vehicle are evaluated (speed, transverse acceleration, etc.). The additional steering torque to be applied can be computed in a data processing device by using a suitable algorithm. 
         [0005]    Driver assistance system for transverse guidance can be constructed as pure warning systems or as independently operating systems. The so-called LDW (Lane Departure Warning) uses vibration warning to warn the vehicle operator from leaving the lane, in particular in the vicinity of road boundaries. The so-called LDW plus system applies in addition a steering torque which returns the automobile to the lane. The underlying LDW algorithms are pure warning systems. The so-called HC (Heading Control Assist) systems are used to keep the vehicle in the center of the lane. The HC assist system includes a so-called fairway which represents a predetermined travel strip within which no active steering intervention occurs. The vehicle is controlled back into its original lane only after exceeding a certain distance from the lane center. This fairway is absent in the HC continuous system, so that steering interventions can be constantly felt on the steering wheel. The driver notices all interventions due to the rigid coupling of the steering wheel with the automatic steering system. With a continuous steering assist and the associated continuous steering interventions, the steering wheel appears to develop a live of its own. 
         [0006]    It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method and an automobile, which reduces dangerous situations for the vehicle operator and for other road users. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention relates to a method for operating an automobile with an environmental detection device which may be particularly configured as a sensor for detecting a vehicle environment. 
         [0008]    According to one aspect of the present invention, a method for operating an automobile having an environmental detection device, a steering angle actuating device which is configured to adjust a steering angle of the automobile independent of an operator, a steering wheel for manually adjusting a steering angle of the automobile by an operator, and a decoupling device for at least partially decoupling a rotation of the steering wheel from an adjustment of the steering angle of the automobile caused by the steering angle actuating device, includes the steps of:
       a) detecting with the environmental detection device an object in an environment of the automobile;   b) evaluating a collision risk of the automobile with the object; and   c) depending on the evaluation of the collision risk, adjusting the steering angle of the automobile with the steering angle actuating device; and   d) depending on the adjustment of the steering angle in step c), decoupling the steering wheel with the decoupling device, so that the rotation of the steering wheel caused by the adjustment of the steering angle is smaller than if an identical adjustment is made when the steering wheel is not decoupled.       
 
         [0013]    When evaluating a collision risk of the automobile with the object detected by the environmental detection device, the evaluation may determine that the risk of a collision with the object is either affirmed or denied. In addition, a quantitative evaluation of the collision risk may also include determining a probability value for the collision. 
         [0014]    The steering angle of the automobile may or may not be adjusted. If the steering angle is adjusted, the type and/or the degree of the adjustment can be made so as to depend on the evaluation, in particular on a quantitative evaluation value. In particular, the speed and/or rate of the adjustment can also depend on evaluation values. 
         [0015]    Depending on the adjustment, the steering wheel may either be decoupled or not decoupled. In addition to completely decouple the steering wheel or not to decouple the steering wheel at all, the steering may be decoupled to a degree that depends on the type of the adjustment and/or of the associated adjustment values. In particular, the steering wheel may either not perform a rotation or such a rotation occurs always in the same direction as the adjustment of the steering angle, however with a maximum speed that corresponds to the speed with which the steering wheel would rotate if it were not decoupled. 
         [0016]    The method allows an automobile to automatically evade potential collision objects in an emergency. The potential collision object and the automobile and its occupants are safely protected from accidents. Because such automatic emergency evasion maneuvers represent highly dynamic processes, rapid steering movements are generally required. If these interventions in the steering were automatic and the steering wheel were coupled like for manual steering, then jerky and rapid rotations would occur on the steering wheel. This could be problematic in that a vehicle operator who rests, for example, his thumb on the steering wheel could break his thumb due to the rapid rotations. A steering wheel acting nervously in this manner would significantly diminish the acceptance of emergency evasion systems. The proposed method eliminates these significant disadvantages. It enables significantly reduced rotary movements of the steering wheel even in dynamic and automatic emergency evasion maneuvers, so that the response of the steering wheel is not only viewed as being less intrusive, but the risk of injury to the vehicle operator is also significantly reduced. 
         [0017]    According to an advantageous feature of the present invention, the degree of the decoupling in step d) depends on a speed of the adjustment of the steering angle and increases in particular with increasing speed of the adjustment. Alternatively or in addition, the degree of the decoupling in step d) may depend on the rate of the adjustment of the steering angle and may in particular increase with increasing rate of the adjustment. Moreover, the steering wheel may also be increasingly more decoupled the faster the steering wheel rotates and/or the faster it accelerates in particular in an emergency evasion situation, thus commensurately reducing its rotary movement. In this way, the rotary movement of the steering wheel can be adapted to the requirements of the respective vehicle steering characteristic. The faster the steering angle is adjusted, the faster would a non-decoupled steering wheel rotate and the greater would be the risk for a vehicle operator who rests his hands on the steering wheel. With increasing degree of the decoupling, the vehicle operator is therefore safely protected from injury to his hand and lower arm. The applied steering torque can be concealed on the steering wheel so that the driver senses an acceptable steering wheel movement and/or the steering wheel rotation speed stays within manageable parameters. 
         [0018]    According to another advantageous feature of the present invention, the steering wheel may be completely decoupled in step d), so that the steering wheel does not perform a rotary movement during each adjustment of the steering angle. The hands of the vehicle operator are then well protected even with very rapid, jerky automatic steering movements. 
         [0019]    According to another advantageous feature of the present invention, the steering wheel may not be decoupled in step d) when the steering angle is adjusted in step c) by a change steering angle which is smaller than a predetermined threshold value, whereas the steering wheel may be decoupled in step d) when the steering angle is adjusted in step c) by a change steering angle which is greater than or equal to the predetermined threshold value. For only small rotary movements of the steering wheel below the threshold value, the vehicle operator receives via the steering wheel a haptic feedback message which corresponds to a natural vehicle characteristic during a steering movement. Only when the adjustment angles become so large that the hands of the vehicle operator could be at risk, is the steering wheel decoupled for protecting the vehicle operator. This represents a good compromise between a natural driving characteristic and a protection of the vehicle operator. Decoupling for values greater than or equal to the predetermined threshold value may again be either complete or may have a level adapted to respective adjustment characteristics. 
         [0020]    According to another advantageous feature of the present invention, the decoupling device may include a superposition device which has an actuator motor and in particular a gear and intervenes in the rotation of a steering column, which may be rotated by way of the steering wheel, through decoupling such that a rotation of the steering column caused by the steering angle actuating device results in a smaller rotation of the steering wheel than if the intervention had not taken place. This design ensures effective and reliable decoupling of the steering wheel and can also operate with sufficient speed for very rapid automatic steering movements in emergency evasion situations. A multi-step adjustment of the level of the decoupling is also possible. 
         [0021]    According to another advantageous feature of the present invention, decoupling is implemented with a control device which is configured to control the steering angle actuating device so as to cause an adjustment of the steering angle of the automobile and which is configured to control the actuator motor depending on the control of the steering angle actuating device. This design ensures that the steering wheel can be decoupled almost without delay relative to the adjustment of the steering angle. The reaction times for the decoupling are kept small with respect to the start of the adjustment. Adjustment and decoupling can thus occur in a coordinated manner. 
         [0022]    According to another advantageous feature of the present invention, the steering wheel may always be decoupled with the decoupling device when the steering angle of the automobile is adjusted with the steering angle actuating device. An undesirable rotary movement of the steering wheel is thus prevented even if a collision risk is not present in the case of an automatically performed transverse guidance. In particular, when a driver assistance system completely takes over the steering task from the driver, no intrusive interventions in the steering wheel occur. This improves the driving comfort and the bodily stress for the vehicle operator. 
         [0023]    According to another advantageous feature of the present invention, the environmental detection device may include a distance sensor and/or an ultrasound sensor and/or a camera and/or a radar sensor and/or a lidar sensor. This type of sensors or detectors ensures reliable detection of an object in step a) of the method and enables high-quality evaluation in step b). 
         [0024]    According to another aspect of the invention, an automobile according to the invention includes an environmental detection device which is configured to detect an object in the environment of the automobile, a steering angle actuating device which is configured to adjust a steering angle of the automobile independent of an operator, a steering wheel for manual adjustment of a steering angle of the automobile by an operator, a decoupling device for at least partially decoupling a rotation of the steering wheel from an adjustment of the steering angle of the automobile caused by the steering angle actuating device, and a data processing device which is configured to evaluate a collision risk of the automobile with the object detected by the environmental detection device and to set an adjustment of the steering angle of the automobile depending on the evaluation. The data processing device is further configured to set, depending on the set adjustment, a decoupling of the steering wheel with the decoupling device such that a resulting rotary movement of the steering wheel during execution of the set adjustment of the steering angle is smaller than if the same adjustment would be made when the steering wheel is not decoupled. The data processing device may particularly be incorporated in a driver assistance system of an automobile and may also include a control device configured to control the steering angle actuating device and/or an actuator motor of the decoupling device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0025]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0026]      FIG. 1  shows a schematic diagram of an automobile with a steering angle actuating device and a decoupling device according to the invention; 
           [0027]      FIG. 2  shows a schematic diagram of an emergency evasion situation in traffic according to the invention; and 
           [0028]      FIG. 3  shows a graphical representation of a threshold-dependent decoupling according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0030]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown a front region of an automobile  1  in a schematic top view. A steering rack  12  allows the two front wheels  13  of the automobile  1  to be steered. The steering rack  12  is connected via a control rod  9  with a steering wheel  4  to allow manual steering by a vehicle operator. A rotary movement performed by the vehicle operator on the steering wheel  4  is transmitted to the steering rack  12  and finally to the wheels  13 , allowing a steering angle a to be set. 
         [0031]    In addition, the automobile  1  includes a steering angle actuating device capable of automatically applying additional steering torque to the steering system. In the exemplary embodiment, the steering angle actuating device is implemented as an electric servo steering (Electric Power Steering) EPS  3 . The EPS  3  includes a motor and a gear for transmitting a force to the steering rack  12 . Forces introduced in this manner affect the wheels  13  and cause the steering angle a to change. The forces simultaneously also act on the steering wheel  4 . The connection between the steering rack  12  and the steering wheel  4  via the control rod  9  has a fixed geometry with systems lacking superposition steering (i.e., the gear ratio is constant). Each displacement of the steering rack  12  would then simultaneously also cause the steering wheel  4  to rotate. 
         [0032]    A superposition steering  5  allows an adaptation of the steering gear ratio from the steering wheel  4  to the steering rack  12 . The superposition steering  5  can be used to disguise interventions by the EPS  3  on the steering wheel  4 . To this end, the superposition steering  5  includes a gear  8  and an actuator motor  7 . The superposition steering  5  is connected with a control device  10 , to which the EPS  3  is also connected. When the motor of the EPS  3  is controlled by the control device  10 , the actuator motor  7  of the superposition steering  5  is activated to the same degree to disguise the steering movements on the steering wheel  4  caused by the EPS  3 . The gear ratio of the two ends of the control rod  9  can be adapted by the gear  8 , so that the desired rotation of the steering wheel  4  can be adjusted. However, the steering wheel  4  can also be completely decoupled, so that it no longer rotates for any movement of the steering rack  12 . 
         [0033]    The control device  10  is connected with a computer  11  providing driver assistance in form of automatic transverse guidance. The computer  11  is particularly configured to provide transverse guidance assistance in form of a lane maintaining support system or a lane assist. Based on a predetermined algorithm, the computer  11  determines interventions in the steering system  9  and accordingly controls the control device  10 , which then controls the EPS  3  and the superposition steering  5  so as to implement the commands of the computer  11 . 
         [0034]    The computer  11  also includes an algorithm capable of executing a method for automatic emergency evasion maneuvers. For this purpose, the computer  11  is connected with an environmental detection device in form of a distance sensor  2 . 
         [0035]      FIG. 2  shows in a schematic top view onto a roadway  14 , with the automobile  1  moving in the right lane in a travel direction (in the Figure, from left to right). An additional automobile  6  is located on the lane in front. A possible scenario for an emergency evasion situation will now be illustrated, describing the steering reaction of the automobile  1 : the automobile  6  suddenly brakes and finally comes to a stop. The automobile  6  thus represents a potential collision object for the automobile  1  which is still moving. Because a normal driving situation originally existed, decoupling of the steering wheel  4  from the steering rack  12  was not necessary in section B 1 . The operator of the automobile  1  can manually operate the steering without restrictions and receives intermediate feedback on the steering wheel  4  about the set steering angle a. 
         [0036]    The automobile  6  is located in the detection region E of the distance sensor  2 . The distance sensor  2  recognizes that the distance between the automobile  1  and the automobile  6  becomes increasingly smaller and transmits the data to the computer  11 . An algorithm executed in the computer  11  evaluates the collision risk of the automobile  1  with the automobile  6  and comes to the conclusion that an automatic emergency evasion maneuver appears to be necessary to avoid an accident. A trajectory T is computed as well as an associated course of the steering angle a for realizing this trajectory T. To implement this computation, the computer  11  transmits suitable data to the control device  10  which then transmits suitable control signals to the EPS  3  for automatically adjusting the required steering angles a via the steering rack  12 . Adaptive steering which is automatically implemented by the EPS  3  thus occurs in section B 2 . 
         [0037]    To prevent a risk to the vehicle operator by a rapidly rotating steering wheel  4 , the steering wheel  4  is in this exemplary embodiment in section B 2  at least partially decoupled from the steering rack  12 . The control device  10  hereby controls the actuator motor  7  so as to reduce the rotation of the steering wheel  4  by way of the gear  8 . According to the trajectory T in section B 2 , the steering wheel  4  still performs a rotary movement; however, this rotary movement is significantly smaller than if decoupling had not taken place. The vehicle operator receives haptic feedback about the automatically performed steering operation by way of slow tracking of the steering wheel  4 ; however, his hands are no longer at risk from jerky movements of the steering wheel  4 . 
         [0038]    The steering wheel  4  is again completely coupled to the steering rack  12  in section B 3  by suitable commands from the computer  11  only when a collision risk no longer exists. The vehicle operator can now manually steer back into the right lane. 
         [0039]      FIG. 3  shows an alternative approach for decoupling. The degree of the decoupling as a function of the change steering angle Δa in a graphical illustration. The steering wheel  4  is not decoupled at all before reaching a threshold value a 0 . Complete decoupling only occurs when the change steering angle Δa exceeds this threshold value a 0  and the steering wheel no longer co-rotates. In particular, the threshold value a 0  should be smaller than 360° to disguise dangerously fast multiple revolutions of the steering wheel. 
         [0040]    In summary, with the presented idea of intelligent coupling of the EPS  3  and adaptive steering, both emergency evasion trajectories can be driven and the thumb of the vehicle operator can be protected. This is achieved by at least partially decoupling the steering wheel  4  at least during the automatic emergency evasion maneuver. 
         [0041]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.