Vehicle With an Operator Control Providing Haptic Feedback for Indicating a Potential Collision

Abstract

A vehicle has an operator control configured to provide a force as haptic feedback, a coupling configured for hitching a towable implement, a sensor arrangement configured to determine at least one sensor value, and a control unit configured to anticipate a potential collision between the vehicle and the towable implement based on the at least one sensor value and to increase the force if a potential collision is anticipated.

Claims

1. A vehicle, comprising: an operator control configured to provide a force as haptic feedback; a coupling configured for hitching a towable implement; a sensor arrangement configured to determine at least one sensor value; and a control unit configured to anticipate a potential collision between the vehicle and the towable implement based on the at least one sensor value; and increase the force if a potential collision is anticipated.

2. The vehicle of claim 1, wherein control unit configured to decrease the force if no potential collision is anticipated.

3. The vehicle of claim 1, wherein the at least one sensor value comprises a value indicative of a distance between the vehicle and a hitched towable implement.

4. The vehicle of claim 3, wherein the control unit is configured to determine a distance threshold value; and anticipate a potential collision if the value indicative of the distance violates the distance threshold value.

5. The vehicle of claim 3, wherein the value indicative of the distance between the vehicle and a hitched towable implement is a hitching angle between the vehicle and the hitched towable implement.

6. The vehicle of claim 1, wherein the at least one sensor value comprises a value indicative of a steering angle.

7. The vehicle of claim 1, wherein the control unit is configured to determine a pivoting direction of the vehicle in respect of the towable implement; determine a steering direction of the steering angle.

8. The vehicle of claim 1, wherein the at least one sensor value comprises a value indicative of a driving direction of the vehicle.

9. The vehicle of claim 7, wherein the control unit is configured to determine a distance threshold value; determine a steering threshold angle in relation to the distance threshold value; determine whether the value indicative of the steering angle violates the steering threshold angle; and anticipate a potential collision if the steering angle violates the steering threshold angle; the pivoting direction and the steering direction have the same direction; and driving direction is forward.

10. The vehicle of claim 9, wherein the control unit is configured to anticipate no potential collision if the pivoting direction and the steering direction have different directions; and the driving direction is forward.

11. The vehicle of claim 9, wherein the control unit is configured to anticipate no potential collision if the pivoting direction and the steering direction have the same direction; and driving direction is rearward.

12. The vehicle of claim 9, wherein the control unit is configured to anticipate a potential collision if the steering angle violates the steering threshold angle; the pivoting direction and the steering direction have different directions; and the driving direction is rearward.

13. The vehicle of claim 9, wherein the control unit is configured to increase the force if a potential collision is anticipated and if the operator control is operated in a direction controversially to reduce the steering angle below the steering threshold angle.

14. The vehicle of claim 9, wherein the control unit is configured to decrease the force if a potential collision is anticipated and if the operator control is operated in a direction to reduce the steering angle below the steering threshold angle.

15. A method of providing a force as haptic feedback for an operator control of a vehicle connectable with a towable implement, comprising determining at least one sensor value; and anticipating a potential collision between the vehicle and the towable implement based on the at least one sensor value; and increasing the force if a potential collision is anticipated.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Several aspects of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0042] FIG. 1 illustrates a vehicle with an operator control and a sensor arrangement.

[0043] FIG. 2 illustrates a simplified block diagram of the vehicle of FIG. 1.

[0044] FIG. 3 illustrates schematically an example of an operator control.

[0045] FIG. 4 illustrates the vehicle of FIG. 1 with a towable implement.

[0046] FIG. 5A illustrates the vehicle of FIG. 1 with a towable implement having a shorter drawbar.

[0047] FIG. 5B illustrates the vehicle of FIG. 1 with a towable implement having a longer drawbar.

[0048] FIG. 6 illustrates a simplified view of a control unit of the vehicle shown in FIG. 1.

[0049] FIG. 7A illustrates the vehicle of FIG. 1 with a towable implement wherein a steering direction and a pivoting direction are directed in the same direction.

[0050] FIG. 7B illustrates the vehicle of FIG. 1 with a towable implement wherein the steering direction and the pivoting direction are directed in different directions.

[0051] FIG. 8 illustrates a flow chart of a method executable by the control unit of FIG. 6.

DETAILED DESCRIPTION

[0052] FIG. 1 shows schematically a vehicle 8, for example an agricultural vehicle such as a tractor. The vehicle 8 may be of any other type such as a harvester, a sprayer, a combine, a truck or a passenger car. The vehicle 8 comprises left and right front wheels 28 and left and right rear wheels 30. The rear wheels 30 provide a tractive force to drive the vehicle 8 in a forward or a backward direction. The front wheels 28 are steerable by an operator control 10 of the vehicle 8. The operator control 10 may comprise a steering wheel 12 and/or a steering lever 11 for demanding a steering angle of the front wheels 28. The operator control 10 is manually moveable out of a neutral position .sub.N to a left direction .sub.L for steering the front wheels 28 to the left direction .sub.L or to a right direction .sub.R for steering the front wheels 28 to the right direction .sub.R. The demanded steering angle from the operator control 10 is received by a control unit 9 of the vehicle 8. Then, the control unit 9 initiates an adjustment of the steering angle of the front wheels 28 as demanded. In dependence of the steering angle , the vehicle 8 will turn in a corresponding direction to drive a curve. The radius of the curve depends on the steering angle and decreases the more, the more the steering angle increases (and vice versa).

[0053] The vehicle 8 comprises a coupling 4 for hitching a towable implement 5 (see FIG. 4). The towable implement 5 may be a trailer or any other agricultural towable implement that may be pulled by the vehicle 8 over an agricultural field such as a plough. A sensor 23 configured to determine a hitching angle between the vehicle 8 and the towable implement 5 is attached to the coupling 4 (or alternatively to any other part of the vehicle 8). The hitching angle defines an angle between the vehicle 8 and the towable implement 5. When the vehicle 8 and the towable implement 5 are in a straight alignment, the hitching angle is zero or neutral (see FIG. 4). The hitching angle increases if the vehicle 8 deflects in respect of the towable implement 5 (see FIG. 5A; FIG. 5B), for example when the vehicle 8 drives a curve. I. e., the hitching angle is a measure of the deflection between the vehicle 8 and the towable implement 5. The direction into which the vehicle 8 deflects in respect of the towable implement 5 is defined as pivoting direction. As exemplarily illustrated in FIG. 5A, the vehicle 8 has a pivoting direction in the right direction in respect of the towable implement 5a. For example, the sensor 23 may be a camera to determine the hitching angle between the drawbar 26 of the towable implement 5 and the coupling 4 of the vehicle 8 as well as the pivoting direction. Alternatively, other types of sensors may be used.

[0054] The vehicle 8 also comprises a sensor 24 for determining the steering angle of the front wheel 28 and a sensor 25 for determining the steering angle of the right front wheel 28. Sensor 24 may also detect the steering direction of the left front wheel 28 and sensor 25 may also detect the steering direction of the right front wheel 28. The sensor values determined by the sensors 24 and 25 are transmitted to the control unit 9.

[0055] The vehicle 8 also comprises a left sensor 2 configured to determine a distance between the vehicle 8 and the towable implement 5 at a left corner of the vehicle 8 as well as a right sensor 6 configured to determine a distance between the vehicle 8 and the towable implement 5 at a right corner of the vehicle 8. Thus, the sensor 2 can determine a pivoting direction of the vehicle 8 to the left direction and the sensor 6 can determine a pivoting direction of the vehicle 8 to the right direction analogously to the sensor 23 for determining the hitching angle . The sensor values determined by the sensors 2 and 6 are transmitted to the control unit 9. Consequently, the control unit 9 can determine for each hitching angle a corresponding distance value and convert one value to the other.

[0056] The sensors 2 and 6 may be distance sensors such as an ultrasonic sensor or a radar sensor. But alternative types of sensors are also possible. The sensor 2 and 6 may be attached to a part of the vehicle 8 behind the rear wheels 30, for example at a fender of the vehicle 8.

[0057] All sensors 2, 6, 23, 24 and 25 may be part of a sensor arrangement 14.

[0058] The vehicle 8 also comprises a display 13 connected with the control unit 9. The display 13 is configured to show any parameters, sensor values or settings. The display 13 may be a touch sensitive display so that the operator of the vehicle 8 may input any commands or define any parameters such as a threshold value for any one of the sensor values.

[0059] FIG. 2 shows a very simplified block diagram of a vehicle 8. The vehicle 8 comprises the control unit 9 as shown in FIG. 6, the sensor arrangement 14 and the operator control 10. An exemplaric embodiment of an operator control 10 is shown in FIG. 3 in more detail. The control unit 9 is configured to receive signals from the sensor arrangement 14 and from the operator control 10.

[0060] The sensor arrangement 14 may also comprise a position determination unit providing position and time signals for determining an absolute position of the vehicle 8 at a specific point of time. The position determination unit may comprise an inertial measurement unit (IMU) and/or a global navigation satellite system (GNSS) receiver. The IMU may provide additional orientation information for improving the accuracy of the global pose estimates. The IMU could provide additional information about the orientation and movement of the vehicle 8 for improving the accuracy of the position estimation and the reference points of the GNSS receiver.

[0061] The operator control 10 is configured to provide a force F as a haptic feedback. For example, the force F may be a dynamic force such as a vibration or a static force. The static force may be a resistance against a movement of the operator control 10 in a specific direction. The force F can be controlled by the control unit 9, for example increased or decreased. The higher the force F is increased, the more manual force is needed to operate the operator control 10. The force F can be increased up to a force level that prevents a manual operation of the operator control 10. The force F may be controlled independently for each possible movement direction of the operator control 10. I. e., the force F may be higher when the operator control 10 is operated in one direction and may be lower when the operator control 10 is operated in another direction.

[0062] FIG. 3 shows exemplarily a steering lever 11 as one of the possible embodiments of an operator control 10. The steering lever 11 is manually moveable out of a neutral position .sub.N to a left direction .sub.L up to a maximum left deflection .sub.max,L or to a right direction .sub.R up to a maximum right deflection .sub.max, R for demanding a corresponding adjustment of the steering angle of the vehicle 8. The control unit 9 receives the angle of operation of the steering lever 11 from the operator control 10 and interprets the deflection as demand for adjusting the steering angle of the front wheels 28 accordingly.

[0063] In the housing of the operator control 10, a feedback actuator is integrated for providing a haptic feedback to the steering lever 11. The feedback actuator is controlled by the control unit 9. For example, the control unit 9 may control the feedback actuator to vibrate the steering lever 11. Moreover, the control unit 9 may control the feedback actuator to generate a force F against a manual movement of the steering lever 11 in any one of the movement directions, for example against a movement in the right direction .sub.R. The operator of the steering lever 11 feels the force F as a resistance against a movement of the steering lever 11 in the corresponding direction. The more the steering lever 11 is moved towards a maximum deflection .sub.max,L, .sub.max,R, the more the force F may be increased. The force F may be increased to a force level preventing a further manual operation of the steering lever 11 to avoid that the steering lever 11 will be deflected to the maximum deflection. Thus, maximum movement of the steering lever 11 in a movement direction can be limited, for example to 75% of the maximum deflection. Moreover, maximum movement of the steering lever 11 can be limited before the steering angle increases up to a value causing a collision between the vehicle 8 and the towable implement 5.

[0064] FIG. 4 shows the vehicle 8 and the towable implement 5, both forming a vehicle-implement combination 1. The steering angle is in a neutral position for driving the vehicle 8 in a straight direction. The towable implement 5 is hitched to the coupling 4 of the vehicle 8. The vehicle 8 and the towable implement 5 are in a straight alignment so that the hitching angle is zero or neutral. In this configuration, the current distance between the vehicle 8 and the towable implement 5 has a maximum distance d.sub.max.

[0065] Sensor 2 has a sensing range 3 and the sensor 6 has a sensing range 7 for determining the current distance d.sub.C between the vehicle 8 and the towable implement 5. According to the configuration as shown in FIG. 4, the current distance d.sub.C corresponds to the maximum distance d.sub.max. A distance limit d.sub.lim is predefined (e. g. by the operator) and stored in a memory 21 of the control unit 9 (see FIG. 6). The distance limit d.sub.lim may correspond to a minimum distance that should not be violated to avoid a collision between the vehicle 8 and the towable implement 5. For an effective collision avoidance for example, maximum movement of the steering lever 11 will be limited when the current distance d.sub.C has reached the distance limit d.sub.lim and/or when the hitching angle increases up to a value that corresponds to the distance limit d.sub.lim.

[0066] FIG. 5A and FIG. 5B illustrate the impact of the dimensions of the towable implement 5 on the correlation of the hitching angle with the distance between the vehicle 8 and the towable implement 5. As can be seen, the drawbar 26a of the towable implement 5a (FIG. 5A) is shorter than the drawbar 26b of the towable implement 5b (FIG. 5B). Due to these different dimensions of the towable implements 5a, 5b, the vehicle 8 can be deflected in respect of the towable implement 5b more than in respect of the towable implement 5a in adherence of the same distance d.sub.T between the vehicle 8 and the towable implement 5 wherein the greater deflection in case of the towable implement 5b results in a greater hitching angle .sub.b than the hitching angle .sub.a in case of the towable implement 5a.

[0067] According to the greater hitching angle .sub.b in case of the towable implement 5b, the vehicle 8 can drive a curve of a smaller radius without colliding with the towable implement in contrast to the towable implement 5a. I. e. in contrast to the towable implement 5a with the shorter drawbar 26a, a smaller minimum radius of a curve excluding a collision between the vehicle 8 and the towable implement 5 can be achieved by the vehicle-implement combination 1 with the towable implement 5b having the longer drawbar 26b. Hence, a steering threshold angle .sub.T corresponding with a minimum radius excluding a collision between the towable implement 5 is greater in case of the vehicle-implement combination 1 with the towable implement 5b having the longer drawbar 26b (see .sub.Tb) than in case of the vehicle-implement combination 1 with the towable implement 5a having the shorter drawbar 26a (see .sub.Ta).

[0068] Consequently, in dependence of the dimension of each vehicle-implement combination 1, corresponding threshold values for the hitching angle and the steering angle can be determined in respect of a distance threshold value d.sub.T. For example, the vehicle 8 may turn from a straight driving direction to a right direction and drive a curve. The vehicle 8 may continuously increase the steering angle to drive curves of smaller radius until one of the sensors 2 or 6 detects that the distance threshold d.sub.T between the vehicle 8 and the towable implement 5 has been reached. In case of the vehicle-implement combination 1 with the towable implement 5a having the shorter drawbar 26a, the hitching angle .sub.a may be determined as threshold value for the hitching angle and the steering angle .sub.Ta may be determined as steering threshold angle (see FIG. 5A). In case of the vehicle-implement combination 1 with the towable implement 5b having the longer drawbar 26b, the hitching angle .sub.b may be determined as threshold value for the hitching angle and the steering angle .sub.Tb may be determined as steering threshold angle (see FIG. 5B). As mentioned above, the hitching angle can be determined by the sensor 23 and the steering angles by the sensors 24 and 25 (see also FIG. 1).

[0069] FIG. 6 shows the control unit 9 comprising an interface 19, a controller 20 and a memory 21. The control unit 9 may receive and send signals or data via the interface 19. The interface 19 may be a wireless interface or a connector. The controller 20 may store the data or signals received by the control unit 9 in the memory 21. The memory 21 may contain additional data or executable computer program products, for example in terms of a computer-implemented method, that may be retrieved, processed or executed by the controller 20. Data or signals resulting from the processing of data or signals or from the execution of a computer program product may be stored to the memory 21 or sent to the interface 19 by the controller 20.

[0070] FIG. 8 shows a flow chart of a method for providing a force F as haptic feedback for an operator control 10. The method may be at least partly a computer-implemented method stored as a computer program product in the memory 21 of the control unit 9. The control unit 9 is configured to carry out the method. Computer-implemented parts of the method may be executed by the controller 20 of the control unit 9. The method is described by way of example of several steps without any restriction in respect of that steps. I. e. the number or the order of steps may be adapted, for example single steps may be excluded and/or added and executed earlier or later than described. The method starts with step S100 and proceeds to step S101.

[0071] At step S101, the control unit 9 receives one or more sensor signals from the sensor arrangement 14, for example the angle of operation of the operator control 10, the steering angle , the hitching angle and/or a current distance value d.sub.C. As also disclosed above, the control unit 9 can convert the current distance value d.sub.C to a corresponding hitching angle and vice versa. Hence, the hitching angle is also a value indicative of the current distance d.sub.C between the vehicle 8 and the towable implement 5.

[0072] By way of example, an operator may control now the vehicle-implement combination 1 as follows. The vehicle-implement combination 1 may be in a straight configuration as shown in FIG. 4 and the operator may start driving in a straight forward direction. Then, the control unit 9 receives the distance d.sub.max as current distance value d.sub.C, a neutral position .sub.N from the operator control 10, a neutral hitching value as hitching angle and a neutral steering value as steering angle . When operator begins to operate the operator control 10 out of the neutral position .sub.N to a right direction .sub.R for steering the front wheels 28 of the vehicle 8 to the right direction .sub.R, then the vehicle 8 will drive a curve to the right direction. The pivoting direction of the vehicle 8 in respect of the towable implement 5 will also correspond to the right direction while the hitching angle increases as exemplarily illustrated in FIG. 5A. Hence, the control unit 9 receives the distance d.sub.T as current distance value d.sub.C, the position from the operator control 10, the hitching value .sub.a as hitching angle and the steering value .sub.Ta as steering angle . The operator may continue to move the operator control 10 in the right direction .sub.R for increasing the steering angle and driving a curve of a smaller radius as exemplarily illustrated in FIG. 7A. Hence, the hitching angle is still increasing and the control unit 9 receives the current distance value d.sub.C, the hitching angle and the steering angle as shown in FIG. 7A, as well as the position from the operator control 10. Thereafter, the operator may operate the operator control 10 in the opposite direction, here the left direction .sub.L, to steer the front wheels 28 of the vehicle 8 to the left direction .sub.L accordingly, as illustrated in FIG. 7B. Again, the control unit 9 receives the current distance value d.sub.C, the hitching angle y and the steering angle as shown in FIG. 7B, as well as the position from the operator control 10.

[0073] As mentioned above, the sensor arrangement 14 comprises sensors for detecting the corresponding values as the sensors 24 and 25 for detecting the steering angle , the sensors 2 and 6 for detecting the distance between the vehicle 8 and the towable implement 5 and sensor 23 for detecting the hitching angle , and for sending corresponding sensor signals to the control unit 9. The control unit 9 can also receive the position from the operator control 10 and convert the position to a corresponding steering angle . Hence, the position is also a value indicative of the steering angle .

[0074] The method proceeds to step S102 and the control unit 9 determines the pivoting direction of the vehicle 8 in respect of the towable implement 5. The control unit 9 determines also the steering direction of the front wheels 28. The control unit 9 may receive sensor signals representing the pivoting direction and/or the steering direction directly from the sensor arrangement 14 or the control unit 9 may calculate the values based on the received hitching angle and steering angle . In case of a straight configuration of the vehicle-implement combination 1 as illustrated in FIG. 4, the control unit 9 determines a neutral pivoting direction and a neutral steering direction. In case of the configurations shown in FIG. 5A and FIG. 7A, the control units 9 determines that the pivoting direction and the steering direction correspond both with the right direction. In case of the configuration shown in FIG. 7B, the control unit 9 determines that the pivoting direction corresponds still with the right direction but that the steering direction corresponds with the left direction.

[0075] The method proceeds to step S103 and the control unit 9 receives a value indicative of the driving direction of the vehicle 8. The driving direction can be forward or rearward and may be determined by the control unit 9 based on the signals received from the position determination unit. Moreover, the driving direction may be determined by the control unit 9 based on signals provided by wheel speed sensors of the vehicle 8.

[0076] The method proceeds to step S104 and the control unit 9 determines a distance threshold value d.sub.T. The distance threshold value d.sub.T can be stored in the memory 21 of the control unit 9 and read out by the controller 20. The operator of the vehicle 8 may define the distance threshold value d.sub.T and use the touch sensitive display 13 to enter and save the distance threshold value d.sub.T in the memory 21.

[0077] The method may proceed to an optional step S105. Alternatively, the method may directly proceed to step S106. At step S105, the control unit 9 may optionally check whether the value indicative of the current distance value d.sub.C violates the distance threshold value dr. The value indicative of the current distance value d.sub.C may be a distance value or a value derived from any other appropriate value such as the hitching angle. The distance threshold value d.sub.T is violated if the value indicative of the current distance d.sub.C between the vehicle 8 and the towable implement 5 is smaller than the distance threshold value d.sub.T as can be seen in FIG. 7A and FIG. 7B. In case of a violation of the distance threshold value d.sub.T, the method proceeds to step S112. Otherwise, the method steps to step S106.

[0078] At step S106, the control unit 9 determines a steering threshold angle .sub.Ta, .sub.Tb in relation to the distance threshold value dr. I. e., the control unit 9 determines a steering angle value as steering threshold angle at which the vehicle 8 deflects (or pivots) in respect of the towable implement 5 until the distance between the vehicle 8 and the towable implement 5 corresponds with the distance threshold value d.sub.T. As can be seen in a comparison of FIG. 5A and FIG. 5B, the steering threshold angle .sub.Ta, .sub.Tb depends on the dimensions of the towable implement 5 such as the length of the drawbar 26. The distance d.sub.T between the vehicle 8 and the towable implement 5 are the same for the towable implement 5a with the shorter drawbar 26a (FIG. 5A) and the towable implement 5b with the longer drawbar 26b (FIG. 5B). But the towable implement 5b with the longer drawbar 26b allows a greater hitching angle .sub.b when the distance threshold value d.sub.T has been reached (see FIG. 5B) wherein the greater hitching angle .sub.b results in a greater steering threshold angle .sub.Tb.

[0079] The control unit 9 may determine the steering threshold angle .sub.Ta, .sub.Tb when the vehicle 8 continuously increases the steering angle to drive curves of smaller radius until one of the sensors 2 or 6 detects that the distance threshold d.sub.T between the vehicle 8 and the towable implement 5 has been reached. At this moment, the control unit 9 receives the value of the current steering angle from the sensor 24, 25 and stores this value as steering threshold angle .sub.Ta, .sub.Tb in the memory 21. The control unit 9 may automatically repeat step S105 if an exchange of the towable implement 5 has been detected.

[0080] The method proceeds to step S107 and the control unit 9 checks whether the value indicative of the steering angle violates the steering threshold angle .sub.Ta, .sub.Tb. The value indicative of the steering angle may be a steering angle or a value derived from any other appropriate value such as the position of the operator control 10. The steering threshold angle .sub.Ta, .sub.Tb is violated if the value indicative of the steering angle exceeds the steering threshold angle, as for example steering angle shown in FIG. 7A. In case of a violation of the steering threshold angle .sub.Ta, .sub.Tb, the method steps to step S109. Otherwise, the method proceeds to step S108.

[0081] At step S108, the control unit 9 anticipates no potential collision between the vehicle 8 and the towable implement 5. In response to the detected absence of a potential collision, the method proceeds to step S116.

[0082] At step S109, the control unit 9 checks whether the pivoting direction and the steering direction have the same direction. As can be seen in FIG. 7A, the vehicle 8 is deflected in respect of the towable implement 5 in the right direction. The front wheels 28 are also turned to the right direction. Hence, the pivoting direction and the steering direction have the same direction. In contrast, FIG. 7B shows the vehicle-implement combination 1 wherein the pivoting direction and the steering direction are different. The pivoting direction corresponds to the right direction since the vehicle 8 is deflected to the right direction in respect of the towable implement 5. But the steering direction corresponds with the left direction since the front wheels 28 are turned to the left direction. If the pivoting direction and the steering direction have the same direction, the method proceeds with step S110. Otherwise, the method proceeds to S111.

[0083] At step S110, the control unit 9 checks whether the driving direction of the vehicle 8 is forward. If so, the method proceeds with step S112. If not, the method proceeds with step S108.

[0084] At step S111, the control unit 9 checks whether the driving direction of the vehicle 8 is rearward. If so, the method proceeds with step S112. If not, the method proceeds with step S108.

[0085] At step S112, the control unit 9 anticipates a potential collision between the vehicle 8 and the towable implement 5. The potential collision has been detected based on a first set of conditions that the steering angle violates the steering threshold angle .sub.Ta, .sub.Tb (see step S107), the pivoting direction and the steering direction have the same direction (see step S109) and the driving direction is forward (see step S110) or based on a second set of conditions that the steering angle violates the steering threshold angle .sub.Ta, .sub.Tb (see step S107), the pivoting direction and the steering direction have different directions (see step S109) and the driving direction is rearward (see step S111). When the vehicle 8 of the vehicle-implement combination 1 shown in FIG. 7A is driving forward, the first set of conditions would be fulfilled. The pivoting direction and the steering direction have the same direction. The steering angle is greater than the steering threshold angle .sub.Ta shown in FIG. 5A so that the hitching angle will increase when the vehicle 8 is driving forward. Consequently, the current distance d.sub.C will still decrease and the vehicle 8 may collide with the towable implement 5 if the situation does not change. The situation would change, if the vehicle 8 would drive rearward, for example. Then, the hitching angle would decrease and the current distance d.sub.C would increase. When the vehicle 8 of the vehicle-implement combination 1 shown in FIG. 7B is driving rearward, the second set of conditions would be fulfilled. The pivoting direction and the steering direction have different directions. The steering angle is greater than the steering threshold angle so that the hitching angle will increase when the vehicle 8 is driving rearward. Consequently, the current distance d.sub.C will still decrease and the vehicle 8 may collide with the towable implement 5 if the situation does not change. The situation would change, if the vehicle 8 would drive forward, for example. Then, the hitching angle would decrease and the current distance d.sub.C would increase. In response to the detected potential collision, the method proceeds to step S113.

[0086] At step S113, the control unit 9 checks whether the operator control 10 is operated in a direction .sub.R, .sub.L to reduce the steering angle below the steering threshold angle .sub.Ta, .sub.Tb. If so, the method proceeds to step S115. Otherwise, the method proceeds to step S114. For example, in case of a fulfillment of the first set of conditions as explained for step S112, a potential collision could be avoided if the operator control 10 would be controlled in a left direction to reduce the steering angle below the steering threshold angle .sub.Ta (see FIG. 7A with vehicle 8 moving forward). Analogously, in case of a fulfillment of the second set of conditions as explained for step S112, a potential collision could be avoided if the operator control 10 would be controlled in a right direction to reduce the steering angle below the steering threshold angle (see FIG. 7B with vehicle 8 moving rearward). I. e., the operator control 10 may be operated in a direction for increasing the steering angle over the steering threshold angle and in another direction for decreasing the steering angle below the steering threshold angle.

[0087] At step S114, the control unit 9 controls the feedback actuator of the operator control 10 to increase the force F as haptic feedback in response to a manual operation of the operator control 10 in a direction controversially to reduce the steering angle below the steering threshold angle .sub.Ta. So, the operator feels the haptic feedback as a resistance against an operation of the operator control 10. The force F may increase the more the operator control 10 is operated in a direction a that may cause a violation of the steering threshold angle .sub.Ta, .sub.Tb. Optionally, the force F may be increased to a force level that prevents a manual operation of the operator control 10 to avoid a steering angle that may cause a collision between the vehicle 8 and the towable implement 5. For instance, a movement of the operator control 10 to increase the steering angle may be blocked when the current distance dc has reached the distance limit d.sub.lim (see FIG. 4).

[0088] At step S115, the control unit 9 controls the feedback actuator of the operator control 10 to reduce the force F as haptic feedback in response to a manual operation of the operator control 10 in a direction to reduce the steering angle below the steering threshold angle .sub.Ta. The force F may be fully reduced or removed so that the operator may not feel any haptic feedback provided by the operator control 10.

[0089] At step S116, the control unit 9 controls the feedback actuator of the operator control 10 to decrease any force F providing a haptic feedback. The force F may be completely removed so that no haptic feedback may induced by the feedback actuator. I. e., the operator can operate the operator control 10 without recognizing any resistance against an operation of the operator control 10.

[0090] Hence, the control unit 9 is configured to determine whether an operation of the operator control 10 in the one or the other direction may increase the probability of a collision between the vehicle 8 and the towable implement 5 and to increase the force F as haptic feedback against an operation in the direction that increases the probability of a collision whereas operations of the operator control 10 without increasing the probability of a collision may be free of any force feedback.

[0091] After steps S114, S115 and S116, the method proceeds to step S117 and ends. The method may be repeated again and start with step S100.

[0092] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.

LISTING OF DRAWING ELEMENTS

[0093] 1 vehicle-implement combination 26a drawbar [0094] 2 sensor 26b drawbar [0095] 3 sensing range 28 front wheel [0096] 4 coupling 30 rear wheel [0097] 5 towable implement [0098] 5a towable implement [0099] 5b towable implement [0100] 6 sensor [0101] 7 sensing range [0102] 8 vehicle [0103] 9 control unit [0104] 10 operator control [0105] 11 steering lever [0106] 12 steering wheel [0107] 13 display [0108] 14 sensor arrangement [0109] 19 interface [0110] 20 controller [0111] 21 memory [0112] 23 sensor [0113] 24 sensor [0114] 25 sensor [0115] 26 drawbar