Method and device for detecting contact of hands with a steering wheel of a vehicle

Abstract

The invention relates to a method for detecting contact of hands with a steering wheel (51) of a vehicle, wherein a test signal (14) is applied to the steering wheel (51) by means of an actuator (2), wherein a reaction (9) on the steering wheel (51) to the test signal (14) is detected by means of a sensor (3), and wherein a decision (6) is made, on the basis of the detected reaction (9), as to whether at least one hand of the driver is in contact with the steering wheel (51) or not, wherein the test signal (14) is applied according to a predefined torque curve (5), and wherein the torque curve (5) initially rises rapidly to a predefined minimum torque (16) which corresponds to a minimum friction (12) of a steering system (50) of the vehicle. The invention also relates to a device (1) for detecting contact of hands with a steering wheel (51) of a vehicle.

Description

[0001] Description

[0002] Method and device for detecting contact of hands with a steering wheel of a vehicle

[0003] The invention relates to a method and a device for detecting contact of hands with a steering wheel of a vehicle.

[0004] Modern vehicles use sensors to monitor driver activity. For example, a capacitive sensor on the vehicle's steering wheel can be used to determine whether or not the driver has at least one hand on the steering wheel (also known as hands-on detection). The capacitively recorded sensor data can be used to determine a multi-stage status (e.g., no contact, lightly gripped left / right, strong gripped on both sides, etc.), which is then transmitted to support functions such as a longitudinal and / or lateral guidance assistance system. For example, such a status can be fed into an adaptive cruise control (ACC) system as an input. If contact between at least one hand and the steering wheel is detected, a pull-off procedure to follow a vehicle in front is activated, for example.Driver observation cameras are also known, which can detect driver activity.

[0005] In addition, there are methods that detect driver activity, particularly with regard to hands-on detection, using artificial intelligence methods or rule-based approaches. For example, an artificial intelligence method, in particular an artificial neural network, can be trained to perform hands-on detection based on a detected torque, a detected steering angle and / or changes in these variables. The rule-based approach, on the other hand, passively evaluates steering signals (e.g. steering torque, steering speed and / or steering angle) against threshold values ​​and / or signal curves or works actively with torque application, in which a test signal is applied to the steering wheel by means of an actuator. This test signal is intended to induce a counter-torque from hands arranged on the steering wheel, which can be detected by a sensor.As soon as such a counter-torque is detected, it is assumed that at least one hand is on the steering wheel. Such a method is known, for example, from DE 102013 209459 A1. The invention is based on the object of improving a method and a device for detecting contact between hands and a steering wheel of a vehicle.

[0006] The object is achieved according to the invention by a method having the features of patent claim 1 and a device having the features of patent claim 10. Advantageous embodiments of the invention emerge from the subclaims.

[0007] In particular, a method for detecting contact of hands with a steering wheel of a vehicle is provided, wherein a test signal is impressed on the steering wheel by means of an actuator, wherein a reaction at the steering wheel to the test signal is detected by means of a sensor, and wherein, based on the detected reaction, a decision is made as to whether or not at least one hand of the driver is in contact with the steering wheel, wherein the impression of the test signal takes place according to a predetermined torque curve, and wherein the torque curve increases abruptly at an beginning to a predetermined minimum torque which corresponds to a minimum friction of a steering system of the vehicle.

[0008] Furthermore, in particular, a device for detecting contact of hands with a steering wheel of a vehicle is provided, comprising an actuator configured to apply a test signal to the steering wheel, a sensor configured to detect a reaction to the test signal on the steering wheel, and a control unit, wherein the control unit is configured to initiate the application of the test signal, to evaluate a detected reaction, and, based on the detected reaction, to make a decision as to whether or not at least one of the driver's hands is in contact with the steering wheel, wherein the application of the test signal occurs according to a predetermined torque curve, and wherein the torque curve increases abruptly at an initial point to a predetermined minimum torque, which corresponds to a minimum friction of a steering system of the vehicle.

[0009] The method and device make it possible to overcome system-related friction in the steering system in the shortest possible time, so that the detection of a counter-reaction to an imposed test signal can take place almost instantaneously, without a driver with their hands on the steering wheel perceiving the test signal as disturbing. This is achieved by only jumping to the specified minimum torque, but subsequently increasing the torque more slowly. This is based on the idea that the driver cannot perceive the test signal until the minimum friction is overcome, meaning that only after the minimum friction has been overcome must care be taken to ensure that the test signal does not become disturbing to the driver. Furthermore, every steering system has its own unique friction.However, for steering systems installed in vehicles, it is possible to define a tolerance band that encompasses the minimum and maximum possible friction for a large number of similar steering systems. Based on this, the minimum possible friction of the tolerance band is specified as the minimum friction for the method and device. This makes it possible to immediately overcome this system-related minimum friction by a sudden increase when the test signal is applied, so that a system reaction can occur more quickly and a reaction on the steering wheel caused by hands positioned on the steering wheel can be detected as quickly as possible.

[0010] An advantage of the method and device is that the reaction (i.e., in particular, a counter-torque on the steering wheel caused by at least one hand) can be detected more quickly. A decision as to whether or not at least one of the driver's hands is in contact with the steering wheel can thus also be made more quickly. Consequently, a corresponding signal can also be provided to a driver assistance function more quickly, thus increasing driving comfort.

[0011] A further advantage is that the method and device eliminate the need for a capacitive sensor on the steering wheel, for example, since reliable hands-on detection can be achieved without it. This saves effort, costs, and installation space.

[0012] The actuator is, in particular, an actuator of the steering system, for example, an electric motor of the steering system. The sensor is, in particular, a sensor of the steering system, for example, a torque sensor and / or a steering angle sensor on a steering assistance unit. In principle, multiple actuators and / or multiple sensors can also be provided.

[0013] Parts of the device, in particular the control unit, can be designed individually or collectively as a combination of hardware and software, for example as program code that is executed on a microcontroller or microprocessor. However, it can also be provided that parts are designed individually or collectively as an application-specific integrated circuit (ASIC) and / or field-programmable gate array (FPGA). In one embodiment, it is provided that the method is only carried out in the case when it cannot otherwise be reliably determined whether at least one hand is arranged on the steering wheel. This allows the method to be started as required. In particular, this makes it possible to dispense with the application of the test signal if another sensor (e.g. capacitive sensor or driver camera) or another method (e.g.using artificial intelligence and / or a rule-based approach) it has been reliably determined that at least one hand is in contact with the steering wheel.

[0014] In one embodiment, the torque curve increases with a predetermined first gradient to a predetermined value after reaching the minimum torque. This ensures that the test signal on the steering wheel is not perceived as disturbing by a driver with their hands on the steering wheel, yet a reaction can be elicited as quickly as possible. The first gradient can be determined, for example, using empirical test series.

[0015] In one embodiment, the torque curve drops after a predetermined period of time with a second gradient, at least down to the predetermined minimum torque. This allows the applied test signal to be slowly returned to zero. This return can also be designed in such a way that it is not perceived as disturbing by the driver. The second gradient can be determined, for example, using empirical test series. The second gradient can also correspond to the first gradient with the opposite sign.

[0016] In one embodiment, the torque curve, when a counter-torque is detected, drops with a third gradient at least down to the specified minimum torque. This allows the case in which no reaction is evoked and detected and the case in which a counter-torque is detected as a reaction to be treated differently. Particularly in the case in which a counter-torque is detected, care must be taken to design the (third) gradient in such a way that the torque change on the steering wheel is not perceived as disturbing.

[0017] In a further embodiment, it is provided that the third gradient is smaller in magnitude than the second gradient. This allows the test signal to be returned to zero more slowly when a counter-torque is detected than in the case where no counter-torque was detected. In one embodiment, it is provided that, based on the decision made, an enable signal for at least one assistance system is generated and provided, with enablement occurring when at least one of the driver's hands is in contact with the steering wheel. This allows the enablement of assistance systems to be controlled.

[0018] In particular, in one embodiment it can be provided that the release signal enables a (re-)start process for an adaptive cruise control (ACC).

[0019] In one embodiment, the method is only carried out if at least one assistance system transmits a readiness signal. This allows the method to be started as needed. For example, an adaptive cruise control (ACC) system can transmit such a readiness signal if a vehicle in front starts moving again from a standstill and following would be possible. In a further development, it can also be provided that the method is only started once the readiness signal has been transmitted and, in addition, it cannot be reliably determined otherwise whether at least one hand is on the steering wheel.

[0020] Further features of the device design will become apparent from the description of embodiments of the method. The advantages of the device are the same as those of the embodiments of the method.

[0021] The invention will be explained in more detail below using preferred embodiments with reference to the figures. Herein:

[0022] Fig. 1 is a schematic representation of an embodiment of the device for detecting contact of hands with a steering wheel of a vehicle;

[0023] Fig. 2a is a schematic diagram illustrating a conventional test signal over time (state of the art);

[0024] Fig. 2b is a schematic representation to illustrate a test signal according to the invention over time;

[0025] Fig. 3 is a schematic representation illustrating another embodiment of the method and device. Fig. 1 shows a schematic representation of an embodiment of the device 1 for detecting contact between hands and a steering wheel 51 of a vehicle. The device 1 is, in particular, part of a steering system 50 of the vehicle. The steering system 50 comprises, in addition to the steering wheel 51, a steering rod 52, a steering assistance unit 53, and a rack 54. The device 1 is, in particular, configured to carry out the method described in this disclosure, wherein the method is explained in more detail with reference to the device 1.

[0026] The device 1 comprises an actuator 2, a sensor 3, and a control unit 4. The actuator 2 can be an actuator of the steering assistance unit 53, for example, an electric motor. The actuator 2 is configured to apply a test signal 14 to the steering wheel 51. The test signal 14 is, in particular, a torque that is applied to the steering wheel 51. The sensor 3 is configured to detect a reaction 9 to the test signal 14 at the steering wheel 51. The sensor 3 can, for example, be a torque sensor on a steering assistance unit 53 of the steering system 50.

[0027] The control unit 4 comprises, for example, a computing device 4-1, for example a microcontroller or a microprocessor, and a memory 4-2. The control unit 4 is configured to initiate the application of the test signal 14. To this end, the control unit 4 controls the actuator 2 accordingly. Furthermore, the control unit 4 is configured to evaluate a detected reaction 9 and, based on the detected reaction 9, to make a decision 6 as to whether or not at least one of the driver's hands is in contact with the steering wheel 51.

[0028] The test signal 14 is applied according to a predetermined torque curve 5, which is stored, for example, in a memory 4-2 of the control unit 4. The torque curve 5 is implemented by the actuator 2. The torque curve 5 initially increases abruptly to a predetermined minimum torque, which corresponds to a minimum friction of a steering system 50 of the vehicle.

[0029] Fig. 2a shows a schematic representation illustrating a conventional test signal 10 over time (time axis t), as used in the prior art. The test signal 10 corresponds to a torque curve 5. This conventional test signal 10 comprises a ramp in which an applied torque 11 is increased linearly from zero to a predetermined value, held there for a predetermined period of time, and then linearly reduced back to zero. In this process, a system-related minimum friction 12 must be overcome. A system response 13 of the steering system is delayed compared to the conventional test signal 10.

[0030] Fig. 2b shows a schematic representation to illustrate a test signal 14 according to the invention over time (time axis t). The test signal 14 corresponds to a torque curve 5. The test signal 14 according to the invention has a jump 15 at the beginning, which jumps to a predetermined minimum torque 16, which corresponds to a minimum friction 12 of the vehicle's steering system. Furthermore, for clarity, a maximum friction 17 of the steering system and an average friction value 18 are also shown. These values ​​are determined statistically and relate in particular to a large number of installed steering systems of the same design.

[0031] Since the conventional test signal 10 is also shown in Fig. 2b alongside the test signal 14 according to the invention, the advantage of faster detection of a steering wheel reaction can also be seen. Thus, the system response 19 when the test signal 14 according to the invention is applied occurs earlier with a time Δt than the system response 13 when the conventional test signal 10 is applied, since the minimum friction 12 is overcome more quickly by the jump 15.

[0032] It can be provided that the method is only carried out in the case when it cannot otherwise be reliably determined whether at least one hand is arranged on the steering wheel 51. For this purpose, the control unit 4 receives, for example, a signal 58 (Fig. 1) to start the method, or generates such a signal 58 itself if, for example, an artificial intelligence method or a rule-based approach, which can also be executed on the control unit 4, cannot reliably determine, based on acquired sensor data from the sensor 3 (and / or other sensors), whether or not a hand is in contact with the steering wheel 51.

[0033] It can be provided that the torque curve 5 increases after reaching the minimum torque 16 with a predetermined first gradient 20 (Fig. 2b) to a predetermined (maximum) value 21.

[0034] It can be provided that the torque curve 5 drops after a predetermined period of time with a second gradient 22 (Fig. 2b) at least down to the predetermined minimum torque 16. The first gradient 20, the predetermined value 21, and the second gradient 22 can be determined, for example, based on empirical test series, in which it is determined, in particular, at which gradients 20, 22 a change in the torque on the steering wheel is not yet perceived as disturbing.

[0035] Fig. 3 shows a schematic representation to illustrate a further embodiment of the method and device. In this embodiment, it is provided that the torque curve 5 drops with a third gradient 24 at least down to the predetermined minimum torque 16 upon detection of a counter-torque 23. In principle, the course of the test signal 14 according to the invention or of the torque curve 5 in this embodiment is otherwise the same as that shown in Fig. 2b. The same reference numerals denote the same terms and features. For clarification, two different curves with counter-torques 23 are shown by way of example. These can arise when the driver has one or both hands on the steering wheel. The counter-torque 23 is detected in particular when a tolerance range 25 around the system response 19 is exceeded (or undershot). This is shown schematically for the times t1 and t2 for the two example curves of the counter-torques 23.After detecting the counter torques 23, the torque curve 5 is then adjusted so that it drops with the third gradient 24 at least down to the specified minimum torque 16, as illustrated by way of example in Fig. 3. The third gradient 24 can have the same value as the second gradient 22.

[0036] It can also be provided that the third gradient 24 is smaller in magnitude than the second gradient 22. This allows the test signal 14 to be reduced even more smoothly.

[0037] It can be provided that, based on the decision 6 made (Fig. 6), an enable signal 7 is generated and provided for at least one assistance system 56, wherein an enable occurs when at least one of the driver's hands is in contact with the steering wheel 51. The enable signal 7 can then be transmitted to the assistance system 56.

[0038] In a further development, it can be provided that the release signal 7 releases a (re-)start process for an adaptive cruise control 57.

[0039] It can be provided that the method is only carried out if at least one assistance system 56 transmits a readiness signal 8. It can also be provided that the signals 8, 58 are logically linked to one another and the method is only carried out if both signals are present.

[0040] The torque curves 5 according to the invention shown are selected merely as examples to illustrate the disclosed method and can in principle also be designed differently, in particular with regard to the gradients 20, 22, 24 and the predetermined value 21.

[0041] List of reference symbols

[0042] device

[0043] Actuator

[0044] sensor

[0045] Control unit -1 Computing device -2 Memory

[0046] Moment curve

[0047] Decision

[0048] Release signal

[0049] Ready signal 0 conventional test signal 1 torque 2 minimum friction 3 system response (conventional test signal) 4 inventive test signal 5 jump 6 minimum torque 7 maximum friction 8 mean value (friction) 9 system response (inventive test signal) 0 first gradient 1 specified (maximum) value 2 second gradient 3 counter torque 4 third gradient 5 tolerance range 0 steering system 1 steering wheel 2 handlebar 3 steering support unit 4 rack 6 assistance system 7 adaptive cruise control (ACC) 58 signal t time t1 , t2 times

Claims

Patent claims 1. Method for detecting contact of hands with a steering wheel (51) of a vehicle, wherein a test signal (14) is impressed on the steering wheel (51) by means of an actuator (2), wherein a reaction (9) at the steering wheel (51) to the test signal (14) is detected by means of a sensor (3), and wherein, based on the detected reaction (9), a decision (6) is made as to whether or not at least one hand of the driver is in contact with the steering wheel (51), wherein the impression of the test signal (14) is carried out according to a predetermined torque curve (5), and wherein the torque curve (5) increases abruptly at an beginning to a predetermined minimum torque (16), which corresponds to a minimum friction (12) of a steering system (50) of the vehicle.

2. Method according to claim 1, characterized in that the method is only carried out in the case when it cannot otherwise be determined with certainty whether at least one hand is arranged on the steering wheel (51).

3. Method according to claim 1 or 2, characterized in that the After reaching the minimum torque (16), the torque curve (5) increases with a predetermined first gradient (20) to a predetermined value (21).

4. Method according to one of the preceding claims, characterized in that the torque curve (5) drops after a predetermined period of time with a second gradient (22) at least to the predetermined minimum torque (16).

5. Method according to one of the preceding claims, characterized in that the torque curve (5) drops with a third gradient (24) at least to the predetermined minimum torque (16) upon detection of a counter-torque (23).

6. Method according to claim 5, characterized in that the third gradient (24) is smaller in magnitude than the second gradient (22).

7. Method according to one of the preceding claims, characterized in that, based on the decision made (6), an enable signal (7) is generated and provided for at least one assistance system (56), wherein an enable signal occurs when at least one hand of the driver is in contact with the steering wheel (51).

8. Method according to claim 7, characterized in that the release signal (7) enables a (re-)starting process for an adaptive cruise control (57).

9. Method according to one of the preceding claims, characterized in that the method is only carried out in the case when at least one assistance system (56) transmits a readiness signal (8).

10. Device (1) for detecting contact of hands with a steering wheel (51) of a vehicle, comprising: an actuator (2) which is designed to impress a test signal (14) on the steering wheel (51), a sensor (3) which is designed to detect a reaction (9) to the Test signal (14) on the steering wheel (51), and a control unit (4), wherein the control unit (4) is designed to initiate the application of the test signal (14), to evaluate a detected reaction (9), and, based on the detected reaction (9), to make a decision (6) as to whether or not at least one hand of the driver is in contact with the steering wheel (51), wherein the application of the test signal (14) is carried out according to a predetermined torque curve (5), and wherein the torque curve (5) increases abruptly at an beginning to a predetermined minimum torque (16), which corresponds to a minimum friction (17) of a steering system (50) of the vehicle.

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