METHOD AND DEVICE FOR HAND DETECTION ON A VEHICLE'S STEERING WHEEL

Description

[0001] The present invention relates to a method and a device for hand detection on a steering wheel of a vehicle according to the independent claims.

[0002] Methods for detecting a hand on a vehicle's steering wheel are generally known in the prior art. For example, US 2010 / 0228417 A1 describes a corresponding method in which a vibration signal is triggered in the steering wheel, and the system determines that the driver is not holding the steering wheel if the vibrations are detected. However, in the worst-case scenario, such hands-on detection can be activated by road surface disturbances even though the driver is not touching the steering wheel (false positive detection). To prevent this, the prior art requires costly additional components, such as a camera to detect the driver and their state, or a capacitive steering wheel.

[0003] A generic method for detecting the operating state of a vehicle's steering wheel is known from DE 10 2014 004 077 A1, wherein at least one hand of the vehicle's driver is positioned on the steering wheel in a first operating state and no hand of the driver is positioned on the steering wheel in a second operating state, and wherein a warning message is issued to the driver when the second operating state is detected. In this process, it is verified, by means of detected signals from at least one inertial sensor arranged on the vehicle and / or by means of detected signals from a steering wheel angle sensor arranged on the vehicle and / or by means of detected signals from wheel speed sensors arranged on the vehicle, whether a detected steering movement was executed in the first operating state or in the second operating state.

[0004] A method for detecting driver inattention is known from DE 10 2011 122 394 A1, wherein the inattention is determined as a function of a detected steering quiescence phase and a subsequent detected steering action. The road surface condition of a roadway traveled on is determined by evaluating the wheel rotation speed of at least one wheel of the vehicle over a predetermined period, whereby the determined steering wheel angle is disregarded if the road surface condition is classified as poor. A method for determining the road surface condition of a roadway by recording and evaluating the wheel rotation speeds of at least one wheel of a vehicle traveling on the roadway is known from DE 10 2013 021 269 A1.

[0005] A method for detecting a lack of driver activity at the steering wheel of a motor vehicle is known from US Patent 2013 / 0173085 A1. A torque exerted by the driver's hand on the steering wheel is repeatedly measured, and if, in several successive measurements, the magnitude of any value of the torque exerted by the hand does not exceed a threshold, a lack of driver activity is inferred. The magnitude of the threshold depends on the surface condition, in particular the degree of unevenness, of the road surface on which the vehicle is being driven. The degree of unevenness of the road surface can be derived from a measured vertical acceleration in the vehicle's wheel suspension or from deceleration and / or acceleration signals from at least one wheel of the vehicle.

[0006] Known from US 2005 / 0125153 A1 is a device for preventing lane deviations in motor vehicles comprising a control unit that detects whether a vehicle is in a certain state in which the vehicle is driving on road surface irregularities that are on or near a lane marking line.

[0007] The present invention is based on the objective of preventing false positive hand detection on a steering wheel in an effective and cost-efficient manner.

[0008] The aforementioned task is solved by a hand detection method on a vehicle's steering wheel, whereby a hand torque sensor is used to determine an initial signal for hand detection. This initial signal is the hand torque measured by the hand torque sensor. Specifically, steering torque-based hands-on detection is performed.

[0009] According to the invention, a second signal relating to the wheel speed of at least one wheel of the vehicle is determined by means of a speed sensor in order to validate the first signal. The second signal is primarily the rotational speed. In particular, the wheel speeds of all wheels of the vehicle are determined to validate the first signal. This validation serves to exclude false positive hands-on detection resulting from road surface disturbances. Specifically, the method includes validating the first signal based on the second signal. Road surface disturbances are primarily caused by irregularities in the road surface, for example, by bridges, joints, or potholes. These affect the wheel speeds. Thus, it is possible to validate the first signal with respect to the hand torque. Costly solutions for preventing false positive hands-on detections can be avoided.In particular, existing sensors in the vehicle are used, so that the false positive error rate can be achieved without additional financial expenditure.

[0010] In particular, the first and second signals are continuously monitored. Preferably, the second signal is analyzed with respect to its frequency and / or its amplitude. According to the invention, the second signal is compared with previously defined threshold values ​​with respect to amplitude and / or frequency. In particular, the amplitude of the second signal is analyzed in previously defined frequency ranges. Specifically, the second signal is spectrally analyzed for this purpose. For example, a first frequency range can be defined in which road surface excitations typically lie. The threshold value can, for example, be 20% above the average amplitude of the second signal.

[0011] According to the invention, if a previously defined threshold is exceeded, a road-induced disturbance of the first signal is detected. In other words, it is determined that the road surface is so uneven that the first signal is subject to disturbance and a false positive hand detection could occur. The road-induced disturbance can be triggered, for example, by road surface irregularities such as potholes.

[0012] When the wheel speeds of all wheels of the vehicle are determined, a second signal is recorded for each wheel. A fault can then be detected if every second signal exceeds a predefined threshold.

[0013] According to the invention, the presence of road-induced disturbance is validated by analyzing the steering angle before further steps are initiated. For this purpose, the vehicle's steering angle is monitored, particularly continuously. If road-induced disturbance is actually present due to road excitation, the steering angle should also change, at least briefly. This indicates that road-induced disturbance is indeed present. In particular, the method can provide for determining the presence of road-induced disturbance only after positive validation using the steering angle, even if a previously defined threshold value for the second signal is exceeded.

[0014] When a road-induced disturbance is detected, a predefined threshold for the first signal can be increased to identify a hands-off situation. The first signal is analyzed, particularly with regard to its amplitude and / or frequency. Specifically, at least one threshold for the first signal is defined beforehand. If the first signal is below this threshold, a hands-off situation is detected; conversely, if the first signal is above the predefined threshold, a hands-on detection occurs. Increasing the threshold makes the hands-on detection more robust with respect to false positives.

[0015] In other words, the system detects that the driver's hands are not on the steering wheel, which in turn can trigger further actions, such as prompting the driver, for example, through acoustic and / or visual signals. Increasing the threshold takes road-induced disturbances into account. Specifically, an increase is only implemented after positive validation of the road-induced disturbance via the steering angle. The previously defined threshold is increased by at least 10%, preferably by at least 20%. The threshold for the first signal is thus dynamically adjusted based on information regarding road-induced disturbances derived from the second signal.

[0016] Furthermore, if a road-induced disturbance is detected, hand recognition via the hand torque sensor can be deactivated. This can mean, for example, that the driver can no longer use certain assistance systems for semi-autonomous or autonomous driving. Again, this can only occur after the presence of a road-induced disturbance has been validated using the steering angle.

[0017] In a further aspect, the invention relates to a device for hand detection on a vehicle's steering wheel, comprising a hand torque sensor for determining a first signal and at least one rotational speed sensor for determining a second signal with respect to at least one wheel speed, wherein the device is primarily configured to carry out one of the aforementioned methods. In particular, the device can have a rotational speed sensor for each wheel of the vehicle. The device can include an evaluation unit for validating the first signal based on the second signal. According to the invention, the device also includes a further sensor for determining a steering angle.

[0018] They show, in purely schematic form: Figure 1 shows a process flow of a method according to the invention; and Figure 2 shows a device according to the invention.

[0019] Figure 1Figure 100 shows a method according to the invention for hand detection on a steering wheel of a vehicle, wherein the method 100 comprises determining 101 a first signal by means of a hand torque sensor. The first signal serves to detect a hands-on or hands-off situation with respect to a steering wheel by determining the hand torque by means of a hand torque sensor.

[0020] Furthermore, a second signal regarding wheel speed is determined by means of a speed sensor 102. The first signal and the second signal are continuously monitored 103. Furthermore, a steering angle can be determined 104, in particular this can be continuously monitored 105.

[0021] The first signal is validated using the second signal 106. This is done in particular by analyzing 107 the second signal with respect to its amplitude and / or frequency. The second signal is compared with a previously defined threshold value with respect to amplitude and / or frequency 108. In particular, previously defined threshold values ​​with respect to amplitude are compared in specific frequency ranges.

[0022] When the threshold value is exceeded, a road-induced disturbance can be detected. The road-induced disturbance can be validated beforehand using the steering angle, as this should be affected by the road-induced disturbance in the same way. If a road-induced disturbance is detected, a previously defined threshold value for the first signal for hand detection can be increased. Furthermore, hand detection can be deactivated using the hand torque sensor.

[0023] In Figure 2 A device 10 according to the invention is shown, comprising a hand torque sensor 11 for determining the first signal and a speed sensor 12 for determining the second signal. Furthermore, the device 10 may include a steering angle sensor 13. The device 10 has an evaluation unit 14, which is configured to validate the first signal based on the second signal. Specifically, the evaluation unit 14 analyzes the second signal and, upon exceeding a threshold value, detects the road-induced disturbance and validates it beforehand using the steering angle. A control unit 15 can then, upon detecting a road-induced disturbance, perform actions such as increasing a previously defined threshold value with respect to the first signal or deactivating hand detection using the hand torque sensor 11. Reference symbol list

[0024] 100 Procedure 101 Determining a first signal using a hand torque sensor 102 Determining a second signal regarding wheel speed using a speed sensor 103 Monitoring the first and second signals 104 Determining a steering angle 105 Monitoring the steering angle 106 Validating the first signal 107 Analyzing the second signal with respect to amplitude and / or frequency 108 Comparing the second signal with at least one previously defined threshold 109 Exceeding the threshold 110 Validating using the steering angle 111 Detecting a road-induced disturbance 112 Increasing a previously defined threshold for the first signal 113 Deactivating hand detection using the hand torque sensor 10 Device 11 Hand torque sensor 12 Speed ​​sensor 13 Steering angle sensor 14 Evaluation unit 15 Control unit

Claims

1. Method (100) for detecting a hand on a steering wheel of a vehicle, a first signal for detecting a hand being determined (101) by means of a hand torque sensor (11), a second signal with regard to a wheel speed of at least one wheel of the vehicle being determined (102) by means of a speed sensor (12) for validating (106) the first signal, the second signal being compared (108) with at least one previously defined threshold with regard to amplitude and / or frequency and, when the previously defined threshold is exceeded (109), the presence of a road-induced disturbance of the first signal being ascertained (111), characterized in that a steering angle of the vehicle is monitored (105), the presence of the road-induced disturbance being validated (110) by an analysis of the steering angle.

2. Method (100) according to claim 1, characterized in that the first signal is validated (106) on the basis of the second signal.

3. Method (100) according to claim 1 or claim 2, characterized in that the first signal and the second signal are continuously monitored (103).

4. Method (100) according to any of the preceding claims, characterized in that the second signal is analyzed (107) with regard to amplitude and / or frequency.

5. Method (100) according to any of claims 1 to 4, characterized in that when the presence of a road-induced disturbance is ascertained, a previously defined threshold relating to the first signal for detecting a hands-off situation is increased (112).

6. Method (100) according to any of claims 1 to 5, characterized in that when the presence of a road-induced disturbance is ascertained, hand detection is deactivated (113) by means of the hand torque sensor.

7. Device (10) for detecting a hand on a steering wheel of a vehicle with a hand torque sensor (11) for determining a first signal, the device (10) having a speed sensor (12) for determining a second signal with regard to a wheel speed of at least one wheel of the vehicle for validating the first signal, the device having an evaluation unit (14) which is configured to compare (108) the second signal with at least one previously defined threshold with regard to amplitude and / or frequency and, when the previously defined threshold is exceeded (109), to ascertain (111) the presence of a road-induced disturbance of the first signal, characterized in that the device (10) has a steering angle sensor (13) for determining a steering angle and the evaluation unit (14) is further configured to validate the road-induced disturbance by means of the steering angle.