Abstract
A control system for a vehicle includes: first electrode and second electrodes; at least one sensor electrode disposed on an vehicle component with a surface accessible to a user, the sensor electrode being adapted to generate an electric field above the surface so that a capacitance of the sensor electrode depends on a position of a body part of a user with respect to the vehicle component; and a control unit connected to the sensor electrode and adapted to: identify at least one gesture, corresponding to a motion of the body part with respect to the vehicle component, based on the capacitance of the sensor electrode; identify a control signal that corresponds to the gesture; and output the control signal. The sensor electrode has a first portion and a second portion wherein the capacitance depends on whether the body part is disposed adjacent the first portion or the second portion.
Claims
1. A control system for a vehicle, comprising: at least one sensor electrode disposed on an vehicle component with a surface accessible to a user, the sensor electrode being adapted to generate an electric field above the surface so that a capacitance of the sensor electrode depends on a position of a body part of a user with respect to the vehicle component, and a control unit connected to the at least one sensor electrode and adapted to: identify at least one gesture, corresponding to a motion of the body part with respect to the vehicle component, based on the capacitance of the at least one sensor electrode, identify a control signal for the vehicle that corresponds to the gesture; and output the control signal, wherein at least one sensor electrode has a first portion and a second portion wherein the capacitance depends on whether the body part is disposed adjacent the first portion or the second portion.
2. The control system according to claim 1, wherein the vehicle component is a steering wheel.
3. The control system according to claim 2, wherein at least one sensor electrode is disposed underneath a cover layer of the vehicle component.
4. The control system according to claim 1, wherein at least one sensor electrode is a conductive foil electrode.
5. The control system according to claim 1, wherein the control unit is adapted to identify a plurality of gestures based on the capacitance of a single sensor electrode.
6. The control system according to claim 1, wherein the control unit is configured to identify at least one tapping gesture.
7. The control system according to claim 1, wherein the control unit is configured to identify at least one swiping gesture.
8. The control system according to claim 1, wherein the control unit is configured to distinguish a gesture corresponding to a control signal from a random motion of the body part and to ignore the random motion.
9. The control system according to claim 1, wherein the control unit is configured to distinguish a gesture corresponding to a control signal from a random motion of the body part by applying a polynomial classifier and/or a support vector machine.
10. The control system according to claim 1, wherein at least one sensor electrode has a width that changes along a length of the sensor electrode.
11. The control system according to claim 1, wherein the width changes continuously along the length.
12. The control system according to claim 1, wherein the width changes discontinuously along the length.
13. The control system according to claim 1, wherein the control unit is adapted to identify at least one gesture based on the capacitances of a plurality of sensor electrodes.
14. The control system according to claim 1, wherein at least two sensor electrodes are disposed proximate to each other along the surface of the vehicle component so that the capacitances of at least two sensor electrodes are influenceable simultaneously by a single body part.
15. The control system according to claim 1, wherein in order to identify the at least one gesture and, the control unit is configured to analyse an amplitude, a gradient, a duration and/or a time interval of a capacitance change with respect to a nominal value as a function of time.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Further details and advantages of the present invention will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawing, wherein:
[0029] FIG. 1 is a schematic view of an embodiment of the inventive control system;
[0030] FIG. 2 is a schematic view of a first sensor electrode;
[0031] FIG. 3 is a schematic view of a second sensor electrode;
[0032] FIG. 4 is a schematic view of a third sensor electrode;
[0033] FIG. 5 is a schematic view of a fourth and fifth sensor electrode;
[0034] FIG. 6 is a flowchart illustrating several steps of signal processing in the control system from FIG. 1;
[0035] FIG. 7 illustrates a first gesture by a user;
[0036] FIG. 8 illustrates a second gesture by user;
[0037] FIG. 9A illustrates a third gesture by a user;
[0038] FIG. 9B corresponds to a view along the direction IX B in FIG. 9A;
[0039] FIG. 10 shows a time evolution of a capacitance corresponding to the first gesture;
[0040] FIG. 11 shows a time evolution of the capacitance corresponding to the second gesture;
[0041] FIG. 12 shows a time evolution of the capacitance corresponding to the third gesture; and
[0042] FIG. 13 shows a time evolution of the capacitance corresponding to a fourth gesture.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0043] FIG. 1 schematically shows an inventive control system 1 for a vehicle, in this case for a passenger car. The control system 1 comprises a plurality of sensor electrodes 5-9 which are disposed on a steering wheel 2 of the vehicle. More specifically, the sensor electrodes 5-9 are disposed near the outer periphery of the steering wheel 2, underneath a surface 3 of the steering wheel 2. The surface 3 is covered by a cover layer 4, which may be made of leather, plastic or the like. The function of the cover layer 4 is to electrically isolate the sensor electrodes 5-9, to mechanically protect them and to provide favorable haptic properties for a user (i.e. the driver of the vehicle). The sensor electrodes 5-9 are conducting foil electrodes, which can be very thin, e.g. less than 0.2 mm, and highly flexible, wherefore they can be easily integrated in almost any location of the steering wheel 2 without (significantly) increasing the dimensions of the steering wheel 2. Each sensor electrode 5-9 is electrically connected to a control unit 10 by a conductor 11. The routing of the conductors 11 in FIG. 1 has been simplified and the position of the control unit 10 does not correspond to a realistic position with respect to the steering wheel 2.
[0044] The control unit 10 can apply an electrical signal to each of the sensor electrodes 5-9, e.g. a constant voltage or a sinusoidal voltage with a constant amplitude. Furthermore, the control unit 10 is configured to measure a quantity that is representative of the capacitance of the respective sensor electrode 5-9 with respect to the vehicle ground. Such a quantity could be the capacitance itself or, for example, a sinusoidal current flowing into the respective electrode 5-9, from which the capacitance could be calculated. As the electric signal is applied, each of the electrodes 5-9 generates an electric field above the surface 3. If an object like a hand 40 of the user enters the electric field, the electric field and the capacitance of the sensor electrode 5-9 is changed.
[0045] Furthermore, the capacitance depends on the position of the hand 40 with respect to the steering wheel 2 and the respective sensor electrode 5-9. Therefore, if the position of the hand 40 changes over time, the same applies to the capacitance. A motion of the hand 40 may correspond to a predefined gesture G.sub.1-G.sub.3 by which the user may control a vehicle system 20, e.g. an infotainment system, a communication system a navigation system, an air-conditioning system or the like. The respective gesture G.sub.1-G.sub.3 is performed on the outer periphery of the steering wheel 2, wherefore the user can keep his hand 40 on the steering wheel, thereby maintaining full control of the vehicle. The control unit 10 is configured to identify the gesture G.sub.1-G.sub.3 and the corresponding control signal S. When the control signal S has been identified, it is output by the control unit 10 to the vehicle system 20. It is understood that the control signal S can be an analogue signal or, in particular, a digital signal.
[0046] FIGS. 2 to 5 show different embodiments of sensor electrodes 5-9 that can be used in the control system 1. Normally, not all of these embodiments would be used on a single steering wheel 2, as shown in FIG. 1. Rather, FIG. 1 is to be understood as illustrating different possibilities for the electrode layout. FIG. 2 shows a first sensor electrode 5 which has a rectangular shape. With this design, it is normally not possible to identify a swiping gesture G.sub.1, G.sub.2, but a tapping gesture G.sub.3 (as shown in FIG. 9) can be identified by the time evolution of the capacitance. During a tapping gesture G.sub.3, the hand 40 (or one or several fingers) of the user quickly approaches the sensor electrode 5, remains in the proximity of the sensor electrode 5 for a short time interval and is afterwards quickly removed. This gives rise to a capacitance change (with respect to a nominal value of the capacitance) that has a high gradient and a short duration (as shown in FIGS. 12 and 13, the latter of which shows a double tap).
[0047] FIG. 3 shows a second sensor electrode 6 with a triangular shape. In other words, a width of the sensor electrodes 6 decreases linearly along its length from a first end 6.1 to a second end 6.2. Of course, it is also possible to identify a tapping gesture G.sub.3 with this second sensor electrode 6. Furthermore, it is conceivable to identify a swiping gesture G.sub.1, G.sub.2, where the user moves his hand 40 (or finger(s)) over the length of the sensor electrode 6 from the first end 6.1 to the second end 6.2 or vice versa. This is because the capacitance change is roughly proportional to the area of the sensor electrode 6 that is covered by the hand 40. Therefore, the capacitance change is largest when the hand 40 is positioned over the first end 6.1 and smallest when the hand 40 is positioned over the second end 6.2. In general, a swiping gesture G.sub.1, G.sub.2 could be identified by a gradient of the capacitance change (corresponding to the motion of the hand 40 over the length of the sensor electrode 6) and possibly by its duration. For instance, the swiping gesture G.sub.1, G.sub.2 should be performed in a time interval between e.g. 0.2 seconds and 2 seconds. If the duration of the capacitance change is shorter or longer, the corresponding hand movement is not identified as a swiping gesture G.sub.1, G.sub.2, but e.g. as a random motion performed by the user. If such a random motion is identified, it is ignored by the control unit 10. By applying various criteria, the control unit 10 may not only distinguish different gestures G.sub.1-G.sub.3 but also distinguish random motion from a gesture G.sub.1-G.sub.3 intended as an input to the control system 1. All this can be achieved by measuring and analysing the capacitance of a single sensor electrode 5-9.
[0048] While FIG. 3 shows a sensor electrode 6 where the width changes continuously over its length, FIG. 4 shows a third sensor electrode 7 having a width that changes discontinuously or stepwise over its length. The third sensor electrode 7 comprises a first portion 7.1 having a larger width and a second portion 7.2 having a smaller width. If the hand 40 is positioned adjacent the first portion 7.1, the capacitance change with respect to a nominal value (corresponding to the absence of the hand 40) is larger than if the hand 40 is positioned adjacent the second portion 7.2. Therefore, if the user performs a series of swiping gestures G.sub.1 from left to right as illustrated in FIG. 7, this gives rise to a time evolution of the capacitance as shown in FIG. 10. Measurement of the capacitance can be performed by a measurement module 10.1 of the control unit 10 as shown in the flowchart of FIG. 6. The “raw” signal as shown in FIG. 10 is further processed by the signal processing module 10.2, which can perform a signal feature computation (e.g. to determine a gradient, a duration, and amplitude and/or a time interval between consecutive signals) and signal filtering (e.g. to remove noise). The determined features can then be forwarded to a gesture separation module 10.3, which differentiates between different gestures G.sub.1-G.sub.3 and also between (intended) gestures and random motion. This may be achieved by applying a polynomial classifier and/or a support vector machine. A support vector machine could be programmed (or “trained”) before the vehicle is delivered. Alternatively or additionally it would be conceivable that the control unit 10 is configured for a learning or training mode performed by the user, where the user performs certain gestures G.sub.1-G.sub.3 corresponding to control signals S and the control unit 10 learns to distinguish these gestures G.sub.1-G.sub.3 performed by this specific user.
[0049] FIG. 8 illustrates a swiping gesture G.sub.2 from right to left. The corresponding time evolution of the capacitance is shown in FIG. 11 for a sequence of consecutive swiping gestures G.sub.2. By comparing the FIG. 10 and FIG. 11, it is evident that as swiping from left to right is performed, the capacitance change starts with a high amplitude as the hand 40 is placed over the first portion 7.1 and continues with the drop to a low amplitude as the hand 40 reaches the second portion 7.2. On the other hand, as swiping from right to left is performed, the capacitance change starts with a comparatively low amplitude, which abruptly increases as the hand 40 is moved from the second portion 7.2 to the first portion 7.1.
[0050] FIGS. 9A and 9B illustrate a tapping gesture G.sub.3, where the hand 40 quickly approaches the sensor electrode 7 (e.g. the first portion 7.1), remains adjacent the sensor electrode 7 for a very short time interval and then quickly moves away. As shown in FIG. 12, each tap gives rise to a very short pulse in the capacitance change, which can be clearly distinguished from the swiping gestures G.sub.1, G.sub.2 of FIGS. 10 and 11. FIG. 13 shows the time evolution of the capacitance for a sequence of double taps, which give rise to pairs of short pulses.
[0051] While it is possible to identify a gesture G.sub.1-G.sub.3 by analysing the capacitance of a single sensor electrode 5-9, the control unit 10 may also identify a gesture G.sub.1-G.sub.3 based on the capacitances of a plurality of sensor electrodes 5-9. FIG. 5 shows a configuration where a fourth sensor electrode 8 and fifth sensor electrode 9 are disposed proximate to each other. Each sensor electrode 8, 9 is triangular in shape. While the width of the fourth sensor electrode 8 decreases along its length, the width of the fifth sensor electrode 9 increases. Since these two electrodes 8, 9 are positioned closely together, there capacitances can be influenced simultaneously by the hand 40 or even a single finger. As the respective body part is moved e.g. from left to right, the capacitance change of the fourth sensor electrode 8 decreases while the capacitance change of the fifth sensor electrode 9 increases at the same time. By comparing the capacitance changes of both sensor electrode 8, 9 it is possible to determine the current position of the body part with higher accuracy, since the ratio of the capacitance changes is more or less independent of the size of the body part and its distance from the sensor electrodes 8, 9.
