User interface with customizable haptic feedback and methods for customizing haptic feedback of the user interface, as well as corresponding use

Abstract

In various embodiments, a user interface (1) with adjustable haptic feedback is provided, comprising: a keypad (2) connected to a keypad holder (3) via an elastic element (5); a moving-coil actuator comprising a permanent magnet (4) and a coil (6); and a control circuit connected to the coil (6) and configured to apply a control voltage U(t) to it; wherein an adjusting element (10) with a variable resistance value is provided at a coil terminal (8). Furthermore, a method for adjusting the haptic feedback of the user interface is provided, as well as the use of a switchable resistor (11) in a control current path of a coil (6) of a moving-coil actuator for adjusting the haptic feedback of the user interface (1).

Description

The present invention relates to an operating surface with adjustable haptic feedback and to a method for adjusting haptic feedback of the operating surface and to a corresponding use.The interaction between the driver and the vehicle takes place via touch-sensitive buttons or operating elements. In addition, a touch force can also be sensed here and converted into an input. In vehicles, these may be equipped with various types of feedback. In addition to the acoustic feedback (e.g. audible click noise) and optical feedback (e.g. visible symbol, color or brightness change) that are typically already known and widely used, click sensations that can be touched by the fingers can also be provided via a touch surface as haptic feedback.The haptic feedback can be generated purely passively, that is to say mechanically, for example by means of rubber switching mats or microswitches or snap discs, which corresponds to the technology which is currently usually used. Alternatively, the desired feedback can be generated actively, i.e. mechatronically, by means of electromechanical or electromagnetic actuators, which are actively actuated and convert electrical energy into mechanical energy, for example kinetic energy. Examples of such electromechanical actuators are tension rod electromagnets, which are also referred to as reluctance force actuators and are common in high-quality smartphones), translatory or rotational imbalance motors, which correspond to DC motors and are used in normal smartphones, and translatory voice coil actuators ("voice coil actuators"), which are used in loudspeakers (corresponds to a loudspeaker without acoustic diaphragm).Voice coil actuators have a permanent magnet, an electric coil for generating a magnetic field, and a moving mass which acts as an interface to the user's finger. The permanent magnet can be part of this moving mass. By means of a voltage applied to the coil, the permanent magnet can be set in motion by induction. The movement energy can in turn be transmitted to the mass that is then moving (e.g. operating surface), which is then perceived as haptic feedback by the user, for example his finger.An important quality feature for the subjective sensation of active haptic feedback is the ringing behavior. If the active haptic feedback continues to oscillate for a long time, then this can be perceived by the user as "poor" or "inferior". It is better if the haptic feedback is very easily perceptible for a short time and then decays again rapidly.Document DE 10 2016 005 642 A1 discloses an operating element for detecting a manual input of a user in a motor vehicle, comprising an actuator, which has a drive device and is coupled to the operating element in such a way that, as feedback to the manual input, it brings about a deflection of an operating surface of the operating element that is mounted in a manner capable of oscillating by corresponding actuation of the drive device. The control element further comprises an acceleration sensor, which is coupled to the control surface for measuring an acceleration of the control surface deflected by the drive device of the actuator upon a manual input, and a control circuit, the controlled variable of which represents the measured acceleration, wherein the control circuit is designed to control the drive device of the actuator in such a way that the deflection of the control surface is attenuated.The document DE 10 2017 004 148 A1 discloses an operating device, in particular for a motor vehicle, having an operating surface for manual action by means of an element, wherein the element is in particular the finger of a human hand. A sensor interacts with the operating surface in such a way that the sensor generates a signal when the element approaches the operating surface and / or when the operating surface is touched by means of the element and / or when pressure is applied by means of the element to the operating surface. The signal serves for switching and / or triggering a function in the manner of a switching signal. Furthermore, an actuator is operatively connected to the operating surface in such a way that by actuating the actuator a haptics for the operating surface can be produced. The actuator is electrically driven and can be operated by means of a PWM control signal in such a way that the operating surface can be moved in a pre-selectable manner, in particular within a pre-selectable path and / or a pre-selectable time.The document DE 10 2018 001 985 A1 has the task of reducing the decay time of the force of an electromagnet in spite of a free-wheeling diode in the electrical control, wherein this additional function is selectively intended to become effective only if necessary. This is achieved in that an electrical circuit by means of an electronic circuit breaker brings about or interrupts an electrical connection between a first output of the superordinate electrical control and a first connection of a magnetic coil in accordance with the state of the electronic circuit breaker. The electronic circuit breaker is actuated at least by means of a first diode, which is on the other hand connected to a second terminal of the solenoid, and wherein, when the electronic circuit breaker is opened, the electrical current of the solenoid flows through an electrical braking means which opposes this electrical current with a predetermined electrical resistance and / or a predetermined braking voltage.Against this background, the object of the present invention can be seen in providing a touch surface with a haptic feedback which is improved with regard to its ringing behavior.This object is achieved by means of the subject matter of the independent claims. Further preferred embodiments are found in the dependent claims.The object of the invention is to provide an active haptic which, in the context of this description, denotes the generation of a haptic feedback (for example, tactile with the fingers) in the case of operating elements, for example in the case of operating systems in the central console or roof console.In various embodiments of the invention, an operating surface with adjustable haptic feedback is provided. An operator control panel is understood here to mean a pressure-sensitive and / or touch-sensitive operator control panel which represents an interface between a user and an electronic device and is configured to convert inputs of the user into electronic signals. An operator control panel in the sense of the present invention can have, for example, a keypad, an area on a touchpad or touchscreen, each with active haptic feedback.The control panel according to the invention has a touch element which is connected to a touch element holder via an elastic element. The elastic element can be a spring, for example. The touch element may correspond to the touch surface that a user touches or interacts with to make a corresponding input. The touch element can have, for example, an arbitrarily shaped operating surface, for example in the form of an operating button, which is mounted in a holder and can be operated by pressing.The control surface according to the invention also has a voice coil actuator which has a permanent magnet and a coil. The voice coil actuator can be connected rigidly or mechanically via a second elastic element, i.e. not rigidly to the sensing element. In principle, the permanent magnet can be fastened to the sensing element and the coil to the sensing element holding frame (or vice versa). The entire voice coil actuator can likewise be fastened to the sensing element. A connection of the voice coil actuator (as a whole or a part thereof) to the sensing element by means of an elastic element can be advantageous since accelerations (inertial forces) can thus arise. In addition, this results in more degrees of freedom for the dynamic design of the system, which is then characterized by two natural frequencies interacting with one another (e.g. small mass and first elastic element with a small spring constant for the sensing element and large mass and second elastic element with a large spring constant for the voice coil actuator.Furthermore, the control panel according to the invention has a drive circuit which is connected to the coil and is configured to apply a drive voltage to the latter. For this purpose, the drive circuit can be connected to the two terminals of the coil in order to apply the drive voltage as a drive signal to these two terminals. In this case, an adapter element is connected at a coil connection (for example between a coil connection and the windings of the coil), which adapter element has a variable resistance value. For this purpose, an adjustable resistor can be provided in the current path, that is to say one which can be deactivated if required and makes a current path low-ohmic relative to the state in which the resistor is activated (and can then be activated again accordingly). The activation and deactivation of the resistor can be realized by deactivating or activating a low-impedance bypass current path. The adjustable resistance can be realized as desired, for example by means of at least one discrete resistor or by means of a potentiometer, wherein the resistance adjustment can take place in discrete steps or continuously.The operating surface according to the invention is based on the core idea of configuring the resistance of at least one of the connection lines of the coil to be switchable with respect to its resistance. For this purpose, an ohmic resistor can be connected in series with the exchange coil actuator, namely such that this ohmic resistor can be switched on and off in its effect. By changing the resistance of the at least one connecting line, the ringing of a haptic feedback actively generated thereby can be adapted, in particular shortened. Viewed mechanically, the resistance changes the self-damping behavior of the actuator. The (electronic) switching on and off of the ohmic resistor takes place here as a function of the time profile of the drive voltage which is present at the coil of the exchange coil actuator. "As a function of the drive voltage" can, but need not mean, that the switching on and off of the resistor takes place synchronously with the switching off or on of the drive voltage / of the drive signal. In either case, a predetermined delay time may be taken into account to produce a desired haptic effect.According to further embodiments of the control panel according to the invention, the matching element can have a parallel circuit comprising a switch and a resistor. Depending on whether the switch is open or closed, a high-resistance or low-resistance current path leading through the matching element is provided.According to further embodiments of the control panel according to the invention, the drive circuit can be configured to adapt the resistance value or to deactivate the resistor as a function of the drive voltage. In other words, the resistance value or resistance can be changed / deactivated in temporal correlation with a change, in particular with a deactivation (zero signal) of the drive voltage, that is to say before it, substantially simultaneously with or after the drive voltage is deactivated. As already mentioned, the resistor can preferably be deactivated when the control voltage is switched off or only after the elapse of the delay time.According to the invention, a method for adapting a haptic feedback of the operator control surface according to the invention described herein is likewise provided, comprising increasing a self-damping of the voice coil actuator as a function of the switching off of a control signal of the coil of the voice coil actuator, which control signal leads to excitation of the voice coil actuator. The term as a function of this is to be understood as including a temporal and causal correlation, wherein, as already explained, the time interval between the two events can be positive or negative and can lie between zero and a freely determinable value. According to one embodiment, the term can be understood, for example, as "immediately after the switch-off". The switching off of the drive signal of the coil can basically mean a change of the drive voltage such that the current flowing through the coil because of the applied drive voltage comes to an end and as a result the magnetic field induced by the coil and acting on the permanent magnet comes to an end. For this purpose, for example, the potential difference applied between the coil terminals, i.e. the drive voltage, can be set to zero. In other words, the power supply may be short-circuited. After the switching off of the control signal, however, a current flow through the coil i) is initially still maintained by self-induction and ii) by induction by the permanent magnet still oscillating because of mass inertia. This current flow decays with the time constant of the system. By deactivating the resistor in the circuit, the self-damping of the voice coil actuator is increased, as a result of which the ringing can be adapted, in particular reduced, both with regard to its duration and its amplitude.According to further embodiments of the method according to the invention, increasing the intrinsic damping of the voice coil actuator can comprise reducing the resistance value, for example deactivating a resistor. By deactivating the resistor, the corresponding current path is switched to a low impedance.According to further embodiments of the method according to the invention, increasing the intrinsic attenuation can comprise activating the switch in the matching element. The switch can be a bypass switch, by means of which a low-resistance current path bypassing the resistor is provided.Furthermore, according to the invention, use of a variable resistor in a control current path of a coil of a voice coil actuator for adapting a haptic feedback of an operating surface is provided, wherein the voice coil actuator is connected to a touch element of the operating surface and is configured to generate the haptic feedback at said touch element. As already explained, the variable resistor can be a connectable resistor.According to a further embodiment of the use according to the invention, the haptic feedback of the operating surface can be adapted by bridging the switch by means of a bypass after a control signal applied to the coil of the voice coil actuator has been switched off.The present invention has the advantage that the ringing behavior of the voice coil actuator and thus the active haptics of an operating surface can be adapted or positively influenced by a cost-effective, technically simple to implement and very easily controllable technical circuit measure.It is understood that the features mentioned above and those still to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone.Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. FIG. 1 illustrates the basic structure of an operating surface with haptic feedback according to the prior art. FIG. 2 shows an exemplary drive circuit with a matching element for use in an operating surface with haptic feedback according to the present invention. FIG. 3 shows different signal curves during the operation of an operating surface with haptic feedback.FIG. 1 illustrates the basic structure of an operating surface 1 with haptic feedback according to the prior art. The control panel 1 has a touch element 2 which is connected to a touch element holder 3 via an elastic element 5 (e.g. spring). The sensing element 2 can be mounted in the sensing element holder.Furthermore, a voice coil actuator is provided, which has a permanent magnet 4 and a coil 6 and is connected to the sensing element 2. The coil 6 is connected to the sensing element 2, which is not explicitly shown in the figure. The touch element 2 corresponds to the element with which the user can interact, for example, by means of his finger F. In the embodiment shown, the mechanical connection between sensing element 2 and voice coil actuator is not rigid, but rather is realized by means of a second elastic element 9 (e.g. spring). If the connection is rigid, then the coil 6 can be fastened to the probe holder instead of to the probe 2. By means of a drive circuit which is connected to the coil 6 or the coil connections 8 (not explicitly shown in the figure), a drive voltage U(t) can be applied to the latter as a drive signal. The current I(t) flowing through the coil 6 as a result induces a magnetic field which exerts a force on the permanent magnet 6.By applying a suitable control voltage U(t), the voice coil actuator mass, in this case the permanent magnet 4, is excited to move. This movement results in inertial forces which are transmitted via the second elastic element 9 to the touch element 2 and are thus perceived as haptic feedback by the finger F of the user.As noted above, the ringing behavior is critically the subjective sensation of the active haptic feedback generated. In the optimum case, the haptic feedback decays quickly and does not die down for a long time, which is perceived as "poor" and "inferior".The invention provides an operating surface in which the ringing behavior of the oscillating mass, i.e. of the permanent magnet 4, can be adapted in order to achieve a shorter ringing (in comparison to ringing without performing the adaptation).The exchange coil actuator used in the pushbutton switch 1 has a natural intrinsic damping which is attributable to the intrinsic induction by the moving permanent magnet 4 (or, depending on which element is movable, optionally then to the moving coil 6). The voice coil actuator is motor and generator at the same time in analogy to a conventional direct current motor.The generator property of the voice coil actuator is responsible for the self-damping. In simplified terms, the inherent attenuation is proportional to a squared constant c 2, divided by the ohmic resistance that the current flowing through the coil 6 "sees". The inherent attenuation is consequently proportional to the reciprocal of the ohmic resistance, i.e. the ohmic resistance from the point of view of the coil current I(t). The constant c, also referred to as motor constant, having the unit (generated) force per unit current (amperes) depends on various geometric, electrical and magnetic variables of the system.From a technical point of view, it is desirable that the self-attenuation at the beginning of the excitation is small, whereby a fast build-up of current is possible, which leads to a fast build-up of force that provides the haptic feedback. However, in order to keep the ringing short at the end of the intended excitation of the permanent magnet 4, it is desirable that the intrinsic damping be large.In the prior art, the intrinsic damping of the actuator is (approximately) a constant and is selected such that it represents a compromise between a good initial behavior (low intrinsic damping) and a good final behavior (high intrinsic damping).The present invention starts at this point and provides a modified control panel in which the self-attenuation can be adjusted. FIG. 2 illustrates the correspondingly adapted system. Only the part of the operating surface adapted within the scope of the invention is shown here. In order to obtain an operator control surface according to the invention, the voice coil actuator (i.e. permanent magnet 4 together with coil 6 and its connections 8) in FIG. 1 must be replaced by the voice coil actuator according to the invention shown in FIG. 2.According to the invention, in the plunger-coil actuator, a coil connection 8 is made switchable with respect to its resistance. For this purpose, a matching element 10 is arranged on one of the coil connections 8, which matching element has a parallel circuit composed of a resistor 11 and a switch 11. The switch 12 functions as a bypass switch in order to bypass the resistor 11 and to switch the current path with low impedance.In other words, an ohmic resistor 11 is connected in series with a replacement coil actuator, namely such that this ohmic resistor 11 can be switched on and off in its effect by the bypass switch 12 being opened and closed accordingly. The aim here is to keep the ringing, which corresponds to active haptic feedback of the operating surface, short. The (electronic) switching on and off of the ohmic resistor 11 takes place as a function of the drive voltage U(t).In FIG. 3, three diagrams a)- c) show different signal profiles during the operation of an operating surface with active haptic feedback. In all diagrams, the time is plotted in arbitrary units on the x-axis and the correspondingly considered quantity on the y-axis. The state of the drive voltage U(t) is shown in the first diagram a), wherein a high level means that a variable drive voltage U(t) different from zero is present at the coil 4, and wherein a zero level means that no drive voltage U(t) is present or is zero. As the square-wave pulse 31 indicates, the drive voltage U(t) was switched on at a time t 1 and switched off again a short time later at a time t 2.The deflection x(t) of the voice coil actuator, for example of the permanent magnet 4, relative to the coil 6 is shown in the second diagram b). During the period between times t 1 and t 2, the voice coil actuator is activated and vibrates. The displacement is described by the solid line curve. At the time t2at which the control voltage U(t) is deactivated, the deflection x(t) is described by the first curve 32, which represents the behavior of a conventional voice coil actuator in which no adjustment of the resistance value according to the invention is carried out. The first curve 32 describes a damped oscillation which comes to a standstill over time. The second curve 33, which is shown in the second diagram b), reflects the behavior of the voice coil actuator in the control panel according to the invention, at which the resistance value in the circuit has been adapted at the time t 2. Compared to the first curve 32, it can be seen that here the intrinsic damping is significantly stronger, as a result of which the ringing is shorter and the amplitude decreases more quickly.Finally, the state S(t) of the switch 12 is shown in the third and last diagram c), wherein a high level means that the switch 12 is open (i.e. bypass inactive, high resistance) and wherein a zero level means that the switch is closed (i.e. bypass active, low resistance). As the third graph 34 indicates, the switch 12 is first open and is closed at time t 3. With reference to diagram b), t2=t3, i.e. the switch 12 is closed simultaneously with the deactivation of the drive voltage U(t). However, it should be noted that this is not a basic requirement. The decisive factor is that the switch 12 is closed as a function of the control voltage U(t), in particular as a function of the time t2at which it is deactivated. However, the time t 3 can in principle be shortly before t 2 (lead), coincide with t 2 (scenario in FIG. 3 ) or else be shortly after t 2 (lead). The setting of a suitable lead or lag is a design parameter which can be adapted to the underlying specific operator control surface system.In the case of an operating surface 1 known from the prior art, the voice coil actuator is excited by means of the control voltage U(t) and, after switching off the control voltage U(t) at the time t2, the relatively low intrinsic damping leads to a slow decay of the oscillation according to the first curve 32 in the second diagram b) in FIG. 3.In the case of the operator control panel 1 according to the invention with the voice coil actuator shown in FIG. 2, the switch 12 is open at the beginning of the actuation by means of the actuation voltage U(t) if a low intrinsic damping of the voice coil actuator is desirable. As a result, the resistor 11 is active and accordingly one of the coil connections 8 has a high impedance.Toward the end of the actuation, when the actuation voltage U(t) is switched off and when a high intrinsic damping of the exchange coil actuator is desirable, the switch 12 is closed. As a result, the bypass is activated and the resistance value is possibly significantly reduced (for example, by the resistor 11 being deactivated / deactivated), since there is now a low-impedance current path to the coil 6. Due to the relatively high intrinsic damping, the excitation of the exchange coil actuator decays significantly more quickly, which is evident from the second curve 33 (in particular compared to the first curve 32). As a result, an actively adaptable haptic behavior can be provided by means of the control panel 1 according to the invention compared to the prior art.

Claims

Operator control panel (1) with adjustable haptic feedback, comprising: a touch element (2) which is connected to a touch element holder (3) via an elastic element (5); a voice coil actuator which comprises a permanent magnet (4) and a coil (6); and a drive circuit which is connected to the coil (6) and is configured to apply a drive voltage U(t) to the latter; wherein an adjustment element (10) which has a variable resistance value is provided at a coil connection (8).Control panel (1) according to Claim 1, wherein the matching element (10) has a parallel circuit comprising a switch (12) and a resistor (11).The control panel (1) according to claim 1 or 2, wherein the drive circuit is configured to change the resistance value depending on the drive voltage.Method for adapting a haptic feedback of the operator control surface (1) according to one of Claims 1 to 3, comprising: increasing a self-attenuation of the voice coil actuator as a function of the switching-off of the control signal U(t) which leads to excitation of the voice coil actuator.The method of claim 4, wherein increasing the self-attenuation comprises reducing the resistance value.Method according to Claim 4 or 5, if dependent on Claim 2, wherein the increase in the intrinsic attenuation comprises activating the switch (12) in the matching element (10).Use of a variable resistor (11) in a drive current path of a coil (6) of a voice coil actuator for adapting a haptic feedback of an operator control surface (1), wherein the voice coil actuator is connected to a touch element (2) of the operator control surface (1) and is configured to generate the haptic feedback thereon.Use of a variable resistor (11) according to Claim 7, wherein the haptic feedback of the operator control surface (1) is adapted by the resistor (11) being bypassed by means of a bypass after a drive signal U(t) which is applied to a coil (6) of the voice coil actuator has been switched off.

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