Steering wheel wire time division multiplexing method and device and vehicle

Abstract

This application discloses a method, apparatus, and vehicle for time-division multiplexing of steering wheel heating wires, belonging to the field of vehicle control technology. The apparatus includes a hands-off detection unit, a first switch, and a metal wire; the first end of the hands-off detection unit, the metal wire, and the first end of the first switch are connected in series; the second end of the hands-off detection unit is connected to the second end of the first switch; the method includes the following steps: in response to a steering wheel hands-off detection mode, a first waveform is applied from the first end of the hands-off detection unit to the first end of the first switch via the metal wire, and a second waveform is applied from the second end of the hands-off detection unit to the second end of the first switch, wherein the second waveform and the first waveform have the same frequency. This solution can avoid interference from parasitic capacitance charging and discharging on steering wheel hands-off detection in a time-division multiplexing scenario for steering wheel heating wires, thereby effectively improving the accuracy of steering wheel hands-off detection.

Description

Technical Field

[0001] This application relates to the field of vehicle control technology, specifically to a method, device, and vehicle for time-division multiplexing of steering wheel wires. Background Technology

[0002] With the rapid development of automotive driver assistance and autonomous driving technologies, steering wheel hands-off detection has become an important function to ensure the safety of human-machine co-driving. Currently, the mainstream capacitive hands-off detection is based on the principle of self-capacitance sensing. It determines whether the driver is holding the steering wheel by detecting the change in capacitance between the steering wheel wire and the vehicle body reference ground. It has advantages such as fast response, moderate cost, and easy integration, and is widely used in various passenger vehicles.

[0003] To further reduce hardware costs and steering wheel structural complexity, the same metal wire is used alternately for steering wheel heating and steering wheel hands-off detection, with switching devices used to switch between the two functions. However, for technical solutions that use switching devices such as MOSFETs to control the on / off of the heating and detection circuits, the MOSFETs themselves have parasitic capacitances such as gate-source and drain-source capacitances. In hands-off detection mode, these parasitic capacitances charge and discharge with the detection waveform, changing the initial capacitance value of the system and thus interfering with the capacitance detection signal. This leads to decreased hands-off detection accuracy and may result in false positives or false negatives. Summary of the Invention

[0004] A method, apparatus, and vehicle for time-division multiplexing of steering wheel wires are provided, aiming to solve the problem that parasitic capacitance exists in the off-hand detection mode when using switching devices to control the on / off of the heating circuit and the detection circuit, resulting in low off-hand detection accuracy.

[0005] In a first aspect, a method for time-division multiplexing of steering wheel wires is provided, which is applied to a steering wheel wire time-division multiplexing device, wherein the steering wheel wire time-division multiplexing device includes a hands-off detection unit, a first switch, and a wire; The first end of the off-hand detection unit, the metal wire, and the first end of the first switch are connected in series; the second end of the off-hand detection unit is connected to the second end of the first switch. The method includes the following steps: In response to the steering wheel off-hand detection mode, a first waveform is applied from the first end of the off-hand detection unit to the first end of the first switch via the metal wire, and a second waveform is applied from the second end of the off-hand detection unit to the second end of the first switch, wherein the second waveform has the same frequency as the first waveform.

[0006] Optionally, the first switch is a MOSFET, with its first terminal being the source and its second terminal including a drain and a gate.

[0007] Optionally, the steering wheel wire time-sharing multiplexing device further includes a resistor-capacitor coupling circuit constructed by a first capacitor and a resistor connected in parallel, and a second capacitor connected in parallel with the resistor-capacitor coupling circuit. The resistor-capacitor coupling circuit is connected in series between the hands-off detection unit and the first switch. A second waveform is applied from the second end of the off-hand detection unit to the second end of the first switch, including: The second waveform is applied to the drain of the first switch from the second terminal of the off-hand detection unit via the RC coupling circuit or the second capacitor; and, The second waveform is applied to the gate of the first switch from the second end of the off-hand detection unit via the second capacitor or the RC coupling circuit.

[0008] Optionally, the steering wheel wire time-division multiplexing device further includes: a second switch, wherein the second switch is a MOSFET; the second switch is connected to the wire and a common ground respectively; the method further includes: In the steering wheel off-hand detection mode, both the first switch and the second switch are controlled to be in the off state, and the metal wire and the off-hand detection unit are electrically connected.

[0009] Optionally, the steering wheel wire time-sharing multiplexing device further includes a heating control unit, which is connected to the first switch; the method further includes: In response to the steering wheel heating mode, both the first switch and the second switch are turned on, and the heating control unit is controlled to heat the metal wire via the first switch.

[0010] Optionally, the steering wheel wire time-division multiplexing device includes: a main control unit, a hands-off detection unit, a first switch, and a wire; The first end of the off-hand detection unit, the metal wire, and the first end of the first switch are connected in series; the second end of the off-hand detection unit is connected to the second end of the first switch. The main control unit is electrically connected to the hands-off detection unit and the first switch respectively. The main control unit is configured to: in response to the hands-off detection mode, load a first waveform from the first end of the hands-off detection unit to the first end of the first switch via the metal wire, and load a second waveform from the second end of the hands-off detection unit to the second end of the first switch respectively, wherein the second waveform has the same frequency as the first waveform.

[0011] Optionally, the first switch is a MOSFET; The first terminal of the first switch is the source, and the second terminal includes the drain and the gate.

[0012] Secondly, a steering wheel wire time-sharing multiplexing device is also provided. The steering wheel wire time-sharing multiplexing device further includes: a resistor-capacitor coupling circuit constructed by a first capacitor and a resistor connected in parallel, and a second capacitor connected in parallel with the resistor-capacitor coupling circuit. The resistor-capacitor coupling circuit is connected in series between the off-hand detection unit and the first switch. The main control unit is further configured to: control the second terminal of the off-hand detection unit to be connected to the drain of the first switch via the RC coupling circuit or the second capacitor; and, The second terminal of the off-hand detection unit is connected to the gate of the first switch via the second capacitor or the RC coupling circuit; Optionally, the steering wheel wire time-division multiplexing device further includes: a second switch, wherein the second switch is a MOSFET; The drain of the second switch is connected to the metal wire, the source is connected to the common ground, and the gate is connected to the main control unit.

[0013] Secondly, a vehicle is also provided, comprising: Steering wheel; and, The steering wheel wire time-division multiplexing device as described in any of the preceding claims, wherein the steering wheel wire time-division multiplexing device is used to perform the steps of the steering wheel wire time-division multiplexing method as described in any of the preceding claims.

[0014] Beneficial effects: This application connects the first end of the hands-off detection unit, the metal wire, and the first end of the first switch in series; the second end of the hands-off detection unit is connected to the second end of the first switch; in response to the steering wheel hands-off detection mode, a first waveform is applied from the first end of the hands-off detection unit to the first end of the first switch via the metal wire, and a second waveform is applied from the second end of the hands-off detection unit to the second end of the first switch respectively. The second waveform has the same frequency as the first waveform, so that in the scenario of time-division multiplexing of the steering wheel heating wire, the parasitic capacitance charging and discharging is avoided from interfering with the steering wheel hands-off detection, thereby effectively improving the steering wheel hands-off detection accuracy. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a time-division multiplexing device for steering wheel wires provided in an exemplary embodiment of this disclosure; Figure 2This is a schematic diagram of the functional units of a steering wheel wire time-division multiplexing device provided in an exemplary embodiment of this disclosure; Figure 3 This is a schematic diagram of the circuit structure of a steering wheel wire time-division multiplexing device provided in an exemplary embodiment of this disclosure; Figure 4 This is a schematic diagram of a time-division multiplexing method for steering wheel wires provided by an exemplary embodiment of this disclosure.

[0017] Figure label: 10. Steering wheel end; 11. Metal wire; 20. Single board end; 21. Main control unit; 22. Hand-off detection unit; 23. Heating control unit; 24. First switch; 25. Second switch; 26. Resistor; 27. First capacitor; 28. Second capacitor; 30. Power supply unit. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0020] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0021] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0022] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0023] This application provides a method and apparatus for time-division multiplexing of steering wheel heating wires to solve the problem that the parasitic capacitance of the switching device interferes with the off-hand detection performance in the time-division multiplexing scenario of steering wheel heating wires in related technologies, and realizes low-cost and high-stability time-division multiplexing of steering wheel off-hand detection and heating functions.

[0024] On the one hand, please refer to Figure 1 The steering wheel wire time-division multiplexing device of this application includes a hands-off detection unit, a first switch, and a wire. The wire is installed inside the vehicle's steering wheel and serves as both a steering wheel heating wire and a hands-off detection electrode. Optionally, the first switch is an electronic switch. The first end of the hands-off detection unit, the wire, and the first end of the first switch are connected in series to form a detection channel. The second end of the hands-off detection unit is connected to the second end of the first switch to form a compensation signal channel. Optionally, the hands-off detection unit can use an AS8579 chip, which integrates capacitive sensing detection and has dedicated detection and compensation channels.

[0025] The device also includes a main control unit, which is electrically connected to the control terminals of the hands-off detection unit and the first switch, respectively, for recognizing and responding to the hands-off detection mode. Optionally, the main control unit can be an automotive-grade microcontroller unit (MCU), an automotive domain controller (DCU), or an automotive body control module (BCM).

[0026] After the vehicle is powered on, the main control unit monitors the vehicle's operating status in real time. When it detects that the vehicle has entered assisted driving or autonomous driving mode, or receives a hands-off detection enable command from the body controller, it responds to the hands-off detection mode. After entering the hands-off detection mode, the main control unit first completes the initialization of the entire vehicle system: configuring parameters such as the operating frequency, output amplitude, and detection threshold of the hands-off detection unit; at the same time, it keeps the first switch in the off state, disconnecting the heating circuit, and the metal wire only works as a detection electrode.

[0027] The main control unit sends a detection start command to the hands-off detection unit, controlling the hands-off detection unit to output a first waveform from its first terminal. This first waveform is a periodic alternating waveform, such as a sine wave or square wave, generated by the internal oscillation circuit of the hands-off detection unit. The first waveform passes through the electrical connection path, sequentially through the first terminal of the hands-off detection unit and the metal wire, and is applied to the first terminal of the first switch. After the first waveform is applied, a stable alternating electric field is formed on the metal wire, used to sense the capacitance change caused by the driver's hand contact, providing the basic excitation signal for hands-off detection.

[0028] While the hands-free detection unit outputs the first waveform, it simultaneously outputs a second waveform from its second terminal. The second waveform is generated by the internal synchronization circuit of the hands-free detection unit, maintaining the same frequency as the first waveform, and its phase is synchronized with or has a fixed phase difference from the first waveform. The second terminal of the hands-free detection unit, through a preset electrical connection, simultaneously loads the second waveform onto the second terminal of the first switch.

[0029] After the second waveform is applied, a synchronous alternating voltage is formed between the second and first terminals of the first switch, which keeps the voltage difference across the parasitic capacitance of the first switch constant, avoids interference from the charging and discharging of the parasitic capacitance on the first waveform, and ensures the stability of the detection signal on the metal wire.

[0030] During the continuous loading of the first and second waveforms, the hands-off detection unit acquires the capacitance change signal on the metal wire in real time. When the driver grips the steering wheel, the human body, as a conductor, changes the electric field distribution around the metal wire, causing a change in the detected capacitance value. The hands-off detection unit converts this change into an electrical signal and outputs it to the main control unit. The main control unit determines whether the driver is still gripping the steering wheel based on the capacitance change and reports the result to the vehicle control system.

[0031] In some embodiments, the first switch is a MOSFET, with its first terminal being the source (S) and its second terminal including a drain (D) and a gate (G). The first terminal of the off-hand detection unit, the metal wire, and the source (S) of the first switch are connected in series.

[0032] Optionally, the device also includes an RC coupling circuit and a second capacitor. The RC coupling circuit is constructed by connecting a first capacitor and a resistor in parallel, and is used to achieve AC coupling. The resistor is used to stabilize the drain potential and suppress high-frequency interference; the first capacitor is used to isolate DC, preventing external power supply or drive signals from affecting the compensation waveform. The second capacitor is used to block DC and AC, allowing the second waveform to be effectively applied to the gate of the first switch. The second capacitor and the RC coupling circuit are connected in parallel, and both are connected in series between the second terminal of the off-hand detection unit and the first switch. Specifically, one path from the second terminal of the off-hand detection unit is connected to the drain of the first switch via the RC coupling circuit, and the other path is connected to the gate of the first switch via the second capacitor, forming two independent compensation waveform transmission channels.

[0033] When the vehicle's main control unit determines that it has entered the assisted driving or hands-off detection enabled state, it responds to the steering wheel hands-off detection mode. The main control unit controls the first switch to be in the off state, that is, controls the gate input of the first switch to be at the off level, the heating circuit is not connected, and the metal wire is only used as a detection electrode.

[0034] Then, the main control unit controls the off-hand detection unit to output a first waveform from the first terminal. The first waveform is transmitted to the source of the first switch via a metal wire, forming an alternating detection potential at the source to establish a capacitance detection electric field. Simultaneously, the main control unit controls the off-hand detection unit to output a second waveform with the same frequency as the first waveform from the second terminal. The second waveform is transmitted to the drain of the first switch via a RC coupling circuit consisting of a first capacitor and a resistor connected in parallel.

[0035] Because parasitic capacitances may exist between the gate and source, drain and source, and drain and gate of a MOSFET, this embodiment uses two independent compensated waveform transmission channels to synchronously load the second waveform onto the drain and gate of the first switch, a MOSFET. Since the first and second waveforms have the same frequency and phase synchronization, the alternating waveforms of the drain, gate, and source of the first switch maintain the same frequency change, keeping the voltage difference between the gate and source constant, preventing charging and discharging. Furthermore, because the waveforms loaded onto the drain and gate of the first switch are in phase and frequency, there is no gate-drain parasitic capacitance. Therefore, parasitic capacitances do not interfere with the detection circuit, and the capacitance change collected by the off-hand detection unit is only caused by the driver's hand contact, thus significantly improving detection accuracy.

[0036] In some embodiments, the device further includes a second switch, which is a MOS transistor. The drain (D) of the second switch is connected to a metal wire, the source (S) is connected to a common ground, and the gate (G) is connected to a main control unit. The main control unit is used to output control signals to drive the first switch and the second switch to be turned on or off.

[0037] When the device responds and enters the hands-off detection mode, the main control unit outputs a shutdown level to the gates of the first switch and the second switch respectively, keeping both switches in the off state. At this time, the first switch is open to cut off the electrical path between the external power supply and the metal wire, preventing the external power supply signal from interfering with the hands-off detection; the second switch is open to cut off the electrical path between the metal wire and the common ground, preventing stray signals or parasitic parameters from being introduced into the common ground and affecting the detection stability.

[0038] With both the first and second switches off, the metal wire maintains electrical connection only with the hands-off detection unit, acting as an independent capacitive sensing electrode for hands-off detection. The electric field distribution on the metal wire is unaffected by the power supply and grounding circuits. The hands-off detection unit can accurately detect capacitance changes caused by the driver's hand contact through the metal wire, thus achieving high-precision and high-stability steering wheel hands-off detection. Throughout the entire steering wheel hands-off detection mode, the main control unit continuously keeps the first and second switches off, maintaining the electrical connection between the metal wire and the hands-off detection unit until the device receives a mode switching command and exits the hands-off detection mode.

[0039] In some embodiments, the device further includes a heating control unit. Optionally, the heating control unit is an on-board high-side drive chip used to provide a stable, reliable, and protective heating drive power supply for the metal wire, and the heating control unit is connected to the first switch.

[0040] When the device receives a heating command, the ambient temperature is below a preset threshold, or the user actively triggers the heating function, it responds and enters the steering wheel heating mode. At this time, the main control unit outputs a conduction level to the gates of the first and second switches, respectively, ensuring both switches are in a conducting state. Simultaneously, the main control unit controls the heating control unit to start outputting power. External power flows through the heating control unit and the first switch to the metal wire, then returns to the common ground via the conducting second switch, forming a complete heating current loop. This causes the metal wire to generate heat under the influence of the current, achieving the steering wheel heating function. In the steering wheel heating mode, the hands-off detection unit stops outputting the first and second waveforms; the metal wire only functions as a heating element, achieving time-division multiplexing with the hands-off detection function. When the heating command ends, the temperature reaches the preset value, or a stop heating command is received, the main control unit controls the first and second switches to open, the heating control unit stops outputting power, the device exits the heating mode, and can re-enter the steering wheel hands-off detection mode.

[0041] For example, please refer to Figure 2 , Figure 2The diagram shows the functional unit composition of a time-division multiplexing device for steering wheel wires. The internal circuit structure of this device is divided into two main parts: the steering wheel end and the single-board end. The steering wheel end includes the metal wire. The single-board end consists of an MCU control unit, a first switch, a second switch, a hands-off detection unit (such as an AS8579 chip), a power supply unit, an external communication unit, and a heating control unit. Optionally, the switching assembly is a single MOSFET. The MCU control unit connects to the power supply unit, the external communication unit, the hands-off detection unit, and the heating control unit via bidirectional interfaces to achieve timing control, mode switching, and state management of the entire system. The power supply unit provides stable onboard power support for the entire device, while the external communication unit enables data interaction between the device and the vehicle body system through a vehicle communication interface. The hands-off detection unit has a SEN0 detection channel and a VAR_SEN compensation channel. The SEN0 channel is connected to the metal wire and is used to output a detection excitation signal and acquire capacitance changes. The VAR_SEN compensation channel is connected to the MOSFET pin of the first switch and suppresses parasitic capacitance interference of the switching device by outputting a compensation waveform with the same frequency as the detection signal. The heating control unit is connected to the first switch and provides heating drive current to the metal wire. Both the first and second switches are MOSFETs. The first switch connects the heating control unit to the metal wire, and the second switch connects the metal wire to the common ground (GND). The gates of both switches are driven by the MCU control unit. In the hands-off detection mode, they are simultaneously disconnected, so that the metal wire is only electrically connected to the hands-off detection unit for capacitive hands-off detection. In the heating mode, they are simultaneously turned on, so that the heating control unit, the first switch, the metal wire, and the second switch form a complete heating circuit to realize the steering wheel heating function. Thus, the function switching of the metal wire in the two modes is realized through time-division multiplexing.

[0042] For example, please refer to Figure 3 , Figure 3 The diagram shows a circuit structure of a time-division multiplexing device for steering wheel wires. The device's internal circuitry is divided into two main parts: the steering wheel end 10 and the single-board end 20. The single-board end 20 includes an MCU control unit, a switching assembly, and a hands-off detection unit 22 (such as an AS8579 chip). Optionally, the switching assembly is a MOSFET.

[0043] The detection channel (SEN0) of the off-hand detection unit 22 corresponds to the first end of the off-hand detection unit 22, and the compensation channel (VAR_SEN) corresponds to the second end of the off-hand detection unit 22. The detection channel is connected to one end of the metal wire 11, and the other end of the metal wire 11 is connected to the source of the first switch 24, forming a series channel constructed by the detection channel of the off-hand detection unit 22, the metal wire 11, and the source of the first switch 24 (e.g., ...). Figure 3The link indicated by the red dashed line in the diagram is shown); the compensation channel is formed by a resistor-capacitor coupling circuit consisting of resistor 26 (R1) and first capacitor 27 (C1) connected in parallel, and second capacitor 28 (C2), which are respectively connected to the drain and gate of first switch 24 to form (as shown in the diagram). Figure 3 (The link indicated by the green dashed line in the diagram is shown). Specifically, resistor 26 and first capacitor 27 are connected in parallel, with one end connected to the compensation channel and the other end connected to the drain of the first switch; one end of second capacitor 28 is connected to the compensation channel and the other end is connected to the gate of the first switch 24. This connection method in this embodiment allows the compensation waveform output by the compensation channel to be applied synchronously to the drain and gate of the first switch 24, thereby suppressing parasitic capacitance interference between the gate and source, and between the drain and source of the first switch 24.

[0044] Both the first switch 24 and the second switch 25 use N-channel MOSFETs to meet the requirements of high-current heating and rapid switching. The drain of the first switch 24 is connected to the output terminal of the heating control unit 23 to receive the heating power signal; the source of the first switch 24 is connected to one end of the metal wire 11, and simultaneously forms a series channel with the detection channel of the off-hand detection unit 22; the gate of the first switch 24 is connected to the control output terminal of the main control unit 21 to receive the switching control signal from the main control unit 21. The drain of the second switch 25 is connected to the other end of the metal wire 11, the source of the second switch 25 is connected to the vehicle common ground, and the gate of the second switch 25 is also connected to the control output terminal of the main control unit 21, whose on / off state is controlled by the main control unit 21.

[0045] The RC coupling circuit consists of a resistor 26 and a first capacitor 27 connected in parallel, working together with a second capacitor 28. One end of the resistor 26 and the first capacitor 27 is connected to the compensation channel of the off-hand detection unit 22, and the other end is connected to the drain of the first switch 24. One end of the second capacitor 28 is connected to the compensation channel, and the other end is connected to the gate of the first switch 24. This circuit can couple the compensation waveform output from the compensation channel to the drain and gate of the first switch 24 without DC component, while isolating the gate DC control signal output from the main control unit 21, avoiding mutual interference between the two signals.

[0046] The main control unit 21 uses an MCU control unit, which is connected to the off-hand detection unit 22 via a communication interface such as Serial Peripheral Interface (SPI) or Inter-Integrated Circuit (I2C). It can configure the operating mode and waveform parameters of the off-hand detection unit 22. It is connected to the gates of the first switch 24 and the second switch 25, outputting high and low level signals to control the on and off states of the first switch 24 and the second switch 25. Optionally, the heating control unit 23 uses a high-side driver chip. When both the first switch 24 and the second switch 25 are on, the input terminal of the heating control unit 23 is connected to the power supply unit 30, and the output terminal is connected to the drain of the first switch 24. It can output heating power according to the instructions of the main control unit 21 to provide heating current (e.g., ...) to the metal wire 11. Figure 3 (The link pointed to by the blue dashed line in the diagram is shown). In addition, since the high-side drive chip has overcurrent, overtemperature, and short-circuit protection functions, the use of a high-side drive chip in the heating control unit 23 of this embodiment can ensure the safety of heating operation.

[0047] On the other hand, embodiments of this application provide a time-division multiplexing method for steering wheel wires, applied to the apparatus of the above embodiments. This apparatus has two operating modes: a steering wheel off-hand detection mode and a steering wheel heating mode. These two modes are time-division multiplexed by controlling the on / off states of a first switch and a second switch through a main control unit, allowing the wires to perform different functions in the two modes. Please refer to... Figure 4 The method includes the following steps: Step 100: In response to the steering wheel off-hand detection mode, a first waveform is applied from the first end of the off-hand detection unit to the first end of the first switch via a metal wire, and a second waveform is applied from the second end of the off-hand detection unit to the second end of the first switch. The second waveform has the same frequency as the first waveform.

[0048] Specifically, when the main control unit receives a hands-off detection command from the vehicle system, or when the hands-off detection function is triggered according to preset conditions, the device enters the steering wheel hands-off detection mode. The specific control process is as follows: The main control unit outputs a low-level signal to the gate of the first switch, controlling the first switch to be in the open state; simultaneously, it outputs a low-level signal to the gate of the second switch, controlling the second switch to also be in the open state. At this time, the heating circuit is cut off, and the output power of the heating control unit cannot flow to the metal wire through the first switch. The metal wire is no longer used for heating, but is used as a capacitive sensing electrode.

[0049] The main control unit sends a command to the off-hand detection unit via the communication interface to configure it to enter the off-hand detection working mode. After receiving the command, the off-hand detection unit outputs a first waveform from the first end (i.e., the detection channel). This waveform is an AC signal with a fixed frequency, which is loaded onto the source of the first switch through a metal wire. At the same time, the off-hand detection unit outputs a second waveform from the second end (i.e., the compensation channel). This waveform has the same frequency as the first waveform and its phase is synchronized with the first waveform.

[0050] The first waveform serves as the excitation signal for the hands-off detection. After being applied to the metal wire, it creates an alternating electric field around the wire. When the driver grips the steering wheel, the human body acts as a conductor, forming a coupling capacitance with the metal wire. This changes the capacitance of the metal wire to ground. The hands-off detection unit collects this capacitance change through a detection channel to determine whether the driver is gripping the steering wheel. The second waveform serves as a compensation signal, synchronously applied to the drain and gate of the first switch via an RC coupling circuit, thereby suppressing interference from the parasitic capacitance of the first switch on the detection signal.

[0051] The parasitic capacitances of the first switch include the gate-source capacitance Cgs, the drain-source capacitance Cds, and the gate-drain capacitance Cgd. In off-hand detection mode, these capacitances couple with the first waveform output by the detection channel, generating additional charging and discharging current. This causes a shift in the capacitance to ground of the metal wire, affecting the accuracy of off-hand detection. This application compensates by outputting a second waveform with the same frequency as the first waveform through a compensation channel, synchronously driving the drain and gate of the first switch. This ensures that: the voltage difference (Vgs) across the gate-source capacitance Cgs remains constant, with no alternating voltage component, thus preventing charging and discharging current; the voltage difference (Vds) across the drain-source capacitance Cds remains constant, also preventing charging and discharging current; and the voltage difference (Vgd) across the gate-drain capacitance Cgd also remains constant due to the synchronous driving of the drain and gate, preventing the generation of charging and discharging current.

[0052] Based on the above analysis, it can be seen that none of the parasitic capacitances of the first switch will interfere with the first waveform of the detection channel. The capacitance change signal collected by the hands-off detection unit only reflects the driver's hand grip state, which can effectively improve the accuracy and stability of hands-off detection.

[0053] Optionally, the hands-off detection unit continuously collects the capacitance signal of the metal wire through the detection channel, converts it into a digital signal, and transmits it to the main control unit through the communication interface. The main control unit determines the driver's hand grip state based on a preset capacitance threshold and feeds back the detection result to the vehicle system, providing a safety judgment basis for assisted driving or autonomous driving functions. During the continuous hands-off detection mode, the main control unit keeps the first and second switches in the off state, while controlling the hands-off detection unit to continuously output the first and second waveforms to ensure the continuous operation of the detection.

[0054] As another embodiment, the method further includes: Step 200: In response to the steering wheel heating mode, control both the first switch and the second switch to be turned on, and control the heating control unit to heat the metal wire via the first switch.

[0055] Specifically, when the main control unit receives a steering wheel heating command from the vehicle system, or when the heating function is triggered according to preset conditions (such as the ambient temperature being lower than a set value), the device enters the steering wheel heating mode. The specific control process is as follows: The main control unit outputs a high-level signal to the gate of the first switch, controlling the first switch to be in the conducting state; simultaneously, it outputs a high-level signal to the gate of the second switch, controlling the second switch to also be in the conducting state. At this time, the heating circuit is turned on, and the current path flows sequentially from the external power supply of the vehicle to the heating control unit, the drain of the first switch, the source of the first switch, the metal wire, the drain of the second switch, the source of the second switch, and the common ground of the vehicle, thus forming a complete heating circuit.

[0056] The heating control unit outputs a stable heating current to the drain of the first switch according to the instructions of the main control unit. The current flows through the conducting first switch to the metal wire, which generates heat under the action of the current, thus realizing the heating function of the steering wheel. The main control unit can control the heating power of the metal wire by controlling the output current of the heating control unit, thereby controlling the heating temperature of the steering wheel. At the same time, the heating control unit has overcurrent, overtemperature, and short-circuit protection functions. When excessive current, excessive temperature, or short circuit is detected, the output power is automatically cut off to ensure the safety of the heating operation.

[0057] In steering wheel heating mode, the hands-off detection unit is in standby mode. The main control unit sends a command to the hands-off detection unit via the communication interface, causing it to stop outputting the first and second waveforms to avoid interference between the heating current and the detection signal. At this time, the main function of the metal wire is heating, and the hands-off detection function is suspended until the device switches back to hands-off detection mode.

[0058] When the main control unit receives a heating stop command from the vehicle system, or detects that the steering wheel temperature has reached a set threshold, the control device exits the heating mode. The specific process is as follows: the main control unit outputs a low-level signal to the gates (G poles) of the first and second switches, controlling the two switches to open and cut off the heating circuit; simultaneously, it sends a command to the hands-free detection unit to restore its working state and prepare to enter the hands-free detection mode. During the mode switching process, the main control unit ensures that the heating circuit is completely cut off before activating the hands-free detection function, avoiding signal interference between the two modes.

[0059] Optionally, to avoid interference between the heating current and the detection signal, the timing control process followed by the mode switching in this embodiment includes: When switching from off-hand detection mode to heating mode, the main control unit first controls the off-hand detection unit to stop outputting the first and second waveforms. After the detection signal completely stops, it then controls the first and second switches to turn on, starting the heating circuit. When switching from heating mode to off-hand detection mode, the main control unit first controls the heating control unit to cut off the heating power supply. After the heating circuit current completely disappears, it then controls the first and second switches to turn off, subsequently starting the off-hand detection unit and outputting the first and second waveforms. This timing control process effectively avoids signal crosstalk between the two modes, thus ensuring the stability of time-division multiplexing.

[0060] In the event of a fault such as a communication failure in the off-hand detection unit, an over-temperature protection failure in the heating control unit, or a MOSFET conduction failure, the main control unit enters a fault protection state. It prioritizes cutting off the heating circuit, stopping the heating mode, and maintaining the off-hand detection unit in standby mode. At the same time, it sends fault information to the vehicle system to ensure driving safety.

[0061] In summary, the steering wheel wire time-division multiplexing method and device proposed in this application can bring at least the following beneficial effects: By adopting a time-division multiplexing scheme for metal wires, there is no need to deploy additional off-hand detection electrodes. The heating wire can be directly reused as the detection electrode, which can significantly reduce hardware costs and structural complexity.

[0062] By outputting a second waveform at the same frequency as the first waveform through the off-hand detection unit, the drain and gate of the first switch are driven synchronously. This can eliminate the interference of parasitic capacitance on the detection signal from the source, and is not affected by changes in the external environment. The accuracy and stability of off-hand detection are significantly improved, and the false positive rate and false negative rate are greatly reduced.

[0063] The main control unit, through strict timing control, can achieve orderly switching between heating mode and off-hand detection mode, avoiding signal crosstalk between the two modes. It also has fault protection function to ensure the safe and stable operation of the device.

[0064] This time-division multiplexing solution for metal wires can be directly applied to vehicles with steering wheel heating functions without requiring significant modifications to the steering wheel structure. It can be achieved simply by modifying the switching devices of the heating circuit and adding a compensation waveform drive circuit, demonstrating strong versatility and adaptability.

[0065] On the other hand, this embodiment provides a vehicle, including: A steering wheel; and a steering wheel wire time-division multiplexing device as described in any of the preceding claims, wherein the steering wheel wire time-division multiplexing device is used to perform the steps of the steering wheel wire time-division multiplexing method as described in any of the preceding claims.

[0066] This embodiment also provides a computer-readable storage medium having a computer program stored thereon, the computer program being loaded by a processor to perform the steps of any of the methods in the above embodiments.

[0067] In the embodiments of this application, the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0068] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0069] The above provides a detailed description of a steering wheel wire time-division multiplexing method, device, and vehicle provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for time-division multiplexing of steering wheel wires, characterized in that, A time-sharing multiplexing device for steering wheel wires, the steering wheel wire time-sharing multiplexing device includes a hands-off detection unit, a first switch and a wire; The first end of the off-hand detection unit, the metal wire, and the first end of the first switch are connected in series; the second end of the off-hand detection unit is connected to the second end of the first switch. The method includes the following steps: In response to the steering wheel off-hand detection mode, a first waveform is applied from the first end of the off-hand detection unit to the first end of the first switch via the metal wire, and a second waveform is applied from the second end of the off-hand detection unit to the second end of the first switch, wherein the second waveform has the same frequency as the first waveform.

2. The method for time-division multiplexing of steering wheel wires according to claim 1, characterized in that, The first switch is a MOSFET, with its first terminal being the source and its second terminal including the drain and gate.

3. The method for time-division multiplexing of steering wheel wires according to claim 2, characterized in that, The steering wheel wire time-sharing multiplexing device also includes a resistor-capacitor coupling circuit constructed by a first capacitor and a resistor connected in parallel, and a second capacitor connected in parallel with the resistor-capacitor coupling circuit. The resistor-capacitor coupling circuit is connected in series between the hands-off detection unit and the first switch. A second waveform is applied from the second end of the off-hand detection unit to the second end of the first switch, including: The second waveform is applied from the second end of the off-hand detection unit through the resistor-capacitor coupling circuit or the second capacitor to the drain of the first switch; as well as, The second waveform is applied to the gate of the first switch from the second end of the off-hand detection unit via the second capacitor or the RC coupling circuit.

4. The method for time-division multiplexing of steering wheel wires according to claim 2 or 3, characterized in that, The steering wheel wire time-division multiplexing device further includes: a second switch, wherein the second switch is a MOSFET; the second switch is connected to the wire and a common ground respectively; the method further includes: In the steering wheel off-hand detection mode, both the first switch and the second switch are controlled to be in the off state, and the metal wire and the off-hand detection unit are electrically connected.

5. The method for time-division multiplexing of steering wheel wires according to claim 4, characterized in that, The steering wheel wire time-sharing multiplexing device further includes a heating control unit, which is connected to the first switch; the method further includes: In response to the steering wheel heating mode, both the first switch and the second switch are turned on, and the heating control unit is controlled to heat the metal wire via the first switch.

6. A time-division multiplexing device for steering wheel wires, characterized in that, The steering wheel wire time-division multiplexing device includes: a main control unit, a hands-off detection unit, a first switch, and a wire; The first end of the off-hand detection unit, the metal wire, and the first end of the first switch are connected in series; the second end of the off-hand detection unit is connected to the second end of the first switch. The main control unit is electrically connected to the hands-off detection unit and the first switch respectively. The main control unit is configured to: in response to the hands-off detection mode, load a first waveform from the first end of the hands-off detection unit to the first end of the first switch via the metal wire, and load a second waveform from the second end of the hands-off detection unit to the second end of the first switch respectively, wherein the second waveform has the same frequency as the first waveform.

7. The steering wheel wire time-division multiplexing device according to claim 6, characterized in that, The first switch is a MOSFET; The first terminal of the first switch is the source, and the second terminal includes the drain and the gate.

8. The steering wheel wire time-division multiplexing device according to claim 7, characterized in that, The steering wheel wire time-sharing multiplexing device further includes: a resistor-capacitor coupling circuit constructed by a first capacitor and a resistor connected in parallel, and a second capacitor connected in parallel with the resistor-capacitor coupling circuit. The resistor-capacitor coupling circuit is connected in series between the hands-off detection unit and the first switch. The main control unit is further configured to: control the second terminal of the off-hand detection unit to be connected to the drain of the first switch via the RC coupling circuit or the second capacitor; and, The second terminal of the off-hand detection unit is connected to the gate of the first switch via the second capacitor or the RC coupling circuit.

9. The steering wheel wire time-division multiplexing device according to claim 7, characterized in that, The steering wheel wire time-division multiplexing device further includes: a second switch, and the second switch is a MOSFET; The drain of the second switch is connected to the metal wire, the source is connected to the common ground, and the gate is connected to the main control unit.

10. A vehicle, characterized in that, include: steering wheel; as well as, The steering wheel wire time-division multiplexing device as described in any one of claims 6 to 9, wherein the steering wheel wire time-division multiplexing device is used to perform the steps of the steering wheel wire time-division multiplexing method as described in any one of claims 1 to 5.

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