A signal conditioning circuit for an active wheel speed sensor and method thereof

Abstract

The application discloses a signal conditioning circuit and method thereof for an active wheel speed sensor, relates to the technical field of vehicle electronics, and aims to solve the technical problem that the output of a multi-threshold comparator of an existing signal conditioning circuit for an active wheel speed sensor is prone to conflict under dynamic working conditions, resulting in misjudgment or missed judgment. To this end, the application provides a signal conditioning circuit and method thereof, which comprises: collecting a multi-threshold comparator output vector [C1, C2, C3] and the number of times of its flip N_trans in real time; synchronously acquiring OVP / OCP / open circuit diagnosis flag states; constructing a period characteristic vector X_k, which contains current levels, jitter conditions, protection states and wheel speed parameters; setting an M-period sliding window to perform current level mode statistics and jitter intensity calculation; generating a window-level diagnosis label S_w based on the window statistics result; adopting an instantaneous judgment and window diagnosis combined decision mechanism to output a final state; and dynamically adjusting decision parameters and threshold hysteresis according to long-term operation data.

Description

A signal conditioning circuit and method for an active wheel speed sensor Technical Field

[0001] This invention relates to the field of vehicle electronics technology, and more specifically, to a signal conditioning circuit and method for an active wheel speed sensor. Background Technology

[0002] Active wheel speed sensors (WSS) play a crucial role in modern automobiles, providing critical wheel speed information for systems such as anti-lock braking (ABS) and electronic stability program (ESP). With the development of automotive electronics technology, the requirements for WSS interface chips are also increasing. They need to support multiple WSS standards simultaneously, such as Level 2 active WSS and Level 3 active WSS compliant with VDA standards, and be capable of diagnosing various faults, including open circuits, short circuits to the battery, and short circuits to ground.

[0003] In existing WSS interface chip designs, multi-threshold comparators are typically used to detect sensor current, and the back-end digital logic generates the WSS_Out signal and diagnostic flags. For example, a mirrored current Isense is generated through a current mirror circuit, and then Isense is sent to multiple comparators to be compared with different reference currents (Iref1 / Iref2 / Iref3) to determine the current level (e.g., 7mA / 14mA / 28mA). Simultaneously, the chip also integrates overvoltage protection (OVP), overcurrent protection (OCP), and open-circuit diagnostics to ensure system safety and reliability.

[0004] However, this traditional design faces significant challenges under dynamic conditions such as vehicle acceleration and deceleration, ABS start-stop, and poor wiring harness contact. Under these conditions, the sensor current may change rapidly within a pulse width modulation (PWM) cycle, even crossing multiple thresholds, or exhibiting brief overshoot / ringing when a fault first occurs. This can lead to multiple comparator outputs changing simultaneously, resulting in conflicting level and fault judgments. For example, it's possible to meet both the normal level condition and the suspected short circuit condition; or multiple current level judgments may fluctuate back and forth, causing errors in direction encoding parsing.

[0005] The reason for this is that multi-threshold comparators and diagnostic logic are essentially multi-input discrete decision systems, but traditional approaches often employ static rules based on priority encoding and state machines. For example, if the current is less than Iref_min, it is judged as an open circuit; if the current is greater than Iref_max, it is judged as a short circuit; and if it falls between different thresholds, it is judged as 7mA / 14mA / 28mA. These rules are mostly manually set and fail to fully utilize the long-term collected sensor behavior data for statistical learning.

[0006] To address the above problems, this invention proposes a solution. Summary of the Invention

[0007] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a signal conditioning circuit and method for an active wheel speed sensor to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A signal conditioning circuit and method for an active wheel speed sensor, comprising the following steps:

[0010] Real-time acquisition of multi-threshold comparator output vector and the number of times it flips ;

[0011] Synchronously acquire the status of overvoltage protection (OVP), overcurrent protection (OCP), and open circuit diagnostic (OPEN) flags;

[0012] Constructing periodic feature vectors It includes current level, vibration status, protection status and wheel speed parameters;

[0013] Set an M-period sliding window for the periodic feature vector. Perform current level pattern statistics and jitter intensity calculation;

[0014] Window-level diagnostic labels are generated based on the statistical results of the sliding window. ;

[0015] Using instantaneous decision and the window-level diagnostic label The joint decision-making mechanism outputs the final state.

[0016] In a preferred embodiment, the multi-threshold comparator output vector This indicates whether the comparator corresponding to different current levels was set to 1 during the current gear tooth cycle.

[0017] In a preferred embodiment, the number of flips This indicates the number of toggles output by the multi-threshold comparator within the current gear tooth cycle.

[0018] In a preferred embodiment, the periodic feature vector It also includes: the period of the gear tooth cycle. and pulse width .

[0019] In a preferred embodiment, the current level pattern statistics include counting the number of occurrences of each current level pattern within the M-cycle sliding window.

[0020] In a preferred embodiment, the jitter intensity calculation includes calculating the number of flips within the M-period sliding window. The sum of .

[0021] In a preferred embodiment, the window-level diagnostic label The generation criteria include: the proportion of the current level mode, the jitter intensity, the number of times the OVP, OCP and OPEN flags are triggered, and the wheel speed smoothness.

[0022] In a preferred embodiment, the instantaneous decision is based on single-cycle characteristics. Instantaneous candidate states are generated according to preset rules; the joint decision-making mechanism includes: if the... If the jitter is determined to be noise-induced, then the switching of the instantaneous candidate state is subjected to jitter removal processing.

[0023] In a preferred embodiment, the method further includes adaptively adjusting the decision parameters and threshold hysteresis based on long-term operating data.

[0024] A signal conditioning circuit for an active wheel speed sensor, comprising:

[0025] The power input terminal VCC, the sensor high-side pin WSS_HS and the sensor low-side pin WSS_LS, as well as the standby control pin STB and the wheel speed output pin WSS_Out;

[0026] Controlled high-side switch m4 and controlled low-side switch m5. High-side switch m4 is connected in series between the power input terminal VCC and the sensor high-side pin WSS_HS. Low-side switch m5 is connected in series between the sensor low-side pin WSS_LS and ground. The control terminals of high-side switch m4 and low-side switch m5 are connected to STB and internal control logic to switch the power supply path of the sensor between standby mode and working mode.

[0027] High-end current limiting switch m9 and low-end current limiting switch m10 are connected in series between the power input terminal VCC and the high-end switch m4, and low-end current limiting switch m10 is connected in series between the low-end switch m5 and ground. They are used to limit the current flowing through the active wheel speed sensor under abnormal operating conditions.

[0028] The current mirror circuit includes a main mirror tube m3 arranged in the sensor current path and multiple mirror tubes m2, m6, m7, m8, m11, m12, m13 and m14 connected to the main mirror tube m3 in a mirror manner. It is used to mirror the working current flowing through the active wheel speed sensor into a mirror current Isense that is reduced by a predetermined ratio.

[0029] A multi-threshold comparator circuit includes at least three comparators Comp. One input of each comparator is used to receive the detection voltage generated by the mirror current Isense, and the other input is used to receive different threshold voltages generated by the reference current sources Iref1, Iref2, Iref3 and the reference voltage source Vref, respectively, so as to output the corresponding digital comparison results at different current levels, thereby forming the multi-threshold comparator output vector [C1,C2,C3].

[0030] Overvoltage protection circuit, which is connected to WSS_HS and / or VCC nodes, is used to control the high-side switch m4 and related clamping devices to operate when the node voltage exceeds the preset overvoltage threshold, and outputs the overvoltage protection flag F_OVP;

[0031] The overcurrent protection circuit is electrically connected to the high-side current limiting switch m9 and the low-side current limiting switch m10. It is used to limit the operating current of the active wheel speed sensor when the current flowing through the current limiting switch exceeds the preset overcurrent threshold, and outputs the overcurrent protection flag F_OCP.

[0032] The open-circuit diagnostic circuit includes a pull-up current source connected to the low-side pin WSS_LS of the sensor and a diagnostic comparator connected to the low-side pin WSS_LS of the sensor. It is used to pull up the voltage of the low-side pin WSS_LS of the sensor to a predetermined level when the active wheel speed sensor or wiring harness is open-circuited, and output the open-circuit diagnostic flag F_OPEN.

[0033] The digital logic circuit is connected to the outputs of the multi-threshold comparator circuit, the overvoltage protection circuit, the overcurrent protection circuit, and the open-circuit diagnostic circuit, respectively. The digital logic circuit encodes and makes decisions based on the multi-threshold comparator output vector [C1,C2,C3] and the protection and diagnostic flags, and outputs the wheel speed signal and / or diagnostic information through the wheel speed output pin WSS_Out.

[0034] The technical effects and advantages of the signal conditioning circuit and method for an active wheel speed sensor of the present invention are as follows:

[0035] This invention effectively solves the conflict and misjudgment problems of traditional static rules under dynamic operating conditions by fusing multi-source observations of multi-threshold comparator outputs, protection / diagnostic flags, and wheel speed time characteristics, and conducting comprehensive analysis on three time scales: single-tooth cycle, multi-cycle window, and long-term operation. By introducing window-level diagnostic labels to constrain instantaneous decisions, the false alarm rate and false negative rate are significantly reduced, improving the accuracy of wheel speed signals and fault diagnosis.

[0036] Based on the hardware circuit diagram, this invention optimizes signal processing methods to effectively resolve transient conflicts and suppress jitter. Through a well-designed processing flow, it ensures stable and reliable wheel speed and fault diagnosis results while meeting the real-time requirements of the ABS system.

[0037] This invention introduces a parameter adaptive adjustment mechanism based on long-term operating data. By statistically learning from historical operating data, diagnostic strategies and priorities can be dynamically optimized, enabling the system to better adapt to complex and ever-changing application scenarios such as multi-supplier sensors and multi-vehicle wiring harness topologies, thereby improving the system's robustness and versatility.

[0038] This invention can effectively identify early signs of failure such as progressive poor contact, avoiding the safety hazard of braking system failure under extreme conditions due to the failure to identify abnormal wheel speed signals in time, thereby improving the driving safety of the entire vehicle. Attached Figure Description

[0039] Figure 1 is a structural diagram of a signal conditioning circuit for an active wheel speed sensor according to the present invention;

[0040] Figure 2 is a flowchart of a signal processing method for a signal conditioning circuit of an active wheel speed sensor according to the present invention;

[0041] List of reference numerals in the attached diagram: m2 - Image transistor; m3 - Main image transistor; m4 - High-side switch; m5 - Low-side switch; m6 - Image transistor; m7 - Image transistor; m8 - Image transistor; m9 - High-side current limiting switch; m10 - Low-side current limiting switch; m11 - Image transistor; m12 - Image transistor; m13 - Image transistor; m14 - Image transistor; Isense - Image current; Comparator; Iref1 - Reference current 1; Iref2 - Reference current 2; Iref3 - Reference current 3; Vref - Reference voltage; WSS_Out - Wheel speed sensor output; STB - Control pin; WSS_HS - Wheel speed sensor high side; WSS_LS - Wheel speed sensor low side; VCC - Power supply. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0043] This invention provides a signal conditioning circuit and method for an active wheel speed sensor, aiming to solve the problem in the prior art where the output of a multi-threshold comparator is prone to conflict under dynamic operating conditions, leading to misjudgment or missed judgment.

[0044] The existing circuit diagram of the present invention is shown in Figure 1. In a specific embodiment, it specifically includes: a power input terminal VCC, a sensor high-side pin WSS_HS and a low-side pin WSS_LS, a standby control pin STB, a wheel speed output pin WSS_Out, and high-side switches m4, m5, m9, m10, m2, m3, m6, m7, m8, m11, m12, m13, and m14 arranged in the sensor current path, a comparator Comp, reference current sources Iref1, Iref2, Iref3 and a reference voltage source Vref, and protection and diagnostic logic circuits for generating overvoltage protection flag F_OVP, overcurrent protection flag F_OCP and open-circuit diagnostic flag F_OPEN.

[0045] The external active wheel speed sensor is connected to the WSS_HS and WSS_LS pins respectively, forming a two-wire power supply and signal loop. VCC provides operating power to WSS_HS through high-side current limiting switches m9 and m4. High-side current limiting switch m9 limits the current flowing through the high-side branch under abnormal conditions such as short circuit to ground. The WSS_LS terminal is connected to ground through low-side switch m5 and low-side current limiting switch m10. Low-side current limiting switch m10 limits the current in the low-side branch under abnormal conditions such as short circuit to battery. The gates of high-side switch m4 and low-side switch m5 are controlled by the STB pin and internal control logic, respectively, to switch the sensor's power supply path between standby and operating modes.

[0046] To accurately sample the sensor current without disrupting its operating point, this embodiment incorporates a current mirror circuit in the sensor current path. Specifically, the main mirror transistor m3 is connected in series in the sensor current path to sense the operating current flowing between WSS_HS and WSS_LS. Transistors m2, m6, m7, m8, m11, m12, m13, and m14, mirrored by the main mirror transistor m3, form a multi-stage current mirror network that replicates the sensor current as a mirrored current Isense by scaling it down to a predetermined ratio (e.g., 1:1000). This current mirror structure achieves electrical isolation between the high-voltage sensor side and the low-voltage signal processing side, and significantly reduces the power consumption and voltage stress on the subsequent comparators and logic circuits.

[0047] The mirrored current Isense is fed into a multi-threshold comparator circuit for current level discrimination. In this embodiment, the comparator Comp may include three or more comparison channels. One input of each comparison channel receives the detection voltage generated by Isense through a resistor or a current-to-voltage conversion unit, and the other input receives different threshold voltages generated by reference current sources Iref1, Iref2, Iref3 and reference voltage source Vref, respectively. By comparing the mirrored current with each threshold voltage, comparison results corresponding to different operating current levels such as 7mA, 14mA, and 28mA can be divided at the hardware level. These results are combined to form the multi-threshold comparator output vector [C1, C2, C3], providing basic digital measurements for subsequent software or logic judgments.

[0048] To improve the safety of the vehicle system under abnormal operating conditions, this embodiment integrates overvoltage and overcurrent protection circuits at the high-side, low-side, and sensor pins. The overvoltage protection circuit samples the WSS_HS and / or VCC node voltages. When the detected voltage exceeds a set threshold, it controls the high-side switch m4 and related clamping devices to conduct, clamping the WSS_HS voltage within a safe range and outputting an overvoltage protection flag F_OVP in the digital domain. The overcurrent protection circuit detects the current flowing through the high-side current-limiting switch m9 and the low-side current-limiting switch m10. When the current exceeds a preset limit, it reduces the conduction capability of m4 and m5 or shuts them off to limit the sensor current, while simultaneously outputting an overcurrent protection flag F_OCP.

[0049] For open-circuit diagnosis, the circuit includes a pull-up current source and a matching diagnostic comparator at the WSS_LS terminal. When an open-circuit fault occurs in the sensor or wiring harness, the normal current loop is interrupted, and the pull-up current source pulls the WSS_LS voltage high. Based on this, the diagnostic comparator generates an open-circuit diagnostic flag F_OPEN. This open-circuit flag can be used as a standalone diagnostic output, or it can be fed into subsequent digital logic along with the multi-threshold comparator output vector [C1, C2, C3] to form a richer range of fault type discriminations.

[0050] The multi-threshold comparison results [C1, C2, C3] and the protection / diagnostic flags F_OVP, F_OCP, and F_OPEN are uniformly sent to the digital logic circuit. The digital logic circuit encodes and de-jitters the comparison results according to the sensor protocol and system configuration, generating the wheel speed sensor output signal WSS_Out. Fault signals can be superimposed on WSS_Out as needed, or various fault flags can be output through a dedicated diagnostic register. The WSS_Out pin is directly connected to the microcontroller (MCU) and is used to provide wheel speed and diagnostic information to the vehicle's ABS / ESP and other upper-level control systems. The signal processing method proposed in subsequent embodiments of this invention performs multi-source comprehensive analysis on the above [C1, C2, C3], the number of flips, F_OVP, F_OCP, F_OPEN, and WSS_Out time characteristics without changing the hardware topology, to achieve robust judgment of wheel speed signals and fault states under dynamic conditions. Specifically:

[0051] Example 1: This example provides a signal processing method for a signal conditioning circuit of an active wheel speed sensor, the flowchart of which is shown in Figure 2, and includes the following steps:

[0052] Step S1: Acquisition of multi-source observation signals based on Figure 1. This step is mainly responsible for acquiring various digital signals from the hardware circuit and treating them as multi-source observation data.

[0053] S1.1 Utilizes current mirroring and multi-threshold comparison to form multi-source observations:

[0054] An external active WSS is connected between WSS_HS and WSS_LS. When the WSS is working, the current flows in through the high-side switch m4, and then the main mirror transistor m3 acts as the main mirror transistor, generating a proportionally reduced mirror current Isense through mirror transistors m2, m6, m7, m8, m11, m12, m13, and m14.

[0055] The mirrored current Isense is fed into multiple comparators Comp, which compare it with multiple thresholds formed by the reference currents Iref1, Iref2, Iref3 and the reference voltage Vref, to obtain multi-channel digital comparison results. For example:

[0056] This indicates that the Isense value is greater than the threshold of 1, corresponding to a current level of 7mA.

[0057] This indicates that the Isense value is greater than the threshold value of 2, corresponding to a current level of 14mA.

[0058] This indicates that Isense > threshold 3?, corresponding to a current level of 28mA.

[0059] It should be noted that this invention does not actually only consider the instantaneous level of a single comparator, but simultaneously observes the comparison results of each threshold to obtain a level vector reflecting the current current level range. .

[0060] S1.2 Acquisition, Protection, and Diagnostic Markers:

[0061] Meanwhile, the protection and diagnostic flags in the acquisition circuit are:

[0062] OVP logic monitors nodes such as WSS_HS and power supply VCC, and provides overvoltage protection flags. ;

[0063] The OCP logic provides overcurrent protection flags based on the operating status of the current-limiting branches of the high-end current-limiting switch m9 and the low-end current-limiting switch m10. ;

[0064] The open-circuit diagnostic circuit pulls up WSS_LS through a pull-up current source, and the corresponding diagnostic comparator outputs an open-circuit diagnostic flag. .

[0065] These flags, together with the multi-threshold comparison output, constitute fault-related observations.

[0066] S1.3 collects WSS_Out and time information:

[0067] The backend logic generates a WSS_Out pulse signal based on the comparator output. This signal is then recorded by a counter.

[0068] adjacent rising edge interval (kth tooth cycle), representing the current wheel speed;

[0069] Pulse width from rising edge to falling edge (Related to 7mA / 14mA / 28mA combinations and direction coding), indicating current level coding or direction information.

[0070] This allows for the simultaneous acquisition of three types of information: current level determination, protection status, and wheel speed time characteristics, rather than relying on only one type of signal for judgment. This provides raw data for subsequent comprehensive analysis and facilitates analysis.

[0071] Step S2: Construct comprehensive diagnostic features for a single tooth cycle:

[0072] Within the k-th tooth cycle, defined by two adjacent rising edges of WSS_Out, the following observations are obtained from S1, and a periodic feature vector is constructed. :

[0073] Current level logic vector: : Whether the three comparators were set to 1 during this cycle.

[0074] Number of flips: The number of times the comparator output flips within this cycle reflects whether the current level fluctuates.

[0075] Protection and diagnostic status: , , : Whether overvoltage / overcurrent / open circuit diagnosis is triggered during this cycle.

[0076] Wheel speed waveform parameters: period (Corresponding to current wheel speed); Pulse width (Corresponding current level code or direction information).

[0077] Define periodic eigenvectors:

[0078] ;

[0079] It should be noted that this invention, for each gear tooth cycle, does not only consider whether the current is 7mA / 14mA / 28mA, but also simultaneously considers the current level, jitter, whether protection is enabled, whether there is an open circuit, and the corresponding gear speed / pulse width information to form a multi-dimensional feature vector, which is used for subsequent decision-making.

[0080] Step S3: Stability and consistency analysis based on multi-period windows:

[0081] Even considering a single cycle, it may still be affected by instantaneous disturbances. Therefore, a window-level comprehensive analysis is performed over M consecutive tooth cycles. Let the current analysis window be... ,structure:

[0082] Current level statistics: This window counts the frequency of each current level pattern. For example:

[0083] L7: ;

[0084] L14: ;

[0085] L28: .

[0086] jitter intensity index: This reflects whether the current level judgment frequently crosses the threshold during that time period.

[0087] Protection status statistics: , , .

[0088] Wheel speed smoothness: Calculating periodic sequences variance Observe whether the wheel speed is stable. Very small but The large value indicates that the wheel speed is stable, but the current judgment is fluctuating, which is more like a noise problem than a change in actual operating conditions.

[0089] Based on this, define window-level diagnostic labels. :

[0090] If the proportion of a certain current level exceeds the threshold, such as L7 or L14 exceeding 90%, at the same time Smaller, and , , If all values ​​are close to 0, the window is considered to be in a normal and stable operating condition.

[0091] like Small, meaning the wheel speed is stable, but Big, and , , If all values ​​are 0, it is determined to be noise-induced current decision jitter.

[0092] like Significantly greater than 0, and for the vast majority of periods If the value is consistently 1, it is considered a suspected short-circuit hard fault.

[0093] like Larger Mostly 0, and If there is a clear signal disappearance segment in the sequence, it is judged as a suspected open circuit or poor contact.

[0094] This invention utilizes four types of information simultaneously: current level mode, jitter intensity, protection indicator, and wheel speed stability. Through window statistics, it elevates instantaneous observations to segment-level health status, which is used to distinguish several different root causes, including normal, noise, short circuit, open circuit, and poor contact.

[0095] Step S4: Comprehensive judgment and resolution of conflict state:

[0096] In practical applications, a basic hardware state machine may produce contradictory instantaneous outputs at a given moment. To resolve such conflicts, this solution obtains window-level diagnostic labels in S3. Based on this, a joint decision-making mechanism of instantaneous judgment and window diagnosis is introduced, specifically including:

[0097] S4.1 Instantaneous Candidate Decision Generation:

[0098] Based on single-period characteristics Generate instantaneous candidate states according to existing rules: .

[0099] S4.2 Integrated Diagnostic Constraint Instantaneous Output:

[0100] Use the window it belongs to right Add constraints:

[0101] like It was determined to be noise-induced jitter, and If the switching between 7mA and 14mA is frequent within adjacent cycles, these switchings are treated as noise, and the state is de-jittered at the output layer. For example, the same state is required for N consecutive cycles before a real switching occurs.

[0102] like It was judged as a suspected short-circuit hard fault, even in certain cycles. The fault is not immediately removed even after the current returns to normal briefly. Instead, the fault flag is removed only after the window-level indicators have returned to normal for a period of time.

[0103] like If the circuit is suspected to be open or there is a poor connection, then for a single normal cycle... Take a cautious approach and prioritize outputting diagnostic results for intermittent faults.

[0104] Through the above steps, the judgment of the instantaneous state machine is no longer the final conclusion, but is output after being integrated with window-level and history-level diagnosis, thus avoiding misjudgment caused by instantaneous waveforms.

[0105] Example 2: Based on Example 1, this example further introduces long-term comprehensive analysis to achieve adaptive adjustment of parameters.

[0106] Step S5: Adaptive parameter adjustment based on long-term operating data:

[0107] Building upon S3 and S4, this invention can also perform long-term statistical analysis of diagnostic results over a longer timescale, such as hundreds or thousands of windows, and can be used to adjust configurable reference parameters in the basic circuit, specifically including:

[0108] S5.1 Long-term statistics and health assessment:

[0109] Statistics are performed for each platform / each wheel speed channel in the MCU or external host computer:

[0110] The cumulative occurrence time of various states, namely, the occurrence time of normal, noise jitter, short circuit, open circuit, intermittent poor contact, etc.

[0111] The corresponding temperature, voltage, and vehicle operating conditions can be provided by other bus signals.

[0112] Construct a health curve for the channel over time to identify long-term trend problems, such as a gradual increase in the frequency of short-circuit events in a certain channel.

[0113] S5.2 Using statistical results to reverse adjust comparison and diagnostic strategies:

[0114] For channels that frequently experience noise-induced jitter, adjust the registers appropriately:

[0115] Increase the hysteresis of certain thresholds, for example, by adjusting the hysteresis voltage or current values ​​of the thresholds Iref1, Iref2, and Iref3 of the comparator Comp, so that it is less likely to trigger a flip when the current fluctuation is small.

[0116] Alternatively, adjust the window length M or the debounce count N. For example, increase the value of M to perform statistics over a longer time window, or increase the value of N to require a longer period of stable state before confirming a state transition.

[0117] For channels that frequently generate false alarms within a specific temperature / voltage range, a temperature / voltage-related threshold offset can be introduced into the software. The judgment can be compensated. For example, when the temperature rises, the sensor current may decrease slightly. In this case, the comparison threshold can be fine-tuned to avoid misjudging it as a low current level.

[0118] This invention integrates not only the instantaneous signal and local window signal of the current channel, but also the statistical behavior over a long period, under multiple operating conditions, and across multiple channels. These statistical characteristics are used to inversely optimize the system's decision-making strategy, forming a closed loop. Through this adaptive adjustment, the system can better adapt to environmental changes and sensor aging, further improving the accuracy and robustness of diagnosis.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A signal conditioning method for an active wheel speed sensor, characterized in that, The process includes the following steps: Real-time acquisition of the multi-threshold comparator output vector. and the number of times it flips The multi-threshold comparator output vector is described above. This indicates whether the comparators corresponding to different current levels were set to 1 within the current gear tooth cycle; the number of toggles... This indicates the number of toggles in the output of the multi-threshold comparator within the current gear tooth cycle; it also synchronously acquires the status of overvoltage protection, overcurrent protection, and open-circuit diagnostic flags; and constructs a periodic feature vector. It includes current level, jitter status, protection status, and wheel speed parameters; the periodic feature vector It also includes: the period of the gear tooth cycle. and pulse width Set an M-period sliding window for the periodic feature vector. Perform current level pattern statistics and jitter intensity calculation; wherein, the current level pattern statistics include counting the number of occurrences of each current level pattern within the M-cycle sliding window; the jitter intensity calculation includes calculating the number of flips within the M-cycle sliding window. The sum; generating window-level diagnostic labels based on the statistical results of the sliding window. ; wherein, the window-level diagnostic label The generation criteria include: the proportion of the current level mode, the jitter intensity, the number of triggers of the overvoltage protection, overcurrent protection, and open circuit diagnostic flags, and the wheel speed smoothness; the window-level diagnostic label. The conditions are categorized into normal stable operating conditions, noise-induced jitter, suspected short-circuit hard faults, and suspected open circuits or poor contact; instantaneous decision-making is employed in conjunction with the aforementioned window-level diagnostic labels. The joint decision-making mechanism outputs the final state; wherein, the instantaneous decision is based on single-cycle characteristics. Instantaneous candidate states are generated according to preset rules; the joint decision-making mechanism includes: if the... If the jitter is determined to be noise-induced, then de-jitter processing is performed on the switching of the instantaneous candidate state; if the window-level diagnostic label If a suspected short-circuit hard fault is identified, the fault flag should be removed only after the window-level indicators have returned to normal for a period of time; if the aforementioned window-level diagnostic label... If the fault is suspected to be an open circuit or poor contact, the diagnostic results for intermittent faults will be output first.

2. The signal conditioning method for an active wheel speed sensor according to claim 1, characterized in that: The method further includes adaptively adjusting at least one of the following based on long-term operating data: the window length M of the M-period sliding window, the counting parameter N used for de-jitter processing in the preset rules, and the threshold hysteresis of the multi-threshold comparator.

3. A signal conditioning circuit for an active wheel speed sensor, used to implement the method according to any one of claims 1-2, characterized in that, include: The system includes a power input terminal VCC, a sensor high-side pin WSS_HS, a sensor low-side pin WSS_LS, a standby control pin STB, and a wheel speed output pin WSS_Out; a power supply switching circuit, including a high-side switching circuit and a low-side switching circuit. The input terminal of the high-side switching circuit is connected to the power input terminal VCC, and the output terminal is connected to the sensor high-side pin WSS_HS. The input terminal of the low-side switching circuit is connected to the sensor low-side pin WSS_LS, and the output terminal is connected to ground. The control terminals of the high-side and low-side switching circuits are connected to STB and internal control logic; a current mirror circuit, located in the sensor current path between the high-side and low-side switching circuits, includes a main mirror transistor m3 connected in series in the sensor current path and multiple mirror transistors connected in parallel with the main mirror transistor m3, used to mirror the sensor operating current into a proportionally scaled mirror current Isense; and a multi-threshold comparison circuit, including multiple comparators Comp and multiple comparators... The system connects to reference current sources Iref1, Iref2, Iref3 and reference voltage source Vref. One input of each comparator receives the detection voltage obtained from the mirrored current Isense, and the other input receives different threshold voltages to output multi-channel comparison results representing different current levels. A protection circuit, connected to the power supply switch circuit, limits the sensor current when a short circuit to ground, a short circuit to the power supply, or an overvoltage is detected, and generates an overvoltage flag F_OVP and an overcurrent flag F_OCP. A diagnostic circuit, connected to the sensor's low-side pin WSS_LS, includes a pull-up current source and a diagnostic comparator, generating an open-circuit flag F_OPEN when the sensor or wiring harness is open. A digital logic circuit, whose inputs are connected to the outputs of the multi-threshold comparison circuit, protection circuit, and diagnostic circuit, generates a wheel speed signal and diagnostic results based on the multi-channel comparison results, overvoltage flag, overcurrent flag, and open-circuit flag, and outputs the wheel speed signal via the wheel speed output pin WSS_Out.

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