Method and system for detecting failure of parking mechanism of electromechanical brake

Abstract

The application discloses a kind of electronic mechanical brake's parking mechanism failure detection method and system, belong to automobile brake technical field.The method includes: after releasing ratchet pawl self-locking, first current is passed to electromagnet connected with pawl;Again, the current is linearly reduced to the second current corresponding to the lower limit of normal working force value of return spring, and the first preset threshold thrust is output;After stopping motor to maintain torque, if it is monitored that parking release, it is judged that return spring force is normal, otherwise, it is judged that abnormal attenuation.In abnormal attenuation, the current can be further reduced to the third current corresponding to minimum holding force to carry out secondary detection, and the attenuation degree is distinguished.Accordingly, graded alarm and vehicle control are carried out.The passive element of the present application is converted into an electrical signal event that can be actively detected, and a double-wheel alternating redundancy testing strategy is used, which fundamentally eliminates the single-point failure risk of parking failure to release or unexpected locking, and greatly improves the system functional safety level.

Description

Technical Field

[0001] This invention relates to the field of automotive braking technology, specifically to a method and system for detecting the failure of the parking mechanism of an electromechanical brake. Background Technology

[0002] Electromechanical braking (EMB) systems, as a core development direction of brake-by-wire technology, are key braking actuators for new energy vehicles and highly automated vehicles. To meet the parking requirements of vehicles, parking brake functionality is typically integrated into EMB calipers. Currently, EMB systems generally employ a ratchet-pawl-based mechanical parking mechanism. Its basic workflow is as follows: after the EMB caliper motor builds up pressure to the target clamping force, it drives the pawl to engage with the ratchet, maintaining the clamping force through mechanical locking to achieve parking; when releasing the parking brake, the motor must first build up pressure again to eliminate the locking force on the engagement surface, and then drive the pawl to disengage from the ratchet.

[0003] The prior art, entitled "An Electromechanical Parking Self-Locking Mechanism and Control Method," discloses a parking structure for an electromechanical braking system. This scheme mainly consists of a controller, a brake motor, a ratchet, a pawl, a solenoid valve, and an elastic element. The solenoid valve employs a monostable design; when energized, its push rod extends to push the pawl into the locking position; when de-energized, the push rod retracts and disengages from the pawl. The elastic element is used to pull the pawl from the locked position to the unlocked position when the solenoid valve is de-energized. When the parking is locked, the motor builds up pressure and maintains it; the solenoid valve is energized to push the pawl into the engagement position; subsequently, the motor is de-energized, and the load reaction force locks the pawl in place; finally, the solenoid valve is de-energized. When the parking is unlocked, the solenoid valve remains de-energized; after the motor rotates forward to eliminate the pressure on the engagement surface, the pawl automatically resets under the pulling force of the elastic element.

[0004] However, the aforementioned existing technical solutions have significant technical flaws. In these solutions, the parking unlock function heavily relies on the proper functioning of the elastic element. If the elastic element experiences fatigue, plastic deformation, or even breakage due to prolonged use, resulting in performance degradation or failure, the pawl will not reliably return to the unlocked position under the action of the elastic element after the motor rotates forward to release the locking force between the ratchet and pawl. This situation leads to the vehicle parking lock remaining locked, causing the vehicle to break down and severely impacting the user experience. More seriously, if the ratchet and pawl unexpectedly and temporarily separate during driving due to vibration or other factors, the degraded elastic element may not provide sufficient holding force to stabilize the pawl in the released position, causing the pawl to unexpectedly engage with the ratchet, triggering unexpected braking of a single wheel and causing the vehicle to momentarily yaw and become unstable, seriously threatening driving safety. Therefore, existing parking mechanisms are insufficient in terms of functional safety, reliability, and life-cycle robustness, urgently requiring a highly reliable parking control solution to address these issues. Summary of the Invention

[0005] The purpose of this application is to address the shortcomings of the aforementioned background technology and to provide a method and system for detecting the failure of the parking mechanism of an electromechanical brake.

[0006] The technical solution of this application is: a method for detecting the failure of the parking mechanism of an electromechanical brake, wherein the parking mechanism includes a ratchet fixedly connected to the motor shaft, a pawl hinged to the housing and capable of engaging or disengaging with the ratchet, an electromagnet, and a return spring; wherein the electromagnet and the return spring are both connected to the pawl. This includes a primary detection process; the primary detection process includes: After the first wheel of the vehicle is locked in place, the electromechanical brake motor is driven to apply braking force to release the engagement lock between the ratchet and the pawl. A positive first current is supplied to the electromagnet to maintain the engagement of the pawl, and then the current is linearly reduced to a preset positive second current, so that the electromagnet's push rod outputs a first preset threshold thrust. Stop the motor output to maintain braking torque and monitor whether the pawl separates from the ratchet, causing the parking brake to release; If parking brake release is detected, the return spring force is considered normal; if parking brake release is not detected, the return spring force is considered to have abnormally decreased.

[0007] According to the failure detection method of the parking mechanism of an electromechanical brake provided in this application, the first preset threshold thrust is calibrated as: the force corresponding to the lower limit of the normal working force value of the return spring. This force value is converted into the equivalent thrust value of the electromagnet push rod end through the lever ratio of the pawl. The positive second current is determined based on the equivalent thrust value through the corresponding curve of electromagnet thrust and current calibrated on the test bench.

[0008] According to the parking mechanism failure detection method of the electromechanical brake provided in this application, after determining that the return spring force has abnormally decreased, a secondary detection process is also included; the secondary detection process includes: After the wheels are locked in place, the motor is driven again to apply braking force to release the engagement between the ratchet and the pawl. A positive first current is supplied to the electromagnet to maintain the engagement of the pawl. Then, the current is linearly reduced to a preset positive third current, so that the electromagnet's push rod outputs a second preset threshold thrust. Stop the motor output to maintain braking torque and monitor whether the parking brake is released; If parking brake release is not detected, it is determined that the return spring force has been severely weakened and cannot maintain the normal release position of the pawl; if parking brake release is detected, it is determined that although the return spring force has weakened, it can still maintain the normal release position of the pawl.

[0009] According to the parking mechanism failure detection method of the electromechanical brake provided in this application, the second preset threshold thrust is calibrated as: the force corresponding to the minimum holding force required to maintain the pawl in the normal release position. The minimum holding force is used to overcome the pawl's own weight, motion friction resistance and vehicle vibration interference. The force value is converted into the equivalent thrust value of the electromagnet push rod end through the lever ratio of the pawl. The positive third current is determined based on the equivalent thrust value.

[0010] According to the parking mechanism failure detection method of the electromechanical brake provided in this application, when the secondary detection determines that the return spring force has been severely weakened, but the parking mechanism can still achieve controllable locking and releasing through electromagnet, the vehicle is allowed to drive normally while the yellow parking fault light is illuminated. When the secondary detection determines that the return spring force has been severely weakened and the electromagnet has also malfunctioned and cannot control the parking release, the vehicle will be controlled to illuminate the red parking fault warning light and the vehicle will be prevented from continuing to move.

[0011] According to the method for detecting the failure of the parking mechanism of an electromechanical brake provided in this application, the first-level detection process and / or the second-level detection process are executed during the vehicle power-off self-test stage; and are only started when the vehicle braking domain controller determines that both rear wheels of the vehicle are in a stable parking state.

[0012] According to the present application, a method for detecting the failure of the parking mechanism of an electromechanical brake is applied to a vehicle having a first wheel and a second wheel. When detecting the first wheel and the second wheel, the following steps are performed: After controlling the first wheel to keep it in the parking lock state and confirming that its parking force can independently maintain the vehicle's stable parking, the inspection process is performed on the second wheel. After the inspection process of the second wheel is completed and it is controlled to return to the parking lock state, and it is confirmed that it can independently maintain the stable parking of the vehicle, the inspection process is performed on the first wheel. After the first wheel inspection process is completed, control both wheels to return to the parking state and restore the parking clamping force of both wheels to the standard force value corresponding to the common parking.

[0013] This application also relates to a parking mechanism failure detection system for an electromechanical brake, used to implement the above-described method, the detection system comprising: The ratchet is rigidly connected coaxially to the ball screw shaft of the electromechanical brake caliper; The pawl is hinged to the caliper housing in the middle, and its head can engage or disengage with the ratchet. An electromagnet, the end of its push rod is connected to the tail of a pawl; The return spring has its movable end connected to the tail of the pawl; Motor rotation angle sensor, used to monitor the rotation angle signal of the motor rotor in real time; The control unit is configured as follows: Control the on / off timing and current value of the motor and electromagnet; Receive and process signals from the motor angle sensor to determine the parking release status; and Perform the first-level detection procedure for the return spring force.

[0014] According to the parking mechanism failure detection system of the electromechanical brake provided in this application, the control unit is configured to: automatically execute a secondary detection process after determining that the return spring force has abnormally decayed, distinguish the degree of decay of the return spring force based on the monitoring results of the motor rotation angle sensor; and generate a graded fault alarm signal according to the preset judgment logic to control the vehicle instrument panel to illuminate a yellow or red warning light.

[0015] According to the present application, a parking mechanism failure detection system for an electromechanical brake includes two independent rear wheel parking calipers. The control unit is further configured to execute a dual-wheel alternating test mode during the vehicle's power-down self-test, ensuring that one of the parking calipers maintains stable parking of the vehicle throughout the process.

[0016] The advantages of this application are: First, it implements a dual-redundant safety architecture for the parking release function, which fundamentally eliminates the risk of single-point failure when the parking cannot be released.

[0017] This application establishes a parallel redundant drive mechanism by connecting an electromagnet push rod and a return spring in parallel to the tail of the pawl. When the electromagnet is energized, it actively pushes the pawl into or pulls it out of the engaged position, while the return spring consistently provides the ground-state force that tends the pawl towards the disengaged position. Even if the electromagnet completely fails due to coil burnout, an open circuit in the drive circuit, or other reasons, losing its active constraint on the pawl, the return spring can still act as an independent second drive source to stabilize the pawl in the released posture. This completely avoids the serious operational obstacle of traditional single-actuator solutions where the vehicle cannot be released from parking lock when the actuator is jammed or disabled, leading to vehicle breakdown on the road. It is particularly suitable for unattended L3 and higher-level autonomous driving scenarios, ensuring that the vehicle has the basic ability to disengage from the parking lock and enter a drivable state under any circumstances.

[0018] Second, a self-detection mechanism for graded return spring force was constructed throughout the entire life cycle, enabling accurate identification and graded early warning of spring performance degradation.

[0019] This application quantifies the mechanical state of the return spring into three levels: "normal," "slightly degraded but still able to maintain release," and "severely degraded and unable to guarantee release," through a progressive design of a first-level and a second-level testing process. In the first-level test, with the ratchet and pawl engaged and locked, a first preset threshold thrust, calibrated to the lower limit of the return spring's normal operating force, is used to probe the pawl's state. If the pawl is still pulled back to the release position by the spring when the tension is insufficient, the spring is considered healthy; otherwise, the second-level in-depth test is initiated. The second-level test then examines whether the pawl can maintain its normal release position again under a second preset threshold thrust at an even lower level. This stepped stress test, utilizing the precisely adjustable characteristics of electromagnet thrust, exposes hidden gradual degradation problems as clear electrical signal judgment standards. This allows repair shops or vehicle controllers to receive graded warnings before the spring force causes actual driving hazards, significantly reducing the probability of sudden parking release anomalies.

[0020] Third, by using the electromagnet to actively maintain the pawl, it effectively prevents unexpected parking lock-up caused by external disturbances during driving.

[0021] This application clarifies that during certain testing phases or under normal electromagnet operating conditions, the pawl can be maintained in engagement or disengagement by an electromagnet. This design ensures that even when the vehicle is traveling on bumpy roads, experiencing continuous vibration and impact, or affected by factors such as the pawl's own weight or changes in the frictional resistance of moving parts, the pawl will not accidentally jump into the ratchet's teeth, avoiding the extreme and dangerous situation of a single rear wheel suddenly locking up. When the return spring is slightly worn but still effectively functioning, the electromagnet acts as the active force source to supplement the holding force on the pawl; insufficient holding force only occurs when the spring is severely worn and the electromagnet is completely failed, a double fault. This active holding mechanism eliminates the problem of insufficient anti-interference capability that may be encountered when relying solely on spring holding, reducing the probability of unexpected braking during driving to an extremely low level required by functional safety standards.

[0022] Fourth, a dual-wheel alternating redundant testing strategy was designed to ensure the vehicle's parking safety while performing complete testing and diagnosis.

[0023] The testing process controls the first wheel to remain fully locked and independently bear the vehicle's parking force. Only after confirming safety is the second wheel released for a full-stroke electromagnet and spring force test. After the second wheel completes its test, it is locked again and independently bears the force before the first wheel is tested. This alternating redundant testing logic dynamically switches the testing and safe bearing tasks between the parking mechanisms of the left and right rear wheels. At any given time, at least one wheel maintains sufficient parking clamping force, eliminating the risk of vehicle slippage caused by both wheels being in the testing and release state simultaneously. As a result, the vehicle can safely complete all testing items during the power-off self-test phase without affecting the user's normal parking, leaving, and locking operations. This seamlessly integrates high-reliability diagnostics into daily usage processes, providing a foundation for the large-scale safe operation and maintenance of new energy vehicles and autonomous driving fleets. Attached Figure Description

[0024] Figure 1 This application includes a schematic diagram of the parking mechanism structure. Figure 2 This application provides a schematic diagram of the failure detection process for the parking mechanism of an electromechanical brake. Wherein: 1—ratchet; 2—pawl; 3—electromagnet; 4—return spring. Detailed Implementation

[0025] The embodiments of this application are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0026] In the description of this application, it should be understood that the terms "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are 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. Therefore, they should not be construed as limitations on this application.

[0027] 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 technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0028] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] This application provides a method and system for detecting parking mechanism failures in electromechanical brakes (EMBs), aiming to solve the problem of parking mechanisms failing to release or locking unexpectedly due to a single failure point (especially the electromagnet or return spring), and to improve the functional safety level of the system. This application constructs a closed-loop safety architecture with dual redundant drive, full life-cycle self-testing, and hierarchical control.

[0030] Specifically, the parking mechanism failure detection system of the electromechanical brake in this application includes an actuator layer and a sensing and electronic control layer, such as... Figure 1 As shown, the actuator layer includes a ratchet 1, a pawl 2, an electromagnet 3, and a return spring 4. The ratchet 1 is rigidly connected to the ball screw shaft of the EMB caliper on the same axis and rotates with the motor. It has evenly distributed circumferential tooth grooves. One end of the pawl 2 is hinged to the caliper housing through a pin to form a lever structure. Its head can be inserted into the ratchet tooth groove to achieve engagement and locking, or allow the ratchet to rotate freely when disengaged. The electromagnet 4 is a bidirectional stabilizing electromagnet. Its push rod end is movably connected to the tail of the pawl 2. By controlling the direction of the current, the push rod can be driven to extend or retract, actively controlling the engagement and disengagement of the pawl 2. The return spring 3 is usually a tension spring. Its movable end is also connected to the tail of the pawl 2, and its fixed end is connected to the housing. Its function is to provide the pawl 2 with a ground state return force that continuously points to the disengaged position.

[0031] The sensing and control layer includes a motor angle sensor and a control unit. The motor angle sensor is integrated inside the EMB motor and is used to monitor the rotor angle, speed, and position signals in real time. The control unit, as the core of the system, is configured to implement the following detection algorithms and logic. It includes at least a microcontroller (MCU), an electromagnet drive circuit, a motor drive circuit, and an external communication interface.

[0032] This application involves a basic health status assessment of the return spring to determine whether its force value has abnormally decreased. The entire Level 1 inspection process is performed after the vehicle meets specific safety conditions. The control unit first confirms that the first wheel (such as the left rear wheel) has completed the standard parking lock action, that is, the motor drives the ball screw to push the piston to generate clamping force, and at the same time the ratchet and pawl engage and lock at a specific position; A sufficiently large positive initial current is supplied to the electromagnet, causing the push rod to generate a thrust higher than the spring force, which actively and firmly presses the pawl into the engagement position. This step ensures that the initial conditions of the test are uniform and controllable. The EMB motor is driven to apply an additional braking force directional torque. This is intended to eliminate the huge self-locking force between the ratchet and pawl teeth, so that the two are in a critical state of just disengaging but not yet separated. In this state, the constraint force of the pawl is provided entirely by the electromagnet push rod and the return spring. Subsequently, the control unit executes a controlled current linear decay algorithm, which uses PID closed-loop control or a preset ramp function to smoothly and linearly reduce the electromagnet current from the first current to a preset positive second current.

[0033] The positive second current is calculated through bench calibration based on the lower limit of the normal operating force of the spring, which is a safety boundary. The specific calibration process is as follows: Define the maximum allowable spring force attenuation in engineering, i.e., the lower limit of the normal operating force. F smin This force value is converted into the equivalent thrust required at the end of the electromagnet push rod based on the lever ratio of the lever arm from the pawl tail to the hinge point to the lever arm from the head to the hinge point. F eq Finally, based on the thrust and current characteristic curves of the electromagnet measured on the test bench, the generation... F eq The current value required for the thrust is the positive second current. At this time, the electromagnet outputs a boundary thrust that is exactly equal to or slightly less than the separation force that the spring should provide in a healthy state, which is called the first preset threshold thrust.

[0034] Once the current drops to the second positive current and stabilizes, the motor immediately stops outputting torque to maintain balance. At this time, the pawl is in a monitoring window where it is only subjected to the combined action of the electromagnet thrust (which has dropped to the first preset threshold) and the return spring pull.

[0035] The control unit acquires signals from the motor angle sensor at high frequency. When the parking brake is released, the ratchet will rotate slightly due to the rolling trend of the wheels, causing the motor rotor to rotate synchronously, and the sensor can then capture this angle change.

[0036] If parking release is detected: This indicates that when the electromagnet's thrust drops to the first preset threshold, the return spring's tension overcomes the electromagnet's thrust, successfully pulling the pawl back to the disengaged position. This directly proves that the return spring force is greater than its normal operating force lower limit, thus determining that the return spring force is normal.

[0037] If parking release is not detected, it indicates that even if the electromagnet's thrust has decreased to a level that a normal spring could overcome, the spring still failed to pull the pawl back. This directly proves that the actual output force of the return spring is less than its design lower limit, indicating that the return spring force has abnormally decreased.

[0038] Traditional detection passively waits for a fault to occur. The detection method of this application actively creates a force balance critical point, transforming the mechanical properties of the passive component, the return spring, into an electrical signal event that can be actively detected and interpreted by the electronic control system, thus achieving a leap from post-fault remediation to pre-fault prevention.

[0039] Through a rigorous conversion and calibration process involving the lower limit of spring force, lever ratio conversion, electromagnet thrust, and calibration current, the vague mechanical perception is transformed into a precise current threshold, making the physical meaning of the boundary between normal and abnormal situations clear and avoiding misjudgment and omission.

[0040] The current linear decay algorithm and the decision logic based on a single sensor (motor angle sensor) greatly simplify the system complexity. No additional force or displacement sensor is required. It is low-cost, highly reliable, and easy to deploy and implement in vehicle controllers.

[0041] In some embodiments of this application, this embodiment provides a detailed explanation of the method for calibrating the first preset threshold thrust and the positive second current.

[0042] The entire calibration process is completed in advance on the test bench and the calibration parameters are stored in the memory of the control unit, following a rigorous force and electrical mapping chain.

[0043] Through engineering analysis (such as FMEA, simulation, and field measurements), the minimum spring force required to ensure the ratchet pawl reliably and quickly returns from the engaged position to the disengaged position without electromagnet assistance was determined. This force must be able to overcome interference such as the ratchet pawl's own weight, pin friction torque, and vehicle vibration. Any decrease in force below this value is defined as abnormal. This value is... F smin .

[0044] The return spring acts at the tail end (the point of force application is A, and the lever arm is...). L A The reaction force of the ratchet on the pawl is at the head (the point of application of the force is B, and the lever arm is). L B The electromagnet push rod is usually also connected to the tail end, assuming that the push rod connection point coincides with or is approximately the point of action of the return spring.

[0045] To simulate the spring's return capability at the ratchet using the electromagnet's thrust during testing, the spring force acting on the tail needs to be converted into an equivalent thrust at the electromagnet's push rod end. Based on the principle of torque balance: F smin *LA=F eq *LA (Assuming they act at the same point), but since the electromagnet push rod and spring may act at different points on the tail, a more general formula is: Fsmin *Lspring= F eq *L solenoid .

[0046] calculate: F eq =(L spring / L solenoid )*F smin .in, L spring and L solenoid These are the effective lever arms of the spring and the electromagnet actuator at the pawl hinge point, respectively. This calculation yields the equivalent thrust value that the electromagnet actuator needs to output. F eq .

[0047] Under constant temperature conditions, different magnitudes of constant current were applied to electromagnet samples of the same model. A high-precision mechanical sensor was used to measure the thrust value output by the push rod at the corresponding stroke position, and the thrust-current characteristic curve was plotted, i.e., electromagnet thrust-current curve calibration. I 2 =g(F eq ) ).

[0048] Based on the required equivalent thrust calculated in the previous step F eq By performing a lookup table or interpolation on this curve, the corresponding electromagnet driving current value can be uniquely determined, and this current is the positive second current. I 2 The function here represents this mapping relationship.

[0049] Thus, the abstract judgment of whether a spring is functioning properly has been precisely transformed into a concrete, executable electrical command. I 2 During the test, simply reducing the current to... I 2 The electromagnet then outputs force. F eq Used to test whether the spring force is greater than F smin .

[0050] Every link in the entire calibration chain in this embodiment is based on explicit physical laws (torque balance, electromagnetic force characteristics), rather than empirical or black-box models, which makes the calibration results highly interpretable and robust.

[0051] Bench calibration can effectively compensate for the effects of individual manufacturing differences and mechanical friction differences in electromagnets, enabling each product to obtain a precise detection threshold tailored to its own characteristics, thus ensuring consistency in testing during mass production.

[0052] This precise force-electric mapping model is not only used for primary detection, but also provides a scalable and quantifiable calibration framework for subsequent, more refined secondary detection.

[0053] In a further embodiment of this application, this embodiment describes a secondary detection process that is automatically triggered after the primary detection determines that the return spring force has abnormally decayed, in order to achieve graded identification of the degree of decay.

[0054] The secondary detection process is automatically activated by the control unit only when the primary detection process determines that the return spring force has abnormally weakened.

[0055] The initial steps of the secondary test are exactly the same as those of the primary test, with the aim of resetting the test environment and establishing the same starting point for force equilibrium: Control the wheels to lock the parking brake again, then drive the motor to apply braking force and release the ratchet pawl from engagement.

[0056] A positive current is supplied to the electromagnet to strongly maintain the engagement of the pawl.

[0057] The control unit executes a linear current decay algorithm, but the target current this time is a preset positive third current, causing the electromagnet push rod to output a second preset threshold thrust.

[0058] The second preset threshold thrust is less than the first preset threshold thrust. It is not used to determine whether the spring force meets the standard, but rather to determine whether the spring force has decayed to a dangerous level where it cannot overcome the minimum resistance required for the pawl to maintain its released state. The calibration of this minimum holding force considers three factors: ① the pawl's own weight component; ② the kinetic frictional resistance at the hinge and push rod connection; ③ the maximum vibrational inertial force interference generated on the pawl in both moving and stationary states.

[0059] Once the current drops to the third positive current and stabilizes, the motor stops to maintain torque. The control unit then monitors whether the parking brake has been released again via the motor angle sensor.

[0060] If parking brake release is detected: This indicates that although the force of the return spring is outside the normal range, it is still greater than the minimum holding force required to maintain its released position. Even after the external constraint force of the electromagnet is removed, the pawl can still be pulled back to the disengaged position by the spring. This is considered a slight and controllable decrease in the return spring force, which can still maintain the pawl's normal released position.

[0061] If parking release is not detected: This indicates that the force of the return spring has weakened to the point where it cannot even overcome the weight of the pawl itself, friction, and vibration; that is, it has lost even the ability to maintain itself in the disengaged position. The spring alone is no longer sufficient to disengage the pawl from the engaged state. This is considered a severe and dangerous weakening of the return spring force, making it unable to maintain the pawl's normal release position.

[0062] This embodiment achieves precise grading of health status by further subdividing abnormal attenuation into severe attenuation. The previously vague fault state is precisely quantified into two levels: usable but with anomalies, and unusable and high-risk. This provides precise input for subsequent grading and processing strategies. For components judged to have only slight attenuation, the system can recognize that they still possess some core functions (releasing the pawl), thus guiding the vehicle to take relatively mild safety measures (such as only issuing an alarm while allowing limp driving), maximizing vehicle availability and avoiding overreaction. Secondary detection is essentially an active detection of whether the system's last line of defense has collapsed. It can expose the risk of potential pawl malfunction before a fault scenario requiring electromagnets to disengage the pawl occurs, greatly improving preventative safety levels.

[0063] In a preferred embodiment of this application, this embodiment is a detailed elaboration of the above-mentioned second preset threshold thrust and positive third current calibration method.

[0064] Similar to the method described above for obtaining the first preset threshold, this calibration is also performed on a test bench, with the aim of defining unacceptable absolute failure boundaries.

[0065] First, determine the minimum static holding force required to keep the pawl in the normal disengaged position and prevent it from accidentally falling into the ratchet tooth groove due to its own weight, vibration, or other reasons. This force is not a disengaging force, but a holding force.

[0066] It can be calculated using the following formula: F holdmin =max(F gravity (Angle)+ F friction ,F vibrationadd ),in F gravity This represents the maximum weight component of the pawl under different vehicle body postures. F friction For maximum static friction, F vibrationadd This refers to the equivalent additional holding force required to ensure a greater than 99.99% probability of accidental locking after taking into account random vibrations of a specified level (such as ISO 16750-3 standard). Typically, a safety factor greater than 1 is added. KThis value was determined through a combination of multibody dynamics simulation and experimental calibration.

[0067] Perform mechanical transformation. F eqhold =(L pawltail / L solenoid )*F holdmin .in, L pawltail This is the lever arm from the pawl's center of gravity to the hinge point (vector calculation is required if there is an angle). If the lever arm of the electromagnet push rod connection point differs from that of the spring connection point, then the counter-stress arm must be used. This conversion yields the equivalent thrust value that the electromagnet push rod end needs to output. F eqhold .

[0068] Construct electrical mapping relationships, I 3 =g(F eqhold ) The corresponding positive third current value can be obtained by searching or interpolating on the electromagnet thrust-current curve. I 3 The current value drives the electromagnet to output the second preset threshold thrust that determines life or death.

[0069] This embodiment is illustrated by... F vibrationadd This approach equates random vibration, a dynamic disturbance, to a static force, allowing a simple static threshold detection to cover various dynamic driving scenarios throughout the vehicle's entire lifecycle, greatly simplifying the complexity of online detection. Safety factor. K The introduction of this feature allows designers to quantitatively design and manage the probability of unexpected locking, the highest-risk event, which is exactly the safety margin design concept required by functional safety standards (such as ISO 26262).

[0070] In other embodiments of this application, a comprehensive description is provided of the system response and hierarchical control logic based on the hierarchical detection results, which is specifically configured and executed by the control unit.

[0071] Based on the detection results, the control unit drives the vehicle's instrument panel to perform graded alarms and control the vehicle's operating status: Scenario 1: Determined as slightly attenuated or normal The return spring is functional or largely intact. The parking release function is protected by both a spring and an electromagnet, ensuring a high level of system safety. No malfunction indicators are illuminated, and all vehicle functions are normal.

[0072] Scenario 2: Determined to be severely degraded, but the electromagnet functions normally. The return spring has essentially lost its ability to independently maintain the pawl's disengagement. At this point, the parking release action (pulling the pawl out of the ratchet or holding it in the disengaged position) relies entirely on the electromagnet. The dual-redundancy architecture degenerates into a single-dependency architecture, but the vehicle still possesses controllable release and locking capabilities.

[0073] The control unit sends a command to the instrument cluster domain controller via the CAN bus to illuminate the yellow parking malfunction indicator lamp. At this time, the vehicle control logic switches to safe limp mode, allowing the vehicle to drive normally, but will prompt the user that the parking system performance is limited and should be inspected as soon as possible. At the same time, the control unit performs rigorous diagnostics and confirmations every time the parking system is locked and released to ensure that the electromagnet operates without error.

[0074] Scenario 3: Determined to be severely degraded, and the electromagnet is malfunctioning. This is a double fault: the return spring is unable to disengage the pawl, and the electromagnet responsible for active release is also malfunctioning. The ratchet and pawl may be locked and unable to disengage.

[0075] The control unit sends high-priority alarm commands through redundant communication lines, illuminating the red parking malfunction warning light and displaying graphic and textual information such as parking system malfunction and prohibition of driving on the instrument panel. Simultaneously, the control unit, in conjunction with the vehicle control unit (VCU), actively prevents the vehicle from continuing to move (e.g., by prohibiting high-voltage power supply or limiting drive torque output to 0), fundamentally eliminating serious accidents such as brake disc / pad burnout, motor overload, or even disintegration of the parking mechanism caused by forced driving due to the parking brake failing to release.

[0076] In the case of single-point failure (severe spring decay only), this embodiment distinguishes between functional loss and functional degradation, allowing the vehicle to limp to a repair shop under a yellow warning, greatly improving user experience and vehicle availability, and avoiding direct breakdown. For extreme and dangerous scenarios involving dual failures, the implementation of a red alert and a prohibition on driving physically blocks the path to harm, upholding the automotive industry's paramount principle of safety above all else. The yellow (warning / repair) and red (danger / prohibition) graded alarms align with globally accepted automotive human-machine interface intuition, accurately and clearly conveying system status and risk levels to the driver, avoiding unnecessary panic or misleading operations.

[0077] In some embodiments of this application, the timing and safety prerequisites for executing all the above-described detection processes are specifically defined.

[0078] In this embodiment, the failure detection is performed during the vehicle's power-down self-test phase. When the driver stops the vehicle, shifts into Park, and turns off the start switch (or the vehicle controller receives a power-down hibernation request), the high-voltage power to the vehicle is not completely disconnected and is powered by the battery. During this phase, the control unit starts and executes the detection process.

[0079] The reasons for choosing to perform the test at this time are threefold: first, it ensures that the vehicle is completely stationary and there is no risk of driving; second, it serves as a health check-in for each driving cycle, achieving periodic coverage throughout the entire lifecycle and ensuring that no hidden degradation is missed; and third, it has no impact on the user experience, as all tests are completed silently after the user leaves the vehicle.

[0080] This embodiment sets a safety prerequisite: both rear wheels must be in a stable parking state. Before performing the test, the control unit receives a status message from the vehicle braking domain controller to confirm that the EMB of both rear wheels has been successfully applied and locked with a standard parking force sufficient to stop the vehicle at the current slope (determined with the assistance of longitudinal acceleration sensor data). Subsequent single-wheel alternating tests are only allowed to start if this condition is true.

[0081] This is the cornerstone for ensuring the safety of subsequent single-round inspections. A stable baseline for the system has been established, ensuring that the entire vehicle is in a reliable, double-safe parking state before any release inspection is performed.

[0082] This limitation transforms high-risk online testing into zero-risk silent self-checking, establishing an absolute safety prerequisite for testing. By seamlessly embedding the detection into every normal user power-off and vehicle locking process, it requires no additional user operation, takes up no user time, and absolutely does not affect driving safety, yet achieves full-coverage detection for each trip cycle—an ideal vehicle health management execution mode. Enforcing the prerequisite of confirming effective dual-wheel parking logically and perfectly severs the risk chain of accidental vehicle rollover caused by detection, thus improving safety.

[0083] In a further embodiment of this application, this embodiment details a complete safety sequence method for performing dual-wheel alternating tests in a system comprising two independent rear wheel parking calipers.

[0084] The control unit is configured to execute according to the following timing sequence when a detection cycle is triggered (preconditions are met): Phase 1: Preparation and Security Anchoring The control unit (ECU) designates the first wheel (e.g., the left rear wheel) as the safety anchor point via the vehicle network. It instructs its EMB not to participate in subsequent testing.

[0085] The control unit actively increases the motor torque of the first wheel, raising the parking clamping force to a calibrated high safety force value that independently maintains vehicle stability, for example, by adding a 30% margin to the standard force value required for the current slope.

[0086] The control unit monitors the motor angle sensor and / or clamping force estimate of the first wheel to confirm that its parking force has been independently established and stabilized, and continues to monitor it.

[0087] Phase Two: Deploying and Testing the Second Wheel The control unit instructs the second wheel (e.g., the right rear wheel) to be the wheel under test and drives its EMB motor to fully release the parking brake.

[0088] Perform Level 1 and / or Level 2 inspection procedures on the second wheel. During this process, the vehicle is reliably parked using only the first wheel as a safety anchor point.

[0089] Phase 3: Restore the second wheel as the anchor point and release the first wheel. After the second wheel inspection process is completed, the control unit immediately instructs its EMB to perform standard parking lock and also increases the clamping force to the high safety force value of the aforementioned independent parking.

[0090] The control unit monitors and confirms that the second wheel has independently established a stable parking force. At this point, the role of the safety anchor point has switched from the first wheel to the second wheel.

[0091] The control unit commands the first wheel EMB to fully release the parking brake.

[0092] Phase Four: Testing the original first wheel and finally restoring it. Perform a complete inspection process on the first wheel.

[0093] After the test is completed, the control unit instructs the first wheel EMB to also perform the standard parking lock.

[0094] The control unit simultaneously sends commands to the EMBs of both rear wheels to adjust the motor torque, reducing the parking clamping force of both wheels from the high force value of independent parking to the standard parking force value of both wheels, thus balancing parking safety and structural protection. A complete dual-wheel alternating self-check cycle ends.

[0095] The dual-wheel alternating test sequence described in this embodiment is the core execution logic that ensures the safe and reliable implementation of the entire self-test function. By clearly defining and dynamically switching the role of the safety anchor point, this process ensures that at least one wheel provides reinforced, independent, and reliable ultra-safe parking force at any given time. This fundamentally eliminates the risk of vehicle slippage caused by releasing both wheels during testing, perfectly embodying the fail-safe or fail-operational design concept in the ISO 26262 functional safety standard. Protecting the anchor point wheel under independent parking high force ensures maximum safety. After all tests are completed, the clamping force of both wheels is intelligently reduced to the standard value, avoiding wear and tear on the calipers and brake discs that have been under excessive stress for a long time, thus balancing safety and durability. The control unit, acting as the central brain, coordinates the working status of the left and right EMB calipers through the OEM network, making the entire complex test sequence operate precisely as a whole system, achieving a high degree of unity between efficiency and safety.

[0096] In practical applications, such as Figure 2 As shown, the failure detection method for the parking mechanism of the electromechanical brake in this application is as follows: When a driving cycle ends and the driver turns off the ignition switch, the vehicle's braking domain controller wakes up the EMB control unit and enters power-down self-test mode. The control unit first obtains the vehicle status via the CAN bus: the gear is in P, the vehicle speed is 0, and both rear wheel EMBs report that the parking force has reached the standard. With the prerequisites met, the self-test begins.

[0097] Step 1: Establish the left-side safety anchor point The control unit instructs the left rear wheel EMB to perform enhanced parking, increasing the clamping force to the independent parking force value. F holdvehicle The force value was confirmed to be stable using its motor angle sensor and a clamping force estimation model based on motor current. The safety anchor point was successfully established.

[0098] Step 2: Inspect the right rear wheel The control unit commands the right rear wheel EMB to release the parking brake. The diagnostic process begins: Level 1 testing: Control the right rear wheel EMB to lock, then apply braking force with a micro-motion to release the ratchet pawl lock.

[0099] Based on the calibration parameters of the caliper retrieved from memory, a positive first current is applied to the electromagnet. I 1 Then, a linear current decay algorithm is run to smoothly reduce the current to the positive second current within a fixed time. I 2 This generates the first preset threshold thrust corresponding to the lower limit of the normal operation of the return spring.

[0100] Stop the motor torque and monitor the motor rotation angle at high frequency. If the rotation angle exceeds the limit, the first-level test passes, the right rear wheel return spring is recorded as normal, and the second-level test is skipped. If the rotation angle does not change, the return spring force is recorded as abnormal, and the second-level test is immediately and automatically initiated.

[0101] Level 2 test (if Level 1 fails): Repeatedly lock, unlock, and apply the first positive current. I 1 The steps.

[0102] The current is smoothly reduced to the positive third current by running a linear current decay algorithm. I 3 This generates a second preset threshold thrust, corresponding to the minimum holding force required to maintain the release of the pawl.

[0103] Stop the motor torque and monitor the motor rotation angle. If the rotation angle exceeds the limit, it is determined that the spring force has slightly decreased and can maintain the release position. If the rotation angle remains unchanged, a serious judgment is made: the spring force has severely decreased and cannot maintain the release position.

[0104] The inspection process for the right rear wheel is complete; the diagnostic results are recorded.

[0105] Step 3: Anchor point switching, from right to left. The control unit commanded the right rear wheel EMB to immediately execute enhanced parking brake. F holdvehicle After confirming that its independent parking force was stable, the safety anchor point was successfully switched to the right rear wheel.

[0106] Step 4: Inspect the left rear wheel The control unit instructs the left rear wheel EMB to release the parking brake, and performs a first-level and (possibly) second-level diagnostic procedure on the left rear wheel according to the same logic as in step two, and records the diagnostic results.

[0107] Step 5: Restore the standard two-wheel parking position. After the left rear wheel detection is complete, the control unit instructs the left rear wheel EMB to perform enhanced parking. After briefly confirming that both wheels are in a high-force anchoring state, the control unit simultaneously sends commands to both the left and right EMBs to increase the target clamping force from... F holdvehicle Simultaneously reduce to the calibrated standard force value for joint parking of both wheels. F standard Finally, both EMBs reported that the connection had been reached. F standard The self-check process is complete.

[0108] Step 6: Tiered Fault Response and Status Setting The control unit integrates the diagnostic results of the left and right wheels and implements tiered control: If any wheel is determined to have severe wear by the secondary detection: The system immediately tested the function of the electromagnet on that side.

[0109] If the electromagnet functions normally: it stores the fault code and sends a yellow parking system warning signal to the CAN network. The yellow parking malfunction indicator light illuminates on the instrument panel. The vehicle can be driven normally the next time power is applied.

[0110] If the electromagnet also malfunctions: Store the highest priority fault code, send a red parking system warning signal and a prohibition on driving signal to the CAN network. The instrument panel illuminates a red parking fault warning light and sends a torque limit command to the VCU to prohibit driving.

[0111] If there is only slight degradation: only the fault code is stored as a non-emergency repair reminder, and the warning light visible to the user is not immediately illuminated. The user is prompted to have the fault checked during the next maintenance.

[0112] If everything is normal: Clear historical intermittent fault codes, and the system will safely enter hibernation.

[0113] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A method for detecting the failure of the parking mechanism of an electromechanical brake, wherein the parking mechanism includes a ratchet fixedly connected to the motor shaft, a pawl hinged to the housing and capable of engaging or disengaging with the ratchet, an electromagnet, and a return spring; wherein the electromagnet and the return spring are both connected to the pawl; Its features are: This includes a primary detection process; the primary detection process includes: After the first wheel of the vehicle is locked in place, the electromechanical brake motor is driven to apply braking force to release the engagement lock between the ratchet and the pawl. A positive first current is supplied to the electromagnet to maintain the engagement of the pawl, and then the current is linearly reduced to a preset positive second current, so that the electromagnet's push rod outputs a first preset threshold thrust. Stop the motor output to maintain braking torque and monitor whether the pawl separates from the ratchet, causing the parking brake to release; If parking brake release is detected, the return spring force is considered normal; if parking brake release is not detected, the return spring force is considered to have abnormally decreased.

2. The method for detecting the failure of the parking mechanism of an electromechanical brake according to claim 1, characterized in that: The first preset threshold thrust is calibrated as the force corresponding to the lower limit of the normal working force value of the return spring. This force value is converted into the equivalent thrust value of the electromagnet push rod end through the lever ratio of the pawl. The positive second current is determined based on the equivalent thrust value through the corresponding curve of electromagnet thrust and current calibrated on the test bench.

3. The method for detecting the failure of the parking mechanism of an electromechanical brake according to claim 1, characterized in that: After determining that the return spring force has abnormally decreased, a secondary detection process is also included; The secondary detection process includes: After the wheels are locked in place, the drive motor is used again to apply braking force to release the engagement between the ratchet and the pawl. A positive first current is supplied to the electromagnet to maintain the engagement of the pawl. Then, the current is linearly reduced to a preset positive third current, so that the electromagnet's push rod outputs a second preset threshold thrust. Stop the motor output to maintain braking torque and monitor whether the parking brake is released; If parking brake release is not detected, it is determined that the return spring force has been severely weakened and cannot maintain the normal release position of the pawl; if parking brake release is detected, it is determined that although the return spring force has weakened, it can still maintain the normal release position of the pawl.

4. The method for detecting the failure of the parking mechanism of an electromechanical brake according to claim 3, characterized in that: The second preset threshold thrust is defined as: the minimum holding force required to maintain the pawl in the normal release position. This minimum holding force is used to overcome the pawl's own weight, motion friction resistance, and vehicle vibration interference. This force value is converted into an equivalent thrust value at the end of the electromagnet push rod through the pawl's leverage ratio. The positive third current is determined based on this equivalent thrust value.

5. The method for detecting the failure of the parking mechanism of an electromechanical brake according to claim 3, characterized in that: When the secondary detection determines that the return spring force has been severely weakened, but the parking mechanism can still achieve controllable locking and releasing through the electromagnet, the vehicle is allowed to drive normally while the yellow parking malfunction light is illuminated. When the secondary detection determines that the return spring force has been severely weakened and the electromagnet has also malfunctioned and cannot control the parking release, the vehicle will be controlled to illuminate the red parking fault warning light and the vehicle will be prevented from continuing to move.

6. A method for detecting the failure of the parking mechanism of an electromechanical brake according to claim 1 or 3, characterized in that: The first-level and / or second-level detection processes are executed during the vehicle's power-off self-test phase; and are only initiated when the vehicle's braking domain controller determines that both rear wheels of the vehicle are in a stable parking state.

7. The method for detecting the failure of the parking mechanism of an electromechanical brake according to claim 3, characterized in that: The method is applied to a vehicle having a first wheel and a second wheel, and when detecting the first wheel and the second wheel, the following steps are performed: After controlling the first wheel to keep it in the parking lock state and confirming that its parking force can independently maintain the vehicle's stable parking, the inspection process is performed on the second wheel. After the inspection process of the second wheel is completed and it is controlled to return to the parking lock state, and it is confirmed that it can independently maintain the stable parking of the vehicle, the inspection process is performed on the first wheel. After the first wheel inspection process is completed, control both wheels to return to the parking state and restore the parking clamping force of both wheels to the standard force value corresponding to the common parking.

8. A parking mechanism failure detection system for an electromechanical brake, used to implement the method as described in any one of claims 1 to 7, characterized in that, The detection system includes: The ratchet is rigidly connected coaxially to the ball screw shaft of the electromechanical brake caliper; The pawl is hinged to the caliper housing in the middle, and its head can engage or disengage with the ratchet. An electromagnet, the end of its push rod is connected to the tail of a pawl; The return spring has its movable end connected to the tail of the pawl; Motor rotation angle sensor, used to monitor the rotation angle signal of the motor rotor in real time; The control unit is configured as follows: Control the on / off timing and current value of the motor and electromagnet; Receive and process signals from the motor angle sensor to determine the parking release status; and Perform the first-level detection procedure for the return spring force.

9. A parking mechanism failure detection system for an electromechanical brake according to claim 8, characterized in that: The control unit is configured to: automatically execute a secondary detection process after determining that the return spring force has abnormally decreased, distinguish the degree of decrease of the return spring force based on the monitoring results of the motor angle sensor; and generate a graded fault alarm signal according to the preset judgment logic to control the vehicle instrument panel to illuminate a yellow or red warning light.

10. A parking mechanism failure detection system for an electromechanical brake according to claim 8, characterized in that: It includes two independent rear wheel parking calipers, and the control unit is further configured to: execute a dual-wheel alternating test mode during the vehicle's power-down self-test, ensuring that one of the parking calipers maintains stable parking of the vehicle throughout the process.

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