A fully decoupled brake-by-wire system and control method thereof

Abstract

The application relates to the field of automobile braking technology and discloses a full-decoupling brake-by-wire system and a control method thereof, which comprises a control unit, various isolation valves, various pressure relief valves, a servo cylinder piston and a servo motor; the control unit dynamically divides a certain interval and a tentative interval based on the real-time position of the servo cylinder piston; when a braking request is not acquired, the servo motor is controlled to drive the piston to retreat and execute a mechanical zero-finding process; when a braking request is acquired in the zero-finding process, the mechanical zero-finding process is interrupted, the servo motor is preferentially controlled to drive the piston to move forward and build pressure to respond to the braking request; in addition, the control unit adopts different motor control modes to match corresponding actions when the piston is in the certain interval or the tentative interval. The application solves the conflict between finding a mechanical zero point and a sudden braking action, guarantees the preferential execution of a braking instruction and the safety of system operation.

Description

Technical Field

[0001] This invention relates to the field of automotive braking technology, specifically to a fully decoupled brake-by-wire system and its control method. Background Technology

[0002] With the development of automotive electrification, brake-by-wire systems have been widely used in vehicle chassis control. Fully decoupled brake-by-wire systems typically utilize a control unit to command a servo motor, driving a servo cylinder piston to move back and forth, thereby outputting brake fluid to the wheel-side braking circuit. During normal operation, the control unit relies on the piston's absolute position information to achieve closed-loop control of the braking pressure. Because the system may lose the piston's absolute position coordinates during sleep or power-off periods, upon each power-on wake-up, it is usually necessary to control the servo cylinder piston to move to its bottom mechanical boundary to complete mechanical zeroing, thereby recalibrating the position reference.

[0003] Existing brake-by-wire systems exhibit several control deficiencies when executing the aforementioned mechanical zeroing process. First, during the piston retraction process to find the mechanical zero point, if the driver depresses the brake pedal, triggering an emergency braking request, the existing control architecture often struggles to immediately interrupt the underlying zeroing process and instantly switch the motor rotation direction. This leads to a delay in forward pressure build-up, affecting braking response time. Second, during the initial zeroing phase after power-on, the actual piston stroke is unknown to the control unit. If the system directly uses a conventional pressure closed-loop control mode to drive the piston within this unknown region, the piston may reach excessive speed upon contact with the mechanical boundary, causing mechanical impact and abnormal noise, reducing hardware lifespan. Furthermore, in some existing systems, under extreme conditions or with pipeline deformation, the amount of brake fluid discharged in a single piston stroke may not reach the target braking pressure. In such cases, the transition between pressure holding, fluid replenishment, and secondary pressure build-up is not smooth, easily causing brake pressure fluctuations. Therefore, current technology lacks a brake-by-wire system that can effectively coordinate mechanical zeroing and sudden braking requests, and adaptively adjust the motor control strategy based on the uncertainty of the piston position. Summary of the Invention

[0004] The technical problem solved by this invention is that existing brake-by-wire systems, when encountering a sudden braking request during mechanical zeroing, have difficulty quickly switching to pressure-building state, and lack targeted control strategies in areas where the position of the servo cylinder piston is unknown, resulting in braking response delays and reduced control accuracy and smoothness during the pressure-building process.

[0005] To address the above problems, the present invention provides the following technical solution:

[0006] The first aspect of this invention provides a fully decoupled brake-by-wire system, comprising: Control unit, multiple isolation valves, multiple pressure relief valves, servo cylinder piston, and servo motor; The control unit is communicatively connected to the plurality of isolation valves, the plurality of pressure relief valves, and the servo motor; The control unit is configured to execute the following control logic: After the fully decoupled brake-by-wire system is powered on, the certainty interval and the trial interval are dynamically divided based on the real-time position of the servo cylinder piston. When no braking request is received, the servo motor is controlled to drive the servo cylinder piston to reverse and retract to perform a mechanical zeroing process; When the braking request is obtained during the execution of the mechanical zeroing process, the mechanical zeroing process is interrupted, and the servo motor is prioritized to drive the servo cylinder piston to rotate forward and build pressure in response to the braking request. When the servo cylinder piston is in the certainty interval or the probing interval, an independent motor control mode is used to match the pressure building action and the mechanical zeroing action. This invention achieves seamless switching and coordination between the mechanical zeroing action and the pressure building response action by dynamically dividing the interval and configuring different motor control modes, effectively improving the system's braking response speed and control smoothness.

[0007] Furthermore, the control unit is specifically used for: Record the initial wake-up position of the system, and when the braking request is received and the servo cylinder piston is controlled to move forward to build up pressure, record and update the forward push extreme position in real time; And when the mechanical zeroing action of controlling the servo cylinder piston to retract in the absence of the braking request is interrupted, the retraction extreme position is recorded and updated in real time; The travel range between the retraction extreme position and the forward extreme position is defined as the confidence interval, and the unsweeped unknown range within the set upper and lower mechanical boundaries, excluding the confidence interval, is defined as the trial interval. As the forward extreme position expands towards the upper boundary of the mechanism, and the retraction extreme position expands towards the lower boundary of the mechanism, the coverage of the confidence interval is increased in real time, and the range of the trial interval is correspondingly reduced. By dynamically recording and expanding the extreme positions, the system can grasp the piston's swept safe stroke in real time, providing a precise position determination basis for subsequent control mode switching.

[0008] Furthermore, the independent motor control modes include a pressure closed-loop control mode and a target flow control mode; When the real-time position of the servo cylinder piston is within the certainty interval and the braking request is received, the control unit adopts the pressure closed-loop control mode, performs closed-loop calculation based on the deviation between the acquired target braking pressure and the acquired actual braking pressure, and outputs a real-time changing control command to drive the servo motor. When the real-time position of the servo cylinder piston exceeds the forward extreme position or exceeds the retraction extreme position and enters the trial interval, the control unit switches the control mode of the servo motor to the fixed target flow control mode, calculates a fixed speed command based on the set fixed target flow value, and instructs the servo motor to maintain a constant speed. Pressure closed-loop control within the certainty interval of the known stroke improves pressure following accuracy. Within the trial range of unknown stroke, constant flow control is used to limit the movement speed, prevent the piston from impacting the unknown mechanical boundary at high speed, and protect the system hardware.

[0009] Furthermore, when executing the braking request priority interruption and forward pressure build-up control, the control unit specifically performs the following logic: When the braking request is obtained during the mechanical zeroing process, a stop retraction command is sent to the servo motor, the position coordinates of the servo cylinder piston are read and updated to the retraction extreme position, and the fully decoupled wire control braking system is controlled to switch to the valve control state corresponding to the wire control braking mode, and the servo motor is instructed to rotate forward to drive the servo cylinder piston to move forward to build pressure; The pressure closed-loop control mode is maintained when the servo cylinder piston is within the certainty range. When the servo cylinder piston surpasses the forward push extreme position and enters the probing interval, the system switches to the target flow control mode, and the latest position coordinates of the servo cylinder piston are overwritten in real time as the updated forward push extreme position. This logic ensures that when the system encounters a sudden braking demand during the zero-finding and return process, it can quickly interrupt the zero-finding action and smoothly transition to the positive pressure-building mode.

[0010] Furthermore, during the process of controlling the forward movement of the servo cylinder piston to build up pressure, the control unit executes mechanical contact recognition and relay-style pressure building and fluid replenishment logic: When the control unit obtains that the actual control current of the servo motor is greater than or equal to the set forward stall current threshold, and the position change rate of the servo cylinder piston is less than or equal to the set speed minimum value, it confirms that the servo cylinder piston has reached the frontmost mechanical boundary position, and calculates the mechanical zero point position at the rear bottom based on the known total servo cylinder stroke, and equivalently determines that the mechanical zeroing is completed, and updates the certainty interval to the full stroke of the servo cylinder. If the actual braking pressure does not reach the target braking pressure, a relay-type pressure-building and fluid replenishment mechanism is triggered: the corresponding isolation valve is de-energized and closed, maintaining pressure in the wheel-side braking circuit of the fully decoupled brake-by-wire system. The servo motor is then instructed to reverse, driving the servo cylinder piston back a set stroke to replenish fluid. After completing the replenishment, the servo motor is again instructed to rotate forward, and the corresponding isolation valve is opened to restore hydraulic connection and continue outputting brake fluid to the wheel-side braking circuit. This mechanism not only allows for rapid zero-point calculation and calibration when the piston reaches its maximum position, but also provides relay-type brake fluid replenishment when brake fluid is insufficient in a single stroke, ensuring braking safety under extreme conditions.

[0011] Furthermore, when the braking request is not received, the control unit performs backtracking and smooth degradation control, specifically executing the following logic: During the process of controlling the servo cylinder piston to reverse and retract for mechanical zeroing, when the servo cylinder piston is within the certainty range and the actual braking pressure has not dropped to the set small pressure threshold, the pressure closed-loop control mode is used to drive the servo motor to reverse. When the actual braking pressure drops to the minimum pressure threshold, or when the servo cylinder piston has retracted to the previously determined extreme retraction position but the actual braking pressure is still greater than zero, the smooth degrading control logic is triggered. This actively interrupts the pressure closed-loop control mode and switches to the target flow control mode, continuing the reverse retraction according to a fixed speed command. This process prevents system hydraulic oscillations and abnormal noises caused by a sudden drop in braking pressure, achieving smooth pressure reduction and zero-point degrading.

[0012] Furthermore, the control unit executes the mechanical zeroing completion determination logic, specifically for executing the following logic: In the target flow control mode, the servo cylinder piston is driven to move towards the bottom mechanical lower boundary within the test range. When the absolute value of the actual feedback torque of the servo motor is greater than or equal to the set stall torque threshold, and the actual operating speed drops below the set speed judgment threshold for a set time, it is confirmed that the servo cylinder piston has reached the mechanical zero point position and the mechanical zeroing is determined to be completed. The control unit marks the current absolute physical position as the mechanical zero point, eliminates the trial interval, and extends the certainty interval to the full stroke of the servo cylinder. This logic clarifies the correspondence between the motor control state and the mechanical boundary, achieving precise and safe calibration of the mechanical zero point at the bottom of the system.

[0013] Furthermore, the hardware structure of the fully decoupled brake-by-wire system also includes: Brake pedal, reservoir, first piston and spring of manual cylinder, second piston and spring of manual cylinder, isolation valve 1 of manual cylinder circuit, isolation valve 2 of manual cylinder circuit, isolation valve of analog cylinder circuit, isolation valve 1 of servo cylinder circuit, isolation valve 2 of servo cylinder circuit, ball screw transmission mechanism, servo cylinder body and check valve. The fully decoupled brake-by-wire system includes, in its wheel-side adjustment structure, isolation valve one, isolation valve two, isolation valve three, isolation valve four, and pressure relief valve one, pressure relief valve two, pressure relief valve three, and pressure relief valve four.

[0014] Furthermore, in the backup braking operation state where the fully decoupled brake-by-wire system is not powered on, the manual cylinder circuit isolation valve one, manual cylinder circuit isolation valve two, and isolation valves one through four are all open, while pressure relief valves one through four are all closed. The simulated cylinder circuit isolation valve, servo cylinder circuit isolation valve one, and servo cylinder circuit isolation valve two are all closed. After the first piston and spring of the manual cylinder or the second piston and spring of the manual cylinder pass the inlet, braking hydraulic pressure is established on the wheel-side braking circuit. This hydraulic circuit structure realizes a purely mechanical backup braking system in the absence of electricity or electronic failure, meeting the safety redundancy requirements of the vehicle chassis.

[0015] A second aspect of the present invention provides a control method for a fully decoupled brake-by-wire system, applied to the aforementioned fully decoupled brake-by-wire system, comprising the following steps: Determine the power-on status of the fully decoupled brake-by-wire system, and record the initial wake-up position of the servo cylinder piston after the fully decoupled brake-by-wire system is powered on and woken up. Determine if a braking request exists; when the braking request exists, control the servo motor to rotate forward to build up pressure and update the forward extreme position according to the extreme position of the servo cylinder piston; when the braking request does not exist, control the servo motor to drive the servo cylinder piston to rotate backward to perform a mechanical zeroing process, and update the backward extreme position according to the zeroing interruption position. The travel range between the retraction extreme position and the forward extreme position is dynamically divided into a certainty interval, and the unsweeped range outside the certainty interval is divided into a trial interval; if the braking request is obtained during the execution of the mechanical zeroing process, the current mechanical zeroing process is interrupted, and the servo motor is controlled to rotate forward to drive the servo cylinder piston to push forward in response to the braking request. When the servo cylinder piston is running within the certain range, the servo motor is driven by a pressure closed-loop control mode; When the servo cylinder piston moves beyond the certainty zone and into the probing zone, the system switches to a target flow control mode, controlling the servo motor to maintain a constant speed according to a fixed speed command until the mechanical zeroing process is completed and the certainty zone is extended to the full stroke of the servo cylinder. Through the above steps, the control system can intelligently coordinate the switching of the motor control mode and the interruption of the zeroing process based on the position range of the servo cylinder piston and the braking request, ensuring the safe and orderly execution of the system's pressure build-up response and mechanical position calibration actions.

[0016] This invention provides a fully decoupled brake-by-wire system and its control method. It offers the following advantages: 1. This invention divides the known range and the trial range based on the real-time position of the servo cylinder piston. In the swept known range, a pressure closed-loop control mode is adopted, and in the unswept trial range, a target flow control mode is adopted. Through the combination of the above range division and control mode, the system can ensure the control accuracy of braking pressure within the known stroke range, and limit the piston's movement speed by a fixed speed command within the unknown stroke range to prevent the piston from hitting the mechanical boundary when moving at high speed in the unknown area.

[0017] 2. In the process of controlling the piston of the servo cylinder to reverse and retract to perform mechanical zeroing, if a braking request is obtained, the zeroing process is interrupted and the servo motor is controlled to rotate forward to build pressure. At the same time, the interruption position coordinates of the piston are read and recorded in real time to update the extreme position. This control logic solves the action conflict problem when the system encounters a braking command during the search for the mechanical zero point, ensures the priority execution of the braking action, and provides a position reference for subsequent zeroing actions.

[0018] 3. This invention employs a relay-type pressure-building and fluid replenishment mechanism during the pressure-building process of the servo cylinder piston. When the system identifies, based on current and speed characteristics, that the piston has reached the front mechanical boundary and the actual braking pressure has not reached the target braking pressure, it controls the corresponding isolation valve to close the wheel-side circuit to maintain pressure, and instructs the motor to reverse and retract to replenish fluid before pushing forward again to build pressure. This mechanism solves the problem that the displacement of a single servo cylinder stroke is insufficient to establish the target braking pressure, ensuring that the system can still output sufficient brake fluid even under conditions with high brake fluid demand. Attached Figure Description

[0019] Figure 1 This is a partial schematic diagram of the fully decoupled brake-by-wire system of the present invention; Figure 2 This is a macroscopic flow logic block diagram of the system power-on and braking response of the present invention; Figure 3 This is a schematic diagram of the first scenario of the process of interrupting the change-making and expanding the certainty interval according to the present invention. Figure 4This is a schematic diagram of the second scenario of the priority braking and forward contact zeroing process of the present invention.

[0020] The components include: 1. Brake pedal; 2. Input lever; 3. Pedal travel sensor; 4. Liquid reservoir; 5. First piston and spring of the manual cylinder; 6. Second piston and spring of the manual cylinder; 7. Manual cylinder pressure sensor P1; 8. Manual cylinder circuit isolation valve one; 9. Manual cylinder circuit isolation valve two; 10. Simulation cylinder circuit isolation valve; 11. Simulation cylinder; 12. Servo cylinder circuit isolation valve one; 13. Servo cylinder circuit isolation valve two; 14. Servo cylinder pressure sensor P2; 15. Servo cylinder body; 16. Servo cylinder piston; 17. Ball screw transmission mechanism; 18. Servo motor; 19. Test isolation valve; 20. Isolation valve one; 21. Isolation valve two; 22. Isolation valve three; 23. Isolation valve four; 24. Pressure relief valve one; 25. Pressure relief valve two; 26. Pressure relief valve three; 27. Pressure relief valve four; 28. Check valve; 29. ​​Compensation orifice structure. Detailed Implementation

[0021] The technical solutions in 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] See attached document Figure 1 , Figure 1 This is a partial schematic diagram of a fully decoupled brake-by-wire system according to an embodiment of the present invention. The present invention provides a control method that prioritizes braking during the zeroing process of the servo cylinder piston in a fully decoupled brake-by-wire system. This control method is executed based on a fully decoupled brake-by-wire system. The fully decoupled brake-by-wire system may include: a brake pedal 1, an input lever 2, a pedal travel sensor 3, a reservoir 4, a first piston and spring of a manual cylinder 5, a second piston and spring of a manual cylinder 6, and a manual cylinder pressure sensor P17.

[0023] The hydraulic circuit of the fully decoupled wire-controlled braking system may also include: manual cylinder circuit isolation valve 1 (8), manual cylinder circuit isolation valve 2 (9), analog cylinder circuit isolation valve 10, analog cylinder (11), servo cylinder circuit isolation valve 1 (12), servo cylinder circuit isolation valve 2 (13), servo cylinder pressure sensor P2 (14), servo cylinder body (15), servo cylinder piston (16), ball screw transmission mechanism (17), servo motor (18), and test isolation valve (19).

[0024] The wheel-side adjustment structure includes isolation valve 1 20, isolation valve 21, isolation valve 3 22, isolation valve 4 23, and pressure relief valve 1 24, pressure relief valve 25, pressure relief valve 3 26, and pressure relief valve 4 27. A one-way valve 28 and a compensation orifice structure 29 are also connected to the system circuit. The brake fluid circuit is filled with brake fluid, and the fluid level in the reservoir 4 is maintained between the set lower and upper limits.

[0025] In backup braking mode, the system is powered down and does not involve drive control of the isolation valves, pressure relief valves, or servo motors. When the driver depresses brake pedal 1, input lever 2 moves to the left, pushing the first piston and spring 5 of the manual cylinder and the second piston and spring 6 of the manual cylinder to move to the left simultaneously, compressing the pistons and springs. After the piston of the manual cylinder moves to the left and passes the brake fluid inlet of the reservoir 4 and the two piston chambers of the manual cylinder, the brake fluid at the rear end of the manual cylinder is sealed and compressed.

[0026] At this time, the manual cylinder circuit isolation valve 8, the manual cylinder circuit isolation valve 9, and isolation valves 20 to 23 are all open. The pressure relief valves 24 to 27 are all closed. The pressure from both piston chambers of the manual cylinder to the wheel edge is greater than zero. The analog cylinder circuit isolation valve 10, the servo cylinder circuit isolation valves 12 and 23 at the servo pressure build-up end are all closed. These valve states result in zero pressure in the circuit after analog cylinder circuit isolation valve 10 to analog cylinder 11, after servo cylinder circuit isolation valves 12 and 23, and within servo cylinder 15.

[0027] In online control braking mode, the system is powered on and enters the online braking mode. The analog cylinder circuit isolation valve 10, manual cylinder circuit isolation valve one 8, manual cylinder circuit isolation valve two 9, servo cylinder circuit isolation valve one 12, and servo cylinder circuit isolation valve two 13 are all energized and activated. When the brake pedal 1 is pressed, the pedal travel sensor 3 and the manual cylinder pressure sensor P17 output corresponding signals. The system identifies the braking intention based on the changes in these signals.

[0028] Due to the action of the manual cylinder circuit isolation valve 8 and the manual cylinder circuit isolation valve 9, the hydraulic pressure generated by manual operation is maintained before these two valves, forming a low-pressure circuit region. At this time, the pressure value measured by the manual cylinder pressure sensor P17 corresponds to the pressure in the manual cylinder and the simulated cylinder region.

[0029] The system controls the servo motor 18 to rotate according to the braking intention, driving the ball screw transmission mechanism 17 to push the servo cylinder piston 16 to the left, and the system compresses the brake fluid to build up pressure. The hydraulic circuit after the manual cylinder circuit isolation valve 18 and the manual cylinder circuit isolation valve 29 receives the pressure generated by the movement of the servo cylinder piston 16, forming a high-pressure circuit area. The servo cylinder pressure sensor P214 measures the hydraulic pressure in the area before and after the servo cylinder body 15, the servo cylinder circuit isolation valve 12 and the servo cylinder circuit isolation valve 23, the area before and after each isolation valve, and the area from the front end of each pressure relief valve to the wheel edge.

[0030] Figure 2 This is a macroscopic flow logic block diagram of the system power-on and braking response according to an embodiment of the present invention. The fully decoupled brake-by-wire system uses a brushless motor, and the system calculates the servo cylinder piston position based on the rotor angle. Each time power is applied or the motor position information is inaccurate, the system needs to perform a mechanical boundary check process for the servo cylinder piston position, i.e., a mechanical zeroing action. After the mechanical boundary position is determined, the system executes relevant soft limit protection control. The macroscopic flow logic prioritizing braking and zeroing states may include: S100: Determine the system power-on status. When the system is not powered on, the system enters the mechanical backup braking mode; when the system completes power-on wake-up and there is no fault, the system executes step S200.

[0031] S200: Determine if a braking request exists. When the system determines that a braking request exists, the system prioritizes responding to the current braking request and directly interrupts the mechanical zeroing process; when the system determines that no braking request exists, the system executes step S300.

[0032] S300: Determine whether the mechanical zeroing process is complete. If the mechanical zeroing process is not complete, the system executes the mechanical zeroing process; if the mechanical zeroing process is complete, the system executes step S400.

[0033] S400: Enter normal brake-by-wire mode. In normal brake-by-wire mode, when the system receives a braking request, it enters pressure control mode to respond to the braking request; when the system does not receive a braking request, it enters flow control mode to achieve smooth pressure change control during the opening of the compensation orifice structure 29.

[0034] See attached document Figure 3 With appendix Figure 4 It illustrates a scenario where the change-giving process is interrupted and priority braking occurs. (Combined with the attached...) Figure 3 With appendix Figure 4 As can be seen, in the control method provided by the present invention for prioritizing braking when the piston of the servo cylinder in the fully decoupled brake-by-wire system is zeroing, the execution of the control strategy depends on the definition of the physical boundary of the servo cylinder piston 16 stroke and the real-time recording of dynamic position parameters during system operation.

[0035] To establish a precise position reference, the system's internal control logic uses the movement trajectory of the servo cylinder piston 16 to create a one-dimensional position coordinate system. The direction in which the servo cylinder piston 16 moves towards the top of the servo cylinder is defined as the positive direction. When the servo cylinder piston 16 moves forward in the positive direction or the servo motor 18 rotates forward, it compresses the brake fluid within the servo cylinder 15, increasing the braking pressure. The direction in which the servo cylinder piston 16 moves towards the bottom of the servo cylinder is defined as the negative direction. When the servo cylinder piston 16 moves backward in the negative direction or the servo motor 18 rotates in the reverse direction, it decreases the braking pressure.

[0036] Under the above coordinate system, the following absolute physical boundaries are defined: The upper mechanical boundary (Top) corresponds to the top structure inside the servo cylinder 15, i.e., the physical limit position of the servo motor 18 in the forward rotation and pressure building direction. The lower mechanical boundary (Bottom) corresponds to the bottom structure inside the servo cylinder 15, i.e., the physical limit stop position of the servo motor 18 in the reverse rotation and mechanical zeroing direction.

[0037] Regarding the method of calculating the real-time position of the servo cylinder piston 16 by the rotor angle of the servo motor 18, those skilled in the art can perform position calculation based on the position sensor signal of the brushless motor combined with the reduction ratio and the lead screw. The method of obtaining absolute or relative displacement values ​​is a well-known technology in the field and will not be described in detail here.

[0038] The system monitors and records the dynamic position coordinates of the servo cylinder piston 16 under different working conditions in real time through the control unit. The specific update and calibration process includes: S500: Records the initial wake-up position of the system. When the system is first powered on and wakes up, or when the system undergoes an unexpected reset and restart, before the servo motor 18 performs any control actions, the system reads the current position coordinates of the servo cylinder piston 16. The system stores this coordinate value in memory and defines it as the initial wake-up position s. This initial wake-up position s is the reference origin for subsequent dynamic interval division.

[0039] S600: Record and update the forward push extreme position. After receiving a braking request, the system controls the servo motor 18 to rotate forward, driving the servo cylinder piston 16 to move forward and build pressure. During this process, the system monitors the real-time position. When the braking request is canceled, the system retrieves all position data recorded in this continuous forward rotation pressure building event and extracts the position coordinates that are numerically closest to the upper mechanical boundary Top. The system records this extracted coordinate as the forward push extreme position a. During system operation, as multiple forward push pressure building events occur, the system will extract and update the corresponding forward push extreme positions in real time, for example, the forward push extreme positions a1 and a2 recorded for two independent forward push processes respectively.

[0040] S700: Record and update the retraction extreme position. In the absence of a braking request, the system controls the servo motor 18 to reverse, driving the servo cylinder piston 16 to retract in an attempt to perform a mechanical zeroing action. When this zeroing process is interrupted by a sudden braking request, the system retrieves all position data recorded during this zeroing attempt and extracts the position coordinates numerically closest to the mechanical lower boundary (Bottom). The system records this extracted coordinate as the retraction extreme position b. During system operation, as the zeroing process is repeatedly attempted and interrupted, the system will extract and update the corresponding retraction extreme positions in real time, for example, the retraction extreme positions b1 and b2 recorded during two interrupted retraction attempts.

[0041] See attached document Figure 3 With appendix Figure 4 This creates stroke regions with different control attributes. The stroke of the servo cylinder piston 16 is divided into a certainty range and a trial range in real time.

[0042] The system executes the division, expansion, and reset processes of the interval through the following control logic: S800: Define and initialize the stroke range. The system defines the stroke range that the servo cylinder piston 16 has swept through in the current power-on cycle and confirmed to be free of mechanical interference as the confidence range. The system defines the unknown range within the set absolute physical boundaries that the servo cylinder piston 16 has not yet swept through, excluding the confidence range, as the trial range.

[0043] In the position coordinate system, the boundary of the confidence interval is jointly determined by the retreating extreme position b and the forward extreme position a, that is, the confidence interval is the travel range between the retreating extreme position b and the forward extreme position a. Correspondingly, the trial interval includes two parts: one part is the unsweeped area between the lower mechanical boundary Bottom and the retreating extreme position b, and the other part is the unsweeped area between the forward extreme position a and the upper mechanical boundary Top.

[0044] When the system is powered on and reads the initial wake-up position s, and the servo motor 18 has not yet performed a forward or backward movement, the system sets the initial values ​​of both the forward extreme position a and the backward extreme position b to the initial wake-up position s. In this initial state, the system is certain that the interval represents the single point position where the initial wake-up position s is located, and all other valid physical travels except for this position are classified as trial intervals.

[0045] S900: Real-time extended confidence interval. During the alternating execution of the system interrupting the mechanical zero-finding action in response to a braking request and attempting to resume the mechanical zero-finding action after canceling the braking request, the forward extreme position a and the retraction extreme position b will be updated according to the actual movement of the servo cylinder piston 16.

[0046] When the servo motor 18 rotates forward, driving the servo cylinder piston 16 forward, and the system detects that the real-time position exceeds the currently set forward extreme position 'a', it indicates that the servo cylinder piston 16 has entered the forward probing range. The system extracts the current real-time position data to overwrite and update the forward extreme position 'a'.

[0047] When the servo motor 18 reverses and drives the servo cylinder piston 16 to retract, and the system detects that the real-time position exceeds the currently set retraction extreme position b, it indicates that the servo cylinder piston 16 has entered the subsequent probing range. The system extracts the current real-time position data to overwrite and update the retraction extreme position b.

[0048] As the system control pushes the extreme position a towards the upper mechanical boundary Top, and the retracts the extreme position b towards the lower mechanical boundary Bottom, the coverage of the certainty interval within the control unit gradually expands, while the range of the trial interval correspondingly shrinks.

[0049] S1000: Range conversion after mechanical zeroing is completed. After the system confirms that the mechanical zeroing process has been completed, the uncertainty regarding the mechanical boundary position within the system is eliminated. The system directly extends the coverage of the confirmed range to the full stroke of the servo cylinder. The system determines that all effective physical strokes of the servo cylinder piston 16 are confirmed ranges, and no further trial ranges are set.

[0050] S1100: Range Reset Mechanism After Abnormal Reset. When the system experiences a power-on re-energization or an unexpected system reset during operation, the internally recorded position coordinates become invalid, and the mechanical zero-point state is reset to an unknown state. The control unit clears the original forward extreme value position 'a' and backward extreme value position 'b' data from the memory. The system re-acquires the current position of the servo cylinder piston 16 as the new initial wake-up position 's', and resets the certainty range and trial range based on this new initial wake-up position 's'. The system then re-enters the range initialization and expansion process.

[0051] Combined with appendix Figure 3 With appendix Figure 4 In the implementation scenario, the drive control algorithm of servo motor 18 is dynamically matched and switched. The system configures independent control modes for the confidence interval and the trial interval to balance the system's pressure build-up response speed and the smooth operation of the mechanical structure. The system's differentiated motor control strategies may include: S1200: Speed-limited control strategy within the trial range. When the servo motor 18 drives the servo cylinder piston 16 to push forward past the forward extreme position a, or reverse backward past the backward extreme position b, the control unit determines that the servo cylinder piston 16 has entered the trial range. The control unit switches the control mode of the servo motor 18 to the target flow control mode.

[0052] In this control mode, the control unit calculates a fixed speed command based on the fixed target flow rate set by the system, combined with the reduction ratio and lead parameters of the ball screw transmission mechanism 17, and the effective working area of ​​the servo cylinder piston 16, through kinematic conversion. The control unit then instructs the servo motor 18 to maintain a constant speed according to this fixed speed command.

[0053] This control mode prevents the motor speed from rising uncontrollably when the servo cylinder piston 16 operates in an unexplored area due to the target pressure not being reached. By limiting the operating speed, the system restricts the collision speed when the servo cylinder piston 16 interferes with the mechanical boundary, thus avoiding the problems of high-intensity mechanical impact and noise vibration generated by the system.

[0054] S1300: High-response pressure control strategy within the certainty interval. When the real-time position coordinates of the servo cylinder piston 16 are within the certainty interval and the system receives a braking request, the control unit sets the control mode of the servo motor 18 to pressure closed-loop control mode.

[0055] In this control mode, the control unit acquires the target braking pressure value corresponding to the braking intention and simultaneously collects the actual braking pressure value fed back by the servo cylinder pressure sensor P214. The control unit performs closed-loop calculations based on the deviation between the target braking pressure and the actual braking pressure, and outputs real-time control commands to drive the servo motor 18. Since the system is certain that the specified range has no mechanical interference risk, the system accepts the conventional speed-limiting control logic constraints of the brake-by-wire mode within this range, allowing the servo motor 18 to operate at a higher speed to eliminate pressure deviation.

[0056] For the specific proportional-integral regulation algorithm and the underlying current loop control logic in the pressure closed-loop control, those skilled in the art can configure the parameters according to the characteristics of the brushless motor. The specific closed-loop feedback calculation process is a well-known technology in this field and will not be elaborated here.

[0057] S1400: Smooth transition control strategy within the confidence interval. Even if the servo cylinder piston 16 is within the confidence interval, the system will intervene in low-pressure conditions when there is no braking request and the servo cylinder piston 16 is reversing and retracting for mechanical zeroing.

[0058] When the control unit detects that the actual braking pressure of the system has decreased and is approaching the set minimum pressure threshold, or when the servo cylinder piston 16 retracts to the previously determined extreme retraction position b but the actual braking pressure has not yet dropped to zero, the control unit actively interrupts the pressure closed-loop control mode. The control unit switches the servo motor 18 to the target flow control mode.

[0059] This intervention mechanism prevents abrupt changes in speed commands from the pressure closed-loop control system due to deviation fluctuations during periods of low system pressure. This mechanism ensures a smooth pressure transition during the opening of the system compensation orifice structure 29 and avoids mechanical collisions caused by the zero-finding and retraction process.

[0060] See attached document Figure 3 The first scenario diagram shows the system needing to locate the mechanical zero point. In the absence of a braking request, the system control performs a backtracking zero-finding and smooth degradation control. This process involves extending the confidence interval backward and smoothly switching the pressure closed loop to target flow control. The control steps performed by the system may include: S1500: Start-up retraction zeroing and brake fluid compensation. After system power-on wake-up or reset restart, in the absence of external braking requests, the system enters the mechanical zeroing process. The system controls the servo motor 18 to reverse, driving the servo cylinder piston 16 to retract towards the bottom of the servo cylinder via the ball screw transmission mechanism 17. At this time, the fully decoupled wire-controlled braking system is in the valve-controlled state corresponding to the backup braking mode, and the system cuts off the hydraulic connection between the servo pressure-building end and the wheel-side brake. Both servo cylinder circuit isolation valve one 12 and servo cylinder circuit isolation valve two 13 remain closed. As the servo cylinder piston 16 retracts, the closed volume inside the servo cylinder body 15 increases and generates negative pressure. Brake fluid in the reservoir 4 is drawn into the servo cylinder body 15 through the one-way valve 28, thus replenishing the brake fluid.

[0061] S1600: Initial retraction control within the confirmed range. When the position coordinates of the servo cylinder piston 16 are within the currently known confirmed range, and the actual braking pressure inside the system has not yet dropped to a set range close to zero, the control unit uses a pressure closed-loop control mode to drive the servo motor 18 in reverse. The control unit collects the actual braking pressure signal fed back by the servo cylinder pressure sensor P214, performs closed-loop adjustment with the goal of reducing system pressure, and outputs corresponding control commands to drive the servo motor 18 to retract.

[0062] S1700: Real-time monitoring of smooth degradation trigger conditions. During the continuous retraction of the servo cylinder piston 16 to perform mechanical zeroing, the system monitors the braking pressure and piston position information in real time to determine whether a degradation switch in the motor control mode is necessary. The degradation trigger conditions set by the control unit include two cases: the first case is that the actual braking pressure measured by the servo cylinder pressure sensor P214 drops to the system-calibrated low pressure threshold, which is set to a low pressure state close to zero, for example, 1 bar; the second case is that the servo cylinder piston 16 has retracted to the extreme retraction position b of the previously determined confidence interval boundary, but the actual braking pressure is still greater than zero. When the system meets either of these two cases, the control unit determines to trigger the smooth degradation control logic.

[0063] S1800: Execute the degraded target flow control. When the system determines that the degraded conditions have been triggered, the control unit actively interrupts the original pressure closed-loop control mode. The control unit switches the control mode of the servo motor 18 to the target flow control mode. The system instructs the servo motor 18 to continue reversing and retracting at a set fixed speed. As the servo cylinder piston 16 passes the original retraction extreme position b and enters the subsequent trial range, the system extracts the new position coordinates and updates the retraction extreme position b.

[0064] For the torque confirmation and mechanical zero-point calibration after the servo motor 18 bottoms out during retraction, those skilled in the art can compare the phase current or output negative torque value fed back by the servo motor 18 with the set threshold. The method of confirming the mechanical zero point by detecting excessive negative torque during motor stall is a well-known technique in the field and will not be elaborated further here. Through this degraded control, the system avoids abrupt changes in motor speed commands due to minute pressure fluctuations in the pressure closed-loop algorithm within the low-pressure blind zone, preventing the servo cylinder piston 16 from impacting the mechanical stop at the bottom of the servo cylinder body 15 at high speed, thus mitigating the impact intensity during the mechanical zero-finding process.

[0065] When the vehicle is performing mechanical zeroing by reversing the servo cylinder piston 16, and the system receives a braking request, the control unit executes the braking priority logic. This process involves the interruption of the mechanical zeroing action, the mode switching of the system's hydraulic circuit, and the evolution of the servo motor 18 control algorithm along the stroke range.

[0066] The emergency braking request priority interruption and forward pressure build-up control executed by the control unit specifically includes the following steps: S1900: Interruption of retraction and hydraulic system mode switching. The control unit acquires signals from the brake pedal travel sensor 3 and the manual cylinder pressure sensor P17 in real time. When the brake request flag position is detected, the control unit sends a stop retraction command to the servo motor 18, interrupting the current mechanical zeroing process. The control unit reads the position coordinates of the servo cylinder piston 16 at this time, records these coordinates as the updated retraction extreme value position b, and confirms that the interval update is the travel range between the current position and the forward push extreme value position a. Simultaneously, the control unit controls the brake-by-wire system to enter the valve control state corresponding to the brake-by-wire mode. Both the servo cylinder circuit isolation valve 12 and the servo cylinder circuit isolation valve 23 are energized and opened, while the check valve 28 is closed due to the positive pressure of the system.

[0067] S2000: Closed-loop response within the confidence interval. After the system completes the valve control state switch, the control unit instructs the servo motor 18 to rotate forward, driving the servo cylinder piston 16 forward through the ball screw transmission mechanism 17 to compress the brake fluid in the closed hydraulic circuit to build up braking pressure. In the initial stage of forward rotation and pressure building, the control unit compares the real-time acquired position coordinates of the servo cylinder piston 16 with the recorded forward extreme value position 'a'. When the servo cylinder piston 16 is within the confidence interval, the control unit calls the pressure closed-loop control algorithm, allowing the servo motor 18 to run at a higher speed to eliminate the deviation between the target pressure and the actual pressure, shortening the pressure building response time of the braking system.

[0068] S2100: Mode switching for crossing the extreme point and entering the trial zone. As the servo cylinder piston 16 continues to move forward, when its real-time position coordinate exceeds the forward extreme position a, the system determines that the servo cylinder piston 16 has crossed the certainty zone and entered the forward trial zone. To prevent the motor speed from rising unrestricted due to the system not reaching the target braking pressure, the control unit performs a control mode switch based on the real-time position zone attribute of the servo cylinder piston 16. Specifically, when the real-time position coordinate of the servo cylinder piston 16 is less than or equal to the forward extreme position a, the control unit maintains the pressure closed-loop control mode; when the real-time position coordinate of the servo cylinder piston 16 is greater than the forward extreme position a, the control unit switches the control mode of the servo motor 18 to the target flow control mode. After entering the trial zone, the control unit outputs a fixed speed command to control the servo cylinder piston 16 to move forward, and at the same time, the system writes the latest position coordinates of the servo cylinder piston 16 along its path into the memory of the forward extreme position a in real time.

[0069] S2200: Mechanical contact detection and relay-type pressure building and fluid replenishment. Because the actual usable forward stroke of the servo cylinder piston 16 is uncertain before mechanical zeroing is completed, under conditions of high braking demand, when the servo cylinder piston 16 moves forward to the mechanical boundary at the very front of the servo cylinder, the actual system pressure may still not have reached the target braking pressure. The system monitors the rate of change of the servo cylinder piston position and the actual control current of the servo motor 18 in real time.

[0070] Regarding the process of determining mechanical stop contact by the relationship between servo motor torque and piston position, those skilled in the art can determine the stall based on the characteristics of a sharp increase in current and a sudden drop in speed. The method of determining mechanical stop contact by the relationship between torque and position is a well-known technology in the field and will not be elaborated here.

[0071] When the control unit detects that the servo cylinder piston 16 has reached its limit, the system determines that the forward mechanical zeroing is complete and updates the confirmed range to the full stroke of the servo cylinder. Due to a brake pressure gap, the control unit triggers a relay-type pressure-building and fluid replenishment mechanism. The control unit de-energizes and closes the servo cylinder circuit isolation valve 12 and the servo cylinder circuit isolation valve 23, maintaining pressure in the wheel-side brake circuit. The control unit instructs the servo motor 18 to reverse, causing the servo cylinder piston 16 to retract a certain stroke, drawing brake fluid through the one-way valve 28 and replenishing it into the servo cylinder. After completing the fluid replenishment, the control unit again controls the servo motor 18 to rotate forward, simultaneously opening the servo cylinder circuit isolation valve 12 and the servo cylinder circuit isolation valve 23, continuing to output high-pressure brake fluid to the brake circuit until the actual braking pressure meets the driver's braking needs.

[0072] During vehicle operation, when a sudden braking request ends or the driver releases the brake pedal 1, the system resumes the interrupted mechanical zeroing process. The control unit dynamically continues the retraction action and continuously expands the coverage of the confidence interval based on the current position of the servo cylinder piston 16 and historical extreme value records.

[0073] The zero-finding continuation and confirmation interval expansion logic executed by the control unit specifically includes the following steps: S2300: Brake Release Recognition and Forward Extreme Value Update. The control unit acquires the pedal travel sensor 3 signal of brake pedal 1 and the system target pressure command in real time. When the system detects that the braking request has disappeared or the target braking pressure has dropped to zero, the control unit terminates the forward rotation pressure-building action of the servo motor 18. The control unit extracts the coordinates of the foremost position reached by the servo cylinder piston 16 during this forward pressure-building process and records these coordinates as the updated forward extreme value position a. The system extends the boundary of the confirmed interval to the travel area between the updated forward extreme value position a and the historical return extreme value position b.

[0074] S2400: Pressure reduction and retraction within the confirmed range. After the system terminates pressure build-up, it resumes mechanical zeroing. The control unit instructs the servo motor 18 to reverse, driving the servo cylinder piston 16 backward via the ball screw transmission mechanism 17, releasing the system braking pressure. During the retraction of the servo cylinder piston 16 from the forward extreme position a to the backward extreme position b, since this range has been identified as a confirmed range without mechanical interference, the control unit activates the pressure closed-loop control mode. The control unit outputs a control command based on the deviation between the actual braking pressure and the target zero pressure, driving the servo motor 18 to reverse, thereby reducing the system pressure.

[0075] S2500: Smooth Degradation and Reverse Probing Continuation. During the retraction and pressure reduction process of the servo cylinder piston 16, the control unit determines the degradation switching conditions in real time. When the actual braking pressure drops to a set threshold close to zero, or when the servo cylinder piston 16 has retracted to the previously determined retraction extreme position b but the actual braking pressure is still greater than zero, the control unit actively interrupts the pressure closed-loop control. The control unit switches the control mode of the servo motor 18 to a target flow control mode. The system controls the servo cylinder piston 16 to pass the retraction extreme position b at a set fixed speed, continuing to retract into the subsequent probing range, and simultaneously extracts new position coordinates to extend and update the retraction extreme position b backward.

[0076] S2600: Multi-condition Cycle and Global Evolution of Range. In practical applications, the mechanical zeroing process and sudden braking response alternate multiple times. The control unit continuously updates the extreme values ​​at both ends through multiple interruptions and resuming processes. Specifically, the system updates the furthest position reached by the servo cylinder piston 16 as the retraction extreme value position b in real time, and simultaneously updates the furthest position reached by the servo cylinder piston 16 as the forward push extreme value position a in real time. The range of the confidence interval continuously expands as the forward push extreme value position a and the retraction extreme value position b expand, while the range of the trial interval shrinks accordingly. When the servo cylinder piston 16 retracts to the mechanical boundary at the bottom of the servo cylinder, and the system completes the mechanical zero-point calibration through torque verification, the control unit determines that the mechanical zeroing is complete. The control unit sets the corresponding zeroing completion flag position, expands the confidence interval to the full stroke of the servo cylinder, and the system enters the brake-by-wire mode.

[0077] During the operation of the vehicle braking system, if there is no sudden braking request to interrupt it, or if the system has undergone multiple alternating retractions after the brakes are released, and the servo cylinder piston 16 retracts to the mechanical boundary at the bottom of the servo cylinder, the control unit performs a routine mechanical zeroing completion determination. This determination process confirms the absolute mechanical zero position by identifying the motor stall characteristics and globally resets the stroke range attributes.

[0078] The routine zero-finding completion determination control performed by the control unit specifically includes the following steps: S2700: Bottom-out retraction in target flow mode. The control unit controls the servo motor 18 to continuously reverse in target flow control mode. The ball screw transmission mechanism 17 drives the servo cylinder piston 16 to move towards the bottom mechanical boundary of the servo cylinder body 15 within the trial range. During this stage, the system outputs a constant speed command to reduce the impact intensity when the servo cylinder piston 16 physically contacts the bottom mechanical limit stop by limiting its operating speed.

[0079] S2800: Bottom Limit Contact and Stall Torque Confirmation. When the servo cylinder piston 16 abuts against the bottom mechanical stop, its backward physical displacement ceases. The control unit performs mechanical zeroing torque verification by monitoring changes in the operating parameters of the servo motor 18. Specifically, the control unit acquires the actual feedback torque and actual operating speed of the servo motor 18 in real time. When the control unit determines that the absolute value of the actual feedback torque is greater than or equal to the system-calibrated stall torque threshold, and the actual operating speed drops below a set near-zero speed judgment threshold, the system confirms that the servo cylinder piston 16 has reached the mechanical zero position.

[0080] The correspondence between the calculation of the actual feedback torque of the servo motor 18 and the sampling of the phase current can be calculated and configured by those skilled in the art based on the vector control principle of the motor. The underlying motor parameter analysis and stall state feature extraction process are well-known technologies in the field and will not be described in detail here.

[0081] S2900: Zero-point physical calibration and full coverage of the assurance interval. When the control unit determines that the above-mentioned stall conditions are met and the set confirmation time is maintained, the system considers the mechanical zeroing process complete. The control unit stops the servo motor 18 from reversing and marks the current absolute physical position of the servo cylinder piston 16 as the system's mechanical zero point, simultaneously setting the mechanical zeroing completion flag. Based on this mechanical zero-point position, the control unit updates the system's assurance interval to the entire physical stroke range of the servo cylinder piston 16. After mechanical zeroing is completed, the original trial interval is eliminated, and all stroke areas are defined as assurance intervals.

[0082] S3000: Switching to normal brake-by-wire mode. After completing zero-point calibration and ensuring full coverage of the control range, the fully decoupled brake-by-wire system enters normal brake-by-wire mode. During subsequent operation, once the control unit receives the braking intention, it no longer needs to perform range attribute judgments. The system allows the servo motor 18 to directly respond to braking commands using pressure closed-loop control mode throughout the entire stroke of the servo cylinder. The system utilizes full-stroke, blind-zone-free pressure closed-loop regulation to achieve following control of the braking pressure.

[0083] After power-on wake-up or system reset and restart, the initial absolute position of the servo cylinder piston 16 is unknown. When the system prioritizes responding to the braking request and controls the servo cylinder piston 16 to move forward to build pressure, the servo cylinder piston 16 may move to the mechanical boundary at the very front of the servo cylinder before reaching the target braking pressure. The control unit performs top-touch recognition and relay fluid replenishment pressure building control for this condition, specifically including the following steps: S3100: Forward Mechanical Top-Hit Feature Monitoring and Recognition. During the forward rotation of the servo motor 18 driving the servo cylinder piston 16 to move forward and build up pressure, the control unit acquires the position change rate of the servo cylinder piston 16 and the actual control current of the servo motor 18. When the control unit determines that the actual control current is greater than or equal to the set forward stall current threshold, and the position change rate of the servo cylinder piston 16 is less than or equal to the set minimum speed value, the system confirms that the servo cylinder piston 16 has reached the foremost mechanical boundary position.

[0084] The relationship between the increase in the actual control current of the servo motor and the decrease in the piston speed is used to determine the mechanical stop contact. Those skilled in the art can make logical judgments based on the positive correlation between the motor operating current and the load torque. The feature extraction process of the underlying stall state is a well-known technology in the field and will not be described in detail here.

[0085] S3200: Stroke Calculation and Confidence Range Coverage. After the control unit determines that the forward mechanical contact has reached its limit, the system assumes that the servo cylinder piston 16 has reached the absolute front boundary. Since the total servo cylinder stroke is a known fixed hardware parameter, the control unit calculates the mechanical zero point position at the rear bottom by combining the current front boundary position with the total servo cylinder stroke. The system then effectively assumes that mechanical zeroing is complete. The control unit sets the mechanical zeroing completion flag, updating the system's confidence range to the full stroke range of the servo cylinder piston 16, eliminating the position trial range.

[0086] S3300: Hydraulic circuit isolation and reverse fluid replenishment. When forward contact occurs, the actual pressure of the braking system does not reach the target braking pressure, and the control unit triggers the relay pressure-building and fluid replenishment mechanism. The control unit controls the servo cylinder circuit isolation valve 12 and servo cylinder circuit isolation valve 23 to de-energize and close, maintaining pressure in the wheel-side braking circuit. The control unit commands the servo motor 18 to reverse, driving the servo cylinder piston 16 to retract backward through the ball screw transmission mechanism 17. The internal volume of the servo cylinder body 15 expands, and brake fluid is drawn in through the one-way valve 28 and replenished into the servo cylinder body 15.

[0087] S3400: Isolation Valve Opening and Relay Closed-Loop Pressure Build-up. After the servo cylinder piston 16 retracts a certain stroke, the control unit stops the reverse command of the servo motor 18. The control unit controls the servo motor 18 to rotate forward, driving the servo cylinder piston 16 to move forward. When the pressure inside the servo cylinder body 15 rises to match the current holding pressure of the wheel-side brake circuit, the control unit controls the servo cylinder circuit isolation valve one 12 and servo cylinder circuit isolation valve two 13 to be energized and opened. The brake fluid replenished in the servo cylinder body 15 flows into the system execution circuit. The control unit calls the pressure closed-loop control mode within the full stroke confidence range, and the servo motor 18 outputs the corresponding positive torque to relay and increase the system hydraulic pressure until the actual braking pressure meets the current braking request target.

Claims

1. A fully decoupled brake-by-wire system, characterized in that, It includes a control unit, multiple isolation valves, multiple pressure relief valves, a servo cylinder piston (16), and a servo motor (18). The control unit is communicatively connected to the plurality of isolation valves, the plurality of pressure relief valves and the servo motor (18); The control unit is used to execute the following control logic: After the fully decoupled brake-by-wire system is powered on, the certainty interval and the trial interval are dynamically divided based on the real-time position of the servo cylinder piston (16). When no braking request is received, the servo motor (18) is controlled to drive the servo cylinder piston (16) to reverse and retract to perform the mechanical zeroing process; When the braking request is obtained during the execution of the mechanical zeroing process, the mechanical zeroing process is interrupted, and the servo motor (18) is prioritized to drive the servo cylinder piston (16) to rotate forward and build pressure in response to the braking request. When the servo cylinder piston (16) is in the certainty range or the probing range, an independent motor control mode is used to match the pressure building action and the mechanical zeroing action.

2. The system according to claim 1, characterized in that, The control unit is specifically used for: Record the initial wake-up position of the system, and when the braking request is received and the servo cylinder piston (16) is controlled to move forward to build pressure, record and update the forward push extreme position in real time; And when the mechanical zeroing action of controlling the servo cylinder piston (16) to retract is interrupted in the absence of the braking request, the retraction extreme position is recorded and updated in real time; The travel range between the retraction extreme position and the forward extreme position is defined as the confidence interval, and the unsweeped unknown range within the set upper and lower mechanical boundaries, excluding the confidence interval, is defined as the trial interval. As the forward extreme position expands towards the upper boundary of the machine and the backward extreme position expands towards the lower boundary of the machine, the coverage of the confidence interval is expanded in real time and the range of the trial interval is correspondingly reduced.

3. The system according to claim 2, characterized in that, The independent motor control modes include pressure closed-loop control mode and target flow control mode; When the real-time position of the servo cylinder piston (16) is within the certain range and the braking request is obtained, the control unit adopts the pressure closed-loop control mode, performs closed-loop calculation based on the deviation between the obtained target braking pressure and the obtained actual braking pressure, and outputs real-time changing control commands to drive the servo motor (18) to move. When the real-time position of the servo cylinder piston (16) exceeds the forward extreme position or the retraction extreme position and enters the trial range, the control unit switches the control mode of the servo motor (18) to the fixed target flow control mode, calculates the fixed speed command based on the set fixed target flow value, and commands the servo motor (18) to maintain a constant speed.

4. The system according to claim 3, characterized in that, When executing the braking request priority interruption and forward pressure build-up control, the control unit specifically performs the following logic: When the braking request is obtained during the mechanical zeroing process, a stop retraction command is sent to the servo motor (18), the position coordinates of the servo cylinder piston (16) are read and updated to the retraction extreme position, and the fully decoupled line control braking system is controlled to switch to the valve control state corresponding to the line control braking mode, and the servo motor (18) is instructed to rotate forward to drive the servo cylinder piston (16) to move forward to build pressure; The pressure closed-loop control mode is maintained when the servo cylinder piston (16) is within the certainty range; When the servo cylinder piston (16) exceeds the forward extreme position and enters the trial range, the target flow control mode is switched, and the latest position coordinates of the servo cylinder piston (16) are written in real time as the updated forward extreme position.

5. The system according to claim 4, characterized in that, During the process of controlling the forward movement of the servo cylinder piston (16) to build up pressure, the control unit executes the mechanical contact recognition and relay-type pressure building and fluid replenishment logic: When the control unit obtains that the actual control current of the servo motor (18) is greater than or equal to the set forward stall current threshold, and the position change rate of the servo cylinder piston (16) is less than or equal to the set speed minimum value, it confirms that the servo cylinder piston (16) has reached the frontmost mechanical boundary position, and calculates the mechanical zero point position at the rear bottom based on the known total servo cylinder stroke, and equivalently determines that the mechanical zeroing is completed, and updates the certainty interval to the full stroke of the servo cylinder; If the actual braking pressure does not reach the target braking pressure at this time, a relay-type pressure-building and fluid replenishment mechanism is triggered: The corresponding isolation valve is de-energized and closed, and the pressure of the wheel-side brake circuit of the fully decoupled brake-by-wire system is maintained. The servo motor (18) is instructed to reverse and drive the servo cylinder piston (16) to retract the set stroke to replenish the fluid. After the fluid replenishment action is completed, the servo motor (18) is instructed to rotate forward and push forward again, and the corresponding isolation valve is controlled to open to restore the hydraulic connection and continue to output brake fluid to the wheel-side brake circuit.

6. The system according to claim 3, characterized in that, When no braking request is received, the control unit performs backtracking and smooth degradation control, specifically executing the following logic: During the process of controlling the servo cylinder piston (16) to reverse and retract to perform mechanical zeroing, when the servo cylinder piston (16) is within the certain range and the actual braking pressure has not dropped to the set small pressure threshold, the pressure closed-loop control mode is used to drive the servo motor (18) to reverse. When the actual braking pressure drops to the minimum pressure threshold, or when the servo cylinder piston (16) has retracted to the previously determined retraction extreme position but the actual braking pressure is still greater than zero, the smooth degradation control logic is triggered, the pressure closed-loop control mode is actively interrupted, and the fixed target flow control mode is switched to continue reversing and retracting according to the fixed speed command.

7. The system according to claim 6, characterized in that, The control unit executes the mechanical zeroing completion determination logic, specifically for executing the following logic: In the target flow control mode, the servo cylinder piston (16) is driven to move to the bottom mechanical lower boundary within the test range. When the absolute value of the actual feedback torque of the servo motor (18) is greater than or equal to the set stall torque threshold, and the actual operating speed drops below the set speed judgment threshold and continues for a set time, it is confirmed that the servo cylinder piston (16) has reached the mechanical zero point position and the mechanical zeroing is determined to be completed. The control unit marks the current absolute physical position as the mechanical zero point, eliminates the trial interval, and extends the certainty interval to the full stroke of the servo cylinder.

8. The system according to claim 1, characterized in that, The hardware structure of the fully decoupled brake-by-wire system also includes: brake pedal (1), reservoir (4), first piston and spring of manual cylinder (5), second piston and spring of manual cylinder (6), first isolation valve of manual cylinder circuit (8), second isolation valve of manual cylinder circuit (9), isolation valve of analog cylinder circuit (10), first isolation valve of servo cylinder circuit (12), second isolation valve of servo cylinder circuit (13), ball screw transmission mechanism (17), servo cylinder body (15), and check valve (28). The fully decoupled brake-by-wire system includes, in the wheel-side adjustment structure, isolation valve one (20), isolation valve two (21), isolation valve three (22), isolation valve four (23), and pressure relief valve one (24), pressure relief valve two (25), pressure relief valve three (26), and pressure relief valve four (27).

9. The system according to claim 8, characterized in that, In the backup braking working state where the fully decoupled brake-by-wire system is not powered on and awakened, the manual cylinder circuit isolation valve one (8), the manual cylinder circuit isolation valve two (9), and isolation valves one (20) to four (23) are all in the open state, the pressure relief valve one (24) to four (27) are all in the closed state, the simulated cylinder circuit isolation valve (10), the servo cylinder circuit isolation valve one (12), and the servo cylinder circuit isolation valve two (13) are all in the closed state, and the first piston and spring (5) of the manual cylinder or the second piston and spring (6) of the manual cylinder establishes braking hydraulic pressure on the wheel-side braking circuit after passing the inlet.

10. A control method for a fully decoupled brake-by-wire system, applied to the fully decoupled brake-by-wire system as described in any one of claims 1-9, characterized in that, Includes the following steps: Determine the power-on status of the fully decoupled brake-by-wire system, and after the fully decoupled brake-by-wire system is powered on and awakened, record the initial awakening position of the servo cylinder piston (16); Determine if a braking request exists; When the braking request is present, the servo motor (18) is controlled to rotate forward to build up pressure and the forward extreme position is updated according to the extreme position of the servo cylinder piston (16); When there is no braking request, the servo motor (18) is controlled to drive the servo cylinder piston (16) to reverse and retract to perform the mechanical zeroing process, and the retraction extreme value position is updated according to the zeroing interruption position; The travel range between the regression extreme position and the forward extreme position is dynamically divided into a certainty interval, and the unsweeped range outside the certainty interval is divided into a probing interval. If the braking request is obtained during the execution of the mechanical zeroing process, the current mechanical zeroing process is interrupted, and the servo motor (18) is controlled to rotate forward to drive the servo cylinder piston (16) to push forward in response to the braking request. When the servo cylinder piston (16) is running within the certain range, the servo motor (18) is driven by a pressure closed-loop control mode. When the servo cylinder piston (16) moves beyond the certainty interval and enters the probing interval, the system switches to a target flow control mode and controls the servo motor (18) to maintain a constant speed according to a fixed speed command until the mechanical zeroing process is completed and the certainty interval is extended to the full stroke of the servo cylinder.

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