AMT downshift control method and vehicle

Abstract

This application discloses an AMT downshift control method and vehicle, relating to the field of automatic transmission control. The method acquires the output shaft and input shaft speeds and calculates the speed difference before shifting; controls clutch engagement to increase the input shaft speed; during engagement, it acquires the intermediate shaft speed change rate in real time and calculates the estimated change in speed difference accordingly; it subtracts the estimated change in speed difference from the current pre-shift speed difference to obtain the equivalent remaining speed difference; it determines whether the equivalent remaining speed difference is less than or equal to a preset engagement speed difference; if so, it triggers a disengagement mechanism to control clutch disengagement in advance; and controls the sliding sleeve to complete engagement when the speed difference meets the engagement conditions. If the disengagement conditions are not met, it fine-tunes the clutch engagement depth based on a closed-loop angular acceleration deviation. This invention transforms the physical execution delay of the clutch into feedforward speed compensation, effectively avoiding input shaft speed overshoot during downshifting and ensuring smooth engagement of the transmission system.

Description

Technical Field

[0001] This application relates to the field of sound control, and more particularly to an AMT downshift control method and vehicle. Background Technology

[0002] When an automatic mechanical transmission performs a downshift, because the target gear ratio is higher than the current gear, the control system needs to moderately engage the clutch to ensure smooth mechanical engagement between the master transmission sliding sleeve and the target gear engagement ring. This involves actively increasing the transmission input shaft speed using the frictional torque transmitted from the engine side to eliminate the speed difference before the shift. In traditional downshift speed synchronization control strategies, the system typically only uses the actual transient speed of the current input shaft and the target synchronization speed as a comparison benchmark. Only when the actual speed enters the allowable synchronization tolerance range does the control unit issue an electrical disengagement command to the clutch actuator.

[0003] However, in commercial vehicles, the clutch actuator, upon receiving an electrical control signal, experiences an inherent physical time delay between the system issuing a disengagement command and the clutch pressure plate fully retracting and releasing torque transmission. This delay is limited by the lag in solenoid valve operation, the physical time required for pneumatic or hydraulic line inflation / deflation, and the physical inertia of mechanical components. During this delay period, the clutch does not immediately disengage, and the input shaft continues to accelerate under the influence of driving torque. Consequently, at the moment of physical disengagement, the input shaft speed has already exceeded the synchronous speed threshold corresponding to the target gear. This physical lag causes speed overshoot, resulting in the transmission system missing the speed window for mechanical gear engagement. Furthermore, existing synchronous control logic relies heavily on preset open-loop torque estimation models or static displacement characteristic curves when controlling clutch engagement depth, failing to provide real-time dynamic compensation for the nonlinear drift of the friction coefficient caused by temperature fluctuations or long-term wear of the clutch friction plates. When friction characteristics change, the initially set engagement torque cannot force the input shaft to accelerate according to the expected target angular acceleration, resulting in steady-state errors in the speed trajectory and preventing the system from converging to synchronous speed within the specified time period. The aforementioned speed overshoot and steady-state synchronization error directly lead to an excessive relative angular velocity between the sliding sleeve and the target gear ring when the shifting actuator is activated, which in turn causes physical interference at the tooth ends and abnormal mechanical wear. Summary of the Invention

[0004] The purpose of this invention is to provide an AMT downshift control method and vehicle, which at least solves a technical problem in existing automatic mechanical transmissions during downshifting, where the input shaft speed overshoots and the speed synchronization has steady-state errors due to the physical response delay of the clutch actuator.

[0005] This invention provides the following solution:

[0006] This invention provides a first aspect: an AMT downshift control method, which includes issuing commands and monitoring the status of underlying transmission system hardware actions, comprising the following steps:

[0007] The output shaft speed, input shaft speed, and speed ratio corresponding to the target gear are obtained, and the speed difference before shifting is calculated; based on the obtained oil temperature and the target gear, the preset shifting speed difference is obtained;

[0008] Control the clutch engagement to increase the input shaft speed; during the clutch engagement process, acquire the intermediate shaft speed and calculate the intermediate shaft speed change rate, and obtain the estimated change in speed difference based on the intermediate shaft speed change rate;

[0009] Subtract the estimated change in speed difference from the current speed difference before shifting to obtain the equivalent remaining speed difference; determine whether the equivalent remaining speed difference is less than or equal to the preset shifting speed difference;

[0010] If the difference is less than or equal to the target gear, the clutch is disengaged to a preset position, and when the speed difference before shifting meets the preset shifting speed difference condition, the sliding sleeve is moved toward the target gear ring to complete the shifting.

[0011] The innovative principle of this invention lies in using the intermediate shaft angular acceleration (i.e., the rate of change of intermediate shaft rotational speed) as a feedforward prediction parameter, and calculating the estimated change in rotational speed difference accordingly. The system uses this estimated change in rotational speed difference to perform a subtraction operation to compensate for the current dynamic rotational speed difference, obtaining an equivalent residual rotational speed difference.

[0012] The system uses this equivalent remaining speed difference as the trigger condition for controlling the clutch to disengage prematurely, thereby converting the physical response delay time of the clutch actuator into a speed compensation amount at the current control moment. This mechanism matches the physical hysteresis period corresponding to the clutch solenoid valve's disengagement action with the physical time for the input shaft to eliminate the remaining speed difference.

[0013] Preferably, controlling clutch engagement includes: calculating the difference between the preset gear shift speed difference and the current speed difference before shifting, as a speed difference deviation; obtaining a target speed difference change rate based on the target gear and the speed difference deviation; obtaining a clutch target torque based on the target speed difference change rate; and controlling clutch engagement using the clutch target torque as a control target.

[0014] In one specific embodiment, after determining whether the equivalent remaining speed difference is less than or equal to the preset gear shifting speed difference, the system introduces a closed-loop dynamic fine-tuning control mechanism, which further includes the following control steps:

[0015] If the equivalent remaining speed difference is greater than the preset gear shifting speed difference, then the difference between the current target speed difference change rate and the actual equivalent angular acceleration is calculated to obtain the acceleration deviation, wherein the actual equivalent angular acceleration is obtained by converting the current intermediate shaft speed change rate to the input shaft.

[0016] The clutch torque compensation amount is calculated based on the acceleration deviation.

[0017] The target clutch torque is summed with the clutch torque compensation amount to obtain the corrected final target clutch torque;

[0018] Using the corrected final clutch target torque as the control target, the clutch actuator is driven to fine-tune the clutch engagement depth;

[0019] In the next control cycle, the latest intermediate shaft speed change rate is reacquired, and the estimated change in speed difference is updated accordingly.

[0020] The updated equivalent remaining speed difference is obtained by subtracting the updated estimated change in speed difference from the current speed difference before the shift;

[0021] Determine whether the updated equivalent remaining speed difference is less than or equal to the preset gear shifting speed difference; if it is less than or equal to, trigger the separation mechanism and control the clutch to disengage to the preset position; if it is greater than, return to the step of obtaining the acceleration deviation and fine-tuning the clutch engagement depth.

[0022] Preferably, after the control clutch is disengaged to a preset position, when the speed difference before shifting meets a preset shifting speed difference condition, the sliding sleeve is controlled to move towards the target gear ring to complete the shifting, which includes: continuously calculating the real-time speed difference before shifting; determining whether the real-time speed difference before shifting falls within a preset absolute synchronization tolerance range; if the condition is not met, then continuously waiting and continuing to calculate the real-time speed difference before shifting; if the condition is met, then determining that the preset shifting speed difference condition is met, and activating the actuator to control the sliding sleeve to engage the gear.

[0023] Preferably, before acquiring the output shaft speed, input shaft speed, and the speed ratio corresponding to the target gear, and calculating the speed difference before shifting, the system performs power decoupling in the pre-downshift phase, specifically including: controlling the engine to perform torque reduction operation and controlling the clutch to perform disengagement operation; determining whether the engine torque reduction operation and the clutch disengagement operation are both completed, and if so, controlling the transmission to perform disengagement operation; determining whether the disengagement operation is completed, and if so, controlling the front and rear auxiliary gearboxes of the transmission to perform corresponding shifting operations.

[0024] In one specific embodiment, after the control sliding sleeve moves towards the target gear ring to complete gear engagement, the system performs a power recovery operation, which specifically includes: determining in real time whether gear engagement is complete; if gear engagement is not complete, continuing to apply control actions to control the sliding sleeve to engage gear; if gear engagement is complete, controlling the clutch to fully engage and sending a torque recovery request to the engine control unit; determining whether the clutch is fully engaged and engine torque recovery is complete; and ending the downshift control process after both determinations are completed.

[0025] Preferably, the method for calculating the speed difference before shifting is as follows: calculate the product of the output shaft speed and the speed ratio, and calculate the absolute value of the difference between the product and the input shaft speed, and use the absolute value as the speed difference before shifting; the estimated change in speed difference is used to characterize the compensation value for the change in speed difference generated from the time the control unit issues the clutch disengagement command to the time the clutch actually disengages torque transmission.

[0026] The technical effects of the control method provided by the present invention are as follows: by introducing an equivalent remaining speed difference determination mechanism through feedforward, the physical time difference introduced by the clutch execution delay is offset, and the objective phenomenon of the input shaft speed exceeding the synchronization window threshold is avoided; by calculating the acceleration deviation through closed-loop feedback and generating the clutch torque compensation amount, the torque transmission error introduced by the clutch friction characteristic drift is continuously corrected, so that the input shaft can approach the gear engagement synchronization range according to the target angular acceleration.

[0027] A second aspect of the present invention provides a vehicle in which the transmission system is controlled by applying or based on the AMT downshift control method described in any one of the first aspects above.

[0028] Preferably, the underlying hardware architecture of the vehicle includes an engine, an AMT transmission, a clutch disposed between the engine and the AMT transmission, a clutch actuator (such as a pneumatic actuator), and a multi-source sensor assembly. The vehicle is equipped with an electronic control system (such as a transmission control unit), which interacts with the multi-source sensor assembly and the clutch actuator via a vehicle communication bus (such as a CAN bus) to acquire parameters such as input shaft speed, output shaft speed, intermediate shaft speed, and oil temperature in real time, and to execute the AMT downshift control method.

[0029] By leveraging the dynamic prediction mechanism based on intermediate shaft acceleration in the downshift control method, the vehicle can effectively overcome the inherent physical response delay between the issuance of control commands and actual mechanical disengagement in the underlying hardware (especially pneumatic actuators). By triggering the predictive separation mechanism in advance when the equivalent remaining speed difference reaches the target, the vehicle can accurately lock the target synchronous speed window during downshifting, avoiding speed overshoot due to response lag. This significantly reduces the risk of abnormal wear and gear breakage of internal mechanical components (such as sliding sleeves and gear rings) in the vehicle's transmission system, extends hardware lifespan, and improves the smoothness and power continuity of the vehicle during downshifting. It is particularly suitable for commercial vehicles with high requirements for shift quality, load-bearing capacity, and reliability.

[0030] The above solution achieves the following beneficial technical effects:

[0031] This application calculates the estimated change in speed difference by obtaining the intermediate shaft speed change rate, calculates the equivalent remaining speed difference by subtracting the estimated change from the current speed difference, and uses whether the equivalent remaining speed difference is less than or equal to the preset gear engagement speed difference as the criterion for triggering clutch disengagement. This technical feature advances the inherent physical response delay time of the clutch actuator into a speed compensation value, offsetting the control time difference caused by the lag in the pneumatic actuator action, and avoiding the overshoot phenomenon of the input shaft speed exceeding the synchronization window threshold due to delayed commands.

[0032] When the separation condition is not met, this application obtains the acceleration deviation by subtracting the target speed difference change rate from the actual equivalent angular acceleration calculated from the intermediate shaft speed change rate. Based on this, the clutch torque compensation is calculated and superimposed on the clutch target torque to correct the final clutch engagement depth. This closed-loop fine-tuning mechanism corrects the static torque transmission error caused by the nonlinear drift of friction characteristics due to clutch friction plate wear or temperature changes, enabling the input shaft speed to approach the gear engagement synchronization range according to the predetermined target angular acceleration.

[0033] After the clutch completes the disengagement action, this application continuously calculates the real-time speed difference and uses whether the real-time speed difference falls within the preset absolute synchronization tolerance range as a prerequisite for activating the gear shifting actuator to perform the gear engagement action. This ensures that the main gearbox sliding sleeve and the target gear ring only make mechanical contact within the physical boundary where the relative angular velocity approaches zero and the transmission power is completely decoupled. This eliminates physical interference during the tooth end meshing process and reduces the mechanical wear rate of the actuator fork and the engagement gear ring. Attached Figure Description

[0034] Figure 1 This is a general flowchart of a method provided in one embodiment of the present invention.

[0035] Figure 2This is a flowchart of the power decoupling and mechanical preparation control during downshifting provided in one embodiment of the present invention.

[0036] Figure 3 This is a flowchart of a predictive separation control based on intermediate shaft acceleration provided in one embodiment of the present invention.

[0037] Figure 4 This is a flowchart of a state-updated secondary predictive separation control provided in one embodiment of the present invention.

[0038] Figure 5 This is a flowchart of absolute speed synchronization gear shifting and power recovery control provided in one embodiment of the present invention.

[0039] Figure 6 This is a comparison diagram of the downshift speed trajectory between conventional feedback control and predictive control provided by an embodiment of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0041] See attached document Figure 1 The AMT downshift control method provided by this invention relies on the underlying hardware architecture of the vehicle's transmission system. This hardware architecture includes a transmission control unit and multiple sensors and actuators connected to it. To obtain the real-time operating status of the vehicle's transmission system, the system is equipped with an input shaft speed sensor, an output shaft speed sensor, and an intermediate shaft speed sensor to collect real-time speed signals of the corresponding shafts in the transmission. An oil temperature sensor is installed inside the transmission to obtain the temperature of the transmission lubricating oil; this temperature parameter is directly related to the response hysteresis characteristics of the hydraulic or pneumatic actuators within the system. A clutch position sensor is installed at the clutch assembly to provide feedback on the actual displacement state of the clutch release bearing or shift fork. The actuators include a clutch actuator for driving clutch engagement and disengagement, and a shift actuator for controlling the gear shifting of the master gearbox sliding sleeve, the front auxiliary gearbox, and the rear auxiliary gearbox.

[0042] In this embodiment, the gear shifting actuator uses a pneumatic solenoid valve to drive a cylinder to achieve the mechanical push-pull action. Considering the slight time delay difference in data transmission from multiple sensors via the CAN bus under actual vehicle operating conditions, to prevent phase errors introduced by the algorithm, as a preferred method, the transmission control unit timestamps and aligns the data acquired from each speed sensor and temperature sensor using an internal system clock pulse to ensure that the input variables participating in a single logical operation belong to the cross-sectional data of the same physical moment.

[0043] For the local area network communication mechanism and underlying electrical signal drive circuit between the transmission control unit and various sensors, engine control unit and actuators, those skilled in the art can use conventional vehicle electrical wiring and communication protocol standards to set it up. Its structure and circuit connection relationship are well known in the art and will not be described in detail here.

[0044] Based on the aforementioned hardware architecture, upon receiving a downshift request, the transmission control unit executes its internally stored control logic program to complete the speed synchronization and gear switching during the AMT downshift process. Due to the inherent mechanical and pneumatic response delays in commercial vehicle actuators, conventional feedback control can lead to excessive input shaft speed increases. This invention introduces intermediate shaft angular acceleration as a feedforward prediction parameter to trigger clutch disengagement before the speed reaches the synchronization window.

[0045] The overall workflow is logically linked through the following steps:

[0046] In step S100, after triggering the downshift command, the transmission system disengages from its original power coupling state. The transmission control unit, in coordination with the engine control unit, performs engine torque reduction and controls the clutch to disengage. After confirming power cut-off, the transmission master gear sleeve is moved to neutral, and the front and / or rear auxiliary gearboxes are switched to the corresponding predetermined gear according to the target gear requirement, completing the mechanical preparation before shifting.

[0047] In step S200, due to power cutoff, the input shaft speed decreases. Based on the kinematic principle of gear transmission, downshifting means increasing the gear ratio of the target gear. Under the condition that the output shaft speed corresponding to the vehicle speed is basically maintained due to the vehicle's inertia, the input shaft speed needs to be increased to near the theoretical synchronous speed corresponding to the target gear to achieve smooth engagement of the sliding sleeve. Therefore, the transmission control unit sends a target speed request or target torque request to the engine control unit, ensuring the engine side has the speed difference or positive drive torque to accelerate the input shaft. Simultaneously, the transmission control unit controls the clutch to gradually engage with a predetermined torque, allowing engine power to be transmitted to the input shaft via the clutch, thereby accelerating the input shaft. The system acquires the output shaft speed, input shaft speed, and the gear ratio corresponding to the target gear, and calculates the current speed difference. The specific calculation method for this current speed difference is as follows: calculate the product of the output shaft speed and the target gear ratio, and calculate the absolute value of the difference between this product and the input shaft speed. This absolute value is used as the current speed difference. This current speed difference characterizes the degree of deviation between the actual current input shaft speed and the theoretical synchronous speed of the target gear. The calculation formulas involved in this step are as follows:

[0048] ;

[0049] in, Indicates the engine speed difference before shifting gears; This indicates the output shaft speed, which is acquired by the output shaft speed sensor and processed by a first-order low-pass filter. Its range is usually from 0 to the maximum output shaft speed corresponding to the vehicle's maximum speed limit. This indicates the gear ratio corresponding to the target gear. This parameter is a fixed mechanical constant, and its specific value is uniquely determined by the physical gear ratio between the driving gear and the driven gear in the corresponding gear within the transmission. Furthermore, it typically satisfies this condition during downshifting. >1; This indicates the input shaft speed.

[0050] In a physical sense, the formula This represents the equivalent theoretical speed of the target gear ring gear, calculated as follows: The dynamic speed difference between the sliding gear sleeve to be engaged and the target gear ring at the current moment was quantified.

[0051] The system synchronously obtains a preset gear shift speed difference based on the acquired oil temperature and target gear. This preset gear shift speed difference is the threshold threshold of the speed synchronization window that allows the sliding sleeve to smoothly engage the target gear ring. It typically increases appropriately as the oil temperature decreases to compensate for the shifting resistance caused by the increased viscosity of the lubricating oil at low temperatures. Based on the speed difference, the system calculates the target clutch torque and controls the clutch to initially engage based on this target torque.

[0052] In step S300, during the process of controlling the clutch engagement to increase the input shaft speed, there is a time lag between the physical actuator receiving the command and actually generating mechanical displacement. The system acquires the intermediate shaft speed in real time and calculates the intermediate shaft speed change rate after filtering. This change rate is used to characterize the angular acceleration of the transmission shaft system. In this embodiment, the intermediate shaft speed change rate, rather than the input shaft speed change rate, is chosen as the core prediction parameter because the intermediate shaft forms a kinematic coupling relationship with the input shaft with a fixed transmission ratio through the main gearbox's constant mesh gear. The intermediate shaft speed change rate can more quickly reflect the acceleration effect of the clutch's current transmitted torque on the input shaft system, while reducing the impact of low-frequency fluctuations introduced by the clutch damping spring and the elastic deformation of the transmission shaft on the prediction results.

[0053] Based on the intermediate shaft speed change rate, the system obtains the estimated change in speed difference through a preset mapping relationship or equivalent calculation formula. This estimated change in speed difference is used to characterize the compensation value by which the current speed difference is expected to continue to decrease during the period from when the control unit issues a clutch disengagement command to when the clutch actually disengages torque transmission. To improve control stability, when the calculated estimated change in speed difference is less than zero, the system corrects it to zero; when the calculated estimated change in speed difference exceeds a preset upper limit, the system performs amplitude limiting processing according to the preset upper limit.

[0054] In step S400, to balance control speed and smoothness, the system calculates the equivalent remaining speed difference based on the current speed difference and the estimated change in speed difference. Specifically, the system subtracts the estimated change in speed difference from the current speed difference to obtain the equivalent remaining speed difference. This equivalent remaining speed difference characterizes the expected speed difference state when the clutch actually disengages if a clutch disengagement command is issued immediately at the current moment.

[0055] The system determines whether the equivalent remaining speed difference is less than or equal to the preset gear engagement speed difference. If the equivalent remaining speed difference is greater than the preset gear engagement speed difference, it indicates that even considering the mechanical delay of the clutch actuator, the input shaft speed has not yet entered the synchronization window for gear engagement at the end of the delay. At this time, the system does not trigger early disengagement but instead enters the closed-loop fine-tuning stage. The system dynamically corrects the clutch engagement depth and engagement rate by comparing the actual rate of change of the intermediate shaft speed with the rate of change of the target speed difference; the current torque transmitted by the clutch can be estimated based on the actual clutch position, the clutch torque-displacement characteristic curve, and relevant correction parameters, and is used as an auxiliary monitoring quantity for closed-loop control.

[0056] In step S500, after closed-loop adjustment, a new dynamic balance is established in the torque transmission state of the clutch. The system obtains the latest intermediate shaft speed change rate and updates the estimated change in speed difference accordingly, then recalculates the equivalent remaining speed difference. When the equivalent remaining speed difference obtained by subtracting the updated estimated change in speed difference from the current speed difference is less than or equal to the preset gear engagement speed difference, it indicates that the system predicts that when the clutch actually disengages, the input shaft speed will enter the synchronization window corresponding to the target gear. The system immediately triggers the disengagement mechanism, controls the clutch to disengage to the preset position, and cuts off the power source of the input shaft.

[0057] In step S600, after confirming that the clutch has completed its disengagement, the transmission system establishes physical isolation. The system continuously monitors the real-time speed difference. When the real-time speed difference enters the allowable synchronization window corresponding to the preset gear shift speed difference, or enters an absolute synchronization tolerance range that is more stringent than the preset gear shift speed difference, the system activates the gear shift actuator and controls the sliding sleeve to move towards the target gear ring to complete the gear engagement.

[0058] See attached document Figure 2 The following section will further elaborate on the mechanical control details of the pre-downshifting process in conjunction with the aforementioned step S100. In this embodiment, the core objective of this stage is to safely and smoothly disconnect the original transmission path, establishing a basic physical isolation environment for subsequent speed synchronization.

[0059] In step S110, while the vehicle is maintaining its original gear, the engine torque is directly applied through the transmission system to the meshing tooth surfaces of the master gear sliding sleeve and the engagement gear ring. At this time, there is transmission friction resistance between the meshing surfaces. If the actuator is directly driven to forcibly disengage, it can easily lead to wear of the shift fork or damage to the mechanical structure. Based on this physical characteristic, the transmission control unit, upon receiving the downshift command, simultaneously triggers the control logic to decouple the power source from the transmission system.

[0060] In practice, the transmission control unit sends a torque reduction request to the engine control unit via the vehicle communication bus, controlling the engine to perform a torque reduction operation, thereby quickly reducing the driving torque on the input side. Along with the torque reduction control, the transmission control unit activates the clutch solenoid valve, controlling the clutch to perform a disengagement operation, thus cutting off the physical power transmission path between the engine flywheel and the transmission input shaft.

[0061] Regarding how the engine control unit responds to the bus torque reduction request and the current drive method of the clutch proportional solenoid valve, those skilled in the art can develop and set it based on the conventional commercial vehicle electronic control protocol and underlying drive circuit. The specific implementation mechanism is a well-known technology in this field and will not be elaborated here.

[0062] In step S120, to avoid triggering subsequent actions before decoupling is complete, the system establishes a state closed-loop determination mechanism. The system incorporates the actual output torque of the engine. and clutch position status As a status monitoring variable, the transmission control unit continuously reads the real-time feedback from the engine control unit according to a preset control cycle. Simultaneously, data is collected in real time via the clutch position sensor. The system determines whether the engine has completed the torque reduction operation and the clutch has completed the disengagement operation.

[0063] As a preferred judgment logic: the system internally calibrates a safe torque threshold and a fully disengaged position threshold. The safe torque threshold is typically set to a small positive value close to 0, specifically derived from the drag torque calibration under the target engine's idle no-load condition. The fully disengaged position threshold is determined by the maximum effective travel endpoint during clutch assembly calibration. Considering the fluctuations in the actual vehicle bus signal, the system acquires... The torque drops to no more than the safe torque threshold and Once the complete separation threshold is reached, an internal timer is started. Only when the above two conditions are continuously met within a preset anti-shake time window (e.g., 20ms to 50ms) will the system confirm at the logical level that the power cut-off decoupling action has been completed.

[0064] In step S130, after confirming the completion of the power cut-off action, the torsional stress between the original engaged gear pairs is released, and the system enters the mechanical disengagement execution stage. The transmission control unit outputs a drive signal to the shift actuator to control the transmission to perform the disengagement operation. During this process, the pneumatic solenoid valve in the actuator operates according to the command, guiding high-pressure gas into the master gear disengagement cylinder, pushing the mechanical shift fork to disengage the sliding gear sleeve in the master gear from the currently engaged gear ring, causing it to move and remain in the master gear neutral position.

[0065] Step S140: Given the inherent response hysteresis in the pneumatic system's air charging / discharging and the movement of mechanical components, the system introduces an actuator stop state. A safety check is performed. The control unit continuously acquires data via a stroke sensor located inside the cylinder. The signal determines whether the aforementioned neutral gear operation has been completed. Specifically, the system is calibrated with a neutral position tolerance zone, when... When the signal indicates that the sliding sleeve has moved into the neutral position tolerance zone, the main gearbox is considered to have completed disengagement. After determining that the main gearbox sliding sleeve has returned to the neutral position, the system initiates coordinated control for the multiple auxiliary gearboxes. Based on the target gear requirement given by the driver, the system determines whether the front and rear auxiliary gearboxes need to switch gears. For auxiliary gearboxes that need to switch, the control unit triggers the corresponding shift cylinder according to the air circuit logic corresponding to the target gear, causing the auxiliary gearbox gear set to switch to the predetermined state required for the target gear. For auxiliary gearboxes that do not need to switch, the system maintains their current gear state. Thus, the main gearbox is in neutral, while the auxiliary gearboxes are in the pre-selected or ready state corresponding to the target gear.

[0066] After all shifting operations of the front and rear auxiliary gearboxes are completed, the internal mechanical structure of the transmission assembly is updated. Since the main gearbox is in neutral and the clutch remains disengaged, the input shaft is in a free deceleration state without power input, causing a drop in input shaft speed. Based on this physical state, the system has the prerequisite to reintroduce external power for active speed regulation, and then proceeds to the subsequent active synchronization process of acquiring speed and controlling clutch engagement.

[0067] Following the acquisition of basic speed information in step S200 above, after confirming that the transmission path is decoupled and that the conditions for active speed regulation are met, the system enters the initial clutch engagement stage. In this embodiment, the core purpose of this stage is to establish a precise feedforward control target, and to guide the clutch to engage appropriately by calculating the desired torque value, thereby avoiding shift shocks and excessively long power interruptions caused by excessive or insufficient driving torque.

[0068] In step S210, the system needs to establish the final target boundary for speed synchronization control. Since the viscous resistance of the lubricating oil inside the transmission is significantly affected by physical temperature, and the structural dimensions of the sliding sleeves and the synchronizer capacity differ for different gears, the system obtains a preset shift speed difference based on the acquired oil temperature and the target gear. As a preferred engineering implementation, the transmission control unit pre-stores a two-dimensional calibration data table with oil temperature and gear as input dimensions.

[0069] The system calculates the preset gear shift speed difference based on real-time sensor data by looking up tables and combining them with a linear interpolation algorithm. This value represents the limit speed difference threshold at which the sliding sleeve can smoothly engage without gear knocking under the current operating conditions. Generally, the lower the oil temperature or the lower the target gear, the larger the tolerance range corresponding to this threshold is set to accommodate greater mechanical resistance.

[0070] Step S220, based on the previously calculated speed difference before shifting... The system calculates the difference between the preset gear shift speed difference and the current speed difference before the shift, as the speed difference deviation. To ensure the rigor of the control logic, the system first determines the current speed difference before calculation. Have the preset conditions been met? When the difference in gear shift speed is greater than the preset difference, the following deviation calculation formula is applied:

[0071] ;

[0072] in, Indicates the deviation in rotational speed; This represents the preset gear shift speed difference. At a physical level, due to the significant speed difference at the initial stage of gear shifting, the calculated speed difference deviation directly quantifies the total speed compensation amount missing between the current input shaft speed and the safe gear shift window.

[0073] Conversely, if the system determines that the current speed difference is less than or equal to the preset gear shifting speed difference, such as in a coasting downshifting situation at a specific vehicle speed, it indicates that the deviation between the current input shaft speed and the theoretical synchronous speed of the target gear has met the allowable gear shifting conditions. At this time, the system no longer performs active acceleration control, nor does it perform predictive disengagement judgment based on delay compensation. Instead, it controls or maintains the clutch in a fully disengaged position and directly enters the subsequent target gear shifting confirmation process, activating closed-loop fine-tuning logic as needed to maintain the synchronization state.

[0074] Step S230: To convert the total speed difference requiring compensation into a dynamic process parameter controllable by the system actuator, the system obtains the target speed difference change rate based on the target gear and the speed difference deviation. Specifically, for different target gears, the vehicle system pre-calibrates the desired synchronization time constant. The formula for calculating the target speed difference change rate is as follows:

[0075] ;

[0076] in, Indicates the rate of change of the target speed difference; This represents the expected synchronization time constant corresponding to the target gear. The calibration of this time constant is based on the balance between vehicle power and driving comfort; in commercial vehicle downshifting conditions, its value is typically calibrated between 0.2s and 0.6s. To ensure the robustness of the system's underlying digital operations and avoid calculation overflow errors caused by the denominator approaching zero in the microprocessor, the control unit... A minimum safety limit protection of 0.05s is forcibly set.

[0077] The formula linearly distributes the rotational speed deviation to be eliminated over a predetermined time, transforming it into the target angular acceleration requirement of the input shaft during this synchronization process.

[0078] Step S240: Based on the dynamic transmission principle of the mechanical system, the rate of increase in the input shaft speed directly depends on the magnitude of the net driving torque applied to the shaft system. The system obtains the target clutch torque based on the rate of change of the target speed difference. The calculation formula for this process is as follows:

[0079] ;

[0080] in, Indicates the target torque of the clutch; The equivalent moment of inertia of the input shaft and its rigidly connected rotating components at its front end is represented by a constant determined by the inherent parameters of the physical structure of the transmission system; coefficient. The unit used to convert the rate of change of rotational speed difference from revolutions per minute per second to the standard unit of angular acceleration, rad / s². This represents the combined resistance torque of the input shaft system under the current operating conditions.

[0081] In this embodiment, the combined drag torque This mainly covers bearing operating friction and gear oil churning resistance. The system obtains this resistance torque by: pre-setting a resistance torque MAP in the transmission control unit, using the current input shaft speed and transmission oil temperature as input parameters, and obtaining the dynamically changing resistance torque compensation value by looking up a table. Through this dynamic formula, the system achieves a feedforward mapping from kinematic target parameters to dynamic physical execution parameters.

[0082] In step S250, after calculating the target clutch torque, the transmission control unit uses this target clutch torque as the control target to control clutch engagement. To translate the numerical target torque into actual control actions on the physical mechanical hardware, those skilled in the art can use a characteristic curve relating the clutch transmitted torque to the release bearing displacement for mapping. The system consults this characteristic curve to convert the target torque into a clutch position control command, thereby driving the clutch actuator to push the shift fork to the designated position.

[0083] In subsequent closed-loop control, the current torque transmitted by the clutch used by the system can be estimated based on the actual displacement fed back by the clutch position sensor, the clutch torque-displacement characteristic curve, the clutch friction characteristic correction coefficient, and the oil temperature or friction plate temperature correction parameters, without relying on an independent torque sensor. This estimated torque is used to assist in judging the actual torque transmission state of the clutch and, together with the intermediate shaft speed change rate, participates in the closed-loop correction of the clutch engagement depth.

[0084] See attached document Figure 3The present invention will be further described in detail below with reference to the specific steps of the foregoing embodiments. Continuing from the initial engagement of the clutch according to the target torque in step S200, the input shaft speed begins to rise under the drive of the clutch friction torque, and the transmission system enters the dynamic speed synchronization process. Due to the solenoid valve response lag and the physical time delay of cylinder charging and discharging in the pneumatic clutch actuator of heavy commercial vehicles, if the disengagement action is triggered solely by closed-loop feedback of the current instantaneous speed, it will cause overshoot of the input shaft speed during the period from sending the command to actual disengagement. Based on this physical causal relationship, this embodiment introduces a feedforward prediction mechanism based on the intermediate shaft acceleration to compensate for the speed error caused by mechanical delay.

[0085] In step S310, the system acquires the intermediate shaft speed in real time and calculates the rate of change of the intermediate shaft speed. The technical reason for choosing the intermediate shaft speed instead of directly using the input shaft speed for derivative calculation is that the intermediate shaft forms a kinematic coupling relationship with the input shaft with a fixed transmission ratio through the constant mesh gear of the main gearbox. Its speed dynamics can more quickly reflect the acceleration effect of the clutch-transmitted torque on the input side shaft system, while reducing the low-frequency speed oscillation interference introduced by the deformation of the torsional damping spring inside the clutch driven plate.

[0086] Considering that the raw digital signals acquired by the sensors are usually mixed with high-frequency electrical noise, directly performing differential operations on them would cause the noise amplitude to be amplified sharply. As a preferred method, when the transmission control unit acquires the intermediate shaft speed data during the clutch engagement process, it first smooths the data using a moving average filtering algorithm, and then calculates the intermediate shaft speed change rate using first-order difference calculation at a fixed time step.

[0087] In step S320, after acquiring the shaft angular acceleration, the system obtains the estimated change in speed difference based on the intermediate shaft speed change rate. The technical purpose of this estimated change in speed difference is to convert the speed difference change caused by the clutch actuator continuing to occur within a future delay time into a compensation value at the current control moment. The system internally calibrates a clutch system delay time constant, which characterizes the physical hysteresis period from the control unit issuing the separation electrical signal to the actual disengagement of the clutch friction plates.

[0088] As one implementation method, the system can obtain the estimated change in speed difference by querying a preset mapping relationship;

[0089] As another implementation, this mapping relationship can also be determined according to the following equivalent calculation formula:

[0090] ;

[0091] in, This indicates the estimated change in the speed difference; This represents the rate of change of the intermediate shaft speed after filtering and differential processing, and its unit is rad / s². This parameter represents the physical transmission ratio of the constant mesh gears in the main gearbox. It is used to equivalently convert the angular acceleration of the intermediate shaft to the input shaft end and is a fixed structural constant. This represents the time delay constant of the clutch system.

[0092] In this embodiment, The value range is typically calibrated to be between 0.1s and 0.3s based on the actual vehicle's air passage diameter and cylinder volume. (Coefficient) This is used to convert the radians per second after integrating the physical angular acceleration into revolutions per minute (RPM) units, consistent with those mentioned earlier.

[0093] To avoid abnormal prediction results caused by sensor noise or transient disturbances, the system performs boundary processing on the estimated change in speed difference. When the rate of change of the intermediate shaft speed is less than or equal to zero, or when the calculated estimated change in speed difference is less than zero, the system corrects the estimated change in speed difference to zero. When the calculated estimated change in speed difference is greater than the preset maximum allowable compensation value, the system limits it to that maximum allowable compensation value. This maximum allowable compensation value can be pre-calibrated based on the target gear, the clutch system delay time constant, and the maximum allowable acceleration of the input shaft.

[0094] Step S330: After completing the preliminary calculation, the system performs a predictive judgment based on the current synchronization state. The system subtracts the estimated change in speed difference from the current speed difference to obtain the equivalent remaining speed difference. This equivalent remaining speed difference represents the speed difference state that the system expects to reach when the clutch actually disengages if the clutch disengagement command is issued immediately at the current moment.

[0095] Subsequently, the system determines whether the equivalent remaining speed difference is less than or equal to the preset gear shifting speed difference. If the equivalent remaining speed difference is less than or equal to the preset gear shifting speed difference, it indicates that, considering the clutch execution delay, the input shaft speed is expected to enter the target gear synchronization window when the clutch is fully disengaged.

[0096] If the equivalent remaining speed difference is greater than the preset gear shift speed difference, it indicates that the conditions for early disengagement are not yet met.

[0097] This logic transforms static threshold judgment into predictive judgment that includes actuator delay time, thereby reducing the probability of input shaft speed overshoot.

[0098] In step S340, if the system determines that the current equivalent remaining speed difference has not yet met the condition of being less than or equal to the preset gear shifting speed difference, its physical meaning is that even with the added compensation for the actuator's action delay, the current speed increase is still insufficient to make it reach the synchronization window at the end of the delay period. Under this condition, in order to prevent the power interruption time from being too long or the input shaft speed from climbing slowly, the system does not trigger the early disengagement action. The transmission control unit instead maintains the current clutch engagement command and guides the control flow into the subsequent closed-loop fine-tuning stage of comparing the actual speed change rate with the target speed change rate, so as to continuously correct the clutch engagement depth.

[0099] The present invention will be further described in detail below with reference to the specific steps of the foregoing embodiments. In this embodiment, following the aforementioned step S340, when the system determines that the current equivalent remaining speed difference has not yet met the preset gear shifting speed difference condition, it indicates that the current actual speed increase of the input shaft has failed to reach the expected synchronous trajectory. Since the friction coefficient of the clutch friction plate will drift nonlinearly with changes in operating temperature, wear degree, and clamping force, relying solely on the feedforward target torque set in step S200 will usually produce steady-state errors. Based on the technical objective of eliminating this physical error, the system enters the closed-loop dynamic fine-tuning stage, and corrects the clutch engagement depth in real time by comparing the deviation between the actual response and the target setting.

[0100] In step S410, the system needs to acquire feedback parameters reflecting the current true synchronization rate. Considering the time discreteness of the digital control system, to ensure the physical time uniformity of the comparison reference, the system synchronously extracts the target speed difference change rate generated in the previous steps within the same control clock cycle. and the rate of change of intermediate shaft speed after filtering at the current sampling time. The system then converts this into the actual equivalent angular acceleration of the input shaft, and calculates the difference between the target rotational speed difference rate and this actual equivalent angular acceleration to obtain the acceleration deviation. The formula corresponding to this calculation step is as follows:

[0101] ;

[0102] in, Indicates acceleration deviation; This refers to the physical transmission ratio of the constantly meshing gears in the main gearbox of the transmission.

[0103] This formula quantifies the dynamic gap between the expected rate of speed increase of the vehicle's powertrain and the actual rate of speed increase.

[0104] Step S420: After obtaining the acceleration deviation, the system needs to convert the kinematic deviation into a dynamic compensation torque. As a preferred implementation, the transmission control unit is equipped with a proportional-integral closed-loop controller. The system uses the acceleration deviation as the input variable of this controller to calculate the clutch torque compensation amount. The specific formula for the continuous-domain theoretical calculation of the clutch torque compensation amount is as follows:

[0105] ;

[0106] in, Indicates the amount of clutch torque compensation; This represents the proportional control gain coefficient; This represents the integral control gain coefficient; This indicates the settling time of the closed-loop control.

[0107] In the actual microprocessor of the transmission control unit, this continuous formula is transformed into a discrete-time difference equation for execution, where the integral term is approximated by the product of the accumulated sum of historical errors and the system sampling period. The proportional term is used to quickly respond to the rate error at the current instant, while the integral term is used to accumulate and eliminate the long-term static friction torque decay error caused by clutch wear.

[0108] The aforementioned gain coefficient and The specific value is not fixed. As an optimal setting in engineering, it is determined by looking up a table based on the current input shaft speed and transmission oil temperature using a two-dimensional MAP stored inside the control unit. The initial calibration data of this two-dimensional MAP comes from the step response test on the transmission bench and is corrected in the actual vehicle calibration with the boundary condition of not generating control overshoot. To ensure the stability of the control system and prevent control command overflow caused by failure to reach the target for a long time, the control unit sets upper and lower limit thresholds to prevent integral saturation for the integral term, constraining it to within 10% of the maximum physical torque that the clutch can transmit.

[0109] In step S430, based on the calculated torque compensation amount, the system dynamically updates the initial feedforward torque setpoint. The system then uses the clutch target torque calculated in step S240. With the clutch torque compensation amount The summation is performed to obtain the corrected final clutch target torque. This corrected torque value represents the actual frictional torque that must be applied under the current physical conditions to force the input shaft speed back to the ideal synchronization trajectory. To prevent sudden changes in torque command from causing mechanical shock to the transmission shaft system, the system further sets a rate-of-change limit on the corrected final clutch target torque, that is, limits the span of the torque gradient per unit time.

[0110] In step S440, the transmission control unit converts the corrected final clutch target torque into a specific electrical signal command, driving the clutch actuator to adjust the position of the mechanical shift fork, thereby fine-tuning the clamping force of the clutch pressure plate. With the change in clamping force, a new dynamic equilibrium is established in the clutch torque transmission state, and the actual angular acceleration of the input shaft changes physically. For the clutch position closed-loop PID control algorithm and the hardware drive for the underlying solenoid valve PWM duty cycle adjustment, those skilled in the art can develop and configure it based on the conventional execution mechanism of commercial vehicle electronic control units.

[0111] In step S450, after completing a single closed-loop position adjustment, the rotational speed change status of the physical transmission shaft system is updated. In the next control clock cycle, the system re-acquires the latest intermediate shaft rotational speed change rate and updates the aforementioned estimated speed difference change accordingly. With the periodic iteration of this closed-loop fine-tuning process, the system repeatedly executes the prediction and judgment logic in step S330. When the updated equivalent remaining speed difference reaches a condition less than or equal to the preset gear shifting speed difference, the system immediately exits the current closed-loop fine-tuning process, triggering the subsequent clutch early disengagement and gear shifting mechanism.

[0112] See attached document Figure 4 In this embodiment, following step S450 in the aforementioned closed-loop fine-tuning process, the physical state of the transmission system is continuously updated as the clutch engagement depth is corrected in real time, and the angular acceleration of the input shaft exhibits a dynamic process of continuous evolution.

[0113] In step S510, the system performs rolling prediction and evaluation of the rotational speed state using the latest sensor data in each digital control cycle. When the system determines that the updated equivalent residual speed difference has decreased and meets the condition of being less than or equal to the preset shifting speed difference, it indicates that the current physical state has entered the expected separation trigger boundary.

[0114] To avoid false logic triggering due to electrical noise or mechanical vibration within a single sampling period, a time-debounce mechanism is introduced as a preferred determination method. The transmission control unit requires that the equivalent remaining speed difference stably satisfy the above inequality condition over multiple consecutive control cycles (e.g., 3 to 5 control cycles) before finally confirming the arrival of the prediction window at the logic level.

[0115] Based on the robust judgments made across these multiple dimensions, the transmission control unit immediately issues a disengagement command to the clutch actuator. This mechanism advances the inherent mechanical delay time of the clutch system into a speed advance, ensuring that the action cycle of the clutch solenoid valve's de-energization and exhaust is matched with the physical time axis for eliminating the remaining speed difference. This effectively reduces the probability of input shaft speed overshoot, which is prone to occur in conventional control.

[0116] In step S520, after the separation command is issued, the system needs to monitor the actual physical separation process. After receiving the electrical signal, the pneumatic valve of the clutch actuator opens the exhaust port, the compressed gas in the separation cylinder begins to be released, and the clutch pressure plate gradually retracts under the restoring force of the diaphragm spring.

[0117] To prevent mechanical gear grinding or abnormal wear caused by engaging a gear while the power is not completely disconnected, the system continuously reads real-time travel data from the clutch position sensor during this period. Only when this real-time travel data reaches a pre-calibrated fully disengaged position threshold, the system performs multi-source cross-verification, combining this with feedback from the engine control unit to check if the actual output torque is close to zero. This verifies, at multiple logic levels, that the engine flywheel and transmission input shaft have returned to a state of no-power coupling isolation.

[0118] In step S530, after confirming complete clutch disengagement, the physical connection of the transmission system's main trunk has been severed. At this point, the system's control line smoothly transitions from clutch state control to the main gearbox mechanical engagement stage. To ensure the integrity of the system's underlying logic, a timeout fallback mechanism is implemented here to address the issues of prior prediction and synchronization effectiveness. If, within the preset timeout threshold after complete clutch disengagement, the actual speed difference exhibits abnormal divergence and fails to approach the safe tolerance range according to the feedforward predicted trajectory (e.g., sensor signal failure due to sudden severe vehicle vibration), the system will abort the current downshifting process and trigger the exception handling mechanism.

[0119] Under normal operating conditions without extreme external disturbances, the input shaft speed is now steadily climbing and approaching the target synchronization point along the predicted trajectory, thanks to the precise physical intervention provided by the previous acceleration feedforward prediction and closed-loop dynamic fine-tuning. Based on this physical isolation and speed approach state, the system control flow then enters the final stage of absolute speed synchronization and mechanical gear engagement.

[0120] See attached document Figure 5 In this embodiment, following the aforementioned predictive clutch disengagement action, after confirming that the clutch is completely physically disengaged, the system enters the final mechanical gear engagement and power recovery phase. The technical objective of this phase is to achieve shock-free mechanical engagement and smoothly restore the vehicle's driving force.

[0121] In step S610, the system continuously monitors the relative motion state of the transmission shaft system to establish an absolute synchronization judgment benchmark. Under ideal feedforward prediction conditions, the input shaft speed is exactly at the expected synchronization point the instant the clutch is fully disengaged. However, considering that the transmission input shaft operates due to its own inertia after the clutch is disengaged, its speed will experience a slight natural drop due to the influence of internal resistance torque. The transmission control unit extracts the current speed difference before the shift in real time to confirm whether the transient speed has indeed and reliably fallen within the preset absolute synchronization tolerance range.

[0122] As a preferred engineering implementation, the absolute synchronization tolerance range is typically defined as a very small positive and negative value range. Its specific boundary is determined based on the target gear position, the chamfer geometry of the gear ring and sliding sleeve, and the mechanical clearance of the synchronizer. To ensure the robustness of the control system, a synchronization waiting timeout monitoring mechanism is implemented.

[0123] If the actual speed difference fails to enter the aforementioned absolute synchronization tolerance range within the preset time threshold after entering this stage, it usually indicates that the target speed has changed abruptly due to severe external operating conditions such as rapid deceleration of the vehicle. At this time, the system will terminate the current pure inertial waiting state and reactivate the aforementioned clutch closed-loop fine-tuning logic to actively increase or decrease the input shaft speed.

[0124] Under normal operating conditions without severe external interference, when the speed difference is detected to enter this range, it physically indicates that the relative angular velocity difference between the two meshing parts has approached zero. To avoid logical misjudgments caused by shaft torsional vibration or sensor signal glitches, the system, based on multi-time-dimensional weighted logic, requires that the speed difference remain within the tolerance range for multiple consecutive control cycles before finally outputting an absolute synchronization confirmation signal at the logical level.

[0125] In step S620, based on the confirmation of the absolute synchronization state, the system performs the physical engagement of the mechanical gears. The transmission control unit outputs a drive duty cycle command to the main working solenoid valve of the pneumatic shift actuator.

[0126] Specifically, high-pressure gas is distributed through the gas path into the corresponding working chamber of the main gearbox shift cylinder, pushing the mechanical shift fork to move the sliding tooth sleeve towards the target gear ring. Considering that physical interference between the tooth ends is prone to occur during gear shifting in actual mechanical transmission systems, the system introduces displacement derivative judgment logic when monitoring the physical stroke of the shift fork. If the system detects that the main working solenoid valve is continuously driven, but the gradient of the displacement feedback signal approaches zero and does not reach the endpoint coordinate within a preset small time period, it determines that mechanical jamming has occurred.

[0127] As a preferred method of handling abnormal situations, the system will control the clutch to perform a slight engagement action, using the weak rotational friction torque transmitted by the input shaft to disturb the gear sleeve angle, thereby assisting it to slide past the dead point of the top tooth.

[0128] During normal dynamic processes without interference, the system collects the physical stroke data of the shift fork in real time through a displacement sensor built into the actuator, and performs a closed-loop comparison with the pre-stored coordinates of the gear engagement endpoint in the controller. When the displacement feedback signal is stable within the allowable mechanical tolerance range of the endpoint coordinate for multiple consecutive sampling cycles, the system confirms that the sliding sleeve and the target gear ring have achieved full-width physical engagement, and then cuts off the cylinder's air charging command to maintain pressure and preserve the current state.

[0129] In step S630, after successfully detecting successful mechanical engagement of the target gear, the physical connection of the transmission system backbone has been re-established, and the system subsequently initiates clutch engagement control. The transmission control unit sends a position follow command to the clutch actuator, controlling the clutch pressure plate to move towards the flywheel.

[0130] To balance smooth engagement with power interruption time, the clutch engagement process typically employs a segmented rate control strategy based on stroke nodes. Before the clutch friction plates reach the semi-engagement point, the system sets a larger rate of position change to quickly eliminate mechanical free travel. After passing the semi-engagement point and beginning to establish frictional torque transmission capability, the system, considering the current accelerator pedal opening and the vehicle's dynamic load, switches to a smaller rate of position change for smooth engagement until the clutch reaches a fully locked, rigid transmission state. For the specific control algorithms of clutch position closed-loop following and segmented rate scheduling, those skilled in the art can adaptively calibrate them based on conventional commercial vehicle control strategies.

[0131] In step S640, as the clutch engagement process progresses, the system synchronously performs coordinated recovery of the vehicle's drive torque. The transmission control unit sends a torque recovery request to the engine control unit via the vehicle communication bus. The system combines the real-time torque estimate corresponding to the current clutch travel with the driver's initial power demand, and gradually releases the previous torque reduction restriction according to a preset torque gradient. The rate of increase in engine output torque and the clutch engagement rate maintain strict synchronization on the time axis, ensuring that the engine speed does not experience transient overspeed during torque transfer, and that the vehicle's drive force smoothly transitions to the expected level under the current operating conditions. At this point, the complete closed-loop downshift speed synchronization and control process is complete.

[0132] To further aid in understanding the technical solution of this invention and to verify its effectiveness in a real physical environment, a detailed description is provided below using a specific application example of a heavy commercial vehicle, along with relevant experimental verification and effect comparison data.

[0133] Specific application example: Heavy-duty commercial vehicle downshifting from 12th to 11th gear

[0134] In this embodiment, a fully loaded heavy-duty tractor is cruising. Encountering a long, gentle slope ahead, the driver presses the accelerator pedal. Based on the current vehicle speed (80 km / h) and load request, the vehicle's underlying system triggers a shift from 12th gear (direct drive, gear ratio...) to... ) downshift to 11th gear (gear ratio) The downshift command.

[0135] Initial state and target calculation: After disengaging 12th gear and completing power decoupling (corresponding to step S100), the transmission output shaft speed... Due to the vehicle's significant inertia, the speed remains stable at 1500 rpm. The system obtains the target equivalent theoretical speed based on the target gear ratio. At this point, the input shaft rotates at rpm due to power cutoff. Maintaining around 1500 rpm, the system calculates the initial speed difference before the shift. rpm.

[0136] Feedforward parameter calibration and initial setup: Based on the current normal operating transmission oil temperature (85℃), the system looks up the preset shift speed difference in a table. rpm, meaning that as long as the actual input shaft speed is within the safe range of 1890 rpm to 1950 rpm, gear shifting can be performed without impact. The system sets the expected synchronization time constant for this downshifting condition. s. According to the formula The calculated rate of change of the target speed difference is approximately rpm / s. Based on this dynamic target, the system calculates the target clutch torque. This drives the clutch to engage, and the input shaft speed begins to increase rapidly.

[0137] Predictive separation control triggering (core logic demonstration): For the pneumatic clutch configured for this commercial vehicle, the system pre-calibrates the clutch system delay time constant. s. As the clutch engages, the input shaft speed continuously increases. Assume that the control time axis reaches... At time s, the current actual input shaft speed Reaching 1750 rpm, the current speed difference is... rpm. At this point, the actual equivalent acceleration of the intermediate shaft extracted by the system through filtering (converted to the input shaft end) is approximately rpm / s. According to the formula The estimated change in the speed difference was calculated within a future delay of 0.15 seconds. rpm. The system calculates the equivalent residual speed difference: .because (Preset shift point speed difference), the system determines that the predicted synchronization point has been reached, and the transmission control unit immediately (at) At time s, the solenoid valve is de-energized and disconnected.

[0138] During the subsequent 0.15-second physical delay, the clutch continued to transmit torque, and the input shaft speed continued to increase by approximately 150 rpm due to inertia. When the time was up... s, the clutch has just completed its physical disengagement, at which point the actual input shaft speed precisely falls on The final actual speed difference was 20 rpm, within the safe window of 30 rpm. The system then seamlessly engaged mechanical gears, eliminating speed overshoot.

[0139] To further verify the actual technical effectiveness of the aforementioned predictive control logic, this embodiment, based on real vehicle downshifting conditions, collected and compared physical motion state data of the feedforward prediction scheme of this invention and the conventional feedback control scheme. (See attached diagram.) Figure 6 , Figure 6 This is a comparison diagram of downshift speed trajectories of conventional feedback control and predictive control according to an embodiment of the present invention.

[0140] In the downshifting condition set in this embodiment, the initial physical starting point of the input shaft speed is 1500 rpm. The target equivalent theoretical speed calculated based on the target gear ratio is set to 1920 rpm, which is shown as a horizontal dotted line in the figure. At the same time, the preset shift speed difference calibrated based on the current internal lubricating oil temperature of the transmission is limited to ±30 rpm, which physically defines the synchronization window that allows for shock-free shifting, i.e., the gray shaded area corresponding to 1890 rpm to 1950 rpm in the figure. As the clutch gradually engages according to the previously estimated target torque, the input shaft receives driving torque and begins to climb towards the target speed with a relatively constant angular acceleration.

[0141] Observe the gray dashed line trajectory in the figure, which represents the conventional feedback control logic without introducing delay prediction compensation. Under this traditional control mechanism, the system mechanically relies solely on real-time closed-loop monitoring of the current actual speed state. When the time axis is extended to approximately 0.39 seconds, the actual speed of the input shaft just reaches 1890 rpm, which is exactly the lower boundary of the synchronization window. Only at this moment does the control unit meet the condition and trigger the clutch disengagement command (as indicated by the white circle on the trajectory).

[0142] However, due to an objective 0.15-second delay in the action of the pneumatic actuator in commercial vehicles during the solenoid valve exhaust and cylinder depressurization process, the clutch friction plates do not completely disengage during this insurmountable physical delay period, and continue to transmit engine drive torque to the input shaft. Driven by this residual driving force, the input shaft speed exceeds the target boundary and continues to climb, eventually surging to a peak of approximately 2040 rpm around 0.54 seconds later. This peak completely penetrates the preset safe synchronization window, constituting a severe speed overshoot of approximately 140 rpm. This control lag not only induces severe mechanical gear engagement and jerking shocks when forcibly shifting gears, but also forces the underlying system to passively spend a significant amount of time waiting for the high speed to naturally drop back to within the window due to internal resistance after power is cut off, severely delaying the recovery rhythm of the vehicle's power.

[0143] In contrast, the solid black line in the figure clearly demonstrates the anti-hysteresis advantage of the predictive control strategy proposed in this invention. At 0.25 seconds into the synchronous acceleration process (as indicated by the black square), although the actual input shaft speed is only 1750 rpm, still some distance from the target synchronization window, the system does not passively wait. The control unit extracts the current shaft angular acceleration in real time and performs feedforward calculations based on the 0.15-second clutch system delay time constant. The system predicts that during the uncontrollable depressurization delay period in the future, the current acceleration will irreversibly cause a speed increase of approximately 150 rpm. Based on the calculated equivalent remaining speed difference (i.e., 20 rpm), which fully meets the criterion of being less than the preset gear shift speed difference (30 rpm), the system breaks free from conventional logic and decisively issues a disengagement command at this advanced moment of 0.25 seconds.

[0144] As pre-planned commands are issued, the lag time of the physical actuator is cleverly transformed into a period of coasting and ramping up the rotational speed. At 0.4 seconds, the instant the clutch completes its mechanical stroke and physically disengages, the ramping up of the input shaft speed abruptly stops, its value precisely locked at 1900 rpm, remaining within the gray safety shift window of 1890 rpm to 1950 rpm. Subsequently, due to the disconnection of the power source, the input shaft speed exhibits a slight and smooth natural drop, and the system seamlessly triggers the mechanical engagement of the master gear sliding sleeve.

[0145] Cross-comparison of the above-mentioned actual operating trajectories confirms that the technical solution of this invention successfully bridges the time gap of the aerodynamic system by utilizing kinematic prediction variables, smoothing out the destructive overshoot of approximately 140 rpm. This mechanism, while avoiding mechanical shock and unnecessary wear on friction components, minimizes the ineffective waiting gap during downshifting, enabling heavy vehicles to achieve both high-standard smoothness and agile response during power transfer in complex road conditions.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An AMT downshift control method, characterized in that, Includes the following steps: Obtain the output shaft speed, input shaft speed, and the speed ratio corresponding to the target gear, and calculate the speed difference before shifting; Based on the obtained oil temperature and the target gear, obtain the preset gear shift speed difference; Control the clutch engagement to increase the input shaft speed; During the process of controlling clutch engagement, the intermediate shaft speed is obtained and the intermediate shaft speed change rate is calculated. Based on the intermediate shaft speed change rate, the estimated change in speed difference is obtained. Subtract the estimated change in speed difference from the current speed difference before the shift to obtain the equivalent remaining speed difference; Determine whether the equivalent remaining speed difference is less than or equal to the preset gear shifting speed difference; If the difference is less than or equal to the target gear, the clutch is disengaged to a preset position, and when the speed difference before shifting meets the preset shifting speed difference condition, the sliding sleeve is moved toward the target gear ring to complete the shifting.

2. The AMT downshift control method according to claim 1, characterized in that, The control of clutch engagement includes: Calculate the difference between the preset gear shift speed difference and the speed difference before the current gear shift, and use it as the speed difference deviation; The target speed difference change rate is obtained based on the target gear and the speed difference deviation. The target torque of the clutch is obtained based on the rate of change of the target speed difference. The clutch engagement is controlled by using the target clutch torque as the control target.

3. The AMT downshift control method according to claim 2, characterized in that, After determining whether the equivalent remaining speed difference is less than or equal to the preset gear shifting speed difference, the method further includes: If the equivalent remaining speed difference is greater than the preset gear shift speed difference, then the difference between the current target speed difference change rate and the actual equivalent angular acceleration is calculated to obtain the acceleration deviation. The actual equivalent angular acceleration is obtained by converting the current rate of change of the intermediate shaft rotation speed to the input shaft. The clutch torque compensation amount is calculated based on the acceleration deviation.

4. The AMT downshift control method according to claim 3, characterized in that, After calculating and obtaining the clutch torque compensation amount based on the acceleration deviation, the method further includes: The target clutch torque is summed with the clutch torque compensation amount to obtain the corrected final target clutch torque; Using the corrected final clutch target torque as the control target, the clutch actuator is driven to fine-tune the clutch engagement depth.

5. The AMT downshift control method according to claim 4, characterized in that, After the drive clutch actuator fine-tunes the clutch engagement depth, the following is also included: In the next control cycle, the latest intermediate shaft speed change rate is reacquired, and the estimated change in speed difference is updated accordingly. The updated equivalent remaining speed difference is obtained by subtracting the updated estimated change in speed difference from the current speed difference before the shift.

6. The AMT downshift control method according to claim 5, characterized in that, After obtaining the updated equivalent remaining speed difference, the method further includes: Determine whether the updated equivalent remaining speed difference is less than or equal to the preset gear shift speed difference; If it is less than or equal to, the separation mechanism is triggered, controlling the clutch to disengage to the preset position; If it is greater than the specified value, then return to the step of obtaining the acceleration deviation and fine-tuning the clutch engagement depth.

7. The AMT downshift control method according to claim 1, characterized in that, After the control clutch disengages to a preset position, when the speed difference before shifting satisfies a preset shifting speed difference condition, the control sliding sleeve moves towards the target gear ring to complete the shifting, including: Continuously calculate the real-time speed difference before the gear shift; Determine whether the real-time speed difference before the gear shift falls within the preset absolute synchronization tolerance range; If the condition is not met, continue to wait and continue to calculate the real-time speed difference before the gear shift; If this condition is met, it is determined that the preset gear shift speed difference condition is met, and the actuator is activated to control the sliding sleeve to engage gears.

8. The AMT downshift control method according to claim 1, characterized in that, Before acquiring the output shaft speed, input shaft speed, and speed ratio corresponding to the target gear, and calculating the speed difference before shifting, the method further includes: Control the engine to perform torque reduction operation and control the clutch to perform disengagement operation; Determine whether the engine has completed the torque reduction operation and the clutch has completed the disengagement operation. If both are completed, control the transmission to perform the disengagement operation. Determine whether the disengagement operation is completed. If completed, control the front and rear auxiliary gearboxes of the transmission to perform the corresponding shifting operation.

9. The AMT downshift control method according to claim 1, characterized in that, After the control sliding sleeve moves toward the target gear ring to complete gear engagement, the following is also included: The system determines in real time whether the gear shift is complete. If the gear shift is not complete, the system continues to apply control actions to control the sliding sleeve to shift gears. If the gear shift is completed, control the clutch to fully engage and send a torque restoration request to the engine; The system determines whether the clutch is fully engaged and whether the engine torque has been restored. Once both are determined to be complete, the downshift control process ends.

10. A vehicle controlled based on the AMT downshift control method according to any one of claims 1-9.

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