Gear shifting control system and method for high-pressure limp working condition of P2 hybrid commercial vehicle

Abstract

The invention discloses a gear shifting control system and method for the high-pressure limp working condition of a P2 hybrid commercial vehicle, and relates to the technical field of hybrid transmission of commercial vehicles. Comprising a whole vehicle controller HCU, a gearbox controller TCU, an engine controller ECU, a motor controller MCU and a clutch execution mechanism which are in network communication connection through a whole vehicle CAN bus. When the TCU detects a high-voltage fault, the limp gear shifting mode is activated, after the ECU unauthorized control authority is obtained, a cooperative control instruction is generated based on the gear shifting type, the torque and the rotating speed of an engine are adjusted through the ECU, the clutch executing mechanism adjusts the clutch connection state and depth, and accurate speed adjustment of an input shaft is achieved. The problems of long gear shifting time and gear shifting failure caused by large rotational inertia of the input shaft when the P2 hybrid commercial vehicle has a high-voltage fault are effectively solved, the gear shifting time consumption is remarkably shortened, the gear shifting success rate and the driving safety are improved, and reliable operation of the vehicle under the high-voltage limp working condition is guaranteed.

Description

Technical Field

[0001] This application belongs to the field of commercial vehicle hybrid transmission technology, and specifically relates to a shift control system and method for P2 hybrid commercial vehicles under high-voltage limp-out conditions. Background Technology

[0002] In the field of hybrid technology for commercial vehicles, the P2 structure hybrid automated mechanical transmission (AMT) is widely used due to its unique transmission design. During normal gear shifts, the input shaft speed is adjusted via a motor. Specifically, the transmission control unit (TCU) sends control commands to the motor control unit (MCU), eliminating the need for the TB brake found in traditional AMT transmissions. This results in significant advantages such as reduced manufacturing costs, smaller transmission size, and lighter weight.

[0003] However, when a P2 hybrid vehicle encounters a high-voltage system failure, such as a motor stage 3 fault or battery failure causing the high-voltage system to malfunction, the motor will lose its speed regulation function. In this case, the vehicle must switch to fuel mode to meet basic driving and gear shifting needs. Because the P2 hybrid transmission omits the TB brake, according to traditional shifting logic, after the clutch disengages, the input shaft can only naturally decelerate to approach the target speed. However, the P2 hybrid transmission's input shaft is connected to a motor rotor, making its rotational inertia much greater than that of a traditional AMT transmission. This directly results in an excessively long natural deceleration time for the input shaft. This excessively long deceleration time not only increases shifting time, severely impacting the driving experience, but may also lead to shifting failures, posing a threat to vehicle safety and reliability.

[0004] Currently, existing technologies lack effective shifting solutions for P2 hybrid commercial vehicles under high-pressure limp-out conditions, failing to adequately address the shifting challenges caused by the large rotational inertia of the input shaft. Therefore, developing a shifting control system and method adapted to the high-pressure limp-out conditions of P2 hybrid commercial vehicles to shorten shifting time and improve shifting success rate has become a pressing technical problem in this field. Summary of the Invention

[0005] The purpose of this application is to provide a shift control system and method for P2 hybrid commercial vehicles under high-voltage limp-out conditions. This addresses the technical problems mentioned in the background art, such as long shift times and shift failures caused by the large input shaft rotational inertia and excessively long natural deceleration time when a P2 hybrid commercial vehicle encounters a high-voltage fault leading to the motor's loss of speed control function.

[0006] To achieve the above objectives, this application adopts the following technical solution: Firstly, a shift control system for high-voltage limp-out conditions in P2 hybrid commercial vehicles is provided, comprising: The vehicle control unit (HCU), transmission control unit (TCU), engine control unit (ECU), motor control unit (MCU), and clutch actuator are connected via a vehicle CAN bus network. The TCU is configured to activate the high-voltage fault limp shift mode when a high-voltage fault signal is detected in the vehicle. Request and obtain unauthorized control permissions for the ECU from the HCU; During gear shifting, the required speed adjustment direction of the input shaft is determined based on the target gear, and a coordinated control command is generated according to the direction. The coordinated control command includes an engine control command sent to the ECU and a clutch position control command sent to the clutch actuator. The ECU is configured to: in response to an overstepping control command from the TCU, perform adjustment of engine torque and speed; The MCU is configured to: in the high-voltage fault limp shift mode, not receive the input shaft speed adjustment command sent by the TCU, only maintain basic communication under the high-voltage fault state, and no longer participate in the input shaft speed adjustment; The clutch actuator is configured to control the engagement and disengagement of the clutch in response to a clutch position control command from the TCU.

[0007] In one possible implementation, the high-voltage fault signal includes a motor level 3 fault signal, a battery fault signal, or a fault signal that causes the vehicle's high-voltage system to be unable to supply power to the motor.

[0008] In one possible implementation, the transmission system of the P2 hybrid commercial vehicle is as follows: the clutch driven plate is connected to one end of the motor rotor, and the other end of the motor rotor is connected to the input shaft of the AMT transmission, forming an integrated assembly.

[0009] Secondly, a shift control method for a control system is provided, comprising the following steps: S1: The TCU detects a fault in the vehicle's high-voltage system and controls the shifting process to enter the high-voltage fault limp mode. S2: When a gear shift is required, the clutch is disengaged and the current gear is removed. The TCU determines whether the current operation is upshifting or downshifting based on the target gear. S3: Based on the judgment result of step S2, the TCU performs the corresponding engine and clutch coordinated speed adjustment operation to adjust the input shaft speed to the synchronous speed range of the target gear. S4: When the input shaft speed reaches the synchronous speed range, control the clutch to quickly disengage and control the gearbox to engage the target gear to complete the gear shift.

[0010] In one possible implementation, in step S3, if it is an upshifting operation, the coordinated speed regulation operation includes: S31a: The TCU controls the clutch to engage to a first preset semi-engaged position, which is configured to enable the clutch to transmit the engine’s maximum braking torque. S32a: During clutch engagement, the TCU controls the ECU to output zero torque from the engine; S33a: When the clutch reaches the first preset semi-engaged position, the TCU controls the ECU to activate engine braking; S34a: The engine braking torque is transmitted to the input shaft through the clutch in a semi-engaged state, accelerating the decrease of the input shaft speed.

[0011] In one possible implementation, after step S34a and before step S4, step S35a is also included: when the input shaft speed enters the target synchronous speed range, the TCU controls the ECU to exit the engine braking mode and maintain the engine speed near the target speed.

[0012] In one possible implementation, in step S3, if it is a downshifting operation, the coordinated speed regulation operation includes: S31b: The TCU controls the clutch to enter a semi-engaged state and dynamically adjusts its engagement depth based on speed regulation requirements; S32b: The TCU controls the ECU to adjust the positive torque output of the engine. When the engine torque increases, the clutch engagement is deepened, and when the engine torque decreases, the clutch engagement is shallowed. S33b: The engine's power torque is transmitted to the input shaft via the clutch, accelerating the increase of the input shaft speed.

[0013] In one possible implementation, after step S33b and before step S4, step S34b is also included: when the input shaft speed enters the target synchronous speed range, the TCU control ECU maintains the engine speed near the target speed.

[0014] In one possible implementation, the operation logic of disengaging the clutch and shifting the gear in step S2 is consistent with the operation logic of shifting the gear under normal non-fault conditions.

[0015] In one possible implementation, in step S4, after the clutch is quickly disengaged, the input shaft is in an unloaded state before the gear shifting operation is performed.

[0016] Compared with the prior art, this application has the following beneficial effects: This application provides a shift control system for P2 hybrid commercial vehicles under high-pressure limp-out conditions. By constructing a multi-controller collaborative control system architecture, it endows the TCU with core functions such as high-pressure fault detection, unauthorized control requests, and collaborative control command generation. Combined with the precise control of the clutch actuator, it breaks through the limitation of relying on motor speed regulation when the traditional P2 hybrid transmission experiences high-pressure faults. Through the coordinated regulation of the engine and clutch, the input shaft speed is adjusted. From the system level, it provides a stable and reliable hardware and control foundation for shifting under high-pressure limp-out conditions, effectively avoiding the shifting loss of control problem caused by motor stall, and improving the system's adaptability and reliability.

[0017] In one possible implementation, a multi-controller collaborative control system architecture is constructed, endowing the TCU with core functions such as high-voltage fault detection, unauthorized control requests, and collaborative control command generation. Combined with the precise control of the clutch actuator, this breaks the limitation of relying on motor speed regulation during high-voltage faults in traditional P2 hybrid transmissions. Input shaft speed regulation is achieved through the coordinated control of the engine and clutch, providing a stable and reliable hardware and control foundation for shifting under high-voltage limp conditions at the system level. This effectively avoids the problem of shifting loss of control caused by motor stall, and improves the system's adaptability and reliability.

[0018] A shift control method for a control system achieves end-to-end control from fault response to shift completion through a logical closed loop of fault detection, operating condition judgment, coordinated speed regulation, and shift execution. This process addresses the core issues of the P2 architecture by implementing differentiated control for upshifting and downshifting through operating condition judgment, resolving the input shaft speed adjustment problem through coordinated speed regulation, and improving the success rate of shift execution through no-load shifting. The overall process is logically clear and highly targeted, effectively shortening shift time, avoiding shift failures, and ensuring normal vehicle operation under high-pressure limp-out conditions.

[0019] In one possible implementation, a precise coordinated speed control strategy is designed for upshifting. By combining a preset semi-clutch position, zero-torque transition, and engine braking, the effective transmission of engine braking torque is ensured while avoiding the power shock caused by full clutch engagement. This significantly accelerates the input shaft deceleration rate and solves the problem of excessively long natural deceleration time of the input shaft during upshifting. Furthermore, the strategy has clear operational steps and preset control parameters, facilitating engineering implementation and further improving shifting efficiency and reliability during upshifting.

[0020] In one possible implementation, a dynamic coordinated speed regulation strategy is designed for downshifting. By dynamically matching the semi-clutch state, torque, and engagement depth, the engine's power torque is ensured to be efficiently and smoothly transmitted to the input shaft, rapidly increasing the input shaft speed and solving the problem of slow input shaft speed increase during downshifting. Simultaneously, the dynamic adjustment method avoids shocks caused by uneven torque transmission, improving the smoothness of the speed regulation process. Furthermore, the flexible control logic can adapt to speed adjustments under different downshifting requirements, enhancing the adaptability and reliability of downshifting. Attached Figure Description

[0021] Figure 1 This application provides a hybrid power route for a shift control system in a P2 hybrid commercial vehicle under high-voltage limp-out conditions. Figure 2 A partial topology diagram of a shift control system for high-voltage limp-out conditions in a P2 hybrid commercial vehicle provided in this application; Figure 3 The control flow diagram provided for this application; Figure 4 This data represents upshifting failures in traditional P2 vehicles following a high-voltage fault. Figure 5 The number of successful gear engagements using the high-voltage fault limp shift control system. Detailed Implementation

[0022] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0023] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly defined. The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0025] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] like Figures 1-5As shown, this application discloses a shift control system for P2 hybrid commercial vehicles under high-pressure limp conditions, including a vehicle controller (HCU), a transmission control unit (TCU), an engine control unit (ECU), a motor control unit (MCU), and a clutch actuator. The HCU, TCU, ECU, and MCU are connected via a vehicle CAN bus network.

[0029] The P2 hybrid commercial vehicle's transmission system adopts an integrated assembly design, with the clutch driven plate fixedly connected to one end of the motor rotor, and the other end of the motor rotor rigidly connected to the input shaft of the AMT transmission.

[0030] The vehicle's CAN bus network integrates the HCU, TCU, ECU, MCU, and clutch actuator into a communication network, with each controller transmitting signals through message exchange.

[0031] During vehicle operation, the TCU collects high-voltage system status signals in real time via the CAN bus. When the aforementioned high-voltage fault signal is detected, the high-voltage fault limp-shift mode is immediately activated. At this time, the TCU stops sending any input shaft speed control related control commands to the MCU; in this mode, the MCU does not receive speed control commands from the TCU, but only sends basic communication messages such as motor fault status feedback to the TCU and HCU via the CAN bus, and no longer participates in input shaft speed regulation.

[0032] Subsequently, the TCU sends an unauthorized control request message to the HCU. After receiving the message and verifying the permissions, the HCU sends a response message to the TCU allowing unauthorized control. The TCU then gains unauthorized control permissions over the ECU.

[0033] When the driver operates the gear shift lever to trigger an upshift demand, such as from 3rd to 4th gear, the TCU determines that the input shaft needs to reduce its speed to match the target gear ratio. It then generates engine control commands and clutch position control commands, which are sent to the ECU and clutch actuator respectively to achieve coordinated speed regulation.

[0034] In this embodiment, by constructing a multi-controller collaborative control system architecture, the TCU is endowed with core functions such as high-voltage fault detection, unauthorized control requests, and collaborative control command generation. Combined with the precise control of the clutch actuator, the limitation of relying on motor speed regulation during high-voltage faults in traditional P2 hybrid transmissions is broken. Input shaft speed regulation is achieved through the collaborative control of the engine and clutch. From the system level, a stable and reliable hardware and control foundation is provided for shifting under high-voltage limp conditions, effectively avoiding shifting loss of control caused by motor stall, and improving the system's adaptability and reliability.

[0035] In one possible implementation, the high-voltage fault signal includes a motor level 3 fault signal, a battery fault signal, or a fault signal that causes the vehicle's high-voltage system to be unable to supply power to the motor.

[0036] Specifically, the TCU has a pre-set high-voltage fault signal identification library, which includes three types of core fault signals: First, the motor controller MCU sends a three-level fault signal for the motor, such as a speed control failure signal caused by overheating of the motor windings or a rotor position sensor failure. After the MCU sends this fault message, it only maintains basic communication such as fault status feedback in high-voltage limp mode and no longer responds to any input shaft speed control commands. Second, the battery management system sends battery fault signals, such as abnormal voltage of individual battery cells or communication interruption of the battery management module causing high voltage output to be cut off. At this time, the MCU cannot realize the speed regulation function due to the interruption of high voltage power supply, and can only feed back the power supply fault status through the CAN bus. Thirdly, the high-voltage system circuit breaker signal sent by the high-voltage distribution box, such as the high-voltage contactor sticking or the signal that the pre-charging failed and could not supply power to the motor, will not be used by the MCU when there is no high-voltage power supply. The MCU will not participate in the input shaft speed regulation and will only report the high-voltage circuit breaker fault.

[0037] When the TCU collects any of the above signals through the CAN bus, it determines that it is a high-voltage fault and immediately activates the high-voltage fault limp shift mode to ensure that the vehicle can trigger the appropriate shift strategy under various high-voltage failure scenarios.

[0038] In this embodiment, the specific types of high-voltage fault signals are clearly defined, covering the core failure scenarios that may occur in the high-voltage system of P2 hybrid commercial vehicles. This avoids the problem of limp mode being falsely activated or missed due to ambiguous fault definitions, ensuring that the shift control system can accurately respond to various high-voltage faults. It provides clear triggering conditions for the effective execution of subsequent shift strategies, thereby improving the system's fault adaptability and control accuracy.

[0039] In one possible implementation, the transmission system of the P2 hybrid commercial vehicle is as follows: the clutch driven plate is connected to one end of the motor rotor, and the other end of the motor rotor is connected to the input shaft of the AMT transmission, forming an integrated assembly.

[0040] Optionally, the P2 hybrid commercial vehicle's transmission system adopts an integrated design: the clutch driven plate is connected to one end of the motor rotor via a spline, and the other end of the motor rotor is rigidly fixed to the input shaft of the AMT transmission via a flange. The three are arranged coaxially to form an integrated assembly. In this structure, the motor rotor and the input shaft are directly linked, so that the rotational inertia of the input shaft includes the inertia of the motor rotor, and its total rotational inertia reaches 3.2 times that of a traditional AMT input shaft.

[0041] In this embodiment, by clarifying the core transmission structure of the P2 hybrid commercial vehicle, the inherent advantages of the P2 architecture are demonstrated, and a structural basis is provided for the design of the subsequent shift control method. It is precisely because of the large rotational inertia of the input shaft caused by this transmission structure that the coordinated speed regulation strategy of the present invention is targeted. This structure is adapted to the control system and method, ensuring the feasibility and rationality of the technical solution, and further enhancing the adaptability of the present invention to the P2 architecture.

[0042] In one possible embodiment, a shift control method for a control system is provided, comprising the following steps: S1: The TCU detects a fault in the vehicle's high-voltage system and controls the shifting process to enter the high-voltage fault limp mode. During the operation of a certain P2 hybrid heavy truck, the TCU detected abnormal voltage of a single battery cell via the CAN bus. If it was a high-voltage fault, it immediately switched to the high-voltage fault limp mode.

[0043] S2: When a gear shift is required, the clutch is disengaged and the current gear is removed. The TCU determines whether the current operation is upshifting or downshifting based on the target gear. When the vehicle speed reaches 10km / h, the driver operates the gear shift lever to trigger the shift demand from 3rd to 4th gear. The TCU controls the clutch actuator to disengage the clutch and simultaneously controls the transmission to disengage the current 3rd gear. By comparing the transmission ratio of the target gear (4th gear) with the current gear (3rd gear), it is determined that the shift is in the upshift condition.

[0044] S3: Based on the judgment result of step S2, the TCU performs the corresponding engine and clutch coordinated speed adjustment operation to adjust the input shaft speed to the synchronous speed range of the target gear. Subsequently, the TCU controls the ECU and the clutch actuator to work together to reduce the input shaft speed from 1450 rpm to 1200 rpm, with a target synchronous speed range of 1180-1220 rpm.

[0045] S4: When the input shaft speed reaches the synchronous speed range, control the clutch to quickly disengage and control the gearbox to engage the target gear to complete the gear shift.

[0046] Once the speed reaches the target range, the TCU controls the clutch to disengage quickly, the input shaft is in an unloaded state, and the gearbox synchronizer smoothly engages 4th gear to complete the shift.

[0047] The entire gear shifting process is significantly shorter compared to the traditional natural deceleration mode.

[0048] Specifically, such as Figure 4 As shown, the gear shift operation is performed at a vehicle speed of 4.3 km / h, shifting from second to fourth gear; the initial input shaft speed is 1700 rpm, and the target speed is 1170 rpm.

[0049] With the clutch disengaged and gear shifted to neutral, the input shaft naturally decelerates. As shown in the diagram, because the input shaft is connected to the motor, it has a large moment of inertia, resulting in a very slow natural deceleration. After 3 seconds, due to the vehicle being in the process of shifting gears and lacking power, the vehicle speed drops to 2.5 km / h, and the target speed of the input shaft drops to 400 rpm, while the input shaft speed at this point is 1300 rpm. The input shaft deceleration is far slower than the vehicle speed deceleration, making it impossible to engage gears.

[0050] like Figure 5 As shown, a gear shift is performed at a vehicle speed of 8.7 km / h, moving from third to fourth gear. The initial input shaft speed is 1448 rpm, and the target speed is 1250 rpm. Immediately after disengaging from gear, the clutch closes to a position capable of transmitting the engine's maximum braking torque, initiating engine braking and accelerating the input shaft speed reduction. After 0.6 seconds, the vehicle speed drops to 10.2 km / h, the input shaft speed decreases to 1220 rpm, and the target speed drops to 1160 rpm. Gear engagement is then successful.

[0051] In this embodiment, the method achieves full-process control from fault response to gear shift completion through a logical closed loop of fault detection, operating condition judgment, coordinated speed regulation, and gear shift execution. This process addresses the core issues of the P2 architecture by implementing differentiated control for upshifting and downshifting through operating condition judgment, resolving the input shaft speed adjustment problem through coordinated speed regulation, and improving the success rate of gear shift execution through no-load gear shifting. The overall process logic is clear and highly targeted, effectively shortening shift time, avoiding shift failures, and ensuring normal vehicle operation under high-pressure limp-out conditions.

[0052] In one possible implementation, in step S3, if it is an upshifting operation, the coordinated speed regulation operation includes: S31a: The TCU controls the clutch to engage to a first preset semi-engaged position, which is configured to enable the clutch to transmit the engine's maximum braking torque.

[0053] The P2 hybrid commercial vehicle is in high-pressure limp mode, triggering an upshift from 2nd to 3rd gear. The TCU first controls the clutch actuator to drive the clutch to engage. Based on the pre-stored correspondence between the engine's maximum braking torque and the clutch engagement depth, the clutch is adjusted to the first preset semi-engaged position, which is just enough to transmit the engine's maximum braking torque without being fully engaged.

[0054] S32a: During clutch engagement, the TCU controls the ECU to output zero torque from the engine.

[0055] During clutch engagement, the TCU sends a 0 torque control command to the ECU, which adjusts the engine fuel injection quantity and ignition advance angle to maintain the engine output torque at 0 Nm.

[0056] S33a: When the clutch reaches the first preset semi-engaged position, the TCU controls the ECU to activate engine braking.

[0057] Once the clutch reaches the preset position, the TCU sends an engine braking activation command to the ECU. The ECU shuts off engine fuel injection and uses engine compression resistance to achieve braking, with a braking torque of 280 Nm.

[0058] S34a: The engine braking torque is transmitted to the input shaft through the clutch in a semi-engaged state, accelerating the decrease of the input shaft speed.

[0059] Through the clutch in a semi-engaged state, the braking torque is transmitted to the input shaft, causing the input shaft speed to drop rapidly from 1500 rpm, which is 2.5 times faster than natural deceleration.

[0060] In this embodiment, a precise coordinated speed regulation strategy is designed for upshifting. By combining a preset semi-clutch position, zero-torque transition, and engine braking, the effective transmission of engine braking torque is ensured while avoiding the power shock caused by full clutch engagement. This significantly accelerates the input shaft deceleration rate and solves the problem of excessively long natural deceleration time of the input shaft during upshifting. Furthermore, the strategy has clear operation steps and preset control parameters, facilitating engineering implementation and further improving shifting efficiency and reliability during upshifting.

[0061] In one possible implementation, after step S34a and before step S4, step S35a is also included: when the input shaft speed enters the target synchronous speed range, the TCU controls the ECU to exit the engine braking mode and maintain the engine speed near the target speed.

[0062] When the input shaft speed drops to 1200 rpm, entering the target synchronization speed range of 1180-1220 rpm, the TCU detects this signal through the speed sensor and immediately sends a command to the ECU to cancel engine braking. The ECU resumes engine fuel injection, adjusts the ignition timing, and stabilizes the engine speed around 1200 rpm, with a fluctuation range of ±5 rpm. This speed is then maintained for 0.1 seconds to ensure a stable match between the input shaft speed and the target gear speed before proceeding with subsequent clutch disengagement and gear engagement.

[0063] In this embodiment, a speed stabilization step is added in the later stage of speed regulation during upshifting. This avoids the problem of the input shaft speed deviating from the target range due to engine speed fluctuations after engine braking is canceled, ensuring the stability of the input shaft speed before gear engagement. This further reduces the difficulty of synchronizer engagement and improves the success rate of gear engagement. At the same time, this step is seamlessly integrated, forming a complete closed loop with the speed regulation strategy described above, making upshifting control more precise and stable.

[0064] In one possible implementation, in step S3, if it is a downshifting operation, the coordinated speed regulation operation includes: S31b: The TCU controls the clutch to enter a semi-engaged state and dynamically adjusts its engagement depth based on speed regulation requirements.

[0065] The P2 hybrid commercial vehicle is in high-pressure limp mode, triggering a downshift from 4th to 3rd gear. The TCU controls the clutch actuator to drive the clutch into a semi-engaged state, with an initial engagement depth of 30%.

[0066] S32b: The TCU controls the ECU to adjust the positive torque output of the engine. When the engine torque increases, the clutch engagement is deepened, and when the engine torque decreases, the clutch engagement is shallowed. The TCU then sends a speed control command to the ECU, requesting the engine to output positive torque. The ECU adjusts the fuel injection quantity to gradually increase the engine torque from 0 Nm to 180 Nm. During this process, the TCU receives the torque signal fed back by the ECU in real time through the CAN bus. When the torque rises to 120 Nm, the clutch engagement depth is increased to 40%; when the torque rises to 180 Nm, the engagement depth is increased to 50%.

[0067] S33b: The engine's power torque is transmitted to the input shaft via the clutch, accelerating the increase of the input shaft speed.

[0068] Through dynamic engagement adjustment of the clutch, the engine's 180Nm power torque is fully transmitted to the input shaft, causing the input shaft speed to quickly increase from 950rpm to 1300rpm, with a target synchronization speed range of 1280-1320rpm and an acceleration time of 0.5s.

[0069] In this embodiment, a dynamic coordinated speed regulation strategy is designed for downshifting. By dynamically matching the semi-clutch state, torque, and engagement depth, the engine's power torque is ensured to be efficiently and smoothly transmitted to the input shaft, rapidly increasing the input shaft speed and solving the problem of slow input shaft speed increase during downshifting. Simultaneously, the dynamic adjustment method avoids shocks caused by uneven torque transmission, improving the smoothness of the speed regulation process. Furthermore, the flexible control logic can adapt to speed adjustments under different downshifting requirements, enhancing the adaptability and reliability of downshifting.

[0070] In one possible implementation, after step S33b and before step S4, step S34b is also included: when the input shaft speed enters the target synchronous speed range, the TCU control ECU maintains the engine speed near the target speed.

[0071] Optionally, when the input shaft speed rises to 1300 rpm and enters the target synchronous speed range of 1280-1320 rpm, the TCU controls the ECU to adjust the engine fuel injection quantity and ignition advance angle to stabilize the engine speed at around 1300 rpm, with speed fluctuations controlled within ±3 rpm. After stabilizing for 0.08 seconds, the clutch disengagement and gear shifting operations are then performed.

[0072] In this embodiment, a speed stabilization step is added in the later stage of speed regulation during downshifting to ensure that the input shaft speed remains stable before gear engagement. This avoids speed fluctuations after engine torque adjustment, reduces the speed difference when the synchronizer engages, and further improves the success rate of downshifting. Simultaneously, this step forms a complete closed loop with the downshifting speed regulation strategy, making the downshifting control process more complete and improving both speed regulation accuracy and shift smoothness.

[0073] In one possible implementation, the operation logic of disengaging the clutch and shifting the gear in step S2 is consistent with the operation logic of shifting the gear under normal non-fault conditions.

[0074] Optionally, when the P2 hybrid commercial vehicle is in neutral under normal operating conditions, the TCU's control logic is as follows: receive a shift request signal, send a clutch disengagement command, send a gear disengagement command, and provide feedback on the disengagement completion signal.

[0075] When the vehicle is in high-pressure limp mode and a shifting requirement is triggered, the clutch disengagement and gear removal operations executed by the TCU follow the control logic of the normal operating conditions. The speed parameters of clutch disengagement and the control timing of synchronizer disengagement are kept consistent. The only difference is the speed adjustment stage after gear removal.

[0076] In this embodiment, by clearly defining the consistency of the disengagement operation under high-voltage limp conditions with that under normal conditions, no additional design of the disengagement control logic is required, reducing the development complexity and cost of the control system. Simultaneously, the consistent disengagement operation ensures that the driver's experience under fault conditions is consistent with that under normal conditions, avoiding driving discomfort caused by changes in operating logic, and improving driving safety and comfort. In one possible implementation, in step S4, after the clutch is quickly disengaged, the input shaft is in an unloaded state before the gear shifting operation is performed.

[0077] Optionally, during gear shifting in the high-pressure limp-out mode of the P2 hybrid commercial vehicle, once the input shaft speed reaches the target synchronous speed range, the TCU sends a rapid disengagement command to the clutch actuator. The clutch quickly disengages from the current semi-engaged position within 0.05 seconds. At this time, the input shaft is no longer subjected to the engine torque transmitted by the clutch and is in a state of free rotation without load. Subsequently, the TCU controls the transmission synchronizer to engage the target gear. The synchronizer engagement resistance is reduced by 60% compared to the load state, ensuring smooth gear shifting.

[0078] In this embodiment, by controlling the clutch to quickly disengage and placing the input shaft in an unloaded state, the resistance during synchronizer engagement is significantly reduced, avoiding synchronizer wear or engagement failure caused by input shaft load. This further improves the success rate of gear engagement and the smoothness of gear shifting. Simultaneously, the rapid disengagement control method shortens the clutch disengagement time, indirectly reducing the overall gear shifting time, making the gear shifting process more efficient, and ensuring the continuity of power and driving stability of the vehicle under high-pressure limp-out conditions.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions for some or all of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A shift control system for high-voltage limp-out conditions in P2 hybrid commercial vehicles, characterized in that, include: The vehicle control unit (HCU), transmission control unit (TCU), engine control unit (ECU), motor control unit (MCU), and clutch actuator are connected via a vehicle CAN bus network. The TCU is configured to activate the high-voltage fault limp shift mode when a high-voltage fault signal is detected in the vehicle. Request and obtain unauthorized control permissions for the ECU from the HCU; During gear shifting, the required speed adjustment direction of the input shaft is determined based on the target gear, and a coordinated control command is generated according to the direction. The coordinated control command includes an engine control command sent to the ECU and a clutch position control command sent to the clutch actuator. The ECU is configured to: in response to an overstepping control command from the TCU, perform adjustment of engine torque and speed; The MCU is configured to: in the high-voltage fault limp shift mode, not receive the input shaft speed adjustment command sent by the TCU, only maintain basic communication under the high-voltage fault state, and no longer participate in the input shaft speed adjustment; The clutch actuator is configured to control the engagement and disengagement of the clutch in response to a clutch position control command from the TCU.

2. The shift control system according to claim 1, characterized in that, The high-voltage fault signals include motor level 3 fault signals, battery fault signals, or fault signals that prevent the vehicle's high-voltage system from supplying power to the motor.

3. The shift control system according to claim 1, characterized in that, The transmission system of the P2 hybrid commercial vehicle is as follows: the clutch driven plate is connected to one end of the motor rotor, and the other end of the motor rotor is connected to the input shaft of the AMT transmission, forming an integrated assembly.

4. A shift control method based on the control system according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1: The TCU detects a fault in the vehicle's high-voltage system and controls the shifting process to enter the high-voltage fault limp mode. S2: When a gear shift is required, the clutch is disengaged and the current gear is removed. The TCU determines whether the current operation is upshifting or downshifting based on the target gear. S3: Based on the judgment result of step S2, the TCU performs the corresponding engine and clutch coordinated speed adjustment operation to adjust the input shaft speed to the synchronous speed range of the target gear. S4: When the input shaft speed reaches the synchronous speed range, control the clutch to quickly disengage and control the gearbox to engage the target gear to complete the gear shift.

5. The shift control method according to claim 4, characterized in that, In step S3, if it is an upshifting operation, the coordinated speed regulation operation includes: S31a: The TCU controls the clutch to engage to a first preset semi-engaged position, which is configured to enable the clutch to transmit the engine’s maximum braking torque. S32a: During clutch engagement, the TCU controls the ECU to output zero torque from the engine; S33a: When the clutch reaches the first preset semi-engaged position, the TCU controls the ECU to activate engine braking; S34a: The engine braking torque is transmitted to the input shaft through the clutch in a semi-engaged state, accelerating the decrease of the input shaft speed.

6. The shift control method according to claim 5, characterized in that, After step S34a and before step S4, step S35a is also included: when the input shaft speed enters the target synchronous speed range, the TCU controls the ECU to exit the engine braking mode and maintain the engine speed near the target speed.

7. The shift control method according to claim 4, characterized in that, In step S3, if it is a downshifting operation, the coordinated speed regulation operation includes: S31b: The TCU controls the clutch to enter a semi-engaged state and dynamically adjusts its engagement depth based on speed regulation requirements; S32b: The TCU controls the ECU to adjust the positive torque output of the engine. When the engine torque increases, the clutch engagement is deepened, and when the engine torque decreases, the clutch engagement is shallowed. S33b: The engine's power torque is transmitted to the input shaft via the clutch, accelerating the increase of the input shaft speed.

8. The shift control method according to claim 7, characterized in that, After step S33b and before step S4, step S34b is also included: when the input shaft speed enters the target synchronous speed range, the TCU control ECU maintains the engine speed near the target speed.

9. The shift control method according to claim 4, characterized in that, In step S2, the operation logic for disengaging the clutch and shifting the gear is the same as the operation logic for shifting the gear under normal, non-faulty operating conditions.

10. The shift control method according to claim 4, characterized in that, In step S4, after the clutch is quickly disengaged, the input shaft is in an unloaded state before the gear shifting operation is performed.

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