A new energy vehicle steep slope braking control method and device

Abstract

The application belongs to the technical field of vehicle control, and discloses a new energy vehicle steep slope braking control method and device, the method comprising: in response to a steep slope braking instruction, obtaining a vehicle speed when a brake pedal is released to obtain a downhill stable vehicle speed; obtaining a slope signal based on a slope sensor and obtaining a load signal based on a load sensor; performing calculation based on the slope signal and the load signal to obtain an original required braking torque; performing calculation according to a current output braking torque of a motor and the original required braking torque to obtain a final required braking torque; in response to a pedal start signal, adjusting the downhill stable vehicle speed according to the final required braking torque to obtain a current downhill vehicle speed. The application can formulate the control of steep slope braking for steep slope working conditions, and guarantee driving safety.

Description

Technical Field

[0001] This application relates to the field of vehicle control technology, and in particular to a method and device for controlling steep slope braking of new energy vehicles. Background Technology

[0002] In the case of new energy commercial vehicles descending steep slopes, the existing conventional operating method is for the driver to activate the auxiliary braking function and simultaneously depress the brake pedal, so that the vehicle speed can be controlled by the coordinated action of auxiliary braking and mechanical braking.

[0003] However, this operating method has significant drawbacks. Relying solely on auxiliary braking often results in insufficient braking force, causing the vehicle to continuously accelerate downhill. Relying solely on the brake pedal for mechanical braking leads to excessively rapid brake wear, and on continuous inclines, the high temperatures generated by friction can easily cause brake fade, resulting in reduced braking performance or even brake failure. Therefore, the driver must simultaneously adjust the brake pedal opening while activating auxiliary braking to ensure the two braking forces work in tandem for safe descent. This highly driver-dependent operating method involves a heavy workload and a poor driving experience, easily leading to fatigue during prolonged driving and posing safety hazards.

[0004] Therefore, how to safely and efficiently control the braking of new energy vehicles on steep slopes has become an urgent problem to be solved. Summary of the Invention

[0005] This application provides a method and device for controlling steep slope braking in new energy vehicles. After a steep slope braking command is triggered, the vehicle speed when the brake pedal is released is recorded as the stable downhill speed. The initial required braking torque is calculated based on signals collected by a slope sensor and a load sensor, and then combined with the current output braking torque of the motor to obtain the final required braking torque. When the driver generates a pedal activation signal, the stable downhill speed is adjusted based on this final required braking torque to obtain the current downhill speed. The driver does not need to operate the brake pedal for extended periods, reducing operational burden and alleviating driving fatigue. By matching the required braking force with slope and load signals, the braking capacity of the motor is prioritized, reducing the operating frequency and wear of the mechanical brakes and avoiding brake fade caused by continuous downhill driving. Furthermore, the driver can flexibly adjust the downhill speed when pressing the pedal, achieving coordination between braking control and driving intention, ensuring smooth driving; and it also facilitates the recovery of braking energy, improving overall vehicle energy efficiency.

[0006] In a first aspect, embodiments of this application provide a method for controlling steep slope braking of a new energy vehicle, the method comprising: In response to a steep slope braking command, the vehicle speed when the brake pedal is released is obtained, and the stable downhill speed is then calculated. Slope signals are acquired based on slope sensors, and load signals are acquired based on load sensors. The original required braking torque is obtained by calculating based on the slope signal and load signal; The final required braking torque is calculated based on the current output braking torque of the motor and the original required braking torque. In response to the pedal start signal, the downhill stable speed is adjusted according to the final required braking torque to obtain the current downhill speed.

[0007] Furthermore, based on the slope signal and load signal, the original required braking torque is calculated, including: The current downward force of the vehicle is calculated based on the slope signal and load signal; The total braking force is calculated based on rolling resistance and sliding force. The wheel-end braking torque is calculated based on the tire rolling radius and total braking force. The original required braking torque is calculated based on the total transmission ratio, transmission efficiency, and wheel-end braking torque.

[0008] Furthermore, it also includes: The braking torque gap is calculated based on the current output braking torque of the motor and the original required braking torque. If the braking torque gap is less than or equal to zero, the mechanical brake will not be output; If the braking torque shortfall is greater than zero, mechanical braking will compensate for the braking torque shortfall.

[0009] Furthermore, it also includes: The required mechanical braking torque at the wheel end is calculated based on the total transmission ratio, transmission efficiency, and braking torque gap. The brake air pressure is calculated based on the linear proportionality coefficient of air pressure-torque and the torque required for mechanical braking at the wheel end.

[0010] Furthermore, it also includes: The speed deviation is calculated based on the vehicle's current speed and the stable downhill speed. The corrected torque increment is calculated based on the proportional, integral, derivative, and speed deviation of the vehicle speed PID controller. The final required braking torque is calculated based on the original required braking torque and the corrected torque increment.

[0011] Furthermore, the pedal activation signal includes the accelerator pedal activation signal; In response to the pedal start signal, the downhill stable speed is adjusted according to the final required braking torque to obtain the current downhill speed, including: In response to the accelerator pedal activation signal, a positive torque is requested; If it is determined that the negative torque has not triggered the braking safety threshold, the vehicle speed is adjusted to the current downhill speed according to the PID control. The braking safety threshold is 90% of the sum of the vehicle's current maximum mechanical braking force and the motor's current output braking torque.

[0012] Furthermore, the pedal activation signal includes the brake pedal activation signal; In response to the pedal start signal, the downhill stable speed is adjusted according to the final required braking torque to obtain the current downhill speed, including: In response to the brake pedal activation signal, a negative torque is requested; If mechanical braking is not applied, the negative torque responding to mechanical braking is superimposed on the negative torque of electric braking to obtain the current downhill speed; If mechanical braking has been applied, when the negative torque value of mechanical braking is less than or equal to the negative torque value requested by the brake pedal opening, the brake pedal activation signal is responded to, and the current downhill speed is obtained.

[0013] Furthermore, it also includes: If the drive motor speed is greater than the first safe speed threshold, the current vehicle operating condition is determined to be a motor pre-overspeed state, and the instrument panel pop-up displays the first warning message; If the drive motor speed exceeds the second safe speed threshold, the current vehicle operating condition is determined to be an overspeed state of the motor. Emergency braking of the vehicle is performed according to the maximum mechanical braking value, and the instrument panel pop-up displays the second warning information.

[0014] Secondly, embodiments of this application provide a steep slope braking control device for new energy vehicles, the device comprising: The switch module is used to respond to the steep slope braking command, obtain the vehicle speed when the brake pedal is released, and obtain the stable downhill vehicle speed; The sensing module is used to acquire slope signals based on the slope sensor and load signals based on the load sensor. The first calculation module is used to calculate the original required braking torque based on the slope signal and load signal; The second calculation module is used to calculate the final required braking torque based on the current output braking torque of the motor and the original required braking torque. The adjustment module is used to respond to the pedal start signal and adjust the downhill stable speed according to the final required braking torque to obtain the current downhill speed.

[0015] Furthermore, the first calculation module is specifically used to: calculate the current downward force of the vehicle based on the slope signal and the load signal; calculate the total braking force based on the rolling resistance and the downward force; calculate the wheel-end braking torque based on the tire rolling radius and the total braking force; and calculate the original required braking torque based on the total transmission ratio, transmission efficiency, and wheel-end braking torque.

[0016] In summary, compared with the prior art, the beneficial effects of the technical solution provided in this application include at least the following: This application provides a method for controlling steep slope braking in new energy vehicles. After a steep slope braking command is triggered, the vehicle speed when the brake pedal is released is recorded as the stable downhill speed. The initial required braking torque is calculated based on signals collected by a slope sensor and a load sensor, and then combined with the current output braking torque of the motor to obtain the final required braking torque. When the driver generates a pedal activation signal, the stable downhill speed is adjusted based on this final required braking torque to obtain the current downhill speed. The driver does not need to operate the brake pedal for extended periods, reducing operational burden and alleviating driving fatigue. By matching the required braking force with slope and load signals, the braking capacity of the motor is prioritized, reducing the operating frequency and wear of the mechanical brakes and avoiding brake fade caused by continuous downhill driving. Furthermore, the driver can flexibly adjust the downhill speed when pressing the pedal, achieving coordination between braking control and driving intention, ensuring smooth driving; and it also helps recover braking energy, improving overall vehicle energy efficiency. Attached Figure Description

[0017] Figure 1 A flowchart of a steep slope braking control method for a new energy vehicle is provided as an exemplary embodiment of this application.

[0018] Figure 2 This is a structural diagram of a steep slope braking control device for a new energy vehicle, provided as an exemplary embodiment of this application. Detailed Implementation

[0019] The technical solutions in 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.

[0020] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0021] Before describing the various embodiments of this application, we will first further explain the existing vehicle braking strategies and the optimization methods implemented in this application.

[0022] Currently, the braking systems of new energy commercial vehicles are divided into electric braking and mechanical braking. Electric braking typically includes regenerative braking (activated by pressing the brake pedal) and auxiliary regenerative braking (activated when there is no accelerator or brake pedal). These two functions calculate the negative torque of the motor independently and cannot be superimposed, thus failing to fully utilize the electric braking capacity. Electric braking provides deceleration by controlling the negative torque of the vehicle's drive motor to achieve braking. Simultaneously, this type of braking can generate reverse current by reversing the motor's magnetic field lines, charging the power battery and improving the vehicle's range. However, when the power battery charge exceeds a set threshold, electric braking typically cannot engage to protect the battery, resulting in an unreasonable braking force connection logic and potential safety hazards during steep downhill driving. Mechanical braking in new energy commercial vehicles is usually pneumatic braking, which uses compressed air to create friction in an air chamber to achieve vehicle deceleration and braking.

[0023] Based on the current braking method, the operating conditions of electric braking need to be readjusted. By resetting the entry conditions for regenerative braking and auxiliary regenerative braking, the negative torque requested by the two forms of braking is changed from independent calculation to superimposed calculation. This allows the vehicle to request a larger negative torque from the motor when descending steep slopes, improving vehicle safety and providing a larger negative current to increase the amount of recharge. In this operating mode, when the negative torque requested by electric braking reaches the maximum value of the motor, and the vehicle deceleration still cannot maintain the current stable speed, mechanical braking is requested to intervene, further increasing the vehicle deceleration. Additionally, in cases where the power battery charge is higher than a set threshold and mechanical braking cannot operate, mechanical braking acts as the main braking actuator to provide the vehicle's braking torque.

[0024] Please see Figure 1 This application provides a method for controlling steep slope braking of new energy vehicles, which specifically includes the following steps: Step S1: In response to the steep slope braking command, obtain the vehicle speed when the brake pedal is released, and obtain the stable downhill vehicle speed.

[0025] In one feasible implementation, in the vehicle's cab, when the driver turns on a switch while descending a steep slope, the vehicle enters a steep slope braking pre-start state, triggering calculation conditions; using the brake pedal as an enable signal, when the driver releases the brake pedal, the vehicle speed at that moment is recorded as the downhill stable speed.

[0026] The system includes a steep slope braking switch button, which requires no additional operation initially, aligns with driving intuition, and simplifies the preparation process for descending a slope. In subsequent control, braking intervention is based on the vehicle's stable downhill speed, effectively suppressing the tendency for the speed to continuously increase during descent, helping to maintain a uniform speed, reducing the driver's workload from frequent active braking, and alleviating the strain on the braking system from prolonged operation.

[0027] Step S2: Obtain slope signal based on slope sensor and load signal based on load sensor.

[0028] The system acquires slope and load signals via slope and load sensors respectively, directly obtaining the two key physical quantities that determine the inertial force during downhill driving: the current road slope and the vehicle's load. Introducing the slope signal allows the system to distinguish between gentle and steep slopes, while the load signal identifies empty and heavily loaded states. The combination of these two signals provides an accurate basis for dynamically calculating the appropriate braking force needed to maintain a stable downhill speed, eliminating reliance on a single preset value. Furthermore, regardless of whether facing continuously changing long slopes or varying load weights, braking intervention automatically matches the actual resistance requirements, avoiding excessive or insufficient braking force and maintaining a stable speed. The driver no longer needs to manually and repeatedly adjust the brake pedal based on changes in slope and load, resulting in a smoother downhill experience and reducing the burden on the braking system from prolonged operation.

[0029] Step S3: Calculate the original required braking torque based on the slope signal and load signal.

[0030] In some embodiments, the original required braking torque is calculated based on the slope signal and the load signal, including: The current downward force of the vehicle is calculated based on the slope signal and load signal; The total braking force is calculated based on rolling resistance and sliding force. The wheel-end braking torque is calculated based on the tire rolling radius and total braking force. The original required braking torque is calculated based on the total transmission ratio, transmission efficiency, and wheel-end braking torque.

[0031] In one feasible implementation, the slope signal is based on the slope signal transmitted by the slope sensor and the load sensor. and load signal Calculate the component of gravity that propels the vehicle forward, i.e., the force that pulls it down. Based on the value of the gravitational force component, the corresponding electric braking negative torque is requested. If it exceeds the upper limit of the electric braking negative torque, mechanical braking is requested to be superimposed. The braking torque of the mechanical braking is calculated by comparing the deviation between the vehicle speed and the deceleration.

[0032] The original required braking torque can be calculated using the following formula: ; in, For the original required braking torque, This refers to the wheel-end braking torque. The total transmission ratio is... For transmission efficiency, For total braking force, The tire's rolling radius, For downward force, For rolling resistance, This represents the total weight of the vehicle. The slope angle is downhill. The rolling resistance coefficient, For the total mass of the vehicle. This is the acceleration due to gravity.

[0033] The system performs multi-step calculations based on gradient and load signals to arrive at the final executable initial braking torque requirement. This calculation incorporates actual physical quantities such as gradient angle, total vehicle weight, and transmission losses, ensuring the initial braking torque automatically matches and offsets the actual braking demand required for downhill driving, avoiding underestimation or overestimation of braking force. When the upper limit of electric braking torque is insufficient, the system automatically applies mechanical braking and dynamically corrects the mechanical braking torque by comparing the deviation between vehicle speed and deceleration, ensuring accurate and reliable total braking force.

[0034] Step S4: Calculate the final required braking torque based on the current output braking torque of the motor and the original required braking torque.

[0035] In some embodiments, it also includes: The braking torque gap is calculated based on the current output braking torque of the motor and the original required braking torque. If the braking torque gap is less than or equal to zero, the mechanical brake will not be output; If the braking torque shortfall is greater than zero, mechanical braking will compensate for the braking torque shortfall.

[0036] In one feasible implementation, by comparing the actual output capacity of the motor with the original required braking torque, it can be determined whether mechanical braking intervention is necessary. ; like ≤0, mechanical brake does not output; if >0, mechanical braking intervenes to compensate for the torque shortfall.

[0037] in, For braking torque gap, This is the braking torque that the motor can currently output. This value is obtained by the VCU through calculation of the combined capabilities of the battery, rear axle, motor, and other systems.

[0038] In some embodiments, it also includes: The required mechanical braking torque at the wheel end is calculated based on the total transmission ratio, transmission efficiency, and braking torque gap. The brake air pressure is calculated based on the linear proportionality coefficient of air pressure-torque and the torque required for mechanical braking at the wheel end.

[0039] In one feasible implementation, the braking torque gap is converted into the required mechanical braking torque at the wheel end according to the following formula: ; in, The torque required for mechanical braking at the wheel ends.

[0040] Finally, it is converted into the required mechanical braking air pressure value: ; in, For braking air pressure, It is the air pressure-torque linear proportionality coefficient, obtained through vehicle calibration.

[0041] The above control calculation is for steady-state steep slope torque control. When there is a deviation between the current vehicle speed and the set downhill stable vehicle speed, the torque demand needs to be dynamically corrected through PID control to maintain vehicle stability.

[0042] The system calculates a braking torque gap by measuring the difference between the motor's current output braking torque and the original required braking torque, and uses this gap to determine the timing of mechanical braking intervention. When the gap is less than or equal to zero, braking is provided solely by the motor, fully recovering downhill potential energy. When the gap is greater than zero, mechanical braking is initiated. The required wheel-end mechanical braking torque is calculated based on the gap size, the overall transmission ratio, and transmission efficiency. This torque is then converted into precise braking air pressure using a linear proportional coefficient between air pressure and torque, ensuring that the mechanical braking force precisely compensates for the insufficient electric braking. Therefore, the final required braking torque always matches the braking force needed to maintain a stable downhill speed, resulting in more efficient energy utilization and a stable speed. Combined with PID dynamic correction of speed deviation to adjust torque demand in real time, speed fluctuations can be further suppressed, ensuring smooth braking intervention throughout the downhill process and reducing the driver's intervention burden.

[0043] In some embodiments, it also includes: The speed deviation is calculated based on the vehicle's current speed and the stable downhill speed. The corrected torque increment is calculated based on the proportional, integral, derivative, and speed deviation of the vehicle speed PID controller. The final required braking torque is calculated based on the original required braking torque and the corrected torque increment.

[0044] In one feasible implementation, ; in, For vehicle speed deviation, The vehicle's current speed. To set a stable downhill speed.

[0045] ; in, To correct the torque increment, , , These are the proportional, integral, and derivative coefficients of the PID controller for vehicle speed.

[0046] After superimposing PID correction, the final required braking torque can be calculated: ; in, To meet the final braking torque requirement.

[0047] The corrected torque increment is directly superimposed on the original required braking torque to obtain the final required braking torque. The proportional calculation enables a rapid response to instantaneous fluctuations in vehicle speed, the integral calculation continuously accumulates historical deviations to eliminate residual errors, and the differential calculation captures the trend of vehicle speed changes, allowing the entire braking intervention to actively and accurately follow actual vehicle speed changes.

[0048] Step S5: In response to the pedal start signal, adjust the downhill stable speed according to the final required braking torque to obtain the current downhill speed.

[0049] In some embodiments, the pedal activation signal includes an accelerator pedal activation signal; In response to the pedal start signal, the downhill stable speed is adjusted according to the final required braking torque to obtain the current downhill speed, including: In response to the accelerator pedal activation signal, a positive torque is requested; If it is determined that the negative torque has not triggered the braking safety threshold, the vehicle speed is adjusted to the current downhill speed according to the PID control. The braking safety threshold is 90% of the sum of the vehicle's current maximum mechanical braking force and the motor's current output braking torque.

[0050] In some embodiments, the pedal activation signal includes a brake pedal activation signal; In response to the pedal start signal, the downhill stable speed is adjusted according to the final required braking torque to obtain the current downhill speed, including: In response to the brake pedal activation signal, a negative torque is requested; If mechanical braking is not applied, the negative torque responding to mechanical braking is superimposed on the negative torque of electric braking to obtain the current downhill speed; If mechanical braking has been applied, when the negative torque value of mechanical braking is less than or equal to the negative torque value requested by the brake pedal opening, the brake pedal activation signal is responded to, and the current downhill speed is obtained.

[0051] The system utilizes the accelerator and brake pedals as signal sources for the driver to actively adjust the vehicle speed, making steep slope braking no longer a single, fixed speed process. When the accelerator pedal is pressed to request positive torque, the system uses PID control to smoothly adjust the vehicle speed to the new current downhill speed, provided the required negative torque does not exceed 90% of the sum of the vehicle's current maximum mechanical braking force and the motor's current output braking torque. This preserves sufficient braking reserve to prevent unexpected situations. When the brake pedal is pressed to request additional negative torque, if mechanical braking has not been triggered previously, mechanical braking is prioritized and superimposed on the electric braking. If mechanical braking is already engaged, further response is only provided when the requested brake pedal value exceeds the current mechanical braking force, avoiding sudden changes in braking force. Therefore, the driver can flexibly adjust the desired speed at any time during steep slope descent, with intuitive and natural operation, without needing to exit or reset the function, resulting in more consistent downhill speed adjustments.

[0052] In one feasible implementation, during steep slope braking, if the driver wants to increase the downhill speed by pressing the accelerator pedal to request positive torque, and it is determined that the negative torque has not triggered the braking safety threshold, the safety threshold is set to 90% of the sum of the vehicle's current maximum mechanical braking force and the motor's current output braking torque. The vehicle uses a PID control method to achieve a smooth transition of the motor from negative torque to positive torque. When the accelerator pedal is released, the vehicle speed is updated to the downhill stable speed, and the vehicle recalculates the braking negative torque at this speed to maintain a stable downhill descent. If the vehicle's negative torque is greater than or equal to the braking safety threshold when the accelerator pedal is pressed, the positive torque requested by the accelerator pedal will not be responded to in order to ensure vehicle safety, and a pop-up window on the instrument panel will display a warning.

[0053] During steep slope braking, if the driver wants to reduce the downhill speed, they request negative torque by pressing the brake pedal. If the mechanical brakes are not engaged, the negative torque responding to the mechanical brakes is added to the negative torque of the electric brakes to increase the vehicle's acceleration and achieve deceleration. When the brake pedal is released, the vehicle speed is updated to the stable downhill speed, and the vehicle recalculates the braking negative torque at this speed to maintain a stable downhill descent. If the mechanical brakes are already engaged when the brake pedal is pressed, the current mechanical brake negative torque value is compared with the requested negative torque value corresponding to the brake pedal opening. If the mechanical brake negative torque value is less than or equal to the requested negative torque value at the brake pedal opening, the brake pedal request is responded to; otherwise, it is not responded to.

[0054] In some embodiments, it also includes: If the drive motor speed is greater than the first safe speed threshold, the current vehicle operating condition is determined to be a motor pre-overspeed state, and the instrument panel pop-up displays the first warning message; If the drive motor speed exceeds the second safe speed threshold, the current vehicle operating condition is determined to be an overspeed state of the motor. Emergency braking of the vehicle is performed according to the maximum mechanical braking value, and the instrument panel pop-up displays the second warning information.

[0055] In one feasible implementation, during steep slope braking, to prevent the vehicle from losing control due to excessive slope, the drive motor speed needs to be monitored. When the drive motor speed exceeds the first safe speed threshold, the current vehicle operating condition is determined to be a motor pre-overspeed state, and a warning is displayed in the instrument panel pop-up window to remind the driver to drive cautiously. When the drive motor speed exceeds the second safe speed threshold, the current vehicle operating condition is determined to be a motor overspeed state. To ensure driving safety, the maximum mechanical braking value is requested for emergency braking of the vehicle, and a warning is displayed in the instrument panel pop-up window simultaneously to eliminate the risk of motor damage and vehicle loss of control.

[0056] The steep slope braking control method for new energy vehicles provided in the above embodiments can record the vehicle speed when the brake pedal is released as the stable downhill speed after the steep slope braking command is triggered. The original required braking torque is calculated based on signals collected by the slope sensor and load sensor, and then combined with the current output braking torque of the motor to obtain the final required braking torque. When the driver generates a pedal activation signal, the stable downhill speed is adjusted based on this final required braking torque to obtain the current downhill speed. The driver does not need to operate the brake pedal for extended periods, reducing operational burden and alleviating driving fatigue. By matching the required braking force with the slope and load signals, the braking capacity of the motor is prioritized, reducing the operating frequency and wear of the mechanical brakes and avoiding brake fade caused by continuous downhill driving. Furthermore, the driver can flexibly adjust the downhill speed when pressing the pedal, achieving coordination between braking control and driving intention, ensuring smooth driving; and it also helps recover braking energy, improving overall vehicle energy efficiency.

[0057] In some embodiments, such as a heavy-duty pure electric dump truck, when the steep slope braking switch is activated during a downhill descent and the accelerator and brake pedals are released, the vehicle speed is 8 km / h. At this moment, the vehicle will dynamically adjust the braking torque at 8 km / h to maintain stable descent. To ensure vehicle safety, this stable speed range is set between 3 and 30 km / h. If the driver then depresses the accelerator to 15 km / h and releases it, the VCU calculates that the current required torque is -1800 Nm to maintain stable descent. This absolute value is less than 90% of the sum of the vehicle's motor's current output braking torque of 2000 Nm and the current maximum mechanical braking force of 20000 Nm, i.e., 19800 Nm. Therefore, the vehicle will maintain a stable descent at 15 km / h.

[0058] When the gradient increases, the total braking force to maintain vehicle stability downhill increases to -5000Nm (electric braking -2000Nm + mechanical braking -3000Nm). When the driver depresses the brake pedal to 10%, the corresponding requested mechanical braking negative torque value is calculated through the map table to be -2000Nm. Its absolute value is less than the absolute value of the mechanical braking of -3000Nm to maintain vehicle stability at this moment. At this time, the mechanical braking request of the brake pedal is not responded to, and the mechanical braking calculated by the VCU is maintained to keep the vehicle stable. If the brake pedal is open to 20% at the same time, the corresponding requested mechanical braking negative torque value is calculated through the map table to be -4000Nm. Its absolute value is greater than the absolute value of the mechanical braking of -3000Nm to maintain vehicle stability at this moment. At this time, the mechanical braking request of the brake pedal is responded to, and the total braking force of -6000Nm is used to reduce the vehicle speed. When the brake pedal is released, the vehicle speed is 10km / h. Then, the braking force is calculated and updated to -4500Nm to maintain vehicle stability based on the vehicle speed.

[0059] When the vehicle is descending a steep slope at a speed of 20 km / h, if the motor speed is higher than the requested shift speed of 2800 rpm, a warning will be displayed in the instrument panel, advising the driver to reduce the speed. When the slope becomes steeper and the vehicle suddenly slides downhill, causing the motor speed to rise rapidly to 95% of the maximum motor speed of 3600 rpm, i.e., above 3420 rpm, the maximum mechanical braking torque will be requested to achieve emergency braking of the vehicle to ensure driving safety, and a warning will be displayed in the instrument panel at the same time.

[0060] Please see Figure 2 Another embodiment of this application provides a steep slope braking control device for new energy vehicles, the device comprising: The switch module 101 is used to respond to the steep slope braking command, obtain the vehicle speed when the brake pedal is released, and obtain the stable downhill vehicle speed.

[0061] The sensing module 102 is used to acquire slope signals based on the slope sensor and load signals based on the load sensor.

[0062] The first calculation module 103 is used to calculate the original required braking torque based on the slope signal and the load signal.

[0063] The second calculation module 104 is used to calculate the final required braking torque based on the current output braking torque of the motor and the original required braking torque.

[0064] The adjustment module 105 is used to respond to the pedal start signal and adjust the downhill stable speed according to the final required braking torque to obtain the current downhill speed.

[0065] In some embodiments, the first calculation module 103 is specifically used to: calculate the current downward force of the vehicle based on the slope signal and the load signal; calculate the total braking force based on the rolling resistance and the downward force; calculate the wheel-end braking torque based on the tire rolling radius and the total braking force; and calculate the original required braking torque based on the total transmission ratio, transmission efficiency and wheel-end braking torque.

[0066] The specific limitations of the steep slope braking control device for new energy vehicles provided in this embodiment can be found in the embodiment of the steep slope braking control method for new energy vehicles described above, and will not be repeated here. Each module in the above-described steep slope braking control device for new energy vehicles can be implemented entirely or partially through software, hardware, or a combination thereof. Each module can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0067] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0068] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for controlling steep slope braking in new energy vehicles, characterized in that, The method includes: In response to a steep slope braking command, the vehicle speed when the brake pedal is released is obtained, and the stable downhill speed is then calculated. Slope signals are acquired based on slope sensors, and load signals are acquired based on load sensors. The original required braking torque is obtained by calculating based on the slope signal and load signal; The final required braking torque is calculated based on the current output braking torque of the motor and the original required braking torque. In response to the pedal start signal, the downhill stable speed is adjusted according to the final required braking torque to obtain the current downhill speed.

2. The steep slope braking control method for new energy vehicles according to claim 1, characterized in that, The calculation based on the slope signal and load signal to obtain the original required braking torque includes: The current downward force of the vehicle is calculated based on the slope signal and load signal; The total braking force is calculated based on the rolling resistance and the downward force. The wheel-end braking torque is calculated based on the tire rolling radius and the total braking force. The original required braking torque is calculated based on the total transmission ratio, transmission efficiency, and the wheel-end braking torque.

3. The steep slope braking control method for new energy vehicles according to claim 1, characterized in that, Also includes: The braking torque gap is calculated based on the current output braking torque of the motor and the original required braking torque. If the braking torque gap is less than or equal to zero, the mechanical brake will not be output; If the braking torque gap is greater than zero, then mechanical braking will compensate for the braking torque gap.

4. The steep slope braking control method for new energy vehicles according to claim 3, characterized in that, Also includes: The required mechanical braking torque at the wheel end is calculated based on the total transmission ratio, transmission efficiency, and the braking torque gap. The braking pressure is calculated based on the linear proportionality coefficient between air pressure and torque and the required torque for mechanical braking at the wheel end.

5. The steep slope braking control method for new energy vehicles according to claim 1, characterized in that, Also includes: The speed deviation is calculated based on the vehicle's current speed and the downhill stable speed. The corrected torque increment is calculated based on the proportional, integral, and derivative functions of the vehicle speed PID controller and the vehicle speed deviation. The final required braking torque is calculated based on the original required braking torque and the corrected torque increment.

6. The steep slope braking control method for new energy vehicles according to claim 1, characterized in that, The pedal activation signal includes the accelerator pedal activation signal; The process of responding to the pedal start signal and adjusting the downhill stable speed according to the final required braking torque to obtain the current downhill speed includes: In response to the accelerator pedal activation signal, a positive torque is requested; If it is determined that the negative torque has not triggered the braking safety threshold, the vehicle speed is adjusted to the current downhill speed according to the PID control. The braking safety threshold is 90% of the sum of the vehicle's current maximum mechanical braking force and the motor's current output braking torque.

7. The steep slope braking control method for new energy vehicles according to claim 1, characterized in that, The pedal activation signal includes the brake pedal activation signal; The process of responding to the pedal start signal and adjusting the downhill stable speed according to the final required braking torque to obtain the current downhill speed includes: In response to the brake pedal activation signal, a negative torque is requested; If mechanical braking is not applied, the negative torque responding to mechanical braking is superimposed on the negative torque of electric braking to obtain the current downhill speed; If mechanical braking has been applied, when the negative torque value of mechanical braking is less than or equal to the negative torque value requested by the brake pedal opening, the brake pedal activation signal is responded to, and the current downhill speed is obtained.

8. The steep slope braking control method for new energy vehicles according to claim 1, characterized in that, Also includes: If the drive motor speed is greater than the first safe speed threshold, the current vehicle operating condition is determined to be a motor pre-overspeed state, and the instrument panel pop-up displays the first warning message; If the drive motor speed exceeds the second safe speed threshold, the current vehicle operating condition is determined to be an overspeed state of the motor. Emergency braking of the vehicle is performed according to the maximum mechanical braking value, and the instrument panel pop-up displays the second warning information.

9. A steep slope braking control device for new energy vehicles, characterized in that, The device includes: The switch module is used to respond to the steep slope braking command, obtain the vehicle speed when the brake pedal is released, and obtain the stable downhill vehicle speed; The sensing module is used to acquire slope signals based on the slope sensor and load signals based on the load sensor. The first calculation module is used to calculate the original required braking torque based on the slope signal and load signal; The second calculation module is used to calculate the final required braking torque based on the current output braking torque of the motor and the original required braking torque. The adjustment module is used to adjust the downhill stable speed in response to the pedal start signal, according to the final required braking torque, to obtain the current downhill speed.

10. The steep slope braking control device for new energy vehicles according to claim 9, characterized in that, The first calculation module is specifically used to: calculate the current downward force of the vehicle based on the slope signal and the load signal; calculate the total braking force based on the rolling resistance and the downward force; and calculate the wheel-end braking torque based on the tire rolling radius and the total braking force. The original required braking torque is calculated based on the total transmission ratio, transmission efficiency, and the wheel-end braking torque.

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