A method for smooth switching control of electric-pneumatic braking in commercial vehicles

Abstract

This invention provides a smooth switching control method for electric-pneumatic braking in commercial vehicles, which improves braking smoothness, optimizes energy recovery efficiency, and has strong adaptability. Based on the motor's capacity, it predicts the maximum sustainable braking torque corresponding to the motor's capacity within a set future time period. Combining this with the difference in the current available braking torque of the motor, it linearly increases or decreases the pneumatic braking pressure in advance. This controls the electric motor's power to decrease or increase linearly at a rate matching the increase / decrease rate of the pneumatic braking pressure, ensuring that the sum of the electric motor's power and the pneumatic braking force always equals the total braking force required at the current brake pedal depth, achieving a smooth, shock-free switching between electric and pneumatic braking.

Description

Technical Field

[0001] This invention relates to the technical field of commercial vehicle braking control, specifically to a method for smooth switching control of electric-pneumatic braking in commercial vehicles. Background Technology

[0002] With the rapid development of new energy commercial vehicles, the coordinated control of electric braking and air braking has become one of the core technologies for improving vehicle braking performance and reducing energy consumption.

[0003] Most existing commercial vehicle electro-pneumatic braking coordinated control technologies employ a control logic of "real-time assessment of the motor's current braking capacity + post-event compensation." When the electric braking capacity is insufficient, the pneumatic brake is then activated to compensate. However, this control method has significant drawbacks: 1. The braking capacity of the motor is affected by multiple factors such as battery SOC, motor speed, and motor temperature, and has dynamic change characteristics. Existing technology can only assess the current capacity in real time and cannot predict the decline trend of motor capacity in the future, resulting in a lag in the timing of air brake activation. 2. When the motor capacity suddenly drops, the air brake needs to be activated quickly to make up for the braking force gap. At this time, the air brake pressure will suddenly increase, resulting in obvious braking shock during the switching between electric brake and air brake, which affects the ride smoothness and may also aggravate the wear of the braking system and reduce braking safety. Therefore, there is an urgent need for a control method that can predict changes in motor braking capacity in advance and achieve a smooth, shock-free switching between electric and pneumatic braking. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a smooth switching control method for electric-pneumatic braking in commercial vehicles, which improves braking smoothness, optimizes energy recovery efficiency, and has strong adaptability.

[0005] A method for smooth switching between electric and pneumatic braking in commercial vehicles is characterized by: predicting the maximum sustainable braking torque corresponding to the motor's capacity within a set time period based on the motor's capacity, and combining the difference in the current available braking torque of the motor, linearly increasing or decreasing the pneumatic braking pressure in advance, thereby controlling the electric motor's power to decrease or increase linearly at a rate matching the increase or decrease rate of the pneumatic braking pressure, ensuring that the superposition value of the electric motor's power and the pneumatic braking force is always equal to the total braking force requirement corresponding to the current brake pedal depth, thus achieving a shock-free smooth switching between electric and pneumatic braking.

[0006] Its further feature is that it includes the following steps: S1. Real-time parameter acquisition: Real-time acquisition of key parameters during the operation of commercial vehicles; S2. Establish a motor capacity prediction model to predict the maximum sustainable braking torque; S3. Determine the trend of motor capacity change: Compare the predicted maximum sustainable braking torque with the current available braking torque of the motor and calculate the torque difference; When the torque difference is greater than the preset threshold, that is, when it is predicted that the motor braking capacity will decrease and the rate of decrease is greater than the preset attenuation rate, start the advance compensation control. S4. Increase the air brake pressure linearly in advance; S5. Achieve smooth switching between electric and pneumatic braking: While the pneumatic braking pressure increases linearly, the electric motor power decreases linearly at a rate matching the rate of increase in pneumatic braking pressure, ensuring that the superposition of the electric motor power and the pneumatic braking force is always equal to the total braking force requirement corresponding to the current brake pedal depth, thus achieving a smooth and shock-free switching between electric and pneumatic braking. S6. Reverse Smooth Switching: When the recovery of motor braking capacity is predicted, the air braking pressure is linearly reduced while the motor braking force is linearly increased, realizing a reverse smooth switching from air braking to electric braking and maximizing the recovery of braking energy.

[0007] Its further characteristic is: In step S1, key parameters during the operation of the commercial vehicle are collected in real time through the vehicle controller, battery management system and motor controller. Key parameters include battery SOC, motor speed, motor temperature, electronic control temperature, brake pedal depth and current vehicle speed. In step S2, based on the collected battery SOC, motor speed, and motor control temperature parameters, and focusing on the trends of battery SOC change, motor speed change, and motor control temperature change, a motor braking capacity prediction model is established. The maximum sustainable braking torque that the motor can output within a preset time period is predicted through the motor braking capacity prediction model. The motor braking capacity prediction model outputs a dynamic prediction value of the maximum sustainable braking torque based on the changing trend of the parameters through linear fitting and fuzzy control algorithms. The motor braking capacity prediction model is optimized through a self-learning algorithm, and the prediction parameters are dynamically corrected based on historical operating data to improve prediction accuracy. The historical operating data includes the actual motor capabilities under different SOC change trends, speed change trends, and temperature change trends. In step S4, based on the rate and magnitude of decrease in the motor's braking capacity, as well as the total braking force requirement corresponding to the current brake pedal depth, the required compensation pressure increment for the air brake is calculated, and the air brake system is controlled to linearly increase the air brake pressure in advance.

[0008] The beneficial effects of using this invention are as follows: Improved braking smoothness: By linearly increasing the air brake pressure in advance, a smooth, shock-free switch between electro-pneumatic braking is achieved, eliminating the braking shock caused by sudden pressure changes in existing technologies, improving driving comfort, and reducing mechanical wear of the braking system, thus extending the service life of braking components. Optimize energy recovery efficiency: Achieve smooth reverse switching from air braking to electric braking. When the motor capacity is restored, it can quickly switch back to electric braking mode to maximize the recovery of braking energy, reduce energy consumption of commercial vehicles, and extend driving range. High adaptability: The control strategy is optimized for the characteristics of air braking systems in commercial vehicles, making it compatible with different types of new energy commercial vehicles (pure electric and hybrid). It can also adaptively adjust according to vehicle speed, load, battery and motor status, making it highly practical and easy to apply in industrial applications. Detailed Implementation

[0009] The basic parameters of the 49-ton P2 hybrid tractor are as follows: Motor parameters: peak power 100kW, maximum regenerative braking torque 1000Nm, the maximum braking torque that the motor can provide varies with external characteristics; Electronic control parameters: Regenerative braking torque decreases linearly above 85℃ (torque decreases from 100% to 0 in the 85℃-90℃ range); Battery parameters: The normal operating range of SOC is 20%-95%. When the SOC is higher than 90%, the regenerative braking torque decreases linearly (in the 90%-95% range, the torque decreases from 100% to 0). Air brake parameters: working pressure of air brake system is 0.4-1MPa, maximum output shaft end braking torque is 16000Nm, and pressure response lag time is ≤30ms; The tire radius r = 0.52 m, the rear axle ratio i0 = 4.11, and the relationship between air pressure and output shaft torque is T (kNm) = 16 * P (MPa). The following example is based on the gear ratio of 5 in the current gearbox position.

[0010] The specific implementation process of the commercial vehicle electro-pneumatic braking smooth switching control method is as follows: S1. Real-time parameter acquisition: The vehicle is fully loaded with 49 tons, going downhill, with a current speed of 60 km / h. The brake pedal depth corresponds to a total braking force requirement of 5000 Nm at the output shaft end. The real-time parameters are as follows: Battery SOC: Current value 85%, SOC trend: continuously rising, rising rate 0.5% / 100ms; Motor speed: Current value 950 r / min, speed change trend: continuously increasing, increase rate 100 rpm / 100 ms; Electrically controlled temperature: Current temperature 85℃, temperature change trend: continuously rising, rising rate 2℃ / 100ms; Other influencing factors remain unchanged.

[0011] S2. Establish a motor capacity prediction model to predict the maximum sustainable braking torque: Based on the above three parameters and their changing trends, the following results were obtained through calculation using the motor regenerative braking capability prediction model: Battery SOC: The SOC is predicted to be 85.5% after 100ms. This will affect the maximum braking torque that the motor can provide. Motor speed: It is predicted that the speed will rise to 1050 r / min after 100ms. This will reduce the maximum braking torque that the motor can provide from 1000 Nm to 910 Nm. Electrical temperature control: It is predicted that the temperature will rise to 87℃ after 100ms. This will reduce the maximum braking torque of the motor from 1000Nm to 600Nm. In summary, after 100ms, the maximum braking torque provided by the motor decreases from 1000Nm to 600Nm. The decrease is 40%, and the rate of decrease is 40Nm / 10ms.

[0012] S3. Determine the trend of motor capacity change: The calculated difference between the predicted torque and the current torque is 400 Nm, which is greater than the preset threshold of 100 Nm, and the rate of decrease is greater than the preset attenuation rate. Therefore, it is determined that the regenerative braking capability of the motor is about to decrease, and advance compensation control is initiated.

[0013] S4. Increase air brake pressure linearly in advance: The total braking force requirement at the output shaft end is 5000 Nm. The current motor power, converted to the output shaft end, is also 5000 Nm. It is predicted that it will drop to 3000 Nm after 100 ms. Therefore, air brakes are needed to supplement the braking force by 2000 Nm. Considering the characteristics of the air brake system, the required air brake pressure increment is calculated to be 0.125 MPa. The air brake system is controlled to increase the pressure linearly at a slope of 0.0125 MPa / 10 ms, rising from 0 MPa to 0.125 MPa within 100 ms to complete the advance compensation.

[0014] S5. Enables smooth switching between electric and pneumatic braking: While the air brake pressure increases linearly, the control motor braking torque decreases linearly at a rate matching the rate of increase in air brake pressure, that is, it decreases from 1000Nm at a rate of 40Nm / 10ms, and drops to 600Nm within 100ms. During this process, the superposition value of the electric motor power and the air brake force, when converted to the output shaft end, always remains at 5000Nm, which is consistent with the total braking force requirement corresponding to the brake pedal depth, realizing a smooth and shock-free switch from electric braking to air braking, and the driver and passengers do not have a noticeable sense of jerking.

[0015] S6, Reverse Smooth Switching: When the regenerative braking capability of the motor is restored, the reverse switching is performed as follows: the maximum sustainable regenerative braking torque of the motor can be restored to 1000Nm. At this time, the control air brake pressure decreases linearly at a slope of 0.0125MPa / 10ms, and drops to 0MPa in 100ms; at the same time, the control motor force increases linearly from 600Nm to 1000Nm. The total braking force always remains consistent with the brake pedal demand, realizing a smooth reverse switching from air braking to electric braking and maximizing the recovery of braking energy.

[0016] It combines three core parameters—battery SOC, motor speed, and motor temperature—and focuses on capturing the changing trends of these three parameters to establish a predictive model for motor braking capacity. This model enables the prediction of the motor's maximum sustainable braking torque in the future, rather than just assessing its current capacity. Furthermore, based on the prediction of motor capacity decline and recovery, it initiates a linear increase or decrease in air braking pressure in advance, rather than waiting until the motor braking capacity is insufficient or fully recovered before abruptly replenishing or stopping the air supply, thus solving the problem of air braking response lag.

[0017] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0018] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for smooth switching control of electric-pneumatic braking in commercial vehicles, characterized in that: Based on the motor's capacity, it predicts the maximum sustainable braking torque corresponding to the motor's capacity within a set time in the future. Combined with the difference in the current available braking torque of the motor, it controls the electric motor's power to decrease or increase linearly at a rate that matches the rate of increase or decrease of the air braking pressure by increasing or decreasing the air braking pressure in advance. This ensures that the superposition value of the electric motor's power and the air braking force is always equal to the total braking force requirement corresponding to the current brake pedal depth, thus achieving a smooth and shock-free switch between electric braking and air braking.

2. The method for smooth switching control of electric-pneumatic braking in commercial vehicles according to claim 1, characterized in that, It includes the following steps: S1. Real-time parameter acquisition: Real-time acquisition of key parameters during the operation of commercial vehicles; S2. Establish a motor capacity prediction model to predict the maximum sustainable braking torque; S3. Determine the trend of motor capacity change: Compare the predicted maximum sustainable braking torque with the current available braking torque of the motor, and calculate the torque difference. When the torque difference is greater than the preset threshold, that is, when it is predicted that the motor braking capacity will decrease and the rate of decrease is greater than the preset attenuation rate, the advance compensation control is activated. S4. Increase the air brake pressure linearly in advance; S5. Achieve smooth switching between electric and pneumatic braking: While the pneumatic braking pressure increases linearly, the electric motor power decreases linearly at a rate matching the rate of increase in pneumatic braking pressure, ensuring that the superposition of the electric motor power and the pneumatic braking force is always equal to the total braking force requirement corresponding to the current brake pedal depth, thus achieving a smooth and shock-free switching between electric and pneumatic braking. S6. Reverse Smooth Switching: When the recovery of motor braking capacity is predicted, the air braking pressure is linearly reduced while the motor braking force is linearly increased, realizing a reverse smooth switching from air braking to electric braking and maximizing the recovery of braking energy.

3. The method for smooth switching control of electric-pneumatic braking in commercial vehicles according to claim 2, characterized in that: In step S1, key parameters during the operation of the commercial vehicle are collected in real time through the vehicle controller, battery management system and motor controller. These key parameters include battery SOC, motor speed, motor temperature, electronic control temperature, brake pedal depth and current vehicle speed.

4. The method for smooth switching control of electric-pneumatic braking in commercial vehicles according to claim 3, characterized in that: In step S2, based on the collected battery SOC, motor speed, and motor control temperature parameters, and focusing on the trends of battery SOC change, motor speed change, and motor control temperature change, a motor braking capacity prediction model is established. The maximum sustainable braking torque that the motor can output within a preset time period is predicted through the motor braking capacity prediction model.

5. The method for smooth switching control of electric-pneumatic braking in commercial vehicles according to claim 4, characterized in that: The motor braking capacity prediction model outputs a predicted value of the dynamic maximum sustainable braking torque based on the changing trend of the parameters through linear fitting and fuzzy control algorithms.

6. The method for smooth switching control of electric-pneumatic braking in commercial vehicles according to claim 5, characterized in that: The motor braking capacity prediction model is optimized through a self-learning algorithm, which dynamically corrects the prediction parameters based on historical operating data to improve prediction accuracy.

7. The method for smooth switching control of electric-pneumatic braking in commercial vehicles according to claim 6, characterized in that: The historical operating data includes the actual motor capabilities under different SOC change trends, speed change trends, and temperature change trends.

8. The method for smooth switching control of electric-pneumatic braking in commercial vehicles according to claim 2, characterized in that: In step S4, based on the rate and magnitude of decrease in the motor's braking capacity, as well as the total braking force requirement corresponding to the current brake pedal depth, the required compensation pressure increment for the air brake is calculated, and the air brake system is controlled to linearly increase the air brake pressure in advance.