A composite braking deceleration control method

Abstract

The present invention discloses a composite braking deceleration control method, which uses vehicle status information to evaluate the available electric motor torque of the vehicle in real time and calculates the maximum deceleration that can be provided by the electric motor braking in combination with the mass estimation value. The target braking deceleration is then distributed into the electric braking demand torque and the air braking demand deceleration according to the set rules and sent to the corresponding subsystems. At the same time, the actual deceleration of the vehicle body is detected and compared with the target braking deceleration. If there is an error, the deceleration is first adjusted by taking advantage of the motor's fast and precise adjustment until the motor reaches the maximum negative torque or zero torque. If the error cannot be eliminated, the air brake is adjusted to reduce the error between the actual deceleration of the vehicle body and the target braking deceleration while the motor braking remains stable. The present invention detects the actual deceleration value of the vehicle body and forms a closed loop with the target braking deceleration. The electric brake is first adjusted by the motor, and then the air brake is adjusted after the motor reaches its capacity limit to ensure precise control of the deceleration.

Description

Technical Field

[0001] The present invention relates to the technical field of braking control for new energy vehicles, and more specifically to a composite braking deceleration control method. Background Art

[0002] In recent years, the intelligent development of new energy vehicles has been rapid, and the installation rate of various advanced driver assistance systems (ADAS) in vehicles has continued to increase, such as ACC adaptive cruise control and highway pilot systems. These systems require the underlying support of wire-controlled brake technology, especially the application of autonomous driving technology, which requires more precise control of braking deceleration.

[0003] Pneumatic brake systems are widely used on large vehicles, but existing systems often rely on open-loop control, resulting in low precision. Furthermore, the deceleration assist braking function provided by existing pneumatic brake systems is mostly based on no-load calibration, resulting in significant control errors for commercial vehicles with large load variations. Furthermore, the motor braking torque fluctuates significantly throughout the braking process, with torque being limited at high speeds and unable to provide braking torque at low speeds, necessitating real-time evaluation.

[0004] Patent publication number CN 114407870A discloses a control method, device, storage medium, and commercial vehicle for an electric composite brake system. After determining the required braking deceleration using a braking signal, the required braking torque is determined based on the vehicle's state, and the front and rear axle braking torques are determined from the required braking torques. The vehicle's target electric braking torque is then determined based on the rear axle's required braking torque and the maximum electric braking torque. The vehicle's target braking pressure is then determined based on the front and rear axle required braking torques and an inverse model of the braking system. This invention applies the maximum motor braking torque to the rear axle by comparing it with the maximum required torque of the rear axle. This prevents the electric brake from adjusting if there are errors in the pneumatic brake control. Furthermore, the actual deceleration of the vehicle body is not taken into account, making accurate deceleration control impossible. Summary of the Invention

[0005] The present invention provides a compound braking deceleration control method to solve the problem that the existing compound braking method cannot ensure the accuracy of deceleration control.

[0006] The present invention adopts the following technical solutions:

[0007] A composite braking deceleration control method comprises the following steps:

[0008] S01. Real-time evaluation of the available motor torque Tmax of the vehicle;

[0009] S02, calculating the maximum deceleration a1_max that can be provided by the motor braking based on the available motor braking torque Tmax of the vehicle evaluated in real time in step S01 and the estimated vehicle mass;

[0010] S03. Allocate the target braking deceleration a0_req into the electric braking required deceleration a1 and the air braking required deceleration a2 according to the rules;

[0011] S04. Calculate the motor required torque T1 according to a1 and the estimated vehicle mass value, send the value of T1 to the motor control system, and send the value of a2 to the pneumatic braking control system;

[0012] S05. Detect the error between the actual vehicle body deceleration and the target braking deceleration a0_req, and use the reserved torque of the motor to adjust the deceleration;

[0013] S06. If the actual motor torque reaches the maximum motor torque or zero torque and remains, the deceleration error is adjusted by the air brake to make the actual vehicle body deceleration consistent with the target braking deceleration.

[0014] In a preferred embodiment, the above step S01 is to evaluate the available electric motor braking torque Tmax of the vehicle in real time according to the vehicle state information, specifically including: evaluating the current available braking torque of the motor according to the motor speed combined with the external characteristic curve of the motor, evaluating the current maximum recoverable torque of the battery according to the motor speed combined with the real-time charge and discharge power of the battery, evaluating the maximum anti-dragging torque that the drive system can withstand according to the maximum anti-dragging torque value that the rear axle can withstand, and taking the minimum of the three; at the same time, make a threshold judgment on stopping energy recovery according to the battery SOC value. [[ID=十五]] [[ID=十六]]

[0015] [[ID=十七]]In a preferred embodiment, the specific allocation rules of the above step S03 are as follows: a). Reserve a part of the maximum deceleration that the electric motor braking can provide as the deceleration error electric braking adjustment amount a3, a3 = a1_max * k, k is the adjustment coefficient, and the value of k is preferably 0.2; calculate the reserved torque T3 of the motor according to a3 and the estimated vehicle mass value, and T3 is the upper limit value of the electric braking adjustment torque; b). If (a1_max - a3) >= a0_req, then a1 = a0_req * 0.5, a2 = a0_req * 0.5; c). If (a1_max - a3) < a0_req, then a1 = a1_max - a3, a2 = a0_req - a1.

[0016] In a preferred embodiment, the specific process of the above step S05 is as follows: Detect the value of the actual vehicle body deceleration. If there is an error between the actual vehicle body deceleration a0_rel and the target braking deceleration a0_req after time t, then adjust the deceleration through the motor control system within the range of the reserved torque T3 value of the motor to make the actual vehicle body deceleration consistent with the target braking deceleration.

[0017] In some preferred embodiments, the above time t is 0.2s, and the detection of the actual vehicle body deceleration is obtained by reading the value of the acceleration sensor or by differentiating the speed.

[0018] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following advantages:

[0019] Without changing the original vehicle's air brake system, the present invention uses vehicle status information to evaluate the available electric motor torque in real time and, combined with mass estimation, calculates the maximum deceleration that can be provided by the electric motor brake. The target braking deceleration is then distributed into the electric brake demand torque and the air brake demand deceleration according to a set rule and sent to the corresponding subsystems. Simultaneously, the actual vehicle deceleration is detected and compared with the target braking deceleration. If an error exists, the deceleration is first adjusted by leveraging the motor's fast and precise adjustment until the motor reaches maximum negative torque or zero torque. If the error still cannot be eliminated, the air brake is adjusted while the motor brake remains stable to reduce the error between the actual vehicle deceleration and the target braking deceleration. By setting a target deceleration distribution rule, the present invention ensures that the air brake provides a base braking force under all braking conditions, improving the reliability of the braking process. A portion of the motor brake adjustment torque is reserved during the distribution, ensuring that the motor has adjustment capability under most braking conditions. Furthermore, by detecting the actual vehicle deceleration, the motor's fast and precise adjustment advantage is prioritized for error adjustment. When the motor torque reaches its limit, the air brake deceleration is adjusted, ensuring the accuracy of deceleration control while avoiding the oscillation caused by the superposition of the two adjustments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural block diagram of the composite braking deceleration control system of the present invention.

[0021] Figure 2 This is a flow chart of the compound braking deceleration control method of the present invention. DETAILED DESCRIPTION

[0022] The following describes specific embodiments of the present invention with reference to the accompanying drawings. Numerous details are provided below to provide a comprehensive understanding of the present invention, but those skilled in the art will appreciate that the present invention can be practiced without these details. Well-known components, methods, and processes are not described in detail below.

[0023] The present invention provides a composite braking deceleration control method based on the following composite braking deceleration control system. Figure 1The combined braking deceleration control system includes a vehicle control unit (VCU) 100 (the upper-level controller), a motor control system 200, a pneumatic brake control system 300, and a vehicle acceleration sensor 400. The vehicle acceleration sensor 400 detects the actual vehicle deceleration, while the VCU 100 sends torque commands to the motor control system 200 and deceleration commands to the pneumatic brake system 300. The motor control system 200 primarily brakes the vehicle's rear wheels, while the pneumatic brake system 300 handles both front and rear wheel braking.

[0024] Reference Figure 2 The composite braking deceleration control method of the present invention comprises the following steps:

[0025] S01. Evaluate the available motor torque Tmax of the vehicle in real time.

[0026] This step S01 is to evaluate the available electric motor braking torque Tmax of the vehicle in real time based on the vehicle status information, specifically including: evaluating the current available braking torque of the motor based on the motor speed combined with the motor external characteristic curve, evaluating the current maximum recoverable torque of the battery based on the motor speed combined with the real-time charge and discharge power of the battery, evaluating the maximum tolerable reverse drag torque of the transmission system based on the maximum tolerable reverse drag torque value of the rear axle, and making a threshold judgment for stopping energy recovery based on the battery SOC value.

[0027] This real-time evaluation method for motor braking capability fully considers the external characteristic limitations of the motor itself, the limitations of the transmission system's reverse drag torque, and the limitations of the power battery and SOC; the real-time available motor braking torque of the vehicle should be the smaller of the three.

[0028] S02 : Calculate the maximum deceleration a1_max that can be provided by the motor braking based on the available motor braking torque Tmax of the vehicle evaluated in real time in step S01 and the estimated vehicle mass.

[0029] S03. Allocate the target braking deceleration a0_req into the electric braking required deceleration a1 and the pneumatic braking required deceleration a2 according to the rules. The specific allocation rules are as follows:

[0030] a) The maximum deceleration that can be provided by the reserved motor braking is used as the deceleration error electric brake adjustment amount a3, where a3 = a1_max*k, where k is the adjustment coefficient and the k value is preferably 0.2; the motor reserved torque T3 is calculated based on a3 and the estimated vehicle mass. T3 is the upper limit of the electric brake adjustment torque;

[0031] b) If (a1_max-a3)>=a0_req, then a1=a0_req*0.5, a2=a0_req*0.5;

[0032] c), if (a1_max - a3) < a0_req, then a1 = a1_max - a3, a2 = a0_req - a1.

[0033] According to this target deceleration distribution rule, it is ensured that pneumatic braking provides the basic braking force under any braking condition, improving the reliability of the braking process, and reserving part of the electric braking adjustment ability during distribution, so that the motor has adjustment ability under most braking conditions.

[0034] S04. Calculate the motor required torque T1 based on a1 and the estimated vehicle mass value, send the T1 value to the motor control system, and send the a2 value to the pneumatic braking control system.

[0035] S05. Detect the error between the actual vehicle body deceleration and the target braking deceleration a0_req, and use the reserved torque of the motor to adjust the deceleration.

[0036] If there is an error between the actual vehicle body deceleration a0_rel and the target braking deceleration a0_req after time t, then adjust the deceleration through the motor control system within the range of the T3 value to make the actual vehicle body deceleration consistent with the target braking deceleration. In an embodiment, the time t is preferably 0.2 s; the detection of the actual vehicle body deceleration can be achieved by reading the value of the acceleration sensor or by differentiating the speed.

[0037] S06. If the actual motor torque reaches the maximum motor torque or zero torque and remains, the deceleration error is adjusted by pneumatic braking to make the actual vehicle body deceleration consistent with the target braking deceleration.

[0038] Specifically, if the actual motor torque reaches the maximum motor torque and remains stable after step S05, then adjust the pneumatic braking required deceleration a2 according to the error between the actual vehicle body deceleration a0_rel and the target braking deceleration a0_req to make the actual vehicle body deceleration consistent with the target braking deceleration.

[0039] Similarly, if the actual motor torque reaches the zero motor torque and remains stable after step 5, then adjust the pneumatic braking required deceleration a2 according to the error between the actual vehicle body deceleration a0_rel and the target braking deceleration a0_req to make the actual vehicle body deceleration consistent with the target braking deceleration.

[0040] This deceleration precise control method includes detecting the actual vehicle body deceleration value, forming a closed loop with the target braking deceleration, first using the motor for electric braking adjustment, and then adjusting by pneumatic braking after the motor reaches its capacity limit, ensuring the precise control of the deceleration. [[ID=Q]]

[0041] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A compound braking deceleration control method, characterized in that: It includes the following steps: S01. Real-time evaluate the available electric motor braking torque Tmax of the vehicle; S02. According to the available electric motor braking torque Tmax of the vehicle evaluated in real time in step S01, and combined with the estimated vehicle mass, calculate the maximum deceleration a1_max that the electric motor braking can provide; S03. Allocate the target braking deceleration a0_req into the electric braking demand deceleration a1 and the air braking demand deceleration a2 according to the rules; S04. Calculate the motor demand torque T1 according to a1 and the estimated vehicle mass, send the value of T1 to the motor control system, and send the value of a2 to the pneumatic braking control system; S05. Detect the error between the actual vehicle deceleration and the target braking deceleration a0_req, and use the reserved torque of the motor to adjust the deceleration; S06. If the actual motor torque reaches the maximum torque or zero torque of the motor and remains, the deceleration error is adjusted by the air brake to make the actual vehicle deceleration consistent with the target braking deceleration.

2. The method for controlling compound braking deceleration according to claim 1, wherein: The step S01 is to real-time evaluate the available electric motor braking torque Tmax of the vehicle according to the vehicle state information, which specifically includes: evaluating the current available braking torque of the motor according to the motor speed combined with the external characteristic curve of the motor, evaluating the current maximum recoverable torque of the battery according to the motor speed combined with the real-time charge-discharge power of the battery, evaluating the maximum anti-dragging torque that the drive system can bear according to the maximum anti-dragging torque value that the rear axle can bear, and taking the minimum of the three; at the same time, make a threshold judgment for stopping energy recovery according to the battery SOC value.

3. The method for controlling compound braking deceleration according to claim 1, wherein: The specific allocation rules of the step S03 are as follows: a). Reserve a part of the maximum deceleration that the electric motor braking can provide as the deceleration error electric braking adjustment amount a3, a3 = a1_max * k, where k is the adjustment coefficient; calculate the reserved torque T3 of the motor according to a3 and the estimated vehicle mass, and T3 is the upper limit value of the electric braking adjustment torque; b). If (a1_max - a3) >= a0_req, then a1 = a0_req * 0.5, a2 = a0_req * 0.5; c). If (a1_max - a3) < a0_req, then a1 = a1_max - a3, a2 = a0_req - a1.

4. The method for controlling compound braking deceleration according to claim 3, wherein: The value of k is 0.

2.

5. The method for controlling compound braking deceleration according to claim 3, wherein: The specific process of the step S05 is as follows: Detect the value of the actual vehicle deceleration. If there is an error between the actual vehicle deceleration a0_rel and the target braking deceleration a0_req after time t, perform deceleration adjustment through the motor control system within the range of the reserved torque T3 value of the motor to make the actual vehicle deceleration consistent with the target braking deceleration.

6. The method for controlling compound braking deceleration according to claim 5, wherein: The detection of the actual vehicle deceleration is obtained by reading the value of the acceleration sensor or by differentiating the speed.

7. The method for controlling compound braking deceleration according to claim 5, wherein: The time t is 0.2s.

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