Pure electric bus motor torque smoothing control method and system

Abstract

The present invention discloses a pure electric bus motor torque smoothing control method and system. The method and system respectively calculate the motor target torque of two adjacent execution time periods based on the calculation execution cycle of the whole vehicle controller. In addition, the maximum rising rate and the maximum falling rate of the motor torque under the current running state of the motor are calculated based on the current torque of the motor, so as to realize dynamic control of the rising rate and the falling rate of the output torque of the pure electric bus driving motor. The motor target torque of the previous execution time period is added to the maximum rising rate and the maximum falling rate of the motor torque respectively, and the sum obtained by comparing the sum with the motor target torque of the next execution time period respectively, so as to realize the purpose of smoothing the motor target torque of the next execution time period, thereby preventing the sudden change of the motor torque from bringing impact to the components of the vehicle transmission system, and avoiding the abnormal noise of the transmission components due to the transmission impact torque.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy electric vehicles, and in particular to a method and system for smoothing the torque of a motor of a pure electric bus. Background Art

[0002] As the power source of electric vehicles, motor drive has incomparable advantages over internal combustion engines in terms of driving efficiency and response speed. Due to the external characteristics of motors with high torque at low speed and constant power at high speed, the transmission system of electric vehicles has been greatly simplified. Due to the fast response speed of motor torque, in order to meet the requirements of vehicle power smoothness, the motor torque needs to be smoothed. Existing technologies limit the rise and fall rates of motor torque, usually setting a fixed rise and fall rate value. In a software execution cycle, the torque change amplitude of the motor output is constrained.

[0003] Although the existing solution can smooth the output torque of the vehicle motor and limit the rising rate and falling rate of the motor torque, since it is set to a fixed value, if it is set too large, the rising rate or falling rate will be large, and the smoothing effect of the motor torque will be affected. If it is set too small, the response speed of the motor torque will be affected.

[0004] Especially before and after the motor torque passes the 0 torque point, if the rate of decrease or increase of the motor torque is set too large, the force state of the transmission system changes, which can easily cause the gears of the transmission components to be subjected to a certain impact force and damage the transmission components. Especially for vehicles where the central motor is directly connected to the drive axle through the transmission shaft, due to the small moment of inertia of the transmission system components, if the smoothness of the motor torque is not well controlled, it is very easy to cause the main reduction gear of the drive axle to be abnormally stressed and damaged. That is, when the direction of the motor torque changes, the force direction of the transmission components also changes, and the active and driven gears of the vehicle's rear axle main reducer also switch the force direction; when the active and driven gears change from being stressed to being unstressed, or from being unstressed to being stressed, or from being stressed in the positive direction to being stressed in the reverse direction, or from being stressed in the reverse direction to being stressed in the positive direction, there is a certain backlash between the positive and negative directions of the active and driven gears, and the active and driven gears of the main reducer have a very small free travel due to the influence of the backlash. When the gear is stressed, the moment of inertia of the active gear end is added to the driven gear end. The free travel will increase the torque impact of the driving gear on the driven gear, which has the potential risk of causing mechanical failure of the gear. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies and propose a pure electric bus motor torque smoothing control method and system to prevent sudden changes in motor torque from impacting vehicle transmission system components and to avoid abnormal noise generated by transmission components due to transmission impact torque.

[0006] In order to achieve the above technical objectives, the present invention provides a pure electric bus motor torque smoothing control method, which comprises the following steps:

[0007] Based on the calculation execution cycle of the vehicle controller, the motor target torque of two adjacent execution time cycles is calculated respectively, and based on the current torque of the motor, the maximum increase rate and the maximum decrease rate of the motor torque under the current operating state of the motor are calculated;

[0008] The motor target torque of the last execution time period is added to the maximum increase rate of the motor torque and the maximum decrease rate of the motor torque, and the sum is compared with the motor target torque of the next execution time period;

[0009] If the motor target torque of the next execution time period is greater than the sum of the motor target torque of the previous execution time period and the maximum increase rate of the motor torque, the motor target torque of the next execution time period is the sum of the motor target torque of the previous execution time period and the maximum increase rate of the motor torque;

[0010] If the motor target torque of the next execution time period is less than the sum of the motor target torque of the previous execution time period and the motor torque maximum decrease rate, the motor target torque of the next execution time period is the sum of the motor target torque of the previous execution time period and the motor torque maximum decrease rate.

[0011] The present invention also provides a pure electric bus motor torque smoothing control system, which includes the following functional modules:

[0012] A parameter calculation module is used to calculate the motor target torque of two adjacent execution time periods based on the calculation execution cycle of the vehicle controller, and calculate the maximum increase rate and maximum decrease rate of the motor torque under the current running state of the motor based on the current torque of the motor;

[0013] A parameter comparison module, used for adding the motor target torque of the last execution time period to the maximum increase rate of the motor torque and the maximum decrease rate of the motor torque, and comparing the sums obtained with the motor target torque of the next execution time period;

[0014] A maximum torque limiting module, for setting the motor target torque of the next execution time period to the sum of the motor target torque of the previous execution time period and the maximum increase rate of the motor torque if the motor target torque of the next execution time period is greater than the sum of the motor target torque of the previous execution time period and the motor torque maximum increase rate;

[0015] The minimum torque limiting module is used to set the motor target torque of the next execution time period to the sum of the motor target torque of the previous execution time period and the maximum decrease rate of the motor torque if the motor target torque of the next execution time period is less than the sum of the motor target torque of the previous execution time period and the motor torque maximum decrease rate.

[0016] Compared with the prior art, the pure electric bus motor torque smoothing control method and system described in the present invention dynamically controls the output torque rise rate and decrease rate of the pure electric bus drive motor based on the current torque of the motor, and achieves the purpose of smoothing the motor target torque of the next execution time period based on the sum of the motor target torque of the previous execution time period and the maximum motor torque rise rate and the maximum motor torque decrease rate, thereby preventing the sudden change of the motor torque from causing impact on the vehicle transmission system components, and avoiding abnormal noise caused by the transmission impact torque of the transmission components. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flowchart of a method for smoothing the motor torque of a pure electric bus according to the present invention;

[0018] Figure 2 This is a module block diagram of a pure electric bus motor torque smoothing control system described in the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] In a pure electric bus, the motor is directly connected to the rear axle main reducer through the transmission shaft, the battery supplies power to the motor controller through the DC bus, the motor controller output voltage is connected to the motor through the three-phase power line, the motor controller communicates with the VCU through the CAN bus, the motor controller receives the control instructions of the VCU to control the operation of the motor, and feeds back the state of the motor to the VCU, the VCU receives the whole vehicle operation information, such as direction information, to determine whether the vehicle is moving forward or backward, brake pedal signals, accelerator pedal signals, to determine whether the vehicle needs to slow down or accelerate. The VCU determines the vehicle operation signal, obtains the motor operation target mode and target torque through internal calculations, and sends the command to the motor controller through the CAN bus. The motor control completes the control of the motor operation state according to the motor operation target mode and target torque instructions sent by the VCU.

[0021] The present invention controls the motor torque through the VCU, and the maximum increase rate and the maximum decrease rate of the motor torque are used to constrain the change amplitude of the motor torque. Figure 1 As shown in the figure, the present invention provides a method for smoothly controlling the motor torque of a pure electric bus, which includes the following steps:

[0022] S1. Based on the calculation execution cycle of the vehicle controller, calculate the motor target torque for two adjacent execution time cycles respectively, and calculate the maximum motor torque rising rate and the maximum motor torque falling rate in the current operating state of the motor based on the current motor torque;

[0023] S2. Add the motor target torque of the previous execution time cycle to the maximum motor torque rising rate and the maximum motor torque falling rate respectively, and compare the obtained sums with the motor target torque of the next execution time cycle respectively;

[0024] S3. If the motor target torque of the next execution time cycle is greater than the sum of the motor target torque of the previous execution time cycle and the maximum motor torque rising rate, then the motor target torque of the next execution time cycle is the sum of the motor target torque of the previous execution time cycle and the maximum motor torque rising rate;

[0025] S4. If the motor target torque of the next execution time cycle is less than the sum of the motor target torque of the previous execution time cycle and the maximum motor torque falling rate, then the motor target torque of the next execution time cycle is the sum of the motor target torque of the previous execution time cycle and the maximum motor torque falling rate.

[0026] The maximum rising rate and the maximum falling rate of the motor torque are calculated according to the current actual torque of the motor. The current motor torque is the motor target torque sent by the vehicle controller to the motor controller in the previous execution time cycle. The maximum rising rate and the maximum falling rate of the motor torque are linearly related to the current motor torque. When the current motor torque decreases, the maximum rising rate and the maximum falling rate of the motor torque also decrease; when the current motor torque increases, the maximum rising rate and the maximum falling rate of the motor torque also increase; when the motor torque is zero, the rising rate and the falling rate of the motor torque are a constant value; the constant value is relatively small.

[0027] Specifically, the maximum rising rate and the maximum falling rate of the motor torque and the current motor torque are in a piecewise linear function relationship. Taking the motor operation in the first quadrant as an example, the calculation method of the maximum rising rate of the motor torque is as follows:

[0028] When the current motor torque T is 0: △T1 = a;

[0029] When the motor torque 0 < T ≤ T1: △T1 = k1*T + b1;

[0030] When the motor torque T1 < T ≤ T2: △T1 = k2*T + b2;

[0031] When the motor torque T2 < T ≤ Tmax: △T1 = k3 * T + b3;

[0032] Where a is a constant, and its value depends on the minimum control torque accuracy of the motor and the ideal transmission torque of the driving and driven gears of the main reducer from the unloaded state to the instant of loading. Taking a motor with a peak torque of 2800 N.m as an example, a is generally 1 - 4 Nm; △T1 is the maximum rising rate of the motor torque, and △T1 > 0;

[0033] T1 and T2 are respectively the critical values of the motor torque segmentation, T1 < T2. Usually, the value range of T1 is about 50 - 100 N.m, and the value range of T2 is about 200 - 500 N.m; Tmax is the maximum torque of the motor; k1, k2, k3 are the linear function coefficient parameters between △T1 and T, and their magnitudes increase in sequence. For example, they can be respectively taken as 0.05, 0.2, 0.4; b1, b2, b3 are the constant term parameters of the linear function between △T2 and T, and their magnitudes decrease in sequence. For example, they can be respectively taken as 1.5, -6, -46.

[0034] The calculation method of the maximum descending rate of the motor torque is as follows:

[0035] When the current motor torque T = 0: △T2 = d;

[0036] When the motor torque 0 < T ≤ T1: △T2 = j1 * T + c1;

[0037] When the motor torque T1 < T ≤ T2: △T2 = j2 * T + c2;

[0038] When the motor torque T2 < T ≤ Tmax: △T2 = j3 * T + c3;

[0039] Where d is a constant, and its value depends on the minimum control torque accuracy of the motor and the ideal transmission torque of the driving and driven gears of the main reducer from the unloaded state to the instant of loading. Taking a motor with a peak torque of 2800 N.m as an example, d is generally 1 - 4 Nm; △T2 is the maximum descending rate of the motor torque, △T2 < 0; T1 and T2 are respectively the critical values of the motor torque segmentation, T1 < T2; Tmax is the maximum torque of the motor; j1, j2, j3 are the linear function coefficients between △T and T, and their magnitudes decrease in sequence. For example, they can be respectively taken as -0.05, -0.2, -0.4, and c1, b2, c3 are the constant term parameters of the linear function between △T2 and T, and their magnitudes increase in sequence. For example, they can be respectively taken as -1.5, 6, 46. The j1, j2, j3, c1, b2, c3 are respectively the opposite numbers of k1, k2, k3, b1, b2, b3 one by one.

[0040] From the above formula, it can be concluded that the maximum rate of increase and the maximum rate of decrease of the motor torque are obviously constrained by the current torque of the motor. Since the motor of a pure electric bus can operate in four quadrants, when the motor operates in any quadrant, the calculation method of the maximum rate of increase and the maximum rate of decrease of the motor torque is the same as the calculation method when the motor operates in the first quadrant.

[0041] The pure electric bus motor torque smoothing control method of the present invention realizes dynamic control of the output torque rising rate and falling rate of the pure electric bus driving motor based on the current torque of the motor, and realizes the purpose of smoothing the motor target torque of the next execution time period based on the sum of the motor target torque of the previous execution time period and the maximum motor torque rising rate and the maximum motor torque falling rate, thereby preventing the sudden change of the motor torque from bringing impact to the vehicle transmission system components, and avoiding abnormal noise of the transmission components due to the transmission impact torque.

[0042] Based on the above pure electric bus motor torque smoothing control method, the present invention also provides a pure electric bus motor torque smoothing control system, such as Figure 2 As shown, it includes the following functional modules:

[0043] The parameter calculation module 10 is used to calculate the motor target torque of two adjacent execution time periods based on the calculation execution cycle of the vehicle controller;

[0044] A parameter comparison module 20 is used to add the motor target torque of the last execution time period to the motor torque maximum increase rate and the motor torque maximum decrease rate, and compare the sum with the motor target torque of the next execution time period;

[0045] The maximum torque limiting module 30 is used for, if the motor target torque of the next execution time period is greater than the sum of the motor target torque of the previous execution time period and the maximum increase rate of the motor torque, then the motor target torque of the next execution time period is the sum of the motor target torque of the previous execution time period and the maximum increase rate of the motor torque;

[0046] The minimum torque limiting module 40 is configured to set the motor target torque of the next execution time period to the sum of the motor target torque of the previous execution time period and the maximum motor torque decrease rate if the motor target torque of the next execution time period is less than the sum of the motor target torque of the previous execution time period and the motor torque maximum decrease rate.

[0047] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0048] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for smoothing the torque of a pure electric bus motor, characterized in that: It includes the following steps: Based on the calculation execution cycle of the vehicle controller, calculate the motor target torque for two adjacent execution time cycles respectively, and calculate the maximum motor torque rising rate and the maximum motor torque falling rate in the current operating state of the motor based on the current motor torque; Add the motor target torque of the previous execution time cycle to the maximum motor torque rising rate and the maximum motor torque falling rate respectively, and compare the obtained sums with the motor target torque of the next execution time cycle; If the motor target torque of the next execution time cycle is greater than the sum of the motor target torque of the previous execution time cycle and the maximum motor torque rising rate, then the motor target torque of the next execution time cycle is the sum of the motor target torque of the previous execution time cycle and the maximum motor torque rising rate; If the motor target torque of the next execution time cycle is less than the sum of the motor target torque of the previous execution time cycle and the maximum motor torque falling rate, then the motor target torque of the next execution time cycle is the sum of the motor target torque of the previous execution time cycle and the maximum motor torque falling rate; The calculation method of the maximum motor torque rising rate is as follows: When the current motor torque T is 0: △T1 = a; When the motor torque 0 < T ≤ T1: △T1 = k1*T + b1; When the motor torque T1 < T ≤ T2: △T1 = k2*T + b2; When the motor torque T2 < T ≤ Tmax: △T1 = k3*T + b3; Where, a is a constant, △T1 is the maximum motor torque rising rate, and △T1 > 0; T1 and T2 are the critical values of motor torque segmentation respectively, T1 < T2; Tmax is the maximum motor torque; k1, k2, and k3 are the linear function coefficient parameters between △T1 and T, and their magnitudes increase in sequence; b1, b2, and b3 are the constant term parameters of the linear function between △T2 and T, and their magnitudes decrease in sequence.

2. According to claim 1, a pure electric bus motor torque smoothing control method is characterized in that: The maximum motor torque rising rate and the maximum motor torque falling rate are linearly related to the current motor torque, and the current motor torque is the motor target torque sent by the vehicle controller to the motor controller in the previous execution time cycle.

3. According to claim 1, a pure electric bus motor torque smoothing control method is characterized in that: The maximum motor torque rising rate and the maximum motor torque falling rate and the current motor torque are piecewise linear function relationships.

4. A pure electric bus motor torque smoothing control method according to claim 1, characterized in that: The calculation method of the maximum motor torque falling rate is as follows: When the current motor torque T is 0: △T2 = d; When the motor torque 0 < T ≤ T1: △T2 = j1*T + c1; When the motor torque T1 < T ≤ T2: △T2 = j2*T + c2; When the motor torque T2 < T ≤ Tmax: △T2 = j3*T + c3; Where, d is a constant, △T2 is the maximum motor torque falling rate, △T2 < 0; T1 and T2 are the critical values of motor torque segmentation respectively, T1 < T2; Tmax is the maximum motor torque; j1, j2, and j3 are the linear function coefficients between △T and T, and their magnitudes decrease in sequence, c1, b2, and c3 are the constant term parameters of the linear function between △T2 and T, and their magnitudes increase in sequence.

5. A pure electric bus motor torque smoothing control method according to claim 4, characterized in that: When the motor operates in any quadrant, the calculation methods of the maximum motor torque rising rate and the maximum motor torque falling rate are the same as those when the motor operates in the first quadrant.

6. A pure electric bus motor torque smoothing control method according to claim 5, characterized in that: The j1, j2, j3, c1, b2, c3 are respectively the opposites of k1, k2, k3, b1, b2, b3 in one-to-one correspondence.

7. A pure electric bus motor torque smoothing control system, characterized in that: It includes the following functional modules: A parameter calculation module, which is used to calculate the motor target torque for two adjacent execution time periods respectively based on the calculation execution cycle of the vehicle controller, and calculate the maximum motor torque rising rate and the maximum motor torque falling rate of the motor in the current operating state of the motor based on the current motor torque; A parameter comparison module, which is used to add the motor target torque of the previous execution time period to the maximum motor torque rising rate and the maximum motor torque falling rate respectively, and compare the obtained sums with the motor target torque of the next execution time period respectively; A maximum torque limit module, which is used to make the motor target torque of the next execution time period be the sum of the motor target torque of the previous execution time period and the maximum motor torque rising rate if the motor target torque of the next execution time period is greater than the sum of the motor target torque of the previous execution time period and the maximum motor torque rising rate; A minimum torque limit module, which is used to make the motor target torque of the next execution time period be the sum of the motor target torque of the previous execution time period and the maximum motor torque falling rate if the motor target torque of the next execution time period is less than the sum of the motor target torque of the previous execution time period and the maximum motor torque falling rate; The calculation method of the maximum motor torque rising rate is as follows: When the current motor torque T is 0: △T1 = a; When the motor torque 0 < T ≤ T1: △T1 = k1 * T + b1; When the motor torque T1 < T ≤ T2: △T1 = k2 * T + b2; When the motor torque T2 < T ≤ Tmax: △T1 = k3 * T + b3; Where, a is a constant, △T1 is the maximum motor torque rising rate, and △T1 > 0; T1 and T2 are respectively the critical values of the motor torque segmentation, T1 < T2; Tmax is the maximum motor torque; k1, k2, k3 are the first-order function coefficient parameters between △T1 and T, and their magnitudes increase in sequence; b1, b2, b3 are the constant term parameters of the first-order function between △T2 and T, and their magnitudes decrease in sequence.

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