Energy-saving motor torque control method and device for pure electric vehicle and storage medium

Abstract

The invention discloses an energy-saving motor torque control method for a pure electric vehicle, and the method comprises the steps: calculating a first expected motor torque according to the collected opening degree of an accelerator pedal or the opening degree of a brake pedal and the rotating speed of a motor; based on the first expected motor torque, the expected speed of the vehicle at the next moment is calculated through a vehicle running resistance equation, according to the expected speed, the second expected motor torque of the energy-saving running mode is calculated through a state matrix of the vehicle and a corresponding cost function, and the weight coefficient of the cost function is determined through fuzzy logic control; and determining the first expected motor torque or the second expected motor torque as the required motor torque according to the difference between the first expected motor torque and the second expected motor torque. The invention further discloses a device for achieving the energy-saving motor torque control method for the pure electric vehicle and a computer storage medium. On the basis of meeting the drivability, the energy consumption of the battery can be better reduced, and the endurance mileage of the automobile is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicle power control, and in particular to a motor torque control method, device and storage medium for energy-saving pure electric vehicles. Background Art

[0002] Pure electric vehicles are more environmentally friendly than traditional fuel vehicles and have become a means of transportation for more and more people. However, when driving at high speeds, the battery consumes a lot of energy, and driving electric vehicles often causes people to have range anxiety. The existing electric vehicle control system uses kinetic energy recovery strategies to reduce energy consumption, and also uses motor output torque control methods to save electricity during non-braking processes. However, these motor output torque control methods are usually designed to achieve a specific range. In the energy-saving state, it is often difficult to meet the driver's driving intentions, and the vehicle's feedback to the driver is poor. Summary of the invention

[0003] In view of the above-mentioned defects of the prior art, the present invention provides a motor torque control method for energy-saving pure electric vehicles, which reduces the energy consumption of the vehicle while meeting the drivability and conforming to the driver's driving intention. Another object of the present invention is to provide a motor torque control device for energy-saving pure electric vehicles and a corresponding computer storage medium.

[0004] The technical solution of the present invention is as follows: A motor torque control method for energy saving of a pure electric vehicle comprises the following steps:

[0005] Calculating a first expected motor torque in a torque regulation mode according to the acquired accelerator pedal opening or brake pedal opening and motor speed;

[0006] Based on the first expected motor torque, the expected speed of the vehicle at the next moment is calculated by the vehicle driving resistance equation, and according to the expected speed, the second expected motor torque of the energy-saving driving mode is calculated by the vehicle state matrix and the corresponding cost function, wherein the weight coefficient of the cost function is determined by fuzzy logic control based on the change rate of the accelerator pedal opening or the brake pedal opening and the current vehicle speed;

[0007] When the difference between the first expected motor torque and the second expected motor torque is within a set threshold range, the first expected motor torque is used as the required motor torque; otherwise, the second expected motor torque is used as the required motor torque.

[0008] Furthermore, when calculating the first expected motor torque, the accelerator pedal opening or the brake pedal opening and the motor speed are used as inputs to perform a two-dimensional table lookup to obtain the torque.

[0009] Furthermore, the vehicle driving resistance equation is:

[0010]

[0011] Where δ is the vehicle rotation mass conversion coefficient; F is the driving force; m is the vehicle mass; f is the rolling resistance coefficient; C D is the air resistance coefficient; A is the frontal area of ​​the vehicle; ρ is the air density; v k is the speed of the vehicle; θ is the inclination angle of the road; F k =T mot / r,T mot is the first desired motor torque, r is the wheel radius, and v is the desired speed at the next moment k+1 =v k +a k ×t step , t step The time interval between the next moment and the current moment.

[0012] Furthermore, the state matrix of the vehicle is

[0013]

[0014] Among them, v(k+1), v(k) are the vehicle speeds at time k+1 and k respectively, a(k+1), a(k) are the vehicle accelerations at time k+1 and k respectively, j(k+1), j(k) are the vehicle impact degrees at time k+1 and k respectively, τ is the time constant;

[0015] The cost function is

[0016] J Energy =ω1·J fol +ω2·J com +ω3·J eco

[0017] J fol =(v des -v real ) 2

[0018] J com =a 2 +j 2

[0019]

[0020] Among them, J fol is a follow-up indicator, J com is the comfort index, J eco is the economic index, ω1, ω2, ω3 are the weight coefficients of each index, v des is the expected speed v des =vk+1 , v real is the actual vehicle speed, Where σ is the battery charge and discharge efficiency, C N is the battery capacity and I is the battery current.

[0021] Furthermore, when the weight coefficient of the cost function is determined, the change rate of the accelerator pedal opening or the brake pedal opening and the current vehicle speed are divided into {small, medium, large}, and the weight coefficient of the cost function is divided into {small, medium-small, medium, medium-large, large}.

[0022] The present invention also provides an energy-saving motor torque control device for a pure electric vehicle, comprising:

[0023] A first torque calculation module, used for calculating a first expected motor torque of a torque regulation mode according to the acquired accelerator pedal opening or brake pedal opening and motor speed;

[0024] a second torque calculation module, configured to calculate an expected speed of the vehicle at a next moment through a vehicle driving resistance equation based on the first expected motor torque, and calculate a second expected motor torque of the energy-saving driving mode according to the expected speed through a state matrix of the vehicle and a corresponding cost function, wherein a weight coefficient of the cost function is determined by fuzzy logic control based on a rate of change of an accelerator pedal opening or a brake pedal opening and a current vehicle speed;

[0025] And, an actual torque output module is used to use the first expected motor torque as the required motor torque when the difference between the first expected motor torque and the second expected motor torque is within a set threshold range, and otherwise use the second expected motor torque as the required motor torque.

[0026] The present invention also provides a computer storage medium on which a computer program is stored. When the computer program is executed by a processor, the motor torque control method for energy saving of the pure electric vehicle is implemented.

[0027] Compared with the prior art, the advantages of the technical solution provided by the present invention are:

[0028] The present invention solves a suitable driving mode based on designing a cost function and establishing a state equation. In order to allow the driver to obtain corresponding driving feedback, a suitable motor torque request value is obtained through fuzzy logic design and subsequent expected torque difference judgment. This can better reduce battery energy consumption and increase the vehicle's cruising range while satisfying drivability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the motor torque control method for energy saving in pure electric vehicles. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading this description, various equivalent modifications to this description by those skilled in the art fall within the scope defined by the claims attached to this application.

[0031] The energy-saving motor torque control device of a pure electric vehicle according to the embodiment of the present invention comprises:

[0032] A first torque calculation module, used for calculating a first expected motor torque of a torque regulation mode according to the acquired accelerator pedal opening or brake pedal opening and motor speed;

[0033] a second torque calculation module, for calculating an expected speed of the vehicle at a next moment through a vehicle driving resistance equation based on the first expected motor torque, and calculating a second expected motor torque of the energy-saving driving mode according to the expected speed through a state matrix of the vehicle and a corresponding cost function, wherein a weight coefficient of the cost function is determined by fuzzy logic control based on a rate of change of an accelerator pedal opening or a brake pedal opening and a current vehicle speed;

[0034] And, an actual torque output module is used to use the first expected motor torque as the required motor torque when the difference between the first expected motor torque and the second expected motor torque is within a set threshold range, and otherwise use the second expected motor torque as the required motor torque.

[0035] The motor torque control device realizes the energy-saving motor torque control method of pure electric vehicles. Figure 1 As shown, the specific implementation steps include the following:

[0036] First, the first torque calculation module obtains the driver's intention signal through analog signal and digital signal acquisition and CAN message, so as to calculate the first expected motor torque of the torque adjustment mode;

[0037] The analog signals include accelerator pedal signal and brake pedal signal; the signal obtained in the CAN message is the motor speed.

[0038] The expected torque of the torque regulation mode is obtained based on a two-dimensional table lookup module, with the accelerator pedal signal or the brake pedal signal, the motor speed as input, and the motor torque as output. The specific value is obtained based on the actual vehicle calibration.

[0039] Then, the second torque calculation module calculates the second expected motor torque according to the first expected motor torque calculated by the first torque calculation module, specifically:

[0040] According to the motor torque obtained above, the vehicle speed at the next moment can be calculated through the vehicle driving resistance equation. The vehicle driving resistance equation is:

[0041]

[0042] Where δ is the vehicle rotation mass conversion coefficient; F is the driving force; m is the vehicle mass; f is the rolling resistance coefficient; C D is the air resistance coefficient; A is the frontal area of ​​the vehicle; ρ is the air density; v k is the speed of the vehicle; θ is the inclination angle of the road; F k =T mot / r,T mot is the first desired motor torque, r is the wheel radius, and v is the desired speed at the next moment k+1 =v k +a k ×t step , t step The time interval between the next moment and the current moment.

[0043] The expected speed v at the next moment k+1 As the speed in the vehicle energy-saving control mode, the expected torque of the motor under energy-saving driving is calculated through the vehicle's state matrix and the corresponding cost function is designed.

[0044] The state matrix is ​​as follows:

[0045] X(k+1)=A·X(k)+B·u(k)

[0046] Expands to:

[0047]

[0048] Among them, v(k+1), v(k) are the vehicle speeds at time k+1 and k respectively, a(k+1), a(k) are the vehicle accelerations at time k+1 and k respectively, j(k+1), j(k) are the vehicle impact degrees at time k+1 and k respectively, that is, The parameter that can characterize comfort, t step is the acquisition step length, and τ is the time constant. The acceleration uses the first-order inertial link to represent the actual transmission characteristics, that is, Transformed into the transmission state at time k, we can get Similarly, the relationship between j(k+1) and j(k) can be obtained.

[0049] The corresponding cost function is as follows:

[0050] J Energy =ω1·J fol +ω2·Jcom +ω3·J eco

[0051] J fol =(v des -v real ) 2

[0052] J com =a 2 +j 2

[0053]

[0054] Among them, J fol is a follow-up indicator, J com is the comfort index, J eco is the economic index, ω1, ω2, ω3 are the weight coefficients of each index, Where σ is the battery charge and discharge efficiency, C N is the battery capacity and I is the battery current.

[0055]

[0056] P is the motor power, U is the motor voltage, T is the torque, n is the speed, and η is the motor efficiency.

[0057] The weight coefficient of each indicator is determined according to fuzzy logic, with the absolute value of the change rate of the accelerator pedal and the brake pedal and the vehicle speed as input, and the economic weight coefficient as output. The specific logic is as follows:

[0058]

[0059] Among them, the economic weight coefficient is divided into {S, MS, M, MB, B} according to the fuzzy subset, which respectively represents {small,

[0060] The fuzzy domain of vehicle speed is set to [0, 120], and its fuzzy subsets are divided into {small, medium, medium, medium-large, large}.

[0061] medium, large}, represented by the letters {S, M, B}, when the vehicle speed v∈[0,40) is small, v∈[40,80) is medium, and v∈

[0062] [80,120] is large. The absolute value fuzzy domain of the rate of change of the accelerator pedal and brake pedal opening is set to [0,300], and its fuzzy subsets are divided into {small, medium, large}, represented by letters {S, M, B}, |d acc| or|d brk| ∈[0,50) is small, |d acc| or|d brk|∈[50,100) is the middle, |d acc| or|d brk| ∈[100,300] is large. The following and comfort weights ω1 and ω2 are fixed values, and the specific weight coefficients representing the three performances need to be calibrated according to the vehicle type. In this embodiment, in order to take into account both the computational complexity and the vehicle's energy efficiency, N=10 is taken as the prediction step length. Within the prediction step length at time k, the vehicle's state is as follows:

[0063]

[0064] Let X k =[X(k+1),...,X(k+9),X(k+10)] T , U k =[u(k+1),...,u(k+9)] T , the vehicle state under the prediction step can be expressed as follows:

[0065]

[0066] According to the above cost function, let J driv =ω1·J fol +ω2·J com , X ref (k)=(v des ,0,0) T , we can get the prediction step size:

[0067]

[0068] Where Q = diag[ω 1， ω 2， ω2] 3×3 ,

[0069] For the economic index, since the coefficient does not affect the rate of change, it can be ignored. According to the driving force resistance equation, the motor torque is a linear function of the acceleration. The new economic index J is taken as eco .

[0070]

[0071] Based on the least squares method, the entire prediction process can be solved to obtain a des =min(J driv +J eco ), and then the second expected motor torque in the energy-saving control mode can be obtained by reverse deduction based on the driving force resistance equation.

[0072] Finally, the actual required motor torque is determined based on the difference between the first expected motor torque and the second expected motor torque calculated above, and a threshold of the difference is set, which is determined according to the vehicle type. When the difference between the first expected motor torque and the second expected motor torque exceeds the threshold, the torque adjustment mode is adopted to better allow the driver to get driving feedback. Otherwise, the motor torque is requested in the energy-saving control mode.

[0073] It should also be pointed out that the energy-saving motor torque control method for a pure electric vehicle in the above-mentioned embodiment can form a computer program product. Therefore, the computer program product implemented in this application can be stored on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.).

Claims

1. A motor torque control method for energy saving of a pure electric vehicle, characterized in that: Includes steps: Calculating a first expected motor torque in a torque regulation mode according to the acquired accelerator pedal opening or brake pedal opening and motor speed; Based on the first expected motor torque, the expected speed of the vehicle at the next moment is calculated by the vehicle driving resistance equation, and according to the expected speed, the second expected motor torque of the energy-saving driving mode is calculated by the vehicle state matrix and the corresponding cost function, wherein the weight coefficient of the cost function is determined by fuzzy logic control based on the change rate of the accelerator pedal opening or the brake pedal opening and the current vehicle speed; When the difference between the first expected motor torque and the second expected motor torque is within a set threshold range, the first expected motor torque is used as the required motor torque; otherwise, the second expected motor torque is used as the required motor torque.

2. The energy-saving motor torque control method of a pure electric vehicle according to claim 1 is characterized in that: When calculating the first expected motor torque, the accelerator pedal opening or the brake pedal opening and the motor speed are used as inputs to perform a two-dimensional table lookup to obtain the torque.

3. The energy-saving motor torque control method of a pure electric vehicle according to claim 1, characterized in that: The vehicle driving resistance equation is: Where δ is the vehicle rotation mass conversion coefficient; F is the driving force; m is the vehicle mass; f is the rolling resistance coefficient; C D is the air resistance coefficient; A is the frontal area of ​​the vehicle; ρ is the air density; v k is the speed of the vehicle; θ is the inclination angle of the road; F k =T mot / r,T mot is the first desired motor torque, r is the wheel radius, and v is the desired speed at the next moment k+1 =v k +a k ×t step , t step The time interval between the next moment and the current moment.

4. The energy-saving motor torque control method of a pure electric vehicle according to claim 1 is characterized in that: The state matrix of the vehicle is Among them, v(k+1), v(k) are the vehicle speeds at time k+1 and k respectively, a(k+1), a(k) are the vehicle accelerations at time k+1 and k respectively, j(k+1), j(k) are the vehicle impact degrees at time k+1 and k respectively, τ is the time constant; The cost function is I Energy =ω1·J fol +ω2·J com +ω3·J eco J fol =(in des -v real ) 2 I com that 2 +j 2 Among them, J fol is a follow-up indicator, J com is the comfort index, J eco is the economic index, ω1, ω2, ω3 are the weight coefficients of each index, v des is the expected speed v des =v k+1 , v real is the actual vehicle speed, Where σ is the battery charge and discharge efficiency, C N is the battery capacity and I is the battery current.

5. The energy-saving motor torque control method of a pure electric vehicle according to claim 1, characterized in that: When the weight coefficient of the cost function is determined, the change rate of the accelerator pedal opening or the brake pedal opening and the current vehicle speed are divided into {small, medium, large}, and the weight coefficient of the cost function is divided into {small, medium-small, medium, medium-large, large}.

6. A motor torque control device for energy saving of a pure electric vehicle, characterized in that: include: A first torque calculation module, used for calculating a first expected motor torque of a torque regulation mode according to the acquired accelerator pedal opening or brake pedal opening and motor speed; a second torque calculation module, configured to calculate an expected speed of the vehicle at a next moment through a vehicle driving resistance equation based on the first expected motor torque, and calculate a second expected motor torque of the energy-saving driving mode according to the expected speed through a state matrix of the vehicle and a corresponding cost function, wherein a weight coefficient of the cost function is determined by fuzzy logic control based on a rate of change of an accelerator pedal opening or a brake pedal opening and a current vehicle speed; And, an actual torque output module is used to use the first expected motor torque as the required motor torque when the difference between the first expected motor torque and the second expected motor torque is within a set threshold range, and otherwise use the second expected motor torque as the required motor torque.

7. The energy-saving motor torque control device for a pure electric vehicle according to claim 6 is characterized in that: The vehicle driving resistance equation is: Where δ is the vehicle rotation mass conversion coefficient; F is the driving force; m is the vehicle mass; f is the rolling resistance coefficient; C D is the air resistance coefficient; A is the frontal area of ​​the vehicle; ρ is the air density; v k is the speed of the vehicle; θ is the inclination angle of the road; F k =T mot / r,T mot is the first desired motor torque, r is the wheel radius, and v is the desired speed at the next moment k+1 =v k +a k ×t step , t step The time interval between the next moment and the current moment.

8. The energy-saving motor torque control device for a pure electric vehicle according to claim 6, characterized in that: The state matrix of the vehicle is Among them, v(k+1), v(k) are the vehicle speeds at time k+1 and k respectively, a(k+1), a(k) are the vehicle accelerations at time k+1 and k respectively, j(k+1), j(k) are the vehicle impact degrees at time k+1 and k respectively, τ is the time constant; The cost function is I Energy =ω1·J fol +ω2·J com +ω3·J eco J fol =(in des -v real ) 2 I com that 2 +j 2 Among them, J fol is a follow-up indicator, J com is the comfort index, J eco is the economic index, ω1, ω2, ω3 are the weight coefficients of each index, v des is the expected speed v des =v k+1 , v real is the actual vehicle speed, Where σ is the battery charge and discharge efficiency, C N is the battery capacity and I is the battery current.

9. The energy-saving motor torque control device for a pure electric vehicle according to claim 6, characterized in that: When the weight coefficient of the cost function is determined, the change rate of the accelerator pedal opening or the brake pedal opening and the current vehicle speed are divided into {small, medium, large}, and the weight coefficient of the cost function is divided into {small, medium-small, medium, medium-large, large}.

10. A computer storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for controlling the energy-saving motor torque of a pure electric vehicle according to any one of claims 1 to 5 is implemented.

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