A control method for vehicle energy recovery

Abstract

The present invention provides a method for controlling vehicle energy recovery, wherein the control comprises the following steps: Step 1: obtaining the current vehicle speed V k and the vehicle speed V at the previous moment k‑1 Calculate the difference between the above two vehicle speeds and collect the slope of the current vehicle road surface; Step 2, determine whether it is a downhill gliding condition. If it is gliding but not a downhill condition, enter the basic gliding energy recovery system, where the recovery torque of the basic gliding energy recovery is a lookup table T according to the vehicle speed. base If it is a downhill coasting condition, go to step 3; Step 3: Get the expected vehicle speed V des and real-time vehicle speed V k ; and calculate the expected vehicle speed V des and real-time vehicle speed V k The difference is used as the control deviation of the main controller; Step 4, the control variable of the main controller is obtained according to the control deviation of the main controller; Step 5, the control variable of the main controller is used as the given value of the Fu controller to obtain the control variable of the sub-controller. This control method has the advantages of good energy saving and high comfort.

Description

Technical Field

[0001] The present invention relates to the field of vehicle kinetic energy recovery, and in particular to a control method for vehicle energy recovery. Background Art

[0002] In order to improve the endurance of electric vehicles, electric vehicles are generally equipped with a sliding energy recovery system and a braking energy recovery system. During the motor braking process, the motor can be operated in a power generation state, which can generate a braking torque on the drive shaft, slow down the car to achieve a braking effect, and at the same time convert part of the car's braking energy into electrical energy and store it. On a long downhill, a system with sliding energy recovery can not only achieve the purpose of energy saving, but also effectively reduce the wear of the brakes and the thermal decay of the brakes. In order to improve the contribution to energy saving, the traditional sliding energy recovery system generally increases or decreases the sliding energy recovery strength in proportion to the vehicle speed and slope. The higher the speed and the greater the slope, the greater the sliding energy recovery, and the lower the speed and the smaller the slope, the smaller the sliding energy recovery. The traditional sliding energy recovery system has the following disadvantages: because the vehicle speed is not controlled when going downhill, it is sometimes necessary to step on the brake pedal frequently, and the driving comfort is poor. The increase or decrease of the motor braking torque of the sliding energy recovery caused by the change of vehicle speed will also affect the driving comfort. In the prior art, as described in patent CN210234676U, closed-loop PID control is performed on the vehicle speed during the downhill coasting energy recovery process to improve driving comfort.

[0003] The traditional coasting energy recovery system has the following disadvantages: because the vehicle speed is not controlled when going downhill, the brake pedal needs to be pressed frequently, which makes driving comfort poor. The sudden increase or decrease of the motor braking torque of the coasting energy recovery caused by the change of vehicle speed will also affect driving comfort.

[0004] For the vehicle speed control problem of gliding energy recovery in downhill conditions, common methods include the solution of CN210234676U, that is, in the process of gliding energy recovery in downhill conditions, PID (proportional integral differential) control is applied to control the motor braking torque and then control the vehicle speed. Due to bus delays, motor response delays and other interferences in motor control, this method will cause a large control error for a period of time at the beginning of control, and the system takes a long time to reach the balance point, resulting in inaccurate vehicle speed control and delays. And before reaching the balance point, the system sometimes continuously adjusts the motor braking torque command, so that the vehicle will shake due to the continuous addition and subtraction of negative torque by the motor. Summary of the invention

[0005] The present invention provides a control method for vehicle energy recovery based on the existing technical problems.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A control method for vehicle energy recovery includes a main controller and a sub-controller, wherein the main controller is used to control the vehicle speed, and the sub-controller is used to control the motor torque, and the control includes the following steps:

[0008] Step 1: Get the current vehicle speed V k and the vehicle speed V at the previous moment k-1 Calculate the difference between the two vehicle speeds and collect the slope of the current vehicle road surface;

[0009] Step 2: Determine whether it is a downhill gliding condition. If it is gliding but not a downhill gliding condition, enter the basic gliding energy recovery system, where the recovery torque of the basic gliding energy recovery is a table lookup based on the vehicle speed T base If it is a downhill sliding condition, go to the third step;

[0010] Step 3: Get the expected vehicle speed V des and real-time vehicle speed V k ; and calculate the expected vehicle speed V des and real-time vehicle speed V k The difference is taken as the control deviation of the main controller;

[0011] Step 4: derive the control variable of the main controller according to the control deviation of the main controller;

[0012] Step 5: Use the obtained control variable of the main controller as the given value of the Fu controller to obtain the control variable of the sub-controller;

[0013] Step 6: Output the control variables of the sub-controller to the motor controller.

[0014] As a preferred embodiment, the control variable acquisition model of the main controller in step 4 is as follows: the control deviation e of the proportional integral control of the main controller V =V des -V K The control variable of the main controller is ′U k =k p_1 (V des -V K )+k i_1 ∫(V des -V K )dt where k p_1 , k i_1 are the proportional and integral coefficients respectively.

[0015] As a preferred embodiment, in step 5, the control deviation of the proportional integral control of the sub-controller is e T =′U k -T K, the control variable of the sub-controller is U k =k p_2 (′U k -T K )+k i_2 ∫(′U k -T K )dt

[0016] where k p_2 , k i_2 are the proportional and integral coefficients respectively.

[0017] As a preferred embodiment, an anti-shake link is added between step 5 and step 6. When P1≤|U k -U k-1 |≤P2, output the control variable U at the previous moment k-1 Used by the motor controller to control the motor to generate negative torque; |U k -U k-1 |<P1 or |U k -U k-1 |>P2 outputs the control variable U at the current moment k Used by the motor controller to control the motor to generate negative torque.

[0018] As a preferred method, after the anti-shake link, it is determined whether a motor failure occurs or the MCU does not execute the motor braking torque command according to the motor braking torque command and the actual motor torque response. If these situations occur, the mechanical braking torque is used to compensate the expected motor braking torque, i.e., T com =U k ; Otherwise, the control variable of the sub-controller is output to the motor controller.

[0019] Preferably, the vehicle speed signal is acquired by a vehicle speed sensor.

[0020] As a preferred method of determining the downhill condition, when the slope is greater than k and lasts for a period of time t k , it is judged that this is a downhill condition.

[0021] This solution has the following beneficial effects:

[0022] The present invention proposes a new control method for the problem of low vehicle speed control accuracy and slow control steady state due to bus delay, motor response delay and other interference in motor control in downhill sliding energy recovery, as well as the problem of vehicle shaking during motor braking torque control. The method described in the present invention can improve the vehicle speed control accuracy and quickly enter a stable state when the system enters regenerative braking, and can also prevent the vehicle from generating large shaking during motor braking torque control, thereby ensuring safety and comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of cascade control.

[0024] Figure 2 This is the flow chart of motor braking torque control during coasting energy recovery. DETAILED DESCRIPTION

[0025] Example 1

[0026] A control method for vehicle energy recovery includes a main controller and a sub-controller, wherein the main controller is used to control the vehicle speed, and the sub-controller is used to control the motor torque, thereby improving the control accuracy of the vehicle speed, shortening the transition time of the system, and allowing the system to quickly reach a steady state. The control includes the following steps:

[0027] Step 1: Get the current vehicle speed V k and the vehicle speed V at the previous moment k-1 Calculate the difference between the two vehicle speeds and collect the slope of the current vehicle road surface;

[0028] Step 2: Determine whether it is a downhill gliding condition. If it is gliding but not a downhill gliding condition, enter the basic gliding energy recovery system, where the recovery torque of the basic gliding energy recovery is a table lookup based on the vehicle speed T base If it is a downhill sliding condition, go to the third step;

[0029] Step 3: Get the expected vehicle speed V des and real-time vehicle speed V k ; and calculate the expected vehicle speed V des and real-time vehicle speed V k The difference is taken as the control deviation of the main controller;

[0030] Step 4: derive the control variable of the main controller according to the control deviation of the main controller;

[0031] Step 5: Use the obtained control variable of the main controller as the given value of the Fu controller to obtain the control variable of the sub-controller;

[0032] Step 6: Output the control variables of the sub-controller to the motor controller.

[0033] In this embodiment, the control variable acquisition model of the main controller in step 4 is as follows: The control deviation e of the proportional integral control of the main controller V =V des -V K The control variable of the main controller is ′U k =k p_1 (V des -V K )+k i_1 ∫(V des -VK )dt

[0034] where k p_1 , k i_1 are the proportional and integral coefficients respectively.

[0035] In step 5, the control deviation of the proportional integral control of the sub-controller is e T =′U k -T K , the control variable of the sub-controller is U k =k p_2 (′U k -T K )+j i_2 ∫(′U k -T K )dt

[0036] where k p_2 , k i_2 are the proportional and integral coefficients respectively.

[0037] Before the system reaches the balance point, the system sometimes continuously adjusts the motor braking torque command. As the motor continuously adds and subtracts negative torque within a certain range, the vehicle will shake, so an anti-shake link needs to be added. In order to achieve the purpose of anti-shake, the following judgment should be made after the sub-controller PI link. An anti-shake link is also added between step 5 and step 6. When P1≤|U k -U k-1 |≤P2, output the control variable U at the previous moment k-1 Used by the motor controller to control the motor to generate negative torque; |U k -U k-1 |<P1 or |U k -U k-1 |>P2 outputs the control variable U at the current moment k The motor controller is used to control the motor to generate negative torque. k is the control variable of the current sub-controller PI controller, U k-1 is the control variable of the sub-controller PI controller at the previous moment. P1 and P2 can be calibrated according to the actual control situation.

[0038] In this embodiment, after the anti-shake link, it is determined whether a motor failure occurs or the MCU does not execute the motor braking torque command according to the motor braking torque command and the actual motor torque response. If these situations occur, the mechanical braking torque is used to compensate the expected motor braking torque, i.e., T com =U kOtherwise, the control variable of the sub-controller is output to the motor controller. If a motor failure occurs and the MCU does not respond to the braking torque command requested by the regenerative braking controller under special working conditions, a mechanical torque compensation T is required. com , to prevent dangerous situations from occurring.

[0039] In this embodiment, the vehicle speed signal is obtained by a vehicle speed sensor. The method for determining the downhill condition is: when the slope>k, and lasts for a period of time t k , it is judged that this is a downhill condition.

[0040] The present invention proposes a new control method for the problem of low vehicle speed control accuracy and slow control steady state due to bus delay, motor response delay and other interference in motor control in downhill sliding energy recovery, as well as the problem of vehicle shaking during motor braking torque control. The method described in the present invention can improve the vehicle speed control accuracy and quickly enter a stable state when the system enters regenerative braking, and can also prevent the vehicle from generating large shaking during motor braking torque control, thereby ensuring safety and comfort.

Claims

1. A control method for vehicle energy recovery, characterized in that: It includes a main controller and a sub-controller. The main controller is used to control the vehicle speed, and the sub-controller is used to control the motor torque. The control includes the following steps: Step 1: Get the current vehicle speed and the previous speed Calculate the difference between the two vehicle speeds and collect the slope of the current vehicle road surface; Step 2: Determine whether it is a downhill gliding condition. If it is gliding but not a downhill gliding condition, enter the basic gliding energy recovery system, where the recovery torque of the basic gliding energy recovery is a table lookup based on the vehicle speed. If it is a downhill sliding condition, go to the third step; Step 3: Get the expected speed and real-time speed ; and calculate the expected vehicle speed and real-time speed The difference is taken as the control deviation of the main controller; Step 4: derive the control variable of the main controller according to the control deviation of the main controller; Step 5: Use the obtained control variable of the main controller as the given value of the Fu controller to obtain the control variable of the sub-controller; Step 6: Output the control variable of the sub-controller to the motor controller; the control variable acquisition model of the main controller in step 4 is as follows: the control deviation of the proportional integral control of the main controller Control variables of the main controller in , are proportional and integral coefficients respectively; in step 5, the control deviation of the proportional integral control of the sub-controller is , the control variable of the sub-controller is in , are proportional and integral coefficients respectively; an anti-shake link is added between step 5 and step 6. When , the control variable of the previous moment is output To the motor controller to control the motor to generate negative torque; or Output the control variable at the current moment The motor controller is used to control the motor to generate negative torque; is the control variable of the current sub-controller PI controller, is the control variable of the sub-controller PI controller at the previous moment, , It can be calibrated according to the actual control situation.

2. The vehicle recycling control method according to claim 1, characterized in that: After the anti-shake link, the motor braking torque command and the actual motor torque response are used to determine whether a motor failure occurs or the MCU does not execute the motor braking torque command. If these situations occur, the mechanical braking torque is used to compensate for the expected motor braking torque. = ; Otherwise, the control variable of the sub-controller is output to the motor controller.

3. The vehicle recycling control method according to claim 1, characterized in that: The vehicle speed signal is obtained by the vehicle speed sensor.

4. The vehicle recycling control method according to claim 1, characterized in that: The method for determining a downhill condition is: when the slope is greater than k and lasts for a period of time , it is judged that this is a downhill condition.

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