A method and device for controlling hill driving of electric vehicle

Abstract

The present invention belongs to the field of electric vehicle control technology, and specifically relates to a method and device for controlling hill driving of an electric vehicle. When it is determined that the vehicle is slipping and the current slip motor speed is greater than the set slow slip speed, the method applies a reverse torque to the motor, and eventually causes the vehicle to continue to slip slowly at a speed lower than the set low speed; the applied reverse torque is positively correlated with the current slip motor speed; if the current slip motor speed is greater than or equal to the set limit speed, the applied reverse torque is the peak torque of the motor; the set limit speed is the motor speed corresponding to the set low speed. The reverse torque applied by the present invention does not stop the vehicle directly on the slope, but eventually causes the vehicle to continue to slip slowly at a very low speed, which can alleviate the degree of vehicle slippage during the slope parking and starting (or accelerator and brake pedal switching) stage to a certain extent, and avoid the risk of damage to the motor or motor controller caused by the continuous stall of the traditional hill-holding function motor.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric vehicle control, and in particular relates to a method and device for controlling hill driving of an electric vehicle. Background Art

[0002] When a vehicle stops on an uphill road, its own weight generates a downward force parallel to the slope, known as slope resistance. This resistance can cause the vehicle to slide backward down the slope, a phenomenon known as rolling. When a vehicle stops and then starts again while climbing, the driver must immediately apply the accelerator after applying the brakes. Otherwise, rolling will occur, which can be particularly frustrating for inexperienced drivers, leading to accidents.

[0003] To address this issue, a common method in the prior art is to stall the motor, applying a driving force to the motor to balance the vehicle's slope resistance, allowing the vehicle to remain stationary on the slope. However, stalling the motor to maintain the vehicle stationary on the slope cannot be prolonged, as this can cause excessive temperature rise and damage to the motor or motor controller. Summary of the Invention

[0004] The present invention provides a method and device for controlling hill driving of an electric vehicle, which are used to solve the problem that the prior art method causes damage to the motor or the motor controller.

[0005] To solve the above technical problems, the technical solutions included in the present invention and the corresponding beneficial effects of the technical solutions are as follows:

[0006] The present invention provides a method for controlling hill driving of an electric vehicle, comprising the following steps:

[0007] 1) Determine whether the vehicle is slipping;

[0008] 2) If the vehicle starts to slip, determine whether the current slip motor speed is greater than the set slow slip speed;

[0009] 3) If the current coasting motor speed is greater than the set slow coasting speed, reverse torque is applied to the motor, ultimately causing the vehicle to continue coasting at a speed lower than the set low speed.

[0010] Among them, the applied reverse torque is positively correlated with the current coasting motor speed; if the current coasting motor speed is the set slow coasting speed, the applied reverse torque is zero; if the current coasting motor speed is greater than or equal to the set limit speed, the applied reverse torque is the motor peak torque; the set limit speed is the motor speed corresponding to the set low vehicle speed, and the set limit speed is greater than the set slow coasting speed.

[0011] The beneficial effects of the above technical solution are as follows: the present invention addresses the possible sliding phenomenon of the vehicle on a slope by turning on a slow sliding control mode. The slow sliding control mode applies a reverse torque to the motor when it is found that the vehicle is sliding and the current sliding motor speed is greater than the set slow sliding speed. The greater the current sliding motor speed, the greater the reverse torque applied, and ultimately the vehicle is maintained at a state below the set low speed and continues to slide slowly. The reverse torque applied by this method does not stop the vehicle directly on the slope, but eventually causes the vehicle to continue to slide slowly at a very low speed. This can alleviate the degree of vehicle sliding backward during the slope parking and starting stage (or switching between the accelerator and brake pedals) to a certain extent, and can avoid the risk of damage to the motor or motor controller caused by the continuous stalling of the traditional hill-holding function motor.

[0012] Furthermore, in step 2), after determining that the vehicle is slipping, whether the motor speed is greater than the set slow slip speed is determined only after the following process is completed: if the vehicle is slipping, the vehicle is controlled to enter a hill-holding control mode and maintain it for a set time; the hill-holding control mode controls the motor to output a stall torque with zero speed as the target; and the vehicle is controlled to exit the hill-holding control mode to reduce the motor output torque.

[0013] Its beneficial effect is: after entering the hill-holding control mode and maintaining it for a set time, the slow rolling control mode will be used as a supplementary control mode after exiting the hill-holding control mode, alleviating the sudden and large-scale rolling caused by directly withdrawing the torque after exiting the hill-holding control mode, and avoiding the discomfort caused by the rapid increase in the vehicle's rolling speed after exiting (or failing) the single hill-holding mode.

[0014] Furthermore, the relationship between the applied reverse torque and the current coasting motor speed, the set slow coasting speed, and the set limit speed is:

[0015] T e =K*△n=K*(n-n1)

[0016]

[0017] Among them, T e is the applied reverse torque, K is the set proportional coefficient, T max is the peak torque of the motor, n2 is the set limit speed, n1 is the set slow coasting speed, and n is the current coasting motor speed.

[0018] The beneficial effect is that the applied reverse torque is linearly positively correlated with the current sliding motor speed, and the applied reverse torque can be simply and quickly calculated.

[0019] Furthermore, in step 1), whether the vehicle is slipping is determined based on the following conditions: if the vehicle gear is in N, D or R, the brake pedal and accelerator pedal openings are both zero, and the motor rotation direction changes, then it is determined that the vehicle is slipping; wherein, the change in the motor rotation direction includes: the motor rotation direction changes from forward to reverse, the motor rotation direction changes from reverse to forward, or the motor speed changes from zero to non-zero.

[0020] Its beneficial effects are: N gear is also included in the conditions for judging whether the vehicle is rolling, which expands the application scope of the vehicle starting on a slope or short-term parking on a slope, improves the convenience of vehicle operation, and reduces the safety risks caused by rapid rolling due to misoperation (shifting into N gear).

[0021] Furthermore, the slow rolling speed is set to 30r / min.

[0022] Furthermore, the set limit speed is 200r / min.

[0023] The present invention also provides a hill driving control device for an electric vehicle, comprising a memory and a processor, wherein the processor is configured to execute instructions stored in the memory to implement the hill driving control method for an electric vehicle described above and achieve the same beneficial effects as the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of a hill-running control method for an electric vehicle with only a slow-slip control mode according to the present invention;

[0025] Figure 2 Schematic diagram of the relationship between the reverse torque applied in the slow-rolling control mode of the present invention and the current rolling motor speed, the set slow-rolling speed, and the set limit speed;

[0026] Figure 3 This is a flow chart of a method for controlling a hill-going vehicle of the present invention, which combines a hill-holding control mode with a slow-slip control mode;

[0027] Figure 4 It is a structural schematic diagram of the hill-climbing control device for an electric vehicle of the present invention. DETAILED DESCRIPTION

[0028] Method Example 1:

[0029] An embodiment of a method for controlling hill driving of an electric vehicle according to the present invention has the following process: Figure 1 When the control method introduced in this embodiment is used to control the vehicle, there is only a slow-climbing control mode but no hill-holding control mode.

[0030] Step 1: First, determine whether the vehicle is experiencing a rollback phenomenon. If the vehicle exhibits the following states (the following three states are in an AND relationship), it is determined that the vehicle is experiencing a rollback phenomenon:

[0031] 1) The vehicle is in N gear, R gear, or D gear;

[0032] 2) The brake is not pressed and the accelerator is not pressed;

[0033] 3) Considering the rotation direction of the motor in the previous state of the motor, if the rotation direction of the motor changes, such as from forward rotation to reverse rotation, from reverse rotation to forward rotation, or the motor speed changes from zero (stationary) to non-zero.

[0034] Step 2: When it is determined that the vehicle is experiencing a rollback phenomenon, judge the current rollback motor speed n. Determine whether the current rollback motor speed n is greater than the set slow rollback speed n1 (= 30 r / min): If n < n1, no action is taken; if n ≥ n1, the vehicle enters the slow rollback control mode and Step 3 is executed.

[0035] Step 3: When n ≥ n1, at this time, according to the slope condition of the vehicle, within the range of the motor system's ability, apply a reverse torque T to the motor e to prevent the rollback motor speed from increasing further. During this process, the vehicle continues to slowly roll back at a speed between n1 and n2. n2 is the set limit speed, which needs to be set according to the vehicle's power system parameters. Generally, it can be set as the motor speed corresponding to a vehicle speed of 1 - 2 km / h, for example, 200 r / min.

[0036] Moreover, the applied reverse torque T e should be positively correlated with the current rollback motor speed n, and when n = n1, T e = 0, when n ≥ n2, T e = T max , T max is the peak torque of the motor output by the motor system (unit: N·m). For example, the applied reverse torque T e and the current rollback motor speed n can be a linear relationship, and its relationship diagram is as shown in Figure 2 the curve ① in, and the slope of the curve ① is the set proportionality coefficient K, and the set proportionality coefficient is: Therefore, the magnitude of the applied reverse torque T e is: T e = K * △n = K * (n - n1), and when n > n2, T e = T max . Also, for example, the applied reverse torque T e and the current rollback motor speed n can be a non-linear relationship, and its relationship diagram is as shown in Figure 2As shown by curve ② in the figure, at this time, it is necessary to calibrate a set of applied reverse torques T according to the actual operating conditions of the vehicle and in combination with ramps at several different angles. e The corresponding relationship curve with the current vehicle coasting motor speed n is used to improve the driving smoothness.

[0037] For the ramp driving control method of the electric vehicle of the present invention, the applied reverse torque does not directly stop the vehicle on the ramp, but finally makes the vehicle coast slowly at a very low speed, which can alleviate the vehicle backward degree during the ramp parking start (or the throttle and brake pedal switching) stage to a certain extent, and can avoid the damage risk to the motor or the motor controller caused by the continuous stall of the motor in the traditional slope holding function. Moreover, when judging whether the vehicle has a coasting phenomenon, the situation of the N gear is also taken into account, expanding the application range of the vehicle ramp start, improving the vehicle operation convenience, and reducing the safety risk caused by the rapid coasting due to misoperation (shifting into the N gear).

[0038] Method Embodiment 2:

[0039] An embodiment of a ramp driving control method for an electric vehicle of the present invention has a flow as Figure 3 shown. When controlling the vehicle using the control method introduced in this embodiment, the slow coasting control mode and the slope holding control mode are combined.

[0040] Step 1, first judge whether the vehicle has a coasting phenomenon. If the vehicle has the following states (the following three states are in an AND relationship), it is determined that the vehicle has a coasting phenomenon:

[0041] 1) The vehicle is in N gear, R gear or D gear;

[0042] 2) Neither the brake nor the accelerator is depressed;

[0043] 3) Combining the rotation direction of the motor in the previous state of the motor, if the rotation direction of the motor changes, for example, from the original forward rotation to reverse rotation, from the original reverse rotation to forward rotation, or the motor speed changes from zero (stationary) to non-zero.

[0044] Step 2, when it is determined that the vehicle has a coasting phenomenon, control the vehicle to enter the slope holding control mode and continue for a set time (3 - 5 s). During the vehicle enters the slope holding control mode, control the motor to output a stall torque with zero speed as the target. After the set time arrives, control the vehicle to exit the slope holding control mode, and the motor controller reduces the torque output.

[0045] Step 3, after the vehicle exits the slope holding control mode, judge the current coasting motor speed n, and judge whether the current coasting motor speed n is greater than the set slow coasting speed n1 (for example, n1 = 30 r / min, which can be set according to actual requirements): If n < n1, no processing is performed; if n ≥ n1, the vehicle enters the slow coasting control mode and executes Step 4.

[0046] Step 4: When n≥n1, it is necessary to apply a reverse torque T to the motor within the capacity of the motor system according to the slope of the vehicle. e This prevents the motor from increasing further during the rollover, ultimately causing the vehicle to continue to roll slowly at speeds between n1 and n2. n2 is the set speed limit, which needs to be set based on the vehicle's powertrain parameters. It can generally be set to the motor speed corresponding to a vehicle speed of 1 to 2 km / h, for example, 200 r / min.

[0047] Moreover, the applied reverse torque T e It needs to be positively correlated with the current sliding motor speed n, and when n=n1, T e =0, n≥n2, T e =T max , T max The peak torque of the motor applied to the motor system (unit: Nm). For example, the applied reverse torque T e It can be linearly related to the current sliding motor speed n, as shown in the figure below: Figure 2 As shown in curve ① in the figure, the slope of curve ① is the set proportional coefficient K, and the set proportional coefficient is: Therefore, the applied reverse torque T e The size is: T e =K*△n=K*(n-n1), and when n>n2, T e =T max For example, the applied reverse torque T e It can be nonlinearly related to the current sliding motor speed n, as shown in the following diagram: Figure 2 As shown in curve ② in the figure, it is necessary to calibrate a set of applied reverse torques T according to the actual operating conditions of the vehicle and several ramps with different angles. e The corresponding relationship curve with the current coasting motor speed n is used to improve driving smoothness.

[0048] The hill-driving control method for an electric vehicle of the present invention combines a hill-holding control mode with a slow-rolling control mode. When a hill-rolling phenomenon occurs, the vehicle first enters the hill-holding control mode, but this control mode only lasts for a very short period of time (3 to 5 seconds). After exiting the hill-holding control mode, the vehicle enters the slow-rolling control mode. The slow-rolling control mode is used as a supplementary control mode after exiting the hill-holding control mode to alleviate the sudden and large-scale hill-rolling caused by directly withdrawing the torque after exiting the hill-holding control mode, and avoid the discomfort caused by the rapid increase in the vehicle's rolling speed after exiting (or failing) the single hill-holding mode.

[0049] Device Example:

[0050] An embodiment of a hill-climbing control device for an electric vehicle according to the present invention is as follows: Figure 4As shown, the system includes a memory, a processor, and an internal bus. The processor and memory communicate and exchange data with each other via the internal bus. The memory includes at least one software function module stored in the memory. The processor executes various functional applications and data processing by running the software programs and modules stored in the memory, thereby implementing the hill-driving control method for an electric vehicle described in Method Examples 1 and 2 of the present invention.

[0051] The processor may be a microprocessor MCU, a programmable logic device FPGA or other processing devices.

[0052] The memory can be various types of memories that use electrical energy to store information, such as RAM, ROM, etc.; it can also be various types of memories that use magnetic energy to store information, such as hard disks, floppy disks, magnetic tapes, magnetic core memories, bubble memories, USB flash drives, etc.; it can also be various types of memories that use optical methods to store information, such as CDs, DVDs, etc.; of course, it can also be other types of memories, such as quantum memories, graphene memories, etc.

Claims

1. A method for controlling an electric vehicle on a slope, characterized in that: The steps include: 1) Determine whether the vehicle is slipping; 2) If the vehicle starts to slip, determine whether the current slip motor speed is greater than the set slow slip speed; 3) If the current coasting motor speed is greater than the set slow coasting speed, reverse torque is applied to the motor, ultimately causing the vehicle to continue coasting at a speed lower than the set low speed. Among them, the applied reverse torque is nonlinearly positively correlated with the current coasting motor speed. This relationship is calibrated according to the actual operating conditions of the vehicle and combined with ramps of different angles to improve driving smoothness; if the current coasting motor speed is the set slow coasting speed, the applied reverse torque is zero; if the current coasting motor speed is greater than or equal to the set limit speed, the applied reverse torque is the motor peak torque; the set limit speed is the motor speed corresponding to the set low vehicle speed, and the set limit speed is greater than the set slow coasting speed.

2. The hill-running control method for an electric vehicle according to claim 1, wherein: In step 2), after determining that the vehicle is slipping, it is determined whether the motor speed is greater than the set slip speed only after the following process is completed: If the vehicle starts to roll, the vehicle will enter the hill-holding control mode and continue for the set time; The hill-holding control mode controls the motor to output stall torque with zero speed as the target; Control the vehicle to exit the hill-holding control mode to reduce the motor output torque.

3. The hill-running control method for an electric vehicle according to claim 1 or 2, characterized in that: In step 1), whether the vehicle is rolling is determined based on the following conditions: if the vehicle gear is in N gear, D gear or R gear, the brake pedal and accelerator pedal openings are both zero, and the motor rotation direction changes, then it is determined that the vehicle is rolling; wherein, the change in the motor rotation direction includes: the motor rotation direction changes from forward to reverse, the motor rotation direction changes from reverse to forward, or the motor speed changes from zero to non-zero.

4. The hill-running control method for an electric vehicle according to claim 1 or 2, characterized in that: The set slow rolling speed is 30r / min.

5. The hill-running control method for an electric vehicle according to claim 1 or 2, characterized in that: The set limit speed is 200r / min.

6. A hill-climbing control device for an electric vehicle, characterized in that: The method comprises a memory and a processor, wherein the processor is configured to execute instructions stored in the memory to implement the hill-driving control method for an electric vehicle according to any one of claims 1 to 5.

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