A vehicle speed control method and device for low-speed driving of an electric vehicle

Abstract

The embodiment of the application discloses a kind of electric vehicle low-speed driving vehicle speed control method and device, method includes: in the vehicle stationary state control vehicle start moving, and based on drive motor speed, driving wheel speed and driven wheel speed calculation determines first vehicle speed;If first vehicle speed is lower than set speed threshold, using integral control determines first integral torque, and first integral torque is as total drive torque control vehicle operation;If first vehicle speed is not lower than set speed threshold, based on drive motor speed calculation determines second vehicle speed;Based on second vehicle speed, variable speed integral control is carried out, and based on the result of variable speed integral control, total drive torque controls vehicle operation.The above scheme divides the low-speed driving of vehicle into different control stages, and the control of different control stages can adapt to the problem of inaccurate sensor, starting resistance change and the like under low-speed driving condition to a certain extent, to realize the low-speed stable driving of vehicle.

Description

Technical Field

[0001] This application relates to the field of vehicle dynamics control technology, and more specifically, to a method and device for controlling the speed of an electric vehicle at low speeds. Background Technology

[0002] In some scenarios, vehicles need to maintain stable low-speed driving, such as in situations involving stopping at a fixed point or short-distance movement. For typical electric vehicles, low-speed control is usually achieved through cruise control or creep control, while there are also solutions that combine braking system control to further improve the smoothness of starting.

[0003] Traditional electric vehicle cruise control or crawl control does not take into account issues such as sensor accuracy at low speeds, inaccurate braking force control, and sudden changes in driving resistance during start-up. This may lead to overshoot and inaccurate speed control at low speeds, and it is also impossible to further utilize stable speed control to achieve precise control of small displacements. Summary of the Invention

[0004] In view of the above, this application provides the following technical solution:

[0005] A method for controlling the speed of an electric vehicle at low speeds, comprising:

[0006] Control the vehicle to start moving when the vehicle is stationary, and calculate and determine the first vehicle speed based on the speed of the drive motor, the speed of the drive wheels and the speed of the driven wheels;

[0007] If the first vehicle speed is lower than the set speed threshold, integral control is used to determine the first integral torque, and the first integral torque is used as the total drive torque to control the vehicle operation.

[0008] If the first vehicle speed is not lower than the set speed threshold, the second vehicle speed is calculated and determined based on the drive motor speed.

[0009] Based on the second vehicle speed, integral speed control is performed, and based on the result of the integral speed control, the total drive torque is determined to control the vehicle operation.

[0010] Optionally, the step of controlling the vehicle to start moving while the vehicle is stationary, and calculating and determining the first vehicle speed based on the speed of the drive motor, the speed of the drive wheels, and the speed of the driven wheels, includes:

[0011] The maximum speed among the vehicle speeds calculated based on the rotational speed of each drive motor, the rotational speed of each drive wheel, and the speed calculated based on each driven wheel is determined as the first vehicle speed.

[0012] Optionally, the set speed threshold is determined based on the minimum resolution rotational speed of the drive motor, drive wheel, and driven wheel.

[0013] Optionally, the step of determining the second vehicle speed based on the drive motor speed if the first vehicle speed is not lower than the set speed threshold includes:

[0014] If the first vehicle speed is not lower than the set speed threshold, calculate the vehicle speed corresponding to the speed of all drive motors and determine the maximum vehicle speed among all vehicle speeds;

[0015] The second vehicle speed is obtained by performing low-pass filtering based on the maximum vehicle speed.

[0016] Optionally, the step of performing variable speed integral control based on the second vehicle speed and determining the total drive torque to control vehicle operation based on the result of the variable speed integral control includes:

[0017] Based on the second vehicle speed, variable speed integral control is performed to determine the second integral torque and the proportional torque, wherein the update frequencies of the second integral torque and the proportional torque are different.

[0018] The range of values ​​for the total control torque is determined based on the second integral torque and the proportional torque.

[0019] The total control torque is used as the total drive torque to control the vehicle's operation.

[0020] Optionally, the step of performing variable speed integral control based on the second vehicle speed to determine the second integral torque and proportional torque includes:

[0021] Determine whether the integration conditions are met;

[0022] If the conditions are not met, the second vehicle speed will be used as the feedback vehicle speed to determine the proportional torque;

[0023] If satisfied, the second vehicle speed is used as the feedback vehicle speed to determine the integral torque.

[0024] Optionally, before calculating and determining the first vehicle speed based on the drive motor speed, drive wheel speed, and driven wheel speed, the method further includes:

[0025] If the vehicle is not stationary, control the vehicle to decelerate and coast until the speed reaches 0.

[0026] Optionally, if the vehicle is not stationary, controlling the vehicle to decelerate until the speed reaches 0 includes:

[0027] The third vehicle speed is determined by using the Kalman filter method based on the speed of the drive motor, the speed of the drive wheel, and the speed of the driven wheel.

[0028] If none of the set conditions are met, the process proceeds to the step of calculating and determining the first vehicle speed based on the drive motor speed, drive wheel speed, and driven wheel speed. The set conditions include:

[0029] The third vehicle speed is greater than the coasting speed threshold, the gear is in parking or neutral, and there is a braking signal.

[0030] Optionally, the coasting speed threshold is determined based on the sensor's lowest resolution speed.

[0031] Optionally, a vehicle speed control device for low-speed driving of an electric vehicle includes:

[0032] The first vehicle speed determination module is used to control the vehicle to start moving when the vehicle is stationary, and to calculate and determine the first vehicle speed based on the speed of the drive motor, the speed of the drive wheel and the speed of the driven wheel.

[0033] The integral torque determination module is used to determine the first integral torque by integral control when the first vehicle speed is lower than a set speed threshold, and to use the first integral torque as the total drive torque to control the vehicle operation.

[0034] The second vehicle speed determination module is used to calculate and determine the second vehicle speed based on the drive motor speed when the first vehicle speed is not lower than the set speed threshold.

[0035] The variable speed integral control module is used to perform variable speed integral control based on the second vehicle speed, and to determine the total drive torque to control vehicle operation based on the result of the variable speed integral control.

[0036] As can be seen from the above technical solutions, this application discloses a vehicle speed control method and device for low-speed driving of an electric vehicle. The method includes: controlling the vehicle to start moving when the vehicle is stationary, and calculating and determining a first vehicle speed based on the speed of the drive motor, the speed of the drive wheels, and the speed of the driven wheels; if the first vehicle speed is lower than a set speed threshold, using integral control to determine a first integral torque, and using the first integral torque as the total drive torque to control the vehicle's operation; if the first vehicle speed is not lower than the set speed threshold, calculating and determining a second vehicle speed based on the speed of the drive motor; performing variable speed integral control based on the second vehicle speed, and determining the total drive torque based on the result of the variable speed integral control to control the vehicle's operation. The above solution divides the low-speed driving of the vehicle into different control stages. The control of different control stages can, to a certain extent, adapt to problems such as inaccurate sensors and changes in starting resistance under low-speed driving conditions, and achieve stable low-speed driving of the vehicle without relying on the braking system. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 This is a flowchart of a method for controlling the speed of an electric vehicle at low speeds, as disclosed in an embodiment of this application.

[0039] Figure 2 This is a flowchart of the variable speed integral stabilized vehicle speed control disclosed in the embodiments of this application;

[0040] Figure 3 This is a flowchart illustrating the vehicle speed control scheme for low-speed driving of an electric vehicle disclosed in an embodiment of this application.

[0041] Figure 4 This is a schematic diagram of the signal interface of the vehicle speed control scheme for low-speed driving of electric vehicles disclosed in an embodiment of this application;

[0042] Figure 5 This is a schematic diagram of the structure of a vehicle speed control device for low-speed driving of an electric vehicle disclosed in an embodiment of this application. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] Figure 1 This is a flowchart illustrating a method for controlling the speed of an electric vehicle at low speeds, as disclosed in an embodiment of this application. See also... Figure 1 As shown, the speed control method for low-speed driving of electric vehicles may include:

[0045] Step 101: Control the vehicle to start moving while the vehicle is stationary, and calculate and determine the first vehicle speed based on the speed of the drive motor, the speed of the drive wheels and the speed of the driven wheels.

[0046] The vehicle speed control method for low-speed driving of electric vehicles disclosed in this application needs to be performed with the vehicle stationary. Step 101 is the processing performed during the vehicle start-up phase. The first vehicle speed is determined based on the speed of the drive motor, the speed of the drive wheels, and the speed of the driven wheels. Specifically, the first vehicle speed can be determined by the maximum speed among the speeds calculated based on the speeds of each drive motor, each drive wheel, and each driven wheel. Since this application aims to achieve stable low-speed driving, the maximum extreme value among the calculated speeds is selected as the final first vehicle speed to ensure the effectiveness of low-speed control.

[0047] Step 102: If the first vehicle speed is lower than the set speed threshold, integral control is used to determine the first integral torque, and the first integral torque is used as the total drive torque to control the vehicle operation.

[0048] The set speed threshold can be understood as the vehicle's starting speed threshold, which can be calculated and determined based on the minimum resolution rotational speed of the drive motor, drive wheels, and driven wheels.

[0049] If the first vehicle speed is lower than the set speed threshold, the vehicle speed control adopts integral control and obtains integral torque. Then, the integral torque obtained by integral control (corresponding to the first integral torque) is used as the total drive torque output to control the vehicle's drive motor to work.

[0050] The first vehicle speed is used to determine the vehicle's starting state. Integral control can estimate the starting resistance and compensate for changes in resistance, thus making it applicable to different road conditions and solving the problem of resistance changes when starting on different roads.

[0051] Step 103: If the first vehicle speed is not lower than the set speed threshold, the second vehicle speed is calculated and determined based on the drive motor speed.

[0052] If the first vehicle speed is not lower than the set speed threshold, a second vehicle speed needs to be determined first. The second vehicle speed is the actual vehicle speed calculated based on the drive motor speed. After the second vehicle speed is determined, variable speed integral control can be further performed based on the determined second vehicle speed to achieve stable low-speed driving of the vehicle.

[0053] Step 104: Perform variable speed integral control based on the second vehicle speed, and determine the total drive torque to control vehicle operation based on the result of the variable speed integral control.

[0054] The variable speed integral control method can solve the problem that the speed sensors on the vehicle are limited by the lowest resolution and cannot accurately measure the vehicle speed, thus enabling stable control of the vehicle's driving state when the vehicle speed is lower than the sensor speed resolution.

[0055] The vehicle speed control method for low-speed driving of electric vehicles described in this embodiment divides the low-speed driving of the vehicle into different control stages. The control of different control stages can, to a certain extent, adapt to problems such as inaccurate sensors and changes in starting resistance under low-speed driving conditions, and achieve stable low-speed driving of the vehicle without relying on the braking system.

[0056] To better understand the solution proposed in this application, the implementation process of the solution in practical applications will be introduced below.

[0057] Before implementing low-speed vehicle control, the control system needs to be initialized to ensure the normal operation of related control processes. When control begins, the control loop variables i = 0 and j = 0 are set, and the integral torque (the torque calculated by the integral control term in PID control) T is set... i (0) = 0. Here, i and j are loop variables in the algorithm, recording the historical values ​​of certain variables, and are either incremented or reset to 0 when subsequent conditions are met. In this invention, i is used for control counting, incrementing by 1 for each control operation; j is used for integral control counting, incrementing by 1 for each control operation, but being reset to 0 and integral control performed when the condition is met.

[0058] The processes corresponding to steps 101 and 102 in the above embodiments can be considered as the start-up control phase in this application. In the start-up control phase, a first vehicle speed is first calculated. Since in some implementations the vehicle is not initially stationary, it is necessary to first control the vehicle to coast and decelerate to a stationary state before proceeding with the vehicle start-up control phase. Therefore, in this application, the coasting and deceleration phase can be considered the first phase, the vehicle start-up control phase the second phase, and the subsequent vehicle speed control phase the third phase. Correspondingly, the first vehicle speed corresponds to the second phase (start-up control phase), which can be represented by the second mode vehicle speed v2.

[0059] In this application, integral control is used during the vehicle's initial acceleration phase, and it is only executed when the vehicle is stationary. The calculation of the first vehicle speed includes:

[0060] For each driving wheel, driven wheel, and drive motor, calculate its corresponding vehicle speed according to equations (1) to (3).

[0061]

[0062]

[0063]

[0064] Where v dk The vehicle speed is calculated using the k-th drive wheel, v. rk The vehicle speed is calculated using the k-th driven wheel, v. mk The vehicle speed is calculated using the kth drive motor. m It is the reduction ratio of the drive motor, and r is the rolling radius of the wheel (in meters). Both are common parameters of the vehicle.

[0065] The first vehicle speed is calculated according to formula (4), and the maximum value of all calculated vehicle speeds is taken.

[0066] v2=max{v d1 v d1 , ..., v dD v r1 vr1 , ..., v rR v m1 v m2 , ..., v mM Equation (4)

[0067] Where M is the number of drive motors, D is the number of drive wheels, and R is the number of driven wheels. Of course, in actual situations, the vehicle may not have drive wheels, so R may be 0. If R = 0, the terms with R are not included in the calculation. The meaning of Equation (4) is that the maximum speed among the vehicle speed calculated based on the speed of each drive motor, the speed calculated based on the speed of each drive wheel, and the speed calculated based on each driven wheel is determined as the first vehicle speed.

[0068] If the first vehicle speed is lower than a set speed threshold, integral control is used to determine the first integral torque. That is, if the condition v2 < v is met... s Integral control is performed at startup. Where v s The starting speed threshold can be calculated by substituting the minimum resolution speeds of the drive wheel, driven wheel, and drive motor into equations (1) to (3) to calculate the speed corresponding to each minimum resolution speed, and taking the maximum value among the corresponding speeds to obtain the starting speed threshold v. s When the initial vehicle speed is below the set speed threshold, pure integral control is used, with the integral torque T measured each time. i Accumulate sequentially:

[0069]

[0070] Where T s This is the starting integral torque, determined based on calibration experiments; in this embodiment, it is taken as 10 Nm. G is the vehicle mass (in kg), g is the acceleration due to gravity, and θ is the acceleration due to gravity. g It is a slope signal.

[0071] Let the total drive torque T d =T i (i), Output drive torque vector T d for:

[0072]

[0073] Finally, set the control loop variable i = i + 1, and return to the step of calculating the first vehicle speed.

[0074] Relying on the initial vehicle speed to identify vehicle start-up, integral torque T i It can approximate the vehicle's starting resistance and solve the problem of varying starting resistance when relying solely on motor control.

[0075] If the first vehicle speed is not lower than the set speed threshold, that is, condition v2 is not met. <vs Then, we can let the control loop variable i = i + 1, and then calculate and determine the second vehicle speed. The second vehicle speed corresponds to the third stage mentioned above, so the second vehicle speed can be represented by the third mode vehicle speed v3.

[0076] The third stage is the variable-speed integral-type stable speed control stage. Variable-speed integral-type control means that the frequency of integral control is not synchronized with the proportional control, allowing for N-stage operation. i After the proportional control, an integral control is performed to update the integral control torque. At this stage, the second vehicle speed needs to be calculated first.

[0077] The calculation of the second vehicle speed may include: if the first vehicle speed is not lower than the set speed threshold, determining the maximum vehicle speed among all vehicle speeds calculated from the speeds of all drive motors; and performing low-pass filtering based on the maximum vehicle speed to obtain the second vehicle speed.

[0078] Specifically, to calculate the second vehicle speed, we can first calculate the vehicle speed v corresponding to each drive motor according to the method in equation (3). mk k = 1, 2, ..., M. Then calculate the maximum vehicle speed v of the drive motor according to equation (7). mx .

[0079] v mx =max{v m1 v m2 , ..., v mM Equation (7)

[0080] Finally, the second vehicle speed v3 is calculated using low-pass filtering according to equation (8).

[0081]

[0082] Where λ is the filtering parameter, and its value range is (0, 1). It is determined according to the calibration experiment. In this embodiment, the value can be 0.1.

[0083] After obtaining the second vehicle speed, the low-speed integral control phase begins. First, it is determined whether the integral condition is met. In this embodiment, the integral condition is j = N. i N i It is the integration interval step size, with a value range of [1, +∞), taking positive integers, determined according to the calibration experiment. In the calibration experiment, N i Starting from 1, gradually increase the step size N until the vehicle speed v3 in mode 3 (corresponding to the second vehicle speed) does not overshoot, then determine the integral interval step size N. i The value of is 30 in this embodiment.

[0084] If the integral condition is met, the vehicle speed v3 in mode 3 is used as the feedback speed, and the integral torque T is updated. i :

[0085] T i (i)=max{-T imax ,min{T imax T i (i-1)+K i (v d -v3)}} Equation (9)

[0086] Equation (9) does not have the case where the loop variable i = 0. In the equation, T... imax This is the maximum integral torque, determined through calibration tests. In the calibration test, the vehicle is loaded to 120% of its rated load and calibrated on a level road. The maximum integral torque T is... ima x is gradually increased from 0 until the vehicle can start and drive stably, at which point the maximum integral torque T is determined. imax The value of K is 1000 Nm in this embodiment. i This is the integral control coefficient, determined through calibration experiments. The calibration method involves taking the largest possible value under both unloaded and fully loaded vehicle conditions, ensuring that the vehicle speed v3 in mode 3 does not overshoot. In this embodiment, the value is 20 Nms / km. d The target vehicle speed is the input to the algorithm; the integral torque T is... i Similar to the meaning of integral torque mentioned earlier, after entering the third stage for the first time, T i (i-1) is obtained from equation (5). Finally, set the control loop variable j = 0 to enter the low-speed PI control stage.

[0087] If the integral condition is not met, then let the control loop variable j = j + 1, and let the integral torque T i (i)=T i (i-1), enter the low-speed PI control stage.

[0088] Using the vehicle speed in mode 3 as the feedback speed for control, when the sensor measurement is inaccurate at low speeds, the maximum vehicle speed is used for filtering, which can make the vehicle speed estimation as accurate as possible and prevent the estimated vehicle speed from oscillating.

[0089] If the integral torque of the low-speed PI control is calculated during the low-speed integral control phase, then the proportional torque T needs to be calculated during the low-speed PI control phase. p Proportional torque T p The third mode vehicle speed v3 is also used as the feedback vehicle speed for calculation:

[0090] T p =K p (v d -v3) Equation (10)

[0091] In the formula K pIt is a proportional control coefficient, determined through calibration experiments. In this embodiment, the value is 75 Nms / km.

[0092] To obtain the integral torque T i and proportional torque T p Then, the total control torque T can be determined based on these two factors. c Size restrictions:

[0093] T c =max{0,min{T max T i (i)+T p Equation (11)

[0094] In the formula T max This is the maximum control torque, which is the sum of the maximum drive torques of all motors.

[0095]

[0096] In the formula T kmax It is the maximum driving torque of the k-th drive motor, k = 1, 2, ..., M.

[0097] Obtain the control torque T c Then, set the total drive torque T d =T c Output drive torque vector T d for:

[0098]

[0099] Finally, set the control loop variable i = i + 1 and return to the step of calculating the second vehicle speed.

[0100] In summary, the process of variable speed integral stabilized vehicle speed control is as follows: Figure 2 As shown. Combined with Figure 2 As shown, the step of performing variable speed integral control based on the second vehicle speed, and determining the total drive torque to control vehicle operation based on the result of the variable speed integral control, may include:

[0101] Step 201: Perform variable speed integral control based on the second vehicle speed to determine the second integral torque and the proportional torque. The update frequencies of the second integral torque and the proportional torque are different.

[0102] Specifically, this may include: determining whether the integral condition is met; if not, using the second vehicle speed as the feedback speed to determine the proportional torque; if it is met, using the second vehicle speed as the feedback speed to determine the integral torque.

[0103] Step 202: Determine the range of values ​​for the total control torque based on the second integral torque and the proportional torque.

[0104] Step 203: Use the total control torque as the total drive torque to control the vehicle operation.

[0105] In the vehicle speed control method for low-speed driving of electric vehicles described in this embodiment, the second vehicle speed uses multiple sensor signals and is filtered to prevent control oscillation overshoot. In addition, the use of variable speed integral method can solve the problem of sensor inaccuracy when the sensor is at the lowest resolution corresponding to the vehicle speed.

[0106] In other implementations, before calculating and determining the first vehicle speed, the following may also be included: if the vehicle is not stationary, control the vehicle to decelerate and coast until the speed is 0.

[0107] Specifically, the third vehicle speed can be determined using the Kalman filter method based on the speed of the drive motor, the speed of the drive wheel, and the speed of the driven wheel. If none of the set conditions are met, the process proceeds to the step of calculating and determining the first vehicle speed. The set conditions may include, but are not limited to, the following: the third vehicle speed is greater than the coasting speed threshold, the gear is in parking or neutral, and there is a braking signal.

[0108] The vehicle coasting deceleration phase is the first phase mentioned above, and the third vehicle speed can be the first mode vehicle speed v1. During the vehicle coasting deceleration phase, the third speed is first calculated using the motor speed vector ω. m Drive wheel speed vector ω d Driven wheel speed vector ω r Using the Kalman filter method as input, the estimated longitudinal vehicle speed is obtained to calculate the third vehicle speed v1.

[0109] When the following four conditions apply: v1 > v z (Vehicle speed is high when entering control), G in =P (Parking gear), G in =N (gear position is N, i.e., neutral), B in =1 (brake pedal depressed), when one of these conditions is met, the output torque is 0, that is, the drive motor torque vector T d =0, let the control loop variable i = i + 1, return to step 2) re-evaluate the conditions; if none of the four conditions are met, continue to step 3).

[0110] Where v z This refers to the coasting speed threshold, which can be determined based on the sensor's lowest resolution speed. Specifically, the coasting speed threshold can be set to a low speed that cannot be achieved by normal vehicle speed control (the sensor's lowest resolution speed, or a low speed that cannot be achieved by crawling, cruise control, etc.). In this embodiment, it can be set to 2 km / h.

[0111] Based on the above, a complete process of vehicle coasting deceleration, start-up control to variable speed integral-type stable speed control is as follows: Figure 3 As shown, it can be combined with Figure 3 Understand the relevant content of the previous embodiments.

[0112] This application addresses the problems existing in the prior art by proposing a vehicle speed control method for low-speed driving of electric vehicles that does not rely on the braking system. It can calculate the torque required by the vehicle under low-speed driving conditions when the low-speed driving sensor is inaccurate and the driving resistance is unknown, thereby achieving stable vehicle speed control.

[0113] Figure 4 This is a schematic diagram of the signal interface for a low-speed electric vehicle speed control scheme disclosed in an embodiment of this application. See also... Figure 4 As shown, the control inputs include the brake pedal active signal B. in (B in ={0 - invalid, 1 - valid}), gear signal G in (G in ={D, P, R, N}, meaning the gears include four positions: D, P, R, and N; the motor speed vector ω m (ω m =[ω m1 ,...,ω mM [ ], that is, the speed vector composed of the speed of each drive motor, where M is the number of drive motors (the unit of the input signal is rpm), and the speed vector of the drive wheel ω. d (ω d =[ω d1 ,...,ω dD [ ], that is, the speed vector composed of the speed of each driving wheel, where D is the number of driving wheels (the unit of the input signal is rpm), and the driven wheel speed vector ω. r (ω r =[ω r1 ,...,ω rR ], which is the speed vector composed of the speeds of each drive wheel, where R is the number of drive wheels, and the unit of the input signal is rpm. If the vehicle is an all-wheel drive vehicle, then there is no driven wheel speed vector ω. r ), slope signal θ g (Input signal unit is deg), target vehicle speed v d (Input signal unit is km / h).

[0114] The control output includes: drive motor torque vector T d (T d =[T d1 , ..., T dD [This refers to the torque vector composed of the torque of each drive motor, with the output signal unit being Nm].

[0115] The vehicle speed control method for low-speed driving of electric vehicles provided in this application can, to a certain extent, adapt to problems such as inaccurate sensors and changes in starting resistance under low-speed driving conditions, and achieve stable low-speed driving of the vehicle without relying on the braking system. Using the content of this application, it is further possible to achieve precise control of small displacements, low-speed cruise control, smoother creep control, and starting control.

[0116] For the foregoing method embodiments, in order to simplify the description, they are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, because according to this application, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0117] The methods described in the above-disclosed embodiments of this application are detailed in terms of the methods. The methods of this application can be implemented by various forms of apparatus. Therefore, this application also discloses an apparatus. Specific embodiments are given below for detailed description.

[0118] Figure 5 This is a schematic diagram of a vehicle speed control device for low-speed driving of an electric vehicle disclosed in an embodiment of this application. See also... Figure 5 As shown, the vehicle speed control device 50 for low-speed driving of an electric vehicle may include:

[0119] The first vehicle speed determination module 501 is used to control the vehicle to start moving when the vehicle is stationary, and to calculate and determine the first vehicle speed based on the speed of the drive motor, the speed of the drive wheel and the speed of the driven wheel.

[0120] The integral torque determination module 502 is used to determine the first integral torque by integral control when the first vehicle speed is lower than the set speed threshold, and to use the first integral torque as the total drive torque to control the vehicle operation.

[0121] The second vehicle speed determination module 503 is used to calculate and determine the second vehicle speed based on the drive motor speed when the first vehicle speed is not lower than the set speed threshold.

[0122] The variable speed integral control module 504 is used to perform variable speed integral control based on the second vehicle speed, and to determine the total drive torque to control vehicle operation based on the result of the variable speed integral control.

[0123] The vehicle speed control device for low-speed driving of electric vehicles described in this embodiment divides the low-speed driving of the vehicle into different control stages. The control of different control stages can, to a certain extent, adapt to problems such as inaccurate sensors and changes in starting resistance under low-speed driving conditions, and achieve stable low-speed driving of the vehicle without relying on the braking system.

[0124] For details on the implementation of the vehicle speed control device for low-speed driving of electric vehicles and its various modules, please refer to the relevant sections of the method embodiments; they will not be repeated here.

[0125] The vehicle speed control device for low-speed driving of any of the above embodiments includes a processor and a memory. The first vehicle speed determination module, integral torque determination module, second vehicle speed determination module, and variable speed integral control module in the above embodiments are all stored as program modules in the memory. The processor executes the above program modules stored in the memory to realize the corresponding functions.

[0126] The processor contains a kernel, which retrieves the corresponding program modules from memory. One or more kernels can be configured, and the processing of backtracking data can be achieved by adjusting kernel parameters.

[0127] The memory may include non-permanent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0128] In an exemplary embodiment, a computer-readable storage medium is also provided, which can be directly loaded into the internal memory of a computer, and contains software code. After being loaded and executed by the computer, the computer program can implement the steps shown in any embodiment of the vehicle speed control method for low-speed driving of electric vehicles described above.

[0129] In an exemplary embodiment, a computer program product is also provided, which can be directly loaded into the internal memory of a computer and contains software code. After being loaded and executed by the computer, the computer program can implement the steps shown in any embodiment of the vehicle speed control method for low-speed driving of electric vehicles described above.

[0130] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0131] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0132] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0133] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling the speed of an electric vehicle at low speeds, characterized in that, include: Controlling the vehicle to start moving while the vehicle is stationary, and calculating and determining the first vehicle speed based on the speed of the drive motor, the speed of the drive wheel, and the speed of the driven wheel, including: determining the maximum vehicle speed among the vehicle speeds calculated based on the speed of each drive motor, the vehicle speeds calculated based on the speed of each drive wheel, and the vehicle speeds calculated based on the speed of each driven wheel as the first vehicle speed; If the first vehicle speed is lower than the set speed threshold, integral control is used to determine the first integral torque, and the first integral torque is used as the total driving torque to control the vehicle operation. The set speed threshold is calculated and determined based on the minimum resolution rotational speed of the drive motor, drive wheel and driven wheel. If the first vehicle speed is not lower than the set speed threshold, the second vehicle speed is calculated and determined based on the drive motor speed, including: calculating the vehicle speed corresponding to all drive motor speeds and determining the maximum vehicle speed among all vehicle speeds, and performing low-pass filtering based on the maximum vehicle speed to obtain the second vehicle speed; Based on the second vehicle speed, integral speed control is performed, and based on the result of the integral speed control, the total drive torque is determined to control the vehicle operation.

2. The vehicle speed control method for low-speed driving of an electric vehicle according to claim 1, characterized in that, The step of performing variable speed integral control based on the second vehicle speed, and determining the total drive torque to control vehicle operation based on the result of the variable speed integral control, includes: Based on the second vehicle speed, variable speed integral control is performed to determine the second integral torque and the proportional torque, wherein the update frequencies of the second integral torque and the proportional torque are different. The range of values ​​for the total control torque is determined based on the second integral torque and the proportional torque. The total control torque is used as the total drive torque to control the vehicle's operation.

3. The vehicle speed control method for low-speed driving of an electric vehicle according to claim 2, characterized in that, The step of performing variable speed integral control based on the second vehicle speed to determine the second integral torque and proportional torque includes: Determine whether the integration conditions are met; If the conditions are not met, the second vehicle speed will be used as the feedback vehicle speed to determine the proportional torque; If satisfied, the second vehicle speed is used as the feedback vehicle speed to determine the integral torque.

4. The vehicle speed control method for low-speed driving of an electric vehicle according to claim 1, characterized in that, Before calculating and determining the first vehicle speed based on the drive motor speed, drive wheel speed, and driven wheel speed, the process also includes: If the vehicle is not stationary, control the vehicle to decelerate and coast until the speed reaches 0.

5. The vehicle speed control method for low-speed driving of an electric vehicle according to claim 4, characterized in that, If the vehicle is not stationary, controlling the vehicle to decelerate and coast until the speed reaches 0 includes: The third vehicle speed is determined by using the Kalman filter method based on the speed of the drive motor, the speed of the drive wheel, and the speed of the driven wheel. If none of the set conditions are met, the process proceeds to the step of calculating and determining the first vehicle speed based on the drive motor speed, drive wheel speed, and driven wheel speed. The set conditions include: The third vehicle speed is greater than the coasting speed threshold, the gear is in parking or neutral, and there is a braking signal.

6. The vehicle speed control method for low-speed driving of an electric vehicle according to claim 5, characterized in that, The coasting speed threshold is determined based on the lowest resolution speed of the sensor.

7. A speed control device for low-speed driving of an electric vehicle, characterized in that, include: The first vehicle speed determination module is used to control the vehicle to start moving when the vehicle is stationary, and to calculate and determine the first vehicle speed based on the speed of the drive motor, the speed of the drive wheel, and the speed of the driven wheel. The first vehicle speed is determined by the maximum speed among the vehicle speeds calculated based on the speed of each drive motor, the vehicle speeds calculated based on the speed of each drive wheel, and the vehicle speeds calculated based on each driven wheel. The integral torque determination module is used to determine the first integral torque by integral control when the first vehicle speed is lower than a set speed threshold, and to use the first integral torque as the total driving torque to control the vehicle operation. The set speed threshold is calculated and determined based on the minimum resolution rotational speed of the drive motor, drive wheel and driven wheel. The second vehicle speed determination module is used to calculate and determine the second vehicle speed based on the drive motor speed when the first vehicle speed is not lower than the set speed threshold. The module includes: calculating the vehicle speed corresponding to all drive motor speeds and determining the maximum vehicle speed among all vehicle speeds, and performing low-pass filtering based on the maximum vehicle speed to obtain the second vehicle speed. The variable speed integral control module is used to perform variable speed integral control based on the second vehicle speed, and to determine the total drive torque to control vehicle operation based on the result of the variable speed integral control.

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