A single-pedal electric direct-drive vehicle control method

Abstract

The present application belongs to the technical field of pure electric vehicle control strategy, and particularly relates to a single-pedal electric direct-drive vehicle control method. The method first acquires the road slope of the road where the vehicle is located, the pedal displacement of the vehicle and the pedal displacement rate; then judges the working interval of the vehicle, which is a driving interval, a coasting interval or a braking interval; in the case that the vehicle is in the driving interval, if the road slope is greater than 0, the torque value corresponding to the pedal opening is increased; and if the road slope is greater than a slope threshold value, the pedal displacement is greater than a pedal displacement threshold value or the pedal displacement rate threshold value is greater than a pedal displacement rate threshold value, the torque value corresponding to the increased pedal opening also needs to be compensated. In the case that the vehicle is in the driving interval, the torque value corresponding to the pedal opening is increased, and then in the case that the slope is large, the pedal displacement is large or the pedal displacement rate is large, the motor torque is also compensated, so as to meet the demand of the vehicle.

Description

Technical Field

[0001] This invention belongs to the technical field of pure electric vehicle control strategy, specifically relating to a control method for a single-pedal electric direct-drive vehicle. Background Technology

[0002] my country's new energy vehicle industry is developing rapidly, presenting a thriving scene. Compared with traditional cars, pure electric vehicles have many advantages. For example, compared with traditional vehicles, pure electric vehicles can achieve zero emissions during operation, making them more environmentally friendly; they are not absolutely dependent on gasoline and are less affected by oil crises; and the energy conversion efficiency of electric motors has an absolute advantage over internal combustion engines. However, pure electric vehicles also have their own shortcomings, with range being a fatal weakness.

[0003] Regenerative braking technology is an important technology for improving the driving range of pure electric vehicles. Compared to regenerative braking technology based on the brake pedal, single-pedal technology integrates the regenerative braking function into the accelerator pedal. The driver can drive the car with just one pedal, which not only greatly reduces the difficulty of driving, but also improves the efficiency of regenerative braking and effectively enhances the energy recovery effect.

[0004] Currently, the simplest control strategy is to output motor torque based solely on pedal opening. However, some drivers frequently mis-press the pedal, and the pedal opening cannot accurately reflect the driver's intention. Chinese invention patent application CN111098717A discloses a single-pedal control method for electric vehicles. This method determines the vehicle's driving state based on pedal opening value, the rate of change of pedal opening value, vehicle speed, and vehicle acceleration. The parameters used in this scheme are all vehicle-specific parameters. If the vehicle is in a harsh environment, the driver may misjudge the environmental conditions, resulting in the pedal depth not fully reflecting the driver's intention. Therefore, outputting motor torque solely based on vehicle-specific parameters still cannot accurately reflect the driver's intention. Summary of the Invention

[0005] The purpose of this invention is to provide a single-pedal electric direct-drive vehicle control method to solve the problem that outputting motor torque based solely on the vehicle's own parameters cannot accurately reflect the driver's intentions.

[0006] To address the aforementioned technical problems, this invention provides a one-pedal electric direct-drive vehicle control method, comprising the following steps:

[0007] 1) Obtain the road gradient, pedal displacement, and pedal displacement rate of the road where the vehicle is located;

[0008] 2) Determine the working range of the vehicle, which is the driving range, coasting range, or braking range;

[0009] 3) When the vehicle is in the driving range, if the road slope is greater than 0, the torque value corresponding to the pedal opening will be increased; and if the road slope is greater than the slope threshold, the pedal displacement is greater than the pedal displacement threshold, or the pedal displacement rate threshold is greater than the pedal displacement rate threshold, the torque value corresponding to the increased pedal opening will also need to be compensated.

[0010] Its beneficial effects are as follows: When the vehicle is in the driving range, the present invention increases the torque value corresponding to the pedal opening, which can enable the vehicle to reach the driver's required state as soon as possible. Furthermore, when the slope is large, the torque value needs to be compensated so that the vehicle can still reach the driver's required state as soon as possible under such harsh conditions. Moreover, when the pedal displacement is large or the pedal displacement rate is large, it reflects that the driver urgently needs another steady state of the vehicle. The motor torque is also compensated to meet the vehicle's need for another steady state.

[0011] Furthermore, in step 1), the vehicle's current speed also needs to be obtained; in step 2), if the current speed... This indicates that the vehicle is in the braking range, if the current speed This indicates that the vehicle is in the coasting zone, if the current speed This indicates that the vehicle is in the driving range; among which, This is the dividing line between the braking section and the coasting section. This is the boundary between the coasting section and the driving section, and the calculation formulas are as follows:

[0012]

[0013]

[0014] In the formula, This is the vehicle's maximum speed. For characteristic coefficients, For pedal opening, This represents the maximum pedal opening corresponding to the coasting zone when the vehicle is at its maximum speed. It is the difference between the maximum and minimum pedal opening corresponding to the coasting zone when the vehicle is at its maximum speed.

[0015] Its beneficial effects are: the driver's intention can be accurately judged based on the current vehicle speed and pedal displacement, making it easier to output motor torque according to different driver intentions.

[0016] Furthermore, the maximum dynamic torque variation compensation value is calculated according to the following formula:

[0017]

[0018]

[0019]

[0020]

[0021] In the formula, For total gravity, The rolling resistance coefficient, For road slope, This is the drag coefficient. For windward area, For vehicle speed, For steady-state velocity, For total mass, The rolling resistance coefficient, Where is the rolling radius, This is the compensation value for maximum torque variation. This is the minimum torque variation compensation value. Current vehicle speed The maximum speed, This is the compensation value for the maximum dynamic torque variation. This represents the highest torque change rate.

[0022] Furthermore, in step 3), if the road slope is equal to 0, the torque value corresponding to the pedal opening is reduced.

[0023] Its beneficial effect is that reducing the torque value corresponding to the pedal opening when the vehicle is on a flat road can ensure vehicle driving safety.

[0024] Furthermore, in step 3), if the road slope is less than 0, the negative torque value corresponding to the pedal opening is increased.

[0025] Its beneficial effect is that increasing the negative torque value corresponding to the pedal opening when the vehicle is going downhill can ensure the safety of getting off the vehicle.

[0026] Furthermore, when the vehicle is in the braking range: if the pedal displacement is greater than 0, or the pedal displacement is equal to 0 and the road gradient is greater than 0, no braking is performed; if the pedal displacement is equal to 0 and the road gradient is less than or equal to 0, then if both the pedal displacement and the pedal displacement rate are greater than the corresponding threshold, the motor braking energy recovery is performed at the maximum value and the brake is increased; otherwise, only the motor braking energy recovery is performed; if the pedal is completely released, only the brake is performed.

[0027] Its beneficial effects are as follows: different braking energy recovery methods are adopted according to pedal displacement, pedal displacement rate, and road slope, including four methods: no motor braking energy recovery, only motor braking energy recovery, only brake braking, and using brake braking as compensation torque. It can maximize braking energy recovery while meeting the vehicle braking requirements, improve the efficiency of braking energy recovery, enhance the braking energy recovery effect, and ensure vehicle driving safety.

[0028] Furthermore, when the vehicle is in the coasting zone, the motor does not provide torque.

[0029] Its beneficial effect is that the motor does not provide torque when the vehicle is coasting, which can reduce the vehicle's energy consumption. Attached Figure Description

[0030] Figure 1 This is the overall control framework diagram of the present invention;

[0031] Figure 2 This is an architecture diagram of the electric direct-drive commercial vehicle single-pedal system and its control method of the present invention;

[0032] Figure 3 This is the single-pedal torque response diagram of the present invention;

[0033] Figure 4 This is a flowchart of the single-pedal electric direct-drive vehicle control method of the present invention;

[0034] Figure 5(a) is a single-pedal control map for flat roads;

[0035] Figure 5(b) is a single-pedal control map for uphill driving;

[0036] Figure 5(c) is a single-pedal control map for downhill driving. Detailed Implementation

[0037] This invention targets a single-pedal electric direct-drive vehicle. The control strategy employed includes: acquiring four parameters: current vehicle speed, pedal displacement, pedal displacement rate, and road gradient. The pedal opening corresponds to the motor torque to determine the required torque; the maximum power output is limited by the road gradient; and torque compensation is determined based on pedal displacement, pedal displacement rate, and road gradient. The braking energy recovery method (no motor braking energy recovery, only motor braking energy recovery, only brake braking, or using brake braking as compensation torque) is determined based on pedal displacement, pedal displacement rate, and road gradient. The impact on the driver from rapid transitions from driving to braking is reduced by modifying the torque change value, and the probability of motor stalling is reduced. The magnitude of braking energy recovery is determined using three parameters: pedal displacement, pedal displacement rate, and road gradient. To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] Method Implementation Examples:

[0039] This embodiment refers to an electric direct-drive commercial vehicle, such as... Figure 1 , Figure 2 and Figure 4 As shown, the specific control process is as follows:

[0040] Step one: Obtain the road gradient, the vehicle's current speed, pedal displacement (a variable value, the result of which is the current pedal value minus the pedal length of the previous step), and pedal displacement rate, and send these to the VCU. The VCU then forwards this information to the single-pedal controller. The parameters are obtained as follows:

[0041] The road gradient is directly sent to the VCU by the gradient sensor. The current vehicle speed is calculated from the motor speed. Since the vehicle in this embodiment uses an electric direct drive system without a gearbox, this not only reduces the mechanical efficiency loss of the gearbox but also meets the requirements of commercial vehicles for maximum speed, as commercial vehicles do not have high requirements for maximum speed. The motor speed is fed back to the VCU by the MCU via the CAN bus, and the VCU calculates the current vehicle speed as follows:

[0042]

[0043] In the formula, Current vehicle speed This refers to the motor speed. The radius of the wheel's rolling motion. The main reducer transmission ratio.

[0044] The pedal displacement is calibrated to the pedal voltage value as the pedal opening value. In this embodiment, a floor-mounted accelerator pedal is used. This pedal uses a sensor to detect the pedal displacement opening, and the voltage change is transmitted to the VCU via a wiring harness connector. After calibration, the voltage value corresponds to the pedal displacement. The pedal displacement rate is calculated from the pedal displacement, and the formula for calculating the pedal displacement rate is:

[0045]

[0046] In the formula, For pedal displacement rate, For the present Depress accelerator pedal opening This refers to the previous step's accelerator pedal opening. The time is one step.

[0047] Step two: Divide the vehicle into three ranges based on the current speed and pedal opening, specifically as follows: Figure 3 The diagram uses a two-dimensional coordinate system, with the horizontal axis representing the pedal opening P and the vertical axis representing the vehicle speed. This allows the single-pedal controller to determine the vehicle's operating range—driving, coasting, or braking—based on the current vehicle speed and pedal opening, thereby enabling driver intent recognition. Different strategies are employed depending on the vehicle's operating range. If this indicates the vehicle is in the braking range, proceed to step three. If this indicates the vehicle is in the coasting zone, proceed to step four. If this indicates the vehicle is in the driving zone, proceed to step five. The dividing lines between the three zones are as follows:

[0048] The expression for the boundary between the coasting section and the braking section is:

[0049]

[0050] The expression for the boundary between the coasting section and the driving section is:

[0051]

[0052] In the formula, This is the vehicle's maximum speed. For characteristic coefficients, For pedal opening, This represents the maximum pedal opening corresponding to the coasting zone when the vehicle is at its maximum speed. It is the difference between the maximum and minimum pedal opening corresponding to the coasting zone when the vehicle is at its maximum speed.

[0053] Step 3: Once the vehicle is in the braking range, the braking strategy is executed. The braking strategy considers pedal displacement, pedal displacement rate, and road gradient before entering the regenerative braking system. The regenerative braking system includes four braking schemes: no regenerative braking, only motor regenerative braking, only brake braking, and both motor and brake regenerative braking. The specific scheme to be executed is determined based on the following conditions:

[0054] 1) When the pedal displacement is greater than 0, do not brake; otherwise, determine whether the road slope is greater than 0. If the road slope is greater than 0, do not brake; otherwise, proceed to step 2.

[0055] 2) When the road gradient is less than or equal to 0, simultaneously determine the pedal displacement and pedal displacement rate: if the pedal displacement and pedal rate are both greater than their respective thresholds, then the motor braking energy recovery will be performed at the maximum value and the brake will be increased; otherwise, only the motor braking energy recovery will be performed.

[0056] 3) When the pedal is fully released (pedal value is zero), it is considered an emergency braking situation. To ensure driving safety, only the brakes will be applied.

[0057] Step four: The vehicle is in the coasting zone, and the motor does not provide torque at this time. The coasting state is between the vehicle's braking state and driving state. When the vehicle is in the coasting state, it is subject to rolling resistance and air resistance, and the motor does not provide torque.

[0058] Step 5: The vehicle is in the driving range. At this time, the accelerator pedal and motor speed are used as inputs, and the motor torque is used as the output. The accelerator pedal reflects the driver's driving needs, and the motor speed provides the maximum power that the motor can provide in the current state. When the speed does not exceed the rated speed, the maximum torque that the motor can provide is the maximum torque of the motor, which is the constant torque part. When the motor speed exceeds the rated speed, since the maximum power that the car can provide is constant, the maximum torque that the accelerator pedal can provide will gradually decrease, which is the constant power part. The single-pedal control maps for flat roads, uphill, and downhill are shown in Figures 5(a), 5(b), and 5(c), respectively. The specific control strategies for the vehicle in the driving range can be divided into the following three modes:

[0059] 1) Single-pedal mode 1: When the slope is greater than 0, increase the torque value corresponding to the pedal opening. In the motor torque compensation mechanism, the changes in pedal displacement and displacement rate can reflect the driver's current demand for another vehicle steady state. When both displacement and displacement rate are relatively large, it reflects that the driver urgently needs another vehicle steady state. When the slope is greater than threshold a, or the pedal displacement is greater than threshold b, or the pedal displacement rate is greater than threshold c, the motor torque is compensated.

[0060] The current dynamics formula for vehicle movement is:

[0061]

[0062] The steady-state velocity is:

[0063]

[0064] The upper limit of the torque change rate is:

[0065]

[0066] The maximum dynamic torque variation compensation value is:

[0067]

[0068] in, For total gravity, The rolling resistance coefficient, For road slope, This is the drag coefficient. For windward area, For the speed of the car, For steady-state velocity, For total mass, The rolling resistance coefficient, Where is the rolling radius, This is the compensation value for maximum torque variation. This is the minimum torque variation compensation value. Current vehicle speed The maximum speed, This is the compensation value for the maximum dynamic torque variation. This represents the highest torque change rate.

[0069] 2) Single pedal mode 2: When the road slope is 0, reduce the torque value corresponding to the pedal opening.

[0070] 3) Single pedal mode 3: When the road slope is less than 0, increase the negative torque value corresponding to the pedal opening.

[0071] In summary, the data obtained by this invention includes road slope, which enables more accurate judgment of the driver's intentions in operating conditions with large slope changes; by setting different pedal torque responses based on road slope, the energy consumption of the vehicle is reduced; and when there are large changes in pedal displacement and pedal displacement rate, a torque compensation mechanism is added to meet the vehicle's demand for another steady state.

Claims

1. A single-pedal electric direct-drive vehicle control method, characterized by, The method comprises the following steps: 1) obtaining the current vehicle speed, the road slope of the road where the vehicle is located, the pedal displacement and the pedal displacement rate of the vehicle; 2) determining the working interval of the vehicle, which is a driving interval, a coasting interval or a braking interval; 3) if the vehicle is in the driving interval, if the road slope is greater than 0, the torque value corresponding to the pedal opening degree is increased; and if the road slope is greater than a slope threshold value, the pedal displacement is greater than a pedal displacement threshold value, or the pedal displacement rate threshold value is greater than a pedal displacement rate threshold value, the torque value corresponding to the increased pedal opening degree needs to be compensated; if the current speed if the current speed if the current speed if the current speed is the demarcation line between the braking interval and the coasting interval, is the demarcation line between the coasting interval and the driving interval. wherein is the maximum vehicle speed, is a characteristic coefficient, is the pedal opening, is the maximum value of the pedal opening corresponding to the glide area at the maximum vehicle speed, is the difference between the maximum and minimum values of the pedal opening corresponding to the glide area at the maximum vehicle speed; The maximum dynamic torque change compensation value is calculated according to the following formula: wherein, is the total weight, is the rolling resistance coefficient, is the road slope, is the wind resistance coefficient, is the windward area, is the vehicle travel speed, is the steady state speed, is the total mass, is the rolling radius, is the maximum torque variation compensation value, is the minimum torque variation compensation value, is the current vehicle speed, is the maximum vehicle speed, is the maximum dynamic torque variation compensation value, is the maximum torque variation rate value, is the main reducer transmission ratio.

2. The single-pedal electric direct-drive vehicle control method according to claim 1, characterized by, In step 3), if the road slope is equal to 0, the torque value corresponding to the pedal opening degree is reduced.

3. The single-pedal electric direct-drive vehicle control method according to claim 1, characterized by, In step 3), if the road slope is less than 0, the negative torque value corresponding to the pedal opening degree is increased.

4. The single-pedal electric direct-drive vehicle control method of claim 1, wherein, In the case where the vehicle is in the braking interval: If the pedal displacement is greater than 0, or the pedal displacement is equal to 0 and the road slope is greater than 0, no braking is performed; If the pedal displacement is equal to 0 and the road slope is less than or equal to 0, if the pedal displacement and the pedal displacement rate are both greater than the corresponding threshold values, the motor braking energy recovery is recovered at the maximum value and the brake is increased, otherwise only the motor braking energy recovery is performed; If the pedal is completely released, only the brake is applied.

5. The single-pedal electric direct-drive vehicle control method of claim 1, wherein, In the case where the vehicle is in the coasting interval, the motor does not provide torque.

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