Slope-adaptive abrupt slope slow descent control method and vehicle

Abstract

The invention relates to a gradient-adaptive abrupt slope slow descent control method and a vehicle, and belongs to the field of vehicle control. According to the current actual rotating speed of the motor and the pre-obtained corresponding relation between the rotating speed of the motor and the torque of the motor, the feed-forward torque is obtained according to the torque of the motor, the feed-forward torque is superposed to a torque output value of vehicle speed closed-loop control, and the vehicle is controlled to reach the HDC target vehicle speed; the corresponding relation is in positive correlation within the peak torque range of the motor, and the motor rotating speed in the corresponding relation is divided into an acceleration interval, a gradient self-adaptive interval and a deceleration interval along with increase of the rotating speed; the gradient adaptive interval corresponds to an HDC target motor rotating speed interval; the minimum value of the motor torque corresponding to the gradient self-adaptive interval is obtained by the full-load mass, the minimum gradient of the HDC and the first-gear target vehicle speed, and the maximum value of the motor torque corresponding to the gradient self-adaptive interval is obtained by the full-load mass, the maximum gradient of the HDC and the highest-gear target vehicle speed; and the vehicle speed is ensured to be stably reduced or increased to the target vehicle speed along with the increase or decrease of the motor torque.

Description

Technical Field

[0001] The invention relates to a slope-adaptive steep slope descent control method and a vehicle, belonging to the field of whole vehicle control. Background Art

[0002] With the upgrading of automobile electronic control and intelligence, people pay more and more attention to the safety and comfort of automobiles. Hill Down Control (HDC) is an automatic control system for vehicles driving downhill. When the vehicle encounters a long downhill steep slope, the steep slope descent function can automatically control the vehicle to stabilize at a low speed and achieve smooth descent when the driver releases the accelerator and brake pedals. Passenger cars mainly identify the slope of the road through slope sensors or high-precision maps. When encountering a long downhill steep slope, they control the hydraulic brake (fuel vehicle) or electric brake (new energy vehicle) to achieve a low speed and smooth descent. However, commercial vehicles are relatively long. For example, tractors can be tens of meters long, and the front and compartment are separated. The slope sensor is generally installed inside the front of the vehicle. Therefore, the slope information obtained by the slope sensor is difficult to cover the entire length of the vehicle body. In addition, the weight of commercial vehicles is large, and the weight variation between empty and full load is large, which can reach more than 60,000 kg, and the maximum variation range can reach 300% of the empty weight. At the same time, the road conditions of commercial vehicles are poor. For example, heavy-loaded dump trucks often work under mine roads. It is difficult to rely on slope sensors or high-precision maps to obtain the accurate slope of the road surface, and it is impossible to provide accurate input for vehicle control.

[0003] The Chinese patent authorization announcement document with announcement number CN114179621B discloses a vehicle steep slope descent control method and device. When the vehicle enters the steep slope descent mode, the method controls the actual vehicle speed to the steep slope descent speed according to the energy recovery torque, thus solving the problem of achieving a smooth descent of the vehicle through hydraulic braking.

[0004] The Chinese patent application publication number CN116985770A discloses a steep slope descent pre-control method and device. When the vehicle driving state information meets the steep slope descent pre-control conditions, the method brakes the vehicle by actively building up pressure, thereby improving the driver's sense of driving safety.

[0005] However, both solutions require the vehicle to detect the slope of the current slope. When the vehicle cannot effectively collect slope information, the HDC function cannot be entered. For commercial vehicles with separate front and body, the slope information obtained by the slope sensor cannot accurately reflect the slope of the entire vehicle. At the same time, the weight of commercial vehicles varies greatly when fully loaded and unloaded, making these two solutions difficult to apply to commercial vehicles. Summary of the invention

[0006] The purpose of the present invention is to provide a slope-adaptive steep slope descent control method and vehicle, so as to solve the problem that the existing steep slope descent technology is heavily dependent on the acquired slope information and is not suitable for commercial vehicles with large mass changes and separated front and body types.

[0007] To achieve the above object, the solution of the present invention includes:

[0008] The present invention provides a slope-adaptive steep slope descent control method. In the HDC mode, the vehicle obtains a feedforward torque according to the corresponding motor torque based on the current actual motor speed and the pre-acquired correspondence between the motor speed and the motor torque, and superimposes the feedforward torque on the torque output value of the closed-loop speed control to control the vehicle to the HDC target speed.

[0009] The motor speed and motor torque in the corresponding relationship are positively correlated within the motor peak torque range, and the motor speed in the corresponding relationship is divided into an acceleration interval, a slope adaptation interval and a deceleration interval as the speed increases; the slope adaptation interval corresponds to the HDC target motor speed interval; the minimum motor torque corresponding to the slope adaptation interval is calculated based on the full load mass, the minimum slope adapted to the HDC mode, and the first gear target vehicle speed, and the maximum motor torque corresponding to the slope adaptation interval is calculated based on the full load mass, the maximum slope adapted to the HDC mode, and the highest gear target vehicle speed.

[0010] Furthermore, the positive correlation between the motor torque and the motor speed in the corresponding relationship within the motor peak torque range is an exponential relationship, and the exponential relationship is an exponential relationship of a monotonically increasing part of a parabola opening upward.

[0011] Furthermore, the corresponding motor torque is multiplied by the mass coefficient to be used as the feedforward torque; the mass coefficient is determined according to the ratio of the current actual mass of the vehicle to the full-load mass.

[0012] Furthermore, the parameters of the vehicle speed closed-loop controller in the vehicle speed closed-loop control are parameters that make the absolute value of the torque output value of the vehicle speed closed-loop control less than or equal to the absolute value of the feedforward torque.

[0013] Furthermore, after the feedforward torque is superimposed on the torque output value of the vehicle speed closed-loop control to obtain the total torque used to drive the motor response, the opening of the accelerator pedal and the brake pedal are also judged. If the accelerator pedal opening is greater than zero and less than a preset value, the total torque is reduced. If the brake pedal opening is greater than zero and less than a preset value, the total torque is increased.

[0014] The driver is allowed to operate the brake pedal and accelerator pedal to control the vehicle, effectively avoiding frequent exit of the HDC function.

[0015] Furthermore, the upper and lower limits of the total torque are set according to the rated torque and the maximum allowable torque of the motor. When the total torque changes and deviates from the upper or lower limit, the motor is controlled to reduce or increase the total torque.

[0016] By limiting the upper and lower limits of the total torque, it can be ensured that the motor outputs the total torque within a safe range.

[0017] Furthermore, in the vehicle speed closed-loop control, the change rate of the total torque is also limited by the parameters of the vehicle speed closed-loop controller. When it is detected that the change rate of the total torque exceeds a preset threshold, the parameters of the vehicle speed closed-loop controller are automatically adjusted.

[0018] By limiting the total torque change rate, vehicle shaking caused by excessive total torque changes can be avoided.

[0019] Further, the HDC target motor speed interval is located in the overlapping portion of the motor speed intervals corresponding to different gears of the vehicle, and the motor speed interval is determined by the motor speed corresponding to the upshift vehicle speed and the downshift vehicle speed of the corresponding gear.

[0020] The target vehicle speeds of different gears correspond to the same motor speed range, which can make the actual vehicle speed basically consistent on different slopes, effectively ensuring the stability of the vehicle.

[0021] Furthermore, before the vehicle enters HDC mode, it is determined whether the conditions for HDC enabling are met. The conditions for HDC enabling include that the HDC function is turned on, the accelerator pedal and brake pedal opening are 0, the current vehicle speed is less than or equal to a preset vehicle speed enabling threshold, and the vehicle has no faults that affect the operation of HDC.

[0022] A vehicle includes an HDC controller, wherein the HDC controller includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, a steep slope descent control method is implemented.

[0023] The beneficial effects of the present invention are as follows: the present invention is a pioneering invention, and the present invention can adaptively adjust the obtained feedforward torque according to the corresponding relationship between the current actual speed of the motor and the pre-acquired motor speed and motor torque, and superimpose the feedforward torque on the torque output value of the closed-loop control of the vehicle speed; in the corresponding relationship, the motor torque and the motor speed are positively correlated within the motor peak torque range, and at the same time, the motor speed is divided into three sections, namely, an acceleration interval, a slope adaptive interval and a deceleration interval, as the speed increases. The slope adaptive interval in the middle section corresponds to the HDC target motor speed interval, and the minimum motor torque corresponding to the lowest motor speed in the slope adaptive interval is calculated according to the full load mass, the HDC minimum slope, and the first gear target vehicle speed. The maximum motor torque corresponding to the slope adaptive interval is calculated according to the full load mass, the HDC maximum slope, and the highest gear target vehicle speed. The motor torque corresponding to the acceleration interval is less than the minimum motor torque corresponding to the slope adaptive interval.

[0024] When the motor speed is in the acceleration range when the vehicle enters HDC mode, that is, the motor speed needs to be increased to reach the HDC target motor speed range. At this time, a minimum motor torque value that is less than the corresponding slope adaptation range is given as the feedforward torque according to the corresponding relationship. In steep slope descent, the motor torque is used to counteract the reverse torque of the vehicle sliding down the slope. Therefore, a feedforward torque that is less than the motor torque corresponding to the slope adaptation range will gradually accelerate the vehicle and the motor speed will gradually increase until it enters the slope adaptation range. The maximum motor torque corresponding to the slope adaptation range is calculated based on the most extreme conditions of steep slope descent such as full vehicle load, maximum slope and highest gear speed. Therefore, in the process of increasing the vehicle motor speed, the feedforward torque (that is, reverse braking torque) increases with the increase of the motor speed. In this process, combined with the closed-loop fine-tuning error of the vehicle speed, the motor speed will eventually be controlled within the slope adaptation range, and the vehicle speed will also be controlled within the HDC target speed range.

[0025] The motor torque corresponding to the deceleration interval is greater than the maximum value of the motor torque corresponding to the slope adaptation interval. When the motor speed is in the deceleration interval when the vehicle enters the HDC mode, that is, the motor speed needs to be reduced to reach the HDC target motor speed interval. At this time, a maximum value of the motor torque greater than that corresponding to the slope adaptation interval is given as the feedforward torque according to the corresponding relationship. Therefore, a feedforward torque greater than the motor torque corresponding to the slope adaptation interval will gradually decelerate the vehicle and the motor speed will gradually decrease until it enters the slope adaptation interval. In the process of decreasing the vehicle motor speed, the feedforward torque decreases as the motor speed decreases. In this process, combined with the vehicle speed closed-loop fine-tuning error, the motor speed will eventually be controlled within the slope adaptation interval, and the vehicle speed will also be controlled within the HDC target speed range.

[0026] The solution of the present invention effectively ensures that the vehicle speed when going downhill is steadily reduced or increased to the target speed as the motor torque increases or decreases. At the same time, the present invention does not rely on slope information and is suitable for commercial vehicles with separate head and compartment and large weight variations. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a steep slope descent control process with adaptive slope of the present invention;

[0028] Figure 2 It is a schematic diagram of a slope adaptive feed-forward torque curve designed by the present invention;

[0029] Figure 3 It is a flow chart of realizing the closed-loop control logic of the driver according to the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0031] The idea of ​​the present invention is that when the vehicle enters the HDC function, the feedforward torque obtained for preventing the vehicle from accelerating down the slope is superimposed on the torque output value of the closed-loop control of the vehicle speed, so that the actual vehicle speed reaches the target speed smoothly. Considering that HDC should not rely on the road slope and is suitable for commercial vehicles with a separated front and body and a large weight variation, the feedforward torque can be adaptively adjusted through the correspondence between the current actual speed of the motor and the pre-obtained motor speed and motor torque, and the feedforward torque can be superimposed on the torque output value of the closed-loop control of the vehicle speed. The motor speed and motor torque in the corresponding relationship are positively correlated within the range of the motor peak torque. At the same time, the motor speed is divided into three sections, namely, the acceleration section, the slope adaptation section and the deceleration section, with the increase of the speed. The slope adaptation section in the middle section corresponds to the HDC target motor speed section. The minimum motor torque corresponding to the slope adaptation section is calculated according to the full load mass, the minimum slope adapted by the HDC mode, and the first gear target speed. The maximum motor torque corresponding to the slope adaptation section is calculated according to the full load mass, the maximum slope adapted by the HDC mode, and the highest gear target speed. The motor torque corresponding to the acceleration section is less than the minimum motor torque corresponding to the slope adaptation section. When the motor speed of the vehicle is in the acceleration section, a feedforward torque less than the motor torque corresponding to the slope adaptation section will cause the vehicle to gradually accelerate and cooperate with the closed-loop control of the speed to smoothly control the vehicle speed to the target speed. The motor torque corresponding to the deceleration section is greater than the maximum motor torque corresponding to the slope adaptation section. When the motor speed of the vehicle is in the deceleration section, a feedforward torque greater than the motor torque corresponding to the slope adaptation section will cause the vehicle to gradually decelerate and cooperate with the closed-loop control of the speed to smoothly control the vehicle speed to the target speed.

[0032] Method Example:

[0033] The present embodiment provides a slope-adaptive steep slope descent control method, comprising the following steps: first, determining the feedforward torque through vehicle slope adaptive feedforward control; then determining the torque output value of vehicle speed closed-loop control through vehicle mass adaptive feedback control, and superimposing the feedforward torque on the feedback torque to control the vehicle speed to the HDC target speed.

[0034] Specifically, the vehicle slope adaptive feedforward control is that the vehicle obtains the feedforward torque according to the correspondence between the current actual motor speed and the pre-acquired motor speed and motor torque, and the motor speed and motor torque are calculated. The motor speed and motor torque in the corresponding relationship are positively correlated within the range of the motor peak torque, and the motor speed in the corresponding relationship is divided into an acceleration interval, a slope adaptive interval and a deceleration interval as the speed increases.

[0035] Now combined Figure 2 , a design method for the correspondence between motor speed and motor torque is introduced. In the figure, the horizontal axis represents the motor speed, the vertical axis represents the motor torque, and the curve represents the slope adaptive feedforward torque curve. Within the peak torque range of the motor, the motor speed and the motor torque present an exponential relationship of the monotonically increasing part of the open upward parabola; and the motor speed is divided into an acceleration interval, a slope adaptive interval and a deceleration interval as the speed increases. Among them, the slope adaptive interval corresponds to the HDC target motor speed interval. The minimum motor torque corresponding to the slope adaptive interval is calculated based on the mass of the vehicle when fully loaded, the minimum slope adapted to the HDC mode, and the target speed of the vehicle in first gear. The maximum motor torque corresponding to the slope adaptive interval is calculated based on the mass of the vehicle when fully loaded, the maximum slope adapted to the HDC mode, and the target speed of the vehicle in the highest gear. The motor torque corresponding to the acceleration interval is smaller than the motor torque in the HDC target motor speed interval. In this interval, a feedforward torque smaller than the motor torque corresponding to the slope adaptation interval is given, so that the vehicle gradually accelerates, and the motor speed gradually increases to the slope adaptation interval; the motor torque corresponding to the deceleration interval is greater than the feedforward torque in the HDC target motor speed interval. In this interval, a feedforward torque greater than the motor torque corresponding to the slope adaptation interval is given, so that the vehicle gradually decelerates, and the motor speed gradually decreases to the slope adaptation interval.

[0036] In the vehicle mass adaptive feedback control after obtaining the feedforward torque, the torque output value of the speed closed loop, i.e. the feedback torque, is determined based on the difference between the current vehicle speed and the target vehicle speed and the difference is subjected to proportional-integral control. This further corrects the feedforward torque steady-state error caused by mass grading error or slope change, thereby achieving adaptive control of different vehicle masses.

[0037] In the quality adaptive feedback control process, the parameters of the closed-loop controller are also designed, such as the proportional-integral coefficient, to limit the absolute value of the feedback torque to be less than or equal to the absolute value of the feedforward torque;

[0038] After the feedback torque is obtained, the sum of the feedforward torque and the feedback torque is taken as the HDC total torque through the HDC total torque control.

[0039] During the HDC total torque control process, the HDC total torque is also subject to gradient limitation and amplitude limitation. The gradient limitation limits the change rate of the HDC total torque through an algorithm. When it is detected that the change rate of the HDC total torque exceeds a preset threshold, the change rate of the HDC total torque is adjusted to the preset threshold to prevent vehicle shaking caused by excessive changes in the HDC total torque. The amplitude limitation sets the upper and lower limits of the HDC total torque based on the peak power and peak torque of the motor. When the HDC total torque deviates from the upper or lower limit of the HDC total torque during the change process, the motor is controlled to reduce or increase the HDC total torque to ensure that the motor torque changes within a safe torque range.

[0040] As another embodiment, in the process of obtaining the feed-forward torque, vehicle mass graded control is also performed to correct the excessive feed-forward torque caused by changes in vehicle load and a large difference from the fully loaded mass.

[0041] Specifically, the vehicle mass grading control is the driver setting the vehicle mass level through the handle, function button or central control screen according to the actual load of the vehicle, and the motor torque is multiplied by the mass coefficient according to the corresponding relationship to obtain the feedforward torque. Among them, the vehicle is divided into several mass levels from no load to full load, such as no load, 1 / 4 load, 2 / 4 load, 3 / 4 load and full load. If the driver judges that the actual load of the vehicle is close to 2 / 4 load, it is set according to 2 / 4 load; the mass coefficient is the ratio of the vehicle mass corresponding to the vehicle mass level to the full load mass.

[0042] Specifically, the HDC target speed range is determined by multi-gear vehicle speed control, which determines the steep slope descent target speed according to the gearbox gear set by the driver. Among them, the design principles of different gear target speeds include: first, the motor speed corresponding to the upshift speed and downshift speed of different gears is determined according to the tire rolling radius, the main reduction ratio and the gearbox speed ratio, and then the motor speed range of each gear is determined, that is, [downshift motor speed, upshift motor speed] is used as the motor speed range of each gear; secondly, the motor speed range with a high overlap of the motor speed range of each gear is selected, and a motor speed range is selected in the range as the HDC target motor speed range; the HDC target motor speed range should not be too large, so as to ensure that the speed change range corresponding to the range is relatively small; finally, the target speed range of different gears is determined according to the HDC target motor speed range, the tire rolling radius, the main reduction ratio and the gearbox speed ratio, and the middle value of the target speed range is taken as the HDC target speed of the gear.

[0043] As other implementations, HDC enabling judgment and driver closed-loop control steps are also provided. The overall process is as follows: Figure 1 shown.

[0044] Specifically, the specific conditions for enabling HDC are: the hill descent function switch is turned on, the accelerator pedal opening and the brake pedal opening are 0, the vehicle speed is less than or equal to the vehicle speed enabling threshold (for example, the vehicle speed enabling threshold is 15km / h), and the vehicle has no faults that affect the operation of HDC (for example, motor failure, communication failure).

[0045] Specifically, the driver closed-loop control allows the driver to manipulate the accelerator pedal and the brake pedal to a certain extent, thereby correcting the HDC total torque and ensuring that the HDC function will not exit. Figure 3 A driver closed-loop control process shown in FIG. 1 first determines whether the brake pedal opening is 0. When the brake pedal opening is not 0, it means that the driver wants to control the vehicle through the brake pedal at this time. It is further determined whether the brake pedal opening is less than a threshold value 1. If it is less than, the HDC total torque increases appropriately, and as the brake pedal opening increases, the increase in the HDC total torque also increases accordingly, but will not exceed the torque size limited by the external characteristics of the motor. If it is greater than or equal to, the vehicle exits the HDC function; if the brake pedal opening is 0, it is further determined whether the accelerator pedal is 0. If it is not 0, it means that the driver wants to control the vehicle through the accelerator pedal at this time. It is further determined whether the accelerator pedal opening is less than a threshold value 2. If it is less than, the HDC total torque decreases appropriately, and as the accelerator pedal opening increases, the decrease in the HDC total torque also increases accordingly, but it can be reduced to 0 at most. If it is greater than or equal to, the vehicle exits the HDC function; if the accelerator pedal is also 0, the HDC total torque remains unchanged.

[0046] Vehicle Example:

[0047] This embodiment provides a vehicle which, when entering the steep slope descent function, adopts a slope-adaptive steep slope descent control method as described in the method embodiment. Since the introduction of this method is clear enough, it will not be repeated here.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A slope adaptive steep slope descent control method, characterized in that: In HDC mode, the vehicle obtains a feedforward torque according to the corresponding motor torque based on the current actual motor speed and the pre-acquired correspondence between the motor speed and the motor torque, and superimposes the feedforward torque on the torque output value of the closed-loop speed control to control the vehicle to the HDC target speed. The motor speed and motor torque in the corresponding relationship are positively correlated within the motor peak torque range, and the motor speed in the corresponding relationship is divided into an acceleration interval, a slope adaptation interval and a deceleration interval as the speed increases; the slope adaptation interval corresponds to the HDC target motor speed interval; the minimum motor torque corresponding to the slope adaptation interval is calculated based on the full load mass, the minimum slope adapted to the HDC mode, and the first gear target vehicle speed, and the maximum motor torque corresponding to the slope adaptation interval is calculated based on the full load mass, the maximum slope adapted to the HDC mode, and the highest gear target vehicle speed.

2. The slope-adaptive steep slope descent control method according to claim 1, characterized in that: The positive correlation between the motor torque and the motor speed in the corresponding relationship within the motor peak torque range is an exponential relationship, and the exponential relationship is an exponential relationship of a monotonically increasing part of a parabola opening upward.

3. The slope-adaptive steep slope descent control method according to claim 1, characterized in that: The corresponding motor torque obtained is multiplied by a mass coefficient and used as the feedforward torque; the mass coefficient is determined according to the ratio of the current actual mass of the vehicle to the full-load mass.

4. The slope-adaptive steep slope descent control method according to claim 1, characterized in that: The parameters of the vehicle speed closed-loop controller in the vehicle speed closed-loop control are parameters that make the absolute value of the torque output value of the vehicle speed closed-loop control less than or equal to the absolute value of the feedforward torque.

5. The slope-adaptive steep slope descent control method according to claim 2, characterized in that: After the feedforward torque is superimposed on the torque output value of the vehicle speed closed-loop control to obtain the total torque used to drive the motor response, the opening of the accelerator pedal and the brake pedal are also judged. If the accelerator pedal opening is greater than zero and less than a preset value, the total torque is reduced. If the brake pedal opening is greater than zero and less than a preset value, the total torque is increased.

6. The slope-adaptive steep slope descent control method according to claim 5, characterized in that: The upper and lower limits of the total torque are also set according to the rated torque and the maximum allowable torque of the motor. When the total torque changes and deviates from the upper or lower limit range, the motor is controlled to reduce or increase the total torque.

7. The slope-adaptive steep slope descent control method according to claim 5, characterized in that: In the vehicle speed closed-loop control, the change rate of the total torque is also limited by the parameters of the vehicle speed closed-loop controller. When it is detected that the change rate of the total torque exceeds a preset threshold, the parameters of the vehicle speed closed-loop controller are automatically adjusted.

8. The slope-adaptive steep slope descent control method according to claim 1, characterized in that: The HDC target motor speed interval is located in the overlapping portion of the motor speed intervals corresponding to different gears of the vehicle, and the motor speed interval is determined by the motor speed corresponding to the upshift vehicle speed and the downshift vehicle speed of the corresponding gear.

9. The slope-adaptive steep slope descent control method according to claim 1, characterized in that: Before the vehicle enters the HDC mode, it is also determined whether the HDC enabling conditions are met. The HDC enabling conditions include that the HDC function is turned on, the accelerator pedal and the brake pedal opening are 0, the current vehicle speed is less than or equal to a preset vehicle speed enabling threshold, and the vehicle has no faults that affect the operation of HDC.

10. A vehicle, comprising an HDC controller, characterized in that: The HDC controller includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the slope-adaptive steep slope descent control method according to any one of claims 1 to 9 is implemented.

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