ACC driving brake control method and system

Abstract

The invention discloses an ACC driving and braking control method and system, and relates to the technical field of ACC adaptive cruise, and the method comprises the steps: a sensing layer collects vehicle information, and a decision control layer processes the input information of the sensing layer and outputs an expected acceleration; according to the relation between the expected acceleration and the actual acceleration and a set hysteresis interval, switching between a driving mode and a braking mode is carried out; in the braking mode, according to the SOC state of the battery and the braking performance of the motor, braking force distribution and energy recovery are conducted, and the EBS is requested to conduct pressure braking; and calculating an expected driving force and a braking torque by using the driving and braking kinetic model, and controlling a vehicle driving system actuator and a braking actuator. VCU reverse dragging braking is utilized to the maximum extent, the energy loss of mechanical braking is reduced, the energy recovery efficiency is improved, the energy consumption per hundred kilometers is further reduced, the speed reduction process is more linear, the comfort is further improved, the speed reduction feeling is further weakened, and braking force distribution is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of ACC adaptive cruise control, and in particular to an ACC driving braking control method and system. Background Art

[0002] Adaptive cruise control (ACC) is an intelligent driving assistance system for cars that can automatically adjust the speed of the vehicle to maintain a safe distance based on the speed and distance of the vehicle in front. Currently, conventional ACC systems have some problems in braking:

[0003] The actual range when the intelligent driving function is turned on is much lower than the theoretical range, with a rate of less than 90%. When the intelligent assisted driving function is turned on, the actual vehicle range is about 10% lower than that under manual driving conditions. That is, the main reason for the theoretical range is that the energy recovery mode is not enabled in the intelligent driving mode.

[0004] When negative torque recovery is enabled in some ACC modes, the deceleration process may be jerky due to the unstable switching between negative torque and brake pressure, affecting the driving experience.

[0005] Existing technical problems: When negative torque recovery is enabled in some ACC modes, there is occasionally a delay in the negative torque response of the motor, and the brake pressure intervenes too late, resulting in late deceleration and a risk of collision.

[0006] In summary, the existing technology has some problems in ACC negative torque braking, and an ACC driving braking method that comprehensively considers the actuator response and actual scenarios is needed to solve these problems. This mechanism can fully utilize the motor's reverse negative torque for braking according to the real-time situation of the vehicle, thereby improving the vehicle's endurance and the smoothness and safety of the ACC system. Summary of the invention

[0007] In view of the above-mentioned existing problems, the purpose of the present invention is to comprehensively consider the delay and efficiency problems of actuators such as power, and design an ACC drive braking control method based on model predictive control. By calibrating parameters and changing algorithm modes, and optimizing the vehicle control strategy and energy recovery mode under the intelligent driving mode, the maximum utilization of VCU anti-drag braking can be achieved, which can reduce the energy loss of mechanical braking; the overall improvement of the comprehensive cruising range of intelligent driving can be achieved, and the comfort of the braking process can be improved.

[0008] In order to solve the above technical problems, an ACC driving braking control method is proposed, including:

[0009] The perception layer collects a first data set; the decision control layer processes the first data collected by the perception layer, performs acceleration change constraints, and outputs a first result; based on the comparison between the calculated first result and the actual result, a hysteresis interval is set to control switching between the driving mode and the braking mode.

[0010] As a preferred solution of the ACC driving and braking control method described in the present invention, the first data includes: the perception layer collects vehicle driving environment information and the vehicle's own state including vehicle speed, driving torque, acceleration, braking pressure, target distance, and speed information;

[0011] The decision control layer processes the first data collected by the perception layer, constrains the acceleration change through the synovial control principle, and outputs a first result;

[0012] Switching between driving and braking modes is performed according to the relationship between the first result and the actual acceleration, and the set hysteresis interval;

[0013] In braking mode, the braking force is distributed according to the battery SOC status and the motor braking performance, energy is recovered, and the EBS is requested to perform pressure braking;

[0014] The driving and braking dynamics model is used to calculate the expected driving force and braking torque, and control the vehicle drive system actuator and brake actuator.

[0015] As a preferred embodiment of the ACC driving and braking control method described in the present invention, the first result includes obtaining the acceleration value corresponding to the vehicle at each vehicle speed by testing the vehicle under various steady-speed conditions, setting a hysteresis interval on the acceleration value curve, and switching the vehicle driving and braking mode according to the expected acceleration and the size of the hysteresis interval.

[0016] As a preferred solution of the ACC driving braking control method described in the present invention, the braking force distribution includes: when the system is in the braking mode, part of the energy is converted into electrical energy, the battery SOC state is monitored, the motor braking performance is tested during the actual vehicle calibration, the executable deceleration size under different torques and different slopes is tested, different SOCs, speeds, and the time to reach the maximum deceleration are comprehensively considered, the driving force for executing braking requested by the VCU is limited, and a hysteresis interval is set to switch the braking mode;

[0017] The braking force distribution includes that when the system limit is lower than the specified vehicle speed threshold, the system is switched to pure pressure braking in any state, a hysteresis interval is set synchronously, a negative torque unloading judgment is performed, and pressure braking is requested based on the result.

[0018] As a preferred solution of the ACC driving brake control method described in the present invention, the energy recovery includes driving the electric motor to control the braking process of the vehicle, and recovering the braking energy to the maximum extent while accurately controlling the vehicle, according to the longitudinal driving equation of the vehicle:

[0019] F=F q +F k +F f +F z

[0020] Among them, F represents the driving force of the car acting on the driving wheels, F q Indicates the rolling resistance of the vehicle, F k Indicates air resistance, F f Indicates slope resistance, F z It means that the car needs to overcome acceleration resistance when accelerating.

[0021] The driving force F is transmitted to the driving wheel through the transmission system by the torque generated by the motor end:

[0022]

[0023] Where T represents the engine torque, i c represents the transmission ratio of the transmission, i j represents the transmission ratio of the main reduction, β represents the mechanical efficiency of the entire transmission system, and r represents the wheel rolling radius.

[0024] As a preferred solution of the ACC driving and braking control method described in the present invention, the expected driving force and braking torque include the VCU expected torque converted according to the longitudinal driving equation of the vehicle:

[0025]

[0026] The braking inverse dynamics model of the vehicle deceleration process is:

[0027] γ·m·a fnl =FF b -F q -F k -F f

[0028] Among them, F b is the expected braking force, and the expected braking torque is expressed as:

[0029]

[0030] Normal braking force F b There is a linear relationship with the brake pressure P:

[0031] Fb =w·P

[0032] Can be calibrated as:

[0033]

[0034] Where w is the linear coefficient.

[0035] Another object of the present invention is to provide an ACC drive braking control system, which improves the stability and accuracy of the adaptive cruise control (ACC) system, ensures that the vehicle acceleration can quickly and stably follow the expected acceleration request value, optimizes the intelligent switching of driving and braking modes, considers the delay and efficiency of the actuator, and adjusts the expected acceleration in real time to adapt to complex driving environments, thereby comprehensively improving driving smoothness, ride comfort and driving safety, while improving energy utilization.

[0036] As a preferred solution of the ACC driving brake control system described in the present invention, it is characterized by including a perception layer, a decision control layer, and an execution layer.

[0037] The perception layer inputs and monitors driving environment information and the vehicle's own status.

[0038] The decision control layer processes the target distance and speed information input by the perception layer and outputs the expected acceleration for control.

[0039] The execution layer uses the expected acceleration output by the decision control layer as input to switch between the driving and braking modes.

[0040] As a preferred solution of an ACC drive braking control system described in the present invention, the decision control layer includes controlling the actuator of the controlled vehicle so that the vehicle acceleration quickly and stably follows the output of the expected acceleration request value, the decision control layer collects the vehicle speed, driving torque, acceleration, and braking pressure, collects the distance, speed, and acceleration information of the target vehicle through the perception layer for comprehensive processing, predicts the motion state of the vehicle and the target vehicle, considers the actuator delay and efficiency issues, and uses the sliding film control principle to constrain the acceleration change to perform system execution planning decisions, and finally outputs the expected acceleration.

[0041] After receiving the expected acceleration control signal from the ACC decision control layer, the execution layer intervenes in the vehicle's drive system actuator and brake actuator according to the driving environment information input by the sensing end and the vehicle's own state, so that the actual acceleration of the vehicle follows the expected acceleration output by the ACC decision, accepts the expected acceleration and converts the driving torque required for vehicle acceleration and the negative torque and braking pressure required for braking through the inverse longitudinal dynamics model, and switches the driving and braking modes following the changes in the vehicle's expected acceleration.

[0042] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that the processor implements the steps of an ACC driving braking control method when executing the computer program.

[0043] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of the ACC driving braking control method are implemented.

[0044] Beneficial effects of the present invention: When braking in the intelligent driving mode demonstrated in an actual vehicle, the present invention achieves maximum utilization of VCU reverse braking, reduces energy loss of mechanical braking, and improves efficiency of energy recovery by calibrating parameters and changing algorithm modes.

[0045] Intelligent driving has added an energy recovery mode, and after optimization, the overall comprehensive cruising range of intelligent driving has been improved; the energy consumption per 100 kilometers has been further reduced.

[0046] Braking performance verification: the deceleration process is more linear. In small deceleration conditions, there is no need to apply pressure braking, and the braking effect is more comfortable simply by relying on the motor's reverse drag.

[0047] 1) Comfort is further improved (the proportion of acceleration change rate in a certain range);

[0048] 2) The deceleration feeling is further reduced: During the dynamic and static braking process, the overall deceleration of the optimized system is lower than the average deceleration before optimization;

[0049] 3) Optimization of braking force distribution: The maximum braking pressure applied by the actual vehicle is further reduced, further avoiding braking energy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0051] Figure 1 An overall flow chart of an ACC driving and braking control method provided by an embodiment of the present invention.

[0052] Figure 2 An acceleration control mode logic of an ACC driving braking control method is provided in one embodiment of the present invention.

[0053] Figure 3A torque and pressure change curve diagram of an ACC driving brake control method provided by an embodiment of the present invention Figure 1 .

[0054] Figure 4 A torque and pressure change curve diagram of an ACC driving brake control method provided by an embodiment of the present invention Figure 2 .

[0055] Figure 5 A comparison of cruise control simulation results for an ACC driving and braking control method provided by an embodiment of the present invention.

[0056] Figure 6 A simulation comparison of the following distance and the design value of an ACC driving braking control method provided by an embodiment of the present invention.

[0057] Figure 7 A comparison of simulation results of torque and pressure changes during the stop-go process of an ACC driving and braking control method provided by an embodiment of the present invention.

[0058] Figure 8 This is a real vehicle test result of a pure negative torque deceleration scenario of an ACC driving braking control method provided by an embodiment of the present invention.

[0059] Fig. 9 The negative torque & brake pressure mixed deceleration actual vehicle test results of an ACC driving brake control method provided by an embodiment of the present invention.

[0060] Fig.10 The pure pressure braking actual vehicle test results of an ACC driving brake control method provided by an embodiment of the present invention.

[0061] Fig.11 An actual road test route under CLTC conditions for an ACC driving braking control method provided by an embodiment of the present invention.

[0062] Fig.12 The test results of the endurance and energy consumption of an ACC driving braking control method before and after adding energy recovery are provided in one embodiment of the present invention.

[0063] Fig.13 The actual vehicle test results of the average deceleration before and after adding energy recovery of an ACC driving braking control method provided by an embodiment of the present invention.

[0064] Fig.14 The actual vehicle test results of the average braking pressure before and after adding energy recovery of an ACC driving brake control method provided by an embodiment of the present invention.

[0065] Fig.15A block diagram of an ACC driving brake working system of an ACC driving brake control system provided by an embodiment of the present invention.

[0066] Fig.16 A hardware simulation environment diagram of an ACC driving brake control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0067] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0068] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0069] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0070] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0071] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0072] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] Example 1, reference Figure 1-Figure 4 , which is the first embodiment of the present invention, provides an ACC driving brake control method, comprising:

[0074] S1: The perception layer collects the first data set.

[0075] The first data includes the sensing layer collecting vehicle driving environment information and vehicle status including vehicle speed, driving torque, acceleration, braking pressure, target distance, and speed information;

[0076] S2: The decision control layer processes the first data collected by the perception layer, performs acceleration change constraints, and outputs a first result.

[0077] The decision control layer processes the first data collected by the perception layer, constrains the acceleration change through the synovial control principle, and outputs a first result;

[0078] Switching between driving and braking modes is performed according to the relationship between the first result and the actual acceleration result, and the set hysteresis interval;

[0079] In braking mode, the braking force is distributed according to the battery SOC status and the motor braking performance, energy is recovered, and the EBS is requested to perform pressure braking;

[0080] The driving and braking dynamics model is used to calculate the expected driving force and braking torque, and control the vehicle drive system actuator and brake actuator.

[0081] By testing the vehicle under various steady-speed conditions, the acceleration value corresponding to the vehicle at various speeds is obtained, a hysteresis interval is set on the acceleration value curve, and the vehicle drive and braking mode is switched according to the expected acceleration and the size of the hysteresis interval.

[0082] S3: According to the comparison between the calculated first result and the actual result, the hysteresis interval is set to control the switching between the driving mode and the braking mode.

[0083] Furthermore, the superimposed braking energy recovery system can achieve active braking by controlling the motor, but considering that the adaptive cruise system requires the braking system to have the ability of active braking, rapid pressure increase during emergency braking, and precise pressure control. However, the motor braking torque is limited by the battery charging power, and cannot achieve fast and high-intensity braking; secondly, the motor braking torque response rate is slow, and emergency braking cannot be achieved. A reasonable driving and braking mode switching strategy helps to improve the system control accuracy.

[0084] Acceleration control mode state machine management: Based on the ACC status, the driver's current operation (Override / Go request) and the current vehicle status (whether the expected acceleration is within the threshold / whether there is pressure at the wheel end), the acceleration braking control (brake control), drive control (torque control), brake coasting control (brake coasting control) and coasting control (coasting control) instructions are obtained respectively.

[0085] Judgment conditions: 1. General situation:

[0086] brkCtrl->ToqCtrl:6->12->14; First look at the braking slide, before jumping to the braking slide, the braking force will slowly drop to 0, then the braking slide will be performed when there is no wheel cylinder braking force, and then the slide state will be entered when a small acceleration is required, and the torque control state will be entered when a large acceleration is required. (The braking slide and the slide are actually both slides, but the braking control is allowed in the braking slide state, but at this time, the wheel end torque is generally no longer applied. If the wheel end torque is applied, it will re-enter the braking state).

[0087] ToqCtrl->brkCtrl:9->13; first jump to the coasting state, and then enter the coasting state when the acceleration request is less than the upper limit of the coasting acceleration (this value is close to the natural acceleration when there is no torque and no pressure, which is slightly larger) and the acceleration error is very small. If a larger deceleration is still needed at this time, or braking is needed, jump to the braking state.

[0088] 2. Abnormal situation:

[0089] Starting stage: NoCtrl->ToqCtrl:1->3; when starting, you need to jump directly from non-control to torque control brkCtrl->ToqCtrl:5; when starting, you need to jump directly from brake control to torque control.

[0090] Slow retreat: brkCtrl->NoCtrl:2. When slow retreating, the state must be ensured to be in braking control. That is, in any state, as long as the slow retreat conditions are met, it must jump to braking control, and then exit after braking is completed.

[0091] Braking and sliding -> sliding parameters: speed difference > SpdErrBrkgHyst (0.07) || acceleration increment > BrkAcceltnDelta 0.1 (i.e. acceleration increase) (follow-stop comfort parameters)

[0092] Coasting->Drive parameters: Acceleration deviation>AcceltnErr(0).

[0093] The ACC control mode jump conditions are shown in Table 1 below:

[0094] Table 1

[0095]

[0096]

[0097] The definitions are explained in Table 2 below:

[0098] Table 2

[0099]

[0100]

[0101] It should be noted that vehicle control is a dynamic process, and the ACC control process needs to take into account wind resistance, rolling resistance, uphill and downhill conditions, so acceleration and deceleration cannot be simply judged based on the positive and negative acceleration. By testing the vehicle at various steady speed conditions, the acceleration value a corresponding to the vehicle at each speed is obtained. v .

[0102] Existing system technology, when the expected acceleration a fnl Greater than a v It will switch to driving mode; when the expected acceleration is less than zero, it will switch to braking mode, resulting in frequent switching of control modes and affecting the driving experience.

[0103] like Figure 2 As shown in a v The curve sets a hysteresis interval 2a z1 , where a z1 The value is 0.1m / s 2 Up to 0.2m / s 2 ;, improve the smoothness of system control mode switching.

[0104]

[0105] When the expected acceleration a fnl The value is greater than a v +a z1 When the expected acceleration value is less than av -a z1 When the vehicle switches to braking control, it decelerates by braking. When the desired acceleration is at -a v -a z1 and a v +a z1 , the vehicle maintains its original control mode unchanged.

[0106] S4: In the braking mode, according to the battery SOC state and the electric motor braking performance, the braking force is distributed, energy recovery is carried out, and the EBS is requested to perform pressure braking.

[0107] Furthermore, as Figure 3 shown, when the system switches to the braking mode, the precise braking force distribution strategy helps to maximize the use of the electric motor braking force while ensuring safety, improve the energy recovery efficiency, and enhance the driving and riding experience.

[0108] When the system switches to the braking mode, with the precise braking force distribution strategy, when the system is in the braking mode, part of the energy is converted into electrical energy, and the battery SOC state is monitored to avoid battery damage caused by overcharging.

[0109] At the same time, considering that in emergency conditions, the electric motor braking force response ability is insufficient and the braking time response is relatively slow, it is necessary to directly request the EBS to perform pressure braking to ensure safety. During the vehicle calibration, the electric motor braking performance is tested, and the executable deceleration a tq magnitude at different torques and different slopes is tested. Considering different SOCs, speeds, and the time to reach the maximum deceleration comprehensively, the driving force for executing braking requested by the VCU is restricted. At the same time, to avoid frequent switching between driving force braking and pressure driving, a hysteresis interval of 2a z1 is set.

[0110] When SOC < 13% or SOC < 90%, a full pressure braking request is made; when 13% < SOC < 90%, a requested braking force distribution is carried out; SOC is the available state of the remaining power, which is directly sent from the vehicle's motor controller to the intelligent driving controller for use.

[0111]

[0112] The schematic diagram of the motor torque and pressure change curve under driving braking is as Figure 3 .

[0113] It should be noted that as Figure 4 shown, considering the ACC stop-and-go scenario, there is frequent switching of the driving motor between forward and reverse rotations, which affects the motor life. At the same time, the motor control is unstable and the response is not sensitive enough at low speeds. The system restricts speeds below the specified vehicle speed threshold V limt, the system switches to pure pressure braking in any state. To avoid frequent switching of negative torque or specified pressure, set the synchronous setting hysteresis interval V z , V z The value ranges from 4km / h to 6km / h.

[0114]

[0115] Wherein, V is the current speed of the vehicle.

[0116] It should also be noted that the core of the braking energy recovery control strategy is to control the power of the electric motor during the vehicle braking process, and to recover the braking energy to the maximum extent while accurately controlling the vehicle, thereby achieving the purpose of protecting the battery and improving the endurance.

[0117] According to the longitudinal driving equation of the car:

[0118] F=F q +F k +F f +F z

[0119] Among them, F represents the driving force of the car acting on the driving wheels, F q Indicates the rolling resistance of the vehicle, F k Indicates air resistance, F f Indicates slope resistance, F z It means that the car needs to overcome acceleration resistance when accelerating.

[0120] The driving force F is transmitted to the driving wheel through the transmission system by the torque generated by the motor end:

[0121]

[0122] Where T represents the engine torque, i c represents the transmission ratio of the transmission, i j It represents the transmission ratio of the main reduction, β represents the mechanical efficiency of the entire transmission system, r represents the rolling radius of the wheel, rolling resistance and air resistance exist under any driving conditions, and for rolling resistance, there is:

[0123] F q =T l ·q

[0124] Among them, T l It represents wheel load, q represents rolling resistance coefficient. The rolling resistance coefficient is related to vehicle speed, road type, etc. The empirical value is generally between 0.01-0.018, which is modified as a calibration value.

[0125] For air resistance:

[0126]

[0127] Among them, k represents the air resistance coefficient, s represents the windward surface area of ​​the car, that is, the projection area of ​​the vehicle's driving direction, and ρ represents the air density, generally ρ = 1.2258Ns 2 .m -4 ;v x Indicates relative vehicle speed, which is taken as the vehicle speed when there is no wind.

[0128] For ramp resistance:

[0129] F f =G·sinα

[0130] Among them, G is the gravity acting on the car, and α is the road slope angle.

[0131] For driving resistance:

[0132] F z =γ·m·a fnl

[0133] Among them, γ represents the vehicle rotation mass conversion coefficient, m represents the vehicle curb mass, a fnl It is the expected acceleration of multi-objective following vehicle output by the decision layer.

[0134] S5: Utilize the driving and braking dynamics model to calculate the expected driving force and braking torque, and control the vehicle driving system actuator and the braking actuator.

[0135] Specifically, the VCU expected torque is calculated based on the longitudinal driving equation of the vehicle:

[0136]

[0137] The braking inverse dynamics model of the vehicle deceleration process is:

[0138] γ·m·a fnl =FF b -F q -F k -F f

[0139] Among them, F b is the expected braking force, and the expected braking torque is expressed as:

[0140]

[0141] Normal braking force F b There is a linear relationship with the brake pressure P:

[0142] F b =w·P

[0143] Can be calibrated as:

[0144]

[0145] Where w is the linear coefficient.

[0146] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0147] Example 2, reference Figure 5-Figure 14 , Fig.16 , which is the second embodiment of the present invention, provides an ACC driving braking control method. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0148] After completing the design of the adaptive cruise control system based on model predictive control, the HIL hardware-in-the-loop simulation platform, using the Carsim vehicle model, established the corresponding vehicle control module based on the Matlab / Simulink environment to establish a system simulation control model, analyze the torque response, brake following, cruise control and other related parameters, and verify the effectiveness and reliability of the system.

[0149] Fig.16 The hardware and system principles for the hardware-in-the-loop simulation platform are established. The simulation platform uses a real autonomous driving controller as the test piece, and the peripherals are matched with virtual scene simulation, real-time simulation system and environmental perception simulation system to jointly construct a virtual operating environment for the controller under test. It is mainly composed of virtual scene simulation system, real-time simulation system, host computer system, perception simulation system and motor and pressure brake controller. The torque request command issued by the system is executed by VCU, and the pressure request command issued is executed by EBS.

[0150] The results are compared as follows:

[0151] Combined with daily ACC usage scenarios, we designed cruise conditions, stop&go conditions and other simulation conditions. We observed the vehicle following distance, acceleration following, speed steady state, requested and responded driving torque, requested and responded brake pressure following control effects.

[0152] The initial speed of the cruise condition is set at 10km / h. When the system reaches steady-state driving, the cruise target speed is set to 30km / h and 60km / h, and then gradually decelerated to 30km / h and 10km / h. The simulation results of the cruise condition are shown below. Figure 5. It can be seen that the system can quickly execute the desired speed, and the actual speed quickly converges to the desired vehicle speed in a short time, with a deviation of ±1km / h, completing the speed tracking control in the acceleration scenario. During the acceleration and deceleration process, the motor torque change closely follows the requested torque, the tracking error is <100ms, the tracking error is less than 3%, and the overshoot is less than 3%. Acceleration and uniform speed control are achieved by controlling the motor, and deceleration control is achieved through negative torque. In the case of small deceleration, the system uses torque for gliding deceleration, and the torque trend is basically consistent with the trend of system acceleration change; at the same time, the braking pressure is always 0 in the case of small deceleration, which is consistent with the design, further proving that the system has a good tracking effect on the set cruise speed during acceleration and deceleration.

[0153] The stop&go condition tests the system's safety and following ability. Figure 6 The acceleration distance of the following vehicle is compared with the design value. The requested acceleration and the design acceleration trend are well matched, the peak deviation is within 3%, and the accuracy is good; the acceleration decreases and increases smoothly, proving that the acceleration and deceleration process, the torque and brake pressure switching logic are in line with the design. The actual vehicle spacing can stably follow the changes in the safe vehicle spacing. The deviation between the actual distance of the following process and the design value is within 0.6m, and the average distance of the following stop is 3.2m, which meets the following stop distance requirement (3±0.5m) required by the system.

[0154] Figure 7 The simulation results of torque and pressure change in the process of stop and go are compared. From the speed change curve, it can be seen that the vehicle follows the front vehicle to start, accelerate, decelerate, and stop. Point A is the vehicle decelerating from 90kph. First, negative torque deceleration is performed. After reaching the maximum negative torque limit of the system, pressure braking intervenes. The acceleration of the whole process is smooth. Figure 6 As shown. Point B is in the process of stop-and-go, and negative torque is requested for braking first. When the speed is lower than 12kph, the system directly requests pressure braking and synchronously requests torque release to 0. The torque switches smoothly during the whole process, and the pressure rises rapidly. During the torque and pressure switching process, the acceleration is smooth and the vehicle will not experience setbacks. It can be seen that the ACC control strategy controls the vehicle to safely and smoothly follow the target vehicle in front under stop-and-go conditions, and always maintains a safe distance from the target vehicle in front, with good followability and safety.

[0155] The simulation results show that in each scenario test, the intelligent driving braking energy system based on model predictive control can accurately achieve acceleration and uniform speed control by controlling the motor, and can also achieve deceleration control through motor torque and pressure braking, and the control following effect is good, which can effectively verify that the system has complete control stability and can meet the functional test requirements of the ACC system.

[0156] Actual vehicle test verification:

[0157] The ACC system is installed on a certain vehicle model to verify the effectiveness of the system design and the actual energy-saving effect. The rationality of the braking energy recovery control strategy is verified through cruise control conditions, stop&go conditions, cruise following, and front vehicle jamming, and the energy-saving effect of adding braking energy recovery strategy control in ACC mode is verified through CLTC conditions.

[0158] Braking energy recovery control strategy verification:

[0159] Figure 8 This is the actual vehicle test result of the pure negative torque deceleration scenario. The driver operates the control button to decelerate from 80km / h to 60km / h, 40km / h and 20km / h. From the two sets of curves, the time from the start of the request torque to the actual torque response is ≤50ms, and the silent time delay is small; the time from the request torque to the actual torque reaching 95% of the request torque is ≤100ms, and the request response delay is small; the difference between the maximum value of the actual torque and the requested torque is less than 5N.m, and the overshoot is less than 5%; steady-state error: the difference between the actual torque and the requested torque after stabilization is less than 5Nm, the system steady state is good, and there is no oscillation phenomenon in the steady state. It can be seen that during the cruising process, the system uses the negative torque of the motor to decelerate, the deceleration of the whole vehicle is smooth and linear, and the control is comfortable and precise. The ACC system is installed on a certain model to verify the effectiveness of the system design and the actual energy-saving effect. The rationality of the brake energy recovery control strategy is verified by carrying out cruise control conditions, stop&go conditions, cruise following, and vehicle cutting in through the vehicle in front on a real vehicle. The energy-saving effect of adding brake energy recovery strategy control in ACC mode is verified through CLTC conditions.

[0160] Braking energy recovery control strategy verification:

[0161] Figure 8 This is the actual vehicle test result of the pure negative torque deceleration scenario. The driver operates the control button to control the deceleration, from 80km / h to 60km / h, 40km / h and 20km / h. From the two sets of curves, the time from the start of the request torque to the actual torque response is ≤50ms, and the silent time delay is small; the time from the request torque to the actual torque reaching 95% of the request torque is ≤100ms, and the request response delay is small; the difference between the maximum value of the actual torque and the requested torque is less than 5N.m, and the overshoot is <5%; steady-state error: the difference between the actual torque and the requested torque after stabilization is <5Nm, the system steady state is good, and there is no oscillation phenomenon in the steady state. It can be seen that during the cruising process, the system uses the negative torque of the motor to decelerate, the deceleration of the whole vehicle is smooth and linear, and the control is comfortable and precise.

[0162] Fig. 9This is the actual vehicle test result of negative torque & brake pressure mixed deceleration. When the front vehicle decelerates slightly, such as point A, the system requests negative torque deceleration for braking, and the deceleration & negative torque slope is small, which is in a stable deceleration process. As the front vehicle decelerates sharply, the system requests an increase in deceleration and an increase in slope, and the system cannot meet the requirements by relying on negative torque deceleration. At this time, the negative torque is quickly pulled down to the maximum value, and the superimposed request pressure enters the hybrid braking mode. From the acceleration response curve of the whole vehicle, it can be seen that the negative torque + pressure mixed deceleration is switched in time. When the two are superimposed on deceleration, the VCU response driving torque tracking silent time is basically less than 100ms, the overshoot is less than 10N.m, and the tracking error is about 150ms; the EBS response pressure follow-up is better, the maximum silent time is 98ms, the overshoot is less than 5%, and the tracking error is about 135ms. The acceleration curve of the whole vehicle is smooth, the speed drops smoothly, there is no setback in the deceleration process, and the control comfort and accuracy are high.

[0163] When the vehicle in front is trying to squeeze in or brakes suddenly, the situation is critical. If the motor performs negative torque braking, the vehicle will decelerate and there will be a risk of collision. To avoid the risk of collision due to untimely deceleration, the system directly requests pressure braking. Fig.10 This is the result of a pure pressure braking test. As can be seen from the box in the figure, when the system decelerates suddenly, it will quickly request torque unloading, the torque is kept at 0, and the torque tracking error is less than 100ms. At the same time, the system quickly requests pressure braking, the silent time is basically 100ms, and basically no overshoot occurs. The whole process is torque unloading, the pressure braking connection and switching are natural, the deceleration drops smoothly and quickly, and there is no setback during the deceleration process, which can meet the safety braking requirements in emergency situations.

[0164] Energy saving improvement verification-1. Endurance verification

[0165] According to the CLTC operating conditions, road tests of more than 2,000 km were carried out in congested urban areas (40km / h-60km / h), suburban expressways (60km / h-80km / h), and highways (80km / h-120km / h). The SOC power was 100% before each test and 25% at the end of the test. Fig.11 It is the actual road test route of a certain vehicle model (theoretical range 300) under the reference CLTC working condition. Table 3 is the actual vehicle test results under various scenarios.

[0166] Table 3 Actual vehicle test results in various scenarios

[0167]

[0168] Based on the weighted average of different test results, the comprehensive cruising range in the optimized ACC mode is improved by 16.9% compared with the range before optimization; compared with the manual driving mode, the overall cruising range is improved by 9.7%; the energy consumption per 100 kilometers is reduced by 1.75Kwh, a reduction of 14.9%, with obvious energy-saving effects. Fig.12 The endurance and energy consumption test results before and after optimization to increase the energy recovery mode.

[0169] 2. Optimized braking performance

[0170] According to the CLTC working conditions and the daily ACC braking use scenarios, three braking conditions at different speeds were designed: following a stationary target, dynamic following, and following a vehicle with deceleration. The braking verification scenarios and test results are shown in Table 4; egoV is the ego vehicle speed, gvtV is the target vehicle speed, and the average weighted braking pressure and braking deceleration under the same working conditions are taken.

[0171] Table 4 Braking verification scenarios and test results

[0172]

[0173]

[0174] Fig.13 In order to increase the comparison of the actual vehicle test results of the average deceleration before and after energy recovery, it can be seen that the deceleration feeling is further weakened: in the dynamic and static braking process, the overall deceleration of the optimized system is about 0.2m / s^2 lower than the average deceleration before optimization. The reduction in average deceleration further reduces the energy consumption of the whole vehicle.

[0175] Fig.14 In order to increase the average braking pressure before and after energy recovery, the actual vehicle test results show that the average maximum braking pressure issued by the actual vehicle is reduced by about 4 bar, further avoiding braking energy loss.

[0176] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0177] Embodiment 3, the third embodiment of the present invention, is different from the first two embodiments in that:

[0178] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0179] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0180] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0181] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0182] Example 4, reference Fig.15 , which is the fourth embodiment of the present invention, and this embodiment provides an ACC driving braking control system, including a perception layer 100, a decision control layer 200, and an execution layer 300.

[0183] The perception layer 100 inputs and monitors the driving environment information and the vehicle's own status.

[0184] The decision control layer 200 processes the target distance and speed information input by the perception layer 100 and outputs the expected acceleration for control.

[0185] The decision control layer 200 controls the actuator of the controlled vehicle so that the vehicle acceleration quickly and stably follows the output desired acceleration request value. The decision control layer 200 collects the vehicle speed, driving torque, acceleration, and brake pressure, and collects the distance, speed, acceleration and other information of the target vehicle through the perception layer 100 for comprehensive processing, predicts the motion state of the vehicle and the target vehicle, considers the actuator delay and efficiency issues, and uses the sliding film control principle to constrain the acceleration change to make system execution planning decisions, and finally outputs the desired acceleration.

[0186] The execution layer 300 uses the desired acceleration output by the decision control layer 200 as input to switch between the driving and braking modes.

[0187] After receiving the expected acceleration control signal from the ACC decision control layer 200, the execution layer 300 intervenes in the vehicle's drive system actuator and brake actuator according to the driving environment information input by the sensing end and the vehicle's own state, so that the actual acceleration of the vehicle follows the expected acceleration output by the ACC decision. The system is fast, stable and accurate, such as EBS pressure braking and braking or VCU driving caused by VCU energy recovery.

[0188] The desired acceleration is accepted and converted into the driving torque required for vehicle acceleration and the negative torque and braking pressure required for braking through the inverse longitudinal dynamics model. The driving and braking modes are switched according to the changes in the desired acceleration of the vehicle.

[0189] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An ACC driving brake control method, characterized in that: include, The perception layer collects a first data set; The decision control layer processes the first data collected by the perception layer, performs acceleration change constraints, and outputs a first result; According to the comparison between the calculated first result and the actual result, the hysteresis interval is set to control the switching between the driving mode and the braking mode.

2. The ACC driving brake control method according to claim 1, characterized in that: The first data includes the sensing layer collecting vehicle driving environment information and vehicle status including vehicle speed, driving torque, acceleration, braking pressure, target distance, and speed information; The decision control layer processes the first data collected by the perception layer, constrains the acceleration change through the synovial control principle, and outputs a first result; Switching between driving and braking modes is performed according to the relationship between the first result and the actual acceleration result, and the set hysteresis interval; In braking mode, the braking force is distributed according to the battery SOC status and the motor braking performance, energy is recovered, and the EBS is requested to perform pressure braking; The driving and braking dynamics model is used to calculate the expected driving force and braking torque, and control the vehicle drive system actuator and brake actuator.

3. An ACC driving brake control method as claimed in claim 2, characterized in that: The first result includes obtaining the acceleration value corresponding to the vehicle at each vehicle speed by testing the vehicle under various steady-speed conditions, setting a hysteresis interval on the acceleration value curve, and switching the vehicle drive braking mode according to the expected acceleration and the size of the hysteresis interval.

4. The ACC driving brake control method according to claim 3, characterized in that: The braking force distribution includes: when the system is in braking mode, part of the energy is converted into electrical energy, the battery SOC state is monitored, the motor braking performance is tested during actual vehicle calibration, the executable deceleration size under different torques and different slopes is tested, different SOCs, speeds, and the time to reach the maximum deceleration are comprehensively considered, the driving force for executing braking requested by the VCU is limited, and a hysteresis interval is set for switching the braking mode; The braking force distribution includes that when the system limit is lower than the specified vehicle speed threshold, the system is switched to pure pressure braking in any state, a hysteresis interval is set synchronously, a negative torque unloading judgment is performed, and pressure braking is requested based on the result.

5. The ACC driving brake control method according to claim 4, characterized in that: The energy recovery includes controlling the electric motor power during the vehicle braking process, and recovering the braking energy to the maximum extent while accurately controlling the vehicle. According to the longitudinal driving equation of the vehicle: F=F q +F k +F f +F z Among them, F represents the driving force of the car acting on the driving wheels, F q Indicates the rolling resistance of the vehicle, F k Indicates air resistance, F f Indicates slope resistance, F z It means that the car needs to overcome the acceleration resistance when accelerating; The driving force F is transmitted to the driving wheel through the transmission system by the torque generated by the motor end: Where T represents the engine torque, i c represents the transmission ratio of the transmission, i j represents the transmission ratio of the main reduction, β represents the mechanical efficiency of the entire transmission system, and r represents the wheel rolling radius.

6. An ACC driving brake control method as claimed in claim 5, characterized in that: The desired driving force and braking torque include the VCU desired torque converted according to the longitudinal driving equation of the vehicle: The braking inverse dynamics model of the vehicle deceleration process is: γ·m·a fnl =F-F b -F q -F k -F f Among them, F b is the expected braking force, and the expected braking torque is expressed as: Normal braking force F b There is a linear relationship with the brake pressure P: F b =w·P Can be calibrated as: Where w is the linear coefficient.

7. A system using an ACC driving brake control method as claimed in any one of claims 1 to 6, characterized in that: Includes perception layer, decision-making control layer, and execution layer; The perception layer inputs the monitoring driving environment information and the vehicle's own status; The decision control layer processes the target distance and speed information input by the perception layer and outputs the expected acceleration for control; The execution layer uses the expected acceleration output by the decision control layer as input to switch between the driving and braking modes.

8. An ACC driving brake control system as claimed in claim 7, characterized in that: The decision control layer includes controlling the actuator of the controlled vehicle so that the vehicle acceleration quickly and stably follows the output of the desired acceleration request value. The decision control layer collects the speed, driving torque, acceleration, and brake pressure of the vehicle, collects the distance, speed, and acceleration information of the target vehicle through the perception layer for comprehensive processing, predicts the motion state of the vehicle and the target vehicle, considers the actuator delay and efficiency issues, and performs acceleration change constraints through the sliding film control principle to perform system execution planning decisions, and finally outputs the desired acceleration; After receiving the expected acceleration control signal from the ACC decision control layer, the execution layer intervenes in the vehicle's drive system actuator and brake actuator according to the driving environment information input by the sensing end and the vehicle's own state, so that the actual acceleration of the vehicle follows the expected acceleration output by the ACC decision, accepts the expected acceleration and converts the driving torque required for vehicle acceleration and the negative torque and braking pressure required for braking through the inverse longitudinal dynamics model, and switches the driving and braking modes following the changes in the vehicle's expected acceleration.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of an ACC driving braking control method according to any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of an ACC driving and braking control method according to any one of claims 1 to 6 are implemented.

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