A method and system for determining expected acceleration of an adaptive cruise system

Abstract

The present invention discloses a method for determining the expected acceleration of an adaptive cruise system, including establishing a kinematic model of an adaptive cruise system following a vehicle; obtaining the control quantity of the adaptive cruise system according to the control optimization strategy and the constraint conditions corresponding to each control optimization strategy under the kinematic model of following a vehicle; wherein the control optimization strategy includes at least one of a scene determination and switching logic strategy, a cruise control strategy, and an autonomous following vehicle control strategy; and also discloses a method for determining the expected acceleration of an adaptive cruise system, including: a motion model building module, used to establish a kinematic model of an adaptive cruise system following a vehicle. The beneficial effect of the present invention is that it can determine the expected acceleration that satisfies the relative vehicle distance and the main vehicle speed while converging to the safe vehicle distance and the target vehicle speed, and satisfies the driving comfort.

Description

Technical Field

[0001] The present invention relates to the field of intelligent driving technology, and in particular to a method and system for determining expected acceleration of an adaptive cruise system. Background Art

[0002] Adaptive cruise control system, also known as ACC system, is developed based on traditional cruise control technology. It not only has the ability to cruise at a constant speed, but also has the function of automatically adjusting the vehicle's speed using information from on-board sensors to maintain a safe distance between the vehicle and the vehicle in front.

[0003] At present, the typical adaptive cruise function is to realize the longitudinal automatic driving of the car under specific working conditions, free the driver's feet, reduce the driver's operating burden, and promptly remind the driver when there is a risk of collision until active braking intervention is performed to avoid collision or reduce the risk of collision. The adaptive cruise system controls the main vehicle to cruise at the target speed set by the driver when there is no target vehicle in the detection range of the front sensor; when the target vehicle in front is within the detection range of the main vehicle and the speed of the target vehicle is less than the cruising speed set by the main vehicle, the main vehicle follows the target vehicle with a certain control strategy. Therefore, the adaptive cruise control vehicle generally uses a sensor system with radar as the main camera as the auxiliary to detect traffic environment information, such as the relative distance and relative speed between the target vehicle and the main vehicle. The adaptive cruise main control system uses traffic environment information, the driving state of the main vehicle, the motion parameters of the main vehicle, and the safe distance calculated by the safe distance model to determine the current control state of the main vehicle and send action instructions to each actuator.

[0004] Generally, the design of adaptive cruise control system adopts hierarchical design, in which the expected acceleration decision algorithm of the decision layer is based on the inter-vehicle distance algorithm. The selection and setting of the safe distance model is very critical to the adaptive cruise control system. When performing inter-vehicle distance control, the safe distance model calculates the safety state of the main vehicle in real time, and decides whether to accelerate or decelerate the main vehicle according to the driving conditions of the front vehicle. If the safe distance is set too small, the main vehicle will often be in an unsafe state when the front vehicle follows, which will cause the driver to be nervous. If the safe distance is set too large, other vehicles will frequently merge, which will reduce the driver's trust in adaptive cruise control. Therefore, it is very important to select a reliable and appropriate safe distance calculation model. At present, the fixed inter-vehicle safety time distance model is widely used in the existing technology, that is, the safe distance is equal to the main vehicle speed multiplied by the time constant, plus the minimum safe distance when parking. However, this model is too limited and affects the safety and comfort of driving.

[0005] In order to solve the problem that the distance and speed errors of the driver assistance system are not easy to converge synchronously in the front vehicle following control, a main vehicle and front vehicle motion model considering the dynamic response of the main vehicle to the expected acceleration is established to provide a model reference for the front vehicle following control. In the existing technology, the acceleration decision system often fails to reflect the motion relationship between the main vehicle and the main target vehicle, and the expected acceleration determined by the decision fails to meet the requirement that the relative distance and the main vehicle speed converge to the safe distance and the target speed at the same time. In the actual driving scene, the main problems are that the relative distance is too large, and the vehicles in the adjacent lanes cut into the lanes, affecting the traffic flow; the relative distance is too small, causing frequent vehicle braking / driving switching and safety risks; and the decision process of the existing acceleration decision system generally does not consider the driver's behavior experience, and the expected acceleration output is too large, which seriously affects the driving comfort; and the structures and mathematical models involved in some acceleration decision systems are too complex, and sometimes even use knowledge such as machine self-learning and neural networks, and the cost-effective vehicle embedded controller cannot meet its requirements for computing power. Summary of the invention

[0006] The purpose of the present invention is to provide a method and system for determining the expected acceleration of an adaptive cruise system that can reflect the motion relationship between a host vehicle and a target vehicle, determine the expected acceleration that satisfies the relative vehicle distance and the host vehicle speed while converging to a safe vehicle distance and a target vehicle speed, and meet the driving comfort.

[0007] For this reason, the technical solution adopted by the present invention is:

[0008] A method for determining expected acceleration of an adaptive cruise control system, comprising:

[0009] Establish the kinematic model of the adaptive cruise control system following the vehicle;

[0010] Under the vehicle following kinematic model, according to the control optimization strategy and the constraint conditions corresponding to each control optimization strategy, a control amount of the adaptive cruise system is obtained;

[0011] Wherein, the control optimization strategy includes at least one of a scene determination and switching logic strategy, a cruise control strategy, and an autonomous vehicle following control strategy;

[0012] The scene determination and switching logic strategy includes two stages, the first stage is the calculation of the target following distance, and the second stage is the determination of the scene and the switching logic;

[0013] The cruise control strategy includes a planning control phase and a proportional regulation phase;

[0014] When the vehicle speed is lower than the lower speed limit of the cruise control ratio stage or higher than the upper speed limit of the cruise control ratio stage, it is in the planning control stage;

[0015] When the vehicle speed is higher than the lower speed limit of the cruise control proportional stage and lower than the upper speed limit of the cruise control proportional stage, it is in the proportional adjustment stage;

[0016] Among them, the upper and lower speed limits of the cruise control ratio stage are determined by checking the ACC cruise control strategy map chart based on the target cruise speed;

[0017] The autonomous following control strategy includes three steps. The first step is to calculate the target following distance. The second step is to make a target acceleration decision by using a normalized dual-parameter proportional adjustment method. The third step is to constrain the target acceleration.

[0018] Preferably, in the first stage of the scene determination and switching logic strategy, the target following distance is calculated by the formula: y=k*x+b,

[0019] Among them, y is the target following distance, x is the set target cruising speed, k is the safe headway, and b is the minimum safe distance;

[0020] In the second stage, the specific strategy for determining the scene and switching logic is to switch between the cruise control mode and the autonomous following control mode. The switching strategy is as follows:

[0021] (1) When no vehicle is detected in front of the vehicle or the relative distance is greater than k2*y, the motion state of the vehicle in front does not affect the vehicle, and the vehicle works in the cruise control mode;

[0022] (2) When the relative distance between the vehicle and the vehicle ahead is less than k1*y, the vehicle operates in autonomous following mode;

[0023] (3) When the relative distance between the vehicle and the vehicle ahead is greater than k1*y and less than k2*y, if the relative distance changes from greater than k2*y to greater than k1*y and less than k2*y, the operating mode is cruise control; if the relative distance changes from less than k1*y to greater than k1*y and less than k2*y, the operating mode is autonomous following;

[0024] Among them, k1 and k2 are the critical distance coefficients for scene judgment, which are determined by the following vehicle level and the target cruising speed.

[0025] Preferably, in the cruise control strategy, the goal of the planning control stage is to make the vehicle speed approach the target cruising speed at a fixed constant acceleration, and the planning control stage is divided into a planning stabilization stage and a planning transition stage;

[0026] When the constant acceleration is fixed, it is in the planning stable stage. The fixed constant acceleration is determined by checking the ACC cruise control strategy map chart based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration. In the planning stable stage, when the current vehicle speed is less than the target vehicle speed, the constant acceleration is positive, and when the current vehicle speed is greater than the target vehicle speed, the constant acceleration is negative.

[0027] When there is a difference between the actual acceleration and the constant acceleration, it is in the planning transition stage. The control goal of this stage is to make the actual acceleration reach the constant acceleration value at a preset acceleration change rate. The acceleration change rate is determined based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration and the ACC cruise control strategy map chart.

[0028] Preferably, in the cruise control strategy, when the actual vehicle speed is between the upper and lower speed limits of the cruise proportional stage, it is in the proportional adjustment stage, and the proportional adjustment stage is based on formula a goal =a base *Δv / Δv max Determine, where a goal is the target acceleration, a base is the reference acceleration in the proportional phase, which is determined by checking the map chart according to the target cruising speed. Δv is the difference between the current speed and the target cruising speed. max It is the difference between the target cruising speed and the upper or lower speed limit of the proportional stage.

[0029] Preferably, in the autonomous following vehicle control strategy, the calculation formula of the first step target following vehicle distance is:

[0030] d goal =v goal *t safe +d min

[0031] Among them, d goal is the target following distance; v goal is the target following speed; t safe is the safety time distance corresponding to the set following level; d min is the minimum safe distance for following a vehicle;

[0032] The second step is to use the normalized dual-parameter proportional adjustment method to make the target acceleration decision, namely:

[0033]

[0034] Among them, a goal is the target acceleration; f v is the proportion of the acceleration decision quantity based on speed difference in the final decision quantity; f d is the proportion of the acceleration decision quantity based on the distance difference in the final decision quantity, f v +f d =1; a v-base is the speed difference reference acceleration; v cur is the current vehicle speed; v max and v minThe speed range boundary for the adaptive cruise control system function. d v-base is the distance difference reference acceleration; d cur is the relative distance between the current vehicle and the vehicle in front; d max and d min is the distance boundary that the ACC sensor can detect, f v According to the current vehicle speed, the ACC autonomous following control strategy map is checked and determined;

[0035] The third step is to constrain the target acceleration. During the following process, when the vehicle speed is equal to the set cruising speed and the target acceleration is greater than 0, or the vehicle speed is greater than the cruising speed and the target acceleration is not less than 0, the target acceleration needs to be constrained and set to a value not greater than 0. The specific value is determined by checking the ACC autonomous following control strategy spectrum chart based on the set cruising speed.

[0036] An expected acceleration decision system for an adaptive cruise control system, comprising:

[0037] The motion model building module is used to build the kinematic model of the adaptive cruise system following the vehicle;

[0038] Under the vehicle following kinematic model, according to the control optimization strategy and the constraint conditions corresponding to each control optimization strategy, a control amount of the adaptive cruise system is obtained;

[0039] Wherein, the control optimization strategy includes at least one of a scene and switching logic module, a cruise control module, and an autonomous following vehicle control module;

[0040] The scene determination and switching logic module includes:

[0041] The following distance judgment submodule is used to obtain the target following distance at the set cruising speed;

[0042] The scene determination submodule is used to switch between cruise control mode and autonomous following control mode;

[0043] The cruise control module comprises:

[0044] The planning control submodule is used to make the vehicle speed approach the target cruising speed at a fixed constant acceleration;

[0045] The proportional regulation submodule is used to stably maintain the target cruising speed, so that the speed converges to the target speed and the acceleration converges to 0;

[0046] The autonomous following vehicle control module comprises:

[0047] The following distance judgment submodule is used to obtain the target following distance in the autonomous following process;

[0048] The target acceleration decision submodule is used to obtain the target acceleration of the autonomous following vehicle;

[0049] The target acceleration constraint submodule is used to ensure safety and compliance with the functional definition.

[0050] Preferably, in the following vehicle distance determination submodule in the scene determination and switching logic module, the calculation formula of the target following vehicle distance is: y=k*x+b,

[0051] Among them, y is the target following distance, x is the set target cruising speed, k is the safe headway, and b is the minimum safe distance;

[0052] In the scene determination submodule, the specific strategy for determining the scene and the switching logic is to switch between the cruise control mode and the autonomous following control mode. The switching strategy is as follows:

[0053] (1) When no vehicle is detected in front of the vehicle or the relative distance is greater than k2*y, the motion state of the vehicle in front does not affect the vehicle, and the vehicle works in the cruise control mode;

[0054] (2) When the relative distance between the vehicle and the vehicle ahead is less than k1*y, the vehicle operates in autonomous following mode;

[0055] (3) When the relative distance between the vehicle and the vehicle ahead is greater than k1*y and less than k2*y, if the relative distance changes from greater than k2*y to greater than k1*y and less than k2*y, the operating mode is cruise control; if the relative distance changes from less than k1*y to greater than k1*y and less than k2*y, the operating mode is autonomous following;

[0056] Among them, k1 and k2 are the critical distance coefficients for scene judgment, which are determined by the following vehicle level and the target cruising speed.

[0057] Preferably, the planning control submodule is divided into a planning stabilization submodule and a planning transition submodule;

[0058] In the planning stability submodule, the constant acceleration is a fixed value, and the fixed constant acceleration is determined by checking the ACC cruise control strategy map chart based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration; in the planning stability submodule, when the current vehicle speed is less than the target vehicle speed, the constant acceleration is positive, and when the current vehicle speed is greater than the target vehicle speed, the constant acceleration is negative;

[0059] In the planning transition submodule, there is a difference between the actual acceleration and the constant acceleration, and the acceleration change rate is determined based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration by looking up the ACC cruise control strategy map chart.

[0060] Preferably, in the ratio adjustment submodule, the actual vehicle speed is between the upper and lower limits of the speed in the cruise ratio stage, and the target acceleration is calculated according to formula a goal =a base *Δv / Δv max Determine, where a goal is the target acceleration, a base is the reference acceleration in the proportional phase, which is determined by checking the MAP according to the target cruising speed. Δv is the difference between the current speed and the target cruising speed. max It is the difference between the target cruising speed and the upper or lower speed limit of the proportional stage.

[0061] Preferably, in the following distance determination submodule of the autonomous following control module, the calculation formula of the target following distance is:

[0062] d goal =v goal *t safe +d min

[0063] Among them, d goal is the target following distance; v goal is the target following speed; t safe is the safety time distance corresponding to the set following level; d min is the minimum safe distance for following a vehicle;

[0064] The target acceleration decision submodule adopts a normalized dual-parameter proportional adjustment method to make a target acceleration decision, namely:

[0065]

[0066] Among them, a goal is the target acceleration; f v is the proportion of the acceleration decision quantity based on speed difference in the final decision quantity; f d is the proportion of the acceleration decision quantity based on the distance difference in the final decision quantity, f v +f d =1; a v-base is the speed difference reference acceleration; v cur is the current vehicle speed; v max and v min The speed range boundary for the adaptive cruise control system function. d v-base is the distance difference reference acceleration; d cur is the relative distance between the current vehicle and the vehicle in front; d max and d min is the distance boundary that the ACC sensor can detect, f vAccording to the current vehicle speed, the ACC autonomous following control strategy map is checked and determined;

[0067] In the target acceleration constraint submodule, during the following process, when the vehicle speed is equal to the set cruising speed and the target acceleration is greater than 0, or the vehicle speed is greater than the cruising speed and the target acceleration is not less than 0, the target acceleration needs to be constrained and set to a value not greater than 0. The specific value is determined by checking the ACC autonomous following control strategy map based on the set cruising speed.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] 1. The critical distance coefficient in the scene determination and switching logic is determined by a two-dimensional pulse diagram consisting of the target cruising speed and the following vehicle level. The target cruising speed and the following vehicle level are set by the driver.

[0070] 2. Cruise control is divided into three stages, and a corresponding expected acceleration decision strategy is formulated based on the characteristics of each stage in the entire cruise control process. Evaluation indicators such as acceleration change rate, baseline acceleration, constant acceleration, speed upper and lower limits are introduced to ensure that the entire cruise process can respond quickly without reducing comfort, which is more in line with the driver's experience and behavior.

[0071] 3. Autonomous vehicle following control uses a normalized dual-parameter proportional adjustment method to make target acceleration decisions. The expected acceleration is determined by comprehensively considering the proportion of the acceleration decision based on speed difference in the final decision and the proportion of the acceleration decision based on distance difference in the final decision.

[0072] 4. All indirect parameters used in the acceleration decision algorithm do not need to be solved through complex mathematical equations. They can be obtained by checking the relevant pulse spectrum diagram. The pulse spectrum diagram is produced through multiple offline real vehicle calibration optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 This is the ACC scene determination and switching logic model diagram;

[0074] Figure 2 It is a cruise control strategy and process model diagram;

[0075] Figure 3 It is a schematic diagram of the expected acceleration decision system of the present invention. DETAILED DESCRIPTION

[0076] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0077] An embodiment of the present invention provides a method for determining an expected acceleration of an adaptive cruise control system, comprising:

[0078] Establish the kinematic model of the adaptive cruise control system following the vehicle;

[0079] Usually, the design of the adaptive cruise control system adopts a hierarchical design, which may include a decision layer and a control layer. The decision layer determines the desired acceleration of the vehicle and outputs the desired acceleration to the control layer, so that the actual acceleration of the vehicle converges to the desired acceleration output by the decision layer.

[0080] Under the vehicle following kinematic model, according to the control optimization strategy and the constraint conditions corresponding to each control optimization strategy, a control amount of the adaptive cruise system is obtained;

[0081] The control optimization strategy may be a combination of a scene and switching logic strategy, a cruise control strategy, and an autonomous following vehicle control strategy;

[0082] The scene determination and switching logic strategy includes two stages, the first stage is the calculation of the target following distance, and the second stage is the determination of the scene and the switching logic;

[0083] In the first stage, the target following distance is calculated as: y = k*x + b,

[0084] Among them, y is the target following distance, x is the set target cruising speed, k is the safe headway, and b is the minimum safe distance;

[0085] In the second stage, the specific strategy for determining the scene and switching logic is to switch between the cruise control mode and the autonomous following control mode, such as Figure 1 As shown, the switching strategy is as follows:

[0086] (1) When no vehicle is detected in front of the vehicle or the relative distance is greater than k2*y, see Figure 1 Middle area ①: At this time, the movement of the front vehicle does not affect the vehicle, and the vehicle works in the cruise control mode;

[0087] (2) When the relative distance between the vehicle and the vehicle ahead is less than k1*y, Figure 1 Middle area ③: At this time, the vehicle is working in autonomous following mode;

[0088] (3) When the relative distance between the vehicle and the vehicle ahead is greater than k1*y and less than k2*y, Figure 1 In the middle area ②, when the relative distance changes from greater than k2*y to greater than k1*y and less than k2*y, that is, when entering from area ①, the working mode is cruise control; when the relative distance changes from less than k1*y to greater than k1*y and less than k2*y, that is, when entering from area ③, the working mode is autonomous following;

[0089] Among them, k1 and k2 are the scene judgment critical distance coefficients, which are determined by the following vehicle level and the target cruising speed. Table 1 shows the map diagram that needs to be calibrated for scene judgment and switching logic.

[0090] Table 1 ACC scene determination and switching logic spectrum

[0091]

[0092] like Figure 2 As shown, the cruise control strategy can be divided into a planning control stage and a proportional adjustment stage according to the actual speed of the vehicle;

[0093] When the vehicle speed is lower than the lower speed limit of the cruise control ratio stage or higher than the upper speed limit of the cruise control ratio stage, it is in the planning control stage. Figure 2 As shown in the ac segment and ge segment;

[0094] When the vehicle speed is higher than the lower speed limit of the cruise control ratio stage and lower than the upper speed limit of the cruise control ratio stage, it is in the ratio adjustment stage. Figure 2 As shown in the cd and ed segments;

[0095] Among them, the upper and lower limits of the cruise control ratio stage are determined according to the target cruise speed by looking up the ACC cruise control strategy map shown in Table 2;

[0096] The goal of the planning control stage is to make the vehicle speed approach the target cruising speed at a fixed constant acceleration. The planning control stage is divided into a planning stabilization stage and a planning transition stage.

[0097] When the constant acceleration is fixed, it is in the planning stability stage, such as Figure 2 As shown in the bc and fe segments in the figure, the fixed constant acceleration is determined based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration by looking up the ACC cruise control strategy map shown in Table 2. At this stage, when the current vehicle speed is less than the target vehicle speed, the constant acceleration is positive, and when the current vehicle speed is greater than the target vehicle speed, the constant acceleration is negative.

[0098] When there is a difference between the actual acceleration and the normal acceleration, it is in the planning transition stage, such as Figure 2The control target of this stage is to make the actual acceleration reach the constant acceleration value at a certain acceleration change rate. The acceleration change rate is determined by the difference between the current vehicle speed and the target vehicle speed and the ACC cruise control strategy map shown in Table 2 to meet the comfort requirements during speed changes.

[0099] When the initial acceleration of the ab segment is negative, such as when the brake pedal is released to enter ACC control, in order to avoid the continuous decrease in vehicle speed caused by negative acceleration, on the premise of satisfying the limit constraint of the acceleration change rate for comfort, the target acceleration is determined by directly looking up the ACC cruise control strategy map diagram shown in Table 2 at the current vehicle speed; when the initial acceleration of the gf segment is positive, such as when the accelerator pedal is released to enter ACC control, in order to avoid the continuous increase in vehicle speed caused by positive acceleration, on the premise of satisfying the limit constraint of the acceleration change rate for comfort, the target acceleration is determined by directly looking up the ACC cruise control strategy map diagram shown in Table 2 at the current vehicle speed.

[0100] When the actual vehicle speed is between the upper and lower speed limits of the cruise proportional stage, it is in the proportional adjustment stage, such as Figure 2 The main control goal of this stage is to make the speed converge to the target speed and the acceleration converge to 0, so as to achieve the purpose of stably maintaining the target cruising speed. goal =a base *Δv / Δv max OK, goai is the target acceleration, a base is the reference acceleration in the proportional phase, which is determined by checking the MAP according to the target cruising speed. Δv is the difference between the current speed and the target cruising speed. max It is the difference between the target cruising speed and the upper or lower speed limit of the proportional stage.

[0101] Table 2 shows the relevant map of cruise control strategy.

[0102] Table 2 ACC cruise control strategy map

[0103]

[0104]

[0105] In the scheme of the present invention, various parameters are mainly determined by the pulse spectrograms related thereto. As shown in Table 2, the pulse spectrograms involved in the scheme of the present invention mainly include one-dimensional pulse spectrograms and two-dimensional pulse spectrograms.

[0106] In the ACC cruise control strategy map in Table 2, there is a cruise control ratio phase reference acceleration MAP, which is a one-dimensional map. The cruise control ratio phase reference acceleration MAP obtained through calibration under actual driving conditions is shown in Table 3:

[0107] Table 3 Correspondence between reference acceleration and target cruising speed in the cruise control ratio stage

[0108] Target cruising speed (x value) v1 v2 v3 v4 v5 v6 v7 Baseline acceleration value (y value) A1 A2 A3 A4 A5 A6 A7

[0109] According to Table 3, a certain target cruising speed value corresponds to a certain reference acceleration value. If at a certain moment, the target cruising speed value obtained by the adaptive cruise system is v. First, determine that the range of v falls between v3 and v4. There is no doubt that the reference acceleration value A corresponding to the target cruising speed v will fall between A3 and A4. Assume that in the calibrated spectrum, in each small interval, there is an approximate linear relationship between the x and y values. Based on this assumption, the method for determining the A value is:

[0110] A=(A4-A3) / (v4-v3)

[0111] The above example illustrates that the core of the one-dimensional spectrum graph usage method is to take some special values ​​at certain intervals under actual working conditions, calibrate the spectrum graph to determine the interval range where the x-axis parameter falls, and assume that there is a linear relationship between x and y in a certain small interval range.

[0112] The autonomous following control strategy includes three steps. The first step is to calculate the target following distance. The second step is to make a target acceleration decision by using a normalized dual-parameter proportional adjustment method. The third step is to constrain the target acceleration.

[0113] The control goal of the autonomous following process is to achieve dual-parameter convergence of the vehicle speed and the relative distance to the preceding vehicle. In the autonomous following control strategy, the calculation formula for the first step target following distance is:

[0114] d goal =v goal *t safe +d min

[0115] Among them, d goal is the target following distance; v goal is the target following speed; t safe is the safety time distance corresponding to the set following level; d min is the minimum following safety distance,

[0116] The second step is to use the normalized dual-parameter proportional adjustment method to make the target acceleration decision, namely:

[0117]

[0118] Among them, a goal is the target acceleration; f v is the proportion of the acceleration decision quantity based on speed difference in the final decision quantity; f d is the proportion of the acceleration decision quantity based on the distance difference in the final decision quantity, f v +f d =1; a v-base is the speed difference reference acceleration; v cur is the current vehicle speed; v max and v min The speed range boundary for the adaptive cruise control system function. d v-base is the distance difference reference acceleration; d cur is the relative distance between the current vehicle and the vehicle in front; d max and d min is the distance boundary that the ACC sensor can detect, f v According to the current vehicle speed, the ACC autonomous following control strategy map is checked and determined;

[0119] The third step is to constrain the target acceleration. During the following process, when the vehicle speed is equal to the set cruising speed and the target acceleration is greater than 0, or the vehicle speed is greater than the cruising speed and the target acceleration is not less than 0, in order to ensure safety and compliance with the function definition, the target acceleration needs to be constrained and set to a value not greater than 0. The specific value is determined by looking up the ACC autonomous following control strategy spectrum diagram shown in Table 4 based on the set cruising speed.

[0120] The autonomous following control uses the same control logic as the cruise control strategy to avoid long-term speed drops and increases when the brake pedal is released and the accelerator pedal is released. The comfort during the autonomous following process is constrained by the maximum allowed acceleration change rate, which is determined by looking up the ACC autonomous following control strategy map shown in Table 4 by speed difference and distance difference.

[0121] Table 4 shows the spectrum diagram related to the autonomous following control strategy.

[0122] Table 4 ACC autonomous following control strategy spectrum

[0123]

[0124]

[0125] Among them, the ACC autonomous following control strategy map in Table 4 contains a maximum acceleration change rate MAP allowed by ACC following control, which is a two-dimensional map. The maximum acceleration change rate (z value) is determined by the speed difference between the target vehicle speed and the current vehicle speed (x value) and the distance difference between the target vehicle distance and the current distance (y value). The maximum acceleration change rate MAP allowed by ACC following control is obtained through special value calibration under actual driving conditions as shown in Table 5:

[0126] Table 5 Correspondence between the maximum acceleration change rate and speed difference and distance difference of ACC autonomous following control strategy

[0127] X / Y X1 X2 X3 X4 X5 X6 X7 Y1 Z1，1 Z2，1 Z3，1 Z4，1 Z5，1 Z6，1 Z7，1 Y2 Z1，2 Z2，2 Z3，2 Z4，2 Z5，2 Z6，2 Z7，2 Y3 Z1，3 Z2，3 Z3，3 Z4，3 Z5，3 Z6，3 Z7，3 Y4 Z1，4 Z2，4 Z3，4 Z4，4 Z5，4 Z6，4 Z7，4 Y5 Z1.5 Z2，5 Z3，5 Z4，5 Z5，5 Z6，5 Z7，5 Y6 Z1.6 Z2，6 Z3，6 Z4，6 Z5，6 Z6，6 Z7，6 Y7 Z1.7 Z2，7 Z3，7 Z4，7 Z5，7 Z6，7 Z7，7

[0128] As shown in Table 5, a certain speed difference between the target speed of the vehicle and the current speed (x value) plus a certain distance difference between the target distance of the vehicle and the current distance (y value) corresponds to a certain maximum acceleration change rate (z value). At a certain moment, the adaptive cruise system collects the speed difference X between the target speed of the vehicle and the current speed and the distance difference Y between the target distance of the vehicle and the current distance. First, determine that the range of X values ​​falls between X3 and X4, and the range of Y values ​​falls between Y3 and Y4. (It should be pointed out that there is no correlation between the range of X and Y values. When the X value falls between X3 and X4, Y can fall in any interval). Then, when Y=Y3 and Y=Y4 are fixed respectively, the interval (X3, X4) of Z on the x-axis is interpolated to obtain two values ​​of Z3 and Z4. At this time, a one-dimensional value table is actually formed, as shown in Table 6:

[0129] Table 6 Correspondence between the maximum acceleration change rate and distance difference of ACC autonomous following control strategy

[0130] y Y3 Y4 z Z3 Z4

[0131] According to Table 6, by checking the one-dimensional spectrum diagram, we can get the maximum acceleration change rate Z when the value of y is Y.

[0132] Through the above specific examples, it is explained that the core of the method of using the two-dimensional pulse spectrum diagram is dimensionality reduction processing: first fix a variable, perform a one-dimensional pulse spectrum diagram table lookup processing on a number axis, and the result is a one-dimensional pulse spectrum diagram, and then perform table lookup processing on this one-dimensional pulse spectrum diagram.

[0133] On the other hand, this embodiment further provides an expected acceleration decision system for an adaptive cruise system, comprising:

[0134] The motion model building module is used to build the kinematic model of the adaptive cruise system following the vehicle;

[0135] Under the vehicle following kinematic model, according to the control optimization strategy and the constraint conditions corresponding to each control optimization strategy, a control amount of the adaptive cruise system is obtained;

[0136] Wherein, the control optimization strategy includes at least one of a scene determination and switching logic module, a cruise control module, and an autonomous following vehicle control module;

[0137] like Figure 3 As shown, the scene determination and switching logic module 1 includes:

[0138] The following vehicle distance judgment submodule 4 is used to obtain the target following vehicle distance at the set cruising speed;

[0139] The scene determination submodule 5 is used for switching between the cruise control mode and the autonomous following control mode;

[0140] The cruise control module 2 includes:

[0141] Planning control submodule 6, used to make the vehicle speed approach the target cruising speed at a fixed constant acceleration;

[0142] The proportional adjustment submodule 7 is used to stably maintain the target cruising speed, so that the speed converges to the target speed and the acceleration converges to 0;

[0143] The autonomous following vehicle control module 3 includes:

[0144] A following distance determination submodule 8 is used to obtain a target following distance in the autonomous following process;

[0145] The target acceleration decision submodule 9 is used to obtain the target acceleration of the autonomous following vehicle;

[0146] The target acceleration constraint submodule 10 is used to ensure safety and compliance with the function definition.

[0147] In the following vehicle distance determination submodule in the scene determination and switching logic module, the calculation formula of the target following vehicle distance is: y=k*x+b,

[0148] Among them, y is the target following distance, x is the set target cruising speed, k is the safe headway, and b is the minimum safe distance;

[0149] In the scene determination submodule, the specific strategy for determining the scene and the switching logic is to switch between the cruise control mode and the autonomous following control mode. The switching strategy is as follows:

[0150] (1) When no vehicle is detected in front of the vehicle or the relative distance is greater than k2*y, the motion state of the vehicle in front does not affect the vehicle, and the vehicle works in the cruise control mode;

[0151] (2) When the relative distance between the vehicle and the vehicle ahead is less than k1*y, the vehicle operates in autonomous following mode;

[0152] (3) When the relative distance between the vehicle and the vehicle ahead is greater than k1*y and less than k2*y, if the relative distance changes from greater than k2*y to greater than k1*y and less than k2*y, the operating mode is cruise control; if the relative distance changes from less than k1*y to greater than k1*y and less than k2*y, the operating mode is autonomous following;

[0153] Among them, k1 and k2 are the critical distance coefficients for scene judgment, which are determined by the following vehicle level and the target cruising speed.

[0154] The planning control submodule is divided into a planning stabilization submodule and a planning transition submodule;

[0155] In the planning stability submodule, the constant acceleration is a fixed value, and the fixed constant acceleration is determined by checking the ACC cruise control strategy map chart based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration; in the planning stability submodule, when the current vehicle speed is less than the target vehicle speed, the constant acceleration is positive, and when the current vehicle speed is greater than the target vehicle speed, the constant acceleration is negative;

[0156] In the planning transition submodule, there is a difference between the actual acceleration and the constant acceleration, and the acceleration change rate is determined based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration by looking up the ACC cruise control strategy map chart.

[0157] In the proportional adjustment submodule, the actual vehicle speed is between the upper and lower limits of the speed in the cruise proportional stage, and the target acceleration is calculated according to formula a goal =a base *Δv / Δv max Determine, where a goal is the target acceleration, a base is the reference acceleration in the proportional phase, which is determined by checking the MAP according to the target cruising speed. Δv is the difference between the current speed and the target cruising speed. max It is the difference between the target cruising speed and the upper or lower speed limit of the proportional stage.

[0158] In the following distance judgment submodule of the autonomous following control module, the calculation formula of the target following distance is:

[0159] d gaal =v goal *t safe +d min

[0160] Among them, a goal is the target following distance; v goal is the target following speed; t safeis the safety time distance corresponding to the set following level; d min is the minimum safe distance for following a vehicle;

[0161] The target acceleration decision submodule adopts a normalized dual-parameter proportional adjustment method to make a target acceleration decision, namely:

[0162]

[0163] Among them, a goal is the target acceleration; f v is the proportion of the acceleration decision quantity based on speed difference in the final decision quantity; f d is the proportion of the acceleration decision quantity based on the distance difference in the final decision quantity, f v +f d =1; a v-base is the speed difference reference acceleration; v cur is the current vehicle speed; v max and v min The speed range boundary for the adaptive cruise control system function. d v-base is the distance difference reference acceleration; d cur is the relative distance between the current vehicle and the vehicle in front; d max and d min is the distance boundary that the ACC sensor can detect, f v Determine based on the current vehicle speed by looking up the ACC autonomous following control strategy map shown in Table 4;

[0164] In the target acceleration constraint submodule, during the following process, when the vehicle speed is equal to the set cruising speed and the target acceleration is greater than 0, or the vehicle speed is greater than the cruising speed and the target acceleration is not less than 0, the target acceleration needs to be constrained and set to a value not greater than 0. The specific value is determined by looking up the ACC autonomous following control strategy spectrum diagram shown in Table 4 based on the set cruising speed.

[0165] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for determining expected acceleration of an adaptive cruise control system, characterized in that: include Establish the kinematic model of the adaptive cruise control system following the vehicle; Under the vehicle following kinematic model, according to the control optimization strategy and the constraint conditions corresponding to each control optimization strategy, a control amount of the adaptive cruise system is obtained; Wherein, the control optimization strategy includes at least one of a scene determination and switching logic strategy, a cruise control strategy, and an autonomous vehicle following control strategy; The scene determination and switching logic strategy includes two stages, the first stage is the calculation of the target following distance, and the second stage is the determination of the scene and the switching logic; The cruise control strategy includes a planning control phase and a proportional regulation phase; When the vehicle speed is lower than the lower speed limit of the cruise control ratio stage or higher than the upper speed limit of the cruise control ratio stage, it is in the planning control stage; When the vehicle speed is higher than the lower speed limit of the cruise control proportional stage and lower than the upper speed limit of the cruise control proportional stage, it is in the proportional adjustment stage; Among them, the upper and lower speed limits of the cruise control ratio stage are determined by checking the ACC cruise control strategy map chart based on the target cruise speed; The autonomous following control strategy includes three steps: the first step is to calculate the target following distance; the second step is to use a normalized dual-parameter proportional adjustment method to make a target acceleration decision; and the third step is to constrain the target acceleration. In the cruise control strategy, the goal of the planning control stage is to make the vehicle speed approach the target cruising speed at a fixed constant acceleration, and the planning control stage is divided into a planning stabilization stage and a planning transition stage; When the constant acceleration is fixed, it is in the planning stable stage. The fixed constant acceleration is determined by checking the ACC cruise control strategy map chart based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration. In the planning stable stage, when the current vehicle speed is less than the target vehicle speed, the constant acceleration is positive, and when the current vehicle speed is greater than the target vehicle speed, the constant acceleration is negative. When there is a difference between the actual acceleration and the constant acceleration, it is in the planning transition stage. The control goal of this stage is to make the actual acceleration reach the constant acceleration value at a preset acceleration change rate. The acceleration change rate is determined based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration and the ACC cruise control strategy map chart.

2. The method for determining the expected acceleration of an adaptive cruise control system according to claim 1, characterized in that: In the first stage of the scene determination and switching logic strategy, the target following distance is calculated as follows: y=k*x+b, Among them, y is the target following distance, x is the set target cruising speed, k is the safe headway, and b is the minimum safe distance; In the second stage, the specific strategy for determining the scene and switching logic is to switch between the cruise control mode and the autonomous following control mode. The switching strategy is as follows: (1) When no vehicle is detected in front of the vehicle or the relative distance is greater than k2*y, the motion state of the vehicle in front does not affect the vehicle, and the vehicle works in the cruise control mode; (2) When the relative distance between the vehicle and the vehicle ahead is less than k1*y, the vehicle operates in autonomous following mode; (3) When the relative distance between the vehicle and the vehicle ahead is greater than k1*y and less than k2*y, if the relative distance changes from greater than k2*y to greater than k1*y and less than k2*y, the operating mode is cruise control; if the relative distance changes from less than k1*y to greater than k1*y and less than k2*y, the operating mode is autonomous following; Among them, k1 and k2 are the critical distance coefficients for scene judgment, which are determined by the following vehicle level and the target cruising speed.

3. The method for determining the expected acceleration of an adaptive cruise control system according to claim 1, characterized in that: In the cruise control strategy, when the actual vehicle speed is between the upper and lower speed limits of the cruise proportional phase, it is in the proportional adjustment phase. The proportional adjustment phase is based on formula a. goal =a base *Δv / Δv max Determine, where a goal is the target acceleration, a base is the reference acceleration in the proportional phase, which is determined by checking the MAP according to the target cruising speed. Δv is the difference between the current speed and the target cruising speed. max It is the difference between the target cruising speed and the upper or lower speed limit of the proportional stage.

4. The method for determining the expected acceleration of an adaptive cruise control system according to claim 1, characterized in that: In the autonomous following control strategy, the calculation formula of the first step target following distance is: d goal =v goal *t safe +d min Among them, d goal is the target following distance; v goal is the target following speed; t safe is the safety time distance corresponding to the set following level; d min is the minimum safe following distance; The second step is to use the normalized dual-parameter proportional adjustment method to make the target acceleration decision, namely: Among them, a goal is the target acceleration; f v is the proportion of the acceleration decision quantity based on speed difference in the final decision quantity; f d is the proportion of the acceleration decision quantity based on the distance difference in the final decision quantity, f v +f d =1; a v-ba is the speed difference reference acceleration; v cur is the current vehicle speed; v max and v min The speed range boundary for the adaptive cruise control system function. d v-ba is the distance difference reference acceleration; d cur is the relative distance between the current vehicle and the vehicle in front; d max and d min is the distance boundary that the ACC sensor can detect. f v According to the current vehicle speed, the ACC autonomous following control strategy map is checked and determined; The third step is to constrain the target acceleration. During the following process, when the vehicle speed is equal to the set cruising speed and the target acceleration is greater than 0, or the vehicle speed is greater than the cruising speed and the target acceleration is not less than 0, the target acceleration needs to be constrained and set to a value not greater than 0. The specific value is determined by checking the ACC autonomous following control strategy spectrum chart based on the set cruising speed.

5. A desired acceleration decision system for an adaptive cruise control system, characterized in that: include: The motion model building module is used to build the kinematic model of the adaptive cruise system following the vehicle; Under the vehicle following kinematic model, according to the control optimization strategy and the constraint conditions corresponding to each control optimization strategy, a control amount of the adaptive cruise system is obtained; Wherein, the control optimization strategy includes at least one of a scene determination and switching logic module, a cruise control module, and an autonomous following vehicle control module; The scene determination and switching logic module includes: The following distance judgment submodule is used to obtain the target following distance at the set cruising speed; The scene determination submodule is used to switch between cruise control mode and autonomous following control mode; The cruise control module comprises: The planning control submodule is used to make the vehicle speed approach the target cruising speed at a fixed constant acceleration; The proportional regulation submodule is used to stably maintain the target cruising speed, so that the speed converges to the target speed and the acceleration converges to 0; The autonomous following vehicle control module comprises: The following distance judgment submodule is used to obtain the target following distance in the autonomous following process; The target acceleration decision submodule is used to obtain the target acceleration of the autonomous following vehicle; The target acceleration constraint submodule is used to ensure safety and compliance with the functional definition.

6. The desired acceleration decision system of the adaptive cruise system according to claim 5, characterized in that: In the following vehicle distance determination submodule in the scene determination and switching logic module, the calculation formula of the target following vehicle distance is: y=k*x+b, Among them, y is the target following distance, x is the set target cruising speed, k is the safe headway, and b is the minimum safe distance; In the scene determination submodule, the specific strategy for determining the scene and the switching logic is to switch between the cruise control mode and the autonomous following control mode. The switching strategy is as follows: (1) When no vehicle is detected in front of the vehicle or the relative distance is greater than k2*y, the motion state of the vehicle in front does not affect the vehicle, and the vehicle works in the cruise control mode; (2) When the relative distance between the vehicle and the vehicle ahead is less than k1*y, the vehicle operates in autonomous following mode; (3) When the relative distance between the vehicle and the vehicle ahead is greater than k1*y and less than k2*y, if the relative distance changes from greater than k2*y to greater than k1*y and less than k2*y, the operating mode is cruise control; if the relative distance changes from less than k1*y to greater than k1*y and less than k2*y, the operating mode is autonomous following; Among them, k1 and k2 are the critical distance coefficients for scene judgment, which are determined by the following vehicle level and the target cruising speed.

7. The desired acceleration decision system of the adaptive cruise system according to claim 5, characterized in that: The planning control submodule is divided into a planning stability submodule and a planning transition submodule; In the planning stability submodule, the constant acceleration is a fixed value, and the fixed constant acceleration is determined by checking the ACC cruise control strategy map chart based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration; in the planning stability submodule, when the current vehicle speed is less than the target vehicle speed, the constant acceleration is positive, and when the current vehicle speed is greater than the target vehicle speed, the constant acceleration is negative; In the planning transition submodule, there is a difference between the actual acceleration and the constant acceleration, and the acceleration change rate is determined based on the difference between the current vehicle speed and the target vehicle speed and the current acceleration by looking up the ACC cruise control strategy map chart.

8. The desired acceleration decision system of the adaptive cruise system according to claim 5, characterized in that: In the proportional adjustment submodule, the actual vehicle speed is between the upper and lower limits of the speed in the cruise proportional stage, and the target acceleration is calculated according to formula a goal =a base *Δv / Δv max Determine, where a goal is the target acceleration, a base is the reference acceleration in the proportional phase, which is determined by checking the MAP according to the target cruising speed. Δv is the difference between the current speed and the target cruising speed. max It is the difference between the target cruising speed and the upper or lower speed limit of the proportional stage.

9. The desired acceleration decision system of the adaptive cruise system according to claim 5, characterized in that: In the following distance judgment submodule of the autonomous following control module, the calculation formula of the target following distance is: d goal =v goal *t safe +d min Among them, d goal is the target following distance; v goal is the target following speed; t safe is the safety time distance corresponding to the set following level; d min is the minimum safe following distance; The target acceleration decision submodule adopts a normalized dual-parameter proportional adjustment method to make a target acceleration decision, namely: Among them, a goal is the target acceleration; f v is the proportion of the acceleration decision quantity based on speed difference in the final decision quantity; f d is the proportion of the acceleration decision quantity based on the distance difference in the final decision quantity, f v +f d =1; a v-base is the speed difference reference acceleration; v cur is the current vehicle speed; v max and v min The speed range boundary for the adaptive cruise control system function. d v-base is the distance difference reference acceleration; d cur is the relative distance between the current vehicle and the vehicle in front; d max and d min is the distance boundary that the ACC sensor can detect. f v According to the current vehicle speed, the ACC autonomous following control strategy map is checked and determined; In the target acceleration constraint submodule, during the following process, when the vehicle speed is equal to the set cruising speed and the target acceleration is greater than 0, or the vehicle speed is greater than the cruising speed and the target acceleration is not less than 0, the target acceleration needs to be constrained and set to a value not greater than 0. The specific value is determined by checking the ACC autonomous following control strategy map based on the set cruising speed.

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