System and method for taking acceleration lag into account in a lead vehicle to improve host vehicle operation

Abstract

Procedure that includes: Obtaining information about a lead vehicle (140) by a processing circuit arrangement of a host vehicle (100), wherein the lead vehicle (140) is traveling directly in front of the host vehicle (100) and the information includes the speed of the lead vehicle (140) and a distance g between the host vehicle (100) and the lead vehicle (140); based on detecting a change in the speed of the lead vehicle (140) in the information, calculating, using the processing circuit arrangement, a corresponding target acceleration for the host vehicle (100) using a perceived acceleration of the lead vehicle (140), wherein the perceived acceleration of the lead vehicle (140) is based on the change in speed specified by the information; based on a review of the parameters involved in the calculation of the corresponding target acceleration, calculate, using the processing circuit arrangement, a modified target acceleration for the host vehicle (100) using a lag for the lead vehicle (140), resulting in an intended acceleration of the lead vehicle (140) that differs from the perceived acceleration; and Implement the modified target acceleration for the host vehicle (100); characterized by the fact that The corresponding target acceleration for the host vehicle (100) is calculated using the processing circuit arrangement such that the distance g is maintained within a specified range of distance values.

Description

INTRODUCTION

[0001] The present invention relates to taking into account the acceleration lag in a lead vehicle in order to improve host vehicle operation. In particular, the invention relates to a method and a system according to the preamble of claim 1 and claim 6 respectively, as is known essentially from DE 601 26 905 T2.

[0002] Further state of the art can be found in the documents DE 691 23 947 T2, DE 10 2017 221 643 A1 and DE 10 2010 006 087 A1, which each deal with the distance control of host vehicles behind lead vehicles.

[0003] Vehicles (e.g., passenger cars, trucks, construction equipment, automated factory systems) use sensors to perform semi-autonomous or autonomous operation. Examples of sensors (e.g., a camera, radar system, lidar system, inertial measurement unit, accelerometer) provide information about the vehicle and its environment. Examples of semi-autonomous operations include adaptive cruise control (ACC) and collision avoidance. ACC is a driver assistance system that maintains a driver-specified speed for the host vehicle (i.e., the vehicle implementing the ACC system), while adjusting this speed as needed to maintain a safe distance from a lead vehicle (i.e., a vehicle directly in front of the host vehicle). A collision avoidance system autonomously applies the brakes of the host vehicle to prevent a collision with a lead vehicle.Autonomous vehicles incorporate both adaptive cruise control (ACC) and collision avoidance functionalities. Previous approaches to mitigating head-on collisions in autonomous and semi-autonomous vehicles are outdated. These approaches rely on the vehicle reacting to detected changes in the speed or distance of a lead vehicle. Therefore, it is desirable to incorporate acceleration lag in the lead vehicle to improve the host vehicle's performance. SUMMARY

[0004] According to the invention, a method is presented which is characterized by the features of claim 1.

[0005] The method involves obtaining information about a lead vehicle from a host vehicle via a processing circuit. The lead vehicle travels directly in front of the host vehicle, and the information includes the lead vehicle's speed and a distance g between the host and lead vehicles. The method also includes calculating a corresponding target acceleration for the host vehicle, using a perceived acceleration of the lead vehicle, to maintain the distance g within a specified range of distance values. This is achieved by detecting a change in the lead vehicle's speed in the information using the processing circuit. The perceived acceleration of the lead vehicle is based on the change in speed indicated by the information.Based on an examination of the parameters involved in calculating the corresponding target acceleration, a modified target acceleration for the host vehicle is calculated using a lag for the lead vehicle that results in an intended acceleration of the lead vehicle that differs from the perceived acceleration. The modified target acceleration is then implemented for the host vehicle.

[0006] In addition to one or more of the features described herein, obtaining information about the lead vehicle includes obtaining the measured speed of the lead vehicle using a sensor, wherein the sensor includes a radar system, a lidar system or a camera.

[0007] In addition to one or more of the features described here, calculating the corresponding target acceleration for the host vehicle includes determining a target distance g* as: g*=g0+max[0,(ϑHT+(ϑHΔϑ2aHb))], where g0 is a fixed minimum distance value, ϑ H where T is the current speed of the host vehicle, T is a known constant relating to a time associated with a safe distance, and Δϑ is the difference between a current speed ϑ L of the lead vehicle and the current speed ϑ H of the host vehicle is, a H where is the current acceleration of the host vehicle and b is a known constant that limits the deceleration.

[0008] In addition to one or more of the features described here, performing the parameter check includes determining whether the target distance g* is within the specified range of distance values, whereby the calculation of the modified target acceleration is not performed if the target distance g* is within the specified range of distance values.

[0009] In addition to one or more of the features described here, calculating the corresponding target acceleration for the host vehicle includes determining the target acceleration ϑ̇. H (t) for the host vehicle as: ϑ˙H(t)=aH(1−(ϑHϑHf)δ)−aH((g*(ϑHΔϑ)g)2), where ϑ Hf where g is the final speed of the host vehicle required to achieve the target distance g*, and g is the current distance.

[0010] In addition to one or more of the features described here, performing the parameter check includes determining whether there is a difference between the current acceleration of the host vehicle and the corresponding target acceleration within a specified range.

[0011] In addition to one or more of the features described here, the modified target acceleration of the host vehicle is determined using: aest=ϑ˙H(t)(1−e(t−φ)τ) calculated, whereby The lag time constant τ and the delay constant φ can be obtained from a lookup table for a type of lead vehicle.

[0012] In addition to one or more of the features described here, the modified target acceleration of the host vehicle is determined by adding one or more model-based factors to a est calculated.

[0013] In addition to one or more of the features described here, the model-based factors include a statistical model of an acceleration factor of the deceleration of the lead vehicle and a smoothness factor.

[0014] In addition to one or more of the features described herein, the procedure also includes updating the lookup table for the type of lead vehicle based on a result of implementing the new corresponding target acceleration for the host vehicle.

[0015] Furthermore, according to the invention, a system in a host vehicle is presented, wherein the system is characterized by the features of claim 6. The system comprises one or more sensors to provide information about a lead vehicle. The lead vehicle travels directly in front of the host vehicle, and the information includes the speed of the lead vehicle and a distance g between the host vehicle and the lead vehicle. The system also includes a controller to calculate a corresponding target acceleration for the host vehicle based on the detection of a change in the speed of the lead vehicle in the information, using a perceived acceleration of the lead vehicle, in order to maintain the distance g within a specified range of distance values.The perceived acceleration of the lead vehicle is based on the change in velocity indicated by the information. Based on an examination of the parameters involved in calculating the corresponding target acceleration, a modified target acceleration for the host vehicle is calculated using a lag for the lead vehicle that results in an intended acceleration of the lead vehicle that differs from the perceived acceleration. The modified target acceleration is then implemented in the host vehicle.

[0016] In addition to one or more of the features described here, the one or more sensors include a radar system, a lidar system, or a camera.

[0017] In addition to one or more of the features described here, the controller calculates the corresponding target acceleration for the host vehicle by determining a target distance g* as: g*=g0+max[0,(ϑHT+(ϑHΔϑ2aHb))], where g0 is a fixed minimum distance value, ϑ H where T is the current speed of the host vehicle, T is a known constant relating to a time associated with a safe distance, and Δϑ is the difference between a current speed ϑ L of the lead vehicle and the current speed ϑ H of the host vehicle is, a H where is the current acceleration of the host vehicle and b is a known constant that limits the deceleration.

[0018] In addition to one or more of the features described here, the controller performs the parameter check by determining whether the target distance g* is within the specified range of distance values, whereby the calculation of the modified target acceleration is not performed if the target distance g* is within the specified range of distance values.

[0019] In addition to one or more of the features described here, the controller calculates the corresponding target acceleration for the host vehicle by determining the target acceleration ϑ̇. H (t) for the host vehicle as: ϑ˙H(t)=aH(1−(ϑHϑHf)δ)−aH((g*(ϑHΔϑ)g)2), where ϑ Hf where g is the final speed of the host vehicle required to achieve the target distance g*, and g is the current distance.

[0020] In addition to one or more of the features described here, the controller performs the parameter check by determining whether there is a difference between the current acceleration of the host vehicle and the corresponding target acceleration within a specified range.

[0021] In addition to one or more of the features described here, the controller calculates the modified target acceleration of the host vehicle as: aest=ϑ˙H(t)(1−e(t−φ)τ), where The lag time constant τ and the inhibition constant φ can be obtained from a lookup table for a type of lead vehicle.

[0022] In addition to one or more of the features described here, the controller calculates the modified target acceleration of the host vehicle by adding one or more model-based factors.

[0023] In addition to one or more of the features described here, the model-based factors include a statistical model of an acceleration factor of the deceleration of the lead vehicle and a smoothness factor.

[0024] In addition to one or more of the features described herein, the controller updates the lookup table for the type of lead vehicle based on a result of implementing the new corresponding target acceleration for the host vehicle.

[0025] The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, advantages, and details appear only as examples in the following detailed description, which refers to the drawings, wherein: Fig. 1. A block diagram illustrating an exemplary scenario that includes an estimate of the actual acceleration of a lead vehicle to improve the operation of a host vehicle according to one or more embodiments; and Fig. 2 a process flow of a method for improving the operation of a host vehicle by estimating an actual acceleration of a lead vehicle according to one or more embodiments. DETAILED DESCRIPTION

[0027] The following description is merely exemplary. It should be recognized that throughout the drawings, corresponding reference symbols indicate the same or corresponding parts and features.

[0028] As previously stated, systems use various sensors to enable semi-autonomous and autonomous operation of a host vehicle. Such systems, like adaptive cruise control (ACC) and collision avoidance systems, require, for example, the detection of the relative position and acceleration of a lead vehicle. Acceleration is the rate of change of velocity over time and can result in either an increase or a decrease in speed. Deceleration, in particular, is acceleration that causes a decrease in speed. The perceived or measured acceleration of the lead vehicle can be inaccurate due to a lag in the lead vehicle's response. That is, the final (i.e., intended) acceleration commanded in the lead vehicle by a driver or controller may not correspond exactly to the acceleration perceived before the lag.The lag between a signal (e.g., a driver applying the brake or accelerator pedal), which results in the perceived acceleration initially measured by the host vehicle, and the intended final speed of the lead vehicle based on the application signal, can vary depending on the type of lead vehicle.

[0029] As a result of this lag inherent in a given lead vehicle, the semi-autonomous or autonomous operation of the host vehicle, which is based on responding to perceived acceleration (i.e., the change in measured or sampled velocity), may cause the host vehicle to operate in a way that increases or decreases the distance between the host vehicle and the lead vehicle beyond an acceptable range. Consequently, sudden acceleration or braking may be necessary in the host vehicle, resulting in an uncomfortable ride for the host vehicle's occupants. The embodiments of the systems and methods described in detail herein relate to taking into account the acceleration lag in a lead vehicle in order to improve the host vehicle's operation.Specifically, a more accurate target acceleration of the host vehicle can be determined, taking into account the lag that causes the intended acceleration of the lead vehicle to differ from the perceived acceleration of the lead vehicle.

[0030] According to an exemplary embodiment, Fig. 1 A block diagram illustrating an exemplary scenario that incorporates consideration of acceleration lag in a lead vehicle 140 to improve the operation of a host vehicle 100. The in Fig. The exemplary host vehicle 100 shown is a passenger car 101. The exemplary command vehicle 140 is a truck. A distance g between the host vehicle 100 and the command vehicle 140 is specified. This distance g is within an acceptable range, defined by a minimum distance gmin and a maximum distance gmax, as also specified. The host vehicle 100 contains the sensors 120, which receive information about the host vehicle 100, and the sensors 130, which receive information about its surroundings, including the presence, position, and acceleration of the command vehicle 140.

[0031] The host vehicle 100 also includes a controller 110, which receives information from sensors 120 and 130 and controls the semi-autonomous or autonomous operation of the vehicle 100. This operation may include the control of the adaptive cruise control (ACC) or collision avoidance system. The controller 110 may include a processing circuit arrangement that may contain an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or grouped), and memory that executes one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.

[0032] Fig.Section 2 describes a process flow of a method 200 for improving the operation of a host vehicle 100, taking into account acceleration lag in a guide vehicle 140, according to one or more embodiments. The processes can be executed by the controller 110 of the host vehicle 100. In section 210, obtaining the type, acceleration, velocity, and position of the guide vehicle 140 involves using the sensors 130 (e.g., the lidar system, radar system, camera) according to known techniques. The type of the guide vehicle 140 (e.g., small car, truck) facilitates the use of a lookup table to determine the lag time constants τ. acc (Acceleration lag) and τ dec (Retardation lag) and the inhibition constants φ acc (Acceleration lag) and φ dec(delay lag). As further discussed with regard to block 240, the relevant values ​​from the lookup table can be accessed as part of the prediction. The process in block 210 is executed continuously. When a change in speed (i.e., an acceleration) is perceived (i.e., measured) for the lead vehicle 140, the process 200 proceeds to block 220.

[0033] In block 220, the calculation of a target acceleration ϑ̇ refers to H (t) for the host vehicle 100 to determine the acceleration perceived as necessary to maintain the distance g between the area defined by the minimum distance gmin and a maximum distance gmax, based on the observed actions of the lead vehicle 140. This is calculated based on Eqs. 1 and 2: g*=g0+max[0,(ϑHT+(ϑHΔϑ2aHb))], ϑ˙H(t)=aH(1−(ϑHϑHf)δ)−aH((g*(ϑHΔϑ)g)2).

[0034] In Eq. 1, g* is the target distance g, which lies within the range defined by the minimum distance gmin and a maximum distance gmax. The minimum distance g0 is a setting (e.g., of the ACC system) that specifies, for example, the operator's preference for the minimum distance. The current speed ϑ H The speed of the host vehicle 100 is known, for example, based on sensors 120, where T is a known constant based on a traffic model. The constant T represents a time value associated with a safe following distance and is used because the target distance g* is influenced by the traffic model (the target g* can be reduced, for example, at higher traffic density). The difference Δϑ is the difference between the current speed ϑ Lof the lead vehicle 140, which is determined according to the sensors 130, and the current speed of the host vehicle 100. The current acceleration a H The acceleration of the host vehicle 100 is known based on the sensors 120 of the host vehicle 100, where b is a deceleration constant that limits the deceleration in braking scenarios. The free acceleration component δ is known.

[0035] As Eq. 2 indicates, the target acceleration ϑ̇ H (t) for the host vehicle 100 using the perceived (i.e., measured) speed ϑ L The speed of the lead vehicle 140 (as part of the difference Δϑ) is calculated. The final speed ϑ Hf The speed of the host vehicle 100 is that required to achieve the target distance g* given the final speed of the lead vehicle 140. The final speed ϑ Hf of the host vehicle 100 is based on the perceived speed ϑ Lof the lead vehicle 140, because the lag (i.e., the potential for a subsequent further increase in the rate of change of speed) is not taken into account in Eq. 2. As previously stated, this calculation of the target acceleration ϑ̇ H (t) for the host vehicle 100 (and the final speed ϑ Hf ) due to the lag between the perceived and the intended acceleration of the lead vehicle 140 will be inaccurate. Consequently, before this target acceleration ϑ̇ H (t) is implemented for the host vehicle 100, the check is performed in block 230.

[0036] Block 230 performs a check using the two parameters obtained from Eqs. 1 and 2. One check determines whether the target distance g*, derived from Eq. 1, lies outside the threshold range defined by the minimum distance gmin and the maximum distance gmax. Another check is whether there is an acceleration difference between the target acceleration ϑ̇. H (t) for the host vehicle 100 (which is calculated according to Eq. 2 in block 220) and the current acceleration of the host vehicle 100 is outside a threshold range of the acceleration difference. Because the lead vehicle 140 can decelerate or accelerate, the calculated target acceleration ϑ̇ H(t) for the host vehicle 100, and consequently the acceleration difference can be an increase or a decrease. Both the minimum distance gmin and the maximum distance gmax, as well as the threshold acceleration difference, can be set based on the traffic model.

[0037] Based on the check in block 230, the intended acceleration of the lead vehicle 140 may or may not need to be taken into account. If both the target distance g* and the acceleration difference (according to the check in block 230) are within the threshold ranges, then the control of the host vehicle in block 250 will be carried out using the calculated target acceleration ϑ̇. H(t) is executed. Then the processes that began in block 210 are resumed. If the target distance g* and the acceleration difference (according to the check in block 230) are outside the threshold ranges, then the processes in block 240 are executed.

[0038] In block 240, obtaining a modified target acceleration implies a est For the host vehicle 100, a prediction of the intended acceleration of the lead vehicle 140 is made. That is, instead of using the target acceleration ϑ̇ calculated (using Eq. 2). H (t) instead the modified target acceleration a est The calculation is performed for the host vehicle 100. By taking into account the lag for the type of lead vehicle 140, the calculation of the modified target acceleration a is considered. estFor the host vehicle 100, the intended acceleration of the lead vehicle 140 is used instead of the perceived acceleration. To be clear, the intended acceleration of the lead vehicle 140 is the acceleration that would be perceived after the lag associated with the lead vehicle 140.

[0039] As previously stated, the relevant lag time constant τ and the inhibition constant φ, corresponding to the type of lead vehicle 140 (e.g., truck, compact car), can be obtained from a lookup table as part of the prediction in block 240 or earlier (e.g., in block 210). That is, the lookup table can provide the values ​​of τ acc , τ dec , φ acc and φ decfor each of several vehicle types. As discussed with respect to block 260, the entry in the lookup table for the vehicle type corresponding to the lead vehicle 140 can be updated (in block 260) for use the next time the host vehicle 100 encounters a lead vehicle of the same type, with the controller 110 performing the processing in block 240.

[0040] Specifically, in block 240 the modified target acceleration a est Calculated for host vehicle 100 using Eq. 3: aest=ϑ˙H(t)(1−e(t−φ)τ)+r_factor+f_factor

[0041] In Eq. 3, the target acceleration ϑ̇ is H (t) for the host vehicle 100 (from block 220) the calculation result using Eq. 2, which does not take into account any lag associated with the lead vehicle 140. The lag time constant ̇ τ is τ acc(if the acceleration a L of the lead vehicle 140 to an increased speed ϑ L of the lead vehicle 140) or τ dec (if the acceleration a L of the lead vehicle 140 to a reduced speed ϑ L of the lead vehicle 140). The inhibition constant φ is similar. acc (if the acceleration a L of the lead vehicle 140 to an increased speed ϑ L of the lead vehicle 140) or φ dec (if the acceleration a L of the lead vehicle 140 to a reduced speed ϑ Lof the lead vehicle 140). The additional components in Eq. 3, r_factor and f_factor, are optional. The r_factor, which is the statistical model of the acceleration factor of the deceleration of the lead vehicle 140, can be obtained from a model and is a function of the perceived acceleration of the lead vehicle 140. The f_factor, which is the smoothness factor, is based on previously calculated calibrations that take passenger comfort into account and is a function of the difference Δϑ.

[0042] After the modified target acceleration a est The processes in block 250 are reached when block 250 has been calculated according to Eq. 3 (in block 240). When block 250 is reached by block 240, the operation of the host vehicle 100 is based on the modified target acceleration a calculated according to Eq. 3. esttaking into account the lag associated with the type of lead vehicle 140. However, if block 250 is reached by the test in block 230, the target acceleration ϑ̇ is set. H (t) according to Eq. 2 is used to control the operation of the host vehicle 100.

[0043] In block 260, updating the lag of the lead vehicle type 140 refers to updating τ acc and φ acc or τ acc and φ dec This is based on whether the scenario includes the lead vehicle 140 increasing or decreasing its speed. The update is based on the actual distance g, which is calculated from the processing in block 240 and the implementation in block 250 (the modified target acceleration a), compared to the target distance g*. est). This means that the lag time constant τ and the inhibition constant φ can be set in the lookup table for the entry assigned to the type of lead vehicle 140 if the actual distance g is less than or greater than the target distance g*, after the acceleration of the host vehicle 100 is based on taking into account the intended acceleration of the lead vehicle 140.

Claims

[1] Procedure that includes: Obtaining information about a lead vehicle (140) by a processing circuit arrangement of a host vehicle (100), wherein the lead vehicle (140) is traveling directly in front of the host vehicle (100) and the information includes the speed of the lead vehicle (140) and a distance g between the host vehicle (100) and the lead vehicle (140); based on detecting a change in the speed of the lead vehicle (140) in the information, calculating, using the processing circuit arrangement, a corresponding target acceleration for the host vehicle (100) using a perceived acceleration of the lead vehicle (140), wherein the perceived acceleration of the lead vehicle (140) is based on the change in speed specified by the information; based on a review of the parameters involved in the calculation of the corresponding target acceleration, calculate, using the processing circuit arrangement, a modified target acceleration for the host vehicle (100) using a lag for the lead vehicle (140), resulting in an intended acceleration of the lead vehicle (140) that differs from the perceived acceleration; and Implement the modified target acceleration for the host vehicle (100); characterized by , that The corresponding target acceleration for the host vehicle (100) is calculated using the processing circuit arrangement such that the distance g is maintained within a specified range of distance values. [2] Method according to claim 1, wherein obtaining information about the lead vehicle (140) includes obtaining the measured speed of the lead vehicle (140) using a sensor (130) and the sensor (130) includes a radar system, a lidar system or a camera. [3] Method according to claim 1, wherein calculating the corresponding target acceleration for the host vehicle (100) is the determination of a target distance g* as: g*=g0+max[0,(ϑHT+(ϑHΔϑ2aHb))] contains, whereby g0 is a fixed minimum distance value, ϑ H where (100) is the current speed of the host vehicle, T is a known constant relating to a time associated with a safe distance, and Δϑ is the difference between a current speed ϑ L of the lead vehicle (140) and the current speed ϑ H of the host vehicle (100) is, a Hwhere (100) is the current acceleration of the host vehicle and b is a known constant that limits the deceleration. [4] Method according to claim 3, wherein performing the parameter check includes determining whether the target distance g* is within the specified range of distance values, wherein the calculation of the modified target acceleration is not performed if the target distance g* is within the specified range of distance values. [5] Method according to claim 3, wherein calculating the corresponding target acceleration for the host vehicle (100) is the determination of the target acceleration ϑ̇ H (t) for the host vehicle (100) as: ϑ˙H(t)=aH(1−(ϑHϑHf)δ)−aH((g*(ϑHΔϑ)g)2) contains, whereby ϑ Hfa final speed of the host vehicle (100) required to achieve the target distance g*, and g is a current distance, performing the parameter check includes determining whether there is a difference between a current acceleration of the host vehicle (100) and the corresponding target acceleration within a specified range, and the modified target acceleration of the host vehicle (100) using: aest=ϑ˙H(t)(1−e(t−φ)τ) is calculated, whereby the lag time constant τ and the inhibition constant φ are obtained from a lookup table for a type of lead vehicle (140), the modified target acceleration of the host vehicle (100) by adding one or more model-based factors to a estis calculated and the model-based factors include a statistical model of an acceleration factor of the deceleration of the lead vehicle (140) and a smoothness factor, the procedure also including updating the lookup table for the type of lead vehicle (140) based on a result of implementing the new corresponding target acceleration for the host vehicle (100). [6] System in a host vehicle (100), wherein the system comprises: one or more sensors (120) configured to provide information about a lead vehicle (140), wherein the lead vehicle (140) is traveling directly in front of the host vehicle (100), and the information includes the speed of the lead vehicle (140) and a distance g between the host vehicle (100) and the lead vehicle (140); and a controller (110) configured to calculate, based on the detection of a change in the speed of the lead vehicle (140) in the information, a corresponding target acceleration for the host vehicle (100) using a perceived acceleration of the lead vehicle (140), wherein the perceived acceleration of the lead vehicle (140) is based on the change in speed indicated by the information, to calculate, based on a check of the parameters involved in calculating the corresponding target acceleration, a modified target acceleration for the host vehicle (100) using a lag for the lead vehicle (140) that results in an intended acceleration of the lead vehicle (140) that differs from the perceived acceleration, and to implement the modified target acceleration in the host vehicle (100); characterized by , that the controller (110) is further configured to calculate the appropriate target acceleration for the host vehicle (100) such that the distance g is maintained within a specified range of distance values. [7] System according to claim 6, wherein one or more sensors (130) include a radar system, a lidar system or a camera. [8] System according to claim 6, wherein the controller (110) is configured to determine the appropriate target acceleration for the host vehicle (100) by determining a target distance g* as: g*=g0+max[0,(ϑHT+(ϑHΔϑ2aHb))] to calculate, whereby g0 is a fixed minimum distance value, ϑ H where (100) is the current speed of the host vehicle, T is a known constant relating to a time associated with a safe distance, and Δϑ is the difference between a current speed ϑ Lof the lead vehicle (140) and the current speed ϑ H of the host vehicle (100) is, a H where (100) is the current acceleration of the host vehicle and b is a known constant that limits the deceleration. [9] System according to claim 8, wherein the controller (110) is configured to perform the parameter check by determining whether the target distance g* is within the specified range of distance values, wherein the calculation of the modified target acceleration is not performed if the target distance g* is within the specified range of distance values. [10] System according to claim 8, wherein the controller (110) is configured to determine the corresponding target acceleration for the host vehicle (100) by determining the target acceleration ϑ̇ H (t) for the host vehicle (100) as: ϑ˙H(t)=aH(1−(ϑHϑHf)δ)−aH((g*(ϑHΔϑ)g)2) to calculate, whereby D Hf a final speed of the host vehicle (100) required to achieve the target distance g*, and g is a current distance, the controller (110) is configured to perform the parameter check by determining whether there is a difference between a current acceleration of the host vehicle (100) and the corresponding target acceleration within a specified range, the controller (110) is configured to define the modified target acceleration of the host vehicle (100) as: aest=ϑ˙H(t)(1−e(t−φ)τ) to calculate, whereby the lag time constant τ and the inhibition constant φ are obtained from a lookup table for a type of lead vehicle (140), the controller (110) is configured, the modified target acceleration of the host vehicle (100) is obtained by adding one or more model-based factors to a estto calculate, wherein the model-based factors include a statistical model of an acceleration factor of the deceleration of the lead vehicle (140) and a smoothness factor, and the controller (110) is configured to update the lookup table for the type of lead vehicle (140) based on a result of implementing the new corresponding target acceleration for the host vehicle (100).

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