Autonomous vehicle

Abstract

The present application improves the practicability of an autonomous vehicle following a preceding vehicle. An autonomous vehicle is configured to drive itself in such a way that the distance between itself and the preceding vehicle is a set distance according to the relative position of the preceding vehicle in real time, and to determine a steering index of itself as a target, i.e., a target steering index, and to turn the wheels according to the target steering index. In the case where a plurality of following vehicles form a queue and follow a leading vehicle, at least one of the parameters related to the control of the braking of the autonomous vehicle and the parameters related to the turning of the wheels of the autonomous vehicle is changed according to the number of the following vehicle. The following driving in the queue can be properly performed.

Description

Technical Field

[0001] This invention relates to an autonomous vehicle capable of following other vehicles. Background Technology

[0002] When a vehicle follows another vehicle that is acting as a lead vehicle, the technology described in the following patent document is available as a technique that provides information to the interior of the lead vehicle to assist in following the vehicle's movement based on the driving parameters of the following vehicle.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-142906 Summary of the Invention

[0004] The technology described in the aforementioned patent documents is based on the premise that one following vehicle follows one lead vehicle. In situations where multiple following vehicles form a convoy and follow one lead vehicle, this technology may not be fully utilized. Developing an effective technology for situations where multiple following vehicles travel in a convoy helps improve the practicality of autonomous vehicles. This invention was made in view of this practical situation, and its objective is to provide a highly practical autonomous vehicle.

[0005] To address the aforementioned issues, the present invention provides an autonomous driving vehicle that follows another vehicle, wherein the autonomous driving vehicle is configured as follows:

[0006] Based on its real-time relative position to the vehicle directly in front, the system brakes itself to maintain a set distance from the vehicle ahead. It also determines a target steering index, which becomes the target vehicle, and steers the wheels accordingly.

[0007] The autonomous vehicle is further configured to, when it and one or more other autonomous vehicles of the same structure follow the lead vehicle as multiple following vehicles in a queue, perform at least one of a) and b): a) change the control-related parameters of its own braking and driving based on which number of the following vehicle it is, i.e., brake-driven related parameter change processing; b) change the steering-related parameters of its own wheels based on which number of the following vehicle it is, i.e., steering-related parameter change processing.

[0008] Invention Effects

[0009] The autonomous vehicle of the present invention is configured to detect its relative position to the vehicle directly in front of it and follow the vehicle in front of it based on that relative position. When such a vehicle is in a convoy with other vehicles, that is, when they are lined up in a line along the direction of travel, the autonomous vehicle according to the present invention can change its driving action according to its position in the convoy, thus enabling it to follow appropriately within the convoy.

[0010] [Method of Invention]

[0011] The autonomous vehicle of the present invention (hereinafter, sometimes referred to as "the autonomous vehicle" or simply "the vehicle") may not be a vehicle that can only drive autonomously. For example, it may be able to operate remotely, and it may also be a vehicle that can be driven manually by a driver.

[0012] If the control of the vehicle following directly in front of the vehicle is called "follow-driving control", then this vehicle, as a type of autonomous driving control, executes this follow-driving control. As described above, follow-driving control includes: "distance control" which controls the driving force (a concept that integrates driving force and braking force) applied to the vehicle so that the distance between the vehicle directly in front and the vehicle is a set distance; and "steering control" which determines the target steering index based on the relative position of the vehicle directly in front and the vehicle, and turns the vehicle's wheels according to the target steering index.

[0013] "Braking force related parameters" and "steering force related parameters" are control parameters used to change the responsiveness of the aforementioned vehicle distance control and steering control, respectively. In other words, they can be considered as braking force, wheel steering amount, or coefficients that increase or decrease their components, i.e., gains. "Braking force related parameter change processing" and "steering force related parameter change processing" are processes used to change these braking force related parameters and steering force related parameters, respectively. Through these processes, the characteristics of vehicle distance control and steering control are changed according to the vehicle's position in the following vehicle convoy. In summary, braking force related parameter change processing, for example, only requires determining the braking force related parameters for the following vehicles (i.e., the vehicle itself) to ensure that the vehicle distance between the leading vehicle and each following vehicle does not deviate significantly, in other words, to ensure that the speed of each vehicle does not deviate significantly. Similarly, steering force related parameter change processing, for example, only requires determining the steering force related parameters for each following vehicle to ensure that the driving trajectory (driving line) of the following vehicle (i.e., the vehicle itself) does not differ significantly from the driving trajectory of the leading vehicle when turning.

[0014] In the following driving control (hereinafter sometimes referred to as "this following driving control") performed by this vehicle, the "lead vehicle" is the vehicle leading the convoy, and the "following vehicle" is the vehicle following the vehicle directly in front. This vehicle is capable of handling situations where multiple following vehicles form a convoy and follow their lead vehicle. In this following driving control, if the vehicle is at the very front of these following vehicles, the lead vehicle becomes the vehicle directly in front; if the vehicle is not at the very front of these following vehicles, another following vehicle becomes the vehicle directly in front. Furthermore, the lead vehicle can be an autonomously driven vehicle, a remotely operated vehicle, or a vehicle driven by a driver.

[0015] In this following control system, the "relative position to the vehicle directly in front" includes the distance between the vehicle and the vehicle in front and their relative orientation. "Relative orientation" is a parameter indicating the direction in which the vehicle in front is located relative to the vehicle, i.e., relative to itself. Specifically, it can be considered the angle between the vehicle's front and rear axles and the line connecting the vehicle in front and itself (hereinafter, sometimes referred to as the "direction line of the vehicle in front"). The relative position can be obtained using standard methods with the vehicle's own sensors, such as LiDAR, millimeter-wave radar, or cameras. There are no particular limitations on the location of the vehicle in front or the vehicle itself that serves as the reference for the relative position. Since the vehicle in front is located using the aforementioned sensors, the reference location of the vehicle in front can, for example, be the center of the rear end of the vehicle in front. In other words, the vehicle in front can be located using this location as the point of focus. Since this following control system controls the vehicle's own movement, the reference location of the vehicle itself can, for example, be set at the location of its own center of gravity.

[0016] Specifically, the aforementioned vehicle distance control, for example, simply involves determining a target vehicle distance that is the distance between the vehicle directly in front and itself, and controlling the driving force to make the actual vehicle distance the target vehicle distance. Regarding the target vehicle distance, it can be determined based on the speed of either the vehicle itself or the vehicle directly in front, taking into account the possibility of rear-ending the vehicle directly in front. On the other hand, as described above, steering control is as follows: a target steering index is determined, and the wheels are turned so that the actual steering amount becomes the target steering amount. This "steering index" is not particularly limited as long as it can determine the target steering amount. For example, it can be its own yaw rate, its own steering curvature, its own turning radius, etc. From the viewpoint that the target steering amount can be determined through relatively simple processing, the steering index is preferably steering curvature or turning radius. Incidentally, steering curvature can be defined as the reciprocal of the turning radius, so determining the steering amount based on the turning radius and determining the steering amount based on the steering curvature have the same meaning. Furthermore, straight-line driving of the vehicle can be considered as a steering where the wheel steering amount becomes 0, so steering control can be performed at any time during straight-line driving.

[0017] As will be explained in detail later, in the case of following in a convoy, the further back a vehicle is, the more likely it is to experience erratic distances with the vehicle in front, in other words, potentially leading to unstable distance control. In other words, regarding the speed of each following vehicle, the further back the vehicle is, the more likely it is to experience erratic distances. In view of this, the braking-related parameter change processing is preferably a process used to suppress uneven distances between each following vehicle and the vehicle in front. From another perspective, the braking-related parameter change processing is preferably configured such that the vehicle located further behind multiple following vehicles exhibits a lower responsiveness to changes in distance, i.e., a lower responsiveness related to its own braking force control. Specifically, for example, if the vehicle is configured to control braking force according to a PD feedback control rule based on the deviation of its actual distance from the vehicle in front relative to a set distance, and the braking-related parameter is set as the differential gain in this feedback control rule, the braking-related parameter change processing can be configured such that, to suppress over-response, the differential gain is made smaller the vehicle is further behind multiple following vehicles. In addition, when the workshop distance is controlled according to the PD feedback control rule, not only the derivative gain can be used as a braking-driven parameter, but the proportional gain can also be used as a braking-driven parameter and the proportional gain can be changed.

[0018] Furthermore, as will be explained in detail later, based on the aforementioned steering control, following vehicles are more likely to turn further inside than the leading vehicle. In the case of a convoy where multiple following vehicles follow the leading vehicle, the later the following vehicle, the more likely it is to turn further inside. In view of this, the steering-related parameter change processing is preferably configured to suppress the overall movement of multiple following vehicles inside their leading vehicle during steering. For example, if the vehicle is configured to determine the target steering amount of the wheels based on a target steering index and to cause the wheels to turn so that the actual steering amount becomes the target steering amount, the steering-related parameter is set as the adjustment gain when determining the target steering amount, and the steering-related parameter change processing can be configured to change this adjustment gain. Furthermore, if the leading vehicle is directly in front of the vehicle, the processing can be configured to minimize the target steering amount compared to other following vehicles. When using this processing, if the leading vehicle is not directly in front of the vehicle, it is preferable that the change in adjustment gain from the reference gain is smaller than the change in the following vehicle directly in front, regardless of whether the adjustment gain is greater than the reference gain. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the hardware structure of the autonomous vehicle in an embodiment.

[0020] Figure 2 This is a schematic diagram illustrating the basic following control performed in an autonomous vehicle in an embodiment.

[0021] Figure 3 It is a diagram representing the state of multiple following vehicles forming a queue and following the lead vehicle.

[0022] Figure 4 It is a chart showing the speed changes of the leading vehicle and multiple following vehicles.

[0023] Figure 5 This diagram illustrates the IN cut-in phenomenon that occurs when following a vehicle and turning.

[0024] Figure 6 It is a diagram showing the driving lines of multiple following vehicles when turning.

[0025] Figure 7 This is a flowchart of the following driving control program executed in the autonomous vehicle of the embodiment. Detailed Implementation

[0026] Hereinafter, an autonomous vehicle, as an embodiment of the present invention, will be described in detail with reference to the accompanying drawings, as a means of carrying out the present invention. Furthermore, in addition to the embodiments described below, the present invention can be implemented in various ways with various modifications and improvements based on the knowledge of those skilled in the art, starting from the methods described in the [Manifestations of the Invention] section above.

[0027] Example

[0028] [A] Structure of autonomous vehicles

[0029] The autonomous vehicle in the embodiment (hereinafter, sometimes referred to as "this autonomous vehicle" or simply "this vehicle") is as follows: Figure 1 The diagram schematically illustrates a vehicle with left and right front wheels 10f and left and right rear wheels 10r, as shown in the hardware structure. When it is not necessary to distinguish between the front and rear wheels 10f and 10r, they are sometimes collectively referred to as wheels 10. The following references... Figure 1 The structure of this vehicle will be described, but its structure is the same as that of a general vehicle except for the parts related to autonomous driving, which will be described later. Therefore, it will be described simply.

[0030] In this vehicle, the front wheels 10f serve as drive wheels and are driven by the drive unit 12. This vehicle is a BEV (Battery Electric Vehicle), and the drive unit 12 comprises an electric motor (drive motor 14) as the drive source, a transmission 16, a differential gear 18, etc. Furthermore, each of the four wheels 10 is equipped with a wheel brake device 20. Each wheel brake device 20 is a typical electric brake device; although detailed descriptions and illustrations are omitted, it is driven by an electric motor. The four wheel brake devices 20 constitute one braking system 22 in this vehicle. Furthermore, the drive unit 12 and the braking system 22 constitute one braking drive system 24 for this vehicle.

[0031] In this vehicle, the front wheels 10f serve as steering wheels and are equipped with a steering device 26 for turning the front wheels 10f. The steering device 26 is a steer-by-wire type steering device, having a steering actuator 28 and a reaction force actuator 30 that are mechanically separated from each other. The steering actuator 28 has a steering motor as a drive source, and the force of the steering motor causes the steering rods (rack rods) 32 connected to the left and right ends of the left and right front wheels 10f respectively to move left and right, so that the left and right front wheels 10f turn together. The reaction force actuator 30 holds the steering wheel 34, which serves as a steering operation component, and has a reaction force motor as a drive source, which applies an operating reaction force to the steering wheel 34 for its operation.

[0032] This vehicle is equipped with a brake drive electronic control unit 40 for controlling the brake drive device 24, a steering electronic control unit 42 for controlling the steering device, and an autonomous driving electronic control unit 44 for performing autonomous driving of the vehicle. These units are connected to a controllable area network (CAN) 46. Hereinafter, these units are sometimes referred to as the brake drive ECU 40, steering ECU 42, and autonomous driving ECU 44. Incidentally, the brake drive ECU 40 comprises a computer, a drive motor 14, and drivers (drive circuits) for the electric motors of each wheel braking device 20; the steering ECU 42 comprises a computer, a steering motor, and drivers for the reaction force motor; and the autonomous driving ECU 44 comprises a computer as a main component. Furthermore, these units 40, 42, and 44 constitute one controller for the vehicle.

[0033] Furthermore, this vehicle is equipped with an accelerator pedal 50 as an accelerator control component and a brake pedal 52 as a brake control component, both of which are connected to the CAN 46. Additionally, this vehicle is equipped with sensors including a wheel speed sensor 54 for detecting the rotational speed (hereinafter sometimes referred to as "wheel speed") vw of each wheel 10, an steering angle sensor 56 for detecting the steering wheel 34's operating angle ω as the amount of steering input, a steering angle sensor 58 for detecting the steering angle δ of the front wheels 10f as the amount of steering input, two cameras 60 for monitoring the front of the vehicle, a millimeter-wave radar 62, and a yaw rate sensor 64 for detecting the yaw rate γ. These sensors are also connected to the CAN 46. Furthermore, in this vehicle, the steering angle δ is detected as the amount of movement of the steering lever 32 in the left-right direction.

[0034] This vehicle can be manually driven, meaning it can be driven by a driver. Simply put, in manual driving, the brake drive ECU 40 determines the driving force Fd to be applied to the vehicle based on the amount of operation of the accelerator pedal 50, and controls the drive unit 12 based on this driving force Fd. Furthermore, the brake drive ECU 40 determines the braking force Fb to be applied to the vehicle based on the amount of operation of the brake pedal 52, and controls regenerative braking based on the drive unit 12 based on this braking force Fb, and controls the braking device 22 to generate the insufficient portion of regenerative braking in the braking force Fb. Incidentally, the brake drive ECU 40 has the function of detecting the vehicle's travel speed (hereinafter, sometimes referred to as "vehicle speed") vo based on the wheel speed vw of each wheel 10. Additionally, in the following description, the force combining the driving force Fd and the braking force Fb will be treated as the braking drive force Fd / b.

[0035] Furthermore, during manual driving, the steering ECU 42 determines the target steering angle δ of the front wheel 10f based on the steering wheel 34's operating angle ω, according to the following formula. * ,

[0036] δ * =η·ω η: Steering gear ratio

[0037] The steering device 26 is controlled to make the actual steering angle δ become the target steering angle δ. * .

[0038] [B] Follow-up driving control

[0039] This vehicle also performs autonomous driving without driver intervention. Autonomous driving control, which governs this autonomous driving, is executed by the autonomous driving ECU 44. When following a vehicle directly in front, the autonomous driving ECU 44, as a type of autonomous driving control, executes follow-driving control (hereinafter, sometimes referred to as "this follow-driving control"). The follow-driving control will be explained in detail below. First, the basic follow-driving control, which forms the basis of the follow-driving control, will be explained. Then, the contents of this follow-driving control will be explained sequentially.

[0040] (a) Basic control of following driving

[0041] like Figure 2 As shown, the autonomous driving ECU 44 essentially acquires the relative positions of the vehicle PV directly ahead and the vehicle itself (hereinafter, sometimes referred to as "the vehicle") OV, which is the following vehicle, and performs following driving control based on these relative positions. The relative positions include the inter-vehicle distance L between the vehicle PV directly ahead and the vehicle itself OV, and the azimuth angle θ, which is the relative orientation. The azimuth angle θ is a parameter indicating the direction in which the vehicle PV directly ahead is positioned. Specifically, the autonomous driving ECU 44 determines a gaze point MP, which serves as the reference for the relative position of the vehicle PV directly ahead, based on information obtained from the two cameras 60 and the millimeter-wave radar 62, and measures the distance L between this gaze point MP and the position of the center of gravity Go, which serves as the reference for the vehicle itself OV. Furthermore, the autonomous driving ECU 44 determines the line connecting the gaze point MP and the position of the center of gravity Go, i.e., the forward vehicle direction line Ld, and measures the angle θ formed by the forward vehicle direction line Ld and the front-rear axis Lx of the vehicle itself OV. Incidentally, the gaze point MP is set at the center of the rear end face of the vehicle PV directly ahead.

[0042] In this following driving control, the steering index, i.e., the steering curvature ε, is used as the indicator for the vehicle's OV steering. Then, the autonomous driving ECU 44 determines the driving line Lr, i.e., the steering driving line Lrt, for moving the current vehicle OV to the position of the vehicle PV directly in front at that moment during steering, based on the aforementioned inter-vehicle distance L and azimuth angle θ. The steering curvature ε of the steering driving line Lrt is then determined as the target steering curvature ε. * Incidentally, the steering curvature ε is the reciprocal of the steering radius R. The acquisition of these factors—distance L, azimuth angle θ, and target steering curvature ε—is crucial. * The decision is made in real time. Specifically, it is repeated at set control time intervals Δtc (e.g., several msec to tens of msec).

[0043] Following control includes distance control, which controls the distance L between the vehicle ahead (PV) and the vehicle's (OV), and steering control, which controls the steering of the vehicle's (OV). Distance control can also be termed braking force control, which controls the braking force Fd / b applied to the vehicle's (OV), and steering control can also be termed steering control, which controls the steering angle δ of the front wheels 10f of the vehicle's (OV). Furthermore, the concept of steering also includes the case where the steering angle δ is 0, i.e., the straight-ahead state; therefore, steering control is also performed during straight-ahead driving. Incidentally, the target steering curvature ε during straight-ahead following is... * The decision is 0.

[0044] In shop floor distance control, the goal is to make the shop floor distance L equal to the target shop floor distance L. * The braking force Fd / b is controlled in this manner. Specifically, the autonomous driving ECU44 determines the vehicle speed vo detected by the braking drive ECU40 as described above, and determines the forward vehicle speed vp, which is the driving speed of the vehicle PV directly in front, according to the following formula, based on the vehicle speed vo and the vehicle distance change rate (dL / dt) which is the change rate of the vehicle distance L.

[0045] vp = v0 + (dL / dt)·Δt

[0046] Regarding the distance L of the target workshop * To take into account vehicles such as PV that collide with the vehicle OV directly in front, the speed-dependent determination coefficient ξ is used, which increases as the speed of the vehicle directly in front increases, and is determined according to the following formula.

[0047] L * =L0+ξ·vp L0: Baseline workshop distance

[0048] The autonomous driving ECU44 determines the distance L between the determined target vehicles based on the distance L. * The deviation of the actual workshop distance L from the workshop distance ΔL (=L)* -L), according to the PD feedback control rule, specifically, the braking force Fd / b to be applied to the vehicle's OV is determined according to the following formula.

[0049] Fd / b=βp·ΔL+βd·(dΔL / dt)

[0050] Incidentally, βp is the proportional gain and βd is the differential gain.

[0051] The autonomous driving ECU 44 sends the determined braking force Fd / b to the braking drive ECU 40. Based on this braking force Fd / b, the braking drive ECU 40, similar to the manual driving scenario described earlier, controls the braking drive device 24, specifically the drive device 12 and the braking device 22. Specifically, when the braking force Fd / b is positive, the braking drive ECU 40 uses this braking force Fd / b as the driving force Fd to be applied to control the drive device 12. When the braking force Fd / b is negative, it uses this braking force Fd / b as the braking force Fb to generate regenerative braking force in the drive device 12, and controls the braking device 22 to generate the insufficient portion of the regenerative braking force.

[0052] In the steering control within the basic following control, the autonomous driving ECU44, as described above, uses the determined steering curvature ε as the target steering curvature ε. * (As a target steering indicator). Then, the autonomous driving ECU44 determines the target steering curvature ε. * The target steering angle δ of the front wheel 10f is determined. * And regarding the target's rudder angle δ * The information is sent to the steering ECU 42. The steering ECU 42 controls the steering actuator 28 to make the actual steering angle δ become the target steering angle δ. * Additionally, the processing used to determine the aforementioned braking force Fd / b and the processing used to determine the target steering angle δ... * The processing can be repeated at the set control time interval Δtc (e.g., several msec to tens of msec).

[0053] (b) Problems during convoy movement

[0054] like Figure 3As shown, this vehicle forms a queue with other vehicles performing the same follow-driving control. In other words, multiple vehicles line up in the direction of travel to follow the lead vehicle LV. The diagram shows a lead vehicle LV being followed by a queue of three follower vehicles FV, ​​one of which is this vehicle. Furthermore, in the diagram, the three follower vehicles FV are sequentially numbered FV1, FV2, and FV3 from the front. Incidentally, this vehicle can be any one of the follower vehicles FV1, FV2, or FV3.

[0055] i) Disorder of workshop distances

[0056] Based on the aforementioned basic following control, as described above, the vehicle PV directly ahead is identified and the braking force Fd / b is calculated. Therefore, a certain degree of delay occurs until the braking force Fd / b is calculated. Furthermore, sometimes noise is present in the information detected by the millimeter-wave radar 62 and camera 60; in this case, it can be predicted that the distance control in the noisy portion will become unstable. When following vehicles FV form a queue and follow the lead vehicle LV, the aforementioned delay or instability of the following vehicle FV1, which is the foremost following vehicle FV, is relatively small. However, further, the following vehicles FV further back will exhibit a certain degree of delay or instability when performing distance control as the vehicle PV directly ahead; therefore, the delay or instability of the following vehicles FV further back is greater. That is, the further back the following vehicle FV is, the more likely it is to cause fluctuations in the distance L information up to the vehicle PV directly ahead, relative to the target distance L. * The deviations ΔL1, ΔL2, and ΔL3 in the vehicle-to-vehicle distances L1, L2, and L3 are affected by the changes in the movement of the vehicle PV directly in front. Therefore, the more rearward a following vehicle is, the greater the turbulence in vehicle-to-vehicle distance control. Furthermore, the speed v of the following vehicle FV, i.e., the following vehicle speed vf, also becomes volatile, and the amplitude of the volatile FV is greater for the most rearward following vehicle.

[0057] Figure 4 The chart shows the change in speed v of the lead vehicle LV and the three following vehicles FV in the convoy over time t. As the chart shows, when the speed v of the lead vehicle LV (i.e., the lead vehicle speed vl) changes, the change in the speed vf of the following vehicles is greater than the change in the lead vehicle speed vl, with the change being greater for the later-arriving following vehicles FV. That is, the chart shows that the turbulence of the following speed vf1 of the foremost following vehicle FV1, the turbulence of the following speed vf2 of the second following vehicle FV2, and the turbulence of the following speed vf3 of the third following vehicle FV3 increases sequentially.

[0058] ii) IN engagement phenomenon during turning

[0059] When the above-mentioned basic following control is executed, an IN cut-in phenomenon occurs. For example... Figure 5 As shown, the IN-intercept phenomenon refers to the situation where, when a following vehicle OV turns to follow a turning vehicle PV directly in front, the following vehicle OV travels on a turning line Lrt that is further inside the turning line of the vehicle directly in front (Lrtp), which is the turning line of the vehicle directly in front (PV). In short, this phenomenon occurs because at the point when the vehicle directly in front (PV) begins to turn, the aforementioned azimuth angle θ deviates from 0, and therefore, at that point, the following vehicle OV also begins to turn. Specifically, this is because the vehicle directly in front (PV) begins to turn from the turning start position Psp (marked with ☆), while the following vehicle OV begins to turn from the turning start position Pso (marked with ★).

[0060] Due to the aforementioned IN-intercept phenomenon, the vehicle's OV (Outbound Vehicle) cannot properly follow the steering wheel when turning. Furthermore, in extreme cases, the IN-intercept phenomenon may also cause interference between the vehicle's OV and structures located on the inside of the steering path.

[0061] When performing basic following control, multiple following vehicles (FVs) form a convoy and follow the lead vehicle (LV) as it turns, such as... Figure 6 The diagram schematically illustrates the steering of the following vehicles (FVs). In the figure, the steering line Lrt of the leading vehicle LV is represented by a solid line as Lrtl, while the steering lines Lrt of the three following vehicles FV1, FV2, and FV3 are represented by dashed lines as Lrtf1, Lrtf2, and Lrtf3, respectively. As shown, according to the basic control of following, the further back the following vehicle (FV) is, the more it turns inward than the leading vehicle LV. That is, the further back the following vehicle (FV) is, the more pronounced the IN (intercept) phenomenon (intercepting the following vehicle) becomes.

[0062] (c) Countermeasures to the problem of queuing.

[0063] To address the aforementioned issues, in vehicle distance control and steering control, the autonomous driving ECU44 modifies the parameters used to change the characteristics of these controls based on the vehicle's (OV) position relative to the preceding (FV) vehicles in the queue. The following provides a detailed explanation of the parameter changes for both vehicle distance control and steering control. Furthermore, regarding the question of which FV (FV) the vehicle's (OV) position relative to in the queue (hereinafter, this "number" is sometimes referred to as sequence n), the control center (CC) (see reference...)... Figure 3 The system wirelessly transmits relevant information, and the autonomous driving ECU44 uses this information to determine the vehicle's OV sequence n. Incidentally, the sequence n is sequentially 1, 2, 3, ...

[0064] i) Workshop distance control

[0065] In workshop distance control, the following formula is related to the determination of the aforementioned braking driving force Fd / b.

[0066] Fd / b=βp·ΔL+βd·(dΔL / dt)

[0067] The differential gain βd is set as a braking-related parameter, and the autonomous driving ECU 44 performs a braking-related parameter change process to modify this differential gain βd. In other words, the autonomous driving ECU 44 determines the differential gain βd to be βdn based on the sequence n of the vehicle's OV. Specifically, the differential gain βdn is preset; when the sequence n of the vehicle's OV is 1, it is determined to be βd1; when the sequence n of the vehicle's OV is 2, it is determined to be βd2; when the sequence n of the vehicle's OV is 3, it is determined to be βd3, and so on (the same applies below).

[0068] Furthermore, the differential gain βdn is set smaller so that the responsiveness of the vehicle distance control, i.e., the braking drive responsiveness, becomes lower as the sequence n moves further back. In other words, it is set smaller to suppress the over-response of the following vehicle FV that moves further back.

[0069] βd1>βd2>βd3……

[0070] Thus, by reducing the differential gain βdn of the FV of the following vehicles further back, the stability of following motion in the entire platoon can be improved.

[0071] The braking-related parameter change processing given here is an example. As long as it is a process to suppress the unevenness of the inter-vehicle distance L between the vehicle directly in front (PV) and the vehicle's (OV) for each following vehicle (FV), the specific method is not particularly limited. For example, it could also be a process of changing the gain βp of the aforementioned proportional term.

[0072] ii) Steering control

[0073] In steering control, the autonomous driving ECU44 determines the target steering angle δ as described above. * As shown in the following formula,

[0074] δ * =Kn·δ *

[0075] Multiply by the adjustment gain Kn. The adjustment gain Kn is a steering-related parameter. The autonomous driving ECU44 performs a process of changing the adjustment gain Kn according to the sequence n as a steering-related parameter change process. The adjustment gain Kn is set to K1 when the sequence n of the vehicle's OV is 1, K2 when the sequence n of the vehicle's OV is 2, K3 when the sequence n of the vehicle's OV is 3, and so on (the same applies below). The autonomous driving ECU44 determines the adjustment gain Kn by selecting it from K1, K2, K3, etc., according to the sequence n. Incidentally, the larger the adjustment gain Kn, the higher the target steering angle δ. * The larger the value of ε, the greater the steering curvature ε (and thus the smaller the steering radius R). Conversely, the smaller the adjustment gain Kn, the greater the target steering angle δ. * The smaller the value, the slower the steering becomes. In other words, the vehicle exhibits a steering behavior that appears to slow down, thereby suppressing the in-vehicle (OV) cutoff phenomenon relative to the vehicle (PV) directly in front.

[0076] The adjustment gain Kn is set to suppress the overall steering of multiple following vehicle FVs from becoming inside the leading vehicle LV during steering, i.e., to suppress the overall IN-cut phenomenon. In other words, when K0 (=1) is set as the base gain, K1, K2, K3... are set so that the steering travel line Lrtf (e.g., the average travel line) of the multiple following vehicle FVs is closer to the leading vehicle's steering travel line Lrtl than the steering travel line Lrtf of the multiple following vehicle FVs when the adjustment gain Kn of all following vehicle FVs is set to the base gain K0. Specifically, it is set as follows.

[0077] K1<K0, K2>K0, K3<K0,…

[0078] |K1-K0|>|K2-K0|>|K3-K0|……

[0079] The example of changing braking-related parameters given here is one example. As long as the processing follows the principle that multiple following vehicle FVs as a whole do not travel further inside than the leading vehicle LV during steering, or that any individual following vehicle FV does not travel further inside than the leading vehicle LV, the specific method is not particularly limited. For example, under the assumption that the vehicle at the very front of the following vehicle FVs undergoes IN-cutting, the adjustment gain K2 of the second following vehicle FV can be set to K2 < K0, and the adjustment gain K3 of the third following vehicle FV can be set to K3 > K0. Furthermore, in following driving control, as long as the target steering curvature ε is considered... * The target operating angle ω is determined as the steering wheel operating angle 34. * And based on the target operating angle ω * Determine the target steering angle δ *Alternatively, the steering gear ratio η can be changed instead of the change in the adjustment gain Kn.

[0080] (d) Follow-up driving control process

[0081] The following driving control described above is repeatedly executed by the autonomous driving ECU44 at the aforementioned control time interval Δt. Figure 7 The following describes the following driving control procedure as shown in the flowchart. The process flow of the driving control is briefly explained below.

[0082] In the following driving control procedure, firstly, in step 1 (hereinafter referred to as "S1"; the following steps are also the same), the inter-vehicle distance L and azimuth angle θ, which are the relative positions with the vehicle PV directly in front, are obtained. In S2, the vehicle speed vo, which is the driving speed of the current vehicle OV, and the speed vp, which is the driving speed of the vehicle PV directly in front, are determined. In the subsequent S3, based on the reference inter-vehicle distance L0, the speed vp, and the speed dependence determination coefficient ξ, the target inter-vehicle distance L is determined as described above. * In the next step, S4, the steering line Lrt is determined based on the inter-vehicle distance L and the azimuth angle θ. In S5, the target steering curvature ε is determined based on this steering line Lrt. * .

[0083] In the next step S6, the sequence n of the vehicle OV traveling in the convoy is determined based on the information sent from the control center CC. In the subsequent S7, the differential gain βdn is determined based on this sequence n, as described above. In S8, the adjustment gain Kn is determined based on the sequence n, as described above. Then, in S9, the distance L relative to the target workshop is determined. * The current distance L between the workshop and the vehicle is calculated as the workshop distance deviation ΔL. Based on this workshop distance deviation ΔL, and using the determined differential term gain βdn, the braking force Fd / b to be generated is determined according to the PD feedback control rule. Information about this braking force Fd / b is sent to the braking drive ECU 40 in S10. Then, in S11, based on the determined target steering curvature ε... * The target steering angle δ of the front wheel 10f is determined. * In S12, the determined adjustment gain Kn is multiplied by the target rudder angle δ. * To perform target rudder angle δ * The adjustment was made to the target rudder angle δ. * The information is sent to the steering ECU42 in S13.

[0084] Symbol Explanation

[0085] 10 - Wheels, 12 - Drive unit, 22 - Braking system, 24 - Brake-drive unit, 26 - Steering system, 40 - Brake-drive electronic control unit (Brake-drive ECU), 42 - Steering electronic control unit (Steering ECU), 44 - Autonomous driving electronic control unit (Autonomous driving ECU), 60 - Camera, 62 - Millimeter-wave radar, OV - This vehicle, PV - Vehicle directly in front, FV - Following vehicle (FV1, FV2, FV3, ...), LV - Leading vehicle, n - Sequence, v - Vehicle speed, vo - Vehicle speed, vp - Vehicle speed directly in front, δ - Steering angle, δ * - Target steering angle, Fd / b - Braking force, βp - Proportional gain, βdn - Differential gain (related parameter of braking force), MP - Point of gaze, Go - Center of gravity, L - Vehicle distance, L * - Target distance to the workshop, θ - azimuth angle (relative phase), Lr - driving line, ε - steering curvature (steering index), ε * - Target steering curvature (target steering index), Kn - Adjustment gain (rudder-related parameters).

Claims

1. An autonomous driving vehicle that follows another vehicle, said autonomous driving vehicle being characterized in that it is configured as follows: Based on its real-time relative position to the vehicle directly in front, the system adjusts its braking distance to a set value, determines a target steering index (the steering index that becomes the target vehicle), and adjusts the rudder accordingly. The autonomous vehicle is further configured to perform at least one of the following processes (a) and (b) when it and one or more other autonomous vehicles with the same structure follow the lead vehicle as multiple following vehicles in a queue: a) changing the control-related parameters of its own braking and driving based on which number of the following vehicle it is; b) changing the steering-related parameters of its own wheels based on which number of the following vehicle it is.

2. The autonomous vehicle according to claim 1, characterized in that, The braking-related parameter change processing is used to suppress the unevenness of the inter-vehicle distance between each following vehicle and the vehicle directly in front.

3. The autonomous vehicle according to claim 1, characterized in that, The braking-related parameter change processing is as follows: the vehicle that is further behind the multiple following vehicles has a lower responsiveness to changes in the inter-vehicle distance.

4. The autonomous vehicle according to claim 1, characterized in that, The autonomous vehicle is configured to control braking force according to a PD feedback control rule based on the deviation between itself and the actual inter-vehicle distance relative to the set distance. The braking-driven related parameter is the differential gain in the feedback control rule. The braking-driven related parameter is modified as follows: the differential gain is smaller the vehicle is located further behind the multiple following vehicles.

5. The autonomous vehicle according to claim 1, characterized in that, The steering-related parameter change processing is as follows: to suppress the multiple following vehicles that form a queue and follow the lead vehicle during steering from traveling as a whole inside the lead vehicle.

6. The autonomous vehicle according to claim 1, characterized in that, The autonomous vehicle is configured to determine the target steering amount of the wheels based on the target steering index, and to make the wheels turn so that the actual steering amount becomes the target steering amount. The steering-related parameters are the adjustment gain when determining the target steering amount, and the steering-related parameter change processing is the process of changing the adjustment gain.

7. The autonomous vehicle according to claim 6, characterized in that, The change of steering-related parameters is processed as follows: when the leading vehicle is the vehicle directly in front of itself, the adjustment gain is set to minimize the target steering amount compared to other following vehicles.

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