Vehicle travel support device and vehicle travel support method

Abstract

Provided are a vehicle travel support device and a vehicle travel support method capable of reducing jerk in a vehicle and the rate of change of jerk when controlling the distance between the vehicle and an object and the speed of the vehicle, and capable of suppressing an increase in travel distance. The vehicle travel support device: sets a target speed of a vehicle and a target distance of the distance between the vehicle and an object; performs four-stage filter processing consisting of a first filter, a second filter, a third filter, and a fourth filter on the target distance in virtual time to calculate a distance plan that is a transient target distance at each future time; calculates a speed plan that is a transient target speed at each future time on the basis of the distance plan and the target speed; calculates an acceleration command value of the vehicle on the basis of at least the speed plan; and controls the vehicle on the basis of the acceleration command value.

Description

Vehicle driving support device and vehicle driving support method

[0001] The present disclosure relates to a vehicle driving assistance device and a vehicle driving assistance method.

[0002] Conventionally, tracking control devices have been put into practical use that recognize other vehicles ahead of the vehicle, maintain a distance based on the vehicle speed, and travel at a constant speed at a set vehicle speed if there are no other vehicles. In the technology of Patent Document 1, a trajectory generation unit plans a target speed as shown in Figure 12 of Patent Document 1, and a travel control unit controls the vehicle to follow the speed pattern.

[0003] Patent No. 6327424 Patent No. 5929885

[0004] In conventional vehicle control systems, the planned target speed is configured with constant acceleration motion, so sudden changes in jerk and jerk change rate occur when acceleration / deceleration begins, resulting in a deterioration in ride comfort. Furthermore, if the vehicle control unit controls the vehicle to prevent sudden changes in jerk and jerk change rate, deviations from the original driving plan may occur, and the vehicle may come too close to the vehicle ahead.

[0005] Therefore, the present disclosure aims to provide a vehicle driving assistance device and a vehicle driving assistance method that can reduce the jerk and jerk change rate that occur in the vehicle when controlling the distance between the vehicle and an object and the speed of the vehicle, and can suppress an increase in driving distance.

[0006] The vehicle driving assistance device according to the present disclosure includes an information acquisition unit that acquires information about the host vehicle and information about an object present in the vicinity of the host vehicle; a target determination unit that sets a target speed for the host vehicle and a target distance that is a target value for the distance between the host vehicle and the object based on the information about the host vehicle and the information about the object; a plan generation unit that calculates, based on the target distance, a distance plan that is a transient target distance for each future time until a time when the distance reaches the target distance and the speed of the host vehicle reaches the target speed, and calculates, based on the distance plan and the target speed, a speed plan that is the transient target speed for each future time; and a vehicle control unit that calculates an acceleration command value for the host vehicle based on at least the speed plan, and controls the host vehicle based on the acceleration command value, wherein the plan generation unit calculates the distance plan by performing four-stage filtering on the target distance, the four-stage filtering being composed of a first filter, a second filter, a third filter, and a fourth filter, in a virtual time that represents each future time from the present to the arrival time.

[0007] The vehicle driving assistance method according to the present disclosure includes an information acquisition step of acquiring information about the host vehicle and information about an object present in the vicinity of the host vehicle; a target determination step of setting a target speed of the host vehicle and a target distance, which is a target value for the distance between the host vehicle and the object, based on the information about the host vehicle and the information about the object; a plan generation step of calculating, based on the target distance, a distance plan, which is a transient target distance for each future time until a time when the distance reaches the target distance and the speed of the host vehicle reaches the target speed, and calculating, based on the distance plan and the target speed, a speed plan, which is the transient target speed for each future time; and a vehicle control step of calculating, based on at least the speed plan, an acceleration command value for the host vehicle, and controlling the host vehicle based on the acceleration command value, wherein the plan generation step calculates the distance plan by performing four-stage filtering on the target distance, which is composed of a first filter, a second filter, a third filter, and a fourth filter, in a virtual time representing each future time from the present to the arrival time.

[0008] According to the vehicle driving assistance device and vehicle driving assistance method disclosed herein, by using four-stage filtering, it is possible to reduce the jerk and jerk change rate generated in the host vehicle during acceleration and deceleration until the target distance and target speed are reached, thereby improving the ride comfort of the host vehicle. Furthermore, by managing the arrival time, it is possible to prevent an increase in the travel distance until the target distance and target speed are reached.

[0009] 1 is a schematic block diagram of a vehicle driving assistance device according to a first embodiment. FIG. 2 is a schematic hardware configuration diagram of the vehicle driving assistance device according to the first embodiment. FIG. 3 is a diagram for explaining setting of an object according to the first embodiment. FIG. 4 is a diagram for explaining setting of an object according to the first embodiment. FIG. 5 is a time chart for explaining processing by a first filter according to the first embodiment. FIG. 6 is a time chart for explaining processing by a second filter according to the first embodiment. FIG. 7 is a time chart for explaining processing by a third filter according to the first embodiment. FIG. 8 is a time chart for explaining processing by a fourth filter according to the first embodiment. FIG. 9 is a flowchart for explaining general processing of the vehicle driving assistance device according to the first embodiment. FIG. 10 is a schematic block diagram of a vehicle driving assistance device according to a second embodiment. FIG. 11 is a diagram for explaining setting of an object according to the second embodiment. FIG. 12 is a time chart for explaining four-stage filter processing and setting of a time constant according to the second embodiment. FIG. 13 is a flowchart for explaining general processing of the vehicle driving assistance device according to the second embodiment. FIG. 14 is a schematic block diagram of a vehicle driving assistance device according to a third embodiment. FIG. 15 is a time chart for explaining four-stage filter processing and setting of a time constant according to the third embodiment. FIG. 16 is a flowchart for explaining general processing of the vehicle driving assistance device according to the third embodiment. FIG. 10 is a diagram for explaining the setting of an object according to the fourth embodiment.

[0010] 1. First Embodiment A vehicle driving assistance device 50 according to a first embodiment will be described with reference to the drawings. In this embodiment, the vehicle driving assistance device 50 is provided in the subject vehicle.

[0011] As shown in FIG. 1, the vehicle is equipped with a surroundings monitoring device 31, a position detection device 32, a vehicle state detection device 33, a map information database 34, a wireless communication device 35, a vehicle driving assistance device 50, a drive control device 36, a power motor 8, an electric steering device 7, an electric braking device 9, and a human interface device 37.

[0012] The periphery monitoring device 31 is a device such as a camera or radar that monitors the periphery of the vehicle. The radar may be a millimeter wave radar, a laser radar, or an ultrasonic radar. The wireless communication device 35 performs wireless communication with a base station using a cellular wireless communication standard such as 4G or 5G. The wireless communication device 35 performs wireless communication with roadside devices, surrounding vehicles, etc.

[0013] The position detection device 32 is a device that detects the current position (latitude, longitude, altitude) of the vehicle, and uses a GPS antenna or the like that receives signals output from artificial satellites such as the Global Navigation Satellite System (GNSS). Note that various methods may be used to detect the current position of the vehicle, such as a map matching method, a dead reckoning method, or a method that uses detected information around the vehicle.

[0014] The map information database 34 stores road information such as road shapes (e.g., number of lanes, location of each lane, shape of each lane, type of each lane, road type, speed limit, shape of intersection, etc.), road signs (speed limit signs and associated speed limits, stop signs, etc.), road markings (stop lines, pedestrian crossings, etc.), toll gates (location of toll gate entrances, speed limits through toll gates, etc.), traffic lights, etc. The map information database 34 is mainly composed of a storage device. The map information database 34 may be provided in a server outside the vehicle connected to a network, and the vehicle driving assistance device 50 may obtain necessary road information from the server outside the vehicle via the wireless communication device 35.

[0015] The drive control device 36 includes a power control device, a brake control device, an automatic steering control device, a light control device, etc. The power control device controls the output of a power machine 8 such as an internal combustion engine or a motor. The brake control device controls the braking operation of the electric brake device 9. The automatic steering control device controls the electric steering device 7. The light control device controls turn signals, hazard lights, etc.

[0016] The vehicle state detection device 33 is a detection device that detects the state of the host vehicle, such as the driving state and running state of the host vehicle. In this embodiment, the vehicle state detection device 33 detects the speed, acceleration, yaw rate, steering angle, lateral acceleration, etc. of the host vehicle as the running state of the host vehicle. For example, the vehicle state detection device 33 may be provided with a speed sensor, an acceleration sensor, an angular velocity sensor, a steering angle sensor, etc. that detect the rotational speed of the wheels.

[0017] The vehicle state detection device 33 detects the driver's acceleration / deceleration operations, steering angle operations, and lane change operations as the driving state of the vehicle. For example, the vehicle state detection device 33 may include an accelerator position sensor, a brake position sensor, a steering angle sensor (steering wheel angle sensor), a steering torque sensor, a turn signal position switch, and the like.

[0018] The human interface device 37 is a device that receives input from the driver through a speaker, a display screen, an input device, etc., and transmits information to the driver.

[0019] 1-1. Vehicle driving support device 50 The vehicle driving support device 50 includes processing units such as an information acquisition unit 51, a target determination unit 52, a plan generation unit 53, and a vehicle control unit 54. Each process of the vehicle driving support device 50 is realized by a processing circuit included in the vehicle driving support device 50. Specifically, as shown in FIG. 2 , the vehicle driving support device 50 includes an arithmetic processing device 90 such as a CPU (Central Processing Unit), a storage device 91, an input / output device 92 that inputs and outputs external signals to the arithmetic processing device 90, and the like.

[0020] The arithmetic processing device 90 may be an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), a GPU (Graphics Processing Unit), an AI (Artificial Intelligence) chip, various logic circuits, various signal processing circuits, etc. Furthermore, the arithmetic processing device 90 may be a plurality of the same or different types, and each process may be shared and executed. As the storage device 91, various storage devices such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EEPROM (Electrically Erasable Programmable Read Only Memory), a hard disk, etc. may be used.

[0021] The input / output device 92 includes a communication device, an A / D converter, an input / output port, a drive circuit, etc. The input / output device 92 is connected to the surroundings monitoring device 31, the position detection device 32, the vehicle state detection device 33, the map information database 34, the wireless communication device 35, the drive control device 36, the human interface device 37, etc., and communicates with these devices.

[0022] The processing of each of the processing units 51 to 54 included in the vehicle driving support device 50 is realized by the arithmetic processing unit 90 executing software (programs) stored in the storage device 91 and cooperating with other hardware of the vehicle driving support device 50, such as the storage device 91 and the input / output device 92. Setting data such as time constants used by each of the processing units 51 to 54 is stored in the storage device 91, such as an EEPROM.

[0023] 1-1-1 Information Acquisition Unit 51 The information acquisition unit 51 acquires information about the vehicle itself and information about objects present around the vehicle itself.

[0024] 3, the target object is set to another vehicle (hereinafter referred to as the target vehicle) traveling in front of or behind the host vehicle in the travel lane in which the host vehicle is traveling. With this configuration, the plan generation unit 53 (described later) can suppress the occurrence of excessive jerk and jerk change rate when the host vehicle accelerates or decelerates to follow a leading vehicle or when the host vehicle accelerates or decelerates to ensure a sufficient inter-vehicle distance between the host vehicle and a following vehicle.

[0025] 4, the target object is set to another vehicle (target vehicle) traveling in the lane to which the host vehicle is to move. In this case, the target object occurs when changing lanes, merging into lanes, branching into lanes, etc. With this configuration, the plan generation unit 53 (described later) can suppress the occurrence of excessive jerk and jerk change rate during acceleration and deceleration when maintaining a sufficient inter-vehicle distance between the host vehicle and another vehicle traveling in the lane to which the host vehicle is to move.

[0026] In this embodiment, the information acquisition unit 51 acquires at least the speed v of the host vehicle, the speed vtgt of the target vehicle, the distance d between the host vehicle and the target vehicle, and the relative speed vrel of the target vehicle with respect to the host vehicle.

[0027] The information acquisition unit 51 acquires the running state of the host vehicle as information about the host vehicle. In this embodiment, the information acquisition unit 51 acquires the position, moving direction, speed, acceleration, etc. of the host vehicle based on the position information of the host vehicle acquired from the position detection device 32 and the host vehicle state acquired from the vehicle state detection device 33.

[0028] The information acquisition unit 51 acquires road information around the vehicle from the map information database 34 based on the vehicle's position information acquired from the position detection device 32. The acquired road information includes road shapes (e.g., the number of lanes, the position of each lane, the shape of each lane, the type of each lane, the road type, the speed limit, the shape of an intersection, etc.), road signs (speed limit signs and the associated speed limits, stop signs, etc.), road markings (stop lines, crosswalks, etc.), toll gate information (the location of the toll gate entrance, the speed at which the toll gate is passed, etc.), traffic lights, etc. The shape of each lane includes the center position, lane width, lane curvature, etc. The lane shape is set at each point along the longitudinal direction of the lane. The types of each lane include a main lane, a merging lane merging into the main lane, etc. The lane shape also includes the start position of the merging lane, the end position of the merging lane, and the length of the merging lane.

[0029] The information acquisition unit 51 also detects the shape and type of road dividing lines, etc., based on detection information of white lines, road shoulders, etc., acquired from the periphery monitoring device 31, and determines the shape and position of each lane, the number of lanes, and the type of each lane, etc., based on the detected shape and type of road dividing lines, etc. The shape of each lane includes the center position of the lane, lane width, lane curvature, etc. The type of each lane includes a main lane, a merging lane, etc.

[0030] Furthermore, the information acquisition unit 51 acquires information on road signs, road markings, traffic lights, and toll booths based on the detection information acquired from the periphery monitoring device 31. The information acquisition unit 51 may acquire the current status of traffic lights and the like from an external device via wireless communication.

[0031] The information acquisition unit 51 acquires information about other vehicles in the vicinity of the host vehicle. In this embodiment, the information acquisition unit 51 acquires the relative position, relative speed, and distance of other vehicles relative to the host vehicle, as well as the position, movement direction, speed, and acceleration of the other vehicles, based on the detection information acquired from the periphery monitoring device 31 and the position information of the host vehicle acquired from the position detection device 32. In addition to other vehicles, the information acquisition unit 51 also acquires information about obstacles, pedestrians, traffic regulations such as lane restrictions, and the like.

[0032] The information acquisition unit 51 may acquire, via communication from outside the host vehicle, the driving conditions of other vehicles (such as the positions, moving directions, and speeds of other vehicles), as well as road information (such as lane information) and traffic information (such as obstacles and congestion levels) around the host vehicle. For example, the information acquisition unit 51 may acquire, via wireless communication or the like, the driving conditions of other vehicles, as well as road information and traffic information around the host vehicle, from other vehicles or a server to which other vehicles have uploaded information. Furthermore, the information acquisition unit 51 may acquire, via wireless communication or the like, the driving conditions of other vehicles, as well as road information and traffic information in a monitoring area, from roadside devices such as cameras that monitor road conditions, etc.

[0033] The information acquisition unit 51 acquires lane information corresponding to the lane in which the host vehicle is traveling, based on the position of the host vehicle. The information acquisition unit 51 also acquires lane information corresponding to the lane in which each other vehicle is traveling, based on the positions of each other vehicle. The acquired lane information includes the shape, position, and type of the lane, as well as lane information of surrounding lanes.

[0034] 1-1-2. Target determination unit 52 The target determination unit 52 sets a target speed v* of the host vehicle and a target distance d*, which is a target value for the distance between the host vehicle and the target object, based on information about the host vehicle and information about the target object (the target vehicle in this example).

[0035] In this embodiment, the target determination unit 52 sets the target speed v* of the host vehicle based on the speed vtgt of the object (the target vehicle in this example). For example, as shown in the following equation, the target determination unit 52 sets the target speed v* of the host vehicle to the speed vtgt of the target vehicle. For example, the speed vtgt of the target vehicle is calculated by adding the relative speed vrel of the target vehicle with respect to the host vehicle to the speed v of the host vehicle.

[0036] In this embodiment, the target determination unit 52 sets the target distance d* based on the speed vtgt of the target vehicle. If the target vehicle is a preceding vehicle of the subject vehicle or a preceding vehicle traveling in the lane to which the subject vehicle is to move, equation (2) is used, and the target distance d* is a positive value. If the target vehicle is a following vehicle of the subject vehicle or a following vehicle traveling in the lane to which the subject vehicle is to move, equation (3) is used, and the target distance d* is a negative value.

[0037] Here, Thw is the inter-vehicle time, which is multiplied by the speed vtgt of the target vehicle to calculate a distance component proportional to the speed vtgt of the target vehicle. For example, the inter-vehicle time Thw may be set to 1 to 2 seconds and may be changed by the driver via the human interface device 37. Dstop is the target distance when the target vehicle is stopped. For example, Dstop is set to a predetermined value and may be changed by the driver via the human interface device 37.

[0038] 1-1-3. Plan Generation Unit 53 The plan generation unit 53 calculates, based on the target distance d*, a distance plan dplan(t) which is a transitional target distance for each future time t up to the arrival time Trech at which the distance d reaches the target distance d* and the speed v of the host vehicle reaches the target speed v*, and also calculates, based on the distance plan dplan(t) and the target speed v*, a speed plan vplan(t) which is a transitional target speed for each future time t.

[0039] The plan generation unit 53 performs a four-stage filter process Fd consisting of a first filter F1d, a second filter F2d, a third filter F3d, and a fourth filter F4d on the target distance d* in a virtual time representing each future time t from the present to the arrival time Trch, and calculates a distance plan dplan(t), which is a transient target distance for each future time t.

[0040] According to this configuration, by using the four-stage filtering Fd, it is possible to reduce the jerk and the rate of change of the jerk that occur in the host vehicle when accelerating and decelerating until the target distance d* and the target speed v* are reached, thereby improving the ride comfort of the host vehicle. Furthermore, by managing the arrival time Trch, it is possible to prevent an increase in the travel distance until the target distance d* and the target speed v* are reached.

[0041] In this embodiment, as shown in equations (4) to (6), the plan generating unit 53 calculates a distance plan dplan(t), which is a transitional target distance for each future time t, by adding a four-stage filter value obtained by performing four-stage filtering Fd in virtual time on an input value din, which changes in a stepwise manner from a value obtained by subtracting the target distance d* from the initial distance d0 at the current time t=0, to the target distance d*. The initial distance d0 is set to the actual distance at the current time t=0.

[0042] As shown in equation (4), the input value din of the four-stage filter processing changes in a stepwise manner from the value obtained by subtracting the target distance d* from the initial distance d0 to 0 at the current time t=0.

[0043] The transfer function Fd(s) of the four-stage filter processing is expressed by Equation (5). In this embodiment, the first filter F1d, the second filter F2d, the third filter F3d, and the fourth filter F4d are each a moving average filter. The first time constant τ1d of the first filter F1d, the second time constant τ2d of the second filter F2d, the third time constant τ3d of the third filter F3d, and the fourth time constant τ4d of the fourth filter F4d are each a moving average time. Here, s is a Laplace operator.

[0044] Then, as shown in equation (6), the plan generation unit 53 adds the target distance d* to the value obtained by performing four-stage filter processing Fd on the input value din of the four-stage filter processing, and calculates the distance plan dplan(t), which is the transient target distance at each time t.

[0045] Here, L -1 represents the inverse Laplace transform. Note that in actual four-stage filtering, a discretized formula is used.

[0046] In this embodiment, as shown in equation (7), the plan generating unit 53 calculates a speed plan vplan(t), which is a transient target speed at each future time t, by subtracting the time differential value of the output value of the four-stage filtering from the target speed v*. The time differential value of the distance plan dplan(t) may be used instead of the time differential value of the output value of the four-stage filtering.

[0047] The plan generation unit 53 calculates a time differential value of the initial output value of the four-stage filter processing at the current time t=0 such that the speed plan vplan(0) at the current time t=0 matches the current speed v of the host vehicle, calculates an initial output value of the four-stage filter processing at the current time t=0 such that the four-stage distance plan dplan(0) at the current time t=0 matches the initial distance d0, and sets initial internal calculation values ​​of each filter of the four-stage filter processing such that the time differential value of the output value of the four-stage filter processing matches the time differential value of the initial output value at the current time t=0 and the output value of the four-stage filter processing matches the initial output value. When the calculation formula for the speed plan vplan(t) of Equation (7) is used, the value obtained by subtracting the current speed v of the host vehicle from the target speed v* is calculated as the time differential value of the initial output value of the four-stage filter processing. When the distance plan dplan(t) of equation (6) is used, the value obtained by subtracting the target distance d* from the initial distance d0 is calculated as the initial output value of the four-stage filter processing.

[0048] Note that other mathematically equivalent calculation methods may be used. For example, the plan generator 53 may perform four-stage filtering Fd in virtual time on input values ​​that change stepwise from the initial distance d0 to the target distance d* at the current time t = 0 to calculate the distance plan dplan(t), which is a transient target distance. In this case, the plan generator 53 subtracts the time derivative of the distance plan dplan(t), which is the output value of the four-stage filtering, from the target speed v* to calculate the speed plan vplan(t).

[0049] Alternatively, the plan generating unit 53 may calculate the distance plan dplan(t), which is a transient target distance for each future time t, by adding a four-stage filtered value obtained by performing four-stage filtering Fd in virtual time on an input value that changes in a stepwise manner from 0 to a value obtained by subtracting the initial distance d0 from the target distance d* at the current time t = 0, and the initial distance d0. In this case, the plan generating unit 53 calculates the speed plan vplan(t) by subtracting the output value of the four-stage filtering or the time derivative value of the distance plan dplan(t) from the target speed v*.

[0050] <Explanation of the Operation of Four-Stage Filter Processing> Figures 5 to 8 show the behavior of each value before and after each filter processing from the first filter to the fourth filter. At the current time t = 0, the target distance d* is reduced in a stepwise manner from 40 m to 20 m. The speed v of the host vehicle at the current time t = 0 matches the target speed v*. The first time constant τ1d is set to 8 seconds, the second time constant τ2d is set to 4 seconds, the third time constant τ3d is set to 2 seconds, and the fourth time constant τ4d is set to 1 second.

[0051] FIG. 5 shows the behavior before and after processing by the first filter F1d. The horizontal axis represents virtual time starting from the current time t=0. For illustrative purposes, times before the current time t=0 are also shown. The first graph in FIG. 5 shows the transient target distance corresponding to the input / output values ​​of the first filter F1d. For illustrative purposes, the target distance d* is added to the input / output values ​​of the first filter F1d. The second graph in FIG. 5 shows the transient target speed obtained by subtracting the time derivative of the target distance in the first graph in FIG. 5 from the target speed v*. At time t=0, the target distance d* (dotted line) decreases in a stepwise manner from the initial distance d0 of 40 m to 20 m. The target distance after processing by the first filter F1d (solid line) changes at a constant slope from time t=0 and reaches the target distance d* of 20 m at time t=8 seconds, which corresponds to the first time constant τ1d. Furthermore, the target speed (solid line) after processing by the first filter F1d increases in a stepwise manner from 20 m / s to 22.5 m / s at time t = 0, and then decreases in a stepwise manner from 22.5 m / s to 20 m / s at time t = 8 seconds, forming a pulse waveform.

[0052] Similarly, Figure 6 shows behavior before and after processing by the second filter F2d. The first graph in Figure 6 shows the output value (dotted line) of the first filter F1d, which becomes the input value of the second filter F2d, and the output value (solid line) of the second filter F2d. The second graph in Figure 6 shows the transient target speed (dotted line) after processing by the first filter F1d in Figure 5 and the transient target speed (solid line) obtained by subtracting the time-differentiated value of the target distance after processing by the second filter F2d in the first graph in Figure 6 from the target speed v*. The third graph in Figure 6 shows the acceleration (solid line) obtained by time-differentiating the target speed in the second graph in Figure 6. In Figure 6, every four seconds, corresponding to the second time constant τ2d, the intervals alternate between an interval in which the target speed increases at a constant gradient (acceleration), an interval in which the target speed remains constant, and an interval in which the target speed decreases at a constant gradient (acceleration). Furthermore, the target distance after processing by the second filter F2d reaches the target distance d* of 20 m at time t=12 seconds, which corresponds to the sum of the first time constant τ1d and the second time constant τ2d.

[0053] Similarly, Figure 7 shows the behavior before and after processing by the third filter F3d. The first graph in Figure 7 shows the output value (dotted line) of the second filter F2d, which becomes the input value of the third filter F3d, and the output value (solid line) of the third filter F3d. The second graph in Figure 7 shows the transient target speed (dotted line) after processing by the second filter F2d in Figure 6 and the transient target speed (solid line) obtained by subtracting the time-differentiated value of the target distance after processing by the third filter F3d in the first graph in Figure 7 from the target speed v*. The third graph in Figure 7 shows the transient acceleration (dotted line) after processing by the second filter F2d in Figure 6 and the acceleration (solid line) obtained by time-differentiating the target speed after processing by the third filter F3d in the second graph in Figure 7. The fourth graph in Figure 7 shows the jerk (solid line) obtained by time-differentiating the acceleration in the third graph in Figure 7. 7, the section where acceleration increases at a constant gradient (jerk), the section where acceleration is constant, and the section where acceleration decreases at a constant gradient (jerk) alternate every two seconds, which corresponds to the third time constant τ3d. Furthermore, the target distance after processing by the third filter F3d reaches the target distance d* of 20 m at time t = 14 seconds, which corresponds to the sum of the first time constant τ1d, the second time constant τ2d, and the third time constant τ3d.

[0054] Similarly, Figure 8 shows behavior before and after processing by the fourth filter F4d. The first graph in Figure 8 shows the output value (dotted line) of the third filter F3d, which becomes the input value of the fourth filter F4d, and the output value (solid line) of the fourth filter F4d. The second graph in Figure 8 shows the transient target speed (dotted line) after processing by the third filter F3d in Figure 7 and the transient target speed (solid line) obtained by subtracting the time-differentiated value of the target distance after processing by the fourth filter F4d in the first graph in Figure 8 from the target speed v*. The third graph in Figure 8 shows the transient acceleration (dotted line) after processing by the third filter F3d in Figure 7 and the acceleration (solid line) obtained by time-differentiating the target speed after processing by the fourth filter F4d in the second graph in Figure 8. The fourth graph in Figure 8 shows the transient jerk (dotted line) after processing by the third filter F3d in Figure 7 and the jerk (solid line) obtained by time-differentiating the acceleration after processing by the fourth filter F4d in the third graph in Figure 8. The fifth graph in FIG. 8 shows the jerk rate of change (solid line) obtained by time-differentiating the jerk in the fourth graph in FIG. 8 . In FIG. 8 , every second corresponding to the fourth time constant τ4d, the jerk alternates between a section in which the jerk increases at a constant rate (jerk rate of change), a section in which the jerk remains constant, and a section in which the jerk decreases at a constant rate (jerk rate of change). Furthermore, the target distance after processing by the fourth filter F4d reaches the target distance d* of 20 m at time t = 15 seconds, which corresponds to the sum of the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d. In other words, the sum of τ1d + τ2d + τ3d + τ4d is the arrival time Trch, and the arrival time Trch can be set by adjusting each time constant.

[0055] Furthermore, the jerk and the rate of change of the jerk can be suppressed to 0 or a finite value. Therefore, by using the four-stage filter processing, it is possible to obtain a distance plan dplan(t) and a speed plan vplan(t) that can suppress sudden changes in acceleration and jerk.

[0056] The relationship τ1d ≥ τ2d ≥ τ3d ≥ τ4d is set. τ1d, τ2d, τ3d, and τ4d correspond to the speed, acceleration, jerk, and jerk change rate, respectively, and as each time constant increases, the absolute value of the corresponding state quantity decreases.

[0057] Therefore, in order to minimize the jerk change rate while keeping the total value of τ1d+τ2d+τ3d+τ4d corresponding to the arrival time Trch the same, it is sufficient to set τ1d=τ2d=τ3d=τ4d=Trch / 4.

[0058] The plan generator 53 sets the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d based on the arrival time Trch so that the sum of the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d matches the target arrival time Trch. This configuration enables the arrival time Trch to be managed with high accuracy. In this case, the plan generator 53 may set the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d to the same value (arrival time Trch / 4).

[0059] Alternatively, the plan generator 53 may set the total value of the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d as the reaching time Trch.

[0060] Even if the set values ​​of the time constants of the filters are interchanged, i.e., even if the time constants of the filters have any magnitude relationship, the frequency characteristics of the transfer function Fd(s) of the four-stage filter processing of equation (5) do not change, and therefore the output values ​​of the four-stage filter processing will be the same value. In other words, the time constants of the filters may have any magnitude relationship.

[0061] 1-1-4 Vehicle Control Unit 54 The vehicle control unit 54 calculates an acceleration command value aref of the host vehicle based on at least the speed plan vplan(t), and controls the host vehicle based on the acceleration command value aref.

[0062] For example, as shown in equation (8), after generating the distance plan dplan(t) and the speed plan vplan(t), the vehicle control unit 54 calculates the acceleration command value aref(t) at the current real time tr based on the deviation between the distance plan dplan(t) corresponding to the real time tr, which is the elapsed time up to the present, and the actual distance dr, and the deviation between the speed plan vplan(t) corresponding to the real time tr and the actual speed vr, where Kdp is a proportional gain and Kdd is a differential gain.

[0063] Alternatively, as shown in equation (9), after generating the distance plan dplan(t) and the speed plan vplan(t), the vehicle control unit 54 may generate the acceleration command value aref(t) at the current actual time tr based on the deviation between the speed plan vplan(t) corresponding to the actual time tr, which is the elapsed time up to the present, and the actual speed vr. Here, Ksp is a proportional gain, and Ksi is an integral gain.

[0064] Alternatively, the plan generating unit 53 may be configured to calculate an acceleration plan aplan(t), which is a transient target acceleration at each future time t, based on the speed plan vplan(t). The plan generating unit 53 may calculate the acceleration plan aplan(t) using Equation (10), which is obtained by further time-differentiating Equation (7) for calculating the speed plan vplan(t), or may calculate the acceleration plan aplan(t) by time-differentiating the speed plan vplan(t).

[0065] In this case, as shown in equation (11), the vehicle control unit 54 may further add the acceleration plan aplan(tr) corresponding to the actual time tr to the right side of equation (8) to calculate the acceleration command value aref(tr) at the current actual time tr.

[0066] Alternatively, as shown in equation (12), the vehicle control unit 54 may further add the acceleration plan aplan(tr) corresponding to the actual time tr to the right side of equation (9) to calculate the acceleration command value aref(tr) at the current actual time tr.

[0067] By using the acceleration plan aplan, the acceleration command value aref can be changed in a feedforward manner, thereby improving the tracking ability.

[0068] The vehicle control unit 54 calculates a command value for the output of the power unit 8 and a command value for the braking force of the electric brake device 9 based on the acceleration command value aref(tr) at the current actual time tr, and transmits each command value to the power control device and the brake control device.

[0069] The power control device controls the output of a power machine 8 such as an internal combustion engine or a motor according to an output command value. The brake control device controls the braking operation of an electric brake device 9 according to a braking force command value.

[0070] 1-1-5. Flowchart Next, a general processing procedure (vehicle driving support method) of the vehicle driving support device 50 according to this embodiment will be described using the flowchart shown in Fig. 9. The processing of the flowchart in Fig. 9 is executed, for example, at predetermined calculation intervals. Note that processing steps that are unnecessary at the time of execution are skipped as appropriate.

[0071] In step S11, as described above, the information acquisition unit 51 determines whether or not there is an object for which distance control is to be performed around the vehicle, and if there is, proceeds to step S12; if there is no object, terminates the processing.

[0072] In step S12, as described above, the information acquisition unit 51 acquires information about the host vehicle and information about objects present around the host vehicle.

[0073] In step S13, as described above, the target determination unit 52 sets the target speed v* of the host vehicle and the target distance d*, which is the target value of the distance between the host vehicle and the target vehicle, based on information about the host vehicle and information about the target vehicle.

[0074] The process of setting this target velocity v* and target distance d* is executed, for example, when a new object is set, when the state of the object changes, or when a specific condition is met.

[0075] In step S14, as described above, the plan generation unit 53 calculates, based on the target distance d*, a distance plan dplan(t) which is a transitional target distance for each future time t up to the arrival time Trch at which the distance d reaches the target distance d* and the speed v of the host vehicle reaches the target speed v*, and also calculates, based on the distance plan dplan(t) and the target speed v*, a speed plan vplan(t) which is a transitional target speed for each future time t. At this time, the plan generation unit 53 performs four-stage filtering Fd consisting of a first filter F1d, a second filter F2d, a third filter F3d, and a fourth filter F4d on the target distance d* in a virtual time representing each future time t from the present to the arrival time Trch, to calculate the distance plan dplan(t).

[0076] The processing of the distance plan dplan(t) and the speed plan vplan(t) is executed, for example, when a new object is set, when the state of the object changes, or when a specific condition is met.

[0077] In step S15, as described above, the vehicle control unit 54 calculates the acceleration command value aref of the host vehicle based on at least the speed plan vplan(t), and controls the host vehicle based on the acceleration command value aref.

[0078] 2. Second Embodiment Next, a vehicle driving assistance device 50 according to a second embodiment will be described. Description of components that are the same as those in the first embodiment will be omitted. The basic configuration of the vehicle driving assistance device 50 according to this embodiment is the same as that of the first embodiment, but differs from the first embodiment in that a planning and design unit 55 is further provided.

[0079] 10 is a schematic block diagram of a vehicle driving assistance device 50 according to this embodiment. The vehicle driving assistance device 50 further includes a planning and design unit 55.

[0080] The planning and design unit 55 sets a first time constant τ1d, a second time constant τ2d, a third time constant τ3d, and a fourth time constant τ4d based on distance information regarding the distance between the host vehicle and the object, the target speed v*, and the target distance d*. The plan generation unit 53 performs four-stage filtering using the time constants set by the planning and design unit 55.

[0081] In this embodiment, the planning and design unit 55 sets the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d so that the travel distance Xrch of the vehicle from the present to the arrival time Trch, which is obtained by time-integrating the speed plan vplan(t), matches the target travel distance Xtrv.

[0082] According to this configuration, the jerk and jerk change rate occurring in the vehicle can be reduced while the travel distance Xrch up to the arrival time Trch can be made to match the target travel distance Xtrv, thereby preventing the travel distance from increasing.

[0083] For example, as shown in FIG. 11, when the vehicle is traveling in a merging lane and the target object is another vehicle traveling on the main lane where the merging lane merges, the planning and design unit 55 sets the target traveling distance Xtrv to a distance equal to or less than the distance Xend from the vehicle to the end of the merging lane.

[0084] With this configuration, the jerk and jerk change rate occurring in the host vehicle can be reduced, while the distance between the host vehicle and the main lane vehicle can be made to reach the target distance d* and the speed of the host vehicle can be made to reach the target speed v* by the time the host vehicle reaches the end of the merging lane, allowing the host vehicle to merge safely onto the main lane.

[0085] <Explanation of Time Constant Setting Method> FIGS. 12 and 13 show the behavior of each value after four-stage filter processing to explain the time constant setting method according to this embodiment. At the current time t=0, the target distance d* is increased in steps from 10 m to 20 m. The host vehicle's speed v at the current time t=0 is 20 m / s, and the target speed v* is 25 m / s, which are different. Therefore, as described in the first embodiment, the initial internal calculation values ​​of each filter in the four-stage filter processing at the current time t=0 are set so that the speed plan vplan(0) at the current time t=0 matches the current host vehicle's speed v and the distance plan dplan(0) at the current time t=0 matches the initial distance d0. In FIG. 12, τ1d = τ2d = 5 seconds, τ3d = 2 seconds, and τ4d = 1 second are set. In FIG. 13, τ1d = τ2d = τ3d = τ4d = 1¾ seconds are set.

[0086] The horizontal axis represents virtual time starting from the current time t = 0. The first graph in Figures 12 and 13 shows the distance plan dplan(t), the second graph shows the speed plan vplan(t), the third graph shows the acceleration obtained by time-differentiating the second speed plan vplan(t), the fourth graph shows the jerk obtained by time-differentiating the third acceleration, and the fifth graph shows the jerk rate of change obtained by time-differentiating the fourth jerk.

[0087] At time t = 13 seconds (arrival time Trch), which corresponds to the sum of the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d, the distance plan dplan reaches the target distance d* of 20 m, and the speed plan vplan reaches the target speed v* of 25 m / s.

[0088] The travel distance Xrch of the host vehicle up to the arrival time Trch is given by equation (13) and corresponds to the area of ​​the shaded portion in FIGS.

[0089] When the target velocity v* is constant, the amount of change in the distance until the arrival time Trch, that is, the amount of change from the initial distance d0 to the target distance d* (d*-d0) is expressed by equation (14).

[0090] When the speed vtgt of the target vehicle that becomes the target speed v* is constant, the travel distance of the target vehicle until the arrival time Trch is expressed as in equation (15).

[0091] By rearranging equations (13) to (15) and replacing the vehicle's mileage Xrch with the target mileage Xtrv, the relationship shown in equation (16) holds among the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, the fourth time constant τ4d, the target mileage Xtrv, the initial distance d0, the target distance d*, and the target speed v*.

[0092] Therefore, the planning and design unit 55 uses equation (16) to set the total value of the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d based on the initial distance d0 corresponding to the actual distance at the current time, the target speed v*, the target distance d*, and the target traveling distance Xtrv, and distributes the total value at a predetermined distribution ratio to set the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d.

[0093] For example, when τ1d = τ2d is set as in Fig. 12, the section from time t = 6 seconds to time t = 8 seconds in Fig. 8 disappears. As a result, in Fig. 12, it is possible to reduce the fluctuations in jerk and the fluctuations in the rate of change of jerk in the section from time t = 4 seconds to time t = 10 seconds in Fig. 8.

[0094] For example, when setting τ1d = τ2d, the planning and design unit 55 uses equations (17) to (19) to distribute the total value and set the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d. Here, Kr3d is a preset distribution ratio of the third time constant τ3d to the total value, and Kr4d is a preset distribution ratio of the fourth time constant τ4d to the total value. The distribution ratios of the time constants of each filter are set to satisfy the relationship τ1d = τ2d ≥ τ3d ≥ τ4d. For example, they are set to satisfy 0 ≤ Kr3d ≤ 1 / 4 and 0 ≤ Kr4d ≤ 1 / 4.

[0095] By appropriately setting the third time constant τ3d and the fourth time constant τ4d, control that takes ride comfort into consideration becomes possible. In the example of Fig. 12, the total value is set to 13 seconds, Kr3d = 2 / 13, and Kr4d = 1 / 13.

[0096] The distribution ratio of the time constants of each filter may be set to any value. The sum of the distribution ratios of the time constants of each filter is 1. Furthermore, as described above, since the result of the four-stage filter processing does not change, the set values ​​of the time constants of each filter may be interchanged.

[0097] Alternatively, when τ1d=τ2d=τ3d=τ4d are set as in FIG. 13, the distribution ratio of each time constant is set to 1 / 4.

[0098] The fluctuation in acceleration in Fig. 12 is smaller than the fluctuation in acceleration in Fig. 13. Furthermore, the fluctuation in jerk and jerk change rate in Fig. 13 is smaller than the fluctuation in jerk and jerk change rate in Fig. 12. Thus, as the distribution ratio Kr3d of the third time constant τ3d increases, the fluctuation in jerk can be reduced. As the distribution ratio Kr4d of the fourth time constant τ4d increases, the fluctuation in jerk change rate can be reduced.

[0099] When the time constant settings of each filter are interchangeable, the fluctuation in the jerk change rate can be reduced as the smallest time constant increases, and the fluctuation in the jerk change rate can be reduced as the second smallest time constant increases. When all time constants are set to the same value, this is equivalent to the smallest time constant being maximized, and the fluctuation in the jerk change rate can be minimized. Therefore, by adjusting the time constant settings of each filter, the fluctuation in the jerk and the jerk change rate can be adjusted, and the ride comfort can be optimized.

[0100] <Flowchart> Next, a general processing procedure (vehicle driving support method) of the vehicle driving support device 50 according to this embodiment will be described using the flowchart shown in Fig. 14. The processing of the flowchart in Fig. 14 is executed, for example, at predetermined calculation intervals. Note that processing steps that are unnecessary at the time of execution are skipped as appropriate.

[0101] Steps S11 to S15 in Fig. 14 are the same as steps S11 to S15 in Fig. 9 of the first embodiment, and therefore will not be described here. Step S21 is added between step S13 and step S14.

[0102] In step S21, as described above, the planning and designing unit 55 sets the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d based on the distance information regarding the distance between the host vehicle and the object, the target speed v*, and the target distance d*. In this embodiment, as described above, the planning and designing unit 55 sets the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d so that the traveling distance Xrch of the host vehicle from the present to the arrival time Trch, which is obtained by time-integrating the speed plan vplan(t), matches the target traveling distance Xtrv.

[0103] In step S14 , the plan generating unit 53 performs four-stage filtering using the time constants set by the plan design unit 55 .

[0104] 3. Third Embodiment Next, a vehicle driving assistance device 50 according to a third embodiment will be described. Description of components similar to those of the first embodiment will be omitted. The basic configuration of the vehicle driving assistance device 50 according to this embodiment is similar to that of the first embodiment, but differs from the first embodiment in that a planning and design unit 55 is further provided, similar to the second embodiment.

[0105] 15 is a schematic block diagram of a vehicle driving assistance device 50 according to this embodiment. As in the second embodiment, the vehicle driving assistance device 50 further includes a planning and design unit 55.

[0106] In this embodiment, the planning and designing unit 55 sets the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d based on speed information related to the speed of the host vehicle, distance information related to the distance between the host vehicle and the object, the target speed v*, and the target distance d*. The plan generating unit 53 performs four-stage filtering using the time constants set by the planning and designing unit 55.

[0107] <Derivation of a Method for Setting Time Constants> FIG. 16 shows the behavior of each value after four-stage filtering to explain a method for setting time constants according to this embodiment. The example in FIG. 16 illustrates a case in which a host vehicle is following a preceding vehicle traveling at a slower speed than the host vehicle. At the current time t=0, the target distance d* is reduced in steps from 40 m to 20 m. The host vehicle's speed v at the current time t=0 is 20 m / s, and the target speed v* set for the target vehicle's speed vtgt is 15 m / s, which are different from each other. Therefore, as described in the first embodiment, the initial internal calculation values ​​of each filter in the four-stage filtering at the current time t=0 are set so that the speed plan vplan(0) at the current time t=0 matches the current host vehicle's speed v and the distance plan dplan(0) at the current time t=0 matches the initial distance d0. In FIG. 16, τ1d = τ2d = 5 seconds, τ3d = 2 seconds, and τ4d = 1 second are set.

[0108] The horizontal axis represents virtual time starting from the current time t = 0. The first graph in Fig. 16 shows the distance plan dplan(t), the second graph shows the speed plan vplan(t), the third graph shows the acceleration obtained by time-differentiating the second speed plan vplan(t), the fourth graph shows the jerk obtained by time-differentiating the third acceleration, and the fifth graph shows the jerk rate of change obtained by time-differentiating the fourth jerk.

[0109] 16, the absolute value of the jerk gradually increases from time t = 0 second to time t = 1 second, becomes constant from time t = 1 second to time t = 2 seconds, and gradually decreases from time t = 2 seconds to time t = 3 seconds. Similarly, from time t5 to time t8, the absolute value of the jerk increases, then becomes constant, and then decreases.

[0110] The jerk change rate dj(t) in Fig. 16 is expressed by equation (20), where dJ is the target maximum jerk change rate and is a positive value (absolute value), and τ1d = τ2d.

[0111] By sequentially integrating the jerk change rate dj(t) over time, the jerk j(t), acceleration a(t), velocity v(t), and distance d(t) can be obtained as shown in equations (21) to (24).

[0112] By substituting equation (20) into equations (21) to (24) and performing calculations, equations (25) to (28) are obtained, where C10 to C83 are constants.

[0113] At the current time t=0, the speed v(0) of the host vehicle is the initial speed v0, and the distance d(0) is the initial distance d0. Furthermore, at each time t, the jerk j, acceleration a, speed v, and distance d are continuous. Although details are omitted, from these, by solving equations (25) to (28) in chronological order, the above-mentioned constants C10 to C83 can be derived.

[0114] The derived constants C10 to C83 are expressed by equations including the initial velocity v0, the initial distance d0, the target velocity v*, the target distance d*, the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d. Rearranging these, the relational expression required to achieve the target is given by equation (29).

[0115] <Method of Setting Each Time Constant> Using Equation (29), the planning and design unit 55 sets the sum of the first time constant τ1d or the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d based on the initial speed v0 corresponding to the actual speed of the host vehicle at the current time, the initial distance d0 corresponding to the actual distance at the current time, the target speed v*, and the target distance d*, and distributes the sum using a predetermined distribution ratio to set the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d. Note that τ1d = τ2d is set. For example, the distribution ratio of the time constants of each filter is set so as to satisfy the relationship τ1d = τ2d ≧ τ3d ≧ τ4d.

[0116] When the set values ​​of the time constants of the filters are interchangeable, the time constants of any two filters may be set to the same value, rather than τ1d = τ2d. Also, the distribution ratio of the time constants of the filters may be set to any value.

[0117] For example, in equation (25), C10 = 0, so when t = τ4d, C20 = -dJ × τ4d. C20 is the value of jerk j when τ4d ≦ t ≦ τ3d in equation (25) and is the maximum absolute value of jerk j. τ4d is the time t at which the maximum absolute value of jerk j is reached. Replacing C20 with the target maximum jerk j* and rearranging the equation, τ4d = j* / dJ, is obtained, and τ4d can be set to the value obtained by dividing the target maximum jerk j* by the target maximum jerk change rate dJ. Note that the target maximum jerk j* is a positive value (absolute value) and can be set in advance. The target maximum jerk change rate dJ is a positive value (absolute value) and can be set in advance. Therefore, by setting τ4d as described above, the absolute value of the jerk can be limited to an upper limit. Here, τ4d is the smallest time constant, and when the set values ​​of the time constants of the filters are interchanged, τ4d is replaced with the smallest time constant.

[0118] Therefore, the planning design unit 55 sets the smallest time constant (in this example, the fourth time constant τ4d) among the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d so that the maximum absolute value of the jerk change rate dj at each future time t, obtained by differentiating the speed plan vplan(t) with respect to time third order, coincides with the target maximum jerk change rate dJ, and the maximum absolute value of the jerk j at each future time t, obtained by differentiating the speed plan vplan(t) with respect to second order, coincides with the target maximum jerk j*.

[0119] Specifically, the planning and design unit 55 sets the smallest time constant (τ4d in this example) to the value obtained by dividing the target maximum jerk j* by the target maximum jerk change rate dJ (τ4d = j* / dJ). The other time constants (τ1d, τ2d, and τ3d in this example) may be set so as to satisfy equation (29).

[0120] Furthermore, by solving the constants in equations (25) and (26) in chronological order, C40 = 0 when t = τ3d + τ4d in equation (26), resulting in C41 = -dJ × τ3d × τ4d. C41 is the value of acceleration a at τ3d + τ4d ≦ t ≦ τ1d in equation (26) and is the maximum absolute value of acceleration a. τ3d + τ4d is the time t at which acceleration a reaches its maximum absolute value. Replacing C41 with the target maximum acceleration a* and rearranging the equation yields τ3d × τ4d = a* / dJ, where τ3d × τ4d can be set to the value obtained by dividing the target maximum acceleration a* by the target maximum jerk change rate dJ. Note that the target maximum acceleration a* is a positive value (absolute value) and can be set in advance. Therefore, by setting τ3d and τ4d as described above, the absolute value of acceleration can be limited to an upper limit. Here, τ3d is the second smallest time constant, and when the set values ​​of the time constants of the filters are interchanged, τ3d is replaced with the second smallest time constant.

[0121] Therefore, the planning design unit 55 sets the smallest time constant (in this example, the fourth time constant τ4d) and the second smallest time constant (in this example, the third time constant τ3d) among the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d so that the maximum absolute value of the jerk change rate dj at each future time t, obtained by differentiating the speed plan vplan(t) with respect to time three times, coincides with the target maximum jerk change rate dJ, and the maximum absolute value of the acceleration a at each future time t, obtained by differentiating the speed plan vplan(t) with respect to one time, coincides with the target maximum acceleration a*.

[0122] Specifically, the planning and design unit 55 sets the smallest time constant (τ4d in this example) and the second smallest time constant (τ3d in this example) so that the product of the smallest time constant (τ4d in this example) and the second smallest time constant (τ3d in this example) is the value obtained by dividing the target maximum acceleration a* by the target maximum jerk change rate dJ (τ3d × τ4d = a* / dJ). For example, if the smallest time constant (τ4d) is set to j* / dJ (τ4d = j* / dJ) to limit the upper limit of the absolute value of the jerk j by the target maximum jerk j*, then the second smallest time constant (τ3d) may be set to the value obtained by dividing the target maximum acceleration a* by the target maximum jerk j* (τ3d = a* / j*). Alternatively, the smallest time constant (τ4d) and the second smallest time constant (τ3d) may be set to a predetermined ratio while satisfying τ4d × τ3d = a* / dJ. The other time constants (τ1d and τ2d in this example) may be set so as to satisfy equation (29).

[0123] Although details are omitted, there are various methods for setting the time constants for setting the vehicle speed v in equation (27) and the distance d in equation (28) to their target values.

[0124] Note that if τ1d = τ2d is not set, the number of time intervals increases, but as with equation (20), the absolute value of the jerk change rate dj(t) in each time interval is set to be the target maximum jerk change rate dJ or 0. Even in this case, each constant C is derived in the same way, and a derived result (function) similar to equation (29) that sets each time constant is obtained based on the initial speed v0, initial distance d0, target speed v*, and target distance d*. Therefore, as with each of the configurations described above, the planning and design unit 55 can set the first time constant τ1d, the second time constant τ2d, the third time constant τ3d, and the fourth time constant τ4d based on the initial distance d0, target speed v*, and target distance d*. Furthermore, even when the target speed v*, initial speed v0, target distance d*, and initial distance d0 are different from those in the example of FIG. 16, if the absolute value of the jerk change rate dj(t) in each time interval is set to be the target maximum jerk change rate dJ or 0, a similar derived result (function) can be obtained, and each time constant can be set as in each of the configurations described above.

[0125] <Flowchart> Next, a general processing procedure (vehicle driving support method) of the vehicle driving support device 50 according to this embodiment will be described using the flowchart shown in Fig. 17. The processing of the flowchart in Fig. 17 is executed, for example, at predetermined calculation intervals. Note that processing steps that are unnecessary at the time of execution are skipped as appropriate.

[0126] Steps S11 to S15 in Fig. 17 are the same as steps S11 to S15 in Fig. 9 of the first embodiment, and therefore will not be described here. Step S31 is added between step S13 and step S14.

[0127] In step S31, as described above, the planning and design unit 55 sets the first time constant τ1d of the first filter, the second time constant τ2d of the second filter, the third time constant τ3d of the third filter, and the fourth time constant τ4d of the fourth filter based on speed information regarding the speed of the vehicle, distance information regarding the distance between the vehicle and the object, the target speed v*, and the target distance d*.

[0128] In step S14 , the plan generating unit 53 performs four-stage filtering using the time constants set by the plan design unit 55 .

[0129] 4. Fourth Embodiment Next, a vehicle driving assistance device 50 according to a fourth embodiment will be described. Description of components similar to those of the first, second, or third embodiment will be omitted. The basic configuration of the vehicle driving assistance device 50 according to this embodiment is similar to that of the first, second, or third embodiment, but the processing of the vehicle control unit 54 differs from that of the first, second, or third embodiment.

[0130] In this embodiment, the vehicle control unit 54 uses a dynamic vehicle model that represents the behavior of the host vehicle to calculate a predicted value de of the distance and a predicted value ve of the host vehicle at each future time t, calculates an acceleration command value aref for each future time based on an evaluation value for the distance deviation, which is the deviation between the distance plan dplan and the predicted distance value de, and an evaluation value for the speed deviation, which is the deviation between the speed plan vplan and the predicted speed value ve, and controls the host vehicle based on the acceleration command value aref.

[0131] The dynamic vehicle model is a model for predicting the behavior of the host vehicle from the current time t=0 to a time point in the future by a prediction period Th, for each fixed period Tper. Various known vehicle models, such as a two-wheeled model, can be used. The vehicle control unit 54 solves an optimization problem for each fixed period Tper to find a control input u that minimizes an evaluation function J that evaluates each of a distance deviation and a speed deviation, and calculates the solution as an acceleration command value aref.

[0132] In this case, the number of prediction points in time for the predicted distance value dek and the predicted velocity value vek is N. The number of points in time N is calculated by N = Th / Tper. The period from the current time t = 0 to a point in the future by the prediction period Th is called the "horizon."

[0133] The calculation process of the acceleration command value aref by the vehicle control unit 54 will be described in more detail below. Equation (30) expresses that a control input u that minimizes the evaluation function J is obtained. Here, x is a vehicle state quantity, and x0 is the initial value of the vehicle state quantity x. Also, x' is a predicted value of the vehicle state quantity x. f(x, u) is a vector value function related to the dynamic vehicle model.

[0134] The vehicle state quantity x and the control input u are set as shown in equation (31), where [...] T represents the transposed matrix.

[0135] The dynamic vehicle model can be expressed as in equation (32): where Ta is the response delay of the drive control device with respect to the acceleration command value aref.

[0136] The evaluation function J is expressed as in equation (33). Here, xk is the predicted value of the vehicle state quantity at prediction time point k (k = 0, ..., N-1), and uk is the control input at prediction time point k (k = 0, ..., N-1). h is a vector value function related to the evaluation item, and hN is a vector value function related to the evaluation item at prediction time point N. rk is the target value at prediction time point k (k = 0, ..., N-1). W and WN are weight matrices, which are diagonal matrices having weights for each evaluation item in the diagonal components.

[0137] The vehicle control unit 54 sets the vector value functions h and hN related to the evaluation items as shown in Equation (34). Here, dek is the predicted value of the distance at prediction time k (k = 0, ..., N), vek is the predicted value of the speed of the host vehicle at prediction time k (k = 0, ..., N), and arefk is the acceleration command value at prediction time k (k = 0, ..., N).

[0138] The vehicle control unit 54 sets the target values ​​rk and rN shown in equation (35) so that the predicted distance value dek, the predicted speed value vek, and the acceleration command value aref,k are each small. Here, dplan,k is a value corresponding to the prediction time point k in the distance plan dplan(t) of equation (6), and dplan,N is a value corresponding to the prediction time point N in the distance plan dplan(t) of equation (6).

[0139] The vehicle control unit 54 uses the evaluation function J to evaluate the deviation between the vector value function h and the target value r k , and the deviation between the vector value function h N and the target value r N . The vehicle control unit 54 periodically solves an optimization problem that finds a control input u that minimizes the evaluation value of each deviation, and sets the acceleration command value aref(k) at each prediction time point k of the obtained solution as the acceleration command value aref(t) at each future time t. The process of solving the optimization problem itself is a well-known technique, so a detailed description will be omitted. As in the first embodiment, the vehicle control unit 54 controls the host vehicle based on the acceleration command value aref(t) at each time t.

[0140] In the above configuration, the vehicle control unit 54 determines the control input u that minimizes the evaluation value of each deviation. However, the vehicle control unit 54 may also be configured to determine the control input u that minimizes the evaluation value of each deviation below a preset threshold. Furthermore, if the vehicle control unit 54 is unable to determine the control input u that minimizes the evaluation value of each deviation below the threshold after performing the iterative calculation a predetermined number of times, the vehicle control unit 54 may also be configured to determine the control input u that minimizes the evaluation value among the multiple evaluation values ​​determined by the iterative calculation.

[0141] Furthermore, the vehicle control unit 54 determines the control input u that minimizes the evaluation value of each deviation. However, by inverting the sign of the evaluation function J, the vehicle control unit 54 may also determine the control input u that maximizes the evaluation value of each deviation. Alternatively, the vehicle control unit 54 may determine the control input u that maximizes the evaluation value of each deviation, even if the vehicle control unit 54 performs the iterative calculation a predetermined number of times. If the vehicle control unit 54 is unable to determine the control input u that maximizes the evaluation value of each deviation even after performing the iterative calculation a predetermined number of times, the vehicle control unit 54 may also determine the control input u that maximizes the evaluation value among the multiple evaluation values ​​determined by the iterative calculation.

[0142] In this embodiment, by evaluating the deviation of the distance plan and the deviation of the speed plan, it is possible to calculate an acceleration command value for smoothly following the distance plan and the speed plan within the horizon. Furthermore, by incorporating the response delay of the drive / braking control device into the dynamic vehicle model, it is possible to calculate a control amount that takes into account the delay of the vehicle in response to the acceleration command value.

[0143] Furthermore, the plan generating unit 53 may further calculate an acceleration plan aplan(t) using equation (10) and output the calculated acceleration plan to the vehicle control unit 54. The vehicle control unit 54 may then set the target value rk as shown in equation (36) and calculate the acceleration command value aref through optimization calculation. aplan,k is a value corresponding to the prediction time point k in the acceleration plan aplan(t) of equation (10).

[0144] 5. Fifth Embodiment Next, a vehicle driving assistance device 50 according to a fifth embodiment will be described. Description of components similar to those of the first, second, third, or fourth embodiment will be omitted. The basic configuration of the vehicle driving assistance device 50 according to this embodiment is similar to that of the first, second, third, or fourth embodiment, but differs from the first, second, third, or fourth embodiment in that the target object is set at a stop position.

[0145] In this embodiment, the information acquisition unit 51 sets the object to a stop position ahead of the vehicle. For example, the stop position may be set to various stop lines (e.g., a stop line, a stop line at a pedestrian crossing, or a stop line at an intersection), a stop line at a traffic light, the position of a stopped vehicle or obstacle ahead, or a stop position due to various factors. An example in which the stop position is a stop line at an intersection is shown in FIG. 18 .

[0146] The information acquisition unit 51 also acquires information about a traffic light ahead of the vehicle, and when the light is red, for example, sets the stop position to the stop line of the traffic light or the position in front of the vehicle ahead that is stopped at the red light. When the information acquisition unit 51 detects another vehicle, pedestrian, or the like crossing the intersection or road ahead of the vehicle, it sets the position in front of the vehicle as the stop position.

[0147] The target determination unit 52 sets a target speed v* of the vehicle and a target distance d*, which is the target value of the distance between the vehicle and the target vehicle, based on information about the vehicle and information about the target object (in this example, the stopping position).

[0148] In this embodiment, the target determination unit 52 sets the target speed v* of the host vehicle to 0, which is the speed at the stopping position (v* = 0). The target determination unit 52 also sets the target distance d* to the distance from the position of the host vehicle to the stopping position.

[0149] The configurations of the plan generation unit 53, the vehicle control unit 54, and the plan design unit 55 are the same as those in the first, second, third, or fourth embodiment, and therefore will not be described here.

[0150] Other Embodiments (1) In the above embodiments, the first filter F1d, the second filter F2d, the third filter F3d, and the fourth filter F4d are each a moving average filter. However, the first filter F1d, the second filter F2d, the third filter F3d, and the fourth filter F4d may each be a low-pass filter such as a first-order lag filter.

[0151] Although various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this disclosure specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0152] 50: Vehicle driving assistance device, 51: Information acquisition unit, 52: Target determination unit, 53: Plan generation unit, 54: Vehicle control unit, 55: Plan design unit, F1d: First filter, F2d: Second filter, F3d: Third filter, F4d: Fourth filter, Fd: Fourth stage filter processing, τ1d: First time constant, τ2d: Second time constant, τ3d: Third time constant, τ4d: Fourth time constant, Trch: Arrival time, Xend: To end distance, Xrch: travel distance, Xtrv: target travel distance, a*: target maximum acceleration, aplan: acceleration plan, aref: acceleration command value, d*: target distance, dJ: target maximum jerk change rate, dj: jerk change rate, dplan: distance plan, j: jerk, j*: target maximum jerk, v: speed of host vehicle, v*: target speed, vplan: speed plan, vr: actual speed, vtgt: speed of target vehicle

Claims

1. A vehicle driving assistance device comprising: an information acquisition unit that acquires information about the host vehicle and information about an object present in the vicinity of the host vehicle; a target determination unit that sets a target speed of the host vehicle and a target distance which is a target value of the distance between the host vehicle and the object based on the information about the host vehicle and the information about the object; a plan generation unit that calculates a distance plan which is a transitional target distance for each future time until a time when the distance reaches the target distance and the speed of the host vehicle reaches the target speed based on the target distance, and calculates a speed plan which is the transitional target speed for each future time based on the distance plan and the target speed; and a vehicle control unit that calculates an acceleration command value of the host vehicle based on at least the speed plan, and controls the host vehicle based on the acceleration command value, wherein the plan generation unit calculates the distance plan by performing four-stage filter processing consisting of a first filter, a second filter, a third filter, and a fourth filter on the target distance in a virtual time which represents each future time from the present to the arrival time.

2. A vehicle driving assistance device according to claim 1, wherein the object is another vehicle driving in front or behind the vehicle in the driving lane in which the vehicle is driving.

3. The vehicle driving assistance device according to claim 1, wherein the object is another vehicle traveling in the lane to which the host vehicle is moving.

4. The vehicle driving assistance device according to claim 1, wherein the object is a stopping position present in front of the host vehicle.

5. A vehicle driving assistance device according to any one of claims 1 to 4, wherein each of the first filter, the second filter, the third filter, and the fourth filter is a moving average filter, and each of a first time constant which is a time constant of the first filter, a second time constant which is a time constant of the second filter, a third time constant which is a time constant of the third filter, and a fourth time constant which is a time constant of the fourth filter is a moving average time of the moving average filter.

6. A vehicle driving assistance device as described in any one of claims 1 to 5, wherein the plan generation unit sets the first time constant, the second time constant, the third time constant, and the fourth time constant based on the arrival time so that a total value of a first time constant which is a time constant of the first filter, a second time constant which is a time constant of the second filter, a third time constant which is a time constant of the third filter, and a fourth time constant which is a time constant of the fourth filter matches a target arrival time.

7. A vehicle driving assistance device according to any one of claims 1 to 5, wherein the plan generation unit sets the arrival time to the sum of a first time constant which is a time constant of the first filter, a second time constant which is a time constant of the second filter, a third time constant which is a time constant of the third filter, and a fourth time constant which is a time constant of the fourth filter.

8. A vehicle driving assistance device as described in any one of claims 1 to 7, wherein the plan generation unit sets a first time constant which is a time constant of the first filter, a second time constant which is a time constant of the second filter, a third time constant which is a time constant of the third filter, and a fourth time constant which is a time constant of the fourth filter to the same value.

9. A vehicle driving assistance device as described in any one of claims 1 to 5, further comprising a planning and design unit that sets a first time constant which is a time constant of the first filter, a second time constant which is a time constant of the second filter, a third time constant which is a time constant of the third filter, and a fourth time constant which is a time constant of the fourth filter based on speed information regarding the speed of the vehicle, distance information regarding the distance, the target speed, and the target distance.

10. A vehicle driving assistance device as described in claim 9, wherein the planning design unit sets the smallest time constant among the first time constant, the second time constant, the third time constant, and the fourth time constant so that the maximum absolute value of the jerk change rate at each future time point obtained by third-order time differentiation of the speed plan coincides with the target maximum jerk change rate, and so that the maximum absolute value of the jerk at each future time point obtained by second-order time differentiation of the speed plan coincides with the target maximum jerk.

11. The vehicle driving assistance device according to claim 10, wherein the planning and designing unit sets the smallest time constant to a value obtained by dividing the target maximum jerk by a target maximum jerk change rate.

12. A vehicle driving assistance device as described in any one of claims 9 to 11, wherein the planning design unit sets the smallest and second smallest time constants among the first time constant, the second time constant, the third time constant, and the fourth time constant so that the maximum absolute value of the jerk change rate at each future time obtained by third-order time differentiation of the speed plan coincides with a target maximum jerk change rate, and the maximum absolute value of the acceleration at each future time obtained by first-order time differentiation of the speed plan coincides with a target maximum acceleration.

13. A vehicle driving assistance device as described in claim 12, wherein the planning and design unit sets the smallest time constant and the second smallest time constant so that the product of the smallest time constant and the second smallest time constant becomes the target maximum acceleration divided by the target maximum jerk change rate.

14. A vehicle driving assistance device as described in any one of claims 1 to 5, further comprising a planning and design unit that sets a first time constant that is a time constant of the first filter, a second time constant that is a time constant of the second filter, a third time constant that is a time constant of the third filter, and a fourth time constant that is a time constant of the fourth filter based on distance information regarding the distance, the target speed, and the target distance.

15. A vehicle driving assistance device as described in claim 14, wherein the planning and design unit sets the first time constant, the second time constant, the third time constant, and the fourth time constant so that the travel distance of the vehicle from the present to the arrival time, obtained by time-integrating the speed plan, matches the target travel distance.

16. A vehicle driving assistance device as described in claim 15, wherein the planning and design unit sets the target driving distance to a distance equal to or less than the distance from the vehicle to the end of the merging lane when the vehicle is driving in a merging lane and the object is another vehicle driving on a main lane into which the merging lane merges.

17. A vehicle driving assistance device as described in any one of claims 1 to 16, wherein the vehicle control unit calculates a predicted value of the distance and a predicted value of the speed of the vehicle at each future time using a dynamic vehicle model representing the behavior of the vehicle, and calculates the acceleration command value at each future time based on an evaluation value for a distance deviation, which is the deviation between the distance plan and the predicted value of the distance, and an evaluation value for a speed deviation, which is the deviation between the speed plan and the predicted value of the speed.

18. A vehicle driving support method comprising: an information acquisition step of acquiring information about the host vehicle and information about an object present in the vicinity of the host vehicle; a target determination step of setting a target speed of the host vehicle and a target distance which is a target value of the distance between the host vehicle and the object based on the information about the host vehicle and the information about the object; a plan generation step of calculating a distance plan which is a transitional target distance for each future time until a time when the distance reaches the target distance and the speed of the host vehicle reaches the target speed based on the target distance, and calculating a speed plan which is the transitional target speed for each future time based on the distance plan and the target speed; and a vehicle control step of calculating an acceleration command value of the host vehicle based on at least the speed plan, and controlling the host vehicle based on the acceleration command value, wherein in the plan generation step, a four-stage filter process consisting of a first filter, a second filter, a third filter, and a fourth filter is performed on the target distance in a virtual time which represents each future time from the present to the arrival time, to calculate the distance plan.

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