CONTROL SYSTEM FOR A VEHICLE

Abstract

Control system for a vehicle, comprising: a steering control unit (13) configured to control a steering angle of a wheel of the vehicle; and an electronic control unit (14) configured to to obtain a target steering angle set as a target for moving the vehicle, to adjust the acquired target steering angle so that the target steering angle does not exceed a first protection value determined to prevent a change in the steering angle of the vehicle that is greater than or equal to a first reference, output the adjusted target steering angle to the steering control unit (13) so that the steering control unit (13) controls the steering angle to the adjusted target steering angle, and to change the first protection value in response to a situation of the vehicle, characterized in that the electronic control unit (14) is configured to change the first protection value based on an actual steering angle of the vehicle, which is a controlled result of the steering control unit (13), wherein the actual steering angle corresponds to the situation of the vehicle.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a control system for a vehicle according to the preamble of claim 1. 2. Description of the state of the art

[0002] Generally, a technique for assisted steering or automatic steering is known for causing a vehicle to move along a trajectory to guide the vehicle to a target position (see, for example, Japanese Patent Application Laid-Open No. 2006-008009 (JP 2006-008009 A), Japanese Patent Application Laid-Open No. 2013-112188 (JP 2013-112188 A)). JP 2013-112188 A discloses a control system according to the preamble of claim 1.

[0003] However, in the existing state of the art, a vehicle is merely caused to move along a preset movement path, and driving comfort in the case where the vehicle is steered to move along the movement path is not taken into consideration so much. SUMMARY OF THE INVENTION

[0004] One aspect of the invention provides a control system for a vehicle. The control system includes a steering control unit and an electronic control unit. The steering control unit is configured to control a steering angle of a wheel of the vehicle. The electronic control unit is configured to acquire a target steering angle set as a target for moving the vehicle, adjust the acquired target steering angle so that the target steering angle does not exceed a first guard value determined to prevent a change in the steering angle of the vehicle that is greater than or equal to a first reference, output the adjusted target steering angle to the steering control unit so that the steering control unit controls the steering angle to the adjusted target steering angle, and change the first guard value in response to a situation of the vehicle.Thus, for example, it is possible to provide driving comfort for an occupant by preventing an abrupt change in the steering angle of the vehicle.

[0005] In the control system according to the above aspect, the electronic control unit is configured to change the first protection value based on the actual steering angle of the vehicle, which is a controlled result of the steering control unit, as the situation of the vehicle. Thus, for example, it is possible to provide ride comfort to a passenger by changing the first protection value based on the actual steering angle.

[0006] In the control system according to the above aspect, the electronic control unit may be configured to change the first protection value based on the rate at which the actual steering angle of the vehicle changes according to the control of the steering control unit, as the situation of the vehicle. Thus, for example, it is possible to provide ride comfort for a passenger by changing the first protection value based on the rate at which the actual steering angle changes.

[0007] In the control system according to the above aspect, the electronic control unit may be configured to adjust the first protection value so that a change or fluctuation of the first protection value per unit time increases as a change or fluctuation in the actual steering angle per unit time controlled by the steering control unit increases. Thus, for example, it is possible to improve the moving performance of the vehicle along with ride comfort for an occupant by increasing the change or fluctuation of the first protection value per unit time.

[0008] In the control system according to the above aspect, the electronic control unit may be configured to adjust the target steering angle so that the target steering angle does not exceed the first protection value determined to prevent a change in the steering angle of the vehicle in a first direction that is greater than or equal to the first reference, and then, at a time when a direction in which the target steering angle changes changes from the first direction to a second direction that is a direction opposite to the first direction, adjust the target steering angle so that the target steering angle does not exceed a second protection value determined to prevent a change in the steering angle of the vehicle in the second direction that is greater than or equal to a second reference.Thus, for example, it is possible to provide driving comfort for an occupant by, when the direction of the steering angle has changed, preventing an abrupt change of the steering angle in that direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Features, advantages and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which like reference numerals designate like elements, and in which: Fig. 1 is an exemplary perspective view of a vehicle according to an embodiment in a state of looking through a part of a passenger compartment; Fig. 2 an exemplary top view (bird's eye view) of the vehicle according to the embodiment; Fig. 3 is a view of an example of a dashboard of the vehicle according to the embodiment when viewed from the rear side of the vehicle; Fig. 4 is an exemplary block diagram of the configuration of a parking assistance system according to the embodiment; Fig. 5 is an exemplary block diagram of the configuration of an ECU of the parking assist system according to the embodiment; Fig. 6 is a block diagram showing the configuration of a steering angle control unit according to the embodiment; Fig. 7 is a graph showing the relationship between a target steering angle and a protection value according to the embodiment; Fig. 8 is a graph showing the relationship between a target steering angle and a protection value according to the embodiment; Fig. 9 is a flowchart showing the procedure of a process until the process switches to the parking assist control in the ECU according to the embodiment; and Fig. 10 is a flowchart showing the procedure of parking assist control in the ECU according to the embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0010] An exemplary embodiment of the invention will be described below. The configuration of the embodiment described below and the operation, results, and advantageous effects obtained by the configuration are illustrative. The invention can be implemented by a configuration other than the configuration described in the following embodiment, and can obtain at least one of various advantageous effects based on a basic configuration or second advantageous effects.

[0011] A vehicle 1 according to the present embodiment may be, for example, an automobile that uses an internal combustion engine (not shown) as a drive source, that is, an internal combustion engine automobile; may be an automobile that uses an electric motor (not shown) as a drive source, that is, an electric automobile, a fuel cell automobile, or the like; may be a hybrid automobile that uses both the internal combustion engine and the electric motor as drive sources; or may be an automobile that includes another drive source. Various transmissions may be mounted on the vehicle 1. Various devices such as a system and components required to operate an internal combustion engine or an electric motor may be mounted on the vehicle 1.The system, a number, a layout and the like of a device relating to driving wheels 3 in the vehicle 1 can be set variously.

[0012] As in Fig. As shown in Fig. 1, a vehicle body 2 forms a passenger compartment 2a in which an occupant (not shown) sits. A steering unit 4, an accelerator operation unit 5, a brake operation unit 6, a shift operation unit 7, and the like are provided near a seat 2b of a driver as an occupant within the passenger compartment 2a. The steering unit 4 is, for example, a steering wheel protruding from an instrument panel 24. The accelerator operation unit 5 is, for example, an accelerator pedal located near a driver's foot. The brake operation unit 6 is, for example, a brake pedal located near a driver's foot. The shift operation unit 7 is, for example, a shift lever protruding from a center console. The steering unit 4, the accelerator operation unit 5, the brake operation unit 6, the shift operation unit 7, and the like are not limited to these components.

[0013] A display device 8 and an audio output device 9 are provided inside the passenger compartment 2a. The display device 8 serves as a display output unit. The audio output device 9 serves as an audio output unit. The display device 8 is, for example, a liquid crystal display (LCD), an organic electroluminescent display (OELD), or the like. The audio output device 9 is, for example, a speaker. The display device 8 is covered with, for example, a light-transmitting operation input unit 10 such as a touch screen. An occupant is allowed to visually recognize an image displayed on the display screen of the display device 8 via the operation input unit 10.An occupant is allowed to perform an input operation by operating the operation input unit 10 by touching, pressing, or moving the operation input unit 10 with a finger or the like at a position corresponding to an image displayed on the display screen of the display device 8. These display device 8, audio output device 9, operation input unit 10, and the like are provided, for example, in a monitor device 11 located at the center in the vehicle width direction, that is, a transverse direction, of the instrument panel 24. The monitor device 11 may include an operation input unit (not shown) such as a switch, a numeric keypad, a joystick, and a push button. An audio output device (not shown) may be provided at another position within the passenger compartment 2a that is different from the monitor device 11.Audio data can be output from the audio output device 9 of the monitor device 11 and another audio output device. The monitor device 11 is shared, for example, with a navigation system or an audio system.

[0014] A display device 12, which is different from the display device 8, is provided inside the passenger compartment 2a. As shown in Fig. 3, the display device 12 is provided, for example, in an instrument panel unit 25 in the instrument panel 24 and is located substantially in the center of the instrument panel unit 25 between a speed display unit 25a and a rotational speed display unit 25b. The size of the screen 12a of the display device 12 is smaller than the size of the screen 8a ( Fig. 3) the display device 8. An image showing information for assisting in parking the vehicle 1 may be displayed primarily on the display device 12. The amount of information displayed on the display device 12 may be smaller than the amount of information displayed on the display device 8. The display device 12 is, for example, an LCD, an OELD, or the like. Information displayed on the display device 12 may be displayed on the display device 8.

[0015] As in Fig. 1 and Fig. 2, the vehicle is, for example, a four-wheeled vehicle and includes two right and left front wheels 3F and two right and left rear wheels 3R. Each of these four wheels 3 may be configured to be steerable. As shown in Fig. As shown in Figure 4, the vehicle 1 includes a steering system 13 that steers at least two of the wheels 3. The steering system 13 includes an actuator 13a and a torque sensor 13b. The steering system 13 is electrically controlled by an electronic control unit (ECU) 14 or the like to actuate the actuator 13a. The steering system 13 is, for example, an electric power steering system, a steer-by-wire (SBW) system, or the like. The steering system 13 adds torque, i.e., an assist torque, to the steering unit 4 using the actuator 13a to compensate for a steering force or steer the wheels 3 using the actuator 13a. In this case, the actuator 13a may steer one of the wheels 3 or steer a plurality of the wheels 3. The torque sensor 13b detects, for example, a torque applied by a driver to the steering unit 4.

[0016] As in Fig. 2, for example, four imaging units 15a to 15d are provided on the vehicle body 2 as a plurality of imaging units 15. Each of the imaging units 15 is, for example, a digital camera including an imaging device such as a charge-coupled device (CCD) and a CMOS image sensor (CIS). Each of the imaging units 15 is capable of outputting moving image data at a predetermined frame rate. Each of the imaging units 15 has a wide-angle lens or a fisheye lens and is capable of capturing an image in, for example, the range of 140° to the range of 190° in the horizontal direction. The optical axis of each of the imaging units 15 is set to be directed obliquely downward.Thus, each of the imaging units 15 sequentially captures a road surface on which the vehicle 1 can move and an external environment around the vehicle body 2, including an area in which the vehicle 1 can be parked, and outputs the captured image as captured image data.

[0017] The imaging unit 15a is located, for example, at the front of the vehicle body 2, that is, a front end 2c in the vehicle longitudinal direction, and is provided on a front bumper or the like. The imaging unit 15b is located, for example, at the left side of the vehicle body 2, that is, a left end 2d in the vehicle width direction, and is provided on a door mirror 2g serving as a projecting portion on the left side. The imaging unit 15c is located, for example, at a rear end 2e of the vehicle body 2 and is provided on a lower wall portion of a door 2h of a rear luggage compartment. The imaging unit 15d is located, for example, at a right side 2f of the vehicle body 2 and is provided on a right door mirror 2g.The ECU 14 is capable of generating an image having a wider viewing angle or generating an imaginary bird's-eye view of the vehicle 1 from above by performing operation processing and image processing based on the image data obtained by the imaging units 15. A bird's-eye view image may be referred to as a top view image.

[0018] The ECU 14 identifies dividing lines or the like on a road surface around the vehicle 1 from the images of the imaging units 15 and detects (extracts) parking spaces indicated by the dividing lines or the like.

[0019] As in Fig. 1 and Fig. 2, for example, four distance measuring units 16a to 16d and eight distance measuring units 17a to 17h are provided on the vehicle body 2 as a plurality of distance measuring units 16, 17. Each of the distance measuring units 16, 17 is, for example, a sonar that emits an ultrasonic wave and receives the reflected wave. The sonar may also be referred to as a sonar sensor or an ultrasonic detector. The ECU 14 is capable of detecting whether an object such as an obstacle is located around the vehicle 1 or measuring a distance to the object based on the detected results of the distance measuring units 16, 17. That is, each of the distance measuring units 16, 17 is an example of a detection unit that detects an object. Each of the distance measuring units 17 can be used, for example, to detect an object at a relatively close distance.Each of the distance measuring units 16 can be used, for example, to detect an object at a relatively long distance that is far away from an object detected by each of the distance measuring units 17. The distance measuring units 17 can be used, for example, to detect an object in front of or behind the vehicle 1. The distance measuring units 16 can be used, for example, to detect an object to the side of the vehicle 1.

[0020] As in Fig. As shown in Fig. 4, in a parking assist system 100, in addition to the ECU 14, the monitor device 11, the steering system 13, the distance measuring units 16, 17, and the like, a braking system 18, a steering angle sensor 19, an accelerator sensor 20, a shift sensor 21, a wheel speed sensor 22, and the like are electrically connected to each other via an on-vehicle network 23 serving as an electrical communication line. The on-vehicle network 23 is provided, for example, as a controller area network (CAN). The ECU 14 is capable of controlling the steering system 13, the braking system 18, and the like by transmitting control signals through the on-vehicle network 23.The ECU 14 is capable of receiving detected results from the torque sensor 13b, a brake sensor 18b, the steering angle sensor 19, the distance measuring units 16, the distance measuring units 17, the accelerator sensor 20, the shift sensor 21, the wheel speed sensor 22 and the like, and operation signals of the operation input unit 10 and the like via the vehicle-side network 23.

[0021] The ECU 14, for example, includes a central processing unit (CPU) 14a, a read-only memory (ROM) 14b, a random access memory (RAM) 14c, a display control unit 14d, an audio control unit 14e, a solid-state drive or flash memory (SSD) 14f, and the like. The CPU 14a is capable of, for example, performing various operation processing and control, such as image processing on images displayed on the display devices 8, 12, determining a movement target position of the vehicle 1, calculating a movement path of the vehicle 1, calculating whether there is interference with an object, automatically controlling the vehicle 1, and canceling automatic control.The CPU 14a is capable of reading a program installed and stored in a non-volatile memory device such as the ROM 14b and executing operation processing according to the program. The RAM 14c temporarily stores various pieces of data used for calculation in the CPU 14a. The display control unit 14d mainly performs image processing using image data obtained by the imaging units 15, synthesis of image data displayed on the display device 8, and the like within the operation processing in the ECU 14. The audio control unit 14e mainly processes audio data output from the audio output device 9 within the operation processing in the ECU 14.The SSD 14f is a rewritable non-volatile memory unit and is capable of storing data even when the power of the ECU 14 is turned off. The CPU 14a, the ROM 14b, the RAM 14c, and the like may be integrated within the same housing. The ECU 14 may be constituted by another logical operation processor such as a digital signal processor (DSP), a logic circuit, and the like instead of the CPU 14a. A hard disk drive (HDD) may be provided instead of the SSD 14f. The SSD 14f or the HDD may be provided separately from the ECU 14.

[0022] The braking system 18 is, for example, an anti-lock braking system (ABS) that prevents the brake from locking the wheels, a sideskid prevention device (electronic stability control (ESC)) that prevents the vehicle from sliding sideways during cornering, an electric braking system that amplifies braking force (performs brake assist), a brake-by-wire (BBW) system, or the like. The braking system 18 imparts braking force to the wheels 3 and, by extension, to the vehicle 1 via the actuator 18a. The braking system 18 is capable of performing various controls by detecting wheel locking by the brake, wheel spin, a sign of sideskid, and the like from, for example, a rotation difference between the right and left wheels 3.The brake sensor 18b is, for example, a sensor that detects the position of a movable unit of the brake operation unit 6. The brake sensor 18b is capable of detecting the position of the brake pedal, which serves as the movable unit. The brake sensor 18b includes a displacement sensor.

[0023] The steering angle sensor 19 is, for example, a sensor that detects a steering amount of the steering unit 4, such as the steering wheel. The steering angle sensor 19 is provided, for example, using a Hall element or the like. The ECU 14 acquires a driver's steering amount of the steering unit 4, a steering amount of each wheel 3 during automatic steering, or the like from the steering angle sensor 19 and executes various controls. The steering angle sensor 19 detects a rotation angle of a rotating portion included in the steering unit 4. The steering angle sensor 19 is an example of an angle sensor.

[0024] The accelerator sensor 20 is, for example, a sensor that detects the position of a movable unit of the accelerator operation unit 5. The accelerator sensor 20 is capable of detecting the position of the accelerator pedal, which serves as the movable unit. The accelerator sensor 20 includes a displacement sensor.

[0025] The switch sensor 21 is, for example, a sensor that detects the position of a movable unit of the switch operation unit 7. The switch sensor 21 is capable of detecting the position of a lever, an arm, a button, or the like serving as the movable unit. The switch sensor 21 may comprise a displacement sensor or may be provided as a switch.

[0026] The wheel speed sensor 22 is a sensor that detects a rotation amount or rotation speed of each wheel 3 per unit time. The wheel speed sensor 22 outputs a wheel speed pulse number indicating the detected rotation speed as a sensor value. The wheel speed sensor 22 can be provided using, for example, a Hall element or the like. The ECU 14 calculates a movement amount and the like of the vehicle 1 based on the sensor value acquired from the wheel speed sensor 22 and performs various controls. There is a case where the wheel speed sensor 22 is provided in the braking system 18. In this case, the ECU 14 acquires the detected result of the wheel speed sensor 22 via the braking system 18.

[0027] The configurations, arrangement, electrical connection types and the like of the various sensors and actuators described above are illustrative and can be set (changed) in various ways.

[0028] As in Fig. 5, the ECU 14 includes a sensor information acquisition unit 501, a detection unit 502, a target position setting unit 503, a path generation unit 504, a position detection unit 505, and a steering angle control unit 506. Fig. The components shown in Figure 5 are implemented when the CPU 14a of the ECU 14 executes programs stored in the ROM 14b. These components may be configured to be implemented by hardware.

[0029] The ECU 14 in the vehicle 1 according to the present embodiment performs parking assistance for guiding the vehicle 1 to a target position (for example, a parking position of the vehicle 1). For example, the ECU 14 according to the present embodiment displays guidance information on the display device 12 to prompt the driver to operate the accelerator pedal, the brake pedal, and the shift operation unit 7. For example, when the driver operates at least one or more of the accelerator pedal and the shift operation unit 7 according to the guidance information and then the vehicle 1 has moved, the ECU 14 controls the steering system 13 according to a distance the vehicle 1 has moved, so that the vehicle 1 moves along a set moving path. Thus, since steering is performed according to the moved distance, the vehicle 1 is able to move to the target position.

[0030] The sensor information acquisition unit 501 acquires information from various sensors provided in the vehicle 1. The sensor information acquisition unit 501 according to the present embodiment acquires wheel speed information from the wheel speed sensor 22, measured distance information from the distance measuring units 16, 17, steering angle information from the steering angle sensor 19, accelerator information from the accelerator sensor 20, shift information from the shift sensor 21, brake information from the brake sensor 18b, and steering torque information from the torque sensor 13b. The sensor information acquisition unit 501 according to the present embodiment acquires speed information of the vehicle 1 based on the wheel speed information from the wheel speed sensor 22. In addition, the sensor information acquisition unit 501 may acquire acceleration from an acceleration sensor (not shown).

[0031] The detection unit 502 detects an obstacle around the vehicle 1 based on the measured distance information acquired by the sensor information acquisition unit 501 from the distance measuring units 16, 17. The detection unit 502 detects an area in which the vehicle 1 can be parked based on the measured distance information acquired by the sensor information acquisition unit 501 from the distance measuring units 16, 17.

[0032] The target position setting unit 503 sets a target position, which is a destination to which the vehicle 1 is traveling. The target position setting unit 503 according to the present embodiment sets the target position to the area where the vehicle 1 can be parked, which is detected by the detection unit 502. When there are a plurality of available parking areas, an area selected from the plurality of available parking areas by the driver via the operation unit 14g is set for the target position.

[0033] The path generation unit 504 generates a movement path of the vehicle 1 to the target position set by the target position setting unit 503. The path generation unit 504 according to the present embodiment may set a switching point at which the traveling direction of the vehicle 1 is changed and then generate the movement path.

[0034] The position detection unit 505 detects the current position of the vehicle 1. The position detection unit 505 according to the present embodiment detects the current position of the moving vehicle 1 based on the measured distance information, steering angle information, wheel speed information, and speed information of the vehicle 1 acquired by the sensor information acquisition unit 501.

[0035] The steering angle control unit 506 guides the steering system 13 to a steering angle based on the movement path set by the path generation unit 504 and the current position detected by the position detection unit 505, so that the vehicle 1 moves along the movement path. The steering system 13 controls the actuator 13a according to the commanded steering angle.

[0036] Furthermore, existing steering assist or automatic steering technology controls a vehicle to move along a generated path toward a target position. Therefore, abrupt steering is permitted depending on the generated path. If abrupt steering is performed, there is a possibility that an occupant may experience discomfort or be frightened.

[0037] That is, if a change or fluctuation in the vehicle's lateral g-force (a time-differential value of lateral g-force ("lateral G")) increases due to abrupt steering or the like, an occupant experiences discomfort. Lateral g-force is an inertial force generated in the lateral direction perpendicular to the vehicle's traveling direction in a plane of motion (ground plane) of the vehicle 1.

[0038] Furthermore, humans are more sensitive to changes in lateral g-force than to the magnitude of the lateral g-force. Therefore, humans tend to be more startled or uncomfortable by changes in lateral g-force than by changes in the magnitude of the lateral g-force.

[0039] The change in lateral g-force corresponds to a steering speed (a change in a steering angle per unit time or a differential value of the steering angle). That is, as the steering speed increases, the change in lateral g-force increases. In other words, by suppressing an abrupt change in steering speed, it becomes possible to prevent the generation of lateral g-force that causes an occupant to feel uncomfortable.

[0040] The steering angle control unit 506 according to the present embodiment performs control for restricting a steering angle to which the steering system 13 is instructed (hereinafter referred to as a command steering angle) so that the steering speed does not change abruptly. In the present embodiment, a guard value for restricting the command steering angle is set; however, as described above, a steering speed, which is a change in a steering angle per unit time, interferes with human perception. Therefore, the steering angle control unit 506 changes the guard value for restricting the command steering angle in response to the steering speed.

[0041] Next, the configuration of the steering angle control unit is described. Fig. 6 is a block diagram showing the configuration of the steering angle control unit 506 according to the present embodiment. As shown in Fig. 6, the steering angle control unit 506 includes a target steering angle acquisition unit 601, a first protection processing unit 602, a first calculation unit 603, a PI control unit 604, a second calculation unit 605, and a second protection processing unit 606.

[0042] The target steering angle acquisition unit 601 acquires a target steering angle set as a target for moving the vehicle 1 based on the moving path generated by the path generation unit 504 and the current position of the vehicle 1 detected by the position detection unit 505.

[0043] The first protection processing unit 602 adjusts the target steering angle acquired by the target steering angle acquisition unit 601 so that the target steering angle does not exceed a protection value determined to prevent a change in the vehicle's steering angle greater than or equal to a predetermined reference (first reference). Thus, the adjusted steering angle is output to the steering system 13, so that the steering system 13 controls the steering angle to the adjusted steering angle. The predetermined reference (first reference) is a reference determined to prevent a passenger from experiencing discomfort due to an abrupt change in the steering angle and is a reference set based on current measurements and the like.

[0044] In addition, the first protection processing unit 602 changes the protection value to adjust the target steering angle in response to a situation of the vehicle 1. The present embodiment is an example in which the protection value is changed in response to the steering angle of the vehicle 1.

[0045] Fig. Fig. 7 is a graph showing the relationship between the target steering angle and the protection value according to the present embodiment. In the Fig. In the example shown in Figure 7, the circular symbols indicate the target steering angles, and the rectangular symbols indicate the steering angles adjusted by the first protection processing unit 602. A transition 720 is a transition of the actual steering angle of the vehicle 1.

[0046] In the Fig. In the example shown in Figure 7, the steering angle adjusted by the first protection processing unit 602 is output to the steering system 13 as the command steering angle. In the present embodiment, the positive direction of the steering angle corresponds to the direction toward the right side of the wheels, and the negative direction of the steering angle corresponds to the direction toward the left side of the wheels.

[0047] In the Fig. In the example shown in Figure 7, at time 0, the target steering angle, the adjusted steering angle, and the actual steering angle are all zero. This means that vehicle 1 is driving straight ahead.

[0048] The value of the target steering angle 701 is 10 at time T1, the value of a target steering angle 702 is 20 at time T2 and the value of a target steering angle (not shown) is 30 at time T3. The numerical values ​​of the Fig. The steering angles shown in Figure 7 are shown for convenience of explanation. In addition, time T1, time T2, and time T3 each represent a time at which one unit time has elapsed from the last time.

[0049] There is a possibility that abrupt steering may be performed when the steering system 13 performs steering according to the above target steering angles 701, 702, and the like. The first protection processing unit 602 according to the present embodiment restricts the target steering angle so that a steering angle larger than the protection value is not output.

[0050] In Fig. 7, the first protection processing unit 602 sets a protection value 711 at time T1, a protection value 712 at time T2, and a protection value 713 at time T3.

[0051] The Fig. The protection values ​​711, 712, 713 shown in Figure 7 are set based on the actual steering angle, and are more specifically set based on the amount of increase in the actual steering angle. That is, the first protection processing unit 602 sets a protection value once every unit time based on a predetermined width of the protection value and the amount of increase in the actual steering angle, that is, the steering speed.

[0052] In the present embodiment, the first protection processing unit 602 calculates a protection value by the following mathematical expression (1).

[0053] Current protection value = last protection value + predetermined width of protection value “3” + amount of increase in the actual steering angle (1)

[0054] That is, at time T1, the first protection processing unit 602 calculates the protection value “3” by adding the predetermined width “3” of the protection value to the protection value “0” at time 0. The protection value “3” is used instead of the target steering angle.

[0055] Subsequently, at time T2, it is assumed that the actual steering angle increases to "2" because the guard value "3" is used as the command steering angle. The first guard processing unit 602 sets a value obtained by adding the actual steering angle (steering speed) increase amount "2" to the predetermined width "3" of the guard value for the increase amount "5" and calculates the guard value "8" by adding the last guard value "3" to the increase amount "5." The guard value "8" is used instead of the target steering angle.

[0056] At time T3, it is assumed that the actual steering angle increases to "6" because the guard value "8" is used as the command steering angle. The first guard processing unit 602 sets a value obtained by adding the actual steering angle (steering speed) increase amount "4" (current actual steering angle "6" - last actual steering angle "2") to the predetermined width "3" of the guard value for the increase amount "7", and calculates the guard value "15" by adding the last guard value "8" to the increase amount "7". The guard value "15" is used instead of the target steering angle.

[0057] The first protection processing unit 602 sets the protection value so that a change in the protection value per unit time increases as the steering speed (change in the actual steering angle per unit time) controlled by the steering system 13 increases.

[0058] In this way, because the protection value is adjusted based on the steering speed, it is possible to suppress abrupt changes in the lateral g-force on the occupant. This means that it is possible to prevent the occupant from experiencing anxiety or discomfort due to abrupt changes in the lateral g-force.

[0059] In the present embodiment, the change in the protection value increases as the steering speed increases. Therefore, when the vehicle 1 attempts to continue turning in a certain direction, it is possible to execute control to gradually increase the steering angle to turn in that direction. That is, in the present embodiment, it is possible to achieve both prevention of an abrupt change in the lateral g-force and the turning performance of the vehicle 1.

[0060] Next, the case where the target steering angle has changed in an opposite direction (from the right-hand direction to the left-hand direction) will be described. In such a case, the target steering angle changes from increasing to decreasing, or from decreasing to increasing. In this case, the first protection processing unit 602 sets a protection value in the opposite direction so that an abrupt change in the lateral g-force does not occur.

[0061] Fig. Fig. 8 is a graph showing the relationship between the target steering angle and the protection value according to the present embodiment. In the Fig. 8, the circular characters indicate the target steering angles and the rectangular characters indicate the steering angles adjusted by the first protection processing unit 602. A transition 802 is a transition of the actual steering angle of the vehicle 1. In the example of Fig. 8, the steering angle adjusted by the first protection processing unit 602 is output to the steering system 13 as an instruction steering angle.

[0062] The target steering angle increases to the value "18" of a target steering angle 801 at time T1 and the value "22" of a target steering angle 802 at time T2; however, the target steering angle decreases to the value "11" of the target steering angle 803 at time T3 and the value "1" of a target steering angle 804 at time T4. Time T1, time T2, time T3, and time T4 are each a time at which one time unit has elapsed from the last time.

[0063] When existing steering is performed according to the above target steering angles 801 to 804, the steering wheel is turned to increase its steering angle and then abruptly returned. Thus, there is a possibility that an abrupt change in lateral g-force is exerted on a passenger. The first protection processing unit 602 according to the present embodiment sets a protection value so that an abrupt change in lateral g-force does not occur, and then performs control so that a steering angle greater than the protection value is not output.

[0064] In Fig. 8, the first protection processing unit 602 sets a value “13” for a protection value 811 at time T1, a value “18” for a protection value 812 at time T2, a value “18” for a protection value 813 at time T3, a value “15” for a protection value 814 at time T4, and a value “10” for a protection value 815 at time T5.

[0065] In the Fig. In the example shown in Fig. 8, the target steering angle increases until time T2; however, the target steering angle decreases after a time T2. The first protection processing unit 602 sets the protection value 812 for stopping a change in the steering angle in the positive direction at time T2 at which the target steering angle begins to decrease, and then, after a time T3, sets the protection value based on a change (to the negative side) in the actual steering angle, that is, a steering speed, and the width "-3" of the protection value.

[0066] In this way, when the target steering angle changes from an arbitrary direction to a direction opposite to the arbitrary direction, the first protection processing unit 602 according to the present embodiment executes control to stop a change in the actual steering angle and then sets the protection value based on the width of the protection value in the opposite direction and the change in the actual steering angle.

[0067] In this way, the first protection processing unit 602 adjusts the target steering angle so that the target steering angle does not exceed a first protection value determined to prevent a change in the steering angle of the vehicle 1 that is greater than or equal to a predetermined reference (second reference) in a first direction (for example, a direction on the right side), and then, at the time when the direction in which the target steering angle changes changes from the first direction to a second direction (for example, a direction on the left side), which is a direction opposite to the first direction, adjusts the target steering angle so that the target steering angle does not exceed a second protection value determined to prevent an abrupt change in the steering angle of the vehicle 1 in the second direction.The predetermined reference (second reference) is a reference determined in advance to prevent discomfort of an occupant due to an abrupt change in the steering angle, and is a reference set based on an actual measurement or the like.

[0068] The first protection processing unit 602 outputs the set protection value as the adjusted target steering angle.

[0069] The first protection processing unit 602 may compare the set protection value with the input target steering angle and may output the target steering angle when it is determined that the input target steering angle causes a smaller change in the actual steering angle.

[0070] Referring back to Fig. 6, the first calculation unit 603 calculates a difference between the target steering angle adjusted by the first protection processing unit 602 and the actual steering angle (steering angle information) of the vehicle 1 acquired by the sensor information acquisition unit 501.

[0071] The PI control unit 604 calculates a feedback correction amount for the steering angle by performing PI control on the difference of the steering angle calculated by the first calculation unit 603.

[0072] The second calculation unit 605 calculates a command steering angle to be output to the steering system 13 by adding the feedback correction amount to the target steering angle adjusted by the first protection processing unit 602.

[0073] That is, the steering angle control unit 506 corrects the command steering angle to be output to the steering system 13 based on the difference between the target steering angle and the actual steering angle of the vehicle 1 acquired by the sensor information acquisition unit 501. Thus, it is possible to improve the accuracy at the time when the vehicle 1 moves along the movement path.

[0074] The second protection processing unit 606 determines whether the input command steering angle exceeds a preset threshold. If the second protection processing unit 606 determines that the input command steering angle exceeds the preset threshold, the second protection processing unit 606 adjusts the command steering angle so that the command steering angle does not exceed the threshold and then outputs the command steering angle. If the second protection processing unit 606 determines that the input command steering angle does not exceed the preset threshold, the second protection processing unit 606 outputs the input command steering angle.

[0075] In the present embodiment, the case where the target steering angle is adjusted based on the guard value that changes in response to the actual steering angle before feedback is described. Instead, the target steering angle may be adjusted based on the guard value that changes in response to the actual steering angle after feedback.

[0076] For example, the target steering angle may be adjusted in the second protection processing unit 606.

[0077] Next, a process in the ECU 14 of the vehicle 1 according to the present embodiment will be described until the process shifts to the parking assist control. Fig. 9 is a flowchart showing the procedure of the above-described process in the ECU 14 according to the present embodiment.

[0078] First, the detection unit 502 detects an obstacle and also detects an area in which the vehicle 1 can be parked based on the measured distance information acquired by the sensor information acquisition unit 501 (step S901).

[0079] The ECU 14 determines whether a selected parking assist mode has been received from the driver via the operation input unit 10 (step S902). If the ECU 14 determines that a selected parking assist mode has not been received from the driver (No in step S902), an obstacle or the like is repeatedly detected in step S901, assuming that the vehicle 1 continues normal driving.

[0080] On the other hand, if the ECU 14 determines that a selected parking assist mode has been received from the driver via the operation input unit 10 (Yes in step S902), the target position setting unit 503 sets a target position for parking the vehicle 1 from the available parking area acquired in step S901 (step S903). In the present embodiment, when there are a plurality of available parking areas, the available parking area is selected and received by the driver; however, the target position setting unit 503 may automatically select the available parking area.

[0081] The path generation unit 504 generates a movement path to the target position of the vehicle 1 (step S904).

[0082] Subsequently, the ECU 14 executes parking assist control for moving the vehicle 1 to the target position based on the generated movement path (step S905).

[0083] Thus, a parking assist control is started by the ECU 14. Next, the parking assist control executed in step S905 of Fig. 9 in the ECU 14 of the vehicle 1 according to the present embodiment will be described. Fig. 10 is a flowchart showing the procedure of the above-described process in the ECU 14 according to the present embodiment.

[0084] First, the sensor information acquisition unit 501 acquires various pieces of information, such as at least the wheel speed information, the steering angle information, and the steering torque information, from the various sensors (step S1001). At the same time, the speed of the vehicle 1 is acquired from the wheel speed information. In addition, the acceleration is acquired from the acceleration sensor.

[0085] Subsequently, the position detection unit 505 detects the current position of the vehicle 1 based on various pieces of information acquired by the sensor information acquisition unit 501 (step S1002).

[0086] The ECU 14 determines whether the detected current position is the target position (step S1003).

[0087] When the ECU 14 determines that the detected current position is not the target position (No in step S1003), the target steering angle acquisition unit 601 of the steering angle control unit 506 acquires a target steering angle corresponding to the position of the vehicle in the current movement path based on the movement path and the current position (step S1004).

[0088] The first protection processing unit 602 adjusts the target steering angle so that the target steering angle does not exceed the protection value set based on the width of the protection value and a change in the actual steering angle (step S1005).

[0089] In addition, the first calculation unit 603 calculates the difference between the adjusted target steering angle and the actual steering angle, the PI control unit 604 calculates a feedback correction amount by performing PI control on the difference, and then the second calculation unit 605 calculates a command steering angle by correcting the target steering angle using the feedback correction amount (by subtracting the feedback correction amount from the target steering angle) (step S1006).

[0090] The second protection processing unit 606 adjusts the input command steering angle based on the preset threshold (step S1007). The second protection processing unit 606 outputs the command steering angle to the steering system 13 (step S1008). Thus, steering control based on the command steering angle is executed in the steering system 13.

[0091] On the other hand, when the ECU 14 determines in step S1003 that the detected current position is the target position (Yes in step S1003), the ECU 14 ends the process.

[0092] With the procedure described above, it is possible to output the command steering angle adjusted so that a lateral g-force does not change abruptly. Thus, in the steering control via the steering system 13, it is possible to improve the accuracy with which the vehicle 1 moves along the movement path.

[0093] In the above-described embodiment, the case where the width of the protection value for increasing or decreasing is ±3 at the time the protection value changes is described. However, the above embodiment does not limit the width of the protection value for increasing or decreasing to ±3. In an alternative embodiment, an example is described in which the width of the protection value is changed. Components of the alternative embodiment are similar to those of the above-described embodiment, and the description thereof is omitted.

[0094] The first protection processing unit 602 according to the above-described embodiment uses the protection value derived using the actual steering angle and the width of the protection value fixed at "±3". In contrast, the first protection processing unit 602 according to the present alternative embodiment is configured to change the width of the protection value.

[0095] In the present alternative embodiment, the speed of the vehicle 1 is used as the situation of the vehicle 1 to change the width of the protection value. That is, as the vehicle speed increases, a change in the lateral g-force increases. The first protection processing unit 602 according to the present alternative embodiment adjusts the width of the protection value so that the width of the protection value decreases as the vehicle speed increases. For example, as the vehicle speed increases, the width of the protection value is changed in the order of "±3", "±2", and "±1".

[0096] In this way, in the present alternative embodiment, the width of the protection value is adjusted based on the speed of the vehicle 1. Thus, it is possible to suppress a change in the lateral g-force, which is assumed to increase as the speed of the vehicle 1 increases, so that it is possible to provide ride comfort for an occupant.

[0097] As described above, according to the above-described embodiment and the alternative embodiment, the target steering angle set according to the movement path is adjusted so as not to exceed the protection value changed in response to the situation (for example, steering speed) of the vehicle, so that it is possible to provide ride comfort to an occupant by suppressing an abrupt change in lateral g-force.

[0098] In addition, in the present embodiment, at the time of preventing an abrupt change in lateral g-force, the protection value increases as the steering speed of the vehicle 1 increases, so that it is possible to improve the turning performance of the vehicle 1.

[0099] Some embodiments of the invention have been described above; however, these embodiments are merely illustrative and are not intended to limit the scope of the invention. These novel embodiments may be implemented in other various forms and may be variously omitted, substituted, or changed without departing from the spirit of the invention. The scope and spirit of the invention include these embodiments and modifications thereof, and the invention described in the appended claims and equivalents thereof encompass these embodiments and modifications thereof.

[0100] For example, the control unit (for example, the steering angle control unit) changes the width of change of the first protection value per unit time in response to the speed of the vehicle.

[0101] A control system for a vehicle comprises a steering control unit (13) and an electronic control unit (14). The steering control unit (13) is configured to control a steering angle of a wheel of a vehicle. The electronic control unit (14) is configured to acquire a target steering angle set as a target for moving the vehicle, adjust the acquired target steering angle so that the target steering angle does not exceed a first protection value determined to prevent a change in the steering angle of the vehicle that is greater than or equal to a first reference, output the adjusted target steering angle to the steering control unit so that the steering control unit controls the steering angle to the adjusted target steering angle, and change the first protection value in response to a situation of the vehicle.

Claims

[1] Control system for a vehicle, comprising: a steering control unit (13) configured to control a steering angle of a wheel of the vehicle; and an electronic control unit (14) configured to to obtain a target steering angle set as a target for moving the vehicle, to adjust the acquired target steering angle so that the target steering angle does not exceed a first protection value determined to prevent a change in the steering angle of the vehicle that is greater than or equal to a first reference, output the adjusted target steering angle to the steering control unit (13) so that the steering control unit (13) controls the steering angle to the adjusted target steering angle, and to change the first protection value in response to a situation of the vehicle, characterized by , that the electronic control unit (14) is configured to change the first protection value based on an actual steering angle of the vehicle, which is a controlled result of the steering control unit (13), wherein the actual steering angle corresponds to the situation of the vehicle. [2] Control system according to claim 1, characterized by in that the electronic control unit (14) is configured to change the first protection value based on a rate at which the actual steering angle of the vehicle changes according to the control of the steering control unit (13), wherein the rate at which the actual steering angle of the vehicle changes corresponds to the situation of the vehicle. [3] Control system according to claim 1 or 2, characterized byin that the electronic control unit (14) is configured to set the first protection value such that a change in the first protection value per unit time increases as a change in the actual steering angle per unit time controlled by the steering control unit (13) increases. [4] Control system according to one of claims 1 to 3, characterized byin that the electronic control unit (14) is configured to adjust the target steering angle so that the target steering angle does not exceed the first protection value determined to prevent a change in the steering angle of the vehicle in a first direction that is greater than or equal to the first reference, and then, at the time when a direction in which the target steering angle changes changes from the first direction to a second direction that is a direction opposite to the first direction, adjust the target steering angle so that the target steering angle does not exceed a second protection value determined to prevent a change in the steering angle of the vehicle in the second direction that is greater than or equal to a second reference.

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