Vehicle control system

Abstract

The present invention provides a vehicle control device that can efficiently reduce the risk of secondary collisions when a following vehicle makes contact with the vehicle in question. [Solution] The braking device comprises a first member that rotates with the wheel and a second member that is pressed against the first member to generate a frictional force between them. The processor controls the braking device so that no braking force is applied and the clearance between the first member and the second member is reduced to a normal level when predetermined conditions are met regarding the time required to reach the rear end of the vehicle, which cannot avoid contact with another vehicle, and the accelerator pedal of the vehicle is pressed to "0" and the speed of the vehicle is below a threshold. Subsequently, when it is detected that another vehicle has come into contact with the vehicle, or when it is detected that the speed of the vehicle has decreased to "0" without the other vehicle coming into contact with the vehicle, the processor controls the braking device so that the second member is pressed against the first member and the vehicle is braked.

Description

Technical Field

[0001] The present invention relates to a vehicle control device that suppresses the occurrence of contact (secondary contact) between the host vehicle and an object when the host vehicle is pushed forward due to the approach of another vehicle from the rear of the host vehicle and contact with the host vehicle.

Background Art

[0002] A vehicle control device that brakes the host vehicle when another vehicle (following vehicle) approaches and contacts (collides with) the host vehicle from the rear of the host vehicle has been proposed (for example, see Patent Document 1 below). This vehicle control device (hereinafter referred to as the "conventional device") brakes the host vehicle when it detects that the following vehicle has contacted the host vehicle under the condition that the speed of the host vehicle is below a threshold value (low speed or "0"). Thereby, it is expected to reduce the contact risk (secondary contact risk) between the host vehicle and an object (for example, a preceding vehicle) when the host vehicle is pushed forward.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] Incidentally, a vehicle's braking system comprises a first member (brake disc) that rotates with the wheel, and a second member (brake pad) that is pressed against the first member to generate frictional force between them and the first member, thereby braking the vehicle. In normal driving conditions (when no braking control is being performed), a predetermined clearance is provided between the first member and the second member. Conventional systems begin to drive the second member of the braking system from the moment they detect that a following vehicle has made contact with the vehicle. Therefore, it takes some time from the moment the second member begins to move toward the first member until the clearance between the first and second members becomes "0" (until the second member is pressed against the first member). Consequently, during this time, the vehicle may be pushed forward, and the risk of secondary contact may not be reduced to a sufficient extent.

[0005] One of the objectives of the present invention is to provide a vehicle control device that can efficiently reduce the risk of secondary contact when a following vehicle comes into contact with the vehicle itself.

[0006] To achieve the above objective, the vehicle control device (1) of the present invention is: An on-board sensor for acquiring information about the vehicle itself (V0) (sp0, AD) and information about another vehicle approaching from the rear (V1) (D, sp1, TTC), A processor (10) configured to control the vehicle's braking system (30) so that the vehicle is braked when predetermined conditions relating to contact between the other vehicle and the vehicle are met, It is equipped with. The braking device comprises a first member that rotates together with the wheel and a second member that is pressed against the first member and generates a frictional force between itself and the first member. The processor is configured to determine that contact between the other vehicle and the own vehicle cannot be avoided, and that predetermined conditions relating to the time required (TTC) for the other vehicle to reach the rear end of the own vehicle are met, and the accelerator pedal depression depth (AD) of the own vehicle is "0", and the speed of the own vehicle is below a threshold (sp0th), in which case the braking force from the braking device is not applied to the wheels, and the clearance (C) between the first member and the second member is reduced to a lower level than normal. Subsequently, if it is detected that the other vehicle has come into contact with the own vehicle, or if it is detected that the speed of the own vehicle has decreased to "0" without the other vehicle coming into contact with the own vehicle, the processor controls the braking device so that the second member is pressed against the first member and the own vehicle is braked.

[0007] The processor of the vehicle control device according to the present invention reduces the clearance between the first and second members of the braking device when contact between the vehicle and another vehicle (following vehicle) is unavoidable, compared to the normal driving state. This shortens the time required for the second member to move toward the first member and press against the first member when the vehicle and the following vehicle make contact, or when the vehicle's speed becomes "0". Therefore, according to the present invention, the risk of secondary contact (contact between the vehicle and other objects) is efficiently reduced when a following vehicle makes contact with the vehicle while the vehicle is traveling at a low speed or stopped. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram of a vehicle control device according to one embodiment of the present invention. [Figure 2] Figure 2 is a flowchart of the program executed by the CPU to implement the emergency braking function.

[0009] (Summary) A vehicle control device 1 according to one embodiment of the present invention is applied, for example, to a vehicle V0 equipped with an autonomous driving function (hereinafter referred to as "the vehicle"). The vehicle control device 1 includes a function (emergency braking function) that controls the braking device so that the vehicle brakes suddenly when predetermined conditions (contact between the vehicle and a following vehicle V1 and the vehicle, or the possibility thereof) are met.

[0010] (Specific configuration) As shown in Figure 1, the vehicle control device 1 includes an ECU 10, an on-board sensor 20, and a braking device 30.

[0011] The ECU10 includes a microcomputer equipped with a CPU10a, ROM10b, RAM10c, timer10d, etc. The ECU10 is connected to other ECUs (for example, an ECU that controls airbags (hereinafter referred to as the "airbag ECU")) via a CAN (communication network).

[0012] The on-board sensor 20 includes a millimeter-wave radar 21. The millimeter-wave radar 21 comprises a transmitting / receiving unit and a signal processing unit (not shown). The transmitting / receiving unit radiates millimeter-wave radio waves (hereinafter referred to as "millimeter waves") toward the rear of the vehicle and receives millimeter waves (reflected waves) reflected by a three-dimensional object (following vehicle V1) located within the radiation range. The signal processing unit calculates the distance between the vehicle and the three-dimensional object (following vehicle V1), the velocity of the three-dimensional object relative to the vehicle (relative velocity vr), etc., based on the time from when the transmitting / receiving unit radiates the millimeter waves until the reflected waves are received, the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, etc., and provides the calculation results to the ECU 10.

[0013] In addition, the on-board sensor 20 includes a speed sensor 22. The speed sensor 22 detects the rotational speed (wheel speed) of each wheel and calculates the vehicle's speed sp0 (measured value) based on the wheel speed. The speed sensor 22 provides the calculation result to the ECU 10.

[0014] Furthermore, the on-board sensor 20 includes an accelerator pedal sensor 23. The accelerator pedal sensor 23 detects the accelerator pedal depression depth AD (accelerator opening) and provides the detection result to the ECU 10.

[0015] The braking system 30 applies braking force to the wheel (brake disc). The braking system 30 includes a brake ECU, a brake caliper, etc. The brake caliper includes an actuator that presses a brake pad (second member) against a brake disc (first member) that rotates with the wheel. The brake ECU obtains information (target value BFt) representing the target braking force BF from other ECUs. The brake ECU drives the brake actuator of the brake caliper to match the braking force BF applied to the wheel (brake disc) to the target value (BFt).

[0016] Under normal driving conditions (where the target value BFt is "0"), a clearance C is provided between the brake disc and the brake pad. When the predetermined conditions described later are met, the ECU 10 controls the brake actuator so that the brake pad does not come into contact with the brake disc (a braking force BF is not applied to the brake disc) and the clearance C is reduced compared to the normal driving conditions. Hereinafter, this process will be referred to as the "emergency braking preparation process".

[0017] (Emergency braking function) The ECU 10 controls the braking system 30 so that the vehicle brakes suddenly when predetermined conditions (contact or possibility of contact) between the following vehicle V1 and the vehicle itself are met.

[0018] Incidentally, as described above, in the normal driving state, a clearance C is provided between the brake disc and the brake pad of the braking device 30. Therefore, when the brake pad is moved toward the brake disc from the moment the following vehicle V1 contacts the host vehicle, it takes a little time until the brake pad is pressed against the brake disc and braking force is applied. Thus, when the following conditions X (conditions X1 to X3) are satisfied, the ECU 10 executes a braking preparation process (a process of reducing the clearance C). Condition X1... The speed sp0 of the host vehicle is less than or equal to the threshold value sp0th. Condition X2... The accelerator pedal is released. Condition X3... It is impossible to avoid contact between the following vehicle V1 and the host vehicle. Note that based on the information acquired from the in-vehicle sensor 20 (millimeter-wave radar 21), the ECU 10 determines that condition X3 is satisfied when the time to collision TTC (= inter-vehicle distance D / relative speed vr) is less than or equal to the threshold value TTCth until the following vehicle V1 contacts the host vehicle.

[0019] When either of the following conditions Y1 or condition Y is satisfied in the state where the above-described braking preparation process is completed (the state where the clearance C is reduced more than normal), the ECU 10 controls the braking device 30 so that the host vehicle is suddenly braked. That is, the ECU 10 determines a target value BFt so that the braking force BF becomes maximum, and transmits the target value BFt to the brake ECU of the braking device 30. Condition Y1... The host vehicle and an object (the following vehicle V1) have come into contact (collided). Condition Y2... Although the host vehicle and an object (the following vehicle V1) have not come into contact (collided), the speed sp0 of the host vehicle has decreased to "0". Note that the airbag ECU can detect that the host vehicle has come into contact with an object (e.g., the following vehicle V1) based on a sudden change in the acceleration of the host vehicle. When the airbag ECU detects contact between the host vehicle and an object, it provides information indicating the occurrence of such contact to another ECU (ECU10). When ECU10 acquires the information, it determines that condition Y1 is satisfied. As a scene where condition Y2 is satisfied, for example, a scene is assumed in which the host vehicle gently decelerates due to engine braking (or the brake pedal being lightly depressed) during a traffic jam and the speed sp0 becomes "0". In this scene, the possibility of the following vehicle V1 coming into contact with the host vehicle is higher than when the host vehicle is moving forward. Therefore, ECU10 brakes the host vehicle from a stage before the following vehicle V1 comes into contact with the host vehicle.

[0020] When the accelerator pedal is depressed (AD > 0) while the clearance C has been reduced from the normal driving state by the braking preparation process, ECU10 executes a release process for controlling the braking device 30 so that the clearance C returns to the normal state. Also, when the conditions Y1 and Y2 are not satisfied and the time Δt during which the state of the accelerator pedal being released continues exceeds the threshold value Δtth while the clearance C has been reduced from the normal driving state by the braking preparation process, ECU10 executes the release process.

[0021] Next, referring to FIG. 2, a program PR1 executed by the CPU10a (hereinafter simply referred to as "CPU") of ECU10 to realize the above-described emergency braking function will be described. ECU10 executes the program PR1 at a predetermined period when the ignition switch is in the ON state.

[0022] (Program PR1) The CPU starts the execution of the program PR1 from step 100 and proceeds to step 101.

[0023] In step 101, the CPU determines whether the vehicle's speed sp0 is less than or equal to the threshold sp0th. If the CPU determines that the speed sp0 is less than or equal to the threshold sp0th (101: Yes), it proceeds to step 102. On the other hand, if the CPU does not determine that the speed sp0 is less than or equal to the threshold sp0th (101: No), it returns to step 101.

[0024] In step 102, the CPU determines whether the accelerator pedal is released or not (whether the pedal depression depth AD is "0" or not). If the CPU determines that the accelerator pedal is released (102: Yes), it proceeds to step 103. On the other hand, if the CPU does not determine that the accelerator pedal is released (102: No), it returns to step 101.

[0025] In step 103, the CPU determines whether contact between the vehicle and the following vehicle V1 is unavoidable (TTC ≤ TTCth). If the CPU determines that contact between the vehicle and the following vehicle V1 is unavoidable (103: Yes), it proceeds to step 104. On the other hand, if the CPU does not determine that contact between the vehicle and the following vehicle V1 is unavoidable (103: No), it returns to step 101.

[0026] In step 104, the CPU performs emergency braking preparation processing. Next, the CPU proceeds to step 105.

[0027] In step 105, the CPU determines whether or not the vehicle itself made contact with the following vehicle V1. If the CPU determines that the vehicle itself made contact with the following vehicle V1 (105: Yes), it proceeds to step 107. On the other hand, if the CPU does not determine that the vehicle itself made contact with the following vehicle V1 (105: No), it proceeds to step 106.

[0028] In step 106, the CPU determines whether its own vehicle has stopped (sp0 = "0"). If the CPU determines that its own vehicle has stopped (106: Yes), it proceeds to step 107. On the other hand, if the CPU does not determine that its own vehicle has stopped (106: No), it proceeds to step 108.

[0029] In step 107, the CPU controls the braking device 30 so that the vehicle is subjected to sudden braking. Next, the CPU proceeds to step 111 and terminates the execution of program PR1.

[0030] In step 108, the CPU determines whether the accelerator pedal has been pressed. If the CPU determines that the accelerator pedal has been pressed (108: Yes), it proceeds to step 110. On the other hand, if the CPU does not determine that the accelerator pedal has been pressed (108: No), it proceeds to step 109.

[0031] In step 109, the CPU determines whether time Δt has exceeded the threshold Δtth. If the CPU determines that time Δt has exceeded the threshold Δtth (109: Yes), it proceeds to step 110. On the other hand, if the CPU does not determine that time Δt has exceeded the threshold Δtth (109: No), it returns to step 105.

[0032] In step 110, the CPU performs the release process. Next, the CPU proceeds to step 111 and terminates the execution of program PR1.

[0033] (effect) The ECU 10 of the vehicle control device 1 reduces the clearance C between the brake disc and brake pad of the braking device 30 compared to normal driving conditions when contact between the vehicle and the following vehicle V1 is unavoidable. This shortens the time required for the brake pad to move toward the brake disc and press against the brake disc when the vehicle and the following vehicle V1 come into contact, or when the vehicle's speed sp0 becomes "0". Therefore, according to this embodiment, the risk of secondary contact (contact between the vehicle and other objects) is efficiently reduced when the following vehicle V1 comes into contact with the vehicle while the vehicle is traveling at a low speed or stopped. [Explanation of Symbols]

[0034] 1...Vehicle control unit, 10...ECU, 20...On-board sensor, 30...Braking system

Claims

[Claim 1] An on-board sensor for acquiring information about the vehicle itself and information about other vehicles approaching from behind, A processor configured to control the braking system of the vehicle so that the vehicle is braked when predetermined conditions related to contact between the other vehicle and the vehicle are met, A vehicle control device equipped with, The braking device comprises a first member that rotates together with the wheel, and a second member that is pressed against the first member and generates a frictional force between itself and the first member. The processor is configured to control the braking device such that, when it is determined that contact between the other vehicle and the own vehicle cannot be avoided, a predetermined condition relating to the time required for the other vehicle to reach the rear end of the own vehicle is met, the accelerator pedal of the own vehicle is depressed to "0", the speed of the own vehicle is below a threshold, the braking device does not apply braking force to the wheels, and the clearance between the first member and the second member is reduced to a lower level than normal. Subsequently, when it is detected that the other vehicle has come into contact with the own vehicle, or when it is detected that the speed of the own vehicle has decreased to "0" without the other vehicle coming into contact with the own vehicle, the braking device is controlled such that the second member is pressed against the first member and the own vehicle is braked.

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